United States Department of Agriculture

Agricultural 

Research 

Service

Agriculture Handbook 

Number 66

Revised February 2016

The Commercial Storage 

of Fruits, Vegetables, and 

Florist and Nursery Stocks

Agricultural 

Research 

Service

Agriculture Handbook 

Number 66

The Commercial Storage 

of Fruits, Vegetables, and 

Florist and Nursery Stocks

Edited by Kenneth C. Gross, Chien Yi Wang, and Mikal Saltveit

_______________________________________________________________

Gross and Wang are formerly with the Food Quality Laboratory, Beltsville 

Agricultural Research Center, USDA, Agricultural Research Service, 

Beltsville, MD. They are now retired. Saltveit is with the Department of 

Plant Sciences, University of California, Davis, CA.

United States Department of Agriculture
ii

Abstract

Gross, Kenneth C., Chien Yi Wang, and Mikal 

Saltveit, eds. 2016. The Commercial Storage of 

Fruits, Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Agriculture Handbook 66 (AH-66) represents 

a complete revision and major expansion of 

the 1986 edition. It has been reorganized and 

now includes 17 Chapters and 138 Commodity 

Summaries written by nearly a hundred experts 

in plant science and postharvest technology. 

This version, like the previous editions of AH66 in 1954, 1968, 1977, and 1986, presents 

summaries of current storage requirements 

of fresh fruits, vegetables, cut flowers, and 

other horticultural crops. However, this highly 

expanded version also includes information on 

quality characteristics, maturity indices, grading, 

packaging, precooling, retail display, chilling 

sensitivity, ethylene production and sensitivity, 

respiration rates, physiological disorders, 

postharvest pathology, quarantine issues, and 

suitability as fresh-cut product. A large number 

of fruits and vegetables were added, as well 

as sections on food safety, nutritional quality, 

texture, and fresh-cut produce. The purpose of 

storing plant material is to lengthen the time it 

can be consumed or utilized. In doing so, it is 

critical to provide an environment that minimizes 

deterioration, maintains microbial safety, and 

retains other quality attributes. AH-66 provides 

guidelines and other important information for 

storing and handling horticultural commodities

to accomplish this.

Keywords: carbon dioxide, chilling injury, 

cold storage, controlled atmosphere storage, 

cut flowers, ethylene, flavor, food safety, 

fresh-cut, fresh produce, fruit softening, heat 

load, 1-methylcyclopropene, microbial safety, 

minimally processed, modified-atmosphere 

packaging, potted plants, nutritional quality, nuts, 

orchids, packaging film, perishable, postharvest 

biology, precooling, respiration, sensory 

evaluation, shelf-life, texture.

The information contained in AH-66 has been 

assembled from material prepared by nearly a 

hundred authors from around the world. All of the 

information contained herein was peer reviewed 

and edited for scientific content. Every effort was 

made to provide the most accurate and current 

information available.

The contributors’ professional affiliations 

and addresses were up-to-date at the time of 

submission of their chapters, and the editors 

made all reasonable efforts to update any changes 

received during the review and publishing process. 

However, due to the large number of contributors 

and countries represented, it is not inconceivable 

that some of the contributors may have changed 

organizations in the interim and thus are no 

longer at the addresses given in this handbook. In 

cases where the editors received specific address 

changes or death notices, all such updates are 

reflected in this volume.

Mention of trade names or commercial products 

in this report is solely for the purpose of providing specific information and does not imply 

recommendation or endorsement by the U.S. 

Department of Agriculture.

This publication reports experimental results 

and other information involving pesticides. It 

does not contain recommendations for their use 

nor does it imply that uses discussed here have 

been registered. All uses of pesticides must be 

registered by appropriate State and/or Federal 

agencies before they can be recommended.

While supplies last, printed copies of this 

publication may be obtained at no cost from the 

USDA-ARS Food Quality Laboratory, Building 

002, Room 117, 10300 Baltimore Avenue, 

Beltsville, MD 20705-2350. 

Copies of this publication may be purchased 

in various formats (microfiche, photocopy, 

CD, and print on demand) from the National 

Technical Information Service, 5285 Port Royal 

Road, Springfield, VA 22161, (800) 553-6847, 

http//:www.ntis.gov.
iii

This publication in its entirety is freely accessible 

on the Internet at http://www.ars.usda.gov/is/np/

indexpubs.

ARS Mission

The Agricultural Research Service conducts 

research to develop and transfer solutions to 

agricultural problems of high national priority 

and provides information access and dissemination to—ensure high-quality, safe food and other 

agricultural products; assess the nutritional needs 

of Americans; sustain a competitive agricultural 

economy; enhance the natural resource base 

and the environment; and provide economic 

opportunities for rural citizens, communities, and 

society as a whole.

The U.S. Department of Agriculture (USDA) 

prohibits discrimination in all its programs and 

activities on the basis of race, color, national 

origin, age, disability, and where applicable, sex, 

marital status, familial status, parental status, 

religion, sexual orientation, genetic information, 

political beliefs, reprisal, or because all or part 

of an individual’s income is derived from any 

public assistance program. (Not all prohibited 

bases apply to all programs.) Persons with 

disabilities who require alternative means for 

communication of program information (Braille, 

large print, audiotape, etc.) should contact USDA’s 

TARGET Center at (202) 720-2600 (voice and 

TDD). To file a complaint of discrimination, 

write to USDA, Director, Office of Civil Rights, 

1400 Independence Avenue, S.W., Washington, 

D.C. 20250-9410, or call (800) 795-3272 (voice) 

or (202) 720-6382 (TDD). USDA is an equal 

opportunity provider and employer.

Revised February 2016
iv

Acknowledgments

The editors gratefully acknowledge the generous 

assistance and helpful contributions of the 

following reviewers: Douglas Adams, Leo Gene 

Albrigo, Douglas Archbold, Reginaldo BaezSanudo, Elizabeth Baldwin, Randolph Beaudry, 

John Beaulieu, Shimshon Ben-Yehoshua, Paul 

Blankenship, Sylvia Blankenship, William 

Bramlage, Jeffery Brecht, Kathleen Brown, 

Jem Burdon, Arthur Cameron, Marita Cantwell, 

William Conway, Stephen Drake, Bob Elliott, 

Timothy Facteau, Ian Ferguson, Louise Ferguson, 

Charles Forney, Maria Gil-Munoz, Gustavo 

Gonzalez-Aguilar, Jim Gorny, Robert Griesbach, 

Laurie Houck, Don Huber, Benjamin Juven, Adel 

Kader, Angelos Kanellis, Stan Kays, Dangyang 

Ke, Walter Kender, Saichol Ketsa, Lisa Kitinoja, 

Wei Chin Lin, Werner Lipton, Bruce Lish, Keith 

Stanley Mayberry, Don Maynard, Elizabeth 

Mitcham, Yosef Mizrahi, Robert John Mullen, 

Timothy Ng, Chuck Orman, Robert Paull, 

Penelope Perkins-Veazie, David Picha, Robert 

Prange, William Proebsting, Stanley Prussia, 

Michael Reid, Mark Ritenour, Mark Roh, Bill 

Romig, Vincent Rubatzky, Carl Sams, Steven 

Sargent, Philip Shaw, Krista Shellie, Richard 

Snyder, Meisheng Tian, Peter Toivonen, Ronald 

Voss, Yin-Tung Wang, Bruce Whitaker, George 

Wilson, Allan Woolf, Elhadi Yahia, Charles Yang, 

Devon Zagory, and Francis Zee.
v

Abbreviations

APHIS Animal and Plant Health Inspection 

Service, USDA

ARS Agricultural Research Service, USDA

BTU British thermal unit

bu bushel

CaCl2 calcium chloride

CDC Centers for Disease Control 

and Prevention

CO2 carbon dioxide

cm centimeter

cfu colony forming units

CA controlled atmosphere

CFM cubic feet per minute

ed., eds. editor; editors

EPA Environmental Protection Agency

FDA Food and Drug Administration, HHS

ft feet

GC gas chromatograph

GRAS generally recognized as safe

h hour

HAT high temperature forced-air treatment

Hg mercury

HHS United States Department of Health 

and Human Services

HWB hot water brushing

HWT hot water treatment

in inch

J Joules

kg kilogram

L liter

MS mass spectrometer

m meter

mL milliliter

MA modified atmosphere

MAP modified atmosphere packaging

μL microliter

min minute

mo month

N Newtons

N2 nitrogen

nL nanoliter

oz ounce, Avoirdupois

O2 oxygen

OTR oxygen transmission rate

ppb parts per billion

ppm parts per million

% percent

lb pound, avoirdupois

RH relative humidity

sec second

T short ton

STS silver thiosulfate

NaOCl sodium hypochlorite

SSC soluble solids content

SO2 sulfur dioxide

TA total acidity

SSC total soluble solids

U.S. United States

USDA United States Department 

of Agriculture

VHT vapor heat treatment
vi
vii

Contents

Introduction...........................................................1 

Temperature Conversion Chart.............................2

Metric Conversion Chart.......................................3

Commodity Cross-Reference................................4

Respiration and Ethylene Production Rates..........7

Postharvest Biology and Technology

Precooling and Storage Facilities........................11

Heat Load Calculation ........................................19

Controlled Atmosphere Storage..........................22

Temperature Preconditioning..............................26

Modified Atmosphere Packaging........................42

Wholesale Distribution Center Storage ..............54

Grocery Store Display Storage ...........................59

Chilling and Freezing Injury...............................62

Respiratory Metabolism......................................68

Ethylene Effects..................................................76

1-Methylcyclopropane (MCP)............................83

Texture ................................................................89

Postharvest Pathology.......................................111

Flavor................................................................128

Food Safety .......................................................149

Nutritional Quality and Its 

 Importance in Human Health........................166

Commodity Summaries

-----Fruits and Vegetables-----

Annual Culinary Herbs.....................................173

Apple.................................................................176

Apricot ..............................................................195

Arazá .................................................................198

Artichoke...........................................................202

Asian Pear.........................................................205

Asparagus..........................................................210

Atemoya............................................................214

Avocado ............................................................216

Banana and Plantain..........................................224

Bean ..................................................................230

Beet ...................................................................234

Blackberry.........................................................237

Blueberry...........................................................240

Bok Choy ..........................................................243

Breadfruit ..........................................................245

Broccoli.............................................................248

Brussels Sprouts................................................252

Cabbage.............................................................255

Carambola .........................................................261

Carrot ................................................................264

Cassava .............................................................268

Cauliflower........................................................271

Celeriac .............................................................275

Celery................................................................277

Cherimoya.........................................................280

Cherry (Sweet)..................................................282

Chicory (Belgian Endive or Witloof Chicory)..286

Chinese Cabbage...............................................289

Coconut.............................................................294

Cranberry ..........................................................297

Cucumber..........................................................302

Currant, Gooseberry, and Elderberry ................306

Date ...................................................................311

Dragon Fruit......................................................315

Durian ...............................................................318

Eggplant ............................................................322

Endive and Escarole..........................................326

Fennel................................................................328

Fig .....................................................................330

Garlic.................................................................333

Ginger ...............................................................336

Ginseng .............................................................338

Grape (American) .............................................340

Grape (Muscadine)............................................342

Grape (Table) ....................................................344

Grapefruit..........................................................349

Greens for Cooking...........................................353

Guava ................................................................356

Honeydew Melon..............................................358

Horseradish .......................................................362

Jerusalem Artichoke..........................................365

Jicama ...............................................................369

Kiwifruit............................................................372

Kohlrabi ............................................................377

Leek...................................................................379

Lemon ...............................................................382

Lettuce...............................................................386

Lime ..................................................................390

Litchi.................................................................392

Longan ..............................................................395

Longkong ..........................................................398

Loquat ...............................................................401

Luffa..................................................................403

Mandarin (Tangerine) .......................................405

Mango ...............................................................408

Mangosteen.......................................................412

Mushroom.........................................................415

Nectarine ...........................................................418
viii

Netted Melon ....................................................423

Nopalitos...........................................................427

Okra...................................................................430

Olive..................................................................433

Onion.................................................................436

Orange...............................................................441

Papaya ...............................................................447

Parsley...............................................................453

Parsnip...............................................................457

Passion Fruit......................................................460

Pea.....................................................................463

Peach.................................................................466

Pear ...................................................................471

Pepper ...............................................................481

Perennial Culinary Herbs..................................485

Persimmon ........................................................487

Pineapple...........................................................491

Plum and Fresh Prune .......................................497

Pomegranate......................................................501

Potato ................................................................506

Prickly Pear.......................................................511

Pumpkin and Winter Squash.............................514

Quince ...............................................................518

Radicchio ..........................................................521

Radish ...............................................................524

Rambutan ..........................................................527

Raspberry ..........................................................530

Rhubarb.............................................................533

Rutabaga ...........................................................535

Salad Greens .....................................................538

Salsify ...............................................................541

Sapodilla and Related Fruit...............................543

Black Sapote ...............................................543

Lucuma .......................................................543

Mamey Apple..............................................544

Sapodilla .....................................................544

Sapote..........................................................546

Star Apple....................................................546

White Sapote...............................................547

Southern Pea .....................................................550

Sprouts..............................................................553

Squash...............................................................556

Strawberry.........................................................560

Sweet Corn........................................................562

Sweetpotato.......................................................566

Swiss Chard ......................................................571

Tamarillo ...........................................................573

Tamarind ...........................................................575

Taro ...................................................................577

Tomatillo...........................................................579

Tomato ..............................................................581

Truffle................................................................588

Turnip................................................................590

Waterchestnut....................................................592

Water Convolvulus............................................595

Watercress.........................................................597

Watermelon .......................................................599

Wax Apple.........................................................602

-----Fresh-Cut Produce-----

Fresh-Cut Fruits................................................604

Fresh-Cut Vegetables........................................624

-----Floral Crops and Nursery Stock-----

Bedding Plants and Seedlings...........................642

Christmas Trees.................................................650

Cut Flowers and Greens....................................659

Flower Bulbs.....................................................709

Flowering Potted Plants....................................722

Foliage Plants....................................................725

Herbaceous Perennials......................................727

Orchids..............................................................732

Seeds and Pollen ...............................................735

-----------Nuts-----------

Almond .............................................................744

Hazelnut ............................................................748

Macadamia Nut.................................................754

Peanut................................................................757

Pecan.................................................................768

Pistachio............................................................772

Walnut...............................................................777
1

Introduction

This latest edition of Agriculture Handbook 

66 (AH-66) represents a complete revision of 

the 1986 edition. It has been reorganized and 

now includes 17 chapters and 138 commodity 

summaries written by nearly a hundred experts 

in plant biology and postharvest technology. This 

version—like the previous editions of AH-66 in 

1954, 1968, 1977, and 1986—presents summaries 

of current storage requirements of fresh fruits, 

vegetables, cut flowers, and other horticultural 

crops. However, this highly improved and 

expanded version also includes information on 

quality characteristics, maturity indices, grading, 

packaging, precooling, retail display, chilling 

sensitivity, ethylene production and sensitivity, 

respiration rates, physiological disorders, 

postharvest pathology, quarantine issues, and 

suitability as fresh-cut product. In addition, a large 

number of fruits and vegetables were added, as 

well as sections on food safety, nutritional quality, 

texture, and fresh-cut produce.

The purpose of storing plant material is to 

lengthen the time it can be stored and marketed 

prior to consumption or other use. In doing so, it is 

critical to provide an environment that minimizes 

deterioration and maintains microbial safety and 

quality. The primary intent of AH-66 is to provide 

guidelines for optimal handling and storage of 

produce in order to accomplish this.

AH-66 is intended as a general reference, and 

the recommendations should not be considered 

absolute, but rather as safe limits at which 

products can ordinarily be handled and stored. A 

draft version of the data presented in this volume 

is available at http://www.ba.ars.usda.gov/hb66. 

Updates to the online data will be made as they 

become available, and users are encouraged to 

periodically check for any new information.

Each contribution in this volume was peer 

reviewed by at least one individual knowledgeable 

in that particular area or commodity, as well as 

two editors. This review process helped to ensure 

that the information in this edition of AH-66 is 

as accurate and current as possible. The editors 

would like to express their sincere appreciation

to all of the contributors and to the reviewers,

who are listed in the Acknowledgments.

 The original edition of AH-66, published in 

1954, was written by R.C. Wright, D.H. Rose, 

and T.M. Whiteman, all from USDA Agricultural 

Research Service (ARS). Then, in 1968, the 

handbook was revised by J.M. Lutz and R.E. 

Hardenburg, also from USDA-ARS. A major 

revision by R.E. Hardenburg, A.E. Watada, and 

C.Y. Wang, at USDA-ARS Horticultural Crops 

Quality Laboratory (now Food Quality Laboratory) in Beltsville, MD, was published in 

1986. In 1990, 10,000 copies of the 1986 edition 

were reprinted, of which few remain today. The 

volume has also been translated into several 

languages. It was clearly time for an extensive 

revision, both to bring the content up to date and 

to increase its availability.

Most temperatures are given in both oC and oF. 

Nevertheless, a “Temperature Conversion Chart” 

is included in this volume. Though temperatures 

are sometimes expressed to the first decimal place 

due to conversion, this does not mean that this 

level of accuracy is recommended, necessary, or 

possible in a commercial situation. Generally, 

storage temperatures can only be expected 

to be maintained within ±1 oC. Also, see the 

“Metric Conversion Chart” for some common 

metric conversions. Respiration and ethylene 

production rates for many fruits and vegetables 

are also summarized in the sections “Respiration” 

and “Ethylene Effects.” A“Commodity CrossReference” index has been included to aid in 

finding the commodity summary for produce

 called by various names in different cultures 

and geographical locations.

“In this work, when it shall be found that much is 

omitted,let it not be forgotten that much likewise is 

performed.”

Dr. Samuel Johnson, 

English lexicographer and essayist, 1775
2

Temperature Conversion Chart

°C = 5/9 (°F - 32)

°F = (9/5 × °C) + 32

°C °F °C °F 

-2 28.4 23 73.4

-1 30.2 24 75.2

0 32.0 25 77.0

1 33.8 26 78.8

2 35.6 27 80.6

3 37.4 28 82.4

4 39.2 29 84.2

5 41.0 30 86.0

6 42.8 31 87.8

7 44.6 32 89.6

8 46.4 33 91.4

9 48.2 34 93.2

10 50.0 35 95.0

11 51.8 36 96.8

12 53.6 37 98.6

13 55.4 38 100.4

14 57.2 39 102.2

15 59.0 40 104.4

16 60.8 45 113.0

17 62.6 50 122.0

18 64.4 55 131.0

19 66.2 60 140.0

20 68.0 65 149.0

21 69.8 70 158.0

22 71.6 75 167.0
3

Metric Conversion Chart

Mass

1.0 avoirdupois pound (lb) = 0.454 kilogram (kg) = 454 grams (g)

1.0 kilogram (kg) = 2.2 pounds (lb) = 35.2 avoirdupois ounces (oz) = 32.15 troy ounces

1.0 avoirdupois ounce (oz) = 0.9115 troy ounce = 0.0284 kilogram (kg) = 28.4 grams (g)

1 short ton (T) = 2,000 pounds (lb) = 907.2 kilograms (kg) = 0.893 long ton = 0.907 metric tonne

Length

1 inch (in) = 2.54 centimeters (cm)

1 centimeter (cm) = 0.394 inch (in)

1 foot (ft) = 30.48 centimeters (cm)

1 yard (yd) = 91.44 centimeters (cm) or 0.9144 meter (m)

1 meter (m) = 3.28 feet (ft) = 1.0936 yards (yd)

1 mile (mi) = 1.61 kilometers (km)

1 kilometer (km) = 0.621 mile (mi)

Volume

1 quart (qt) = 0.946 liter (L)

1 liter (L) = 1.057 quarts (qt)

1 cup (c) = 0.24 liter (L)

1 pint (pt) = 0.47 liter (L)

1 quart (qt) = 0.95 liter (L)

1 U.S. bushel (bu) = 35.24 liters (L)

1 liter (L) = 0.2838 bushel (bu)

1 U.S. gallon (gal) = 3.785 liters (L)

1 liter (L) = 0.2642 gallon (gal)

1 cubic foot (ft3

) = 28.32 liters (L)

1 cubic yard (yd3

) = 0.76 cubic meter (m3)

1 liter (L) = 61.02 cubic inches (in3

)

Area

1 acre = 0.4047 hectare

1 hectare = 2.47 acres

1 square meter (m2

) = 1550 square inches (in2) = 1.196 square yards (yd2) = 10.76 square feet (ft2)

1 square inch (in2

) = 6.45 square centimeters (cm2)

1 square foot (ft2

) = 0.0929 square meter (m2)

Energy/Work

1 joule (J) = 0.00094 British thermal units (BTU) = 1 watt per second (W s-1)

1 British thermal unit (BTU) = 1,055 joules (J) = 0.252 kilocalorie (kcal)
4

Commodity Cross-Reference

To find... See...

Abogado Avocado

Alligator pear Avocado

Alfalfa sprouts Sprouts

Anon Sapodilla

Apple cactus Dragon fruit

Apple pear (misleading) Asian pear

Araçá boi Arazá

Avocat Avocado

Basil Annual culinary herbs

Bean sprouts Sprouts

Beets Beet

Belgian endive Chicory

Bell pepper Pepper

Bhendi Okra

Bhindi Okra

Boy-toyo Bok choy

Cactus fruit Prickly pear

Cactus pad Nopalitos

Cactus pear Prickly pear

Caimito Sapodilla

Calabaza Pumpkin

Calabrese Broccoli

Canary melon Honeydew melon

Cantelope Netted melon

Casaba melon Honeydew melon

Cassave Cassava

Cay mang cut Mangosteen

Chervil Annual culinary herbs

Chico mamey Sapodilla

Chico zapote Sapodilla

Chiku Sapodilla

Chile pepper Pepper

Chinese apple Pomegranate

Chinese chard Bok choy

Chinese chive Perennial culinary herbs

Chinese date plum Persimmon

Chinese long bean Bean

Chinese okra Luffa

Chinese pear Asian pear

Chive Perennial culinary herbs

Ciku Sapodilla

Claytonia Salad greens

Cocoyam Taro

Collards Greens for cooking

Coriander Annual culinary herbs

Corn salad Salad greens

To find... See...

Crenshaw melon Honeydew melon

Custard apple Avocado

Daikon Radish

Dandelion Salad greens

Dasheen Taro

Date Plum Persimmon

Dill Annual culinary herbs

Dilly Sapodilla

Duku Longkong

Dulian Durian

Duren Durian

Duyin Durian

Eddoe Taro

Elderberry Currant

Escarole Endive and Escarole

Field salad Salad greens

Filbert Hazelnut

Fire dragon fruit Dragon fruit

Flat bean Bean

French bean Bean

French sorrel Salad greens

Garden sorrel Salad greens 

Gooseberry Currant

Globe artichoke Artichoke

Collard greens Greens for Cooking

Gombo Okra

Green bean Bean

Green cabbage Cabbage

Green onion Onion

Grosse sapote Sapodilla

Groundnut Peanut

Gumbo Okra

Hamburg parsley Parsley

Husk tomato Tomatillo

Japanese pear Asian pear

Java plum Wax apple

Kadu Durian

Kale Greens for cooking

Kang kong Water convolvulus

Kong xin cai Water convolvulus

La pitahaya rouge Dragon fruit

Lady’s finger Okra

Lamb’s lettuce Salad greens

Langsat Longkong

Lanson Longkong

Lychee Litchi

Long bean Bean

Lucuma Sapodilla
5

To find... See...

Malanga Taro

Malay apple Wax apple

Mamey Sapodilla

Mandioca Cassava

Manggistan Mangosteen

Mangis Mangosteen

Mangkhut Mangosteen

Mangostan Mangosteen

Mangostanier Mangosteen

Mangostao Mangosteen

Manggustan Mangosteen

Manioc Cassava

Marjoram Perennial culinary herbs

Marmalade fruit Sapodilla

Matai Waterchestnut

Melon, Honeydew melon Honeydew melon

Melon, Netted Netted melon

Mesetor Mangosteen

Miner’s lettuce Salad greens

Mongkhut Mangosteen

Mung bean sprouts Sprouts

Muskmelon Netted melon

Mustard cabbage Bok choy

Mustard greens Greens for cooking

Nachi Asian pear

Nasberry Sapodilla

Néspero Sapodilla

Noplaes Nopalitos

Oregano Perennial culinary herbs

Oriental pear Asian pear

Oxheart cabbage Cabbage

Oyster plant Salsify

Pak-choy Bok choy

Pake boong Water convolvulvus

Pak-tsoi Bok choy

Palta Avocado

Paprika Pepper

Peppermint Perennial culinary herbs

Pichi Arazá

Pitahaya Dragon fruit

Pitaya roja Dragon fruit

Pod bean Bean

Quaio Okra

Quingumbo Okra

Rape Greens for cooking

Red beet Beet

Rian Durian

Rocket salad Salad greens

To find... See...

Roquette Salad greens

Rose apple Wax apple

Rose water apple Wax apple

Rosemary Perennial culinary herbs

Round sorrel Salad greens

Rucola Salad greens

Rugula Salad greens

Runner bean Bean

Rupina caspi Arazá

Sage Perennial culinary herbs

Salad chervil Annual culinary herbs

Salad pear Asian pear

Sand apple Asian pear

Sapota Sapodilla

Sapote Sapodilla

Saurieng Durian

Savory Annual culinary herbs

Savoy cabbage Cabbage

Sementah Mangosteen

Semetah Mangosteen

Sha Li pear Asian pear

Shalea pear Asian pear

Shallot Onion

Snap bean Bean

Sororia Arazá

Sorrel Salad greens

Spearmint Perennial culinary herbs

Spinach Greens for cooking

Sponge gourd Luffa

Spring onion Onion

Sprouting broccoli Broccoli

Star apple Sapodilla

Star fruit Carambola

Stinkvrucht Durian

Stinky rose Garlic

Strawberry pear Dragon fruit

String bean Bean

Sugar pea Pea

Summer savory Annual culinary herbs

Summer squash Squash

Sunchokes Jerusalem artichoke

Swedes Rutabaga

Swedish turnips Rutabaga

Sweetsop Sapodilla

Sweet cherry Cherry, sweet

Sweet pepper Pepper

Table beet Beet

Taisai Bok choy
6

To find... See...

Tamarindo Tamarind

Tangerine Mandarin and Tangerine

Tannier Taro

Tarragon Perennial culinary herbs

Thang loy Dragon fruit

Thureen Durian

Thurian Durian

Thyme Perennial culinary herbs

Tree tomato Tamarillo

Turnip-rooted cabbage Kohlrabi or Rutabaga

Turnip greens Greens for cooking

Vegetable oyster Salsify

Water cabbage Water convolvulvus

White celery mustard Bok choy

White sapote Sapodilla

Whitloof Chicory

Winter purslane Salad greens

Winter spinach Water convolvulvus

Yard-long bean Bean

Yellow pitaya Dragon fruit

Yellow wax bean Bean

Yuca Cassava

Zapote Sapodilla

Zucchini Squash
7

Respiration and Ethylene Production Rates

The values in table 1 are approximations or the average rates of a range; see individual sections on each 

commodity for more specific information and references. Values in parentheses after ethylene rates are the 

temperatures at which ethylene production was measured. For respiration data, to get mL kg-1 h-1, divide 

the mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 at 20 °C (68 °F). To calculate heat 

production, multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1 or by 61 to get kcal tonne-1 day-1.

Table 1. Rates of respiration and ethylene production

_________________________________________________________________________________

 Respiration

Commodity _________________________________________ C2H4 Production

0 °C 5 °C 10 °C 15 °C 20 °C 25 °C

_________________________________________________________________________________

——————————mg kg-1 h-1————————- μL kg-1 h-1

Apple

Fall 3 6 9 15 20 nd1 varies greatly

Summer 5 8 17 25 31 nd varies greatly

Apricot 6 nd 16 nd 40 nd <0.1 (0 °C)

Arazá (ripe) nd nd 601 nd 1283 nd nd

Artichoke 30 43 71 110 193 nd <0.1

Asian Pear 5 nd nd nd 25 nd varies greatly

Asparagus2 60 105 215 235 270 nd 2.6 (20 °C)

Atemoya nd nd 119 168 250 nd 200 (20 °C)

Avocado nd 35 105 nd 190 nd >100 (ripe; 20 °C)

Banana (ripe) nd nd 80 1403 280 nd 5.0 (15 °C)

Basil 36 nd 71 nd 167 nd very low7

Beans

Snap 20 34 58 92 130 nd <0.05 (5 °C)

Long 40 46 92 202 220 nd <0.05 (5 °C)

Beets 5 11 18 31 60 nd <0.1 (0 °C)

Blackberry 19 36 62 75 115 nd varies; 0.1 to 2.0

Blueberry 6 11 29 48 70 101 varies; 0.5 to 10.0

Bok Choy 6 11 20 39 56 nd <0.2

Breadfruit nd nd nd 329 nd 480 1.2

Broccoli 21 34 81 170 300 nd <0.1 (20 °C)

Brussels sprouts 40 70 147 200 276 nd <0.25 (7.5 °C)

Cabbage 5 11 18 28 42 62 <1.1 (20 °C)

Carambola nd 15 22 27 65 nd <3.0 (20 °C)

Carrot (topped) 15 20 31 40 25 nd <0.1 (20 °C)

Cassava nd nd nd nd nd 40 1.7 (25 °C)

Cauliflower 17 21 34 46 79 92 <1.0 (20 °C)

Celeriac 7 13 23 35 45 nd <0.1 (20 °C)

Celery 15 20 31 40 71 nd <0.1 (20 °C)

Cherimoya nd nd 119 182 300 nd 200 (20 °C)

Cherry, Sweet 8 22 28 46 65 nd <0.1 (0 °C)

Chervil 12 nd 80 nd 170 nd very low
8

Table 1. Rates of respiration and ethylene production—Continued

_________________________________________________________________________________

 Respiration

Commodity _________________________________________ C2H4 Production

0 °C 5 °C 10 °C 15 °C 20 °C 25 °C

_________________________________________________________________________________

——————————mg kg-1 h-1————————- μL kg-1 h-1

Chicory 3 6 13 21 37 nd <0.1 (0 °C)

Chinese Cabbage 10 12 18 26 39 nd <0.1 (20 °C)

Chinese Chive 54 nd 99 nd 432 nd very low

Chive 22 nd 110 nd 540 nd very low

Coconut nd nd nd nd nd 50 very low

Coriander 22 30 nd nd nd nd very low

Cranberry 4 5 8 nd 16 nd 0.6 (5 °C)

Cucumber nd nd 26 29 31 37 0.6 (20 °C)

Currant, Black 16 28 42 96 142 nd nd

Dill 22 nd 103 324 nd nd <0.1 (20 °C)

Dragon Fruit nd nd nd nd 105 nd <0.1

Durian nd nd nd nd 2654 nd 40 (ripe)

Eggplant

American nd nd nd 695 nd nd 0.4 (12.5 °C)

Japanese nd nd nd 1315 nd nd 0.4 (12.5 °C)

White egg nd nd nd 1135 nd nd 0.4 (12.5 °C)

Endive/Escarole 45 52 73 100 133 200 very low

Fennel 196 nd nd nd 32 nd 4.3 (20 °C)

Fig 6 13 21 nd 50 nd 0.6 (0 °C)

Garlic

Bulbs 8 16 24 22 20 nd very low

Fresh peeled 24 35 85 nd nd nd very low

Ginger nd nd nd nd 63 nd very low

Ginseng 6 nd 15 33 nd 95 very low

Gooseberry 7 12 23 52 81 nd nd

Grape, American 3 5 8 16 33 39 <0.1 (20 °C)

Grape, Muscadine 106 13 nd nd 51 nd <0.1 (20 °C)

Grape, Table 3 7 13 nd 27 nd <0.1 (20 °C)

Grapefruit nd nd nd <10 nd nd <0.1 (20 °C)

Guava nd nd 34 nd 74 nd 10 (20 °C)

Honeydew Melon nd 8 14 24 30 33 very low

Horseradish 8 14 25 32 40 nd <1.0

Jerusalem Artichoke 10 12 19 50 nd nd nd

Jicama 6 11 14 nd 6 nd very low 

Kiwifruit (ripe) 3 6 12 nd 19 nd 75

Kohlrabi 10 16 31 46 nd nd <0.1 (20 °C)

Leek 15 25 60 96 110 115 <0.1

Lemon nd nd 11 19 24 nd <0.1 (20 °C)

Lettuce

Head 12 17 31 39 56 82 very low

Leaf 23 30 39 63 101 147 very low
9

Table 1. Rates of respiration and ethylene production—Continued

_________________________________________________________________________________

 Respiration

Commodity _________________________________________ C2H4 Production

0 °C 5 °C 10 °C 15 °C 20 °C 25 °C

_________________________________________________________________________________

——————————mg kg-1 h-1————————- μL kg-1 h-1

Lime nd nd ,10 nd nd nd <0.1 (20 °C)

Litchi nd 13 24 nd 60 102 very low

Longan nd 7 21 nd 42 nd very low

Longkong nd nd 458 nd nd nd 4.0

Loquat 119 12 31 nd 80 nd very low

Luffa 14 27 36 63 79 nd <0.1 (20 °C)

Mamey Apple nd nd nd nd nd 35 400.0 (27 °C)

Mandarin (Tangerine) nd 6 8 16 25 nd <0.1 (20 °C)

Mango nd 16 35 58 113 nd 1.5 (20 °C)

Mangosteen nd nd nd nd nd 21 0.03

Marjoram 28 nd 68 nd nd nd very low

Mint 20 nd 76 nd 252 nd very low

Mushroom 35 70 97 nd 264 nd <0.1 (20 °C)

Nectarine (ripe) 5 nd 20 nd 87 nd 5.0 (0 °C)

Netted Melon 6 10 15 37 55 67 55.0

Nopalitos nd 18 40 56 74 nd very low

Okra 215 40 91 146 261 345 0.5

Olive nd 15 28 nd 60 nd <0.5 (20 °C)

Onion 3 5 7 7 8 nd <0.1 (20 °C)

Orange 4 6 8 18 28 nd <0.1 (20 °C)

Oregano 22 nd 101 nd 176 nd very low

Papaya (ripe) nd 5 nd 19 80 nd 8.0

Parsley 30 60 114 150 199 274 very low

Parsnip 12 13 22 37 nd nd <0.1 (20 °C)

Passion Fruit nd 44 59 141 262 nd 280.0 (20 °C)

Pea

Garden 38 64 86 175 271 313 <0.1 (20 °C)

Edible Pod 39 64 89 176 273 nd <0.1 (20 °C)

Peach (ripe) 5 nd 20 nd 87 nd 5.0 (0 °C)

Pepper nd 7 12 27 34 nd <0.2 (20 °C)

Persimmon 6 nd nd nd 22 nd <0.5 (20 °C)

Pineapple nd 2 6 13 24 nd <1.0 (20 °C)

Plum (ripe) 3 nd 10 nd 20 nd <5.0 (0 °C)

Pomegranate nd 6 12 nd 24 nd <0.1 (10 °C)

Potato (cured) nd 12 16 17 22 nd <0.1 (20 °C)

Prickly Pear nd nd nd nd 32 nd 0.2 (20 °C)

Radicchio 8 1310 2311 nd nd 45 0.3 (6 °C)

Radish

Topped 16 20 34 74 130 172 very low

Bunched with tops 6 10 16 32 51 75 very low

Rambutan (mature) nd nd nd nd nd 70 very low
10

Table 1. Rates of respiration and ethylene production—Continued

_________________________________________________________________________________

 Respiration

Commodity _________________________________________ C2H4 Production

0 °C 5 °C 10 °C 15 °C 20 °C 25 °C

_________________________________________________________________________________

——————————mg kg-1 h-1————————- μL kg-1 h-1

Raspberry 176 23 35 42 125 nd ≤12.0 (20 °C)

Rhubarb 11 15 25 40 49 nd nd

Rutabaga 5 10 14 26 37 nd <0.1 (20 °C)

Sage 36 nd 103 nd 157 nd very low

Salad Greens

Rocket Salad 42 113 nd nd nd nd very low

Lamb’s Lettuce 12 6711 81 nd 139 nd very low

Salsify 25 43 49 nd 193 nd very low

Sapodilla nd nd nd nd nd 16 3.7 (20 °C)

Sapote nd nd nd nd nd nd >100 (20 °C)

Southern Pea

Whole Pods 246 25 nd nd 148 nd nd

Shelled Peas 296 nd nd nd 126 nd nd

Spinach 21 45 110 179 230 nd very low

Sprouts (mung bean) 23 42 96 nd nd nd <0.1 (10 °C)

Squash, Summer 25 32 67 153 164 nd <1.0 (20 °C)

Squash, Winter nd nd 995 nd nd nd very low

Star Apple nd nd nd nd 38 nd 0.1 (20 °C)

Strawberry 16 nd 75 nd 150 nd <0.1 (20 °C)

Sweet Corn 41 63 105 159 261 359 very low

Swiss Chard 196 nd nd nd 29 nd 0.14 (20 °C)

Tamarillo nd nd nd nd 27 nd <0.1

Tarragon 40 nd 99 nd 234 nd very low

Thyme 38 nd 82 nd 203 nd very low

Tomatillo 

(mature green) nd 13 16 nd 32 nd 10.0 (20 °C)

Tomato nd nd 15 22 35 43 10.0 (20 °C)

Truffles 28 35 45 nd nd nd very low

Turnip 8 10 16 23 25 nd very low

Waterchestnut 10 25 42 79 114 nd nd

Water Convolvulus nd nd nd nd nd 100 <2.0

Watercress 22 50 110 175 322 377 <1.0 (20 °C)

Watermelon nd 4 8 nd 21 nd <1.0 (20 °C)

Wax Apple nd nd 5 nd 10 nd very little _________________________________________________________________________________

1

 nd = Not determined. 

2

 1 day after harvest. 

3

 At 13 °C. 

4

 At 22 °C. 

5

 At 12.5 °C. 

6

 At 2 °C. 

7 Although not accurately measured, “very 

low” is considered to be <0.05 μL kg-1 h-1. 8

 At 9 °C. 

9

 At 1 °C. 

10 At 6 °C. 

11 At 7.5 °C.
11

Precooling and Storage Facilities

James F. Thompson

Thompson is with the Department of Biological & 

Agricultural Engineering, University of California, 

Davis, CA. He is now retired.

In-Field Temperature Management

Temperature management of perishable 

commodities begins with proper handling at 

harvest. Generally, produce should be harvested 

in the morning so that it will be at the coolest 

possible temperature during the delay between 

harvest and initial cooling. Exceptions to this 

recommendation are produce, such as some 

citrus fruit, that are damaged if they are handled 

when they are turgid in the morning (Eckert and 

Eaks 1989), or situations in which the produce is 

harvested in the late afternoon so that it can be 

transported to a local market during the cool night 

hours. Produce should be shaded to protect it from 

solar heat gain. Reduce the time between picking 

and initial cooling; this is particularly critical 

because fruits and vegetables transpire and respire 

at high rates at field temperatures (Maxie et al. 

1959, Harvey and Harris 1986, d’Sousa and Ingle 

1989, Robbins and Moore 1992).

Initial Cooling Methods

Produce is usually cooled to its long-term storage 

temperature in special facilities designed to 

rapidly remove produce heat. 

Forced-air cooling is the most widely adaptable 

method and is commonly used for many fruits, 

fruit-type vegetables, and cut flowers (Parsons et 

al. 1970, 1972, Rij et al. 1979, Baird et al. 1988, 

Thompson et al. 1998). 

Hydrocooling uses water as the cooling medium 

and is less widely used than forced-air cooling 

because some products do not tolerate water 

contact and because it requires the use of waterresistant packaging. It is commonly used for root-, 

stem-, and flower-type vegetables; melons; and 

some tree fruits (Pentzer et al. 1936, Toussaint 

1955, Stewart and Lipton 1960, Bennett 1963, 

Perry and Perkins 1968, Mitchell 1971). 

Vacuum- and water spray vacuum-cooling

are usually reserved for crops, such as leafy 

vegetables, that release water vapor rapidly, 

allowing them to be quickly cooled (Barger 1963, 

Harvey 1963). 

Package icing uses crushed ice to cool and 

maintain product temperature and is used for 

a very few commodities, mainly those whose 

purchasers have a strong traditional demand for 

this method. It is still common for broccoli. 

Room cooling is accomplished by placing warm 

produce in a refrigerated room. Cooling times are 

at least 24 h and can be much longer if produce is 

not packaged correctly or if no provision is made 

to allow airflow past boxes. It is used for a few 

commodities, such as citrus and CA-stored apples, 

which can have acceptable, though not optimal, 

quality without use of rapid cooling. 

Transport cooling in refrigerated ships and 

containers is used for products, such as bananas, 

in areas with no cooling infrastructure. Highway 

trailers have insufficient airflow to cool produce 

and should never be depended on for initial 

cooling. 

Table 1 is a summary comparison of the six initial 

cooling methods.
12Table 1. Comparison of typical product effects and cost for six common cooling methods

__________________________________________________________________________________________________________________

Forced-air Hydro Vacuum Water spray Ice Room

__________________________________________________________________________________________________________________Typical cooling time (h) 1 to 10 0.1 to 1.0 0.3 to 2.0 0.3 to 2.0 0.1 to 0.3* 20 to 100Product moisture loss (%) 0.1 to 2.0 0 to 0.5 2.0 to 4.0 No data No data 0.1 to 2.0Water contact with product No Yes No Yes Yes, unless bagged NoPotential for decay contamination Low High† None High† Low LowCapital cost Low Low Medium Medium High Low‡Energy efficiency Low High High Medium Low LowWater-resistant packaging needed No Yes No Yes Yes NoPortable Sometimes Rarely done Common Common Common NoFeasibility of in-line cooling Rarely done Yes No No Rarely done No__________________________________________________________________________________________________________________Source: Thompson et al. 1998*Top icing can take much longer. †Recirculated water must be constantly sanitized to minimize accumulation of decay-causing pathogens. ‡Low if product is also stored in cooler as is done with apples; otherwise long cooling times make it an expensive system.
13

Forced-Air Cooling

Refrigerated air is used as the cooling medium 

with this system. It is forced through produce 

packed in boxes or pallet bins. A number of 

airflow systems are used, but the tunnel cooler is 

the most common (Thompson et al. 1998). Two 

rows of packages, bins, or palletized product are 

placed on either side of an air-return channel. A 

tarp is placed over the product and the channel, 

and a fan removes air from the channel, drawing 

air through the product. The product is cooled 

in batches. Cooling times range from 1 h for cut 

flowers to more than 6 h for larger fruit, packed in 

airflow-restricting materials such as bags or paper 

wraps.

The cold-wall system is adapted to cooling 

smaller quantities of produce (Thompson et al. 

1998). Individual pallets or cartloads of packages 

are placed against a plenum wall. Usually the 

plenum has a slightly lower air pressure than 

the room, and air is pulled through the product. 

Some coolers, particularly for cut flowers, use a 

pressurized plenum and air is pushed through the 

product. Cold-wall systems do not use floor space 

as efficiently as tunnel coolers and require more 

management because each pallet is 

cooled individually.

The serpentine air system is designed for cooling 

produce in pallet bins (Thompson et al. 1998). 

Stacks of even numbers of bins are placed against 

a negative pressure plenum wall. Bottom openings 

for forklift tines are used for air supply and air 

return channels. Air flows vertically up or down 

through the product. The forklift openings are 

limited in dimension, which restricts airflow 

and causes slow cooling. This system is used for 

partially cooling product that will be packaged 

later and finish-cooled after packing and for 

cooling product in long-term storage. The system 

uses cold room volume very efficiently.

Cooling time in forced-air coolers is controlled 

by volumetric airflow rate and product diameter 

(Flockens and Meffert 1972, Gan and Woods 

1989). Coolers often operate with 1 L kg-1 sec1

of produce, with a typical range of 0.5 to 2.0 L 

kg-1 sec-1 (1 L kg-1 sec-1 equals approximately 

1 CFM lb-1). At 1 L kg-1 sec-1, grapes with a 

small minimum diameter will cool in about 2 h, 

while cantaloupes with a much larger diameter 

require more than 5 h. Boxes should have about 

5% sidewall vent area to accommodate airflow 

without excessive pressure drop across the box 

(Wang and Tupin 1968, Mitchell et al. 1971). 

Internal packaging materials should be selected to 

restrict airflow as little as possible.

Forced-air cooling causes some moisture loss. 

Loss may not be detectable for produce items 

with a low transpiration coefficient, like citrus 

fruits, or it may equal several percent of initial 

weight for produce with a high transpiration 

coefficient (Sastry and Baird 1978). Moisture loss 

is linearly related to difference between initial and 

final product temperatures. High initial produce 

temperatures cause higher moisture loss than 

lower temperatures when cooling starts. Moisture 

loss can be reduced at the expense of longer 

cooling times by wrapping product in plastic or 

packing it in bags.

Details of fan selection, air plenum design, 

refrigeration sizing, product cooling times, and 

operational guidelines can be found in Thompson 

et al. (1998). Forced-air coolers are the least 

energy efficient type of cooler but are widely 

used because they are adaptable to a wide range 

of products and packaging systems (Thompson 

et al. 2002). Small units can be installed in many 

existing cold storage facilities.

Hydrocooling

Cooling is accomplished with this technique 

by moving cold water around produce with a 

shower system or by immersing produce directly 

in cold water. Shower coolers distribute water 

using a perforated metal pan that is flooded with 

cold water from the refrigeration evaporator 

(Thompson et al. 1998). Shower-type coolers can 

be built with a moving conveyor for continuous 

flow operation, or they can be operated in a batch 

mode. Immersion coolers are suited for produce 

that sinks in water (Thompson et al. 1998). They 
14

usually cool more slowly than shower coolers 

because water flows at slower rates past the 

product.

Water is a better heat-transfer medium than air, 

and consequently hydrocoolers cool produce much 

faster than forced-air coolers. In well designed 

shower coolers, small diameter produce, like 

cherries, cools in less than 10 min. Large diameter 

products like melons cool in 45 to 60 min (Stewart 

and Lipton 1960, Stewart and Couey 1963, 

Thompson et al. 1998). Immersion coolers usually 

have longer cooling times than shower coolers 

because water speed past produce is slower.

Packages for hydrocooled produce must allow 

vertical water flow and tolerate water contact. 

Plastic or wood containers work well in 

hydrocoolers. Corrugated fiberboard must be waxdipped to withstand water contact.

Hydrocoolers cause no moisture loss in cooling. 

In fact, they can rehydrate slightly wilted produce. 

Hydrocooler water spreads plant decay organisms 

and thus must be obtained from a clean source 

and treated (usually with hypochlorous acid 

from sodium hypochlorite or gaseous chlorine) 

to minimize the levels of decay organisms 

(Thompson et al. 1998).

Calculations of hydrocooler size, refrigeration 

capacity, water flow needs, and typical product 

cooling times can be found in Thompson et al. 

(1998). Hydrocoolers can be fairly energy efficient 

and are the least expensive cooling method to 

purchase (Thompson 1992).

Package Icing

Packing a product with crushed or flaked ice can 

quickly cool it and provides a source of cooling 

during subsequent handling. It also maintains high 

humidity around the product, reducing moisture 

loss. Its disadvantages are that it has high capital 

and operating costs, requires a package that will 

withstand constant water contact, and usually 

adds a great amount of weight to the package. 

In addition, meltwater can damage neighboring 

produce in a shipment of mixed commodities. 

Cut flowers are sometimes cooled initially with 

a forced-air system, and a small amount of ice in 

a sealed package is secured in the container. This 

greatly reduces the amount of ice needed and 

eliminates meltwater damage, while providing 

some temperature control during subsequent 

transit and handling.

Vacuum Cooling

This method achieves cooling by causing water 

to rapidly evaporate from a product. Water loss 

of about 1% causes 6 °C (11 °F) product cooling 

(Barger 1963). Product is placed in a steel vessel 

and vacuum pumps reduce pressure in the vessel 

from 760 mm Hg to 4.6 mm Hg (Thompson et al. 

(1998). Water boils at a pressure of 20 to 30 mm 

Hg depending on temperature. This causes rapid 

moisture evaporation and produce cooling. At the 

end of the cooling cycle, pressure equals 4.6 mm 

Hg and water boils at 0 °C (32 °F). If the product 

is held at this pressure long enough, it will cool to 

0 °C (32 °F). For produce that releases moisture 

rapidly, like leafy green vegetables, cooling can 

be accomplished in 20 to 30 min, even when 

the product is wrapped in plastic film (Cheyney 

et al. 1979). The produce loses 2 to 4% of its 

weight during cooling, depending on its initial 

temperature. Spraying the produce with water 

before cooling minimizes product moisture loss. 

Some coolers are fitted with water spray systems 

that are activated during the cooling cycle.

Procedures for estimating vacuum pump capacity, 

refrigeration capacity, and condensing coil design 

can be found in Wang and Gitlin (undated). Use 

Thompson et al. (1998) and assume a -9 to -7 °C 

(15 to 20 °F) refrigerant evaporating temperature 

to estimate compressor horsepower. Vacuum 

coolers are very energy efficient (Thompson et 

al. 1987) and are cost competitive if well utilized 

(Thompson 1992).
15

Marine Transport Cooling

Perishable products should be cooled before 

being loaded into a refrigerated transport vehicle. 

However, some production areas do not have 

cooling facilities, and transport cooling is the only 

feasible option. Citrus and bananas in the tropics 

are often cooled during marine transport.

Refrigerated containers and ships supply 

refrigerated air through a floor plenum. Fastest 

possible cooling is obtained by using packages 

that allow vertical airflow and by loading the 

cargo so that refrigerated air is forced through the 

product. Boxes should have top and bottom vents, 

and interior packaging materials should not block 

air flow. The load or dunnage material must cover 

the entire floor to prevent refrigerated air from 

traveling up though spaces between pallet loads 

and bypassing the load. Proper packaging and 

loading will allow product to cool in 1 to 2 days 

(Heap 1998). Improper practices will prevent the 

load from cooling and the product will arrive at 

destination too warm and in poor quality.

Cooling Time Calculations

Rate of cooling is directly related to the 

temperature difference between the cooling 

medium and the product. Initially, when the 

product is warm, temperature drops quite rapidly; 

later, the rate slows as product temperature drops. 

The product is considered “half cool” when its 

temperature drops to half the difference between 

its initial temperature and the cooling medium 

temperature. After another half-cooling period, 

the product is considered “three-quarters” cool. 

Product is usually finished cooling at “seveneighths” or “fifteen-sixteenths” cool. Cooling time 

predictions can be done with equations presented 

in Thompson et al. (1998) or with a graphical 

method like that in Sargent et al. (1988).

Cold Storage

Building Design and Layout 

The floor area needed for refrigerated storage 

can be calculated by determining the maximum 

amount of product the facility will be expected to 

handle in units of volume (m3

 or ft3) divided by 

the storage height. Storage height is usually about 

2 m, the height of a pallet load. Product height can 

be increased by adding pallet racks or, if boxes 

are strong enough, by stacking pallets up to three 

high. Pallet bins are sometimes stacked to a height 

of over 3 m. Add to this area space for corridors 

and space for lift truck movement.

Airflow Design

Adequate airflow is needed to distribute 

refrigerated air throughout the facility to maintain 

uniform air temperatures. Most cold storage 

is designed to have an air flow capacity of 0.3 

m3 min-1 tonne-1 of product (100 ft3

 min-1 ton1). 

In long-term storage, the product will reach 

setpoint temperature within a few days to about 

1 week after the facility is filled. Airflow can 

then be reduced to about 20 to 40% of the design 

capacity and still maintain adequate temperature 

uniformity. This can be done by intermittent 

operation of fans or by keeping the fans constantly 

on but reducing their speed with an electronic 

speed control system. Slow air speeds reduce 

moisture loss from the product (Kroca and 

Hellickson 1993).

Airflow must be distributed uniformly throughout 

the coldroom to minimize temperature variability. 

For product in pallet loads, one of three systems is 

commonly used (Thompson et al. 1998). All three 

require placement of pallets in lanes separated 

by 10 to 15 cm (4 to 6 in). In rooms where the 

air must travel more than 15 m (50 ft), air is 

distributed through ceiling ducts or a plenum and 

returns to evaporators through a long opening 

in a plenum wall. Another system distributes air 

into the pallet lanes, and the air returns across 

the ceiling. Pallet bin storage can use the same 

systems, or air can be distributed through forklift 

openings or with a serpentine airflow system, as is 

used in some forced-air coolers.
16

Refrigeration Load

Determining the refrigeration capacity needed 

for a facility is based on estimating heat input to 

the cold storage from the following: uncooled 

product; product respiration; heat conduction 

through walls, floors, and roof; air infiltration 

through doors; lights; motors; equipment; and 

personnel. However these estimates cannot be 

done exactly. Over the life of a facility, it may 

be used for different products, the amount of 

product may change, and equipment performance 

deteriorates over time. Coldroom designers make 

estimates based on methods presented in Stoecker 

(1998) or ASHRAE (1999) and then add perhaps 

20 to 30% extra capacity as a cushion. As a rule 

of thumb, refrigerated produce storage requires 10 

to 14 kW of refrigeration capacity per 1,000 m3

 of 

storage volume and refrigerated shipping docks 

require 14 to 25 kW per 1,000 m3

 (Stoecker 1998).

Refrigeration Equipment

Most cold storage uses vapor recompression, also 

called mechanical refrigeration. A few facilities 

use absorption refrigeration, though this is only 

cost effective if there is an inexpensive source 

of low-temperature heat available. Detailed 

discussions of equipment selection and design are 

given in Stoecker (1998) and ASHRAE (1999).

The key design constraints for produce storage is 

uniformly maintaining desired temperature and 

relative humidity (RH). Uniform temperature is 

maintained by adequate refrigeration capacity, 

uniform air distribution, minimal temperature 

difference between the evaporator coil and the air 

temperature, and a precise temperature control 

system. High RH is needed to reduce product 

moisture loss. Most fresh produce requires 85 

to 95% RH, while dried commodities, such as 

onion and ginger, need a low RH. High RH is 

obtained by minimizing temperature variation in 

the room and by operating the evaporator coil at 

a temperature close to the setpoint temperature 

of the room. This is done by installing a coil 

with a high surface area and by using a control 

system that maintains the refrigerant at its highest 

possible temperature.

Humidifiers may be needed to add moisture to 

paper or wood packaging materials; otherwise, 

packaging will absorb water from the product. 

Alternatively, the product can be packed in plastic 

packages that do not absorb water or in plastic 

bags that slow moisture loss. Plastic materials 

with minimum amounts of venting retard moisture 

loss from the produce (Crisosto et al. 1994) 

and may allow the cold storage to be held at a 

lower humidity. Products with low transpiration 

coefficients lose water slowly (Sastry and Baird 

1978) and may not need special provision for high 

RH storage, especially if they are not stored for a 

long time.

Alternative Refrigeration Options

In areas with limited capital for investment in 

refrigeration, there are other options besides 

using mechanical refrigeration for temperature 

control, though none of them provide the optimum 

conditions that refrigeration does (Thompson 

1999). Evaporative cooling drops air temperature 

to within a few degrees of the wet bulb 

temperature of the outside air and is sometimes 

used in dry climates. In these same climates, the 

nighttime air temperature tends to be lower and 

product can be ventilated with cool night air. 

Soil temperature at 2 m (6 ft) below the surface 

is equal to the average annual air temperature. 

Storage facilities can be built underground to 

take advantage of these lower temperatures. Well 

water is also usually equal to average annual air 

temperature and can sometimes be used to cool 

products. Using ice formed in winter and storing 

products at high altitudes are also occasionally 

used to provide cool storage temperatures. 

Unfortunately, few of the above options work well 

in humid, tropical climates.

Ethylene Control

Certain types of produce are sensitive to damage 

from ethylene; thus it is necessary to minimize 

ethylene level in their storage environment. Unless 

outside temperatures are very low or very high, 

ventilation is an inexpensive method of reducing 

ethylene levels. Ethylene can also be absorbed on 

commercially available potassium permanganate 
17

pellets. A few products, especially floral and 

ornamental crops, can be chemically treated to 

make them insensitive to ethylene damage.

Controlled Atmosphere Facilities

Storage rooms can be built for controlled 

atmosphere (CA) storage for about 5% additional 

cost if they are properly designed initially. The 

extra cost is for sealing joints between walls, 

ceilings, and floors and for installing gas-tight 

doors. Tilt-up concrete, metal panels, urethane 

foam, and plywood have all been successfully 

used as gas barriers. These storage rooms also 

need equipment for monitoring and controlling 

gas levels (Waelti and Bartsch 1990).

References

ASHRAE [American Society of Heating, 

Refrigerating, and Air-Conditioning Engineers]. 

1999. ASHRAE Handbook Series (4 books). 

ASHRAE, Atlanta, GA.

Baird, C.D., J.J. Gaffney, and M.T. Talbot. 

1988. Design criteria for efficient and costeffective forced-air cooling systems for fruits and 

vegetables. ASHRAE Trans. 94:1434-1454.

Barger, W.R. 1963. Vacuum cooling: a comparison 

of cooling different vegetables. Marketing 

Research Report 600, U.S. Department of 

Agriculture, Washington, DC.

Bennett, A.H. 1963. Thermal characteristics of 

peaches as related to hydro-cooling. Technical 

Bull. 1292, U.S. Department of Agriculture, 

Washington, DC.

Cheyney, C.C., R.F. Kasmire, and L.L. Morris. 

1979. Vacuum cooling of wrapped lettuce. Calif. 

Agric. 33:18-19.

Crisosto, C.H., J.L Smilanick, N.K. Dokoozlian, 

and D.A. Luvisi. 1994. Maintaining Table Grape 

Postharvest Quality for Long Distance Markets, 

International Symposium on Table Grape 

Production, American Society for Enology and 

Viticulture, Anaheim, CA.

d’Sousa, M.C., and M. Ingle. 1989. Effect of 

delayed cooling on the poststorage flesh firmness 

of apples. J. Food Sci. 54:493-494.

Eckert, J.L., and I.L. Eaks. 1989. Postharvest 

disorders and diseases of citrus fruits. In W. 

Ruther, ed, The Citrus Industry, Vol. 5, pp. 

179-260, Department of Agriculture and 

Natural Resources, Pub. no. 3326, University of 

California, Davis, CA.

Flockens, I.H., and H.F.T. Meffert. 1972. 

Biophysical properties of horticultural products as 

related to loss of moisture during cooling down. J. 

Sci. Food Agric. 23:285-298.

Gan, G., and J.L. Woods. 1989. A deep bed 

simulation of vegetable cooling. In V.A. Dodd and 

P.M. Grace, eds, Land and Water Use, pp. 2301-

2308. Balkema, Rotterdam, The Netherlands.

Harvey, J.M., and C.M. Harris. 1986. In-storage 

softening of kiwifruit: effects of delayed cooling. 

Int. J. Refrig. 9:352-355.

Harvey, J.M. 1963. Improved techniques for 

vacuum cooling vegetables. ASHRAE J. 5:41-44.

Heap, R. 1998. Transport of foodstuffs by sea. 

In R. Heap, M. Kierstan, and G. Ford, eds., Food 

Transportation, pp. 75-96. Blackie Academic and 

Professional, London, UK.

Kroca, R.W., and M.L. Hellickson. 1993. Energy 

savings in evaporator fan-cycled apple storages. 

Appl. Eng. Agric. 9:553-560.

Maxie, E.C., F.G. Mitchell, and A. Greathead. 

1959. Studies on strawberry quality. Calif. Agric., 

Feb. 1:16.

Mitchell, F.G., R.A. Parsons, and G. Mayer. 1971. 

Cooling trials with plastic tray pack nectarines in 

various containers. Calif. Agric. 25(9):13-15.

Parsons, R.A., F.G. Mitchell, and G. Mayer. 1970. 

Forced-air cooling of palletized fresh fruit. Paper 

70-875, ASAE, St. Joseph, MI.
18

Parsons, R.A. 1972. Forced-air cooling of fruit in 

bulk bins. SP-01-72:38-41, American Society of 

Agricultural Engineers, St. Joseph, MI.

Perry, R., and R. Perkins. 1968. Hydro-cooling 

sweet corn. Paper 68-800, American Society of 

Agricultural Engineers, St. Joseph, MI.

Pentzer, W.T., R.L. Perry, G.C. Hanna, et al. 1936. 

Precooling and Shipping California Asparagus. 

University of California Agricultural Experiment 

Station Bulletin 600, Univ. of California, Davis, 

CA.

Rij, R. E., J.F. Thompson, and D. S. Farnham. 

1979. Handling, precooling, and temperature 

management of cut flower crops for truck 

transportation. USDA-SEA Adv. Agric. Technol. 

AAT-W-5. June.

Robbins, J., and P.P. Moore. 1992. Fruit quality 

of stored fresh red raspberries after a delay in 

cooling. HortTechnology 2(4):468-470.

Sargent, S.A., M.T. Talbot, and J.K. Brecht. 1988. 

Evaluating precooling methods for vegetable 

packinghouse operations. Proceedings of the 

Florida State Horticulture Society 101:175-182.

Sastry, S.K., and C.D. Baird. 1978. Transpiration 

rates of certain fruits and vegetables. ASHRAE 

Trans. 84(2):237-255.

Stewart, K.S., and H.M. Couey. 1963. Hydrocooling vegetables—a practical guide to 

predicting final temperatures and cooling 

times. Mkt. Res. Rpt. 637, U.S. Department of 

Agriculture, Agricultural Marketing Service, 

Washington, DC.

Stewart, J.K., and W.J. Lipton. 1960. Factors 

influencing heat loss in cantaloupes during hydrocooling. Marketing Research Report 421, U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

Stoecker, W.F. 1998. Industrial Refrigeration 

Handbook. McGraw-Hill, New York, NY.

Thompson, J.F. 1999. Cold-storage systems. In

F.W. Bakker-Arkema, ed., CIGR Handbook of 

Agricultural Engineering, vol. IV, pp. 339-361. 

ASAE, St. Joseph, MI.

Thompson, J.F., F.G. Mitchell, and R.F. Kasmire. 

2002. Cooling horticultural commodities. In

A.A.Kader, ed., Postharvest Technology of 

Horticultural Crops, pp. 97-112. DANR Pub. no. 

3311, University of California, Davis, CA.

Thompson, J.F., F.G. Mitchell., T.R. Rumsey, et al. 

1998. Commercial cooling of fruits, vegetables, 

and flowers. DANR Pub. no. 21567, University of 

California, Davis, CA.

Toussaint, W.D., T.T. Hatlow, and G. Abshier. 

1955. Hydro-cooling peaches in the North 

Carolina sandhills. Env. Infor. Ser. no. 320, North 

Carolina Agricultural Experiment Station, North 

Carolina State University, Raleigh, NC.

Wang, J.K., and K. Tunpun. 1968. Forced-air 

cooling of tomatoes in cartons. Trans. Am. Soc. 

Agric. Eng. 12:804-806.

Waelti, H., and J.A. Bartsch. 1990. CA storage 

facilities. In M. Calderon and R. Barkai-Golan, 

eds., Food Preservation by Modified Atmospheres, 

pp. 373-389. CRC Press, Boca Raton, FL.
19

Heat Load Calculation

Some factors need to be considered in determining refrigeration required for a cold-storage plant. 

Examples are simplified to illustrate steps necessary to calculate heat load of a refrigerated storage 

area during cooling and normal storage operation. More information on load calculations can be found 

in Patchen (1971), Ryall and Lipton (1979), ASHRAE (1981), and Bartsch and Blanpied (1984). The 

information presented here is adapted from pages 14 to 16 of the previous USDA Agriculture Handbook 

Number 66 (Hardenberg et al. 1986). Examples are shown in metric units for pears in storage at -1.1 

oC (30 oF). To convert respiration rate of fruits and vegetables expressed in mg CO2

 kg-1 h-1 to heat 

production in kJ, multiply mg CO2

 kg-1 h-1 by 61 to get kcal tonne-1 day-1 (1 kcal = 4,186 kJ).

Conditions Example ________________________________ _________________________________________

Storage size 15×15×4.5 m

Outside surface area (including floor) 720 m2

Inside dimensions 14.7×14.7×4.2 m

Volume 908 m3

Insulation 7.6 cm of polyurethane with a conductivity value 

(k) = 1.3 kJ per m2 per cm thickness per oC;

coefficient of transmission (U) = 1.1 kJ h-1 m-2 oC-1

Ambient conditions at harvest 30 oC and 50% RH

Fruit temperature at harvest, 21 oC; in storage, -1.1 oC

Storage capacity 600 bins at 500 kg fruit per bin = 300,000 kg of fruit

Bin weight 63.5 kg; total weight of bins = 38,100 kg

Loading weight and time 200 bins (100,000 kg fruit per day); 3 days to fill

Cooling rate 1st day, 21 to 4.5 oC; 2nd day, 4.5 to -1.1 oC

Air changes from door openings:

 during cooling 6 per day

 during storage 1.8 per day

Specific heat pears, 0.86; wood bins, 0.5

Heat load to lower air:

 from 30 to -1.1 oC (50% RH) 74.5 kJ m-3

 from 7.2 to -1.1 oC (70% RH) 15.3 kJ m-3

Miscellaneous heat loads lights, 2,400 W per h (3.6 kJ W-1)

fans at 3,112 kJ per HP

electric forklifts, 36,920 kJ each for 8 h

workers, 1,000 kJ per h per person
20

A. Load during cooling and filling storage: temperature difference (TD) from 30 oC to -1.1 oC = 31.1 

oC, assuming 31.1 oC TD on all surfaces:

 kJ per 24 h

1. Building-transmission load: area (720 m2

) × U (1.1 kJ) × TD (31.1 oC) × h (24) = 591,149

2. Air-change load from doors: vol (908 m3) × heat load (74.5 kJ) × air changes (6) = 405,876

3. Product cooling (field heat removal):

First day

Fruit (100,000 kg) × specific heat (0.86) × TD (21 to 4.5 oC) × 

 kJ factor (4.186) = 5,939,934

Bin weight (12,700 kg) × specific heat (0.5) × TD (21 to 4.5 oC) ×

 kJ factor (4.186) = 438,588

Second day

Fruit weight (100,000 kg) × specific heat (0.86) × TD (4.5 to -1.1 oC) ×

 kJ factor (4.186) = 2,015,977

Bin weight (12,700 kg) × specific heat (0.5) × TD (4.5 to -1.1 oC) ×

 kJ factor (4.186) = 148,854

4. Heat of respiration during cooling (vital heat):

First day

 Average temperature of 13 oC; respiration rate of 12,206 kJ per tonne

 per 24 h; tons of fruit (100) × rate (12,206) = 1,220,600

Second day

 Average temperature of 1.7 oC; respiration rate of 1,741 kJ per tonne

 per 24 h; tonnes of fruit (100) × rate (1,741) = 174,100

Maximum heat accumulated in storage before cooling completed: total fruit 

weight of 300,000 kg - 2 day loading weight of 200,000 kg = 100,000 kg 

(100 tonnes); respiration rate at -1.1 oC is 812 kJ per tonne per 24 h; tonnes 

of fruit (100) × respiration rate (812) = 81,200

5. Miscellaneous heat loads:

Lights: W (2,400) × kJ per W (3.6) × h (8) = 69,120

Fans: HP (3) × kJ per HP (3,112) × h (24) = 224,064

Forklifts: 2 × 36,920 kJ per forklift for 8 h = 73,840

Labor: workers (2) × kJ per h (1,000) × h (8) = 16,000

Total heat load during cooling:

Building transmission 519,149

Air change 405,876

Product cooling 8,543,353

Production respiration 1,475,900

Miscellaneous 383,024

Subtotal 11,399,302

Add 10% to be cautious 1,139,930

Total required refrigeration 12,539,232
21

Assuming refrigeration equipment operates 18 h per day: 12,539,232 ÷ 18 h = 696,624 kJ h-1. Since a 

tonne of refrigeration absorbs 12,660 kJ per 24 h: 696,624 ÷ 12,660 = 55 tonnes of peak refrigeration 

capacity is required.

B. Load during normal storage operation (average outside ambient conditions, 7.2 oC at 70% RH; 

storage temperature, -1.1 oC; TD = 7.2 o to -1.1 oC = 8.3 oC).

 kJ per 24 h

1. Building-transmission load: area (720 m2

) × U (1.1 kJ) × TD (8.3 oC) × h (24) = 157,766

2. Air-change load from doors: vol (908 m3) × heat load (15.3 kJ) × air changes (1.8) = 25,006

Product load (respiration, no cooling):

3. Respiration rate at -1.1 oC is 812 kJ per tonne per 24 h; tonne fruit (300) × rate (812) = 243,600

4. Miscellaneous head loads:

Lights: W (2,400) × kJ per W (3.6) × h (4) = 34,560

Fans: HP (3) × kJ per HP (3,112) × h (24) = 224,064

Labor: people (1) × kJ per h (1,000) × h (4) = 4,000

Total load during storage:

Building transmission 157,766

Air change 25,006

Product load (respiration) 243,600

Miscellaneous 262,624

Subtotal 688,996

Add 10% to be cautious 68,899

Total required refrigeration 757,895

Assuming refrigeration equipment operates 18 hours per day: 757,895 ÷ 18 h = 42,105 kJ h-1 and 

42,105 ÷ 12,660 = 3.3 tonnes of refrigeration capacity is needed during normal storage.

References

ASHRAE [American Society of Heating, 

Refrigerating and Air Conditioning Engineers]. 

1981. American Society of Heating, Refrigeration 

and Air Conditioning Engineers Handbook 1982 

Applications. ASHRAE, Atlanta, GA.

Bartsch, J.A., and G.D. Blanpied. 1984. 

Refrigeration and controlled atmosphere storage 

for horticultural crops. NRAES no. 22, Northeast 

Region Agricultural Engineer Service, Cornell 

University, Ithaca, NY.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks, pp. 

14-16. Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Patchen, G.O. 1971. Storage for apples and pears. 

Marketing Research Report 924, U.S. Department 

of Agriculture, Washington, DC.

Ryall, A.L., and W.J. Lipton. 1979. Vegetables and 

melons. In Handling, Transportation and Storage 

of Fruits and Vegetables, 2nd ed., vol. 1. AVI Pub. 

Co., Westport, CT.
22

Controlled Atmosphere Storage

Adel A. Kader

Kader was with the Department of Plant Sciences, 

University of California, Davis, CA. He is 

deceased.

Introduction

Controlled atmosphere (CA) storage involves 

maintaining an atmospheric composition that is 

different from air composition (about 78% N2

, 

21% O2

, and 0.03% CO2); generally, O2 below 

8% and CO2

 above 1% are used. Atmosphere 

modification should be considered as a supplement 

to maintenance of optimum ranges of temperature 

and RH for each commodity in preserving quality 

and safety of fresh fruits, ornamentals, vegetables, 

and their products throughout postharvest 

handling. This chapter gives an overview of 

responses to CA; specific CA considerations are 

given in individual commodity summaries.

Biological Basis of CA Effects

Exposure of fresh horticultural crops to low O2

and/or elevated CO2

 atmospheres within the 

range tolerated by each commodity reduces 

their respiration and ethylene production rates; 

however, outside this range respiration and 

ethylene production rates can be stimulated, 

indicating a stress response. This stress can 

contribute to incidence of physiological disorders 

and increased susceptibility to decay. Elevated 

CO2

-induced stresses are additive to and 

sometimes synergistic with stresses caused by low 

O2

, physical or chemical injuries, and exposure 

to temperatures, RH, and/or C2

H4 concentrations 

outside the optimum range for the commodity.

The shift from aerobic to anaerobic respiration 

depends on fruit maturity and ripeness stage 

(gas diffusion characteristics), temperature, 

and duration of exposure to stress-inducing 

concentrations of O2

 and/or CO2. Up to a point, 

fruits and vegetables are able to recover from 

the detrimental effects of low O2

 and high CO2

stresses (fermentative metabolism) and resume 

normal respiratory metabolism upon transfer to 

air. Plant tissues have the capacity for recovery 

from the stresses caused by brief exposure 

to fungistatic atmospheres (>10% CO2

) or 

insecticidal atmospheres (<1% O2

 and/or 40 to 

80% CO2

). Postclimacteric fruits are less tolerant 

and have lower capacity for recovery following 

exposure to reduced O2

 or elevated CO2 levels 

than preclimacteric fruits. The speed and extent of 

recovery depend on duration and levels of stresses 

and underlying, metabolically driven cellular 

repair.

Elevated-CO2

 atmospheres inhibit activity of 

ACC synthase (key regulatory site of ethylene 

biosynthesis), while ACC oxidase activity is 

stimulated at low CO2

 and inhibited at high CO2

concentrations and/or low O2

 levels. Ethylene 

action is inhibited by elevated CO2

 atmospheres. 

Optimum atmospheric compositions retard 

chlorophyll loss (green color), biosynthesis 

of carotenoids (yellow and orange colors) 

and anthocyanins (red and blue colors), and 

biosynthesis and oxidation of phenolic compounds 

(brown color). Controlled atmospheres slow 

down the activity of cell wall degrading enzymes 

involved in softening and enzymes involved in 

lignification, leading to toughening of vegetables. 

Low O2

 and/or high CO2 atmospheres influence 

flavor by reducing loss of acidity, starch to 

sugar conversion, sugar interconversions, and 

biosynthesis of flavor volatiles. When produce 

is kept in an optimum atmosphere, ascorbic acid 

and other vitamins are retained, resulting in better 

nutritional quality.

Severe stress CA conditions decrease 

cytoplasmic pH and ATP levels and reduce 

pyruvate dehydrogenase activity, while pyruvate 

decarboxylase, alcohol dehydrogenase, and lactate 

dehydrogenase are induced or activated. This 

causes accumulation of acetaldehyde, ethanol, 

ethyl acetate, and/or lactate, which may be 

detrimental to the commodities if they are exposed 

to stress CA conditions beyond their tolerance. 

Specific responses to CA depend on cultivar, 
23

maturity and ripeness stage, storage temperature 

and duration, and in some cases ethylene 

concentrations.

N2

 is an inert component of CA. Replacing N2

with argon or helium may increase diffusivity of 

O2

, CO2, and C2H4, but they have no direct effect 

on plant tissues and are more expensive than N2

 as 

a CA component. 

Super-atmospheric levels of O2 up to about 80% 

may accelerate ethylene-induced degreening 

of nonclimacteric commodities and ripening 

of climacteric fruits, respiration and ethylene 

production rates, and incidence of some 

physiological disorders (such as scald on apples and 

russet spotting on lettuce). At levels above 80% O2

, 

some commodities and postharvest pathogens suffer 

from O2

 toxicity. Use of super-atmospheric O2 levels 

in CA will likely be limited to situations in which they 

reduce the negative effects of fungistatic, elevated CO2

atmospheres on commodities that are sensitive to CO2

-

induced injury.

Beneficial Effects of CA (Optimum 

Composition for the Commodity)—A 

Summary

• Retardation of senescence (including 

ripening) and associated biochemical 

and physiological changes, particularly 

slowing down rates of respiration, ethylene 

production, softening, and compositional 

changes.

• Reduction of sensitivity to ethylene action at 

O2 levels <8% and/or CO2 levels >1%.

• Alleviation of certain physiological disorders 

such as chilling injury of avocado and some 

storage disorders, including scald of apples.

• CA can have a direct or indirect effect on 

postharvest pathogens (bacteria and fungi) 

and consequently decay incidence and 

severity. For example, CO2

 at 10 to 15% 

significantly inhibits development of botrytis 

rot on strawberries, cherries, and other 

perishables.

• Low O2 (<1%) and/or elevated CO2 (40 to 

60%) can be a useful tool for insect control 

in some fresh and dried fruits, flowers, and 

vegetables and in dried nuts and grains.

Detrimental Effects of CA (Above or 

Below Optimum Composition for the 

Commodity)—A Summary

• Initiation and/or aggravation of certain 

physiological disorders such as internal 

browning in apples and pears, brown stain 

of lettuce, and chilling injury of some 

commodities.

• Irregular ripening of fruits, such as banana, 

mango, pear, and tomato, can result from 

exposure to O2

 levels below 2% and/or CO2

levels above 5% for >1 mo.

• Development of off flavors and off odors 

at very low O2 concentrations (as a result 

of anaerobic respiration) and very high 

CO2

 levels (as a result of fermentative 

metabolism).

• Increased susceptibility to decay when the 

fruit is physiologically injured by too low O2

or too high CO2

 concentrations.

Commercial Application of CA Storage

Several refinements in CA storage have been made 

in recent years to improve quality maintenance. 

These include creating nitrogen by separation 

from compressed air using molecular sieve beds 

or membrane systems, low-O2

 (1.0 to 1.5%) 

storage, low-ethylene (<1 μL L-1) CA storage, 

rapid-CA (rapid establishment of optimal levels 

of O2

 and CO2), and programmed- (or sequential-) 

CA storage—for example, storage in 1% O2

for 2 to 6 weeks followed by storage in 2 to 

3% O2

 for the remainder of the storage period. 

Other developments, which may expand use of 

atmospheric modification during transport and 

distribution, include improved technologies for 

establishing, monitoring, and maintaining CA 

using edible coatings or polymeric films with 

appropriate gas permeability to create a desired 
24

atmospheric composition around and within the 

commodity. Modified atmosphere packaging 

(MAP) is widely used in marketing fresh-cut 

produce.

Applications of CA to cut flowers are very limited 

because decay caused by Botrytis cinerea is often 

a limiting factor to postharvest life, and fungistatic 

CO2

 levels damage flower petals and/or associated 

stem and leaves. Also, it is less expensive to treat 

flowers with anti-ethylene chemicals than to use 

CA to minimize ethylene action.

Commercial use of CA storage is greatest on 

apples and pears worldwide, less on cabbages, 

Table 1. Classification of horticultural crops according to their CA storage potential at 

optimum temperatures and RH.

________________________________________________________________________________________

Storage duration Commodities _________________________________________________________________________________

Months

>12 Almond, Brazil nut, cashew, filbert, macadamia, pecan, pistachio, walnut, 

 dried fruits and vegetables

6 to 12 Some cultivars of apples and European pears

3 to 6 Cabbage, Chinese cabbage, kiwifruit, persimmon, pomegranate, some 

 cultivars of Asian pears

1 to 3 Avocado, banana, cherry, grape (no SO2), mango, olive, onion (sweet 

 cultivars), some cultivars of nectarine, peach and plum, tomato (mature-green)

<1 Asparagus, broccoli, cane berries, fig, lettuce, muskmelons, papaya, 

 pineapple, strawberry, sweet corn, fresh-cut fruits and vegetables, some cut 

flowers

_________________________________________________________________________________________

sweet onions, kiwifruits, avocados, persimmons, 

pomegranates, and nuts and dried fruits and 

vegetables (table 1). Atmospheric modification 

during long-distance transport is used with 

apples, asparagus, avocados, bananas, broccoli, 

cane berries, cherries, figs, kiwifruits, mangos, 

melons, nectarines, peaches, pears, plums, 

and strawberries. Continued technological 

developments in the future to provide CA 

during transport and storage at a reasonable cost 

(positive benefit/cost ratio) are essential to greater 

applications on fresh horticultural commodities 

and their products.
25

Additional Reading and Reference Material

Calderon, M., and R. Barkai-Golan, eds. 1990. 

Food Preservation by Modified Atmospheres. 

CRC Press, Boca Raton, FL.

El-Goorani, M.A., and N.F. Sommer. 1981. 

Effects of modified atmospheres on postharvest 

pathogens of fruits and vegetables. Hort. Rev. 

3:412-461.

Gorny, J., ed. 1997. Fresh-Cut Fruits and 

Vegetables and MAP, CA’97 Proceedings, vol. 

5. Postharvest Hort. Ser. no. 19, University of 

California, Davis, CA.

Kader, A.A. 1986. Biochemical and physiological 

basis for effects of controlled and modified 

atmospheres on fruits and vegetables. Food 

Technol. 405:99-100, 102-104.

Kader, A.A., ed. 1997. Fruits Other Than Apples 

and Pears, CA’97 Proceedings, vol. 3. Postharvest 

Hort. Ser. no. 17, University of California, Davis 

CA.

Kader, A.A., D. Zagory, and E.L. Kerbel. 1989. 

Modified atmosphere packaging of fruits and 

vegetables. CRC Crit. Rev. Food Sci. Nutr. 28:1-

30.

Mitcham, E.J., ed. 1997. Apples and Pears, CA’97 

Proceedings, vol. 2. Postharvest Hort. Ser. no. 16, 

University of California, Davis, CA.

Raghavan, G.S.V., P. Alvo, Y. Gairepy, and C. 

Vigneault. 1996. Refrigerated and controlled 

modified atmosphere storage. In L.P. Somogyi 

et al., eds, Processing Fruits: Science and 

Technology, vol. 1, Biology, Principles and 

Applications, pp. 135-167. Technomic Pub. Co., 

Lancaster, PA.

Saltveit, M.E., ed. 1997. Vegetables and 

Ornamentals, CA’97 Proceedings, vol. 4. 

Postharvest Hort. Ser. no. 18, University of 

California, Davis, CA.

Thompson, A.K. 1998. Controlled Atmosphere 

Storage of Fruits and Vegetables. CAB 

International, Wallingford, U.K.

Thompson, J.F., and E.J. Mitcham, eds. 1997. 

Technology and Disinfestation Studies, CA’97 

Proceedings, vol. 1. Postharvest Hort. Ser. no. 15, 

University of California, Davis, CA.

Vigneault, C., V.G.S. Raghavan, and R. Prange. 

1994. Techniques for controlled atmosphere 

storage of fruit and vegetables. Tech. Bull 1993-

18E, Agriculture Canada, Kentville, N.S.

Wang, C.Y. 1990. Physiological and biochemical 

effects of controlled atmosphere on fruits and 

vegetables. In M. Calderon and R. Barkai-Golan, 

eds, Food Preservation by Modified Atmospheres, 

pp. 197-223. CRC Press, Boca Raton, FL.

Weichmann, J. 1986. The effect of controlled 

atmosphere storage on the sensory and nutritional 

quality of fruits and vegetables. Hort. Rev. 8:101-

127.

Yahia, E.M. 1998. Modified and controlled 

atmosphere for tropical fruits. Hort. Rev. 22:123-

183.

Zagory, D., and A.A. Kader. 1989. Quality 

maintenance in fresh fruits and vegetables by 

controlled atmospheres. In J.J. Jen, ed., Quality 

Factors of Fruits and Vegetables: Chemistry and 

Technology, pp. 174-188. American Chemical 

Society, Washington, DC
26

Temperature Preconditioning

Susan Lurie and Joshua D. Klein

Lurie is with the Department of Postharvest 

Science, Volcani Center, Bet-Dagan, Israel; and 

Klein is with the Department of Field Crops, 

Volcani Center, Bet-Dagan, Israel.

Introduction

Temperature preconditioning of fruits and 

vegetables has been practiced for more than 70 

years, since Baker (1939, 1952) described heat 

treatments for disinfestation of fruit flies in citrus. 

There is renewed interest in high temperature as 

a postharvest treatment for control of both insect 

pests and fungal pathogens in fresh produce. In 

part, this is because of the deregistration of a 

number of compounds that, until recently, have 

been used for effective control of postharvest 

disorders. In addition, there is increased consumer 

demand for produce that has had minimal, or 

ideally no, chemical treatment. 

Heat has fungicidal as well as insecticidal action, 

but heat regimes that are optimal for insect control 

may not be optimal for disease control; in some 

cases they may even be detrimental. A thermal 

treatment that is developed for fungus or insect 

control should not damage the commodity being 

treated. In fact, in many cases high temperature 

manipulation before storage may have beneficial 

effects on the commodity treated. These benefits 

include slowing the ripening of climacteric fruit 

and vegetables, enhancing sweetness of produce 

by increasing the amount of sugars or decreasing 

acidity, and prevention of storage disorders such 

as superficial scald on apples and chilling injury 

on subtropical fruits and vegetables (Lurie 1998).

Temperature conditioning before storage may also 

mean an incubation period spent at either ambient 

temperature of 16 to 25 °C (61 to 77 °F) or at a 

temperature below ambient but above that which 

might produce chilling injury: 5 to 12 °C (41 to 

54 °F), depending on the commodity. This type 

of temperature manipulation is often referred to 

as a “curing” period and is used with crops such 

as potatoes, onions, and carrots. Its purpose is 

generally to increase resistance of the commodity 

to pathogen invasion, though it may also increase 

resistance to low-temperature injury in citrus.

In this chapter we discuss temperature 

preconditioning treatments according to their 

purpose; that is, pathogen, insect, or chilling 

injury control. Most of the methods listed here, 

however, are still experimental and have yet to be 

accepted for routine commercial practice.

Commercial Treatments

The greatest number of temperature manipulations 

used commercially are based on high-temperature 

treatments (vapor heat or hot forced-air) for insect 

disinfestation. Temperature regimes are developed 

specifically for each commodity and insect pest. 

The accepted procedures for produce entering 

the United States are described in the Plant 

Protection and Quarantine Treatment Manual 

from USDA, Animal and Plant Health Inspection 

Service (APHIS). The manual is routinely updated 

(APHIS 1998). The latest edition of the manual 

should be consulted for approved treatments for 

particular commodities or pests.

An example of commercial temperature 

conditioning for pest control is Mexican-grown 

mangos, which may be infested with a variety 

of fruit fly larvae or eggs. Officially authorized 

treatments are high-temperature, forced-air 

treatment (HAT) or a hot water dip treatment 

(HWT) before storage and shipment. In HAT, fruit 

are heated until their centers reaches 48 °C (118 

°F). HWT conditions depend on fruit size and can 

vary from 45 to 90 min in water, where the fruit 

interior reaches 46 °C (115 °F).

Vapor-heat (VHT) differs from high-temperature, 

forced-air in that moisture accumulates on the 

surface of the fruit. The water droplets transfer 

heat more efficiently than air, allowing the fruit 

to heat quickly; but there may also be increased 
27

physical injury to the fruit. Papayas grown in 

Hawaii are vapor-heat-treated before being 

exported to Japan.

Citrus can be disinfested by HAT at 44 °C (111 

°F) for 100 min, with an additional 90 min 

spent raising the temperature to 44°C. The usual 

disinfestation method, however, is to hold the fruit 

at low temperature of 0 to 2 °C (32 to 36 °F) for 

10 to 16 days before raising the temperature to the 

normal storage temperature of 6 to 11°C (43 to 52 

°F), depending on cultivar. Since citrus is sensitive 

to chilling, fruit are generally held at 20 °C (68 °F) 

or 16 °C (61 °F) for 3 to 5 days before placing at 

low temperature. This curing treatment decreases 

fruit susceptibility to chilling injury resulting from 

the subsequent disinfestation treatment.

Insect Disinfestation

The development and implementation of heat 

treatments for insect disinfestation have been 

reviewed thoroughly (Couey 1989, Paull 1993). 

Table 1 includes treatment regimes that have 

been reported in the past 20 years. More than half 

the treatments are designed to kill fruit fly eggs 

or larvae, because their presence requires strict 

quarantine in most fruit-importing countries. The 

most recently developed methods include heat 

treatments in combination with low-O2

 or highCO2

 atmospheres.

Antifungal Treatments

Curing is used commercially to increase resistance 

to pathogen invasion. Potatoes are cured at 12 °C 

(54 °F) for 10 to 12 days before storage at 4 to 9 

°C (39 to 48 °F), depending on cultivar and on 

whether they are designated for industry or home 

consumption. Sweet potatoes are also cured at 30 

°C (86 °F) for 5 days before storage at 12 °C (54 

°F). In both cases the curing period allows for 

wound healing and deposition of cell wall material 

to create a physical barrier to pathogens. Kiwifruit 

also benefit from a curing period. If held at 10 °C 

(50 °F) before storage at low temperatures, they 

develop fewer rots after storage. Onions can be 

stored longer if held at 28 °C (82 °F) for 3 days 

before storage.

The two commercial applications of hightemperature antifungal treatments are HWT for 

papayas (Akamine and Arisumi 1953), which has 

been used for almost 50 years, and a hot-water 

brush treatment (HWB) (Fallik 1996a, 1999, 

Prusky et al. 1997). The brush system is in use 

on packing lines for export of corn, mangos, 

peppers, and some citrus from Israel. The machine 

sprays hot water at 50 to 65 °C (122 to 149 °F) on 

produce as it moves along on brush rollers. The 

major benefit appears to be removal of spores and 

dirt, though hot water combined with brushing 

also causes surface cracks to be filled in by the 

natural wax of the commodity, as well as eliciting 

resistance to pathogens in some cases. 

The state of temperature conditioning treatments 

against fungal pathogens was reviewed by BarkaiGolan and Phillips (1991) and Coates and Johnson 

(1993). The majority of the regimes listed in table 

2 were developed in the past 10 years. Dips in 

hot fungicide solution have been used since the 

1950s for pathogen control. As various fungicides 

lose their registration or as pathogens develop 

resistance, there is increased interest in heattreating produce in combination with compounds 

that are generally recognized as safe (GRAS), 

such as calcium chloride or sodium carbonate 

(table 2).

Physiological Benefits of Conditioning 

Treatments

Most thermal treatments have been developed 

as lethal regimes for insects or fungi. Some of 

these regimes, however, also have prophylactic 

effects against physiological disorders such as 

chilling injury (CI). Prevention of CI allows 

the commodity to be stored longer at lower 

temperatures, which in turn permits export in ships 

rather than more costly air freight. In addition, 

a preshipping heat treatment can allow for lowtemperature disinfestations of commodities, such 
28

as citrus, by improving the resistance of fruit to CI 

generally incurred during this treatment.

Other heat treatments have been developed 

specifically to maintain postharvest quality, such 

as increased firmness of apples or decreased 

yellowing of broccoli, or to protect against other 

abiotic stresses, such as irradiation disinfestation 

treatments (table 3). The physiological 

mechanisms of these treatments were previously 

reviewed by Lurie (1998). 
29

Table 1. Thermal treatment of horticultural commodities for insect disinfestation_____________________________________________________________________________________________________________________Insect Latin name Fruit Regime* Temperature/Time Reference_____________________________________________________________________________________________________________________Fruit fliesCaribbean fruit fly Anastrepha suspensa grapefruit HAT Sharp & Gould 1994

mango HAT 52 °C/125 min Miller et al. 1991orange HAT Sharp & McGuire 1996

Mediterranean fruit fly Ceratitis capitata avocado HAT 40 °C/24 h Jang 1996

mango VHT 47 °C/15 min Heather et al. 1997papaya HAT 47 °C at pulp for 3.5 h Armstrong et al. 1995

Melon fruit fly Dacus cucurbitae avocado HAT 40 °C/24 h Jang 1996

Bactrocera cucurbitae

cucumber HAT then HWT 32 °C/24 h then Chan & Linse 1989

 45-46 °C/50-60 min

papaya HAT 4C °C at pulp for 3.5 h Armstrong et al. 1995zucchini VHT Jacobi et al. 1996

Mexican fruit fly Anastrepha ludens grapefruit HAT & CA 44 °C/2 h in 1% O2 Shellie et al. 1997

Bactrocera cucumis

zucchini VHT 45 °C/30 min Jacobi et al. 1996

Oriental fruit fly Dacus dorsalis cucumber HAT then HWT 32 °C/24 h then Chan & Linse 1989

Bactrocera dorsalis 45-46 °C/50-60 min

papaya HAT 47 °C at pulp for 3.5 h Armstrong et al. 1995

Papaya fruit fly Bactrocera payapae mango VHT 47 °C/15 min Heather et al. 1997Queensland fruit fly Bactrocera tyroni avocado HWT & benomyl 46 °C/3 min then Jessup 1994

 1 °C/7 days

litchi VHT 45 °C/30 min Jacobi et al. 1993mango VHT 47 °C/10 min Heather et al. 1997

Jacobi et al. 1995

HWT then VHT 53 °C/15 min then Jacobi & Giles 1997

 47°C/15 min
30Table 1. Thermal treatment of horticultural commodities for insect disinfestation—Continued

_____________________________________________________________________________________________________________________Insect Latin name Fruit Regime* Temperature/Time Reference_____________________________________________________________________________________________________________________Other insectsCoddling moth Cydia pomonella apple HAT or VHT 44 °C/120 min then Neven et al. 1996

 0 °C/4 weeks

cherry HAT & CA 47 °C/44 min in 1% O2; Neven & Mitcham 1996

 15% CO2 Neven & Drake 2000

pear HAT or VHT 44 °C/120 min then Neven et al. 1996

 0°C/4 weeks

HAT & CA 30 °C/ 30 h in 0.3% O2 Chervin et al. 1997

Fuller’s rose beetle Asynonychus godmani lemon HWT 52 °C/8 min Soderstrom et al. 1993Leafroller Cnephasia jactatana apple HAT & CA 40 °C/10 h in 0.4% O2 Whiting et al. 1999

Ctenopseustis 45 °C/5 h in 0.4% O2

obliquana kiwifruit HAT & CA 40 °C/5-7 h in 0.4% O2 Whiting et al. 1997

40 °C/6 h in 2% O2; Hoy & Whiting 1998 5% CO2

Light brown apple moth Epiphyas postvittana apple HAT & CA 40 °C/17-20 h in Lay-Yee et al. 1997

 1.2% O2; 1% CO2 Dentener et al. 2000

HWT & ethanol 45 °C/13 min in Hoy & Whiting 1998

 50% ethanol

HAT & CA

kiwifruit

pear HAT & CA 30 °C/30 h in 0.3% O2 Chervin et al. 1997

Longtailed mealybug Pseudococcus longispinus persimmon HWT 48 °C/26 min or Lester et al. 1995

 50 °C/22 min

HAT Dentener et al. 1996, 

 1997
31

Table 1. Thermal treatment of horticultural commodities for insect disinfestation—Continued_____________________________________________________________________________________________________________________Insect Latin name Fruit Regime* Temperature/Time Reference_____________________________________________________________________________________________________________________New Zealand flower thrips Thrips obscuratus apricot HWT 48 °C/3 min then McLaren et al. 1997

nectarine 50 °C/2 min

peach

Obscure mealybug Pseudococcus affinis apple HAT & CA 40 °C/10 h in 0.4% O2 Whiting & Hoy 1997

45 °C/5 h in 0.4% O2

Oriental fruit moth Grapholita molesta pear HAT & CA 30 °C/30 h in 0.3% O2 Chervin et al. 1997Two spotted spider mite Tetranychus urticae apples HWT & ethanol 45 °C/13 min in 50% Dentener et al.

 ethanol 1998

kiwifruit HAT & CA 44 °C/211 min Lay-Yee & Whiting 

 1996

persimmon HWT 47 °C/67 min Lester et al. 1997

White peach scale Pseudaulacaspis pentagona papaya VHT 47 °C/4 h Follet & Gabbard 1999_____________________________________________________________________________________________________________________* HAT: high-temperature forced-air treatment VHT: vapor-heat treatment HWT: hot-water treatment CA: controlled atmosphere
32Table 2. Thermal treatment of horticultural commodities for eradication of and protection from fungal pathogens

_____________________________________________________________________________________________________________________Fungus Common name Crop Regime* Temperature/Time Reference_____________________________________________________________________________________________________________________Alternaria alternata Black spot carrot HWB 100 °C/3 sec Afek et al. 1999

mango HWB 60-70 °C/15-20 sec Prusky et al. 1999

Black mold pepper HWT 50 °C/3 min Fallik et al. 1996b

Botrytis cinerea Grey mold apple HAT & CaCl2 38 °C/4 days and CaCl2 dip Klein et al. 1997

pepper HWT 50 °C/3 min Fallik et al. 1996bstrawberry HWT 45 °C/15 min Garcia et al. 1996tomato HWT 50 °C/2 min Barkai-Golan et al. 1993

HAT 38 °C/2 days Fallik et al. 1993

Botryodiplodia Stem and surface rots papaya HAT 49 °C/20 min Nishijima et al. 1992 theobromae 32 °C/30 min then 

 49 °C/20 min

Chalara paradoxa Crown rot banana HWT 45 °C/20 min or Reyes et al. 1998

 50 °C/10 min

Colletotrichum Anthracnose mango VHT 46-48 °C/24 sec to 8 min Coates et al. 1993 gloeosporioides HWT McGuire 1991

HAT 51.5 °C/125 min Miller et al. 1991

Diplodia natalensis Stem end rot mango HAT 51.5 °C/125 min Miller et al. 1991

HWT McGuire 1991

Mycospharella spp. Stem and surface rots papaya HAT 49 °C/20 min Nishijima et al. 1992

42 °C/30 min then  49°C/20 min

Penicillium digitatum Green mold grapefruit HAT 46 °C/6 h Shellie 1998

HWB 59-62 °C/15 sec Porat et al. 2000
33

Table 2. Thermal treatment of horticultural commodities for eradication of and protection from fungal pathogens—Continued_____________________________________________________________________________________________________________________Fungus Common name Crop Regime* Temperature/Time Reference_____________________________________________________________________________________________________________________

lemon HAT 36 °C/3 days Kim et al. 1991

HWT & Na CO 2 3 45 °C/150 sec in Smilanick et al. 1997

 2% Na CO 2 3

orange HWT 53 °C/3 min Schirra et al. 1997

HWT & Na CO 2 3 41-43 °C/1-2 min in Smilanick et al. 1997

 6% Na CO 2 3

Penicillium expansum Blue mold apple HAT & CaCl2 38 °C/4 days in 4% CaCl2 Sams et al. 1993

HAT 38°C/4 days Fallik et al. 1996c

Penicillium italicum Blue mold cactus pear HAT or HWT 38 °C/24 h or 55 °C/5 min Schirra et al. 1996Penicillium spp. lemon HWT & imazalil 50 °C/3 min + imazalil Schirra et al. 1997Rhizopus stolonifer tomato HWT 50 °C/2 min Barkai-Golan et al. 1993_____________________________________________________________________________________________________________________* HWB: hot water brushing HWT: hot water treatment HAT: high-temperature forced-air treatment VHT: vapor heat treatment
34

Table 3. Physiological benefits of thermal treatments for horticultural crops

____________________________________________________________________________________

Chilling injury

____________________________________________________________________________________

Crop Phenomenon/ Regime* Temperature/Time Reference

Appearance

____________________________________________________________________________________

Apple scald HAT 38 °C/4 days or Lurie et al. 1990

 42 °C/2 days

Avocado skin browning HAT then 38 °C/3-10 h then Woolf et al. 1995

 internal browning, HWT 40 °C/30 min Florissen et al. 1996

 pitting 38 °C/60 min Woolf et al. 1997

 HWT

Cactus pear rind pitting, HAT or HWT 38 °C/24 h or Schirra et al. 1996

 brown staining 55 °C/5 min

Citrus rind pitting HAT 34-36 °C/48-72 h Ben -Yehoshua et al. 

 1987

Gonzalez-Aguilare et 

 al. 1998

HWT 50-54 °C/3 min Schirra & D’Hallewin 

 1997

53 °C/2-3 min Rodov et al. 1995

HWB 59-62 °C/15-30 sec Porat et al. 1999

Mango pitting HAT 38 °C/2 days McCollum et al. 1993

54 °C/20 min Jacobi et al. 1995

Persimmon gel formation HWT 47 °C/90-120 min; Lay-Yee et al. 1997

 50 °C/30-45 min; 

 52 °C/20-30 min

HAT Woolf et al. 1997

Green pepper pitting HAT 40 °C/20 h Mencarelli et al. 1993

Cucumber pitting HWT 42 °C/30 min McCullum et al. 1995

Tomato pitting HAT 38 °C/2-3 days Lurie & Klein 1991

HWT 48 °C/2 min Lurie et al. 1997

42 °C/60 min McDonald et al. 1998, 

 1999

Zucchini pitting HWT 42 °C/30 min Wang 1994

____________________________________________________________________________________
35

Table 3. Physiological benefits of thermal treatments for horticultural crops—Continued

____________________________________________________________________________________

Improved postharvest quality

____________________________________________________________________________________

Commodity Parameter/Attribute Regime* Temperature/Time Reference

____________________________________________________________________________________

Apple increased firmness HAT 38 °C/4 days; Klein & Lurie 1992

 42 °C/2 days

Asparagus inhibited curvature HWT 47 oC/2-5 min Paull & Chen 1999

Broccoli decreased yellowing HWT 50 °C/2 min Forney 1995

45 °C/10 min; Tian et al. 1996, 1997

 47 °C/7.5 min

Collard decreased yellowing HAT 45 °C/30 min Wang 1998

Green onions inhibited elongation HWT 55 °C/2 min Hong et al. 2000

Guava decreased softening HWT 46 °C/35 min McGuire 1997

 and yellowing

Kale decreased yellowing HAT 40 °C/60 min Wang 1998

Potato inhibited sprouting HWT Rangann et al. 1998

____________________________________________________________________________________

* HWT: hot water treatment

 HAT: high-temperature forced-air treatment
36

References

Afek, U., J. Orenstein, and E. Nuriel. 1999. Steam 

treatment to prevent carrot decay during storage. 

Crop Protection 18:639-642.

Akamine, E.K., and T. Arisumi. 1953. Control 

of postharvest storage decay of fruits of papaya 

(Carica papaya L.) with special reference to the 

effect of hot water. Proc. Amer. Soc. Hort. Sci. 

61:270-274.

APHIS [U.S. Department of Agriculture, Animal 

and Plant Health Inspection Service]. 1998. 

Plant Protection and Quarantine Manual. U.S. 

Department of Agriculture, Animal and Plant 

Health Inspection Service, Hyattsville, MD.

Armstrong, J., B. Hu, and S. Brown. 1995. Singletemperature forced hot-air quarantine treatment to 

control fruit flies (Diptera: Tephritidae) in papaya. 

J. Econ. Entomol. 88:678-682.

Baker, A.G. 1939. The basis for treatment of 

products where fruit flies are involved as a 

condition for entry into the United States. Circular 

551, U.S. Department of Agriculture, Washington, 

DC.

Baker, A.G. 1952. The vapor-heat process. In

A. Stefferud, ed., Insects. The Yearbook of 

Agriculture 1952, pp. 401-403. U.S. Department 

of Agriculture, Washington, DC.

Barkai-Golan, R., and D.J. Phillips. 1991. 

Postharvest heat treatment of fresh fruits and 

vegetables for decay control. Plant Dis. 75:1085-

1089.

Barkai-Golan, R., R. Padova, I. Ross, et al. 1993. 

Combined hot water and radiation treatments to 

control decay of tomato fruits. Sci. Hort. 56:101-

105.

Ben-Yehoshua, S., B. Shapiro, and R. Moran. 

1987. Individual seal-packaging enables the use of 

curing at high temperatures to reduce decay and 

heat injury of citrus fruits. HortScience 22:777-

783.

Chan, H.T., and E. Linse. 1989. Conditioning 

cucumbers for quarantine heat treatments. 

HortScience 24:985-989.

Chervin, C., S. Kulkarni, S. Kreidl, et al. 1997. A 

high temperature/low oxygen pulse improves cold 

storage disinfestation. Postharv. Biol. Technol. 

10:239-245.

Coates, L.M., and G.I. Johnson. 1993. Effective 

disease control in heat-disinfected fruit. Postharv. 

News Info. 4:35N-40N.

Coates, L.M., G. I. Johnson, and A. Cooke. 1993. 

Postharvest disease control in mangoes using high 

humidity hot air and fungicide treatments. Ann. 

Appl. Biol. 123:441-448.

Couey, H.M. 1989. Heat treatment for control 

of postharvest diseases and insect pests of fruits. 

HortScience 24:198-201.

Dentener, P.R., S. M. Alexander, P.J. Lester, et 

al. 1996. Hot air treatment for disinfestation of 

lightbrown apple moth and longtailed mealy bug 

on persimmons. Postharv. Biol. Technol. 8:143-

152.

Dentener, P.R., K.V. Bennett, L.E. Hoy, et al. 

1997. Postharvest disinfestation of lightbrown 

apple moth and longtailed mealybug on 

persimmons using heat and cold. Postharv. Biol. 

Technol. 12:255-264.

Dentener, P.R., S.E. Lewthwaite, J.H. Maindonald, 

and P.G. Connolly. 1998. Mortality of twospotted 

spider mite (Acari: Tetranychidae) after exposure 

to ethanol at elevated temperatures. J. Econ. 

Entomol. 91:767-772.

Dentener, P.R., S.E. Lewthwaite, K.V. Bennett, 

et al. 2000. Effect of temperature and treatment 

conditions on the mortality of Epiphyas 

postvittana (Lepidoptera: Tortricidae) exposed to 

ethanol. J. Econ. Entomol. 93:519-525.

Fallik, E., J. D. Klein, S. Grinberg, et al. 1993. 

Effect of postharvest heat treatment of tomatoes 

on fruit ripening and decay caused by Botrytis 

cinerea. Plant Dis. 77:985-988.
37

Fallik, E., Y. Aharoni, O. Yekutieli, et al. 1996a. 

A method for simultaneously cleaning and 

disinfecting agricultural produce. Israel Patent 

Application No. 116965.

Fallik, E., S. Grinberg, S. Alkalai, and S. Lurie. 

1996b. The effectiveness of postharvest hot water 

dipping on the control of gray and black molds 

in sweet red pepper (Capsicum annuum). Plant 

Pathol. 45:644-649.

Fallik, E., S. Grinberg, M. Gambourg, et al. 1996c. 

Prestorage heat treatment reduces pathogenicity of 

Penicillium expansum in apple fruit. Plant Pathol. 

45:92-97.

Fallik, E., S. Grinberg, S. Alkalai, et al. 1999. 

A unique rapid hot water treatment to improve 

storage quality of sweet pepper. Postharv. Biol. 

Technol. 15:25-32.

Florissen, P., J.S. Ekman, C. Blumenthal, et al. 

1996. The effects of short heat treatments on 

the induction of chilling injury in avocado fruit 

(Persea americana Mill). Postharv. Biol. Technol. 

8:129-141.

Follet, P.A., and Z. Gabbard. 1999. Efficacy of the 

papaya vapor heat quarantine treatment against 

white peach scale in Hawaii. HortTechnology 

9:506.

Forney, C.F. 1995. Hot water dips extend shelf-life 

of fresh broccoli. HortScience 30:1054-1057.

Garcia, J.M., C. Aguilera, and A.M. Jimenez. 

1996. Grey mold in and quality of strawberry fruit 

following postharvest heat treatment. HortScience 

31:255-257.

Gonzalez-Aguilar, G.A., L. Zacarias, and 

M.T. Lafuente. 1998. Ripening affects hightemperature-induced polyamines and their changes 

during cold storage of hybrid Fortune mandarins. 

J. Agric. Fd. Chem. 46:3503-3508.

Hallman, G.J., J.J. Gaffney, and J.L. Sharp. 1990. 

Vapor heat treatment for grapefruit infested with 

Caribbean fruit fly (Diptera: Tephritidae). J. Econ. 

Entomol. 83:1475-1478.

Heather, N.W., R.J. Corcoran, and R.A. Kopittke. 

1997. Hot air disinfestation of Australian 

‘Kensington’ mangoes against two fruit flies 

(Diptera: Tephritidae). Postharv. Biol. Technol. 

10:99-105.

Hong, G., G. Peiser, and M.I. Cantwell. 2000. Use 

of controlled atmospheres and heat treatment to 

maintain quality of intact and minimally processed 

green onions. Postharv. Biol. Technol. 20:53-61.

Hoy, L.E., and D. C. Whiting. 1998. Mortality 

responses of three leafroller (Lepidoptera: 

Tortricidae) species on kiwifruit to a hightemperature controlled atmosphere treatment. N.Z. 

J. Crop Hort. Sci. 26:11-15.

Jacobi, K.K., Wong, L.S., and J.E. Giles. 1993. 

Lychee (Lichi chinensis Sonn.) fruit quality 

following vapour heat treatment and cool storage. 

Postharv. Biol. Technol. 3:111-119.

Jacobi, K.K., J. Giles, E. MacRae, and T. 

Wegrzyn. 1995a. Conditioning ‘Kensington’ 

mango with hot air alleviates hot water 

disinfestation injuries. HortScience 30:562-565.

Jacobi, K.K., L.S. Wong, and J.E. Giles. 1996. 

Postharvest quality of zucchini (Cucurbita pepo

L.) following high humidity hot air disinfestation 

treatments and cool storage. Postharv. Biol. 

Technol. 7:309-316.

Jacobi, K.K., and J.E. Giles. 1997. Quality of 

‘Kensington’ mango (Mangifera indica Linn.) 

fruit following combined vapor heat disinfestation 

and hot water disease control. Postharv. Biol. 

Technol. 12:285-292.

Jang, E.B. 1996. Systems approach to quarantine 

security: postharvest application of sequential 

mortality in the Hawaiian grown ‘Sharwil’ 

avocado system. J. Econ. Entomol. 89:950-956.
38

Jessup, A.J. 1994. Quarantine disinfestation 

of ‘Hass’ avocados against Bactrocera tryoni 

(Diptera: Tephritidae) with a hot fungicide dip 

followed by cold storage. J. Econ. Entomol. 

87:127-130.

Kim, J.J., S. Ben-Yehoshua, B. Shapiro, et al. 

1991. Accumulation of scoparone in heat-treated 

lemon fruit inoculated with Penicillium digitatum

Sacc. Plant Physiol. 97:880-885.

Klein, J.D., and S. Lurie. 1992. Prestorage heating 

of apple fruit for enhanced postharvest quality: 

interaction of time and temperature. HortScience 

27:326-328.

Klein, J., W. Conway, B. Whitaker, and C. Sams. 

1997. Botrytis cinerea decay in apples is inhibited 

by postharvest heat and calcium treatments. J. 

Amer. Soc. Hort. Sci. 122:91-94.

Lay-Yee, M., and D.C. Whiting. 1996. Response 

of ‘Hayward’ kiwifruit to high-temperature 

controlled atmosphere treatments for control of 

two-spotted spider mite (Tetranychus urticae).

Postharv. Biol. Technol. 7:73-81.

Lay-Yee, M., S. Ball, S.K. Forbes, and A.B. 

Woolf. 1997a. Hot water treatment for insect 

disinfestation and reduction of chilling sensitivity 

of ‘Fuyu’ persimmon. Postharv. Biol. Technol. 

10:81-89.

Lay-Yee, M., D.C. Whiting, and K.J. Rose. 1997b. 

Response of ‘Royal Gala’ and ‘Granny Smith’ 

apples to high-temperature controlled atmosphere 

treatments for control of Epiphyas postvittana and 

Nysius huttoni. Postharv. Biol. Technol. 12:127-

136.

Lester, P.L., P.R. Dentener, R.J. Petry, and 

S.M. Alexander. 1995. Hot-water immersion 

for disinfestation of lightbrown apple moth 

(Epiphyas postvittana) and longtailed mealy bug 

(Pseudococcus longispinus) on persimmons. 

Postharv. Biol. Technol. 6:349-356.

Lester, P.J., P.R. Dentener, K.V. Bennett, and P.G. 

Connolly. 1997. Postharvest disinfestations of 

diapausing and nondiapausing twospotted spider 

mite (Tetranychus urticae) on persimmons: hot 

water immersion and coolstorage. Entom. Exper. 

Appl. 83:189-193.

Lurie, S. 1998. Postharvest heat treatments. 

Postharv. Biol. Technol. 14:257-269.

Lurie, S., and J.D. Klein. 1991. Acquisition of low 

temperature tolerance in tomatoes by exposure to 

high temperature stress. J. Amer. Soc. Hort. Sci. 

116:1007-1012.

Lurie, S., J.D. Klein, and R. Ben-Arie. 1990. 

Postharvest heat treatment as a possible means of 

reducing superficial scald of apples. J. Hort. Sci. 

65:503-509.

Lurie, S. M. Laamim, Z. Lapsker, and E. Fallik. 

1997. Heat treatments to decrease chilling injury 

in tomato fruit. Effects on lipids, pericarp lesions 

and fungal growth. Physiol. Plant. 100:297-302.

McCollum, T.G., S. D’Aquino, and R.E. 

McDonald. 1993. Heat treatment inhibits mango 

chilling injury. HortScience 28:197-198.

McCollum, G., H. Doostdar, R. Mayer, and R. 

McDonald. 1995. Immersion of cucumber in 

heated water alters chilling-induced physiological 

changes. Postharv. Biol. Technol. 6:55-64.

McDonald, R.E., T.G. McCollum, and E.A. 

Baldwin. 1998. Heat treatment of mature-green 

tomatoes: differential effects of ethylene and 

partial ripening. J. Amer. Soc. Hort. Sci. 123:457-

462.

McDonald, R.E., T.G. McCollum, and E.A. 

Baldwin. 1999. Temperature of water heat 

treatments influences tomato fruit quality 

following low-temperature storage. Postharv. Biol. 

Technol. 16:147-155.
39

McGuire, R.G. 1991. Concomitant decay 

reductions when mangoes are treated with heat to 

control infestations of Caribbean fruit fly. Plant 

Dis. 75:946-949.

McGuire, R.G. 1997. Market quality of guavas 

after hot-water quarantine treatment and 

application of carnauba wax coating. HortScience 

32:271-274.

McLaren, G.F., R.M. McDonald, J.A. Fraser, et 

al. 1997. Disinfestation of New Zealand flower 

thrips from stonefruit using hot water. Acta Hort. 

464:524.

Mencarelli, F., B. Ceccantoni, A. Bolini, and G. 

Anelli. 1993. Influence of heat treatment on the 

physiological response of sweet pepper kept at 

chilling temperature. Acta Hort. 343:238-243.

Miller, W.R., R.E. McDonald, and J.L. Sharp. 

1991. Quality changes during storage and ripening 

of ‘Tommy Atkins’ mangos treated with heated 

forced air. HortScience 26:395-397.

Neven, L., and E. Mitcham. 1996. CATTS: 

controlled atmosphere/temperature treatment 

system. A novel tool for the development of 

quarantine treatments. Amer. Entomol. 42:56-59.

Neven, L.G., and S.R. Drake. 2000. Comparison 

of alternative postharvest quarantine treatments 

for sweet cherries. Postharv. Biol. Technol. 

20:107-114.

Neven, L.G., L.M. Rehfield, and K.C. Shellie. 

1996. Moist and vapor forced air treatments of 

apples and pears: effects on the mortality of fifth 

instar codling moth (Lepidoptera: Tortricidae). J. 

Econ. Entomol. 89:700-704.

Nishijima, K.A., K. Miura, J.W. Armstrong, et al. 

1992. Effect of forced, hot-air treatment of papaya 

fruit on fruit quality and incidence of postharvest 

diseases. Plant Dis. 76:723-727.

Nishijima, K., H. Chan, S. Sanxter, and E. Linse. 

1995. Reduced heat shock period of ‘Sharwil’ 

avocado for cold tolerance in quarantine cold 

treatment. HortScience 30:1052-1053.

Paull, R.E. 1994. Response of tropical 

horticultural commodities to insect disinfestation 

treatments. HortScience 29:988-996.

Paull, R.E., and N.J. Chen. 1999. Heat treatment 

prevents postharvest geotropic curvature of 

asparagus spears (Asparagus officinallis L.). 

Postharv. Biol. Technol. 16:37-41.

Porat, R., A. Daus, B. Weiss, et al. 2000. 

Reduction of postharvest decay in organic citrus 

fruit by a short hot water brushing treatment. 

Postharv. Biol. Technol. 18:151-157.

Porat, R., D. Pavoncello, J. Peretz, et al. 1999. 

Effects of various heat treatments on the induction 

of cold tolerance and on the postharvest qualities 

of ‘Star Ruby’ grapefruit. J. Amer. Soc. Hort. Sci. 

124:184-188.

Prusky, D., Y. Fuchs, I. Kobiler, et al. 1999. Effect 

of hot water brushing, prochloraz treatment and 

waxing on incidence of black spot decay caused 

by Alternaria alternata in mango fruits. Postharv. 

Biol. Technol. 15:165-174.

Ranagann, B., G.S.V. Raghavan, and A.C. 

Kushalappa. 1998. Hot water dipping to enhance 

storability of potatoes. Postharv. Biol. Technol. 

13:215-223.

Reyes, M.E.Q., W. Nishijima, and R.E. Paull. 

1998. Control of crown rot in ‘Santa Catarine 

Prata’ and ‘Williams’ banana with hot water 

treatment. Postharvest Biol. Technol. 14:71-75.

Rodov, V., S. Ben-Yehoshua, R. Albagli, and D.Q. 

Fang. 1995. Reducing chilling injury and decay 

of stored citrus fruit by hot water dips. Postharv. 

Biol. Technol. 5:119-127.
40

Sams, C.E., W.S. Conway, J.A. Abbott, et al. 

1993. Firmness and decay of apples following 

postharvest pressure infiltration of calcium and 

heat treatment. J. Amer. Soc. Hort. Sci. 118:623-

627.

Schirra, M., and G. D’Hallewin. 1997. Storage 

performance of Fortune mandarins following hot 

water dips. Postharv. Biol. Technol. 10:229-238.

Schirra, M., G. Barbera, S. D’Aquino, T. La 

Mantia, and R.E. McDonald. 1996. Hot dips and 

high-temperature conditioning to improve shelf 

quality of late-crop cactus pear fruit. Trop. Sci. 

36:159-165.

Schirra, M., M. Agabbio, S. D’Aquino, and T.G. 

McCollum. 1997. Postharvest heat conditioning 

effects on early ripening ‘Gialla’ cactus pear fruit. 

HortScience 32:702-704.

Schirra, M., P. Cabras, A. Angioni, et al. 1997. 

Effect of heated solutions on decay control and 

residues of imazalil in lemons. J. Agric. Fd Chem. 

45:4127-4130.

Sharp, J.L., and W.P. Gould. 1994. Control of 

Caribbean fruit fly (Diptera: Tephritidae) in 

grapefruit by forced hot air and hydro-cooling. J. 

Econ. Entomol. 87:131-133.

Sharp, J.L., and R.G. McGuire. 1996. Control 

of Caribbean fruit fly (Diptera: Tephritidae) in 

navel orange by forced hot air. J. Econ. Entomol. 

89:1181-1185.

Shellie, K.C., R.L. Mangan, and S.J. Ingle. 1997. 

Tolerance of grapefruit and Mexican fruit fly 

larvae to heated controlled atmospheres. Postharv. 

Biol. Technol. 10:179-186.

Shellie, K.C. 1998. Reduction of green mold 

on grapefruit after hot forced-air quarantine 

treatment. Plant Dis. 82:380-382.

Smilanick, J.L., D.A. Margosan, and D.J. Henson. 

1995. Evaluation of heated solutions of sulfur 

dioxide, ethanol, and hydrogen peroxide to control 

postharvest green mold of lemons. Plant Dis. 

79:742-747.

Smilanick, J.L., B.E. Mackey, R. Reese, et al. 

1997. Influence of concentration of soda ash, 

temperature, and immersion period on the control 

of postharvest green mold of oranges. Plant Dis. 

80:230-234.

Sonderstrom, E.L., D.G. Brandl, and B.E. 

Mackay. 1993. High temperature for control 

of Asynonychus godmani (Coleoptera: 

Curculionidae) eggs on lemon fruit. J. Econ. 

Entomol. 86:1773-1780.

Tian, M.S., A.B. Woolf, J.H. Bowen, and I.B. 

Ferguson. 1996. Changes in color and chlorophyll 

fluorescence of broccoli florets following hot 

water treatment. J. Amer. Soc. Hort. Sci. 121:310-

313.

Tian, M.S., T. Islam, D.G. Stevenson, and 

D.E. Irving. 1997. Color, ethylene production, 

respiration, and compositional changes in broccoli 

dipped in hot water. J. Amer. Soc. Hort. Sci. 

122:112-116.

Wang, C.Y. 1994. Combined treatment of heat 

shock and low temperature conditioning reduces 

chilling injury in zucchini squash. Postharv. Biol. 

Technol. 4:65-73.

Wang, C.Y. 1998. Heat treatment affects 

postharvest quality of kale and collard, but not of 

brussels sprouts. HortScience 33:881-883.

Whiting, D.C., and L.E. Hoy. 1997. High 

temperature controlled atmosphere and air 

treatments to control obscure mealybug 

(Hemiptera: Pseudococcidae) on apples. J. Econ. 

Entomol. 90:546-550.
41

Whiting, D.C., L.E. Jamieson, K.J. Spooner, 

and M. Lay-Yee. 1999. Combination of hightemperature controlled atmosphere and cold 

storage as a quarantine treatment against 

Ctenopseustis obliquana and Epiphyas postvittana 

on ‘Royal Gala’ apples. Postharv. Biol. Technol. 

16:119-126.

Woolf, A.B., C.B. Watkins, J.H. Bowen, et al. 

1995. Reducing external chilling injury in stored 

‘Hass’ avocados with dry heat treatments. J. Amer. 

Soc. Hort. Sci. 120:1050-1056.

Woolf, A.B., and M. Lay-Yee. 1997. Pretreatments 

at 38 °C of ‘Hass’ avocado confer thermotolerance 

to 50 °C hot water treatments. HortScience 

32:705-708.

Woolf, A.B., S. Ball, K. Spooner, et al. 1997. 

Reduction of chilling injury in the sweet 

persimmon ‘Fuyu’ during storage by dry air heat 

treatments. Postharv. Biol. Technol. 11:155-164.
42

Modified Atmosphere Packaging

Nazir Mir and Randolph M. Beaudry

Mir and Beaudry are with Michigan State 

University, East Lansing, MI.

Introduction

Modified-atmosphere packaging (MAP) of fresh 

fruits and vegetables refers to the technique of 

sealing actively respiring produce in polymeric 

film packages to modify the O2

 and CO2 levels 

within the package atmosphere. It is often 

desirable to generate an atmosphere low in O2

 and/

or high in CO2

 to influence the metabolism of the 

product being packaged or the activity of decaycausing organisms to increase storability and/or 

shelf-life. For some products, modifying both O2

and CO2

 may be desirable; indeed, altering the O2

level automatically alters CO2

 level. In addition to 

atmosphere modification, MAP vastly improves 

moisture retention, which can have a greater 

influence on preserving quality than O2

 and 

CO2

 levels. Furthermore, packaging isolates the 

product from the external environment and helps 

to ensure conditions that, if not sterile, at least 

reduce exposure to pathogens and contaminants.

MAP was first evaluated in the mid to late 1940s 

for its ability to reduce O2

 levels sufficiently to 

slow the ripening of apple fruit. The primary 

limitation of MAP application in the early 

studies was technical in nature—specifically, 

the lack of consistent control of O2

 levels in the 

package. Since then, the types and properties 

of polymers have increased to provide a wider 

range of gas permeability, tensile strength, 

flexibility, printability, and clarity. As a result, 

successful modified atmosphere (MA) packaging 

systems have been developed for a number of 

commodities.

It is important to recognize that while atmosphere 

modification can improve the storability of some 

fruits and vegetables, it has the potential to induce 

undesirable effects. Fermentation and off flavors 

may develop if decreased O2

 levels cannot sustain 

aerobic respiration (Kays 1997). Similarly, injury 

will occur if CO2

 exceeds tolerable levels. Ranges 

of nondamaging O2

 and CO2 levels have been 

published for a number of fruits and vegetables 

(Kader 1997a, Kupferman 1997, Richardson and 

Kupferman 1997, Saltveit 1997, Beaudry 1999, 

2000), minimally processed products (Gorny 

1997), and flowers and ornamentals (Reid 1997). 

Horticultural crops differ in their tolerance for 

O2

 (table 1) and CO2 (table 2). ). The range of O2

and CO2

 levels for fruits (figure 1) and vegetables 

(figure 2) can overlap or be distinct.
43

Table 1. O2

 limits below which injury can occur for selected horticultural crops held 

at typical storage temperatures

O2 Commodities

%

<0.5 Chopped greenleaf*, redleaf*, romaine* and iceberg lettuce*; spinach; sliced 

pear; broccoli*; mushroom

1.0 Broccoli florets, chopped butterhead lettuce, sliced apple, brussels sprouts, 

cantaloupe, cucumber, crisphead lettuce, onion bulbs, apricot, avocado, 

banana*, cherimoya, atemoya, sweet cherry, cranberry, grape, kiwifruit*, 

litchi, nectarine, peach, plum, rambutan, sweetsop

1.5 Most apples*, most pears*

2.0 Shredded and cut carrots, artichoke, cabbage*, cauliflower, celery, bell and 

chili peppers, sweet corn, tomato, blackberry, durian, fig, mango, olive, 

papaya, pineapple, pomegranate, raspberry, strawberry

2.5 Shredded cabbage, blueberry

3.0 Cubed or sliced cantaloup, low-permeability apples* and pears*, grapefruit, 

persimmon

4.0 Sliced mushrooms

5.0 Green snap beans, lemon, lime, orange

10.0 Asparagus

14.0 Orange sections

Source: Gorny 1997, Kader 1997a, Kupferman 1997, Richardson and Kupferman 1997, Saltveit 

1997, and Beaudry 2000

* Considered to have very good to excellent potential to respond to low O2.
44

Table 2. CO2

 partial pressures above which injury will occur for selected 

horticultural crops

______________________________________________________________________

CO2 Commodities ______________________________________________________________________________

kPa

2 Lettuce (crisphead), pear

3 Artichoke, tomato

5 Apple (most cultivars), apricot, cauliflower, cucumber, grape, nashi, olive, 

 orange, peach (clingstone), potato, pepper (bell)

7 Banana, bean (green snap), kiwifruit

8 Papaya

10 Asparagus, brussels sprouts, cabbage, celery, grapefruit, lemon, lime, mango, 

 nectarine, peach (freestone), persimmon, pineapple, sweet corn

15 Avocado, broccoli, lychee, plum, pomegranate, sweetsop

20 Cantaloupe (muskmelon), durian, mushroom, rambutan

25 Blackberry, blueberry, fig, raspberry, strawberry

30 Cherimoya

______________________________________________________________________________

Source: modified from Herner 1987, Kader 1997a, and Saltveit 1997

Figure 1. Recommended O2 and CO2 combinations for the 

storage of fruit. The chart depicts atmospheres theoretically 

attainable by MAP by film permeation alone (low-density 

polyethylene, LDPE, lower boundary) and via perforations 

alone (upper, dashed line) or their combination (shaded 

area). Data are adapted from Kader (1997) and reprinted 

with permission from Beaudry (1999). Copyright 1999 by 

Elsevier Science.

Figure 2. Recommended O2

 and CO2 combinations for 

the storage of vegetables. The chart depicts atmospheres 

theoretically attainable by MAP using low-density 

polyethylene (LDPE, lower boundary) and perforated 

packages (upper, dashed line); redrawn from Mannapperuma 

et al. (1989). The shaded area represents atmospheres 

observed in commercial MA packages of mixed lettucebased salads (Cameron et al. 1995). Reprinted with 

permission from Beaudry (1999). Copyright 1999 by Elsevier 

Science.
45

The composition of the atmosphere within 

a package results from the interaction 

of a number of factors that include the 

permeability characteristics of the package, 

the respiratory behavior of the plant material, 

and the environment. The films making up 

the package are selected to have specific 

permeability characteristics, and changes in 

these characteristics over time, temperature, 

and humidity follow known physical laws. The 

environment can be controlled to provide specific 

conditions. In contrast to these known and 

controllable factors are the often unknown and 

uncontrollable responses of the plant material. 

Plant species and cultivar, cultural practices, 

stage of development, manner of harvest, tissue 

type, and postharvest handling—all of these 

factors contribute and influence the response of 

the material to the generated atmosphere. The 

scope of plant responses can be further modified 

by initial gas flush of the package before sealing 

and inclusion of chemical treatments to slow 

unwanted processes or reduce decay. Each of 

these components of the packaging process can be 

examined separately to better illustrate how each 

contributes to packaging strategies.

Package Parameters

Atmosphere modification in MAP requires 

actively respiring plant tissue and a barrier 

through which gas exchange is restricted. The 

reduced O2

 and increased CO2 resulting from 

tissue respiration create gradients across the film 

barrier that provide the driving force for gas 

movement into and out of the package. The levels 

of O2

 and CO2 within a package depend on the 

interaction between commodity respiration and the 

permeability properties of the packaging film or 

microperforations (Beaudry et al. 1992, Kader et 

al. 1997a).

There are two strategies for creating film. The first 

employs continuous films that control movement 

of O2

 and CO2 into or out of the package. The 

second uses perforated films with small holes, 

or microperforations, as the primary route of gas 

exchange.

Continuous Films: The movement of O2

 and CO2

is usually directly proportional to the difference 

in gas concentration across the film. Steady-state 

(constant) O2

 and CO2 levels are achieved in the 

package when the O2

 uptake and CO2 production 

by the product are equal to that permeating 

through the film, a situation that exists only when 

the respiratory rate is constant.

Perforated Films: The rate of gas movement 

through a perforated film is the sum of gas 

diffusion through the perforation and gas 

permeation through the polymeric film. Generally, 

total gas flow through the perforations is much 

greater than gas movement through the film. Gas 

transmission through microperforations has been 

modeled (Fishman et al. 1996). The rate of gas 

exchange through perforations in a film is so much 

greater than through continuous films that a 1-mm 

perforation in a 0.0025 mm (1 mil) thick lowdensity polyethylene (LDPE) film has nearly the 

same gas flux as a half a square meter area of the 

film. As might be surmised, perforated packages 

are more suitable for produce having a high O2

demand.

Gas Exchange Properties of Continuous and 

Perforated Films

The relative permeability of the package to O2

and CO2

 differs substantially between continuous 

and perforated films and results in considerable 

differences in gas exchange behavior. In packages 

composed of continuous films, the permeability 

of the package to CO2

 is usually 2 to 8 times that 

of O2

 permeability. If the rate of O2 uptake by the 

product is roughly the same as its production of 

CO2

 (the normal case unless fermentation is taking 

place), the CO2

 gradient will be much lower 

than the O2

 gradient. For example, low-density 

polyethylene (LDPE) has permeability to CO2

that is four times that of O2

. In a LDPE package 

having a 10% O2

 steady-state atmosphere, the 

CO2

 level could be calculated as (21 - 10%)/4, 

or 2.75% CO2

. (Air contains 78% N2, 21% 

O2

, and 0.03% CO2.) For perforated films, the 

permeability to CO2

 is only 0.77 times that of O2. 

As a result, in a package relying on perforations 
46

for gas exchange, CO2

 levels climb to roughly 

the same extent that O2

 levels decline (that is, the 

gradients are nearly equal) such that the sum of 

O2

 and CO2 concentrations is usually in the range 

of 18 to 20%. For any given O2

 level, therefore, 

the perforated package will have a considerably 

higher level of CO2

 compared with the continuous 

film package. To extend the example above, if a 

package were designed to have a 10% O2

 steadystate atmosphere using perforations as the route 

of gas exchange, the CO2

 level would be 0.77 × 

(21 - 10%), or 8.8%, which is about 3-fold greater 

than in the continuous film package. The relative 

elevation of CO2

 in perforated film packages may 

be critically important in package design, if CO2

 is 

needed to help control decay or degreening.

MAP relying on a combination of perforation 

and permeation has features of both systems, 

with attainable combinations of O2 and CO2

 being 

between those of packages relying on permeation 

and those relying on perforations (Mannapperuma 

et al. 1989, Beaudry 1999) (figures 1 and 2). 

The temperature sensitivity for permeation, and 

the permeability of O2

 and CO2, is somewhere 

between those for perforated packages and 

continuous film packages.

Temperature is extremely important in package 

design, and continuous and perforated films 

differ in their response to temperature changes. 

The O2

 and CO2 permeability of continuous films 

increases with temperature, while the diffusion 

of gases through perforations is extremely 

insensitive to temperature changes. For instance, 

O2

 permeation through LDPE can increase 200% 

from 0 to 15 °C, but the exchange of O2

 through 

perforations will increase only 11% across this 

temperature range.

Depending on the rates of respiration and 

transmission through the package, atmosphere 

modification can be achieved rapidly or relatively 

slowly. At low temperatures, atmosphere 

modification can take several days, such that 

some package systems would not achieve steadystate conditions before the end of their shelf-life. 

In many cases, purging the package atmosphere 

with CO2

, N2, or a combination of gases is often 

desirable during filling and sealing to rapidly 

obtain the maximum benefits of MAP.

Respiratory Parameters

The maximal rate of respiration for most fruit 

and vegetable products undergoes a 4- to 6-fold 

increase from 0 to 15 °C (Beaudry et al. 1992, 

Cameron et al. 1994,1995, Lakakul et al. 1999). 

This means that product respiration increases at 

2 or 3 times the rate of LDPE permeability and 

30 times the rate of perforation permeability 

with increasing temperature. When respiratory 

demand for O2

 increases faster than O2 permeation 

as temperature increases, O2

 levels decline and 

may pose a risk to product quality, limiting the 

usefulness of MAP in some situations.

Safe levels of O2

 and CO2 are important for 

package design. A lower O2

 limit has been 

associated with onset of fermentation and 

accumulation of ethanol and acetaldehyde 

(Beaudry et al. 1992). Fermentation is linked 

to the development of off flavors and tissue 

damage. Effect of temperature on lower O2

 limit 

has been measured for a number of commodities 

including whole apple, apple slices, blueberry, and 

raspberry. In each case, lower O2

 limit increased 

with temperature. Lower O2

 limits vary from 0.15 

to 5% (table 1) and are influenced by temperature, 

commodity, and cultivar (Beaudry and Gran 

1993).

Integrating Package, Product, and 

Environment

Mathematical models can integrate the film 

permeability to O2

, to CO2, and to H2O and the 

respiratory response of the commodity to O2

 (and 

in some cases to CO2

), along with its lower O2

limit and upper CO2

 limit (Beaudry et al. 1992, 

Cameron et al. 1994, Fishman et al. 1996, Hertog 

et al. 1998, Lakakul et al. 1999). These models 

enable the reasonably accurate prediction of 

package performance; that is, O2

-, CO2-, and H2O-
47

content in the package headspace under a variety 

of environmental conditions prior to construction 

of the package. Additionally, they permit the 

identification of limiting features of the film, 

package design, and product and environment 

conditions. Models typically include temperature 

dependency but can also be developed to predict 

effects of package volume, resistance to heat flow, 

and developmental changes in product physiology 

on headspace gases.

Predicting and Controlling O2

 and CO2 Content

A model can be developed to predict the 

steady-state concentration of O2 in the package 

headspace. Steady-state models incorporating 

temperature effects on respiration and 

permeability have been published for many 

commodities. In addition, more complex dynamic 

models have been developed to account for 

temporal changes in package volume, product 

respiration, and the humidity and temperature of 

the environment (Fishman et al. 1996, Hertog et 

al. 1998).

Package performance can be depicted in a number 

of ways. Perhaps the most instructive format is 

describing the effects of temperature on package 

O2

 levels. For example, a package was designed 

to produce low O2

 and high CO2 levels for 100 

g of apple slices at 0 °C (Lakakul et al. 1999). 

The practical O2

 limit was set 3-fold higher than 

the fermentation threshold to prevent variation 

in respiration and permeability from causing a 

reduction in package O2

 below the lower limit. 

If the package relied on perforations for gas 

exchange, it would undergo a rapid decline in 

O2

 by the time the package reached 6 °C (43 oF). 

Films with higher temperature sensitivity would 

be less prone to risk fermentation. In this example, 

packages were designed to maintain aerobic 

O2

 levels at 15 °C, the highest temperature to 

which they would be exposed. The performance 

of the packages can then be predicted at lower 

temperatures likely to be encountered during 

storage. A package O2

 model can also be used 

to predict very specific package criteria. For 

instance, the 100 g of apple slices described above 

were in a container with a film area of 120 cm2

. 

Film thickness and composition with different 

permeability characteristics could be selected to 

protect against fermentation. 

A package model can also be used to clarify the 

nature of the mismatch between the temperature 

sensitivity of O2

 uptake and O2 flux through 

the film and denote methods to ameliorate this 

problem. One method would be to choose a film 

with permeability changes for O2

 similar to that 

of the respiration of the product, so if temperature 

increases, respiration and permeability of the film 

increase an equivalent amount. 

Another solution to the MAP temperature problem 

is to develop a package system that senses either 

the environment or the physiological status of the 

enclosed product and responds by increasing the 

permeability to O2

 (Cameron et al. 1993). Such 

“sense-and-respond” packaging is technically 

difficult to develop, and progress has only been 

conceptual at this time (Smyth et al. 1999). A third 

approach is to design packages to function at the 

highest temperatures typically encountered in the 

distribution and retail cool chain and, as far as 

possible, maintain control over the temperature 

of the packaged product, thereby adapting to the 

limitations imposed by the film. Most companies 

using MAP have adopted this simple solution. 

Generally, the lowest temperature feasible is 

maintained, since temperature has a much more 

significant influence on preserving quality than the 

application of low O2

 (Kays 1997).

Variation in the respiration rate of the product 

and the variation in film or pore permeability can 

influence package design. Variation in product 

respiration and package permeability has been 

measured for broccoli, and the effect on package 

O2

 modeled (Cameron et al. 1993). Cameron et al. 

(1993) concluded that there is an estimable risk of 

the package O2

 falling sufficiently low to promote 

fermentation in any product. Packages should 

be designed to generate O2

 levels well above the 

lower limit to ensure aerobic conditions.

Products such as broccoli, mushrooms, and 

leeks have very high rates of respiration, and 

most continuous films do not have the capacity 
48

to provide enough O2

 to avoid fermentation. 

Accordingly, there is commercial interest in 

developing films with high gas transmission rates. 

Films that have improved rates of gas transmission 

by virtue of their polymeric nature are often 

blends of two or three different polymers, whith 

each polymer performing a specific function 

such as strength, transparency, and improved gas 

transmission. Similarly, films can be laminated to 

achieve needed properties.

The plastic polymer can also be mixed with an 

inert inorganic material such as CaCO3

 and SiO2

to generate micoporous films. Gas permeabilities 

can be manipulated by adjusting the filler 

content, particle size of the filler, and degree of 

stretching. The average pore size ranges from 

0.14 to 1.4 μm in diameter (Mizutani, 1989). 

Films using microperforations can attain very 

high gas transmission rates. The diameter of 

microperforation generally ranges from 40 to 

200 μm; and, by altering the size and thickness 

of microperforations, gas permeability through 

a package can be altered to meet well-defined 

product requirements. Microperforated films have 

also been used to extend storage of strawberries 

and nectarines (Meyers 1985) and apple (Watkins 

et al. 1988).

Water Vapor

Plant tissues tend to lose moisture when RH is 

below 99 to 99.5%. Generally, water loss results in 

visible wilting or wrinkling of the surface of most 

commodities when it exceeds 4 to 6% of total 

fresh weight (Kays 1997). Fortunately, most MAP 

films are relatively impermeable to water. The 

RH is very near saturation in most continuous or 

perforated film packages. A saturated atmosphere 

at 20 oC (68 oF) has only 2.1% H2

O, and most 

external environments are at 30 to 60% RH, 

yielding a water vapor gradient of about 1%. 

The O2

 gradient can be several-fold higher. 

Because of the small driving force and the rapid 

rate of release of water vapor from the product, 

perforations have a much greater effect on the O2

level than on RH. Fishman et al. (1996) calculated 

that perforating a continuous film increased O2

flow 40-fold more than it increased H2

O flow. 

Only four perforations were required to achieve 

near-ambient O2

 levels, while 40 perforations only 

reduced RH to 95%

Condensation on the inner surface of the film 

is a common problem with MAP. A drop of 

only 0.2 °C in the film temperature can result 

in condensation in a package with an internal 

RH of 99% at 10 °C. Cold-storage rooms have 

temperature swings of several degrees, so 

condensation is possible in almost any MAP. 

Fortunately, there are film surface treatments that 

result in droplet dispersion, so the condensing 

water forms a thin, uniform layer that is virtually 

invisible. Condensation could also be reduced in 

MAPs for a few commodities, such as tomato, 

that tolerate low humidity by including materials 

in the package that reduce RH. Salts enclosed 

in permeable sachets can reduce humidity in 

MAPs of tomato fruit (Shirazi and Cameron 

1992). The possibility of using films with very 

high water permeability has been examined using 

mathematical models (Cameron et al. 1995). 

However, since the external humidity would 

be critical in maintaining the proper package 

RH, this approach would encounter difficulty in 

maintaining a specific humidity level in shipping 

and storage environments.

Temperature Management

Product temperature affects storability more than 

any other factor. Precooling and temperature 

maintenance during handling and shipping are 

critical in preserving quality. Temperature also 

significantly affects film permeability and thereby 

the O2

 and CO2 content of the package. The 

elevated rate of respiration at high temperature 

could be used to rapidly establish the desired 

package atmosphere, but this would only be useful 

in the few situations in which it would be more 

important to rapidly establish the atmosphere than 

to slow physiological processes—for example, 

to reduce cut-surface browning. Cameron et al. 

(1995) calculated that, at 25 oC (77 oF), a package 

of blueberry fruit could attain a steady-state 

atmosphere in less than 2 days, whereas it required 

approximately 20 days at 0 °C (32 oF).
49

The temperature of the produce in the package is 

managed by circulating cool air around the outside 

of the package. The film and the headspace 

atmosphere are barriers to heat movement, prevent 

rapid cooling, and reduce the effectiveness of 

refrigeration. A “safe radius” for the distance from 

the center of the package to the circulated air can 

be calculated based on the heat of respiration 

and the rate at which heat can be removed by 

the cooler air (Sharp et al. 1993). For instance, 

the center of a package of broccoli must have a 

radius of less than 14 cm to keep it within 1 °C of 

the refrigerated air. Slower-respiring pear would 

function as well with a larger package having an 

effective radius of 50 cm.

Plant Responses to MAP

Some of the most important factors that affect 

shelf-life of fresh horticultural products are 

ripening and senescence, decay, and cut-surface 

browning. The effect of MA on these factors has 

been well characterized. The application of MA 

to affect these limiting factors can be restricted 

for some crops by adverse or nonbeneficial 

physiological responses; for example, induction 

of fermentation. Fresh product quality can be 

maximized more effectively by good temperature 

management than by atmosphere modification.

Ripening and Senescence

Low O2

 and elevated CO2 can significantly reduce 

the rates of ripening and senescence primarily 

by reducing the synthesis and perception of 

ethylene (Burg and Burg 1967, Abeles et al. 

1992). Changes in respiration and starch, sugars, 

chlorophyll, and cell wall constituents during 

ripening and/or senescence can be reduced and, 

in some cases, nearly arrested by eliminating 

ethylene action through the use of low O2

/high 

CO2

 atmospheres.

Chlorophyll loss, a desirable trait for many 

climacteric fruits, results in quality loss for many 

vegetables. Chlorophyll degradation during the 

senescence of green vegetables can be inhibited 

by low O2

 and elevated CO2, a response that in 

some cases is partly mediated by ethylene, as with 

broccoli (Ku and Wills 1999). 

While low O2 and elevated CO2 atmospheres are 

commonly used to minimize ethylene-dependent 

responses attendant to ripening in CA rooms, 

this goal may not be fully compatible with MAP. 

The problem with the incorporation of MAP for 

ripening control is not one of efficacy, but rather 

one of logistics. Modified atmospheres are most 

effective at reducing ripening prior to the onset 

of ripening, rather than at a later stage. However, 

packaged products are usually intended for 

immediate consumption and an unripe product 

is not immediately edible or is of lesser quality 

than the ripe product. Thus, the advantage of 

improved shelf-life by retarding ripening runs 

counter to the needs of the consumer when retail 

MAP systems are used. Nevertheless, MAP can 

reduce the rate of ripening of some commodities 

such as tomato even during its later stages (Yang 

and Chinnan 1988). More potential for using MAP 

to control ripening may exist at the packinghouse 

or distributor level, as in the case of overseas 

shipment of apples (Watkins et al. 1998), rather 

than at the retail level.

Decay

Decay control is a particularly important problem 

for many crops. Levels of >10% CO2

 effectively 

slow or stop the growth of numerous decay 

organisms (Brown 1922). Low O2

 has a very 

limited effect on decay organism activity or 

survival at levels above the fermentation threshold 

of most commodities. While not all horticultural 

commodities can withstand CO2

 levels sufficient 

to inhibit fungal activity, a number of highly 

perishable commodities are not adversely affected 

(table 2). Notable among these are strawberry, 

blueberry, blackberry, raspberry, and cherry, 

which can be stored successfully under a CO2

atmosphere of 10 to 20%.

Packaging strategies to enhance CO2

 include 

initial purging with high levels of CO2

. This 

strategy relies on continued respiration to replace 

CO2

 lost from the package and is in commercial 

use for many berry crops. The choice of film type 
50

markedly alters the CO2

 content of a package. In 

particular, perforated and continuous films differ 

in their discrimination between O2

 and CO2. 

Perforated films will generate a higher partial 

pressure of CO2

 for a given concentration of O2 in 

the package. Perforated packages can accumulate 

CO2

 to levels within the fungistatic range. For 

example, a perforated package that generates 1% 

O2

 could accumulate a 15% CO2 atmosphere.

While high RH reduces water loss, it also 

aggravates decay development. Strategies to 

reduce humidity in packages using salt sachets for 

the purpose of limiting decay have been explored 

(Shirazi and Cameron 1992). A number of 

effective chemical additives can be used at various 

points during processing and packaging to reduce 

decay. 

Cut-Surface Browning

Mostly, low-O2

 MAP is used to reduce the 

browning of cut surfaces on lightly processed 

products such as lettuce and salad mixes. 

Atmosphere modification is often used in 

conjunction with processing aids to retard 

brown color development. Smyth et al. (1998) 

demonstrated that O2

 levels below 2% but above 

the fermentation threshold of about 0.5% reduced 

the rate of browning in lettuce. The partial 

pressure of O2

 in commercial packages of lettuce 

and salad products is often below the fermentation 

threshold (Cameron et al. 1995, Peiser et al. 

1997). However, the fermentation of lettuce, if not 

severe, results in very few off flavors (Smyth et al. 

1998).

Negative Responses

Respiration is reduced as O2

 becomes limiting, but 

there is usually a limit to which O2

 can be reduced. 

The lower O2

 limit is frequently considered to be 

the level of O2

 that induces fermentation. This 

fermentation threshold is not always the lower O2

limit in commercial practice, however, because 

lower O2

 levels may confer benefits that outweigh 

the loss in flavor or other quality parameters. 

Ethanol, acetaldehyde, ethyl acetate, and lactate 

are products of fermentation that can contribute to 

the development of off flavors as well as physical 

injury (Kays 1997, Mattheis and Fellman 2000).

Production of compounds that contribute to 

the characteristic aromas of many fruit, such as 

apples, bananas, pears, peaches, and strawberries, 

can be adversely affected by low O2

 and elevated 

CO2 (Song et al. 1998, Mattheis and Fellman 

2000). Synthesis of aroma compounds are 

generally suppressed by high CO2

 and low O2, in 

part by their action on ethylene perception but also 

via action of O2

 on oxidative processes, including 

respiration required for substrate production. Most 

products that suffered moderate suppression of 

aroma volatile production due to low-O2

 storage 

atmospheres will eventually develop characteristic 

flavors. However, low-O2

 MAP may suppress 

aroma production so consumers perceive reduced 

quality upon opening the container.

Conclusion

A number of critical points need to be considered 

in package design and application:

•	 Not all plant materials benefit from MAP. 

Those that do may differ in their responses 

to the atmospheres generated.

•	 Consideration should be given to the 

factor most limiting to the delivery of a 

product to the consumer, and the packaging 

strategy should be developed accordingly.

•	 Reduction of water loss by packaging has 

a marked influence on storability. Elevated 

humidity prevents desiccation but can also 

enhance decay.

•	 Temperature control is of critical 

importance and, by itself, has a greater 

impact than atmosphere modification for 

most products. Temperature should be 

near the storage/shipping temperature as 

soon as possible after packaging except in 

those cases for which a slightly elevated 

temperature is needed to assist in rapid 

atmosphere generation.

•	 Heat transmission from product through 

the package, carton, and pallet stack needs 

to be considered in the development of 

handling procedures.
51

•	 If a package is designed to produce low-O2

or high-CO2

 levels at low temperatures, 

temperatures more than a few degrees 

above the target temperature should be 

avoided, or low-O2

 injury may result.

•	 Package modeling can improve 

understanding of how package, plant, and 

environmental factors interact and can be 

useful in package design.

References

Abeles, F.B., P.W. Morgan, and M.E. Saltveit 

Jr. 1992. Ethylene in Plant Biology, 2nd ed. 

Academic Press, San Diego, CA.

Beaudry, R.M. 2000. Responses of horticultural 

commodities to low oxygen: limits to the 

expanded use of modified atmosphere packaging. 

HortTechnology 10:491-500.

Beaudry, R.M. 1999. Effect of O2

 and CO2 partial 

pressure on selected phenomena affecting fruit 

and vegetable quality. Postharvest Biol. Technol. 

15:293-303.

Beaudry, R.M., A.C. Cameron, A. Shirazi, and 

D.L. Dostal-Lange. 1992. Modified-atmosphere 

packaging of blueberry fruit: effect of temperature 

on package O2

 and CO2. J. Amer. Soc. Hort. Sci. 

117:436-441.

Beaudry, R.M., and C.D. Gran. 1993. Using 

a modified-atmosphere packaging approach 

to answer some postharvest questions: factors 

affecting the lower oxygen limit. Acta Hort. 

362:203-212.

Brown, W. 1922. On the germination and growth 

of fungi at various temperatures and in various 

concentrations of oxygen and carbon dioxide. 

Ann. Bot. 36:257-283.

Burg, S.P., and E.A. Burg. 1967. Molecular 

requirements for the biological activity of 

ethylene. Plant Physiol. 42: 114-152.

Cameron, A.C., R.M. Beaudry, N.H. Banks, 

and M.V. Yelanich. 1994. Modified-atmosphere 

packaging of blueberry fruit: Modeling respiration 

and package oxygen partial pressures as a function 

of temperature. J. Amer. Soc. Hort. Sci. 119:534-

539.

Cameron, A.C., B.D. Patterson, P.C. Talasila, and 

D.W. Joles. 1993. Modeling the risk in modified 

atmosphere packaging: a case for sense-andrespond packaging. In G. Blanpied, J. Bartsch, and 

J. Hicks, eds., Proceedings of the 6th International 

Controlled Atmosphere Research Conference, pp. 

95-102. NRAES-71, Cornell University, Ithaca, 

NY.

Cameron, A.C., P.C. Talasila, and D.J. Joles. 

1995. Predicting the film permeability needs 

for modified atmosphere packaging of lightly 

processed fruits and vegetables. HortScience 

30:25-34.

Fishman, S., V. Rodov, and S. Ben-Yehoshua. 

1996. Mathematical model for perforation effect 

on oxygen and water vapor dynamics in modifiedatmosphere packages. J. Food Sci. 61:956-961.

Gorny, J.R. 1997. A summary of CA and MA 

requirements and recommendations for fresh-cut 

(minimally-processed) fruits and vegetables. In

J. Gorny, ed., Fresh-Cut Fruits and Vegetables 

and MAP, CA’97 Proceedings, vol. 5, pp. 30-

66. Postharvest Hort. Ser. no. 19, University of 

California, Davis, CA.

Herner, R.C. 1987. High CO2

 effects on plant 

organs. In J. Weichman, ed., Postharvest 

Physiology of Vegetables, pp. 239-253. Marcel 

Dekker, New York, NY.

Hertog, M.L.A.T.M., H.W. Peppelenbos, R.G. 

Evelo, and L.M.M. Tijskens. 1998. A dynamic 

and generic model of gas exchange of respiring 

produce: the effects of oxygen, carbon dioxide and 

temperature. Postharvest Biol. Technol. 14:335-

349.
52

Kader, A.A. 1997a. A summary of CA 

requirements and recommendations for fruits other 

than apples and pears. In A. Kader, ed., Fruits 

Other Than Apples and Pears, CA’97 Proceedings, 

vol. 2, pp. 1-36. Postharvest Hort. Ser. no. 17, 

University of California, Davis, CA.

Kader, A.A. 1997b. Biological bases of O2

 and 

CO2

 effects on postharvest life of horticultural 

perishables. In M.E. Saltveit, ed., Vegetables and 

Ornamentals, CA’97 Proceedings, vol. 4, pp. 160-

163. Postharvest Hort. Ser. no. 18, University of 

California, Davis, CA.

Kader, A.A., D. Zagory, and E.L. Kerbel. 1989. 

Modified atmosphere packaging of fruits and 

vegetables. Crit. Rev. Food Sci. 28:1-30.

Kays, S.J. 1997. Postharvest Physiology of 

Perishable Plant Products, Van Nostrand Reinhold, 

New York, NY.

Ku, V.V.V., and R.B.H. Wills. 1999. Effect of 

1-methylcyclopropene on the storage-life of 

broccoli. Postharvest Biol. Technol. 17:127-132.

Kupferman, E. 1997. Controlled atmosphere 

storage of apples. In E.J. Mitcham, ed., Apples 

and Pears, CA’97 Proceedings, vol. 3, pp. 1-30. 

Postharvest Hort. Ser. no. 16, University of 

California, Davis, CA.

Lakakul, R., R.M. Beaudry, and R.J. Hernandez. 

1999. Modeling respiration of apple slices in 

modified-atmosphere packages. J. Food Sci. 

64:105-110.

Mannapperuma, J., D. Zagory, R.P. Singh, and 

A.A. Kader. 1989. Design of polymeric packages 

for modified atmosphere storage of fresh produce. 

In J.K. Fellman, ed., Proceedings of the 5th 

International Controlled Atmosphere Research 

Conference, Other Commodities and Storage 

Recommendations, Wenatchee, WA, Vol. 2, pp. 

225-233.

Mattheis, J.P., and J.P. Fellman. 2000. Impact of 

modified atmosphere packaging and controlled 

atmosphere on aroma, flavor and quality of 

horticultural produce. HortTechnology 10:507-

510.

Meyers, R.A. 1985. Modified atmosphere 

packaging and process. U.S. Patent 4515266.

Mizutani, Y. 1989. Microporous polypropylene 

sheets. Ind. Eng. Chem. Res. 32:221-227.

Peiser, G., G. Lopez-Galvez, and M. Cantwell. 

1997. Changes in off-odor volatiles of salad 

products during storage. In J. Gorny, ed., FreshCut Fruits and Vegetables and MAP, CA’97 

Proceedings, vol. 5, pp. 23-28. Postharvest Hort. 

Ser. no. 19, University of California, Davis, CA.

Reid, M.S. 1997. A summary of CA and 

MA requirements and recommendations for 

ornamentals and cut flowers. In M.E. Saltveit, ed., 

Vegetables and Ornamentals, CA’97 Proceedings, 

vol. 4, pp. 129-136. Postharvest Hort. Ser. no. 18, 

University of California, Davis, CA.

Richardson, D.G., and E. Kupferman. 1997. 

Controlled atmosphere storage of pears. In

E.J. Mitcham, ed., Apples and Pears, CA’97 

Proceedings, vol. 2, pp. 31-35. Postharvest Hort. 

Ser. no. 16, University of California, Davis, CA.

Saltveit, M.E. 1997. A summary of CA and MA 

recommendations for harvested vegetables. In

M.E. Saltveit, ed., Vegetables and Ornamentals, 

CA’97 Proceedings, vol. 4, pp. 98-117. 

Postharvest Hort. Ser. no. 18, University of 

California, Davis, CA.

Sharp, A.K., A.R. Irving, and S.C. Morris. 1993. 

Does temperature variation limit the use of MA 

packaging during shipment in freight containers? 

In G. Blanpied, J. Bartsch, and J. Hicks, eds., 

Proceedings of the 6th International Controlled 

Atmosphere Research Conference, pp. 238-251. 

Cornell University, Ithaca, NY.
53

Shirazi, A., and A.C. Cameron. 1992. Controlling 

relative humidity in modified-atmosphere 

packages of tomato fruit. HortScience 27:336-339.

Smyth, A.B., J. Song, and A.C. Cameron. 1998. 

Modified-atmosphere packaged cut iceberg 

lettuce: effect of temperature and O

2

 partial 

pressure on respiration and quality. J. Ag. Food 

Chem. 46:4556-4562.

Smyth, A.B., P.C. Talasila, and A.C. Cameron. 

1999. An ethanol biosensor can detect low-oxygen 

injury in modified atmosphere packages of freshcut produce. Postharvest Biol. Technol. 15:127-

134.

Song, J., W. Deng, L. Fan, et al. 1998. Aroma 

volatiles and quality changes in modified 

atmosphere packaging. In J.R. Gorny, ed., FreshCut Fruits and Vegetables and MAP, CA’97 

Proceedings, vol. 5, pp. 89-95. Postharvest Hort. 

Ser. no. 19, University of California, Davis, CA.

Watkins, C.B., E.W. Hewett, and C.J. Thompson. 

1988. Effect of microperforated polyethylene bags 

on the storage quality of ‘Cox Orange Pippin’ 

apples. International Symposium on Postharvest 

Handling of Fruits and Vegetables, Acta Hort. 

(ISHS) 258:225-236.

Watkins, C.B., P.L. Brookfield, H.J. Elgar, and 

S.P. McLeod. 1998. Development of a modified 

atmosphere package for export of apple fruit. In

S. Ben-Yehoshua, ed., Proceedings of the 1997 

International Congress for Plastics in Agriculture, 

pp. 586-592, Laser Pages Publishing Ltd, 

Jerusalem, Israel.

Yang, C.C., and M.S. Chinnan. 1988. Modeling 

the effect of O

2

 and CO

2

 on respiration and quality 

of stored tomatoes. Trans. ASAE 31:920-925.
54

Wholesale Distribution Center 

Storage

James F. Thompson and Adel A. Kader

Thompson is formerly with the Biological and 

Agricultural Engineering Department, University 

of California, Davis, CA. He is now retired. Kader 

was with the Department of Pomology, University 

of California, Davis, CA. He is deceased.

Most produce is shipped from the point of 

production to regional or local distributors, such 

as terminal markets, independent wholesalers, or 

chain store distribution centers. Produce orders 

are assembled at these sites and then shipped to 

retail stores, restaurants, or institutions such as 

schools or hospitals. Produce and floral items 

lose quality during these marketing steps, and the 

amount of quality loss accumulates at each step. 

The consumer will receive quality produce only 

if each operation in the handling chain minimizes 

abuse caused by mechanical damage, improper 

temperature and RH, moisture loss, ethylene 

damage, odor contamination, and excessive 

storage time.

Large wholesale distribution facilities, whether 

independently owned or integrated with a retail 

chain, strive to receive only the amount of produce 

that can be shipped the following day. A few fruits 

such as mature green avocados, bananas, mangos, 

and tomatoes are ripened before shipment to retail 

stores and may be held in special ripening rooms 

for several days.

Products should be received at their proper longterm storage temperature and then stored at that 

temperature. Fruits and vegetables can be divided 

into three categories or groups according to 

their optimum temperature requirements (table 

1). The RH of the storage atmosphere should 

be 85 to 95%; however, for vegetables stored at 

low temperatures, it should be 90 to 98%. The 

lowest temperature range of 0 to 2 °C (32 to 36 

°F) should be used for the majority of the green, 

nonfruit vegetables and temperate fruits and 

melons. If there is enough capacity in the facility, 

the fruits should be stored separately from the 

vegetables. This allows installing equipment to 

maintain higher RH (90 to 98%) for the vegetables 

as many of them are quite susceptible to water 

loss and wilting. Table 2 shows cut flowers and 

nursery items divided into the recommended three 

categories or groups. If handled with produce, the 

floral items in group 1 should be in the group 1A 

vegetable room to minimize exposure to ethylene 

produced by many fruits.
55

Table 1. Compatible fresh fruits and vegetables during 7-day storage*

Groups 1A and 1B Group 2 Group 3

0-2 °C; group 1A: 90-98% RH; group 1B: 85-95% RH 7-10 °C; 85-95% RH 13-18 °C; 85-95% RH

Group 1A

Vegetables Alfalfa sprouts Chinese cabbage† Mint† Basil† Bitter melon

Amaranth† Chinese turnip Mushroom Beans, snap, green, wax Boniato†Anise† Collard† Mustard greens† Cactus leaves (nopales) † CassavaArtichoke Corn, sweet, baby Parsley† Calabaza Dry onionArugula† Cut vegetables Parsnip Chayote† GingerAsparagus† Daikon† Radicchio Cowpea (Southern pea) JicamaBeans, fava, lima Endive†-chicory Radish Cucumber† PotatoBean sprouts Escarole† Rutabaga Eggplant† PumpkinBeet Fennel† Rhubarb Kiwano (horned melon) Squash, winter (hard rind) †Belgian endive† Garlic Salsify Long bean Sweet potato†Bok choy† Green onion† Scorzonera Malanga† Taro (dasheen)Broccoli† Herbs† (not basil) Shallot† Okra† Tomato, ripe, partially ripe, 

& mature green

Broccoflower† Horseradish Snow pea† Pepper, bell, chili Yam†Brussels sprouts† Jerusalem artichoke Spinach† Squash, summer (soft rind) †Cabbage† Kailon† Sweet pea† TomatilloCarrot† Kale† Swiss chard† Winged beanCauliflower† Kohlrabi TurnipCeleriac Leek† Turnip greens†Celery† Lettuce† Water chestnutChard† Watercress†
56Table 1. Compatible fresh fruits and vegetables during 7-day storage*—Continued

Groups 1A and 1B Group 2 Group 3

0-2 °C; group 1A: 90-98% RH; group 1B: 85-95% RH 7-10 °C; 85-95% RH 13-18 °C; 85-95% RH

Group 1B

Fruits and Apple‡ Elderberry Prune† Avocado, unripe‡ Lime† Atemoya‡ Sapodilla‡ melons Apricot‡ Fig Quince† Babaco Limequat Banana‡ Sapote‡

Avocado, ripe‡ Gooseberry Raspberry Cactus pear, tuna Mandarin Breadfruit‡ Soursop‡Barbados cherry Grape Strawberry Calamondin Mango, ripe‡ Canistel‡ WatermelonBlackberry Kiwifruit†‡ Carambola Olive Casaba melonBlueberry Loganberry Cranberry Orange Cherimoya‡Boysenberry Longan Custard apple‡ Passion fruit Crenshaw melon‡Caimito Loquat Durian, ripe‡ Pepino Honeydew melon‡Cantaloup‡ Lychee Feijoa Pineapple JaboticabaCashew apple Nectarine Granadilla‡ Pummelo Jackfruit‡Cherry Peach Grapefruit† Sugar apple Mamey‡Coconut Pear (Asian & European) Guava‡ Tamarillo Mangosteen‡Currant Persimmon† Juan canary melon‡ Tamarind Papaya‡Fresh-cut fruits‡ Plum, ripe† Kumquat Tangelo Persian melon‡Date Plumcot, ripe† Lemon† Tangerine Plantain‡Dewberry Pomegranate Ugli fruit Rambutan

Source: Thompson et al. 1996*Ethylene should be kept below 1 μL L-1 (1 ppm) in the storage area.†Sensitive to ethylene damage.‡Produces significant ethylene.
57

Table 2. Compatible flowers, florist’s foliage, and nursery items during 7-day storage†

Group 1* Group 2 Group 3

0-2 °C; 85-95% RH 7-10 °C; 85-95% RH 13-18°C; 85-95% RH

Flowers Acacia Gaillardia Protea Anemone African violet

Alstroemeria Gardenia Rannunculas Bird of paradise Anthurium

Allium Gerbera Rose Camellia Ginger

Aster Gladiolus Snapdragon Eucharis Heliconia

Bouvardia Gypsophlia Snowdrop Gloriosa Orchid, cattleya, vandal

Buddleia Heather Squill Godetia Poinsettia

Calendula Hyacinth Statice Sweet-william Bulbs, corms, rhizomes,

Candytuft Iris Stephanotis tubers, & roots

Carnation Laceflower Stevia Nursery stock

Chrysanthemum Lilac Stock 

Clarkia Lily Strawflower

Columbine Lily-of-the-valley Sweet pea 

Coreopsis Lupine Tulip 

Cornflower Marigolds Violet 

Cosmos Mignonette Zinnia 

Crocus Narcissus Cuttings & 

 scions 

Dahlia Orchid, 

 cymbidium 

Daisy, English, Ornithogalum

 Marguerite, 

 Shasta 

Delphinium Poppy 

Feverfew Peony 

Forget-me-not Phlox 

Foxglove Primrose 

Freesia

Florist’s Adiantum Gallax Pittosporum Chamaedorea Dieffenbachia

 foliage (maidenhair) 

 (greens) Asparagus Ground pine Rhododendron Cordyline Staghorn fern

 (plumose)

Buxus Hedera Salal (lemon Palm

 (boxwood) leaf) 

Camellia Ilex (holly) Scotch-broom Podocarpus

Cedar Juniper Smilax 

Croton Leatherleaf Vaccinium

 (huckleberry) 

Dracaena Leucothoe Woodwardia 

 fern 

Fern, dagger, 

 wood Magnolia 

Eucalyptus Mistletoe 

 Mountain-laurel 

 Myrtus (myrtle) 

 Philodendron 

*Can be stored with group 1A vegetables in a mixed produce storage.

†

 Ethylene should be kept below 1 μL L-1 (1 ppm) in the storage area.
58

The two warmer temperature ranges in tables 1 

and 2 are for chilling-sensitive produce (groups 

2 and 3). The highest-temperature room can also 

be used to ripen fruit that only require a warm 

environment to ripen. If refrigerated space is 

limited, low-temperature fruits, vegetables, and 

flowers can be mixed in a room; air-conditioned 

space at 20 to 25 °C (68 to 77 °F) can be used for 

highest-temperature products (group 3).

Many green vegetables and most floral products 

are quite sensitive to ethylene damage. Ethylene 

must be kept away from these products. Minimize 

ethylene from nearby banana-ripening rooms by—

•	 using ethylene levels of 100 μL L-1 in the 

ripening rooms instead of the higher levels 

often used in commercial operations,

•	 venting ripening rooms to the outside after 

the exposure period is complete and before 

rooms are opened,

•	 ventilating the area around ripening rooms 

at least once a day or install an ethylene 

scrubber, and

•	 using battery-powered forklifts instead 

of internal combustion-driven units (for 

example, propane-powered units).

Floral products are particularly sensitive to 

ethylene. Some distribution facilities have found 

that the previously described precautions are 

inadequate in preventing damage to flowers. They 

have chosen to handle flowers with dairy or meat 

products, where ethylene is low, or they require 

that all floral products be chemically treated to 

resist ethylene damage.

Weak fiberboard containers are usually the cause 

of mechanical damage to produce between 

packing and retail display. If products arrive at the 

distribution facility in crushed boxes, store buyers 

must work with suppliers to use stronger boxes or 

ensure that packed boxes are correctly stacked and 

palletized.

The distribution center assembles pallets of mixed 

products to be shipped to retail outlets. Products 

can easily be damaged when boxes with different 

footprints are stacked and heavy bags of product 

are placed on weak boxes. Placing only strong 

containers on the bottom layers of a pallet load 

can minimize some of this damage. Plastic foam 

and returnable plastic containers are often stronger 

than typical fiberboard boxes and can reduce 

mechanical damage.

Most distribution facilities have special ripening 

rooms or areas reserved for fruit ripening. 

Ripening rooms are used extensively for bananas 

and may also be used to ripen avocados, kiwifruit, 

mangoes, tomatoes, nectarines, peaches, plums, 

and European pears. Pressurized or forced-air 

ripening rooms allow better control of ripening 

compared with older methods of space-stacking 

boxes in a warm room. The new designs force 

temperature-controlled air through the boxes to 

maintain fairly uniform product temperature. 

Ethylene gas (100 to 150 μL L-1) is added to the 

atmosphere on a schedule appropriate for each 

product, and CO2

 levels are kept below 1% by 

ventilating the rooms with outside air. Ripening 

is done with air temperature in the range of 15 

to 25 °C (59 to 77 °F), and water vapor is added 

to the air to keep RH above 85 to 95% in order 

to reduce moisture loss. The ripening of some 

products, like stone fruit and pears that were 

treated with ethylene at the packing operation, can 

be promoted by warming them to 13 to 18 °C (55 

to 64 °F).

Reference

Thompson, J., A.A. Kader, and K. Sylva. 1996. 

Compatibility chart for fruits and vegetables in 

short-term transport and storage. Nat. Res. Pub. 

no. 21560, University of California, Division of 

Agriculture and Natural Resources, Oakland, CA.
59

Grocery Store Display Storage

Adel A. Kader and James F. Thompson

Kader was with the Department of Plant 

Sciences, University of California, Davis, CA. 

He is deceased. Thompson is formerly with 

the Biological and Agricultural Engineering 

Department, University of California, Davis, CA. 

He is now retired.

Introduction

Fresh produce received at the grocery store is kept 

in storage rooms and display areas (in cabinets 

and cases or on racks and tables) for a few hours 

to a few days before purchase by consumers or 

removal by produce personnel. During this time, 

the key factors in maintaining quality are careful 

handling to minimize mechanical injuries, storage 

and display within optimum ranges of temperature 

and RH, and proper sanitation of storage and 

display areas. Expedited handling and effective 

rotation of the produce (first in, first out) is also 

recommended.

Storage Room

The number and size of storage rooms depend 

on store size and frequency of produce delivery 

to the grocery store. If three rooms are available 

for produce, they are best designated for shortterm storage of the three groups of fruits and 

vegetables mentioned in the chapter Wholesale 

Distribution Center Storage; that is, group 1 at 0 

to 2 oC (32 to 36 °F), group 2 at 7 to 10 °C (45 

to 50 °F), and group 3 at 13 to 18 oC (55 to 64 

°F). If only two rooms are available, one should 

be used for group 1 at 0 to 2 oC (32 to 36 °F) and 

the other for groups 2 and 3 (at a compromise 

temperature range of 10 to 14 oC [50 to 57 °F]). 

If only one room is available, it should be kept 

at a compromise temperature of 5 oC (41 °F) and 

used for groups 1 and 2, while group 3 should 

be kept in an air-conditioned area. Cut flowers 

and other ornamentals that are best kept at 0 to 2 

°C (32 to 36 °F) can be combined with group 1 

fruits and vegetables, because ethylene production 

and action at this temperature range are minimal. 

Ornamentals that are chilling-sensitive and 

ethylene-sensitive should be handled in a separate 

area from the ethylene-producing fruits of group 3 

to avoid ethylene damage.

All produce items should be near their optimum 

storage temperature when received at the grocery 

store and should be unloaded and moved quickly 

to their appropriate storage area. Keeping 

cold commodities at warmer temperatures for 

more than a few minutes can result in water 

condensation on the commodity, which may 

encourage the growth of decay-producing 

pathogens. RH should be kept within the optimum 

range of 85 to 95% for most commodities to 

minimize water loss. Good air circulation within 

the storage room is essential to maintain proper 

product temperature and RH. Thus, space for 

air movement should be kept around stacks or 

pallets of boxes and between them and the room 

walls. Enough fresh, ethylene-free air should be 

introduced into storage rooms to keep ethylene <1 

μL L-1 (<1 ppm), and preferably <0.1 μL L-1 (<0.1 

ppm) if it can be done economically using fresh 

air exchanges and/or ethylene scrubbing systems.

Display Fixtures

Most produce items in groups 1 and 2 should be 

displayed in refrigerated display cases. Display 

at store ambient air temperature is acceptable for 

some commodities, including produce that does 

not lose water quickly and has a long shelf-life 

like apple, pear, kiwifruit, and orange. Produce 

that is on sale (special promotion) or that will 

be on display for a few hours (like grapes and 

strawberries) can also be stored at ambient 

temperatures.

Ideally, the display case temperature range should 

match the recommended range for each group of 

commodities: 0 to 2 oC (32 to 36 °F) for group 

1, including all fresh-cut products, and 7 to 10 

°C (45 to 50 °F) for group 2. Since display cases 

usually do not have the refrigeration capacity to 

cool the products, it is important to ensure that 

the product is near its recommended temperature 
60

when it is placed in the display case. The produce 

should not obstruct the discharge air and return air 

outlets to maintain good cold air circulation within 

the case. Also, produce should not be stacked 

so densely that cold air circulation is blocked or 

so high that it is out of the refrigerated zone and 

becomes exposed to ambient air temperatures.

Refrigerated display cases have either a 

horizontal or a vertical air flow system and either 

single-tier or multi-tier display shelves. They 

should be equipped with easy-to-read, accurate 

thermometers, which should be calibrated and 

monitored regularly. Performance of refrigerated 

display cases is influenced primarily by their 

refrigeration capacity, defrost options, and air 

circulation system. Important secondary factors 

include temperature, RH, and movement of 

surrounding air and radiant heat from the lighting 

sources.

A 1989 survey of temperatures of fresh-cut 

salads kept in refrigerated display cases in a 

representative sample of grocery stores indicated 

an overall mean temperature of about 9 oC (48 

oF), with more than 78% having temperatures 

above about 7 oC (45 °F) and more than 17.5% 

having temperature above about 13 oC (55 °F) 

(R.W. Daniels, Audits International, personal 

communication, 1989). A survey of temperatures 

of fresh-cut vegetable products kept in refrigerated 

display cases in some grocery stores indicates an 

overall mean of about 5 oC (41 °F) with more than 

40% of the products having temperature above 

about 7 oC (45 °F) (Jeff Leshuk, Sensitech Inc., 

personal communication, 1989). This indicates 

significant improvements in maintaining the 

cold chain within the grocery stores, but more 

improvements are needed to bring the temperature 

range for fresh-cut products close to the 

recommended 0 to 2 °C (32 to 36 °F).

Water-loss reduction can be achieved by 

protecting produce from excessive air movement; 

packaging in perforated polymeric films 

(as moisture barriers); periodically adding 

sanitized, clean water by misting (only useful for 

commodities that tolerate wetting, such as those 

listed in table 1); and/or displaying on crushed 

ice (only useful for products that tolerate direct 

contact with ice). If ice is used, proper drainage 

of the melt water should be provided. It should 

be remembered that ice is not an effective way to 

keep the product cold unless it is well surrounded 

by the ice.

Table 1. Produce that benefit from misting while displayed in refrigerated cases

______________________________________________________________________________

Artichoke Corn, sweet Peppers

Asparagus* Eggplant Radishes

Beans, snap Endive Rhubarb

Beets Kale Shallots, green

Broccoli Leeks Spinach

Brussels sprouts Lettuce Sprouts

Cabbage Mustard greens Squash, summer

Carrots Onions, green Swiss chard

Cauliflower Parsley Turnips

Celery Parsnips Watercress

Collards Peas

______________________________________________________________________________

*Asparagus should be displayed vertically with cut ends on a wet absorbent pad.
61

Non-refrigerated display tables or racks are used 

for most group 3 fruits and vegetables, which 

should be displayed separately. Some of the fruits 

in groups 1 and 2, such as avocado, kiwifruit, and 

pear, may be displayed on non-refrigerated display 

tables or racks at ambient produce department 

temperatures to enhance their ripening. Daylightsimulating fluorescent bulbs can provide adequate 

lighting in the produce department without giving 

off heat.

During handling at the grocery store, all 

precautions should be taken to minimize potential 

chemical or microbial contamination to maintain 

safety of produce. All display tables, cases, 

cabinets, and other fixtures must be cleaned and 

sanitized regularly. Unmarketable produce should 

be collected separately from the other waste 

products and used for composting.

Further Reading

Anonymous. 1987. Professional Produce 

Manager’s Manual. National-American Wholesale 

Grocers’ Association (International Food Service 

Distributers), Falls Church, VA and Produce 

Marketing Association, Newark, DE.

Anonymous. 2011. Retail Fruit and Vegetable 

Marketing Guide, pp. 56. California Department 

of Public Health, Network for a Healthy 

California, Sacramento, CA. At

http://ucce.ucdavis.edu/files/datastore/234-2083.

pdf 

Nunes, M.C.N., J.P. Emond, M. Rauth, S. Dea, 

and K.V. Chau. 2009. Environmental conditions 

encountered during typical consumer retail display 

affect fruit and vegetable quality and waste. 

Postharv. Biol. Technol. 51:232-241.

Produce Marketing Association. 2002. The Fresh 

Produce Manual. Produce Marketing Association, 

Newark, DE.

Thompson, J.F., and A.A. Kader. 2009. From the 

Farm to Your Table, A Consumer’s Guide to Fresh 

Fruits and Vegetables. Publication no. 21643, 

Department of Agriculture and Natural Resources, 

University of California, Oakland, CA. At 

http://anrcatalog.ucdavis.edu/Items/21643.aspx
62

Chilling and Freezing Injury

Chien Yi Wang

Wang is formerly with the Food Quality 

Laboratory, Henry A. Wallace Beltsville 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. He is now retired.

Chilling Injury

Many fruits, vegetables, and ornamentals of 

tropical or subtropical origin are sensitive to low 

temperatures (Paull 1990). These crops are injured 

after a period of exposure to chilling temperatures 

below 10 to 15 °C (50 to 59 °F) but above their 

freezing points (Lyons 1973, Wang 1990). Certain 

horticultural crops of temperate origin are also 

susceptible to chilling injury (Bramlage and Meir 

1990). Those temperate crops, in general, have 

lower threshold temperatures of <5 °C (41 °F). 

At these chilling temperatures, the tissues weaken 

because they are unable to carry on normal 

metabolic processes. Various physiological and 

biochemical alterations and cellular dysfunctions 

occur in chilling-sensitive species in response 

to chilling stress (Wang 1982, Wang and Adams 

1982, Raison and Orr 1990). When chilling stress 

is prolonged, these alterations and dysfunctions 

will lead to the development of a variety of 

chilling injury symptoms such as surface lesions, 

internal discoloration, water-soaking of the tissue, 

and failure to ripen normally (Saltveit and Morris 

1990). Often, products that are chilled will still 

look sound when remaining in low temperatures. 

However, symptoms of chilling injury become 

evident shortly after they are moved to warmer 

temperatures. Fruits and vegetables that have 

been chilled may be particularly susceptible to 

decay. Weak pathogens such as Alternaria spp., 

which do not grow readily on healthy tissues, 

can attack tissues that have been weakened by 

low-temperature exposure (McColloch and 

Worthington 1952, McColloch 1962).

Both temperature and duration of exposure are 

involved in the development of chilling injury. 

Damage may occur in a short time if temperatures 

are considerably below the threshold level, but a 

product may be able to withstand temperatures 

a few degrees into the critical zone for a longer 

time before injury becomes irreversible. Maturity 

at harvest and degree of ripeness are important 

factors in determining chilling sensitivity in some 

fruits like avocados (Kosiyachinda and Young 

1976), honeydew melons (Lipton 1978), and 

tomatoes (McColloch et al. 1966). The effects of 

chilling are cumulative in some commodities. Low 

temperatures in transit, or even in the field shortly 

before harvest, add to the total effects of chilling 

that occur in cold storage.

Treatments shown to alleviate chilling injury 

include intermittent warming; high- or lowtemperature preconditioning; CA storage; 

pretreatments with ethylene, abscisic acid, methyl 

jasmonate, and other natural compounds; calcium 

or other chemical applications; hypobaric storage; 

waxing; film packaging; and genetic manipulation 

(Ryall and Lipton 1979, Wang 1993, 1994, Meir et 

al. 1996).

Chilling injury is discussed more specifically 

under each commodity. Many of the commodities 

susceptible to chilling injury are listed in table 

1 with threshold temperatures and some of the 

symptoms.
63

Table 1. Fresh produce susceptible to chilling injury when stored at low but 

nonfreezing temperatures

__________________________________________________________________

 Lowest Safe Temperature Symptoms of injury when stored

Commodity o C o F between 0 oC and safe temperature* __________________________________________________________________________

Apples—certain

cultivars 2-3† 36-38 Internal browning, brown core, soggy 

 breakdown, soft scald

Asparagus 0-2 32-36 Dull, gray-green, limp tips

Atemoya 4 39 Skin darkening, failure to ripen, pulp 

 discoloration

Avocados 4.5-13† 40-55 Grayish-brown discoloration of flesh

Bael 3 38 Brown spots on skin

Bananas 11.5-13† 53-56 Dull color when ripened

Bean (lima) 1-4.5 34-40 Rusty brown specks, spots or areas

Bean (snap) 7† 45 Pitting and russeting

Breadfruit 7-12 45-53 Abnormal ripening, dull brown 

 discoloration

Choyote 5-10 41-50 Dull brown discoloration, pitting, flesh 

 darkening

Cranberries 2 36 Rubbery texture, red flesh

Cucumbers 7 45 Pitting, water-soaked spots, decay

Eggplants 7 45 Surface scald, alternaria rot, blackening of 

 seeds

Ginger 7 45 Softening, tissue breakdown, decay

Guavas 4.5† 40 Pulp injury, decay

Grapefruit 10† 50 Scald, pitting, watery breakdown

Jicama 13-18 55-65 Surface decay, discoloration

Lemons 11-13† 52-55 Pitting, membranous staining, red blotch

Limes 7-9 45-48 Pitting, turning tan with time

Lychee 3 38 Skin browning

Mangos 10-13† 50-55 Grayish scald-like discoloration of skin, 

 uneven ripening

Mangosteen 4-8 39-47 Hardening and browning of the cortex

Melons

Cantaloupe 2-5† 36-41 Pitting, surface decay

Honeydew 7-10 45-50 Reddish-tan discoloration, pitting, surface 

 decay, failure to ripen

Casaba 7-10 45-50 Pitting, surface decay, failure to ripen

Crenshaw and 

 Persian 7-10 45-50 Pitting, surface decay, failure to ripen

Okra 7 45 Discoloration, water-soaked areas, pitting, 

 decay

Olive, fresh 7 45 Internal browning

Oranges 3† 38 Pitting, brown stain

Papayas 7 45 Pitting, failure to ripen, off flavors, decay
64

Table 1. Fresh produce susceptible to chilling injury when stored at low but 

nonfreezing temperatures—Continued

__________________________________________________________________

 Lowest Safe Temperature Symptoms of injury when stored

Commodity o C o F between 0 oC and safe temperature*

__________________________________________________________________________

Passion fruit 10 50 Dark red discoloration on skin, loss of 

flavor, decay

Peppers, sweet 7 45 Sheet pitting, alternaria rot on pods and 

 calyxes, darkening of seeds

Pineapples 7-10† 45-50 Dull green when ripe, internal browning

Pomegranates 4.5 40 Pitting, external and internal browning

Potatoes 3† 38 Mahogany browning, sweetening

Pumpkins and 

hardshell squash 10 50 Decay, especially alternaria rot

Rambutan 10 50 Darkening of exocarp

Sweet potatoes 13 55 Decay, pitting, internal discoloration, 

 hardcore when cooked

Tamarillos 3-4 37-40 Surface pitting, discoloration

Taro 10 50 Internal browning, decay

Tomatoes

Ripe 7-10† 45-50 Water soaking and softening, decay

Mature-green 13 55 Poor color when ripe, alternaria rot

Water convolvulus 10 50 Darkening of leaves and stems

Watermelons 4.5 40 Pitting, objectionable flavor

___________________________________________________________________________

*Symptoms often become apparent only after removal to warm temperatures, as in marketing.

†

See individual commodity sections in this Handbook.
65

Freezing Injury

The recommended storage temperatures for 

commodities that are not susceptible to chilling 

injury are as low as possible but slightly above 

the freezing point. Freezing injury occurs 

when ice crystals form in the tissues. Cultivars, 

locations, and growing conditions may affect 

the freezing point. To be on the safe side, the 

highest temperature at which freezing of a 

specific commodity may occur should be used as 

a guide for recommending the optimum storage 

temperature. More detailed discussion of freezing 

points and factors affecting them can be found 

in McColloch (1953), Whiteman (1957), and 

Parsons and Day (1970,1971). The most common 

symptom of freezing injury is a water-soaked 

appearance. Tissues injured by freezing generally 

lose rigidity and become mushy upon thawing. 

The susceptibility of different fresh fruits and 

vegetables to freezing injury varies widely. Some 

commodities may be frozen and thawed a number 

of times with little or no injury, whereas others are 

permanently injured by even a slight freezing. All 

fruits and vegetables can be categorized into three 

groups based on their sensitivity to freezing: most 

susceptible—those that are likely to be injured by 

even one light freezing, moderately susceptible—

those that will recover from one or two light 

freezing periods, and least susceptible—those that 

can be lightly frozen several times without serious 

damage. Table 2 shows the relative susceptibility 

of a number of fruits and vegetables to freezing 

injury.

Table 2. Susceptibility of fresh fruits and vegetables to freezing injury

__________________________________________________________________________

Most susceptible Moderately susceptible Least susceptible __________________________________________________________________________

Apricots Apples Beets

Asparagus Broccoli Brussels sprouts

Avocados Carrots Cabbage, mature and savory

Bananas Cauliflower Dates

Beans, snap Celery Kale

Berries (except cranberries) Cranberries Kohlrabi

Cucumbers Grapefruit Parsnips

Eggplants Grapes Rutabagas

Lemons Onion (dry) Salsify

Lettuce Oranges Turnips

Limes Parsley

Okra Pears

Peaches Peas

Peppers, sweet Radishes

Plums Spinach

Potatoes Squash, winter

Squash, summer

Sweet potatoes

Tomatoes

___________________________________________________________________________
66

The freezing point of the commodity is no 

indication of the damage to be expected by 

freezing. For example, both tomatoes and parsnips 

have freezing points of -1.1 to -0.6 °C (30 to 31 

°F), but parsnips can be frozen and thawed several 

times without apparent injury, whereas tomatoes 

are ruined after only one freezing. The severity 

of freezing injury is influenced by a combination 

of time and temperature. For example, apples 

that would be injured little by exposure to 

temperatures slightly below the freezing point 

for a few days would be severely injured by just 

a few hours of exposure to -7 to -10 °C (19 to 

14 °F). The susceptibility to freezing injury is 

not necessarily similar for the same type of fruit 

or vegetable. For example, leafy lettuce is very 

susceptible to freezing injury, whereas some other 

leafy vegetables, such as kale and cabbage, can 

withstand several light freezing periods without 

serious injury. 

When left undisturbed, most fruits and vegetables 

can usually be cooled one to several degrees 

below their freezing point before they actually 

freeze. This cooling without freezing is known 

as undercooling or supercooling. They may 

remain undercooled for several hours, but 

they will usually start to freeze immediately if 

jarred or moved. If permitted to warm above 

the freezing point, many commodities that have 

been undercooled may escape having ice crystals 

form in them. For example, potatoes, which are 

very sensitive to freezing damage, showed no 

freezing symptoms from having been undercooled 

for a short time to -4 °C (25 °F), about 3 °C (5 

°F) below their freezing point, when they were 

carefully warmed after undercooling (Hruschka et 

al. 1961).

Plant tissues are very sensitive to bruising while 

frozen, and this sensitivity is another reason for 

leaving commodities undisturbed until they have 

warmed. Selecting a suitable thawing temperature 

involves a compromise. Fast thawing damages 

tissues, but very slow thawing such as at 0 to 1 °C 

(32 to 34 °F) allows ice to remain in the tissues 

too long and causes injury. Research on the rate 

of thawing has suggested that thawing at 4 °C (39 

°F) causes the least damage for most commodities 

(Lutz 1936). Even though a number of fruits and 

vegetables are somewhat tolerant to freezing, 

commodities recovered from freezing often have 

shorter storage life and are more susceptible 

to invasion by microorganisms. For example, 

apples that recover from freezing are softer than 

normal fruit, and carrots that have been frozen 

are especially subject to decay. Therefore, it is 

best to avoid subjecting fresh produce to freezing 

temperatures in the first place.

References

Bramlage, W.J., and S. Meir. 1990. Chilling injury 

of crops of temperate origin. In C.Y. Wang, ed., 

Chilling Injury of Horticultural Crops, pp. 37-49. 

CRC Press, Boca Raton, FL.

Hruschka, H.W., R.V. Akeley, and E.H. Ralph. 

1961. Seed potato productivity after cooling, 

supercooling or freezing. Marketing Research 

Report 507, U.S. Department of Agriculture, 

Washington, DC.

Kosiyachinda, S., and R.E. Young. 1976. Chilling 

sensitivity of avocado fruit at different stages of 

the respiratory climacteric. J. Amer. Soc. Hort. 

Sci. 101:665-667.

Lipton, W.J. 1978. Chilling injury of ‘Honey Dew’ 

muskmelons: symptoms and relation to degree of 

ripeness at harvest. HortScience 13:45-46.

Lutz, J.M. 1936. The influence of rate of thawing 

on freezing injury of apples, potatoes and onions. 

Proc. Amer. Soc. Hort. Sci. 33:227-233.

Lyons, J.M. 1973. Chilling injury in plants. Ann. 

Rev. Plant Physiol. 24:445-466.

McColloch, L.P. 1953. Injuries from chilling 

and freezing. In Plant Diseases, the Yearbook of 

Agriculture 1953, pp. 826-830. U.S. Department 

of Agriculture, Washington, DC.
67

Saltveit, M.E., and L.L. Morris. 1990. Overview 

on chilling injury of horticultural crops. In C.Y. 

Wang, ed., Chilling Injury of Horticultural Crops, 

pp. 3-15. CRC Press, Boca Raton, FL.

Wang, C.Y. 1982. Physiological and biochemical 

responses of plants to chilling stress. HortScience 

17:173-186. 

Wang, C.Y. 1990. Chilling Injury of Horticultural 

Crops. CRC Press, Boca Raton, FL.

Wang, C.Y. 1993. Approaches to reduce chilling 

injury of fruits and vegetables. Hort. Rev. 15:63-

95.

Wang, C.Y. 1994. Reduction of chilling injury by 

methyl jasmonate. Acta. Hort. 368:901-907.

Wang, C.Y., and D.O. Adams. 1982. Chillinginduced ethylene production in cucumbers 

(Cucumis sativus L). Plant Physiol. 69:424-427.

Whiteman, T.M. 1957. Freezing points of fruits, 

vegetables and florist stocks. Marketing Research 

Report 196, U.S. Department of Agriculture, 

Washington, DC.

McColloch, L.P. 1962. Alternaria rot following 

chilling injury of acorn squashes. Marketing 

Research Report 518, U.S. Department of 

Agriculture, Washington, DC.

McColloch, L.P., and J.T. Worthington. 1952. 

Low temperature as a factor in the susceptibility 

of mature-green tomatoes to Alternaria rot. 

Phytopathology 42:425-427.

McColloch, L.P., J.N. Yeatman, and P. Loyd. 

1966. Color changes and chilling injury of pink 

tomatoes held at various temperatures. Marketing 

Research Report 735, U.S. Department of 

Agriculture, Washington, DC.

Meir, S., S. Philosoph-Hadas, S. Lurie, et al. 1996. 

Reduction of chilling injury in stored avocado, 

grapefruit, and bell pepper by methyl jasmonate. 

Can. J. Bot. 74:870-874.

Parsons, C.S., and R.H. Day. 1970. Freezing 

injury of root crops: Beets, carrots, parsnips, 

radishes, and turnips. Marketing Research Report 

866, U.S. Department of Agriculture, Washington, 

DC.

Parsons, C.S., and R.H. Day. 1971. Freezing 

injury to bell peppers. Marketing Research Report 

895, U.S. Department of Agriculture, Washington, 

DC.

Paull, R.E. 1990. Chilling injury of crops of 

tropical and subtropical origin. In C.Y. Wang, ed., 

Chilling Injury of Horticultural Crops, pp. 17-36. 

CRC Press, Boca Raton, FL.

Raison, J.K., and G.R. Orr. 1990. Proposals for 

a better understanding of the molecular basis of 

chilling injury. In C.Y. Wang, ed., Chilling Injury 

of Horticultural Crops, pp. 145-164. CRC Press, 

Boca Raton, FL.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melons, 2nd ed. 

AVI Publishing Company, Westport, CT.
68

Respiratory Metabolism

Mikal E. Saltveit

Saltveit is with Mann Laboratory, Department of 

Vegetable Crops, University of California, Davis, 

CA.

Introduction

All of the commodities covered in this handbook 

are alive and carry on processes characteristic of 

all living things. One of the most important of 

these is respiratory metabolism. The process of 

respiration involves combining O2

 in the air with 

organic molecules in the tissue (usually a sugar) 

to form various intermediate compounds and 

eventually CO2

 and water. Energy produced by 

the series of reactions making up respiration can 

be captured as high-energy bonds in compounds 

used by the cell in subsequent reactions, or it can 

be lost as heat. The energy and organic molecules 

produced during respiration are used by other 

metabolic processes to maintain the health of the 

commodity. Heat produced during respiration 

is called “vital heat,” and it contributes to the 

refrigeration load that must be considered in 

designing storage rooms.

There is little the postharvest physiologist can do 

to alter the internal factors affecting respiration 

of harvested commodities, because they are 

largely a function of the commodity itself once 

harvested. However, a major part of postharvest 

technology is devoted to reducing respiration 

and other metabolic reactions associated with 

quality retention by manipulating the external 

environment. 

In general, the storage life of commodities varies 

inversely with the rate of respiration. This is 

because respiration supplies compounds that 

determine the rate of metabolic processes directly 

related to quality parameters such as firmness, 

sugar content, aroma, and flavor. Commodities 

and cultivars with higher rates of respiration 

tend to have shorter storage life than those with 

lower rates of respiration. Storage life of broccoli, 

lettuce, peas, spinach, and sweet corn, all of which 

have high respiration rates, is short in comparison 

to that of apples, cranberries, limes, onions, and 

potatoes, all of which have low respiration rates 

(table 1).

Table 1. Respiration rates of various perishable commodities

_____________________________________________________________________________________________

Class Range at 5 °C Commodities

_____________________________________________________________________________________________

mg CO2 kg-1 h-1

Very Low <5 Nuts, dates

Low 5 to 10 Apple, citrus, grape, kiwifruit, onion, potato

Moderate 10 to 20 Apricot, banana, cherry, peach, nectarine, pear, plum, fig, 

cabbage, carrot, lettuce, pepper, tomato

High 20 to 40 Strawberry, blackberry, raspberry, cauliflower, lima bean, 

avocado

Very High 40 to 60 Artichoke, snap bean, Brussels sprouts, cut flowers

Extremely High >60 Asparagus, broccoli, mushroom, pea, spinach, sweet corn

_____________________________________________________________________________________________
69

Factors Affecting Respiration

Respiration is affected by a wide range of 

environmental factors that include light, chemical 

stress (for example, fumigants), radiation stress, 

water stress, growth regulators, and pathogen 

attack. The most important postharvest factors 

are temperature, atmospheric composition, and 

physical stress.

Temperature. The most important factor 

affecting postharvest life is temperature, because 

temperature has a profound effect on the rates of 

biological reactions; for example, metabolism 

and respiration. Over the physiological range of 

most crops, 0 to 30 °C (32 to 86 °F), increased 

temperatures cause an exponential rise in 

respiration. The Van’t Hoff Rule states that the 

velocity of a biological reaction increases 2 to 

3-fold for every 10 °C (18 °F) rise in temperature.

The temperature quotient for a 10 °C (18 

°F) interval is called the Q10. The Q10 can be 

calculated by dividing the reaction rate at a 

higher temperature by the rate at a 10 °C (18 °F) 

lower temperature: Q10 = R2

/R1. The temperature 

quotient is useful because it allows us to calculate 

the respiration rates at one temperature from a 

known rate at another temperature. However, the 

respiration rate does not follow ideal behavior, and 

the Q10 can vary considerably with temperature. 

At higher temperatures, the Q10 is usually smaller 

than that at lower temperatures.

The following are typical values for Q10 at various 

temperature ranges:

Temperature Q10

0 to 10 °C 2.5 to 4.0

10 to 20 °C 2.0 to 2.5

20 to 30 °C 1.5 to 2.0

30 to 40 °C 1.0 to 1.5

These typical Q10 values allow us to construct a 

table showing the effect of different temperatures 

on the rates of respiration or deterioration 

and relative shelf-life of a typical perishable 

commodity (table 2). This table shows that, if a 

commodity has a mean shelf-life of 13 days at 20 

°C (68 °F), it can be stored for as long as 100 days 

at 0 °C (32 °F) but will last no more than 4 days at 

40 °C (104 °F).

Table 2. Effect of temperature on rate of 

deterioration

________________________________________

Temperature Assumed Relative Relative

Q10 velocity of shelf-life

 deterioration

________________________________________

°C

 0 — 1.0 100

10 3.0 3.0 33

20 2.5 7.5 13

30 2.0 15.0 7

40 1.5 22.5 4

________________________________________

Chilling stress. Although respiration is normally 

reduced at low but nonfreezing temperatures, 

certain commodities, chiefly those originating 

in the tropics and subtropics, exhibit abnormal 

respiration when their temperature falls below 

10 to 12 °C (50 to 54 oF). Typically, the Q10

is much higher at those low temperatures for 

chilling-sensitive crops than it would be for 

chilling-tolerant ones. Respiration may increase 

dramatically at the chilling temperatures or 

when the commodity is returned to nonchilling 

temperatures. This enhanced respiration 

presumably reflects the cells’ efforts to detoxify 

metabolic intermediates that accumulated during 

chilling, as well as to repair damage to membranes 

and other subcellular structures. Enhanced 

respiration is only one of many symptoms that 

signal the onset of chilling injury.

Heat stress. As the temperature rises beyond 

the physiological range, the rate of increase in 

respiration falls. It becomes negative as the tissue 

nears its thermal death point, when metabolism 

is disorderly and enzyme proteins are denatured. 

Many tissues can tolerate high temperatures for 

short periods of time (for example, minutes), 

and this property is used to advantage in killing 
70

surface fungi on some fruits. Continued exposure 

to high temperature results in phytotoxic 

symptoms and then complete tissue collapse. 

However, conditioning and heat shocks—

that is, short exposure to potentially injurious 

temperatures—can modify the tissue’s responses 

to subsequent harmful stresses. 

Atmospheric composition. Adequate O2

 levels 

are required to maintain aerobic respiration. The 

exact level of O2

 that reduces respiration while 

still permitting aerobic respiration varies among 

commodities. In most crops, O2

 levels at around 

2% to 3% produce a beneficial reduction in the 

rate of respiration and other metabolic reactions. 

Levels as low as 1% improve the storage life of 

some crops—for example, apples—but only when 

the storage temperature is optimal. At higher 

storage temperatures, the demand for adenosine 

triphosphate (ATP) may outstrip the supply and 

promote anaerobic respiration (see chapters 

“Controlled Atmosphere Storage” and “Modified 

Atmosphere Packaging”). The need for adequate 

O2

 should be considered in selecting the various 

postharvest handling procedures, such as waxing 

and other surface coatings, film wrapping, and 

packaging. Unintentional modification of the 

atmosphere, by packaging for example, can result 

in production of undesirable fermentative products 

and development of foul odors.

Increasing the CO2

 level around some 

commodities reduces respiration, delays 

senescence, and retards fungal growth. In low 

O2

 environments, however, increased CO2 levels 

can promote fermentative metabolism. Some 

commodities tolerate brief storage in a pure N2

atmosphere (for example, a few days at low 

temperatures) or in very high concentrations of 

CO2

. The biochemical basis for this ability to 

withstand these atmospheres is unknown.

Physical stress. Even mild physical stress can 

perturb respiration, while physical abuse can 

cause a substantial rise in respiration that is often 

associated with increased ethylene evolution. The 

signal produced by physical stress migrates from 

the site of injury and induces a wide range of 

physiological changes in adjacent, non-wounded 

tissue. Some of the more important changes 

include enhanced respiration, ethylene production, 

phenolic metabolism, and wound healing. 

Wound-induced respiration is often transitory, 

lasting a few hours or days. However, in some 

tissues, wounding stimulates developmental 

changes, such as promotion of ripening, that 

result in a prolonged increase in respiration. 

Ethylene stimulates respiration and stress-induced 

ethylene may have many physiological effects on 

commodities besides stimulating respiration.

Stage of development. Respiration rates vary 

among and within commodities. Storage organs 

such as nuts and tubers have low respiration 

rates. Tissues with vegetative or floral meristems 

such as asparagus and broccoli have very high 

respiration rates. As plant organs mature, their rate 

of respiration typically declines. This means that 

commodities harvested during active growth, such 

as many vegetables and immature fruits, have high 

respiration rates. Mature fruits, dormant buds, and 

storage organs have relatively low rates.

After harvest, the respiration rate typically 

declines—slowly in nonclimacteric fruits and 

storage organs and rapidly in vegetative tissues 

and immature fruits. The rapid decline presumably 

reflects depletion of respirable substrates, which 

are typically low in such tissues. An important 

exception to the general decline in respiration 

following harvest is the rapid and sometimes 

dramatic rise in respiration during the ripening of 

climacteric fruit (figure 1). This rise, which has 

been the subject of intense study for many years, 

normally consists of four distinct phases: (1) 

preclimacteric minimum, (2) climacteric rise, (3) 

climacteric peak, and (4) postclimacteric decline.
71

Figure 1. The climacteric pattern of respiration in ripening 

fruit.

The division of fruits into climacteric and 

nonclimacteric types has been very useful for 

postharvest physiologists. However, some fruits, 

kiwifruit and cucumber for example, appear 

to blur the distinction between the groups. 

Respiratory rises also occur during stress and 

other developmental stages, but a true climacteric 

only occurs coincident with fruit ripening. The 

following is a general classification of fruits 

according to their respiratory behavior during 

ripening:

Climacteric Fruits Nonclimacteric Fruits

Apple Papaya Blueberry

Apricot Passion fruit Cacao

Avocado Peach Caju

Banana Pear Cherry

Biriba Persimmon Cucumber

Breadfruit Plum Grape

Cherimoya Sapote Grapefruit

Feijoa Soursop Lemon

Fig Tomato Lime

Guava Watermelon Olive

Jackfruit Orange

Kiwifruit Pepper

Mango Pineapple

Muskmelon Strawberry

Nectarine Tamarillo

Significance of Respiration

Shelf-life and respiration rate. In general, there 

is an inverse relationship between respiration rates 

and postharvest life of fresh commodities. The 

higher the respiration rate, the more perishable 

the commodity usually is; that is, the shorter 

postharvest life it has. Respiration plays a major 

role in the postharvest life of fresh commodities 

because it reflects the metabolic activity of the 

tissue that also includes the loss of substrate, the 

synthesis of new compounds, and the release 

of heat energy. See the section “Summary of 

Respiration and Ethylene Production Rates” in the 

Introduction of this Handbook.

Loss of substrate. Use of various substrates in 

respiration can result in loss of food reserves in 

the tissue and loss of taste quality (especially 

sweetness) and food value to the consumer. 

For certain commodities that are stored for 

extended periods of time, such as onions used for 

dehydrated product, the loss of dry weight due 

to respiration can be significant. When a hexose 

sugar (for example, glucose) is the substrate, 180 

g of sugar is lost for each 264 g of CO2

 produced 

by the commodity. The rate of dry weight loss can 

be estimated as follows: 

Dry weight loss (g kg-1 h-1) = 

Respiration (mg CO2 kg-1 h-1) × 0.068 

or 

% dry weight loss (g 100 g-1 h-1) = 

Respiration (mg CO2 kg-1 h-1) × 68 × 10-6

For example, onions held at 30 °C (86 °F) 

will respire at about 35 mg CO2

 kg-1 h-1. The 

percentage dry weight loss per hour would be 

35 x 0.68/10,000 = 0.0024%, while the percentage 

dry weight loss per month would be 0.0024 x 24 x 

30 = 1.73%.

Synthesis of new compounds. Postharvest 

storage can be used either to prevent any 

reduction in quality or to promote changes that 

increase quality. The quality of most vegetables 

(for example, cucumbers and lettuce) and 

nonclimacteric fruit (for example, strawberries) 

is maximal at harvest, and storage conditions are 
72

optimized to prevent quality loss. In contrast, 

many flowers (for example, carnations and 

roses), nonclimacteric fruit (for example, 

lemons and oranges), and climacteric fruit (for 

example, bananas and tomatoes) are harvested 

before they reach their best quality, and storage 

conditions are optimized to permit development 

of optimum quality. In the first case, the synthesis 

of new compounds is unnecessary because they 

lead to reduced quality (for example, enzymes 

that destroy chlorophyll in lettuce or promote 

lignification in asparagus). In the second case, 

synthesis of pigments and volatiles (for example, 

lycopene in tomatoes and amyl esters in banana), 

loss of chlorophyll (for example, chlorophylldegrading enzymes in banana and lemons), and 

the conversion of starch to sugar (for example, 

sweetening of apples and bananas) is necessary for 

development of maximum quality. These synthetic 

reactions require energy and organic molecules 

derived from respiration.

Release of heat energy. The heat produced by 

respiration (vital heat), about 673 kcal for each 

mole of sugar (180 g) used, can be a major factor 

in establishing the refrigeration requirements 

during transport and storage. Vital heat must 

be considered in selecting proper methods 

for cooling, package design, and stacking of 

packages, as well as selection of refrigerated 

storage facilities (that is, refrigeration capacity, 

air circulation, and ventilation). The approximate 

rates of heat production by various crops at 

different storage temperatures can be calculated 

from the respiration rates for many fruits and 

vegetables given in section “Summary of 

Respiration and Ethylene Production Rates” in the 

Introduction of this Handbook.

Calculation of heat production from the respiration 

equation shows that production of 1 mg of CO2

yields 2.55 cal. In the language of the refrigeration 

engineer, a respiration rate of 1 mg CO2

 kg-1 h-1

indicates heat production of 61.2 kcal tonne-1 day1

(220 BTU ton-1 day-1). The British thermal unit 

(BTU) is the heat required to raise 1 lb of water by 

1 °F.

Some commodities have high respiration rates 

and require considerably more refrigeration than 

more slowly respiring produce to keep them at a 

specified temperature. For example, asparagus, 

broccoli, mushrooms, and peas respire about 10 

times faster than apples, cabbage, lemons, and 

tomatoes.

Meaning of the respiratory quotient (RQ). 

The composition of a commodity frequently 

determines which substrates are used in respiration 

and consequently the value of the respiratory 

quotient (RQ). RQ is defined as the ratio of CO2

produced to O2

 consumed; CO2 and O2 can be 

measured in moles or volumes. Depending on 

the substrate being oxidized, RQ values for fresh 

commodities range from 0.7 to 1.3 for aerobic 

respiration. When carbohydrates are being 

aerobically respired, RQ is near 1, while it is <1 

for lipids and >1 for organic acids. Very high RQ 

values usually indicate anaerobic respiration in 

those tissues that produce ethanol. In such tissues, 

a rapid change in RQ can be used as an indication 

of the shift from aerobic to anaerobic respiration.

Measuring the Rate of Respiration

The rate of any reaction can be determined 

by measuring the rate at which the substrates 

disappear or the products appear. Apart from the 

water produced by respiration, which is relatively 

trivial compared with the very high water content 

of most harvested commodities, all the substrates 

and products of respiration have been used to 

determine the rate of respiration. They are loss 

of substrate (for example, glucose) loss of O2

, 

increase in CO2

, and production of heat. The most 

commonly used method is to measure production 

of CO2

 with either a static or a dynamic system.

In a static system, the commodity is enclosed in an 

airtight container and gas samples are taken after 

sufficient CO2

 has accumulated to be accurately 

detected by any one of a number of commercially 

available instruments (for example, gas 

chromatograph and infrared CO2

 analyzer). If the 

container is properly sealed, CO2

 should increase 

linearly with time. Multiplying the change in 
73

concentration times the container volume and 

dividing by weight of the commodity and duration 

of time between samples gives the production rate. 

In the dynamic system a flow of air (or other 

gas mixture) is passed through the container 

at a known rate. The system will come into 

equilibrium (>99.3%) in about the same time it 

takes for 5 times the volume to flow through the 

container. The difference in CO2

 concentration 

between the inlet and outlet is measured after 

the system has reached equilibrium by taking 

gas samples at both points and analyzing them. 

Multiplying the difference in concentration by 

the flow rate and dividing by the weight of the 

commodity calculates the production rate.

Biochemistry of Respiration

Respiration is the oxidative breakdown of 

complex substrate molecules normally present in 

plant cells, such as starches, sugars, and organic 

acids, to simpler molecules such as CO2

 and H2O. 

Concomitant with this catabolic reaction is the 

production of energy and intermediate molecules 

that are required to sustain the myriad of 

metabolic reactions essential for the maintenance 

of cellular organization and membrane integrity 

of living cells. Since respiration rate is so tightly 

coupled to the rate of metabolism, measurements 

of respiration provide an easy, nondestructive 

means of monitoring the metabolic and 

physiological state of tissues. For example, events 

of senescence and ripening are often signaled by 

abrupt changes in respiration.

Maintaining a supply of high-energy compounds 

like adenosine triphosphate (ATP), nicotinamide 

adenine dinucleotide (NADH), and pyrophosphate 

(PPi) is a primary function of respiration. The 

overall process of aerobic respiration involves 

regeneration of ATP from ADP (adenosine 

diphosphate) and Pi

 (inorganic phosphate) with 

release of CO2

 and H2O. If glucose is used as 

substrate, the overall equation for respiration can 

be written as follows:

C6

H12O6 + 6 O2 → 6 CO2 + 6 H2O + 686 kcal mole-1

The components of this reaction have various 

sources and destinations. The one mole of glucose 

(180 g) can come from stored simple sugars like 

glucose and sucrose or complex polysaccharides 

like starch. Fats and proteins can also provide 

substrates for respiration, but their derivatives 

(fatty acids, glycerol, and amino acids) enter at 

later stages in the overall process and as smaller, 

partially metabolized molecules. The 192 g of 

O2

 (6 moles × 32 g mol-1) used to oxidize the 

1 mole of glucose diffuses into the tissue from 

the surrounding atmosphere, while the 6 moles 

of CO2

 (264 g) diffuses out of the tissue. The 6 

moles of H2

O (108 g) that are produced are simply 

incorporated into the aqueous solution of the cell.

There are three fates for the energy (686 kcal mol-1) 

released by aerobic respiration. Around 13 kcal is 

lost due to the increase in entropy (disorder) when 

the complex glucose molecule is broken down 

into simpler molecules. Of the remaining 673 kcal 

that are capable of doing work, around 281 kcal 

(about 41% of the total energy) is used to produce 

38 ATP molecules (38 ATP × 7.4 kcal ATP-1). 

The remaining 392 kcal (57%) is lost as heat. In 

actuality, most energy is lost as heat since energy is 

lost to heat every time energy is transferred during 

a metabolic reaction.

Aerobic respiration involves a series of three 

complex reactions, each of which is catalyzed by 

a number of specific enzymes that perform one of 

the following actions: add an energy-containing 

phosphate group to the substrate molecule, 

rearrange the molecule, and break down the 

molecule to a simpler one. The three interconnected 

metabolic pathways are glycolysis, tricarboxylic 

acid (TCA) cycle, and electron transport system. 

Glycolysis, the breakdown, or lysing, of glucose, 

occurs in the cytoplasm of the cell. It involves the 

production of two molecules of pyruvate from 

each molecule of glucose. Each of the 10 distinct, 

sequential reactions in glycolysis is catalyzed by 

one enzyme. Two key enzymes in glycolysis are 

phosphofructokinase (PFK) and pyruvate kinase 
74

(PK). Cells can control their rate of energy 

production by altering the rate of glycolysis, 

primarily through controlling PFK and PK 

activity. One of the products of respiration, ATP, 

is used as a negative feedback inhibitor to control 

the activity of PFK. Glycolysis produces two 

molecules of ATP and two molecules of NADH 

from the breakdown of each molecule of glucose.

Tricarboxylic acid (TCA) cycle, which occurs in 

the mitochondrial matrix, involves the breakdown 

of pyruvate into CO2

 in nine sequential, enzymatic 

reactions. Pyruvate is decarboxylated (removal of 

CO2

) to form acetate, which condenses with a coenzyme to form acetyl CoA. This compound then 

enters the cycle by condensation with oxaloacetate 

to form citric acid. Citric acid has three 

carboxyl groups from which the cycle derives 

its name. Through a series of seven successive 

rearrangements, oxidations, and decarboxylations, 

citric acid is converted back into oxaloacetate 

that is then ready to accept another acetyl CoA 

molecule. In addition to producing the many small 

molecules that are used in the synthetic reactions 

of the cell, the TCA cycle also produces one 

molecule of flavin adenine dinucleotide (FADH2

) 

and four molecules of NADH for each molecule 

of pyruvate metabolized. 

Electron transport system, which occurs on 

membranes in the mitochondria, involves 

the production of ATP from the high-energy 

intermediates FADH2

 and NADH. The energy 

contained in a molecule of NADH or FADH2

 is 

more than is needed for most cellular processes. 

In a series of reactions, one NADH molecule 

produces three ATP molecules, while one FADH 

molecule produces two ATP molecules. The 

production of ATP depends not only on the energy 

contained in NADH and FADH2

 but also on the 

chemical environment (pH and ion concentrations) 

within the cell and mitochondria.

In the absence of O2

, NADH and FADH2

accumulate in the reduced form. As the oxidized 

forms (NAD+

 and FAD) are consumed, the TCA 

cycle comes to a halt and glycolysis becomes 

the sole source of ATP production. Regeneration 

of NAD+

 is absolutely essential for the survival 

of the anaerobic cell and takes place during the 

reductive decarboxylation of pyruvate to ethanol 

in fermentative metabolism.

Fermentation, or anaerobic respiration, involves 

the conversion of hexose sugars into alcohol and 

CO2

 in the absence of O2. Pyruvate produced 

through glycolysis via a series of reactions that 

do not require O2

 can be converted to lactic acid, 

malic acid, acetyl CoA, or acetaldehyde. The 

pathway chosen depends on cellular pH, prior 

stresses, and the current metabolic needs of the 

cell. Acidification of the cytoplasm enhances the 

activity of pyruvic decarboxylase that then shunts 

pyruvate to form CO2

 and acetaldehyde. The 

acetaldehyde is converted by the enzyme alcohol 

dehydrogenase to ethanol with the regeneration 

of NAD+

. Two molecules of ATP and 21 kcal of 

heat energy are produced in anaerobic respiration 

(alcoholic fermentation) from each molecule of 

glucose. To maintain the supply of ATP at the 

aerobic rate, 19 times as many glucose molecules 

would be needed, and glycolysis would increase 

19-fold. However, since only two molecules of 

CO2

 are produced during glycolysis, instead of 

six during aerobic respiration, the rate of CO2

production would not increase by 19-fold but only 

by 6.3-fold (that is, 19 ÷ 3). Concomitantly, there 

would be substantial accumulation of ethanol 

and smaller amounts of acetaldehyde. However, 

glycolysis usually increases only 3- to 6-fold. 

The O2 concentration at which a shift from 

predominantly aerobic to predominantly anaerobic 

respiration occurs varies among tissues and is 

known as the extinction point, the anaerobic 

compensation point, and the fermentative 

threshold. Since O2 concentration at any point in a 

fruit or vegetable varies with rates of gas diffusion 

and respiration, some parts of the commodity may 

become anaerobic while others remain aerobic.
75

Further Reading

Abeles, F.B., P.W. Morgan, and M.E. Saltveit. 

1992. Ethylene in Plant Biology, 2nd ed. 

Academic Press, New York, NY.

Biale, J.B., and R.E. Young. 1981. Respiration and 

ripening in fruits—retrospect and prospect. In J. 

Friend and M.J.C. Rhodes, eds., Recent Advances 

in the Biochemistry of Fruits and Vegetables, pp 

1-39. Academic Press, New York, NY.

Kays, S.J. 1991. Postharvest Physiology of 

Perishable Plant Products. Van Nostrand, New 

York, NY. 

Lopez-Galvez, G., M.E. Saltveit, and M. Cantwell. 

1996. Wound-induced phenylalanine ammonia 

lyase activity: factors affecting its induction 

and correlation with the quality of minimally 

processed lettuce. Postharv. Biol. Technol. 9:223-

233.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melon, 2nd ed., 

pp. 1-13. AVI Publishing Company, Westport, CT.

Ryall A.L., and W.T. Pentzer. 1974. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 2, Fruits, pp. 4-12. AVI 

Publishing Company, Westport, CT.

Saltveit, M.E. 1996. Physical and physiological 

changes in minimally processed fruits and 

vegetables. In F.A. Tomás-Barberán, ed., 

Phytochemistry of Fruit and Vegetables, pp. 205-

220. Oxford University Press, New York, NY.

Tomás-Barberán, F.A., J. Loaiza-Velarde, A. 

Bonfanti, and M.E. Saltveit. 1997. Early woundand ethylene-induced changes in phenylpropanoid 

metabolism in harvested lettuce. J. Amer. Soc. 

Hort. Sci. 122(3):399-404.

Wills, R.H.H., T.H. Lee, D. Graham, et al. 1981. 

Postharvest - An Introduction to the Physiology 

and Handling of Fruit and Vegetables. AVI 

Publishing Company, Westport, CT.
76

Ethylene Effects

Mikal E. Saltveit

Saltveit is with Mann Laboratory, Department of 

Plant Sciences, University of California, Davis, 

CA.

Introduction

Ethylene (C2H4) is a simple, naturally occurring 

organic molecule that is a colorless gas at 

biological temperatures. The following is a list of 

biological attributes of ethylene:

•	It is a colorless gas at biological 

temperatures.

•	It is a naturally occurring organic compound.

•	It readily diffuses from tissue.

•	It is produced from methionine via 

aminocyclopropane carboxylate (ACC) by a 

highly regulated metabolic pathway.

•	Key enzymes are ACC synthase and ACC 

oxidase.

•	C2

H4 synthesis is inhibited by C2H4 in 

vegetative and immature reproductive tissue.

•	C2

H4 synthesis is promoted (autocatalytic) 

by C2

H4 in mature reproductive climacteric 

tissue.

•	It is effective at ppm and ppb concentrations 

(1 ppm = 6.5 x 10-9 M at 25 °C).

•	It requires O2

 to be synthesized, and O2 and 

low levels of CO2

 to be active.

Many biotic and abiotic sources contribute 

to the presence of C2

H4 in the postharvest 

environment. Ripening and diseased plant tissues 

are a significant source of C2

H4, as are industrial 

sources, the most prominent ones being internal 

combustion engines and fires. 

Ethylene is biologically active at very low 

concentrations measured in the ppm and ppb 

range. Most plants synthesize small amounts 

of C2

H4 that appear to coordinate growth and 

development. Because it is a gas, C2

H4 readily 

diffuses from sites of production, and continuous 

synthesis is needed to maintain biologically active 

levels in the tissues. Barriers to diffusive loss 

include not only the commodity’s epidermis but 

also postharvest coatings and packaging. Under 

biotic or abiotic stress or during climacteric 

ripening, C2

H4 production can increase 

dramatically, and emanations from stimulated 

tissue can accumulate in packages or storerooms 

and produce unwanted effects in adjacent tissue. 

Other molecules with specific configurations can 

mimic C2

H4 but are less effective. For example, 

C2

H4 analogs propylene (C3H6) and acetylene 

(C2

H2) require 100- and 2,700-fold, respectively, 

the concentration of C2

H4 to elicit the same effect.

Plants produce C2

H4 through an actively 

regulated biosynthetic pathway in which the 

amino acid methionine is converted to ACC 

(1-aminocyclopropane-1-carboxylic acid) and 

then to C2

H4 through a series of biochemical 

reactions. O2

 is required for the synthesis of C2H4

and both O2

 and CO2 are required for its biological 

activity. Each reaction in the synthesis and action 

of C2

H4 involves a biological catalyst, an enzyme 

that focuses the reaction into producing the next 

specific chemical for that pathway. Enzyme 

activity is regulated either through its synthesis 

and/or destruction, or by interactions with 

substrates and products. These interactions can 

create a positive or a negative feedback of C2

H4 on 

its synthesis (figure 1).

Figure 1. Effect of adding and removing ethylene from the 

atmosphere surrounding tissues that respond with a positive 

(ethylene promotes its own synthesis) or negative (ethylene 

inhibits its own synthesis) feedback. Modified from Saltveit 

(1999).

Removal of 

ethylene

Time 

Ethylene concentration 

Addition of 

ethylene

Positive 

feedback

Negative 

feedback

Removal of 

ethylene

Time 

Ethylene concentration 

Addition of 

ethylene

Positive 

feedback

Negative 

feedback
77

In vegetative tissue and in nonclimacteric and 

immature climacteric fruit tissue, C2

H4 suppresses 

its own synthesis, and in ripening climacteric fruit 

C2

H4 enhances its own synthesis. This positive 

feedback of C2

H4 on C2H4 synthesis is called 

autocatalytic C2

H4 production. Plants respond to 

C2

H4 in a number of ways. 

Ethylene stimulates the following:

•	Synthesis of C2

H4 in ripening climacteric 

fruit

•	Ripening of climacteric fruit and some 

nonclimacteric fruit

•	Anthocyanin synthesis in ripening fruit

•	Chlorophyll destruction and yellowing (for 

example, degreening of citrus)

•	Seed germination

•	Adventitious root formation

•	Respiration and phenylpropanoid 

metabolism

•	Flower initiation in bromeliads (for example, 

pineapple)

•	Abscission and senescence

Ethylene inhibits the following:

•	Ethylene synthesis in vegetative tissue and 

nonclimacteric fruit

•	Flowering and flower development in most 

plants

•	Auxin transport

•	Shoot and root elongation; that is, growth

Depending on a number of variables, C2

H4

has both beneficial and deleterious effects on 

harvested fruits, vegetables, and ornamentals.

Beneficial effects:

•	Promotes color development in fruit

•	Stimulates ripening of climacteric fruit

•	Promotes degreening of citrus

•	Stimulates dehiscence in nuts

•	Alters sex expression (Cucurbitaceae)

•	Promotes flowering (for example, in 

pineapple)

•	Reduces lodging of cereals

Detrimental effects:

•	Accelerates senescence

•	Enhances excessive softening of fruits

•	Stimulates chlorophyll loss (for example, 

yellowing)

•	Stimulates sprouting of potato

•	Promotes discoloration (for example, 

browning)

•	Promotes abscission of leaves and flowers

•	Stimulates phenylpropanoid metabolism

Often an C2

H4-induced change in one commodity 

is viewed as beneficial, while the same change 

in another commodity is viewed as detrimental. 

For example, C2

H4 is used to promote ripening 

of bananas, melons, and tomatoes; degreening 

of oranges; and synthesis of pigments in apples. 

Yet the same changes are unwanted when C2

H4

promotes over-ripening of fruit, yellowing of 

broccoli, development of brown russet spot lesions 

in lettuce, and senescence of flowers. Because of 

these diverse and often opposite effects of C2

H4, 

controlling its action in plants is of great economic 

importance to producers, wholesalers, retailers, 

and consumers of fresh fruits, vegetables, and 

ornamentals.

In most vegetative tissues, C2

H4 is only produced 

in biologically active amounts during early stages 

of development or in response to biotic or abiotic 

stress. Mutant plants that do not respond to C2

H4

often grow normally, with only a few insignificant 

alterations in development. Most of the effects 

of C2

H4 on vegetative tissue are therefore the 

result of the tissue’s response to a stress or to the 

intentional or unintentional exposure of tissue to 

active levels of C2

H4.

In contrast to its effects on vegetative tissue, 

biologically produced C2H4 plays a crucial role 

in the development of reproductive tissues and in 

the ripening of certain climacteric fruit. The rates 

of C2

H4 production and its internal concentration 

often vary by orders of magnitude during early 

stages of development and during the initiation 

and development of reproductive structures. 

Increased rates of C2

H4 production are especially 

pronounced during the ripening of climacteric 

fruit such as apples, avocados, bananas, 
78

melons, pears, and tomatoes. In these fruit, the 

autocatalytic production of C2

H4 heralds the 

onset of ripening and is required for many of the 

reactions associated with ripening to continue. See 

section “Summary of Respiration and Ethylene 

Production Rates” in the Introduction of this 

handbook.

Once internal C2

H4 exceeds a level characteristic 

for the species, tissue, and developmental stage, 

the further production of C2

H4 is stimulated by 

presence of previously produced C2

H4. In this way, 

autocatalytic positive feedback can increase rates 

of C2

H4 production and internal concentration 

of C2

H4 by 1,000-fold during ripening. External 

application of C2

H4 can promote the ripening 

of climacteric fruit—for example, avocado, 

banana, honeydew, and tomato—and beneficial 

quality changes in nonclimacteric fruit; for 

example, degreening of lemon and orange. 

Once autocatalytic C2

H4 production has started 

in climacteric fruit, lowering its external 

concentration has an insignificant effect on its 

internal levels, rates of production, or action.

Ethylene is an important plant growth regulator 

that has pronounced effects on many aspects 

of plant growth and development. Regulating 

its effectiveness is commercially important for 

many crops. Controlling its effectiveness can 

mean either increasing its beneficial effects or 

decreasing its detrimental effects. There are a 

number of ways to accomplish either objective.

Reducing Effectiveness of Ethylene 

Use C2H4-tolerant cultivars

Keep atmosphere free of C2

H4 

Maintain at coldest possible temperature

Store under CA or MA or in MAP

Minimize time between exposure and use

Increasing Effectiveness of Ethylene

Use C2

H4-sensitive cultivars

Keep an active level of C2

H4 in the air

Maintain at optimum temperature

Store under adequate levels of O2

 and CO2

Allow sufficient time for plant response

Ethylene Interactions in Plants

There are some significant interactions between 

the plant and its environment that are important in 

understanding how to control biological activity of 

C2

H4 in plants (figure 2).

Figure 2. Interactions among a plant and ethylene in its 

environment (Saltveit 1999). 

Ethylene in the atmosphere can have a direct 

effect on plant tissue by raising the internal 

concentration to an active level. Sources of 

atmospheric C2H4 include exhaust from trucks 

and forklifts, pollution from industrial activity 

and from the burning of fuels, and biosynthesis 

by diseased plants or ripening fruit. In some 

cases, C2

H4, whether applied as a gas or as an 

C2

H4-releasing compound such as ethephon, is 

intentionally added to the plant’s environment 

to stimulate desirable changes. The changes can 

include promotion of flowering in pineapple; 

ripening of avocado, banana, melon, and tomato 

fruit; degreening of citrus; altering sex expression 

in cucurbits; defoliation; and promotion of latex 

secretion by rubber trees.

The activity of C2

H4 inside plants is regulated 

not only by the absolute level of C2H4 but also by 

the responsiveness of tissues and the presence of 

CO2, the natural antagonist of C2H4 action. The 

response of plants to C2H4, therefore, depends on 

a number of factors, only one of which is the rate 

of C2

H4 production by the plant. Tissue sensitivity 

depends on species, cultivar, cultural practices, 

and stage of development.

INTERNAL

ETHYLENE

Ripening or diseased 

fruit, exhaust, 

pollution, etc.

PLANT 

TISSUE

Ethylene

Biosynthesis

Physiological 

response to 

ethylene Abiotic, 

Biotic Stress

EXTERNAL

Inhibitors of 

ethylene action, 

e.g., CO2, Ag, 1-MCP

INTERNAL

ETHYLENE

Ripening or diseased 

fruit, exhaust, 

pollution, etc.

PLANT 

TISSUE

Ethylene

Biosynthesis

Physiological 

response to 

ethylene Abiotic, 

Biotic Stress

EXTERNAL

Inhibitors of 

ethylene action, 

e.g., CO2, Ag, 1-MCP
79

Prior and current stresses have a significant effect 

on modulating the effect of C2

H4. For example, 

wounding stimulates C2

H4 production, as well 

as a host of plant defense responses such as 

increased phenylpropanoid metabolism. Some of 

these responses involve C2

H4, while others do not. 

Increased phenolic metabolism greatly increases 

the susceptibility of some crops like lettuce to 

develop browning—for example, russet spotting—

when exposed to C2

H4 and/or mechanical injury. 

The effect of tissue susceptibility is most clearly 

seen in fruit tissue. Immature climacteric fruit 

respond to C2

H4 with increased respiration and 

reduced C2

H4 production. Once the tissue has 

reached a certain stage of maturity, however, C2

H4

not only promotes increased respiration but also 

increased C2

H4 synthesis.

Controlling the effectiveness of C2

H4 does not 

always involve a reduction in its activity. There 

are many beneficial effects of C2

H4 that can be 

enhanced (see above). The techniques used to 

increase the effectiveness of C2

H4 are almost the 

mirror image of techniques used to reduce its 

effectiveness.

Ethylene action can be enhanced by using 

cultivars that are sensitive and respond uniformly 

to C2

H4 rather than cultivars that are C2H4

insensitive. An effective concentration of C2

H4

should be maintained around the tissue for a 

sufficient time to elicit the full response. However, 

since the response to C2

H4 is log-linear (a log 

increase in C2

H4 concentration results in a linear 

increase in the response), there is an extremely 

large range over which the concentrations are 

effective. The application of C2

H4 must be at 

the proper stage of development and at the 

proper temperature for the desired effects to be 

induced. Ethephon and similar C2

H4-releasing 

chemicals permit the commercial application of 

C2

H4 in the field. After harvest, C2H4 gas, either 

from compressed gas cylinders or catalytically 

generated from alcohol, can be used in enclosed 

storage rooms.

Controlling Ethylene Action

There are roughly three ways to control the action 

of C2

H4 in plants. The first is to prevent the plant 

from being exposed to biologically active levels 

of C2

H4. The second is to prevent the plant tissue 

from perceiving the C2

H4 that is in its surrounding 

atmosphere or that is being produced by the tissue. 

The third is to prevent the plant from responding 

to the perceived C2

H4 by controlling exposure to 

C2

H4.

Preventing Exposure to Ethylene

The following should be done to prevent exposure 

to C2

H4:

•	Keep the air around the commodity C2

H4

free.

•	Use fresh, C2

H4-free air from outside.

•	Scrub C2

H4 from the storage atmosphere.

•	Use sachets of C2

H4 absorbers inside 

packages to reduce levels.

•	Segregate C2

H4-producing commodities 

from C2

H4-sensitive ones.

•	Keep exposure to a minimum (in terms of 

both duration and level).

•	Inhibit C2

H4 synthesis (AVG, ACC synthase, 

low O2

, ACC oxidase).

Risk of exposure to C2

H4 is usually not much of 

a problem in the field because the levels of C2

H4

found even in polluted air rarely reach biologically 

active levels. However, in greenhouses, coldstorage rooms, and transportation vehicles, C2

H4

can frequently accumulate to reach biologically 

active levels. Ethylene found in these enclosed 

spaces comes from varied sources, and the two 

most prominent sources are diseased, stressed, 

or ripening plant tissue and the incomplete 

combustion of organic fuels.

With proper ventilation of enclosed spaces and 

with persistent attention to the condition of 

adjacent plants and the operation of heaters and 

gas-powered forklifts, C2

H4 can be kept below 

biologically active levels. Sometimes the C2

H4

that we are concerned with comes from the 
80

plant itself. Application of inhibitors of C2

H4

biosynthesis, such as AVG and AOA, to the tissue 

before or after harvest can significantly reduce 

this source of C2

H4 exposure. For example, tissue 

can be prevented from making either stress or 

autocatalytic C2

H4 by blocking the biosynthetic 

pathway for C2

H4 synthesis. If exposure cannot be 

prevented or has already occurred, then both the 

duration of exposure and the level of C2

H4 in the 

atmosphere should be kept as low as possible.

Preventing Perception of Ethylene

If significant amounts of C2

H4 are in the 

immediate environment, certain methods can be 

used to block the perception of C2

H4 by the plant. 

Here are some possible methods:

•	Store at the coldest possible temperature.

• Use inhibitor of C2H4 perception: CO2, 

silver (for example, silver thiosulfate), and 

1-methyl cyclopropene (1-MCP).

• Use C2H4-insensitive cultivars.

• Interrupt the C2H4-induced signal.

Since perception is a metabolic process, holding 

the tissue at the lowest possible temperature will 

effectively reduce perception. Specific chemical 

inhibitors can also be used that directly interfere 

with the perception event.

A gaseous inhibitor like CO2

 or 1-MCP can be 

introduced into the atmosphere. The tissue can be 

dipped or fed a nonvolatile inhibitor such as silver 

thiosulfate, but this treatment is limited to nonfood 

crops. Ethylene-resistant cultivars can be selected 

or the tissue genetically engineered to lack the 

necessary biochemical receptors for ethylene or 

the signal pathway necessary to transduce the 

signal into a physiological event.

Even after the molecular perception event has 

occurred, blocking the transduced signal will 

effectively prevent perception. However, effective 

methods to do this will require a far greater 

understanding of the signal pathway than is 

currently available.

Preventing Response by the Plant

The third way to control C2

H4 is to prevent the 

plant from responding to the perceived C2

H4. This 

can be done by interfering with the metabolic 

machinery that is induced by exposure to C2

H4, by 

methods such as the following:

•	Store at coldest possible temperature.

•	Store under CA or MA or in MAP.

•	Inhibit or reduce specific enzyme 

activities using chemical inhibitors (for 

example, AIP) or genetic engineering (for 

example, antisense or other gene knockout 

techniques).

•	Divert protein synthesis—by heat-shock, for 

example.

•	Minimize time before use (for example, 

consumption).

Since all the effects of C2

H4 on plants that we 

are interested in involve metabolic changes, 

reducing the rate of metabolism by lowering 

the temperature, withholding a vital reactant 

(for example, O2

), or by inhibiting a specific 

enzyme (for example, with a chemical or through 

genetic engineering) will prevent a response to 

C2

H4. For example, ripening promoted by C2H4

often entails tissue softening that significantly 

reduces shelf-life. Using antisense technology to 

reduce the activity of enzymes involved in tissue 

softening has produced fruit that remain firmer 

longer. Ethylene also promotes phenylpropanoid 

metabolism in many tissues that use stressproduced C2

H4 as a signal to induce defense 

mechanisms. Interfering with synthesis or activity 

of phenylalanine ammonia lyase (PAL, the first 

enzyme in phenolic metabolism) with chemical 

inhibitors or heat treatment eliminates tissue 

response to C2

H4, preventing development of 

postharvest disorders.
81

Application of Ethylene

The quality of some fruits is increased when they 

are harvested at a mature but unripe stage that 

can withstand the rigors and duration of transport 

and then treated with C2

H4 to promote ripening 

before sale. These fruit include avocados, bananas, 

honeydew melons, lemons, oranges, and tomatoes. 

An effective atmosphere of 100 to 150 μL L-1 C2

H4

in air can be produced by a number of methods. 

The “shot” method introduces a relative large 

amount of gaseous C2H4 into a ripening room by 

metering C2H4 from compressed gas cylinders. 

Ethylene in air mixtures between 3.1% and 32% 

are explosive. While these concentrations are 

more than 200-fold higher than recommended, 

they have been reached when metering equipment 

has malfunctioned. Use of compressed gas 

containing around 3.1% C2

H4 in N2 (“banana 

gas”), eliminates this problem. 

Catalytic converters are instruments that use a 

heated metal catalyst to convert alcohol into C2H4. 

They deliver a continuous flow of low C2H4 into 

the storage room. Ethylene can also be applied in 

aqueous form from decomposition of compounds 

such as Ethrel. While stable at acidic pH, Ethrel 

quickly breaks down to C2H4 as temperature and 

pH increase. Field application is approved for 

many food crops, but postharvest application is 

not approved.

Treatment with C2H4 stimulates many metabolic 

pathways, including respiration. Oxygen use is 

increased, as is the production of CO2

 and heat. 

Rooms designed to hold produce being exposed 

to C2H4 must be designed with extra air-moving 

capacity to ensure that an optimal ripening 

environment is maintained around the crop. 

Exposure to C2H4 must be uniform throughout 

the room and within packages. Heat of respiration 

and excessive CO2 must be removed to maintain 

a proper environment. Loss of water by the crop 

will be increased by the rise in respiratory heat 

production. Maintaining a high RH can lessen 

water loss, but too much water vapor can decrease 

the strength of cardboard boxes and promote 

pathogen growth. Judicious maintenance of proper 

ripening environments will ensure production 

of high-quality fruit. Care must be exercised in 

venting and opening ripening rooms to prevent 

release of sufficient amounts of C2

H4 to adversely 

affect other commodities stored in the same 

warehouse.

Conclusion

Ethylene can be both beneficial and detrimental 

to horticultural crops in storage. Practical uses 

for C2

H4 and treatments to minimize its adverse 

effects have slowly accumulated over almost a 

century of study. The three general methods used 

to modulate C2H4 activity involve controlling 

exposure, altering perception, and varying the 

response of the tissue. An understanding of 

ethylene’s synthetic pathway and mode of action 

has greatly improved the ability of postharvest 

physiologists to devise treatments and storage 

conditions to control C2H4 during the commercial 

storage and handling of horticultural crops. 

Simple methods like ventilation and temperature 

management can be combined with more 

sophisticated treatments like MAP and inhibitors 

of specific induced enzymes to provide conditions 

that optimize both storage life and product quality.

References

Saltveit, M.E. 1999. Effect of ethylene on quality 

of fresh fruits and vegetables. Postharv. Biol. 

Technol. 15:279-292.

Further Reading

Abeles, F.B., P.W. Morgan, and M.E. Saltveit. 

1992. Ethylene in Plant Biology, 2nd ed. 

Academic Press, New York, NY.

Kader, A.A. 1985. Ethylene-induced senescence 

and physiological disorders in harvested 

horticultural crops. HortScience 20:54-57.
82

Lelievre, J.M., A. Latche, B. Jones, et al. 1997. 

Ethylene and fruit ripening. Physiol. Plant. 

101:727-739.

Saltveit, M.E., S.F. Yang, and W.T. Kim. 1998. 

Discovery of ethylene. In S.D. Kung and S.F. 

Yang, eds., Discoveries in Plant Biology, vol. 1, 

pp. 47-70. World Sci. Pub. Co., Singapore.

Watada, A.E. 1986. Effects of ethylene on the 

quality of fruits and vegetables. Food Technol. 

40:82-85.

Weichmann, J. 1987. Postharvest Physiology of 

Vegetables. Marcel Dekker, New York, NY.
83

1-Methylcyclopropene (1-MCP)

Chris B. Watkins

Department of Horticulture, Cornell University, 

Ithaca, NY

Introduction

The plant hormone ethylene affects a wide range 

of physiological processes in horticultural crops, 

including abscission, senescence and ripening, 

chlorophyll loss, softening, physiological 

disorders, sprouting, isocoumarin synthesis, 

lignification, discoloration (browning), decay, 

and stimulation of defense systems (Saltveit 

1999). Depending on the desired use of the 

produce, these effects can be positive or negative. 

However, most postharvest handling is focused 

on controlling ethylene production or action. 

Among the available methods, chemical control of 

ethylene biosynthesis by aminoethoxyvinylglycine 

(AVG) and inhibition of its action by 

1-methylcyclopropene (1-MCP) have become 

useful tools for the horticulture industry as they 

seek to maintain quality of produce after harvest 

(Venburg et al. 2008, Watkins 2008c).

1-MCP belongs to a class of compounds known as 

cyclopropenes. The discovery that cyclopropenes 

inhibit ethylene perception by competitively 

binding to ethylene receptors represented a major 

breakthrough in controlling ethylene responses 

of horticultural products (Blankenship and Dole 

2003). The process of discovery of the effects 

of cyclopropenes and their proposed method of 

action has been described (Sisler and Serek 2003, 

Sisler 2006). 

1-MCP has several characteristics that make it 

conveniently useful by the fresh produce industry. 

It is a gaseous molecule that is easily applied, has 

an excellent safety profile, leaves no residues in 

or on treated produce, and is active at very low 

concentrations (parts per billion).

Of the cyclopropenes, 1-MCP proved to be 

extremely active, but it is unstable in the liquid 

phase. A process has been developed in which 

1-MCP is complexed with α-cyclodextrin, 

maintaining the stability of 1-MCP. After 

application, 1-MCP is released from the complex 

to expose horticultural products to the molecule.

When applied during the preharvest period, 

1-MCP has the useful effects of delaying fruit 

drop, slowing fruit maturation and ripening, and 

maintaining postharvest quality (McArtney et 

al. 2008, Watkins 2010, Watkins et al. 2010). 

Produce must be exposed to 1-MCP at an effective 

rate and for a sufficiently long time to elicit 

physiological responses. In essence, this means 

applying a higher preharvest concentration of 

1-MCP than that used for postharvest application, 

while ensuring stability of the formulation without 

inducing phytotoxicity. 

Some reports on postharvest dipping of fruit into 

aqueous 1-MCP have been published (Choi et 

al. 2008), but this method is not currently used 

commercially.

Registration

The U.S. Environmental Protection Agency 

(EPA) approved use of 1-MCP on floriculture 

and ornamental products in 1999 and on edible 

food products in 2002. By 2011, more than 40 

countries had approved use of 1-MCP. It is 

registered for use on a wide variety of fruits and 

vegetables including apple, apricot, Asian pear, 

avocado, banana, broccoli, calabrese, cauliflower, 

Brussels sprouts, cabbage, carrot, cherimoya, 

cucumber, date, guava, kiwifruit, lime, mango, 

melon, nectarine, papaya, paprika, peach, pear, 

pepper, persimmon, pineapple, plantain, plum, 

plumcot, squash, tomato, and many ornamentals. 

The specific products for which 1-MCP is 

registered in each country vary greatly according 

to the importance of the crop in that country. For 

example, 1-MCP can be applied to tulip bulbs in 

the Netherlands.

Recently, 1-MCP formulations have been 

approved by the EPA and other regulatory 

authorities for preharvest application. 
84

Semicommercial trials have been carried out at 

several locations in the United States, Argentina, 

Brazil, Canada, Chile, New Zealand, and South 

Africa. 

Effects of 1-MCP on Fruits, Vegetables, 

and Ornamental Products

The availability of 1-MCP has provided 

outstanding opportunities for researchers 

to investigate both ethylene-dependent and 

ethylene-independent events during ripening and 

senescence, in addition to developing practical 

uses for 1-MCP. Studies have focused on the 

effects of 1-MCP on quality of horticultural 

crops, specific postharvest issues such as handling 

and packaging, physiological and biochemical 

responses, and storage disorders. A number of 

detailed reviews on the effects of 1-MCP have 

been published (Blankenship and Dole 2003, 

Serek et al. 2006, Watkins 2006,2007, Huber 

2008, Watkins 2008a,2008b,2010). These reviews 

report on the use of an extensive range in 1-MCP 

concentration, depending on the responsiveness of 

the product to the molecule.

Ripening and Senescence. 1-MCP affects many 

ripening and senescence processes, including 

pigments, softening and cell wall metabolism, 

flavor and aroma, and nutritional properties 

(Watkins 2006,2008b, Serek et al. 2006). These 

processes are affected to varying degrees in both 

nonclimacteric and climacteric products. The 

range of responses reflects the enormous diversity 

of these crops in terms of both inherent diversity 

and morphological derivation (Huber 2008). 

Several generalizations can be made about 

responses of crops to 1-MCP:

•	Genotype, cultivar, and maturity effects can 

be highly variable, but responses to 1-MCP 

are typically “concentration × exposure 

time” dependent.

•	Most if not all climacteric fruit are affected 

by 1-MCP treatment, but the capacity to 

interrupt the progression of ripening, once 

initiated, varies by fruit and by attributes 

studied.

•	Nonclimacteric fruit can also respond 

to 1-MCP; such effects are providing 

interesting insights about ethylene-dependent 

and ethylene-independent events during 

ripening.

•	Treated fruit are firmer, slower to soften, 

slower to change peel color and they develop 

aroma and flavor slower, but if 1-MCP 

concentrations and exposure periods are 

appropriate for the product, the final quality 

attained in the ripened fruit is similar to that 

of untreated product.

•	Rate of loss of nutritionally important 

compounds such as vitamin C are 

usually reduced in 1-MCP-treated fruits 

and vegetables, and effects on phenolic 

compounds are minor.

Physiological Disorders. An important area 

of postharvest responses to 1-MCP is its 

effects on physiological disorders (Watkins 

2007,2008a,2008b). These disorders can be 

divided into categories:

•	Ethylene-induced disorders. Examples 

include russet spotting of lettuce and 

isocoumarin accumulation in carrots (Fan 

and Mattheis 2000a), lignification of 

asparagus (Liu and Jiang 2006), and watersoaking of watermelons (Mao et al. 2004). 

These disorders are preventable by inhibition 

of ethylene perception.

•	Senescence-related disorders. Examples 

include senescent breakdown of apples 

(Moran and McManus 2005), senescent 

scald and breakdown of pears (Ekman et 

al. 2004), and yellowing of broccoli (Fan 

and Mattheis 2000b). These disorders are 

also prevented by inhibition of ethylene 

perception.

•	Controlled atmosphere-related storage 

disorders. 1-MCP can increase susceptibility 

of apple fruit to carbon dioxide injuries. 

Incidence of both internal and external forms 

of injury is increased by 1-MCP (DeEll et 

al. 2003, Fawbush et al. 2008, Argenta et al. 

2010).
85

•	Chilling-related disorders that are increased 

by inhibition of ethylene perception. 

Examples include woolliness and internal 

breakdown of peaches and nectarines (Dong 

et al. 2001), chilling injury of citrus and 

bananas (Porat et al. 1999, Jiang et al. 2004), 

and flesh browning of the ‘Empire’ apple 

(Watkins 2008b).

•	Chilling-related disorders that are decreased 

by inhibition of ethylene perception. 

Examples include superficial scald; brown 

core (coreflush) and soft scald of apples 

and pears (Fan et al. 1999); internal flesh 

browning of avocados and pineapples 

(Selvarajah et al. 2001, Pesis et al. 2002); 

and chilling injury of bamboo shoots (Luo 

et al. 2008), melons (Gal et al. 2006), and 

persimmon (Luo 2007).

Pathological Disorders: Disease incidence 

can be increased, decreased, or unaffected by 

1-MCP, depending on the product, although 

results are not always consistent because of the 

complex interaction between host, pathogen, 

and environment (Watkins 2008b). In some 

instances, disease incidence can be lower because 

the beneficial effects of 1-MCP on skin integrity 

and flesh firmness result in greater resistance to 

infection. However, ethylene is necessary for 

defense systems in other plant systems (Marcos et 

al. 2005).

Application

For postharvest use of 1-MCP on both ornamental 

plants and edible food products, material must 

be treated in an enclosed area, such as a storage 

room, greenhouse, trailer, or shipping container. 

Leakage of 1-MCP from the treatment area 

can reduce its concentration and therefore 

effectiveness. 1-MCP can only be applied by 

authorized service providers, not by commercial 

storage operators. Testing of rooms for leakage, 

certification of product quality, and application of 

the proper 1-MCP concentration for the product 

maximize the benefits of treatment.

The apple has been an excellent crop for use of 

1-MCP, which is used extensively around the 

world to maintain quality through the whole 

marketing chain from storage to consumer 

(Watkins 2008b). Applications rates for apples 

vary from 625 to 1,000 nL L-1, depending on 

the country of registration. The major benefit of 

1-MCP to the grower is more time to get high 

quality produce through marketing channels to 

the consumer. The successful use of 1-MCP on 

apples is largely associated with varieties for 

which maintenance of at-harvest quality and only 

moderate softening to a crisp texture is desirable. 

In contrast, challenges exist for effective use of 

1-MCP on fruits that ripen to a melting texture 

or have major color change. For example, failure 

to ripen normally has been shown in avocado, 

banana, pear, and tomato after fruit were treated 

at an early ripening stage or if the applied 

1-MCP concentration was too high (Golding 

et al. 1998, Mir et al. 2004, Hurr et al. 2005, 

Bai et al. 2006). Fruit must ripen uniformly to 

quality characteristics (texture, flavor, aroma, 

color) that are expected by the consumer. Despite 

the challenges, successful 1-MCP treatment of 

avocados, bananas, melons, persimmons, and 

tomatoes has resulted from careful attenuation 

of 1-MCP concentrations or selecting fruit at the 

appropriate ripening stage at harvest. Research 

on reinitiating ripening after 1-MCP treatment 

in extremely sensitive fruit like pear is ongoing 

(Bai et al. 2006, Chiriboga et al. 2011, VillalobosAcuna et al. 2011). A considerable amount of 

research on crops other than apple is proprietary 

and therefore not yet in the public domain.

References

Argenta, L.C., J.P. Mattheis, and X.T. Fan. 

2010. Interactive effects of CA storage, 

1-methylcyclopropene and methyl jasmonate on 

quality of apple fruit. Acta Hort. 857:259-266.
86

Bai, J., J.P. Mattheis, and N. Reed. 

2006. Re-initiating softening ability of 

1-methylcyclopropene-treated ‘Bartlett’ and 

‘d’Anjou’ pears after regular air or controlled 

atmosphere storage. J. Hort. Sci. Biotechnol. 

81:959-964.

Blankenship, S.M., and J.M. Dole. 2003. 

1-Methylcyclopropene: a review. Postharv. Biol. 

Technol. 28:1-25.

Chiriboga, M.A., W.C. Schotsmans, C. 

Larrigaudiere, et al. 2011. How to prevent 

ripening blockage in 1-MCP-treated ‘Conference’ 

pears. J. Sci. Food Agric. 91:1781-1788.

Choi, S.T., P. Tsouvaltzis, C.I. Lim, and D.J. 

Huber. 2008. Suppression of ripening and 

induction of asynchronous ripening in tomato 

and avocado fruits subjected to complete 

or partial exposure to aqueous solutions of 

1-methylcyclopropene. Postharv. Biol. Technol. 

48:206-214.

DeEll, J.R., D.P. Murr, L. Wiley, and M.D. 

Porteous. 2003. 1-Methylcyclopropene (1-

MCP) increases CO2

 injury in apples. Acta Hort. 

600:277-280.

Dong, L., H.W. Zhou, L. Sonego, et al. 2001. 

Ethylene involvement in the cold storage disorder 

of ‘Flavortop’ nectarine. Postharv. Biol. Technol. 

23:105-115.

Ekman, J.H., M. Clayton, W.V. Biasi, and E.J. 

Mitcham. 2004. Interactions between 1-MCP 

concentration, treatment interval and storage 

time for ‘Bartlett’ pears. Postharv. Biol. Technol. 

31:127-136.

Fan, X.T., and J.P. Mattheis. 2000a. 

Reduction of ethylene-induced physiological 

disorders of carrots and iceberg lettuce by 

1-methylcyclopropene. HortScience 35:1312-

1314.

Fan, X.T., and J.P. Mattheis. 2000b. 

Yellowing of broccoli in storage is reduced by 

1-methylcyclopropene. HortScience 35:885-887.

Fan, X.T., J.P. Mattheis, and S. Blankenship. 1999. 

Development of apple superficial scald, soft scald, 

core flush, and greasiness is reduced by MCP. J. 

Agric. Food Chem. 47:3063-3068.

Fawbush, F., J.F. Nock, and C.B. Watkins. 

2008. External carbon dioxide injury and 

1-methylcyclopropene (1-MCP) in the ‘Empire’ 

apple. Postharv. Biol. Technol. 48:92-98.

Gal, S., S. Alkalai-Tuvia, Y. Elkind, and E. Fallik. 

2006. Influence of different concentrations of 

1-methylcyclopropene and times of exposure 

on the quality of ‘Galia’-type melon harvested 

at different stages of maturity. J. Hort. Sci. 

Biotechnol. 81:975-982.

Golding, J.B., D. Shearer, S.G. Wyllie, and W.B. 

McGlasson. 1998. Application of 1-MCP and 

propylene to identify ethylene-dependent ripening 

processes in mature banana fruit. Postharv. Biol. 

Technol. 14:87-98.

Huber, D.J. 2008. Suppression of 

ethylene responses through application of 

1-methylcyclopropene: a powerful tool for 

elucidating ripening and senescence mechanisms 

in climacteric and nonclimacteric fruits and 

vegetables. HortScience 43:106-111.

Hurr, B.M., D.J. Huber, and J.H. Lee. 2005. 

Differential responses in color changes and 

softening of ‘Florida 47’ tomato fruit treated 

at green and advanced ripening stages with the 

ethylene antagonist 1-methylcyclopropene. 

HortTechnology 15:617-622.

Jiang, Y.M., D.C. Joyce, W.B. Jiang, and W.J. Lu. 

2004. Effects of chilling temperatures on ethylene 

binding by banana fruit. Plant Growth Regul. 

43:109-115.

Liu, Z.Y., and W.B. Jiang. 2006. Lignin deposition 

and effect of postharvest treatment on lignification 

of green asparagus (Asparagus officinalis L.). 

Plant Growth Regul. 48:187-193.
87

Luo, Z.S. 2007. Effect of 1-methylcyclopropene 

on ripening of postharvest persimmon (Diospyros 

kaki L.) fruit. LWT—Food Sci. Technol. 40:285-

291.

Luo, Z.S., X.L. Xu, and B.F. Yan. 2008. Use of 

1-methylcyclopropene for alleviating chilling 

injury and lignification of bamboo shoot 

(Phyllostachys praecox f. prevernalis) during cold 

storage. J. Sci. Food Agric. 88:151-157.

Mao, L.C., Y. Karakurt, and D.J. Huber. 2004. 

Incidence of water-soaking and phospholipid 

catabolism in ripe watermelon (Citrullus lanatus)

fruit: induction by ethylene and prophylactic 

effects of 1-methylcyclopropene. Postharv. Biol. 

Technol. 33:1-9.

Marcos, J.F., L. Gonzalez-Candelas, and 

L. Zacarias. 2005. Involvement of ethylene 

biosynthesis and perception in the susceptibility of 

citrus fruits to Penicillium digitatum infection and 

the accumulation of defence-related mRNAs. J. 

Exp. Bot. 56:2183-2193.

McArtney, S.J., J.D. Obermiller, J.R. Schupp, 

et al. 2008. Preharvest 1-methylcyclopropene 

delays fruit maturity and reduces softening and 

superficial scald of apples during long-term 

storage. HortScience 43:366-371.

Mir, N., M. Canoles, R. Beaudry, et al. 

2004. Inhibiting tomato ripening with 

1-methylcyclopropene. J. Amer. Soc. Hort. Sci. 

129:112-120.

Moran, R.E., and P. McManus. 2005. Firmness 

retention, and prevention of coreline browning 

and senescence in ‘Macoun’ apples with 

1-methylcyclopropene. HortScience 40:161-163.

Pesis, E., M. Ackerman, R. Ben-Arie, et al. 2002. 

Ethylene involvement in chilling injury symptoms 

of avocado during cold storage. Postharv. Biol. 

Technol. 24:171-181.

Porat, R., B. Weiss, L. Cohen, et al. 1999. Effects 

of ethylene and 1-methylcyclopropene on the 

postharvest qualities of ‘Shamouti’ oranges. 

Postharv. Biol. Technol. 15:155-163.

Saltveit, M.E. 1999. Effect of ethylene on quality 

of fresh fruits and vegetables. Postharv. Biol. 

Technol. 15:279-292.

Selvarajah, S., A.D. Bauchot, and P. John. 2001. 

Internal browning in cold-stored pineapples 

is suppressed by a postharvest application of 

1-methylcyclopropene. Postharv. Biol. Technol. 

23:167-170.

Serek, M., E.J. Woltering, E.C. Sisler, et al. 2006. 

Controlling ethylene responses in flowers at the 

receptor level. Biotechnol. Adv. 24:368-381.

Sisler, E.C. 2006. The discovery and development 

of compounds counteracting ethylene at the 

receptor level. Biotechnol. Adv. 24:357-367.

Sisler, E.C., and M. Serek. 2003. Compounds 

interacting with the ethylene receptor in plants. 

Plant Biol. 5:473-480.

Venburg, G.D., R. Hopkins, J. Retamales, et al. 

2008. Recent developments in AVG research. Acta 

Hort. 796:43-49.

Villalobos-Acuna, M.G.V., W.V. Biasi, E..J. 

Mitcham, and D. Holcroft. 2011. Fruit temperature 

and ethylene modulate 1-MCP response in 

‘Bartlett’ pears. Postharv. Biol. Technol. 60:17-23.

Watkins, C.B. 2006. The use of 

1-methylcyclopropene (1-MCP) on fruits and 

vegetables. Biotechnol. Adv. 24:389-409.

Watkins, C.B. 2007. The effect of 1-MCP on the 

development of physiological storage disorders in 

horticultural crops. Stewart Postharvest Rev. vol. 

3, article 11.

Watkins, C.B. 2008a. Overview of 

1-methylcyclopropene trials and uses for edible 

horticultural crops. HortScience 43:86-94.
88

Watkins, C.B. 2008b. Postharvest effects on the 

quality of horticultural products: using 1-MCP to 

understand the effects of ethylene on ripening and 

senescence processes. Acta Hort. 768:19-32.

Watkins, C.B. 2008c. Postharvest ripening 

regulation and innovation in storage technology. 

Acta Hort. 796:51-58.

Watkins, C.B. 2010. Managing physiological 

processes in fruits and vegetables with inhibitors 

of ethylene biosynthesis and perception. Acta 

Hort. 880:301-310.

Watkins, C.B., H. James, J.F. Nock, et al. 2010. 

Preharvest application of 1-methylcyclopropene 

(1-MCP) to control fruit drop of apples, and its 

effects on postharvest quality. Acta Hort. 877:365-

374.
89

Texture

Judith A. Abbott and F. Roger Harker

Abbott is formerly with the Food Quality 

Laboratory, Henry A. Wallace Beltsville 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. She is now retired. Harker is with 

the Mt. Albert Research Centre, Horticulture and 

Food Research Institute of New Zealand Ltd., 

Auckland, New Zealand.

Introduction

Texture is a quality attribute critical in determining 

the acceptability of fruits and vegetables. It is 

convenient to define quality as the composite 

of intrinsic characteristics that differentiate 

units of the commodity—individual pieces of 

the product—and to think of acceptability as 

consumers’ perceptions of and reactions to those 

characteristics. Though the term is widely used, 

texture is not a single, well-defined attribute. It is 

a collective term that encompasses the structural 

and mechanical properties of a food and the 

sensory perception of that food in the hand or 

mouth. Though some definitions of texture are 

restricted to only sensory attributes or to sensory 

attributes and mechanical properties directly 

related to them, the term texture is sometimes 

extended to include some mechanical properties 

of commercial interest that may not be of direct 

interest to the consumer, such as resistance to 

mechanical damage. In this review, we will use 

the term texture in the broadest sense.

Many terms are used to describe sensory 

texture of fruits or vegetables, including hard, 

firm, soft, crisp, limp, mealy, tough, leathery, 

melting, gritty, wooly, stringy, dry, and juicy. 

There are no accepted instrumental methods for 

measuring these attributes. In fact, there is some 

disagreement among sensory, horticultural, and 

engineering uses of certain terms, particularly 

firmness, which is discussed below.

Textural attributes of fruits and vegetables are 

related to the structural, physiological, and 

biochemical characteristics of the living cells; 

their changes over time; and their alteration 

by processes such as cooking or freezing. The 

continuous physiological changes in living cells 

plus the inherent variability among individual 

units of the commodity make the assessment of 

fruit or vegetable texture difficult. Because of their 

continuous change, textural measurements are 

often relevant only at the time of evaluation; that 

is, they usually cannot be used to predict condition 

much later in the storage period or marketing 

chain.

Physiological Basis of Texture

To understand the texture of a product, it is 

important to identify the main elements of tissue 

strength and determine which elements are 

responsible for the textural attributes of interest. 

For example, it may be necessary to avoid tough 

strands of vascular material when measuring 

texture of soft tissues because the small amount 

of fiber produces an artificially high reading that 

does not agree with the sensory assessment of 

softness. On the other hand, it is important to 

measure the strength of fibers when determining 

toughness, such as in asparagus spears and 

broccoli stalks. Thus, method development and the 

solution to many texture problems require a good 

understanding of the anatomy of tissues within 

the fruit or vegetable, the structure of its cells, the 

biological changes that occur following harvest, 

and sensory texture perception.

Parenchyma Cells

Fruits are derived from flower parts, while 

vegetables are derived from roots, stems, leaves, 

or flowers, and several that we call vegetables 

are actually fruit (table 1). The common factor is 

that all fruits and vegetables are relatively soft, 

even carrots and apples eaten raw or cooked, 

largely due to the presence of parenchyma cells. 

These parenchyma cells are not lignified, and their 

primary walls are separated by a morphologically 

distinct region known as the middle lamella, 
90

Table 1. Examples of fruits and vegetables derived from various plant parts

____________________________________________________________________________________

Plant part Fruit Vegetable Seasoning or garnish

____________________________________________________________________________________

Root Beet, carrot, cassava (yucca, Licorice

 Manihot), parsnip, radish,

 sweet potato (Ipomoea), 

 turnip, yam (Dioscorea)

Tuber Potato, jerusalem artichoke, 

 taro

Rhizome Ginger, turmeric

Bulb Onion, shallot Garlic

Corm Water chestnut

Sprouted seeds Bean sprouts, etc.

Stem Asparagus Cinnamon (bark)

Leaf buds Cabbage, brussels sprouts,

 belgian endive (etiolated)

Petiole Celery, rhubarb

Leaf Collards, kale, leek, lettuce, Basil, bay, chives, 

 mustard greens, onion cilantro, dill leaf, 

 (green), spinach, marjoram, mint,

 watercress oregano, parsley, 

 rosemary, sage, 

 tarragon, thyme

Flower buds Artichoke (globe), broccoli, Capers, cloves

 cauliflower, lily bud

Flowers Squash blossoms Edible flowers 

 (garnishes)

Floral receptacle Strawberry, fig

Fruit, immature Chayote (christophene, Gherkin (pickled)

 mirliton), cucumber,

 eggplant, beans (green), 

 snap peas, pepper 

 (Capsicum), summer 

 squash, zucchini
91

Table 1. Examples of fruits and vegetables derived from various plant parts—

Continued

____________________________________________________________________________________

Plant part Fruit Vegetable Seasoning or garnish

____________________________________________________________________________________

Fruit, mature Apple, atemoya, avocado, Breadfruit, tomatillo, tomato, Allspice, caper berries,

 blueberry, carambola, winter squashes (pumpkin, juniper, mace, pepper 

 cherimoya, cherry, citrus, hubbard, acorn, etc.) (red, Capsicum),

 cranberry, date, grape, tamarind, vanilla bean

 jackfruit, mango, olive, 

 papaya, peach, pear, 

 pineapple, pomegranate,

 strawberry

 

Seeds Nuts, inclusions in Beans (mature), coconut, Anise, caraway, 

 numerous fruits peanuts, sweet corn, nuts, cardamon, cumin,

 inclusions in numerous dill seed, fennel,

 fruit—type vegetables (for mustard, nutmeg, 

 examples, squashes, pepper (black, Piper),

 tomatoes, and beans) pomegranate, poppy 

 seed, sesame seed

Fungi Mushrooms, truffles

_____________________________________________________________________________________

which separates adjacent cells and is rich in 

pectic substances. The unique mixture of matrix 

(pectic and hemicellulosic) and fibrous (cellulosic) 

polysaccharides in the cell wall mostly determines 

the mechanical properties of these cells. The 

polysaccharides confer on the wall two important 

but seemingly incompatible properties. The first 

is the wall’s plasticity, which enables it to expand 

as the cell enlarges during plant development. 

The second is the wall’s rigidity, which confers 

strength and determines cell shape. However, on 

its own the cell wall is unable to provide much 

mechanical support. Rather, it is the interaction 

between rigidity of the wall and internal 

hydrostatic pressure (turgor) of cell contents that 

provides support.

The arrangement and packing of parenchyma cells 

within the tissue is another factor that influences 

mechanical strength of produce. In carrots, the 

cells are small (approximately 50 μm in diameter), 

isodiametric in shape, and closely packed with 

a high degree of contact between neighboring 

cells and a small volume of intercellular gasfilled spaces. The cells can be arranged either 

as columns or as a staggered array where each 

cell overlays the junction of the two lower 

cells (Sørensen et al. 1999). These differences 

in cell packing may, in part, explain genotypic 

differences in susceptibility to harvest splitting 

in carrot. In apple cortical tissue, the cells are 

large (up to 300 μm in diameter), elongated along 

the direction of the fruit radius, and organized 

into distinct columns (Khan and Vincent 1993). 

As a result of this orientation of apple cells, the 

tissue stiffness (elastic modulus) is higher and 

the strain at failure is lower when tissue plugs are 

compressed in a radial rather than a vertical or 

tangential orientation (Khan and Vincent 1993, 

Abbott and Lu 1996). Up to 25% of the volume of 

apple tissue may be gas-filled intercellular spaces, 

which indicates relatively inefficient cell packing 

and a low degree of cell-to-cell contact, both 

of which correlate well (negatively) with tissue 

stiffness (Vincent 1989).
92

Cell Wall

From a chemical perspective, the primary cell 

wall of parenchyma cells is composed of a 

mixture of cellulose, hemicellulose, and pectin. 

The specific intermolecular interactions among 

these polysaccharides are poorly understood but 

usually assumed to follow the models described 

by Carpita and Gibeaut (1993). The cell wall itself 

is an important constituent of produce, providing 

dietary fiber, thought to protect against colorectal 

cancer (Harris et al. 1993).

Changes that occur in the cell wall during 

ripening of fruit, storage of produce, and cooking 

are critical to the texture of the final product. 

During maturation of some vegetative parts, 

especially stems and petioles, cell walls become 

lignified (Okimoto 1948, Price and Floros 

1993). Lignification results in toughening of 

the product, such as woodiness in asparagus, 

broccoli, pineapple, and rutabaga. During fruit 

ripening, cell wall changes include solublization 

and degradation of pectin and a net loss of 

the noncellulosic neutral sugars galactose and 

arabinose, and there may be a decrease in the 

molecular weight distribution of hemicelluloses 

(Harker et al. 1997). Numerous enzymes have 

been suggested as being critical to these changes 

in the cell wall including polygalacturonases and 

several glycosidases, including β-galactosidase, 

xyloglucanase, endotransglycosylase, and 

cellulases (Dey and del Campillo 1984, Huber 

1992, Seymour and Gross 1996, Harker et al. 

1997). The possible role of expansins—proteins 

that are proposed to disrupt hydrogen bonds 

within the cell wall—has been considered (Civello 

et al. 1999). The use of molecular approaches, 

including antisense technologies, has been a 

powerful tool in the search for an understanding of 

fruit softening (Giovannoni et al. 1989). However, 

no single enzyme has been identified as the major 

determinant of fruit softening, suggesting that wall 

breakdown results from the coordinated action of 

several enzymes or that the key enzyme has not 

been identified.

Cooking often results in degradation of pectic 

polymers via β-elimination, which is usually 

related to the degree of methyl esterification of 

pectin (Waldron et al. 1997). Along with turgor 

loss, this process is responsible for thermal 

softening. However, some vegetables either don’t 

soften or soften very slowly during cooking—for 

example, Chinese water chestnut, sugar beet, and 

beetroot. In Chinese water chestnut, the thermal 

stability of texture is associated with the presence 

of ferulic acid in the cell wall (Waldron et al. 

1997).

Postharvest treatments involving dipping or 

infiltrating with calcium maintain firmness during 

storage of a wide range of fruit (Conway et al. 

1994). Examination of fracture surfaces following 

tensile testing of apple cortex indicated that tissue 

failure from calcium-treated fruit was due to cell 

rupture, whereas failure in control apples was due 

to cell debonding (Glenn and Poovaiah 1990). 

While evidence suggests that calcium influences 

texture through its interaction with the cell 

wall (pectin), it may also affect texture through 

interactions with membranes.

The cell wall may also influence perception 

of juiciness through its ability to hold and 

release fluid. In some fruits, the cell wall swells 

considerably during ripening (Redgwell et al. 

1997). It has been suggested that hydrated cell 

walls and perhaps the presence of free juice 

over the surface of undamaged cells could be 

responsible for the sensation of juiciness in fruit 

with soft melting textures (Harker et al. 1997). 

In stonefruit, loss of juiciness is thought to occur 

when pectates bind water into a gel-like structure 

within the wall (Ben-Arie and Lavee 1971). 

Separation of cells at the middle lamella rather 

than rupture of cells during chewing is at least 

partially responsible for the dry, mealy mouthfeel of overripe apples and wooliness of peaches 

(Harker and Hallett 1992).

Cell Turgor

Plant cells tend to maintain a small positive 

pressure, known as turgor pressure, which 

develops when the concentration of solutes inside 
93

the cell (more specifically inside the plasma 

membrane) is higher than that outside the cell. 

The extracellular solution fills the pores of the cell 

wall, sometimes infiltrates into gas-filled spaces, 

and usually is continuous with vascular (waterconducting) pathways of the plant. Differences in 

solute concentration at the inner and outer surface 

of the plasma membrane cause water to flow into 

the cell by osmosis. This net movement of water 

is halted by the physical constraint of the rigid cell 

wall and, as a result of this, turgor develops inside 

the cell. At equilibrium, 

Ψ = Ψp + Ψπ

Where:

Ψ is the turgor (generally a positive value), 

Ψp is the water potential (water activity, 

generally a negative value) of the tissue, and 

Ψπ is osmotic pressure (generally a positive 

value) of the cell (Tomos 1988).

Turgor has the effect of stressing the cell wall. The 

consequences of this stressing depend on whether 

compressive loads or tensile loads are applied. 

When tissues are subjected to compressive loads, 

higher-turgor tends to make the cell more brittle; 

that is, makes it fail at a lower force (Lin and 

Pitt 1986). When tissues are subjected to tensile 

measurements, turgor tends to harden the cell wall 

and a greater force is needed before cells fail (De 

Belie et al. 2000a). However, turgor is unlikely 

to influence tissue strength if the mechanism 

of failure is cell-to-cell debonding, rather than 

fracturing across individual cells, unless an 

increasing turgor, and thus swelling, reduces cellto-cell contact area (Glenn and Poovaiah 1990, 

Harker and Hallett 1992).

The importance of turgor has been demonstrated 

in a number of ways. The rapid phase of cookinginduced softening of carrot occurs as a result of 

membrane disruption and the elimination of the 

turgor component of texture (Greve et al. 1994). 

Similarly, when produce experiences a freezethaw cycle, the membranes are damaged and the 

tissues become more flaccid in the case of leafy 

vegetables (and softer in the case of fruits) and 

often leak much juice upon thawing. Firmness 

and turgor correlate well in apple (Tong et al. 

1999), and turgor declines during tomato ripening 

(Shackel et al. 1991). Also, turgor is thought to 

play a central role in softening and development 

of mealiness during storage of apples (Hatfield 

and Knee 1988).

Cell-to-Cell Debonding Versus Cell Rupture

The strength of the cell wall relative to the 

adhesion between neighboring cells will determine 

whether cell rupture or cell-to-cell debonding is 

the mechanism of tissue failure. Cell rupture is 

generally associated with crisp and often juicy 

produce, as well as with unripe fruit and raw 

vegetables. Cell-to-cell debonding is frequently 

associated with dry, unpleasant texture such as 

in mealy apples or chilling-injured stonefruit and 

tomato and with juice loss in citrus (Harker et al. 

1997). 

However, a dry texture is not always unacceptable 

to consumers—in banana, for example. In some 

fruits, cell-to-cell debonding does not result in 

a dry texture; rather, a layer of juice covers the 

intact cells exposed following cell separation 

(Harker et al. 1997). Furthermore, cell-to-cell 

debonding is a common outcome of cooking 

of vegetables such as potato (Waldron et al. 

1997) and carrot (Ng and Waldron 1997). In 

fresh produce, cell adhesion is presumed to be a 

function of three factors: strength of the middle 

lamella, the area of cell-to-cell contact, and the 

extent of plasmodesmatal connections (Harker 

et al. 1997). Tissue collapse can also occur 

without cell wall breakdown or cell separation. 

In some tissues, fluids are forced out of cells by 

compressive forces known as “cell relaxation” 

(Peleg et al. 1976) or “exosmosis” (Jackman and 

Stanley 1995).

Other Elements of Tissue Strength

The strength and integrity of many edible plant 

organs are influenced by a number of additional 

factors (Harker et al. 1997). Many fruits and 

vegetables contain a number of tissue zones: 

periderm, pericycle, and phloem parenchyma in 

carrot; skin, outer pericarp, inner pericarp, and 

core in kiwifruit; and outer pericarp, locular gel, 

seeds, and columella in tomato. These tissues 
94

differ in strength and biological properties and 

often need to be considered individually when 

measuring texture. For example, failure of the 

core of kiwifruit to soften to the same extent as 

the pericarp causes a texture that is unacceptable 

to consumers. In some multiple fruit that do 

not adhere to the receptacle, such as raspberry, 

the main element of strength is the adhesion 

between neighboring drupelets due to hair-like 

protuberances. However, it is the skin of many 

types of produce that plays a key role in holding 

the flesh together, particularly in soft fruit. The 

cuticle of epidermal cells and thickened cell walls 

of hypodermal cells contribute to strength of 

simple skins. In harder, inedible skins, specialized 

cells may be present: collenchyma, sclerenchyma, 

tannin-impregnated cells, and cork.

The presence of tough strands of vascular tissue 

may strengthen the flesh but often results in 

an unpleasant fibrous texture. For example, 

toughness of asparagus spears is principally due 

to fiber content and fiber lignification (Lipton 

1990). Rarely is the stringiness desirable, as in 

spaghetti squash. In most commercial fruits, 

with the exception of pineapple (Okimoto 1948), 

fibrousness of the flesh is not a major problem. 

However, some fruits, including peaches and 

muskmelons, can have a problem with stringiness 

(Diehl and Hamann 1979). Generally, the 

perception of stringiness is greater with very 

ripe fruit due to the contrast between the soft 

melting texture of the parenchyma cells and the 

fibrousness of the vascular tissues. Similarly, 

the gritty texture of pear and guava (Harker et 

al. 1997) becomes particularly noticeable when 

the surrounding cells are soft. However, while 

stringiness is caused by vascular tissues, grittiness 

is caused by sclerenchymatous stone cells (Harker 

et al. 1997).

Sensory Evaluation of Texture

People sense texture in numerous ways: the look 

of the product, the feel in the hand, the way it 

feels as they cut it, the sounds as they bite and 

chew it, and, most important of all, the feel of 

the product in the mouth. Szczesniak (1963) 

proposed a texture profile, a systematic approach 

to sensory texture analysis based on mechanical, 

geometrical, and other characteristics. Mechanical 

characteristics included basic parameters 

(hardness, cohesiveness, viscosity, elasticity, 

and adhesiveness) and secondary parameters 

(brittleness or fracturability, chewiness, and 

gumminess). Geometrical properties related to 

size, shape, and orientation of particles. The 

other characteristics comprised moisture and fat 

content. Sherman (1969) and others have proposed 

revisions of the texture profile classification 

scheme, but the original is generally used with 

only minor changes by sensory texture specialists. 

Most sensory analysis textbooks contain a small 

chapter on evaluation of texture; for example, 

Meilgaard et al. (1999). Harker et al. (1997) 

reviewed fruit texture and included extensive 

discussion of oral sensation of textural attributes.

Shewfelt (1999) suggested that the combination 

of characteristics of the product be termed 

“quality” and that the consumer’s perception and 

response to those characteristics be referred to as 

“acceptability.” Texture may be a limiting factor 

in acceptability if textural attributes are outside 

the individual’s range of acceptability for that 

commodity. People have different expectations 

and impose different limits for various 

commodities. The relationship of instrumental 

measurements to specific sensory attributes and 

their relationship to consumer acceptability must 

be considered (Shewfelt 1999). Instruments may 

be designed to imitate human testing methods, 

or fundamental mechanical measurements may 

be statistically related to human perceptions and 

judgments to predict quality categories. Only 

people can judge quality, but instruments that 

measure quality-related attributes are vital for 

research and inspection (Abbott et al. 1997).

Instrumental Measurement of Texture

The ability to measure texture is critical for 

evaluation and control of quality. The complex 

nature of texture is associated with the diversity 

of tissues involved, the attributes required to 

describe textural properties, and changes in these 
95

attributes as the product ripens and senesces. 

Instrumental measurements are preferred over 

sensory evaluations for research and commercial 

applications because they are less subject to 

human influences, are more precise, and can 

provide a common language among researchers, 

companies, regulatory agencies, and customers. 

It is often suggested that the relevance of 

instrumental measurements depends on how well 

they predict sensory attributes (Voisey 1971), but 

there are also valid uses for mechanical property 

measurements that relate only to functional 

behavior of the fruit or vegetable, such as bruise 

resistance or the ability to be sliced for fresh-cut 

preparations.

There have been numerous reviews of methods for 

instrumental measurement of fruit and vegetable 

texture (Bourne 1980, Chen and Sun 1991, 

Abbott et al. 1997, Harker et al. 1997). Interaction 

among characteristics and the continuing 

physiological changes over time complicate the 

measurement of fruit or vegetable texture. For 

example, as the parenchymal tissue of honeydew 

melon softens, the perception of fibers (vascular 

bundles) increases (Diehl and Hamann 1979). On 

the other hand, the fibrousness in asparagus is 

related to active lignification of fiber and vascular 

bundles (Chang 1987). Similar effects can affect 

instrumental measurements. For example, fibers 

are held relatively rigidly in a hard melon and 

thus contribute to the overall force required to cut 

through the flesh, but the fibers in a soft melon can 

be displaced by the instrument’s probe and alter 

distribution of forces within tissue. The displaced 

fibers can also effectively change the shape 

of the probe as it progresses through the flesh 

accumulating a “cap” of fibers.

Most instrumental measurements of texture have 

been developed empirically. While they may 

provide satisfactory assessments of the quality 

of produce, they often do not fulfill engineering 

requirements for fundamental measurements 

(Bourne 1982). Fundamental material properties 

measurements were developed to study the 

strength of materials for construction or 

manufacture. After the failure point of such a 

material is exceeded, there is little interest in the 

subsequent behavior of the material. On the other 

hand, scientists who study food are interested in 

initial failure but they are also interested in the 

continuous breakdown of the food in the mouth 

in preparation for swallowing. As Bourne (1982) 

pointed out, “Food texture measurement might 

be considered more as a study of the weakness 

of materials rather than strength of materials.” In 

fact, both strength and breakdown characteristics 

are important components of texture.

Elastic and Viscoelastic Behavior

Fruits and vegetables exhibit viscoelastic behavior 

under mechanical loading, which means that 

force, distance, and time—in the form of rate, 

extent, and duration of load—determine the 

value of measurements. For example, impact 

of the fruit against a hard surface is very rapid 

loading, whereas the weight of other fruit on an 

individual fruit at the bottom of a bin and the 

force of a carton wall against tightly packed fruit 

are long-term loads. The fruit will respond quite 

differently to the two forms of loading. Because 

of the viscoelastic character of fruit and vegetable 

tissues, every effort should be made to use a 

consistent action and speed when making manual 

texture measurements such as the Magness-Taylor 

puncture test (Blanpied et al. 1978, Harker et al. 

1996). The rate of loading should be controlled 

and specified in mechanized measurements. 

The optimal rate of loading differs for different 

commodities. People use different loading rates 

(chewing speeds) when eating foods of different 

textures (Harker et al. 1997), but the optimum 

loading rate for instrumental measurements 

may not resemble the rate of human mastication 

(Thybo et al. 2000).

There are many types of mechanical loading: 

puncture, compression, shearing, twisting, 

extrusion, crushing, tension, bending, vibration, 

and impact. And there are four basic values that 

can be obtained from mechanical properties tests: 

force (load), deformation (distance, displacement, 

penetration), slope (ratio of force to deformation), 

and area under the force/deformation curve 

(energy). The engineering terms based on these 
96

measurements are stress, strain, modulus, and 

energy, respectively. 

Stress is force per unit area, of either contact or 

cross-section depending on the test. Strain is 

deformation as a percentage of initial height or 

length of the portion of sample subject to loading. 

Modulus of elasticity (tangent, secant, chord, or 

initial tangent) is a measure of stiffness based on 

the stress/strain ratio. 

Force and deformation values are more commonly 

used in food applications than stress and strain 

values and are sufficient, provided that the contact 

area and the distance the probe travels are constant 

and sample dimensions are similar from sample 

to sample. (Sample here means the portion of 

tissue tested, not necessarily the size of the fruit 

or vegetable.) In many horticultural texture tests, 

deformation is kept constant and the force value 

is reported. For example, in penetrometer tests 

of fruit firmness such as the Magness-Taylor test 

discussed below, the force required to insert a 

probe into the flesh to an inscribed mark is read 

from a gauge. No compensation is made for 

different probe diameters (contact areas), so the 

value read is force, not pressure or stress. In a few 

horticultural tests, a known force is applied to the 

product and the deformation after a specified time 

is reported; an example is the tomato creep test 

(Hamson 1952, Ahrens and Huber 1990).

Puncture, compression, bending, and shear tests 

made on instruments such as those listed in table 

2 are made at relatively low speeds, usually 60 

to 300 mm min-1 (0.1 to 20 in min-1). In contrast, 

typical impact velocities in fruit and vegetable 

handling systems are likely to be around 400 mm 

s-1 (945 in min-1), equivalent to a drop of only 8.1 

mm, and sometimes much greater.
97

Table 2. Magness-Taylor fruit firmness tester and related penetrometers____________________________________________________________________________________________________________________Instrument Type* Force† Readout Manufacturer____________________________________________________________________________________________________________________Magness-Taylor MT Manual Gauge D. Ballauff Manufacturing Co., Laurel, MDEffe-gi‡ MT Manual Gauge Effe-gi, Ravenna, ItalyMcCormick‡ MT Manual Gauge McCormick Fruit Tech Co., Yakima, WA

 (manufactured by Effe-gi)

Wagner MT Manual Gauge Wagner Instruments, Greenwich, CT

 (manufactured by Effe-gi)

EPT MT Mechanical Electronic Lake City Technical Products, Kelowna, BC, 

 Canada

U.C. (University MT Mechanical Gauge None. Uses AMETEK force gauge of California) and manual drill pressUniversal testing Universal Mechanical Electronic AMETEK Test and Calibration Instruments  machines or (Paoli, PA) materials testers Chatillon (Largo, FL)

Food Technology Corp. (of General Kinetics,  Inc.)Instron Corp. (Canton, MA)Lloyd Instruments Material Testing Products  (Hampshire, UK)Stable Micro Systems, Ltd. (Surrey, UK)Tinius Olsen Testing Machine Co. (Willow  Grove, PA)

_____________________________________________________________________________________________________________________*MT = Magness-Taylor tester.†MT firmness, regardless of instrument, is measred as force and should be reported in pounds-force (lbf, English units) or Newtons (N, metric units), 

not in kilograms force (kgf), though the gauges of some instruments indicate kg. To convert: lbf x 4.448 = N; kgf x 9.807 = N; N x 0.225 = lbf; N x 0.102 = kgf.

‡Other labels, such as “McCormick,” may occur on Effe-gi instruments.
98

A typical force/deformation (F/D) curve for a 

cylindrical piece of apple tissue compressed at 

constant speed is shown in figure 1. F/D curves 

for puncture tests look similar to compression 

curves. The portion of the initial slope up to point 

(a) in figure 1 represents nondestructive elastic 

deformation; point (a) is the inflection point 

at which the curve begins to have a concavedownward shape and is called the “elastic limit.” 

The region before point (a) is where slope or 

elastic modulus should be measured. Beyond the 

elastic limit, permanent tissue damage begins. 

There may be a bioyield point (b), at which cells 

start to rupture or move with respect to their 

neighbors, causing a noticeable decrease in slope. 

Point (c) marks rupture, where major tissue failure 

causes the force to decrease substantially. In some 

F/D curves, including figure 1, bioyield may not 

be distinguishable from rupture. Beyond rupture, 

the force may again increase, level off, or decrease 

as deformation increases (Bourne 1965). 

At the maximum deformation point specified by 

the user, the probe is withdrawn and the force 

diminishes until contact is lost. In the apple tissue 

shown in figure 1, maximum force occurred at 

maximum deformation, point (c), but other apples 

in the same lot had maxima at rupture point (a) 

or at some point between rupture and maximum 

deformation, such as marked by point (b). Of 

course, F/D curves that differ from the one shown 

in figure 1 are also reported for apple and for other 

commodities. F/D curves for very soft, noncrisp, 

or spongy tissues do not have sharp peaks but 

show gradual increase in force to a rupture point, 

followed by gradual decrease. Some may not 

even show rupture; for example, a cylinder of 

eggplant compressed like apple tissue in figure 

1 may show smoothly increasing force to the 

point of maximum deformation. Samples with a 

mixture of parenchyma and fibers or stone cells 

may have quite jagged F/D curves, with several 

local maxima and ruptures as the probe encounters 

resistant clusters of stone or fiber cells.

Figure 1. Actual force/deformation curve of a cylindrical piece of apple tissue under compression 

of 1 mm s-1 demonstrating elastic limit (a), bioyield (b), and rupture or massive tissue failure (c). 

Maximum force is at point (c) but could also occur at point (a) or point (b) in other apples. Force/

deformation (F/D) for Magness-Taylor puncture would look similar (with somewhat different 

maximum forces) but would terminate at 5/16 in or 8 mm, depending on whether original or metric 

specification was selected to control the universal testing instrument.
99

Firmness of horticultural products can be 

measured at different force or deformation levels 

in all three regions of figure 1, depending on the 

purpose of the measurement and the definitions of 

the quality attributes. F/D characteristics beyond 

the elastic limit may be more important than those 

before it, because they simulate the destruction 

that occurs in bruising or eating (Szczesniak 

1963, Bourne 1968). The two most common 

texture tests of fruits and vegetables, the MagnessTaylor puncture and the Kramer Shear report 

only the maximum force attained, regardless of 

the deformation at which it occurs. On the other 

hand, elastic modulus or Young’s modulus is often 

used by engineers as an index of product firmness. 

The modulus of elasticity is the ratio of stress 

to strain as calculated from the slope of the F/D 

curve before the elastic limit. Any nondestructive 

method should limit the force or deformation 

level to the elastic region so that negligible 

tissue damage is sustained during measurement. 

It is important to recognize and understand 

the fundamental properties measured by both 

destructive tests and nondestructive methods, the 

differences between them, and the factors that can 

affect the tests.

Numerous mechanical instruments have been 

developed over the past century for measuring 

textural attributes of horticultural products. 

Despite the large variations in design, these 

mechanical instruments either measure or control 

functions of force, deformation, and time. The 

types of loading by these instruments include 

puncture, compression, shearing, twisting, 

extrusion, crushing, tension, and bending.

Puncture Tests

Puncture testers based on the original MagnessTaylor pressure tester (MT), also called the 

USDA or Ballauff tester (Magness and Taylor 

1925, Haller 1941) and more correctly called 

the Magness-Taylor fruit firmness tester, are 

used to measure firmness of numerous fruits and 

vegetables to estimate harvest maturity or for 

postharvest evaluation of firmness. There are 

several adaptations of the Magness-Taylor tester 

that differ in instrument size and shape, manual 

or mechanical use, and dial (analog) or digital 

readout (table 2). The term “Magness-Taylor 

firmness” is used generically for the measurements 

made with the several variants of the MT. All 

use rounded-tip probes of specific geometry and 

measure the maximum force required to insert 

the probe 7.94 mm (5/16 in) into the flesh (Haller 

1941). The rounded portion of a Magness-Taylor 

probe is only a portion of a full hemisphere . A 

probe measuring 11.11 mm (28/64 in) in diameter 

with a radius of curvature of 8.73 mm (11/32 in) is 

used for apples. A probe measuring 7.94 mm (5/16 

in) in diameter with a radius of curvature of 5.16 

mm (13/64 in) is used for cucumber, kiwifruit, 

mango, papaya, peaches, pears, and plums. A thin 

slice of skin (about 2 mm thick and slightly larger 

diameter than the probe) should be removed from 

the area to be tested, except for cucumbers, which 

are tested with the skin intact.

A group of U.S. researchers published 

recommendations for making manual 

penetrometer tests (Blanpied et al. 1978), stating 

that steady force should be applied so that the 

probe is inserted to the inscribed depth mark in 

2 s. The probes can also be mounted in materials 

testers (universal F/D testing machines) made by 

numerous manufacturers (Bourne 1974, Breene 

et al. 1974, Abbott et al. 1976, Harker et al. 1996, 

Lehman-Salada 1996). A group sponsored by 

the Commission of the European Communities 

recommended that a materials tester be used to 

drive the probe to a depth of 8 mm at speeds 

between 50 and 250 mm min-1 (Smith 1985). 

Because of the curvature of the MT probes and 

the fact that firmness as measured in puncture 

tests is a combination of shear and compression in 

variable proportions, it is not possible to convert 

measurements made with one size MT probe to 

the other MT size, or to accurately convert to 

or from values for probes of other geometries 

(Bourne 1982). A random sample of 20 to 30 fruit 

of similar size and temperature should be tested 

with punches on two opposite sides, depending 

on uniformity of the lot. Peaches are often more 

variable around the circumference than other fruit 

so a larger number is recommended (Blanpied 

et al. 1978). Similar measurements are made 

on cherry, grape, and strawberry using a 3-mm 
100

probe and on olive using a 1.5-mm probe on 

the U.C. tester (E.J. Mitcham 2000, personal 

communication). Numerous puncture tests with 

flat-faced cylindrical or hemispherical probes and 

a few with conical probes have been conducted. 

None have achieved the acceptance of the 

Magness-Taylor fruit firmness test.

Shear Tests

Shearing in engineering terms does not mean 

cutting with a knife or scissors but, instead, 

sliding adjacent parallel planes of cells past one 

another. Engineering shear tests are seldom used 

on fruits and vegetables, but shear modulus can 

be obtained from compression (Mohsenin 1986), 

torsion (Diehl et al. 1979), impact (Bajema and 

Hyde 1998), extrusion, and dynamic (Ramana 

and Taylor 1992) tests. Although it does not 

measure true shear, the Kramer Shear device 

(FTC Texture Test System, Food Technology 

Corporation, Reston, VA) is used extensively 

in the food processing industry and by some 

fresh-cut processors for quality control. The key 

component of the original Kramer Shear device 

is a multiblade cell with 10 blades 2.9 mm (about 

7/64 in) thick that mesh with slots in the bottom 

of a cell measuring 67×67×63 mm (approximately 

2 5/8×2 5/8×2 1/2 in, internal dimensions) that 

can be used on any materials tester with sufficient 

load capacity. The cell is generally filled with 

randomly oriented pieces of the product, either to 

full capacity or to 100 g. The force measured by 

the test involves compression, shear, extrusion, 

and friction between the tissue and blades. 

While the maximum force to pass the blades 

through the sample may relate to the complex of 

material properties sensed in the mouth during 

chewing, the test does not satisfy requirements 

for engineering tests because of the undefined 

and uncontrolled stresses and strains applied to 

the food. The amount of sample and the pattern 

of loading the cell, size and orientation of pieces, 

etc. affect the maximum force value as well as 

the shape of the F/D curve (Szczesniak et al. 

1970, Voisey and Kloek 1981). The orientation 

of pieces of fruit or vegetable, especially with 

regard to vascular bundles and fibers, and the 

spaces between pieces would be expected to 

affect significantly the F/D profile as the blades 

penetrate through the contents of the shear 

cell; therefore some standardization of loading 

practice is advisable. Adaptations with smaller 

cells and fewer blades are available; for example, 

Stable Micro Systems. As with the MT probe, 

comparisons should not be made between results 

from cells of different geometries.

Compression

Though compression tests are not commonly 

used by the fruit and vegetable industry, they are 

widely used in research on horticultural products. 

They can be made on tissue specimens or intact 

products using a variety of contact geometries 

(Mohsenin 1986, ASAE 2000). Though fruits 

and vegetables are viscoelastic, they are often 

treated as elastic, so the force required to attain 

a specified deformation or to rupture (bruise or 

burst) the product is generally measured. Modulus 

of elasticity, stiffness, force, contact stress, and 

deformation to bioyield and to rupture can be 

calculated from elastic measurements, dimensions 

of the specimen, and Poisson’s ratio (the ratio 

of transverse strain to axial strain at less than 

the elastic limit). For convex specimens such 

as whole or halved fruits, see ASAE Std. 368.4 

(2000). Often, for food science applications only 

maximum force or distance is reported.

Compression tests using pieces of tissue, usually 

cylindrical, excised from the fruit or vegetable are 

quite common in research (Bourne 1968, Khan 

and Vincent 1993, Abbott and Lu 1996, Wann 

1996). Intact product compression tests involve 

contact with small flat or curved indenters or with 

parallel plates significantly larger than the area 

of contact (ASAE 2000). Modulus of elasticity 

values from whole fruit compression represents 

fruit morphology, size, shape, cellular structure, 

strength, and turgor. Though elastic properties can 

be determined nondestructively (discussed below), 

horticultural and food science measurements 

are frequently made beyond the elastic limit. 

Sundstrom and Carter (1983) used rupture force 

of intact watermelons pressed between parallel flat 

plates to evaluate causes of cracking. Jackman et 
101

al. (1990) found that whole tomato compression 

was relatively insensitive to small differences in 

firmness due to chilling injury. Kader et al. (1978) 

compressed tomatoes between a pair of spherical 

indenters as a measure of firmness.

If the viscous element is a significant contributor 

to the texture, as it is for intact tomatoes and 

citrus, measurement of continuing deformation 

under a constant force (creep) (Hamson 1952, 

El Assi et al. 1997) or decrease in force under 

a fixed deformation (relaxation) (Sakurai and 

Nevins 1992, Errington et al. 1997, Kajuna et 

al. 1998, Wu and Abbott 2002) provides textural 

information in addition to elastic properties. 

To minimize the effect of loading position on 

firmness measurement in tomato, Kattan (1957) 

designed a creep tester that applied force around 

the fruit’s circumference with a belt. The failure 

of creep or force-relaxation testers to be adopted 

commercially is due to the time required for 

adequate relaxation, which can be up to 60 s.

Tension Test

Tensile tests measure the force required to stretch 

or pull a sample apart. Failure can be through cell 

rupture, cell separation, or a combination of both. 

Tensile measurement has not been as popular 

as puncture or compression testing because it 

is not intuitively as closely related to crushing 

or chewing as is puncture or compression and 

because it requires gripping or otherwise holding 

the ends of the sample so that they can be pulled 

apart without crushing the tissues where they are 

held. Schoorl and Holt (1983) used clamps to hold 

apple tissue. Stow (1989) and Harker and Hallett 

(1992) used shaped samples held by special 

claw-like hooks. Harker and Hallett (1994) used 

quick-set adhesive to glue the ends to instrument 

fixtures. Researchers often examine the broken 

ends of tensile test samples to determine the mode 

of fracture. Microscopic analyses of the broken 

ends (Lapsley et al. 1992, Harker and Sutherland 

1993, Harker and Hallett 1994, Harker et al. 1997) 

reveal that tissue from unripe fruit generally 

fractures due to individual cells breaking, whereas 

cells from ripe fruits that tend to be crisp (apple 

and watermelon) usually break or rupture and cells 

from ripened soft fruits (banana, nectarine, and 

kiwifruit) tend to separate at the middle lamellae.

Torsion Test

True torsion tests are rarely used on horticultural 

specimens because of the difficulties in shaping 

and holding the tissue (Diehl and Hamann 1979, 

Diehl et al. 1979).

Twist Test

Studman and Yuwana (1992) proposed a simple 

twist tester consisting of a sharp spindle with a 

rectangular blade that is forced into the flesh; the 

torque (twisting force) required to cause crushing 

or yielding of the tissue is measured. Though 

called a “twist test,” this is not to be confused 

with a torsion test: The properties tested are 

likely a combination of shear and compression. 

Harker et al. (1996) found the twist test to be 

more precise than several testers using the MT 

puncture probe; however, Hopkirk et al. (1996) 

suggest that puncture and twist tests may measure 

different mechanical properties, resulting in quite 

different firmness judgments. The twist test has 

the advantage of being able to measure strength 

of tissue zones at specific depths from the surface 

without requiring the excision of tissue samples.

Nondestructive Measurements for Online 

Sorting

Most F/D measurements are destructive, such as 

the familiar Magness-Taylor fruit firmness test 

and the Kramer shear test; or they are too slow 

for online use, such as the Cornell firmness tester. 

However, remember that eating is destructive! 

Rupture forces usually provide the best correlation 

with sensory texture evaluations of foods. 

Unfortunately, destructive tests cannot be used 

to sort fruits and vegetables for subsequent 

sale, so a great deal of research has gone into 

developing nondestructive methods to estimate 

the mechanical properties and the textural quality 

of fruits and vegetables (Chen and Sun 1991, 
102

Abbott et al. 1997, Hung et al. 2001). None of 

these nondestructive methods has attained wide 

commercial acceptance to date.

During development, new instrumental texture 

measurements are most often initially calibrated 

against existing instruments. If they are to be 

used to predict sensory attributes or acceptability, 

the new measurement should also be compared 

directly with descriptive sensory analyses to 

develop calibration equations for quantitative 

attributes (how much of a trait is present) or with 

consumer evaluations to predict acceptability. 

Alternatively, instrumental measurements may 

be compared with commercially useful traits 

like bruising, days from bloom, or storage 

life to develop predictive equations. After the 

relationship between an instrumental measurement 

and a quality attribute or acceptability has been 

well established, the instrumental measurement 

is usually used to replace human evaluations. It is 

advisable to verify the relationships occasionally, 

because changes in factors such as genetics, 

growing or storage conditions, consumer 

preference, or wear on the instrument may change 

the relationships.

Laser Air-Puff Test. A nondestructive, noncontact 

firmness detector was recently patented (Prussia 

et al. 1994) that uses a laser to measure deflection 

caused by a short puff of high-pressure air, 

similar to some devices used by ophthalmologists 

to detect glaucoma. This is essentially a 

nondestructive compression test. Under fixed air 

pressure, firmer products deflect less than softer 

ones. Laser-puff readings correlate well with 

destructive Magness-Taylor firmness values for 

apple, cantaloupe, kiwifruit, nectarine, orange, 

pear, peach, plum, and strawberry (Fan et al. 1994, 

Hung et al. 1998, McGlone et al. 1999, McGlone 

and Jordan 2000).

Impact or Bounce Test. When one object collides 

with another object, its response is related to its 

mechanical properties, its mass, and the contact 

geometry. Numerous studies have been conducted 

on the impact responses of horticultural products 

and a number of impact parameters have been 

proposed to measure firmness, including peak 

force, coefficient of restitution, contact time, and 

the impact frequency spectrum. The coefficient 

of restitution is the ratio of the velocities of the 

product just before and after impact and reflects 

the energy absorbed in the product during impact. 

There is no agreement on the best parameter 

to measure; selection seems to depend on 

commodity, impact method, and the firmness 

reference used by the investigators. Most impact 

tests involve dropping the product onto a sensor 

(Rohrbach 1981, Delwiche et al. 1987, Zapp et 

al. 1990, McGlone and Schaare 1993, Patel et 

al. 1993) or striking the product with the sensor 

(Delwiche et al. 1989, Brusewitz et al. 1991, Chen 

et al. 1996, Bajema and Hyde 1998). Delwiche et 

al. (1989, 1991) developed a single-lane firmness 

sorting system for pear and peach. Impact 

measurements often do not correlate highly 

with the Magness-Taylor puncture measurement 

(Hopkirk et al. 1996). A potential problem with 

impact tests is that bruising may occur unless a 

soft sensor is developed (Thai 1994).

Sonic or Acoustic Tests. Sonic (acoustic) 

vibrations are those within the human audibility 

range of 20 to about 20,000 Hz (vibrations per 

second). Sonic measurements provide a means 

of measuring fruit and vegetable firmness. The 

traditional watermelon ripeness test is based on 

the acoustic principle: One thumps the melon and 

listens to the pitch of the response. 

A number of sonic instruments and laboratory 

prototype sorting machines have been developed 

and tested (Abbott et al. 1968, 1992, Armstrong 

et al. 1990, Peleg et al. 1990, Zhang et al. 1994, 

Stone et al. 1998, Schotte et al. 1999, De Belie 

et al. 2000b, Muramatsu et al. 2000). When an 

object is caused to vibrate, amplitude varies 

with frequency of the vibration and will be 

at a maximum at some particular frequency 

determined by a combination of the shape, size, 

and density of the object; such a condition is 

referred to as resonance. Resonance measurement 

can be achieved by applying an impulse or thump 

that contains a range of frequencies. Modulus of 

elasticity values obtained from resonant frequency 

data have correlated well with those measured by 
103

conventional compression tests, but they often 

correlated poorly with MT puncture forces. Abbott 

et al. (1968) proposed a stiffness coefficient, f2

m, 

which was based on the modulus of elasticity 

using the resonant frequency (f) and mass (m) of 

the specimen; this was later modified by Cooke 

and Rand (1973) to f2

m2/3. 

Farabee and Stone (1991) developed a portable 

sonic instrument for field determination of 

watermelon ripeness and hollow heart detection. 

Kawano et al. (1994) reported a commercial 

sorting machine for detecting internal voids in 

Japanese watermelon. Shmulevich et al. (1995) 

developed a sonic instrument using a lightweight 

flexible piezoelectric film sensor to follow changes 

in fruit during storage. Muramatsu et al. (2000) 

examined the relationship of both phase shifts 

and resonant frequencies to firmness. Nybom 

(1962) and Peleg et al. (1990, 1999) examined 

the sonic energy transmitted by the specimen 

rather than the resonant frequencies. Despite 

considerable research, sonic vibration has not 

yet become a viable option for the horticultural 

industry. However, several advanced commercial 

prototypes are currently being evaluated.

Ultrasonic Tests. Ultrasonic frequencies 

(>20,000 Hz) are widely used in the medical field 

and for analyzing meat. Ultrasonic tests have 

been used with limited success for measuring 

physical and chemical properties of fruits and 

vegetables because of the high attenuation 

(energy absorption) of plant tissues. The 

commonly measured ultrasonic parameters are 

velocity, attenuation, and frequency spectrum 

composition. Bruises in apples (Upchurch et al. 

1987) and hollow heart of potatoes (Cheng and 

Haugh 1994) could be detected in the laboratory 

using ultrasonics. Mizrach and Flitsanov (1999) 

and Mizrach et al. (1994, 1999) have followed 

the softening process in avocados, melons, and 

mangoes, respectively.

Light Scatter Imaging. As light passes through 

tissue, cellular contents such as starch granules, 

cell walls, and intercellular spaces cause scatter. 

The extent of scatter of collumated light such as 

a laser beam may change during ripening due to 

compositional changes and changes in cell-tocell contact. Measurement of the scatter using 

computer vision may thus provide an indirect 

indication of textural changes. Significant 

correlations between mechanical properties and 

image size have been shown in apples (Duprat et 

al. 1995, McGlone et al. 1997, Cho and Han 1999, 

De Belie et al. 2000a) and tomatoes (Tu et al. 

2000).

Juiciness

The importance of juiciness has been 

demonstrated by numerous consumer awareness 

studies; however, there has been little progress 

in developing instrumental measurements of 

juiciness. Intuitively, one would expect total 

moisture content to determine juiciness, but the 

correlations between them are often low for fruits 

and vegetables (Szczesniak and Ilker 1988). 

Apparently, inability of cells to release juice 

has a greater effect. For example, water content 

of juicy and chilling-injured peaches is similar, 

yet injured fruit have a dry mouth-feel. Also, 

mealy apples feel dry to the palate because cells 

separate at the middle lamella, rather than being 

ruptured and releasing juice during chewing. 

Generally, juiciness is characterized as weight or 

percentage of juice released from a fixed weight 

of tissue. Juice can be extracted from tissue by 

the following methods: using a press (like a 

cider press), homogenizing and centrifuging to 

separate juice from solids, using juice extractors, 

and measuring juice released during compression 

testing of excised tissue (Harker et al. 1997).

Summary

Texture measurement has become widely 

accepted by horticultural industries as a critical 

indicator of nonvisual aspects of quality. The 

ability to measure texture has allowed industries 

to set standards for quality at pack-out and to 

monitor deterioration in quality during storage 

and distribution. Furthermore, the study of the 

chemical, physiological, and molecular changes 

that control or influence texture has been 
104

facilitated by the development of methods for 

quantifying texture change. 

Much of the commercial and research interest in 

texture has focused primarily on the mechanical 

properties of the tissues. The diversity of tissues 

involved, the variety of attributes required 

to fully describe textural properties, and the 

changes in these attributes as the product ripens 

and senesces contribute to the complexity of 

texture measurement. This complexity of texture 

can still only be fully measured by sensory 

evaluation, which involves using a panel of 

assessors that have been trained to score defined 

attributes against a set of standards. However, 

instrumental measurements are preferred over 

sensory evaluations for both commercial and 

research applications because instruments are 

more convenient to use, widely available, tend 

to provide consistent values when used by 

different (often untrained) people, and are less 

expensive than sensory panels. These instrumental 

measurements are widely understood and can 

provide a common language among researchers, 

industry, and customers. 

There are numerous empirical and fundamental 

measurements that relate to textural attributes. 

Mechanical methods measure functions of 

force, deformation, and time. Some indirect 

methods measure chemical constituents or 

physical characteristics. Destructive mechanical 

methods generally relate more closely to sensory 

evaluations than do nondestructive measurements, 

but by their destructive nature they cannot be used 

for sorting produce. Therefore, the commodity 

and purpose of measurement, and sometimes 

regulations, guide the choice of textural 

measurement.

References

Abbott, J.A., H.A. Affeldt, and L.A. Liljedahl. 

1992. Firmness measurement of stored ‘Delicious’ 

apples by sensory methods, Magness-Taylor, 

and sonic transmission. J. Am. Soc. Hort. Sci. 

117:590-595.

Abbott, J.A., G.S. Bachman, N.F. Childers, et al. 

1968. Sonic techniques for measuring texture of 

fruits and vegetables. Food Technol. 22:101-112.

Abbott, J.A., and R. Lu. 1996. Anisotropic 

mechanical properties of apples. Trans. Am. Soc. 

Agr. Eng. 39:1451-1459.

Abbott, J.A., R. Lu, B.L. Upchurch, and R.L. 

Stroshine. 1997. Technologies for nondestructive 

quality evaluation of fruits and vegetables. Hort. 

Rev. 20:1-120.

Abbott, J.A., A.E. Watada, and D.R. Massie. 1976. 

Effe-gi, Magness-Taylor, and Instron fruit pressure 

testing devices for apples, peaches, and nectarines. 

J. Am. Soc. Hort. Sci. 101:698-700.

Ahrens, M.J., and D.J. Huber. 1990. Physiology 

and firmness determination of ripening tomato 

fruit. Physiol. Plant. 78:8-14.

Armstrong, P., H.R. Zapp, and G.K. Brown. 1990. 

Impulsive excitation of acoustic vibrations in 

apples for firmness determination. Trans. Am. Soc. 

Agr. Eng. 33:1353-1359.

ASAE [American Society of Agricultural 

Engineers]. 2000. Compression test of food 

materials of convex shape. ASAE Standard 368.4, 

American Society of Agricultural Engineers, St. 

Joseph, MI.

Bajema, R.W., and G.M. Hyde. 1998. 

Instrumented pendulum for impact 

characterization of whole fruit and vegetable 

specimens. Trans. Am. Soc. Agr. Eng.. 41:1399-

1405.
105

Ben-Arie, R., and S. Lavee. 1971. Pectic changes 

occurring in Elberta peaches suffering from woolly 

breakdown. Phytochemistry 10:531-538.

Blanpied, G.D., W.J. Bramlage, D.H. Dewey, et al. 

1978. A standardized method for collecting apple 

pressure test data. N.Y. Food and Life Sciences 

Bull. 74.

Bourne, M.C. 1965. Studies on punch testing of 

apples. Food Technol. 19:413-415.

Bourne, M.C. 1968. Texture profile of ripening 

pears. J. Food Sci. 33:223-226.

Bourne, M.C. 1974. Comparison of results from the 

use of the Magness-Taylor pressure tip in hand- and 

machine-operation. J. Texture Studies 5:105-108.

Bourne, M. C. 1980. Texture evaluation of 

horticultural crops. HortScience 15:51-57.

Bourne, M.C. 1982. Food Texture and Viscosity: 

Concept and Measurement. Academic Press, New 

York, NY.

Breene, W.M., I.J. Jeon, and S.N. Bernard. 1974. 

Observations on texture measurement of raw 

cucumbers with the fruit pressure tester. J. Texture 

Studies 5:317-327.

Brusewitz, G.H., T.G. McCollum, and X. Zhang. 

1991. Impact bruise resistance of peaches. Trans. 

Am. Soc. Agr. Eng. 34:962-965. 

Carpita, N.C., and D.M. Gibeaut. 1993. Structural 

models of primary cell walls in flowering plants: 

consistency of molecular structure with the 

physical properties of the walls during growth. 

Plant J. 3:1-30.

Chang, D.N. 1987. Asparagus. In J. Weichmann, 

ed., Postharvest Physiology of Vegetables, pp. 523-

525. M. Dekker, New York, NY.

Chen, P., M. Ruiz-Altisent, and P. Barreiro. 1996. 

Effect of impacting mass on firmness sensing of 

fruits. Trans. Am. Soc. Agr. Eng. 39:1019-1023.

Chen, P., and Z. Sun. 1991. A review of 

nondestructive methods for quality evaluation and 

sorting of agricultural products. J. Agr. Eng. Res. 

49:85-98.

Cheng, Y., and C.G. Haugh. 1994. Detecting 

hollow heart in potatoes using ultrasound. Trans. 

Am. Soc. Agr. Eng. 37:217-222.

Cho, Y.J., and Y.J. Han. 1999. Nondestructive 

characterization of apple firmness by quantitation 

of laser scatter. J. Texture Stud. 30:625-638.

Civello, P.M., A.L.T. Powell, A. Sabehat, and A.B. 

Bennett. 1999. An expansin gene expressed in 

ripening strawberry fruit. Plant Physiol. 121:1273-

1279.

Conway, W.S., C.E. Sams, C.Y. Wang, and J.A. 

Abbott. 1994. Additive effects of postharvest 

calcium and heat treatment on reducing decay and 

maintaining quality in apples. J. Am. Soc. Hort. 

Sci. 119:49-53.

Cooke, J.R., and R.H. Rand. 1973. A mathematical 

study of resonance in intact fruits and vegetables 

using a 3-media elastic sphere model. J. Agr. Eng. 

Res. 18:141-157.

De Belie, N., I.C. Hallett, F.R. Harker, and J. 

De Baerdemaeker. 2000a. Influence of ripening 

and turgor on the tensile properties of pears: a 

microscopic study of cellular and tissue changes. 

J. Amer. Soc. Hort. Sci. 125:350-356.

De Belie, N., S. Schotte, P. Coucke, and J. 

De Baerdemaeker. 2000b. Development of an 

automated monitoring device to quantify changes 

in firmness of apples during storage. Postharv. 

Biol. Technol. 18:1-8.

Delwiche, M.J., T. McDonald, and S.V. Bowers. 

1987. Determination of peach firmness by analysis 

of impact force. Trans. Am. Soc. Agr. Eng. 

30:249-254.
106

Delwiche, M.J., N. Singh, H. Arevalo, and J. 

Mehlschau. 1991. A second generation fruit 

firmness sorter. Am. Soc. Agr. Eng. Paper 91-

6042.

Delwiche, M.J., S. Tang, and J. J. Mehlschau. 

1989. An impact force response fruit firmness 

sorter. Trans. Am. Soc. Agr. Eng. 32:321-326.

Dey, P.M., and E. del Campillo. 1984. 

Biochemistry of the multiple forms of 

glycosidases in plants. Adv. Enzymol. 56:141-249.

Diehl, K.C., and D.D. Hamann. 1979. 

Relationships between sensory profile parameters 

and fundamental mechanical parameters for raw 

potatoes, melons and apples. J. Text. Stud. 10:401-

420.

Diehl, K.C., D.D. Hamann, and J.K. Whitfield. 

1979. Structural failure in selected raw fruits and 

vegetables. J. Texture Studies 10:371-400.

Duprat, F., H. Chen, M. Grotte, et al. 1995. 

Laser light based machine vision system for 

nondestructive ripeness sensing of Golden 

apples, pp. 85-91. In J. de Baerdemaeker, and 

J. Vandewalle, eds., Proceedings of the 1st 

Workshop on Control Applications in Postharvest 

Processing Technology, June 1995, Ostend, 

Belgium.

El Assi, N.E., D.J. Huber, and J.K. Brecht. 1997. 

Irradiation-induced changes in tomato fruit and 

pericarp firmness, electrolyte efflux, and cell wall 

enzyme activity as influenced by ripening stage. J. 

Am. Soc. Hort. Sci. 122:100-106.

Errington, N., J.R. Mitchell, and G.A. Tucker. 

1997. Changes in the force relaxation and 

compression responses of tomatoes during 

ripening: the effect of continual testing and 

polygalacturonase activity. Postharv. Biol. 

Technol. 11:141-147.

Fan, S., S.E. Prussia, and Y.C. Hung. 1994. 

Evaluating the UGA laser-puff food firmness 

detector. Amer. Soc. Agr. Eng. Paper 94-6540.

Farabee, L.M., and M.L. Stone. 1991. 

Determination of watermelon maturity with sonic 

impulse testing. Amer. Soc. Agr. Eng. Paper 91-

3013.

Giovannoni, J.J., D. DellaPenna, A.B. Bennett, 

and R.L. Fischer. 1989. Expression of a chimeric 

polygalacturonase gene in transgenic rin (ripening 

inhibitor) tomato fruit results in polyuronide 

degradation but not fruit softening. Plant Cell 

1:53-63.

Glenn, G.M., and B.W. Poovaiah. 1990. Calciummediated postharvest changes in texture and 

cell wall structure and composition in ‘Golden 

Delicious’ apples. J. Am. Soc. Hort. Sci. 115:962-

968.

Greve, L.C., K.A. Shackel, H. Ahmadi, et al. 

1994. Impact of heating on carrot firmness: 

contribution of cellular turgor. Jour. Agr. and Food 

Chemistry 42:2896-2899.

Haller, M.H. 1941. Fruit pressure testers and 

their practical applications. Circular 627, U.S. 

Department of Agriculture, Washington, DC.

Hamson, A.R. 1952. Measuring firmness of 

tomatoes in a breeding program. Proc. Am. Soc. 

Hort. Sci. 60:425-433.

Harker, F.R., and I.C. Hallett. 1992. Physiological 

changes associated with development of mealiness 

of apple fruit during cool storage. HortScience 

27:1291-1294.

Harker, F.R.. and I.C. Hallett. 1994. Physiological 

and mechanical properties of kiwifruit tissue 

associated with texture change during cold 

storage. J. Am. Soc. Hort. Sci. 119:987-993.

Harker, F.R., J.H. Maindonald, and P.J. Jackson. 

1996. Penetrometer measurement of apple and 

kiwifruit firmness: operator and instrument 

differences. J. Am. Soc. Hort. Sci.121:927-936.

Harker, F.R., R.J. Redgwell, I.C. Hallett, and S.H. 

Murray. 1997. Texture of fresh fruit. Hort. Rev. 

20:121-224.
107

Harker, F.R., and P.W. Sutherland. 1993. 

Physiological changes associated with fruit 

ripening and the development of mealy texture 

during storage of nectarines. Postharv. Biol. 

Technol. 2:269-277. 

Harris, P.J., A.M. Robertson, M.E. Watson, et al. 

1993. The effects of soluble-fiber polysaccharides 

on the adsorption of a hydrophobic carcinogen to 

an insoluble dietary fiber. Nutr. Cancer 19:43-54.

Hatfield, S.G.S, and M. Knee. 1988. Effects of 

water loss on apples in storage. Intl. J. Food Sci. 

Technol. 23:575-585.

Hopkirk, G., J.H. Maindonald, and A. White. 

1996. Comparison of four new devices for 

measuring kiwifruit firmness. N.Z. J. Crop Hort. 

Sci. 24:273-286.

Huber, D.J. 1992. The inactivation of pectin 

depolymerase associated with isolated tomato fruit 

cell wall: implications for the analysis of pectin 

solubility and molecular weight. Physiol. Plant. 

86:25-32. 

Hung, Y.C., K.H. McWatters, and S.E. Prussia. 

1998. Sorting performance of a nondestructive 

laser air-puff firmness detector. Appl. Eng. Agr. 

14:513-516.

Jackman, R.L., A.G. Marangoni, and D.W. 

Stanley. 1990. Measurement of tomato fruit 

firmness. HortScience 25:781-783.

Jackman, R.L., and D.W. Stanley. 1995. Creep 

behaviour of tomato pericarp tissue as influenced 

by ambient temperature ripening and chilled 

storage. J. Texture Studies.

Kader, A.A., L.L. Morris, and P. Chen. 1978. 

Evaluation of two objective methods and a 

subjective rating scale for measuring tomato fruit 

firmness. J. Am. Soc. Hort. Sci. 103:70-73.

Kajuna, S.T.A.R., W.K. Bilanski, and G.S. Mittal. 

1998. Effect of ripening on the parameters of three 

stress relaxation models for banana and plantain. 

Appl. Eng. Agr. 14:55-61.

Kattan, A.A. 1957. Changes in color and firmness 

during ripening of detached tomatoes, and the use 

of a new instrument for measuring firmness. Proc. 

Am. Soc. Hort. Sci. 70:379-383.

Kawano, S., H. Abe, and M. Iwamoto. 1994. 

Novel applications of nondestructive techniques 

for quality evaluation of fruits and vegetables. 

In G. Brown and Y. Sarig, eds., Nondestructive 

Technologies for Quality Evaluation of Fruits 

and Vegetables, Proceedings of the International 

Workshop, US-Israel BARD Fund, Spokane, 

WA, June 1993, pp. 1-8. American Society of 

Agricultural Engineers, St. Joseph, MI.

Khan, A.A., and J.F.V. Vincent. 1993. 

Compressive stiffness and fracture properties of 

apple and potato parenchyma. J. Texture Studies. 

24:423-435.

Lapsley, K.G., F.E. Escher, and E. Hoehn. 1992. 

The cellular structure of selected apple varieties. 

Food Struct. 11:339-349.

Lehman-Salada, L. 1996. Instrument and operator 

effects on apple firmness readings. HortScience 

31:994-997.

Lin, T.T., and R.E. Pitt. 1986. Rheology of 

apple and potato tissue as affected by cell turgor 

pressure. J. Texture Stud. 17:291-313.

Lipton, W.J. 1990. Postharvest biology of fresh 

asparagus. Hort. Rev. 12:69-155.

Magness, J.R., and G.F. Taylor. 1925. An 

improved type of pressure tester for the 

determination of fruit maturity. Circular 350, U.S. 

Department of Agriculture, Washington, DC

McGlone, V.A., H. Abe, and S. Kawano. 

1997. Kiwifruit firmness by near infrared light 

scattering. J. Near Infrared Spect. 5:83-89.

McGlone, V.A., and R.B. Jordan. 2000. Kiwifruit 

and apricot firmness measurement by the 

noncontact laser air-puff method. Postharv. Biol. 

Technol. 19:47-54.
108

McGlone, V.A., S.M.W. Ko, and R.B. Jordan. 

1999. Noncontact fruit firmness measurement by 

the laser air-puff method. Trans. Amer. Soc. Agr. 

Eng. 42:1391-1397.

McGlone, V.A., and P.N. Schaare. 1993. The 

application of impact response analysis in the New 

Zealand fruit industry. Paper 93-6537, American 

Society of Agricultural Engineers, St. Joseph, MI. 

Meilgaard, M., G.V. Civille, and B.T. Carr. 1999. 

Sensory evaluation techniques. CRC Press, Boca 

Raton, FL.

Mizrach, A., and U. Flitsanov. 1999. 

Nondestructive ultrasonic determination of 

avocado softening process. J. Food Eng. 40:139-

144.

Mizrach, A., U. Flitsanov, Z. Schmilovitch, 

and Y. Fuchs. 1999. Determination of mango 

physiological indices by mechanical wave 

analysis. Postharvest Biol. Technol. 16:179-186.

Mizrach, A., D. C. Teitel, N. Galili, and G. 

Rosenhouse. 1994. Evaluation of some ripening 

parameters of autumn- and winter-grown ‘Galia’ 

melons. Scientia Hort. 56:291-297.

Mohsenin, N.N. 1986. Physical Properties of Plant 

and Animal Materials, 2nd ed. Gordon and Breach 

Science Publishers, New York, NY.

Muramatsu, N., N. Sakurai, N. Wada, et al. 2000. 

Remote sensing of fruit textural changes with a 

laser doppler vibrometer. J. Amer. Soc. Hort. Sci. 

125:120-127.

Ng, A., and K.W. Waldron. 1997. Effect of 

steaming on cell chemistry of potatoes (Solanum 

tuberosum cv. Bintje) in relation to firmness. J. 

Agr. Food Chem. 45:3411-3418.

Okimoto, M.C. 1948. Anatomy and histology of 

the pineapple inflorescence and fruit. Bot. Gaz. 

110:217-231.

Patel, N., V.A. McGlone, P.N. Schaare, and H. 

Hall. 1993. “BerryBounce”: a technique for the 

rapid and nondestructive measurement of firmness 

in small fruit. Acta Hort. 352:189-198.

Peleg, K. 1999. Development of a commercial 

fruit firmness sorter. J. Agric. Eng. Res. 72:231-

238.

Peleg, K., U. Ben-Hanan, and S. Hinga. 1990. 

Classification of avocado by firmness and 

maturity. J. Texture Studies 21:123-129.

Peleg, M., L. Gomez-Brito, and Y. Malevski. 

1976. Compressive failure patterns of some juicy 

fruits. J. Food Sci. 41:1320-1324.

Peyron, M., L. Mioche, and J. Culioli. 1994. Bite 

force and sample deformation during hardness 

assessment of viscoelastic models of foods. J. 

Texture Studies 24:59-76.

Price, J.L., and J.D. Floros. 1993. Quality decline 

in minimally processed fruits and vegetables. Dev. 

Food Sci. 32:405-427.

Prussia, S.E., J.J. Astleford, Y.C. Hung, and R. 

Hewlett. 1994. Nondestructive firmness measuring 

device. U.S. Patent No. 5,372,030.

Ramana, S.V., and A.J. Taylor. 1992. Dynamic 

measurement of tissue rigidity during freezing and 

cooking of vegetables. J. Sci. Food Agr. 58:261-

266.

Redgwell, R.J., E. MacRae, I. Hallett, et al. 1997. 

In vivo and in vitro swelling of cell walls during 

fruit ripening. Planta 203:162-173.

Rohrbach, R.P. 1981. Sorting blueberries to 

improve fresh market shelf life. Paper 81-1501, 

American Society of Agricultural Engineers, St. 

Joseph, MI. 

Sakurai, N., and D.J. Nevins. 1992. Evaluation of 

stress-relaxation in fruit tissue. HortTechnology 

2:398-402.
109

Schoorl, D., and J.E. Holt. 1983. A practical 

method for tensile testing of apple tissue. J. 

Texture Studies 14:155-164.

Schotte, S., N. De Belie, and J. De Baerdemaeker. 

1999. Acoustic impulse-response technique for 

evaluation and modelling of firmness of tomato 

fruit. Postharv. Biol. Technol. 17:105-115.

Seymour, G.B., and K.C. Gross. 1996. Cell wall 

disassembly and fruit softening. Postharv. News 

Info. 7:45N-52N.

Shackel, K.A., C. Greve, J.M. Labavitch, and H. 

Ahmadi. 1991. Cell turgor changes associated 

with ripening in tomato pericarp tissue. Plant 

Physiol. 97:814-816.

Sherman, P. 1969. A texture profile of foodstuffs 

based upon well-defined rheological properties. J. 

Food Sci. 34:458-462.

Shewfelt, R.L. 1999. What is quality? Postharv. 

Biol. Technol. 15:197-200.

Shmulevich, I., N. Galili, and N. Benichou. 

1995. Development of a nondestructive method 

for measuring the shelf-life of mango fruit, pp. 

275-287, In Proceedings of the Food Processing 

Automation IV Conference, Chicago, IL, 

American Society of Agricultural Engineers, St. 

Joseph, MI.

Smith, S.M. 1985. Measurement of the quality 

of apples: recommendations of an EEC 

working group. Commission of the European 

Communities, Brussels, Belgium.

Sørensen, L. 1999. Harvest Splitting in Carrot 

(Daucus carota L.) Storage Roots. Ph.D. Thesis, 

The Royal Veterinary and Agricultural University, 

Copenhagen, Denmark.

Stone, M.L., P.R. Armstrong, D.D. Chen, and G.H. 

Brusewitz. 1998. Peach firmness prediction by 

multiple location impulse testing. Trans. Am. Soc. 

Agr. Eng. 41:115-119.

Stow, J. 1989. The involvement of calcium ions in 

maintenance of apple fruit tissue structure. J. Exp. 

Bot. 40:1053-1057.

Studman, C.J., and L. Yuwana. 1992. Twist test for 

measuring fruit firmness. J. Tex. Stud. 23:215-227.

Sundstrom, F.J., and S.J. Carter. 1983. Influence 

of K and Ca on quality and yield of watermelon. J. 

Am. Soc. Hort. Sci. 108:879-881.

Szczesniak, A.S. 1963. Classification of textural 

characteristics. J. Food Sci. 28:385-389.

Szczesniak, A.S., P.R. Humbaugh, and H.W. 

Block. 1970. Behavior of different foods in the 

standard compression cell of the shear press and 

the effect of sample weight on peak area and 

maximum force. J. Tex. Stud. 1:356-378.

Szczesniak, A.S., and R. Ilker. 1988. The meaning 

of textural characteristics - juiciness in plant 

foodstuffs. J. Texture Studies 19:61-78.

Thai, C.N. 1994. Soft transducer for firmness 

measurement. Paper 94-6538/94-6549, American 

Society of Agricultural Engineers, St. Joseph, MI. 

Thybo, A.K., M. Nielsen, and M. Martens. 

2000. Influence of uniaxial compression rate 

on rheological parameters and sensory texture 

prediction of cooked potatoes. J. Texture Studies 

31:25-40.

Tomos, A.D. 1988. Cellular water relations in 

plants. Water Sci. Rev. 3:186-277.

Tong, C., D. Krueger, Z. Vickers, et al. 1999. 

Comparison of softening-related changes during 

storage of ‘Honeycrisp’ apple, it parents, and 

‘Delicious.’ J. Am. Soc. Hort. Sci. 124:407-415.

Tu, K., P. Jancsok, B. Nicolai, and J. De 

Baerdemaeker. 2000. Use of laser-scattering 

imaging to study tomato-fruit quality in relation 

to acoustic and compression measurements. Int. J. 

Food Sci. Technol. 35:503-510.
110

Upchurch, B.L., G.E. Miles, R.L. Stroshine, et al. 

1987. Ultrasonic measurement for detecting apple 

bruises. Trans. Am. Soc. Agr. Eng. 30:803-809.

Vincent, J.F.V. 1989. Relationship between density 

and stiffness of apple flesh. J. Sci. Food Agr. 

47:443-462.

Voisey, P.W. 1971. Modernization of texture 

instrumentation. J. Texture Studies 2:129-195.

Voisey, P.W., and M. Kloek. 1981. Effect of cell 

size on the performance of the shear-compression 

texture test cell. J. Texture Studies. 12:133-139.

Waldron, K.W., A.C. Smith, A.J. Parr, et al. 1997. 

New approaches to understanding and controlling 

cell separation in relation to fruit and vegetable 

texture. Trends in Food Sc. Technol. 8:213-221.

Wann, E.V. 1996. Physical characteristics of 

mature green and ripe tomato fruit of normal and 

firm genotypes. J. Am. Soc. Hort. Sci. 121:380-

383.

Wu, T., and J.A. Abbott. 2002. Firmness and force 

relaxation characteristics of tomatoes stored intact 

or as slices. Postharv. Biol. Technol. 24:59-68.

Zapp, H.R., S.H. Ehlert, G.K. Brown, et al. 1990. 

Advanced instrumented sphere (IS) for impact 

measurements. Trans. Am. Soc. Agr. Eng. 33:955-

960.

Zhang, X., M.L. Stone, D. Chen, et al. 1994. 

Peach firmness determination by puncture 

resistance, drop impact, and sonic impulse. Trans. 

Am. Soc. Agr. Eng. 37:495-500.
111

Postharvest Pathology

Peter L. Sholberg and William S. Conway

Sholberg is with the Pacific Agri-Food Research 

Centre, Agriculture and Agri-Food Canada, 

Summerland, BC, Canada. Conway is formerly 

with the Food Quality Laboratory, Henry A. 

Wallace Beltsville Agricultural Research Center, 

Agricultural Research Service, U.S. Department 

of Agriculture, Beltsville, MD. He is now retired.

Introduction

Losses caused by postharvest diseases are greater 

than generally realized because the value of fresh 

fruits and vegetables increases several-fold while 

passing from the field to the consumer (Eckert and 

Sommer 1967). Postharvest losses are estimated to 

range from 10 to 30% per year despite the use of 

modern storage facilities and techniques (Harvey 

1978).

Postharvest diseases affect a wide variety of crops, 

particularly in developing countries that lack 

sophisticated postharvest storage facilities (Jeffries 

and Jeger 1990). Infection by fungi and bacteria 

may occur during the growing season; at harvest 

time; during handling, storage, transport and 

marketing; or even after purchase by the consumer 

(Dennis 1983). Reduction of losses in perishable 

food crops resulting from postharvest diseases 

has become a major objective of international 

organizations (Kelman 1989). The reality is that 

there is a portending food crisis that will require 

the concerted efforts of all who are involved 

in food production to redouble their efforts. In 

fact, to adequately feed the world’s expected 10 

billion people within the next 40 to 50 years, food 

production efficiency and distribution will need to 

be improved immensely (Campbell 1998).

Specific causes of postharvest losses of fruits 

and vegetables may be classed as parasitic, 

nonparasitic, or physical (Cappellini and Ceponis 

1984).This chapter deals with the parasitic causes 

that are of microbiological origin that begin as 

latent infections before harvest or occur at harvest 

or afterward during storage. Fungi are more 

commonly found attacking fruit, and bacteria 

are more common as postharvest pathogens of 

vegetables. This chapter will provide a general 

overview of the subject touching on noteworthy 

research where it can be used to illustrate 

postharvest pathology. The reader is encouraged to 

consult the references for specific information on 

the topics that are covered.

Factors that Influence Postharvest 

Pathology

Postharvest losses vary each year. Prevailing 

weather while the crop is growing and at harvest 

contribute greatly to the possibility of decay. 

Certain cultivars are more prone than others to 

decay caused by specific pathogens. Resistance 

of major apple cultivars to the fungi that cause 

blue mold, gray mold, bull’s-eye rot, and Mucor 

rot depended on cultivar (Spotts et al. 1999). 

Condition of the crop, as determined by fertilizer 

and soil factors, is very important in susceptibility 

of the crop to disease. Maturity of the crop at 

harvest, handling, and type of storage have great 

influence on how long the crop can be stored 

without decay. The following sections address 

how these preharvest factors lead to disease in 

specific crops.

Weather. Weather affects many factors related 

to plant diseases, from the amount of inoculum 

that overwinters successfully to the amount of 

pesticide residue that remains on the crop at 

harvest (Conway 1984). Abundant inoculum 

and favorable conditions for infection during the 

season often result in heavy infection by the time 

the produce is harvested. For example, conidia 

of the fungus that causes bull’s-eye rot are raindispersed from cankers and infected bark to fruit, 

especially if rainfall is prolonged near harvest 

time, resulting in rotten fruit in cold storage 

several months later (Spotts 1990).

Pinpoint or storage scab of apple caused by the 

same fungus that causes apple scab and gray mold 

caused by the fungus Botrytis cinerea are also 
112

very much influenced by the weather. Storage 

scab only occurs in years with unusually wet 

summers and early falls, when the fruit remain wet 

for a day or more. These late-season infections 

may not become visible until the apples are in 

storage (Pierson et al. 1971). Flowers and fruit 

are most vulnerable to Botrytis cinerea infection 

when conditions are wet. For example, in grapes 

infection occurs at 15 to 20 oC (59 to 68 oF) in 

the presence of free water after approximately 

15 h (Bulit and Dubos 1988). In wet seasons, 

strawberries and raspberries may be harvested in 

apparently sound condition only to decay during 

transit and marketing (Snowdon 1990).

Postharvest decay involves further development of 

preharvest infections together with new infections 

arising from germination of spores on the fruit 

surface. From these examples it is apparent that 

decay often has a weather component, making 

thorough weather records an important source 

of information for predicting possible decay in 

storage.

Physiological Condition. Condition of produce 

at harvest determines how long the crop can be 

safely stored. For example, apples are picked 

mature but preclimacteric to ensure that they can 

be stored safely for several months. The onset 

of ripening and senescence in various fruit and 

vegetables renders them more susceptible to 

infection by pathogens (Kader 1985). On the other 

hand, fruit and vegetables can be made less prone 

to decay by management of crop nutrition. For 

example, calcium has been more closely related to 

disease resistance than any other cation associated 

with the cell wall (Sams 1994).

In a study on the effect of increased flesh calcium 

content of apples in storage, fruit were treated 

with solutions of CaCl2

 by dipping, vacuum, or 

pressure infiltration. Both vacuum and pressure 

infiltration increased calcium content of the fruit 

sufficiently to significantly reduce decay (Conway 

1982). Increased calcium contents in potatoes 

and peaches have also been documented with 

reduced postharvest decay (Conway 1989). In 

general, produce containing adequate levels of 

calcium do not develop physiological disorders 

and can be stored longer before they breakdown 

or decay. Conversely, high nitrogen content in 

fruit predisposes them to decay (Conway 1984). 

In pears, it has been found that management 

of trees for low nitrogen and high calcium in 

the fruit reduced severity of postharvest fungal 

decay (Sugar et al. 1992). Apple cultivars can 

be selected for resistance to certain postharvest 

diseases (Spotts et al. 1999). For example, ‘Royal 

Gala’ is extremely resistant to wound pathogens, 

‘Granny Smith’ to skin punctures, and ‘Braeburn’ 

to infiltration of fungal spores into the core.

Fungicide Sprays. Certain preharvest sprays 

are known to reduce decay in storage. Several 

studies done on the effectiveness of preharvest 

ziram fungicide application on pome fruit 

showed an average reduction in decay of about 

25 to 50% with a single spray (Sugar and Spotts 

1995). Iprodione was used for several years as a 

preharvest spray 1 day before harvest to prevent 

infection of stone fruit by Monilinia spp. In 

combination with wax and/or oil, its decay control 

spectrum is increased and it will also control 

postharvest fungi such as Rhizopus and Alternaria 

(Ogawa et al. 1992). Cyprodinil prevented gray 

mold infection in apple 3 months after it was 

applied (Sholberg and Bedford 1999). The new 

class of strobilurin fungicides promises to provide 

postharvest control of several diseases in fruits 

and vegetables, is especially effective against fruit 

scab on apples, and should reduce the presence of 

pinpoint scab in storage.

Packing Sanitation. It is important to maintain 

sanitary conditions in all areas where produce is 

packed. Organic matter (culls, extraneous plant 

parts, and soil) can act as substrates for decaycausing pathogens. For example, in apple and 

pear packinghouses, the flumes and dump tank 

accumulate spores (Blanpied and Purnasiri 1968) 

and may act as sources of contamination if steps 

are not taken to destroy or remove them.

Chlorine readily kills microorganisms suspended 

in dump tanks and flumes if the amount of 

available chlorine is adequate. A level of 50 to 

100 ppm of active chlorine provides excellent 
113

fungicidal activity (Spotts and Peters 1980). 

Chlorine measured as hypochlorous acid can 

be obtained by adding chlorine gas, sodium 

hypochlorite, or dry calcium hypochlorite. Though 

chlorine effectively kills spores in water, it does 

not protect wounded tissue against subsequent 

infection from spores lodged in wounds. Organic 

matter in the water inactivates chlorine, and levels 

of chlorine must be constantly monitored. The use 

of a sand filter in association with chlorination 

improves its efficiency probably because it 

removes organic matter (Sholberg and Owen 

1990). Chlorine is sensitive to pH (Dychdala 

1983): Hypochlorite solutions with higher pH 

values (7.5 to 8.5) are more stable but less 

fungicidal, whereas at lower pH values (5.5 to 6.5) 

the solutions are less stable but more fungicidal.

Chlorine dioxide can replace hypochlorite in 

some sanitizing processes, because several 

disadvantages limit the use of chlorine, including 

its unpleasant odor. Chlorine dioxide is not 

corrosive and is effective over a wide pH range 

(Spotts and Peters 1980). Recently in precisely 

controlled tests in water or as a foam, chlorine 

dioxide was found to be effective against common 

postharvest decay fungi on fruit packinghouse 

surfaces (Roberts and Reymond 1994). Peracetic 

acid is another material that could be used (Mari 

et al. 1999). It has greater stability and faster 

biocidal properties than chlorine dioxide but is 

more corrosive.

The search goes on for effective and economical 

sanitizing agents. New and old products alike are 

continually being evaluated under present-day 

packing operations. Interest in ozone has been 

rekindled with development of more efficient 

ozone generators. Acetic acid in the form of a gas 

can be used as a sanitizing agent on several crops 

(Sholberg 1998). It was as effective as SO2

 in 

preventing gray mold decay in table grapes stored 

for 2 months (Sholberg et al. 1996).

Postharvest Treatments. Products or treatments 

used to control postharvest decay can be classified 

as either chemical or biological and should be 

selected only after proper consideration of the 

following conditions (Ogawa and Manji 1984):

• Type of pathogen involved in the decay

• Location of the pathogen in the produce

• Best time for application of the treatment

• Maturity of the host

• Environment during storage, transportation, 

and marketing of produce

Chemical Control

Several fungicides are currently used as 

postharvest treatments for control of a wide 

spectrum of decay-causing microorganisms. 

However, when compared with preharvest pestcontrol products, the number is very small. Many 

products formerly used after harvest are no longer 

permitted because of concerns with residues and 

possible toxic effects, the most notable being 

products that contain benomyl. Other products are 

no longer as effective because of development of 

resistance by the target pathogen. For example, 

intensive and continuous use of fungicides for 

control of blue and green mold on citrus has led 

to resistance by the causal pathogens of these 

diseases (Eckert 1988). Resistance has been 

reported in many other crops to several different 

fungicides with different modes of action (Delp 

1988). Resistance development continues to 

be a major problem and has resulted in the 

Fungicide Resistance Action Committee (FRAC), 

a cooperative effort among various producers of 

fungicides to delay resistance by recommending 

specific management guidelines (FRAC 1998).

Examples of chemicals currently used for 

postharvest treatments are thiabendazole, 

dichloran, and imazalil. However, resistance 

to thiabendazole and imazalil is widespread 

(Holmes and Eckert 1999), and their use as 

effective materials is declining. Preservatives or 

antimicrobial food additives are not generally 

thought of as postharvest treatments, but they do 

control decay and, in some cases, are the only 

means of control. These products include sodium 

benzoate, the parabens, sorbic acid, propionic 

acid, SO2

, acetic acid, nitrites and nitrates, and 

antibiotics such as nisin (Chichester and Tanner 

1972). In California, for example, gray mold of 

stored table grapes is prevented by fumigation 
114

with SO2

 (Luvisi et al. 1992). The demand for 

new postharvest fungicide treatments is strong, 

especially since the loss of iprodione in 1996.

Fludioxinil was granted an emergency registration 

in 1998 to curb potential losses in nectarines, 

peaches, and plums (Forster and Adaskaveg 

1999). Not all postharvest pathogens are currently 

controlled by materials that are available. For 

example, Mucor piriformis, a major postharvest 

pathogen of apples and winter pears in the Pacific 

Northwest is not controlled by any registered 

fungicide (Spotts and Dobson 1989). There is a 

dire need for new fungicide treatments that could 

in part be alleviated by using biological control 

agents (Wisniewski and Wilson 1992, Utkhede 

and Sholberg 1993).

Biological Control

Postharvest biological control is an approach 

that offers several advantages over conventional 

biological control (Wilson and Pusey 1985, Pusey 

1996), such as the following: 

• Exact environmental conditions can be 

established and maintained.

• The biocontrol agent can be targeted much 

more efficiently

• Expensive control procedures are cost 

effective on harvested food.

Several biological control agents have been 

developed, and a few have actually been 

registered for use on fruit crops. The first 

biological control agent developed for postharvest 

use was a strain of Bacillus subtilis (Pusey 

and Wilson 1984). It controlled peach brown 

rot, but when a commercial formulation of the 

bacterium was made, adequate disease control 

was not obtained (Pusey 1989). More recently, 

a strain of Pseudomonas syringae van Hall was 

found that controlled both blue and gray mold 

of pome fruit (Janisiewicz and Marchi 1992). 

It was subsequently registered and is now sold 

commercially for postharvest disease control

(Janisiewicz and Jeffers 1997).

Other bacterial microorganisms have been 

developed for postharvest disease control. 

For example, strains of Bacillus pumilus and 

Pseudomonas fluorescens have been identified that 

exhibit successful control of B. cinerea in field 

trials of strawberry (Swalding and Jeffries 1998). 

Yeasts such as Pichia guilliermondii (Wisniewski 

et al. 1991) and Cryptoccocus laurentii, which 

occur naturally on apple leaves, buds, and fruit 

(Roberts 1990), were the first to be applied for 

control of postharvest decay on fruit. The yeast 

Candida oleophilia has been registered for control 

of postharvest decay on fruit crops. The yeasts 

Cryptococcus infirmo-minutus and Candida sake 

successfully control brown rot and blue mold on 

sweet cherry (Spotts et al. 1998) and on three 

diseases of apple (Vinas et al. 1998), respectively. 

Though there is no doubt that biocontrols are 

effective, they do not always give consistent 

results. This could be because biocontrol efficacy 

is directly affected by the amount of pathogen 

inoculum present (Roberts 1994). Compatibility 

with chemicals used during handling is also 

important. Indications are that biological control 

agents must be combined with other strategies if 

they are to provide acceptable disease control. 

Irradiation for Postharvest Decay Control

Though ultraviolet light has a lethal effect on 

bacteria and fungi that are exposed to the direct 

rays, there is no evidence that it reduces decay of 

packaged fruits and vegetables (Hardenburg et al. 

1986). Low doses of ultraviolet light irradiation 

(254 nm UV-C) reduced postharvest brown rot 

of peaches (Stevens et al. 1998). In this case, the 

low-dose ultraviolet light treatments had two 

effects on brown rot development: reduction in the 

inoculum of the pathogen and induced resistance 

in the host. However, it has not become a practical 

postharvest treatment as yet and requires more 

research.

Gamma radiation has been studied for controlling 

decay, disinfecting, and extending the storage 

life and shelf-life of fresh fruits and vegetables. 

Dosages of 1.5 to 2 kilograys (kGy) and, in some 
115

cases, 3.0 kGy (300 krad) have been effective in 

controlling decay in several products (Hardenburg 

et al. 1986). A dose of 250 grays (Gy) has an 

adverse effect on grapefruits, increasing skin 

pitting, scald, and decay. Low doses of 150 Gy 

for fruit flies and 250 Gy for codling moth are 

acceptable quarantine procedures (Meheriuk 

and Gaunce 1994). Commercial application 

of gamma radiation is limited by the cost and 

size of equipment needed for treatment and by 

uncertainty about consumers’ acceptance of 

irradiated foods (Hardenburg et al. 1986). Gamma 

irradiation may be used more in the future once 

methyl bromide is no longer available to control 

insect infestation in stored products. All uses of 

methyl bromide are being phased out to avoid any 

further damage to the protective layer of ozone 

surrounding the earth.

Effect of Storage Environment on Postharvest 

Decay

Commercial producers and handlers modify 

temperature, RH, and atmospheric composition 

during prestorage, storage, and transit to control 

decay (Spotts 1984). For optimum decay 

control, two or more factors often are modified 

simultaneously. 

Temperature and RH. Proper management of 

temperature is so critical to postharvest disease 

control that all other treatments can be considered 

as supplements to refrigeration (Sommer 1989). 

Fruit rot fungi generally grow optimally at 20 

to 25 oC (68 to 77 °F) and can be conveniently 

divided into those with a growth minimum of 5 

to 10 oC (41 to 50 °F) and those with a growth 

minimum of -6 to 0 oC (21 to 32 °F). Fungi with 

a minimum growth temperature below -2 oC (28 

°F) cannot be completely stopped by refrigeration 

without freezing the fruit. However, temperatures 

as low as possible are desirable because they 

significantly slow growth and thus reduce decay.

High temperature may be used to control 

postharvest decay on crops that are injured by 

low temperatures, such as mango, papaya, pepper, 

and tomato (Spotts 1984). Though hot water 

generally is more effective, hot air has been used 

to control decay in crops that are injured by hot 

water. Heating of pears at temperatures from 21 

to 38 oC (70 to 100 °F) for 1 to 7 days reduced 

postharvest decay (Spotts and Chen 1987). Decay 

in ‘Golden Delicious’ apples was reduced by 

exposure to 38 oC (100 °F) for 4 days (Sams et al. 

1993) and virtually eliminated when treated after 

inoculation (Fallik et al. 1995, Klien et al. 1997). 

Heat treatment eliminates incipient infections and 

improves coverage by fungicides (Couey 1989). 

The primary obstacle to the widespread use of 

heat to control postharvest fruit diseases or insect 

infestation is the sensitivity of many fruit to the 

temperatures required for effective treatment.

Both low and high RH have been related to 

postharvest decay control. Perforated polyethylene 

bags for fruit and vegetable storage create RH 

about 5 to 10% above that in storage rooms. 

Though shrivel and weight loss are reduced, 

decay may increase (Spotts 1984). Crops with 

well-developed cuticle and epidermis, such as 

apples and pears, tolerate lower RH levels, which 

helps prevent storage decay. Often fungal spore 

germination is inhibited at low RH, and small 

differences in RH can have significant effects in 

relation to the degree of postharvest decay (Spotts 

and Peters 1981).

Modified or Controlled Atmospheres.

Alterations in O2

 and CO2 concentrations are 

sometimes provided around fruit and vegetables 

(Spotts 1984). With close control of these gases, 

the synthetic atmosphere is commonly called 

a “controlled atmosphere”; the term “modified 

atmosphere” is used when there is little possibility 

of adjusting gas composition during storage 

or transportation (Sommer 1989). Because the 

pathogen respires as does produce, lowering O2

or raising CO2

 above 5% can suppress pathogenic 

growth in the host. In crops such as stone fruits, a 

direct suppression occurs when fungal respiration 

and growth are reduced by the high CO2

 of the 

modified atmosphere. For example, CO2

 added to 

air has been widely used in the transport of ‘Bing’ 

cherries, primarily to suppress gray mold and 

brown rot. Low O2

 does not appreciably suppress 

fungal growth until the concentration falls below 
116

2%. Important growth reductions result if O2

 is 

lowered to 1% or less, though there is a danger 

that the crop will start respiring anaerobically and 

develop off flavors. Other technologies that have 

been tested for lowering postharvest decay with 

limited success are storage and transport under 

low O2

 and the use of carbon monoxide (Spotts 

1984, Sommer 1989).

Postharvest Diseases of Fruits

Fruit crops are attacked by a wide range of 

microorganisms in the postharvest phase 

(Snowdon 1990, Ogawa and English 1991). Actual 

disease only occurs when the attacking pathogen 

starts to actively grow in the host. Diseases are 

loosely classified according to their signs and 

symptoms. Signs are visible growths of the causal 

agents, and symptoms the discernible responses 

produced by the host. In many diseases there is 

local discoloration and disruption of tissue, with 

the formation of obvious lesions. Postharvest 

diseases are caused primarily by microscopic 

bacteria and fungi, with fungi the most important 

causal agent in fruit crops.

Fungi are further subdivided into classes and 

are described as “lower fungi” (characterized 

by the production of sporangia giving rise to 

numerous sporangiospores) or “higher fungi” 

(described as ascomycetes, deuteromycetes, and 

basidiomycetes.) Ascomycetes are exemplified 

by fruiting bodies that release sexual spores when 

mature. Deuteromycetes, a form of ascomycete, 

only release asexual spores. They are more 

common than the sexual ascomycete stage in 

postharvest crops. Deuteromycetes are further 

subdivided into hyphomycetes and coelomycetes 

based on spore and structural characteristics. The 

agonomycetes contain important soil pathogens 

that form survival structures known as “sclerotia,” 

which allow them to survive in the absence of the 

host. These fungi and the rust and smut fungi are 

examples of basidiomycetes. Table 1 lists many 

important diseases of fruit crops according to host 

and causal agents.

Postharvest Diseases of Vegetables

Postharvest diseases of vegetables are caused by 

microscopic fungi and bacteria (Snowdon 1992, 

Howard et al. 1994). Bacteria are more common 

as pathogens of vegetables than fruit because, 

in general, vegetables are less acidic than fruit. 

Bacteria are visible under the light microscope 

as mostly single-celled rods. Bacteria are capable 

of very rapid multiplication under the right 

conditions of pH, temperature, and nutrition. 

They are classified according to their size, 

shape, reaction to certain stains, and behavior on 

various growth media (Krieg and Holt 1984). The 

term “vegetable” encompasses a range of plant 

parts, and the common definition is a culinary 

one, denoting consumption as a savory rather 

than as a dessert food (Snowdon 1992). Many 

vegetables are fruits in the botanical sense, notable 

examples being tomatoes, peppers, squashes, and 

cucumbers. Table 2 lists many of the important 

diseases of vegetable crops according to host and 

causal agents.
117

Table 1. Important postharvest diseases of fruit

______________________________________________________________________________________

Fruit Disease Causal agent Fungal class/type

______________________________________________________________________________________

Avocado Anthracnose Glomerella cingulata Pyrenomycete

Cercospora spot Pseudocercospora purpurea Hyphomycete

Dothiorella rot Botryosphaeria ribis Loculoascomycete

Scab Sphaceloma persae Coleomycete

Stem-end rots B. theobromae, Deuteromycetes

 Phomopsis perseae,

 Thyronectria pseudotrichia

Banana Anthracnose Colletotrichum musae Coelomycete

Cigar-end rot Trachysphaera fructigena, Deuteromycetes

 Verticillium theobromae

Crown rot C. musae, Deuteromycetes

 Fusarium pallidoroseum,

 V. theobromae

Finger rot B. theobromae Coelomycete

Pitting disease Pyricularia grisea Hyphomycete

Sigatoka disease Mycosphaerella spp. Loculoascomycete

Berries Gray mold Botrytis cinerea Hyphomycete

Leak Mucor spp. Zygomycete

Leather rot Phytophthora spp. Oomycete

Citrus Alternaria rot Alternaria spp. Hyphomycete

Anthracnose C. gloeosporioides Coelomycete

Bacterial canker Xanthomonas campestris Bacterium

Black pit Pseudomonas syringae Bacterium

Black spot Phyllosticta citricarpa Coelomycete

Blue mold Penicillium italicum Hyphomycete

Brown rot Phytophthora spp. Oomycete

Greasy spot Mycosphaerella citri Loculoascomycete

Green mold P. digitatum Hyphomycete

Scab Elsinoe fawcettii Loculoascomycete

Sour rot Geotrichum candidum Hyphomycete

Stem-end rots D. gregaria, Coelomycete

 Phomopsis citri,

 B. theobromae

Kiwifruit Gray mold B. cinerea Hyphomycete

Grape Aspergillus rot Aspergillus niger Hyphomycete

Blue mold Penicillium spp. Hyphomycete

Gray mold B. cinerea Hyphomycete

Rhizopus rot Rhizopus spp. Zygomycete
118

Table 1. Important postharvest diseases of fruit—Continued

______________________________________________________________________________________

Fruit Disease Causal agent Fungal class/type

______________________________________________________________________________________

Mango Anthracnose C. gloeosporioides Coelomycete

Botryodiplodia rot B. theobromae Coelomycete

Stem-end rots B. theobromae, Coelomycete

 Phomopsis spp.

Papaya Anthracnose C. gloeosporioides Coelomycete

Black rot Phoma caricae-papayae Coelomycete

Phytophthora rot P. palmivora Oomycete

Rhizopus rot R. stolonifer Zygomycete

Stem-end rot B. theobromae, Coelomycete

 Phomopsis spp.

Pineapple Black rot Thielaviopsis paradoxa Hyphomycete

Fruitlet core rot Fusarium moniliforme, Hyphomycete

 P. funiculosum

Pome fruit Bitter rot C. gloeosporioides Coelomycete

 (apple, pear) Black rot Sphaeropsis malorum Coelomycete

Blue mold Penicillium expansum, Hyphomycete

 Penicillium spp.

Brown rot Monilinia spp. Hyphomycete

Bull’s-eye rot Cryptosporiopsis curvispora Hyphomycete

Gray mold B. cinerea Hyphomycete

Moldy core Alternaria spp., others Hyphomycete

Mucor rot Mucor piriformis Zygomycete

White rot D. gregaria Coelomycete

Stone fruit Alternaria rot A. alternata Hyphomycete

 (cherry, etc.) Blue mold P. expansum Hyphomycete

Brown rot Monilinia spp. Hyphomycete

Rhizopus rot Rhizopus spp. Zygomycete

____________________________________________________________________________________
119

Table 2. Important postharvest diseases of vegetables

__________________________________________________________________________________

Vegetable Disease Causal Agent Fungal Class/Type __________________________________________________________________________________

Bulbs Bacterial soft rot Erwinia caratovora Bacterium

 (onion, garlic) Black rot Aspergillus niger Hyphomycete

Blue mold rot Penicillium spp. Hyphomycete

Fusarium basal rot Fusarium oxysporum Hyphomycete

Neck rot Botrytis spp. Hyphomycete

Purple blotch Alternaria porri Hyphomycete

Sclerotium rot Sclerotium rolfsii Agonomycete

Smudge Colletotrichum circinans Coelomycete

Crucifers Alternaria leaf spot Alternaria spp. Hyphomycete

 (cabbage, etc.) Bacterial soft rot E. caratovora Bacterium

Black rot Xanthomonas campestris Bacterium

Downy mildew Peronospora parasitica Oomycete

Rhizoctonia rot Rhizoctonia solani Agonomycete

Ring spot Mycosphaerella brassicicola Loculoascomycete

Virus diseases Cauliflower mosaic virus, Virus

 turnip mosaic virus

Watery soft rot Sclerotinia spp. Discomycete

White blister Albugo candida Oomycete

Cucurbits Anthracnose Colletotrichum spp. Coelomycete

 (cucumber, etc.) Bacterial soft rot Erwinia spp. Bacterium

Black rot Didymella bryoniae Loculoascomycete

Botryodiplodia rot Botryodiplodia theobromae Coelomycete

Charcoal rot Macrophomina phaseolina Coelomycete

Fusarium rot Fusarium spp. Hyphomycete

Leak Pythium spp. Oomycete

Rhizopus rot Rhizopus spp. Zygomycete

Sclerotium rot Sclerotium rolfsii Agonomycete

Soil rot R. solani Agonomycete

Legumes Alternaria blight A. alternata Hyphomycete

 (peas, beans) Anthracnose Colletotrichum spp. Coelomycete

Ascochyta pod spot Ascochyta spp. Coelomycete

Bacterial blight Pseudomonas spp., Bacteria

 Xanthomonas spp.

Chocolate spot B. cinerea Hyphomycete

Cottony leak Pythium spp., Oomycete

 Mycosphaerella blight,

 M. pinodes Loculoascomycete

Rust Uromyces spp. Hemibasidiomycete

Sclerotium rot S. rolfsii Agonomycete

Soil rot R. solani Agonomycete

White mold Sclerotinia spp. Discomycete
120

Table 2. Important postharvest diseases of vegetables—Continued

__________________________________________________________________________________

Vegetable Disease Causal Agent Fungal Class/Type __________________________________________________________________________________

Roots/tubers

 Carrots Bacterial soft rot Erwinia spp., Bacteria

 Pseudomonas spp.

Black rot A. radicina Hyphomycete

Cavity spot Disease complex Soil fungi

Chalaropsis rot Chalara spp. Hyphomycete

Crater rot R. carotae Agonomycete

Gray mold rot B. cinerea Hyphomycete

Sclerotium rot S. rolfsii Agonomycete

Watery soft rot Sclerotinia spp. Discomycete

 Potatoes Bacterial soft rot Erwinia spp. Bacteria

Blight Phytophthora infestans Oomycete

Charcoal rot S. bataticola Agonomycete

Common scab Streptomyces scabies Actinomycete

Fusarium rot Fusarium spp. Hyphomycete

Gangrene Phoma exigua Coelomycete

Ring rot Clavibacter michiganensis Bacterium

Sclerotium rot S. rolfsii Agonomycete

Silver scurf Helminthosporium solani Hyphomycete

Watery wound rot Pythium spp. Oomycete

 Sweet potatoes Black rot Ceratocystis fimbriata Pyrenomycete

Fusarium rot Fusarium spp. Hyphomycete

Rhizopus rot Rhizopus spp. Zygomycete

Soil rot Streptomyces ipomoeae Actinomycete

Scurf Monilochaetes infuscans Hyphomycete

Solanaceous plants Alternaria rot A. alternata Hyphomycete

 (tomato, pepper, Anthracnose Colletotrichum spp. Coelomycete

 eggplant) Bacterial canker C. michiganensis Bacterium

Bacterial speck Pseudomonas syringae Bacterium

Bacterial spot X. campestris Bacterium

Fusarium rot Fusarium spp. Hyphomycete

Gray mold rot B. cinerea Hyphomycete

Late blight P. infestans Oomycete

Phoma rot Phoma lycopersici Hyphomycete

Phomopsis rot Phomopsis spp. Coelomycete

Phytophthora rot Phytophthora spp. Oomycete

Pleospora rot Stemphylium herbarum Hyphomycete

Rhizopus rot Rhizopus spp. Zygomycetes
121

Table 2. Important postharvest diseases of vegetables—Continued

__________________________________________________________________________________

Vegetable Disease Causal Agent Fungal Class/Type __________________________________________________________________________________

Sclerotium rot S. rolfsii Agonomycete

Soil rot R. solani Agonomycete

Sour rot Geotrichum candidum Hyphomycete

Watery soft rot Sclerotinia spp. Discomycete

Miscellaneous

 Artichokes Gray mold Botrytis cinerea Hyphomycete

Watery soft rot Sclerotinia sclerotiorum Discomycete

 Asparagus Bacterial soft rot Erwinia or Pseudomonas Bacteria

 spp.

Fusarium rot Fusarium spp. Hyphomycete

Phytophthora rot Phytophthora spp. Oomycete

Purple spot Stemphylium spp. Hyphomycete

 Celery Bacterial soft rot Erwinia or Pseudomonas Bacteria

 spp.

Brown spot Cephalosporium apii Hyphomycete

Cercospora spot Cercospora apii Hyphomycete

Gray mold Botrytis cinerea Hyphomycete

Licorice rot Mycocentrospora acerina Hyphomycete

Phoma rot Phoma apiicola Coelomycete

Pink rot Sclerotinia spp. Discomycete

Septoria spot Septoria apiicola Coelomycete

 Lettuce Bacterial rot Erwinia, Pseudomonas, Bacteria

 Xanthomonas spp.

Gray mold rot B. cinerea Hyphomycete

Rhizoctonia rot R. solani Agonomycete

Ringspot Microdochium Hyphomycete

 panattonianum

Septoria spot S. lactucae Coelomycete

Stemphylium spot Stemphylium herbarum Hyphomycete

Watery soft rot Sclerotinia spp. Discomycete

__________________________________________________________________________________
122

New Directions for Postharvest Plant 

Pathology

Postharvest plant pathology has changed its 

emphasis in the last decade. Food safety has 

emerged as a key element in decay control 

programs. Continued failure to effectively control 

certain postharvest diseases and the need for more 

environmentally friendly crop control materials 

require a new approach to disease control. 

Integrated postharvest decay control is the concept 

that offers the most promise for the future. Society 

can no longer rely on one or two control strategies 

but must enlist the entire spectrum of strategies to 

reduce postharvest losses.

Food Safety Issues

The two most important causes of unsafe food are 

microbial toxins (Hsieh and Gruenwedel 1990) 

and contamination of horticultural products by 

fecal coliforms (Gould 1973). The microbial 

toxins can be subdivided into bacterial toxins 

and toxins produced by fungi or mycotoxins. An 

example of a microbial toxin that is extremely 

toxic are the botulinum toxins produced by the 

anaerobic bacterium Clostridium botulinum. 

Interest in toxins produced by fungi was 

stimulated by the death of 100,000 turkey poults 

in England in 1960. Aflatoxins produced by fungi 

in the peanut meal used to feed the birds was 

the cause. Studies have since shown aflatoxins 

to be potent carcinogens that may occur in nuts 

and grain (Phillips 1984, Ellis et al. 1991). Other 

toxins have been identified that are produced by 

the same fungi that cause postharvest decay. For 

example, patulin produced by Penicillium and 

Aspergillis spp. can be found in apple and pear 

products. Patulin is toxic to many biological 

systems but its role in causing animal and human 

disease is unclear (Hsieh and Gruenwedel 1990). 

Studies on contamination of horticultural products 

by fecal coliforms has increased dramatically 

because of documented incidences of food 

poisoning from apple juice and seed sprouts. 

Definite interactions have been shown between 

plant pathogens and foodborne human pathogens 

such as Salmonella and Listeria. A study involving 

more than 400 samples each of healthy and softrotted commodities collected in retail markets 

indicated that the presence of Salmonella on 

produce affected by bacterial soft rot was twice 

that of healthy samples (Wells and Butterfield 

1997). Controlled experiments with potato, 

carrot, and pepper tissues inoculated with a strain 

of Salmonella confirmed that bacterial soft rot 

infection increased multiplication of Salmonella

by at least three- to ten-fold compared with 

multiplication on uninfected tissues. Similarly, 

populations of Listeria monocytogenes, inoculated 

into decayed apple tissue, continually increased 

on fruit decayed by Glomerella cingulata but 

did not survive after 5 days on fruit decayed by 

Penicillium expansum (Conway et al. 2000). The 

pH of the decayed area declined from pH 4.7 to 

3.7 in the case of P. expansum but increased from 

pH 4.7 to 7.0 in the case of G. cingulata. This 

pH modification may be responsible for affecting 

growth of the foodborne pathogen. 

Contamination of produce with human pathogens 

is an important issue that must be addressed 

along with limiting decay caused by postharvest 

pathogens and maintaining product quality.

Integrated Control of Postharvest 

Diseases

Effective and consistent control of storage 

diseases depends on integration of the following 

practices:

•	Select disease-resistant cultivars where 

possible.

•	Maintain correct crop nutrition by use of leaf 

and soil analysis.

•	Irrigate based on crop requirements and 

avoid overhead irrigation.

•	Apply preharvest treatments to control 

insects and diseases.

•	Harvest crop at the correct maturity for 

storage.

•	Apply postharvest treatments to disinfest and 

control diseases and disorders on produce.
123

•	Maintain good sanitation in packing areas 

and keep dump-water free of contamination.

•	Store produce under conditions least 

conducive to growth of pathogens.

Integration of cultural methods and biological 

treatments with yeast biocontrols has been 

studied on pears (Sugar et al. 1994). It was found 

that early harvest, low fruit nitrogen, high fruit 

calcium, yeast or yeast plus fungicide treatment, 

and controlled atmosphere storage all reduced 

severity of blue mold and side rot. These results 

demonstrated that unrelated cultural and biological 

methods that influenced pear decay susceptibility 

can be combined into an integrated program to 

substantially reduce decay.

In another example of an integrated strategy, 

‘Gala’ apples were heat-treated at 38 o

C (100 °F) 

for 4 days, followed by calcium infiltration with 

2% CaCl2

, and then treated with the microbial 

antagonist, Pseudomonas syringae (Conway 

et al. 1999). The combined strategy was much 

more effective than any single strategy for two 

reasons. First, heat treatment reduced the pathogen 

population on the fruit surface but did not provide 

any residual protection. Second, the residual 

protection was provided by calcium, and the 

biocontrol agent added to the control provided by 

the heat treatment.

As a general rule, alternatives to chemical control 

are often less effective than many fungicides. 

It is highly unlikely that any one alternative 

method alone will give the same level of control 

as fungicides. Therefore, it will generally be 

necessary to combine several alternative methods 

to develop an integrated strategy to successfully 

reduce postharvest decay.

References

Blanpied, G.D., and A. Purnasiri. 1968. 

Penicillium and Botrytis rot of McIntosh apples 

handled in water. Plant Dis. Rep. 52:865-867.

Bulit, J., and B. Dubos. 1988. Botrytis bunch rot 

and blight. In R.C. Pearson and A.C. Goheen, eds., 

Compendium of Grape Diseases, pp. 13-15. APS 

Press, St. Paul, MN.

Campbell, C.L. 1998. Food security and plant 

pathologists. Phytopathol. News 32:70.

Cappellini, R.A., and M.J. Ceponis. 1984. 

Postharvest losses in fresh fruits and vegetables. In

H.E. Moline, ed., Postharvest Pathology of Fruits 

and Vegetables: Postharvest Losses in Perishable 

Crops, pp. 24-30. Bull. 1914 (Pub NE-87), 

University of California, California Agricultural 

Experiment Station, Davis, CA.

Chichester, D.F., and F.W. Tanner. 1972. 

Antimicrobial food additives. In T.E. Furia, ed., 

CRC Handbook of Food Additives, vol. 1, pp. 

115-184. CRC Press, Boca Raton, FL.

Conway, W.S. 1982. Effect of postharvest calcium 

treatment on decay of ‘Delicious’ apples. Plant 

Dis. 66:402-403.

Conway, W.S. 1984. Preharvest factors affecting 

postharvest losses from disease. In H.E. Moline, 

ed., Postharvest Pathology of Fruits and 

Vegetables: Postharvest Losses in Perishable 

Crops, pp. 11-16. Bull. 1914 (Pub NE-87), 

University of California, California Agricultural 

Experiment Station, Davis, CA.

Conway, W.S. 1989. Altering nutritional factors 

after harvest to enhance resistance to postharvest 

disease. Phytopathology 79:1384-1387.

Conway, W.S., W.J. Janisiewicz, J.D. Klein, and 

C.E. Sams. 1999. Strategy for combining heat 

treatment, calcium infiltration, and biological 

control to reduce postharvest decay of ‘Gala’ 

apples. HortScience 34:700-704.
124

Conway, W.S., B. Leverentz, R.A. Saftner, 

et al. 2000. Survival and growth of Listeria 

monocytogenes on fresh-cut apple slices and 

its interaction with Glomeralla cingulata and 

Penicillium expansum. Plant Dis. 84:177-181.

Couey, H.M. 1989. Heat treatment for control 

of postharvest diseases and insect pests of fruits. 

HortScience 24:198-202.

Delp, C.J. 1988. Fungicide Resistance in North 

America, pp. 11-16. APS Press, St. Paul, MN.

Dennis, C. 1983. Postharvest Pathology of Fruits 

and Vegetables. Academic Press, London, UK.

Dychdala, G.R. 1983. Chlorine and chlorine 

compounds. In S.S. Block, ed., Disinfection, 

Sterilization, and Preservation, 3rd ed., pp. 157-

182. Lea & Febiger Co., Philadelphia, PA.

Eckert, J.W., and N.F. Sommer. 1967. Control of 

diseases of fruits and vegetables by postharvest 

treatment. Ann. Rev. Plant Pathol. 5:391-432.

Eckert, J.W. 1988. Dynamics of benzimidazoleresistant penicillia in the development of 

postharvest decay of citrus and pome fruits. In C.J. 

Delp, ed., Fungicide Resistance in North America, 

pp. 31-35. APS Press, St. Paul, MN.

Ellis, W.O., J.P. Smith, B.K. Simpson, and J.H. 

Oldham. 1991. Aflatoxins in food: occurrence, 

biosynthesis, effects on organisms, detection, 

and methods of control. Crit. Rev. Food Sci. Nut. 

30:403-439.

Fallik, E., S. Grinberg, M. Gambourg, et al. 1995. 

Prestorage heat treatment reduces pathogenicity of 

Penicillium expansum in apple fruit. Plant Pathol. 

45:92-97.

Forster, H., and J.E. Adaskaveg. 1999. Fludioxinil, 

a new reduced risk postharvest fungicide for 

management of fungal decays of stonefruit. 

Phytopathology 89:S26.

FRAC [Fungicide Resistance Action Committee]. 

1998. 1998 Status Report and Recommended 

Fungicide Resistance Management Guidelines. 

Global Crop Protection Federation, Brussels, 

Belgium.

Gould, W.A. 1973. Micro-contamination of 

horticultural products. HortScience 8:116-119.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Harvey, J.M. 1978. Reduction of losses in fresh 

fruits and vegetables. Ann. Rev. Phytopath. 

16:321-341.

Holmes, G.J., and J.W. Eckert. 1999. Sensitivity 

of Penicillium digitatum and P. italicum to 

postharvest citrus fungicides in California. 

Phytopathology 89:716-721.

Howard, R.J., J.A. Garland, and W.L. Seaman. 

1994. Diseases and Pests of Vegetable Crops 

in Canada: An Illustrated Compendium. The 

Entomological Society of Canada and The 

Canadian Phytopathological Society, Ottawa, 

Ontario, Canada.

Hsieh, D.P., and S.H. Gruenwedel. 1990. 

Microbial toxins. In C. Winter, J. Seiber, and C. 

Nuckton, eds., Chemicals in the Human Food 

Chain, pp. 239-267. Van Nostrand Reinhold, New 

York, NY.

Janisiewicz, W.J., and A. Marchi. 1992. Control 

of storage rots on various pear cultivars with a 

saprophytic strain of Pseudomonas syringae. Plant 

Dis. 76:555-560.

Janisiewicz, W.J., and S.N. Jeffers. 1997. Efficacy 

of commercial formulation of two biofungicides 

for control of blue mold and gray mold of apples 

in cold storage. Crop Prot. 16:629-633.

Jeffries, P., and M.J. Jeger. 1990. The biological 

control of postharvest diseases of fruit. Biocontrol 

News Info. 11:333-336.
125

Kader, A.A. 1985. Biochemical and physiological 

basis for effects of controlled and modified 

atmospheres on fruits and vegetables. Food 

Technol. 40:99-104.

Kelman, A. 1989. Introduction: the importance of 

research on the control of postharvest diseases of 

perishable food crops. Phytopathology 79:1374.

Klien, J.D., W.S. Conway, B.D. Whitaker, and 

C.E. Sams. 1997. Botrytis cinerea decay in apples 

is inhibited by postharvest heat and calcium 

treatment. J. Amer. Soc. Hort. Sci. 122:91-94.

Krieg, N.R., and J.G. Holt. 1984. Bergey’s Manual 

of Systemic Bacteriology, vol. 1. Williams and 

Wilkins, Baltimore, MD.

Luvisi, D.A., H.H. Shorey, J.L. Smilanick, et al. 

1992. Sulfur Dioxide Fumigation of Table Grapes. 

Bull. 1932, University of California, Division of 

Agriculture and Natural Resources, Davis, CA.

Mari, M., T. Cembali, E. Baraldi, and L. Casalini. 

1999. Peracetic acid and chlorine dioxide for 

postharvest control of Monilinia laxa in stone 

fruits. Plant Dis. 83:773-776.

Meheriuk, M., and A.P. Gaunce. 1994. Temperate 

fruits. In R.E. Paull and J.W. Armstrong, eds., 

Insect Pests and Fresh Horticultural Products: 

Treatments and Responses, pp. 291-307. CAB 

Intl, Wallingford, UK.

Ogawa, J.M., and B.T. Manji. 1984. Control of 

postharvest diseases by chemical and physical 

means. In H.E. Moline, ed., Postharvest Pathology 

of Fruits and Vegetables: Postharvest Losses in 

Perishable Crops, pp. 55-66. Bull. 1914 (Pub 

NE-87), University of California, California 

Agricultural Experiment Station, Davis, CA.

Ogawa, J.M., and H. English. 1991. Diseases of 

Temperate Zone Tree Fruit and Nut Crops. Pub. 

no. 3345, University of California, Division of 

Agriculture and Natural Resources, Davis, CA.

Ogawa, J.M., J.E. Adaskaveg, and K.E. Conn. 

1992. Efficacy of iprodione wax/oil mixtures for 

control of postharvest decay of fruit caused by 

Rhizopus and Alternaria spp. Phytopathology 

82:1064.

Phillips, D.J. 1984. Mycotoxins as a postharvest 

problem. In H.E. Moline, ed., Postharvest 

Pathology of Fruits and Vegetables: Postharvest 

Losses in Perishable Crops, pp. 50-54. Bull. 1914 

(Pub NE-87), University of California, California 

Agricultural Experiment Station, Davis, CA.

Pierson, C.F., M.J. Ceponis, and L.P. McColloch. 

1971. Market Diseases of Apples, Pears, and 

Quinces. Agriculture Handbook 376, U.S. 

Department of Agriculture, Agricultural Research 

Service, Washington, DC.

Pusey, P.L., and C.L. Wilson. 1984. Postharvest 

biological control of stone fruit brown rot by 

Bacillus subtilis. Plant Dis. 68:753-756.

Pusey, P.L. 1989. Use of Bacillus subtilis and 

related organisms as biofungicides. Pesticide Sci. 

27:133-140.

Pusey, P.L. 1996. Micro-organisms as agents in 

plant disease control. In L.G. Copping, ed., Crop 

Protection Agents from Nature: Natural Products 

and Analogues, pp. 426-443. Royal Society of 

Chemistry, Cambridge, United Kingdom.

Roberts, R.G. 1990. Biological control of 

gray mold of apple by Cryptoccus laurentii. 

Phytopathology 80:526-530.

Roberts, R. 1994. Integrating biological control 

into postharvest disease management strategies. 

HortScience 29:758-762.

Roberts, R.G., and S.T. Reymand. 1994. Chlorine 

dioxide for reduction of postharvest pathogen 

inoculum during handling of tree fruits. Appl. 

Environ. Micro. 60:2864-2868.
126

Sams, C.E., W.S. Conway, J.A. Abbott, et al. 

1993. Firmness and decay of apple following 

postharvest pressure infiltration of calcium and 

heat treatment. J. Amer. Soc. Hort. Sci. 118:623-

627.

Sams, C.E. 1994. Management of postharvest 

disease resistance in horticultural crops: 

introduction to the colloquium. HortScience 

29:746.

Sholberg, P.L., and G.R. Owen. 1990. Populations 

of propagules of Penicillium spp. during 

immersion dumping of apples. Can. Plant Dis. 

Surv. 70:11-14.

Sholberg, P.L., A.G. Reynolds, and A.P. Gaunce. 

1996. Fumigation of table grapes with acetic acid 

to prevent postharvest decay. Plant Dis. 80:1425-

1428.

Sholberg, P.L. 1998. Fumigation of fruit with 

short-chain organic acids to reduce the potential of 

postharvest decay. Plant Dis. 82:689-693.

Sholberg, P.L., and K.E. Bedford. 1999. Use of 

cyprodinil for control of Botrytis cinerea on apple. 

Phytopathology 89:S72.

Snowdon, A.L. 1990. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 1, General Introduction and Fruits. CRC 

Press, Boca Raton, FL.

Snowdon, A.L. 1992. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. CRC Press, Boca Raton, FL.

Sommer, N.F. 1989. Suppressing postharvest 

disease with handling practices and controlled 

environments. In J.H. LaRue and R.S. Johnson, 

eds., Peaches, Plums, and Nectarines Growing 

and Handling for Fresh Market, pp. 179-190. Pub. 

no. 3331, University of California, Department of 

Agriculture and Natural Resources, Davis, CA.

Spotts, R.A., and B.B. Peters. 1980. Chlorine and 

chlorine dioxide for control of ‘d’Anjou’ pear 

decay. Plant Dis. 64:1095-1097.

Spotts, R.A., and B.B. Peters. 1981. The effect of 

relative humidity on spore germination of pear 

decay fungi and ‘d’Anjou’ pear decay. Acta Hort. 

124:75-78.

Spotts, R.A. 1984. Environmental modification for 

control of postharvest decay. In H.E. Moline, ed., 

Postharvest Pathology of Fruits and Vegetables: 

Postharvest Losses in Perishable Crops, pp. 67-72. 

Bull. 1914 (Pub NE-87), University of California, 

California Agricultural Experiment Station, Davis, 

CA.

Spotts, R.A., and P.M. Chen. 1987. Prestorage 

heat treatment for control of decay of pear fruit. 

Phytopathology 77:1578-1582.

Spotts, R.A., and R.L. Dobson. 1989. Effects of 

the experimental fungicide RH 886 on Mucor 

piriformis. Pesticide Sci. 25:391-399.

Spotts, R.A. 1990. Bull’s-eye rot. In A.L. Jones 

and H.S. Aldwinckle, eds., Compendium of Apple 

and Pear Diseases, pp. 56. APS Press, St. Paul, 

MN.

Spotts, R.A., L.A. Cervantes, T.J. Facteau, and T. 

Chand-Goyal. 1998. Control of brown rot and blue 

mold of sweet cherry with preharvest iprodione, 

postharvest Cryptococcus infirmo-miniatus, and 

modified packaging. Plant Dis. 82:1158-1160.

Spotts, R.A., L.A. Cervantes, and E.A. Mielke. 

1999. Variability in postharvest decay among 

apple cultivars. Plant Dis. 83:1051-1054.

Stevens, C., V.A. Khan, J.Y. Lu, et al. 1998. The 

germicidal and hormetic effects of UV-C light on 

reducing brown rot disease and yeast microflora of 

peaches. Crop Protection 17:75-84.

Sugar, D., T.L. Righetti, E.E. Sanchez, and H. 

Khemira. 1992. Management of nitrogen and 

calcium in pear tree for enhancement of fruit 

resistance to postharvest decay. HortTechnol. 

2:382-387.
127

Sugar, D., R.G. Roberts, R.J. Hilton, et al. 

1994. Integration of cultural methods with yeast 

treatment for control of postharvest fruit decay in 

pear. Plant Dis. 78:791-795.

Sugar, D. and R. Spotts. 1995. Preharvest 

strategies to reduce postharvest pear decay. Tree 

Fruit Postharvest Journal 6(2):13-14.

Swalding, I.R., and P.J. Jeffries. 1998. 

Antagonistic properties of two bacterial biocontrol 

agents of grey mould disease. Biocontrol Sci. 

Technol. 8:439-448.

Utkhede, R.S., and P.L. Sholberg. 1993. Biological 

control of diseases of temperate fruit trees. Curr. 

Top. Bot. Res. 1:313-334.

Vinas, I., J. Usall, N. Texido, and V. Sanchis. 

1998. Biological control of major postharvest 

pathogens in apple with Candida sake. Int. J. Food 

Micro. 40:9-16.

Wells, J.M., and J.E. Butterfield. 1997. Salmonella 

contamination associated with bacterial soft rot 

of fresh fruits and vegetables in the marketplace. 

Plant Disease 81:867-872.

Wilson, C.L., and P.L. Pusey. 1985. Potential for 

biological control of postharvest plant diseases. 

Plant Disease 69:375-378.

Wisniewski, M., C. Biles, S. Droby, et al. 1991. 

Mode of action of the postharvest biocontrol 

yeast Pichia guilliermondii. 1. Characterization 

of attachment to Botrytis cinerea. Physiol. Molec. 

Plant Pathol. 39:245-258.

Wisniewski, M.E., and C.L. Wilson. 1992. 

Biological control of postharvest diseases of fruits 

and vegetables: recent advances. HortScience 

27:94-98.
128

Flavor

Elizabeth A. Baldwin

Baldwin was with the Citrus and Subtropical 

Products Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, Winter 

Haven, FL. She is now with the U.S. Horticultural 

Research Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, Fort 

Pierce, FL.

Introduction

The quality of fresh produce has traditionally 

been based on external characteristics of size, 

color, and absence of surface defects. Fruit and 

vegetable breeders select for color, size, disease 

resistance, yield, and other easily quantified 

horticultural traits. Because flavor and texture 

characteristics were not a part of the selection 

process, improvements in these quality attributes 

have not kept pace with the more easily quantified 

traits. Public and industry organizations are 

increasingly concerned with the public’s growing 

dissatisfaction over the flavor and texture of some 

horticultural produce.

Flavor and aroma are perhaps the most elusive 

and subjective of quality traits. Flavor is taste 

plus odor and is mainly composed of sweetness, 

sourness, and aroma, which correspond to 

sugars, acids, and volatiles. Other components 

of flavor include bitterness related, for example, 

to sesquiterpene lactones in chicory (Peters and 

Amerongen 1998), saltiness due to various natural 

salts, and astringency related to flavonoids, 

alkaloids (DeRovira 1997), tannins (Taylor 

1993), and other factors. The perception of 

sweetness—that is, sugars—one of the most 

important components of fruit or vegetable 

flavor, is modified by sourness or acid levels and 

aroma compounds. The contribution of aroma 

to the flavor quality of fresh produce has gained 

increasing attention.

Genetics is the primary determinant of flavor of 

fresh produce (Cunningham et al. 1985, Baldwin 

et al. 1991b, 1992), with preharvest environment 

(Romani et al. 1983), cultural practices (Wright 

and Harris 1985), harvest maturity (Fellman et 

al. 1993, Maul et al. 1998, Baldwin et al. 1999a), 

and postharvest handling (Mattheis et al. 1995; 

Fellman et al. 1993; Baldwin et al. 1999a,b) 

having lesser effect. Fruit such as apples and 

bananas that continue to ripen after harvest are 

termed climacteric, while those such as citrus 

and strawberries that do not ripen after harvest 

are termed nonclimacteric. The flavor quality 

of nonclimacteric fruit generally declines after 

harvest, while climacteric fruit can reach their 

best flavor after harvest. Climacteric fruit develop 

better quality if harvested after the start of 

ripening, while fruit of both will be inferior in 

quality if harvested immature, even if held under 

optimal postharvest conditions.

Human perception of flavor is exceedingly 

complex. Taste is the detection of nonvolatile 

compounds (in concentration of parts per hundred) 

by several types of receptors in the tongue for 

sugars or polyalcohols, hydronium ions, sodium 

ions, glucosides and alkaloids, etc. These 

correspond to the perception of sweet, sour, salty 

and bitter tastes in food. Aroma compounds can 

be detected in parts-per-billion concentrations and 

are detected by olfactory nerve endings in the nose 

(DeRovira 1997). The brain processes information 

from these senses to give an integrated flavor 

experience. This integration makes it difficult to 

determine the relative importance of each input 

since the brain can interpret changes in aroma as 

changes in taste (O’Mahony 1995) or vice versa. 

For example, the levels of aroma compounds 

influenced panelist perception of sweetness and 

sourness for tomatoes (Lycopersicon esculentum

Mill.) (Baldwin et al. 1998). Conversely, levels of 

taste components influenced panelist perception of 

aromatic descriptors in mango (Mangifera indica

L.) (Malundo et al. 2000a). The perception of 

certain combinations of chemicals is synergistic, 

while others combinations mute our perception 

in a process called masking. In contrast to 
129

masking is anesthetization or blanking, in which 

olfactory receptors become overloaded. Lighteraroma volatiles (for example, top notes—low 

molecular weight, polar, hydrophilic compounds) 

are perceived first and generally have the major 

impact on perception, while heavier compounds 

are perceived later: for example, background 

notes—high molecular weight, nonpolar, 

hydrophobic compounds (DeRovira 1997). 

Sensory Evaluation

Human perception of flavor can be determined 

by sensory evaluation by taste panels. 

Consumer preference and acceptance vary due 

to socioeconomic, ethnic, and geographical 

background, often necessitating the segmenting of 

subpopulations for a particular study (O’Mahony 

1995). Generally a large number of panelists (for 

example, 50 to 100) rank their perceptions on a 

traditional 9-point hedonic scale, but sometimes 

a simple 3-point scale including the descriptive 

terms outstanding, acceptable, and unacceptable 

can be effective for tomato fruit evaluation. In 

one study, adaptation of logistic regression from 

medical science proved useful, in which a 0 

or 1 indicates whether the consumer would or 

would not purchase a mango (Mangifera indica). 

The consumer was asked to base their decision 

on flavor, which was then related to chemical 

constituents (Malundo et al. 2000b). Difference 

testing can be used to measure slight differences 

between foods (usually due to one particular 

aspect of flavor) and is considered a narrowband approach. Descriptive analysis measures 

intensities of a set of sensory attributes and is 

considered a broadband approach (O’Mahony 

1995). Panelists are trained to detect a range 

of flavor attributes and score their intensity, 

generally on a 150 mm unstructured line. Sensory 

studies for fresh produce can be used to identify 

optimal harvest maturity, evaluate flavor quality 

in breeding programs, determine optimal storage 

and handling conditions, assess effects of 

disinfestation or preconditioning techniques on 

flavor quality, and measure flavor quality over the 

postharvest life of a product.

Taste Components

Fructose, sucrose, and glucose are the sugars that 

affect the perception of sweetness in fruits and 

vegetables. Fructose is the sweetest, and glucose 

is less sweet than sucrose. A single “sucrose 

equivalent” value is the weighted average of these 

various sugars in a sample (Koehler and Kays 

1991). Sugar content is commonly accepted to be 

synonymous with SSC (soluble solids content), 

and an inexpensive refractometer can easily 

measure SSC. However, the quantification of 

individual sugars requires complicated laboratory 

analysis. Breeders often select for higher SSC in 

an attempt to increase sweetness. In some fruits, 

such as orange (Citrus sinensis), SSC relates to 

sweetness; while in others, such as tomato and 

mango, the relationship is not linear (Baldwin et 

al. 1998, 1999a, Malundo et al. 2000a).

Organic acids, such as citrate in citrus and 

tomatoes, tartaric acid in grapes (Vitis sp.), and 

malic acid in apples (Malus pumila), give fruit 

and vegetables their sour flavor. Some fruits, like 

melon (Cucumis melo) or banana (Musa sp.), have 

very little acid (Wyllie et al. 1995). Different acids 

can affect sourness perception, depending on their 

chemical structure. An increase in carboxyl groups 

decreased acidity, while an increase in molecular 

weight or hydrophobicity increased sourness 

(Hartwig and McDaniel 1995). For example, 

acetic acid was perceived as more intensely sour 

than lactic or citric acid.

Acids can be measured individually by HPLC 

(Baldwin et al. 1991a,b), by titration (TA) with 

sodium hydroxide (Jones and Scott 1984), or by 

pH (Baldwin et al. 1998). Sometimes SSC, the 

ratio of SSC/TA, or pH relate better to sourness 

than TA itself (Baldwin et al. 1998, Malundo et al. 

2000a).
130

Aroma Components

Volatiles that we can perceive contribute to food 

flavor. The level at which a compound can be 

detected by smell (the odor threshold) can be 

established in a background similar to a food 

medium as described by the Ascending Method 

of Limits of the American Society for Testing 

and Materials (ASTM 1991). Log odor units are 

calculated from the ratio of the concentration 

of a component in a food to its odor threshold. 

Compounds with positive odor units contribute 

to food flavor. Buttery (1993), for example, 

determined concentrations, odor thresholds, and 

log odor units for those tomato volatiles present 

at levels of 1 ppb or more (about 30 of > 400 

identified compounds). However, the aroma 

perception of volatile compounds is affected by 

the medium of evaluation. For example, both 

the thresholds and descriptors of some volatile 

compounds in tomato were different if the 

background medium contained levels of methanol 

and ethanol similar to that found in fresh tomato 

homogenate or in deodorized homogenate itself 

than if the medium was water (Tandon et al. 2000) 

(table 1).

Table 1. Odor descriptors for tomato aroma compounds in deionized water, 

ethanol/methanol/deionized water mix and deodorized tomato homogenate

_____________________________________________________________________________________

Aroma compound Deionized water EtOH/MeOH/water Tomato 

homogenate

_____________________________________________________________________________________

Hexanal grassy/green rancid/stale oil stale/green/grassy

Trans-2-hexenal floral/grass/apple fruity/almond/vine stale/green/vine

Cis-3-hexenol leafy/cut grass fresh-cut grass green/celery

Hexanol mint/grass alcohol glue/oil

6-methyl-5-hepten-2-one raw greens/nutty alcohol/paint sweet/floral

Cis-3-hexenal grass/tomato-like alcohol/paint tomato/citrus

2-isobutylthiazole fermented/plastic alcohol/tomato-like pungent/bitter

2-pentenal vine/organic solvent acetone/medicine stale/oil

Acetone glue/alcohol alcohol/nutty/spoilt green

β-ionone sweet/perfume-like sweet sweet/floral

Geranylacetone sweet/paint/sharp sweet/floral/leafy sweet/citrus/ester

3-methylbutanol earthy/watermelon rind glue/mint/cinnamon sweet/fresh

Phenylethanol floral/roses alcohol alcohol/nutty

3-methylbutanal bug spray/alcohol fruity/green/leafy stale/rotten

1-penten-3-one glue/oil/pungent nutty/glue/alcohol fresh/sweet

Ethanol earthy/stale pungent/rancid —

Methanol earthy/stale — —

_____________________________________________________________________________________

Source: Tandon et al. 2000
131

Aroma compounds are often only released 

upon cell disruption when previously 

compartmentalized enzymes and substrates 

interact (Buttery 1993). Some aroma compounds 

are bound to sugars as glycosides (celery 

[Apium graveolens], lettuce [Lactuca sativa]), 

or glucosinolates (cabbage [Brassica oleracea],

radish [Raphanus sativus]). This linkage can be 

cleaved by enzyme action or heat during cooking. 

Other aromatic compounds are breakdown 

products of lipids, amino acids, lignin, or pigments 

(Buttery and Ling 1993).

Measurement of aroma compounds is difficult 

and time consuming. Earlier studies employed 

the classical flavor isolation procedures of steam 

distillation and solvent extraction (Teranishi and 

Kint 1993). The disadvantage of this method 

is that it can qualitatively and quantitatively 

modify the flavor profile of a sample (Schamp 

and Dirinck 1982). This method is not easily 

applied to large numbers of samples, and internal 

standards must be incorporated to determine 

recovery. The resulting concentration of material, 

however, allows identification of compounds by 

gas chromatography-mass spectrometry (GCMS). Investigators have employed purge-and-trap 

headspace sampling methods, which involve 

trapping and concentrating volatile components 

on a solid support. Volatiles are later released 

from the trap using heat for analysis by GC-MS. 

This method is excellent for quantification and 

identification of aroma compounds (Schamp and 

Dirinck 1982, Teranishi and Kint 1993).

Static headspace methods are said to more 

closely reflect the true flavor profile; but 

compounds are present at low levels, and some 

may not be detected. Cryofocusing (cold trap) of 

static headspace volatiles (Teranishsi and Kint 

1993) reduces this problem, since samples are 

concentrated without heating that may cause 

adulteration. This method has been used for 

quantification of orange juice volatiles (Moshonas 

and Shaw 1997). The newest method is solidphase micro-extraction (SPME), a rapid sampling 

technique in which volatiles interact with a fibercoated probe inserted into the sample headspace. 

The probe is then transferred to a GC injection 

port where the volatiles are desorbed. It has been 

used on apples, tomatoes (Song et al. 1997), and 

strawberries (Song et al. 1997, Golaszewski et al. 

1998).

Aside from GC and GC-MS methods, there are 

new sensors available that have a broad range of 

selectivity. These sensor arrays, called “electronic 

noses,” are useful to discriminate among samples 

based on the interaction of volatile components 

with the various sensors. The resulting 

response pattern allows a particular sample or 

flavor component(s) to be detected by pattern 

recognition. However, these instruments do not 

give information that leads to identification and 

quantification of individual compounds. Five basic 

sensor technologies have been commercialized 

to date: metal oxide semiconductors, metal oxide 

semiconductor field effect transistors, conducting 

organic polymers, piezoelectric crystals (bulk 

acoustic wave), and quartz crystal microbalance. 

The next generation of electronic noses may use 

fiberoptic, electrochemical, and bimetal sensors 

(Schaller et al. 1998).

Relating Sensory to Chemical Data

Chemical analysis of flavor compounds provides 

little insight into the actual flavor experience. 

However, sensory attributes, preferences, and 

decisions can be statistically related to chemical 

components in foods (Martens et al. 1994). Some 

important or abundant flavor compounds in 

selected fruits and vegetables are shown in table 

2. Correlation of physical measurements with 

sensory analysis gives meaning to instrumental 

data, as was shown with apple and tomato 

(Baldwin et al. 1998). For example, linear 

regression established relationships between levels 

of sesquiterpene lactones and bitterness in chicory 

(Peters and Amerongen 1998). Multivariate 

methods require large data sets, but nonlinear 

regression techniques such as principal component 

or discriminate analysis yielded useful results for 

citrus (Moshonas and Shaw 1997), strawberry 

(Fragaria ananassa) (Shamaila et al. 1992), and 

tomato (Maul et al. 1998). Differences between 
132

samples were found based on measurement of 

volatiles or other flavor compounds. 

Alternatively, sniff ports (olfactometry detectors) 

can be used with GCs, allowing a person to 

determine if odors are detectable as well as their 

relative intensity as the volatile components are 

separated by the GC column. This technique was 

used on apples (Cunningham et al. 1985, Young 

et al. 1996). Descriptive terms can be assigned to 

the respective peaks on the GC chromatogram that 

have odor activity (Acree 1993). The drawback 

to this method is that the interactive effects of 

volatile compounds with each other and with 

sugars and acids, both chemically and in terms of 

human perception, are eliminated.

Factors That Can Affect Flavor of Fruits 

and Vegetables

Effect of Genetics on Flavor

Fruit and vegetable varieties differ in flavor based 

on sensory and chemical analysis. “Charm” 

analysis combines separation on a GC column 

with a sniff port to assign biological activity (odor 

activity) to individual aroma components as they 

are identified and quantified by GC (Cunningham 

et al. 1985). This study with 40 cultivars showed 

that apple aroma was not the result of the same 

compounds in every cultivar, although some 

common volatile compounds were important in all 

cultivars.

Important aroma-specific compounds for 

strawberry included ethyl butanoate, methyl 

butanoate, γ-decalactone, and 2-heptanone 

(Larsen et al. 1992). Strawberry cultivars differed 

in flavor intensity and sweetness, according to 

a trained sensory panel (Podoski et al. 1997). 

Concentrations of several important compounds, 

including α- and ß-ionones, were higher in wild 

compared to cultivated raspberries (Rubus sp.). 

In addition, numerous aroma compounds were 

found only in wild berries, all of which may 

contribute to the stronger and more pleasant aroma 

of wild berries (Martin and MacLeod 1990). In 

tomato, the TA/SSC (Stevens et al. 1977) and 

levels of flavor volatiles varied significantly 

among varieties (Baldwin et al. 1991a,b). 

Insertion of the rin gene to reduce ethylene 

production and slow tomato fruit softening 

resulted in some deterioration in flavor quality 

(Baldwin et al. 2000) and reduction in flavor 

volatiles (Baldwin et al. 1992, 2000). Flavor 

appears to be related to ethylene production 

(Baldwin et al. 1991a, 2000). Transgenic fruit 

with antisense aminocyclopropanecarboxylic 

acid (ACC) synthase (an enzyme in the ethylene 

biosynthetic pathway) had lowered levels of 

many important flavor volatiles (Baldwin et al. 

2000). Fruit with antisense pectinmethylesterase 

(which demethylates pectin in cell walls) had 

lowered levels of methanol, while those with 

downregulated phytoene synthase (phytoene is a 

precursor of carotenoids) had lowered levels of 

carotenoid-derived volatiles (Baldwin et al. 2000).

Effect of Preharvest Factors

Preharvest factors such as sunlight, water 

availability, fertilization, and chemical 

applications affect crop growth and can affect 

internal quality characteristics of the harvested 

product, including flavor. Preharvest treatment 

with aminoethoxyvinylglycine (AVG) suppressed 

volatile production in pears by 50%, which was 

reversed by ethylene exposure (Romani et al. 

1983); and heavy rains prior to harvest dilute 

flavor compounds in tomato. Fruit from tomato 

plants treated with increased levels of N and K 

fertilizer scored lower in sensory analysis and 

showed increased levels of TA, SSC, and several 

volatiles (Wright and Harris 1985). Preharvest 

mite control resulted in sweeter and more flavorful 

field grown strawberries than those receiving no 

treatments, according to a trained sensory panel 

(Podoski et al. 1997).

Effect of Harvest Maturity

Horticultural crops should be harvested at optimal 

eating quality, but practical considerations dictate 

that they are harvested at a stage that minimizes 

physical damage during shipping and handling 

and maximizes shelf-life. The climacteric stage at 

harvest affected ester formation in apples (Fellman 
133

et al. 1993). Harvest maturity affected both the 

sensory and chemical analysis of ripened tomato 

fruit (Maul et al. 1998). Tomatoes harvested at 

the immature green stage resulted in ripened fruit 

with lower volatile levels than mature-greenharvested tomatoes. Harvest maturity also affected 

consumer acceptability for mango and trained 

descriptive panel ratings for sweetness, sourness, 

and various aroma descriptors. Fruit harvested 

later were sweeter and less sour and generally had 

more intense aroma characteristics (Baldwin et al. 

1999a).

Effect of Postharvest Handling

Various techniques are used to extend the shelflife of fruits and vegetables after harvest, to 

control postharvest decay, and to eliminate pests 

(quarantine treatments). These storage techniques 

and treatments involve cold, heat, irradiation, 

chemical applications, and different storage 

atmospheres.

Tomato fruit stored at 36, 41, 50, and 55 °F (2, 5, 

10, and 13 °C) had reduced levels of important 

volatiles and had less-ripe aroma and flavor 

as well as more off flavors compared to fruit 

stored at 68 °F (20 °C), as quantified by a trained 

descriptive panel (Maul et al. 2000). Subjection 

of fruit to heat treatments for preconditioning and 

decay control (McDonald et al. 1996) resulted in 

altered aroma volatile profiles. Heat treatment of 

apples to reduce physiological and pathological 

disorders inhibited emission of volatile esters 

important to apple flavor (Fallik et al. 1997). 

Levels of fructose and glucose, but not sucrose, 

decreased with increased storage time and storage 

temperature for muskmelon. However, sensory 

analysis did not find differences in flavor or 

sweetness between stored and freshly harvested 

melons (Cohen and Hicks 1986).

CA storage altered flavor of apples, and, if 

prolonged, reduced volatile emission compared 

to air-stored fruit, especially lipid-derived 

esters (Mattheis et al. 1995). Low-O2

 storage 

decreased ester content and the enzymatic 

activity responsible for ester biosynthesis in 

apples (Fellman et al. 1993). However, when 

atmospheres induced anaerobic metabolism, 

large concentrations of ethanol and acetaldehyde 

accumulated. The altered synthesis of fruit 

volatiles resulted in increased amounts of ethyl 

acetate and certain ethyl esters at the expense 

of others. Sensory analysis of CA-stored apples 

revealed that intensity of fruity and floral 

descriptors decreased after 10 weeks in CA, while 

sourness and astringency were higher compared 

to apples stored in air. CA storage also increased 

certain volatiles in tomato, compared to air-stored 

fruit (Crouzet et al. 1986).

Use of packaging and edible coatings can create 

a modified atmosphere (MA) with reduced O2

and elevated CO2

 levels, similar to that of CA. 

Lowering O2

 and raising CO2 can maintain the 

quality of many fresh fruits and vegetables for 

extended periods. However, exposure of fresh 

produce to O2

 levels below their tolerance level 

can increase anaerobic respiration and lead to the 

development of off flavors. Use of edible coatings 

affects flavor and the level of volatile flavor 

compounds in citrus (Cohen et al. 1990), apple 

(Saftner et al. 1999), and mango fruit (Baldwin 

et al. 1999b). The coating barrier probably 

induced anaerobic respiration and the synthesis of 

ethanol and acetaldehyde and entrapped volatiles, 

including ethanol and acetaldehyde (Baldwin et 

al. 1999b). In broccoli, sulfur-containing volatiles, 

including methanethiol and dimethyl disulfide, 

are produced in response to anaerobic conditions 

that can be created by MAP (Dan et al. 1997). 

Storing strawberries in MAP altered volatile 

profiles depending on conditions (CO2

, mixed 

gases, or air), enabling separation of the samples 

using multivariate statistics (Shamaila et al. 1992). 

Fruit treated with CO2

 had the greatest change 

in volatile levels. This was confirmed by another 

study in which strawberry fruit stored in a CO2

-

saturated atmosphere exhibited significant changes 

in volatile levels and phenylalanine ammonia 

lyase (PAL) activity (Dourtoglou et al. 1995). The 

amino acid phenylalanine is the precursor to a 

number of volatiles through a pathway in which 

PAL is the key enzyme.
134

In addition to CA, other gaseous treatments of 

fruits and vegetables have been reported. Use 

of ethylene to synchronize ripening has been 

practiced for years on banana and tomato, as well 

as for degreening of citrus. Ethylene gassing of 

tomato fruit alters volatile levels (McDonald 

et al. 1996). Treatment of apple fruit with 

1-methylcyclopropene (1-MCP) and methyl 

jasmonate inhibited both ethylene production and 

production of many volatile alcohols and esters, 

including the formation of esters from alcohols 

(Fan and Mattheis 1999). Treatment of bananas 

with 1-MCP also suppressed volatile production 

and composition, resulting in an increase in 

alcohols and a decrease in related esters (Golding 

et al. 1999). Application of acetaldehyde and 

ethanol vapors to blueberries, tomatoes, and pears 

increased their sugar content, sugar-acid ratio, and 

hedonic sensory rating (Paz et al. 1981).

Other chemical treatments of fresh produce 

may also affect flavor. For example, pressure 

infiltration of apples with calcium chloride 

transiently reduced levels of important flavor 

volatiles (Saftner et al. 1999).

Flavor of Some Popular Fruits and 

Vegetables

Apple. Sucrose is the major sugar in apples, 

though it is slowly hydrolyzed to glucose and 

fructose during latter ripening stages. The major 

organic acid is malate, although some citrate 

is also present (Knee 1993). Eleven aroma 

compounds contribute to apple aroma in most 

of the 40 cultivars, while 27 other compounds 

contributing to flavor where found only in certain 

genetic types (Cunningham et al. 1985). Loss of 

apple flavor after long-term CA storage is a major 

problem, probably due to the reduction of volatile 

synthesis during storage (Mattheis et al.1995).

Peach (Prunus persica). The main sugar in 

peaches is sucrose, but cultivars differ greatly 

in glucose:fructose:sorbitol ratios, which may 

contribute to differences in flavor. The major 

organic acids are malate and citrate, with malate 

levels declining and citrate levels increasing as 

fruit ripen (Brady 1993). Aroma of peaches and 

nectarines is distinguished by the presence of 

γ- and δ-lactones (peach-like and coconut-like, 

respectively), although other esters and aldehydes 

contribute to peach flavor (Do et al. 1969, Crouzet 

et al. 1990). γ-Lactones from C-5 to C-12, 

δ-lactones, and unsaturated lactones represent 

more than 25% of the volatiles, with γ-lactone 

being the second most abundant component after 

benzaldehyde. γ-Undecalactone, although rarely 

reported in natural extracts, has a distinct peach 

odor. It has been named “peach aldehyde” and is 

used in peach flavor formulations (Crouzet et al. 

1990). Ethyl hexanoate and 3-methylbutanoate, 

linalool, α-terpineol, 6-pentyl-α-pyrone (coconut 

odor), and benzyl alcohol are also considered 

important (Crouzet et al. 1990).

Small Fruits

Strawberry. In most berry fruits sucrose, glucose, 

and fructose are present in roughly equivalent 

concentrations (Manning 1993), and citrate is 

the major organic acid. More than 200 volatile 

compounds have been identified in strawberry. 

C-6 aldehydes such as hexanal and trans-2-

hexenal are found, as well as lipoxygenase and 

hydroperoxide lyase. Lipoxygenase acts on 

linolenic acid to form 13- and 9-hydroperoxides, 

which are cleaved by hydroperoxide lyase to form 

hexanal and cis-3-hexenal. The cis-3-hexenal is 

then isomerized to trans-2-hexenal (Perez et al. 

1999), as was reported for tomato (Galliard et al. 

1977, Riley et al. 1996). 2,5-Dimethyl-4-hydroxy3(2H)-furanone (furaneol) and its methyl ether 

(mesifuran) are important aroma components in 

both strawberry and tomato and are considered to 

be glycosidically bound in both fruits (Roscher et 

al. 1997). Of more than 100 volatile compounds 

identified from strawberry, furaneol, ethyl 

hexanoate, and ethyl butanoate are considered to 

be the character-impact compounds (Zabetakis 

and Holden 1997). Sensory analysis of strawberry 

juice showed that furaneol was positively related 

to fresh flavor and negatively related to off flavors, 

while α-terpineol was inversely related to fresh 

flavor (Golaszewski et al. 1998).
135

Raspberry (Rubus idaeus, R. ursinus). The 

main sugars in raspberry are sucrose, glucose, 

and fructose, with citric as the major organic acid 

(Robbins and Fellman 1993). At least 200 volatile 

compounds have been identified in raspberry 

(Honkanen and Hirvi 1990, Dourtoglou et al. 

1995). Impact flavor compounds for raspberry are 

1-(p-hydroxyphenyl)-3-butanone, cis-3-hexenol, 

α- and β-ionones, α-irone, and mesifurane. Other 

abundant volatiles include geraniol, nerol, and 

linalool among others (Paterson et al. 1993). The 

“raspberry ketone,” or character-impact volatile 

for raspberry, is 4-(4-hydroxyphenyl)-butan-2-

one (Larsen and Poll 1990). It had the lowest 

threshold (therefore the largest contribution to 

flavor), followed by α-ionone, β-ionone, geraniol, 

linalool, and benzyl alcohol. Furaneol, linalool, 

and ethyl hexanoate were important general 

aroma compounds, while ethyl butanoate, methyl 

butanoate, γ-decalactone, and 2-heptanone were 

important cultivar-specific compounds (Larsen 

et al. 1992). The most potent flavor compounds 

identified using a retronasal aroma simulator 

in raspberries were β-damascenone, diacetyl, 

1-hexen-3-one, 1-nonen-3-one, 1-octen-3-one, and 

cis-3-hexenal (Roberts and Acree 1996).

Blackberry (Rubus laciniata). Fresh 

blackberry fruit contain 245 aroma compounds 

(Georgilopoulos and Gallois 1987). The most 

abundant were heptan-2-ol, para-cymen-8-ol, 

heptan-2-one, hexanol, α-terpineol, pulegone, 

octanol, isoborneol, mytenol, 4-terpineol, carvone, 

elemincine, and nonanol. Though heptan-2-ol is an 

important flavor compound with an intense fruit 

taste with herbaceous nuances, no single volatile 

was identified as blackberry-like (Marton and 

MacLeod 1990). Some compounds in blackberry 

fruit and leaves are glycosidically bound, such 

as benzyl alcohol, benzoic acid, 3-hydroxy-7,8-

dihydro-β-ionol, and cis-3-hexenol among others 

(Humpf and Schreier 1991).

Blueberry (Vaccinium). Blueberries have 

glucose and fructose as their major soluble sugars 

and citric, malic, and quinic acids (Eck 1986). 

The odor-impact compounds for high-bush 

blueberry (Vaccinium myrtillus) are trans-2-

hexenal, trans-2-hexenol, and linalool, but also 

include geraniol, citronellol, hydroxycitronellol, 

farnesol, and farnesyl acetate. Most volatiles are 

present below their threshold concentrations, 

but hydroxycitronellol was described by 

sensory panelists as blueberry-like. Rabbit-eye 

blueberries (V. ashei) have a different aroma 

than high-bush. Some aroma volatiles unique to 

rabbit-eye blueberries include 1-penten-2-one, 

γ-terpinene, carveol, acetone, cis-caran-3-ol, 

ecineralone, α-cedrene, sabinol, geranyl formate, 

linalyl acetate, undecan-2-one, tridecan-2-one, 

ethyl acetate, ethyl tetradecanoate, dimethyl 

octanedioate, toluene, p-cymene, and β-ionone, 

among others (Honkanen and Hirvi 1990).

Grape (Vitis). Glucose and fructose are the 

predominant sugars in grapes, while tartaric and 

malic acids account for 90% of the TA (Kanellis 

and Roubelakis-Angelakis 1993). Grapes show 

an increase in free and glycosylated aroma 

compounds at the end of ripening, after sugar 

accumulation has slowed (Coombe and McCarthy 

1997). This process is different from that of other 

berries and has been termed “engusting.” The 

volatiles in wine grapes are the most complex 

and are classified into five groups, of which the 

first four have glycosylated forms: monoterpene 

(abundant in “floral” grapes), norisoprenoid, 

benzenoid, aliphatic, and methoxypyrazine. The 

accumulation of flavor volatiles occurs late in 

the berry-ripening cycle, well after accumulation 

of sugar as observed in Muscat berries (Park et 

al. 1991). Different varieties have distinctive 

aroma character. For example, Muscat odor 

is mainly composed of monoterpenes such as 

linalool and geraniol (Webb 1981, Kanellis 

and Roubelakis-Angelakis 1993). Carbernet 

Sauvignon, a V. vinifera cultivar, contains 

methoxyisobutylpyrazine, which has a strong, 

green-bell-pepper-like aroma (Webb 1981). 

Benzyl and 2-phenylethyl alcohols, ethers, 

aldehydes, and hydrocarbons also contribute to 

aroma. American grapes (V. labruscana and V. 

rotundifolia) are not suitable for wine production 

because they possess what has been termed 

“foxy” and candy-like odors due to compounds 

like methyl anthranylate, aminoacetophenone, 

furaneol, and methyl furaneol. ß-Phenylethanol, 

with its rose-like odor, was found to be important 
136

for muscadine (V. rotundifolia) aroma ( Flora and 

Nakayama 1981). The V. vinifera grapes exhibit 

a mild aroma that is more desirable for wine 

production (Shure and Acree 1995).

Banana (Musa). Sucrose is the predominant 

sugar in banana initially, but as ripening proceeds 

glucose and fructose accumulate. Malic, citric, 

and oxalic acids are the predominant organic 

acids, with the astringent taste of unripe bananas 

being attributed in part to oxalate levels (Seymour 

1993). The characteristic aroma of bananas 

arises from a complex mixture of compounds 

including short-chain fatty acids such as acetates, 

butanoates, and 3-methylbutyl esters. Recently, 

nonvolatile glycoside precursors were shown 

to release glycosidically bound volatiles from 

banana pulp by ß-glucosidase, including decan1-ol, 2-phenylethanol, 3-oxy-pentanoic acid, 

3-methylbutanoic acid, and benzoic acid (Perez 

et al. 1997). Esters account for about 70% of the 

volatile compounds and acetates and butyrates 

predominate (Seymour 1993). 3-Methylbutyl 

acetate, however, is considered to dominate 

banana flavor as the key odor-impact volatile 

(Berger 1991), along with butanoate and 

3-methylbutanoate (Engel et al. 1990). Unusual 

phenol derivatives eugenol, 5-methoxyeugenol, 

eugenol-methylether, and elemicin contribute 

background notes for the full-bodied mellow 

aroma of ripe bananas (Engle et al. 1990).

Citrus Fruits

Sweet Orange (Citrus sinensis). The major sugar 

in most citrus types is sucrose, with varying levels 

of glucose and fructose. The major acid is citrate. 

Typical orange aroma is attributed to alcohols, 

aldehydes, esters, hydrocarbons, ketones, and 

other components, of which more than 200 have 

been identified. Of these, esters and aldehydes are 

the primary contributors, followed by alcohols, 

ketones, and hydrocarbons (Bruemmer 1975). 

There is no single impact compound for orange. 

However, octanal, decanal, nonanal, dodecanal, 

ethylbutyrate, and limonene are likely contributors 

to flavor (Shaw and Wilson 1980, Shaw 1991).

Tangerine (Citrus reticulata). Analysis of 

tangerine essence revealed 34 volatile compounds 

that were odor contributors. However, no one 

compound was found to have a characteristic 

tangerine odor (Moshonas and Shaw 1972). 

Later studies suggested that the compounds 

thymol and methyl-N-methylanthranilate 

(dimethylanthranilate) are odor-impact 

compounds for this fruit but that they are modified 

by the presence of monoterpene hydrocarbons. 

Nevertheless, dimethylanthranilate is the most 

potent flavor component (Shaw and Wilson 1980).

Grapefruit (Citrus paradisi). At least 126 

volatile components have been identified in 

grapefruit (Demole et al. 1982). Nootkatone and 

1-p-menthene-8-thiol may be key aroma-impact 

compounds for grapefruit (Demole et al. 1982), 

although aldehydes and esters are also important 

(Shaw and Wilson 1980). 

Mango (Mangifera indica). The major sugars 

in mango are glucose, fructose, and sucrose, 

with sucrose predominating. The major acids 

are citric, malic, and sometimes tartaric at 0.1% 

to 0.4% TA (Nairain et al. 1997, Baldwin et al. 

1999b) and 10 to 16 SSC (Baldwin et al. 1999b). 

Mango varieties differ in amount and type of 

volatile compounds present (more than 150 

compounds identified), often depending on area of 

production. Asian mangoes have more oxygenated 

volatile compounds such as esters, furanones, 

and lactones, giving some varieties pineapple- or 

peach-like aromas (Narain et al. 1997), while 

western mangoes that are hybrids of Asian stock 

have higher levels of certain hydrocarbons such as 

3-carene (MacLeod and de Troconis 1982, Wilson 

et al. 1986, Narain et al. 1997).

Pineapple (Ananas comosus). Besides banana 

and possibly mango, pineapple is the most popular 

fruit from the tropics. SSC can range from 11° 

to 17° Brix, and the major sugars are glucose, 

fructose, and sucrose, with sucrose predominating 

(Salunkhe and Desai 1984, Shukor et al. 1998). 

The major acids are citrate and malate with 

about 0.1 to 0.6% titratable acidity (Salunkhe 

and Desai 1984, Shukor et al. 1998). More than 

120 volatiles have been identified in green and 
137

ripened pineapples with esters dominating at 

more than 80% of the total volatiles (Shukor 

et al. 1998). Contributing aroma volatiles, 

based on odor thresholds, show that pineapple 

aroma is also dominated by esters such as ethyl 

2-methylbutanoate, ethyl acetate, ethyl hexanoate, 

ethyl butanoate, methyl heptanoate, and others.

Melons (Cucumis melo). Sucrose is the principal 

sugar in most melon types, although high levels 

of fructose may be present in some watermelon 

cultivars. Melons contain citrate and malate, 

or only malate in watermelon (Seymour and 

McGlasson 1993). Ethyl 2-methylbutanoate 

and methyl-2-methylpropanoate are among 

the most significant contributors to flavor of 

muskmelon cultivar ‘Makdimon,’ one of the C. 

mello reticulatus cultivars that exhibit strong 

characteristic aromas. Muskmelon and watermelon 

also have cis-non6-enal and cis,cis-nona-3,6,-

dien-1-ol, respectively. The former has a strong 

melon-like aroma, while the latter is reminiscent 

of watermelon rind. 4-Oxononanal and 2-hydroxy5-pentyltetrahydrofuran have fruity and green 

odors and contribute to watermelon aroma. The 

volatile cis-non6-enyl acetate has a pleasant 

honeydew-melon-like aroma (Engle et al. 1990). 

Other varieties have ethyl-2-methylpropanoate, 

2-methylbutyl acetate, 2-methylpropyl acetate, 

and the thioether esters (Wyllie et al. 1995).

Tomato (Lycopersicon esculentum). The SSC/

TA ratio (De Bruyn et al. 1971) or the content of 

SSC or TA are important for flavor (Stevens et al. 

1977, Jones and Scott 1984). The major sugars are 

glucose and fructose in roughly equal amounts, 

while citrate and malate are the major organic 

acids, with citrate predominating (Baldwin et al. 

1991a,b, Hobson and Grierson 1993). However, 

more than 400 volatile compounds were identified, 

of which 16 or so have odor thresholds that would 

indicate that they contribute to flavor (Buttery 

1993, Buttery and Ling 1993). Of these, there is 

no clear odor-impact compound. Buttery (1993) 

suggested that a combination of cis-3-hexenal, 

hexanal, 1-penten-3-one, 3-methylbutanal, trans2-hexenal, 6-methyl-5-hepten-2-one, methyl 

salicylate, 2-isobutylthiazole, and β-ionone at 

the appropriate concentrations produces the 

aroma of a fresh ripe tomato. Of these, cis-3-

hexenal and β-ionone have the highest odor 

units, and 2-isobutylthiazole is unique to tomato. 

Furaneol has an odor threshold indicating it may 

contribute to flavor (Buttery et al. 1995). Volatile 

production occurs at the same time that ethylene 

increase, carotenoid synthesis, and chlorophyll 

breakdown occur (Baldwin et al. 1991a). Enzymes 

important in volatile synthesis from lipids include 

lipoxygenase, hydroperoxide lyase (hydroperoxy 

cleavage), and alcohol dehydrogenase (Galliard et 

al. 1977, Riley et al. 1996). Amino acid precursors 

include alanine, isoleucine, leucine, phenylalanine, 

and valine (Buttery and Ling 1993). Glycosides 

are also precursors to some volatiles (Krammer et 

al. 1994). Furaneol is also reported to be important 

(seems it is found in every fruit). Genetically 

engineered fruit with down- or up-regulated 

alcohol dehydrogenase expression exhibited 

altered levels of some related volatiles (Speirs et 

al. 1998).
138

Table 2. Some important or abundant flavor compounds in selected fruits and vegetables

____________________________________________________________________________________________

Fruit and references Major Major Important aroma

sugars acids compounds

____________________________________________________________________________________________

Apple

Fellman et al. 1993 sucrose malic β-damascenone

Honkanen and Hirvi 1990 glucose citric butyl hexanoate

Knee 1993 fructose isoamyl hexanoate

Mattheis et al. 1995 hexyl hexanoate

Young et al. 1996 ethyl butanoate

 propyl butanoate

hexyl butanoate

butylacetate

2-ethyl-1-butyl acetate

ethyl acetate

butanol

Peach

Brady 1993 sucrose malic benzaldehyde

Crouzet et al. 1990 glucose citric benzyl alcohol

Do et al. 1969 fructose nonanol

 sorbitol

linalool

ethyl hexanoate

3-methylbutanoate

α-terpineol

γ-hexalactone

δ-decalactone

γ-undecalactone

δ-undecalactone

γ-dodecalactone

δ-dodecalactone

α-pyrone

6-pentyl-α-pyrone

Strawberry

Golaszewski et al. 1998 sucrose citric hexanal

Honkanen et al. 1980 glucose cis-3-hexanal

Manning 1993 fructose trans-2-hexanal

Perez et al.1999 furaneol

Roscher et al. 1997 mesifuran

Zabetakis and Holden 1997 ethyl hexanoate

 ethyl butanoate

methyl butanoate

ethyl-2-methyl propanoate
139

Table 2. Some important or abundant flavor compounds in selected fruits and vegetables

—Continued

____________________________________________________________________________________________

Fruit and references Major Major Important aroma

sugars acids compounds

____________________________________________________________________________________________

Raspberry

Dourtoglou et al. 1995 sucrose citric H-(4-hydroxyphenyl-butan-2-one)

Honkanen and Hirvi 1990 glucose (raspberry ketone)

Larsen and Poll 1990 fructose α-ionone

Larsen et al. 1992 β-ionone

Paterson et al. 1993 geraniollinalool

Robbins and Fellman 1993 benzyl alcohol

Roberts and Acree 1996 ethyl hexanoate

 ethyl butanoate

methyl butanoate

γ-decalactone

2-heptanone

cis-3-hexanal

β-damascenone

Grape (references for all grape types)

Coombe and McCarthy 1997

Flora and Nakayama 1981

Kanellis and Roubelakis

 -Angelakis 1993

Park et al. 1991

Shure and Acree 1995

Webb 1981

Concord glucose tartaric methyl anthranilate

 (Vitis labruscana) fructose malic 0-aminoacetophenone

 furaneol

methyl furaneol

β-damascenone

Muscadine β-phenylethanol

 (V. rotundifolia) butyl alcohol

 hexyl alcohol

hexanal

trans-2-hexenal

isoamyl alcohol

acetaldehyde

isobutyraldehyde

ethyl acetate 

ethyl propionate

butyl acetate

propyl acetate

2-methylbutanol

 
140

Table 2. Some important or abundant flavor compounds in selected fruits and vegetables

—Continued

____________________________________________________________________________________________

Fruit and references Major Major Important aroma

sugars acids compounds

____________________________________________________________________________________________

Muscat varieties linalool 

 (V. vinifera) geraniol

 methoxyisobutylpyrazine

Banana

Berger 1991 sucrose malic decan-1-ol

Engel et al. 1990 glucose citric 2-phenylethanol

Perez et al. 1997 fructose oxalic 3-oxy-pentanoic acid

Seymour 1993 3-methylbutanoic acid

 3-methylbutyl acetate

butanoate

3-methylbutanoate

eugenol

5-methoxyeugenol

eugenol-methylether

elemicin

Sweet orange

Bruemmer 1975 sucrose citric geranial

Shaw 1991 glucose neral acetaldehyde

Shaw and Wilson 1980 fructose decanal

 octanal

nonanal

ethyl acetate

ethyl propionate

ethyl butanoate

methyl butanoate

ethyl-2-methyl butanoate

ethyl-3-hydroxy hexanoate

linalool

α-terpineol

limonene

myrcene

α-pinene

valencene

Tangerine

Moshonas and Shaw 1972 sucrose citric acetaldehyde

Shaw and Wilson 1980 glucose decanal

 fructose octanal

 dimethyl anthranilate

thymol

α-sinensal

γ-terpinene

β-pinene
141

Table 2. Some important or abundant flavor compounds in selected fruits and vegetables

—Continued

____________________________________________________________________________________________

Fruit and references Major Major Important aroma

sugars acids compounds

____________________________________________________________________________________________

Grapefruit

Demole et al. 1982 sucrose citric acetaldehyde

Shaw and Wilson 1980 glucose decanal

 ethyl acetate

methyl butanoate

ethyl butanoate

1-p-menthene-8-thiol

nootkatone

limonene

naringin

Mango

Baldwin et al. 1999 sucrose citric ethyl butanoate

MacLeod and de Troconis 1982 glucose malic ethyl-2-butanoate

Nairain et al. 1997 fructose hexanal

Wilson et al. 1986 cis-3-hexanal

 trans-2-hexanal

γ-octalactone

γ-dodecalactone

 furaneol

α-pinene

β-pinene

 3-carene

myrcene

limonene

p-cymene

terpinolene

α-Copaene

caryophyllene

Melon sucrose malic ethylbutyrate

 (Cantaloupe, Honeydew, fructose citric ethyl-2-methyl butyrate

 Watermelon) (watermelon: ethyl butyrate

Engle et al. 1990 malic only) ethyl hexanoate

Seymour and McGlasson 1993 hexyl acetate

Wyllie et al. 1995 3-methylbutyl acetate

 benzyl acetate

cis-6-nonenyl acetate

trans-6-nonenol

cis,cis-3,6-nonadienol

cis-6-nonenal

4-oxononanal

2-hydroxy-5-pentyltetra-hydrofuran 

cis-non6-enyl acetate

methyl acetate

ethyl acetate
142

Table 2. Some important or abundant flavor compounds in selected fruits and vegetables

—Continued

____________________________________________________________________________________________

Fruit and references Major Major Important aroma

sugars acids compounds

____________________________________________________________________________________________

 isopropyl acetate 

 ethyl propanoate

 ethyl isobutanoate

 propyl acetate

 butyl acetate

 methyl-2-methylbutanoate

 ethyl butanoate

 2-methylpropanoate

 2-methylbutyl acetate

 2-methylpropyl acetate

 methyl (methylthio) acetate

 ethyl (methylthio) acetate

 ethyl (methylthio) propanoate

Tomato

Baldwin et al. 1991a,b glucose citric hexanal

Buttery 1993 fructose malic trans-2-hexenal

Buttery and Ling 1993 cis-3-hexenal

Buttery et al. 1995, 1989 cis-3-hexenol

De Bruyn et al. 1971 β-ionone

Hobson and Grierson 1993 β-damascenone

 1-penten-3-one

 3-methylbutanal

 3-methylbutanol

 2-isobutylthiazole1-nitro-

 phenyl-ethane

 trans-2-heptenal

 phenylacetaldehyde

 6-methyl-5-hepten-2-one

 methyl salicylate

 geranylacetone

____________________________________________________________________________________________
143

Conclusion

Flavor of fruits and vegetables is an important 

aspect of quality. Though difficult to define, 

qualify, and quantify, this elusive and complex 

trait is important to consumers and deserves more 

attention from both researchers and industry. 

Flavor quality of fresh and processed fruit and 

vegetable products will be an important factor in 

an increasingly competitive global market. Flavor 

maintenance becomes a challenge as shelf-life 

and marketing distances increase due to new 

storage, handling, and transport technologies. 

However, despite these issues the bottom line for 

flavor quality is still genetic. Breeders need more 

information and analytical tools in order to select 

for flavor quality. Use of wild material may be 

necessary in breeding programs to regain flavor 

characteristics that have been lost from some 

commodities. Use of molecular markers that relate 

to flavor may help identify important enzymes in 

flavor pathways. The effect of harvest maturity 

on flavor quality needs to be determined for each 

commodity. With the current focus on flavor 

quality and current advances in flavor chemistry, 

sensory techniques, and molecular biology, there 

are many opportunities to further efforts on behalf 

of flavor quality in fresh produce.

References

Acree, T.E. 1993. Bioassays for flavor. In T.E. 

Acree and R. Teranishi, eds., Flavor Science: 

Sensible Principles and Techniques, pp. 1-20. ACS 

Books, Washington, DC.

ASTM [American Society for Testing and 

Materials]. 1991. Determination of odor and 

taste thresholds by a force choice ascending 

concentration series methods of limits. ASTM 

Standard Practice E679, pp. 1-5. ASTM, 

Philadelphia, PA.

Baldwin, E.A., M.O. Nisperos, and M.G. 

Moshonas. 1991a. Quantitative analysis of flavor 

and other volatiles and for other constituents of 

two tomato varieties during ripening. J. Amer. 

Soc. Hort. Sci. 116:265-269.

Baldwin, E.A., M.O. Nisperos-Carriedo, and 

M.G. Moshonas. 1991b. Quantitative analysis of 

flavor parameters in six Florida tomato varieties 

(Lycopersicon esculentum Mill). J. Agric. Food 

Chem. 39:1135-1140.

Baldwin, E.A., M.O. Nisperos-Carriedo, and J.W. 

Scott. 1992. Levels of flavor volatiles in a normal 

cultivar, ripening inhibitor and their hybrid. Proc. 

Fla. State Hort. Soc. 104:86-89.

Baldwin, E.A., J.W. Scott, M.A. Einstein, et 

al. 1998. Relationship between sensory and 

instrumental analysis for tomato flavor. J. Amer. 

Soc. Hort. Sci. 12:906-915.

Baldwin, E.A., T.M.M. Malundo, R. Bender, and 

J.K. Brecht. 1999a. Interactive effects of harvest 

maturity, controlled atmosphere and surface 

coatings on mango (Mangifera indica L.) flavor 

quality. HortScience 34:514.

Baldwin, E.A., J.K. Burns, W. Kazokas, et al. 

1999b. Effect of two edible coatings with different 

permeability characteristics on mango (Mangifera 

indica L.) ripening during storage. Postharv. Biol. 

Technol. 17:215-226.

Baldwin, E.A., J.W. Scott, C.K. Shewmaker, and 

W. Schuch. 2000. Flavor trivia and tomato aroma: 

biochemistry and possible mechanisms for control 

of important aroma components. HortScience 

35:1013-1022.

Berger, R.G. 1991. Fruits. In H. Maarse, ed., 

Volatile Compounds in Foods and Beverages, pp. 

283-304. Marcel Dekker, New York, NY.

Brady, C.J. 1993. Grape. In G.B. Seymour, J.E. 

Taylor, and G.A. Tucker, eds., Biochemistry of 

Fruit Ripening, pp. 379-404. Chapman and Hall, 

New York, NY.

Bruemmer, J.H. 1975. Aroma substances of citrus 

fruits and their biogenesis. In F. Drawart, ed., 

Symposium on Fragrance and Flavor Substances, 

pp. 167-176. Verlag Hans Carl, Nuremburg, 

Germany.
144

Buttery, R.G. 1993. Quantitative and sensory 

aspects of flavor of tomato and other vegetable 

and fruits. In T.E. Acree and R. Teranishi, 

eds., Flavor Science: Sensible Principles and 

Techniques, pp. 259-286. ACS, Washington, DC.

Buttery, R.G., and L.C. Ling. 1993. Volatiles 

of tomato fruit and plant parts: relationship and 

biogenesis. In R. Teranishi, R. Buttery, and H. 

Sugisawa, eds., Bioactive Volatile Compounds 

from Plants, American Chemical Society 

Symposium Series no. 525, pp. 23-34. ACS 

Books, Washington, DC.

Buttery, R.G., G.R. Takeoka, and L.C. Ling. 1995. 

Furaneol: odor threshold and importance to tomato 

aroma. J. Agric. Food Chem. 43:1638-1640.

Cohen, E., Y. Shalom, and I. Rosenberger. 1990. 

Postharvest ethanol buildup and off-flavor in 

Murcott tangerine fruits. J. Amer. Soc. Hort. Sci. 

115:775-778.

Cohen, R.A., and J.R. Hicks. 1986. Effect of 

storage on quality and sugars in muskmelon. J. 

Amer. Soc. Hort. Sci. 111:553-557.

Coombe, B.G., and M.G. McCarthy. 1997. 

Identification and naming of the inception of 

aroma development in ripening grape berries. 

Aust. J. Grape and Wine Res. 3:18-20.

Crouzet, J., P. Etievant, and C. Bayonove. 1990. 

Stone fruit: apricot, plum, peach, cherry. In I.D. 

Morton and A.J. Macleod, eds., Food Flavors, Part 

C, The Flavor of Fruits, pp. 43-91. Elsevier, New 

York, NY.

Crouzet, J., A. Signoret, J. Coulibaly, and 

M.H. Roudsari. 1986. Influence of controlled 

atmosphere storage on tomato volatile 

components. In G. Charalambous, ed., The 

Shelf-Life of Foods and Beverages, pp. 355-367. 

Elsevier, Amsterdam, The Netherlands.

Cunningham, D.G., T.E. Acree, J. Barnard, et al. 

1985. Charm analysis of apple volatiles. Food 

Chem. 19:137-147.

Dan, K., S. Todoriki, M. Nagata, and I. Yamashita. 

1997. Formation of volatile sulfur compounds in 

broccoli stored under anaerobic condition. J. Japan 

Soc. Hort. Sci. 65:867-875.

Demole, E., P. Enggist, and G. Ohloff. 1982. 

1-p-Menthene-8-thiole: A powerful flavor impact 

constituent of grapefruit juice (Citrus paradisi

Macfadyen). Helv. Chim. Acta 65:1785-1794.

DeRovira, D. 1997. Manual - Flavor 

Nomenclature Workshop: An Odor Description 

and Sensory Evaluation Workshop. Flavor 

Dynamics, Inc., Somerset, NJ.

De Bruyn, J.W., F. Garretsen, and E. Kooistra. 

1971. Variation in taste and chemical composition 

of the tomato (Lycopersicon esculentum Mill). 

Euphytica 20:214-227.

Do, J.Y., D.K Salunkhe, and L.E. Olson. 1969. 

Isolation, identification and comparison of the 

volatiles of peach fruit as related to harvest 

maturity and artificial ripening. J. Food Sci. 

34:618-621.

Dourtoglou, V., A. Gally, V. Tychopoulos, et al. 

1995. Effects of storage under CO2

 atmosphere 

on the volatiles, phenylalanine ammonialyase activity and water soluble constituents of 

strawberry fruits. In G. Charalamous, ed., Food 

Flavors: Generation, Analysis, and Process 

Influence, pp. 1379-1394. Elsevier, New York, 

NY.

Eck, P. 1986. Blueberry. In S.P. Monselise, ed. 

CRC Handbook of Fruit Set and Development, pp. 

75-85. CRC Press, Boca Raton, FL.

Engle, K.H., J. Heidlas, and R. Tressl. 1990. 

The flavour of tropical fruits (banana, melon, 

pineapple). In I.D. Morton and J.D. MacLeod, 

eds., Food Flavors, Part C, The Flavor of 

Fruits, pp. 195-219. Elsevier, Amsterdam, The 

Netherlands.
145

Fallik, E., D.D. Archbold, T.R. Hamilton-Kemp, 

et al. 1997. Heat treatment temporarily inhibits 

aroma volatile compound emission from Golden 

Delicious apples. J. Agric Food Chem. 45:4038-

4041.

Fan, X., and J.P Mattheis. 1999. Impact of 

1-methylcyclopropene and methyl jasmonate on 

apple volatile production. J. Agric. Food Chem. 

47:2847-2853.

Fellman, J.K., J.P. Mattheis, M.E. Patterson, et 

al. 1993. Study of ester biosynthesis in relation 

to harvest maturity and controlled-atmosphere 

storage of apples (Malus domestica Borkh.). 

Proceedings of the 6th International Controlled 

Atmosphere Research Conference, Ithaca, NY, 

June 1993, pp. 500-507. Natural Resource, 

Agriculture, and Engineering Service, Cornell 

University, Ithaca, NY. 

Flora, L.F., and T.O.M. Nakayama. 1981. Quality 

characteristics of muscadine grape products. 

In R. Teranishi and H. Barrera-Benitez, eds., 

Quality of Selected Fruits and Vegetables of North 

America, pp. 21-27. American Chemical Society, 

Washington, DC.

Galliard, T., J.A. Matthew, A.J. Wright, and M.J. 

Fishwick. 1977. The enzymic breakdown of lipids 

to volatile and nonvolatile carbonyl fragments 

in disrupted tomato fruits. J. Sci. Food Agric. 

28:863-868.

Georgilopoulos, D.N., and A.N. Gallois. 1987. 

Aroma compounds of fresh blackberries (Rubus 

laciniata L.). Z. Lebensm Unters. Forsch. 

184:374-380.

Golaszewski, R., C.A. Sims, S.F. O’Keefe, et al. 

1998. Sensory attributes and volatile components 

of stored strawberry juice. J. Food Sci. 63:734-

738.

Golding, J.B., D. Shearer, W.B. McGlasson, 

and S.G. Wyllie. 1999. Relationships between 

respiration, ethylene, and aroma production in 

ripening banana. J. Agric. Food Chem. 47:1646-

1651.

Hartwig, P., and M. McDaniel. 1995. Flavor 

characteristics of lactic, malic, citric, and acetic 

acids at various pH levels. J. Food Sci. 60:384-

388.

Hobson, G., and D. Grierson.1993. Tomato. In 

G.B. Seymour, J.E. Taylor, and G.A. Tucker, eds., 

Biochemistry of Fruit Ripening, pp. 405-442. 

Chapman and Hall, New York, NY.

Honkanen, E., and T. Hirvi. 1990. The flavour of 

berries. In I.D. Morton and J.D. MacLeod, eds., 

Food Flavors: Part C, The Flavor of Fruits, pp. 

125-193. Elsevier, Amsterdam, The Netherlands.

\

Honkanen, E., T. Pysalo, and T. Hirvi. 1980. The 

aroma of Finnish wild raspberries. Z. Lebensm. 

Unters. Forsch. 171:180-182.

Humpf, H.U., and P. Schreier. 1991. Bound 

aroma compounds from the fruit and the leaves 

of blackberry (Rubus laciniata L.). J. Agric. Food 

Chem. 39:1830-1832.

Jones, R.A., and S.J. Scott. 1984. Genetic 

potential to improve tomato flavor in commercial 

F1 hybrids. J. Amer. Soc. Hort. Sci. 109:318-321.

Kanellis, A.K., and K.A. Roubelakis-Angelakis. 

1993. Grape. In G.B. Seymour, J.E. Taylor, and 

G.A. Tucker, eds., Biochemistry of Fruit Ripening, 

pp. 190-234. Chapman and Hall, New York, NY.

Knee, M. 1993. Apple. In G.B. Seymour, J.E. 

Taylor, and G.A. Tucker, eds., Biochemistry of 

Fruit Ripening, pp. 325-346. Chapman and Hall, 

New York, NY.

Koehler, P.E., and S.J. Kays. 1991. Sweet potato 

flavor: Quantitative and qualitative assessment of 

optimum sweetness. J. Food Qual. 14:241-249.

Krammer, G.E., G.R. Takeoka, and R.G. Buttery. 

1994. Isolation and identification of 2,5-dimethyl4-hydroxy-3(2H)-furanone glucoside from 

tomatoes. J. Agric. Food Chem. 42:1595-1597.
146

Larsen, M., and L. Poll. 1990. Odour thresholds of 

some important aroma compounds in raspberries. 

Z. Lebensm. Unters. Forsch. 191:129-131.

Larsen, M., L. Poll, and C.E. Olsen. 1992. 

Evaluation of the aroma composition of some 

strawberry (Fragaria ananassa Duch) cultivars by 

use of odor threshold values. Z. Lebensm. Unters. 

Forsch 195:536-539.

MacLeod, A.J., and N.G. de Troconis. 1982. 

Volatile flavor components of mango fruit. 

Phytochemistry 21:2523-2526.

Malundo, T.M.M., R.L. Shewfelt, G.O. Ware, and 

E.A. Baldwin. 2001. Sugars and acids influence 

flavor properties of mango. J. Amer. Soc. Hort. 

Sci. 126:115-121.

Malundo, T.M.M., R.L. Shewfelt, G.O. Ware, 

and E.A. Baldwin. 2001. Alternative methods for 

consumer testing and data analysis used to identify 

critical flavor properties of mango (Mangifera 

indica L.). J. Sens. Stud. 16:199-214.

Manning, K. 1993. Soft fruit. In G.B. Seymour, 

J.E. Taylor, and G.A. Tucker, eds., Biochemistry 

of Fruit Ripening, pp. 347-377. Chapman and 

Hall, New York, NY.

Martens, M., E. Risvik, and H. Martens. 1994. 

Matching sensory and instrumental analyses. In 

J.R. Piggott and A. Paterson, eds., Understanding 

Natural Flavors, pp. 60-76. Blackie Academic 

Professional/Chapman and Hall, Gasgow, UK.

Mattheis, J.P., D.A. Buchanan, and J.K. Fellman. 

1995. Volatile compound production by Bisbee 

Delicious apples after sequential atmosphere 

storage. J. Agric. Food Chem. 43:194-199.

Maul, F., S.A. Sargent, M.O. Balaban, et al. 1998. 

Aroma volatile profiles from ripe tomatoes are 

influenced by physiological maturity at harvest: 

an application for electronic nose technology. J. 

Amer. Soc. Hort. Sci. 123:1094-1101.

Maul, F., S.A. Sargent, C.A. Sims, et al. 2000. 

Recommended storage temperatures affect tomato 

flavor and aroma quality. J. Food Sci. 65:1228-

1237.

McDonald, R.E., T.G. McCollum, and E.A. 

Baldwin. 1996. Prestorage heat treatments 

influence free sterols and flavor volatiles of 

tomatoes stored at chilling temperature. J. Amer. 

Soc. Hort. Sci. 12:531-536.

Marton, I.D., and A.J. MacLeod. 1990. Food 

Flavors: Part C. The Flavor of Fruits. Elsevier, 

New York, NY.

Moshonas, M.G., and P.E. Shaw. 1972. Analysis 

of volatile flavor constituents from tangerine 

essence. J. Agric. Food Chem. 20:70-71.

Moshonas, M.G., and P.E. Shaw. 1997. Dynamic 

headspace gas chromatography combined 

with multivariate analysis to classify fresh and 

processed orange juices. J. Ess. Oil Res. 9:133-

139.

Narain, N., P.S. Bora, R. Narain, and P.E. Shaw. 

1997. Quantitative determination of 46 volatile 

constituents in fresh, unpasteurized orange juices 

using dynamic headspace gas chromatography. In 

P. Shaw, H. Chan, and S. Nagy, eds., Tropical and 

Subtropical Fruits, vol. 1, pp. 1-77. AgScience, 

Auburndale, FL.

O’Mahony, M. 1995. Sensory measurement in 

food science: Fitting methods to goals. Food Tech. 

Apr:72-82.

Park, S.K., J.C. Morrison, D.O. Adams, and 

A.C. Noble. 1991. Distribution of free and 

glycosidically bound monoterpenes in the skin and 

mesocarp of Muscat of Alexandria grapes during 

development. J. Agric. Food Chem. 39:514-518.

Paterson, A., J.R. Piggott, and J. Jiang. 1993. 

Approaches to mapping loci that influence flavor 

quality in raspberries. In M.J. Comstock, ed., 

Food Flavor and Safety - Molecular Analysis 

and Design, pp. 109-117. ACS Symp. Ser. 528, 

American Chemical Society, Washington, DC.
147

Paz, O., H.W. Janes, B.A. Prevost, and C. Frenkel. 

1981. Enhancement of fruit sensory quality by 

postharvest applications of acetaldehyde and 

ethanol. J. Food Sci. 47:270-276.

Perez, A.G., A. Cert, J.J. Rios, and J.M. Olias. 

1997. Free and glycosidically bound volatile 

compounds from two banana cultivars: Valery and 

Pequena Enana. J. Agric. Food Chem. 45:4393-

4397.

Perez, A.G., C. Sanz, R. Olias, and J.M. Olais. 

1999. Lipoxygenase and hydroperoxide lyase 

activities in ripening strawberry fruits. J. Agric. 

Food Chem. 47:249-253.

Peters. A.M., and A. Van Amerongen. 1998. 

Relationship between levels of sesquiterpene 

lactones in chicory and sensory evaluation. J. 

Amer. Soc. Hort. Sci. 123:326-329.

Podoski, B.W., C.A. Sims, S.A. Sargent, et al. 

1997. Effects of cultivar, modified atmosphere, 

and preharvest conditions on strawberry quality. 

Proc. Fla. State Hort. Soc. 110:246-252.

Riley, J.C.M., C. Willemot, and J.E. Thompson. 

1996. Lipoxygenase and hydroperoxide lyase 

activities in ripening tomato fruit. Postharv. Biol. 

Technol. 7:97-107.

Robbins, J.A., and J.K. Fellman. 1993. Postharvest 

physiology, storage and handling of red raspberry. 

Postharv. News Info. 4:53-59.

Roberts, D.D., and T.E. Acree. 1996. Effects of 

heating and cream addition on fresh raspberry 

aroma using a retronasal aroma simulator and 

gas chromatography olfactometry. J. Agric. Food 

Chem. 44:3919-3925.

Romani, R., J. Labavitch, T. Yamashita, et al. 

1983. Preharvest AVG treatment of ‘Bartlett’ 

pear fruit: effects on ripening, color change, and 

volatiles. J. Amer. Soc. Hort. Sci. 108:1046-1049.

Roscher, R., P. Schreier, and W. Schwab. 1997. 

Metabolism of 2,5-dimethyl-4-hydroxy-3(2H)-

furanone in detached ripening strawberry fruits. J. 

Agric. Food Chem. 45:3202-3205.

Saftner, R.A., W.S. Conway, and C.E. Sams. 

1999. Postharvest calcium infiltration alone 

and combined with surface coating treatments 

influence volatile levels, respiration, ethylene 

production, and internal atmospheres of ‘Golden 

Delicious’ apples. J. Amer. Soc. Hort. Sci. 

124:553-558.

Salunkhe, D.K., and B. Desai. 1984. Postharvest 

Biotechnology of Fruits, vol. II. CRC Press, Boca 

Raton, FL.

Schaller, E., J.O. Bosset, and F. Escher. 1998. 

‘Electronic noses’ and their application to food. 

Lebens. Wiss. Technol. 31:305-316.

Schamp, N., and P. Dirinck. 1982. The use of 

headspace concentration on Tenax for objective 

evaluation of fresh fruits. In G. Charalambous, 

ed., Chemistry of Foods and Beverages, pp. 25-47. 

Academic Press, New York, NY.

Seymour, G.B. 1993. Banana. In G.B. Seymour, 

J.E. Taylor, and G.A. Tucker, eds., Biochemistry 

of Fruit Ripening, pp. 83-106. Chapman and Hall, 

New York, NY.

Seymour, G.B., and W.B. McGlasson. 1993. 

Melons. In G.B. Seymour, J.E. Taylor, and G.A. 

Tucker, eds., Biochemistry of Fruit Ripening, pp. 

273-290. Chapman and Hall, New York, NY.

Shamaila, M., W.D. Powrie, and B.J. Skura. 1992. 

Analysis of volatile compounds from strawberry 

fruit stored under modified atmosphere packaging 

(MAP). J. Food Sci. 57:1173-1176.

Shaw, P.E. 1991. Fruits II. In H. Maarse, ed., 

Volatile Compounds in Foods and Beverages, pp. 

305-328. Marcel Dekker, New York, NY.
148

Shaw, P.E., and C.W. Wilson. 1980. Importance 

of selected volatile components to natural orange, 

grapefruit, tangerine, and mandarin flavors. In S. 

Nagy and J.A. Attaway, eds., Citrus Nutrition and 

Quality, pp. 167-190. ACS Symp. Ser. no. 143, 

American Chemical Society, Washington, DC.

Shukor, A.R., A. Faridah, H. Abdullah, and Y.K. 

Chan. 1998. Pineapple. In P.E. Shaw, H.T. Chan, 

and S. Nagy, eds., Tropical and Subtropical Fruits, 

vol. 1, pp. 137-190. AgScience, Auburndale, FL.

Shure, K.B., and T.E. Acree. 1995. In vivo and 

in vitro flavor studies of Vitis labruscana cv. 

Concord. In R.L. Rouseff and M.M. Leahy, eds., 

Fruit Flavors: Biogenesis, Characterization, and 

Authentication, pp. 127-133. American Chemical 

Society, Washington, DC.

Song, J., B.D. Gardner, J.F. Holland, and R.M. 

Beaudry. 1997. Rapid analysis of volatile flavor 

compounds in apple fruit using SPME and GC/

time of flight spectrometry. J. Agric. Food Chem. 

45:1801-1807.

Speirs, J., E. Lee, K. Holt, et al. 1998. Genetic 

manipulation of alcohol dehydrogenase levels in 

ripening tomato fruit affects the balance of some 

flavor aldehydes and alcohols. Plant Physiol. 

117:1047-1058.

Stevens M.A., A.A. Kader, M. Albright-Holton, 

and M. Algazi. 1977. Genotypic variation of flavor 

and composition in fresh market tomatoes. J. 

Amer. Soc. Hort. Sci. 102:680-689.

Tandon, K.S., E.A. Baldwin, and R.L. Shewfelt. 

2000. Aroma perception of individual volatile 

compounds in fresh tomatoes (Lycopersicon 

esculentum Mill.) as affected by the medium of 

evaluation. Postharvest Biol. Technol. 20:261-268.

Taylor, J.E. 1993. Exotics. In G.B. Seymour, J.E. 

Taylor, and T.A. Tucker, eds., Biochemistry of 

Fruit Ripening, pp. 151-187. Chapman and Hall, 

London, UK.

Teranishi, R., and S. Kint. 1993. Sample 

preparation. In T. Acree and R. Teranshi, 

eds., Flavor Science: Sensible Principles 

and Techniques, pp. 137-167. ACS Books, 

Washington, DC.

Webb, A.D. 1981. Quality factors in California 

grapes. In R. Teranishi and Harrera-Benitez, eds., 

Quality of Selected Fruits and Vegetables of North 

America, pp. 1-9. American Chemical Society, 

Washington, DC.

Wilson, C.W., P.E. Shaw, and R.J. Knight. 1986. 

Importance of selected volatile compounds to 

mango (Mangifera indica L.) flavor. In B.M. 

Lawrence, B.D. Mookherjee, and B.J. Willis, eds., 

Flavors and Fragrances: A World Perspective, 

Proceedings of the 10th International Congress on 

Essential Oils, Fragrances and Flavors, November 

1986, Washington, DC., pp. 283-294. Elsevier 

Science Publishers, Amsterdam, The Netherlands.

Wright, D.H., and N.D. Harris. 1985. Effect of 

nitrogen and potassium fertilization on tomato 

flavor. J. Agric. Food Chem. 33:355-358.

Wyllie, S.G., D.N. Leach, Y. Wang, and R.L. 

Shewfelt. 1995. Key aroma compounds in melons: 

their development and cultivar dependence. In

R.L. Rouseff and M.M. Leahy, eds., Fruit Flavors: 

Biogenesis, Characterization, and Authentication, 

pp. 248-257. ACS Symposium Series 596, 

American Chemical Society, Washington, DC.

Young, H., J.M. Gilbert, S.H. Murray, and R.D. 

Ball. 1996. Causal effects of aroma compounds 

on Royal Gala apple flavors. J. Sci. Food Agric. 

71:329-326.

Zabetakis, I., and M.A. Holden. 1997. Strawberry 

flavor: analysis and biosynthesis. J. Sci. Food 

Agric. 74:421-434.
149

Food Safety

James R. Gorny and Devon Zagory

Gorny was with the International Fresh-cut 

Produce Association, Alexandria, VA. He is now 

with the Produce Marketing Association, Newark, 

DE. Zagory was with Food Safety & Quality 

Programs, Davis Fresh Technologies, Davis, CA. 

He is now with NSF Agriculture, Davis, CA.

Introduction

Data from the U.S. Center for Disease Control 

and Prevention (CDC) between 1973 and 1987 

indicate that there were 3,699 foodborne illness 

outbreaks in the United States. Only 2% were 

associated with fruits and vegetables, and most 

of those were due to improper home canning. 

In general, produce is a low-risk food, and it is 

unlikely that one will become ill from eating raw 

fruits or vegetables. But a small risk does exist, 

and it is incumbent on all of those involved in 

the production and distribution of fresh produce 

to work to minimize those risks. Safety is the 

perception of acceptable risk, and if no risk is 

acceptable, then nothing can ever truly be safe. 

Many consumers feel that food products should 

have no risk associated with their consumption. 

Unfortunately, the reality is that reducing the 

risk of foodborne illness from consumption of 

fresh fruits and vegetables to absolute zero is an 

impossible task. It should also be kept in mind that 

the health benefits derived from eating at least 5 

servings of fresh fruits and vegetables daily far 

outweigh the very small probability of contracting 

a foodborne illness. 

Fruits and vegetables are unique foods, since 

they are often consumed raw or with minimal 

preparation. To date, there have been no effective 

intervention strategies developed that can 

completely eliminate food safety risks associated 

with consumption of uncooked produce. 

Therefore, preventing contamination with human 

pathogens, dangerous levels of chemical residues, 

or physical contaminants is the only way to ensure 

that these foods are wholesome and safe for 

human consumption. 

Systems that ensure safety and wholesomeness of 

fruits and vegetables during postharvest handling 

and fresh-cut processing fall into four prevention 

programs: Good Agricultural Practices (GAPs), 

Good Manufacturing Practices (GMPs), Sanitation 

Procedures, and Hazard Analysis Critical Control 

Points (HACCPs).

The greatest risk to human health from 

consumption of uncooked produce is from 

pathogenic microorganisms. Raw agricultural 

products, such as fresh produce, should 

be expected to harbor a wide variety of 

microorganisms including the occasional 

pathogen. A vigorous population of nonpathogenic 

bacteria can be an excellent barrier to prevent 

the growth of pathogens, should they be present. 

Nonpathogenic bacteria also act as indicators 

of temperature abuse and age by spoiling the 

product. In the absence of spoilage, high levels 

of pathogens may occur, and the item may be 

consumed because it is not perceived as spoiled. 

There are four groups of human pathogens 

associated with fresh produce:

•	Soil-associated pathogenic bacteria 

(Clostridium botulinum and Listeria 

moncytogenes)

•	Fecal-associated pathogenic bacteria 

(Salmonella spp., Shigella spp., E. coli

O157:H7, and others)

•	Pathogenic parasites (Cryptosporidium and

Cyclospora) 

•	Pathogenic viruses (hepatitis, norwalk virus, 

and others)

Many of these pathogens are spread from humans 

or domestic animals to food to humans. Fruits and 

vegetables may become contaminated by infected 

field workers, food preparers, consumers, crosscontamination, use of contaminated irrigation 

water, use of inadequately composted manure, or 

contact with contaminated soil. To minimize risks, 

growers should implement practices outlined 

in the “Guide to Minimize Microbial Food 

Safety Hazards for Fresh Fruits and Vegetables” 

published by the Center for Food Safety and 
150

Applied Nutrition, Food and Drug Administration 

(FDA 1998). This publication outlines Good 

Agricultural Practices (GAPs) which, when 

followed, can significantly reduce the risk of 

microbial hazards in produce. Growers should be 

aware that agricultural practices that may have 

been acceptable in years past may no longer 

be acceptable. In addition, fresh-cut processors 

should adhere to Good Manufacturing Practices 

(GMPs) 21 [CFR 100-169] to appropriately 

manage food safety risks during processing. Food 

handlers and consumers must act responsibly as 

they are the final link in the food safety chain. 

Prevention of contamination is the only way to 

minimize true food safety risks and ensure food 

safety. Microbial testing cannot guarantee the 

absence of pathogens on fresh produce and, in 

fact, is unlikely to detect pathogens even when 

they are present. For example, if 5 fruit in a 

given lot of 100 individual fruit are harboring 

pathogens (5% contamination rate), how many 

fruit would have to be sampled to be 95% sure 

that one of the infected fruit was found? Table 1 

shows that at 5% contamination rates, it would be 

necessary to test 60 fruit to have a 95% chance of 

finding the pathogen. It is surely not practical to 

test 60 out of every 100 fruits or vegetables. Yet 

testing fewer fruits results in a high likelihood 

that pathogens will be missed, even when they 

are present. For this reason, negative results from 

product pathogen testing have little value and 

can be misleading. Microbial testing can be an 

effective tool, but sampling the finished product is 

not an efficient, cost-effective approach. Sampling 

potential sources of contamination—such as 

irrigation water, cooling and process water, and 

food contact surfaces—and monitoring employee 

hygiene practices are more effective in preventing 

spread of human pathogens.

Table 1. Probability that a given number 

of samples will fail to detect microbial 

contaminants at specified contamination 

levels

_____________________________________

Percent Number of Samples Analyzed

Contaminated 5 10 15 20 30 60

-------------------%----------------

10.0 41 65 79 88 96 >99

5.0 33 40 54 64 79 95

2.0 10 18 26 33 45 70

1.0 5 10 14 18 26 45

0.1 1 1 2 2 3 6

_____________________________________

Source: U.S. Food and Drug Administration

Has the Problem Gotten Worse?

Scientists continue to discover new 

microorganisms that cause foodborne illness, 

and recent advances in diagnostics allow more 

rapid detection of smaller numbers of pathogens 

on foods. Detection methods for pathogenic 

microorganisms are faster and more sensitive, 

allowing investigators to better identify causes of 

outbreaks. In recent years, fresh produce sourcing 

has undergone significant changes, and centralized 

local production has been replaced with 

worldwide sourcing. Agricultural practices and 

hygienic conditions vary greatly among growing 

regions around the world, and increased global 

sourcing increases consumers exposure to diverse 

endemic microflora carried on fresh fruits and 

vegetables. Also, global sourcing means longer 

transportation and handling, giving pathogenic 

microorganisms additional time to proliferate and 

reach levels which can cause illness. Population 

demographics in North America have shifted, with 

a greater number of individuals that are older or 

who have compromised immune systems. They 

are at greater risk from foodborne illness, and the 

consequences of exposure can be deadly. All of 

these circumstances have resulted in increased 

foodborne illness awareness.
151

Figure 1. Increasing number of foodborne illness outbreaks 

associated with fresh produce in the United States. Source: 

CDC Food Borne Outbreak Surveillance System.

Intervention Strategies

Washing produce before preparation or 

consumption is recommended but does not 

guarantee that fresh produce is pathogen-free. 

Studies have demonstrated that washing produce 

in cold chlorinated water will reduce microbial 

populations by 2 or 3 logs (100- to 1000-fold), but 

sterility is not achieved, because microorganisms 

adhere to surfaces of produce and may be present 

in microscopic nooks and crannies on the surface 

of produce (Zhuang et al. 1995). 

Figure 2. The effect of wash-water chlorine concentration on 

the fate of Salmonella montevideo on raw tomatoes. Adapted 

from Zhuang et al. 1995.

Reported Food Borne Illness Outbreaks In the United 

States Due to Fruits and Vegetables

0

5

10

15

20

25

30

74 76 78 80 82 84 86 88 90 92 94 96 98

Two Year Interval

No. Of Outbreaks

This is a problem since some pathogens, such as 

E. coli O157:H7, have an infectious dose of as 

few as 10 to 100 viable cells. To date, there are 

no wash-water treatments that can completely 

eliminate human pathogens from fresh produce. 

Product wash-water, if not properly sanitized, can 

become a source of microbiological contamination 

for every piece of product that passes through 

that water. It is a widespread misconception 

that chlorinated wash-water cleans or sterilizes 

produce as it is washed. Chlorinated wash-water 

does little more to clean produce than potable, 

nonchlorinated water. Chlorine does sanitize 

wash-water and maintains a low microbiological 

count in the water. In this way the water does not 

become a reservoir for mold spores and bacteria to 

infest produce. 

Sodium or calcium hypochlorite is most 

commonly used in produce wash-water. The 

antimicrobial activity of these compounds depends 

on the amount of hypochlorous acid (HOCl) 

present in the water. This, in turn, depends on the 

pH of the water, the amount of organic material 

in the water, and, to some extent, the temperature 

of the water. Above pH 7.5, very little chlorine 

occurs as active hypochlorous acid, but rather as 

inactive hypochlorite (OCl-

). Therefore, the washwater pH should be kept between 6.0 and 7.5 to 

ensure chlorine activity. If the pH falls below 6.0, 

chlorine gas may be formed, which is irritating 

to workers. Organic material in the water will 

reduce chlorine activity, so periodically replacing 

or filtering the water is important to maintain 

S.

cleanliness.

 montevideo

Log CFU/cm

2

0

1

2

3

4

5

0 60 110 210 320

Chlorine (ppm)
152

Figure 3. Effect of pH on chlorine dissociation products.

An effective wash-water sanitation system is 

becoming a necessity in the produce industry due 

to increased concerns with safety of fresh produce. 

Since water can be a source of contamination if 

the water itself becomes contaminated, the ability 

to ensure clean water is an essential element of a 

food safety program. Understanding how different 

sanitizers work and how they are measured and 

monitored is an important element in operating 

a food safety system in an effective and costefficient manner (See table 2.)

Irradiation and Cold Pasteurization

Use of nonthermal irradiation, often called cold 

pasteurization, has been advocated as a means to 

eliminate human pathogens from produce, similar 

to current allowable practices in the meat and 

poultry industry. To date this strategy has been 

ineffective for a number of reasons, including the 

expense of irradiating produce, a lack of facilities 

to treat produce, the damage susceptibility of 

many produce items to irradiation, and perceived 

Table 2. Activities and environmental sensitivities of wash-water sanitizers

_______________________________________________________________________

Sanitizer pH Organic Matter Biocidal Activity _______________________________________________________________________

Hypochlorites 6.0 - 7.5 Very sensitive Oxidizer

Chlorine dioxide 6.0 - 10.0 Sensitive Oxidizer

Ozone 6.0 - 10.0 Somewhat sensitive Oxidizer

Peroxyacetic acid 1.0 - 8.0 Somewhat sensitive Oxidizer

UV light Not affected Somewhat sensitive Disrupts DNA

_______________________________________________________________________

consumer resistance to the use of irradiation for 

foods. Irradiation with a gamma source, such as 

cobalt 60, has been studied by many researchers. 

In the 30 years preceding 1983, more than a 

thousand published reports addressed irradiation 

of fruits and vegetables (Kader and Heintz 1983). 

The accumulated data suggest that irradiation may 

have some applications for disinfestation of fruits 

and vegetables but that irradiation alone will not 

resolve most microbiological issues. Different 

organisms vary in their sensitivity to ionizing 

radiation and many microbes will not be killed at 

the maximum allowable dose of 1 kGy (Brackett 

1987).

Killing microbes with irradiation occurs when the 

irradiated energy interacts with water in microbial 

cells. Reactive chemicals are created that damage 

the cells’ genetic material, or DNA. The ability of 

irradiation to kill a particular microbe is measured 

as the “D-value,” the amount of energy needed 

to kill 90% of the cells of the microbe. Thus, a 

dosage of 2D would kill 99% of the cells, 3D 

kills 99.9% and so on. Of course, the D-value will 

differ for different microorganisms.

Insect pests and some parasites (Cyclospora, 

Cryptosporidium, etc.) have a relatively large 

amount of water and DNA in their cells and so are 

easily killed by irradiation. D-values for gamma 

irradiation of 0.1 kGy are typical. Thus, a dosage 

of 0.5 kGy would give a 5-log reduction. Bacteria 

(E. coli, Salmonella, Listeria, etc.) have less DNA 

and are more resistant to irradiation. D-values 

of 0.3 to 0.7 kGy are typical, depending on the 

bacterium. Thus, it would require 1.5 to 3.5 kGy 

to achieve a 5-log reduction of bacteria. At this 

time, the maximum allowable dosage for treating 

Effect of pH on Chlorine Dissociation Products

0

20

40

60

80

100

0 1 2 3 4 5 6 7 8 9 10

pH

% Chlorine present as HOCl

or OClHOCl

OCl-
153

fruits and vegetables is 1.0 kGy. The implication 

is that gamma irradiation is not approved for use 

at dosages high enough to effectively eliminate 

pathogens from fresh produce. The Food Safety 

and Inspection Service (FSIS) has set the 

maximum absorbed dose levels for refrigerated 

and frozen meat at 4.5 kGy and 7.0 kGy, 

respectively, and 3.0 kGy for poultry.

Spore-forming bacteria (Clostridium, Bacillus, 

etc) are even more resistant to irradiation, and 

viruses (hepatitis, norwalk, etc.) are impossible 

to kill even with the dosages allowable for meat. 

Compared with the amount of radiation used in 

medical devices, the dosages approved for food 

are extremely low. Allowable doses of irradiation 

do not make food sterile. They do not always 

kill all the undesirable microorganisms if they 

are numerous to begin with. Also, an irradiated 

food can be recontaminated if mishandled. 

Consequently, while irradiation may have a future 

role in fruit and vegetable sanitation, it will never 

effectively guarantee pathogen-free produce, nor 

will it ever be a substitute for proper sanitation 

and food safety preventative programs. Different 

fruits and vegetables differ in the maximum 

dose that they will tolerate without unacceptable 

softening or loss of other quality parameters. 

However, the negative impacts of produce 

irradiation such as accelerated softening and 

technical issues (for example, nonhomogenous 

dosing) have hindered the commercialization of 

this technology. 

However, it is unclear if irradiation will ever be 

capable of surface-sterilizing produce without 

irreparably damaging produce beyond salability. 

Irradiation dosages necessary to kill viruses and 

some bacteria are well in excess of the levels 

which induce damage to produce. Though 

irradiation has specific uses in produce, such 

as for phytosanitary and insect quarantine, its 

effectiveness as a food safety tool is limited. 

New irradiation technologies such as pulsed 

electric fields, pulsed UV light, or radio frequency 

technologies may yet play a role as tools for 

ensuring the food safety of produce.

Prevention

Good Agricultural Practices (GAPs)

In 1998 the FDA published “Guidance for 

Industry: Guide to Minimize Microbial Food 

Safety Hazards for Fresh Fruits and Vegetables.” 

Though this document carries no regulatory or 

legal weight, due diligence requires producers 

to take prudent steps to prevent contamination 

of their crops. This document gives guidance 

on those prudent steps. A number of retail 

chains have begun to require independent thirdparty audits of producers based, in part, on this 

document.

The guide identifies eight food safety principles 

within the realm of growing, harvesting, and 

transporting fresh produce and suggests the reader 

“use the general recommendations in the guide 

to develop the most appropriate good agricultural 

and management practices for their operation.” 

The application of the principles is aimed at 

preventing contamination of produce with human 

pathogens. The following sections list the eight 

principles and implementation areas.

The following are the basic principles of GAPs:

•	Prevention of microbial contamination of 

fresh produce is favored over reliance on 

corrective actions once contamination has 

occurred.

•	To minimize microbial food safety hazards 

in fresh produce, growers or packers 

should use GAPs in those areas over which 

they have a degree of control, while not 

increasing other risks to the food supply or 

the environment.

•	Anything that comes in contact with fresh 

produce has the potential of contaminating 

it. For most foodborne pathogens associated 

with produce, the major source of 

contamination is associated with human or 

animal feces.

•	Whenever water comes in contact with fresh 

produce, its source and quality dictate the 

potential for contamination.

•	Practices using manure or municipal 
154

biosolid wastes should be closely managed 

to minimize the potential for microbial 

contamination of fresh produce.

•	Worker hygiene and sanitation practices 

during production, harvesting, sorting, 

packing, and transport play a critical role 

in minimizing the potential for microbial 

contamination of fresh produce.

•	All applicable local, State, and Federal laws 

and regulations, or corresponding or similar 

laws, regulations, or standards for operators 

outside the United States for agricultural 

practices should be followed.

•	Accountability at all levels of the 

agricultural environment (farms, packing 

facility, distribution center, and transport 

operation) is important to a successful food 

safety program. There must be qualified 

personnel and effective monitoring to ensure 

that all elements of the program function 

correctly and to help track produce back 

through the distribution channels to the 

producer.

Land Use. The safety of food grown on any given 

parcel of land is influenced not only by the current 

agricultural practices but also by former land use 

practices. Heavy metals and pesticide residues 

may persist in soils for long periods of time. 

Soil should be tested to ensure that dangerously 

high levels of these compounds are not present. 

Former land use should also be investigated and 

documented to ensure that the production land was 

not formerly used for hazardous waste disposal or 

for industrial purposes that may have left behind 

toxic residues. If production land was previously 

used for agricultural purposes, pesticide use 

records should be reviewed to ensure that proper 

pesticide management practices were followed. 

Production acreage should not have recently been 

used as a feedlot or for animal grazing, because 

fecal contamination of the soil may persist.

Fertilizers. Improperly composted or 

uncomposted manure is a potential source of 

human pathogens. Human pathogens may persist 

in animal manure for weeks or even months. 

E. coli O157:H7 has been found to survive in 

uncomposted dairy manure incorporated into 

soil for up to 250 days (Suslow 1999). Proper 

composting via thermal treatment reduces the 

risk of potential foodborne illness. However, the 

persistence of many human pathogens in untreated 

agricultural soils is unknown. Use of inorganic 

fertilizers, which have been certified to be free of 

heavy metals and other chemical contaminants, is 

recommended.

Irrigation Water. Irrigation water is another 

potential vector by which contaminants may be 

brought into contact with fruits and vegetables. 

Deep-well water is less likely to be contaminated 

with human pathogens than surface water 

supplies. However, all irrigation water sources 

should be periodically tested for contamination 

by pesticides and human pathogens. The 

presence of E. coli is a useful indicator for fecal 

contamination and possible presence of human 

pathogens. Inexpensive test kits for generic E. 

coli are available from several vendors. Overhead 

irrigation systems are more likely than flood, 

furrow, or drip irrigation to spread contamination 

since contaminated water is applied directly to 

the edible portions of fruits and vegetables. Water 

used to mix or spray agricultural chemicals must 

be confirmed to be free of pathogens before use.

Pesticide Use. All pesticide use should be 

done in strict accordance with manufacturer’s 

recommendations as well as Federal, State, and 

local ordinances. Monitoring and documentation 

of proper pesticide use should be done to prevent 

unsafe or illegal residues from contaminating 

fruits and vegetables. All pesticide applications 

should be documented, and proper records of 

application should be available and reviewed by 

management on a regular basis. Appropriately 

trained and licensed individuals should perform 

pesticide use recommendations and applications.

Harvest Operations. During harvest operations, 

field personnel may contaminate fresh fruits and 

vegetables by simply touching them with an 

unclean hand or knife blade. Portable field latrines 

equipped with hand-washing stations must be 

available and used by all harvest crew members. 

Training, monitoring, and enforcement of field 

worker hygiene practices, such as washing hands 
155

after using the bathroom, are necessary to reduce 

the risk of human pathogen contamination. Once 

harvested, produce should not be placed on soil 

before being placed in clean and sanitary field 

containers. Field harvesting tools should be clean 

and sanitary and should not be placed directly 

in contact with soil. Field containers should be 

cleaned and sanitized on a regular basis and 

should be kept free of contaminants such as mud, 

industrial lubricants, metal fasteners, or splinters. 

Plastic bins and containers are recommended as 

they are easier to clean and sanitize than wooden 

ones.

Sanitary Postharvest Handling of Produce. 

Depending on the commodity, produce may be 

field-packed in containers that will go all the way 

to the destination market, or it may be temporarily 

placed in bulk bins, baskets, or bags that will 

be transported to a packing shed. Employees, 

equipment, cold storage facilities, packaging 

materials, and any water that will contact the 

harvested produce must be kept clean and sanitary 

to prevent contamination.

Employee Hygiene. Gloves, hairnets, and clean 

smocks are commonly worn by packing house 

employees in export-oriented packing sheds. The 

cleanliness and personnel hygiene of employees 

handling produce at all stages of production and 

handling must be managed to minimize the risk of 

contamination. Adequate bathroom facilities and 

hand-washing stations must be provided and used 

properly to prevent contamination of produce by 

packing house employees. Shoe- or boot-cleaning 

stations may also be in place to reduce the amount 

of field dirt and contamination that enters the 

packing shed from field operations. Employee 

training in sanitary food handling practices 

should be done when an employee is hired, before 

beginning work, and on a regular basis thereafter. 

All training should be documented and kept on 

file.

Equipment. Food contact surfaces on conveyor 

belts, dump tanks, etc. should be cleaned and 

sanitized on a regularly scheduled basis with 

approved cleaning compounds. A 200 ppm (200 

μL L-1) NaOCl solution (bleach) is an example of 

a food-contact-surface sanitizer. Sanitizers should 

be used only after thorough cleaning with abrasion 

to remove organic material such as dirt or plant 

materials. Steam or high-pressure water should be 

used with care as it may create bacterial aerosols 

and actually help spread contamination throughout 

the packinghouse facility.

Cold Storage Facilities. Cold storage facilities, 

and in particular refrigeration coils, refrigeration 

drip pans, forced-air cooling fans, drain tiles, 

walls, and floors, should be cleaned and sanitized 

on a regular basis. The human pathogen Listeria 

monocytogenes can multiply at refrigerated 

temperatures in moist conditions and may 

contaminate produce if condensation from 

refrigeration units or ceilings drips on to the 

produce. A common environmental pathogen, L. 

monocytogenes, may get on walls, in drains, and 

into cooling systems. Comprehensive sanitation 

programs that target these areas are important in 

preventing establishment of this pathogen.

Packaging Materials. All packaging materials 

should be made of food-contact-grade materials 

to ensure that toxic compounds in the packaging 

materials do not leach out of the package and 

into the produce. Toxic chemical residues may 

be present in some packaging materials due to 

use of recycled base materials. Packages, such 

as boxes and plastic bags, should be stored in 

an enclosed storage area to protect them from 

insects, rodents, dust, dirt, and other potential 

sources of contamination. Plastic field bins and 

totes are preferred to wooden containers since 

plastic surfaces are more amenable to cleaning 

and sanitizing. Field bins should be cleaned and 

sanitized after every use. Wooden containers 

or field totes are almost impossible to sanitize 

since they have a porous surface and wooden 

or metal fasteners, such as nails from wooden 

containers, may accidentally be introduced into 

produce. Cardboard field bins, if reused, should 

be inspected for cleanliness and lined with clean 

plastic bags before reuse to prevent risk of crosscontamination.
156

Produce Wash-Water and Hydrocooling Water.

All water that comes in contact with produce for 

washing, hydrocooling, or vacuum cooling must 

be potable. To achieve this, water should contain 

between 2 and 7 ppm (μL L-1) free chlorine and 

have a pH between 6 and 7. Total chlorine up to 

200 μL L-1 is allowed by law, though 50 to 100 

ppm (μL L-1) is usually sufficient if the pH of 

the water is between 6 and 7. Alternatively, an 

oxidation-reduction potential greater than 650 

mV using any oxidative sanitizer will ensure 

that bacteria in the water are killed on contact. 

Chlorine use prevents cross-contamination of 

produce in the washing or hydrocooling system 

but it will not sterilize the produce. Rinsing 

produce with potable water will reduce the 

number of microorganisms present on the produce 

but will not remove all bacteria.

Refrigerated Transport. Produce is best shipped 

in temperature-controlled refrigerated trucks. 

Maintaining most perishables below 5 °C (41 

°F), except for tropical fruit, will extend shelflife and significantly reduce the growth rate 

of microbes, including human pathogens. Cut 

produce, including tropical fruits, should always 

be stored below 5 °C (41°F). Trucks used during 

transportation should be cleaned and sanitized 

on a regular basis. Trucks that have been used to 

transport live animals, animal products, or toxic 

materials should not be used to transport produce.

Recall and Traceback Plans. Recall of product is 

the last line of defense in a food safety emergency. 

This action may be initiated by the company, 

performed on a voluntary basis, or done at the 

request of the FDA because of a suspected 

hazard in the product. The FDA has defined three 

recall classifications and FDA actions. Class I 

is an emergency situation involving removal of 

products from the market that could lead to an 

immediate or long-term life-threatening situation 

and involve a direct cause-effect relationship; for 

example, C. botulinum in the product. Class II is a 

priority situation in which the consequences may 

be immediate or long term and may be potentially 

life threatening or hazardous to health; for 

example, Salmonella in food. Class III is a routine 

situation in which life-threatening consequences 

(if any) are remote or nonexistent. Products are 

recalled because of adulteration (filth in produce 

relating to aesthetic quality) or misbranding (label 

violation), and the product does not involve a 

health hazard. Every food provider should develop 

a recall or trace-back plan and an organizational 

structure that enable it to remove product from the 

market in a rapid and efficient manner.

Good Manufacturing Practices (GMPs)

GMPs ensure that food for human consumption 

is safe and has been prepared, packed, and held 

under sanitary conditions. GMPs are mandatory 

for the fresh-cut produce industry, but not 

mandatory for packinghouse or field operations 

that simply handle whole produce. However, 

though GMPs are not mandatory for packing 

sheds, they are mostly good common sense 

and are recommended for all produce-handling 

facilities.

The Code of Federal Regulations describes the 

conditions under which food must be processed 

and handled. The regulations cover general 

provisions, buildings and facilities, equipment, 

production and process controls, and defect action 

levels. Many of the GMPs are simple good sense, 

such as washing hands after using the restrooms 

and wearing hairnets when working with food. 

Unlike GAPs, GMPs are regulations and have 

the weight of law: A food processor must comply 

with GMPs. Copies of the Current GMPs (CGMP) 

can be obtained by subscribing to the Federal 

Register or by ordering 21 CFR 100-169 (Code 

of Federal Regulations, Title 21, Food and Drugs, 

Pt. 100-169). Submit a check or money order to 

Superintendent of Documents, U.S. Government 

Printing Office, Washington, DC 20402; or 

telephone the Government Printing Office at 

202-783-3238 to order by credit card.

Personnel GMPs. Personnel working in food 

processing plants or packinghouses can be a 

significant source of food contamination. This 

includes production employees, maintenance 

employees, supervisors, and management. It is the 

responsibility of processing plant management to 

educate and train all food handlers about sanitary 
157

handling of foods. Employees experiencing 

diarrhea, vomiting, open skin sores, boils, fever, 

or disease should report these symptoms to their 

supervisor and should not be allowed to work with 

food products. All food handlers should have clean 

outer garments or frocks and thoroughly wash 

their hands before entering a food processing area, 

especially after toilet use. No jewelry (earrings, 

pendants, rings, etc.), pens, or wrist watches 

should be allowed in food processing areas, 

because these items may fall into food products 

unnoticed. Intact, clean, and sanitary gloves and 

hair restraints should be used by all personnel in 

food handling areas.

Physical Plant and Grounds. Food processing 

plants and produce packing houses should be 

constructed so as to segregate food handling 

activities from the outside environment. The 

physical building itself should have no openings 

or gaps which could allow entrance by rodents, 

insects, or birds. Surrounding grounds should be 

free of clutter such as equipment, litter, waste, 

refuse, or animal feces. No unpaved or dusty roads 

should be adjacent to food handling facilities, 

and areas surrounding the structure should be 

adequately drained so that no standing or pooled 

water is present. Vegetation surrounding the 

processing plant should be kept down to prevent 

the formation of breeding grounds for rodents. 

Rodent traps should be placed on the outside 

perimeter of the grounds and be inspected and 

serviced regularly.

Plant Construction and Design. The most 

important aspect of sanitary food plant and 

produce packinghouse design is sufficient space 

for sanitary operations. Processing areas should 

be designed for easy cleaning and sanitation. 

Floors, walls, and ceilings should be made of a 

cleanable, noncorrosive, nonabsorbent material 

and be in good repair. Floors should have rounded 

corner joints where they meet the wall to allow 

for easy cleaning. Processing plant floors should 

be constructed of sealed concrete or tile to 

withstand the physical and chemical abuses from 

machinery and cleaning chemicals. Equipment 

should be constructed of stainless steel to prevent 

corrosion. Overhead pipes, ducts, and fixtures 

should not be suspended over work areas, and 

horizontal surfaces of these items should be 

minimized to reduce accumulation of dust and 

water condensation. Where possible, overhead 

structures should be hidden above a false ceiling, 

and all hoses, pipes and electrical conduits should 

descend vertically from the ceiling so as to not 

provide horizontal surfaces for accumulation of 

filth. Adequate lighting should be provided and 

all light bulbs should be covered to ensure that 

broken glass cannot contaminate food products. 

All water (rinse, flume, cleaning, ice, etc.) used 

in food processing must be of proper sanitary 

quality. Plumbing should be of adequate size and 

design to handle the amount of product being 

processed. Produce handling environments are 

usually wet; therefore, sloping floors with drains 

should be present to remove excess water from 

the processing area. Sanitary sewer lines should 

be separate from floor drains to ensure that crosscontamination of the processing area from sewage 

backflow does not occur. 

An adequate number of toilets and hand-washing 

stations should be available to accommodate 

all employees. Restroom facilities should not 

open into processing areas. Hot running potable 

water, soap, and hand towels should be available 

at all times. Signs should be posted to instruct 

employees to wash their hands after using the 

restroom. Employee frocks, gloves, and knives 

should never be taken into the restrooms, and 

adequate storage space should be made available 

directly outside the restroom door for temporary 

storage of these items. Heating, ventilation, and 

air-conditioning (HVAC) systems may feature 

filtered positive air pressure in processing plants 

because of the potential for airborne pathogen 

contamination. HVAC units should blow air along 

the ceiling and down the walls to keep the walls 

dry and free of condensation.

Sanitation Procedures. Cleaning and sanitation 

are some of the most important programs in any 

food processing plant or packing shed. Cleaning is 

the removal, through physical action, of debris and 

filth. Sanitation is the application of antimicrobial 
158

compounds. Sanitation cannot be effective until 

surfaces are cleaned. Regular and scheduled 

equipment cleaning and sanitizing ensures that 

food products are being processed under hygienic 

conditions. Cleaning and sanitation is best done 

by a specially trained sanitation and cleaning crew 

and not by production personnel. A sanitation 

program in a food processing plant consists of two 

main elements: a master sanitation schedule and a 

monitoring program.

Master Sanitation Schedule. A written master 

sanitation schedule should be in place to ensure 

that all areas of a food processing plant or packing 

shed are cleaned and sanitized on a regular basis. 

The master sanitation schedule should detail the 

area to be cleaned, the sanitation method, tools, 

cleaning materials, and frequency of cleaning. 

There are five steps involved in cleaning and 

sanitizing:

1. Physical debris removal

2. Rinsing

3. Washing with detergent

4. Second rinsing

5. Sanitizing

It is critical that cleaning—that is, removal of 

debris and food particles—be done prior to any 

sanitation steps, because many sanitizers are 

inactivated by organic materials. Once gross or 

large pieces of food are removed, equipment 

should be rinsed with potable water to remove 

smaller particles. Then, soaps and detergents 

should be applied. Mild abrasion should be used 

to scrub equipment clean and remove caked-on 

food particles and biofilms (layers of bacteria). All 

soaps and detergents used should be approved for 

use on food contact surfaces. After cleaning, soaps 

and detergents should be removed by rinsing 

equipment with potable water. After rinsing, 

equipment should be sanitized to kill microbes. 

Sanitizing consists of rinsing all food contact 

surfaces with bactericidal compounds such as 

chlorine, iodine, or quaternary ammonia. Product 

manufacturer’s directions for sanitizers and 

cleaning chemicals should be strictly followed.

Written sanitation standard operating procedures 

(SSOPs) for cleaning and sanitation should be 

prepared for specific pieces of equipment that 

are cleaned on a regular basis. This ensures that 

the equipment is cleaned properly regardless of 

who does the cleaning. SSOPs should specify the 

following:

•	What: identifies task

•	Why: purpose of task

•	When: frequency of task

•	Who: person responsible for task

•	How: steps for completing task

A sample SSOP for sanitation of drains might take 

the following form:
159

Sanitation of Drains

Goal: Prevent build-up of contaminants (especially Listeria monocytogenes) in drains that 

could cross-contaminate product

Frequency: Daily

Procedure: a. Remove all grates and coverings over drains.

b. Remove and dispose of all debris in drains.

c. Rinse drains and drain coverings to remove loose debris.

d. Mix chlorine-based soap as follows.

e. Apply soap to drains and drain coverings.

f. Scrub drains and drain coverings vigorously with brushes to remove invisible films.

g. Rinse thoroughly to remove soap. Must rinse thoroughly for sanitizing solution to 

 be effective.

h. Mix quarternary ammonia sanitizer solution as follows.

i. Irrigate all drains and spray (or soak) coverings with sanitizer solution. 

j. Replace grates and drain coverings.

k. The Sanitation Crew Chief then inspects all sanitized drains.

l. The Sanitation Crew Chief writes the time and date and signs the sanitation log 

 for drains. If any drain does not pass inspection, the Crew Chief notes that in the 

 log and the crew must rewash and resanitize until it passes inspection.

Cleaners and Sanitizers. There are numerous 

cleaning and sanitizing compounds available for 

use in food processing plants and packing sheds. 

These compounds fall into five categories:

•	Chelators: tie up cations or salts; for 

 example, EDTA (ethylenediaminetetraacetic 

 acid) 

•	Alkalines: excellent detergents; for example, 

 sodium hydroxide

•	Acids: remove mineral deposits; for 

 example, phosphoric acid

•	Wetting agents: emulsify and penetrate soil; 

 for example, alkyl sulfates

•	Sanitizers: kill microbes; for example, 

 sodium hypochlorite
160

Table 3. Comparison of common sanitizers

__________________________________________________________________________________

Chlorine Iodine QUATS Acid-anionic 

surfactants 

__________________________________________________________________________________

Effectiveness against:

Gram-positive bacteria, Good Best Good Good

 (lactics, clostridia, Bacillus, 

Staphylococci)

Gram-negative bacteria (E. coli, Best Good Poor Good

 Salmonella, psychrotrophs)

Yeast and molds Best Good Good Good

Spores Best Poor Fair Fair

Viruses Best Good Poor Poor

Effects on property: 

 

Corrosive Fairly Slightly No Slightly

Affected by hard water No Slightly Type A*, No Slightly

Type B†, Yes

Irritating to skin Yes, >100 μL L-1 Not at levels No Yes

used

Maximum level permitted by 200 μL L-1 25 μL L-1 200 μL L-1 200-400 μL L-1

 FDA without rinse based on type

Affected by organic matter Most affected Somewhat Least affected Somewhat

Cost Cheapest Cheap Expensive Expensive

Tests for active residual Simple Simple Difficult Difficult

Stability in hot solution Unstable; some Highly Stable Stable

 (>150 oF) compounds stable unstable

Leaves active residue No Yes Yes Yes
161

Table 3. Comparison of common sanitizers—Continued

__________________________________________________________________________________

Chlorine Iodine QUATS Acid-anionic 

surfactants 

__________________________________________________________________________________

Incompatible with— Phenols, amines, Starch, silver Anionic wetting Cationic

soft metals agents, soaps, surfactants,

wood, cloth, alkaline

cellulose, nylon cleaners

Effective at neutral pH Yes No Yes No

__________________________________________________________________________________

Source: Adapted from Katsuyama and Strachan (1980)

*Type A: alkyl dimethyl benzyl ammonium chloride.

†

Type B: methyl dodecyl benzyl trimethyl ammonium chloride.

Chlorine is by far the most commonly used 

sanitizer at 100 to 200 μL L-1. It is important that 

water containing chlorine be free from organic 

matter and have a pH between 6.0 and 7.0. If 

either of these conditions is not met, then the 

chlorine is ineffective.

Monitoring Program. Before processing or 

packing begins, sanitation crew performance 

should be evaluated on a daily basis to ensure 

that conditions are hygienic. Visual inspection 

should be performed to ensure that no food 

particles or foreign matter are present on 

processing equipment. In particular, areas that 

are difficult to clean should be inspected, such 

as the underside of conveyors and peeling 

equipment. Unfortunately, visual inspection is 

not enough to ensure that equipment has been 

sanitized properly. The number of microbes 

present on processing equipment after sanitation 

operations should be determined on a regular basis 

to evaluate sanitation crew performance. Such 

determination can be made using one of three 

methods: petri contact plate, surface swabbing, or 

bioluminescence.

Petri Contact Plate. Plastic petri plates or 

films contain sterile agar with growth media 

for microbes and the type of microbes that will 

grow on these plates is determined by the type of 

medium used. In this method, petri plates or films 

are pressed up against food contact surfaces and 

the location is noted. The plates are then incubated 

in the laboratory; if microbes were present on the 

sampled surfaces, they will grow on the agar. A 

low bacteria count per square centimeter means 

that the sanitation crew is doing a good job at 

cleaning and sanitizing. If the number of microbes 

dramatically increases, an evaluation of sanitation 

procedures is in order.

Surface Swabbing. A variation of the petri plate 

method is to use sterile swabs to collect samples 

from food contact surfaces. Wet sterile swabs are 

used to brush an area of a food contact surface. 

The swab is then placed in a container with sterile 

solution. Bacteria are counted after incubation 

as above. Swabs and films for environmental 

sampling are commercially available from several 

companies.

Bioluminescence. The contact petri plate or swab 

methods are good for monitoring sanitation 

crew performance, but results are not available 

immediately. Another microbe detection method, 

called bioluminescence, is capable of detecting the 

presence of microbes immediately. This method 

relies on measuring the amount of ATP (adenosine 

triphosphate) that is present on food contact 

surfaces. ATP is present in all living cells and 

thus is a good indicator of the presence of organic 

material. This test is similar to the swab testing 

method except that the cleanliness of equipment is 

determined within minutes after the swab is taken. 
162

In this test, equipment is swabbed and the amount 

of ATP present is determined by a chemical test 

kit. These test kits are available from a number 

of suppliers. Bioluminescence test results are 

available immediately and can determine if 

cleaning and sanitation procedures must be 

repeated before processing or packing begins.

Hazard Analysis Critical Control Points 

(HACCPs)

HACCP is a food safety system developed by 

the Pillsbury Company to reduce risk associated 

with food eaten by astronauts during space flights. 

HACCP is a system for the prevention of physical, 

chemical, or microbial contamination of food. The 

prime function of HACCP is to prevent identified 

hazards in food preparation through control of the 

process. HACCP functions as the final stage of 

an integrated food safety program and includes 

Good Agricultural Practices (GAPs), Good 

Manufacturing Practices (GMPs), and Sanitation 

Standard Operating Procedures (SSOPs). In fact, 

HACCP can only be effective if these programs 

are in place and functioning properly. There is no 

minimum or maximum number of Critical Control 

Points (CCPs) in any given operation. What is 

important is that all potential hazards be addressed 

through prerequisite programs or HACCP. Those 

hazards that can be controlled or minimized 

through quantitative control of a process may 

be designated CCPs and included in a HACCP 

program. Fresh-cut processors may have as few as 

two Critical Control Points (CCPs) in a perfectly 

adequate HACCP plan.

HACCP is a systems approach to ensure safety 

of a food product; it is not a means of ensuring 

food quality. Prevention of physical, chemical, 

and microbial contamination of produce during 

packing or processing is essential to ensure 

production of a safe product. It is recommended 

that each produce handling operation identify an 

individual for formal HACCP training and to be in 

charge of a team responsible for implementing the 

HACCP program. HACCP programs should be as 

simple as possible, without an excessive number 

of CCPs. Each HACCP program is unique and 

must be tailored to the specific operation.

There are seven basic steps in an HACCP 

program:

1. Conduct a hazard analysis

2. Determine CCPs to control the identified 

hazards

3. Establish critical limits for each CCP

4. Establish CCP monitoring requirements

5. Establish corrective actions to be taken 

when a CCP is outside critical limits

6. Establish record-keeping systems to 

document the HACCP program

7. Establish procedures to verify that the 

HACCP program is functioning as intended.

Assessment of Hazards 

Each unit operation should be evaluated to 

identify potential sources of microbial, chemical, 

and physical hazards that may be introduced 

into produce. Areas that should be evaluated 

are growing and harvesting operations, packing 

shed operations, packaging material and storage 

areas, and all steps in distribution. This process is 

best accomplished by a team consisting of both 

management and production personnel. (Example: 

Hydrocooling water contamination, microbial or 

chemical.)

Determination of CCPs to Control the Identified 

Hazards 

The next step in developing a HACCP program is 

to draw a flow diagram for the specific operation 

and then determine where each of the identified 

hazards may be prevented. Each point that will 

be monitored to control a specific hazard may be 

designated a CCP. (Example: A chlorine injection 

system on a hydrocooler.)

Establishment of CCP Limits 

Once CCPs have been identified, critical limits 

must be set to determine when corrective actions 

need to be taken. Limits must be observable and 

measurable. (Example: Hydrocooler water must 
163

have a chlorine level of 100 to 150 μL L-1 total 

chlorine and a pH of 6.0 to 7.5.)

Establishment of CCP Monitoring Procedures

It is critical to define clearly how often monitoring 

will be done, how measurements will be taken, 

and what documentation will be prepared. 

(Example: Hydrocooler water pH and chlorine 

levels will be monitored hourly using a test kit and 

continuously with a strip chart recorder that has 

been calibrated daily; hourly pH and chlorine level 

measurements will be recorded in writing; and the 

records will be made available for inspection at 

the hydrocooler.)

Corrective Action When Deviations From 

Critical Limits Occur 

When a deviation from the prescribed limits 

occurs, corrective action must be taken to 

eliminate potential contamination. All deviations 

and corrective actions must be documented in 

writing. (Example: Chlorine levels are determined 

to be below 25 μL L-1. Hydrocooling of product 

is stopped, chlorine levels are adjusted, and all 

products that had been hydrocooled since the last 

time the system was verified to be within critical 

limits are disposed of.)

HACCP Recordkeeping Systems 

All paperwork related to the HACCP system 

must be kept in an orderly and accessible manner. 

Paperwork kept should include production records 

(for example, supplier audits), harvesting records 

(for example, harvest dates and lot numbers), CCP 

monitoring records, and deviation file (HACCP 

deviations and corrective actions taken).

HACCP Verification 

Periodic HACCP plan review, including review 

of CCP records, deviations, and random sampling 

must be conducted to ensure that the HACCP 

program is functioning properly.

Application of HACCP 

When considering applying these principles 

to a farm operation, one can immediately see 

the difficulty in controlling naturally occurring 

hazards. For example, bird droppings in an 

orchard may potentially represent a hazard from 

the spread of E. coli O157:H7 or Salmonella spp. 

However, it may not be a CCP because there is 

no way to prevent that hazard by controlling a 

process. Furthermore, there is no way to quantify 

and measure bird droppings to know if they are 

within critical limits. The same would also be true 

of Clostridium botulinum spores in soil. Though 

they may represent a potential hazard, it would not 

be appropriate to establish soil as a CCP because 

it is not practical to measure the spores in soil or 

to control them through any known process. In 

fact, most agricultural hazards cannot, and should 

not, be prevented through HACCP. Instead, the 

use of GAPs has been identified by the FDA and 

the produce industry as a more appropriate way to 

address these hazards.

Another example is a cold storage room in a 

packinghouse where condensed water from 

refrigeration coils may contain the bacterium 

Listeria monocytogenes and could drip on the 

product. This is certainly a significant hazard, 

but is it a CCP? It would not be practical to 

develop a process to prevent water from dripping 

or to quantify and monitor water dripping from 

refrigeration coils. A more appropriate way to deal 

with this hazard is through SSOPs. Refrigeration 

coils and drip pans should be cleaned and 

sanitized according to a predetermined schedule 

to prevent the growth of L. monocytogenes in the 

condensate. This way, the hazard is prevented 

more effectively and more simply than by 

designating a CCP.

There is no minimum or maximum number of 

CCPs in any given operation. What is important 

is that all potential hazards be addressed through 

prerequisite programs or through HACCP. Those 

hazards that can be controlled or minimized 

through quantitative control of a process may 
164

be designated CCPs and included in a HACCP 

program. Fresh-cut processors may have as few as 

two CCPs in an adequate HACCP plan.

The Fresh-Cut Industry

Consumers expect that fresh-cut processors will 

manufacture wholesome and nutritious foods. 

To do this, fresh-cut processors must have 

systems in place to ensure that products being 

manufactured do not have physical, chemical, 

or microbial contaminants introduced during 

processing and packaging. If such systems 

are not in place, consumers are at risk and a 

single incidence of personal injury traced back 

to a specific food manufacturer may put that 

company out of business and result in criminal 

prosecution of the owners and management. 

Ensuring that food products are manufactured 

in a safe and wholesome manner does add cost 

to the final product. However, the long-term 

success of every food processor depends on its 

ability to consistently produce safe products. 

Food safety should not be confused with food 

quality. Food safety programs simply ensure that 

food products are safe to consume and prevent 

injury to consumers. Food safety does not begin 

at the processing plant receiving dock and the 

production of raw ingredients should be done 

following GAPs.

Fresh-cut produce can be damaged through 

peeling, cutting, slicing, or shredding. These same 

operations can transfer pathogenic microbes from 

the surface of the intact produce to the internal 

tissues. Injured cells and released cell fluids 

provide a nourishing environment for microbial 

growth. Maintaining low temperature throughout 

distribution is critical to maintaining quality of 

fresh-cut fruits and vegetables. Low temperatures 

reduce enzymatic reactions and greatly slow down 

the multiplication of spoilage organisms. Low 

temperatures also prevent the multiplication of 

most foodborne pathogens, with the exception of 

Listeria monocytogenes and a few others that are 

capable of growing, albeit slowly, at refrigerated 

temperatures.

Emphasis should be placed on preventing 

contamination by pathogens. The best way to 

prevent the introduction of pathogens into freshcut produce is by employing GAPs, GMPs, 

SSOPs, and, in some cases, by implementing 

an effective HACCP program. Such a program 

identifies potential points of contamination and 

ensures that those potential hazards are controlled 

and monitored to enhance safety. HACCP and 

food safety do not begin and end at the doors of 

the handling facility. They require that the produce 

handler work with both suppliers and customers 

to maintain food safety throughout the production, 

distribution, and marketing chain.

Sprouts—A Special Case

Over the past several years, sprouts have become 

a common fresh produce item linked to foodborne 

illness. A scientific advisory group to the FDA has 

recognized sprouts as a special problem. This is 

because bacterial pathogens that may be present 

at very low levels on sprout seeds at the time of 

sprouting can multiply to very high levels during 

the 3- to 5-day sprouting process.

Most sprout outbreaks have been caused by seed 

that was contaminated with a bacterial pathogen 

before sprouting began. Pathogens can survive 

for months under dry conditions used for seed 

storage. Though contaminated alfalfa seeds have 

been identified as the source in many outbreaks, 

clover, radish, and bean sprouts have also been 

associated with outbreaks. Any type of sprout seed 

may potentially be contaminated with bacterial 

pathogens before sprouting.

The FDA published guidelines for sprout 

processors to reduce the potential for foodborne 

illness related to sprouts. The guidelines include 

treatment of seeds in a sanitizer solution (currently 

a special allowance for 20,000 μL L-1 chlorine) 

prior to sprouting, as well as testing of the sprout 

wash-water for Salmonella, E. coli O157:H7, and 

L. monocytogenes prior to harvest.
165

The FDA has published two related documents, 

entitled “Guidance for Industry: Reducing 

Microbial Food Safety Hazards for Sprouted 

Seeds” and “Guidance for Industry: Sampling 

and Microbial Testing of Spent Irrigation Water 

During Sprout Production.” These guidelines are 

intended to provide recommendations to suppliers 

of seed for sprouting and to sprout producers 

about how to reduce microbial food safety hazards 

found in the production of raw sprouts. The 

guidelines are also intended to help ensure that 

sprouts are not a cause of foodborne illness and 

that those in the sprout industry comply with food 

safety provisions of the Federal Food, Drug, and 

Cosmetic Act.

References

Brackett, R.E. 1987. Microbiological 

consequences of minimally processed fruits and 

vegetables. J Food Quality 10:195-205.

FDA. 1998. Guide to Minimize Microbial Food 

Safety Hazards for Fresh Fruits and Vegetables. 

Food Safety Initiative Staff, HFS-32, U.S. Food 

and Drug Administration, Center for Food Safety 

and Applied Nutrition, 200 C Street, Washington, 

DC.

Kader, A.A., and C.M. Heintz. 1983. Gamma 

irradiation of fresh fruits and vegetables - an 

indexed reference list (1965-1982). Postharvest 

Hort Ser. no. 4, University of California, 

Department of Pomology, Davis, CA.

Katsuyama, A.M., and J.P. Strachan. 1980. 

Principles of Food Processing Sanitation. The 

Food Processors Institute, Washington, DC.

Suslow, T. 1999. Addressing animal manure 

management issues for fresh vegetable production. 

Perishables Handling 98:7-9.

Zhuang, R.Y., L.R. Beuchat, and F.J. Angulo. 

1995. Fate of Salmonella montevideo on and in 

raw tomatoes as affected by temperature and 

treatment with chlorine. Appl. Environ. Microbiol. 

61: 2127-2131.

Further Reading

Guidance for Industry: Reducing Microbial Food 

Safety Hazards for Sprouted Seeds, October 27, 

1999, Federal Register, vol. 64, no. 207. (U.S. 

Food and Drug Administration, Center for Food 

Safety and Applied Nutrition, 200 C Street, 

Washington, DC.; http://www.gpo.gov/fdsys/pkg/

FR-1999-10-27/pdf/99-27976.pdf

Guidance for Industry: Sampling and Microbial 

Testing of Spent Irrigation Water During 

Sprout Production, October 27, 1999, Federal 

Register, vol. 64, no. 207. (U.S. Food and Drug 

Administration, Center for Food Safety and 

Applied Nutrition, 200 C Street, Washington, DC.; 

http://www.gpo.gov/fdsys/pkg/FR-1999-10-27/

pdf/99-27976.pdf

FDA. 1998. Guide to Minimize Microbial Food 

Safety Hazards for Fresh Fruits and Vegetables. 

Food Safety Initiative Staff, HFS-32, U.S. Food 

and Drug Administration, Center for Food Safety 

and Applied Nutrition, 200 C Street, Washington, 

DC. http://www.fda.gov/downloads/Food/

GuidanceComplianceRegulatoryInformation/

GuidanceDocuments/ProduceandPlanProducts/

UCM169112.pdf

Beuchat, L.R. 1998. Surface Decontamination 

of Fruits and Vegetables Eaten Raw: A Review. 

World Health Organization, Geneva, Switzerland.

Current Good Manufacturing Practices (GMPs) 

Regulations 21 CFR 100-169. Superintendent of 

Documents, U.S. Government Printing Office, 732 

North Capitol Street, NW, Washington, DC.
166

Nutritional Quality and Its 

Importance to Human Health

Adel A. Kader, Penelope Perkins-Veazie, and 

Gene E. Lester

Kader was with the Department of Pomology, 

University of California, Davis, CA. He is 

deceased. Perkins-Veazie is formerly with 

the South Central Agricultural Laboratory, 

Agricultural Research Service, U.S. Department 

of Agriculture, Lane, OK. She is now with the 

Department of Horticultural Science, North 

Carolina State University, North Carolina 

Research Campus, Kannapolis, NC. Lester is 

formerly with the Kika de la Garza Subtropical 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Weslaco, TX. He is now with the Office of 

National Programs, Agricultural Research Service, 

U.S. Department of Agriculture, Beltsville, MD.

Fruits, nuts, and vegetables play a significant 

role in human nutrition, especially as sources 

of dietary fiber, minerals, and vitamins—C 

(ascorbic acid), A, thiamine (B1

), niacin (B3), 

pyridoxine (B6

), folacin (also known as folic 

acid or folate), B9

, and E (Quebedeaux and Bliss 

1988, Quebedeaux and Eisa 1990, Craig and Beck 

1999, Wargovich 2000). Their contribution as a 

group is estimated at 91% of vitamin C, 48% of 

vitamin A, 30% of folacin, 27% of vitamin B6

, 

17% of thiamine, and 15% of niacin in the U.S. 

diet. Fruits and vegetables also supply 16% of 

magnesium, 19% of iron, and 9% of calories. 

Legume vegetables, potatoes, and tree nuts, such 

as almond, filbert, pecan, pistachio, and walnut, 

contribute about 5% of the per-capita availability 

of proteins in the U.S. diet, and their proteins are 

of high quality because they contain essential 

amino acids. Nuts are a good source of essential 

fatty acids, fiber, vitamin E, and minerals. 

Other important nutrients supplied by fruits and 

vegetables include riboflavin (B2

), zinc, calcium, 

potassium, and phosphorus. Fruits and vegetables 

remain an important source of nutrients in many 

parts of the world and offer advantages over 

dietary supplements because of low cost and wide 

availability.

Dietary supplements, while advantageous for 

conditions in which specific nutrients are needed 

in abundance such as iron deficiency, may be 

poorly absorbed. Climatic conditions, particularly 

temperature and light intensity, have an especially 

strong effect on the nutritional quality of fruits 

and vegetables (Mozafar 1994). Low temperatures 

favor synthesis of sugars and vitamin C (glucose 

being the precursor to ascorbic acid) and at the 

same time decrease the rate of ascorbic acid 

oxidation. Maximum β-carotene (vitamin A) 

content in tomatoes occurs at a temperature range 

of 15 to 21 oC (59 to 70 oF), but β-carotene content 

is reduced if temperatures are higher or lower 

than this range, principally due to the temperature 

sensitivity of lycopene, the precursor to β-carotene 

and lutein.

The B vitamins are crop specific when it comes 

to temperature sensitivity. Warm-season crops 

(beans, tomatoes, peppers, melons, etc.) produce 

more B vitamins at high (27 to 30 oC, 81 to 86 oF) 

than at low (10 to 15 oC, 59 to 70oF) temperatures. 

Conversely, cool season crops (broccoli, cabbage, 

spinach, peas, etc.) produce more B vitamins at 

low than at high temperatures. Light intensity 

has little effect on the B vitamins; but, as light 

intensity increases, vitamin C increases and total 

carotenoids (vitamin A precursors) and chlorophyll 

decrease (Gross 1991). Higher light intensities 

produce more sugars, leading to more vitamin C, 

and also increase plant temperatures, inhibiting 

β-carotene (vitamin A) production, which protects 

chlorophyll from photobleaching. Soil type, the 

rootstock used for fruit trees, mulching, irrigation, 

fertilization, and other cultural practices influence 

the water and nutrient supply to the plant, which 

can affect the composition and quality attributes 

(appearance, texture, taste, and aroma) of the 

harvested plant parts (Goldman et al. 1999). 

Other environmental factors that affect fruit and 

vegetable nutritional quality are altitude, soil pH 

and salinity, production practices (organic versus 

conventional and greenhouse versus field), ozone, 

insect injury, and plant diseases. 

Maturity at harvest, fruit size, and harvesting 

method influence the commodity’s quality and 

extent of physical injuries. Delays between 
167

harvest and consumption or processing can 

result in losses of flavor and nutritional quality. 

The magnitude of these losses increases with 

exposure to temperature, relative humidity, and/

or concentrations of O2

, CO2, and C2H4 outside 

the ranges that are optimum for each commodity 

during the entire postharvest handling system (Lee 

and Kader 2000). Furthermore, processing and 

cooking methods can greatly affect the nutritional 

value of fruits and vegetables. For instance, watersoluble vitamins such as vitamin C and folate 

are lost when cooking water is discarded, while 

fat-soluble compounds such as lycopene may be 

stabilized or enhanced by cooking.

Fruits, nuts, and vegetables in the daily diet have 

been strongly associated with reduced risk for 

some forms of cancer, heart disease, stroke, and 

other chronic diseases (Quebedeaux and Bliss 

1988, Quebedeaux and Eisa 1990, Produce for 

Better Health Foundation 1999, Prior and Cao 

2000, Southon 2000, Wargovich 2000, TomasBarberan and Espin 2001, Hyson 2002, Goldberg 

2003). Some components of fruits and vegetables 

(phytochemicals) are strong antioxidants and 

function to modify the metabolic activation and 

detoxification and disposition of carcinogens or 

even influence processes that alter the course 

of the tumor cell (Wargovich 2000). Though 

antioxidant capacity varies greatly among fruits 

and vegetables (Prior and Cao 2000, PerkinsVeazie and Collins 2001, Kalt 2002), it is better 

to consume a variety of commodities rather than 

limiting consumption to a few with the highest 

antioxidant capacity. The Dietary Guidelines 

for Americans, 2010 (USDA and HHS 2010) in 

part advises filling half your plate with fruits, 

vegetables, cooked beans, and grains. Such a 

healthy eating pattern also embodies food safety 

principles to avoid foodborne illness. In some 

countries, consumers are encouraged to eat up to 

10 servings of fruits and vegetables per day.

There is increasing evidence that consumption 

of whole foods is better than isolated food 

components such as dietary supplements 

and nutraceuticals. For example, increased 

consumption of carotenoid-rich fruits and 

vegetables was more effective than carotenoid 

dietary supplements in increasing LDL oxidation 

resistance, lowering DNA damage, and inducing 

higher repair activity in human volunteers who 

participated in a study conducted in France, Italy, 

The Netherlands, and Spain (Southon 2000). 

In another study, adding antioxidant (vitamins 

A, C, and E) dietary supplements into the diet 

of cancer treatment patients who were eating a 

balanced diet of fruits and vegetables negatively 

affected their radiotherapy and chemotherapy 

(Seifried et al. 2003). High consumption of 

tomatoes and tomato products has been linked 

to reduced carcinogenesis, particularly prostate 

cancer, and has been thought to be due to the 

presence of lycopene, which gives red tomatoes 

their color (Giovannucci 2002). However, 

use of tomato powder effectively reduced 

prostate carcinogenesis in rats, while lycopene 

supplements, considered the primary active 

ingredient of tomatoes, had no effect (Boileau et 

al. 2003). Similar comparative studies are needed 

on other constituents of fruits and vegetables 

and on the bioavailability of nutrients taken as 

dietary supplements or as foods that contain these 

nutrients.

Examples of the phytochemicals in fruits and 

vegetables that have established or proposed 

positive effects on human health and their 

important sources are shown in tables 1 and 

2. Some changes in these tables are likely as 

the results of additional studies on effects of 

phytochemicals and their bioavailability on human 

health become available in the next few years. 

Meanwhile it is important to evaluate the validity 

and dependability of the results of every study 

before reaching conclusions for the benefit of 

consumers.
168

Table 1. Nutritive constituents of fruits and vegetables that have positive effects 

on human health and their sources

_____________________________________________________________________________

Constituent Sources Established or

proposed effects on 

human wellness

_____________________________________________________________________________

Vitamin C

(ascorbic 

acid)

Broccoli, cabbage, cantaloupe, citrus fruits, 

guava, kiwifruit, leafy greens, pepper, 

pineapple, potato, strawberry, tomato, 

watermelon

Helps prevent scurvy 

and cardiovascular 

disease; aids 

wound healing and 

immune system

Vitamin A

(carotenoids)

Dark-green vegetables (such as collards, spinach, 

and turnip greens), orange vegetables (such as 

carrots, pumpkin, and sweet potato), orangeflesh fruits (such as apricot, cantaloupe, mango, 

nectarine, orange, papaya, peach, persimmon, 

and pineapple), tomato

Helps prevent 

night blindness, 

chronic fatigue, 

psoriasis, heart 

disease, stroke, and 

cataracts

Vitamin K Nuts, lentils, green onions, crucifers (cabbage, 

broccoli, brussel sprouts, etc.), leafy greens

Aids synthesis of 

procoagulant 

factors; helps 

prevent 

osteoporosis

Vitamin E

(tocopherols)

Nuts (such as almonds, cashew nuts, filberts, 

macadamias, pecans, pistachios, peanuts, and 

walnuts), corn, dry beans, lentils and chickpeas, 

dark-green leafy vegetables

Helps prevent heart 

disease, LDL 

oxidation, cancer, 

and diabetes; aids 

immune system

Fiber Most fresh fruits and vegetables, nuts, cooked dry 

beans and peas

Helps prevent 

diabetes and heart 

disease

Folate

(folicin or 

folic acid)

Dark-green leafy vegetables (such as spinach, 

mustard greens, butterhead lettuce, broccoli, 

brussels sprouts, and okra), legumes (cooked 

dry beans, lentils, chickpeas, and green peas), 

asparagus

Helps prevent birth 

defects, cancer, and 

heart disease; aids 

nervous system

Calcium Cooked vegetables (such as beans, greens, okra, 

and tomatoes), peas, papaya, raisins, orange, 

almonds, snap beans, pumpkin, cauliflower, 

rutabaga

Helps prevent 

osteoporosis; 

helps lower blood 

pressure; aids 

muscles, skeleton, 

and teeth
169

Magnesium Spinach, lentils, okra, potato, banana, nuts, corn, 

cashews

Helps prevent 

osteoporosis; aids 

nervous system, 

teeth, and immune 

system

Potassium Baked potato or sweet potato, banana and 

plantain, cooked dry beans, cooked greens, 

dried fruits (such as apricots and prunes), 

winter (orange) squash, cantaloupe

Helps prevent 

hypertension (high 

blood pressure), 

stroke, and 

arteriosclerosis 

--------------------------------------------------------------------------------------------------------------------

Table 1. Nutritive constituents of fruits and vegetables that have positive effects 

on human health and their sources—Continued

_____________________________________________________________________________

Constituent Sources Established or

proposed effects on 

human wellness _____________________________________________________________________________
170

Table 2. Nonnutritive plant constituents that may be beneficial to human health

______________________________________________________________________________

Constituent Compound Sources Established or

proposed effects on

human wellness

_______________________________________________________________________________

Phenolic compounds

 Proanthocyanins Tannins Apple, grape, cranberry, 

pomegranate

Help prevent cancer

 Anthocyanidins Cyanidin, malvidin, 

delphinidin, 

pelargonidin, 

peonidin, 

petunidin

Red, blue, and purple 

fruits (such as apple, 

blackberry, blueberry, 

cranberry, grape, 

nectarine, peach, plum 

& prune, pomegranate, 

raspberry, and 

strawberry)

Help prevent 

heart disease, 

cancer initiation, 

diabetes, 

cataracts, and 

allergies; help 

lower blood 

pressure

 Flavan-3-ols Epicatechin, Apples, apricots, 

blackberries, plums, 

raspberries, strawberries

Help prevent 

platelet 

aggregation and 

cancer

 Flavanones Hesperetin, 

naringenin, 

eriodictyol

Citrus (oranges, grapefruit, 

lemons, limes, 

tangerines, etc.)

Help prevent cancer 

 Flavones Luteolin, apigenin Celeriac, celery, peppers, 

rutabaga, spinach, 

parsley, artichoke, guava, 

pepper

Help prevent 

cancer, allergies, 

and heart disease

 Flavonols Quercetin, 

kaempferol, 

myricetin, rutin

Onions, snap beans, 

broccoli, cranberry, kale, 

peppers, lettuce

Help prevent heart 

disease and 

cancer initiation; 

are capillary 

protectants

 Phenolic acids Caffeic acid, 

chlorogenic acid, 

coumaric acid, 

ellagic acid

Blackberry, raspberry, 

strawberry, apple, peach, 

plum, cherry

Help prevent 

cancer; help 

lower cholesterol

Carotenoids
171

 Lycopene Tomato, watermelon, 

papaya, Brazilian guava, 

autumn-olive, red 

grapefruit

Help prevent 

cancer, heart 

disease, and male 

infertility

 α-Carotene Sweet potatoes, apricots, 

pumpkins, cantaloupes, 

green beans, lima beans, 

broccoli, brussel sprouts, 

cabbage, kale, kiwifruit, 

lettuce, peas, spinach, 

prunes, peaches, mango, 

papaya, squash, carrots

Help prevent/slow 

tumor growth

 β-Carotene Cantaloupes, carrots, 

apricots, broccoli, leafy 

greens (lettuce, swiss 

chard, etc.), mango, 

persimmon, red pepper, 

spinach, sweet potato

Help prevent cancer

 Xanthophylls Lutein, zeaxanthin, 

β-cryptoxanthin

Sweet corn, spinach, 

corn, okra, cantaloupe, 

summer squash, turnip 

greens

Help prevent 

macular 

degeneration

 Monoterpenes Limonene Citrus (grapefruit, 

tangerine, etc.)

Help prevent cancer

Sulfur compounds Glucosinolates, 

isothiocyanates, 

indoles, allicin, 

diallyl isulphide

Broccoli, brussels sprouts, 

mustard greens, 

horseradish, garlic, 

onions, chives, leeks

Help prevent cancer 

and diabetes; 

help lower 

cholesterol and 

blood pressure

_______________________________________________________________________________

Table 2. Nonnutritive plant constituents that may be beneficial to human health—

Continued

______________________________________________________________________________

Constituent Compound Sources Established or

proposed effects on

human wellness

______________________________________________________________________________
172

References

Boileau, T.W., Z. Liao, S. Kim, et al. 2003. 

Prostate carcinogenesis in N-methyl-N-nitrosourea 

(NMU)-testosterone-treated rats fed tomato 

powder, lycopene, or energy-restricted diets. J. 

Natl. Cancer Inst. 95:1578-86.

Craig, W., and L. Beck. 1999. Phytochemicals: 

health protective effects. Can. J. Diet. Pract. Res. 

60:78-84. 

Giovannucci, E. 2002. A review of epidemiologic 

studies of tomatoes, lycopene, and prostate cancer. 

Exp. Biol. Med. (Maywood) 227:852-9.

Goldberg, G., ed. 2003. Plants: Diet and Health. 

The Report of a British Nutrition Foundation 

Task Force. Blackwell Science, Oxford, United 

Kingdom.

Goldman, I.L., A.A. Kader, and C. Heintz. 1999. 

Influence of production, handling, and storage 

on phytonutrient content of foods. Nutr. Rev. 

57:S46-S52.

Gross, J. 1991. Pigments in Vegetables: 

Chlorophylls and Carotenoids. AVI Book, Van 

Nostrand Reinold, New York, NY.

Hyson, D. 2002. The Health Benefits of Fruits 

and Vegetables: A Scientific Overview for 

Health Professionals. Produce for Better Health 

Foundation, Wilmington, DE

Kalt, W. 2002. Health functional phytochemicals 

of fruits. Hort. Rev. 27:269-315.

Lee, S.K. and A.A. Kader. 2000. Preharvest and 

postharvest factors influencing vitamin C content 

of horticultural crops. Postharv. Biol. Technol. 

20:207-220.

Mozafar, A. 1994. Plant Vitamins: Agronomic, 

Physiological and Nutritional Aspects. CRC Press, 

Boca Raton, FL.

Perkins-Veazie, P., and J.K. Collins. 2001. 

Contribution of nonvolatile phytochemicals to 

nutrition and flavor. HortTechnology 11:539-546.

Prior, R.L., and G. Cao. 2000. Antioxidant 

phytochemicals in fruits and vegetables: diet and 

health implications. HortScience 35:588-592.

Produce for Better Health Foundation. 1999. 

Dietary Guidelines: The Case for Fruits and 

Vegetables First. The Foundation, Wilmington, 

DE.

Quebedeaux, B., and F.A. Bliss, eds., 1988. 

Horticulture and Human Health. Contributions 

of Fruits and Vegetables, Proceedings of the 1st 

International Symposium on Horticulture and 

Human Health, Arlington VA, April 12-15, 1987, 

pp. 243. Prentice Hall, Englewood Cliffs, NJ.

Quebedeaux, B., and H.M. Eisa. 1990. 

[Horticulture and Human Health: Contributions of 

Fruits and Vegetables, Proc. 2nd Intl. Symp. Hort. 

and Human Health.] HortScience 25:1473-1532.

Seifried, H.E., S.S. McDonald, D.E. Anderson, et 

al. 2003. The antioxidant conundrum in cancer. 

Cancer Res. 63:4295-4298.

Southon, S. 2000. Increased fruit and vegetable 

consumption within the EU: potential health 

benefits. Food Res. Intl. 33:211-217.

Tomas-Barberan, F.A., and J.C. Espin. 2001. 

Phenolic compounds and related enzymes as 

determinants of quality in fruits and vegetables. J. 

Sci. Food Agric. 81:853-876.

USDA and HHS. 2010. U.S. Department of 

Agriculture and U.S. Department of Health 

and Human Services. Dietary Guidelines for 

Americans, 2010. 7th Edition, U.S. Government 

Printing Office, December 2010, Washington, DC.

Wargovich, M.J. 2000. Anticancer properties of 

fruits and vegetables. HortScience 35:573-575.
173

Annual Culinary Herbs

Kimberly P. Wright

Wright is with Dole Fresh Vegetables, Salinas, 

CA.

Scientific Names and Introduction 

Culinary herbs include basil (Ocimum basilicum

L.), chervil, salad chervil (Anthriscus cerefolium

L. [Hoffm.]), coriander, cilantro, Chinese 

parsley (Coriandrum sativum L.), dill (Anethum 

graveolens L.), and savory/summer savory 

(Satureja montana L.). Leaves of annual herbs are 

typically used, though roots of coriander are also. 

Herbs are grown in both the field and greenhouse.

Quality Characteristics and Criteria 

Herbs should appear fresh and green: no 

yellowing, decay, insect, or mechanical damage. 

Leaves should be uniform in size. Flavor and 

aroma should be strong and characteristic of the 

herb. There are purple forms of basil that should 

have a rich color.

Horticultural Maturity Indices 

Annual herbs should be harvested before 

flowering. Basil still maintains its quality with 

some flowers.

Grades, Sizes, and Packaging 

There are no market grades or sizes for fresh 

herbs. They may be tied or bunched with 

a rubberband, packaged in plastic bags or 

clamshells, then packed in corrugated cartons. 

Perforated polyethylene liners will prevent 

dehydration and maintain quality.

Precooling Conditions 

With the exception of basil, herbs should be 

cooled to just above 0 °C (32 °F) as soon 

as possible after harvest. Vacuum cooling is 

recommended (Aharoni et al. 1988). Basil should 

be cooled to no lower than 12 °C (54 °F).

Optimum Storage Conditions 

Chervil, coriander, dill, and savory should be 

stored at 0 °C (32 °F) and 95 to 100% RH. 

Postharvest life ranges from 1 week for chervil 

(Gorini 1981) to 2 weeks for coriander and dill 

and up to 3 weeks for savory. Basil should be 

stored at 12 °C (54 °F) and 95 to 100% RH 

(Aharoni et al. 1993). At this temperature and RH, 

quality can be maintained for 2 weeks (Lange and 

Cameron 1994).

Controlled Atmosphere (CA) 

Considerations 

A 5 to 10% O2

 + 4 to 6% CO2 CA is only 

moderately beneficial for fresh herbs (Saltveit 

1997). However, MAP lengthens the shelf-life 

of coriander (Loiza and Cantwell 1997), chervil 

(Aharoni et al. 1993), and basil (Lange and 

Cameron 1998).

Retail Outlet Display Considerations

Use of water sprinklers is acceptable. Basil should 

not be displayed at temperatures below 12 °C (54 

°F) because of chilling sensitivity. Other herbs 

should be displayed at 0 °C (32 °F) in refrigerated 

units.

Chilling Sensitivity

Chervil, coriander, dill, and savory are not 

sensitive to chilling and should be stored as cold 

as possible (0 °C [32 °F]) without freezing. Basil 
174

is susceptible to chilling injury if stored below 

12 °C (54 °F). The primary symptom of chilling 

injury is browning or blackening of the leaves 

(Cantwell and Reid 1993).

Ethylene Production and Sensitivity 

Annual herbs produce very little ethylene, but are 

highly susceptible to ethylene exposure (Cantwell 

1997). Symptoms of ethylene damage include 

yellowing and leaf abscission (Cantwell and Reid 

1993).

Respiration Rates

Temperature Basil Chervil Coriander Dill

------------mg CO2 kg-1 h-1------------

0 °C 36 12 22 22

5 °C — — 30 —

7.5 °C — — 46 —

10 °C 71 80 — 103

20 °C 176 170 — 324

Data from Cantwell and Reid (1993) and Loiza 

and Cantwell (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Yellowing and leaf abscission may occur due to 

ethylene exposure, especially if herbs are held at 

10 °C (50 °F) or warmer. Basil is susceptible to 

chilling injury if held below 12 °C (54 °F), the 

main symptom being necrosis and browning or 

blackening of the leaves.

Postharvest Pathology 

Molds and bacterial decay may develop, 

especially on mechanically damaged leaves or 

cut ends of stems. Low temperatures should be 

maintained throughout the cold chain to minimize 

pathological disorders and prolong shelf-life. 

Chilling increases the susceptibility of basil to 

decay.

Quarantine Issues 

There are no quarantine issues.

Suitability as Fresh-Cut Product

Annual herbs are used in some packaged salad 

blends.

Special Considerations

High RH is used to prevent water loss and is 

especially important in maintaining the quality of 

fresh herbs.

References

Aharoni, N., O. Dvir, D. Chalupowisz, and 

Z. Aharon. 1993. Coping with postharvest 

physiology of fresh culinary herbs. Acta Hort. 

344:69-78.

Aharoni, N., A. Reuveni, and O. Dvir. 1989. 

Modified atmospheres in film packages delay 

senescence and decay of fresh herbs. Acta Hort. 

258:255-262.

Cantwell, M. 1997. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu.

Cantwell, M.I., and M.S. Reid. 1993. Postharvest 

physiology and handling of fresh culinary herbs. J. 

Herbs, Spices, Medicinal Plants 1:83-127.

Gorini, F. 1981. Vegetable schedules. 2. 

Leafy vegetables. Chervil. Informatore di 

Ortoflorofrutticoltura 22:3-4.
175

Lange, D.D., and A.C. Cameron. 1994. 

Postharvest shelf-life of sweet basil (Ocimum 

basilicum). HortScience 29:102-103.

Lange, D.D., and A.C. Cameron. 1998. Controlled 

atmosphere storage of sweet basil. HortScience 

33:741-743.

Loaiza, J., and M. Cantwell. 1997. Postharvest 

physiology and quality of cilantro (Coriandrum 

sativum L.). HortScience 32:104-107.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

vol. 4, Vegetables and Ornamentals, pp. 98-

117. Postharvest Hort. Ser. no. 18, University of 

California, Davis, CA.
176

Apple

Chris B. Watkins, Eugene Kupferman, and David 

A. Rosenberger

Watkins is with the Department of Horticulture, 

Cornell University, Ithaca, NY; Kupferman is with 

Washington State University, Fruit Research and 

Extension Center, Wenatchee, WA; Rosenberger 

is with Hudson Valley Laboratory, Cornell 

University, Highland, NY.

Scientific Name and Introduction 

Malus × domestica Borkh., the apple, is a 

perennial of the Rosaceae family. The apple is 

thought to have arisen in the Caucasus region 

of southeastern Europe, and the tree is one of 

the hardiest temperate zone species. The edible 

part of the fruit is composed of fleshy tissue that 

surrounds the five ovaries, as well as some ovary 

or carpel tissue. The parenchyma of the fused 

bases of the calyx, corolla, and stamens constitutes 

the major edible part of the fruit, though this 

tissue is sometimes interpreted as being cortical. 

The skin surrounding the fleshy parenchyma 

tissue is made up of cuticle, epidermal, and 

hypodermal layers, with lenticels allowing gas 

diffusion across the skin. Cracks in the skin 

surface are also important for gaseous exchange. 

The diffusion characteristics of the skin can affect 

the tolerance of different varieties to storage 

conditions. Examples include ‘Golden Delicious,’ 

which tends to shrivel faster than other varieties 

because of breaks in the cuticle, and the Marshall 

‘McIntosh’ strain, which is less tolerant to low O2

in CA storage than other strains because of higher 

resistance of the skin to gas exchange. 

Quality Characteristics 

Quality consists of a combination of visual 

appearance, texture, and flavor. Modern 

consumers demand impeccable appearance, 

optimum texture, and firmness typical of the 

variety.

Skin Color. Each variety has specific commercial 

requirements for skin color ranging from green 

or yellow for varieties such as ‘Golden Delicious’ 

and ‘Granny Smith’ to red for varieties such as 

‘Red Delicious.’ Bicolored apples such as ‘Gala’ 

and ‘Braeburn’ are also popular. Some varieties 

are currently marketable only if they meet strict 

standards for red color intensity and coverage. 

There is a tendency for wholesalers to gradually 

increase color standards, thereby encouraging 

growers to select redder strains of previously 

acceptable bicolored apples. Red color is not an 

indicator of fruit maturity or quality, however. 

With few exceptions, the ground (background) 

color requirement for apples is light green, 

as yellowness is regarded as an indication 

of overmature or senescent fruit. Consumers 

generally prefer ‘Golden Delicious’ apples that 

have a white skin color, rather than green or 

yellow. Consumers demand fully green ‘Granny 

Smith’ apples without a red blush and 100% red 

color for ‘Red Delicious.’

Blemish. A high-quality apple in the marketplace 

is free from blemish, though there may be a 

greater tolerance for defects in certain markets 

such as organic outlets. Occurrences of physically 

induced damage such as bruising or stempunctures and physiological and pathological 

disorders are not acceptable in any market. The 

prevalence of these defects can be affected greatly 

by variety characteristics such as stem length, skin 

tenderness, softness of the fruit, and genetically 

based resistance to physiological and pathological 

disorders. The density of the flesh and the skin 

thickness can also contribute to resistance of fruit 

to bruising under normal handling conditions, 

and susceptibility to bruising can determine the 

commercial success of a variety.

Texture. A universal constituent of quality 

regardless of variety is firmness. Consumers 

demand apples that are crisp and crunchy. Other 

textural or flavor components are secondary. 

All apples are not required to have the same 

firmness values, and optimum values depend on 

the characteristics of an individual variety. For 

example, a crisp ‘Granny Smith’ apple is often 80 

to 98 N (18 to 22 lb-force), while a crisp ‘Golden 

Delicious’ is above 53 N (12 lb-force).
177

Flavor. Sweetness and acidity vary by variety. 

For example, the acidity of ‘Granny Smith’ apples 

is high (0.8 to 1.2% malate) while that of ‘Red 

Delicious’ is low (0.2 to 0.4%). Similarly, sugar 

content of apples also varies by variety. ‘Fuji’ 

apples can have 20% or more SSC. 

Ethylene Production and Sensitivity

The apple is classified as a climacteric fruit, 

exhibiting increased respiration rates during 

maturation and ripening. This rise is associated 

with increases in internal concentrations of 

CO2

 and ethylene, respiration, and autocatalytic 

ethylene production. Endogenous ethylene 

production can vary greatly among varieties. 

In general, early season varieties have high 

ethylene production rates and ripen quickly, 

while late season ones have low ethylene 

production rates and ripen slowly. The timing 

of the climacteric and ripening of apple fruit is 

advanced by exposure to ethylene. Prevention 

or slowing of ethylene production, by affecting 

ethylene synthesis or perception, is a strategy 

for increasing fruit storability. This is achieved 

primarily by use of low storage temperatures and 

application of CA storage technologies (Watkins 

2002, 2003). Methylcyclopropane (1-MCP) is 

available under the commercial name SmartFresh. 

1-MCP is structurally related to ethylene, has a 

nontoxic mode of action, and is applied at very 

low levels with low measurable residues in food 

commodities.

Respiration Rates 

In general, early season varieties have high 

respiration rates, while late season varieties have 

low respiration rates. The respiration rate of 

fruit is directly affected by temperature, and the 

respiratory climacteric is suppressed by storage 

temperatures below 10 °C (50 °F). The lowest 

temperatures for storage must be above freezing 

and above those at which chilling injury will 

develop.

Temperature Summer apples Fall apples

 mg CO2 kg-1 h-1

0 °C 3 to 6 2 to 4

5 °C 5 to 11 5 to 7

10 °C 14 to 20 7 to 10

15 °C 18 to 31 9 to 20

20 °C 20 to 41 15 to 25

Data from Hardenburg et al. (1986).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Horticultural Maturity Indices 

Maturity and Marketing Season. In general, an 

apple fruit harvested when less mature will have 

poor color and flavor and can be more susceptible 

to physiological disorders such as bitter pit and 

superficial scald. Fruit harvested overmature 

tend to be softer and more easily damaged, may 

have watercore, and may be more susceptible 

to diseases and physiological disorders such as 

senescent breakdown. The length of storage of 

apples generally can be increased by harvesting 

fruit before they are fully mature, but quality 

characteristics such as varietal flavor decrease as 

immaturity at harvest increases. Fruit harvested 

early in the harvest window for long-term 

storage (6 to 12 mo) tend to have less flavor than 

those allowed to ripen further on the tree but 

are acceptable if minimal flavor requirements 

are met along with good texture. The challenge 

is to decide appropriate harvest periods for 

each marketing period, which can range from 

immediate on-farm sales to marketing across the 

globe after 11 months of storage. 

Harvest Maturity Indices. A wide range of 

indices have been tested over many years as 

possible indicators of harvest maturity. Several 

common methods have been outlined by Lau 

(1985). Ethylene, measured commonly as internal 

ethylene concentration, and the starch index, in 

which the degree of starch hydrolysis is estimated, 

have become the most widely used maturity 
178

indices. Since a rise in ethylene production is 

associated with initiation of ripening, it has 

been suggested that ethylene production or 

internal ethylene concentration (IEC) should be 

a major determinant of harvest decisions (Lau 

1985). However, relationships between ethylene 

production and optimum harvest dates can be 

poor, and the timing, or presence, of increased 

ethylene production is a function of cultivar. 

Factors such as a growing region, orchard within a 

region, cultivar strain, growing season conditions, 

and nutrition are greatly affected within a cultivar 

(Watkins 2003). Therefore, ethylene production 

may not be relevant for determining harvest of 

some cultivars.

For some bicolored apples, background color is 

considered an important harvest index. In some 

cases, State regulations have been established to 

set minimal harvest maturities; for example, in 

California the starch index for ‘Granny Smith.’ 

While ethylene production is regarded as the only 

physiological indicator of apple fruit maturity, 

fruit of some varieties and growing regions are 

often harvested well before autocatalytic ethylene 

production occurs, and therefore this measurement 

is commercially irrelevant. However, in some 

regions ethylene is used to determine when fruit 

are too mature to be candidates for long-term 

storage. It is generally recognized that no single 

maturity index is appropriate across all varieties; 

growers have learned to rely on a combination of 

indices.

Other indices, such as flesh firmness and soluble 

sugar content, are quality indicators rather than 

maturity indicators, as they are influenced greatly 

by orchard factors; for example, fruit exposure to 

light. During the preharvest season, firmness falls 

and sugar content continues to increase. However, 

these quality indicators provide information 

that can be important to fruit performance in 

storage. Both indices are increasingly used in the 

marketplace as quality criteria by wholesalers, 

especially in Europe.

The three major apple-growing regions in the 

U.S. are the States of Washington, New York, 

and Michigan. They operate apple maturity 

programs in conjunction with their land grant 

universities. Currently in Washington, individual 

packinghouses conduct their own maturity 

programs inline with their marketing strategies. In 

each region, a wide range of maturity and quality 

indices are collected, and the optimum harvest 

period (harvest window) is established for each 

variety (Anonymous 1986, Blanpied and Silsby 

1992, Beaudry et al. 1993. The strength of these 

programs lies not in reliance on absolute maturity 

indices, but in discussion with industry personnel 

on changes in maturity and quality occurring over 

the harvest period. In this way, full participation 

of extension personnel, growers, and storage 

operators can ensure that fruit of appropriate 

storage potential are directed towards short-, 

medium- or long-term storage.

Grades, Sizes, and Packaging

Grade Standards. U.S. grades are U.S. Extra 

Fancy, U.S. Fancy, and U.S. No. 1, based 

primarily on color requirements, but also on 

freedom from decay, disorders, and blemishes, 

as well as firmness of fruit (Childers et al. 1995). 

These Federal guidelines have been adopted 

by many States, but States may have additional 

grading and branding laws. Information pertaining 

to any State can be obtained from the local State 

Department of Agriculture. Washington State 

packers follow the grade standards of either U.S. 

Federal regulations or special Washington State 

Grade Standards promulgated by the Washington 

State Department of Agriculture in conjunction 

with USDA.

Cartons. Sizing is usually carried out by weight 

or fruit diameter but is independent of grade. 

Requirements for fruit size vary greatly by market, 

but in general, larger sizes bring greater returns. 

Most fruit are packed into bushel cartons, usually 

40 lb (18.2 kg), depending on variety, and sold 

by count (fruit per carton). Apples are most often 

packed on four or five soft fiberboard trays made 

from recycled newspaper. In some cases, the tray 

is made of soft polystyrene. Cartons are often 

unvented. However, unvented cartons on pallet 

stacks will cool slowly, detrimentally affecting 
179

product longevity. Venting to improve cooling 

rates of fruit is becoming more common. 

A two-layer carton that is wider, known as the 

60×40 pack, is becoming more common in the 

United States and for export to Europe. It has the 

advantage of minimizing fruit handling as the 

cartons are placed directly onto display racks at 

retail.

Most apples are sold loose, though fruit are 

increasingly available in polyethylene bags of 

3, 5, or 10 lb (1.4, 2.3, or 4.5 kg). These bags 

were originally used for marketing smaller fruit 

but are now used for all qualities and sizes. Bags 

are most often sold in warehouse-type retail 

stores. Consumer packages in which two to six 

apples, or a combination of fruits, are shrinkwrapped are becoming more popular in some 

retail outlets. Shrink-wrapped packages reduce the 

time consumers spend in the produce section and 

also reduce loss caused by consumer sorting and 

handling of individual fruit.

Cooling Conditions 

The rate of cooling of apple fruit affects retention 

of quality, but its importance varies according 

to variety, harvest maturity, nutritional status of 

the fruit, and storage history. It is very important 

to rapidly cool apple varieties that mature in the 

early part of the harvest season (summer varieties) 

since they will soften more rapidly than those that 

mature in the later part of the harvest season.

Within a variety, apples tend to soften more 

rapidly at later stages of maturity than at earlier 

stages. Effects of slow cooling are magnified as 

storage length increases. Therefore, inadequate 

investment of resources at harvest to ensure rapid 

fruit cooling may not be apparent until late in the 

storage period when fruit may not meet minimum 

firmness standards for marketing. For example, 

a 1-day delay at 21 °C (70 °F) before cooling 

results in a 7- to 10-day loss of storage life for 

‘McIntosh.’ The effects of delays before cooling 

of fruit, irrespective of timing of CA conditions, 

are illustrated for ‘Empire’ apples in table 1.

Table 1. Effect of cooling rate on firmness 

of rapid CA Empire apples 

________________________________________

Days to cool Days from Flesh firmness (N)

to 0 °C harvest to after removal

3% O2 from CA

________________________________________

1 4 63

7 4 58

14 4 52

________________________________________

Modified from Blanpied (1986).

Apple fruit can be cooled by room cooling, 

forced-air cooling, or hydrocooling. Forced-air 

cooling and hydrocooling systems can be used to 

rapidly reduce fruit temperatures, but they are not 

widely used for apples in the United States. Room 

cooling, in which normal air flow within the storage 

room cools the fruit, is the predominant method 

in most regions. However, air flows around rather 

than through bins of fruit, so this method is slow 

and inefficient. Rapid cooling is often difficult 

to accomplish when rooms are filled rapidly and 

refrigeration capacity was not designed for a large 

fruit load. This problem can be overcome in two 

ways. First, fruit can be separated and loaded into 

a number of rooms for precooling before being 

moved into long-term storage. A second option is 

to load only the quantity that can be handled by the 

existing refrigeration system. 

When refrigeration capacity is a limiting factor, 

no more than two stacks of bins should be placed 

across the width of the storage room each day, 

and that should be reduced to one stack if the air 

temperature in the room is not down to 0 °C (32 

°F) by the next morning (Bartsch and Blanpied 

1990). Faster cooling will be obtained if bins 

are placed in the downstream discharge of the 

evaporator with pallet runners oriented in the 

same direction as the air flow. Additional bins of 

fruit should be stacked, no more than two high, 

in unfilled refrigeration rooms to cool overnight 

before loading into the CA room the next 

morning. These stacks should be placed randomly 

throughout the unfilled room to maximize air 

exchange with the fruit. Capacity to cool fruit 

depends on refrigeration capacity and room 
180

design. A qualified refrigeration engineer should 

assist in the development of a cooling program.

Maximizing quality maintenance of fruit requires 

attention to temperature not only immediately 

after harvest and during storage but also during 

packing, transport, and retail display. This 

combination of events is sometimes described as 

the “cold chain,” highlighting the importance of 

maintaining the links from harvest to consumer.

Excellent discussions of cooling can be found 

in Kader (1992), Thompson et al. (1998), and 

Bartsch and Blanpied (1990).

Optimum Storage Conditions

Apple producers have learned that apple fruit 

respond dramatically to both temperature and 

atmosphere modification. Rapid temperature 

reduction and the exacting maintenance of low 

temperatures close to the chilling point of the 

variety can provide good to medium quality 

product following 3 to 6 mo of storage and in 

some cases longer. However, modern commercial 

warehouses combine temperature management 

with CA for long-term storage of apples. 

Regular Air Storage. The recommended 

conditions for commercial storage of apples are 

-1 °C to 4 °C (30 to 39 °F) and 90 to 95% RH, 

depending on variety. Typical storage periods for 

a number of varieties in air are shown in table 2. 

The acceptable duration of air storage has become 

shorter over the last several years as quality 

standards in the market have increased. Also, 

short-term CA storage is becoming more common 

as the period available for sale of air-stored fruit 

has decreased.
181

Table 2. Storage characteristics of several apple varieties

______________________________________________________________________________

 

Variety Potential months Superficial Comments

of storage scald

______________ susceptibility

0 oC CA*

Air

______________________________________________________________________________

Braeburn 3-4 8-10 Slight Sensitive to CO2.

 

Cortland 2-3 4-6 Very high Temperature sensitive; McIntosh 

 conditions preferred; scald inhibitor 

 essential.

Delicious 3 12 Moderate Sensitive to CO2 >2%; scald inhibitor

 to very high essential.

 

Empire 2-3 5-10 Slight Avoid late harvest; temperature sensitive; 

scald inhibitor not required; CO2 sensitive.

 

Fuji 4 12 Slight Late harvested fruit may be CO2 sensitive.

 

Gala 2-3 5-6 Slight Loses flavor during storage.

 

Golden Delicious 3-4 8-10 Slight Susceptible to skin shrivel.

 

Granny Smith 3-4 10-11 Very high Sensitive to CO2.

 

Idared 3-4 7-9 Slight Temperature sensitive; tolerant to orchard 

freezing damage.

 

Jonagold 2 5-7 Moderate Avoid late harvest; may develop scald.

 

Jonamac 2 3 Moderate Loses flavor during storage.

 

Law Rome 3-4 7-9 Very high Scald inhibitor essential.

 

Macoun 3 5-7 Slight Can be stored with McIntosh.

 

McIntosh 2-3 5-7 Moderate CO2 sensitive; normal storage is 

sometimes shortened by excessive flesh 

 softening; scald inhibitors recommended.

 
182

Table 2. Storage characteristics of several apple varieties—Continued

______________________________________________________________________________

 

Variety Potential months Superficial Comments

of storage scald

______________ susceptibility

0 oC CA*

Air

______________________________________________________________________________

Mutsu 3-4 6-8 Slight Green apples have low eating quality.

 

Spartan 3-4 6-8 Slight Can be susceptible to high CO2; susceptible 

to skin shrivel at 36 to 38 °F.

 

Stayman 2-3 5-7 High Will tolerate CO2 up to 5%, but usually 

 stored in 2 to 3% CO2; scald inhibitor 

 essential; susceptible to skin shrivel.

______________________________________________________________________________

* The potential months storage are for rapid CA and range from those obtained with standard CA 

to those obtained with low-O2 and low-ethylene CA. Growing region affects storage periods 

obtained even under optimal CA conditions.

Temperatures for air-stored fruit are affected 

by sensitivity of the variety to low-temperature 

disorders. While lower temperatures usually result 

in firmer and greener fruit, some varieties such as 

‘McIntosh’ can develop core browning, soft scald, 

and internal browning when held at temperatures 

below 3 °C (37 °F). However, these disorders 

typically develop only in fruit kept for more than 

several months, so risks of low-temperature injury 

are low for fruit kept in short-term storage (2 to 3 

mo). An additional factor to consider in selecting 

storage temperatures is the effect of temperature 

on RH requirements. It is easier to maintain RH 

above 90% at 1 °C (34 °F) than at 0 °C (32 °F). 

Final decisions should be based on experience 

with the apple variety and advice of extension 

personnel.

Most apple varieties are not sensitive to chilling 

and should be stored as close to 0 °C (32 °F) as 

possible. However, varieties that are susceptible 

to low-temperature disorders should be stored at 

2 to 3 °C (36 to 37 °F). Temperatures also should 

be increased for fruit stored in low-O2

 CA, since 

lower temperatures increase risk of low-O2

 injury.

Temperatures in storage rooms should be monitored 

throughout the storage period using thermocouples 

throughout the room (Bartsch and Blanpied 1990). 

It is dangerous to rely on a single thermometer 

at the door, as temperatures within stacks and 

throughout the room may be lower or higher than 

indicated by such readings. Faster fruit ripening 

and greater refrigeration usage result when fruit 

temperatures are too high (table 3). Excessive 

temperatures after packing due to lack of cooling 

or developing during transport to market can 

reduce quality at the consumer level. Fruit 

temperatures can increase during packing; failure 

to remove heat may result in subsequent loss 

of firmness during transport (Kupferman 1994, 

Watkins 1999). 
183

Table 3. Rates of heat evolution by 10 apple varieties at different temperatures

__________________________________________________________________________

Cultivar Temperature

__________________________________________

 -1 °C 0 °C 2.2 °C 3.3 °C 4.4 °C

__________________________________________________________________________

---------------------- BTU ton-1 day-1----------------------

Delicious 690 760 910 1,010 1,110

Golden Delicious 730 800 970 1,070 1,180

Jonathan 800 880 1,060 1,170 1,290

McIntosh 730 800 970 1,070 1,180

Northern Spy 820 900 1,090 1,200 1,320

Rome Beauty 530 580 700 780 850

Stayman Winesap 820 910 1,100 1,210 1,330

Winesap 530 590 710 780 860

Yellow Newton 510 570 690 760 840

York Imperial 610 670 810 900 990

 

Mean 680 750 900 1,000 1,100

__________________________________________________________________________ 

* To convert BTU ton-1 day-1 to kJ ton-1 day-1, multiply by 1.055.

Adapted from Tolle (1962). 
184

Controlled Atmosphere (CA) 

Considerations 

Apples are the predominant horticultural 

commodity stored under CA conditions, but 

the gas composition and storage temperature 

conditions are specific to variety, growing 

region, and sophistication of the equipment 

available for monitoring and controlling the 

atmospheres. Interactions occur between O2

, 

CO2

, and temperature. For example, low storage 

temperatures increase fruit susceptibility to low-O2

injury. Also when very low O2

 levels are used, 

levels of CO2

 should be reduced to prevent CO2

damage.

The wide range of recommended atmospheres has 

been reported by Kupferman (1997) and reflects 

the above factors as well as strategies employed 

by different industries. Information about CA 

recommendations for varieties in any growing 

region should be obtained from local extension 

personnel.

Until the mid 1970s, 8 to 10 days was often 

required to load a CA room and an additional 

15 to 20 days was needed for fruit respiration to 

lower O2

 to 2.5 to 3%. Fruit quality resulting from 

these conditions gradually became unacceptable 

in the marketplace. Rapid CA is now standard 

practice in many apple industries. Nitrogen flushing 

equipment enables O2

 in CA rooms to be reduced 

to less than 5% within a day or two of harvest, 

though 4 to 7 days from the harvest of the first 

fruit and placing into the storage room with CA 

conditions is considered “rapid CA.” For certain 

varieties, fruit core temperatures must be reduced to 

predetermined thresholds before application of CA. 

Even when rooms are filled over extended periods, 

O2

 concentrations are usually lowered by flushing 

with N2

, and it is becoming more common to use N2

flushing for resealing rooms that are opened briefly 

to remove some of the fruit required for marketing. 

Nitrogen used for flushing is either purchased in 

tanks or generated on site.

An RH of 90 to 95% is recommended for apples to 

prevent shrivel. The major causes of dehydration 

are small coil surface areas and frequent 

defrosting. When CA rooms are designed, the 

refrigeration engineer should demand the largest 

coil size feasible for the room. Operators have 

been reducing the number of defrost cycles to an 

absolute minimum to optimize RH in the room. 

Some operators reduce the O2

 to the minimum 

safe level and then raise the temperature to 1 to 2 

°C (34 to 36 °F) to minimize the need to defrost. 

Some storage rooms are outfitted with highpressure water vapor systems that add moisture to 

the room and are suited for operation at around 0 

°C (32 °F). The air distribution system should be 

designed to prevent condensation of water droplets 

on fruit to prevent decay. The use of plastic, rather 

than wooden bins or poly tubes (bin liners), inside 

wooden bins has also helped minimize shrivel of 

‘Golden Delicious.’ 

Once fruit have been cooled and CA conditions 

established, CA storage regimes fall into one of 

three categories, depending on level of equipment 

and technology involved.

Standard CA involves conservative atmosphere 

conditions used with minimum risk of gas-related 

injuries (table 4). Control of these atmospheres 

may be manual by daily reading and adjustment 

or via computer-controlled equipment. The margin 

of safety is large enough so that fluctuations in 

gas concentrations in manually adjusted storages 

should not cause fruit injury. 
185

Table 4. Atmospheric and temperature requirements for standard CA storage 

of apples 

__________________________________________________________________________

Variety CO2 O2 Temperature Low-O2* __________________________________________________________________________

 

% % °C

Braeburn 0.5 1.5-2 1 yes

 

Cortland 2-3 2-3 0 no

2-3 for 2-3 2

1 mo then 5

Delicious 2 0.7-2 0 yes

 

Empire 2-3† 2 2 yes

 

Fuji 0.5† 1.5-2 0-1 yes

 

Gala 2-3 1-2 0-1 yes

 

Golden Delicious 2-3 1-2 0-1 yes

 

Granny Smith 0.5 1.5-2 1 yes

 

Idared 2-3 2 1 yes

 

Jonagold 2-3 2-3 0 yes

 

Jonamac 2-3 2-3 0 no

2-3 for 2-3 2

1 mo then 5 

Law Rome 2-3 2 0 yes

 

Macoun 5 2-3 2 no

 

Marshall McIntosh 2-3 for 4-4.5 2 no

1 mo then 5 

2-3 for 3 2 no

1 mo then 5

2-3 for 2 3

1 mo then 5
186

Table 4. Atmospheric and temperature requirements for standard CA storage 

of apples—Continued

__________________________________________________________________________

Variety CO2 O2 Temperature Low-O2* ________________________________________________________________________

% % °C

Mutsu 2-3 2 0 yes

 

Spartan 2-3 2-3 0 yes

 

Stayman 2-5 2-3 0 yes

__________________________________________________________________________

Modified from Kupferman (1997).

* Storage potential at 1.5 to 1.8% O2

 (Eastern USA)

†

 CO2 sensitive: keep CO2 well below the O2 level. If not treated with DPA, use 1.5% to 2% 

CO2 during the first 30 days.

Low-O2

 CA storage requires that fruit be kept 

at O2 below 2%, but above the concentration at 

which fermentation will occur. Nondescriptive 

terms such as “ultralow” are sometimes used but 

should be avoided in favor of describing specific 

O2

 percentages. The safe O2 concentration varies 

by variety (table 4) and region. ‘Delicious’ 

apples from British Columbia, Canada, for 

example, can be stored safely at 0.7% (Lau 1997) 

allowing control of superficial scald without 

use of diphenylamine (DPA). Fruit of the same 

cultivar from other growing regions may show 

injury when stored at these low O2

 levels (Lau 

et al. 1998). Strains within a variety can also 

vary in sensitivity (Lau 1997). An extreme case 

is the Marshall strain of ‘McIntosh,’ where O2

below 4 to 4.5% is not safe, whereas 2 to 3% O2

is acceptable for other ‘McIntosh’ strains (Park 

et al. 1993). In general, it is necessary to increase 

storage temperature when low-O2

 CA storage is 

used. A number of guidelines have been developed 

for safe operation of long-term CA storage. 

Using the following techniques, it has also been 

possible to minimize risk of low-O2

 injury in the 

Northeastern United States:

1. Apply low-O2 CA storage only to apples 

harvested early in their harvest window. 

Overmature fruit can be damaged by low-O2

storage.

2. Avoid apples from orchard blocks that average 

fewer than five seeds per apple. Low seed count

can be a problem with some varieties.

3. Reduce core temperatures to 1 to 2 °C within

2 days after harvest for ‘McIntosh’ and 

‘Empire.’ (In Washington, cooling can take 

longer as it is done under CA, with the

exceptions of ‘Fuji’ and ‘Braeburn’).

4. Decrease O2 to under 5% within 7 days after 

harvest, except for ‘Fuji’ and ‘Braeburn.’

5. Raise storage temperatures from 0 to 2 °C to

reduce risk.

6. Obtain automatic gas analysis/control

equipment to eliminate O2 fluctuations that may 

lead to low-O2 injury.

7. Avoid use of postharvest drench with DPA 

where possible; its application has been

associated with low-O2 injury, for example, for 

varieties with low-O2 scald risk.

Low-ethylene CA storage is appropriate because 

apple fruit are climacteric, with autocatalytic 

ethylene production often beginning close to 

harvest. However, rates of ethylene production can 

vary greatly among apple varieties. An important 

physiological effect of CA storage is inhibition 

of either ethylene production or its action, due to 

lowered O2

 or increased CO2.
187

Low-ethylene CA storage has been evaluated as 

a method for reducing superficial scald, as a safe 

substitute for low-O2

 CA storage, and for retarding 

flesh softening and other forms of senescence 

(Blanpied 1990). Low-ethylene CA storage (below 

1 μL L-1) was used successfully in New York for 

storage of the naturally low-ethylene-producing 

‘Empire’ apple, but it has been replaced by low-O2

storage. In general, low-ethylene CA storage has not 

proven successful for maintenance of fruit quality 

if levels of ethylene gas within the fruit cannot be 

controlled, and generally the return on investment 

in this technology has been poor.

Other methods used in conjunction with CA 

storage to maintain quality of apple fruit include 

treatments using short-term stress levels of low 

O2

 or high CO2. In varieties including ‘Granny 

Smith,’ ‘Delicious,’ and ‘Law Rome,’ O2

 of 0.25 

to 0.5% for up to 2 weeks has resulted in control 

of superficial scald (Little et al. 1982, Wang and 

Dilley 2000). High-CO2

 (15 to 20%) treatments 

before application of CA storage were used for 

maintenance of firmness of ‘Golden Delicious’ 

apples in northwestern North America but generally 

are no longer recommended because of fruit 

damage (Blanpied 1990).

Under commercial conditions, fruit from CA 

rooms should be sampled at monthly intervals 

to detect development of any storage problems 

and therefore reduce the chances of major fruit 

losses. Sampling should be carried out by placing 

representative samples of fruit near a sampling 

port in the door of the CA room. Samples should 

be kept in mesh bags rather than plastic bags to 

prevent false positive readings for scald. 

CA and Apple Varieties 

The selection of CA atmospheres and temperature 

must take into consideration the variety and, in 

some cases as mentioned above, the strain of 

a particular variety, in addition to where it was 

grown. Experience in Washington has shown that 

varieties can be divided into two types: those 

tolerant of high CO2 and those that are not. 

‘Gala’ and ‘Golden Delicious’ are CO2

-tolerant 

varieties that also benefit from rapid reduction of 

atmosphere. In Washington, fruit with moderate 

pulp temperatures can be placed into a low-O2

environment without danger of CO2 damage. 

Rapid CA is valuable because it helps retain fruit 

firmness and acidity better than slowly established 

CA on these varieties. Washington-grown ‘Gala’ 

and ‘Golden Delicious’ can be stored as low as 

1.0% O2

 with CO2 levels up to 2.5% at 1 °C (34 

°F). If the temperature is lowered below this point, 

O2

 is raised. Regular storage is 0 °C (32 °F).

‘Fuji,’ ‘Braeburn,’ and ‘Granny Smith’ are in the 

CO2-intolerant category. Their cells are densely 

packed, and air exchange within the fruit is 

therefore reduced. In Washington, these apples 

must have the flesh temperature close to the 

storage temperature before the O2

 is reduced. 

These varieties have a tendency to develop 

internal browning, a CO2 damage symptom that 

is associated with a natural predisposition of the 

variety (and preharvest factors as well as storage 

regime). CO2

 should remain well below the O2

level at all times, and temperatures should be 

slightly elevated. For example, fruit stored at 1.5% 

O2

 are stored with CO2 below 0.5% at 1 °C (34 

°F) if fruit are appropriately mature at harvest. It 

is not advisable to store waxed fruit in boxes with 

polyliners in CA, as this can hinder air exchange 

within fruit.

‘Red Delicious’ is somewhat CO2

-tolerant and 

is also tolerant of rapid CA. However, producers 

have not seen the dramatic positive effects of 

rapid CA on ‘Delicious’ that have been noted on 

‘Golden Delicious’ or ‘Gala.’ ‘Delicious’ fruit 

soften more rapidly in a bin than on the tree, so 

CA should not be delayed after harvest. Typical 

regimes for CA of nonwatercored ‘Delicious’ are 

1.5% O2

 and up to 2.0% CO2 at 0 to 1 °C (32 to 34 

°F).

State regulations on CA storage cover both the 

safe operation and the use of the legal definition 

of “controlled atmosphere” for stored apples. 

Regulations include the rate of establishment 

of CA conditions, the maximum level of O2
188

permitted, and the length of time fruit are in 

CA. Since regulations vary from State to State, 

operators need to contact their State Department 

of Agriculture.

Many precautions must be taken to assure the safe 

operation of CA storage rooms. Operators must be 

aware of the risks of working with O2

 levels below 

those needed for survival. Additional precautions 

must be taken when working with CA generators 

to avoid implosion or explosion hazards. In short, 

workers must be thoroughly trained. Contact your 

local extension office for information about safety 

in CA.

1-Methylcyclopropene (1-MCP) 

Softening, yellowing, respiration, loss of titratable 

acidity, and sometimes a reduction in SSC, as well 

as development of several physiological disorders, 

are delayed or inhibited by 1-MCP application 

(Watkins 2002, Watkins and Miller 2004). 

Responses of fruit to 1-MCP may be affected by 

cultivar and fruit maturity. Volatile production 

by apples also is inhibited by 1-MCP, being 

consistent with the view that volatile production 

is regulated by ethylene. Consumer studies on 

acceptability of 1-MCP treated fruit are required 

to ensure flavor is not unacceptably compromised.

Retail Outlet Display Considerations

Keeping apple fruit cold reduces metabolic rates 

and maintains fruit quality, but the trend in most 

new retail outlets is not to have refrigeration in 

display tables. Moreover, typical displays in U.S. 

supermarkets employ stacking of loose fruit with 

increased risk of bruising. There is some movement 

towards use of display cartons such as the 60×40 

box, which reduces the need to handle fruit and 

ensures more rapid turnover of product.

Physiological Disorders 

A wide variety of physiological disorders are 

found in apple fruit, but susceptibility varies 

by variety, preharvest factors, and postharvest 

conditions (Lidster et al. 1990, Smock 1977). 

Disorders can be considered in three categories:

Disorders That Develop Only on the Tree. The 

most important of these is watercore, in which 

intercellular air spaces in the core and cortical 

tissues become filled with liquid, predominantly 

sorbitol (Marlow and Loescher 1984). Usually 

the occurrence of watercore is associated 

with advancing fruit maturity and low night 

temperatures prior to harvest, but a variant of 

the disorder can occur as a result of heat stress. 

Presence of watercore in fruit at harvest creates 

problems in certain varieties such as ‘Delicious’ 

because fruit with moderate or severe watercore 

can develop breakdown during storage. By 

comparison, grade standards for ‘Fuji’ were 

modified so that watercore in ‘Fuji’ apples is not 

a grade defect in the United States or Canada, 

because watercore is a desirable feature for this 

cultivar due to the sweetness it imparts to the 

fruit. Mild or moderate watercore should not be 

a problem in storage of ‘Fuji’ if fruit are cooled 

prior to reduction of O2

. Severely watercored fruit 

should not be placed in CA since breakdown will 

develop over time.

Disorders That Develop on the Tree and During 

Storage. Bitter pit is a disorder characterized by 

development of discrete pitting of the cortical 

flesh, the pits being brown and becoming 

desiccated with time (Ferguson and Watkins 

1989). The pits may occur predominantly near 

the surface or deep in the cortical tissue. An 

associated disorder, known as lenticel blotch, is 

also observed in some varieties. The incidence 

and severity of bitter pit are affected by variety, 

but within a variety, bitter pit is related to 

harvest date and climate. In susceptible varieties, 

harvest of less mature fruit can result in higher 

bitter pit incidence, as can excessive pruning or 

high temperatures and/or droughty conditions 

during the growing season. Effects of climatic 
189

conditions are at least partly related to low 

calcium concentrations in the fruit. Development 

of bitter pit during storage results in financial loss, 

and a number of strategies have been employed 

to prevent its occurrence (Ferguson and Watkins 

1989). These include prediction of risk based on 

mineral (mainly low calcium) content at harvest 

or infusion of magnesium. Rapid cooling, CA 

storage, and application of postharvest calcium 

drenches may be able to reduce its occurrence. 

Recommended rates for application of calcium 

vary by variety and region; product labels should 

be followed in conjunction with advice of the 

local extension specialist. Preharvest applications 

of calcium may be far more effective than 

postharvest drenching as a means of increasing the 

concentration of fruit calcium and reducing bitter 

pit.

Disorders That Develop During Storage.

These can be divided into senescent breakdown 

disorders, chilling disorders, and disorders 

associated with inappropriate atmospheres during 

storage. Senescent breakdown incidence is related 

to harvest of overmature fruit or fruit with low 

calcium content. It can be exacerbated by storing 

fruit at higher than optimal temperatures. Fruit of 

susceptible varieties are commonly drenched with 

calcium before storage, but incidence of senescent 

breakdown can also be reduced by harvesting fruit 

at a less mature stage, rapid cooling, and reducing 

storage duration. The most common disorders 

associated with temperature and atmospheres 

are superficial scald, soft scald, low-temperature 

breakdown, brown core, internal browning, 

low-O2

 injury, and high-CO2 injury.

Specific Disorders

Superficial scald (storage scald) is a physiological 

disorder associated with long-term storage (Ingle 

and D’Souza 1989). It was the major cause of 

apple fruit loss until the advent of postharvest 

DPA treatments. Variety, climate, and harvest 

date affect susceptibility of fruit to the disorder, 

and decisions about treatment with DPA should 

be made after consultation with a local extension 

specialist. DPA is usually applied with a fungicide 

to reduce decay incidence, and calcium salts may 

also be included at the same time to reduce bitter 

pit or senescent breakdown. Application of label 

rates of clean DPA should prevent DPA-induced 

fruit damage and exceed residue tolerances. The 

risk of DPA damage to fruit increases if DPA is not 

discarded when soil accumulates in the solution. 

Both DPA use and DPA residues on fruit are 

prohibited in some countries. Another antioxidant, 

ethoxyquin, is no longer permitted for use on 

apples. Low levels of O2

 in CA storage reduce 

the risk of scald developing and also may permit 

use of lower DPA concentrations. Alternative 

ways of controlling superficial scald are being 

investigated, and storage operators are reducing 

use of DPA where possible. Low-O2

 and lowethylene CA storage also reduce scald incidence. 

In British Columbia, Canada, 0.7% O2

 storage is 

used as a substitute for DPA treatment (Lau 1997). 

This technique cannot be used universally because 

fruit grown in other regions may be susceptible to 

low-O2

 injury or the risk of scald may be greater 

due to climate or variety.

Soft scald is characterized by irregular but 

sharply defined areas of soft, light-brown tissue 

that may extend into the cortex. Susceptibility of 

fruit to soft scald is variety- and climate-related, 

but effects of harvest maturity are inconclusive. 

Overmaturity is almost always a contributing 

factor in ‘Golden Delicious.’ Storing fruit at 3 °C 

rather than at lower temperatures can sometimes 

control the disorder, and DPA used for control of 

superficial scald may also reduce incidence of soft 

scald. Storage at a lower temperature following 

prompt cooling can reduce the incidence of soft 

scald on ‘Golden Delicious.’

Chilling-related disorders include lowtemperature breakdown, brown core, and internal 

browning. These disorders are affected by variety 

sensitivity to low temperatures and generally 

increase in incidence and severity as the length 

of storage is increased. Climate affects sensitivity 

of fruit to the disorders, with more problems 

occurring after colder, wetter growing seasons. 

Low-temperature breakdown is characterized 

by markedly brown vascular bundles, browning 

of flesh, and a clear halo of unaffected tissue 
190

underneath the skin. In contrast to senescent 

breakdown, the affected tissues are more likely 

to be firmer, moister, and darker in color. Brown 

core (coreflush) involves browning of the flesh, 

initially in the core area and later in the cortex, 

where it becomes difficult to distinguish from 

low-temperature breakdown. Internal browning 

does not involve breakdown of the flesh, but rather 

a graying of flesh that becomes apparent when 

apples are cut. Internal browning and coreflush are 

often associated with higher CO2

, since both can 

occur in CA when CO2

 is higher than O2. 

Low-O2

 injury affects fruit in a number of ways. 

The first indication of injury is loss of flavor, 

followed by fermentation-related odors. These 

odors may disappear if storage problems are 

identified soon enough and severe injury has not 

occurred. Injury symptoms range from purpling 

or browning of the skin in a red-colored variety, 

to development of brown soft patches resembling 

soft scald, to abnormal softening and splitting of 

fruit. As discussed earlier, varieties vary greatly 

in response to low O2

, and susceptibility to injury 

is influenced by a number of preharvest and 

postharvest factors.

CO2

 injury may be external or internal. The 

external form consists of wrinkled, depressed, 

colorless or colored areas restricted to the skin 

surface and usually on the greener side of the fruit. 

Internal forms are expressed as brown heart and/or 

cavities in the flesh. DPA can reduce incidence of 

both external and internal CO2

 injuries.

Postharvest Pathology

The main postharvest diseases of apples that 

develop in storage are blue mold caused by 

Penicillium species and gray mold caused by 

Botrytis cinerea. Blue mold is the most common 

and destructive of all the rots. Most blue mold 

decays are caused by P. expansum, but P. solitum, 

P. commune, and P. crustosum are also common 

postharvest pathogens of apples (Sanderson and 

Spotts 1995). Penicillium species enter fruit 

primarily through cuts, stem punctures, and 

bruises (Wright and Smith 1954). However, some 

cultivars of apples can also be invaded via the 

stem during long-term CA storage (Rosenberger 

1999). 

Numerous other pathogens can also appear in 

stored apples (Pierson et al. 1971, Snowdon 

1990). Some postharvest pathogens infect fruit 

in the field but remain latent or quiescent until 

after apples are harvested and placed into storage. 

These include the Colletotrichum species that 

cause bitter rot; Botryosphaeria species that cause 

black rot and white rot; and Pezicula malicortis, 

the cause of bull’s eye rot (Rosenberger 1990). 

Postharvest decays initiated in the field must 

be controlled using fungicides or other disease 

management strategies during the growing season.

Blue mold and gray mold have been controlled 

since the early 1970s by using postharvest 

applications of benzimidazole fungicides. 

Thiabendazole (TBZ), benomyl, and thiophanatemethyl were all registered for postharvest use on 

apples until the postharvest labels for benomyl and 

thiophanate-methyl were withdrawn in the early 

1990s. TBZ is usually applied immediately after 

harvest in combination with the antioxidant DPA 

(Hardenburg and Spalding 1972). TBZ may be 

applied a second time as a line spray or in wax as 

apples are packed.

Benzimidazole-resistant strains of P. expansum

and B. cinerea were discovered in apple 

storage during the mid to late 1970s. However, 

postharvest application of a benzimidazole plus 

DPA continued to control blue mold and gray 

mold because most benzimidazole-resistant 

strains of the pathogen were highly sensitive to 

DPA (Rosenberger and Meyer 1985, Sharom 

and Edgington 1985). During the mid 1990s, the 

incidence of blue mold began to increase in some 

apple packinghouses where the predominant 

strains of P. expansum had developed resistance 

to the benzimidazole-DPA combination. Gray 

mold is still controlled by the benzimidazoleDPA combination, presumably because it does 

not recycle on field bins as readily as does P. 

expansum, and it therefore has been subjected to 

less selection pressure for fungicide resistance.
191

Captan has a postharvest registration but has 

proven only moderately effective for controlling 

P. expansum and B. cinerea. Captan residues 

are not acceptable in some export markets. 

The fungicide fludioxonil is very effective for 

controlling P. expansum on apples (Rosenberger et 

al. 2000). Fludioxonil is not yet approved for use 

on apples in the United States, but it may receive 

an EPA registration in the near future.

Much effort has been devoted to development 

of biocontrols for postharvest diseases of apples 

(Roberts 1990, Mercier and Wilson 1994, 

Wisniewski et al. 1995, Filonow et al. 1996, 

Chand-Goyal and Spotts 1997, Janisiewicz 

1998). The controlled postharvest environment 

theoretically should allow selection of biocontrol 

agents particularly suited to those environments. 

Many of the biocontrol agents selected and 

developed to date have proven very effective 

in controlled tests, but commercialization of 

biocontrols has been slow. Product developers 

view the market potential for postharvest 

treatments as relatively limited because the 

products are applied in a closed environment 

rather than being sprayed over thousands of 

acres, as are conventional fungicides used to 

protect crops in the field. Furthermore, liabilities 

involved in postharvest treatment of apples are 

considerable, both because of the value of the 

stored crop and because apples as a commodity 

have previously been spotlighted in debates 

relating to food safety issues. In addition, devising 

shelf-stable formulations of biocontrol agents 

has been difficult. Some currently registered 

products must be kept frozen until used. Activity 

of biocontrol organisms may be compromised 

by excessively high pathogen inoculum or by 

presence of other compounds in postharvest 

treatment mixtures.

Biocontrols generally cannot provide eradicant 

activity against established infections. Thus, 

infections by P. expansum that occur during 

harvest can be controlled with TBZ fungicide 

that is applied several hours later, whereas most 

biocontrol agents are ineffective if the pathogen 

is already established in the infection court when 

the biocontrol is applied. Using combinations 

of biocontrols and reduced rates of TBZ may be 

more effective than using either product alone 

(Chand-Goyal and Spotts 1997). When such 

combinations are used, the chemical fungicide 

may provide eradicant and short-term protectant 

activity necessary to prevent decay until the 

biocontrol agents become established in wounds 

or other infection courts. Biocontrols provide 

some protection against TBZ-resistant strains 

of the pathogens for which no other controls are 

currently available.

Regardless of the postharvest fungicide or 

biocontrol strategies that may evolve from 

current research, good sanitation will remain 

essential for reducing disease incidence. Inoculum 

for blue mold recycles from year to year on 

contaminated field bins and in packinghouses 

and cold storage rooms (Rosenberger 2001). 

Recycling of P. expansum on field bins results in 

repeated exposure of the same pathogen strains 

to postharvest fungicide treatments, thereby 

contributing to more rapid selection of fungicideresistant strains. Badly contaminated bins should 

be cleaned and disinfested (steam-cleaned) before 

they are reused for a new crop. Plastic bins may 

carry less inoculum than wooden bins. Plastic bins 

also have the advantage of reducing bruising and 

abrasion where apples contact the sides of bins. 

Careful fruit handling, rapid cooling after harvest, 

and storage at recommended temperatures also 

help limit postharvest decays.

Quarantine Issues 

These vary widely according to marketplace and 

country and guidance should be sought from the 

local Department of Agriculture.

Suitability as Fresh-Cut Product

As with other fruit, methods to reduce senescence 

and browning processes in cut apples are 

important, and commercial products are available 

(Lee and Smith 1995). However, potential for 

improvement is large. 
192

Additional Information

Many States have workshops and materials 

available. Washington, Michigan, and New York 

offer regular CA workshops, and proceedings are 

available from Michigan State University and 

Cornell University. Contact your local extension 

office or horticulture society to obtain information 

for your State.

References

Anonymous. 1986. Apple Maturity Program 

Handbook, 57 pp., Apple Maturity Program, 

Wenatchee, WA.

Bartsch, J.A., and G.D. Blanpied. 1990. 

Refrigeration and Controlled Atmosphere Storage 

for Horticultural Crops. Northeast Regional 

Agricultural Engineering Service Bull. no. 22, 45 

pp., (NRAES) PALS Publishing, Ithaca, NY.

Beaudry, R., P. Schwallier, and M. Lennington. 

1993. Apple maturity prediction: an extension 

tool to aid fruit storage decisions. HortTechnology 

3:233-239.

Blanpied, G.D. 1986. Empire harvest dates and 

storage strategies to meet the market demand for 

fruit quality and condition. Proc. NY State Hort. 

Soc. 131:150-166.

Blanpied, G.D. 1990. Controlled atmosphere 

storage of apples and pears. In M. Calderon and 

R. Barkai-Golan, eds., Food Preservation by 

Modified Atmospheres, pp. 265-299. CRC Press, 

Boca Raton, FL.

Blanpied, G.D., and K.J. Silsby. 1992. Predicting 

harvest date windows for apples. Cooperative 

Extension Information Bulletin 221, Cornell 

University, Ithaca, NY.

Chand-Goyal, T., and R.A. Spotts. 1997. 

Biological control of postharvest diseases of apple 

and pear under semi-commercial and commercial 

conditions using three saprophytic yeasts. Biol. 

Control 10:199-206.

Childers, N.F., J.R. Morris, and G.S. Sibbett. 

1995. Modern Fruit Science - Orchard and 

Small Fruit Culture, pp. 145-170. Horticulture 

Publications, Gainesville, FL.

Ferguson, I.B., and C.B. Watkins. 1989. Bitter pit 

in apple fruit. Hort. Rev. 11:289-355.

Filonow, A.B., H.S. Vishniac, J.A. Anderson, 

and W.J. Janisiewicz. 1996. Biological control 

of Botrytis cinerea in apple by yeasts from 

various habitats and their putative mechanisms of 

antagonism. Biol. Contr. 7:212-220.

Hardenburg, R.E., and D.H. Spalding. 1972. 

Postharvest benomyl and thiabendazole 

treatments, alone and with scald inhibitors, to 

control blue and gray mold in wounded apples. J. 

Amer. Soc. Hort. Sci. 97:154-158.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66. U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Ingle, M., and M.C. d’Souza. 1989. Physiology 

and control of superficial scald of apples. A 

review. HortScience 24:28-31.

Janisiewicz, W.J. 1998. Biocontrol of postharvest 

diseases of temperate fruits: challenges and 

opportunities. In J. Boland and L. Kuykendall, 

eds., Plant-Microbe Interactions and Biological 

Control, pp. 171-198. Marcel Dekker, New York, 

NY.

Kader, A.A. Postharvest Technology of 

Horticultural Crops, DANR Pub. no. 3311, 

University of California, Davis, CA.

Kupferman, E. 1994. Report to the industry on 

fruit quality and packing practices for Washington 

grown apples. Tree Fruit Postharv. J. 5:3-26.
193

Kupferman, E. 1997. Controlled atmosphere 

storage of apples. In A.A. Kader, ed., 7th 

International Controlled Atmosphere Research 

Conference, University of California, Davis, 

July 13-18, 1997, vol. 2, pp. 1-31. University of 

California, Davis, CA.

Lau, O.L. 1985. Harvest guide for B.C. apples. 

British Columbia Orchardist 7:1A-20A.

Lau, O.L. 1997. The effectiveness of 0.7% O2

 to 

attenuate scald symptoms in ‘Delicious’ apples is 

influenced by harvest maturity and cultivar strain. 

J. Amer. Soc. Hort. Sci. 122:691-697.

Lau, O.L., C.L. Barden, S.M. Blankenship, et al. 

1998. A North American cooperative survey of 

‘Starkrimson Delicious’ apple responses to 0.7% 

O2

 storage on superficial scald and other disorders. 

Postharvest Biol. Technol. 13:19-26.

Lee, C.Y., and N.L. Smith. 1995. Minimal 

processing of New York apples. New York’s Food 

and Life Sciences Bull. 145, Cornell University, 

Ithaca, NY.

Lidster, P.D., G.D. Blanpied, and R.K. Prange. 

1990. Controlled-atmosphere disorders of 

commercial fruits and vegetables. Publication 

1847E, Agriculture Canada, Ottawa, Canada.

Little, C.R., J.D. Faragher, and H.S. Taylor. 1982. 

Effects of initial low-O2

 stress treatments in low 

oxygen modified atmosphere storage of ‘Granny 

Smith’ apples. J. Amer. Soc. Hort. Sci. 107:320-

323.

Marlow, G.C., and W.H. Loescher. 1984. 

Watercore. Hort. Rev. 6:189-251.

Mercier, J., and C.L. Wilson. 1994. Colonization 

of apple wounds by naturally occurring microflora 

and introduced Candida oleophila and their effect 

on infection by Botrytis cinerea during storage. 

Biol. Contr. 4:138-144. 

Park Y.M., G.D. Blanpied, Z. Jozwiak, and F.W. 

Liu. 1993. Postharvest studies of resistance to 

gas diffusion in McIntosh apples. Postharv. Biol. 

Technol. 2:329-339.

Pierson, C.F., M.J. Ceponis, and L.P. McColloch. 

1971. Market Diseases of Apples, Pears and 

Quinces. Agriculture Handbook 376, U.S. 

Department of Agriculture, Agricultural Research 

Service, Washington, DC.

Roberts, R.G. 1990. Postharvest biological control 

of gray mold of apple by Cryptococcus laurentii. 

Phytopathology 80:526-530.

Rosenberger, D.A. 1990. Postharvest diseases. 

In A.L. Jones and H.S. Aldwinckle, eds., 

Compendium of Apple and Pear Diseases, pp. 53-

54. APS Press, St. Paul, MN.

Rosenberger, D.A. 1999. Postharvest decays: 

research results and future directions. In CA 

Storage: Meeting the Market Requirements, 

pp. 49-62. NRAES Bull. 136, Northeast Regional 

Agricultural Engineering Service, Ithaca, NY.

Rosenberger, D.A. 2001. Postharvest decay 

control without fungicides. In Storage Workshop 

2001: Apple Handling and Storage, pp. 21-

23. NRAES Bull. 153, Northeast Regional 

Agricultural Engineering Service, Ithaca, NY.

Rosenberger, D.A., and F.W. Meyer. 1985. 

Negatively correlated cross-resistance to 

diphenylamine in benomyl-resistant Penicillium 

expansum. Phytopathology 75:74-79.

Rosenberger, D.A., C.A. Ahlers, and F.W. Meyer. 

2000. Evaluation of Scholar for controlling blue 

mold of apples during storage, 1998-99. Fung. 

Nemat. Tests 55:24.

Sanderson, P.G., and R.A. Spotts. 1995. 

Postharvest decay of winter pear and apple fruit 

caused by species of Penicillium. Phytopathology 

85:103-110.
194

Sharom, M.S., and L.V. Edgington. 1985. 

Temperature dependent negatively correlated 

cross-resistance between benomyl and 

diphenylamine for Botrytis cinerea, Gerlachia 

nivalis, and Monilinia fructicola. Can. J. Plant 

Path. 7:389-394.

Smock, R.M. 1977. Nomenclature for internal 

disorders of apples. HortScience 12:306-308.

Snowdon, A.L. 1990. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 1, General Introduction and Fruits. CRC 

Press, Boca Raton, FL.

Thompson, J.F., F.G. Mitchell, T.R. Rumsey, R.F. 

Kasmire, and C.C. Crisosto. 1998. Commercial 

cooling of fruits, vegetables, and flowers. DANR 

Pub. no. 21567, University of California, Davis, 

CA.

Tolle, W.E. 1962. Film Permeability Requirements 

for Storage of Apples. Technical Bull. 1257, U.S. 

Department of Agriculture, Washington, DC.

Wang, Z., and D.R. Dilley. 2000. Initial low 

oxygen stress controls superficial scald of apples. 

Postharv. Biol. Technol. 18:201-213.

Watkins, C.B. 1999. Maintaining firmness 

of apples: effects of packing, cooling, and 

transport. In CA Storage: Meeting the Market 

Requirements, pp. 65-71. NRAES Bull. 136, 

Northeast Regional Agricultural Engineering 

Service, Ithaca, NY.

Watkins, C.B. 2002. Ethylene synthesis, mode of 

action, consequences and control. In M. Knee, ed., 

Fruit Quality and Its Biological Basis, pp. 180-

224. Sheffield Academic Press, Sheffield, U.K.

Watkins, C.B. 2003. Principles and practices of 

postharvest handling and stress. In D. Feree and 

I.J. Warrington, eds., Apples: Crop Physiology, 

Production and Uses, pp. 585-614. CAB Intl., 

Wallingford, U.K.

Watkins, C.B., and W.B. Miller. 2004. A summary 

of physiological processes or disorders in fruits, 

vegetables and ornamental products that are 

delayed or decreased, increased, or unaffected by 

application of 1-methylcyclopropane (1-MCP). At

http://hort.cals.cornell.edu.

Wisniewski, M.W., S. Droby, E. Chalutz, and Y. 

Eilam. 1995. Effect of Ca2

+ and Mg2+ on Botrytis 

cinerea and Penicillium expansum in vitro and on 

the biocontrol activity of Candida oleophila. Plant 

Pathol. 44:1016-1024.

Wright, T.R., and E. Smith. 1954. Relation of 

bruising and other factors to blue mold decay 

of Delicious apples. USDA Circular 935, U.S. 

Department of Agriculture, Washington, DC.
195

Apricot

Carlos H. Crisosto and Adel A. Kader

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA. Kader was 

with the Department of Plant Sciences, University 

of California, Davis, CA. He is deceased.

Scientific Name and Introduction

The apricot is native to central and western China. 

Apricots were brought to Italy about 100 BC, to 

England in the 13th century, and to North America 

by 1720. Most of the apricots in the United States 

are grown in California, with much smaller 

amounts grown in Washington and Utah.

Quality Characteristics and Criteria

Fruit size, shape, freedom from defects (including 

gel breakdown and pit burn), and freedom from 

decay are all important quality criteria. High 

consumer acceptance is attained for fruit with 

high (>10%) SSC and moderate TA (0.7 to 1.0%). 

Apricots with 2 to 3 lb-force (8.9 to 13.3 N) flesh 

firmness are ready to eat. Most cultivars soften 

very fast, making them susceptible to bruising and 

subsequent decay.

Horticultural Maturity Indices

In California, harvest date is determined by 

changes in skin ground color from green to 

yellow. The exact yellowish-green color depends 

on cultivar and shipping distance. Apricots should 

be picked when still firm because of their high 

bruising susceptibility when fully ripe and soft.

Grades, Sizes, and Packaging

Apricots are always harvested by hand, usually 

into picking bags or plastic totes. Apricots are 

generally handled in half bins or totes and handpacked. In some cases, apricots are dry-dumped 

onto a padded packing line belt. Apricots are 

tray-packed in single and double layers or 

volume-filled (about 10 kg net). Apricots should 

be uniform in size, and not more than 5% in 

each container may vary more than 6 mm when 

measured at the widest part of the cross section.

Optimum Storage Conditions

Apricots are seldom stored in large quantities, 

though they keep for 1 to 2 weeks (or even 3 to 4 

weeks, depending on the cultivar) at -0.5 to 0 oC 

with RH of 90 to 95%. Susceptibility to freezing 

injury depends on SSC, which varies from 10 to 

14%. The highest freezing point is -1.0 oC. 

Controlled Atmosphere (CA) 

Considerations

The major benefits of CA during storage and 

shipment are retaining fruit firmness and ground 

color. CA conditions of 2 to 3% O2

 + 2 to 3% 

CO2

 are suggested for moderate commercial 

benefits; the extent of benefits depends on 

cultivar. Exposure to less than 1% O2

 may result 

in development of off flavors, and higher than 

5% CO2

 for more than 2 weeks can cause flesh 

browning and loss of flavor. The addition of 5 to 

10% CO2

 as a fungistat during transport (less than 

2 weeks) may improve the potential for benefit 

from CA. Prestorage treatment with 20% CO2

for 2 days may reduce incidence of decay during 

subsequent transport and storage in CA or air.

Retail Outlet Display Considerations

Cold-table display is recommended because 

of apricots’ fast ripening. Ripening before 

consumption should ideally be done at 

temperatures of 18 to 24 oC.
196

Chilling Sensitivity

Chilling-sensitive cultivars develop and express 

chilling injury symptoms (gel breakdown, flesh 

browning, and loss of flavor) more rapidly at 5 

°C than at 0 °C. Storage at 0 °C is necessary to 

minimize incidence and severity of chilling injury 

on susceptible cultivars.

Rates of Ethylene Production and 

Sensitivity

Ethylene production rate increases with ripening 

and storage temperature from under 0.1 μL kg-1

h-1 at 0 °C (32 °F) to 4 to 6 μL kg-1 h-1 at 20 °C (68 

°F) for firm-ripe apricots and higher for soft-ripe 

apricots. Exposure to ethylene hastens ripening 

(as indicated by softening and color changes from 

green to yellow). Also, ethylene may encourage 

growth of decay-causing fungi.

Respiration Rate

Temperature mg CO2 kg-1 h-1

0 °C 4 to 8

10 °C 12 to 20

20 °C 30 to 50

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Gel Breakdown or Chilling Injury. Develops 

in cold storage, particularly at 2 to 7 °C (35 

to 45 °F) when apricots are stored for a long 

time period. This physiological problem is 

characterized in early stages by the formation of 

water-soaked areas that subsequently turn brown. 

Breakdown of tissue is sometimes accompanied 

by sponginess and gel formation. Fruit stored at 

these temperatures have short market-life and lose 

flavor.

Pit Burn. Flesh tissue around the stone softens 

and turns brown when the apricots are exposed 

to temperatures above 38 °C (100 °F) before 

harvest. This heat injury increases with higher 

temperatures and longer durations of exposure.

Postharvest Pathology 

Brown rot is caused by Monilia fructicola and is 

the most important postharvest disease of apricot. 

Infection begins during flowering. Fruit rots may 

occur before harvest, but often occur postharvest. 

Orchard sanitation to minimize infection sources, 

preharvest fungicide application, and prompt 

cooling after harvest are control strategies.

Rhizopus rot, caused by Rhizopus stolonifer,

occurs frequently in ripe or near-ripe fruit held 

at 20 to 25 °C (68 to 77 °F). Cooling fruit and 

holding below 5 °C (41 °F) are very effective for 

controlling this fungus.

Quarantine Issues

Apricots are currently exported from California 

to Canada and Mexico and imported from Chile 

and New Zealand. California apricot shipments 

to Canada, except British Columbia, are not 

restricted. For export to British Columbia and 

Mexico, apricots must be free of oriental fruit 

moth (Grapholita molesta/Cydia molesta). Apricot 

shipments require a phytosanitary certificate (PC) 

and a clear statement that the fruit were produced 

and inspected in accordance with the system 

approach guidelines agreed to by APHIS and the 

Canadian Food Inspection Agency. 

For export to Mexico, a PC stating that the 

fruit are free of western fruit tree leaf roller 

(Archips argyrospilus), navel orangeworm 

(Amyelois transitella), oblique banded leaf 

roller (Choristaneura rosaseana), orange tortrix 

(Argyrotaenia citrana), carob moth (Spectrobates 

ceratoniae), omnivorous leaf roller (Platynota 

stultana), and peach twig borer (Anarsia 

lineatella) is needed. Additionally, a clear 

statement is required that the fruit were produced 
197

and inspected in accordance with the Mexico work 

plan. A copy of the work plan for the exportation 

of apricot fruit from the United States to Mexico 

can be obtained from the PPQ regional office in 

Sacramento, CA. The work plan is only valid for 

the current season.

Methyl bromide fumigation is required on apricots 

imported from Chile, but not from New Zealand. 

In some cases, apricots may be precleared. To do 

this, the shipments must be accompanied by a 

PPQ Form 203 signed by the APHIS inspector on 

site in Chile. 

Suitability as Fresh-Cut Product

Fresh-cut apricot wedges should be kept at 0 °C 

(32 °F) and 90 to 95% RH to maintain quality for 

2 to 5 days, depending on cultivar and ripeness. 

Special Considerations

The greatest hazard in handling or shipping 

apricots is decay, mainly brown rot and rhizopus 

rot. Quick cooling of apricots to temperatures of 

4 °C (39 °F) or lower and holding them as near 

to 0 °C (32 °F) as possible will retard ripening, 

softening, and decay. 

Acknowledgments

Most of this information was extracted from the 

University of California, Davis, website on “Fresh 

Produce Facts” at http://postharvest.ucdavis.edu/

produce_information.

References

Andrich, G., and R. Fiorentini. 1986. Effects 

of controlled atmosphere on the storage of new 

apricot cultivars. J. Sci. Food Agr. 37:1203-1208.

Brecht, J., A. Kader, C. Heintz, and R. Norona. 

1982. Controlled atmosphere and ethylene effects 

on quality of California canning apricots and 

clingstone peaches. J. Food Sci. 47:432-436.

Chambroy, V., et al. 1991. Effects of different CO2

treatments on postharvest changes of apricot fruit. 

Acta Hort. 293:675-684.

Claypool, L.L., and R.M. Pangborn. 1972. 

Influence of controlled atmosphere storage on 

quality of canned apricots. J. Amer. Soc. Hort. Sci. 

97:636-638.

Folchi, A., G.C. Pratella, S.P. Tian, and P. 

Bertolini. 1995a. Effect of low oxygen stress in 

apricot at different temperatures. Ital. J. Food Sci. 

7:245-254.

Guelfat-Reich, S., and R. Ben-Arie. 1967. 

Different factors affecting the keeping quality 

of “Canino” apricots in cold storage. In

Proceedings of the 12th International Congress on 

Refrigeration, vol 3, pp. 447-457, Madrid, Spain.

Iwata, T., and M. Kinoshita. 1978. Studies on 

storage and chilling injury of Japanese apricot 

fruits. II. Chilling injury in relation to storage 

temperature, cultivar, maturity, and polyethylene 

packaging. J. Jpn. Soc. Hort. Sci. 47:97-104.

Trurter, A.B., J.C. Combrink, and L.J. von 

Mollendorff. 1994. Controlled-atmosphere storage 

of apricots and nectarines. Decid. Fruit Grower 

44:421-427.

Wankier, B.N., D.K. Salunkhe, and W.F. 

Campbell. 1970. Effects of controlled atmosphere 

storage on biochemical changes in apricot and 

peach fruit. J. Amer. Soc. Hort. Sci. 95:604-609.

Witherspoon, J.M., and J.F. Jackson. 1996. 

Analysis of fresh and dried apricots. In H. 

Linskens and J. Jackson, eds., Modern Methods 

of Plant Analysis, pp. 111-131. Springer-Verlag, 

Berlin, Germany.
198

Arazá

María S. Hernández and J. Pablo FernándezTrujillo

Hernández is with the Instituto Amazónico de 

Investigaciones Científicas (SINCHI), Bogotá, 

Colombia; Fernández-Trujillo is with the 

Department of Agricultural and Food Engineering, 

Technical University of Cartagena, Cartagena, 

Murcia, Spain.

Scientific Name and Introduction

Eugenia stipitata Mac Vaugh, known as the arazá 

(Morton 1987, Arkcoll 1990), is a berry from 

a perennial tree of the Myrtaceae family. Two 

subspecies were described by McVaugh (1956): 

stipitata from Brazil and Peru (also known as 

araçá-boi in Brazil or as pichi in Peru, “the wild 

one”) and sororia from Peru (also called rupina 

caspi, “the domesticated one”). One landrace 

occurs in the western Amazon (Gentil and 

Clement 1997). Arazá is primarily grown in the 

western Amazon as well as in Costa Rica. There 

can be four flowering periods per year with 2-mo 

harvest periods followed by a 1-mo break (Swift 

and Prentice 1983). The main harvest season is 

February to May for subsp. stipitata in Belem, 

Brazil (Morton 1987). There are two main 

production seasons (March to May and October 

to December) in Colombia’s northern Amazon, 

whereas production is year-round in the southern 

Amazon.

Quality Characteristics and Criteria

High-quality arazá fruit are juicy with bright, 

canary-yellow flesh; bright yellow to orange rind; 

and no signs of shriveling, bruises, or skin scald. 

The edible portion is slightly fibrous with an 

exquisite fragrance but has an extremely sour taste 

(Arkcoll 1991). Arazá fruit are known for their 

high acidity (mostly malate, followed by succinate 

and, to a lesser extent, citrate), minerals, a high 

ascorbic acid content, and low concentrations 

of reducing sugars (Gentil and Clement 1997, 

Hernández et al. 2001, 2002a, 2002b). Quality 

defects include susceptibility to anthracnose, scab 

(Sphaceloma sp.), rust (Uromyces sp.), soft fruit 

texture, loss of aroma, skin scald at suboptimum 

temperatures, and high weight losses, particularly 

at low RH (Arkcoll 1991, Galvis and Hernández 

1993b, Tai Chun 1995). The average number of 

seeds per fruit and seed length depends on the 

subspecies (Swift and Prentice 1983, Morton 

1987, Rodriguez 1990, Ferreira 1992,). Thirty 

volatile compounds have been identified in ripe 

arazá fruit, with sesquiterpenes and particularly 

germacrene D as the most abundant compounds 

(Franco and Shibamoto 2000).

Horticultural Maturity Indices

Fruit are harvested green (Hue angle values above 

100°) to avoid fruit softening (Arkcoll 1991, 

Galvis and Hernández 1993a,b). Harvest criteria 

are primarily size and color, and texture to a lesser 

extent. If arazá fruit mature on the tree, shelf-life 

is only about 3 days after harvest.

Grades, Sizes, and Packaging 

Average fruit range from 100 to 200 g, and 

equatorial diameters range from 4 to 10 cm 

(Ferreira 1992). The domesticated round to oblate 

fruit from subspecies sororia reach 50 to 800 

g, while the wild subspecies stipitata reaches 

20 to 56 g (Morton 1987, Rodriguez 1990). In 

Colombia, markets pack fruit in baskets of small 

(smaller than 100 g), medium (150 to 200 g), and 

large (200 to 350 g) fruit.

Precooling Conditions

Arazá should be cooled to around 13 °C (55.4 oF) 

within 24 h of harvest in a refrigerated chamber 

using air with 90 to 95% RH to maximize 

storability.
199

Optimum Storage Conditions

The recommended conditions are 12 to 13 °C 

(53.6 to 55.4 oF) and 90 to 95% RH. Arazá fruit 

can be kept in good condition for 2 weeks at 12 °C 

(53.6 oF), 7 days at 10 °C (50 oF), and 5 days at 20 

°C (68 oF) (Hernández et al. 2001, 2002b).

Controlled Atmosphere (CA) 

Considerations 

MA reduces weight loss, shriveling, development 

of skin scald, decay, softening, and the loss 

of TA (Hernández et al. 2001). Low-density 

polyethylene (LDPE) films have been used for 

MA. However, the effectiveness of MA storage 

depends on maturity, cultivar, temperature, and 

atmosphere. Storage under passive MA using PE 

film resulted in a steady state reached after 6 days 

at 10 °C (50 oF) and gas composition of 5 to 6% 

CO2

 and 13% O2, depending on the LDPE film 

used (Hernández et al. 2001). The use of active 

MA with 5% O2

 and 5% CO2 with LDPE of 38 

mm thickness results in maximum quality, but no 

recommendation can be made for MA storage. If 

O2

 decreases to below 2%, subsequent ripening in 

air may be irregular or inhibited.

Retail Outlet Display Considerations 

Use of molded plastic trays, as well as individual 

seal packaging with high OTR films, is acceptable. 

Weight loss at RH under 90% and bruising are 

serious problems.

Chilling Sensitivity

Arazá fruit are sensitive to chilling below 13 °C 

(55 oF). At 8 to 10 °C, fruit should be stored less 

than 5 days to avoid chilling injury.

Ethylene Production and Sensitivity

Ethylene production and sensitivity have not been 

determined. The fruit are climacteric.

Respiration Rates

Temperature Preclimacteric Climacteric

-------mg CO2 kg-1 h-1-----------

10 oC 40 to 323 601

13 °C 60 to 337 861

20 °C 140 to 310 1,283

Data from Galvis and Hernández (1993a,b) and 

Hernández et al. (2002a).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

The main disorders are skin scald, browning partly 

due to bruises, abnormal ripening or uneven to 

ripe symptoms (blotchy green color, high flesh 

firmness), lack of flesh juiciness, increase in 

acidity, and green skin spots (Tai Chun 1995, 

Hernández et al. 2002a). CaCl2

 application, 

particularly at higher than 4% (w/v), can result in 

abnormal ripening. Green skin spots remain on 

the fruit and small brown spots develop that later 

expand into necrotic lesions that become sites for 

fungal infection.

Postharvest Pathology

The main rot in arazá is anthracnose (Gloesporium 

album) on wounds or chilling-injured (scalded) 

areas (Arkcoll 1991, Hernández et al. 2002a,b). 

Cylindrocladium scoparium rot is characterized 

initially by small, light-brown lesions, which 

evolve to severely damaged areas that can reach 

about 0.3 cm of pulp depth (Nuñes et al. 1995). 

The pathogenicity of Curvularia spp. isolated 

from rotted fruit is under study, though symptoms 

are fruit softness and pink spot areas in the pulp 

that lack juice and fermentative degradation. The 

incidence of rust (Puccinia psidii or Uromyces 

sp.) has been recorded in Manaus and Costa Rica 

(Moraes et al. 1994, Tai Chun 1995). Yeasts are a 
200

minor problem with fruit bruises and/or chemicalscalded areas caused by calcium dips of 4 to 8% 

(Hernández et al. 2003).

Quarantine Issues 

Quarantine pests include Anastrepha obliqua

and A. striata (Diptera:Tephritidae) (Saldanha 

and Silva 1999). The coleoptera Conotrachelus 

eugeniae and Atractomerus immigrans have 

been reported on arazá rinds. Neosilba zadolicha 

(Diptera: Lonchaeidae) larvae are seldom present 

on fruit blemishes caused by these insects 

(Couturier et al. 1996). Mediterranean fruit fly 

(Ceratitis capitata Wied) has been identified in 

Costa Rican orchards (Swift and Prentice 1983, 

Moraes et al. 1994, Tai Chun 1995).

Special Considerations

Fruit are highly susceptible to dehydration and 

shriveling. A warming treatment of 18 h at 20 °C 

(68 oF) with 90% RH after 6 days at 10 °C (50 

oF) reduces skin scald and associated decay and 

extends shelf-life up to 2 weeks (Hernández et al. 

1999, 2002b).

Acknowledgments

Some of the information in this section was 

included in the Ph.D. dissertation of María 

S. Hernández (2001), who was supported by 

COLCIENCIAS (Colombia).

References

Arkcoll, D. 1991. New crops from Brazil. In J. 

Janick and J.E. Simons, eds., Proceedings of the 

National Symposium on New Crops: Exploration, 

Research and Commercialization, pp. 367-371. 

John Wiley & Sons, Indianapolis, IN.

Couturier, G., E. Tanchiva, J. Gonzales, et al. 

1996. Preliminary observations on the insect pests 

of araza (Eugenia stipitata Mc Vaugh, Myrtaceae), 

a new fruit crop in Amazonia. Fruits 51:229-239.

Ferreira, S.A. do N. 1992. Biometria de frutos de 

araçá-boi (Eugenia stipitata Mc. Vaugh) (biometry 

of the araza fruit ). Acta Amazonica 22:295-302.

Franco, M.R.B., and T. Shibamoto. 2000. Volatile 

composition of some Brazilian fruits: umbucaja (Spondias citherea), camu-camu (Myrciaria 

dubia), araca-boi (Eugenia stipitata), and cupuacu 

(Theobroma grandiflorum). J. Agric. Food Chem.

48:1263-1265.

Galvis, J.A., and M.S. Hernández. 1993a. Análisis 

del crecimiento del fruto y determinación del 

momento de cosecha del Arazá [Fruit development 

and harvest date in araza]. Colombia Amazónica 

6:107-121.

Galvis, J.A., and M.S. Hernández. 1993b. 

Comportamiento fisiológico del arazá (Eugenia 

stipitata) bajo diferentes temperaturas de 

almacenamiento [Physiological behavior of 

araza (Eugenia stipitata) under different storage 

temperatures]. Colombia Amazónica 6:123-134.

Gentil, D.F.O., and C.R. Clement 1997. The 

arazá (Eugenia stipitata): results and research 

directions. Acta Horticulturae 452:9-17.

Hernández, M.S., H.E. Arjona, O. Martínez, and 

J.P. Fernández-Trujillo. 1999. Storage disorders of 

arazá fruit (Eugenia stipitata Mc Vaugh) related to 

postharvest treatments. HortScience 34:512.

Hernández, M.S., J.P. Fernández-Trujillo, O. 

Martínez, et al.. 2001. Modified atmosphere 

packaging of araza fruit (Eugenia stipitata

McVaugh). In F. Artés, M.A. Conesa, and M.I. 

Gil, eds., Proceedings of the International Institute 

of Refrigeration Conference on Improving 

Postharvest Technologies of Fruits, Vegetables, 

and Ornamentals, Oct. 19-21, 2000, vol. 2, pp. 

666-673. Murcia, Spain.
201

Hernández, M.S., J. Barrera, J.P. FernándezTrujillo, et al. 2002a. Efecto de la temperatura de 

almacenamiento en la fisiología y calidad del fruto 

de arazá (Eugenia stipitata Mc Vaugh) [Effect of 

storage temperature on postharvest physiology 

and quality of araza fruit]. IV Iberian Congress. 

Spanish Soc. Hort. Sci., Cáceres, May 2001. Actas 

de Horticultura 37:1074-1081.

Hernández, M.S., H.E. Arjona, O. Martínez, 

and J.P. Fernández-Trujillo. 2002b. Influence of 

intermittent warming treatments on the postharvest 

quality of araza fruit (Eugenia stipitata McVaugh). 

In R. Dris and A. Sharma, eds., Food Technology 

and Quality Evaluation, vol. 43, pp. 261-265. Sci. 

Pub. Inc., Plymouth, U.K.

Hernández, M.S., J.P Fernández-Trujillo, and O. 

Martínez. 2003. Postharvest quality of araza fruit 

(Eugenia stipitata McVaugh) treated with calcium 

chloride solutions at two temperatures. Acta Hort. 

628:53-660.

McVaugh, R. 1956. Tropical American Myrtaceae. 

Fieldiana. Botany 29:145-228.

Moraes, V.H. de F., C. Hans, A.G.C. de Souza, and 

I. Cohen. 1994. Native fruit species of economic 

potential from the Brazilian Amazon. Angewandte 

Botanik 68:47-52.

Morton, J.L. 1987. Fruits of Warm Climates. J.L. 

Morton Pub., Miami, FL.

Nuñes, A.M.L., R.L.B. Stein, and F.C. de 

Albuquerque. 1995. Araçá-boi (Eugenia stipitata):

um novo hospedeiro de Cylindrocladium 

scoparium [Araza (Eugenia stipitata): a new host 

of Cylindrocladium scoparium]. Fitopatol. Bras. 

20:488-490.

Rodriguez, S. 1990. Araza (Eugenia stipitata). 

Monografia 1, Corporación Colombiana para 

la Amazonia Araracuara COA, San Jose del 

Guaviare, Colombia.

Saldanha, L.A., and N.M. Silva. 1999. Semiartificial bearing of the larvae of Anastrepha 

obliqua (Diptera:Tephritidae) in Manaus, 

Amazonas-Brazil. Florida Entomologist 82:82-87.

Swift, J.F., and W.E. Prentice. 1983. Native fruit 

species of the ecuadorian Amazon: production 

techniques and processing requirements. Proc. 

Amer. Soc. Hort. Sci. Trop. Reg. 27A:95-100.

Tai Chun, P.A. 1995. Pre- and post-harvest pests 

and diseases of Araza (Eugenia stipitata) in Costa 

Rica. Inter-American Institute for Cooperation on 

Agriculture, Costa Rica.
202

Artichoke

Chien Yi Wang

Wang is formerly with the Food Quality 

Laboratory, Henry A. Wallace Beltsville 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. He is now retired.

Scientific Name and Introduction

Cynara scolymus L., the globe artichoke, is a 

perennial of the Asteraceae (Compositae) family. 

The edible portion includes the tender immature 

flower bud and fleshy central base that is protected 

by a cone of short, thick-stemmed bracts. The 

main types include Green Globe, Desert Globe 

Imperial Star, Emerald, and Big Heart. Artichokes 

are primarily grown in California and are available 

year round.

Quality Characteristics and Criteria

A high-quality artichoke will have tightly closed, 

turgid outer bracts without signs of black tip, 

blistering, or browning. It should be medium to 

dark glossy green in color, and some cultivars may 

have a magenta color at the base of each bract. 

The artichoke should not be soft when squeezed or 

feel heavy for its size. Both thorny and thornless 

cultivars are used commercially.

Horticultural Maturity Indices

The outer bracts of an artichoke ready for harvest 

should be tightly closed, firm, and turgid. They are 

harvested when immature and selected based on 

size and compactness.

Grades, Sizes, and Packaging

Grades include U.S. No. 1 and U.S. No. 2, based 

primarily on external appearance. Buds are 

classified by the number that fit into a standard 

carton of about 10 kg (23 lb.). For example, size 

18 buds means 18 buds per carton (also referred 

to as “18s”). Standard grades include 18s (>13 

cm diameter, 5.4 in), 24s (10 to 13 cm, 4.0 to 4.5 

in), 36s (8.5 to 10 cm, 3.5 to 4.0 in), 48s (7.5 to 

8.5 cm, 3.0 to 3.5 in) or 60s (6.5 to 7.5 cm, 2.75 

to 3 in) buds per box. Smaller buds (2.5 to 6.5 

cm, 1.0 to 2.75 in) are often “jumble packed” at 

an average of 100 to 175 buds per box. The freshproduce market prefers 24s and 36s, but some 

retailers prefer 36s and 48s, since artichokes are 

generally priced by bud, not by weight.

A new grade was adopted for U.S. No. 1 long 

stem globe artichokes in 2006. The stems must 

be smoothly cut to a minimum of at least 20 cm (8 

in) unless otherwise specified to a longer length in 

connection with a grade. 

Precooling Conditions

In order to maintain quality and storage life, 

artichoke buds should be precooled to below 5 °C 

(41 °F) within 24 h of harvest (Lipton and Stewart 

1963). Hydrocooling, forced-air cooling, and 

package-icing are common methods of postharvest 

cooling of artichokes and will generally retard 

deterioration such as discoloration, weight loss, 

and decay.

Optimum Storage Conditions

The recommended conditions for storage of 

artichokes are 0 °C (32 °F) and >95% RH. 

Artichoke buds can be kept in good condition for 

2 weeks at 0 °C (32 °F), 10 days at 5 °C (41 °F), 

and 5 days at 10 °C (50 °F) (Ryall and Lipton 

1979, Saltveit 1991).

Controlled Atmosphere (CA) 

Considerations

A reduction in browning of the outer bracts is the 

major benefit from CA storage when artichokes 

are stored at temperatures higher than 0 °C (32 

°F). However, the effectiveness of CA storage 
203

depends on bud maturity, cultivar, temperature, 

and the particular atmosphere used (Rappaport 

and Watada 1958, Andre et al. 1980, Ryder et al. 

1983). Optimal CA conditions vary widely among 

cultivars, ranging between 1 to 6% O2

 and 2 to 

7% CO2

 (Ryall and Lipton 1979, Saltveit 1997, 

Andre et al. 1980, Escriche et al. 1982). Little 

or no beneficial effect on quality retention can 

be obtained by CA storage when artichoke buds 

are stored at 0 °C (32 °F) (Miccolis and Saltveit 

1988). Therefore, no general recommendation 

can be made for CA storage. O2

 below 2% may 

result in internal blackening (Suslow and Cantwell 

1998).

Retail Outlet Display Considerations 

Use of both top ice and water sprinklers are 

acceptable.

Chilling Sensitivity

Artichokes are not sensitive to chilling and should 

be stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Artichokes produce only very low amounts of 

ethylene and are not particularly sensitive to 

ethylene exposure.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 16 to 44

5 °C 26 to 60

10 °C 44 to 98

15 °C 76 to 144

20 °C 134 to 252

Data from Suslow and Cantwell (1998).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Splitting of the bract tip is a common problem 

caused by rough handling during and after harvest. 

The surfaces of bracts are also easily bruised and 

scratched, so careful handling is important. The 

abraded areas usually turn brown or black, which 

greatly detracts from appearance and quality and 

provides a route through which microorganisms 

can enter. Also, violet discoloration of inner 

bracts occurs, the severity of which was low when 

artichokes were stored at temperatures below 10 

°C (50 °F) or above 25 °C (77 °F) (Bianco 1979) 

and may have been due to low ethylene production 

(Ryder et al. 1983).

Postharvest Pathology

The most common decay found in artichokes is 

gray mold (Botrytis cinerea) (Moline and Lipton 

1987). The lesions most frequently begin on 

wounds and spread to other areas of the bud. 

Since storage at low temperatures slows the 

rate of spread of the disease, fungal growth near 

freezing temperature is minimal. Bacterial soft rot 

(Erwinia carotovora) may be a problem in storage 

and distribution if optimum temperature is not 

maintained. Therefore, low temperatures must be 

maintained throughout the cold chain to minimize 

pathological disorders and prolong shelf-life.

Quarantine Issues

There are no quarantine issues.

Suitability as Fresh-Cut Product

No current potential.
204

Special Considerations

Artichokes must be handled with care to 

avoid mechanical damage and therefore limit 

discoloration and pathological problems. During 

winter, artichokes may have a white or bronze, 

blistered appearance due to being frosted in 

the field. The artichokes are said to have been 

“frost-kissed.” This is purely an appearance issue 

and does not affect eating quality. In fact, this 

condition may enhance the nutty flavor. Avoid 

wilted, moldy, significantly discolored, or woody 

(overmature) artichokes. 

Acknowledgments 

Some of the information included was from the 

Produce Marketing Association’s “Fresh Produce 

Manual” and the University of California, Davis, 

website on “Fresh Produce Facts” at http://

postharvest.ucdavis.edu/produce_information.

References

Andre, P., R. Blanc, M. Buret, et al. 1980. Trails of 

preservation of artichokes by combined utilization 

of vacuum precooling, controlled atmospheres, 

and cold. Revue Hort. 211:33-40.

Bianco, V.V. 1979. Influence of temperature on the 

coloration of interior bracts and the inflorescence 

complex of stored artichokes. In 3rd International 

Congress on Artichoke Studies Abstracts, pp. 166. 

Bari, Italy.

Escriche, A., F. Artes, and J.C. Marin. 1982. 

Conservation d’artichauts en atmosphere 

controlée. In Progress in the Design and Operation 

of Refrigerating Equipment in the Storage of 

Fruits and Vegetables by Refrigeration, pp. 336-

341. Inst. Intl. du Froid, Paris, France.

Lipton, W.J., and J.K. Stewart. 1963. Effects 

of Precooling on Market Quality of Globe 

Artichokes. Marketing Research Report 633, U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

Miccolis, V., and M.E. Saltveit. 1988. Influence of 

temperature and controlled atmosphere on storage 

of ‘Green Globe’ artichoke buds. HortScience 

23:736-741.

Moline, H.E., and W.J. Lipton. 1987. Market 

Diseases of Beets, Chicory, Endive, Escarole, 

Globe Artichokes, Lettuce, Rhubarb, Spinach, and 

Sweet Potatoes. Agriculture Handbook 155, U.S. 

Department of Agriculture, Agricultural Research 

Service, Washington, DC.

Rappaport, L., and A.E. Watada. 1958. Effect of 

temperature on artichoke quality. In Proceedings 

of the Conference on Transport of Perishables, pp. 

142-146. University of California, Davis, CA.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melons. AVI, 

Westport, CT.

Ryder, E.L., N.E. DeVos, and M.A. Bari. 1983. 

The globe artichoke (Cynara scolymus L). 

HortScience 18:646-653.

Saltveit, M.E. 1991. Artichokes. In P. Lidster, 

G. Blanpied, and R. Prange, eds., ControlledAtmosphere Disorders of Commercial Fruits 

and Vegetables, pp. 23-24. Pub. no. 1847/E, 

Agriculture Canada, Ottawa, Ontario, Canada.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Suslow, T., and M. Cantwell. 1998. Globe 

artichoke in “Fresh Produce Facts.” At http://

postharvest.ucdavis.edu/produce_information.
205

Asian Pear

Carlos H. Crisosto

Crisosto is with the Pomology Department, 

University of California, Davis, CA.

Scientific Name and Introduction

The cultivated varieties of Chinese and Japanese 

pears were developed from Pyrus ussuriensis

Maximowicz, P. serotina Rehder (P. pyrifolia

[Burman] Nakai) and possibly other native 

species, according to Kikuchi (1948). Hu (1937) 

included the Chinese varieties ‘Tsu Li’ and 

‘Ya Li’ under the binomial P. bretschneideri

Rehder. Catlin and Olsson (1966) reported that 

the Japanese pears ‘Kikusui,’ ‘Nijisseiki’ (‘20th 

Century’), ‘Seigyoku,’ ‘Shinseiki,’ ‘Chojuro,’ 

‘Doitsu,’ ‘Imamura Aki,’ and ‘Ishiiwase’ were 

varieties of P. serotina, and they were unable to 

distinguish ‘Tsu Li’ and ‘Ya Li’ from the Japanese 

varieties.

Asian pears remain firm and are crisp and juicy 

when eaten ripe, whereas ‘Bartlett’ and other 

Pyrus communis Linnaeus varieties become soft 

and melting when ripe. Asian pears are also called 

Oriental pears, Chinese pears, Japanese pears, 

nashi, sand apples, and salad pears. In fresh-fruit 

market reports, they are usually called “apple 

pears,” an unfortunate and misleading term. 

Though most Japanese pear varieties are roundish, 

their texture and flavor are entirely different from 

those of apples. The main Chinese pear varieties 

are pyriform. Sometimes market reports refer to 

Asian pears as “apple (shalea) pears.” The name 

“shalea” probably is derived from the words “sha 

li,” which means “sand pear” in Chinese. ‘Sha Li’ 

is the name of one of three main groups of pears 

grown in China, as well as the name of an old 

variety in the group (Hu 1937). 

Quality Characteristics and Criteria

Freedom from mechanical injury is desired. 

(‘Nijisseiki’ pears are very sensitive to impact 

and compression bruising; ‘Tsu Li’ and ‘Ya Li’ 

pears increase in susceptibility to bruising after 

storage; and ‘Chojuro’ pears are firmer and more 

resistant to mechanical damage). Flesh firmness 

(penetration force using an 8-mm tip) of 7 to 10 

lb-force, depending on cultivar, is optimum for 

eating. Only small changes in firmness occur 

during storage at 0 °C (32 °F). Asian pears should 

be juicy, not mealy, and sweet with 11 to 14% 

SSC, depending on the cultivar.

Horticultural Maturity Indices

Change in skin color can occur from green to 

yellowish green (‘Nijisseiki,’ ‘Shinseiki,’ ‘Tsu Li,’ 

and ‘Ya Li’) or to golden brown (‘Hosui,’ ‘Kosui,’ 

‘Niitaka,’ and ‘Shinko’). Delayed harvest (which 

does not always mean higher SSC) results in 

increased incidence and severity of physiological 

disorders and greater susceptibility to physical 

injury.

Grades, Sizes, and Packaging

Fruit should be held lightly in the palm of the hand 

and an upward twisting motion used to remove 

the fruit from the spur. A natural abscission layer 

forms at the spur end of the stalk and separation at 

this zone becomes easier as fruit mature. A pulling 

motion can result in damage as the stalk can be 

removed from the fruit.

The skin of Asian pears is very susceptible to 

abrasion and friction marks. Smooth-surfaced 

containers such as polystyrene trays, shallow 

plastic buckets, or plastic trays with foam pads 

should be used for collecting fruit.

Fruit should be placed into trays or buckets with 

the stem end up, preferably in single layers and 

packed firmly to avoid movement. Care must be 

taken to avoid stem punctures if fruit are packed in 

two or more layers. Bulk handling of fruit should 
206

be confined to the use of single trays stacked 

together in a large bin rather than volumes of fruit 

packed into large trays or bins. Once the fruit are 

harvested, they should be placed in the shade and 

not left in direct sunlight.

Optimum Storage Conditions

Asian pears should be stored at 0 oC (32 oF) in 

trays complete with packet pack and polyliners. 

It is necessary to maintain RH above 90% in the 

storage atmosphere because fruit are susceptible 

to water loss. When water loss has been greater 

than 5 to 7%, fruit become dehydrated and have 

a shriveled appearance, especially in ‘Kosui’ and 

‘Hosui.’ Eating quality is also affected and fruit 

lack a crisp and juicy texture.

The continued presence of ethylene in the storage 

environment may increase the development of 

skin browning and fruit senescence. Therefore, 

ethylene levels in the coolstore should be kept 

as low as possible. Asian pears should not be 

stored for long periods with fruit that produce 

high levels of ethylene. Damaged or decayed fruit 

or fruit with disorders produce higher levels of 

ethylene than sound fruit and should not be stored 

alongside sound fruit.

Forced-air cooling is not recommended for Asian 

pears. Results from experiments conducted with 

Asian pears grown in New Zealand indicate that 

there is no benefit to fruit quality (fruit firmness 

and SSC) from rapid precooling. Furthermore, 

fruit are likely to have a higher incidence of 

flesh spot decay during storage if they have been 

rapidly cooled within 24 h of harvest. Therefore, 

it is recommended that fruit be room-cooled after 

harvest.

Optimum Temperature

Optimum storage conditions are 0±1 °C (32±2 °F) 

with RH of 90 to 95%. The freezing point is -1.5 

°C (29 °F); it will vary depending on SSC.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 2 to 8

20 oC 20 to 30

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Controlled Atmosphere (CA) 

Considerations

Based on limited studies, it appears that the 

magnitude of CA benefits for Asian pears is 

cultivar specific and is generally less than that 

for European pears and apples. CA may extend 

storage duration of some Asian cultivars by about 

25% relative to storage in air. O2

 levels of 1 to 3% 

for some cultivars (such as ‘Nijisseiki’) or 3 to 5% 

for others (such as ‘Ya Li’) help retain firmness 

and delay changes in skin color. Asian pears are 

sensitive to CO2 injury (above 2% CO2

 for most 

cultivars) when stored longer than 1 mo.

Retail Outlet Display Considerations

Display shelf should be kept as cold as possible 

without freezing or ice.

Rates of Ethylene Production and 

Sensitivity

Some cultivars (such as ‘Nijisseiki,’ ‘Kosui,’ 

and ‘Niitaka’) produce very little ethylene, less 

than 0.1 μL kg-1 h-1, and have a nonclimacteric 

respiratory pattern (no rise in CO2

 production 

during ripening). Other cultivars, such as ‘Tsu 

Li,’ ‘Ya Li,’ ‘Chojuro,’ ‘Shinsui,’ ‘Kikusui,’ and 

‘Hosui,’ have a climacteric respiratory pattern and 

produce ethylene up to 9 to 14 μL kg-1 h-1 (‘Tsu Li’ 

and ‘Ya Li’) or 1 to 3 μL kg-1 h-1 (other cultivars) 

at 0 °C (32 °F).
207

Exposure of climacteric cultivars to <1 μL L-1

ethylene accelerates loss of green color and 

slightly increases softening at 20 °C (68 °F). The 

effects at 0 °C (32 °F) are minimal.

Physiological Disorders

Internal breakdown and chilling injury can be a 

problem with Chinese pear cultivars such as ‘Ya 

Li,’ ‘Daisui Li,’ ‘Seuri,’ ‘Tse Li,’ ‘Shin Li,’ and 

Korean pears such as ‘Shingo,’ ‘Okysankichi,’ and 

‘Dan Be.’ Internal browning or core breakdown 

is the main worldwide consumer complaint. 

Development of brown to dark-brown watersoaked areas in the core and/or flesh occurs during 

storage, with no visible external indication of 

internal browning. 

Fruit grown under the hot conditions of 

California’s San Joaquin Valley and picked 

later than 180 days after full bloom are likely 

to develop browning during storage. In order 

to apply this information to other locations or 

years, fruit should be picked no later than 3,000 

degree-days as calculated by averaging the daily 

maximum and minimum temperatures, subtracting 

4 and summing the resulting values (Johnson and 

Lakso 1985). The fruit should be picked when 

most of the pears on the tree are still green, though 

it is all right if a few at the top have begun to 

develop some light-yellow spots. Fruit picked 

when the skin is completely yellow will develop 

internal browning within 1 mo after harvest. In 

China, reduction of ‘Ya Li’ internal breakdown has 

been accomplished using a temperature program 

that decreases storage temperature gradually.

Flesh spot decay (FSD) can be a problem with 

Japanese pear cultivars. FSD is more frequent on 

large (<300 g) and overmature fruit. FSD limits 

opportunities to grow and market Japanese pears. 

Symptoms include partial browning of spots and 

development of cavities in the flesh. It appears 

along and around the vascular bundles when the 

symptoms are severe, but there is no external 

indication of the disorder. Generally, FSD is more 

pronounced above the equator of the fruit (towards 

the stem end), but it can also be observed all the 

way down to the calyx. Cavities are usually dry 

and surrounded by apparently healthy tissue. This 

disorder can occur in fruit while still on the tree. 

It is more obvious, however, after 2 to 6 weeks in 

cold storage. The cause of FSD is still unknown. 

However, climatic factors, such as a fluctuating 

hot and cool summer or high rainfall right before 

harvest, may enhance the incidence of this 

disorder. There is no effective way to control FSD 

since definite causes have not been identified. The 

problem is the inability to predict FSD without 

cutting the fruit. Further research needs to be done 

to determine the causes, variety of susceptibility 

in local climates, and other control methods, 

either preharvest or postharvest, that will reduce 

FSD symptoms to a commercially acceptable 

level. Meanwhile, whenever possible, avoid the 

following conditions that might induce FSD: low 

crop load (large fruit), later picking (advanced 

maturity), extreme temperature changes during 

the maturation season, sunburn, erratic irrigation 

or precipitation (frequency, amount, and timing), 

harvesting fruit under warm temperatures, and 

cooling the fruit rapidly. 

Low-O2

 injury manifests itself as discolored 

surface depressions from exposing ‘Nijisseiki’ 

pears to ≤1% O2

 for 4 mo at 0 °C (32 oF) and from 

exposing ‘Ya Li’ and ‘Tsu Li’ pears to ≤1% O2

 for 

2 mo, ≤2% O2

 for 4 mo, or ≤3% O2 for 6 mo at 0 

°C (32 oF).

High-CO2 injury is manifested as core or medial 

flesh browning, with cavities developing in severe 

cases as a result of desiccation of dead tissue. ‘Ya 

Li’ pears can exhibit CO2

 injury after exposure to 

≥5% CO2

 for 6 weeks at 0 oC (32 oF).

Watercore symptoms (glassy, diffuse water-soaked 

areas in flesh; affected areas may taste sweet and 

turn slightly brown) occur in some cultivars (for 

example, ‘Nijisseiki,’ ‘Shinseiki,’ and ‘Hosui’) 

under conditions favoring vigorous tree growth. 

Avoid harvesting overmature fruit to reduce 

watercore incidence and severity.

Superficial scald or skin browning can occur 

after long-term (>16 weeks) storage of ‘Shinsiki’ 

and ‘Nijisseiki’ fruit. Long-term storage can 
208

lead to the development of a skin disorder that 

is characterized by the appearance of scaldlike 

browning symptoms. Initially, the affected areas 

of the skin are light brown in color, but as the 

disorder progresses the skin becomes dark brown 

and develops a bronze, scaldlike appearance. 

The disorder is confined to the skin and is similar 

to superficial scald in apples. Scald appears to 

be a problem associated with packaging in that 

most of the scald appears at the calyx end or that 

portion of the fruit that is tightly confined within 

the pocket of the pocket pack. However, the 

whole fruit surface is susceptible to the disorder, 

which is rapidly induced if Asian pears are stored 

together with apples. To avoid the disorder, 

adequate ventilation during storage and storage of 

fruit in a relatively ethylene-free atmosphere are 

recommended.

Postharvest Pathology

Asian pear fruit are susceptible to many 

pathogens, such as Botrytis, Alternaria, and 

Phomopsis species. These pathogens invade fruit 

through wounds caused by mishandling of fruit 

after harvest. The rots develop slowly in fruit 

during storage and eventually the whole fruit 

becomes affected. Affected flesh areas become 

soft and discolored. Damage to fruit surfaces by 

birds while fruit are on the tree can provide entry 

points for pathogens.

Quarantine Issues

Limited import (Chile) and export (Canada) 

activity is occurring. If imported from Chile, 

Asian pear shipments must be accompanied by 

a PPQ (Plant Pest Quarantine Form 203) signed 

by the USDA, Animal Plant Health Inspection 

Service (APHIS) inspector on site in Chile. If 

shipments were not precleared at origin, sampling 

at arrival time is necessary. APHIS issues rules 

regarding import requirements and provides 

information to assist exporters in targeting markets 

and defining what entry requirements a particular 

country has. In cooperation with the State plant 

boards, APHIS developed a database called 

“Excerpt” to track phytosanitary requirements for 

each country. APHIS also provides phytosanitary 

inspections and certifications that declare fruit are 

free of pests to facilitate compliance with foreign 

regulatory requirements. Issues associated with 

exotic pest quarantines, addressing both imported 

and exported fruit, can change rapidly.

Suitability as Fresh-Cut Product

Preliminary research conducted in the laboratory 

of Dr. Adel Kader at the University of California, 

Davis, CA in 2000 showed that Asian pear slices 

have a very short shelf-life, even at 0 to 2 °C (32 

to 36 °F), due to tissue browning. Dipping slices 

in 1% ascorbate + 1% CaCl2

 for 2 min soon after 

slicing delayed browning, but shelf-life was less 

than 5 days at 2 °C (36 °F).

Special Considerations

The five varieties ‘Shinsui,’ ‘Shinseiki,’ 

‘Kosui,’ ‘Hosui,’ and ‘Nijisseiki’ all have an 

adequate storage life. If fruit are harvested at the 

recommended maturity, a storage life of 12 to 

20 weeks and a subsequent shelf-life of 10 to 15 

days can be expected, depending on the variety. 

The major limitation to the storage life of Asian 

pears is development or enhancement of maturityrelated disorders.

Acknowledgments

Most of this information was taken from the 

University of California, Davis, website “Fresh 

Produce Facts” at http://postharvest.ucdavis.edu/

produce_information.

References

Beutel, J. 1990. Asian pears. In J. Janick and J.E. 

Simon, eds., Advances in New Crops, pp. 304-

308. Timber Press, Portland, OR.
209

Crisosto, C.H., K.R. Day, S. Sibbett, et al. 1994. 

Late harvest and delayed cooling induce internal 

browning of ‘Ya Li’ and ‘Seuri’ Chinese pears. 

HortScience 29:667-670.

Crisosto, C.H., D. Garner, G.M. Crisosto, et al. 

1994. Early harvest prevents internal browning in 

Asian pears. Calif. Agric. 48:17-19.

Davis, L.D., and W.P. Tufts. 1941. Pear growing 

in California. Circular no. 122, California 

Agricultural Extension Service, 87 pp., University 

of California, Davis, CA.

Griggs, W., and B. Iwakiri. 1997. Asian Pear 

Varieties in California. DANR Pub. no. 4068, 

University of California, Oakland, CA.

Hu, C.C. 1937. The variety and distribution of 

pears in China. Nanking J. 7:103-193.

Johnson, R.S., and A.N. Lakso. 1985. Relationship 

between stem length, leaf area, stem weight, and 

accumulated growing degree-days in apple shoots. 

J. Amer. Soc. Hort. Sci. 110:586-590.

Lallu, N. 1990. Fruit growth, handling and 

storage. In A.G. White, ed., Nashi, Asian Pear 

in New Zealand, pp. 53-74. DSIR Publishing, 

Wellington, New Zealand.

Lidster, P.D., G.D. Blanpied, and R.K. Prange, 

eds. 1990. Controlled-Atmosphere Disorders of 

Commercial Fruits and Vegetables. Agric. Canada 

Pub. no. 1847/E, Agriculture Canada, Ottawa, 

Ontario, Canada.

Porritt, S.W., M. Meheriuk, and P.D. Lindster. 

1982. Postharvest Disorders of Apples and Pears. 

Agr. Canada Pub. no. 1737/E, Agriculture Canada, 

Ottawa, Ontario, Canada.

Tian, M.S., C.C. Sheng, and Y. Li. 1987. 

Relationship between ethylene release, membrane 

permeability and activity of polyphenol oxidase 

changes of Duck pears (Pyrus bretschneideri

Rehder) during low-temperature storage. Acta Bot. 

Sinica 29:614-619.
210

Asparagus

Yaguang Luo, Trevor Suslow, and Marita Cantwell

Luo is with the Food Quality Laboratory, Henry A. 

Wallace Beltsville Agricultural Research Center, 

Agricultural Research Service, U.S. Department of 

Agriculture, Beltsville, MD; Suslow and Cantwell 

are with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Asparagus (Asparagus officinalis L.) is a perennial 

of the Liliaceae family. The edible portion of 

asparagus is a rapidly growing stem (shoot) 

with scale leaves that arise at nodes. There are 

two forms of marketed asparagus, namely white 

(blanched) and green. White asparagus is more 

common in Europe and Asia (Lipton 1990); 

green asparagus is popular in the United States 

and is produced predominantly in California and 

Washington. Asparagus has a high metabolic rate 

after harvest and is among the most perishable 

crops.

Quality Characteristics and Criteria

High-quality asparagus spears are dark green and 

firm with tightly closed and compact tips (Suslow 

1998a,b). Spears are straight, tender, and glossy in 

appearance. Spears with green butts are preferred 

over the spears with white butts, as the latter are 

associated with increased toughness. However, a 

small amount of white tissue at the butt will delay 

decay development under typical commercial 

distribution conditions (Lipton 1990, Suslow 

2001).

Horticultural Maturity Indices

Asparagus spears are harvested as they emerge 

through the soil from the underground crowns. 

Typically, spears are cut when they reach 10 to 

25 cm (8 to 10 in) in length, with spear tips still 

tightly closed. Tender, immature (that is, shorter) 

asparagus may be harvested for special markets. 

Grades, Sizes, and Packaging

Harvested spears are prepared for market by 

grading, sizing, and bunching. Grades are based 

on freshness, length and diameter of the stalks, 

color of spears, tightness of the spear tips, and 

the extent of bruising. Sizing is based on spear 

diameter with U.S. No. 1 having a diameter >1 

cm (>0.5 in) and U.S. No 2 having a diameter 

>0.8 cm (>5/16 in). Spears of larger diameter 

are considered to be superior in quality with less 

fiber (Peirce 1987). Spears are tied in bunches 

weighing 0.45 to 1.1 kg (1 to 2.5 lb) and trimmed 

to a standard length of 18 to 25 cm (7 to 10 in). 

Color is also important, with U.S. No. 1 spears 

being green for more than 2/3 their length, while 

U.S. No. 2 are green for more than half their 

length. After trimming the butt-end, the bunches 

are packed upright in trapezoidal-shaped crates to 

minimize geotropic bending (curving away from 

gravity) in transit. The container should include a 

wet pad in contact with the butt end to maintain 

turgidity. Headspace is provided in the carton to 

prevent tip curvature or breakage during spear 

elongation.

Precooling conditions

Asparagus is highly perishable and must be cooled 

immediately to 0 to 2 °C (32 to 36 °F). A 4-h delay 

in cooling resulted in an average 40% increase in 

shear force due to tissue toughening (HernandezRivera et al. 1992). Asparagus is typically partially 

cooled during the washing, selection, and packing 

operation, and then hydrocooled to near 0 °C (32 

°F) after packing. 

Optimum Storage Conditions

The recommended conditions for commercial 

storage of asparagus are 0 to 2 °C (32 to 36 

°F) with 95 to 99% RH, yielding 14 to 21 

days of storage life. Maintaining a low storage 
211

temperature is critical to delay senescence, tissue 

toughening, and flavor loss (King et al. 1993). 

High RH is essential to prevent desiccation and to 

maintain freshness. Typically, asparagus is packed 

and shipped with water-saturated pads in the 

bottom of the containers to maintain high RH and 

to replenish water lost by the spear or water used 

during spear elongation; this practice maintains 

spear turgidity. Excessive free water at elevated 

storage or shipping temperatures may lead to 

increased decay. 

Controlled Atmosphere (CA) 

Considerations

Elevated CO2

 at 5 to 10% is beneficial in 

preventing decay and slowing toughening 

of the spears. Short exposure to higher CO2

concentration is safe and beneficial only if the 

temperature is maintained at 0 to 1 °C (32 to 34 

°F). The combination of intermediate O2

 (2 to 10% 

O2

) may or may not provide benefit compared 

with air enriched with CO2

 alone (Lipton 1990, 

Kleiber and Wills 1992, Lill and Corrigan 1996, 

Saltveit 1997). At O2

 levels below 2%, off odors 

and discoloration may develop. Signs of CO2

injury are small to elongated pits, generally first 

observed just below the tips. Severe CO2

 injury 

results in ribbiness. Asparagus tolerated a 100% 

nitrogen atmosphere for 6 h at 2.5 °C (37 °F) or 

20 °C (68 °F) without affecting sensory quality 

(Torres-Penaranda and Saltveit 1994). High CO2

(40 to 60%) can be applied at 5 °C (41 °F) for up 

to 4 days without affecting sensory quality, and 

may be used as an insect disinfestation treatment 

(Corrigan and Carpenter 1993). 

Retail Outlet Display Considerations

Asparagus is often displayed upright in shallow 

trays containing chilled water. It will also tolerate 

icing on retail displays. The preferred method to 

maintain freshness at retail display is refrigerated 

display with light misting.

Chilling Sensitivity

Asparagus is subject to chilling injury after about 

10 days at 0 °C (32 °F). Symptoms include loss 

of sheen and glossiness and graying of tips. A 

limp, wilted appearance may be observed. Severe 

chilling injury may result in darkened spots or 

streaks near the tips. 

Ethylene Production and Sensitivity

Ethylene production is low to intermediate, 

increases with time after harvest, and varies 

with where the spears are cut relative to the soil 

surface (Lipton 1990). For spears cut at the soil 

surface and held at 20 °C (68 °F) for 45 and 90 

min, ethylene production changes from 2.1 and 

3.1 μL kg-1 h-1 (Haard et al. 1974). Exposure to 

ethylene accelerated the lignification (toughening) 

of asparagus spears (Hennion et al. 1992). 

Prompt cooling and maintaining optimal shipping 

temperatures minimizes ethylene-induced 

toughening.

Respiration Rates

Respiration rates depend on storage temperature, 

time after harvest, and the spear portion on 

which determinations are made (Lipton 1990). 

Freshly harvested asparagus is among the highest 

respiring fresh produce items. However, rates 

decline rapidly after harvest (King et al. 1990, 

Lipton 1990). Respiration rates of the apical tips 

are much higher than those of the basal portions 

of the stems (Saltveit and Kasmire 1985, Lill et 

al. 1990). Listed below are respiration rates of 

asparagus spears held at 20 °C for various times: 

Temperature Time after harvest (days)

0.25 1.0 3.0

 mg CO2 kg-1 h-1 

0 oC 80 60 40

5 oC 145 105 65

10 oC 305 215 120

15 oC 325 235 160

20 oC 500 270 185

Data from Lipton (1957).
212

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Elongation and Tip Bending. Asparagus 

continues to grow and elongate after harvest if not 

immediately cooled and stored at temperatures 

below 5 °C (41 °F). Holding the butt in contact 

with water (the moist pad) promotes spear growth 

and elongation. Tip bending occurs as the result 

of upward growth of the tips when the spears 

are horizontal. If spears are held in an upright 

position, tip bending may still occur if the tips 

reach the top of the package and are physically 

deflected. Postharvest treatment of asparagus 

spears in heated water at 45 to 50 °C (113 to 122 

°F) for 2 to 5 min reduces tip bending (Paull and 

Chen 1999).

Spear Toughening. Tissue lignification and 

fiber development, which progresses from butt 

to tip, cause spear toughening. It develops at >10 

°C (50 °F), rapidly above 15 °C (59 °F), and is 

accelerated by ethylene.

Feathering. Feathering is the appearance of bracts 

of spear tips, which have opened due to outgrowth 

of the underlying buds. Tip feathering is a sign of 

senescence, often observed following extended 

storage at higher than optimal temperature or 

harvesting of overmature spears.

Freezing Injury. Water-soaked appearance and 

tissue softening occur at temperatures below -0.5 

°C (31 °F). 

Postharvest Pathology

The most prominent postharvest disease 

on asparagus is bacteria soft rot, caused by 

Pectobacterium carotovora or Pseudomonas

spp. Decay may occur anywhere on the spears 

in the form of “soft rot pits,” most frequently 

found on the tips or the butts (Snowdon 1992, 

Suslow 2001). Spears with green butts are more 

susceptible to this decay than spears with white 

butts. Storing asparagus at <5 °C (41 °F) controls 

this disease. In some production areas, the fungi 

such as Fusarium, Penicillium, and Phytophthora

are associated with postharvest decay or spoilage 

of asparagus (Snowdon 1992). 

Quarantine Issues

Asparagus may be fumigated during international 

distribution and marketing if live common insects 

(hitchhikers) are found. 

Suitability as Fresh-Cut Product

The tender portion can be prepared as a food 

service product. There is limited minimal 

processing of asparagus, but consumer-oriented 

packing of tips is increasing.

References

Corrigan, V.K., and A. Carpenter. 1993. Effects 

of treatment with elevated carbon dioxide levels 

on the sensory quality of asparagus. N.Z. J. Crop 

Hort. Sci. 21:49-357.

Everson, H.P., K.W. Waldron, J.D. Geeson, 

and K.M. Browne. 1992. Effects of modified 

atmospheres on textural and cell wall changes of 

asparagus during shelf-life. Intl. J. Food Sci. Tech. 

27:187-199.

Haard, N.F., S.C. Sharma, R. Wolfe, and C. 

Frenkel. 1974. Ethylene induced isoperoxidase 

changes during fiber formation in postharvest 

asparagus. J. Food Sci. 39:452-456.

Hennion, S., C.H.A. Little, and C. Hartmann. 

1992. Activities of enzymes involved in 

lignification during the postharvest storage of 

etiolated asparagus spears. Physiol. Plant. 86:74-

478. 
213

Hernandez-Rivera, L., R. Mullen, and M. 

Cantwell. 1992. Textural changes of asparagus 

in relation to delays in cooling and storage 

conditions. HortTech. 2:378-381. 

King, G.A., D.C. Woollard, D.E. Irving, and W.M. 

Borst. 1990. Physiological changes in asparagus 

spear tips after harvest. Physiol. Plant. 80:93-400. 

King, G.A., P.L. Hurst, D.E. Irving, and R.E. 

Lill. 1993. Recent advances in the postharvest 

physiology, storage and handling of green 

asparagus. Postharv. News Info. 4(3):5N-89N. 

Klieber, A., and R.B.H. Wills. 1992. Optimization 

of storage conditions for ‘UC 157’ asparagus. 

Australian J. Expr. Agric. 32:529-534. 

Lill, R.E., and V.K. Corrigan. 1996. Asparagus 

responds to controlled atmospheres in warm 

conditions. Intl. J. Food Sci. Tech. 31:117-121. 

Lill, R.E., G.A. King, and E.M. O’Donoghue. 

1990. Physiological changes in asparagus spears 

immediately after harvest. Scientia Hort. 44:191-

199. 

Lipton, W.J. 1990. Postharvest biology of fresh 

asparagus. Hort. Reviews. 12:69-155. 

Lipton, W.J. 1957. Physiological changes in 

harvested asparagus (Asparagus officinalis)

as related to temperature of holding. Ph.D. 

Dissertation, University of California, Davis, CA.

Paull, R.E., and N.J. Chen. 1999. Heat treatment 

prevents postharvest geotropic curvature of 

asparagus spears (Asparagus officinalis C.). 

Postharv. Biol. Technol. 16:37-41.

Peirce, L.C. 1987. Vegetables—Characteristics, 

Production, and Marketing. John Wiley & Sons, 

New York, NY.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Saltveit, M.E., and R.F. Kasmire. 1985. Changes 

in respiration and composition of different length 

asparagus spears during storage. HortScience 

20:1114-1116. 

Snowdon, A.L. 1992. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, CRC Press, Boca Raton, FL.

Suslow, T.V. 1998a. Asparagus Producers 

and Shippers Quality Assurance Guidance to 

Minimizing Microbial Food Risks. University of 

California Vegetable Research and Information 

Center, Davis, CA, and the California Asparagus 

Commission, El Centro, CA.

Suslow, T.V. 1998b. Asparagus produce facts. 

Recommendations for Maintaining Postharvest 

Quality. At http://postharvest.ucdavis.edu/

produce_information.

Suslow, T. 2001. Progress note on asparagus 

handling and display. University of California 

Perishables Handling Quarterly, no. 106. At http://

postharvest.ucdavis.edu.

Torres-Penaranda, A.V., and M.E. Saltveit. 1994. 

Effects of brief anaerobic exposures on carbon 

dioxide production and quality of harvested 

asparagus. J. Amer. Soc. Hort. Sci. 119:51-555. 
214

Atemoya

Robert E. Paull and Nancy Jung Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Atemoya is a hybrid between Annona squamosa

L. (sweetsop) and A. cherimola Mill. (cherimoya). 

The fruit can vary in external appearance, 

reflecting the different parents (Nakasone and 

Paull 1998). Favorable characteristics from the 

cherimoya include being heart shaped, having 

few seeds, and having smooth skin that does not 

break apart during ripening. There are about six 

varieties, with ‘African Pride’ and ‘Gefner’ being 

the most common. Atemoya are grown in Florida 

and Hawaii.

Quality Characteristics and Criteria

Atemoya fruit should be heart shaped, preferably 

with a smooth, cherimoyalike skin instead of 

the bumpy skin of the sweetsop. Besides shape, 

size, and skin texture, the fruit should be free of 

blemishes and mechanical injury, which can lead 

to skin blackening.

Horticultural Maturity Indices

Fruit skin color changes from darker to lighter 

green and can be greenish yellow. During 

ripening, skin splitting occurs and the skin darkens 

(Paull 1996).

Grades, Sizes, and Packaging

Atemoya fruit are sold in single-layer 4.5 kg (10 

lbs) or 9 kg (20 lbs) fiberboard boxes with foam 

sleeves or paper wrapping. Fruit weighing 250 to 

500 g (9 to 18 oz) are used.

Precooling Conditions

Room or forced-air cooling to 10 to 13 °C (50 to 

55 oF).

Optimum Storage Conditions

Store at 10 to 13 oC (50 to 55 oF) with 90 to 95% 

RH.

Controlled Atmosphere (CA) 

Consideration

There is no published information on this subject. 

The fruit may have similar potential as cherimoya.

Retail Outlet Display Considerations

Ripe fruit can be held at 2 to 5 oC (36 to 41 oF). If 

unripe, display at room temperature. Ripe fruit, if 

split, can be overwrapped.

Chilling Sensitivity

Atemoya fruit are very chilling sensitive, suffering 

skin darkening and loss of aroma and flavor.

Ethylene Production and Sensitivity

Climacteric fruit production rates of ethylene are 

high, up to 100 to 300 μL kg-1 h-1 at 20 oC (68 oF) 

(Brown et al. 1988). Ripening is accelerated by 

exposure to 100 μL L-1 for 24 h.

Respiration Rates

Temperature mg CO2 kg-1 h-1

10 oC 48 to 190

15 oC 54 to 281

20 oC 40 to 460

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 
215

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

The fruit are very susceptible to bruising. 

Preharvest russeting can be a problem.

Postharvest Pathology

As with cherimoya, anthracnose, Phomopsis rot, 

and Rhizopus have been recorded (Sanewski 

1988). 

Quarantine Issues

Atemoya fruit are a fruit fly host. Irradiation and 

heat are potential treatments.

Suitability as Fresh-Cut Product

Atemoya can be sold in pieces but only before 

becoming too soft.

References

Brown, B.I., L.S. Wong, A.P. George, and 

R.J. Nissen. 1988. Comparative studies on the 

postharvest physiology of fruit from different 

species of Annona (custard apple). J. Hort. Sci. 

63:521-528.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Paull, R.E. 1996. Postharvest atemoya splitting 

during ripening. Postharv. Biol. Technol. 8:329-

334.

Sanewski, G.M. 1988. Growing Custard Apples. 

Information Series QI 87014, Queensland 

Department of Primary Industries, Brisbane, 

Queensland, Australia.
216

Avocado

Allan B. Woolf, Anne White, Mary Lu Arpaia, and 

Kenneth C. Gross

Woolf and White are with the Mt. Albert Research 

Centre, Plant and Food Research, Auckland, NZ; 

Arpaia is with the Department of Botany and 

Plant Sciences, University of California Kearney 

Agricultural Center, Parlier, CA; Gross is formerly 

with the Food Quality Laboratory, Henry A. 

Wallace Beltsville Agricultural Research Center, 

Agricultural Research Service, U.S. Department 

of Agriculture, Beltsville, MD. He is now retired.

Scientific Name and Introduction

The avocado originated in Central America and 

southern Mexico. The Aztecs considered the 

avocado an aphrodisiac and called it “huacatl.” In 

Chile, Peru, and Ecuador, it is called “palta,” an 

Incan name. Spanish-speaking people also call it 

“aguacate,” “cura,” or “cupandra.” The avocado 

is known as “abogado” in Spain. Historically, the 

avocado has also been referred to as “alligator 

pear,” “vegetable butter,” “butter pear,” and 

“midshipman’s butter.”

The avocado is botanically classified into three 

races: (1) West Indian (WI), Persea americana

Mill. var. americana (P. gratissima Gaertn.), 

tropical with large variably shaped fruit and lower 

oil content; (2) Mexican (MX), P. americana Mill. 

var. drymifolia Blake (P. drymifolia Schlecht. 

& Cham.), semitropical with smaller elongated, 

thin-skinned fruit and higher oil content; and (3) 

Guatemalan (G), P. nubigena var. guatemalensis

L. Wms., subtropical with mostly round, thickskinned fruit and intermediate oil content (Bergh 

and Lahav 1996). Many of the commercial 

cultivars are hybrids of these three races. There 

is great variability in fruit traits not only between 

races but between cultivars within a race. One of 

the most distinct differences between cultivars 

is the peel color when ripe. The peel of some 

cultivars changes from green to black or purple 

with increasing maturity or ripening.

Avocados are available year-round in the United 

States and are supplied by two major producing 

areas: California (90%) and Florida (10%). 

Fruit (mainly ‘Hass’) are also imported from (in 

approximate order by volume) Chile, Mexico, the 

Dominican Republic, New Zealand, Bahamas, and 

Jamaica.

There are many cultivars of avocados grown 

commercially in the United States, and they 

come in assorted sizes and shapes. The primary 

California cultivar is Hass, a G-MX hybrid that 

accounts for approximately 95% of the planted 

acreage. Other cultivars include ‘Bacon,’ ‘Fuerte,’ 

‘Gwen,’ ‘Lamb Hass,’ ‘Pinkerton,’ ‘Reed,’ and 

‘Zutano.’ With the exception of ‘Reed,’ which 

is believed to be entirely of the G race, the other 

cultivars are considered to be primarily G-MX 

hybrids. ‘Hass’ accounts for 80% of avocado 

consumption in the United States and is the main 

focus of research and development. The main 

Florida cultivars (West Indian and Guatemalan 

races and hybrids) are ‘Simmonds,’ ‘Nadir,’ 

‘Booth 8,’ ‘Choquette,’ and ‘Lula.’

Quality Characteristics and Criteria

For avocado, the major quality criteria used 

during grading are size and skin color, as well as 

freedom from wounds, blemishes, insect damage 

(particularly from caterpillar and thrip scarring), 

spray residues (most commonly copper), and 

other contaminants on the skin. When ripe, the 

key issues are absence of disease (body rot and 

stem end rots), physiological disorders (flesh 

graying), and physical damage (bruising). Many 

of these quality factors depend on the cultivar, and 

consumer preference for size, shape, and color can 

vary from region to region.

While avocados from both Florida and California 

are high-quality fruit, there are significant 

differences in size, texture, and flavor. Florida 

avocados are usually at least twice as large as 

those from California and often sell at a lower 

price. The smaller California avocados have a 

desirable nutlike flavor and a richer, creamier 

texture than the less oily Florida fruit, which are 
217

sometimes marketed as “lite avocados.” These 

differences are mainly due to the fact that different 

horticultural races of the avocado are produced in 

California and Florida.

Avocados are one of the few fruit that contain 

significant quantities of oil; sometimes more than 

30% of fresh weight, depending on cultivar and 

maturity. Oil content is a key part of the sensory 

quality. Oil quality is very similar to that of olive 

oil, with approximately 75% monounsaturated, 

15% saturated, and 10% polyunsaturated fatty 

acids (omega-6). However, there is variation with 

race, cultivar, growing region, and season. The 

high-monounsaturated, high-polyunsaturated, 

and low-saturated fatty acid content makes this a 

“healthy” oil in terms of effect on heart disease. 

In addition, avocado oil contains a range of other 

health-promoting compounds such as chlorophyll, 

carotenoids, α-tocopherol, and β-sitosterol. 

These health factors, along with the absence of 

cholesterol, should be emphasized with consumers 

since avocados are perceived by some as an 

unhealthy or “fat” fruit. Extraction of oil from 

reject avocados is carried out in some countries 

for use in cosmetic products and for culinary 

purposes.

Traditionally, fruit produced in the United States 

have been “clip” harvested (peduncle cut to leave 

a “button” at the top of the fruit). However other 

producing countries (Australia, Israel, Spain, and 

South Africa) are now “snap”-harvesting ‘Hass’ 

fruit. The ultimate success of snap harvesting 

depends on fruit maturity, growing conditions 

(rain), and cultivar (Arpaia and Hofshi 1998).

Horticultural Maturity Indices

The percentage of dry matter in avocado fruit 

is highly correlated to oil content and is the key 

maturity index used in California and worldwide 

(Lee et al. 1983). Minimum dry matter percentage 

ranges from 17 to 25%, depending on cultivar. In 

California, the minimum percentage of dry matter 

at harvest for the major cultivars are ‘Bacon’ 

(17.7%), ‘Fuerte’ (19.0%), ‘Gwen’ (24.2%), 

‘Hass’ (20.8%), ‘Pinkerton’ (21.6%), ‘Reed’ 

(18.7%), and ‘Zutano’ (18.7%). In California, fruit 

are also released into the market at predetermined 

dates based on dry matter and size for each 

cultivar. For example, the size and release dates 

for ‘Hass’ are size 40 and greater on November 

28; Size 48, December 12; Size 60, January 2; and 

Size 70 or smaller, January 16. Florida avocados 

have lower oil content (3 to 15%) and are 

generally harvested at a specific date and weight 

or size.

Avocados can be held on the tree for many months 

after they are physiologically mature because they 

do not ripen until they are harvested. However, 

time to ripen does decrease with increasing time 

on the tree. Freshly harvested avocados tend to 

have “green” skins, though ‘Hass’ fruit that are 

harvested late in the season may have some skin 

darkening at harvest. The peel of ripe ‘Hass’ and 

‘Lamb Hass’ avocados should have a dark, purpleblack or black skin, while green-skinned cultivars 

remain green when ripe. Avocados are ripe when 

the fruit yields slightly to light finger pressure. 

Pulp color, texture, and flavor when ripe are 

cultivar specific. 

Grades, Sizes, and Packaging

California avocados are packed in single-layer 

12.5 lb (5.67 kg) flats or trays, 2-layer 25 lb (11.34 

kg) lugs, and 25 lb (11.34 kg) volume-fill boxes. 

RPCs (returnable plastic containers) are used 

increasingly. There is also increased usage of 

prepacked units such as polyethylene containers 

(“clam shells”) or mesh bags. For Florida 

avocados, the common packages used are singlelayer, 13 lb (6.12 kg) flats; two-layer, 27 lb (12.47 

kg) lugs; 35 lb (15.88 kg) cartons; and 10 lb (4.54 

kg) natural packs.

California avocados are graded as No. 1 or No. 2. 

Florida avocados are graded as U.S. No. 1, U.S. 

No. 2, and U.S. Combination. However, only 

some Florida varieties are graded, while the others 

are marketed as unclassified. In California, fruit 

are weight-sized into the following categories: 

20 (18.75 to 22.0 oz, 532 to 624 g), 24 (15.75 to 

18.75 oz, 447 to 532 g), 28 (13.75 to 15.75 oz, 390 
218

to 447 g), 32 (11.75 to 14.0 oz, 333 to 397 g), 36 

(10.5 to 12.5 oz, 298 to 354 g), 40 (9.50 to 11.50 

oz, 269 to 326 g), 48 (7.50 to 9.50 oz, 213 to 269 

g), 60 (6.25 to 7.50 oz, 177 to 213 g), 70 (4.75 to 

6.25 oz, 135 to 177 g), and 84 (3.75 to 4.75 oz, 

106 to 135 g) count for 25 lb packs, and half these 

values for flats (or single-layer trays). Florida 

fruit are packed by count. Regulations specify that 

the pack shall be at least fairly tight and that the 

weight of the smallest fruit in any container shall 

not be less than 75% that of the largest fruit in the 

same container. Commonly used sizes for Florida 

packages are 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, and 

24 count.

Precooling Conditions

Ripening and associated softening of avocados 

can be delayed by cooling soon after harvest. This 

is critical where long storage periods are required 

or where field temperatures are above 25 °C (77 

°F). Forced or passive air-cooling is generally 

carried out as rapidly after harvest as possible; 

within 24 to 48 h or sooner is recommended. 

Hydrocooling of ‘Hass’ is also used commercially. 

Recommendations as to the target temperature 

(prior to packing) vary between 5 and 15 °C 

(41 and 59 °F) and may be influenced by the 

emphasis on whether fruit should be graded with 

condensation or not. 

Optimum Storage Conditions

Optimum storage conditions vary by cultivar, 

growing conditions, time in the season (maturity), 

and length of storage required. However, in 

general, unripe avocados should be stored at 5 

to 12 oC (41 to 54 oF) with RH of 85 to 95%. 

Optimum storage temperatures for ‘Hass’ are 5 to 

7 °C (41 to 45 °F) for early-season fruit and 4 to 

5.5 °C (40 to 42 °F) for late-season fruit. After 3 

to 4 weeks storage, ‘Hass’ fruit quality is reduced, 

and storing fruit for longer than 6 weeks remains a 

challenge.

Increased physiological disorders—for example, 

chilling disorders and uneven ripening—and rots 

result from suboptimal storage temperatures. 

Therefore, it is important to maintain the 

appropriate temperature for unripe fruit and stack 

containers to allow for proper air circulation and 

temperature control.

Controlled Atmosphere (CA) 

Considerations

CA storage is commonly used for transporting 

fruit to distant markets in refrigerated shipping 

containers. The atmosphere used and technology 

for controlling the atmosphere vary between 

shipping companies. Generally, O2

 levels of 2 to 

5% (or possibly as high as 10%) + 3 to 10% CO2

are used. The primary benefit of low O2

 is that 

of delayed softening and reduction of respiration 

and ethylene production from standard storage 

temperatures. Elevated CO2

 may delay softening 

and reduce sensitivity to external chilling injury 

and allow lower storage temperatures (Faubion et 

al. 1992). Low-O2

 injury may appear as irregular 

brown to dark brown patches on the skin and 

may additionally cause diffuse browning of 

flesh beneath affected skin. CO2

 atmospheres 

above 10% can be detrimental by leading to 

discoloration of the skin and development of off 

flavor, particularly when the O2

 concentration is 

less than 1%. Reducing ethylene levels to below 1 

μL L-1 using ethylene scrubbers during CA storage 

may provide added benefits for retarding ripening 

and decrease development of chilling injury 

(Faubion et al. 1992).

Alternative Technologies for Long-Term 

Storage

1-MCP Treatments. Use of 1-MCP 

(1-methylcyclopropene) is in the experimental 

stage and should be used with caution. Application 

of 1-MCP to avocados delays ripening and thus 

reduces internal chilling injury (flesh graying, 

vascular browning), which is associated with 

ripening during storage if storage times are long 

or temperature management is poor (Pesis et 

al. 2002). The optimum treatment conditions 

are likely to be in the area of 50 to 100 nL L-1
219

(ppb) at about 6 °C (43 °F) for 18 to 24 h. For 

‘Hass,’ 1-MCP treatments will have benefit if 

fruit are stored for longer than 4 weeks. However, 

for other cultivars that exhibit higher levels of 

internal chilling injury at even short storage times, 

1-MCP may be of more benefit. Care should be 

taken because applying higher concentrations 

may result in excessive delays to softening and 

ripening, which in turn are likely to increase 

disease incidence. 1-MCP does not reduce 

external chilling injury (skin blackening) of ‘Hass’ 

avocados.

Step-Down Temperatures. The other key 

technology for maintaining fruit quality 

(particularly preventing internal chilling injury), 

proven over many years by the South African 

industry, is the use of “step-down” temperatures 

(Vorster et al. 1987). Temperatures are typically 

decreased 1 to 2 °C each week during shipping, 

with the final temperature not to drop below 3.5 

°C (38 °F), and with progressively lower initial 

temperatures as fruit maturity increases. These 

temperature regimes have been developed and 

refined over many years and have resulted in a 

protocol for each cultivar for differing times in the 

season and growing region.

Retail Outlet Display Considerations

Avocados are best ripened at 15 to 20 oC (59 to 

68 oF) (Hopkirk et al. 1994). The ripening rate 

at temperatures below 15 oC (59 oF) is relatively 

slow, and ripening at temperatures above 25 oC 

(77 oF) may result in increased decay, uneven 

ripening of the flesh, and off flavors. As for 

bananas, ethylene treatment can be used to 

“precondition” or “preripen” fruit. Avocados are 

very susceptible to bruising during softening 

(Arpaia et al. 1987) and thus should be handled 

carefully during transport and display. Any means 

of minimizing “squeezing” by customers will 

also improve quality. Since quality can decrease 

rapidly during softening, it is best to check 

avocado ripeness every day and to display or use 

the ripest fruit first. If possible, ripe or near-ripe 

fruit should be held at lower temperatures (1 to 6 

°C, 34 to 43 °F) (Young and Kosiyachinda 1976) 

to reduce the proportion of fruit that become 

overripe, with concomitant increase in rots and 

other disorders. Avocados should not receive a 

water sprinkle or top ice.

Chilling Sensitivity

Avocados exhibit two forms of chilling injury, 

internal and external, which are generally induced 

by quite different storage conditions. Internal 

chilling injury manifests as a grayish-brown 

discoloration of the flesh, particularly at the base 

of the fruit around the seed. This can be associated 

with vascular browning, which starts at the base 

of the fruit (rather than at the stem end, which is 

often associated with stem end rots). In ‘Hass,’ 

internal chilling injury tends to occur after about 

4 or more weeks in storage at about 6 °C (43 °F), 

but will be influenced by maturity and growing 

conditions. Cultivars differ in their susceptibility 

to this disorder, with some being very sensitive. 

Calcium levels are a possible explanation for 

differences in internal chilling injury (Chaplin and 

Scott 1980). Another low-temperature disorder, 

“pulp spot,” may be observed in ‘Fuerte’ fruit 

in which small dark spots can be observed in 

the flesh. Internal chilling injury is generally 

associated with softening of fruit during storage 

and thus is increased by the presence of ethylene 

(Chaplin et al. 1983). Internal chilling injury is 

the key limiting factor for long-term storage of 

avocados. 

External chilling injury occurs as irregular 

patches of blackening on the skin (similar to 

apple scald) that can be observed during storage 

but that generally increase slightly in intensity 

after removal from cold storage. The damage is 

first seen in inner cell layers of the exocarp and 

then the outer layers of the skin (Woolf 1997). In 

cultivars that naturally darken during ripening, 

such as ‘Hass,’ the damage will be less apparent 

after ripening but may be distinguished as brown, 

corky skin tissue in ripe fruit. External chilling 

injury is generally induced by temperatures below 

3 °C (38 °F). However, fruit become less sensitive 

with increasing maturity, and ripe fruit are less 

affected. Fruit exposed to low temperatures may 
220

be of poor internal quality when ripe, with a high 

incidence of rots and softening disorders (Woolf et 

al. 1995), but will have lower incidence of internal 

chilling injury (graying). For ‘Hass’ fruit stored 

for long periods at standard storage temperatures 

(for example, 6 to 7 weeks at about 6 °C [43 °F]), 

a form of external chilling injury is expressed that 

is of a very similar appearance to that observed at 

low temperatures. This form of external chilling 

injury will tend to be seen in fruit that are quite 

soft (nearly ripe) at the point of removal from 

storage.

Ethylene Production and Sensitivity

Rates of ethylene production are generally low 

for unripe avocados, less than 0.1 μL kg-1 h-1 at 20 

oC (68 oF), but increase rapidly after harvest up to 

levels greater than 100 μL kg-1 h-1 at 20 oC (68 oF) 

when fully ripe. Therefore, ripe avocados should 

not be stored with fruits and vegetables that are 

sensitive to ethylene damage. Unripe avocados 

are very sensitive to ethylene. They should not 

be stored near ripe fruit or other fresh produce 

that produces more than trace ethylene. Ethylene 

exposure during storage accelerates ripening and 

softening and can increase incidence and severity 

of internal chilling injury and decay. 

Ethylene Treatment (“Preconditioning” or 

“Preripening”)

There is an increasing move at the retail level 

toward “ripe for tonight” programs that generally 

result in significant increases in sales. This is 

achieved by treating avocados with 10 to 100 

μL L-1 ethylene at 17 to 20 oC (63 to 68 oF) for 

approximately 48 to 72 h (early season), 24 to 48 

h (mid season), or 12 to 24 h (late season). This 

significantly reduces both the time to ripen (to 3 

to 6 days, depending on cultivar and maturity) 

and fruit-to-fruit variability in ripening. If fruit are 

stored prior to ethylene treatment, the duration of 

treatment required to achieve maximum rate of 

ripening is reduced. For ‘Hass,’ after 3 to 4 weeks 

of storage, there may be relatively little benefit to 

ethylene treatment (particularly for later-season 

fruit), since the time to ripen decreases during 

storage. Because heat production of avocados 

is much greater than that of many other fruit 

crops, careful attention should be paid to air flow 

and temperature management during ethylene 

treatment and subsequent ripening. Palletized fruit 

may reach temperatures of more than 30 °C (86 

°F), with negative effects on ripe fruit quality. For 

this reason, ethylene treatment of palletized fruit 

should be carried out under forced-air conditions. 

During ethylene treatment, CO2

 levels should be 

maintained at less than 1 to 2% by either continual 

venting of the atmosphere or full venting and 

ethylene reinjection if “shot” systems are used. 

Following ripening, fruit should be precooled to 5 

°C (41 °F).

Respiration Rates

Respiration rate of avocados is relatively high 

compared with many other fruit crops.

Temperature mg CO2 kg-1 h-1

5 oC 20 to 50

10 oC 50 to 160

20 oC 80 to 300

Data from Kader and Arpaia (2001).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

There is a range of physiological disorders of 

avocados (Arpaia et al. 2009), and most of these 

occur following long storage periods. The key 

disorders are flesh graying, vascular browning, 

and pulp spot, which are all symptoms of internal 

chilling injury (see Chilling Sensitivity). If fruit 

are stored for excessively long periods, the 

flesh may also fail to ripen evenly and become 

increasingly susceptible to pathogens. The timing 

of expression of internal chilling injury and its 

severity depend on temperature management, 
221

initial ripeness, cultivar, production area, and fruit 

maturity. External chilling injury may occur if 

fruit are stored at low temperatures (0 to 3 °C [32 

to 38 °F]) or for long periods (more than 6 weeks) 

at standard storage temperatures.

Postharvest Pathology

Rots of avocados are divided into two categories 

on the basis of their location (Snowdon 1990). 

Stem end rots enter the fruit at the stem, or 

peduncle end of the fruit, and move down the fruit 

resulting in discolored flesh, often with associated 

browning of the vascular strands (Johnson and 

Kotze 1994). Body rots invade through the skin 

and are generally manifested as circular brown to 

black spots that may be covered with spore masses 

in the later stages of infection. Decay penetrates 

through to the flesh resulting in discrete areas of 

discolored flesh. In cultivars that darken when ripe 

(‘Hass’), rots may be less obvious externally. Rots 

are rarely observed at harvest or during storage but 

can increase rapidly with fruit softening. Where 

infection pressure is high and physical damage to 

the skin occurs prior to storage, small, soft-black 

circles of infection (“measles”) can occur during 

storage. These generally spread rapidly outwards 

after removal from storage. 

The causal organisms can vary with growing 

environment and country. The following 

pathogens (in order of frequency) have been 

isolated from decayed California avocados: 

Colletotrichum, Dothiorella, Alternaria, and

Phomopsis spp. (Smilanick and Margosan 2001). 

Differences in the pathogens responsible for decay 

exist among countries; for example, New Zealand 

versus Australia (Everett 1996, Arpaia et al. 2009).

Preharvest control methods for postharvest fungal 

decay include good orchard sanitation (removal 

of mummified fruit and dead wood) and effective 

preharvest fungicide application, such as copper, 

which is widely used in some countries (including 

the United States, in Florida) where humid 

growing conditions prevail. Harvesting should not 

be carried out in the rain or when fruit are wet, and 

careful handling to minimize skin damage helps 

reduce rots. Snap picking of fruit can reduce stem 

end rot incidence in dry periods, but it can result 

in increased rots in humid growing environments 

or when fruit are harvested in wet conditions.

Perhaps the most important area for reducing rots 

is that of maintaining good ripe-fruit quality by 

optimizing temperatures during handling, storage, 

transport, and ripening. It is also critical not to 

store fruit for long periods. Ripening fruit at lower 

temperatures—for example, 15 to 20 °C (59 to 

68 °F)—can lead to significant reduction in rots 

compared with higher temperatures (Hopkirk et 

al. 1994). Storing ‘Hass’ fruit for 1 to 3 weeks 

can also reduce rot incidence (as compared with 

nonstored fruit), as can ethylene treatments, which 

both synchronize and hasten ripening. Postharvest 

fungicides (prochloraz, benlate [benomyl], and 

thiabendazole) are used in some countries, but 

these are not registered for use in the United 

States (Darvas et al. 1990). Research on biological 

control agents is being carried out in South Africa, 

New Zealand, and Australia.

Quarantine Issues

Issues relating to quarantine will vary according 

to the marketplace and country of origin, and 

guidance should be sought from the Department 

of Agriculture. If avocados are grown in fruit-flyinfested areas, significant quarantine issues will 

arise. Methyl bromide treatment is an APHISapproved treatment for Mediterranean fruit fly, 

but it results in a significant reduction in fruit 

quality. Because avocados do not tolerate standard 

high-temperature disinfestation treatments, (for 

example, fruit core temperatures of 47 °C [117 

°F] for 20 min), low-temperature disinfestation 

is the most viable approach. Tolerance to 

temperatures that can be used for low-temperature 

disinfestation can be imparted by pretreatments 

at 38 °C (100 °F) (Sanxter et al. 1994, Woolf et 

al. 1995), for example, or by low-temperature 

conditioning (Woolf et al. 2003). However, the 

only commercial disinfestation treatment in use is 

for Queensland fruit fly in ‘Hass’ avocados: 6 to 

8 °C (43 to 47 °F) for 3 to 5 days followed by 16 

days at temperatures <1 °C (34 °F) (Hofman et al. 
222

2003). However, this low-temperature disinfesting 

treatment may not be effective for all fruit fly 

species, since cold tolerance varies.

Suitability as a Fresh-Cut Product

Avocados are not currently marketed as fresh-cut 

products, but they are marketed as chunks, paste, 

and guacamole dips.

Acknowledgments

Some of the above information was taken from the 

previous edition of Agriculture Handbook Number

66; the Produce Marketing Association’s Fresh 

Produce Manual; the University of California, 

Davis, website “Fresh Produce Facts” (http://

postharvest.ucdavis.edu/produce_information); the 

Michigan State University Extension Information 

Management Program Database website (http://

msue.anr.msu.edu); the California Avocado 

Commission website (http://www.avocado.org); 

and the University of Florida website (http://

edis.ifas.ufl.edu). The authors also express their 

appreciation for input and comments on the 

manuscript by Adel Kader, Joe Smilanick, Reuben 

Hofshi, Chris Yearsley, Laurence Eyers, Ian 

Ferguson, and Linda Boyd. 

References

Arpaia, M.L., and R. Hofshi. 1998. Preliminary 

report on the feasibility of “snap” harvesting 

‘Hass’ avocados. Subtrop. Fruit News 6(2):7-9.

Arpaia, M.L., F.G. Mitchell, P.M. Katz, and G. 

Mayer. 1987. Susceptibility of avocado fruit to 

mechanical damage as influenced by variety, 

maturity, and stage of ripeness. Proceedings of 

World Avocado Congress, May 1987, Pretoria, 

Republic of South Africa. South African Avocado 

Growers’ Association Yearbook 10:149-151.

Bergh, B.O., and E. Lahav. 1996. Avocados. In J. 

Janick and J.N. Moore, eds., Fruit Breeding, vol. I, 

Tree and Tropical Fruits, pp. 113-166. John Wiley 

& Sons, New York, NY.

Chaplin, G.R., and K.J. Scott. 1980. Association 

of calcium in chilling injury susceptibility in 

stored avocados. HortScience 15:514-515.

Chaplin, G.R., R.B.H. Wills, and D. Graham. 

1983. Induction of chilling injury in stored 

avocados with exogenous ethylene. HortScience 

18:952-953.

Darvas, J.M., J.M. Kotze, and F.C. Wehner. 

1990. Effect of treatment after picking on the 

incidence of postharvest diseases of avocado. 

Phytophylactica 22:93-96.

Everett, K.R. 1996. Postharvest diseases 

of avocados. At http://www.hortnet.co.nz/

publications/science/everavo1.htm.

Faubion, D.F., F.G. Mitchell, G. Mayer, and M.L. 

Arpaia. 1992. Response of ‘Hass’ avocado fruit 

to postharvest storage in controlled atmosphere 

conditions. In C.J. Lovatt, and P. Holthe, eds., 

Proceedings of 2nd World Avocado Congress, 

Orange, CA, April 1991, pp. 467-472. University 

of California, Riverside, CA.

Hofman, P.J., B.A. Stubbings, M.F. Adkins, et al. 

2003. Low temperature conditioning treatments 

before cold disinfestation improve ‘Hass’ avocado 

fruit quality. Postharv. Biol. Technol. 28:123-133.

Hopkirk, G., A. White, D.J. Beever, and 

S.K. Forbes. 1994. Influence of postharvest 

temperatures and the rate of fruit ripening on 

internal postharvest rots and disorders of New 

Zealand ‘Hass’ avocado fruit. New Zealand J. 

Crop Hortic. Sci. 22:305-311.

Johnson, G.L., and J.M. Kotze. 1994. Stem-end 

rot. In R.C. Ploetz et al., eds., Compendium of 

Tropical Fruit Diseases, pp. 81-83. APS Press, St 

Paul, MN. 
223

Kader, A.A., and M.L. Arpaia. 2001. Avocado. 

Recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.

Kosiyachinda, S., and R.E. Young. 1976. Chilling 

sensitivity of avocado fruit at different stages of 

the respiratory climacteric. J. Amer. Soc. Hort. 

Sci. 101:665.

Lee, S.K., R.E. Young, P.M. Schiffman, and C.W. 

Coggins. 1983. Maturity studies of avocado fruit 

based on picking dates and dry weight. J. Amer. 

Soc. Hort. Sci. 108:390-394.

Pesis, E., M. Ackerman, R. Ben-Arie, et al. 2002. 

Ethylene involvement in chilling injury symptoms 

of avocado during cold storage. Postharv. Biol. 

Technol. 24:171-181.

Sanxter, S.S., K.A. Nishijima, and H. Chan. 1994. 

Heat-treating ‘Sharwil’ avocado for cold tolerance 

in cold treatments. HortScience 29:1166-1168.

Smilanick, J.L., and D.A. Margosan. 2001. 

Management of postharvest decay of avocado 

fruit. In California Avocado Research Symposium, 

Oct. 2001, pp. 115-119. At http://www.

avocadosource.com/arac/symposium_2001/

smilan.pdf. 

Snowdon, A.L. 1990. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 1, General Introduction and Fruits. CRC 

Press, Boca Raton, FL.

Vorster, L.L., J.C. Toerien, and J.J. Bezuidenhout. 

1987. A storage temperature regime for South 

African export avocados. South African Avocado 

Growers’ Association Yearbook 10:146-148.

Wang, C.Y. 1993. Approaches to reduce chilling 

injury of fruits and vegetables. Hort. Rev. 15:63-

95.

M.L. Arpaia, P. Hofman, A. White, and A. Woolf. 

2009. The International Avocado Quality

Manual, 70 pp., University of California, Davis, 

CA.

Woolf, A.B. 1997. Reduction of chilling injury 

in stored ‘Hass’ avocado fruit by 38 °C water 

treatments. HortScience. 32:1247-1251.

Woolf, A.B., C.B. Watkins, J.H. Bowen, et al. 

1995. Reducing external chilling injury in stored 

‘Hass’ avocados with dry heat treatments. J. Amer. 

Soc. Hort. Sci. 120:1050-1056.

Woolf, A.B., K.A. Cox, A. White, and I.B. 

Ferguson. 2003. Low temperature conditioning 

treatments reduce external chilling injury of ‘Hass’ 

avocados. Postharv. Biol. Technol. 13:113-122. 

Young, R.E., and S. Kosiyachinda. 1976. Low 

temperature storage of ripe avocado fruit. In

California Avocado Society Yearbook, pp. 73-76. 

Temecula, CA.
224

Banana and Plantain

Eduardo Kerbel

Kerbel is with Dole Fresh Fruit International, Ltd., 

San Jose, Costa Rica.

Scientific Name and Introduction

Most cultivars of edible bananas and plantains 

are derived from two members of the family 

Musaceae: Musa acuminate and Musa balbisiana

(Simmonds and Shepherd 1955). Before the 

1940s, the cultivar ‘Gros Michel’ dominated the 

international banana trade until it succumbed to 

Fusarium wilt (Panama disease). Since the 1940s, 

the trade has adopted cultivars of the Cavendish 

subgroup. Bananas are eaten mainly raw as a 

dessert fruit because they are sweet when ripe. 

Plantains, also referred to as “cooking bananas,” 

are much starchier and can be eaten either ripe 

or unripe. The edible cultivars of bananas and 

plantains are seedless. The two obvious tissues 

that constitute the fruit are the pulp and the peel. 

The peel is the ovary wall. The pulp originates 

from cell division of the innermost layers of the 

pericarp. The growth of the peel begins to slow 

down as the fruit matures but the growth of the 

pulp continues. Consequently, peel splitting often 

occurs in very mature green fruit (Turner 1997). 

Quality Characteristics and Criteria

A premium quality banana is very clean (free 

from defects such as scars, physical damage, 

insect injury, and latex staining), free from decay, 

has an adequate finger length and diameter, does 

not have excess curvature, and, upon ripening, 

has the desired uniform bright-yellow color and 

sensory attributes in flavor (sweetness and acidity) 

and aroma. Attributes are defined by consumer 

preference.

Horticultural Maturity Indices

Commercially, bananas and plantains must be 

harvested while mature green and transported to 

destination markets where they are ripened under 

controlled conditions (bananas) and controlled or 

natural conditions (plantains). Fruits ripened on 

the plant often split and have poor texture. Harvest 

time represents a compromise between leaving the 

fruit on the plant long enough to maximize yield 

and harvesting it soon enough so that sufficient 

green life remains to market fruit with acceptable 

quality. The stage of maturity for harvesting 

the fruit depends on the market for which it 

is intended and is determined in terms of the 

marketable life required. Plantains tend to mature 

more prematurely than bananas when harvested 

at the same age. One very useful criterion for 

harvesting fruit that is used commercially is age of 

the bunch after emergence from the pseudostem. 

(Emergence can be defined as the day on which 

the first complete hand of fruit is visible.) Because 

bananas are growing rapidly when harvested, 

fruit size (finger length and diameter) and finger 

fullness (angularity) are suitable measures of 

harvest maturity. At a given age, the maturity of 

hands in a stem varies, those hands at the proximal 

end of the stem being more mature than those 

at the distal end. An estimate of maturity of the 

entire stem is then assessed using the second hand 

from the proximal end. It is usual to measure 

length and diameter (caliper grade or calibration) 

of the middle finger on outer whorls of the second 

hand on the stem before running fruit through the 

packing plant processes. 

Grades, Sizes, and Packaging

Minimum acceptable size (length and diameter) 

grade standards for export markets vary depending 

on banana and plantain cultivar and market 

specifications. Hands, clusters, or single fingers 

not meeting these fresh market grades are used 

for processing products or discarded. Bananas are 

packed in corrugated fiberboard boxes as whole 

hands, clusters, or individual fingers holding an 

average weight for premium fruit between 13 

and 18 kg (28 to 40 lb), depending on market 
225

preference. Plantains are packed as individual 

fingers in 18 kg boxes. Most exporters use 

polyethylene film liners and paper pads to reduce 

moisture loss and protect fruit from physical 

damage during handling and transport.

Precooling Conditions

Precooling of bananas or plantains is not generally 

done. Adequate cooling is not initiated until fruit 

are loaded into containers or cargo holds aboard 

ships.

Optimum Storage Conditions

Optimum temperatures for storage and holding 

of green bananas are 13 to 14 oC (56 to 58 

oF) (Thompson and Burden 1995). Because 

marketing quality standards are more relaxed 

for plantains, and plantains are more prone to 

premature ripening during transit and storage, 

it is recommended that green plantains be held 

between 9 and 12 oC (48 to 53 oF). Plantains 

grown during the warmer months tend to attain 

physiological maturity faster than fruit grown 

during the winter months; thus green-life potential 

varies during the year. Optimum RH for holding 

and transporting fruit is 90 to 95%. Holding of 

ripe fruit should be kept to a minimum.

Controlled Atmosphere (CA) 

Considerations

Bananas and plantains respond well to CA. CA 

is used commercially during ocean transport of 

green bananas. Modified atmosphere packaging 

using polyethylene bags (banavac) is used for 

both bananas and plantains, but plantain are 

physiologically more active than bananas and 

have higher respiration rates and so could exhaust 

O2

 more rapidly than bananas. Optimum gas 

levels for most cultivars range between 2 to 

5% O2

 and 2 to 5% CO2 (Bishop 1990, Kader 

1992, Kader 1994, Kader 1997). Main benefits 

of controlled atmosphere include delaying of 

ripening, reduction of crown rot incidence, and 

a much fresher condition (latex flowing through 

the vascular tissues) on arrival at destination. 

Shelf-life can potentially be extended twofold 

to threefold by optimum CA. O2

 levels below 

1 to 1.5% may cause grayish or brown peel 

discoloration, failure to ripen properly, and off 

flavor (Kader 1992, 1994, 1997). CO2

 levels above 

6 to 8% may cause pulp to soften while the peel 

is still green and may confer undesirable texture 

and flavor (Wei and Thompson 1993, Kader 1994, 

Kader 1997). Ripe fruit can tolerate higher levels 

of CO2

. 

The beneficial and detrimental effects of reduced 

O2 and/or elevated CO2 depend on temperature 

and time of exposure. Removal of ethylene gas 

can have an additional benefit on extending 

green-life of bananas and plantains under both 

ambient and modified atmosphere conditions 

(Scott et al. 1970, Liu 1976, Scott 1977, Turner 

1997). CO2

 inhibits the effect of ethylene on 

ripening, and higher levels of O2

 than those under 

CA are necessary for adequate ripening. Thus, 

bananas held under CA should be ventilated with 

fresh air for at least 18 to 24 h before ripening 

(gassing with ethylene) is initiated. An underpeel 

discoloration resembling chilling injury has been 

observed on green bananas when transported long 

distances under CA conditions at temperatures 

below 14 oC (58 oF). This disorder has also been 

associated with high temperatures of 33 to 35 oC 

(91 to 95 oF) in the field (Stover and Simmonds 

1987).

Retail Outlet Display Considerations

Fruit should be displayed at retail in 

nonrefrigerated areas in the produce section. 

Existing refrigerated shelf space in supermarkets 

normally is below the minimum safe temperature 

for bananas and plantains and chilling injury can 

still occur in ripe fruit. Displaying surfaces should 

be cushioned to avoid physical damage to the 

fruit.
226

Chilling Sensitivity

Chilling injury is an important disorder of 

bananas and plantains. Both green and ripe fruit 

are susceptible, with green fruit being slightly 

more sensitive than ripe fruit. Chilling injury 

results from exposing fruit to temperatures below 

about 13 oC (56 oF) for a few hours to a few days, 

depending on cultivar, maturity, condition of 

the fruit, temperature, and duration of exposure 

(Stover 1972, John and Marchal 1995, Turner 

1997). Chilling injury is mainly a peel disorder. 

Symptoms include subepidermal discoloration 

visible as brown or black streaks in a longitudinal 

cut, a dull or grayish (smokey) cast on ripe fruit, 

and failure to ripen. In severe cases, the peel 

turns dark brown or black, and even the flesh can 

turn brown and develop an off taste (John and 

Marchal 1995, Turner 1997). Chilled fruit are 

more sensitive to mechanical injury. Ripe fruit, 

if chilled, turn dull brown when later exposed to 

higher temperatures and are very susceptible to 

handling marks: The slightest pressure can cause 

discoloration. Inflicted chill in green or ripe fruit 

may not become apparent until 18 to 24 h after 

actual damage has occurred.

Ethylene Production and Sensitivity

Bananas and plantains are sensitive to 

physiological levels of ethylene as low as 0.3 to 

0.5 μL L-1 if the O2

 and CO2 levels are similar to 

those found in outside fresh air (Peacock 1972). 

The three main factors affecting response to 

external ethylene are fruit maturity, time from 

harvest when ethylene exposure began, and length 

of exposure to ethylene.

Ethylene production rates:

Temperature μL C2H4 kg-1 h-1

13 oC 0.04 to 2.0

15 oC 0.15 to 5.0

18 oC 0.20 to 8.0

20 oC 0.30 to 10.0

Lower values in the range are for mature-green 

fruit, and higher values are for ripening fruit. 

Data modified from Kader (1998).

Controlled ripening. Mature bananas left to ripen 

naturally will eventually soften, but the change in 

color will not be uniform and the peel will be dull, 

pale yellow, and unattractive. In order for the fruit 

to attain a bright yellow peel color, a firm pulp 

texture, and good flavor, bananas are ripened by 

releasing ethylene into a sealed chamber or room 

and at controlled temperature and RH. Plantains 

are being ripened by this controlled method in 

most markets, but some markets still rely on 

natural ripening. Immediately after harvest, 

bananas do not respond to ethylene treatment 

or, in the best scenario, will initiate ripening but 

will never attain the characteristic bright yellow 

color. One main reason for controlled ripening is 

to provide retailers and wholesalers with fruit at a 

stage of ripeness desired by consumers. 

Generally, very low concentrations of ethylene 

are sufficient to ripen the fruit—10 to 50 μL L-1

(Thompson and Seymour 1982). In commercial 

practice, however, 1,000 μL L-1 is commonly 

used to ensure uniform ripening. This is partly 

because many ripening rooms are not fully gastight and the concentration may be rapidly reduced 

through leakage. Most commercial cultivars 

of bananas and plantains require exposure to 

ethylene for 24 to 48 h at 14 to 18 oC (58 to 64 oF) 

(Thompson and Burden 1995, Robinson 1996). 

However, temperatures of up to 20 oC (68 oF) are 

sometimes necessary (Thompson and Burden 

1995). Optimum RH levels during ripening are 90 

to 95%. (After coloring is underway, RH should 

be reduced to 85% to prevent peel splitting.) 

High RH requirements for proper ripening can be 

attained when the fruit is being packed in partially 

sealed polyethylene liners. Exposure of ripe 

bananas or plantains to temperatures higher than 

those in the ripening range can hasten softening 

and decay, weaken the neck, and cause splitting of 

the peel and poor color development.

The color of the peel is used as an indicator of 

ripening. A scale of 1 to 7 is convenient: 1 is 

dark green, 2 is light green, 3 is more green than 

yellow, 4 is more yellow than green, 5 is yellow 

with green tips, 6 is fully yellow, and 7 is flecking 

(Kader 1992). Room ventilation after gassing 

with ethylene is essential to keep CO2

 below 
227

1% and avoid its effects on delaying ethylene 

action. Use of a forced-air system (pressurized) 

in ripening rooms assures more uniform cooling 

or warming of the fruit as needed and more 

uniform ethylene concentrations throughout the 

ripening. When ripening is done in nonpressurized 

conventional rooms, open stacking of boxes is 

essential to allow adequate air circulation for 

uniform ripening. Many stacking patterns are 

used and the best pattern to be used depends on 

pallet sizes and ripening facilities. Because heat 

rises, the amount of box-op area exposed is most 

important for preventing heat buildup in the stack 

and controlling pulp temperature during ripening. 

Bananas are usually ripened to color stage 3 to 4 

before delivery to distribution centers, retailers, or 

wholesalers.

Within certain limits, the period required for 

ripening bananas can be shortened or extended 

to meet trade requirements by adjusting the 

temperature. Under average conditions, depending 

on initial temperatures chosen and condition of 

the fruit, the ripening cycle can be as short as 4 

days (above 18 oC) or may be extended to 8 to 10 

days (at 14 oC). If initial ripening temperatures are 

too high (above 25 oC), the pulp will soften but 

the peel will remain green (a condition described 

as “cooked” or “boiled” fruit) (Robinson 1996, 

Turner 1997). Uneven ripening can be caused 

by low temperatures and insufficient ethylene. 

Ripening rates and characteristics of the fruit vary 

to some extent between lots depending on cultivar, 

country of origin, weather conditions during the 

growing of the fruit, temperatures during handling 

and transit, and maturity of the fruit. Hard-green 

fruit (less full) will take longer to ripen than more 

advanced and full fruit.

Respiration Rates

Temperature mg CO2 kg-1 h-1

13 oC 20 to 80

15 oC 26 to 140

18 oC 32 to 200

20 oC 40 to 280

Data modified from Kader (1998).

The lower value of the range is for mature-green 

fruit, and the higher value is for ripening fruit. To 

get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate by 

2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 

at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

A condition known as “maturity bronzing” or 

“maturity stain” has been observed in Australia 

and Central America at certain times during the 

year, 20 to 30 days before harvest (Stover and 

Simmonds 1987). The fruit is unacceptable for 

market, although eating quality is unaffected. This 

disorder has been associated with water deficits at 

bunch emergence during rapid fruit growth under 

very humid and hot conditions (Daniells et al. 

1987, Williams et al. 1989, 1990). If bananas and 

plantains are exposed to temperatures above 30 to 

35 oC, ripening can be irreversibly inhibited (hightemperature injury).

Postharvest Pathology

The main postharvest diseases of bananas and 

plantains are crown rot—a disease complex 

caused by several fungi (Colletotrichum musae, 

Fusarium semitectum, Fusarium pallidoroseum, 

Lasiodiplodia theobromae, Botryodiplodia 

theobroame, Ceratocystis paradoxa, Verticillium 

sp., Acremonium sp., and Curvularia sp.)—and 

anthracnose (Colletotrichum musae) (Stover 

1972, Wardlaw 1972, Stover and Simmonds 1987, 

Snowdon 1990, Jeger et al. 1995). Anthracnose 

is a latent infection that occurs in the plantation. 

Though it can appear on green fruit, it is more 

apparent in ripening fruit as numerous small, 

dark, circular spots. Crown-rot organisms 

normally enter after harvest, usually as a result of 

mechanical injury to the fruit. 

Other diseases that from time to time become 

important locally include stem-end rot 

(Lasiodiplodia theobromae / Thielaviopsis 

paradoxa), in which the invaded flesh becomes 
228

brown, soft, and water-soaked, and cigar-end 

rot (Verticillium theobromae / Trachysphaera 

fructigena), in which the rotted tip of the finger is 

dry and appears similar to the ash of a cigar (Stover 

1972, Wardlaw 1972, Stover and Simmonds 

1987, Snowdon 1990, Jeger et al. 1995). Sigatoka 

disease of bananas is caused by Mycosphaerella 

sp. and has been reported in most banana/plantainproducing countries (Snowdon 1990). The potential 

of this fungal disease is such that a flourishing 

banana industry can be destroyed within a few 

years. Fruit symptoms include premature ripening, 

buff-colored pulp, and increased susceptibility to 

chilling injury. Preventive and control measures to 

reduce decay incidence begin with strict sanitation 

in plantation and packing plant, postharvest 

treatment with systemic fungicides, minimizing 

mechanical damage during handling, prompt 

cooling of fruit to lowest safe temperature, and 

expediting transport to final destination.

Quarantine Issues

There are no quarantine issues.

Suitability as Fresh-Cut Product

Bananas and plantains are not good candidates 

for fresh-cut processing because of their very 

high oxidation and browning potential (John and 

Marchal 1995).

Special Considerations

Mechanical damage in bananas and plantains takes 

several forms that vary in importance depending 

on the perceptions of consumers. Banana peel 

is very sensitive to mechanical damage. Export 

markets for bananas require a blemish-free fruit, 

though requirements are a bit more relaxed for 

plantains. Great care during handling is needed at 

all times. Bruising of the pulp is undesirable and 

cannot always be detected from damage to the peel 

(Akkaravessapong 1986). RH levels below 85 to 

90% accentuate symptoms of mechanical damage.

Acknowledgments

Some of the information in this chapter was from 

the University of California, Davis, website “Fresh 

Produce Facts” at http://postharvest.ucdavis.edu/

produce_information. 

References

Akkaravessapong, P. 1986. The ripening of 

bananas increases their susceptibility to mechanical 

damage. M.Sc. (Agric) Prelim. Report, University 

of Western Australia, Perth, Australia. Unpublished 

report.

Bishop, D. 1990. Controlled atmosphere storage. 

In C.J.V. Dellino, ed., Cold and Chilled Storage 

Technology, pp. 66-98. Blackie, London, U.K.

Daniells, J.W., B.J. Watson, P.J. Farrell, and 

J.C. Mulder. 1987. Soil water stress at bunch 

emergence increases maturity bronzing of banana 

fruit. Queen. J. Agric. An. Sci. 44:97-100.

Jeger, M.J., S. Eden-Green, J.M. Thresh, et al. 

1995. Banana diseases. In S. Gowen, ed., Bananas 

and Plantains, pp. 317-381. Chapman and Hall, 

London, U.K.

John, P., and J. Marchal. 1995. Ripening and 

biochemistry of the fruit. In S. Gowen, ed., 

Bananas and Plantains, pp. 434-467. Chapman and 

Hall, London, U.K.

Kader, A.A., ed. 1992. Postharvest Technology of 

Horticultural Crops. Pub. no. 3311, University of 

California, Division of Agriculture and Natural 

Resources, Davis, CA.

Kader, A.A. 1994. Modified and controlled 

atmosphere storage of tropical fruits. In B.R. 

Champ, E. Highley, and G.I. Johnson, eds., 

Postharvest Handling of Tropical Fruits. 

International Conference on Postharvest Handling 

of Tropical Fruits, Chiang Mai, Thailand, July 

1993, pp. 239-249. ACIAR Proceedings no. 50, 

ACIAR, Canberra, Australia.
229

Kader, A.A. 1997. A summary of CA 

recommendations for fruits other than apples 

and pears. In A.A. Kader, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, CA, July 13-18, 

1997, vol. 32, pp. 1-34. University of California, 

Davis, CA.

Kader, A.A. 1998. Bananas. In Fresh Produce 

Facts. At http://postharvest.ucdavis.edu/produce_

information. 

Liu, F.W. 1976. Banana response to low 

concentrations of ethylene. J. Amer. Soc. Hort. Sci. 

101:222-224.

Peacock, B.C. 1972. Role of ethylene in the 

initiation of fruit ripening. Queensland J. Agric. 

Animal Sci. 29:137-145.

Robinson, J.C. 1996. Bananas and Plantains. CAB 

Intl., Wallingford, U.K.

Scott, K.J., W.B. McGlasson, and E.A. Roberts. 

1970. Potassium permanganate as an ethylene 

absorbent in polyethylene bags to delay ripening 

of bananas during storage. Austr. J. Exp. Agric. 

Animal Husb. 10:237-240.

Scott, K.J. 1977. Some Australian contributions 

on postharvest physiology and pathology of the 

banana fruit. Tech. Bull. 38, ASPAC Food and 

Fertilizer Technology Center,Taipei, Taiwan.

Simmonds, N.W., and K. Shepherd. 1955. The 

taxonomy and origins of the cultivated bananas. J. 

Linnean Soc. (Botany) 55:302-312.

Snowdon, A.L. 1990. Postharvest Disease and 

Disorders of Fruits and Vegetables, vol. 1, General 

Introduction and Fruits. CRC Press, Boca Raton, 

FL.

Sommer, N.F., and M.L. Arpaia. 1992. Postharvest 

handling systems: tropical fruits. In A.A. Kader, 

ed., Postharvest Technology of Horticultural 

Crops, 2nd ed., pp. 241-245. DANR Pub no. 3311, 

University of California, Davis, CA.

Stover, R.H. 1972. Banana, Plantain, and Abaca 

Diseases. Commonwealth Agricultural Bureaux, 

Slough, U.K.

Stover, R.H., and N.W. Simmonds. 1987. Bananas. 

Longman Scientific and Technical, Essex, U.K.

Thompson, A.K., and G.B. Seymour. 1982. 

Comparative effects of acethylene and ethylene gas 

on initiation of banana ripening. Ann. Appl. Biol. 

101:407-410.

Thompson, A.K., and O.J. Burden. 1995. 

Harvesting and fruit care. In S. Gowen, ed., 

Bananas and Plantains, pp. 403-433. Chapman and 

Hall, London, U.K.

Turner, D.W. 1997. Bananas and plantains. In S.K. 

Mitra, ed., Postharvest Physiology and Storage of 

Tropical and Subtropical Fruits, pp. 47-83. CAB 

Intl., Wallingford, U.K.

Wardlaw, C.W. 1972. Banana Diseases Including 

Plantain and Abaca. Longman, London, U.K.

Wei, Y., and A.K. Thompson. 1993. Modified 

atmosphere packaging of diploid bananas (Musa

AA). In J. de Baerdemaeker, B. McKenna, M. 

Janssens, A. Thompson, F. Artes Calero, E. 

Hohn, and Z. Somogyi, eds., Proceedings of the 

COST-94 Workshop on Postharvest Treatment 

of Fruit and Vegetables: Systems and Operations 

for Postharvest Quality, September 14-15, 1993, 

Leuven, Belgium, pp. 235-246. Commission of the 

European Communities, Leuven, Belgium.

Williams, M.H., M. Vesk, and M.G. Mullins. 

1989. Characteristics of the surface of banana peel 

in cultivars susceptible and resistant to maturity 

bronzing. Can. J. Bot. 67:2154-2160.

Williams, M.H., M. Vesk, and M.G. Mullins. 1990. 

Development of the banana fruit and occurrence of 

the maturity bronzing disorder. Ann. Bot. 65:9-19.
230

Bean

Marita Cantwell

Cantwell is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Fresh snap or common beans (string beans, yellow 

wax beans, green beans) (Phaseolus vulgaris L.), 

runner or flat beans (P. coccineus L.), and long 

beans (Vigna sesquipedalis) are members of the 

Fabaceae (Leguminosae) family. Both the fleshy 

pod and seeds are consumed. Fresh pod beans 

are available from many production areas in the 

United States, but in the winter months they are 

produced mainly in Florida and Mexico.

Quality Characteristics and Criteria

Beans should be well-formed and straight, bright 

in color with a fresh appearance free of defects, 

and tender (not tough or stringy) but firm. The 

diameter of the pod, rather than length, is a good 

indicator of quality. Buyers prefer pods with no or 

only slight bulges indicating tender, young seeds. 

As the name implies, snap beans should break 

easily when the pod is bent, giving off a distinct 

audible snap. Poor quality is most often associated 

with overmaturity, broken beans, water loss, 

chilling damage, and decay. 

Horticultural Maturity Indices

Snap beans (yellow, green, and purple types) are 

harvested when they are rapidly growing, about 8 

to 10 days after flowering for typical mature snap 

beans. All pod beans should be harvested when the 

pod is a bright color and fleshy, and the seeds are 

small and green. After that period, excessive seed 

development reduces quality and the pod becomes 

pithy and tough and loses its bright color.

Grades, Sizes, and Packaging

U.S. grades for snap beans are U.S. Fancy, 

U.S. No. 1, and U.S. No. 2, based primarily on 

external appearance. Though not sized for market, 

a reasonable size is expected according to the 

characteristics of each variety. Beans are packed 

in 11.4 to 13.6 kg (25 to 30 lb) crates and 6.8 or 

9.1 kg (15 or 20 lb) cartons; presnipped beans for 

foodservice are available in 4.5 kg (10 lb) bags.

Cooling

Snaps beans can be hydrocooled. This is 

especially beneficial in dry climates where 

dehydration is a concern and in situations where 

evaporation of surface moisture occurs rapidly 

after cooling (for example, beans packed in wirebound crates). Hydrocooling is very rapid, but 

significant postharvest decay can occur if the 

product remains wet after cooling. Forced-air 

cooling is the method of choice if beans have 

been packed. Efficient cooling is achieved without 

leaving free moisture on beans, but high relative 

humidity must be maintained to reduce excessive 

water loss (Boyette et al. 1994, Sargent 1995).

Optimum Storage Conditions

Snap beans should be stored at 5 to 7.5 °C (41 

to 46 °F) with 95 to 100% RH. At 5 to 7.5 °C 

(41 to 46 °F), a storage life of 8 to 12 days is 

expected. Good quality can be maintained for 

a few days at temperatures below 5 °C (41 °F), 

but chilling injury will be induced (see Chilling 

Sensitivity). Some chilling may occur even at the 

recommended storage temperature of 5 °C (41 °F) 

after 7 to 8 days, depending on cultivar. Quality 

rapidly decreases above 7.5 °C (46 °F) due to 

yellowing, seed development, and water loss. 

Waxed cartons and plastic film liners reduce water 

loss. The perishability and rates of water loss of 

immature beans are higher than for mature beans. 

Long beans have postharvest requirements similar 

to those of snap beans with similar responses to 

chilling (Zong et al. 1992).
231

Controlled Atmosphere (CA) 

Considerations

At recommended temperatures, 2 to 5% O2

reduces respiration (Saltveit 1997). Snap beans 

benefit from CO2

 levels between 3 and 10% with 

retention of color, reduced discoloration, and 

reduced decay on damaged beans (Cano et al. 

1997, Hardenburg et al. 1986, Trail et al. 1992). 

Higher CO2

 levels (20 to 30%) are used for short 

periods (for example, 24 h) but can cause off 

flavors (Costa et al. 1992).

Retail Outlet Display Considerations

Snap beans should not come in contact with ice 

or water, both of which can produce translucent, 

water-soaked areas on the pods. For the same 

reason, misting is not generally recommended 

unless the beans are seriously dehydrated.

Chilling Sensitivity

Snap and pod beans are chilling sensitive, 

and visual symptoms depend on the storage 

temperature. Below 5 °C (41 °F), chilling injury 

produces a general opaque discoloration of the 

entire bean. A less common symptom is pitting 

on the surface and increased water loss. Discrete 

rusty brown spots appear at 5 to 7.5 °C (41 to 46 

°F). These lesions are very susceptible to attack 

by common fungal pathogens. Beans can be held 

about 2 days at 1 °C (34 °F), 4 days at 2.5 °C 

(37 °F), and 6 to 10 days at 5 °C (41 °F) before 

chilling symptoms appear (Cantwell and Suslow 

2008). No discoloration occurs on beans stored at 

10 °C (50 °F), but undesirable seed development, 

water loss, and yellowing will occur. Different 

varieties differ substantially in susceptibility 

to chilling injury (Watada and Morris 1966b, 

Cantwell and Suslow 2008).

Freezing Injury

Freeze damage occurs at -0.7 °C (30.7 °F) or 

below and appears as water-soaked areas that 

subsequently deteriorate and decay.

Ethylene Production and Sensitivity

Beans produce only very low amounts of 

ethylene (less than 0.05 μL kg-1 h-1 at 5 °C or 41 

°F). Ethylene exposure greater than 0.1 μL L-1

promotes chlorophyll loss, increases browning, 

and reduces green bean storage life by 30 to 50% 

at 5 °C (41 °F ) (Wills and Kim 1996).

Respiration Rates

Beans are rapidly growing when harvested and 

have high respiration rates.

Temperature Snap beans Long beans

------mg CO2 kg-1 h-1------

0 °C 40 80

5 °C 66 90

10 °C 110 175

15 °C 170 374

20 °C 234 396

Snap bean data from Watada and Morris (1966a); 

long bean data from Zong et al. (1992).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

See Chilling Sensitivity.
232

Postharvest Pathology

Various decay organisms may attack fresh pod 

beans as a result of chilling injury, surface 

moisture, or mechanical damage. Common 

decay-causing fungi are those causing “nesting 

decays” (cottony leak caused by Pythium spp. and 

Rhizopus spp), gray mold (Botrytis cinerea), and 

watery soft rot (Sclerotinia spp.). Water-soaked 

spots may be due to lesions caused by bacterial 

infections (Pseudomonas spp. and Xanthomonas 

spp.) (Snowdon 1992).

Quarantine Issues

None. 

Suitability as Fresh-Cut Product

Beans are snipped to remove stems and tails for 

food service. Browning of the cut ends can be 

a problem, and high-CO2

 atmospheres retard 

discoloration.

Special Considerations

Extra careful and expedited postharvest handling 

are required for highly perishable, very fine 

French beans (haricot verts) to avoid physical 

damage and dehydration.

References

Boyette, M.D., J.R. Schultheis, E.A. Estes, 

and W.C. Hurst. 1994. Postharvest cooling and 

handling of green beans and field peas. Bull. AG413-8, North Carolina Cooperative Extension 

Service, Raleigh, NC.

Cano, M.P., M. Monreal, B. de Ancos, and R. 

Alique. 1997. Controlled atmosphere effects on 

chlorophylls and carotenoids changes in green 

beans (Phaseolus vulgaris L., cv. Perona). In

M.E. Saltveit, ed., 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, July 13-18, 1997, vol. 4, pp. 46-

52. University of California, Davis, CA.

Cantwell, M., and T. Suslow. 1998. Snap bean 

produce facts. Recommendations for maintaining 

postharvest quality. At http://postharvest.ucdavis.

edu/produce_information.

Costa, M.A.C., J.K. Brecht, S.A. Sargent, and D.J. 

Huber. 1994. Tolerance of snap beans to elevated 

CO2

 levels. Proceedings of the Annual Meeting of 

the Florida State Horticultural Society 107:271-

273.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Sargent, S.A. 1995. Optimizing packing and 

cooling methods for maintaining high quality snap 

beans. In G.J. Hochmuth and D.N. Maynard, eds., 

FACTS Proceedings, p. 8. University of Florida, 

Gainesville, FL.

Snowdon, A.L. 1992. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. CRC Press, Boca Raton, FL.

Trail, M.A., I.A. Wahem, and J.N. Bizri. 1992. 

Snap bean quality changed minimally when stored 

in low density polyolefin film package. J. Food 

Sci. 57:977-979.

Watada, A.E., and L.L. Morris. 1966a. Growth 

and respiration patterns of snap bean fruits. Plant 

Physiol. 42:757-761.
233

Watada, A.E., and L.L. Morris. 1966b. Effect of 

chilling and nonchilling temperatures on snap 

bean fruits. Proc. Amer. Soc. Hort. Sci. 89:368-

374.

Wills, R.B.H., and G.H. Kim. 1996. Effect of 

ethylene on postharvest quality of green beans. 

Aust. J. Exp. Agric. 36:335-337.

Zong, R.J., M. Cantwell, L. Morris, and V. 

Rubatzky. 1992. Postharvest studies on four fruittype Chinese vegetables. Acta Hort. 318:345-354.
234

Beet

Franciszek Adamicki

Adamicki is with the Department of Vegetable 

Storage, Research Institute of Vegetable Crops,

Skiermiewice, Poland.

Scientific Name and Introduction

Beta vulgaris L. Crassa group—table beet, or red 

beet—is a biennial of the Chenopodiaceae family. 

In the first year, it forms a fleshy storage root 

(enlarged hypocotyl) that is edible. In the early 

stages of plant development, the whole plant may 

be consumed. Beets are grown worldwide, the top 

producers being Germany, Poland, the Russian 

Federation, and the United States.

Quality Characteristics and Criteria

Quality criteria include root shape, root size 

(diameter), color, firmness (turgidity), smoothness, 

cleanness, trimming of rootlets, and freedom 

from defects. Intensive and uniform color with 

minimum zoning is the most important quality 

criterion.

Horticultural Maturity Indices

Fresh-market bunched beets (with tops) are 

harvested as early as 50 to 70 days after planting; 

whereas roots (without tops) are usually harvested 

later but before they reach full maturity, especially 

when they are intended for long-term storage.

Grades, Sizes, and Packaging

Grades U.S. No. 1 and U.S. No. 2 are based 

primarily on external appearance. Unless 

otherwise specified, the diameter of each beet 

shall not be less than 2.5 to 3.8 cm (1 to 1.5 in). 

Standard bunches shall be fairly uniform in size, 

and each bunch of beets shall not weigh less than 

0.5 kg (1.1 lb) and must contain at least 3 beets. 

Fresh-market bunches are packed in small crates 

of 10 to 15 kg (22 to 33 lb) capacity, whereas 

beets intended for storage are packed in 20 kg (44 

lb) polyethylene-lined crates or bins of 500 to 600 

kg (1,100 to 1,320 lb) capacity.

Precooling Conditions

Bunched beets should be precooled to below 4 °C 

(39 °F) within 4 to 6 h of harvest. Hydrocooling, 

forced-air cooling, and package icing are common 

cooling methods. Proper precooling and packaging 

retard subsequent discoloration of the leaves, 

weight loss, and decay. Mature harvested beets 

should be precooled within 24 h after harvest to 

below 5 °C (41 °F) with forced-air cooling.

Optimum Storage Conditions

Bunched beets can be kept for about 10 to 14 days 

at 0 °C (32 °F) and above 98% RH. Topped beets 

should be stored at 1 to 2 °C (33 to 36 °F) and 

98% RH. During storage at 0 to 1 °C (32 to 34 

°F), more black spot and rot occur than at higher 

temperatures (Schouten and Schaik 1980). Red 

beets can be in air-ventilated storage for 4 to 6 

mo and in mechanical refrigerated storage for as 

long as 8 to 10 mo. Before storage, beets should 

be topped and sorted to remove all diseased or 

mechanically damaged roots. Large roots keep 

much better than small ones because they lose 

water and shrivel more slowly.

Red beets can be stored in pits and trenches, 

especially where winter temperatures are low for 

prolonged periods. Insulation of pits (clamps) and 

trenches is needed to avoid injurious temperature 

fluctuations. The temperature in pits (clamps) and 

cellars should not drop below -0.5 °C (31 °F) or 

exceed 5 °C (41 °F) to minimize losses caused by 

freezing, sprouting, and rotting.
235

Controlled Atmosphere (CA) 

Considerations

There is little or no benefit from CA or MA 

storage of beet roots. Elevated levels of CO2

(over 5%) in the atmosphere may promote decay 

(Shipway 1968).

Retail Outlet Display Considerations

Bunched beets should be placed on refrigerated 

shelves at 3 to 5 °C (37 to 41 °F), and beet roots 

should be held below 10 °C (50 °F).

Chilling Sensitivity

Beet roots are not sensitive to chilling and should 

be stored in temperatures as low as possible 

without freezing.

Ethylene Production and Sensitivity

Beet roots produce very low amounts of ethylene, 

(<0.1 μL kg-1 h-1) and are not particularly sensitive 

to ethylene exposure.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 4 to 6

5 °C 10 to 12 

10 °C 16 to 20

15 °C 24 to 38

20 °C 50 to 70

Data from Uddin (1998).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Death of shoots and breakdown of the top part 

of roots are common problems during long-term 

storage at 0 oC (32 °F). Physiological disorders 

can appear quickly during subsequent shelf-life at 

20 oC (68 °F) after storage (Adamicki and Badełek 

1997).

Postharvest Pathology

The most common decay during storage is gray 

mold (Botrytis cinerea Pers.) (Robak and Wiech 

1998). Beet roots are also affected by black rot 

caused by Phoma betae Frank. Water-soaked and 

brown lesions become black and affect mostly the 

tip of the root. Good air circulation and optimal 

storage conditions retard development of black 

rot.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

No current potential.

References

Adamicki, F., and E. Badelek. 1997. The effect of 

temperature and size of roots on storage and shelflife of red beet. Research Report of the Research 

Institute of Vegetable Crops, pp. 10. The Ministry 

of Agriculture and Rural Development, Warsaw, 

Poland.

Elkner, K., E. Badełek, and F. Adamicki. 1997. 

The effect of cultivar and storage conditions on 

quality of red beet. Biuletyn Warzywniczy 46:65-

78. 
236

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Robak, J., and K. Wiech. 1998. Diseases and Pests 

of Vegetable Crops, pp. 352. Plantpress Sp. z.o.o., 

Krakow, Poland.

Ryall, A.L., and W.J. Lipton.1983. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, 2nd ed. AVI Publishing Co., 

Westport, CT.

Schouten, S.P., and A.C.R. Schaik. 1980. Storage 

of red beets. Acta Hort. 116:25-29.

Shipway, M.R. 1968. Refrigerated Storage of Fruit 

and Vegetables. Ministry of Agriculture, Fisheries 

and Food, London, U.K.

Thompson, A.K. 1998. Controlled Atmosphere 

Storage of Fruits and Vegetables. CAB Intl., 

Wallingford, U.K.

Uddin, N. 1998. Fruit and vegetable storage and 

transport database. At http://www.postharvest.

com.au/beetroot.pdf.

Zwart-Roodzant, M.H., P.S. Hak, C.F.G. Kramer, 

et al. 1990. Long term bulk storage of red beets in 

forced ventilated clamps in comparison with long 

term storage in mechanical cooling. Acta. Hort. 

267:163-168.
237

Blackberry

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, N.C. Campus, Kannapolis, NC.

Scientific Name and Introduction

Blackberry (Rubus sp.) is a member of the 

Rosaceae family and is grown as a perennial 

crop. Soft and juicy, blackberries are compound 

fruits made up of many drupelets and attached to 

a receptacle. The fruit detaches from the pedicel 

and the receptacle remains fleshy and firmly 

attached to the drupelets. The commercially 

important cultivars are ‘Chester Thornless,’ 

‘Triple Crown,’ ‘Kotata,’ ‘Shawnee,’ ‘Navaho,’ 

‘Kiowa,’ ‘Brazos,’ ‘Thornless Evergreen,’ and 

‘Arapaho.’ Blackberries are widely grown in the 

South Central and Northwestern United States 

and are found as three plant types. Trailing 

blackberries and dewberries are thorny and must 

be trellised. Semierect blackberries are generally 

thornless and have long, trailing lateral branches. 

Erect blackberries can be found as thorny or 

thornless cultivars and have upright growth with 

lateral branches that remain upright. Blackberryraspberry hybrids include tayberry, loganberry, 

youngberry, and boysenberry (Jennings 1988).

Quality Characteristics and Criteria

High-quality blackberries are free of injury, decay, 

calyxes (caps), and sunscald. They are fully black 

in color, appear and feel turgid, and are of regular 

shape. To meet U.S. No. 1 grade standards, no 

more than 1% of the lot can be affected by mold 

or decay and no more than 5% can have other 

serious damage.

Horticultural Maturity Indices

For the fresh market, blackberry maturity can 

be determined by fruit color, gloss, and ease 

of detachment. Fully black berries should pull 

easily from the pedicel yet be firm, not mushy. 

Blackberries lose acidity with ripening and are 

quite astringent if harvested partially colored. 

Some varieties (for example, ‘Chester Thornless’) 

must be harvested only when fruit are dull black; 

otherwise they are too acid to eat.

Grades, Sizes, and Packaging

Generally, containers of 1 to 2 pints are used, but 

1-quart containers occasionally are used. The most 

common packaging is vented plastic “clamshell” 

boxes packed in units of 12 per carton.

Precooling Conditions

Forced-air cooling to 5 oC within 4 h is 

recommended for best shelf-life. Blackberries 

should be shipped with refrigeration at 

temperatures under 5 oC. A similar protocol is 

used for fruit destined for processing and fruit 

processed within 24 h of harvest.

Optimum Storage Conditions

Blackberries can be held 2 to 14 days, depending 

on cultivar, at -0.5 to 0 oC (31 to 32 oF), with 

higher than 90% RH.

Controlled Atmosphere (CA) 

Considerations

Blackberries benefit from 10 to 20% CO2

 + 5 to 

10% O2

 to reduce decay and softening (Kader 

1997).
238

Retail Outlet Display Conditions

Blackberries should be stored and displayed at the 

coldest refrigeration temperature possible and with 

no mist. As little as 1 day at room temperature can 

stimulate growth of gray mold.

Chilling Sensitivity

Blackberries are not known to be chilling 

sensitive. 

Ethylene Production and Sensitivity

Stimulation of Botrytis cinerea (gray mold) 

growth can occur on blackberries in the presence 

of ethylene. Ethylene production by blackberries 

is widely variable by cultivar and can be as 

little as 0.1 μL kg-1 h-1 or as high as 2 μL kg-1 h-1

(Burdon and Sexton 1993).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 oC 18 to 20

4 to 5 oC 31 to 41

10 oC 62

15 to 16 oC 75

20 oC 100 to 130

Data from Perkins-Veazie et al. (1996) for 

‘Navaho,’ ‘Shawnee,’ and ‘Choctaw’ at 20 oC (68 

°F) and from Robinson et al. (1975) for ‘Bedford 

Giant’ at other temperatures.

To get mL kg-1 h-1, divide the mg kg-1 h-1 rate by 

2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 

at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

The major disorders are red drupelet disorder 

(areas of red drupelets on fully ripe berry), weight 

loss (shrivel), and leakers (berries with leakage of 

juice) (Perkins-Veazie et al. 1996, Mitcham et al. 

1998).

Postharvest Pathology

The most common postharvest diseases are gray 

mold (Botrytis cinerea) and rhizopus rot (Rhizopus 

stolonifer) (Jennings 1988, Ellis et al. 1991).

Quarantine Issues

No known issues.

Suitability as Fresh-Cut Product

Blackberries are incorporated into fruit cups and 

fruit plates.

Special Considerations

Blackberries are easily damaged. They can 

develop red areas after storage, which may be 

due to loss of pigment from water contact or from 

cultivar-dependent red drupelet disorder.

References

Burdon, J.N., and R. Sexton. 1993. Fruit 

abscission and ethylene production of four 

blackberry cultivars (Rubus spp.). Ann. Appl. Biol. 

123:121-123.

Ellis, M.A., R.H. Converse, R.N. Williams, and B. 

Williamson, eds. 1991. Compendium of Raspberry 

and Blackberry Diseases and Insects. APS Press, 

St. Paul, MN.

Jennings, D.L. 1988. Raspberries and 

Blackberries: Their Breeding, Diseases, and 

Growth. Academic Press, New York, NY.

Kader, A.A. 1997. A summary of CA requirements 

and recommendations for fruits other than apples 

and pears. In A.A. Kader, ed., 7th International 
239

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 3, pp. 1-34. University of California, Davis, 

CA.

Mitcham, E.J., C.H. Crisosto, and A.A. Kader. 

1998. Bushberries in fresh produce facts. At http://

postharvest.ucdavis.edu/produce_information.

Perkins-Veazie, P.M., J.K. Collins, and J.R. Clark. 

1996. Cultivar and maturity affect postharvest 

quality of fruit from erect blackberries. 

HortScience 31:258-261.

Robinson, J.E., K.M. Browne, and W.G. Burton. 

1975. Storage characteristics of some vegetables 

and soft fruits. Ann. Appl. Biol. 81:399-408.
240

Blueberry

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, N.C. Campus, Kannapolis, NC.

Scientific Name and Introduction

Blueberries (Vaccinium sp.) are a member of the 

heath family (Ericaceae) grown as a perennial 

crop. Blueberries have a blue to blue-black 

epidermis or skin that is covered by a waxy 

bloom, giving the fruit a light-blue appearance. 

The flesh is juicy and creamy white to green in 

color. Blueberries of commercial importance 

include the lowbush (V. angustifolium Ait.), 

northern (V. corymbosum L.), southern highbush 

(hybrids of V. corymbosum, V. ashei, and V. 

darrowi Camp.), and rabbiteye (V. ashei Reade). 

Lowbush blueberries are much smaller (less than 

1 g) than highbush types and are prized for their 

use in processed products such as pie and pastry 

fillings, pancakes, muffins, jams, and sauces. 

Northern highbush berries are grown primarily 

in the northern tier of the United States and 

require 600 to 1,000 h of chilling below 7 °C 

(45 °F) (Pritts 1992). Southern highbush berries 

require fewer chill hours and can lose fruit to 

frost damage if grown in areas where spring 

temperatures drop below 0 °C (32 °F) during 

bloom and early fruit set. Rabbiteye blueberries 

are hardy only in the Southern United States or 

where winter temperatures remain above 10 °C 

(50 °F). These berries often have a gritty mouth 

feel from seeds and stone cells and lack a welldeveloped calyx but have a longer shelf-life and 

more pigment than highbush berries.

Quality Characteristics and Criteria

High-quality blueberries are free of injury, decay, 

and sunscald. They are are fully blue in color, with 

little or no red at the stem end, and appear and feel 

turgid.

Horticultural Maturity Indices

For fresh market, fruit should be fully blue and 

firm.

Grades, Sizes, and Packaging

Highbush blueberries are graded as U.S. No. 1 or 

are unclassified. Size can be used in connection 

with grade: extra large is fewer than 90 berries 

per cup (250 mL), large is 90 to 129 berries per 

cup, medium is 130 to 189 berries per cup, and 

small is 190 to 250 berries per cup (AMS 1966). 

Blueberries are packaged as 1- or 2-pint units, 

usually in polyethylene or polystyrene-ventilated 

clamshells, and sold as 12-unit trays.

Precooling Conditions

Blueberries for fresh market should be forcedair cooled to under 10 oC (50 °F), graded, then 

maintained under refrigeration at 0 to 3 °C (32 

to 37 °F) within an hour after harvest to remove 

field heat and extend storage life. Precooling to 

5 oC (41 °F) can cause condensation problems 

in lowbush blueberries when packed at ambient 

temperatures but should be incorporated when 

delays between picking and packing exceed 21 h 

(Jackson et al. 1999).

Optimum Storage Conditions

Blueberries should be held at -0.5 to 0 oC (31 to 

32 oF) and at above 90% RH for up to 2 weeks 

for lowbush, northern highbush, and southern 

highbush (Perkins-Veazie et al. 1995, Jackson et 

al. 1999) and up to 4 weeks for rabbiteye (Miller 

et al. 1988).
241

Controlled Atmosphere (CA) 

Considerations

Rabbiteye, highbush, and lowbush blueberries 

benefit from 10 to 15% CO2

 + 1 to 10% O2 when 

held at or below 5 oC (41 °F) (Smittle and Miller 

1988, Prange et al. 1995). Firmness and total 

acidity were maintained and decay decreased with 

a shelf-life up to 6 weeks.

Retail Outlet Display Considerations

Blueberries should be stored and displayed under 

refrigeration with temperatures as close to 0 °C 

(32 °F) as possible.

Chilling Sensitivity

Blueberries are not known to be chilling sensitive. 

Ethylene Production and Sensitivity

Botrytis cinerea (gray mold) growth can be 

stimulated on blueberries in the presence of 

ethylene. Ethylene production ranges from 0.5 to 

2 μL kg-1 h-1 for northern highbush, varying with 

year and cultivar (Suzuki et al. 1997), to 10 μL 

kg-1 h-1 for rabbiteye blueberry (El-Agamy et al. 

1982)

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 oC 2 to 10

4 to 5 oC 9 to 12

10 oC 23 to 35

15 to 16 oC 34 to 62

20 to 21 oC 52 to 87

25 to 27 oC 78 to 124

To get mL kg-1 h-1, divide the mg kg-1 h-1 rate by 

2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 

at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

The major disorders are shrivel (water loss), 

sunscald, and fruit cracking.

Postharvest Pathology

Blueberries are susceptible to Botrytis 

cinerea (gray mold) and anthracnose (ripe rot, 

Colletotrichum gloesosporiodes) (Milholland 

1995). At temperatures above 10 oC (50 °F), 

Rhizopus stolonifer can grow readily in fruit 

packs.

Quarantine Issues

Blueberry maggot (Rhagoletis mendax Curran) is 

the primary postharvest pest limiting shipments 

of unfumigated blueberries to Canada and States 

west of the Rockies. Methyl bromide is currently 

the only USDA-approved method of postharvest 

control. Plum cucurlico (Conotrachelus nenuphar

[Herbst]) and blueberry maggot are quarantine 

pests for shipments to Japan (Guy Hallman, 2000, 

personal communication).

Suitability as Fresh-Cut Product

Fruit can be incorporated into fruit cups and 

prepared fruit trays.

Special Considerations

Bruising caused by improper handling or 

mechanical harvesting reduces the storage life 

of fresh fruit. Mechanical harvesting can reduce 

fruit storage life by half compared with hand 

harvesting.

Acknowledgments

Some of the information in this chapter was from 

the Produce Marketing Association’s “Fresh 

Produce Manual” and the University of California, 
242

Davis, website “Fresh Produce Facts” at http://

postharvest.ucdavis.edu/produce_information. 

References

AMS [USDA Agricultural Marketing Service]. 

1966. United States Standards for Grades of 

Blueberries. U.S. Government Printing Office, 

Washington, DC.

El-Agamy, S.Z.A., M.M. Aly, and R.H. Biggs. 

1982. Fruit maturity as related to ethylene in 

‘Delite’ blueberry. Proceedings of the Annual 

Meeting of the Florida State Horticultural Society 

95:245-246.

Jackson, E.D., K.A. Sanford, R.A. Lawrence, 

et al. 1999. Lowbush blueberry quality changes 

in response to prepacking delays and holding 

temperatures. Postharv. Biol. Technol. 15:117-126.

Kaufman, D. 1992. Harvesting and handling 

blueberries. In M. Pritts and J. Hancock, 

eds., Highbush Blueberry Production Guide. 

NRAES-55, Cooperative Extension Service, 

Ithaca, NY.

Miller, W.R., R.E. McDonald, and T.E. Crocker. 

1988. Fruit quality of rabbiteye blueberries as 

influenced by weekly harvests, cultivars, and 

storage duration. HortScience 23:182-184.

Milholland, R.D. 1995. Anthracnose fruit rot 

(ripe rot). In F. Caruso and D. Ramsdell, eds., 

Compendium of Blueberry and Cranberry 

Diseases, pp. 17. American Phytopathological 

Society, St. Paul, MN.

Perkins-Veazie, P., J.R. Clark, J.K. Collins, and J. 

Magee. 1995. Southern highbush blueberry clones 

differ in postharvest fruit quality. Fruit Var. J. 

49:46-52.

Prange, R.K., S.K. Asiedu, J.R. DeEll, and 

A.R. Westgarth. 1995. Quality of Fundy and 

Blomidon lowbush blueberries: effects of storage 

atmosphere, duration and fungal inoculation. Can. 

J. Plant Sci. 75:479-483.

Pritts, M.P. 1992. Site selection and preparation. 

In M. Pritts and J. Hancock, eds., Highbush 

Blueberry Production Guide. NRAES-55, 

Cooperative Extension Service, Ithaca, NY.

Smittle, D.A., and W.R. Miller. 1988. Rabbiteye 

blueberry storage-life and fruit quality in 

controlled atmospheres and air storage. J. Amer. 

Soc. Hort. Sci. 113:723-728.

Suzuki, A., T. Kikuchi, and K. Aoba. 1997. 

Changes of ethylene evolution, ACC content, 

ethylene forming enzyme activity and respiration 

in fruits of highbush blueberry. J. Japan. Soc. 

Hort. Sci. 66:23-27.
243

Bok Choy

Yaguang Luo

Luo is with the Food Quality Laboratory, Henry A. 

Wallace Beltsville Agricultural Research Center, 

Agricultural Research Service, U.S. Department 

of Agriculture, Beltsville, MD.

Scientific Name and Introduction

Bok choy (Brassica campestris L. ssp. chinensis)

is also known as Chinese chard, boy-toyo, pakchoy, and pak-tsoi (King 1989). Bok choy is a 

nonheading type of Chinese cabbage (Li 1981). It 

is an annual in the Cruciferae family. The edible 

portions are the shiny, dark green leaves and the 

thick, chalk-white stalks (Peirce 1987). Most U.S. 

bok choy is produced in California.

Quality Characteristics and Maturity 

Indices

High-quality bok choy has thick, fleshy, firm 

stalks and glossy, dark-green leaves. Bok choy 

with bruised or slimy spots and wilted leaves 

should be avoided.

Grades, Sizes, and Packaging

Bok choy is mainly supplied to ethnic markets in 

the United States, but many large supermarkets 

are carrying it in their “ethnic” fresh produce 

departments. There are no standard U.S. grades.

Precooling Conditions

Prompt precooling to near 0 °C (32 °F) is 

important to maintain freshness and for extended 

storage. 

Optimum Storage Conditions

The recommended storage conditions for bok 

choy are 0 to 5 °C (32 to 41 °F) with higher than 

95% RH.

Controlled Atmosphere (CA) 

Considerations

Low-O2

 atmospheres of 0.5 to 1.5% retard leaf 

yellowing caused by chlorophyll degradation 

(O’Hare et al. 1995). A combination of 5% CO2

+ 3% O2

 delays leaf yellowing and senescence 

during storage (Wang and Herner 1989).

Retail Outlet Display Considerations

Bok choy is displayed loosely on refrigerated 

shelves. Misting should be done to minimize 

moisture loss and wilting. 

Chilling Sensitivity

Bok choy is not chilling sensitive and should be 

stored as cold as possible without freezing. It 

freezes at -0.5 °C (31 °F). 

Ethylene Production and Sensitivity

Bok choy produces very small amounts of 

ethylene, 0.1 to 0.2 μL kg-1 h-1, and is not overly 

sensitive to ethylene.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 5 to 6

5 °C 10 to 12

10 °C 19 to 21

15 °C 34 to 44

20 °C 48 to 63

Data from Luo and Zheng (2001).
244

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders and Postharvest 

Pathology

Leaf yellowing indicates that senescence has 

occurred during extended storage or storage at 

higher than optimal storage temperatures. Storing 

bok choy at 0 to 5 °C (32 to 41 °F) will mitigate 

this problem. 

Quarantine Issues

None.

Suitability as Fresh-Cut Product

No current potential. 

References 

King, J. 1989. Consumers learning new names: 

bok choy to jicama. Farmline, vol. 10, pp. 11-13. 

Li, C.W. 1981. The origin, evolution, taxonomy 

and hybridization of Chinese cabbage. In N.S. 

Talekar and T.D. Griggs, eds., Chinese Cabbage, 

pp. 1-10. Hong Wen Printing Works, Tainan, 

People’s Republic of China.

Luo, Y., and Y. Zheng. 2001. Respiration rate 

and ethylene production of bok choy at different 

temperature regime. Unpublished data.

O’Hare, T.J, L.G. Smith, L.S. Wong, and G.F. 

Meiburg. 1995. Low-oxygen storage of whole 

and minimally processed pak choi. Australasian 

Postharvest Horticulture Conference, pp. 459-462.

Peirce, L.C. 1987. Vegetables: Characteristics, 

Production, and Marketing. John Wiley & Sons, 

New York, NY.

Wang, H., and R.C. Herner. 1989. Effect of CA 

storage on the ultrastructure of chloroplasts and 

chlorophyll content of Chinese mustard. In E. 

Kupferman, and M. Patterson, eds., Proceedings 

of the 5th International Controlled Atmosphere 

Research Conference, vol. 2, pp. 9-17. Wenatchee, 

WA.
245

Breadfruit

Robert E. Paull and Nancy Jung Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

The tropical breadfruit (Artocarpus altilis

[Parkins] Fosb.) develops from the whole 

inflorescence and is normally round, sometimes 

cylindrical, 15 to 30 cm (6 to 12 in) in diameter, 

and weighs from 0.5 to 3 kg (1.1 to 6.6 lb) 

(Nakasone and Paull 1998). The fruit receptacle 

(core) is surrounded by a pale yellow-white, 

edible pulp that is covered by a yellowish green, 

thin, reticulated skin. Most varieties are seedless 

(Ragone 1991). Seeded varieties have from 10 

to 150, 2.5-cm-long (1-in-long) brown seeds 

(Bennett and Nozzolillo 1987). The tropical 

breadfruit is widely grown in tropical areas.

Quality Characteristics and Criteria

Fruit must be physiologically mature, have green 

skin and firm flesh with uniform shape, and be 

free from decay, sunscald, cracks, bruises, and 

mechanical damage.

Horticultural Maturity Indices

Fruit at different growth stages are harvested for 

different uses. Mature green fruit are harvested as 

a starch vegetable, while some people prefer to eat 

the ripe sweet fruit. Harvested green fruit produce 

copious latex, especially from the cut peduncle 

and injuries on the fruit. Maturity is indicated by 

larger size, a slight change in the skin color to a 

yellowish green, small drops of latex on the rind, 

firm flesh texture, and the segments appearing 

more rounded and smoother than less mature 

fruit. As the fruit starts to ripen, the skin changes 

to a yellowish green. Latex should be allowed to 

drain from the fruit after harvest before washing in 

water to avoid latex stain.

Grades, Sizes, and Packaging

There are no U.S. or international grade standards. 

Fruit are graded according to size and various 

counts per fiberboard carton containing 9 to 18 

kg (20 to 40 lb). Fruit are sold on a weight basis. 

Telescoping two-piece fiberboard cartons are 

generally used for packaging. One-piece cartons 

having dividers to minimize fruit movement and 

rubbing also are used.

Precooling Conditions

Cool and ship fruit as soon as possible after 

harvest. Room cooling to 12 oC (54 oF) is 

generally used. Do not use hydrocooling as it 

leads to skin browning.

Optimum Storage Conditions

Store at 12 to 14 oC (54 to 57 oF) and 90 to 95% 

RH for a maximum of about 20 days.

Controlled Atmosphere (CA) 

Considerations

Film-wrapping delays softening and skin 

discoloration of breadfruit stored at 13 oC (55 

oF) (Thompson et al. 1974). The O2

 levels in 

film-wrapped fruit were less than 5% (Worrell 

and Carrington 1997), while CO2

 rose to 10 to 

30% (Worrell and Carrington 1997). CA studies 

indicated that at 12 oC (54 oF), the best storage 

atmosphere is 2 to 5% O2

 and 5% CO2 for up to 3 

weeks (Ramlochan 1991).

Retail Outlet Display Considerations

Display at 12 to 14 oC (54 to 57 oF). Do not mist.
246

Chilling Sensitivity

Long-term storage is not possible. At 12 oC (54 

oF), chilling injury symptoms begin to develop 

within 7 days (Marriott et al. 1979). Symptoms are 

a brown, scaldlike discoloration of the skin, failure 

to fully soften, poor flavor development, and an 

increase in decay.

Ethylene Production and Sensitivity

Early-maturing fruit have a production rate of 

1.0 to 1.5 μL kg-1 h-1 and late-maturing fruit, 0.7 

to 1.2 μL kg-1 h-1 (Worrell and Carrington 1997). 

Breadfruit are sensitive to ethylene exposure, 

which leads to rapid ripening.

Respiration Rates

Temperature mg CO2 kg-1 h-1

13 oC 94 to 564

25 oC 362 to 597

Data from Worrell and Carrington (1997) and 

Worrell et al. (1998).

To get mL kg-1 h-1, divide the mg kg-1 h-1 rate by 

2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 

at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day..

Physiological Disorders

Mechanical injury leads to rapid deterioration, 

possibly due to wound ethylene inducing 

premature and more rapid ripening. No other 

disorders have been reported (Worrell and 

Carrington 1997).

Postharvest Pathology

Fruit rot due to Phytophthora palmivora and pink 

disease (Botryobasidium salmonicola) have been 

reported (Salunke and Desai 1984). Purseglove 

(1968) reported a fruit rot caused by Rhizopus 

artocarpi in India.

Quarantine Issues

Breadfruit is a fruit fly host and has been 

successfully treated by vapor heat treatment and 

irradiation.

Suitability as Fresh-Cut Product

Possibly, but no products have yet been 

developed.

Special Considerations

Fruit can be boiled, dried, used in breadmaking, 

or fermented. Slices can be fried or stored in brine 

(Whitney 1988, Bates et al. 1991). The sweet ripe 

fruit is eaten as a dessert. The cooked seeds are 

also eaten.

References

Bates, R.P., H.D. Graham, R.F. Matthews, and 

L.R. Clos. 1991. Breadfruit chips: preparation, 

stability, and acceptability. J. Food Sci. 56:1608-

1610.

Bennett, F.D., and C. Nozzolillo. 1987. How many 

seeds in a seeded breadfruit. Econ. Bot. 41:370-

374.

Marriot, J., C. Perkins, and B.D. Been. 1979. 

Some factors affecting the storage of fresh 

breadfruit. Sci. Hort. 10:177-181.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Purseglove, J.W. 1968. Tropical Crops. 

Dicotyledons. Longman, London, U.K.
247

Ragone, D. 1991. Ethnobotany of breadfruit in 

Polynesia. In P.A. Cox and S.A. Banack, eds., 

Islands, Plants, and Polynesians—An Introduction 

to Polynesian Ethnobotany, pp. 203-220. 

Dioscorides Press, Portland, OR.

Ramlochan, R. 1991. Transient Cooling and 

Storage of Breadfruit in Refrigerated and 

Controlled Atmosphere Environment. Thesis, 

University of the West Indies, St. Augustine, 

Trinidad.

Salunke, D.K., and B.B. Desai. 1984. Postharvest 

Biotechnology of Fruits. Vol 2. CRC Press, Boca 

Raton, FL.

Thompson, A.K., B.O. Been, and C. Perkins. 

1974. Storage of fresh breadfruit. Trop. Agric. 

51:407-415.

Whitney, P.J. 1988. The microbiology of 

breadfruit and cassava preservation by pit 

fermentation. Trop. Sci. 28:43-50.

Worrell, D.B., and C.M. Carrington. 1997. 

Breadfruit. In S.K. Mitra, ed., Postharvest 

Physiology and Storage of Tropical and 

Subtropical Fruits, pp. 347-363. CAB Intl., 

Wallingford, U.K.

Worrell, D.B., C.M. Carrington, and D.J. Huber. 

1998. Growth, maturation and ripening of 

breadfruit, Artocarpus altilis (Park.) Fosb. Sci. 

Hort. 76:17-28. 
248

Broccoli

Peter M.A. Toivonen and Charles Forney

Toivenen is with Pacific Agri-Food Research 

Centre, Agriculture and Agri-Food Canada, 

Summerland, British Columbia, Canada; Forney 

is with Atlantic Food and Horticultural Research 

Centre, Agriculture and Agri-Food Canada, 

Kentville, Nova Scotia, Canada.

Scientific Name and Introduction

Brassica oleracea L., Italica group, also known 

as broccoli, calabrese, or sprouting broccoli, is a 

native of southern Europe and a member of the 

Brassicaceae (Cruciferae) family. The crop is 

annual and grows to maturity in about 75 to 95 

days, depending on cultivar, season, and planting 

date. The whole immature influorescence (head) is 

the edible portion, with the floret tissue most often 

preferred by consumers. It grows best in cool 

climates and is available year-round from many 

areas of North America, though a large portion is 

grown in California.

Quality Characteristics and Criteria

High-quality broccoli is either a dark or bright 

green with closed flower buds (termed “beads”). 

The head should be firm to hand pressure 

and compact, and the stalk cleanly cut to the 

appropriate length for a particular grade standard 

or for “crowns” (dissected portions of the whole 

influorescence).

Horticultural Maturity Indices

Ideal maturity is based on head diameter, 

compactness, and tightly closed flowers (beads). 

Overmature heads are characterized by open 

flower buds or enlarged buds on the verge of 

opening, resulting in a loose head.

Grades, Sizes, and Packaging

There are three grades: U.S. Fancy, U.S. No. 

1, and U.S. No. 2. They are based on external 

appearance, level of damage, trimming, and stalk 

diameter (AMS 1943). Two or three heads are 

normally bunched together for the fresh market. 

Such bunches are packed 14 to 18 units in waxed 

cardboard boxes and weigh approximately 10 kg 

(21 lb) (Boyette et al. 1996). Larger heads may 

have the stem trimmed to produce “crowns,” 

and these are packed loose in 9 kg (20 lb) boxes. 

Individual florets are also cut and packed in 2.5 to 

5 kg (5.5 and 11 lb) film bags for hotel, restaurant, 

and institutional use.

Precooling Conditions

Field-packed broccoli is commonly cooled by 

injecting liquid ice into waxed cartons (Cantwell 

and Suslow 1999). Ice maintains the proper 

temperature and RH for transport and distribution. 

Hydrocooling and forced-air cooling are also 

options, but good temperature management is 

required during transport (Cantwell and Suslow 

1999).

Optimum Storage Conditions

Broccoli can be kept in excellent condition for 2 

to 3 weeks at 0 oC (32 oF) with 98 to 100% RH. 

Package icing is required if storage or transport 

conditions cannot maintain the recommended 

temperature or RH (Shewfelt et al. 1983). Use 

of ice is not necessary if temperature can be 

maintained (Kleiber et al. 1993). Perforated plastic 

film packaging is recommended to minimize 

wilting (Toivonen 1997). Loss of quality during 

prolonged storage is caused by wilting, yellowing 

of buds and leaves, loosening or opening of buds, 

and decay.
249

Controlled Atmosphere (CA) 

Considerations

The recommended CA for broccoli is 1 to 2% 

O2

 and 5 to 10% CO2 at 0 to 5 °C (32 to 41 °F) 

(Makhlouf et al. 1989, Cantwell and Suslow 

1999). Optimal CA conditions can double storage 

life, especially when broccoli is held above 

optimum temperatures. However, if O2

 drops to 

below 1% in storage, there is a risk of off odors

caused by the generation of sulfur-containing 

volatiles (Forney et al. 1991). High rates of air 

exchange are recommended in shipping containers 

to avoid accumulation of off odors. Modified 

atmosphere packaging systems generally maintain 

both O2

 and CO2 at 10% to prevent accumulation 

of off odors.

Retail Outlet Display Considerations

Bottom-icing of the refrigerated display will 

prolong shelf-life (Perrin and Gaye 1986). Misting 

of the refrigerated display will also prolong shelflife and preserve quality (Barth et al. 1992).

Chilling Sensitivity

Broccoli is not sensitive to chilling and should be 

stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Broccoli produces very little ethylene, <0.1 

μL kg-1 h-1 at 20 oC (68 oF), but it is extremely 

sensitive to ethylene, with floret yellowing being 

the most prevalent symptom. Exposure to ethylene 

at 2 μL L-1 at 10 oC (50 °F) halves shelf-life 

(Cantwell and Suslow 1999). 

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 20 to 22

5 °C 32 to 36

10 °C 76 to 86

15 °C 160 to 180

20 °C 280 to 320

Data from Cantwell and Suslow (1999).

Respiration rates for cut florets are slightly higher 

(Izumi et al. 1996). 

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Bead (bud) yellowing may occur in overmature 

broccoli when stored at higher-than-optimal 

temperatures or in response to exposure to 

ethylene. Presence of yellow beads ends the 

commercial marketability of broccoli. There 

is sometimes confusion between senescenceassociated yellow bead and yellow-to-light-green 

marginal areas of floret that occur due to shading 

by adjacent floret tissue. This is normal for tissue 

that is not exposed to light during head growth 

(Cantwell and Suslow 1999). A disorder called 

black speck on stems occurs in stored broccoli, 

and certain cultivars are more sensitive than others 

(DeEll and Toivonen 1998).

Postharvest Pathology

Grey mold rot (Botrytis cinerea Pers.:Fr.) is the 

most commonly reported mold in shipped broccoli 

(Ceponis et al. 1987). Erwinia carotovora (Jones) 

Bergey et al. and Pseudomonas spp. bacterial head 

rots are found on shipped and stored broccoli. 

Injury to the bead tissue during handling may 

enhance development of these rots (Liao and 

Wells 1987). While Erwinia carotovora decay 

seldom develops below 5 °C (41 °F), decay caused 
250

by Pseudomonas spp. can be severe (Liao and 

Wells 1987) since it grows relatively well even 

at low storage temperatures (Brocklehurst and 

Lund 1981). A few cultivars of broccoli have been 

identified with some resistance to Pseudomonas

spp. (Canaday et al. 1991).

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Broccoli is commonly converted to fresh-cut floret 

products. Stems are also shredded into a packaged 

coleslaw-type product. 

Special Considerations

Some cultivars have greater storage life potential 

than others (Cantwell and Suslow 1999). If 

long-distance shipping or storage is integral to 

a marketing strategy, then consideration should 

be made for appropriate cultivar selection, 

especially if controlled atmospheres are not 

being used. Freezing injury may occur during 

liquid-ice cooling if excessive salt is used in the 

slurry mixture or if the broccoli is stored below 

-1 oC (30 oF). Thawed buds will be very dark and 

translucent and can later turn brown or may serve 

as sites for development of bacterial decay. Rough 

handling during harvest and packing can damage 

floret tissue and lead to increased levels of decay. 

Hot-water dips prolong shelf-life (Forney 1995).

References

AMS [USDA Agricultural Marketing Service]. 

1943. United States Standards for Grades of 

Bunched Italian Sprouting Broccoli. At http://

www.ams.usda.gov/AMSv1.0/standards.

Barth, M.M., A.K. Perry, S.J. Schmidt, and B.P. 

Klein. 1992. Misting affects market quality and 

enzyme activity of broccoli during retail storage. 

J. Food Sci. 57:954-957.

Boyette, M.D., D.C. Sanders, and G.A. Rutledge. 

1996. Packaging requirements for fresh fruits and 

vegetables. At http://www.bae.ncsu.edu/programs/

extension/publicat/postharv/ag-414-8/index.html.

Brocklehurst, T.F., and B.M. Lund. 1981. 

Properties of pseudomonads causing spoilage of 

vegetables stored at low temperature. J. Appl. 

Bacteriol. 50:259-266.

Canaday, C.H., J.E. Wyatt, and J.A. Mullins. 1991. 

Resistance in broccoli to bacterial soft rot caused 

by Pseudomonas marginalis and fluorescent 

Pseudomonas species. Plant Dis. 75:715-720.

Cantwell, M., and T. Suslow. 1999. Broccoli: 

recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.

Ceponis, M.J., R.A. Cappellini, and G.W. 

Lightner. 1987. Disorders in cabbage, bunched 

broccoli, and cauliflower shipments to the New 

York market, 1972-1985. Plant Dis. 71:1151-1154.

DeEll, J., and P. Toivonen. 1998. Characterization 

and control of black speck in broccoli. Agriculture 

and Agri-Food Canada, Horticulture Research and 

Development Centre Research Summary 1997/98, 

p. 9. Agriculture and Agri-Food Canada, Quebec, 

Canada.

Forney, C.F. 1995. Hot-water dips extend the 

shelf-life of fresh broccoli. HortScience 30:1054-

1057.

Forney, C.F., J.P. Mattheis, and R.K. Austin. 

1991. Volatile compounds produced by broccoli 

under anaerobic conditions. J. Agric. Food Chem. 

39:2257-2259.
251

Gillies, S.L., and P.M.A. Toivonen. 1995. Cooling 

method influences the postharvest quality of 

broccoli. HortScience 30:313-315.

Izumi, H., A.E. Watada, and W. Douglas. 1996. 

Optimum O2

 or CO2 atmosphere for storing 

broccoli florets at various temperatures. J. Amer. 

Soc. Hort. Sci. 121:127-131.

Kleiber, A., L. Jewell, and N. Simbeya. 1993. 

Ice or and ice-replacement agent does not 

improve refrigerated broccoli storage at 1 oC. 

HortTechnology 3:317-318.

Liao, C.H., and J.M. Wells. 1987. Diversity of 

pectolytic, fluorescent pseudomonads causing 

soft rots of fresh vegetables at produce markets. 

Phytopathology 77:673-677.

Makhlouf, J., F. Castaigne, J. Arul, et al. 1989. 

Long-term storage of broccoli under controlled 

atmosphere. HortScience 24:637-639.

Perrin, P.W., and M.M. Gaye. 1986. Effect of 

simulated retail display and overnight storage 

treatments on quality maintenance in fresh 

broccoli. J. Food Sci. 51:146- 149.

Shewfelt, R.L., K.M. Batal, and E.K. 

Heaton. 1983. Broccoli storage: effect of N6-

benzyladenine, packaging, and icing on color of 

fresh broccoli. J. Food Sci. 48:1594-1597.

Toivonen, P.M.A. 1997. The effects of storage 

temperature, storage duration, hydro-cooling, and 

micro-perforated wrap on shelf-life of broccoli 

(Brassica oleracea L., Italica Group). Postharv. 

Biol. Technol. 10:59-65.
252

Brussels Sprouts

Charles Forney and Peter M.A. Toivonen

Forney is with Atlantic Food and Horticulture 

Research Centre, Agriculture and Agri-Food 

Canada, Kentville, Nova Scotia, Canada; 

Toivonen is with Pacific Agri-Food Research 

Centre, Agriculture and Agri-Food Canada, 

Summerland, British Columbia, Canada.

Scientific Name and Introduction

Brassica oleracea L., Gemmifera group, also 

known as brussels sprouts, is a tall-stemmed 

cabbage in which the axillary buds in the axis 

of each leaf form tiny heads or “sprouts.” It 

has a common origin from the wild cabbage of 

southern Europe with other cole crops including 

cabbage, broccoli, and cauliflower (all members 

of the Brassicaceae [Cruciferae] family). Brussels 

sprouts prefer a cool growing environment. Most 

sprouts grown in the United States are from the 

central coast of California.

Quality Characteristics and Criteria

High-quality brussels sprouts are about 2.5 cm (1 

in) in diameter, firm with green outer leaves, and 

a white cut end. The inner leaves are light yellow, 

fairly tightly arranged, and without large air 

pockets between them.

Horticultural Maturity Indices

Harvest maturity is based on sprout size and 

compactness. Sprouts should be 2.5 cm (1 in) or 

more in diameter but not more than 7 cm (2.75 

in) in length. Stem elongation, resulting in space 

between older leaves, is a sign of overmaturity.

Grades, Sizes, and Packaging

There are two grades: U.S. No. 1 and U.S. No. 

2. They are based on size, external appearance, 

decay, and damage (AMS 1954). To meet these 

grades, sprouts should be larger than 2.5 cm (1 

in) in diameter and shorter than 7 cm (2.75 in). 

Brussels sprouts are packaged loose in 11-kg 

(25-lb) cartons or in 3.6- to 4.6-kg (8- to 10-lb) 

flats or cartons containing 12 plastic containers 

of sprouts (Boyette et al. 1996). Plastic liners are 

often used in cartons with loose sprouts to reduce 

moisture loss. In addition, polyethylene bags are 

sometimes used in place of the plastic containers 

for consumer units.

Precooling Conditions

Effective cooling methods include vacuum 

cooling, hydrocooling, icing, and forced-air 

cooling. Vacuum cooling is most effective when 

sprouts are premoistened to reduce wilting 

and can be an effective method of cooling 

even when sprouts are packaged, as long as 

the packaging material is ventilated (Stenvers 

1971). Hydrocooling is also an efficient method 

to rapidly cool sprouts from 20 to 2 °C (68 to 

36°F) in about 15 min (Stewart and Barger 1963). 

Package or top-icing can also be used, especially 

if storage or transport conditions cannot maintain 

recommended temperature or RH. Forced-air 

cooling effectively cools sprouts if packaging is 

properly vented to allow good air movement about 

the product.

Optimum Storage Conditions

Quality can be maintained for 3 to 5 weeks at 0 °C 

(32 °F) and 95 to 100% RH. Storage life is half as 

long at 5 °C (41 °F) and only 10 days at 10 °C (50 

°F). 

Controlled Atmosphere (CA) 

Considerations

Atmosphere modification inhibits yellowing 

and decay and prevents discoloration of the 

cut end when sprouts are held above optimum 

temperatures. At 7.5 °C (46 °F), an atmosphere of 

2.5% O2

 and 10% CO2 can maintain quality for 
253

4 weeks. CO2

 ranging from 5 to 10% and O2 of 1 

to 2% are beneficial (Lyons and Rappaport 1962, 

Isenburg 1969, Lipton and Mackey 1987). CO2

above 10% and O2

 below 0.5% can be injurious. 

CO2

 above 20% causes internal browning and 

pitting of outer leaves (Lyons and Rappaport 

1962), while O2

 at 0.5% or less can induce a 

reddish-tan discoloration of the heart leaves and 

bitter flavor (Lipton and Mackey 1987). Brussels 

sprouts do not produce severe off odors when held 

in low O2

 as do other Brassica vegetables such as 

broccoli (Forney and Jordan 1999).

Retail Outlet Display Considerations

Bottom-icing of the refrigerated display will 

enhance shelf-life of brussels sprouts. Plastic 

overwraps or misting of bulk displays minimize 

wilting.

Chilling Sensitivity

Brussels sprouts are not sensitive to chilling 

and should be stored as cold as possible without 

freezing.

Ethylene Production and Sensitivity

Brussels sprouts produce <0.25 μL kg-1 h-1

ethylene at 7.5 °C (46 °F), though rates increase 

10-fold with prolonged storage (Lipton and 

Mackey 1987). Brussels sprouts are extremely 

sensitive to ethylene, with leaf yellowing and 

abscission being the most prevalent symptoms.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 20 to 60

5 °C 44 to 96

10 °C 126 to 168

15 °C 128 to 272

20 °C 172 to 380

Data from Lyons and Rappaport (1959).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Internal browning, or “tipburn,” is the margins of 

inner leaves in buds turning brown and is caused 

by inadequate transport of calcium to young 

expanding leaves. Growing conditions that favor

rapid growth promote internal browning (Maynard 

and Barker 1972).

Postharvest Pathology

Diseases of importance during storage are 

bacterial soft rots (Erwinia sp. and Pseudomonas

sp.), bacterial leaf spot (Pseudomonas syringae pv. 

maculicola [McCulloch]), black or gray leaf spot 

(Alternaria sp.), and grey mold (Botrytis cinerea

Pers.) (Snowdon 1991).

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Some trimming of the stem-end could be done to 

convert the sprouts to a ready-to-cook form.

Special Considerations

Brussels sprouts can be stored attached to their 

stem to prolong storage life. Packaging in vented 

poly-bags or overwrapped cups reduces wilting. 

Sprout freeze at -0.8 °C (30.6 °F) (Cantwell 2001).
254

References

AMS [USDA Agricultural Marketing Service]. 

1954. United States Standards for Grades of 

Brussels Sprouts. At http://www.ams.usda.gov/

AMSv1.0/standards.

Boyette, M.D., D.C. Sanders, and G.A. Rutledge. 

1996. Packaging requirements for fresh fruits and 

vegetables. At http://www.bae.ncsu.edu/programs/

extension/publicat/postharv/ag-414-8/index.html.

Cantwell, M. 1997. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu.

Forney, C.F., and M.A. Jordan. 1999. Anaerobic 

production of methanethiol and other compounds 

by Brassica vegetables. HortScience 34:696-699.

Isenburg, F.M. 1969. The use of controlled 

atmosphere on cold crops. In D.H. Dewey, 

R.C. Herner, and D.R. Dilley, eds., Controlled 

Atmospheres for the Storage and Transport of 

Horticultural Crops, pp. 95-96. Horticulture 

Report 9, Michigan State University, East 

Lansing, MI. 

Lipton, W.J., and B.E. Mackey. 1987. 

Physiological and quality response of Brussels 

sprouts to storage in controlled atmospheres. Proc. 

Amer. Soc. Hort. Sci. 112:491-496.

Lyons, J.M., and L. Rappaport. 1959. Effect of 

temperature on respiration and quality of Brussels 

sprouts during storage. Proc. Amer. Soc. Hort. Sci. 

73:361-366.

Lyons, J.M., and L. Rappaport. 1962. Effect of 

controlled atmospheres on storage quality of 

Brussels sprouts. Proc. Amer. Soc. Hort. Sci. 

81:324-331.

Maynard, D.N., and A.V. Barker. 1972. Internal 

browning of Brussels sprouts: a calcium 

deficiency disorder. J. Amer. Soc. Hort. Sci. 

97:789-792.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melons. AVI 

Publishing Co., Westport, CT.

Snowdon, A.L. 1991. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. Wolfe Publishing Ltd., London, 

U.K.

Stenvers, N. 1971. Preliminary experiments 

on vacuum cooling of vegetables and berries. 

Sprenger Institute Report 1630 (Suppl.), Sprenger 

Institute, Berlin, Germany.

Stewart, J.K., and W.R. Barger. 1963. Effects of 

cooling method, prepacking and top-icing on the 

quality of brussels sprouts. Proc. Amer. Soc. Hort. 

Sci. 83:488-494.
255

Cabbage

Robert K. Prange

Prange is with Atlantic Food and Horticulture 

Research Centre, Agriculture and Agri-Food 

Canada, Kentville, Nova Scotia, Canada.

Scientific Name and Introduction

Brassica oleracea L. var. capitata L. is red, green 

(domestic or Danish-type), and oxheart (conical 

or pointed-head type) cabbage; B. oleracea var. 

sabauda L. is savoy cabbage. All are biennials 

of the Brassicaceae (Cruciferae) family (Munro 

and Small 1997, Pritchard and Becker 1989). The 

edible portion includes the leaf blades, stalks, and 

core (stem) inside the head. Cabbage is grown in 

most major temperate vegetable-growing areas 

and is available year-round in most markets. The 

major cabbage-producing countries, in order of 

production, are China, the Russian Federation, 

India, Japan, and South Korea (Ghosh and 

Madhavi 1998). In the United States, the major 

fresh-cabbage-producing States are New York, 

California, and Texas; and the major sauerkrautproducing States are New York and Wisconsin. 

(NASS 2005).

Quality Characteristics and Criteria

Cabbage leaves should be green, dark purple, 

or crinkly, depending on the cultivar (Ryall and 

Lipton 1979, Pritchard and Becker 1989). The 

head should be firm and heavy for its size. The 

heads are crisp and fresh if they squeak when 

rubbed together (Ryall and Lipton 1979, Boyette 

et al. 2008a, Cantwell and Suslow 2008). The 

presence of a waxy bloom on the leaves is 

desirable. Yellow leaves on green cultivars suggest 

extensive trimming of the outer leaves. The 

presence of a seedstalk is undesirable.

Horticultural Maturity Indices

Determination of maturity in brassicas is not 

simple and no one index of maturity is reliable 

(Ludford and Isenberg 1987) At maturity, a 

cabbage head should be firm and weigh 0.5 to 

3 kg (1 to 6.6 lb), depending on cabbage type 

and cultivar. The optimum head density of green 

cabbage destined for storage should range between 

0.72 and 0.80 kg L-1 (Pritchard and Becker 1989). 

Immature heads, besides being smaller and 

softer, have an excessive tendency to wilt and 

a less characteristic odor (Pritchard and Becker 

1989). Overmature heads are more susceptible to 

splitting, pathogens, physiological disorders, and 

seed stalk formation (IOS 1991, Pritchard and 

Becker 1989, Boyette et al. 2008a, Cantwell and 

Suslow 2008).

Grades, Sizes, and Packaging

Grades include U.S. No. 1 and U.S. Commercial, 

based on defects (physical and decay), excessive 

wrapper leaves, and off-size heads (AMS 1997). 

Size classification is optional. For the pointedhead-type (oxheart) cabbage, small is less than 

0.7 kg (1.5 lb), medium is 0.7 to 1.4 kg (1.5 to 3 

lb), and large is over 1.4 kg (3 lb). For domestic 

and Danish-type (green) cabbage, small is less 

than 0.9 kg (2 lb), medium is 0.9 to 2.3 kg (2 to 

5 lb), and large is over 2.3 kg (5 lb). Cabbage 

heads are shipped in sacks, wax-coated corrugated 

cardboard cartons, and wire-bound crates of 

various sizes up to 22.7 kg (50 lb). Some cabbage 

is shipped in heavy fiberboard bulk pallet bins 

holding 227 to 455 kg (500 to 1,000 lb) (Boyette 

et al. 2008b).

Precooling Conditions

Cabbage should be cooled as soon as possible 

after harvest to preserve quality and reduce 

wilting. If cabbage is harvested under cool 

conditions, it can be placed in storage and cooled 

without precooling. Hydrocooling before storage 

or forced air-cooling in storage can be used to 

rapidly remove field heat (Boyette et al. 2008a).
256

Optimum Storage Conditions

Cabbage should be stored at 0 °C (32 °F) with 

98 to 100% RH. Storage at -1 °C (31 °F) may 

cause freezing, while storage at 1 °C (34 °F) 

may promote senescence-related storage losses, 

especially if held in long-term storage—for 

example, 6 mo (R. Prange, unpublished data). 

High RH minimizes decay and trimming losses 

(van den Berg 1987). The presence of light in 

the storage room reduces physiological disorders 

such as leaf yellowing and weight loss (Prange 

and Lidster 1991). Cabbage is stored in bins or 

in bulk (IOS 1991). Only three to six wrapper 

leaves should be left on the head (Hardenberg 

et al. 1986). All loose leaves should be trimmed 

before storage because they will interfere with 

air circulation between heads. Air circulation 

in the storage should be sufficient to maintain 

constant and uniform temperature and RH around 

all cabbage heads. Bulk-stored cabbage should 

be ventilated in a vertical direction and the depth 

should not exceed 3 m (9.8 ft). Bin-stored cabbage 

should be arranged to maximize uniform air 

flow around each bin. Storage life depends on 

cultivar (for example, early-maturing cultivars 

tend to have shorter storage life than late-maturing 

cultivars), quality (for example, freedom from 

decay), and storage conditions (Pritchard and 

Becker 1989, IOS 1991, Boyette et al. 2008a). 

The end of storage life is signaled by increased 

respiration rate, core elongation, and sometimes 

rootlet development on the core butt (Guffy and 

Hicks 1985, Pritchard and Becker 1989).

Controlled Atmosphere (CA) 

Considerations

Cabbage is the most common vegetable stored 

under CA (Saltveit 1997, Thompson 1998). Wide 

ranges of O2

 levels from 1.5 to 5% and CO2 levels 

from 0 to 8% have been recommended. Therefore, 

the mid range of 2 to 3% O2

 and 4 to 5% CO2 is 

probably a good general recommendation. Low O2

reduces color and trimming loss and inhibits root 

growth, while elevated CO2

 reduces rot, decay, 

and sprouting (Saltveit 1997). Atmospheres with 

lower than 1.5 to 2% O2

 and/or higher than 8 to 

10% CO2

 may injure stored cabbage. Low-O2 and 

high-CO2

 injury is slow to appear and the extent 

of the injury depends on the cultivar and maturity 

(Masters and Hicks 1990). For example, low-O2

injury does not occur in oxheart cabbage until 

after 35 days when held in 0% O2

 (100% N2) at 

0 to 4 °C (32 to 39 °F) (Schouten et al. 1997), 

and green cabbage does not show low-O2

 injury 

until after 2, 3, or 6 mo, if held at 0 °C (32 °F) 

in 0.5, 1.0 or 1.5% O2

, respectively (Masters and 

Hicks 1990, Menniti et al. 1997). Similarly, CO2

injury is seen after 2 mo if held at 0 °C (32 °F) 

in 20% CO2

 or after 2.5 mo (Menniti et al. 1997) 

or 6 mo (Masters and Hicks 1990) in 10% CO2

. 

Symptoms of low-O2

 and high-CO2 injury are off 

flavors and off odors as well as visible damage 

(Lougheed 1987, Ludford and Isenberg 1987, 

Masters and Hicks 1990, Menniti et al. 1997, 

Schouten et al. 1997). Both low O2

 and high CO2

produce very similar visible damage beginning 

in the meristematic tissue located at the apex of 

the stem in the middle of the cabbage. Damage 

spreads to outer leaves and appears as black spots 

(low O2

) (Schouten et al. 1997) or bronzing (high 

CO2

) (Masters and Hicks 1990). Lougheed (1987) 

suggested there may be no interaction between 

low O2

 and high CO2 in injury, but Kaji et al. 

(1993) showed that high CO2

 (5 to 15%) keeps 

shredded cabbage in good condition if O2

 is high 

(5 to 10%).

Retail Outlet Display Considerations

Damaged outer wrapper leaves should be 

trimmed. Trimming may expose lighter green 

inner leaves, but natural or artificial light can 

increase the chlorophyll content and green color 

(Perrin 1982). The greatest concern is loss of 

moisture, which can be prevented by wrapping 

each head in a clear plastic film, frequent water 

sprinkling, and/or displaying in a refrigerated 

cabinet.

Chilling Sensitivity

Cabbage is not chilling sensitive. The freezing 

point is -0.9 to -0.83 °C (30.4 to 30.5 °F) 
257

(Hardenburg et al. 1986, Pritchard and Becker 

1989). Even though cabbage with core 

temperature of -1.1 °C (30 °F) before harvest can 

show no evidence of freeze damage (Pritchard and 

Becker 1989), storage at -1.0 °C (30.2 °F) is not 

advisable because it can produce freeze damage, 

especially on outer leaves (R. Prange, unpublished 

data). Temperature oscillations during cycling 

of mechanical refrigeration may expose tissue to 

freezing temperatures if the setpoint is too low or 

if the hystersis is too large.

Ethylene Production and Sensitivity

Cabbage produces very little ethylene (<0.1 μL 

kg-1 h-1 at 20 °C [68 °F]) (Kader 1992). Kubo et al. 

(1990) detected only a trace amount of ethylene 

from cabbage at 25 °C (77 °F). When heads are 

stored in the dark at 5 °C (41 °F) in sealed plastic 

bags, ethylene reaches only 1 μL L-1, regardless of 

cultivar (Meinl and Bleiss 1986). 

Cabbage should not be exposed to ethylene after 

harvest. Ethylene increases respiration (Inaba 

et al. 1989), and concentrations as low as 1 μL 

L-1 accelerate senescence and quality loss (for 

example, leaf yellowing, wilting, and abscission 

more in air than in CA) (Hicks and Ludford 1980, 

Pritchard and Becker 1989). Reduced ethylene 

production and phenylalanine ammonia-lyase 

(PAL) activation is linked to less tissue browning 

in shredded cabbage (Takahashi et al. 1996)

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 4 to 6

4 to 5 °C 9 to 12

10 °C 17 to 19

15 to 16 °C 20 to 32

20 to 21 °C 28 to 49

25 to 27 °C 49 to 63

Data from Hardenburg et al. (1986).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

The physiological cause is unknown for some 

disorders of stored cabbage (for example, black 

midrib, black speck of cabbage [pepper spot, 

spotted necrosis], gray speck, and necrotic spot) 

(Bérard 1994). The occurrence of these disorders 

is influenced by cultivar and cultural practices, 

especially mineral nutrition. Some storage 

disorders are clearly frost-induced (for example, 

black blotching, black spot, epidermal detachment, 

frost blemishing, and redheart). Bérard (1994) also 

describes storage disorders caused by dormancy, 

ethylene, and head maturity.

Postharvest Pathology

The major cause of postharvest decay in cabbages 

is the gray mold fungus (Botrytis cinerea) 

(Geeson 1983, Snowden 1991). Gray mold can 

be minimized by using resistant cultivars, using 

preharvest fungicides, practicing strict hygiene, 

avoiding mechanical or frost damage, rapid cooling 

to 0 °C (32 °F), and using CA storage (Snowden 

1991). Alternaria rot, also known as dark, black, 

or gray leaf spot and caused by Alternaria spp., 

infects a wide range of cruciferous vegetables 

and can cause significant storage losses (Geeson 

1983, Snowden 1991, Cerkauskas 1994). Since this 

disease is commonly transmitted through infected 

seed, it can be minimized by using disease-free 

seed, rotation with noncruciferous crops, applying 

preharvest fungicides, destruction of diseased 

material before storage, and using rapid cooling to 

0 °C (32 °F). There are other fungi (such as ring 

spot), bacteria (bacterial rots and watery soft rot, 

for example), and a virus (tobacco mosaic virus) 

that cause significant losses (Dennis 1983, Ceponis 

et al. 1987, Snowden 1991).

Quarantine Issues

None.
258

Suitability as Fresh-Cut Product

Shredded cabbage is suitable as a fresh-cut product, packaged in air or MAP. Gorny (1997) indicates MA 

treatment efficacy as good in extending storage life of shredded cabbage and provides respiration rates at 

different temperatures, atmospheres, and varying amounts of shredding.

Temperature Atmosphere Degree of shredding mg CO2 kg-1 h-1

2 °C (35 °F) air quarter head 8

rough cut (1 × 3 cm) 16 to 18

fine cut (0.5-1.5 cm) 18 to 24

5 °C (41 °F) air quarter head 10 to 12

rough cut (1 × 3 cm) 22 to 34

fine cut (0.5-1.5 cm) 26 to 40

5 °C (41 °F) 5 % O2 quarter head 12 to 14

+ 5 % CO2 rough cut (1 × 3 cm) 26 to 30

fine cut (0.5-1.5 cm) 30 to 40

10 °C (50 °F) air quarter head 19 to 23

rough cut (1 × 3 cm) 42 to 48

fine cut (0.5-1.5 cm) 51 to 57

23 °C (73 °F) air quarter head 54 to 63 

rough cut (1 × 3 cm) 117 to 153

fine cut (0.5-1.5 cm) 153 to 171

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 at 

20 °C (68 °F). To calculate heat production, multiply mg kg-1 h-1 by 220 to get BTU per ton per day or by 

61 to get kcal per tonne per day. Data from Gorny (1997).

References

AMS [USDA Agricultural Marketing Service]. 

1997. United States Standards for Grades of 

Cabbage. U.S. Department of Agriculture, 

Washington, DC. (http://www.ams.usda.gov/

AMSv1.0/standards)

Bérard, L.S. 1994. Storage disorders. In R.J. 

Howard, J.A. Garland, and W.L. Seaman, eds., 

Diseases and Pests of Vegetable Crops in Canada, 

pp. 110-112. Canadian Phytopathological Society 

and Entomological Society of Canada, Ottawa, 

Canada.

Boyette, M.D., D.C. Sanders, and E.A. Estes. 

2008a. Postharvest cooling and handling of 

cabbage and leafy greens. Postharvest Commodity 

Series. (http://www.bae.ncsu.edu/programs/

extension/publicat/postharv/ag-413-5/index)

Boyette, M.D., D.C. Sanders, and G.A. Rutledge. 

2008b. Packaging requirements 

for fresh fruits and vegetables. (http://www.bae.

ncsu.edu/programs/extension/publicat/postharv/

ag-414-8/index)
259

Cantwell, M., and T. Suslow 2008. Cabbages 

(round and Chinese types): recommendations 

for maintaining postharvest quality. (http://

postharvest.ucdavis.edu/produce_information)

Ceponis, M.J., R.A. Cappellini, and G.W. 

Lightner. 1987. Disorders in cabbage, bunched 

broccoli and cauliflower shipments to the New 

York market, 1972-1985. Plant. Dis. 71:1151-

1154.

Cerkauskas, R.F. 1994. Alternaria diseases. In R.J. 

Howard, J.A. Garland, and W.L. Seaman, eds., 

Diseases and Pests of Vegetable Crops in Canada, 

pp. 96-97. Canadian Phytopathological Society 

and Entomological Society of Canada, Ottawa, 

Canada.

Geeson, J.D. 1983. Brassica. In C. Dennis, ed., 

Postharvest Pathology of Fruits and Vegetables, 

pp. 125-126. Academic Press, New York, NY.

Ghosh, S.P., and D.L. Madhavi. 1998. Cabbage. In

D.K. Salunkhe and S.S. Kadam, eds., Handbook 

of Vegetable Science and Technology, pp. 299-

321. Marcel Dekker, New York, NY.

Gorny, J.R. 1997. A summary of CA and MA 

requirements and recommendations for freshcut (minimally processed) fruits and vegetables. 

In J.R. Gorny, ed., 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, July 13-18, 1997, vol. 5, pp. 30-

66. University of California, Davis, CA.

Guffy, S.K., and J.R. Hicks. 1985. Effect of 

cultivar, maturity and storage on respiration, dry 

weight and glucosinolate content of cabbage. Acta 

Hort. 157:211-218.

Hardenburg, R.E., A.E. Watada, and C.Y Wang. 

1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Hicks, J.R., and P.M. Ludford. 1981. Effects of 

low ethylene levels on storage of cabbage. Acta 

Hort. 116:65-73.

Inaba, A., Y. Kubo, and R. Nakamura. 1989. Effect 

of exogenous ethylene on respiration in fruits and 

vegetables with special reference to temperature. 

J. Jap. Soc. Hort. Sci. 58:713-718.

IOS [International Organization for 

Standardization]. 1991. Round-headed cabbage—

guide to cold storage and refrigerated transport. 

Intl. Std. Ref. No. ISO 2167:1991(E), Geneva, 

Switzerland.

Kader, A.A. 1992. Postharvest biology and 

technology: an overview. In A.A. Kader, ed., 

Postharvest Technology of Horticultural Crops, 

pp. 15-20. DANR Pub. no. 3311, University of 

California, Davis, CA.

Kaji, H., M. Ueno, and Y. Osajima. 1993. Storage 

of shredded cabbage under a dynamically 

controlled atmosphere of high O2

 and high CO2. 

Biosci. Biotech. Biochem. 57:1049-1052.

Kubo, Y., A. Inaba, and R. Nakamura. 

1990. Respiration and C2

H4 production in 

various harvested crops held in CO2

-enriched 

atmospheres. J. Amer. Soc. Hort. Sci. 115:975-

978.

Lougheed, E.C. 1987. Interactions of oxygen, 

carbon dioxide, temperature, and ethylene that 

may induce injuries in vegetables. HortScience 

22:791-794.

Ludford, P.M., and F.M.R. Isenberg. 1987. 

Brassica crops. In J. Weichmann, ed., Postharvest 

Physiology of Vegetables, pp. 497-522. Marcel 

Dekker, New York, NY.

Masters, J.F., and J.R. Hicks. 1990. Cabbage. In

P.D. Lidster, G.D. Blanpied, and R.K. Prange, 

eds., Controlled-Atmosphere Disorders of 

Commercial Fruits and Vegetables, pp. 29-30. 

1847/E, Agriculture Canada, Ottawa, Canada.
260

Meinl, G., and W. Bleiss. 1986. Beobactungen zur 

Ethylenbildung und zur seiner Wirkung wahrend 

der lagerung von Kopfkohl (Brassica oleracea

L. var. capitata) (Observations on ethylene 

synthesis and its effects during storage of cabbage 

[Brassica oleracea L. var. capitata]). Archiv für 

Zuchtungforschung 16:267-270. 

Menniti, A.M., M. Maccaferi, and A. Folchi. 1997. 

Physio-pathological responses of cabbage stored 

under controlled atmospheres. Postharv. Biol. 

Technol 10:207-212.

NASS [USDA National Agricultural Statistics 

Service]. 2005. Agricultural Statistics. At http://

www.nass.usda.gov/index.

Perrin, P.W. 1982. Poststorage effect of light, 

temperature and nutrient spray treatments on 

chlorophyll development in cabbage. Can. J. Plant 

Sci. 62:1023-1026.

Prange, R.K., and P.D. Lidster. 1991. Controlled 

atmosphere and lighting effects on storage of 

winter cabbage. Can. J. Plant Sci. 71:263-268.

Pritchard, M.K., and R.F. Becker. 1989. Cabbage. 

In N.A.M. Eskin, ed., Quality and Preservation of 

Vegetables, pp. 265-284. CRC Press, Boca Raton, 

FL.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Schouten, S.P., R.K. Prange, and T.R. Lammers. 

1997. Quality aspects of apples and cabbages 

during anoxia. In E.J. Mitcham, ed., 7th 

International Controlled Atmosphere Research 

Conference, University of California, Davis, July 

13-18, 1997, vol. 2, pp. 189-192. University of 

California, Davis, CA.

Snowden, A.L. 1991. A Colour Atlas of 

Postharvest Diseases and Disorders of Fruits and 

Vegetables, vol. 2, Vegetables. Wolfe Publishing, 

London, U.K.

Takahashi, T., K. Abe, and K. Chachin. 1996. 

Studies on the physiological and chemical changes 

in shredded cabbage. III. Effect of air-exposure at 

low temperature on physiological activities and 

browning of shredded cabbage. J. Jap. Soc. Hort. 

Sci. 43:663-667.

Thompson, A.K. 1998. Controlled Atmosphere 

Storage of Fruits and Vegetables. CAB Intl., 

Wallingford, U.K.

van den Berg, L. 1987. Water vapor pressure. In

J. Weichmann, ed., Postharvest Physiology of 

Vegetables, pp. 203-230. Marcel Dekker, New 

York, NY.
261

Carambola

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

The carambola (Averrhoa carambola L.) is 

a star-shaped fruit that has a waxy skin with 

several smooth brown seeds. The flesh and skin 

are crisp and juicy (Nakasone and Paull 1998). 

The carambola is also referred to as “star fruit.” 

However, the name is not preferred, because there 

is another tropical fruit called star fruit. Carambola 

is grown widely in the tropics and in the warmer 

areas of the subtropics.

Quality Characteristics and Criteria

The carambola is a firm, crisp fruit with shiny 

golden-yellow, orange, or yellow skin when ripe, 

with no brown discoloration on the skin or wings 

(ribs). Browning on the wing edges is due to 

mechanical injury and should not be included in 

the best grades. The shape is oval or elliptical in 

outline, 10 to 13 cm (4 to 5 in) long, and 5 to 8 

cm (2 to 3 in) in diameter. The absence of fiber is 

desirable. Cultivars vary greatly in sweetness and 

acidity, from the tart ‘Golden Star’ and the sweeter 

‘Arkin’ to the low-acid, sweet cultivars derived 

from Malay varieties (Nakasone and Paull 1998). 

Fruit showing wind, insect, or bird damage and 

poor shape are culled (Campbell 1989).

Horticultural Maturity Indices

Harvesting is based on physiological and 

horticultural maturity as indicated by skin color 

change from green to yellowish green, then 

to full yellow or yellowish orange (Campbell 

1989). Optimum sugars are achieved at the full 

yellow color; however, ripe fruit are more fragile 

and easily damaged. Thus, fruit are frequently 

harvested at the color break stage (O’Hare 

1993). Fruit that are 50 to 75% yellow are firmer 

than full-color fruit, and thus are regarded as 

commercially mature. Fruit continue to develop 

color after harvest, though there is little other 

change in quality.

Grades, Sizes, and Packaging

There are no U.S. or international grades. 

Carambola fruit are sold in 3.5-kg (7-lb) flats, 10-

kg (22-lb) single layers, 9-kg (20-lb) suitcases, 

and clam shells (16 fruit in 1 layer or 32 fruit in 

2 layers). Fruit require careful packing to reduce 

damage. A plastic or foam sleeve or wax paper 

should be used.

Precooling Conditions

Cool at 4 to 10 oC (39 to 50 oF) by forced air or 

room cooling as soon as possible.

Optimum Storage Conditions

Though a tropical crop, fruit can be stored at 

4 to 5 oC (39 to 41 oF) with 90 to 95% RH for 

21 to 35 days (Kader 1999). Length of storage 

varies with the ripeness when fruit are placed in 

storage. Lower RH results in more severe rib-edge 

browning. If held at 20 oC (68 oF) and 60% RH, 

fruit have a storage life of 3 to 4 days.

Controlled Atmosphere (CA) 

Considerations

Fruit held at 7 oC (45 oF) in 2.2 to 4.2% O2

 with 

8 to 8.2% CO2

 retained color and firmness more 

than fruit held in air (Revel and Thompson 1994). 

Sealed polyethylene film bags delay degreening 

and have no effect on flavor after 1 week at 20 oC 

(68 oF) on either green or full-colored fruit (Wan 

and Lam 1984) when the final CO2

 content in the 

bag is 2.5 to 4.5% with 15% O2

 content. Waxing 

also delays water loss and degreening (Vines and 

Grierson 1966).
262

Retail Outlet Display Considerations

Do not display green fruit and do not stack more 

than two or three fruit high to avoid mechanical 

injury to the fragile wings (ribs). Misting is 

acceptable.

Chilling Sensitivity

During low-temperature storage at 0 oC (32 oF) 

and 5 oC (41 oF) for 2 and 6 weeks, respectively, 

some small surface pitting and rib-edge browning 

occurred, with severity of injury increasing with 

storage time (Wan and Lam 1984). Greener fruit 

are more susceptible to chilling injury (Wan 

and Lam 1984, Kenney and Hull 1986). Surface 

pitting and rib-edge browning can also be seen 

with desiccation, which may not be true chilling 

injury.

Ethylene Production and Sensitivity

These nonclimacteric fruit have a low production 

rate, under 3 μl C2

H4 kg-1 h-1 at 20 oC (68 oF), 

depending on maturity (Oslund and Davenport 

1983). Ethylene treatment (100 μL L-1 for 24 h) 

slightly hastens degreening but has little effect 

on flavor. Higher rates of ethylene production 

have been recorded after 12 days at 20 oC (68 oF) 

(Shiesh et al. 1987) and may be associated with 

decay.

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 oC 10 to 19

10 oC 15 to 29

15 oC 19 to 34

20 oC 37 to 92

Data from Lam and Wan (1983, 1987).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton 

per day or by 61 to get kcal per tonne per day. 

Respiration rate and pattern depend on cultivar 

and maturity at harvest (Shiesh et al. 1987).

Physiological Disorders

The major problem is physical injury, especially 

on the rib edges, that leads to browning. Injury 

due to abrasion and impact can be avoided by 

careful handling. Browning due to mechanical 

injury can intensify with water loss. Fruit that 

have lost about 5% of their weight due to water 

loss show visible symptoms of dehydration.

Postharvest Pathology

Anthracnose (Colletotrichum gloeosporioides)

is most common, and the symptoms are thin, 

light-brown patches on fruit edges (Watson 

et al. 1988). Diseases caused by Alternaria 

alternata, Cladosporium cladosporioides, and

Botryodiplodia theobroma have been reported. 

These diseases mainly occur at physical injury 

sites with prolonged storage.

Quarantine Issues

Carambola is a fruit fly host. Irradiation and cold 

treatment (14 days at 1 oC) are recommended.

Suitability as Fresh-Cut Product

Slices and pieces have been developed (Matthews 

1989). Vacuum-packed slices held at 4 oC retained 

color, texture, and flavor for 6 weeks if dipped in 

citrate.

References

Campbell, C.A. 1989. Storage and handling of 

Florida carambola. Proceedings of the InterAmerican Society for Tropical Horticulture 33:79-

82.
263

Kader, A.A. 1999. Carambola (star fruit). Produce 

Facts. Perishables Handling Quarterly, no. 93, pp. 

19-20. University of California, Davis, CA.

Kenney, P., and L. Hull. 1986. Effect of storage 

condition on carambola quality. Proceedings of the 

Annual Meeting of the Florida State Horticultural 

Society 99:222-224.

Lam, P.F., and C.K. Wan. 1983. Climacteric nature 

of the carambola (Averrhoa carambola L.) fruit. 

Pertanicka 6:44-47.

Lam, P.F., and C.K. Wan. 1987. Ethylene and 

carbon dioxide production of starfuits (Averrhoa 

carambola L.) stored at various temperatures and 

in different gas and relative humidity atmospheres. 

Trop. Agric. 64:181-184.

Matthews, R.F. 1989. Processing of carambola. 

Proceedings of the Inter-American Society for 

Tropical Horticulture 33:89-90.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

O’Hare, T.J. 1993. Postharvest physiology 

and storage of carambola (starfruit): a review. 

Postharv. Biol. Technol. 2:257-267.

Oslund, C.R., and T.L. Davenport. 1983. Ethylene 

and carbon dioxide in ripening fruit of Averrhoa 

carambola. HortScience 18:229-230.

Revel, L., and A.K. Thompson. 1994. Carambola 

in controlled atmospheres. Trop. Fruits Newsletter, 

Inter-Amer. Inst. Coop. in Agric. 11:7.

Shiesh, C.C., T.S. Lin, and P.L. Tsai. 1987. 

Respiration and ethylene production of harvested 

carambola fruits (Averrhoa carambola L.). J. 

Chinese Soc. Hort. Sci. 33:139-150.

Vines, H.M., and W. Gierson. 1966. Handling and 

physiological studies with carambola. Proceedings 

of the Annual Meeting of the Florida State 

Horticultural Society 79:350-355.

Wan, C.K., and P.F. Lam. 1984. Biochemical 

changes, use of polyethylene bags and chilling 

injury of carambola (Averrhoa carambola L.) 

stored at various temperatures. Pertanika 7:39-46.

Watson, B.J., A.P. George, R.J. Nissen, and B.I. 

Brown. 1988. Carambola a star on the horizon. 

Queensland Agric. J. 114:45-51.
264

Carrot

Yaguang Luo, Trevor Suslow, and Marita Cantwell

Luo is with the Food Quality Laboratory, Henry A. 

Wallace Beltsville Agricultural Research Center, 

Agricultural Research Service, U.S. Department of 

Agriculture, Beltsville, MD; Suslow and Cantwell 

are with the Department of Plant Sciences, Mann 

Laboratory, University of California, Davis, CA. 

Scientific Name and Introduction

Carrots (Daucus carata L.) are biannuals of 

the Apiaceae (Umbelliferae) family. The edible 

portion is the storage taproot, which contains high 

levels of carbohydrates (sugars) and ß-carotene 

(previtamin A). Available year-round, most of the 

carrots in U.S. markets are produced in California, 

with limited production in Michigan, Texas, 

Colorado, Florida, and Washington (Schaffer 

2000).

Quality Characteristics and Criteria

Quality criteria vary with use. High-quality carrots 

are firm, straight from “shoulder” to “tip,” smooth 

with little residual “hairiness,” sweet with no 

bitter or harsh taste, and show no signs of cracking 

or sprouting (Suslow and Cantwell 1998). 

Horticultural Maturity Indices

Harvest maturity varies with the market outlet and 

use. Fresh market carrots are harvested partially 

mature, when the roots are about 1.8 cm (0.75 in) 

or larger in diameter at the upper end (Kotecha et 

al. 1998). Late harvesting may improve storability 

by reducing decay during extended storage 

(Suojara 1999). Fresh-cut processing carrots are 

harvested immature to ensure they are tender and 

sweet.

Grades, Sizes, and Packaging

Carrots can be harvested either bunched or toptrimmed; top-trimmed is the dominant method. 

The common grades for bunched carrots are U.S. 

No. 1 and U.S. Commercial. For topped carrots, 

the grades are U.S. Extra No. 1, U.S. No. 1, U.S. 

No. 1 Jumbo, and U.S. No. 2. Topped carrots are 

typically packed in 0.5- to 2.25-kg (1- to 5-lb) 

perforated plastic “Cello-pack” bags that are 

grouped in 11- or 22- to 22.7-kg (24- or 48- to 50-

lb) cartons or master poly bags. Bunched carrots 

are packed loosely in 12-kg (26-lb) cartons.

Precooling Conditions

Prompt washing and hydrocooling to under 5 °C 

(41 °F) are essential to maintain carrot freshness 

and crispness. Typically, carrots pass through 

several wash and flume steps that remove field 

heat and are then hydrocooled in chlorinated water 

before packing.

Optimum Storage Conditions

Storage at 0 to 1 °C (32 to 34 °F) is essential to 

minimize decay and sprouting during storage. 

High RH is required to prevent desiccation and 

loss of crispness. Mature topped carrots can be 

stored for 7 to 9 mo at 0 °C (32 °F) with 98 to 

100% RH. However, commercial storage and 

distribution conditions rarely achieve the optimum 

storage conditions and topped carrots are often 

stored for 5 to 6 mo at 0 to 5 °C (32 to 41 °F) 

with 90 to 95% RH. Common “Cello-pack” 

carrots are typically immature and may be stored 

successfully for 2 to 3 weeks at 3 to 5 °C (37 to 41 

°F). Bunched carrots are highly perishable due to 

the presence of leaves and can be maintained for 

only 8 to 12 days. Bunched carrots are typically 

shipped and stored with shaved or flaked ice.
265

Controlled Atmosphere (CA) 

Considerations

CA does not extend storage life of carrots beyond 

that in air with high RH (Leshuk and Saltveit 

1990). Low O2

 (1%) inhibited sprouting but also 

promoted decay (Abdel-Rahman and Isenberg 

1974). CO2

 injury appears as soft brown spots 

upon exposure to air. CO2

 levels above 5% 

promote decay. Storage at O2

 levels below 3% can 

result in increased bacterial rot, off flavors, and off 

odors (Leshuk and Saltveit 1990).

Retail Outlet Display Considerations

Carrots are often displayed loosely on a shelf 

with mist or in perforated plastic “Cello-pack” 

consumer packages.

Chilling Sensitivity

Carrots are not chilling sensitive and should be 

stored as cold as possible without freezing. Their 

freezing point is -1.2 °C (29.8 °F).

Ethylene Production and Sensitivity

Carrots produce very little ethylene (<0.1 μL 

kg-1 h-1 at 20 °C [68 °F]). However, exposure to 

ethylene (~ 0.2 μL L-1) induces development of 

the bitter compound isocoumarin (Lafuente et al. 

1996, Talcott and Howard 1999). Induction and 

accumulation of isocoumarin is greatest in the peel 

of cut carrot sections. Exposure of peeled carrot 

to ethylene does not result in development of 

bitterness. Whole or sectioned carrots should not 

be exposed to ethylene in storage.

Respiration Rates

Temperature Topped Bunched

--------------mg CO2 kg-1 h-1-----------------

0 °C 10 to 20 18 to 35

5 °C 13 to 26 25 to 51

10 °C 20 to 42 32 to 62

15 °C 26 to 54 55 to 106

20 °C 46 to 95 87 to 121

Data from Hardenburg et al. (1986).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Bruising, shatter-cracking, longitudinal cracking, 

and tip breakage are signs of excessively rough 

handling. Nantes-type carrots are particularly 

susceptible to mechanical damage (McGarry 

1993). The severity of shatter-cracking is 

partially related to varietal background. Wilting, 

shriveling, and rubberiness are signs of moisture 

loss. Sprouting may occur on topped carrots if 

the storage temperature is too high. Bitterness 

can develop in storage due to the accumulation 

of isocoumarin, caused by disease or exposure 

to ethylene. Harsh flavor may be caused by high 

terpenoid content induced by preharvest water 

stress. Surface browning or oxidative discoloration 

often develops during storage, especially on 

carrots harvested when immature.

Postharvest Pathology

The most prominent storage decays are bacteria 

soft rot (induced by Pectobacterium carotovora

or Pseudomonas marginalis), gray mold rot 

(Botrytis cinerea), rhizopus soft rot (Rhizopus 

spp.), watery soft rot (Sclerotinia sclerotiorum),

and sour rot (Geotrichum candidum) (Snowden 

1992). Ozone is a fungistatic against Botrytis and 
266

Sclerotinia, but tissue damage and color loss occur 

after treatment (Liew and Prange 1994). Good 

sanitation during packing and storage at 0 °C (32 

°F) minimizes postharvest diseases.

Quarantine Issues

None

Suitability as Fresh-Cut Product

A significant portion of fresh carrot production is 

used to produce fresh-cut products such as “baby 

carrots,” carrot coins, shreds, and sticks. Carrots 

directed or consigned to fresh-cut processing 

are typically harvested at an immature stage 

for optimal texture and taste. Fresh-cut carrots 

typically have a shelf-life of 3 to 4 weeks at 0 °C 

(32 °F) and 2 to 3 weeks at 3 to 5 oC (37 to 41 °F). 

Superficial whitening of the cut surface (“white 

blush”) is caused by dehydration and remains a 

problem for processors and shippers (CisnerosZevallos et al. 1995). Low storage temperature 

and retention of surface moisture significantly 

delay development of white blush. Using sharp 

knives is important to reduce tissue damage and 

extend shelf-life (Barry-Ryan and O’Beirne 1998).

References

Abdel-Rahman, M. and F.M.R. Isenberg. 1973. 

Effect of growth regulators and controlled 

atmosphere on stored carrots. J. Agric. Sci., 

53:635.

Barry-Ryan, C., and D. O’Beirne. 1998. Quality 

and shelf-life of fresh-cut carrot slices as affected 

by slicing method. J. Food Sci. 63:851-856.

Cisneros-Zevallos, L., M. Saltveit, and J. Krochta. 

1995. Mechanism of surface white discoloration 

of peeled (minimally processed) carrots during 

storage. J. Food Sci. 60:320-323, 333.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66. U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Kotecha, P.M., B.B. Desai, and D.L. Madhavi. 

1998. Carrot. In D.K. Salunke and S.S. Kadam, 

eds., Handbook of Vegetable Science and 

Technology, pp.119-139. Marcel Dekker, New 

York, NY.

Lafuente, M.T., G. López-Gálvez, M. Cantwell, 

and S.F. Yang. 1996. Factors influencing ethyleneinduced isocoumarin formation and increased 

respiration in carrots. J. Amer. Soc. Hort. Sci. 

121:537-542.

Leshuk, J.A., and M.E. Saltveit. 1990. 

Controlled atmosphere storage requirements and 

recommendations for vegetables. In M. Calderon 

and R. Barkai-Golan, eds., Food Preservation by 

Modified Atmospheres, pp. 315-352. CRC Press, 

Boca Raton, FL.

Liew, C.L., and R.K. Prange. 1994. Effect of 

ozone and storage temperature on postharvest 

diseases and physiology of carrots (Daucus carota

L.). J. Amer. Soc. Hort. Sci. 119:5673-567.

Mazza, G. 1989. Carrots. In N.A.M. Eskin, ed., 

Quality and Preservation of Vegetables, pp. 75-

119. CRC Press, Boca Raton, FL.

McGarry, A. 1993. Influence of water status on 

carrot (Daucus carota L.) fracture properties. J. 

Hort. Sci. 68:431-437.

Shaffer, E., ed. 2000. Produce Availability and 

Merchandising Guide. In The Packer. Vance Pub. 

Corp., Lenexa, KS.

Snowdon, A.L. 1992. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables, pp. 268-293. CRC Press, Boca 

Raton, FL.
267

Suojara, T. 1999. Effect of harvest time on the 

storage performance of carrot. J. Hort. Sci. 

Biotech. 74:484-492.

Suslow, T., J. Mitchell, and M. Cantwell. 1998. 

Carrot Produce Facts. Recommendations for 

Maintaining Postharvest Quality. At http://

postharvest.ucdavis.edu/produce_information.

Talcott, S.T., and L.R. Howard. 1999. 

Determination and distribution of 

6-methoxymellein in fresh and processed carrot 

puree by a rapid spectrophotometric assay. J. 

Agric. Food Chem. 47:3237-3242.
268

Cassava

Steven A. Sargent

Sargent is with the Horticultural Sciences 

Department, University of Florida, Gainesville, 

FL.

Scientific Name and Introduction

Cassava (Manihot esculenta Crantz) is a woody 

perennial shrub of the Euphorbiaceae family and is 

native to the Amazon region and Central America. 

It is widely grown throughout the tropics for its 

starchy root (Rubatsky and Yamaguchi 1997). 

Cassava is called “yuca” in Spanish, “mandioca” 

in Portuguese, “cassave” in Haitian Creole, and 

“manioc” in French. It is consumed in a variety 

of ways, but only after some form of processing. 

Cultivars are classified into two groups based on 

the amounts of hydrogen cyanide present. Sweet 

types contain less than 50 mg kg-1 HCN (fresh 

weight) and are generally sold as fresh roots, 

whereas bitter types have higher amounts of HCN 

along with higher yields and starch content (da 

Conceição 1980). These latter types are processed 

into products including flour (from coarse to finely 

textured), tapioca starch, and fermented starch. In 

2002, 184 million tonnes of cassava was produced 

worldwide; major producers were Africa (Nigeria) 

(99 million tonnes), Asia (52 million tonnes), 

and Latin America and the Caribbean (32 million 

tonnes). Cassava is adapted to semiarid climates 

and has been a traditional crop for subsistence 

farmers, though it is increasingly cultivated as an 

agronomic crop.

Quality Characteristics and Criteria

Fresh cassava roots are highly perishable under 

ambient conditions, becoming unmarketable in 

3 days or less. However, with proper handling, 

fresh roots can be stored up to 30 days, permitting 

export by marine container. The roots should 

be firm, turgid, fairly straight, and free from 

mechanical injury, decay, and vascular streaking. 

The pulp of most common cultivars varies from 

white to light yellow. Principal causes for loss are 

vascular streaking and decay. Extended storage 

can have two adverse effects on quality: starches 

are converted to sugars, and roots become fibrous, 

lengthening cooking time (Booth et al. 1976).

Horticultural Maturity Indices

Harvest maturity is based on the root size desired 

by the market and ranges from 6 to 18 mo after 

the stem sections are planted. Sweet types usually 

grow faster than bitter types. The main stem 

is often trimmed to approximately 1 m (39 in) 

in height a few days before harvest. Plants are 

manually pulled, or the root zone mechanically 

undercut to facilitate plant removal, and individual 

roots are cut. Cassava roots are turgid at harvest 

and must be handled carefully to avoid splitting 

the periderm. Harvest may be delayed until 

market, processing, or other conditions are 

favorable, since cassava roots can be stored in the 

ground for up to 24 mo.

Grades, Sizes, and Packaging

There are no U.S. grade standards for cassava. 

However, shippers should consult with buyers 

to define quality expectations. For example, 

root lengths in excess of 30 cm (11.8 in) are 

undesirable to many importers. Commercially, 

roots are cleaned by brushing, rinsing in water, 

surface-drying, and coating with paraffin wax 

prior to packing in corrugated cartons.

Precooling Conditions

Room cooling is generally sufficient, provided 

that the roots are not held too long at ambient 

temperatures prior to or after packing.

Optimum Storage Conditions

Cassava is very sensitive to water loss, and 

methods used to maintain high RH during storage 

include moist sawdust and plastic films (Booth 
269

1976). Paraffin wax is applied to roots exported 

to the United States. Waxing and holding at 0 

to 5 oC (32 to 41 °F) extends shipping time to 

over 30 days with minimal vascular streaking. A 

water-based carnauba wax maintained postharvest 

quality equivalent to paraffin wax (Sargent et al. 

1995).

Controlled Atmosphere (CA) 

Considerations

No commercial-scale CA recommendations have 

been reported. Vascular streaking during storage 

in air was reduced in unwaxed cassava roots by an 

initial 3-day exposure to 1% O2

 at 25 °C (77 °F) 

(Aracena 1993).

Retail Outlet Display Considerations

Cassava is normally displayed in bulk and should 

be held in refrigerated display cases.

Chilling Sensitivity

Cassava is chilling sensitive, but it can be stored 

at 0 to 5 oC (32 to 41 °F) with minimal symptom 

development, as long as immediately consumed 

when removed from storage before symptoms 

have had time to develop (Ingram and Humphries 

1972).

Ethylene Production and Sensitivity

Cassava roots (‘Valencia’) stored in air at 25 °C 

(77 °F) and 98% RH produced about 1.2 μL kg-1

h-1 of ethylene; however, ethylene production 

doubled at 65% RH (Aracena 1993). Ethylene 

production was 2.1 μL kg-1 h-1 for unwaxed roots 

after 4 days at 25 °C (77 °F) and 1.1 μL kg-1 h-1

for roots coated with paraffin wax. Exposure to 

ethylene promotes vascular streaking.

Respiration Rates

After 1 day of storage in air at 25 °C (77 °F) with 

98% RH, unwaxed roots respired at a rate of 23 

μL CO2

 kg-1 h-1, whereas those treated with 75 μL 

L-1 ethylene respired at a rate of 32 μL kg-1 h-1. 

After 4 days under the same conditions, internal 

CO2

 production was 8 and 11 μL kg-1 h-1, while O2

levels were 9 and 11.5 μL kg-1 h-1 for unwaxed and 

waxed roots, respectively (Aracena 1993).

Physiological Disorders

Vascular streaking appears as blue or purple spots 

when the root is cut transversely and is the result 

of oxidative processes in the vascular bundles. It 

typically develops at wound sites, such as at the 

apical end where the root is cut at harvest or under 

breaks in the peel that can occur during careless 

handling. Vascular streaking is related to oxidation 

of scopoletin, a phenolic compound (Wheatley 

and Schwabe 1985). Storage of unwaxed cassava 

roots in 1% O2

 at 25 °C (77 °F) for 3 days 

significantly reduced vascular streaking during 

storage in air (Aracena 1993). Exposure to 75 

μL L-1 ethylene increased vascular streaking, and 

ethylene induced by wounding or water stress may 

be the immediate cause of vascular streaking.

Postharvest Pathology

There are two major postharvest fungal diseases 

of cassava. Botryodiplodia rot (Botryodiplodia 

theobromae Pat.) invades the pulp beneath the 

skin, initially developing white mold that later 

becomes dark grey (Snowdon 1992). Fusarium 

rot (Fusarium solani, Mart., Sacc.) also grows on 

the pulp, causing a brown discoloration. Other 

pathogens reported by Snowdon (1992) include 

aspergillus rot (Aspergillus flavus), bacterial 

soft rot (Erwinia carotovora ssp. carotovora),

mucor rot (Mucor hiemalis), phytophthora rot 

(Phytophthora cryptogea), rhizopus rot (Rhizopus 

oryzae), sclerotium rot (Corticium rolfsii), and 

trichoderma rot (Trichoderma harzianum Rifai).
270

Quarantine Issues

There are no restrictions on imports from the 

major production areas.

Suitability as Fresh-Cut Product

There is potential for peeled intact or sliced roots, 

but shelf-life is currently limited to 2 or 3 days 

under ideal storage conditions due to vascular 

streaking.

References

Aracena, J.J. 1993. Mechanism of Vascular 

Streaking, a Postharvest Physiological Disorder 

of Cassava Roots. Thesis, Horticultural Sciences 

Department, University of Florida, Gainesville, 

FL.

Booth, R.H. 1976. Storage of fresh cassava 

(Manihot esculenta). I. Postharvest deterioration 

and its control. Exp. Agric. 12:103-111.

Booth, R.H., T.S. de Bucle, O.S. Cardenas, et al. 

1976. Changes in quality of cassava roots during 

storage. J. Food Technol. 11:245-264.

da Conceição, A.C. 1981. A Mandioca. Livraria 

Nobel, Sao Paulo, Brazil. 

Ingram, J.S. and J.R.O. Humphries. 1972. Cassava 

storage—a review. Trop. Sci. 14:131-148.

Rubatsky, V.E., and M. Yamaguchi. 1997. World 

Vegetables: Principles, Production, and Nutritive 

Values, 2nd ed. Chapman & Hall, New York, NY.

Sargent, S.A., T.B.S. Corrê, and A.G. Soares. 

1995. Application of postharvest coatings to fresh 

cassava roots (Manihot esculenta, Crantz) for 

reduction of vascular streaking. In L. Kushwaha, 

R. Serwatowski, and R. Brook, eds., Harvest and 

Postharvest Technologies for Fresh Fruits and 

Vegetables, pp. 331-338. American Society of 

Agricultural Engineers, St. Joseph, MI.

Snowdon, A.L. 1992. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. CRC Press, Boca Raton, FL.

Wheatley, C.C., and W.W. Schwabe. 1985. 

Scopoletin involvement in postharvest 

physiological deterioration of cassava root 

(Manihot esculenta Crantz). J. Expt. Bot. 

36:783-791.
271

Cauliflower

Charles Forney and Peter M.A. Toivonen 

Forney is with Atlantic Food and Horticulture 

Research Centre, Agriculture and Agri-Food 

Canada, Kentville, Nova Scotia, Canada; 

Toivonen is with Pacific Agri-Food Research 

Centre, Agriculture and Agri-Food Canada, 

Summerland, British Columbia, Canada.

Scientific Name and Introduction

Brassica oleracea L., Botrytis group of the 

Brassicaceae (Cruciferae) family, is also known 

as cauliflower. It is derived from the wild cabbage 

that is native to southern Europe. Cauliflower 

produces an edible head of malformed and 

condensed flowers (the curd) whose stalks are 

short, fleshy, and closely crowded. Cauliflower is 

sensitive to its growing environment and requires 

cool temperatures, plenty of moisture, and good 

fertility to produce quality heads. Therefore, 

much of commercial production is in coastal areas 

having moderate temperatures, or the crop is 

grown to take advantage of the cooler times of the 

growing season.

Quality Characteristics and Criteria

Heads of high quality are white to cream in 

color, firm, and compact. The curds should be 

free of mechanical damage, decay, browning, or 

yellowing, which can result from sun exposure. 

Heads should be surrounded by a whorl of 

trimmed green, turgid leaves.

Horticultural Maturity Indices

Harvest maturity is based on head diameter and 

compactness. Mature heads are larger than 15 cm 

(6 in) in diameter. Signs of overmaturity include 

“riciness” caused by protruding immature floral 

parts and browning or spreading of the curds.

Grades, Sizes, and Packaging

There are two grades, U.S. No. 1 and U.S. 

Commercial. Grading is based on size, external 

appearance, decay, damage, and trimming (AMS 

1968). Heads are normally well-trimmed and 

packed in a single layer with 12 to 24 heads in 

a carton weighing 11.4 to 13.6 kg (25 to 30 lb). 

Cauliflower may also be packed in 27-kg (60-

lb) wire-bound crates or 23-kg (50-lb) cartons/

crates (Boyette et al. 1996). Cauliflower is 

commonly packed in the field, where leaves 

are trimmed closely to the head and heads are 

overwrapped with a perforated plastic film. The 

overwrap should have four to six 6-mm (0.25-in) 

holes to allow adequate ventilation but minimize 

dehydration. Individual florets are also cut and 

packed in 2.3- and 4.6-kg (5- and 10-lb) film bags 

for institutional use, or smaller units for consumer 

packs.

Precooling Conditions

Cauliflower is mostly vacuum-cooled or 

hydrocooled prior to storage or marketing. 

Vacuum cooling works well for field-packed heads 

and is more effective if cauliflower is wetted 

before cooling (Stewart and Barger 1961). Forcedair cooling can also be used.

Optimum Storage Conditions

Commercial storage at 0 °C (32 °F) with 95 to 

98% RH can maintain good quality for up to 

3 weeks or more depending on initial quality. 

Increasing RH to 98 to 100% can further reduce 

weight loss and maintain turgidity of the heads 

(van der Berg and Lentz 1977), but free water 

accumulation on the curd must be avoided. 

Storage life is about 7 to 10 days at 5 °C (41 °F), 

5 days at 10 °C (50 °F), and 3 days at 15 °C (59 

°F) (Herregods 1964). Loss of quality during 

prolonged storage includes wilting, browning, 

and spreading of curds; yellowing of leaves; and 

decay.
272

Controlled Atmosphere (CA) 

Considerations

The benefits from CA and modified atmosphere 

are modest (Saltveit 1997). Low O2

 (below 2%) 

in combination with 3 to 5% CO2

 may delay leaf 

yellowing and the onset of curd browning (RomoParada et al. 1989). However, injury may occur 

at below 2% O2

 and/or above 5% CO2 (Lipton 

et al. 1967, Lipton and Harris 1976). Injury may 

not be apparent until curds are cooked, when they 

become soft, grayish, and develop off flavors. 

Storage at CO2 levels above 10% can induce injury 

within 2 days. Unlike broccoli, fresh cauliflower 

does not produce strong off odors when held in 

low-O2

 atmospheres (Forney and Jordan 1999).

Retail Outlet Display Considerations

Bottom-icing of refrigerated displays enhance 

shelf-life of cauliflower. Plastic overwraps are also 

important to minimize wilting during marketing.

Chilling Sensitivity

Cauliflower is not chilling sensitive.

Ethylene Production and Sensitivity

Cauliflower has a very low ethylene production 

rate, <1 μL kg-1 h-1 at 20 oC (68 °F). It is extremely 

sensitive to ethylene, with the most prevalent 

symptoms being curd discoloration and leaf 

yellowing and abscission.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 16 to 18

5 °C 20 to 22

10 °C 32 to 36

15 °C 42 to 50

20 °C 74 to 84

25 °C 86 to 98

Data from Suslow and Cantwell (2008).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Black speck is a disorder in which necrotic lesions 

0.5 to 4 mm (0.02 to 0.16 in) in diameter appear 

on the surface of branches or flower stalks in 

the interior of the curds. This disorder is more 

prevalent on certain cultivars and is most severe 

in cauliflower produced during warm weather and 

rapid growth (Loughton and Riekels 1988). 

Boron deficiency can result in brownish 

discoloration of the curd and pith of the stems and 

may result in hollow stems. In addition, blisters 

and cracks may form on the midribs of leaves 

and curds may taste bitter (Dearborn and Raleigh 

1935). 

Riciness is a developmental disorder in which 

elongation of flower stems causes flower clusters 

to separate, making the head appear granular. 

Overmaturity and storage at elevated temperatures 

encourages development of riciness, which can be 

reduced by timely harvest and storage at 0 °C (32 

°F).

Heads are susceptible to freezing injury, which 

appears as water-soaked and grayish curds, if held 

below 0.8 °C (30.6 °F).

Postharvest Pathology

The major causes of postharvest decay are 

bacterial soft rot caused by Erwinia and 

Pseudomonas spp. and brown rot caused by 

Alternaria spp. (Ceponis et al. 1987). Storing only 

good quality, disease-free heads and maintaining 

good temperature control can best control these 

decay organisms.
273

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Cauliflower is commonly converted to fresh-cut 

floret products.

Special Considerations

Growing conditions can strongly influence the 

quality of fresh cauliflower. Heads must be 

protected from the sun, normally by tying leaves 

subtending the head together, to prevent yellowing 

and strong flavor development in the curd. Only 

high-quality heads should be stored or shipped 

long distances. Heads must be handled gently to 

avoid bruising, which results in rapid browning 

and decay (Suslow and Cantwell 2008).

Acknowledgments

Some of the information in this chapter was 

obtained from the Oregon State University 

website for “Commercial Vegetable Production 

Guides” at http://horticulture.oregonstate.edu/

content/vegetable-production-guides.

References

AMS [USDA Agricultural Marketing Service]. 

1968. U.S. Standards for Grades of Cauliflower. 

U.S. Department of Agriculture, Washington, DC. 

(http://www.ams.usda.gov/AMSv1.0/standards)

Boyette, M.D., D.C. Sanders, and G.A. Rutledge. 

1996. Packaging requirements for fresh fruits and 

vegetables. (http://www.bae.ncsu.edu/programs/

extension/publicat/postharv/ag-414-8/index)

Ceponis, M.J., R.A. Cappellini, and G.W. 

Lightner. 1987. Disorders in cabbage, bunched 

broccoli, and cauliflower shipments to the New 

York market, 1972-1985. Plant Dis. 71:1151-1154.

Dearborn, C.H., and G.J. Raleigh. 1935. A 

preliminary note on the control of internal 

browning of cauliflower by the use of boron. Proc. 

Amer. Soc. Hort. Sci. 33:622-623.

Forney, C.F., and M.A. Jordan. 1999. Anaerobic 

production of methanethiol and other compounds 

by Brassica vegetables. HortScience 34(4):696-

699.

Herregods, H. 1964. The storage of cauliflower. 

Tuinbouwberichten. 28:486-487. 

Leshuk, J.A., and M.E. Saltveit. 1990. 

Controlled atmosphere storage requirements and 

recommendations for vegetables. In M. Calderon 

and R. Barkai-Golan, eds., Food Preservation by 

Modified Atmospheres, pp. 315-352. CRC Press, 

Boca Raton, FL.

Lipton, W.J., and C.M. Harris. 1976. Response of 

stored cauliflower (Brassica oleracea L., Botrytis

group) to low-O2

 atmospheres. J. Amer. Soc. Hort. 

Sci. 101:208-211.

Lipton W.J., C.M. Harris, and H.M. Couey. 1967. 

Culinary quality of cauliflower stored in CO2

-

enriched atmospheres. Proc. Amer. Soc. Hort. Sci. 

91:852-859.

Loughton, A., and J.W. Riekels. 1988. Black speck 

in cauliflower. Can. J. Plant Sci. 68:291-294.

Romo-Parada, L., C. Willemot, F. Castaigne, 

et al. 1989. Effects of controlled atmospheres 

(low oxygen, high carbon dioxide) on storage 

of cauliflower (Brassica oleracea L., Botrytis

Group). J. Food Sci. 54:122-124.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melons. AVI 

Publishing Co., Westport, CT.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 
274

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Stewart, J.K., and W.R. Barger. 1961. Effects of 

cooling method on the quality of asparagus and 

cauliflower. Proc. Amer. Soc. Hort. Sci. 78:295-

301.

Suslow, T., and M. Cantwell. 2008. Cauliflower: 

recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.

van den Berg, L., and C.P. Lentz. 1977. Effect of 

relative humidity on storage-life of vegetables. 

Acta Hort. 62:197-208.
275

Celeriac

Kenneth C. Gross

Gross is formerly with the Food Quality 

Laboratory, Henry A. Wallace Beltsville 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. He is now retired.

Scientific Name and Introduction

Celeriac (Apium graveolens var. rapaceum 

Mill. Gaudin) is a member of the Umbelliferae 

(Apiaceae) family. The harvest portion is a 

bulbous tuber with a crisp texture and a white 

flesh that has a nutty, celerylike flavor. It is also 

known as celery root or apio and can be used fresh 

or cooked. It must be peeled to remove the rough, 

light-brown skin if used fresh. California is the 

primary source of U.S. celeriac.

Quality Characteristics and Criteria

The primary quality characteristics are a firm 

texture and tender flesh. Roots with a soft, spongy 

texture should be avoided.

Horticultural Maturity Indices

Celeriac is harvested when it meets market needs 

for size.

Grades, Sizes, and Packaging

Common packaging is 9.1-kg (20-lb) cartons, 

though 15.9-kg (35-lb) cartons are also used. 

There are no defined grading categories for 

celeriac; it is graded and packed based on relative 

size.

Precooling Conditions

Celeriac can benefit from precooling since it 

retains quality best when stored at 0 °C (32 °F). 

However, since celeriac has a relatively low 

respiration rate, the benefits of precooling must 

be balanced with the desired storage time before 

marketing and consumption.

Optimum Storage Conditions

Celeriac can be stored for 6 to 8 mo at 0 to 2 

°C (32 to 36 °F) with RH of 97 to 98%. Storage 

life can be under 4 mo if temperature exceeds 3 

°C (38 °F). High RH of 90 to 98% is needed to 

prevent moisture loss, which results in shriveling. 

Freezing injury can occur if celeriac is stored 

at temperatures below -1 °C (30 °F) and is 

manifested as water-soaked areas or softening.

Controlled Atmosphere (CA) 

Considerations

CA storage is not recommended for celeriac. 

Storage in low-O2

 and high-CO2 atmospheres 

increased decay during 5 mo storage (Weichmann 

1976, 1977). However, storage in 2% O2

 with 2 to 

3% CO2

 may be beneficial (Cantwell 2001).

Retail Outlet Display Considerations

Water sprinkle and top ice are beneficial.

Chilling Sensitivity

Celeriac is not chilling sensitive and should be 

stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Ethylene production is low, <0.1μL kg-1 h-1 at 20 

°C (68 °F). However, celeriac may be slightly 

sensitive to ethylene. Therefore, celeriac should 
276

not be stored with other fruit or vegetables that 

produce high levels of ethylene.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 5 to 8

5 °C 11 to 15

10 °C 18 to 28

15 °C 32 to 38

20 °C 41 to 49

Data from Morris (2001).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Ethylene exposure may result in toughening of the 

root.

Postharvest Pathology

Decay may become a problem if celeriac is stored 

in a warm, humid environment.

Suitability as Fresh-Cut Product

No current potential is apparent.

Acknowledgments

Much of the information in this chapter was taken 

from the previous edition of this Handbook and 

from the Produce Marketing Association’s “Fresh 

Produce Manual.”

References

Cantwell, M. 2001. Celeriac. At http://postharvest.

ucdavis.edu.

Kurki, L. 1971. Moisture in vegetable storage. 

Acta Hort. 20:146-151.

Morris, S. 2001. Fruit and vegetables storage and 

transport database. At http://www.postharvest.

com.au/celeriac.pdf.

Weichmann, J. 1976. Storage of celeriac. Indus. 

Obst. Gemuseverwert. 61(8):205-207. 

Weichman, J. 1977. CA storage of celeriac. Acta 

Hort. 62:109-118.

Wiersma, O. 1973. Storage of celeriac. 

Betrijfsouteikkeling 4:79-80. 
277

Celery

Yaguang Luo, Trevor Suslow, and Marita Cantwell

Luo is with the Food Quality Laboratory, Henry A. 

Wallace Beltsville Agricultural Research Center, 

Agricultural Research Service, U.S. Department of 

Agriculture, Beltsville, MD; Suslow and Cantwell 

are with Mann Laboratory, Department of Plant 

Sciences, University of California, Davis, CA.

Scientific Name and Introduction

Celery (Apium graveolens L.) is a biennial of the 

Umbelliferae (Apiaceae) family but is planted 

and harvested as an annual crop. The edible 

portion is the long, thick, green fleshy petioles 

and, if present after trimming, associated leaves. 

California supplies 75% of U.S. production, with 

other significant production coming from Florida 

and Michigan (Schaffer 2000).

Quality Characteristics and Criteria

High-quality celery consists of petioles that are 

well-formed, thick, compact, straight, tender, 

and light green (Suslow and Cantwell 2002). 

Additional quality indices are stalk and midrib 

length; absence of defects such as blackheart, 

pithiness, seed stalks, and cracks; and absence of 

insect damage and decay. Any leaves remaining 

on the stalk after trimming should not be wilted, 

yellow, or decayed.

Horticultural Maturity Indices

Celery is harvested when the overall field reaches 

the desired marketable size of 35 to 41 cm (14 to 

16 in) stalk length, and before the outer petioles 

develop “pithiness.” Early harvests before the 

plants reach full size produce stalks with high 

market quality, and the prices received may more 

than compensate for lower yield. 

Grades, Sizes, and Packaging

U.S. grades are U.S. Extra No. 1, U.S. No. 1, and 

U.S. No. 2. Celery may be sold as “unclassified” 

to designate a lot that has not been graded 

according to U.S. standards. In California, freshmarket celery is field-packed in 27.2-kg (60-lb) 

cartons containing 48 stalks or in 12.7-kg (28-lb) 

cartons containing 12 or 18 hearts. Florida celery 

is packed in seven size grades from 18 to 96 stalks 

per crate. Celery hearts are prepared from smaller 

stalks that are trimmed to 20, 25, or 30 cm (8, 10, 

or 12 in) in length, and packed in 8- or 13-kg (18- 

or 28-lb) cartons (Peirce 1987). 

Precooling Conditions

Celery is typically hydrocooled or vacuum-cooled 

with a chilled water spray application. Prompt 

precooling to near 0 °C (32 °F) is essential to 

maintain freshness and crispness, as well as for 

extended storage.

Optimum Storage Conditions

Celery can be stored for up to 5 to 7 weeks at 0 

°C (32 °F) and 95% RH. At optimum conditions, 

celery can be stored for up to 5 to 7 weeks with 

good quality (Hardenburg et al. 1986). Storage 

life is reduced to less than 2 weeks at 5 °C (41 

°F). Inner petioles may continue to grow during 

storage at temperatures above 0 °C (32 °F), 

resulting in quality loss.

Controlled Atmosphere (CA) 

Considerations

CA and MA offer small to moderate benefits 

(Saltveit 1997). CA-stored stalks maintain better 

texture and crispness than those stored in air 

(Gariepy et al. 1984). Reduced O2

 (2 to 4%) 

and elevated CO2

 (3 to 5%) delay senescence, 

leaf yellowing, and decay (Leshuk and Saltveit 

1990). However, low-O2

 or high-CO2 injuries may 

occur when O2

 is under 2% or CO2 is over 10%, 

resulting in off odors, off flavors, and internal leaf 

yellowing.
278

Retail Outlet Display Considerations

Celery stalks can be displayed as twist-tied stalks, 

with or without a plastic sleeve, or in prepackaged 

consumer bags typically used for celery hearts. 

The use of both top ice and misting are acceptable 

to reduce moisture loss and maintain freshness.

Chilling Sensitivity

Celery is not chilling sensitive and should be 

stored as cold as possible without freezing. The 

freezing point for celery is -0.5 °C (31.1 °F) 

(Whiteman 1957).

Ethylene Production and Sensitivity

Celery produces little ethylene, <0.1 μL kg-1 h-1 at 

20 °C (68 °F). The effect of ethylene depends on 

temperature and concentration. Celery is not very 

sensitive to low concentrations of ethylene when 

exposed at low temperatures. Above 5 °C (41 °F), 

ethylene levels higher than 10 μL L-1 accelerate 

yellowing and development of pithiness. 

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 10 to 20

5 °C 13 to 26

10 °C 20 to 42

15 °C 26 to 54

20 °C 46 to 95

Data from Hardenburg et al. (1986).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Pithiness is a major source of quality loss and 

decreased shelf-life (Saltveit and Mangrich 

1996). It is characterized by the appearance of 

whitish regions and air spaces within the tissues 

and reduced tissue density and is caused by the 

breakdown of the internal pith parenchyma tissues 

of the petiole to produce aerenchyma. Pithiness 

may be induced by preharvest factors, including 

cold stress, water stress, bolting (seed stalk 

induction), and root infection. Storage temperature 

has a major impact on development of pithiness 

after preharvest induction. Development of 

pithiness is delayed by storage at 0 °C (32 °F).

Blackheart is a physiological disorder caused by 

cell death resulting from calcium deficiency and 

preharvest water stress. Internal leaves develop 

brown discoloration, which eventually becomes 

deep black.

Brown check is a disorder related to boron 

deficiency. It appears as cracks on the inner petiole 

surface, and exposed tissues become brown and 

are susceptible to pathogen infection and decay.

Crushing or cracking of the petiole are signs 

of mechanical damage and may lead to rapid 

browning and decay. Harvesting, packing, and 

handling should be done with great care to prevent 

damage to the highly sensitive turgid petioles.

Freezing injury occurs below -0.5 °C (31.1 °F). 

Mild freezing causes depressions in the tissues 

that subsequently turn brown. Severely frozen 

tissues develop a wilted and water-soaked 

appearance on thawing.

Postharvest Pathology

The most prominent storage decay is bacteria 

soft rot (primarily caused by Pectobacterium or 

Pseudomonas), gray mold (Botrytis cinerea), and 

watery soft rot (Sclerotinia spp.) (Snowden 1992). 

Storage at 0 °C (32 °F) is important to minimize 

losses due to postharvest decay. Controlled 

atmospheres (1.5% O2

 and 7.5% CO2) suppress 

the growth of Sclerotinia and watery soft rot (Reys 

and Smith 1986, Reys and Smith 1987). However, 

careful maintenance of atmospheric composition 

is required as celery is susceptible to low-O2

 and 

high-CO2

 injury.
279

Quarantine Issues

None. However, export loads of celery may be 

fumigated at entry ports if common insects (aphids 

and thrips) are found.

Suitability as Fresh-Cut Product

The majority of fresh-cut celery is in the form of 

celery sticks (cut petioles). Fresh-cut celery can 

be packed alone or in combination with other 

vegetables, such as carrots and broccoli. The 

shelf-life of fresh-cut celery is typically 12 to 

14 days at 0 to 5 °C (32 to 41 °F). Discoloration 

of vascular tissue, splitting of the cut ends, and 

bacteria decay are major problems limiting shelflife of fresh-cut celery (Robbs et al. 1996, Saltveit 

and Mangrich 1996). 

References

Gariepy, Y., G.S.V. Raghavan, R. Plasse, et al. 

1984. Long-term storage of cabbage, celery, and 

leeks under controlled atmosphere. Acta Hort. 

157:193-201.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Leshuk, J.A., and M.E. Saltveit. 1990. 

Controlled atmosphere storage requirements and 

recommendations for vegetables. In M. Calderon 

and R. Barkai-Golan, eds., Food Preservation by 

Modified Atmospheres, pp. 315-352. CRC Press, 

Boca Raton FL.

Peirce, L.C. 1987. Vegetables—Characteristics, 

Production, and Marketing, pp. 240-245. John 

Wiley & Sons, New York, NY.

Reys, A.A., and R.B. Smith. 1986. Suppression 

of sclerotinia and watery soft rot of celery by 

controlled atmosphere storage. Plant Dis. 72:790-

792.

Reyes, A.A., and R.B. Smith. 1987. Effect of 

oxygen, carbon dioxide, and carbon monoxide on 

celery in storage. HortScience 22:270-271.

Robbs, P.G., J.A. Bartz, G. McFie, and N.C. 

Hodge. 1996. Causes of decay of fresh-cut celery. 

J. Food Sci. 61:444-448.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Saltveit, M.E., and M.E. Mangrich. 1996. Using 

density measurement to study the effect of 

excision, storage, abscisic acid, and ethylene on 

pithiness in celery petioles. J. Amer. Soc. Hort. 

Sci. 121:137-141.

Shaffer, E., ed. 2000. Produce Availability 

and Merchandising Guide. The Packer. Vance 

Publishing Corp., Lenexa, KS.

Snowdon, A.L. 1992. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables, pp. 182-195. CRC Press, Boca 

Raton, FL.

Suslow, T., and M. Cantwell. 2002. Celery 

Produce Facts. Recommendations for Maintaining 

Postharvest Quality. At http://postharvest.ucdavis.

edu/produce_information.

Whiteman, T. 1957. Freezing Points of Fruits, 

Vegetables and Florist Stocks. Marketing Research 

Report 196, U.S. Department of Agriculture, 

Agricultural Marketing Service, Washington, DC. 
280

Cherimoya

Robert E. Paull and Nancy Jung Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

The cherimoya (Annona cherimola Mill.) is a 

heart-shaped fruit having few seeds and a smooth 

skin that does not break apart during ripening. It is 

grown in Florida, California, and Hawaii.

Quality Characteristics and Criteria

Quality is determined by fruit size, shape, and 

skin color, as well as the absence of defects and 

decay. Fruit are very susceptible to mechanical 

injury. Sugar levels can vary from 14 to 18%, with 

moderate acid levels.

Horticultural Maturity Indices

Mature fruit are firm and become very soft during 

ripening. The skin changes color from dark green 

to light green or greenish yellow, and is associated 

with increased surface smoothness. Fruit are 

harvested when mature and are allowed to ripen 

during marketing.

Grades, Sizes, and Packaging

There are no U.S. or international standards. Pack 

fruit in single layers in fiberboard cartons with 

foam sleeve or paper wrapping to avoid bruising. 

Carton size is usually 4 to 8 kg (9 to 18 lb) with 

12 to 24 count. Fruit weight is from 250 to 600 g 

(9 to 21 oz).

Precooling Conditions

Fruit should be precooled as soon as possible after 

harvest to about 12 oC to 15 oC (54 to 59 oF), with 

room cooling or forced-air cooling used most 

often.

Optimum Storage Conditions

Store fruit at 10 to 13 oC (50 to 55 oF) with 90 to 

95% RH for 2 to 3 weeks. If held at 20 oC (68 oF), 

fruit will last 3 to 4 days (Kader and Arpaia 1999). 

Storage is limited by skin darkening, desiccation, 

and disease due to chilling injury. Ripe, soft fruit 

should be held at 0 to 5 oC (32 to 41 oF).

Controlled Atmosphere (CA) 

Considerations

Fruit held in 5% O2

 for 30 days at 10 oC (50 oF) 

ripened in 11 days after removal to air storage 

at 20 oC (68 oF) versus 3 days for fruit held in 

20% O2

 (Palma et al. 1993a). Addition of CO2

at 3% or 6% can also extend storage life beyond 

that of storage in air (Alique and Oliveria 1994). 

However, not all results have been positive, and 

there may be varietal differences (Moreno and 

Dela Plaza 1983). O2

 levels under 1% can lead to 

off flavor.

Retail Outlet Display Considerations

Display at room temperature (approximately 20 

to 23 oC or 68 to 73 oF) if not ripe. Do not use 

misting or ice.

Chilling Sensitivity

Fruit are chilling sensitive, especially at 

temperatures below 10 oC (50 oF). The extent of 

injury depends on duration. Symptoms include 

skin darkening and a failure to fully soften and 

develop full flavor.
281

Ethylene Production and Sensitivity

The cherimoya is a climacteric fruit and has 

high rates of ethylene production (100 to 300 μL 

kg-1 h-1 at 20 oC [68 oF]) (Palma et al. 1993b). 

Exposure to ethylene at 100 μL L-1 for 24 h leads 

to rapid ripening of mature green fruit.

Respiration Rates

Temperature mg CO2 kg-1 h-1

10 oC 47 to 190

15 oC 84 to 280

20 oC 138 to 460

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Chilling injury is the major postharvest disorder, 

in which the skin darkens and the flesh fails to 

soften and can be “mealy” with poor flavor (Palma 

et al. 1993b). The degree of injury depends on 

variety and ripeness stage. Mechanical injury is 

a major problem during handling, which leads 

to unsightly black blemishes that can be sunken. 

Splitting can occur during ripening and provide 

sites for decay. Early-season fruit that frequently 

develop higher sugar levels are more susceptible 

to splitting.

Postharvest Pathology

Anthracnose (Colletotrichum gloeosporioides)

appears as dark lesions and may produce pink 

spore masses under high RH. Black canker 

(Phomopsis anonacearum) appears as purple 

spots that become hard and cracked, while 

Botryodiplodia rot (Botryodiplodia theobroma)

first appears as purple, then black, spots, and 

the flesh becomes brown and corky. These are 

preharvest diseases that require good orchard 

sanitation. Careful handling and sanitation with 

cooling, along with fungicides if approved, can 

minimize the problems.

Quarantine Issues

The cherimoya is a fruit fly host. Other quarantine 

pests include seed borers and scales. Heat 

treatments and irradiation are potential treatments.

Suitability as Fresh-Cut Product

The cherimoya is sold as a fresh-cut product, 

though the shelf-life is unknown. Ripe pieces can 

be held at 0 to 1 oC (32 to 34 oF).

References

Alique, R., and G.S. Oliveira. 1994. Changes in 

sugars and organic acids in cherimoya (Annona 

cherimola Mill.) fruit under controlled atmosphere 

storage. J. Agric. Food Chem. 42:799-803.

Kader, A.A., and M.L. Arpaia. 1999. Cherimoya, 

atemoya and sweet set-sop. Produce Facts. 

Perishables Handling Quarterly, no. 97, pp. 17-18. 

University of California, Davis, CA.

Moreno, J., and J.L. de la Plaza. 1983. The 

respiratory intensity of cherimoya during 

refrigerated storage: a special case of climacteric 

fruit. Acta Hort. 138:179-186.

Palma, T., D.W. Stanley, J.M. Aguilera, and J.P. 

Zoffoli. 1993a. Respiratory behavior of cherimoya 

(Annona cherimola Mill.) under controlled 

atmospheres. HortScience 28:647-649.

Palma, T., J.M. Aguilera, and D.W. Stanley. 

1993b. A review of postharvest events in 

cherimoya. Postharv. Biol. Technol. 2:187-208.

 
282

Cherry (Sweet)

James Mattheis and John Fellman

Mattheis is with the Tree Fruit Research 

Laboratory, Agricultural Research Service, U.S. 

Department of Agriculture, Wenatchee, WA; 

Fellman is with the Department of Horticulture 

and Landscape Architecture, Washington State 

University, Pullman, WA.

Scientific Name and Introduction

Prunus avium L., the sweet cherry, is a stone 

fruit of the Rosaceae family. The edible portion 

consists of outer layers of the mature ovary wall, 

the flesh (mesocarp) and the skin (exocarp). 

The pit (endocarp) encloses the seed. Numerous 

cultivars are grown commercially including 

‘Attika,’ ‘Bing,’ ‘Brooks,’ ‘Burlat,’ ‘Chelan,’ 

‘Lambert,’ ‘Lapins,’ ‘Rainier,’ ‘Tieton,’ ‘Skeena,’ 

and ‘Sweetheart.’ Sweet cherries are primarily 

grown in the Western United States in California, 

Oregon, and Washington. Fruit harvest begins in 

California in May and continues through midAugust in Oregon and Washington.

Quality Characteristics and Criteria

Premium sweet cherries have a bright, shiny 

appearance. Fruit color can be dark red (‘Bing’), 

red (‘Sweetheart’), or yellow with a red blush 

(‘Rainier’ and ‘Royal Ann’). The appearance of 

the stem, which should be green and free from 

brown discoloration, is also critical for marketing. 

Flavor is enhanced by highly soluble solids and 

titratable acid content with a firm, juicy fruit 

texture.

Horticultural Maturity Indices

Fruit color is the most consistent and reliable 

maturity index. Different cultivars can be 

harvested at slightly different color stages. For 

example, ‘Bing’ cherries should be a mahogany 

red color rather than lighter red (immature) or 

purplish red (overmature). ‘Lambert’ cherries can 

be harvested at a brighter, less dark-red color, 

while ‘Van’ cherries can be harvested at a darker 

red color than ‘Bing’ (Crisosto 1991).

Grades, Sizes, and Packaging

Grades include Washington No. 1 and 2, 

Northwest No. 1 and 2, and U.S. No. 1 and 2. 

Grades are based primarily on appearance, and 

the three grading systems differ in tolerance to 

defects. Sizes are typically expressed as row count 

and range from 9 to 12. Packages commonly are 

20-lb cartons, though smaller units are becoming 

more available.

Precooling Conditions

Sweet cherries should be cooled to below 5 oC 

by 4 h after harvest. Room cooling, forced-air 

cooling, and hydrocooling are all used to cool 

sweet cherry fruit. Of these, hydrocooling is the 

most rapid, and chlorine compounds can be added 

to the hydrocooler water to reduce decay potential 

(Do et al. 1966).

Optimum Storage Conditions

Recommended conditions for storage of sweet 

cherries are -1 to 0 oC with RH at over 95%. 

Sweet cherries maintain good quality for 2 to 4 

weeks under these conditions.

Controlled Atmosphere (CA) 

Considerations

Reduction in the amounts of color change 

(darkening), acid and firmness loss, incidence 

of decay, and stem browning are potential 

benefits of CA storage and MAP (modified 

atmosphere packaging). The effectiveness of these 

technologies is determined in part by fruit quality 

at harvest. Fruit harvested at a more advanced 

stage of maturity (low acid, dark color, low 

firmness) will not realize as much benefit from CA 
283

or MAP. Optimal atmosphere conditions for CA 

range from 1 to 5% O2

 with 5 to 20% CO2 (Chen 

1981, Patterson 1982, Mattheis et al. 1997). For 

MAP, 5 to 10% O2

 with 5 to 15% CO2 is effective 

when fruit temperature is maintained at 0 to 5 oC 

(Mattheis and Reed 1994, Meheriuk et al. 1995). 

Temperature control for MAP systems is critical 

because the risk of anaerobiosis increases as 

packaged fruit temperature increases.

Retail Outlet Display Considerations

Refrigeration during display is critical to reduce 

quality loss due to stem browning, shrivel, and 

development of decay. Fruit should be held at 5 

oC or less to slow deterioration. Fruit should be 

refrigerated but not wetted because continuous 

moisture on the surface can cause splitting.

Chilling Sensitivity

Sweet cherries are not sensitive to chilling and 

should be stored as cold as possible without 

freezing. 

Ethylene Production and Sensitivity

Sweet cherries produce very low amounts of 

ethylene but will respond to exogenous or woundinduced ethylene with increased respiration and 

quality loss.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 6 to 10

5 °C 16 to 28

10 °C 20 to 36

15 °C 28 to 64

20 °C 40 to 90

Data from Gerhardt et al. (1942), Micke et al. 

(1965), and Mattheis (1998).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Pitting and bruising are common problems caused 

by harvest injury and rough postharvest handling 

(Facteau and Rowe 1979, Thompson et al. 1997). 

Fruit pitting is a manifestation of subsurface 

damage that develops into sunken areas near the 

fruit surface. Bruising can occur from excess 

compression, drops or large impacts during 

harvest, transport, or packing. Visual symptoms of 

pits and bruises often do not appear until well after 

the fruit have been packed, resulting in visible 

damage appearing in wholesale or retail markets. 

Sweet cherries are also prone to shrivel and water 

loss due to the lack of a well-developed cuticle. 

Water loss can be minimized by prompt cooling 

and storage in a high-RH environment. 

Stem browning is another potential physiological 

disorder. Stem browning can be minimized 

by proper temperature and RH management; 

however, packing procedures that scrape or injure 

stems create wounds that will brown. In addition 

to proper temperature management, use of 

chlorine dioxide in hydrocooler water can reduce 

development of stem browning (Roberts 1989).

Postharvest Pathology

Fungal pathogens including Penicillium expansum

(blue mold), Botrytis cinerea (gray mold), 

Alternaria sp., Monilinia fructiocola (brown 

rot), Rhizopus stolonifer, Cladosporium sp., and 

Aspergillus niger are the main causes of sweet 

cherry decay (Crisosto 1991, Adaskaveg and 

Ogawa 1994, Dugan and Roberts 1997). Many of 

these pathogens infect fruit early in development 

and are present as quiescent infections at harvest 

(Dugan and Roberts 1994). Fruit can also be 

infected via rain splits or wounds that occur at 

harvest or during packing. The use of postharvest 

sanitation and fungicides minimizes postharvest 
284

decay (Willet et al. 1989). Low-temperature 

storage, fungicide application, and MAP with high 

CO2

 (5 to 20%) all slow pathogen growth (English 

and Gerhardt 1942, Gerhardt et al. 1942, 1956, 

DeVries-Patterson et al. 1991, Brash et al. 1992, 

Spotts et al. 1998).

Quarantine Issues

Fruit exported to Japan must be fumigated with 

methyl bromide to control codling moth larvae. 

Fruit shipped into California must be inspected 

and certified free from cherry fruit fly infestation. 

Suitability as Fresh-Cut Product

No current potential.

Special Considerations

Sweet cherries must be cooled promptly after 

harvest and low temperatures maintained 

throughout packing, storage, and transport. 

Low temperatures minimize quality loss as well 

as physiological and pathological disorders. 

Maintenance of low temperature is critical when 

using MAP systems to avoid anaerobic conditions 

and off-flavor development.

References

Adaskaveg, J.E., and J.M. Ogawa. 1994. 

Penetration of iprodione into mesocarp fruit tissue 

and suppression of gray mold and brown rot of 

sweet cherries. Plant Dis. 78:293-296.

Brash, D.W., L.H. Chea, and W. Hunt. 1992. 

Controlled atmospheres inhibit storage rot of 

cherries. In A.J. Popay, ed., Proceedings of the 

45th New Zealand Plant Protection Conference, 

August 11-13, 1992, pp. 136-137. New Zealand 

Plant Protection Society, Auckland, New Zealand.

Chen, P.M., W.M. Mellenthin, S.B. Kelly, and 

T.J. Facteau. 1981. Effects of low oxygen and 

temperature on quality retention of ‘Bing’ cherries 

during prolonged storage. J. Amer. Soc. Hort. Sci. 

106:533-535.

Crisosto, C.H. 1991. Sweet cherry harvesting, 

postharvest handling and storage. Perishables 

Handling Quarterly, no. 71. University of 

California, Davis, CA.

DeVries-Patterson, R.M., A.L. Jones, and A.C. 

Cameron. 1991. Fungistatic effects of carbon 

dioxide in a package environment on the decay of 

Michigan sweet cherries by Monilinia fructicola. 

Plant Dis. 75:943-946.

Do, J.Y., D.K. Salunkhe, D.V. Sisson, and A.A. 

Boe. 1966. Effects of hydrocooling, chemical, 

and packaging treatments on refrigerated life and 

quality of sweet cherries. Food Technol. 20:115-

118.

Dugan, F.M., and R.G. Roberts. 1994. Etiology 

of preharvest colonization of Bing cherry fruit by 

fungi. Phytopathology 84:1031-1036.

Dugan, F.M., and R.G. Roberts. 1997. Preharvest 

fungal colonization affects storage-life of Bing 

Cherry Fruit. J. Phytopathology 145:225-230.

English, H., and F. Gerhardt. 1942. Effect of 

carbon dioxide and temperature on the decay of 

sweet cherries under simulated transit conditions. 

Proc. Am. Soc. Hort. Sci. 40:172-176.

Facteau, T.J., and K.E. Rowe. 1979. Factors 

associated with surface pitting of sweet cherry. J. 

Amer. Soc. Hort. Sci 10:706-710.

Gerhardt, F., H. English, and E. Smith. 1942. 

Respiration, internal atmosphere and moisture 

studies of sweet cherries during storage. Proc. 

Amer. Soc. Hort. Sci. 41:119-123.
285

Gerhardt, F., H. Schomer, and T.R. Wright. 

1956. Sealed Film Lug Liners for Packing Bing 

Cherries. Pub. no. 121, U.S. Department of 

Agriculture, Agricultural Marketing Service, 

Washington, DC.

Mattheis, J.P., and N. Reed. 1994. Response of 

‘Bing’ sweet cherries to modified atmosphere 

packaging. Proceedings of the Oregon 

Horticultural Society, January 1994, pp. 22-28. 

Mattheis, J.P., D.A. Buchanan, and J.K. Fellman. 

1997. Volatile constituents of ‘Bing’ sweet cherry 

fruit following controlled atmosphere storage. J. 

Agric. Food Chem. 45:12-216.

Mattheis, J.P. 1998. ‘Bing’ cherry respiration. 

In Interesting and Valuable Fruit Stuff. At

http://www.ars.usda.gov/Main/site_main.

htm?modecode=53-50-00-00.

Meheriuk, M., B. Girard, L. Moyls, et al. 1995. 

Modified atmosphere packaging of ‘Lapins’ sweet 

cherry. Food Res. Int. 28:239-244.

Patterson, M.E. 1982. CA storage of cherries. 

In D.G. Richardson, M. Meheriuk, and S. 

Blankenship, eds., Controlled Atmospheres for 

Storage and Transport of Perishable Agricultural 

Commodities, pp. 149-154. Timber Press, 

Beaverton, OR.

Roberts, R.G. 1989. The potential for use of 

chlorine dioxide as a postharvest tool for the 

Pacific Northwest fruit industry. In Proceedings 

of the 5th Annual Warehouse Seminar and 

Trade Show, Wenatchee, WA, 1989, pp. 37-40. 

Washington State Horticultural Association, 

Wenatchee, WA.

Spotts, R.A., L.A. Cervantes, T.J. Facteau, and T. 

Chand-Goyal. 1998. Control of brown rot and blue 

mold of sweet cherry with preharvest iprodione, 

postharvest Cryptococcus informo-miniatus, and 

modified atmosphere packaging. Plant Disease 

82:1158-1160.

Thompson, J.F., J.A. Grant, E.M. Kupferman, and 

J. Knutson. 1997. Reducing sweet cherry damage 

in postharvest operations. HortTechnology 7:134-

138.

Willett, M., G. Kupferman, R. Roberts, et al. 

1989. Integrated management of postharvest 

diseases and disorders of apple, pears and 

cherries. Washington State University Postharvest 

Pomology Newsletter 7:1-15.
286

Chicory (Belgian Endive or Witloof 

Chicory)

Vince Rubatzky and Mikal E. Saltveit

Rubatzky and Saltveit are with the Department of 

Plant Sciences, University of California, Davis, 

CA.

Scientific Name and Introduction

Belgium endive or witloof chicory (Cichorium 

intybus L.) is a biennial herbaceous plant 

belonging to the Asteraceae family. In addition 

to chicory’s use a leafy salad vegetable, the roots 

of some cultivars are grown for use as a coffee 

substitute. Related vegetables of commercial value 

include lettuce (Lactuca sativa L., Cichorium 

tribe), endive and escarole (Cichorium endivia

L.), and radicchio (Cichorium intybus L.). The 

edible portion of chicory is the young, enlarged, 

compact, and etiolated terminal bud that is 

composed of young leaves and the partially 

suppressed but enlarging floral stem. In the trade, 

this product is called a chicon. This large bud 

results from the forced growth of the apical bud 

on a defoliated and vernalized root in storage. The 

roots are harvested after a year of growth, partially 

defoliated except for the apical bud, and stored 

until ready for forcing.

Belgium endive is a popular vegetable in 

northern European countries, where it is available 

year-round. The crop is mostly for European 

consumption and of little interest elsewhere. In the 

United States, it is not well known or appreciated 

by the general public. Accordingly, production is 

minor and supply is augmented by air shipments 

from Europe.

Quality Characteristics and Criteria

High-quality chicons are compact and turgid with 

closely overlapping outer leaves having a motherof-pearl luster or milky-white appearance and a 

light yellow tinge on leaf margins. They should 

be sound, free of reddish blemish, frost damage, 

or traces of bruises, disease, insects, parasites, 

or rodent attack. A chicon should feel heavy for 

its size. Leaf tips should not curl back, and the 

base should be well-trimmed perpendicular to the 

upright axis and without discoloration. It should 

be lanceolate in shape, with the length ranging 

from 2 to 3 times the maximum width. Quality is 

decreased by flower stem development in excess 

of three-fourths of the bud’s length.

Development of green leaf color is a quality 

defect. Though leaf greening constitutes 

quality loss for many markets, U.S. consumers 

tolerate a slight amount without significant 

penalty. A small number of cultivars produce 

anthocyanin and are reddish-purple in coloration. 

Elevated temperatures during holding and retail 

presentation are more important than exposure to 

light in inducing greening.

Horticultural Maturity Indices

Depending on temperature, optimum harvest is 

20 to 30 days after forcing. Harvest delays result 

in elongated chicon and loss of compaction. 

Chicons are harvested when outer leaves are 

tightly appressed and density is maximal. The 

basal portions of the outermost leaves should 

be well sheathed. Leaf margins should be thin 

and smooth. Timely harvest maximizes potential 

shelf-life compared to harvesting at a later stage 

of development. Deterioration is mainly due to 

marginal leaf drying or browning, which can occur 

rapidly (Herregods 1971).

Grades, Sizes, and Packaging

Grading is largely determined by uniformity of 

shape, overall appearance, and the ratio of length 

to width. Highest quality chicons are 9 to 17 cm 

(3.5 to 6.8 in) in length and have a maximum 

diameter of 6 cm (2.5 in). The typical ratio of 

length to width is 2:1 to 3:1.

U.S. grades are Extra, Standard, and Baby, 

while European standards are Extra, Class 
287

I, II, and II irregular. Extra category chicons 

are uniformly shaped, meet appropriate size 

dimensions, have outer leaves that measure at 

least half of the chicon length, are firm, and do not 

exhibit greening or a glassy appearance. Lesser 

quality involves less uniformity, less favorable 

appearance, deterioration, and loss of compaction.

Precooling Conditions

Trays holding the forced roots can be moved to a 

cold room for a day or overnight before snapping 

(that is, removal of chicons from the roots). 

Condensation on the chicons when transferred to a 

warmer packing area is undesirable. Precooling in 

this manner wastes energy because the entire roots 

of both marketable and unmarketable chicons are 

cooled. Hydrocooling is very effective, but water 

infiltration is difficult to remove and reduces 

shelf-life. Vacuum cooling is seldom used since 

it is expensive and results in a loss of moisture 

accounting for 2 to 3% of the product’s fresh 

weight. Forced-air cooling is occasionally used, 

but it is not effective in cooling product in film 

packages. Conventional room cooling is the most 

commonly used method. It is the least expensive 

but is relatively slow compared with other 

precooling techniques.

In the United States, chicons are packed in 

pasteboard containers that contain 4.5 kg (10 lb) 

of product. Perforated plastic film bags are also 

used for packaging, as are film-overwrapped trays. 

Perforations account for about 0.5% of the bags 

surface and are intended to limit condensation 

because moisture on the chicons is detrimental to 

maintaining quality. Bags are opaque or covered 

with translucent blue or green paraffin paper to 

exclude light.

Optimum Storage Conditions

Chicons should be stored in the dark at 0 °C (32 

°F) and 95 to 100% RH (Hardenburg et al. 1986). 

Storage life is reduced to 2 to 4 weeks at 2 oC (36 

°F), 1 to 2 weeks At 5 oC (41 °F), and 1 week or 

less at 15 oC (59 °F). There is little greening at 

0 °C (32 °F), even in the presence of light, but 

greening increases with increasing temperature.

Controlled Atmosphere (CA) 

Considerations

Storage life can almost be doubled by storage in 

3 to 4% O2

 with 4 to 5% CO2 at 0 °C (32 °F). CA 

storage delays greening of leaf tips in light and 

leaf spreading.

Retail Outlet Display Considerations

Maintain cold conditions to maximize storage and 

shelf-life and minimize dehydration, but do not 

sprinkle or otherwise wet the product. Packaged 

chicons should be held in conditions similar to 

those of packaged mushrooms, not in wet storage 

areas.

Chilling Sensitivity

Chicory is not chilling sensitive, but it freezes at 

-0.5 °C (31 °F).

Ethylene Production and Sensitivity

Ethylene production is very low, but exposure to 

ethylene can produce physiological disorders such 

as russet spotting and accelerated senescence.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 2 to 3

5 °C 5 to 6

10 °C 12 to 14 

15 °C 20 to 22

20 °C 35 to 38

Data from Saltveit (2002, unpublished).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 
288

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Disorders include brown or hollow core, 

blackheart, foliage pinking, and red discoloration 

of tissue that has been bruised or cut. A similar 

reddish-orange coloration occurs when leaves split 

or are torn. Additional disorders include russet 

spotting, the formation of light hairlike growth 

on leaves, and leaf greening. Other causes of 

chicon deterioration are continued growth of the 

stem, resulting in leaf spreading and opening; leaf 

greening, loss of turgor, and wilting that results 

in a loss of weight, grade, and quality; and the 

appearance of bruises at the base or on the leaves 

that become more apparent at retail. Chicons 

showing any signs of cuts, drying, burses, or torn 

tissue should be excluded from sale.

Postharvest Pathology

The most common decays are Erwinia carotovora, 

Botrytis cinerea, and other pathogens such as 

Phytophthora cryptogea, Sclerotinia sclerotiorum, 

Phoma exigua, and several Pseudomonas spp. 

Infection of the chicons in the forcing facilities 

is most often due to the disease organism being 

introduced on the roots.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Potential is low, but loose leaves are occasionally 

marketed in some prepackaged salad mixes. The 

marketing of detached leaves is occasionally done 

to recover some value from fresh market product 

that is damaged or otherwise would be wasted.

Special Considerations

Chicons must be handled with care to avoid 

mechanical damage to minimize discoloration 

and pathological problems. Temperatures must be 

kept low, and light must be excluded to prevent 

greening. High RH is necessary to prevent loss of 

turgor and wilting.

References

Corey, K.A., D.J. Marchant, and L.F. Whitney. 

1990. Witloof chicory: a new vegetable crop in the 

United States. In J. Janick and J.E. Simon, eds., 

Advances in New Crops, pp. 414-418. Timber 

Press, Portland, OR.

De Proft, M., J. De Greef, K. Van Nerum, and 

G. Goffings. 1986. Ethylene in the production of 

Belgian endive. HortScience 21:1132-1133.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Herregods, M. 1971. The effect of some factors on 

witloof during storage. Acta Hort. 20:36-42.

Rubatzky, V.E., and M. Yamaguchi. 1997. Witloof 

chicory. In World Vegetables—Principles, 

Production, and Nutritive Values, pp. 351-354. 

Chapman & Hall, New York, NY.

Ryder, E.J. 1979. Leafy Salad Vegetables, pp. 171-

194. AVI Pub. Co., Westport, CT.
289

Chinese Cabbage

Robert K. Prange

Prange is with Atlantic Food and Horticulture 

Research Centre, Agriculture and Agri-Food 

Canada, Kentville, Nova Scotia, Canada.

Scientific Name and Introduction

Chinese cabbage, Brassica rapa L. (B. campestris

L.) subsp. pekinensis (Lour.) Hanelt, is an 

annual of the Brassicaceae (Cruciferae) family 

(Munro and Small 1997). The edible portion 

includes the leaf blades and stalks. Two head 

shapes predominate: the wong bok or napa types 

(which are short and broad) and the michihli 

types (which are long and tapered) (Wang and 

Cerkauskas 1999). Chinese cabbage is grown in 

small acreages in most major temperate vegetablegrowing regions and is available year round in 

most markets.

Quality Characteristics and Criteria

Chinese cabbage should have uniform, tightly 

formed heads with crinkly, yellow-green leaf 

blades. Head shape and leaf characteristics can 

vary, depending on the cultivar. There should be 

no evidence of leaf wilting or discoloration.

Horticultural Maturity Indices

Determination of maturity in species of Brassica

is not simple, and no single index of maturity is 

reliable (Ludford and Isenberg 1987). Harvesting 

consists of cutting the whole plant at the soil 

surface when the heads are firm and the outer 

leaves are bright green (Munro and Small 1997). 

In some cultivars, the outer leaves may be tied 

a few weeks before harvest to promote a tighter, 

upright head. Ludford and Isenberg (1987) cite 

reports that Chinese cabbage store better when 

heads are more compact at harvest.

Grades, Sizes, and Packaging

There are no published U.S. standards for grades 

of Chinese cabbage. The wong bok or napa types 

are about 20 to 25 cm (8 to 10 in) in length, 15 to 

20 cm (6 to 8 in) in diameter, and weigh 1.3 to 4.1 

kg (3 to 9 lb). The michihli types are about 38 to 

51 cm (15 to 20 in) in length, 7.6 to 12.7 cm (3 to 

5 in) in diameter, and weigh 0.9 to 2.3 kg (2 to 5 

lb) (Kelley 1999). They are shipped in wax-coated 

corrugated cardboard cartons and wire-bound 

crates of various sizes.

Precooling Conditions

Damaged leaves should be removed, and the 

heads packed into shipping containers and quickly 

cooled (vacuum or hydrovac cooling, forced-air 

cooling, or hydrocooling) to maximize shelf-life 

(Kasmire and Cantwell 1992).

Optimum Storage Conditions

Depending primarily on cultivar, Chinese cabbage 

can be held for 3 to 6 mo at 0 oC (32 oF) and 98% 

RH (Fritz and Weichmann 1980, Apeland 1985, 

van den Berg 1987). The storage temperature 

should be as close as possible to 0 oC (32 oF) 

without freezing (Kasmire and Cantwell 1992). 

Water loss is reduced and storage life extended 

when heads are enclosed in perforated plastic bags 

(Sozzi et al. 1981). Storage life is extended by 

growing Chinese cabbage during cooler growing 

seasons and placing the heads upside down 

during storage (Jin-Cheol Jeong, 1998, personal 

communication).

Controlled Atmosphere (CA) 

Considerations

An atmosphere of 1 to 2% O2

 and 2 to 6% CO2

is effective at extending storage life (Adamicki 

1997, Saltveit 1997). Decay increases and 

offensive odors are produced during continuous 
290

exposure to 7.5% CO2

, or 5 to 10 days exposure 

to 30 to 40% (Herner 1987). Specific CA 

recommendations depend on cultivar, temperature, 

and storage duration. CA storage retains green 

color and ascorbate and sugar content in leaves 

and decreases decay (Wang 1983, Ludford and 

Isenberg 1987).

Retail Outlet Display Considerations

Chinese cabbage is displayed as individual heads 

with the outer leaves removed, frequently with a 

band around the equator to maintain a compressed 

head shape. Heads should be kept as cool as 

possible without freezing and sprinkled with water 

to minimize moisture loss. Exposure to ethylene 

should be avoided.

Chilling Sensitivity

Chinese cabbage may be chilling sensitive. A 

physiological disorder (brown midrib) developed 

after prolonged storage at 0 °C (32 °F) (Apeland 

1985). The critical temperature was 1.5 to 3.0 °C 

(35 to 37 °F) in the three cultivars studied. A 50% 

loss of product occurred after about 150 degreedays (°F) below the cultivar-specific critical 

temperature.

Ethylene Production and Sensitivity

Chinese cabbage produces very little ethylene, 

<0.1 μL kg-1 h-1 at 20 °C (68 °F) (Kader 1992), 

but exposure to less than 0.1 μL L-1 can accelerate 

senescence in air storage. Levels inside cartons of 

Chinese cabbage in wholesale markets have been 

measured at 1.09 μL L-1 (Wills 1998). Ethyleneinduced leaf abscission can be minimized by 

storage in 1% O2

 (Wang 1983). 

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 6 to 14

5 °C 8 to 16

10 °C 15 to 19

15 °C 19 to 30

20 °C 25 to 45

Data from Apeland (1985) and Cantwell and 

Suslow (2001).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Brown midrib, a physiological disorder causing 

significant storage losses, is a symptom of chilling 

injury (Apeland 1985). Elevated levels of CO2

 can 

increase decay and the occurrence of offensive 

odors (Herner 1987).

Postharvest Pathology

Geeson (1983) reported the occurrence of leaf 

spots caused by Alternaria spp., bacterial soft rot 

(Erwinia carotovora), and black discoloration of 

leaf veins, which may be due to Xanthomonas

campestris.

Quarantine Issues

None.
291

Suitability as Fresh-Cut Product

Chinese cabbage is suitable as a fresh-cut product 

packaged in air or modified atmosphere packaging 

(MAP). Gorny (1997) rates MAP treatment as 

moderately effective in extending the storage 

life of shredded Chinese cabbage and provides 

respiration rates at different temperatures, 

atmospheres, and varying amounts of shredding 

(table 1). Kleiber and Kim (1998) state that MAP 

Table 1. Respiration of cut Chinese cabbage under various conditions

__________________________________________________________________

Temperature Atmosphere Degree of shredding Respiration

__________________________________________________________________

 mg CO2 kg-1 h-1

2 °C air half head 10

rough cut (0.5 x 3 cm) 18

fine cut (0.25 - 1.5 cm) 24

5 °C air half head 16

rough cut (0.5 x 3 cm) 32

fine cut (0.25 - 1.5 cm) 40

5 °C 5 % O2 half head 10

+ 5 % CO2 rough cut (0.5 x 3 cm) 22

fine cut (0.25 - 1.5 cm) 28

10 °C air half head 17

rough cut (0.5 x 3 cm) 48

fine cut (0.25 - 1.5 cm) 57

23 °C air half head 31 to 36

rough cut (0.5 x 3 cm) 90 to 99

fine cut (0.25 - 1.5 cm) 117 to 126

__________________________________________________________________

is not essential for shredded Chinese cabbage held 

at 0 or 5 °C (32 or 41 °F), as there is only a transient increase in ethylene production and respiration 

that peaks after 6 to 12 h and 0 to 3 h, respectively. 

The shelf-life-limiting factors are browning on cut 

surfaces and leaf surfaces, as well as appearance of 

black speck (gomasho). If 1% citrate is used as a 

dip, a commercially acceptable shelf-life of 21 days 

at 0 °C (32 °F) or 14 days at 5 °C (41 °F) can be 

achieved without MA.
292

References

Apeland, J. 1985. Chilling injury in Chinese 

cabbage Brassica campestris pekinensis (Lour) 

Olsson. Acta Hort. 157:261-270.

Adamicki, F. 1997. Effect of ultra low oxygen 

on the storage and quality of some vegetables. In

M.E. Saltveit, ed., 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, July 13-18, 1997, vol. 4, pp. 26-

33. University of California, Davis, CA..

Cantwell, M., and T. Suslow. 2001. Cabbages 

(Round and Chinese types). In Fresh Produce 

Facts. At http://postharvest.ucdavis.edu/

postharvest_information.

Fritz, D., and J. Weichmann. 1981. Influence of 

weather conditions during growth on storage 

ability of different Chinese cabbage cultivars. 

Chinese Cabbage. In R.L. Villareal and T.D. 

Griggs, eds., Proceedings of the First International 

Symposium of the Asian Vegetable Research and 

Development Center, Shanhua, Tainan, Taiwan, 

pp. 271-278.

Geeson, J.D. 1983. Brassicas. In C. Dennis, ed., 

Postharvest Pathology of Fruits and Vegetables, 

pp. 125-126. Academic Press, New York, NY.

Gorny, J.R. 1997. A summary of CA and MA 

requirements and recommendations for freshcut (minimally processed) fruits and vegetables. 

In J.R. Gorny, ed., 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, July 13-18, 1997, vol. 5, pp. 30-

66. University of California, Davis, CA.

Herner, R.C. 1987. High CO2

 effects on plant 

organs. In J. Weichmann, ed., Postharvest 

Physiology of Vegetables, pp. 239-253. Marcel 

Dekker, New York, NY.

Kader, A.A. 1992. Postharvest biology and 

technology: an overview. In A.A. Kader, ed., 

Postharvest Technology of Horticultural Crops, 

pp. 15-20. DANR Pub. no. 3311, University of 

California, Davis, CA.

Kasmire, R.F., and M. Cantwell. 1992. 

Postharvest handling systems: flower, leafy and 

stem vegetables. In A.A. Kader, ed., Postharvest 

Technology of Horticultural Crops, pp. 267-270. 

DANR Pub. no. 3311, University of California, 

Davis, CA.

Kelley, William T. 1999. Specialty crops: chinese 

cabbage and related oriental crops. Commercial 

vegetable production. University of Georgia 

College of Agricultural and Environmental 

Sciences. At http://pubs.caes.uga.edu/caespubs/

pubcd/c809-w.htm#chinese_cabbage.

Kleiber, A., and B.-S. Kim. 1998. Minimal 

processing of Chinese cabbage. Acta Hort. 

464:249-251.

Ludford, P.M., and F.M.R. Isenberg. 1987. 

Brassica crops. In J. Weichmann, ed., Postharvest 

Physiology of Vegetables, pp. 497-522. Marcel 

Dekker, New York, NY.

Munro, D.B., and E. Small. 1997. Vegetables 

of Canada. National Research Council, Ottawa, 

Ontario, Canada.

Saltveit, M.E. 1997. A summary of requirements 

and recommendations for the controlled and 

modified atmosphere storage of harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, vol. 

4, Vegetables and Ornamentals, July 13-18, 1997, 

University of California, Davis, CA.

Sozzi, A., F.L. Gorini, and L. Uncini. 1981. 

Storage suitability of the Chinese cabbage as 

affected by lining. Acta Hort. 116:157-162.

van den Berg, L. 1987. Water vapor pressure. In

J. Weichmann, ed., Postharvest Physiology of 

Vegetables, pp. 203-230. Marcel Dekker, New 

York, NY.

Wang, C.Y. 1983. Postharevst response of Chinese 

cabbage to high CO2

 treatment or low O2 storage. 

J. Amer. Soc. Hort. Sci. 108:125-129. 
293

Wang, S.L., and R.F. Cerkauskas. 1999. Recent 

development of production and processing of 

oriental vegetables in Canada. Acta Hort. 483:429-

436.

Wills, R.B.H. 1998. Enhancement of senescence 

in nonclimacteric fruit and vegetables by low 

ethylene levels. Acta Hort. 464:159-162. 
294

Coconut

Robert E. Paull and Saichol Ketsa

Paull is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI; Ketsa is with the Department of 

Horticulture, Kasetsart University, Bangkok, 

Thailand. 

Scientific Name and Introduction

Coconut (Cocos nucifera L.) is marketed at two 

stages of development. At an immature stage, the 

fruit (water coconut) contains mainly water and a 

little jellylike meat instead of the hard, white flesh 

(meat/endosperm) found in mature coconuts. In 

Thailand, and now marketed in the United States, 

immature green nuts are trimmed and shaped, 

removing most of the husk. The final product has 

a flat bottom, round body with a pyramid top, 

and the eyes showing. To prevent browning of 

the remaining husk, nuts are dipped in 1 to 3% 

sodium meta-bisulfite for 2 to 5 min and then 

wrapped in plastic film (Tongdee et al. 1991). 

Sometimes fungicide is included in the sulfite 

solution. Alternatively, the husk is removed before 

dipping in sulfite solution. Fruit are available year 

round from most tropical countries (Seelig 1970).

Quality Characteristics and Criteria

Major quality characteristics are maturity, size, 

and freedom from blemishes, cracking, fiber of 

husked coconuts, and wet or moldy eyes. Check 

for a sloshing sound for presence of coconut water 

in the nut. Coconut milk is obtained by removing 

and grating the hard, white flesh and squeezing out 

the milky juice. Immature, dehusked coconuts are 

about 10 cm (4 in) in diameter, weigh about 500 

g (1.1 lb), have 100 g (3.5 oz) endosperm, 120 g 

(4.2 oz) shell, and 250 g (8.8 oz) water.

Horticultural Maturity Indices

Young coconuts are harvested 6 to 9 mo after 

flowering as they approach full size and the skin 

is still green (Consignado et al. 1976, Srivichai 

1997) and the short stem (rachillae) on the top of 

individual coconuts that originally held the male 

flowers (“rat-tail” in Thai) becomes half green 

and brown. In immature nuts, the skin surface 

around the calyx (cap) on the top of the coconut 

is creamy white or a whitish yellow. When the 

area surrounding the cap is green, the coconut 

is considered mature and is 10 to 12 mo old. At 

maturity the skin begins to change from green to 

yellow, then brown, and the “rat-tail” is entirely 

brown.

Grades, Sizes, and Packaging

There are no specific grades; informal grades are 

generally based on size and weight. Mature U.S. 

dehusked coconuts are sold in 34- to 36-kg (75- to 

80-lb) woven plastic or burlap sacks containing 40 

to 50 coconuts, plastic mesh bags of 12 coconuts, 

and cartons with 20 to 25 film-wrapped coconuts 

weighing 17 to 18 kg (37 to 40 lbs). Immature 

coconuts (water coconuts) are shaped, dipped in 

bisulphate, and film-wrapped. They are sold in 

single-piece cartons containing 10 to 16 nuts. For 

young coconuts, the entire husk is removed, and 

the nuts are then dipped in sodium bisulfite before 

packing.

Precooling Conditions

Room cooling is generally used for mature husked 

nuts. Forced-air cooling and hydrocooling are 

acceptable. A rapid temperature change of 8 oC 

(14 °F) or greater can cause cracking.
295

Optimum Storage Conditions

Mature coconuts with husk can be kept at 

ambient conditions for 3 to 5 mo before the liquid 

endosperm evaporates or before the shell cracks 

due to desiccation or sprouting. Storage at 0 to 

1.5 oC (32 to 35 oF) and 75 to 85% RH is possible 

for up to 60 days for mature, dehusked coconuts 

(Maliyar and Marar 1963), and 13 to 16 oC (55 to 

60 oF) and 80 to 85% RH for 2 weeks or less. Low 

RH and high temperature should be avoided.

Young coconuts are normally held at 3 to 6 oC (37 

to 43 oF) with 90 to 95% RH, while wrapped and 

shaped fruit can be held for 3 to 4 weeks. Shaped 

young coconuts treated with 0.5 to 1.0% sodium 

meta-bisulfite can be held at ambient temperature 

for 2 days before browning occurs, while those 

treated with 2% sodium meta-bisulfite can be held 

at ambient temperature for 2 to 7 days (Tongdee 

et al. 1992). Young coconuts that have not been 

dehusked can be stored for a longer period than 

dehusked or shaped young coconuts. In dehusked 

or shaped coconuts, soluble solids content (SSC) 

declines and total acidity (TA) increases more 

rapidly than in nondehusked coconuts. Thus, the 

taste of dehusked or shaped coconuts sours more 

rapidly than nondehusked coconuts during storage 

(Somboonsup 1985). The husk acts as an insulator 

and may increase the storage life of young 

coconuts.

Controlled Atmosphere (CA) 

Considerations

No data are available on CA storage. Mature 

dehusked coconuts are waxed or film-wrapped to 

reduce water loss. Immature husked nuts can also 

be film-wrapped or waxed; however, the outside 

color changes rapidly from white to brown unless 

they are dipped in sodium bisulfite (Tongdee et al. 

1992).

Retail Outlet Display Considerations

Display coconuts at ambient temperatures and do 

not mist. Nonwrapped or individually wrapped 

shaped coconuts are displayed at ambient 

temperatures or at 10 °C (50 °F).

Chilling Sensitivity

When stored at 0 °C (32 °F), immature nuts have 

green skins that turn brown after 7 days. Few 

other changes occur in other quality characteristics 

at this temperature (Consignado et al. 1976).

Ethylene Production and Sensitivity

Ethylene production is very low to near zero for 

mature husked coconut. There are no reports of 

sensitivity to ethylene.

Respiration Rates

Temperature mg CO2 kg-1 h-1

Immature 10 oC 7 to 8

 20 oC 13 to 24

Mature 10 oC 6 to 7

 20 oC 13 to 26

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 1.9 at 10 °C (50 °F), and 1.8 at 20 °C (68 °F). 

To calculate heat production, multiply mg kg-1 h-1

by 220 to get BTU per ton per day or by 61 to get 

kcal per tonne per day.

Physiological Disorders

Mechanical damage to immature coconuts will 

cause the white coir (the stiff fiber from the outer 

husk) to turn brown and the nut to crack. Younger 

nuts have a lower rupture force than mature nuts 

(Tongdee 1991). A rapid temperature change of 

8 °C (15 °F) or more during storage of mature 

husked coconut can lead to cracking (Burton 

1982), while freezing occurs at -3 °C (27 °F). 
296

Moisture loss causes a loss of water in the nut; this 

loss can be reduced by RH control, film wrapping, 

or waxing of mature nuts.

Postharvest Pathology

Superficial mold growth can occur on wet 

coconuts.

Quarantine Issues

There are no quarantine issues if the nuts are 

mature, have a dry husk, and are free of surface 

insects and soil. Some restrictions exist on the 

importation into certain tropical and subtropical 

countries from regions affected by palm diseases.

Suitability as Fresh-Cut Product

Meat from both immature (jellylike) and mature 

(hard) nuts is sold in trays with overwrap or 

plastic bags for use in desserts. Immature 

coconuts’ jellylike meat and water have to be 

held at 3 to 5 °C (37 to 41 °F) to avoid spoilage. 

The jellylike meat and coconut water packaged 

in small plastic bags are frequently seen held 

on ice in Southeast Asian markets and roadside 

stalls. Nonshredded and shredded meat of mature 

coconuts is packaged in plastic bags for cooking 

and for use in desserts.

References

Burton, B.D. 1982. Prevention of postharvest 

studies cracks in husked coconuts during transit. J. 

Amer. Soc. Hort. Sci. 107:905-907.

Consignado, T.O., P.C. Tabora, and R.P. Creencia. 

1976. Physio-chemical changes in stored young 

coconut. The Phillipine Agriculturist 60:256-270.

Marar, M.M.K., and C.A. Kurhiraman. 1957. 

Studies on the keeping quality of ripe coconut in 

storage. Coconut J. 10(4):37-51.

Muliyar, M.K., and M.M.K. Marar. 1963. Studies 

on the keeping quality of ripe coconuts in storage. 

Indian Coconut J. 17:13-18.

Seelig, R.A. 1970. Coconuts: Fruits and Vegetable 

Facts and Pointers. United Fresh Fruit and 

Vegetable Association, Washington, DC.

Somboonsup, S. 1985. Effect of some postharvest 

handling on quality of fresh coconuts. 

Undergraduate Special Project, Department of 

Horticulture, Kasetsart University, Bangkok, 

Thailand. 

Srivichai, S. 1997. Planting Coconut Palm. 

Agricultural Commodity Publishing, Bangkok, 

Thailand 95 pp. (In Thai). 

Tongdee, S.C. 1991. Postharvest handling of 

tender coconut. ASEAN Food J. 6:74-75.

Tongdee, S.C., A. Suwanagul, and S. Neamprem. 

1992. Control of browning in trimmed green 

coconuts. In B.R. Champ, E. Highley, and G.I. 

Johnson, eds., Postharvest Handling of Tropical 

Fruits. International Conference on Postharvest 

Handling of Tropical Fruits, Chiang Mai, 

Thailand, July 1993, p. 15. ACIAR Proceedings 

no. 50, ACIAR, Canberra, Australia. 
297

Cranberry

Robert K. Prange

Prange is with Atlantic Food and Horticulture 

Research Centre, Agriculture and Agri-Food 

Canada, Kentville, Nova Scotia, Canada.

Scientific Name and Introduction

Vaccinium macrocarpon Ait., the American 

cranberry, is a perennial, woody, creeping, 

evergreen species in the Vacciniaceae (Blueberry) 

family (Dana 1990). It is native to acid bogs from 

Newfoundland south to North Carolina and west 

to Minnesota. It is popular for its tart-flavored red 

fruit. Canada and the United States produce almost 

all of the world’s commercial crop of cranberries.

Between 92 and 95% is processed; the remainder 

is sold fresh during the autumn and early winter. 

The major U.S. cranberry-growing States are, in 

order of production, Wisconsin, Massachusetts, 

New Jersey, Oregon, and Washington (NASS 

2005).

Quality Characteristics and Criteria

Color intensity, glossiness, uniformity, and 

freedom from defects are the major quality 

characteristics for fresh and frozen cranberries 

(Spayd et al. 1990).

Horticultural Maturity Indices

Since the amount of red color (anthocyanin 

content) in the fruit is the major factor determining 

cranberry crop value, harvesting is timed to 

achieve the maximum red color without allowing 

the fruit to become too overmature (Eck 1990). 

Overmaturity results in physiological breakdown 

(see Physiological Disorders).

Grades, Sizes, and Packaging

There is only one grade standard for fresh 

cranberries: U.S. No. 1. Criteria include color (no 

less than 75% of the fruit surface pink or red), 

size (minimum diameter of 10.3 mm or 13/32 in), 

absence of soft or decayed fruit, and freedom from 

other defects. Fresh cranberries are commonly 

packed in cartons containing 24 12-oz polybags, 

or in cartons of 20, 25, or 30 lb (9.0, 11.4, or 13.2 

kg) (AMS 1997). Occasionally, 9 2-lb (0.9-kg) and 

4 5-lb (2.3-kg) polybag cartons are used for some 

retail customers, and wood totes may be used for 

sale of bulk cranberries.

Precooling Conditions

The storage length can be increased if the fruit are 

immediately cooled after harvest and packaged 

just before shipment (Kaufman et al. 1958, Ringel 

et al. 1959). If cranberries are not at the desired 

temperature, they can be forced-air cooled (Spayd 

et al. 1990, Kasmire and Thompson 1992).

Optimum Storage Conditions

The minimum recommended storage temperature 

is 2 °C (35.6 °F). The maximum recommended 

temperature is 4 to 5 °C (39 to 41 °F) (Hardenburg 

et al. 1986, Lidster et al. 1988, Spayd et al. 1990, 

Kader 1997), though there is one recommendation 

of 7 °C (45 °F) (Kasmire and Thompson 1992). 

The recommended RH is 90 to 95% (Hardenburg 

et al. 1986, Spayd et al. 1990, Kader 1997). 

Some researchers have recommended lower RH 

in the belief that it may reduce fungal decay: for 

example, 65 to 70% (Stark et al. 1974), 70 to 75% 

(Wright et al. 1937), and 80 to 90% (Lidster et al. 

1988). Red color can be increased after harvest by 

holding fruit, especially early harvested fruit, at 7 

to 10 °C (45 to 50 °F) for a few weeks rather than 

at the lower recommended temperatures (Levine 

et al. 1941). The expected storage life is 2 to 4 mo.
298

Controlled Atmosphere (CA) 

Considerations

There is no known commercial use of CA in 

cranberry storage. Some research suggests CA 

containing various combinations of O2

 and CO2

does not extend cranberry storage life compared 

with ambient air (Anderson et al. 1963, Stark 

et al. 1969). Conversely, Kader (1992, 1997) 

suggested that a CA condition of 1 to 2% O2

 and 

0 to 5% CO2

 is beneficial. The maximum CO2

tolerance may be above 5%, as Stark et al. (1969) 

used 10% CO2

 without detrimental effects. In a 

2-mo test at 3 °C (37 °F) with 98% RH using 10 

CA combinations of 2%, 21%, and 70% O2

 with 

0%, 15%, and 30% CO2

. Gunes and Watkins 

(2001) concluded that 21% O2

 with 30% CO2 was 

optimal. Cranberries can be held in an anaerobic 

condition (100% N2

) for up to 14 mo at 3.3 °C (38 

°F) in low RH (Stark et al. 1974). Such fruit have 

little decay but a high amount of physiological 

breakdown, making them unacceptable for 

fresh or juice use but still acceptable for use in 

cranberry sauce.

Retail Outlet Display Considerations

Water sprinkling or top-icing are not 

recommended.

Chilling Sensitivity

Cranberry is considered to be a chilling sensitive 

fruit (Wright et al. 1937, Levine et al. 1941, 

Kader 1992). Storage at temperatures near 0 °C 

for more than about 4 weeks may result in lowtemperature breakdown (Lidster et al. 1988). 

Chilling injury symptoms include dull appearance, 

rubbery texture, and increased decay (Mitcham 

et al. 1999). If fruit are held at 0 °C, intermittent 

warming to 21 °C (70 °F) for 1 day a month can 

reduce chilling injury (Hruschka 1970).

Ethylene Production and Sensitivity

Cranberry has a low ethylene production rate of 

0.1 to 1.0 μL kg-1 h-1 at 5 °C (41 °F) (Kader 1992, 

Mitcham et al. 1999). Postharvest treatment of 

fruit with as little as 10 μL L-1 markedly increases 

anthocyanin content, which is enhanced further if 

the fruit are treated in the presence of light (Fudge 

1930, Craker 1971). Eck (1990) and Reid (1992) 

indicate the use of ethephon, a source of ethylene 

approved in some areas of the United States, 

which accelerates cranberry maturity and/or red 

color development. A 1995 U.S. Environmental 

Protection Agency “Reregistration Eligibility 

Decision (RED) on Ethephon” indicates that 

cranberries have been deleted from ethephon 

product labels.

Respiration Rates

Cranberries have a low respiration rate compared 

to other berry crops, which have a moderate to 

high rate (Kader 1992).

Temperature mg CO2 kg-1 h-1

0 °C 4

4 to 5 °C 4 to 5

10 °C 8

15 to 16 °C —

20 to 21 °C 11 to 18

Data from Hardenburg et al. (1986) and Mitcham 

et al. (1999).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Physiological breakdown of cranberry is 

manifested by a soft and rubbery condition, 

dull external appearance, and diffusion of 

red anthocyanin pigment throughout internal 

tissues (Ceponis and Stretch 1981). No fungal 

organisms are associated with this condition. It 
299

is correlated with one or more of the following: 

impact bruising; late-harvested, more intensely 

colored fruit; and immersion of free berries for 8 

h or more in a flooded bog or similar smothering 

effects where cranberries are held in poorly 

ventilated conditions (Graham et al. 1967, 

Patterson et al. 1967, Ceponis and Stretch 1981, 

Massey et al. 1981). Chilling injury can have the 

same symptoms.

Postharvest Pathology

Postharvest cranberry diseases are almost entirely 

caused by fungi, with the exception of ringspot, 

which is thought to be a virus-induced disease 

(Caruso and Ramsdell 1995, Prange and DeEll 

1997). Cranberry is not only attacked by several 

common postharvest fungi but also by a large 

number of fungi that are unknown on other fruit 

crops (Caruso and Ramsdell 1995, Prange and 

DeEll 1997). The principal storage rots, which 

can be found in all the major cranberry-growing 

areas, are end rot, black rot, viscid rot, yellow rot, 

and botryosphaeria fruit rot (Eck 1990, Prange 

and DeEll 1997). Since the occurrence of these 

fungi can vary with location and season and some 

are not easily identified visually, confirmation of 

the causal organism(s) usually requires extensive 

culturing and spore examination. Decay may be 

reduced if storage O2

 is below 1%, since there is 

no decay control at 1% (Anderson et al. 1963), but 

100% N2

 for 3 weeks at 3 °C (38 °F) reduced the 

number of pathogenic species and decay compared 

with air-stored fruit (Lockhart et al. 1971).

Quarantine Issues

There are no current restrictions for shipments 

within Canada and the United States. There has 

been little, if any, international trade in fresh 

cranberries. Such future trade may be subjected to 

quarantine restrictions, depending on the countries 

involved.

Suitability as Fresh-Cut Product

No current potential.

Special Considerations

Cranberries can be stored fresh for 2 to 4 mo, 

depending on season, cultivar, maturity, handling, 

and storage conditions (Hardenburg et al. 1986). 

The storage life of cranberries is limited by the 

development of decay, shrinkage resulting from 

moisture loss, and physiological breakdown 

(Lidster et al. 1988). Early-harvested fruit usually 

have a longer storage potential than late-harvested 

fruit (Doughty et al. 1967). Physical damage, 

which can occur during mechanical harvesting or 

rough hand-harvesting, transport, or mechanical 

cleaning, sorting, and packing, increases 

physiological breakdown, postharvest softening, 

and decay and reduces storage life (Graham et al. 

1967, Patterson et al. 1967, Massey et al. 1981). 

There is more fungal decay and physiological 

breakdown in water-harvested than in handharvested cranberries, especially if cranberries are 

kept in the water more than 1 h after detachment 

from the plant (Mitcham et al. 1999; Blake 

Johnson, 2000, personal communication).

Acknowledgments

Some of the information in this chapter was 

from the Produce Marketing Association’s 

“Fresh Produce Manual” and from B. Johnson 

of Bezanson and Chase Cranberry Company, 

Aylesford, Nova Scotia, Canada.

References

AMS [USDA Agricultural Marketing Service]. 

1997. United States standards

for grades of fresh cranberries. U.S. Department 

of Agriculture, Washington, DC. (http://www.ams.

usda.gov/AMSv1.0/standards)
300

Anderson, R.E., R.E. Hardenburg, and H.C. 

Vaught. 1963. Controlled atmosphere storage 

studies with cranberries. Proc. Amer. Soc. Hort. 

Sci. 83:416-422.

Caruso, F.L., and D.C. Ramsdell. 1995. 

Compendium of Blueberry and Cranberry 

Diseases. APS Press, St. Paul, MN.

Ceponis, M.J., and A.W. Stretch. 1981. The 

influence of water immersion time at harvest 

on physiological breakdown of ‘Early Black’ 

cranberries in storage. HortScience 16:60-61.

Craker, L.E. 1971. Postharvest color promotion in 

cranberry with ethylene. HortScience 6:137-139.

Dana, M.N. 1990. Cranberry management. In

G.J. Galleta and D.G. Himelrick, eds., Small Fruit 

Crop Management, pp. 334-262. Prentice Hall, 

Upper Saddle River, NJ.

Doughty, C.C., M.E. Patterson, and A.Y. Shawa. 

1967. Storage longevity of the ‘McFarlin’ 

cranberry as influenced by certain growth 

retardants and stage of maturity. Proc. Amer. Soc. 

Hort. Sci. 91:192-204.

Eck, P. 1990. The American Cranberry. Rutgers 

University Press, New Brunswick, NJ.

Fudge, B.R. 1930. Increasing the color of 

cranberries after removal from the vines. Bull. 

504, New Jersey Agricultural Experiment Station, 

New Brunswick, NJ.

Graham, S.O., M.E. Patterson, and B. Allan. 1967. 

Bruising as a predisposing factor in the decay of 

stored cranberries. Phytopathology 57:497-501.

Gunes, G., and C.B. Watkins. 2001. Postharvest 

quality of cranberries as affected by controlled 

atmosphere. HortScience 36:571 (Abstract).

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Hruschka, H.W. 1970. Physiological breakdown in 

cranberries—inhibition by intermittent warming 

during cold storage. Plant Dis. Rptr. 54:219-222.

Kader, A.A. 1992. Postharvest biology and 

technology: an overview. In A.A. Kader, ed., 

Postharvest Technology of Horticultural Crops, 

pp. 15-20. DANR Pub. no. 3311, University of 

California, Davis, CA.

Kader, A.A. 1997. A summary of CA requirements 

and recommendations for fruits other than apples 

and pears. In A.A. Kader, 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 3, pp. 1-34. University of California, Davis, 

CA.

Kasmire, R.F., and J.F. Thompson. 1992. Selecting 

a cooling method. In A.A. Kader, ed., Postharvest 

Technology of Horticultural Crops, pp. 63-68. 

DANR Pub. no. 3311, University of California, 

Davis, CA.

Kaufman, J., S.M. Ringel, A.A. Hamer, et al. 

1958. Effect of Precooling on Market Quality of 

Cranberries Shipped by Rail or Truck. Marketing 

Research Report 287, U.S. Department of 

Agriculture, Agricultural Marketing Service, 

Washington, DC.

Levine, A.S., C.R. Fellers, and C.I. Gunness. 

1941. Carbon dioxide-oxygen and storage 

relationships in cranberries. Proc. Amer. Soc. 

Hort. Sci. 38:239-242.

Lidster, P.D., P.D. Hildebrand, L.S. Bérard, and 

S.W. Porritt. 1988. Commercial Storage of Fruits 

and Vegetables. Pub. no. 1532/E, Agriculture and 

Agri-Food Canada, Ottawa, Ontario, Canada.
301

Lockhart, CL., F.R. Forsyth, R. Stark, and 

I.V. Hall. 1971. Nitrogen gas suppresses 

microorganisms on cranberries in short term 

storage. Phytopathology 61:335-336.

Massey, L.M., B.R. Chase, and M.S. Starr. 1981. 

Impact-induced breakdown in commercially 

screened ‘Howes’ cranberries. J. Amer. Soc. Hort. 

Sci. 106:200-203.

Mitcham, E.J., C.H. Crisosto, and A.A. Kader. 

1999. Bushberries: blackberry, blueberry, 

cranberry, raspberry. In Fresh Produce Facts. 

At http://postharvest.ucdavis.edu/produce_

information.

NASS [USDA National Agricultural Statistics 

Service]. 2005. Agricultural Statistics. At http://

www.usda.gov/nass/pubs/agstats.

Patterson, M.E., C.C. Doughty, S.O. Graham, and 

B. Allan. 1967. Effect of bruising on postharvest 

softening, color changes, and detection of 

polygalacturonase enzyme in cranberries. Proc. 

Amer. Soc. Hort. Sci. 90:98-505.

Prange, R.K., and J.R. DeEll. 1997. Preharvest 

factors affecting postharvest quality of berry 

crops. HortScience 32:824-830.

Reid, M.S. 1992. Ethylene in postharvest 

technology. In A.A. Kader, ed., Postharvest 

Technology of Horticultural Crops, pp. 97-108. 

DANR 3311, University of California, Davis, CA.

Ringel, S.M., J. Kaufman, and M.J. Jaffe. 1959. 

Refrigerated Storage of Cranberries. Marketing 

Research Report 312, U.S. Department of 

Agriculture, Agricultural Marketing Service, 

Washington, DC.

Spayd, S.E., J.R. Morris, W.E. Ballinger, and D.G. 

Himelrick. 1990. Maturity standards, harvesting, 

postharvest handling and storage. In G.J. Galleta 

and D.G. Himelrick, eds., Small Fruit Crop 

Management, pp. 504-531. Prentice Hall, Upper 

Saddle River, NJ.

Stark, R., I.V. Hall, F.R. Forsyth, and P.R. Dean. 

1969. Cranberries evaluated for fresh fruit and 

processing quality after reduced O2

 storage. 

Cranberries 34(6):14,16 and 34(7):14,16.

Stark, R., F.R. Forsyth, C.L. Lockhart, and I.V. 

Hall. 1974. Processing quality of cranberries after 

extended storage in N2

 atmosphere with low and 

high relative humidities. Can. Inst. Food Sci. 

Technol. J. 7:9-10.

Wright, R.C., J.B. Demaree, and M.S. Wilcox. 

1937. Some effects of different storage 

temperatures on the keeping of cranberries. Proc. 

Amer. Soc. Hort. Sci. 34:397-401.
302

Cucumber

Mikal E. Saltveit

Saltveit is with the Department of Plant Sciences, 

Mann Laboratory, University of California, Davis, 

CA.

Scientific Name and Introduction

Cucumber (Cucumis sativus L) is a member of 

the Cucurbitaceae family, along with melons, 

squashes, and many other horticulturally important 

species. The fruit are borne on indeterminate, 

tendril-bearing vines of subtropical and tropical 

origin (Robinson and Decker-Walters 1997). The 

inferior ovary has three united carpels in most 

cultivars. Compact, determinate cultivars have 

been developed for home gardeners and for onceover mechanical harvesting (Miller and Wehner 

1989).

Quality Characteristics and Criteria

Fruit are round to oblong or narrowly cylindrical, 

with small tubercles (warts) and spines of 

trichome origin on the rind of some cultivars 

(Miller and Wehner 1989). The rind of slicing 

cucumbers should be dark green and firm with 

no pits or wrinkled (pinched) ends. Spine color is 

associated with mature fruit color and fruit netting. 

Fruit of white-spined cultivars are light green to 

yellow when mature and not netted. Black-spined 

fruit are orange or brown when mature and may 

be netted. The flesh is crisp and white, except in a 

few cultivars where it is pale orange.

Horticultural Maturity Indices

Fruit are harvested at various stages of 

development. Immature fruit are green at the 

edible stage, except for a few cultivars that are 

white or yellow. Fruit are generally harvested 

immature (that is, before the seeds are fully 

enlarged and hardened) with a diameter of <5 cm 

(2 in) for picklers and <6 cm (2 3/8 in) for slicers. 

The minimum length is 14 cm (5.5 in) for slicers. 

Fruit firmness, external glossiness, and formation 

of jellylike material around the seeds are 

indicators of proper harvest maturity. Greenhousegrown parthenocarpic (produced without 

pollination) fruit are harvested 10 to 14 days after 

anthesis after they turn bright green (Kanellis et 

al. 1988). Straight, uniformly cylindrical fruit 

slightly tapered at both ends are of highest quality. 

Cucumbers are listed as nonclimacteric, yet there 

is a burst of ethylene production that precedes 

a rapid loss of chlorophyll in harvested fruit 

(Saltveit and McFeeters 1980).

Grades, Sizes, and Packaging

Grades for table or slicing cucumbers are based on 

length, shape, fruit color, and diameter and include 

U.S. Fancy, Extra 1, No. 1, No. 1 Small, No. 1 

Large, and No. 2. Pickling cucumbers are graded 

by fruit diameter: No. 1 (up to 2.5 cm [1 in]), No. 

2 (2.5 to 3.8 cm [1.0 to 1.5 in]), and No. 3 (3.8 

to 5.0 cm [1.5 to 2.0 in]). Fruit over 5 cm (2 in) 

are too large. Additional quality indices include 

size, freedom from growth or handling defects, 

freedom from decay, and lack of yellowing. Most 

fresh-market cucumbers are packed in fiberboard 

boxes. Fresh market slicers are often waxed to 

reduce moisture loss, while greenhouse slicers are 

wrapped in shrink-plastic to reduce water loss. 

Pickling cucumbers are usually transported from 

the field to the brining facility in large field bins.

Precooling Conditions

The chilling sensitivity of cucumbers does 

not preclude precooling with cold water 

(hydrocooling) or air (forced-air) (Ryall and 

Lipton 1979). However, even though fruit can 

tolerate brief exposure to chilling temperatures, 

they should not be maintained at chilling 

temperatures for more than 6 h.
303

Optimum Storage Conditions

Recommended conditions for commercial storage 

of cucumbers are 10 to 12.5 oC (50 to 54 °F) 

at 95% RH (Hardenburg et al. 1986). Storage 

life is generally less than 14 days, with visual 

and sensory quality rapidly declining thereafter. 

Chilling sensitivity limits storage temperatures 

to a narrow range. Storage below 10 °C (50 °F) 

results in chilling injury in as little as 2 or 3 days, 

while storage at 15 °C (59 °F) results in rapid 

yellowing and loss of quality.

Controlled Atmosphere (CA) 

Considerations

Little benefit is realized from the CA storage 

of cucumber fruit (Leshuk and Saltveit 1990, 

Saltveit 1997). O2

 levels of 3 to 5% delay 

yellowing and decay for a few days (Wang and 

Qi 1997). Cucumbers tolerate CO2

 up to 10%, but 

the benefits are not more than those realized by 

reduced O2

. Parthenocarpic fruit can be stored for 

1 to 3 weeks in 0.5 to 2% O2

 at 12.5 °C (54.5 °F) 

(Kanellis et al. 1988).

Retail Outlet Display Considerations

Chilling temperatures should be avoided. Periodic 

sprays of water or packaging the fruit in ventilated 

films can minimize water loss. Fresh market 

slicers are often waxed to reduce moisture loss, 

while greenhouse slicers are wrapped in shrink 

plastic to reduce water loss. High RH retards 

softening and pitting, symptoms of chilling injury.

Chilling Sensitivity

Cucumbers are chilling sensitive and most fruit 

will be injured if stored below 10 °C (50 °F) for 

more than 2 or 3 days. Sensitivity varies greatly 

with duration of exposure, temperature, cultivar, 

growing conditions, and storage environment 

(Cabrera et al. 1992). CA during chilling and 

high RH after chilling can reduce symptom 

expression. Intermittent warming to nonchilling 

temperatures for 12 h every 2 or 3 days can reduce 

chilling injury of fruit held at 0 to 2 °C (32 to 36 

°F) (Cabrera and Saltveit 1990). Development of 

chilling injury symptoms can be avoided if chilled 

fruit are used immediately after removal from 

storage.

Ethylene Production and Sensitivity

Cucumber fruit produce little ethylene, about 

0.1 to 1.0 μL kg-1 h-1 at 20 °C (68 °F), but they 

are very sensitive to it. Exposure to 1 to 5 μL 

L-1 ethylene accelerates yellowing and decay. 

Reduced O2

 and elevated CO2 minimize the 

response to ethylene exposure.

Respiration Rates

Temperature mg CO2 kg-1 h-1

10 °C 23 to 29

15 °C 24 to 33

20 °C 14 to 48

25 °C 19 to 55

Data from Cantwell and Suslow (2006).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Chilling injury is characterized by surface pitting, 

increased yellowing and disease susceptibility, and 

development of water-soaked areas of the flesh. 

Bruising and compression injuries are common 

when careful harvest and handling procedures are 

not followed.

Postharvest Pathology

Diseases are a significant source of postharvest 

loss, especially in fruit weakened by chilling 

injury. The many bacterial and fungal pathogens 
304

responsible for postharvest losses include 

Alternaria spp., Didymella black rot, Pythium

cottony leak, and Rhizopus soft rot.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Sliced cucumbers are available for the commercial 

food service industry but are not yet on the retail 

market.

Special Considerations

Cucumber fruit are usually treated with approved 

waxes or oils to reduce water loss, reduce abrasion 

injury, and improve appearance. Surface pitting 

and yellowing are common defects that follow 

exposure to chilling temperatures and ethylene. 

Harvesting at the proper maturity and storing at 

temperatures above 10 °C (50 °F) in an ethylenefree atmosphere are necessary for optimal quality 

retention and maximum market life.

The postharvest conditions for slicing cucumbers 

generally apply to fruit intended for pickling. 

However, damage incurred during the mechanical 

harvesting of pickling cultivars increases 

the rate of respiration (from 6 to 20%), the 

rate of water loss, and disease susceptibility. 

Also, since pickling cucumbers are commonly 

shipped in large field bins, prompt precooling 

is very important to remove field heat and 

prevent respiratory activity from raising fruit 

temperature in transit. Hydrocooling is effective 

for precooling, but storage life is halved because 

of the spread of inoculum. Sanitization of water 

is therefore very important. Fruit can be held 

at chilling temperatures for a few days if used 

immediately after removal from storage.

Acknowledgments

Some of the information in this chapter is from the 

Produce Marketing Association’s “Fresh Produce 

Manual.”

References

Cabrera, R.M., and M.E. Saltveit. 1990. 

Physiological response to chilling temperatures 

of intermittently warmed cucumber fruit. J. Amer. 

Soc. Horti. Sci. 115:256-261.

Cabrera, R.M., M.E. Saltveit, and K. Owens. 

1992. Cucumber cultivars differ in their response 

to chilling temperatures. J. Amer. Soc. Horti. Sci. 

117:802-807.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Kanellis, A.K., L.L. Morris, and M.E. Saltveit. 

1988. Responses of parthenocarpic cucumbers 

to low-oxygen storage. J. Amer. Soc. Horti. Sci. 

113:734-737.

Leshuk, J.A., and M.E. Saltveit. 1990. Controlled 

atmospheres and modified atmospheres for 

preservation of vegetables. In M. Calderon, ed., 

Food Preservation by Modified Atmospheres, pp. 

315-352. CRC Press, Boca Raton, FL.

Miller, C.H., and T.C. Wehner. 1989. Cucumbers. 

In N.A.M. Eskin, ed., Quality and Preservation of 

Vegetables, pp. 245-264. CRC Press, Boca Raton, 

FL.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1, Vegetables and 

Melons. AVI Publishing Co., Westport, CT.
305

Robinson, R.W., and D.S. Decker-Walters. 1997. 

Cucurbits. CAB Intl., Wallingford, U.K.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.

Saltveit, M.E., and R.F. McFeeters. 1980. 

Polygalacturonase activity and ethylene 

synthesis during cucumber fruit development and 

maturation. Plant Physiol. 66:1019-1023.

Suslow, T., and M. Cantwell. 2006. Cucumber: 

recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.

Wang, C.Y., and L. Qi. 1997. Controlled 

atmosphere storage affects quality and chilling 

susceptibility of cucumbers. J. Food Quality 

20:559-566.
306

Currant, Gooseberry, and Elderberry

Robert K. Prange

Prange is with Atlantic Food and Horticulture 

Research Centre, Agriculture and Agri-Food 

Canada, Kentville, Nova Scotia, Canada.

Scientific Name and Introduction

Currants and gooseberries are closely related, 

berry-bearing deciduous shrubs in the Ribes L. 

genus of the Saxifragaceae family. Gooseberries 

are sometimes placed in a separate genus, 

Grossularia Mill.

The most common species are R. sativum Syme 

(red, white, and pink currants) and R. nigrum

L. (black currant) (Harmat et al. 1990). White 

currant, an albino form of red currant, is of lower 

acidity and thus is suitable for eating fresh. 

Pink currants have a colorless skin and a pink 

flesh. Black currant fruit differ from red currants 

in being more astringent but having a distinct 

aroma, making it very desirable in processed 

products. Gooseberry cultivars are derived from 

R. uva-crispa L. (European gooseberry) and R. 

hirtellum Michx. (American gooseberry). The 

European gooseberry is much larger than the 

American gooseberry. European cultivars are from 

R. uva-crispa, but American cultivars are virtually 

all from crosses of R. uva-crispa and R. hirtellum. 

A gooseberry fruit may be green, white 

(gray-green), yellow, or shades of red from pink 

to purple to almost black. Skin color is most 

intense on fruit in full sunlight. The four countries 

producing both the most currants and the most 

gooseberries are Germany, Czech Republic, 

Poland, and the Russian Federation. North 

American production of currant and gooseberry 

has been hampered by adaptation and disease 

problems (Harmat et al. 1990). Currant and 

gooseberry are available fresh from mid-May 

to August or longer if stored properly. Virtually 

all commercial production is put into processed 

products with only a small proportion consumed 

fresh.

Also, brownish-purple fruit from a native western 

U.S. species, R. aureum Pursh (buffalo currant, 

albol currant, golden currant) or from a hybrid of 

R. nigrum and R. hirtellum (jostaberry) may be 

available in some local markets.

Sambucus canadensis L., the elderberry, 

is a moderately tall deciduous shrub of the 

Caprifoliaceae family, native to North America. 

The ease in harvesting the purplish-black fruit 

from wild plants may in part account for the 

lack of commercial plantings. Most of the fruit 

is processed, since the uncooked berries are 

astringent and not very edible (Way 1981). 

Selection and breeding, primarily in New York 

and Nova Scotia, have resulted in a number of 

cultivars (Craig 1978, Way 1981, Stang 1990), and 

small-scale production has been reported in New 

York, Ohio, and Oregon (Way 1981).

Quality Characteristics and Criteria

Currant and elderberry fruit are produced on the 

plant in clusters, and gooseberry fruit are borne 

singly or in pairs. Ideally, fruit throughout each 

cluster should be firm and bright, with the proper 

cultivar‐specific color, and free of decay or 

mechanical or insect injury. For the fresh market, 

it is also important to have large and uniform 

fruit throughout the cluster. A long shelf-life 

with retention of both firmness and flavor is also 

desirable for the fresh-fruit market.

Horticultural Maturity Indices

Currants and gooseberries are harvested from midMay through August. Red currants are usually 

harvested before the color changes from bright red 

to a dull red color (Spayd et al. 1990, Audette and 

Lareau 1996). Soluble solids are usually about 9.5 

to 14% and acidity is around 2%. Generally, entire 

clusters of red currant are harvested, as modern 

cultivars have uniform ripening of all berries on a 

cluster. Black currants, which at maturity have an 

opaque, very dark blue color with a soluble solids 

content of 15 to 26%, do not mature evenly in the 

cluster: the larger ones at the base of each cluster 
307

mature first (Audette and Lareau 1996, http://

www.crfg.org/pubs/ff). The entire cluster can be 

harvested, or only mature berries can be picked 

over several harvests. At maturity, gooseberry 

cultivars may be green, white, yellow, or various 

shades of red (pink to purple to almost black). 

Since both immature (green) and ripe gooseberries 

are used, harvest maturity depends entirely on end 

use (Ryall and Pentzer 1982). Green gooseberries 

are very firm and tart, whereas some cultivars, 

when fully mature and soft, are quite sweet. 

Elderberries are harvested in late August and 

September, when the fruit is sufficiently large 

and has changed to an acceptable purplish-black 

color. The fruit do not mature at the same time, so 

several pickings are necessary over a 1- to 2-week 

period (Craig 1978, Way 1981). Harvesting occurs 

in late August and September, depending on 

climate and cultivar. Postharvest decay of currant, 

gooseberry, and elderberry can be minimized by 

avoiding picking wet or overripe fruit.

Grades, Sizes, and Packaging

There are no U.S. fresh fruit standards for 

these fruit. There is a U.S. grade standard for 

processing currants, based on color, attachment 

of stem, and freedom from decay and insect or 

mechanical damage. Processors, who use most of 

the commercial production, may have their own 

standards. Since fresh market volumes are not 

large, container sizes and packaging for the fresh 

market tend to be those used for similar but more 

common berries (for example, raspberries).

Precooling Conditions

Currant, gooseberry, and elderberry fruit are 

relatively perishable. Quick cooling after harvest 

to recommended storage temperatures is desirable, 

using forced-air cooling with 95% RH (Kasmire 

and Thompson 1992, Batzer and Helm 1999).

Optimum Storage Conditions

Since currant, gooseberry, and elderberry are 

not chilling sensitive, the recommended storage 

temperature and RH for all three are -0.5 to 0 

°C (31 to 32 °F) with RH of 95% (Hardenburg 

et al. 1986, Story and Simons 1989). Batzer and 

Helm (1999) recommended slightly warmer 

temperatures of 0 to 1 °C (32 to 34 °C) for red 

currant and gooseberry and 0 to 2 °C (32 to 36 

°F) for black currant, perhaps to avoid accidental 

freezing. With proper cooling, the storage duration 

can be 1.5 , 2.5, and 3 weeks for black currant, red 

currant, and gooseberry, respectively (Batzer and 

Helm 1999).

Controlled Atmosphere (CA) 

Considerations

As summarized by Batzer and Helm (1999) and 

Thompson (1998), research indicates that red 

currant and gooseberry respond very well to CA, 

while black currant benefits only slightly. Storage 

duration of red currant can be extended to 8 to 14 

weeks, depending on cultivar, using 18 to 20% 

CO2

 with 2% O2 at 1 °C (34 °F). For gooseberry, 

storage duration is extended to 6 to 8 weeks using 

10 to 15% CO2

 with 1.5% O2 at 1 °C. Increasing 

the CO2

 up to 20% reduces incidence of storage 

rots (Thompson 1998, Batzer and Helm 1999), 

and lowering the O2

 reduces respiration rate 

(Robinson et al. 1975). Compared with red currant 

and gooseberry, black currant does not respond 

as well to low O2

 and its storage can only be 

extended to 3 weeks at 0 to 2 °C (32 to 36 °F) and 

15 to 20% CO2

.

There is no known information on the effect of CA 

on elderberry.

Retail Outlet Display Considerations

Currant, gooseberry, and elderberry should be kept 

in a refrigerated display but not sprinkled with 

water or top-iced.
308

Chilling Sensitivity

Currant, gooseberry, and elderberry are not 

chilling sensitive (Kader 1992).

Ethylene Production and Sensitivity

No data available.

Respiration Rates

Temperature Gooseberry Black currant

---------mg CO2 kg-1 h-1---------

0 °C 5 to 7 16

4 to 5 °C 8 to 16 27

10°C 12 to 32 40

15 to 16°C 28 to 69 89

20 to 21°C 41 to 105 128

Gooseberry data from Smith (1967), Robinson 

et al. (1975), and Hardenburg et al. (1986); black 

currant data from Robinson et al. (1975).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

CO2 above 20% results in internal breakdown and 

fruit discoloration in some red currant cultivars 

after 13 weeks of storage (Thompson 1998). 

Low O2

 further increases these symptoms. Smith 

(1967) showed that green gooseberry fruit held at 

0 °C (32 °F) in air are damaged by CO2

 that was 

increased from 8 to 12%. Fruit turned yellow and 

had an abnormal flavor. Increasing the temperature 

from 0 to 5 °C (32 to 41 °F) eliminates the 

disorder.

Postharvest Pathology

The main postharvest disease is gray mold rot 

(Botrytis cinerea), which can appear as small 

brown spots on currant and gooseberry fruit 

(Ryall and Pentzer 1982, Dennis 1983, Harmat et 

al. 1990). These enlarge rapidly at temperatures 

above 10 °C (50 °F) and gradually affect the entire 

berry with a soft rot. Currant and gooseberry 

fruit can be susceptible to American powdery 

mildew (Sphaerotheca mors-uva) (Harmat et 

al. 1990, Audette and Lareau 1996). Fruit that 

become contaminated by soil splash after heavy 

rain are frequently infected by Mucor piriformis

(Dennis 1983). Dennis (1983) also reports a fruit 

disease in gooseberry caused by Alternaria and 

Stemphyllum. The infection is usually confined 

to the seeds enclosed in the pericarp. If, however, 

the fruit is stored for a few days at ambient 

temperatures prior to consumption or processing, 

the fungus invades the pericarp tissue. 

Several insects can attack the fruit: currant maggot 

or fruit fly (Epochra canadensis) (North America), 

gooseberry fruitworm (Zophodia convolutella) 

(North America), and currant moth (Incurvaria 

capitella) (Europe) (Harmat et al. 1990). In 

addition, slugs and snails (Helix aspersa and 

Cepaea spp.) will attack fruit (North America 

and Europe) (Harmat et al. 1990). Diseases and 

insects are not generally serious on elderberries 

(Way 1981), perhaps because of the absence 

of extensive plantings. An unidentified mildew 

can be a problem on ripe fruit, especially if the 

weather is cool during ripening and there is poor 

air circulation around the plants (Way 1981).

Birds feeding on ripe currant, gooseberry, and 

elderberry fruit can be a serious pest problem 

(Way 1981, Harmat et al. 1990, Stang 1990). 

In addition to prompt harvesting of ripe fruit, 

various bird repellent measures may have to be 

considered.

Quarantine Issues

None
309

Suitability as Fresh-Cut Product

No current potential

Special Considerations

Ribes species are hosts for the white pine blister 

rust, which causes few problems for currants or 

gooseberries but is dangerous to 5-needle pine 

species. Thus, commercial production of Ribes

species, especially black currant, may be banned 

in some U.S. municipalities (California Rare Fruit 

Growers 1996).

References

Audette, M., and M.J. Lareau. 1996. Currants 

and Gooseberries Culture Guide. Conseil des 

Productions Végétales du Québec, Inc., Québec 

City, Québec, Canada.

Batzer, U., and H.-U. Helm. 1999. Lagerung 

von Beerenobst (Storage of small fruits). 

Erwerbsobstbau 41:51-55. 

California Rare Fruit Growers. 1996. CRFG fruit 

facts: currants. At http://www.crfg.org/pubs/ff/

currants.

Craig, D.L. 1978. Elderberry culture in eastern 

Canada. Pub. no. 1280, Agriculture Canada, 

Ottawa, Ontario, Canada.

Dennis, C. 1983. Soft fruits. In C. Dennis, ed., 

Postharvest Pathology of Fruits and Vegetables, 

pp. 23-42. Academic Press, New York, NY.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Harmat, L., A Porpaczy, D.G. Himelrick, and 

G.J. Galleta. 1990. Currant and gooseberry 

management. In G.J. Galleta and D.G. Himelrick, 

eds., Small Fruit Crop Management, pp. 245-272. 

Prentice Hall, Upper Saddle River, NJ.

Kader, A.A. 1992. Postharvest biology and 

technology: an overview. In A.A. Kader, ed., 

Postharvest Technology of Horticultural Crops, 

pp. 15-20. DANR Pub. no. 3311, University of 

California, Davis, CA.

Kasmire, R.F., and J.F. Thompson. 1992. Selecting 

a cooling method. In A.A. Kader, ed., Postharvest 

Technology of Horticultural Crops, pp. 63-68. 

DANR Pub. no. 3311, University of California, 

Davis, CA.

Robinson, J.E., K.M. Browne, and W.G. Burton. 

1975. Storage characteristics of some vegetables 

and soft fruits. Ann. Appl. Biol. 81:339-408.

Ryall, A.L., and W.T. Pentzer. 1982. Handling, 

Transportation and Storage of Fruits and 

Vegetables, 2nd ed., vol. 2, Fruits and Tree Nuts. 

AVI Publishing Co., Westport, CT.

Spayd, S.E., J.R. Morris, W.E. Ballinger, and D.G. 

Himelrick. 1990. Maturity standards, harvesting, 

postharvest handling, and storage. In G.J. Galleta 

and D.G. Himelrick, eds., Small Fruit Crop 

Management, pp. 504-531. Prentice Hall, Upper 

Saddle River, NJ.

Smith, W.H. 1967. The storage of gooseberries. 

Agricultural Research Council (U.K.) Ditton and 

Covent Garden Laboratories Annual Report 1965-

66, pp. 13-14.

Stang, E.J. 1990. Elderberry, highbush cranberry, 

and juneberry management. In G.J. Galleta 

and D.G. Himelrick, eds., Small Fruit Crop 

Management, pp. 363-382. Prentice Hall, Upper 

Saddle River, NJ.

Story, A., and D.H. Simons. 1989. Handling and 

Storage Practices for Fresh Fruit and Vegetables. 

Australian United Fresh Fruit and Vegetable 

Association Ltd., Victoria, Australia.
310

Thompson, A.K. 1998. Controlled Atmosphere 

Storage of Fruits and Vegetables. CAB Intl., 

Wallingford, U.K.

Way, R.D. 1981. Elderberry culture in New York 

State. Food Life Sci. Bull. 91, New York State 

Agricultural Experiment Station, Geneva, NY.
311

Date

Elhadi M. Yahia 

Yahia is with the Faculty of Natural Sciences, 

Universidad Autónoma de Querétaro, Querétaro, 

Mexico.

Scientific Name and Introduction

Phoenix dactylifera L., the date palm, has been 

a staple in the Middle East and North Africa for 

thousands of years. Date fruit is a drupe with a 

single seed or pit. The fruit has an oblong shape, 

measures about 2.5 to 7.5 cm (1 to 3 in) long, and 

has thick or thin flesh. It tastes astringent when 

premature and becomes sweet when ripe. Dates 

are rich in carbohydrate and other nutrients and 

are a high-energy food.

Quality Characteristics and Criteria

High-quality fresh dates should be of an adequate 

size and proper color and have a small pit and 

thick flesh. They should not be contaminated by 

dirt, sand, or leaf particles or exhibit damage by 

birds, insects, or rodents. There should be no fungi 

or mold infestation nor sugar crystal formation 

or other apparent alterations (Dowson 1982). The 

skin should be smooth with little or no shriveling. 

The color should be golden brown, amber, green, 

or black, depending on the variety. The texture 

may be soft and syrupy or firm and dry, depending 

on the cultivar. 

Horticultural Maturity Indices

Fruit growth follows a sigmoidal curve and is 

usually divided into five stages of development 

known by their Arabic terms: hababouk, kimri, 

khalal, rutab, and tamr. Most dates are harvested 

in the tamr stage when the fruit has about 60 to 

80% sugar content, depending on location and 

cultivars. At this stage, fruit can be harvested 

soft, semidry, or dry depending on destination 

and use. Some varieties with low tannins but 

high sugar content can be harvested at the khalal 

stage (“balah” in North African countries or 

“bisr” in Oman). For other varieties, dates that are 

harvested before reaching full maturity must be 

ripened artificially. Very immature dates cannot 

be properly ripened artificially and will thus be of 

poor quality.

Grades, Sizes, and Packaging

Dates are graded based on uniformity of color 

and size and extent of defects or damage, which 

include discoloration of the flesh, rupture of 

the skin, deformity of the fruit, puffiness of 

the skin, scars, sunburn, insect damage, decay, 

black scald, fermentation, improper ripening, 

mechanical damage, and presence of dirt or other 

foreign material. These criteria are the bases for 

Codex and U.S. grades A, B, C, standard, and 

substandard applied to whole, pitted, or dry dates. 

In general, the total amounts of sugar for different 

grades are usually the same when expressed as a 

percentage of dry weight, but the higher grades 

usually contain higher amounts of sugar per date. 

‘Medjool’ dates in the United States are classified 

into three size categories: jumbo (fewer than 10 

dates per lb or per 0.45 kg), mixed (10 to 15 dates 

per lb), and conventional (more than 15 dates per 

lb). 

Some dates are marketed in 15-lb (6.8-kg) flats 

of fiberboard or wood, others in 5- or 10-lb (2.3- 

or 4.5-kg) cartons. Large, reinforced cartons are 

used for packing dry dates, especially for export. 

Consumer packages are widely used and consist 

of various sizes and shapes, including bags of 

transparent film and trays overwrapped with 

film. Round fiberboard cans with metal tops and 

bottoms containing 500 to 1,000 g (1.1 to 2.2 lb) 

are also used. Rigid, transparent plastic containers 

with a capacity of 200 to 300 g (0.44 to 0.66 lb) 

are commonly used. Small consumer packages 

are also used, such as bags containing 50 to 60 g 

(about 2 oz).
312

Optimum Storage Conditions

Pathological and physiological deterioration 

increases with increasing moisture content and 

storage temperature. Relatively small differences 

in moisture content may have an important effect 

on keeping the quality of ‘Deglet Noor’ fruit. 

At 24 °C (75 °F), ‘Deglet Noor’ dates show 

darkening of the skin 4 times faster when they 

have 24% versus 20% moisture content (Rygg 

1975). At 0 °C (32 °F), dates can be stored in good 

conditions up to 1 year, but some varieties may 

develop sugar spots or crystals. Fully mature soft 

and firm ‘Deglet Noor’ dates can be kept for more 

than 1 year when stored at -17.5 °C (0 °F) but will 

not stand more than 1 mo at 27 °C (80 °F), 3 mo 

at 15 °C (59 °F), or 8 mo at 5 °C (41 °F) (Rygg 

1956). Partially dried dates can be kept for 1 year 

at 0 °C (32 °F) or lower, or for a few weeks at 

ambient temperature. Dry dates can be kept at 20 

°C (68 °F) for years without significant quality 

losses. Optimum RH is 70 to 75%.

Chilling Sensitivity

Ripe dates at the rutab or tamr stages (see 

Horticultural Maturity Indices), commonly 

handled in the world market, are not sensitive 

to chilling and freezing temperatures. However, 

freezing temperatures can injure dates at early 

stages of kimri and khalal.

Ethylene Production and Sensitivity

At 20 °C (68 °F), dates produce less than 0.1 μL 

kg-1 h-1 ethylene at the khalal stage and none at the 

rutab and tamr stages. Ripe dates are not sensitive 

to ethylene exposure.

Respiration Rates

Respiration rates of dates are very low: <5 mg 

CO2

 kg-1 h-1 at 20 °C (68 °F) at the khalal stage 

and <2 mg kg-1 h-1 at the rutab and tamr stages. 

Respiration rates increase as moisture content of 

the fruit increases. Cured ‘Deglet Noor’ dates, 

with 20 to 22% moisture, produced 0.4 mg CO2

kg-1 h-1 at 24 °C and 2 mg CO2

 kg-1 h-1 when 

moisture content increased to 27%. (Rygg 1975).

Physiological Disorders

Darkening is a major problem in dates. Its 

rate varies with cultivar, temperature, and 

moisture content; and it is affected by several 

treatments. It can be reduced by storage in low 

temperatures, low moisture content, or in an inert 

gas. Temperatures above 60 °C (140 °F) cause a 

reddish color and increase the astringency and off 

flavors in ‘Deglet Noor.’

Blacknose, or sugartip, is a severe checking of the 

skin in some cultivars, especially in ‘Deglet Noor.’ 

It is induced by high RH just before the beginning 

of the khalal stage and is characterized by 

darkening, shriveling, and hardening of the flesh 

at the tip of the fruit (Rygg 1975). Black scald 

is characterized by blackening of the flesh and a 

sunken area with a definite line of demarcation at 

the tip or on the sides of the fruit.

Puffiness, or sunken separation, is caused by high 

temperatures and/or high RH before the beginning 

of ripening and may increase during curing. This 

disorder affects only soft cultivars.

Sugar spotting is characterized by light-colored 

spots under the skin and is restricted to the invert 

sugar dates. Almost all dry cultivars, and several 

of the semidry cultivars, contain large amounts of 

sucrose and are less sensitive to sugar spotting. 

Sugar spotting decreases as the temperature 

decreases and when moisture falls below 22%. 

Sugar spots affect appearance and texture. They 

can be removed by warming but can reappear if 

unfavorable conditions persist (Rygg 1975). 

Freezing of dates at a higher temperature 

range results in the rupture of various cellular 

compartments and the appearance of bright, 

yellow-brown spots of crystallized solutes 

(Shomer et al. 1998). Intercellular membranes 
313

and cell walls can be kept intact even after 10 

mo when fruits are frozen at a lower temperature 

range. 

Postharvest Pathology

The most common pathological deterioration 

of dates includes fermentation by yeast and 

molding by fungi. Steam-hydrated dates are 

more resistant to attack by microorganisms 

than natural or nonhydrated dates because of 

the partial sterilization of steam-dehydrated 

fruit. Fungi include Aspergillus spp., Alternaria 

spp., Stemphylium botryosum, Cladosporium

sp., Macrosporium sp., Citromyces ramosus, 

Phomopsis diopspyri, and Penicillium spp. These 

fungi can cause significant losses before or just 

after harvest during rainy or high-RH periods 

and can attack fruit at the khalal or rutab stages. 

However, most of these fungi, except Catenularia

fuliginia Saito, will not grow on dried dates.

Insect Pests

Oligonychus afrasiaticus McGregor and O.

pratensis Banks are mites referred to as “Bou 

Faroua” or “Old World date mite.” They affect 

dates at the hababouk stage. The larva develops 

around the fruit with a white filament netting, 

which in turn causes the fruit to drop prematurely. 

The same is caused by Coccotrypes daclyliperda, 

which leads to fruit drop-off at the immature 

green stage. Parlatoria blanchardi scale also 

attacks the fruit while it is still green. Date or 

carob moth Ectomyelois ceratoniae Zeller, another 

Lepidoptera widely present in different dateproducing areas, causes important postharvest 

losses on stored dates. Several other insects, 

such as Batrachedra amydraula Meyr, date stone 

beetle (Coccotrypes dactyliperda F.), Carpophilus 

hemipterius, Carpophilus multilatus, Urophorus 

humeralis, and Heptoncus luteolus, can cause 

serious damage to dates on the bunch or after 

harvest. Other pests include Vespa orientalis,

Cadra figulilella, Arenipes sabella, and mushroom 

mites (Tyrophagus lintaeri Osborn), which can 

infest stored dates.

Quarantine Issues

Fumigation by phosphine, ionizing radiation, 

the use of low or high temperatures, and MA 

treatments are registered to be used for insect 

control in dates.

Special Considerations

Dates may require postharvest ripening if picked 

early. Soft and semidry cultivars need to be 

dehydrated to eliminate excess RH if they are not 

intended for immediate consumption. Hydration is 

used to soften the texture of hard-type cultivars.

Acknowledgments

Thanks are due to Dr. A. Ait-Oubahou for 

reviewing the manuscript.

References 

Dowson, V.H.W. 1982. Date production and 

protection with special reference to North Africa 

and the Near East. Plant Production and Protection 

Paper 35, United Nations, Food and Agriculture 

Organization, Rome, Italy.

Rygg, G.L. 1975. Date Development, Handling 

and Packing in the United States. Agriculture 

Handbook 482, U.S. Department of Agriculture, 

Agricultural Research Service, Washington, DC.

Rygg, G.L. 1956. Effect of temperature and 

moisture content on the rate of deterioration in 

Deglet Noor dates. Date Growers’ Institute Report 

33.

Further Reading

Abbas, M.F., and M.A. Ibrahim. 1996. The role of 

ethylene in the regulation of fruit ripening in the 

Hillawi date palm (Phoenix dactylifera). J. Sci. 

Food Agric. 72:306-308.
314

Ahmed, M.S.H., Z.S. Al-Hakkak, S.R. Ali, et al. 

1982. Disinfection of commercially packed dates, 

Zahdi, by ionizing radiation. Date Palm J. 1:249.

Al-Taweel, A.A., M.S.H. Ahmed, M.A. Shawki, 

and M.J. Nasser. 1993. Effects of sublethal 

doses of gamma radiation on the mating ability 

and spermatophore transfer of Ephesia cautella

(Lepidoptera: Pyralidae). Insect Sci. Appl. 14:7-

10.

Barreveld, W.H. 1993. Date palm product. 

Agric. Serv. Bull.101, United Nations, Food and 

Agriculture Organization, Rome, Italy.

Benjamin, N.D., H.R. Shabana, A.A. Mahdi 

Hassan, et al. 1976. Effect of different 

temperatures and types of containers on the 

storage of commercial varieties of dates in Iraq. 

Technical Bull. 13, Palm and Dates Research 

Center, Baghdad, Iraq.

Coggins, C.W. Jr., J.C.F. Knapp, and A.L. Ricker. 

1968. Postharvest softening of ‘Deglet Noor’ 

dates: physical, chemical and histological changes. 

Date Growers’ Institute Report 45:3.

Coggins, C.W. Jr., and J.C.F. Knapp. 1969. 

Growth, development and softening of the Deglet 

Noor date fruit. Date Growers’ Institute Report 

46:11-14.

Hasegawa, S., D.C. Smolensky, and V.P. Maier. 

1932. Hydrolytic enzymes in dates and their 

application in softening of tough dates and 

sugarwall dates. Date Growers’ Institute Report 

29:6.

Hasegawa, S., and D.C. Smolensky. 1970. Date 

invertase: properties and activity associated 

with maturation and quality. J. Agr. Food Chem. 

18:902-904.

Hasegawa, S., and D.C. Smolensky. 1971. 

Cellulase in dates and its role in fruit softening. J. 

Fd. Sci. 36:966.

Rygg, G.L., J.R. Furr, R.W. Nixon, and W.W. 

Armstrong. 1953. Factors affecting the spoilage of 

dates at room temperature. Date Growers’ Institute 

Report 30:10-14.

Shomer, I., H. Borchov-Neori, B. Luzki, and 

U. Merin. 1998. Morphological, structural and 

membrane changes in frozen tissues of Madjhoul 

date (Phoenix dactylifera L.) fruits. Postharv. Biol. 

Technol. 14:207-215.

Vandercook, C.E., S. Hasegawa, and V.P. Maier. 

1980. Dates. In S. Nagy and P.E. Shaw, eds., 

Tropical and Subtropical Fruits. AVI Publishing 

Co., Westport, CT.
315

Dragon Fruit

Robert E. Paull 

Paull is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI.

Scientific Name and Introduction

Dragon fruit (Hylocereus spp.), also known as 

strawberry pear or thang loy (Vietnamese), pitaya 

roja (Spanish), and la pitahaya rouge (French), 

grows on a tropical climbing cactus. There is some 

confusion as to what species is being grown as 

they are all referred to as “pitahaya” in Spanish. 

The normally white-fleshed Hylocereus undatus

is grown commercially, as are the red- or purplefleshed H. costaricensis (grown in Nicaragua 

and possibly Guatemala) and H. polyhizus

(grown in Israel). There are yellow clones of H. 

undatus named “pitaya amarilla” (yellow pitaya) 

in Mexico and other Latin-American countries. 

Pitaya amarilla is a different species from the 

other yellow pitaya, Selenicereus megalanthus

(Mizrahi et al. 1997). Dragon fruit is a selfcompatible cultivar in Vietnam (Mizrahi et al. 

1997, Nerd and Mizrahi 1997).

Quality Characteristics and Criteria

Dragon fruit is a large, oblong fruit with a red 

peel and large, green scales. The scales turn 

yellow on ripening. The skin begins to change 

color 25 to 30 days after flowering in both H. 

undatus and H. polyhizus. At about the same 

time flesh firmness approaches a minimum, and 

eating quality approaches a maximum 33 to 37 

days after flowering (Nerd et al. 1999). Fruit can 

be harvested 25 to 45 days after flowering; 32 to 

35 days was recommended by Nerd et al. (1999). 

Fruit size depends on seed number (Weiss et al. 

1994).

The flesh of different species can vary from white 

to various hues of red to very dark red. As the 

fruit matures, acidity reaches a peak just as the 

skin color change occurs, then declines 25 to 30 

days after flowering (Nerd et al. 1999, Le et al. 

2000). At this stage, soluble solids content (SSC) 

increases to about 14% (Nerd et al. 1999, Le et al. 

2000).

Horticultural Maturity Indices

A common index of maturity is skin color change 

to almost full red (Nerd et al. 1999). Harvesting 

indices include color, SSC, total acidity (TA), 

and days from flowering (minimum 32 days). An 

SSC:TA of 40 has been suggested as a harvest 

index.

Grades, Sizes, and Packaging

There are no U.S. or international standards. 

Fruit are generally graded by size and color. Size 

grades suggested for Vietnam are extra large (over 

1.1 lb or 500 g), large (0.84 lb-1.1 lb or 380-500 

g), regular (0.66-0.84 lb or 300-380 g), medium 

(0.57-0.66 lb or 260-300 g), and small (under 0.57 

lb or 260 g) (Le et al. 2000). Fruit exported from 

Israel to Europe are graded by number of fruit per 

8.8-lb (4-kg) cardboard box: 6, 8, 10, 12, 14, and 

16.

Precooling Conditions

There are no reported data. Room cooling and 

hydrocooling are possible.

Optimum Storage Conditions

The recommended storage temperature for dragon 

fruit is 10 °C (50 °F), since 6 °C (43 °F) can 

induce chilling injury (Nerd et al. 1999). The 

lower temperature (6 °C) has been recommended 

for the yellow pitaya Selenicereus megalanthus

(Nerd and Mizrahi 1999), and this agrees with 

minimum growth temperature of 7 °C ( 45 °F) for 

this species (Nerd and Mizrahi 1998). Dragon fruit 

has a storage life of about 14 days at 10 °C (50 

°F); while at 5 °C (41 °F) and 90% RH, a storage 
316

life of 17 days can be achieved (Le et al. 2000) if 

fruit are harvested 30 to 35 days after flowering. 

However, 5 °C (41 °F) may lead to chilling injury 

on return to 20 °C (68 °F), as indicated by peel 

and flesh deterioration and inferior taste (Nerd 

et al. 1999). Thus, 10 °C (50 °F) for a maximum 

of 14 days may be a better recommended storage 

temperature.

Controlled Atmosphere (CA) 

Considerations

No reported CA data are available. Fruit harvested 

28 to 30 days after flowering and stored in a 

modified atmosphere (MA) bag (O2

 transmission 

rate 4,000 mL m-2 day-1) can be held for 35 days 

at 10 °C (50 °F), versus 14 days for air controls 

(Le et al. 2000b). More mature fruit (40 days after 

flowering) in the same MA bag had 50% of the 

shelf-life.

Retail Outlet Display Considerations

Display dragon fruit at 10 oC (50 °F). Do not mist.

Chilling Sensitivity

Flesh translucency is a symptom of chilling 

injury. Other symptoms include softening, wilting, 

darkening of scales, browning of the outer flesh, 

and poor flavor. These symptoms rapidly develop 

on H. undatus and H. polyhizus fruit held at 6 °C 

(42.8 °F) for 2 weeks then transferred to 20 °C 

(68 °F) (Nerd et al. 1999). Fruit harvested 25 days 

after flowering are more sensitive to chilling (6 

°C, 7 days). Sensitivity is significantly reduced 

when fruit are harvested 30 to 35 days after 

flowering (6 °C, 17 days).

Ethylene Production and Sensitivity

Dragon fruit are nonclimacteric, with ethylene 

production rates of 0.025 to 0.091 μL kg-1 h-1

(Nerd et al. 1999). Ethylene treatment does not 

initiate color development (Le et al. 2002).

Respiration Rates

The maximum respiration rate of these 

nonclimacteric fruit (H. undatus and H. polyhizus)

occurs during early fruit growth (Nerd et al. 1999, 

Le et al. 2000). The following respiration rates are 

for mature fruit:

Temperature mg CO2 kg-1 h-1

20 °C 95 to 144

23 °C 75 to 100

Data from Nerd et al. (1999) and Le et al. (2000), 

respectively.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Chilling injury, mechanical injury, and water loss 

are the three major disorders. Mechanical injury 

leads to development of sunken areas. More 

mature fruit are more susceptible to mechanical 

injury (Le et al. 2000). Splitting is a problem 

in fruit more than 35 days after flowering that 

received rainfall or excessive irrigation during 

ripening (Le et al. 2000).

Postharvest Pathology

Bacterial (Xanthomonas campestris) and 

Dothiorella spp. diseases have been reported 

(Barbeau 1990). Postharvest disease has been 

associated with Fusarium lateritium, Aspergillus 

riger, and Aspergillus flavus (Le et al. 2000). 

No commercially significant bacterial or fungal 

diseases have been experienced in Israel.

Quarantine Issues

Dragon fruit are a fruit fly host. Irradiation at 

300 grays has potential for disinfestation. In 

Israel, no insect problems have been observed in 
317

commercial production, and the fruit’s status as a 

fruit fly host may need to be reevaluated.

Suitability as Fresh-Cut Product

Dragon fruit are often available as a fresh-cut 

product in Southeast Asian markets in trays with 

overwrap. There is some potential, as fresh-cut 

fruit can be stored at 4 °C (39 °F) for 8 days (Le et 

al. 2002).

Special Considerations

Fruit are very low in vitamin C but rich in 

potassium (Le et al. 2000).

References

Barbeau, G. 1990. La pitahaya rouge, un nouveau 

fruit exotique. Fruits 45:141-147.

Le, V.T., N. Nguyen, D.D. Nguyen, et al. 2000. 

Quality assurance system for dragon fruit. In

G.I. Johnson, V.T. Le, D.D. Nguyen, and M.C. 

Webb, Quality Assurance in Agricultural Produce. 

19th ASEAN/1st APEC Seminar on Postharvest 

Technology, Ho Chi Minh City, Vietnam, 

November 9-12, 1999, pp. 101-114. ACIAR 

Proceedings no. 100, ACIAR, Canberra, Australia.

Le, V.T., N. Nguyen, D.D. Nguyen, and T.T.H. Ha. 

2002. Dragon fruit quality and storage life: effect 

of harvesting time, use of plant growth regulators 

and modified atmosphere packages. Acta Hort. 

575:611-621. 

Mizrahi, Y., A. Nerd, and P.S. Nobel. 1997. Cacti 

as crops. Hort. Rev. 18:291-319.

Nerd, A., and Y. Mizrahi. 1997. Reproductive 

biology of cactus fruit crops. Hort. Rev. 18:321-

346.

Nerd, A., and Y. Mizrahi. 1998. Fruit development 

and ripening in yellow pitaya. J. Amer. Soc. Hort. 

Sci. 123:560-562.

Nerd, A., and Y. Mizrahi. 1999. The effect of 

ripening stage of fruit quality after storage of 

yellow pitaya. Postharv. Biol. Technol. 15:99-105.

Nerd, A., F. Gutman, and Y. Mizrahi. 1999. 

Ripening and postharvest behaviour of fruits of 

two Hylocereus species (Cactaceae). Postharv. 

Biol. Technol. 17:39-45.

Weiss, J., A. Nerd, and Y. Mizrahi. 1994. 

Flowering behavior and pollination requirements 

in climbing cactus with fruit crop potential. 

HortScience 29:1487-1492. 
318

Durian

Robert E. Paull and Saichol Ketsa

Paull is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI; Ketsa is with the Department of 

Horticulture, Kasetsart University, Bangkok, 

Thailand.

Scientific Name and Introduction

The durian (Durio zibethinus Murray [syn. D. 

acuminatissina Merr]) is often referred to as the 

“King of Fruits” in Southeast Asia. Its qualities 

promote considerable discussion because of its 

unique odor, which can be offensive to some 

people. (The fruit has a strong onion-garlic odor.) 

“Zibethinus” is derived from the word “zibetto,” 

Italian for the civet, a catlike animal with a musky 

odor. This tropical tree is mainly cultivated in Sri 

Lanka, southern India, southern Burma, Thailand, 

Cambodia, Vietnam, Malaysia, Indonesia, Borneo, 

the Philippines (on Mindanao Island), and New 

Guinea. It has spread throughout the tropical 

world under the general name of “durian” (IndoMalay) or variants thereof, such as “duren” 

(Indonesian), “duyin” (Burmese), “thureen” 

(Cambodian), “thurian” (Thai), “saurieng” 

(Vietnamese), “dulian” (Filipino), “stinkvrucht” 

(Dutch), and “kadu” (Sudan). Limited supplies 

are available from the Caribbean and Central and 

South America. Commercial supplies are available 

from Thailand and Malaysia.

Quality Characteristics and Criteria

Weighing up to 8 kg (18 lb), the oval or ellipsoid, 

green to brownish fruit can measure up to 30 

cm (12 in) long and 20 cm (8 in) in diameter. It 

is densely covered with stout, sharp, pyramidal 

spines 1 cm (0.5 in) long on its thick, fibrous 

rind. Fruit are divided into 3 to 5 smooth-walled 

compartments, each containing 1 to 6 glossy, 

creamy to red-brown seeds 2 to 6 cm (0.8 to 2.4 

in) long covered by a white to yellowish, soft, 

sweet pulp (aril). The pulp can be odorless or have 

a strong odor suggesting garlic, onion, or pungent 

cheese with a hint of fruitiness. The edible pulp 

(20 to 35% total mass) has a smooth, custardlike 

texture. In some fruit, seeds are rudimentary or 

small compared with wild types.

Quality criteria include a pulp with sweet flavor 

and good texture, few or small seeds, large aril 

percentage, and marketable weight of 1.5 to 

3.5 kg (3.3 to 7.7 lb), elongated to round shape, 

good shelf-life, good rind color and thickness, 

reduced rind splitting, and freedom from disease 

and insects. Superior varieties have thick, yellow, 

fiberless, and custardlike pulp.

The Thai cultivar ‘Chanee’ has a stronger aroma 

and is smaller than the preferred ‘Monthong’ 

(Golden Pillow). Malaysian cultivars include 

D-2 ‘Dato Nina,’ D-7 ‘Repok B-2,’ D-10 ‘Durian 

Hyan,’ and D-24 and D-98 ‘Katoi.’ 

Horticultural Maturity Indices

At maturity, the fruit naturally falls from the tree 

at the articulation of the fruit stem with the fruit, 

then ripens in 2 to 4 days, with the fruit normally 

splitting into segments of irregular widths at 

the stylar end. Ripening results in an increase in 

soluble sugars and a decrease in starch and pulp 

firmness that occurs before natural fruit splitting 

starts.

To prevent natural fruit fall, fruit may be tied 

to the limb or harvested at maturity. Maturity is 

judged by appearance (fruit stalk thickness and 

flexibility, abscission zone, or carpel sutures), 

number of days after flowering, and a hollow 

sound when tapped with a wood or rattan stick 

or knife. The number of days after flowering and 

tapping are the most reliable criteria (Siriphanich 

1996). ‘Chanee’ durian takes 2 to 4 days, while 

‘Monthong’ durian takes 4 to 6 days to ripen after 

harvest, depending on maturity. Fruit at 85% 

maturity, based on days from anthesis and rind 

characteristics, ripen to excellent quality in under 

1 week at 28 to 31 °C (82 to 88 °F). Ripening 
319

takes longer than 1 week at 22 °C (72 °F). Fruit 

that are 95% mature when harvested have already 

commenced ripening, while 75% mature fruit 

may ripen with an inferior quality. Compared with 

fruit picked from the tree, fruit collected from the 

ground after falling are more subject to disease 

and fracture and have a shorter shelf-life (2 to 3 

days instead of the 7 to 8 days for fruit picked 

from the tree). In Thailand, the fruit is harvested 

with the stem (peduncle) attached, and the stem 

is wrapped in a leaf or paper to reduce wilting 

and maintain the fresh appearance of the stem, 

since stem appearance is also used as a measure of 

freshness. ‘Chanee’ is at optimum eating stage for 

only a few days while ‘Mon Tong’ is at this stage 

for a longer period.

Grades, Sizes, and Packaging

Durian fruit are graded on weight, shape, size, 

and defects (Nanthachai 1994). Defects include 

disease, insects, mechanical injury, and flesh 

disorders. Grades vary with variety (Hiranpradit 

et al. 1992). The fruit is packed into cardboard 

cartons (4 to 6 fruit per carton) or in cartons fitted 

with fiberboard dividers.

Precooling Conditions

Use forced-air or room cooling to 15 °C (59 °F).

Optimum Storage Conditions

This climacteric fruit, when stored at 15 oC (59 

oF), has extended shelf-life (Brooncherm and 

Siriphanich 1991); RH of 85 to 95% is best (Ketsa 

and Pangkool 1994, Sriyook et al. 1994). Fruit 

can be waxed to reduce water loss (Sriyook et al. 

1994). Fruit ripened at a lower RH (75%) have a 

better eating quality and are less juicy and easier 

to dehusk than fruit ripened at a higher RH (Ketsa 

and Pangkool 1994).

Controlled Atmosphere (CA) 

Considerations

Ripening is inhibited by 2% O2

, and fruit fail 

to ripen when removed to air. Fruit stored in up 

to 20% CO2

 in air were not affected in terms of 

ripening or quality (Tongdee et al. 1990). Low 

O2

 (10%) reduces respiration rate and ethylene 

production but does not affect the onset of 

ripening, and ripe fruit quality is not affected. The 

aril remains hard in less mature fruit stored in 10% 

O2

 and 15 or 20% CO2. The commercial potential 

of CA or MA is still unclear (Siriphanich 1996).

Retail Outlet Display Considerations

Display at ambient temperature or hold at 15 

to 18 °C (59 to 64 °F), if available. Do not mist 

or ice. Avoid mixing with other produce during 

storage. The husk can be removed and the whole 

pulp and seed segment can be removed and sold 

in trays with a plastic overwrap. Remove the husk 

as soon as the fruit starts to produce aroma or is 

half-ripe and the pulp is still firm. If fruit splitting 

has started, the pulp is generally too soft and has a 

very short shelf-life.

Chilling Sensitivity

The pulp of half-ripe or nearly fully ripe fruit is 

much less sensitive to chilling injury than the peel, 

and the pulp can be stored for 4 weeks at 5 °C 

(41 °F). Whole fruit stored at under 15 °C (59 °F) 

develop chilling injury shown by the peel turning 

black or dark brown starting at the groove between 

the spines (Brooncherm and Siriphanich 1991). 

Chilling-injured pulp suffers a loss of aroma, does 

not soften, and may develop sunken areas on the 

surface (Siriphanich 1996).

Ethylene Production and Sensitivity

Production of ethylene varies from near zero 

in immature fruit up to 40 μL kg-1 hr-1 at the 

climacteric peak and varies with cultivar (Tongdee 
320

et al. 1987a,b). Most of the ethylene production 

is associated with the husk, as the pulp has a very 

low rate (Siriphanich 1996). Durian can be ripened 

with ethylene gas (Ketsa and Pangkool 1995) or 

ethephon (Atantee 1995). The husk of ripened 

durians will turn yellow or brown if ethylene 

concentration is too high. Thai consumers prefer 

to buy naturally ripened durians since the husk 

remains light green or olive. Durians with a 

yellowish or brownish husk are not regarded as 

fresh. 

Respiration Rates

The respiration rate for durian is 80 to 450 mg 

(45 to 254 μL) CO2

 kg-1 h-1 at 22 °C. To calculate 

heat production, multiply mg kg-1 h-1 by 220 to 

get BTU per ton per day or by 61 to get kcal 

per tonne per day. The peel has a much higher 

respiration rate and ethylene production than the 

pulp (Brooncherm and Siriphanich 1991). The 

climacteric rise seems to occur first in the pulp. 

In ‘Chanee’ and ‘Kan Yao,’ the respiration and 

ethylene production increase during ripening but 

decline when the fruit is overripe, while in ‘Mon 

Tong,’ the climacteric peak does not occur until 

the fruit is overripe (Tongdee et al. 1987b). 

Physiological Disorders

Failure of the aril to soften, or the aril softening 

unevenly, is a frequently observed disorder. 

Another disorder, which occurs especially during 

the rainy season, results in a watery aril that has 

a dull, flat taste. The cause of both disorders is 

unknown (Nanthachai 1994).

Postharvest Pathology

Phytophthora spp. are a major cause of rot in 

immature and mature fruit that leads to high 

losses during rainy weather and if fruit come in 

contact with soil. Another major cause of fruit 

rot is Lasiodiplodia spp. (Tongdee et al. 1987a). 

Fruit on the ground can also be attacked by 

Sclerotum rolfsii. Fruit diseases due to Phomopsis, 

Collectrichum, Fusarium, and Rhizopus can 

sometimes be severe (Siriphanich 1996). 

Sanitation, avoidance of mechanical injury, and 

fungicide can be used for control (Lim 1990).

Quarantine Issues

If the skin is not broken or split, durian is not 

a fruit fly host. The skin must be free of other 

insects such as scales.

Suitability as Fresh-Cut Product

The fruit is most frequently eaten fresh. The 

aril contains 64% water, 2.7% protein, 3.4% 

fat, 27.9% carbohydrate, and 23 mg per 1,000 

g vitamin C. Choice varieties fetch higher 

prices than others. Roadside and market stalls 

in Southeast Asia may cut open the fruit and 

package the soft aril and seed in a shrink-wrapped 

or stretch-wrapped tray. Ripe fruit and soft arils 

are also frozen for export. Partially ripe fruit are 

difficult to open without damaging the pulp.

Special Considerations

Thailand is the largest producer, followed by 

Indonesia and the Malaysian Peninsula. Durian 

is highly prized in Southeast Asia. Consumers in 

Singapore prefer fully ripe fruit with no splitting, 

while Thais prefer the firmer pulp of less ripe fruit 

with less volatiles. Others may prefer the strongflavored durian over the milder cultivars. There is 

a demand among ethnic groups familiar with the 

fruit in large temperate cities.

The pulp is dehydrated and sold as “durian cake” 

boiled with sugar, fermented, or salted. Dried aril 

is used as flavoring in ice cream, confectionery, 

pastry, and soft drinks (Nakasone and Paull 1998). 

Boiled or roasted seeds are eaten as snacks. 

Durian chips can be made from the immature and 

unripe durian pulp, as the lighter-colored flesh 

makes more attractive chips. Durian should not be 

shipped in mixed loads.
321

References

Atantee, S. 1995. Effect of ethephon on ripening 

and quality of durians. Graduate Special Problem, 

Department of Horticulture, Kasetsart University, 

Bangkok, Thailand.

Brooncherm, P., and J. Siriphanich. 1991. 

Postharvest physiology of durian pulp and husk. 

Kasetsart J. (Natural Sci.) 25:119-125.

Hiranpradit, H., N. Lee-Ungulasatian, S. 

Chandraparnik, and S. Jantigoo. 1992. Quality 

standardization of Thai durian, Durio zibethinus

Murr. Acta Hort. 321:695-704.

Ketsa, S., and S. Pangkool. 1994. The effect of 

humidity on ripening of durians. Postharv. Biol. 

Technol. 4:159-165.

Ketsa, S., and S. Pongkool. 2001. Effect of 

maturity stages and ethylene treatment on ripening 

of durian fruits. In C. Frisina, K. Mason, and J. 

Faragher, eds., Proceedings of the Australasian 

Postharvest Horticulture Conference, held at 

Monash University, Melbourne, Australia, 

18 September to 22 September, 1995, pp. 

67-72. Department of Natural Resources 

and Environment, Institute for Horticultural 

Development, Knoxfield, Victoria, Australia.

Lim, T.K. 1990. Durian—Diseases and Disorders, 

pp. 60-72. Tropical Press, Kuala Lumpur, 

Malaysia.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Nanthachai, S., ed. 1994. Durian: Fruit 

Development, Postharvest Physiology, Handling 

and Marketing in ASEAN. ASEAN Food 

Handling Bureau, Kuala Lumpur, Malaysia.

Salakpetch, S., S. Chandraparnik, H. Hiranpradit, 

and U. Punnachit. 1992. Source-sink relationship 

affecting fruit development and fruit quality 

in durian, Durio zibethinus Murr. Acta Hort. 

321:691-694.

Siriphanich, J. 1996. Storage and transportation 

of tropical fruits: a case study on durian. In S. 

Vijaysegaran, M. Pauziah, M.S. Mohamed, and S. 

Ahmed Tarmizi, Proceedings of the International 

Conference on Tropical Fruits, 23-26 July 1996, 

Kuala Lumpur, Malaysia, vol. 1, pp. 439-451. 

MARDI, Kuala Lumpur, Malaysia.

Sriyook, S., S. Siriatiwat, and J. Siriphanich. 

1994. Durian fruit dehiscence—water status and 

ethylene. HortScience 29:1195-1198.

Tongdee, S.C., A. Chayasombat, and S. 

Neamprem. 1987a. Effects of harvest maturity 

on respiration, ethylene production, and 

composition of internal atmospheres of Durian 

(Durio zibethinus, Murray). Proceedings of the 

Durian Workshop, Bangkok, Thailand, pp. 31-36. 

Thailand Institute of Scientific and Technological 

Research, Bangkok, Thailand.

Tongdee, S.C., S. Neamprem, and A. 

Chayasombat. 1987b. Control of postharvest 

infection of phytophthora fruit rot in durian with 

fosetyl-Al and residue levels in fruit. Proceedings 

of the Durian Workshop, Bangkok, Thailand, 

pp. 55-66. Thailand Institute of Scientific and 

Technological Research, Bangkok, Thailand.

Tongdee, S.C., A. Suwanagul, S. Neamprem, and 

U. Bunruengsri. 1990. Effect of surface coatings 

on weight loss and internal atmosphere of durian 

(Durio zibethinus Murray) fruit. ASEAN Food J. 

5:103-107.
322

Eggplant

Jorge H. Siller-Cepeda

Siller-Cepeda is with the Postharvest Physiology 

and Technology Laboratory, CIAD, Culiacán, 

Carretera a El Dorado, Culiacán, Sinaloa, Mexico.

Scientific Name and Introduction

The eggplant (Solanum melongena L.) is an 

annual plant of the Solanaceae or nightshade 

family. The edible portion is the immature fleshy 

pulp of the fruit. The fruit may be oval, round, 

long or pear-shaped. The skin is smooth and shiny, 

and the color may be black and purple, yellow, 

white, or striped. The main types include Standard 

(American), Japanese, Italian, Philippine, Thai, 

and Chinese. Available year-round, eggplants 

are grown primarily in Mexico, the United 

States (mostly in Florida and New Jersey), the 

Dominican Republic, and Jamaica.

Quality Characteristics and Criteria

A high-quality American eggplant is uniformly 

egg-shaped or globular and has a fresh green 

calyx, firm flesh, and dark purple skin. Additional 

quality indices are size, freedom from growth or 

handling defects, and decay. Characteristics of 

other eggplant types include Japanese (elongated, 

slender, and light to dark purple), White (small, 

egg-shaped to globular, and thin-skinned), MiniJapanese (small, elongated, striated purple and 

violet), Chinese (elongated, slender, and light 

purple), and Thai (small, round, and striated dark 

green).

Horticultural Maturity Indices

Eggplant fruit are harvested at a range of 

developmental stages. The time from flowering 

to harvest depends on cultivar and temperature 

and may be 10 to 40 days. Fruit are harvested 

immature before seeds begin to significantly 

enlarge and harden. Firmness and external 

glossiness are also used as harvest indicators. 

Overmature fruit become pithy and bitter.

Grades, Sizes, and Packing

Grades include Fancy, U.S. No. 1, U.S. No. 2, and 

Unclassified. Distinction among grades is based 

solely on size, external appearance, and firmness. 

Size is classified as “small”—32 fruit per box 

with fruit length 12 to 14 cm (4.75 to 5.5 in), 

“medium”—24 fruit per box with fruit length 19 

to 21 cm (7.5 to 8.25 in), “large”—18 fruit per box 

with fruit length 21 to 24 cm (8.25 to 9.5 in), and 

“extra large”—16 fruit per box with fruit length 

24 to 26 cm (9.5 to 10.25 in) (Siller et al. 1995). 

One-piece waxed fiberboard boxes and wirebound crates that can hold up to 15 kg (33 lb) are 

commonly used. Fruit are individually wrapped 

with paper to reduce desiccation and mechanical 

injury.

Precooling Conditions

Rapid cooling to 10 °C (50 °F) immediately after 

harvest is necessary to retard discoloration, weight 

loss, drying of calyx, and decay (Ryall and Lipton 

1979). Hydrocooling and forced-air cooling are 

most effective, but room cooling after washing or 

hydrocooling is common.

Optimum Storage Conditions

Fruit are stored at 10 to 12 °C (50 to 54 °F) 

with 90 to 95% RH because they are chilling 

sensitive (Ryall and Lipton 1979). Visual and 

sensory qualities deteriorate rapidly after 14 days 

of storage, especially if chilled during storage. 

Short-term storage or transit temperatures below 

10 °C (50 °F) are often used to reduce weight loss 

but result in chilling injury after transfer to retail 

conditions.
323

Controlled Atmosphere (CA) 

Considerations

CA storage or shipping offers little benefit. Low 

O2

 levels (3 to 5%) delay deterioration and the 

onset of decay by only a few days. Eggplant 

tolerates up to 10% CO2

, but storage life is 

not extended beyond that under reduced O2

. 

Wrapping fruit with plastic film to create modified 

atmosphere (MA) reduces weight loss and 

maintains firmness due to the high RH, especially 

on Japanese eggplant types, which have a high 

transpiration rate (Díaz Pérez 1998a). Eggplant 

fruit wrapped in high-density polyethylene 

(HDPE) films maintain a fresher flavor, firmness, 

and quality for a longer period than nonwrapped 

fruit (Ben-Yehoshua et al. 1985, Díaz Pérez 

1998b).

Retail Outlet Display Considerations

Eggplants should never be held in contact with 

ice. Odor from ginger, and possibly other odorproducing commodities such as onions, can be 

absorbed by eggplants. Thus, these products 

should not be placed in close proximity to 

eggplants (Cantwell and Suslow 2006).

Chilling Sensitivity

Eggplants will develop chilling injury after storage 

for 6 to 8 days at 5 °C (41 °F) (table 1). Surface 

pitting and scald are definite external symptoms 

(McColloch 1966). Scald refers to brown spots 

or areas that are first flush with the surface but 

may become sunken with time. Browning of the 

flesh and seeds is a conspicuous internal symptom 

of chilling injury, almost invariably followed by 

decay caused by Alternaria sp. (Ryan and Lipton 

1979). Chilling injury is cumulative and may be 

initiated in the field prior to harvest. Symptom 

development can be reduced by storage in 

polyethylene bags or polymeric film overwraps 

that retard water loss; however, increased decay 

from Botrytis is a potential risk.

Table 1. Chilling susceptablity of eggplant by type

_______________________________________________________

Temperature Days to visible chilling symptoms

_______________________________________________________

American Japanese Chinese

eggplant eggplant eggplant

_______________________________________________________

0.0 °C 1 to 2 2 to 3 —

2.5 °C 4 to 5 5 to 6 5 to 6

5.0 °C 6 to 7 8 to 9 10 to 12

7.5 °C 12 12 to 14 15 to 16

_______________________________________________________
324

Ethylene Production and Sensitivity

Rates of ethylene production vary from 0.1 to 

0.7 μL kg-1 h-1 at 12.5 °C (55 °F). Eggplant fruit 

have a moderate to high sensitivity to ethylene 

exposure. Calyx abscission and increased 

deterioration, particularly browning, may be a 

problem if eggplant fruit are exposed to greater 

than 1 μL L-1 ethylene during distribution and 

short-term storage.

Respiration Rates

Temperature American eggplant White eggplant Japanese eggplant

----------------------------------(mg CO2 kg-1 h-1)-----------------------------

12.5 °C 60 to 78 104 to 122 124 to 138

Data from Cantwell and Suslow (1998).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 

10 °C (50 °F), and 1.8 at 20 °C (68 °F). To calculate heat production, multiply mg 

kg-1 h-1 by 220 to get BTU per ton per day or by 61 to get kcal per tonne per day. 

Freezing Injury

Eggplant fruit freeze at -0.8 °C (30.6 °F). 

Symptoms include water-soaked pulp that 

becomes brown and desiccated over time.

Physiological Disorders

Harvesting should be done by cutting the calyxstem free from the plant rather than by tearing. 

Cotton gloves are often worn to protect the fruit. 

Bruising and compression injury is very common 

when not enough attention is paid to careful 

harvest and handling practices. Eggplant fruit 

cannot withstand stacking in bulk containers.

Postharvest Pathology

Postharvest diseases often occur in combination 

with chilling stress. Common fungal pathogens are 

Alternaria (black mold rot), Botrytis (gray mold 

rot), Rhizopus (hairy rot), Phomopsis rot, and 

Phytophtora (soft rot).

Quarantine Issues

None.

Suitability as Fresh-Cut Product

No current potential.

Special Considerations

Moistened paper or waxed cartons are often used 

to reduce water loss. Japanese eggplants lose 

water three times more rapidly than American 

types. Visible signs of water loss are reduction 

of surface sheen, skin wrinkling, spongy flesh, 

and browning of the calyx. Dipping the calyx 

or the whole fruit in dilute aqueous solutions of 

1-naphthalene acetic acid and prochloraz retarded 

calyx senescence (Temkin-Gorodeiski et al. 1993, 

Muy et al. 1998).

References

Ben-Yehoshua, S. 1985. Individual seal-packing 

of fruits and vegetables in plastic film—a new 

postharvest technique. HortScience 20:32-37.

Cantwell, M., and T. Suslow. 2006. Eggplant. In

Fresh Produce Facts. At http://postharvest.ucdavis.

edu/produce_information.
325

Díaz-Pérez, J.C. 1998a. Transpiration rates in 

eggplant fruit as affected by fruit and calyx size. 

Postharv. Biol. Technol. 12:76-82.

Díaz-Pérez, J.C. 1998b. Empaque de berenjena 

(Solanum melongena L.) ‘Clásica’ y ‘Japonesa’ 

con películas de polietileno. Agrociencia 32:71-

74. 

McColloch, L.P. 1966. Chilling injury of eggplant 

fruits. Marketing Research Report 749, U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

Muy, R.D., J. Siller, M. Báez, and V. Pérez. 

1998. Aplicación de tratamientos químicos para 

reducir oxidación del cáliz en Berenjena (Solanum 

melongena L.). In Abstracts of the XXIX National 

Congress of Food Science Technology, vol. 33, pp. 

61-62. Tecnología de Alimentos, Aguascalientes, 

Mexico. 

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melons. AVI 

Publishing Co., Westport, CT.

Siller, J., E. Araiza, M. Báez, et al. 1995. 

Dinámica de crecimiento de berenjena tipo 

‘Clásica.’ In Abstracts of the VI Congress of 

the Mexican Society of Horticultural Sciences, 

Sonora, Mexico, p. 37. Mexican Society of 

Horticultural Sciences, Sonora, Mexico. 

Temkin-Gorodeiski, N., B. Shapiro, S. Grinberg, 

et al. 1993. Postharvest treatments to control 

eggplant deterioration during storage. J. Hort. Sci. 

68:689-693.
326

Endive and Escarole

Mikal E. Saltveit

Saltveit is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Endive (Cichorium endiva L.) is an herbaceous 

member of the Asteraceae family, as are its 

relatives chicory (Cichorium intybus L.), lettuce 

(Lactuca sativa L., Cichorium tribe), and 

radicchio (Cichorium intybus L.). It has two 

forms, a narrow-leafed form called curly endive, 

which resembles dandelion leaves, and a broadleafed form called escarole. The outer leaves of 

endive are dark green and bitter. The inner leaves 

are light green to creamy white and milder in 

flavor. It is used to spice up salads made from 

more blandly flavored lettuces. Endive is grown 

and handled like leaf lettuces.

Quality Characteristics and Criteria

High-quality endive heads should be clean, free of 

browning, crisp, and bright green. Young, tender 

leaves are preferred over tough, older leaves.

Horticultural Maturity Indices

Harvesting is usually by hand when the heads 

reach mature size. The plants are cut at the base 

when fully developed—25 to 30 cm (10 to 12 in) 

across and the center leaves blanched. The heads 

are packed into corrugated paper cartons in the 

field. The leafy heads should be kept clean of 

soil and mud. The leaves should have a spicy and 

mildly bitter taste. Toughness and a strong bitter 

taste develop if harvest is delayed and the crop 

becomes overmature. The product then becomes 

unmarketable.

Grades, Sizes, and Packaging

Similar to those of leaf lettuces. 

Precooling Conditions

Vacuum cooling and hydrocooling to 0 °C (32 °F) 

are preferred. 

Optimum Storage Conditions

These crops are not adapted to prolonged storage 

and will not keep more than 2 to 3 weeks even at 

the optimal storage temperature of 0 °C (32 °F) 

with 95 to 100% RH (Hardenburg et al. 1986). 

Storage life is halved at 5 °C (41 °F). Proper RH 

is essential to prevent wilting. Though endive, 

specialty lettuces, and other leafy greens have 

usually been hand harvested, some mechanical 

harvesters are available for product destined for 

bag mixes. However, the greater degree of injury 

produced by mechanical harvesting may shorten 

shelf-life unless optimal storage conditions are 

strictly maintained. Top ice or package ice is 

desirable for maintaining proper temperature and 

RH. Endive and escarole are often shipped in 

mixed loads with other produce since most orders 

for these products are less than truckload lots.

Controlled Atmosphere (CA) 

Considerations

There are currently no recommended CA 

atmospheres for endive and escarole. However, 

a CA useful to maintain the quality of packaged 

fresh-cut lettuce may be beneficial for either 

whole or fresh-cut endive and escarole.

Retail Outlet Display Considerations

Maintain cold conditions to maximize storage and 

shelf-life, and minimize dehydration with periodic 

sprays of cold water. Conditions should be similar 

to those used for leaf lettuces.
327

Chilling Sensitivity

Endive and escarole are not chilling sensitive, but 

freezing at -0.1 °C (31.8 °F) must be avoided.

Ethylene Production and Sensitivity

Production is very low, but exposure can result in 

leaf yellowing. 

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 45

5 °C 52

10 °C 73

15 °C 100

20 °C 133

25 °C 200

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Similar to those of leaf lettuces. 

Postharvest Pathology

Similar to those of leaf lettuces. 

Quarantine Issues

There are no quarantine issues.

Suitability as Fresh-Cut Product

Very high, especially in salad mixes with other 

leafy greens and lettuces. 

Special Considerations

Endive and escarole must be handled with care 

to avoid mechanical damage and to minimize 

discoloration and pathological problems. 

Temperatures must be kept low and RH high to 

prevent loss of turgor and wilting.

References

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1, Vegetables and 

Melons. AVI Publishing Co., Westport, CT.

Ryder, E.J. 1979. Endive and chicory. Leafy Salad 

Vegetables, pp. 171-194. AVI Publishing Co., 

Westport, CT.
328

Fennel

Fabio Mencarelli

Mencarelli is formerly with the Istituto Tecnologie 

Agroalimentari, University of Tuscia, Viterbo, 

Italy. He is now with the Department of Food 

Science and Technology, University of Viterbo, 

Italy.

Scientific Name and Introduction

Fennel (Foeniculum vulgaris Mill.) belongs to 

the Umbelliferae family and originated in the 

Mediterranean region. There are two varieties: 

seed fennel is var. sativum and edible fennel 

is var. dulce. The edible portion is the white, 

enlarged basal parts of the leaf sheaths that are 

fleshy, turgid, and crisp. The leafy sheaths form a 

“grumolo” that is white, spherical, and the source 

of green stems and fuzzy leaves. Italian production 

accounts for 85% of the world market. Fennel is a 

source of fiber, potassium, and vitamin C.

Quality Characteristics and Criteria

There are no published quality standards, but 

extra fancy fennel is characterized by uniform and 

brilliant white leafy sheaths that are turgid and 

crisp, with no symptoms of cracking or darkening.

Horticultural Maturity Indices

Fennel is harvested by hand when the plant 

reaches a specified size by cutting the plant from 

the taproot. Outer leaves are removed, and the 

remaining leaves are trimmed to 10 to 15 cm (4 to 

6 in) in length. It is harvested year-round, except 

in June and July.

Grades, Sizes, and Packaging

Fennel is sized by the packer and placed in plastic 

or cardboard boxes. Careful packing is necessary 

to avoid scratching the sheaths. Mechanical injury 

produces rapid browning of the leaves.

Precooling Conditions

Hydrocooling is needed in the summer to reduce 

field heat and water loss. Aqueous citrate solutions 

control browning of cut surfaces. Avoid excess 

water infiltration during packing. Forced-air 

cooling can be used, but only when fennel is 

plastic-wrapped. Vacuum cooling was tested with 

mixed results (Sozzi and Ilardi 1992).

Optimum Storage Conditions

Fennel can last for 2 weeks if stored at 0 °C (32 

°F) and 90 to 95% RH.

Controlled Atmosphere (CA) 

Considerations

No CA applications have been reported.

Retail Outlet Display Considerations

Fennel must be kept refrigerated and periodically 

moistened with water sprays. Removal of injured 

sheaths and brown cut surfaces may be needed.

Chilling Sensitivity

Fennel is not chilling sensitive. 

Ethylene Production and Sensitivity

Ethylene production is low at 0 to 2 °C (32 to 36 

°F)—about 0.5 to 1.0 mL kg-1 h-1—and increases to 

2.5 to 6 mL kg-1 h-1 at 20 °C (68 °F) (Mencarelli et 

al. 1996). No data exist on sensitivity to ethylene.
329

Respiration Rates

Temperature mg CO2 kg-1 h-1

2 °C 18 to 20 

20 °C 24 to 40

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Growth after harvest can cause the leaf sheaths 

to loosen and separate (Mencarelli et al. 1996). 

Freezing results in water-soaked spots on the 

outside sheaths and decay of internal young 

sheaths.

Postharvest Pathology

Fennel is resistant to pathogen attack after harvest. 

Free water inside the plant can promote bacterial 

growth.

Quarantine Issues

There are no quarantine issues at this time.

Suitability as Fresh-Cut Product

Browning of cut surfaces is a problem with freshcut fennel. 

Special Considerations

Special attention must be given to mechanical 

harvesting and postharvest handling because 

fennel is highly sensitive to physical injury. 

Removal of the outer sheath at retail markets 

reduces the problem, but the process is time 

consuming.

References

Bianco, V.V. 1990. Il finocchio. In V.V. Bianco and 

F. Pimpini, eds., Orticoltura, pp. 168-183. Patron 

Press, Bologna, Italy. 

Mencarelli, F., R. Massantini, and F. Garosi. 1996. 

Aspetti fisiologici della postraccolta del finocchio 

fresco. Procedura Giornate di Studio sulla 

Coltivazione del Finocchio, 3:29-30, pp. 131-136. 

Italian Horticultural Society, Tarquinia, Viterbo, 

Italy.

Sozzi, A., and V. Ilardi. 1992. Conservazione 

con film microperforato e prerefrigerazione con 

vacuum del finocchio. Colture Protette 4:73-76.
330

Fig

Carlos H. Crisosto and Adel A. Kader

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA. Kader was 

with the Department of Plant Sciences, University 

of California, Davis, CA. He is deceased.

Scientific Name and Introduction

Edible figs are the multiple or compound fruits 

of Ficus carica L., a member of the family 

Moraceae. The plant is a tree or shrub native 

to Asia Minor, from where it spread into the 

Mediterranean region. It was known to the ancient 

Egyptians in 4000 B.C., and later Herodotus (c. 

485 to 425 B.C.) wrote about its cultivation.

Figs were introduced from Europe to North 

America as early as 1600, but commercial 

cultivation did not start until about 1900. The 

largest center of cultivation in the United States is 

in California. Figs thrive only in the hotter parts 

of the moderate zones, while in tropical countries 

they can be cultivated only at higher altitudes.

The best-known cultivated varieties are the 

common, or Adriatic, fig and the Smyrna fig. 

The common fig produces seedless fruit by 

parthenocarpy (production of fruit without 

fertilization), while the Smyrna fig must be 

pollinated in spite of the fact that it does not 

develop any male flowers. The figs are pearshaped structures formed from the rolled-up discs 

of the capitula so that the florets of the capitulum 

occur inside the aperture and are not visible from 

the outside. The capitulum is connected to the 

outside by a small aperture at the top of the fig. 

The female florets develop into tiny achenes. The 

achenes inside the fig represent the infructescence, 

and the edible part is the swollen, fleshy disc of 

the capitulum forming the fruit wall.

Quality Characteristics and Criteria

Skin color and flesh firmness of fresh figs are 

related to their quality and postharvest life. Flavor 

is influenced by stage of ripeness, and overripe 

figs can become undesirable due to fermentative 

products. Other quality indices include absence 

of defects (such as bird-peck, sunburn, scab, skin 

break, and stem shrivel), insects, and decay.

Horticultural Maturity Indices

Fresh market figs must be harvested when almost 

fully ripe and firm to be of good eating quality. 

Skin color and flesh firmness are dependable 

maturity and ripeness indices. ‘Black Mission’ figs 

should be light to dark purple rather than black, 

and should yield to slight pressure. ‘Calimyrna’ 

figs should be yellowish white to light yellow 

and firm. Figs for drying should be allowed to 

fully ripen and partially dry on the tree before 

harvesting and drying to about 17% moisture 

using either solar drying or a dehydrator at 60 oC 

(140 oF).

Grades, Sizes, and Packaging

Fully mature fresh figs are soft, easily bruised, 

and highly perishable. Figs are hand-picked and 

packed in a one-layer box. Pickers wear gloves to 

protect against fig juice. ‘Mission’ fig, a black fig 

with distinctive flavor, and ‘Calimyrna’ fig, a large 

yellowish fig, are the main cultivars sold fresh in 

the United States.

Optimum Storage Conditions

Store at -1 to 0 oC (30 to 32 oF) with 90 to 95% 

RH. Expedited forced-air cooling to 0 oC (32 oF) is 

strongly recommended.
331

Controlled Atmosphere (CA) 

Considerations

CA combinations of 5 to 10% O2

 with 15 to 

20% CO2

 are effective in decay control, firmness 

retention, and reduction of respiration and 

ethylene production. Postharvest life at optimum 

temperature and RH depends on cultivar and 

ripeness at harvest, but ranges from 1 to 2 weeks 

in air and 3 to 4 weeks in CA for California-grown 

‘Black Mission’ and ‘Calimyrna’ figs.

Retail Outlet Display Considerations

Figs should be displayed at 0 to 2 oC (32 to 36 oF) 

and dried with an RH of 90 to 95%.

Chilling Sensitivity

Figs are not chilling sensitive. 

Rates of Ethylene Production and 

Sensitivity 

Temperature μL kg-1 h-1

0 oC 0.4 to 0.8

5 oC 0.8 to 1.5

10 oC 1.5 to 3.0

20 oC 4.0 to 6.0

Figs are climacteric fruit and are slightly sensitive 

to ethylene action on stimulating softening and 

decay severity, especially if kept at 5 oC (41 oF) or 

higher temperatures.

Respiration Rates 

Temperature mg CO2 kg-1 h-1

0 oC 4 to 8

5 oC 10 to 16

10 oC 18 to 24

20 oC 40 to 60

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Extended storage in CA can result in loss of 

characteristic flavor. Figs exposed to <2% O2

 or 

>25% CO2

 develop off flavors due to fermentative 

metabolism.

Postharvest Pathology

Alternaria rot, caused by Alternaria tenuis,

appears as small, round, brown to black spots over 

the fruit surface. Any cracks on the skin make the 

fruit more susceptible to the rot.

Black mold rot, caused by Aspergillus niger, 

appears as dark or yellowish spots in the flesh with 

no external symptoms. At advanced stages the 

skin and flesh turn a slightly pink color and white 

mycelia with black spore masses follow.

Endosepsis (soft rot), caused by Fusarium 

moniliforms, appears in the cavity of the fig 

making the pulp soft, watery, and brown with 

sometimes an offensive odor.

Souring is a preharvest problem resulting from 

yeasts and bacteria carried into figs by insects, 

especially vinegar flies, resulting in odors of 

alcohol or acetic acid.

Recommendations to reduce postharvest diseases 

are the following: controlling orchard insects 

to reduce fruit damage and transmission of 

fungi; using effective control of preharvest 

diseases; enforcing strict sanitation of picking 

and transporting containers; supervising careful 

handling to minimize abrasions, cracks, and other 

physical damage; avoiding picking figs from the 

ground for fresh market; and enforcing prompt 

cooling to 0 oC (32 oF) and maintaining the cold 

chain all the way to the consumer.
332

Quarantine Issues

Currently, there is limited export to Canada. There 

is no import of fresh figs into the United States. 

Issues associated with exotic pest quarantine 

addressing both imported and exported fruit 

change rapidly. The USDA Animal and Plant 

Health Inspection Service (APHIS) issues rules 

regarding import requirements. APHIS provides 

information to assist exporters in targeting 

markets and defining what entry requirements 

a foreign country might have for fruit. In 

cooperation with State plant boards, the agency 

developed the database “Excerpt” to track 

phytosanitary requirements for each country. 

APHIS also provides phytosanitary inspections 

and certifications that declare that fruit are free 

of pests to facilitate compliance with foreign 

regulatory requirements.

Suitability as Fresh-Cut Product

Fresh figs are not well-adapted for use as a freshcut product.

Special Considerations

Handling figs to avoid infection with Aspergillus

species is very important to minimize formation 

of mycotoxins. Solar heating reduces insect 

infestations in ripening and drying figs.

Acknowledgments

Most of the information in this chapter is from the 

University of California, Davis, website on “Fresh 

Produce Facts” at http://postharvest.ucdavis.edu/

produce_information. 

References

Bolin H.R., and A.D. King. 1980. Fig. In S. Nagy 

and P. Shaw, eds., Tropical and Subtropical Fruits 

- Composition, Properties, and Uses, pp. 492-505. 

AVI Publishing Co., Westport, CT.

Chossa, I. 1997. Fig. In S. Mitra, ed., Postharvest 

Physiology and Storage of Tropical and 

Subtropical Fruits, pp. 245-268. CAB Intl., 

Wallingford, U.K.

Colelli, G., F.G. Mitchell, and A.A. Kader. 1991. 

Extension of postharvest life of ‘Mission’ figs by 

CO2

-enriched atmospheres. HortScience 26:1193-

1195.

Condit, J.J. 1947. The Fig. Chronica Botanica Co., 

Waltham, MA.

Obenauf, G., M. Gerdts, G. Leavitt, and J. Crane. 

1978. Commercial dried fig production. Leaflet 

21051, University of California, Division of 

Agricultural Sciences, Davis, CA.
333

Garlic

Marita Cantwell 

Cantwell is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Garlic, Allium sativum L., is a member of the 

onion family (Alliaceae). It is a bulb comprised 

of cloves (thickened storage leaves) individually 

wrapped in dried leaf sheaths or skins attached to 

a compressed stem plate. The whole bulb is also 

wrapped in several layers of dried leaf sheaths.

In the United States, garlic is grown mostly 

in California and neighboring States. Garlic is 

imported principally from Argentina, Chile, China, 

and Mexico. Garlic is produced as an annual 

crop for seed, fresh market, and processed (dried) 

products.

Quality Characteristics and Criteria

High-quality garlic bulbs are clean, white (or other 

color typical of the variety), and well-cured (dried 

neck and outer skins). The cloves should be firm 

to the touch. Cloves from mature bulbs should 

have a high dry weight and soluble solids content 

(SSC)—more than 35% in both cases.

Horticultural Maturity Indices

Garlic can be harvested at different stages of 

development for specialty markets, but most garlic 

is harvested when the bulbs are mature. Harvest 

occurs after the tops have fallen and are dried.

Grades, Sizes, and Packaging

Grades include U.S. No. 1 and unclassified and 

are based primarily on external appearance and 

freedom from defects. Minimum diameter for 

fresh market is 38.1 mm (1.5 in). Garlic is usually 

packed loose in 2.3-, 4.6-, 10-, and 13.6-kg (5-, 

10-, 22-, and 30-lb) cartons and may also be 

packed in smaller-weight net bags or trays for 

retail.

Cooling

Well-cured garlic has a very low respiration rate 

and it is typically cooled when placed in storage. 

High initial airflow may be used to bring pulp 

temperature down rapidly to storage temperature.

Optimum Storage Conditions

The variety of garlic affects potential storage life, 

and the recommended conditions for commercial 

storage depend on the expected storage period. 

Garlic can be kept in good condition for 1 to 2 

mo at ambient temperatures of 20 to 30 °C (68 to 

86 °F) under 75% RH (Hardenburg et al. 1986). 

However, under these conditions, bulbs will 

eventually become soft, spongy, and shriveled due 

to water loss. Garlic can be stored for more than 9 

mo at -1 to 0 °C (30 to 32 °F) with 60 to 70% RH. 

Good airflow throughout the vented bins or other 

storage containers is necessary to prevent any 

moisture accumulation. Garlic can also be held in 

common storage for 3 to 4 mo if temperatures are 

kept cool (cool night air ventilation) with good 

airflow and low RH. Garlic will eventually lose 

dormancy, signaled by internal development of the 

sprout. This occurs most rapidly at intermediate 

storage temperatures of 5 to 18 °C (41 to 64 °F) 

(Mann and Lewis 1956, Hardenburg et al. 1986). 

For long-term storage, garlic should have minimal 

or no internal sprout growth and should be well 

cured (see Special Considerations).

To control sprout development and lengthen 

the storage period, garlic may be treated with 

preharvest applications of sprout inhibitors, such 

as maleic hydrazide, or be irradiated after harvest 

(Hardenburg et al. 1986). Garlic odor is easily 

transferred to other products, so garlic should be 

stored separately. High RH in storage will favor 

mold growth and rooting. Mold growth can also 

be problematic if garlic has not been well cured 

before storing. 
334

Controlled Atmosphere (CA) 

Considerations

Atmospheres with high CO2

 (5 to 15%) are 

beneficial in retarding sprout development and 

decay during storage at 0 to 5 °C (32 to 41 °F). 

Low O2

 (0.5%) alone does not retard sprout 

development of ‘California Late’ stored up to 6 

mo at 0 °C (32 °F). Atmospheres with 15% CO2

may produce a yellow, translucent discoloration 

on some cloves after about 6 mo (Cantwell 2006).

Retail Outlet Display Considerations

Garlic should be kept cool and dry. 

Chilling Sensitivity

Garlic is not chilling sensitive, and the optimum 

storage temperature of -1 °C (30 °F) is just above 

the freezing point of garlic. 

Ethylene Production and Sensitivity

Garlic produces very low amounts of ethylene and 

is not particularly sensitive to ethylene exposure.

Respiration Rates

Temperature Intact bulbs Fresh-peeled

 cloves

---------mg CO2 kg-1 h-1-------

0 °C 4 to 12 24

5 °C 8 to 24 30 to 40

10 °C 12 to 36 70 to 100

15 °C 14 to 30

20 °C 14 to 26

Data modified from Hardenburg et al. (1986) 

with data for intact and fresh-peeled cloves from 

Cantwell (2006).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton 

per day or by 61 to get kcal per tonne per day. 

Respiration rates increase when sprouting begins.

Physiological Disorders

Waxy breakdown is a physiological disorder that 

affects garlic during later stages of growth and is 

often associated with periods of high temperature 

near harvest. Early symptoms are small, lightyellow areas in the clove flesh that darken to 

yellow or amber. Later, the clove becomes 

translucent, sticky, and waxy, but the outer dry 

skins are not usually affected. Waxy breakdown 

is commonly found in stored and shipped garlic, 

rarely in the field. In addition to its association 

with high preharvest temperatures and sunscald, 

low O2

 and inadequate ventilation during handling 

and storage may also be contributing factors.

Postharvest Pathology

Penicillium rots (Pencillium corymbiferum and 

other spp.) are common problems in stored garlic. 

Affected garlic bulbs may show little external 

evidence until decay is advanced. Affected bulbs 

are light in weight and individual cloves are soft, 

spongy, and powdery dry. In an advanced stage 

of decay, the cloves break down in a green or 

gray powdery mass. Low RH in storage retards 

rot development. Less common storage decay 

problems include fusarium basal rot (Fusarium 

oxysporum cepae), which infects the stem plate 

and causes cloves to shatter; dry rot due to 

Botrytis allii; and bacterial rots (Erwinia spp., 

Pseudomonas spp.). 

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Whole-peeled garlic cloves are a popular 

convenience product processed originally for 
335

foodservice but now found in retail food stores. 

Fresh-peeled garlic cloves are packed in rigid 

clear plastic containers or in plastic film liners 

in carton boxes. The mechanical peeling process 

results in broken and damaged pieces, and damage 

is the major factor leading to decay and quality 

loss during storage. Storage at 0 to 5 °C (32 to 41 

°F) is imperative to maintain good quality. A 2- to 

3-week storage life is expected if garlic is kept 

at 5 °C (41 °F) or below. Storage temperatures 

above 5 °C (41 °F) will result in pink and brown 

discoloration on the damaged areas and favor root 

and sprout development.

Special Considerations

Outer cloves of bulbs are easily damaged during 

mechanical harvest and these damaged areas 

discolor and decay during storage. Therefore, 

high-quality garlic for the fresh market is usually 

harvested manually (pulled and trimmed) to avoid 

mechanical damage.

Curing garlic is the process by which the outer 

leaf sheaths and neck tissues of the bulb are dried. 

Warm temperatures, low RH, and good airflow 

are conditions needed for efficient curing. Under 

favorable climatic conditions in California, garlic 

is usually cured in the field. After harvest and 

trimming, it may remain in bins in the field to cure 

further. Curing is essential to maximize storage 

life and minimize decay.

The characteristic odor and flavor of fresh garlic is 

due to the formation of organosulfur compounds 

when the main odorless precursor alliin is 

converted to allicin by the enzyme alliinase. 

The content of alliin decreases during storage, 

but the effect of time, storage temperature, and 

atmosphere has not been well documented. 

Production of allicin occurs at low rates unless the 

garlic cloves are crushed or damaged. Allicin is 

also an important compound since it decomposes 

into other sulfur-containing molecules that have 

purported human health benefits.

References

Cantwell, M. 2000. Garlic. Recommendations 

for maintaining postharvest quality. Perishables 

handling. At http://postharvest.ucdavis.edu/ 

produce_information.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Kwon, J.H., M.W. Byun, and H.O. Cho. 1985. 

Effects of gamma irradiation dose and timing of 

treatment after harvest on the storeability of garlic 

bulbs. J. Food Sci. 50:379-381.

Mann, L.K., and D.A. Lewis. 1956. Rest and 

dormancy in garlic. Hilgardia 26(3):161-189.

Shaffer, E., ed. 2000. Produce Availability and 

Merchandising Guide. In The Packer. Vance Pub. 

Corp., Lenexa, KS.

Snowdon, A.L. 1992. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables, pp. 236-262. CRC Press, Boca 

Raton, FL.

Takagi, H. 1990. Garlic (Allium sativum L.). In

J.L. Brewster and H.D. Rabinowitch, eds., Onions 

and Allied Crops, vol. 3, Biochemistry, Food 

Science and Minor Crops, pp. 109-158. CRC 

Press, Boca Raton, FL.

Yu, T.H., and C.T. Ho. 1993. Chemistry and 

stability of sulfur-containing compounds in the 

genus Allium. In G. Charalambous, ed., Shelflife Studies of Food and Beverages. Chemical 

Biological and Nutritional Aspects, pp. 501-546. 

Elsevier Science, New York, NY. 
336

Ginger

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

The rhizome of ginger (Zingiber officinale) is 

referred to as a “root” and is used as a spice in 

cooking and as a pickled vegetable. The knobby, 

fibrous mature root has a light yellowish-brown 

skin when fresh. The rhizome is also harvested at 

a very early stage, before fiber development has 

taken place, for use in pickles and confectionery.

Quality Characteristics and Criteria

Desired quality characteristics include skin color, 

plumpness of tuber pieces, sheen on skin, and 

absence of vegetative sprouts, blemishes, soil, 

and insect injury. Young ginger is bright yellow to 

brown and has a high sheen with greenish-yellow 

vegetative buds, but no sprouts.

Horticultural Maturity Indices

Mature ginger rhizomes are harvested when the 

plant tops begin to wilt and die. These rhizomes 

should be plump with a dry, bright yellow-brown 

skin. The sheen is soon lost and the skin darkens 

after harvest.

Grades, Sizes, and Packaging

Rhizomes are sold in full, telescoping 13.61-kg 

(30-lb) and 9.06-kg (20-lb) fiberboard cartons or 

in 2.27-kg (5-lb) cartons with film bags.

Precooling Conditions

Forced-air or room cooling to 12 to 14 °C (54 to 

57 °F) should be used.

Optimum Storage Conditions

Mature ginger rhizomes can be stored at 12 to 14 

°C (54 to 57 °F) with 85 to 90% RH for 60 to 90 

days. Storage at 13 °C (55 °F) with 65% RH leads 

to extensive dehydration and a wilted appearance 

(Akamine 1962). Superficial mold growth can 

occur if condensation occurs on rhizomes.

Controlled Atmosphere (CA) 

Considerations

There are no published recommendations.

Retail Outlet Display Considerations

Display fresh young ginger with misting and 

mature ginger at ambient temperature with no 

misting.

Chilling Sensitivity

Mature ginger is chilling sensitive if held below 

12 °C (54 °F). Symptoms include loss of skin 

color and pitting of the skin. In severe cases there 

is internal breakdown.

Ethylene Production and Sensitivity

Very low.

Respiration Rates

Rates are about 5.5 to 6.8 mg CO2 kg-1 h-1 (3.1 to 

3.8 μL kg-1 h-1) at 22 °C (72 °F). 

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 
337

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Dehydration is the most common problem. The 

rhizomes lose their sheen and darken rapidly 

during handling (Akamine 1962). Shriveling of 

the pieces becomes pronounced after the loss of 

about 10% of harvest weight (Paull et al. 1988).

Postharvest Pathology

Fusarium rot (Fusarium spp.) can cause serious 

problems. Symptoms include pale-brown 

discoloration of the vascular strands (Trujillo 

1963) that invades the rest of the rhizome, which 

then becomes brown and dry (Teakle 1965). 

Pythium rot (Pythium spp.) has also been reported. 

The rhizome becomes soft and watery (Haware 

and Joshi 1974). Fungicides are not permitted, but 

reasonable control is obtained if the rhizomes are 

adequately cured and held at 12 to 14 °C (54 to 57 

°F). Saprophytes, such as Penicillium spp., may 

grow on cut ends and injured areas and, though 

not parasitic, they give the cut ends and surface an 

unsightly appearance.

Quarantine Issues

Rhizome pieces free of soil and insect injury 

require no treatment.

Suitability as Fresh-Cut Product

None at this time.

References

Akamine, E.K. 1962. Storage of fresh ginger 

rhizomes. Bull. Hawaii Ag. Exp. Sta. no. 130.

Haware, M.P., and L.K. Joshi. 1974. Studies on 

soft rot of ginger from Madhya Pradesh. Indian 

Phytopath. 27:158-161.

Paull, R.E., N.J. Chen, and T.T.C. Goo. 1988. 

Control of weight loss and sprouting of ginger 

rhizome in storage. HortScience 23:734-736.

Paull, R.E., N.J. Chen, and T.T.C. Goo. 1988. 

Compositional changes in ginger rhizomes during 

storage. J. Amer. Soc. Hortic. Sci. 113:584-588.

Teakle, D.S. 1965. Fusarium rhizome rot of ginger 

in Queensland. Queensland J. Agric. Animal Sci. 

22:263-272.

Trujillo, E.E. 1963. Fusarium yellows and rhizome 

rot of common ginger. Phytopathology 53:1370-

1371.
338

Ginseng

Seung Koo Lee and Sang Don Yun

Lee and Yun are with the Department of 

Horticulture, Seoul National University, Suwon, 

South Korea.

Scientific Name and Introduction

American ginseng (Panax quinquefolium L.), 

Chinese sanch’i ginseng (Panax notoginseng),

Japanese ginseng (chikusetsu-ningin) (Panax 

japonica), and Korean ginseng (Panax ginseng

C.A Meyer) are all perennials of the Araliaceae 

family (Bae 1978). The edible portion is the main 

root with two to five lateral roots. Ginseng is used 

as a cure-all medicine in Asia (Proctor 1990). 

Ginseng is grown primarily between latitudes 30o 

to 48o N in Canada, China, Korea, and the United 

States.

Quality Characteristics and Criteria

High-quality ginseng has a firm main root without 

defects. It should be clearly defined to show a 

head (rhizome), body (main root), and legs (lateral 

roots).

Horticultural Maturity Indices

Ginseng is usually harvested 3 to 5 years after 

transplanting 1-year-old seedlings. The optimum 

time for harvest in Korea is August to October, 

when its medicinal value is highest.

Grades, Sizes, and Packaging

Ginseng is first classified by the age of the root 

and then by external appearance. Size grades are 

“first”—over 6 cm (2.4 in) long and 60 g (0.13 lb), 

“second”—4 to 6 cm (1.8 to 2.7 in) long and 40 to 

60 g (0.09 to 0.13 lb), and “third”—3 to 4 cm (1.2 

to 1.8 in) long and 30 to 40 g (0.07 to 0.09 lb). 

Packaging varies greatly.

Precooling Conditions

Ginseng roots are commonly hydrocooled or 

forced-air cooled to below 5 oC (41 °F). Cooling 

generally retards subsequent deterioration such as 

weight loss and decay.

Optimum Storage Conditions

Ginseng should be stored at 0 oC (32 °F) with 95% 

RH or higher. Roots retain good quality for 2 mo 

at 0 oC (Yun 1998) and 20 days at 25 oC (77 °F) 

(Oh et al. 1979).

Controlled Atmosphere (CA) 

Considerations

Reduced microorganism growth and attenuated 

cavitation are the major benefits of CA. Optimal 

CA is 1% O2

 with >5% CO2 (Lee and Kim 1979, 

Yun and Lee 1998). Cavitation is significantly 

reduced at 15% CO2

 (Yun 1998).

Retail Outlet Display Considerations

Ginseng roots are displayed with green leafy 

vegetables, and water loss is controlled by 

humidification or packaging.

Chilling Sensitivity

Ginseng is not chilling sensitive and should be 

stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Ginseng roots produce only minute amounts of 

ethylene and are not sensitive to ethylene.
339

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 5.5

10 °C 15.0

15 °C 33.0

25 °C 95.0

Data from Lee and Kim (1979).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

The formation of cavities within the root is a 

common problem caused by cultural conditions 

and starch breakdown (Park et al. 1986, Yun 

1998). Other disorders include discolored skin and 

flesh and splitting of the main root.

Postharvest Pathology

Gray mold (Botrytis cinerea) is common in 

ginseng (Oh et al. 1981). Lesions frequently begin 

in wounds and spread to other areas of the roots. 

Storage at low temperatures or using CA slows 

the rate of spread of the disease and should be 

maintained to minimize pathological disorders and 

prolong shelf-life.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

No current potential.

Special Considerations

Careful handling is mandatory because it is easy 

to bruise the surface of main roots and break 

lateral roots. Damaged areas provide a route for 

entry of microorganisms.

References

Bae, H.W. 1978. Korean Ginseng. Korean 

Ginseng and Tobacco Research Institute, Taejon, 

South Korea.

Lee, S.W., and K.S. Kim. 1979. Studies on CA 

storage of fresh ginseng. Korean J. Food Sci. 

Technol. 11:131-137.

Oh, H.I., S.D. Kim, J.H. Do, et al. 1979. Studies 

on storage methods of Korean fresh ginseng. In

Report of Office of Monopoly, pp. 67-73. Office 

of Monopoly, Seoul, Korea.

Oh, H.I., H.W. Noh, J.H. Do, et al. 1981. Physicochemical and microbiological changes during 

storage of fresh ginseng. Korean J. Ginseng Sci. 

5:87-96.

Park, H., J.H. Lee, M.K. Lee, et al. 1986. Study on 

effect of cultural condition on occurrence of inside 

cavity and inside white of red ginseng. In Report 

of Study in Korean Ginseng. Korean Ginseng and 

Tobacco Research Institute, Taejon, South Korea.

Proctor, J.T.A., J.C. Lee, and S.S. Lee. 1990. 

Ginseng production in Korea. HortScience 

25:746-750.

Yun, S.D. 1998. Biochemical Metabolism 

and Quality Changes of Fresh and Processed 

Korean Ginseng as Influenced by CA Storage. 

Dissertation, Seoul National University, Seoul, 

South Korea.

Yun, S.D., and S.K. Lee. 1998. Quality of red 

ginseng processed from the stored roots. Acta 

Hort. 464:534. 
340

Grape (American)

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, N.C. Campus, Kannapolis, NC.

Scientific Name and Introduction

American grapes (Vitis labrusca L.) are grown in 

areas of the United States where V. vinifera has 

marginal survival, usually because of lack of cold 

hardiness. Juice, wine, and table grape varieties 

have been developed from V. labrusca. The best 

known grape cultivars are ‘Concord,’ ‘Catawba,’ 

‘Delaware,’ ‘Niagara,’ ‘Venus,’ ‘Himrod,’ and 

‘Reliance.’

Quality Characteristics and Criteria

High-quality grapes are free of injury, decay, 

cracking, and sunscald; appear and feel turgid; 

have a dry stem scar; and are fully colored. The 

rachis should be green and berries are firmly 

attached to pedicels. Bunches should be compact, 

but berries not too tightly packed.

Horticultural Maturity Indices

For fresh market, berries should be harvested 

when soluble solids content (SSC) is 14 to 18%.

Grades, Sizes, and Packaging

No standard packaging is used with American 

grapes. Grapes are usually packed as intact or 

trimmed clusters (rachis and berries) in bulk in 

lugs, in quart-size vented plastic containers, or in 

plastic slit bags of 2 lb (0.9 kg).

Precooling Conditions

Forced-air cooling to lower the temperature to 

below 2 °C (36 °F) within a day of harvest is 

recommended.

Optimum Storage Conditions

American grapes can be held 4 to 7 weeks at 

-0.5 to 0 °C (31 to 32 °F) with 85 to 90% RH 

(Ginsburg et al. 1978). Exposure to temperatures 

above 0 °C (32 °F) can greatly increase shatter 

and decay, especially in tightly packed clusters.

Controlled Atmosphere (CA) 

Considerations

CA is not currently used for American grapes.

Retail Outlet Display Conditions

Store and display grapes at the coldest 

refrigeration temperature possible. Delays in 

cooling greatly increase shatter and decay (Lutz 

1939).

Chilling Sensitivity

American grapes are not known to be chilling 

sensitive. 

Ethylene Production and Sensitivity

Stimulation of Botrytis cinerea (gray mold) 

growth can occur on berries and stems in the 

presence of ethylene. Ethylene production from 

American grapes is less than 0.1 μL kg-1 h-1.
341

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 oC 3

4 to 5 oC 5

10 oC 8

15 to 16 oC 16

20 to 21 oC 33

25 to 27 oC 39

Data from Lutz (1939).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Disorders encountered on American grapes 

include sunburn, shrivel from low-RH storage, 

and bleaching or stipple near berry pedicels from 

SO2

 application (Morris et al. 1992).

Postharvest Pathology

American grapes are susceptible to gray mold 

(Botrytis cinerea Pers.), ripe rot (Colletotrichum 

gloesporioides [Penz.] Penz. & Sacc.), 

macrophoma rot (Botryosphaeria dothidea

[Moug. Ex Fr.] Ces & de Not.), powdery mildew 

(Uncinula necator [Schw.] Burr.), blue mold 

(Penicillium), alternaria (Alternaria alternata

[Fr.] Keissl), and aladosporium rot (Cladosporium 

herbarum Pers.:Fr.) (Hewitt 1988). Undeveloped 

berries can show infection by black rot 

(Guignardia bidwelli [Ellis] Viala & Ravaz).

Quarantine Issues

None.

Suitability as Fresh-Cut Product

No information at this time.

Special Considerations

Sulfur bisulfite pads used with plastic liners 

can extend shelf-life by 2 to 4 weeks, but many 

cultivars are sensitive to SO2

 injury. Handle 

clusters carefully during and after harvest to 

prevent cracking or berry loosening at pedicels.

References

Ginsburg, L., J.C. Combrink, and A.B. Truter. 

1978. Long and short term storage of table grapes. 

J. Refrig. 1(3):137-142.

Lutz, J.M. 1938. Factors Influencing the Quality 

of American Grapes in Storage. Bull. 606, U.S. 

Department of Agriculture, Washington, DC.

Morris, J.R., O.L. Oswald, G.L. Main, et al. 1992. 

Storage of new seedless grape cultivar with sulfur 

dioxide generators. Am. J. Enol. Vitic. 43:230-

232.

Hewitt, W.B. 1988. Berry rots and raisin 

molds. In R.C. Pearson and A.C. Goheen, eds., 

Compendium of Grape Diseases and Insects, pp. 

26-27. APS, St. Paul, MN.
342

Grape (Muscadine)

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, N.C. Campus, Kannapolis, NC.

Scientific Name and Introduction

Muscadine grapes (Vitis rotundifolia Michx.) 

are grown primarily in the Southern United 

States (Olien 1990). Unlike V. lambrusca and 

V. vinifera, muscadines are borne singly or in 

small clusters of 3 to 10 berries and detach from 

their pedicels when ripe. V. rotundifolia is more 

resistant to disease than bunch grapes. Muscadines 

are often separated into types based on color. 

Most commercially important fresh or processed 

grapes are of the bronze type. Several more recent 

varieties are of the black (dark purple) type. ‘Fry,’ 

‘Noble,’ and ‘Granny Val’ are the most common 

bronze cultivars used for fresh market; ‘Carlos’ 

(bronze) is used for juice and some fresh markets. 

Other promising black cultivars are ‘Nesbitt’ and 

‘Black Beauty.’

Quality Characteristics and Criteria

High-quality muscadines are free of injury, decay, 

and sunscald; appear and feel turgid; have a dry 

stem scar; and are fully black or bronze in color.

Horticultural Maturity Indices

For fresh market, muscadines are mature when 

berries can be detached from their stems or when 

SSC is between 14 and 18% (Smit et al. 1971, 

Ballinger and McClure 1983).

Grades, Sizes, and Packaging

No standard packaging exists; quart size is most 

commonly used. Grapes are generally packaged as 

single or small clusters of berries in plastic, vented 

clamshells.

Precooling Conditions

Use forced-air to lower the temperature to 2 °C or 

below within 12 h of harvest.

Optimum Storage Conditions

Muscadine grapes can be held at -0.5 to 0 °C 

with over 90% RH for 1 to 4 weeks (Lutz 1939, 

Ballinger and McClure 1983). Temperatures of 

20 °C for 2 days after any cold storage interval 

shortens subsequent shelf-life by less than 1 week 

(Ballinger and McClure 1983).

Controlled Atmosphere (CA) 

Considerations

Preliminary data indicate that ‘Fry’ muscadines 

have reduced decay when held in 10% O2

combined with 10 to 15% CO2

 (Perkins-Veazie, 

unpublished).

Retail Outlet Display Conditions

Muscadines should be stored and displayed at the 

coldest refrigeration temperature possible without 

freezing. As little as 2 days at room temperature 

can stimulate growth of molds, especially ripe rot.

Chilling Sensitivity

Muscadines are not known to be chilling sensitive.
343

Ethylene Production and Sensitivity

Stimulation of Botrytis cinerea (gray mold) 

growth can occur on grapes and stems in the 

presence of ethylene. Ethylene production from 

muscadines is less than 0.1 μL kg-1 h-1 (PerkinsVeazie, unpublished).

Respiration Rates

Temperature mg CO2 kg-1 h-1

2 °C 6 to 14

5 °C 8 to 18

20 °C 33 to 68

Data from Perkins-Veazie (2002, unpublished).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Sunburn, bleaching, or stipple from SO2

 (Ballinger 

and Nesbitt 1982) are possible.

Postharvest Pathology

Muscadine grapes are susceptible to botrytis, 

yeasts, ripe rot (Colletotrichum gloesporioides),

macrophoma rot (Botryosphaeria dothidea), and 

blue mold (Penicillium) (Ballinger and McClure 

1983, Pearson and Goheen 1988).

Quarantine Issues

None. 

Suitability as Fresh-Cut Product

Unknown. Processing work with juice and jellies 

indicates that unstable pigments may cause 

browning problems if used for minimal processing 

(Flora 1977).

Special Considerations

Sodium metabisulfite pads and generators (12 to 

21 μL L-1 SO2

) have been used to extend shelflife of muscadines from 2 to 8 weeks (Smit et al. 

1971, Ballinger and Nesbitt 1982, James et al. 

1997).

References

Ballinger, W.E., and W.B. Nesbitt. 1982. Quality 

of muscadine grapes after storage with sulfur 

dioxide generators. J. Amer. Soc. Hort. Sci. 

107:827-830.

Ballinger, W.E., and W.F. McClure. 1983. The 

effect of ripeness on storage quality of ‘Carlos’ 

muscadine grapes. Sci. Hort. 18:241-245.

Flora, L.F. 1977. Storage stability of juices 

and jellies made from muscadine grapes (Vitis

rotundifolia Michx.). Amer. J. Enol. Vitic. 28:171-

173.

James, J., O. Lamikanra, G. Dixon, et al. 1997. 

Shelf-life study of muscadine grapes for the fresh 

market. Proc. Fla. State Hort. Soc. 110:234-237.

Lutz, J.M. 1938. Factors Influencing the Quality 

of American Grapes in Storage. Technical Bull. 

606, U.S. Department of Agriculture, Washington, 

DC.

Olien, W. 1990. The muscadine grape: botany, 

viticulture, history, and current industry. 

HortScience 25:732-739.

Pearson, R.C., and A.C. Goheen, eds. 1988. 

Compendium of Grape Diseases and Insects. APS, 

St. Paul, MN.

Smit, C.J.B., H.L. Cancel, and T.O.M. Nakayama. 

1971. Refrigerated storage of muscadine grapes. 

Amer. J. Enol. Vitic. 22:227-230.
344

Grape (Table) 

Carlos H. Crisosto and Joseph L. Smilanick

Crisosto is with the Pomology Department, 

University of California, Davis, CA; Smilanick is 

formerly with the Horticultural Crops Research 

Laboratory, Agricultural Research Service, U.S. 

Department of Agriculture, Fresno, CA. He is 

now with the Commodity Protection & Quality 

Research Unit, Agricultural Research Service, 

U.S. Department of Agriculture, Parlier, CA.

Scientific Name and Introduction

The table grape (Vitis vinifera L.) is a 

nonclimacteric fruit with a relatively low rate 

of physiological activity. It is subject to serious 

water loss following harvest, which can result in 

stem drying and browning, berry shattering, and 

even wilting and shriveling of berries. Gray mold, 

caused by the fungus Botrytis cinerea, requires 

constant attention and treatment during storage 

and handling. In California, the major cultivars 

are ‘Thompson Seedless’ (Sultanina) and ‘Flame 

Seedless,’ marketed mostly during the summer 

months up to 8 to 10 weeks after harvest. Present 

interest centers on other introduced seedless 

‘Fantasy’ cultivars such as ‘Ruby Seedless’ and 

‘Crimson.’ Seeded ‘Red Globe’ is becoming 

important late in the season.

Quality Characteristics and Criteria

High consumer acceptance is attained for fruit 

with high soluble solids content (SSC) or a high 

ratio of SSC to total acidity (TA)—that is, SSC/TA 

ratio. Berry firmness is also an important factor for 

consumer acceptance as are lack of defects such as 

decay, cracked berries, stem browning, shriveling, 

sunburned, dried berries, and insect damage.

Horticultural Maturity Indices

In California, harvest date is determined by 

SSC of 14 to 17.5%, depending on cultivar 

and production area. In early-production areas, 

an SSC/TA ratio of 20 or higher is used to 

determine minimum maturity for cultivars that 

meet a low minimum SSC. For red- and blackcolored cultivars, there is also a minimum color 

requirement.

Grades, Sizes, and Packaging

Most California table grapes are packed in the 

field. In contrast to South Africa and Chile, few 

grapes are shed-packed in the United States. The 

most common field-packing system is the “avenue 

pack.” Fruit are picked and placed into picking 

lugs. Usually, the picker also trims the cluster. The 

picking lug is then transferred a short distance to 

the packer, who works at a small, portable stand in 

the avenue between vineyard blocks.

Shed-packed fruit are harvested by pickers and 

placed in field lugs without trimming. The fruit 

are then placed in the shade of the vines to await 

transport to the shed. At the packing shed, the field 

lugs are distributed to packers who select, trim, 

and pack the fruit. Often two different grades are 

packed simultaneously by each packer to facilitate 

quality selection. In some operations, trimming, 

color sorting, and a first quality sorting may occur 

in the field. In all of the systems, grapes are nearly 

always packed on a scale to facilitate packing to a 

precise net weight, whether field- or shed-packed. 

In general, mid- and late-season grapes are packed 

in plastic bags or wrapped in paper. For earlyseason grapes, bulk pack is mainly used. In all 

cases, packed lugs are subject to quality inspection 

and check weighing.

After packing and lidding, grapes are palletized 

on disposable or recycled pallets. Some strapping 

in the field before loading is necessary in grapes 

packed in shoebox boxes. Often, loaded pallets 

coming from the field pass through a “pallet 

squeeze,” a device that straightens and tightens 

the stacks of containers. These pallet loads 
345

are unitized, usually by strapping or netting. 

Some palletizing glue is used in shed-packing 

operations. This glue bonds the corrugated 

containers vertically on the pallet so that only 

horizontal strapping is required.

Precooling Conditions

Cooling must start as soon as possible, and SO2

applied, within 12 h of harvest. Many forced-air 

coolers for grapes in California are designed to 

achieve seven-eighths cooling in 6 h or less. After 

cooling is complete, pallets are moved to a storage 

room to await transport.

Optimum Storage Conditions

Ideally, storage rooms should operate at -1 to 0 oC 

(30 to 32 oF) with 90 to 95% RH and a moderate 

airflow of 20 to 40 ft3

 min-1 ton-1 (0.63 to 1.25 kL 

min-1 metric ton-1) of stored grapes. The constant 

low temperature, high RH, and moderate airflow 

are important to limit water loss from fruit stems. 

Fruit should be stored at a pulp temperature 

of -0.5 to 0 oC (31 to 32 oC) throughout their 

postharvest life.

Optimum Temperature

A storage temperature of -1 to 0 oC (30 to 32 

oF) is recommended for mature fruit. Freezing 

damage may occur in less mature grapes. The 

highest freezing point for berries is -3.0 oC (27 

o

F), but the freezing point varies depending on 

SSC. A -2 oC (28 oF) freezing point for stems has 

been reported for wine grapes. More recent table 

grape cultivars are more sensitive to stem freezing 

damage. An RH of 90 to 95% and an air velocity 

of approximately 20 to 40 ft3

 min-1 (0.63 to 1.25 

kL min-1) is suggested during storage.

Controlled Atmosphere (CA) 

Considerations

CA of 2 to 5% O2

 combined with 1 to 5% CO2

during storage or shipment is not currently 

recommended for table grapes, because it is only 

slightly beneficial. SO2

 is used for decay control. 

CO2

 at 10 to 15% in air can be used to control 

grey mold for 2 to 4 weeks depending on cultivar.

Retail Outlet Display Considerations

Use of a cold table for display is recommended.

Chilling Sensitivity

Table grapes are not chilling sensitive.

Ethylene Production and Sensitivity

Table grapes produce less than 0.1 μL kg-1 h-1 at 20 

oC (68 oF) ethylene. They are not very sensitive to 

ethylene.

Respiration Rates 

For grape clusters; that is, berries and stems:

Temperature mg CO2 kg-1 h-1

0 oC 2 to 4

5 oC 6 to 8

10 oC 10 to 16

20 oC 24 to 30

Stem respiration is approximately 15-fold higher 

than berry respiration. 

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.
346

Physiological Disorders

Shatter is a loss of berries from the cap stem. 

In general, shatter increases in severity with 

increasing maturity (that is, the longer fruit remain 

on the vine). Berries of seedless cultivars are 

usually less well attached to the cap stem than 

seeded cultivars. Shatter varies considerably from 

season to season, and there is a large variation 

among varieties. Gibberellin applied at fruit set 

weakens berry attachment. Shatter is mainly 

due to rough handling during field packing with 

additional shatter occurring all the way to final 

retail sale. Shatter incidence can be reduced 

by controlling pack depth and packing density 

(in3

 lb-1), using cluster bagging, practicing 

gentle handling, and maintaining recommended 

temperature and RH. Cane-girdling reduces 

shattering incidence.

Waterberry is associated with fruit ripening 

and most often begins to develop shortly after 

veraison (berry softening). The earliest symptom 

is the development of small (1- to 2-mm) dark 

spots on the cap stems (pedicles) and/or other 

parts of the cluster framework. These spots 

become necrotic and slightly sunken, and they 

expand to affect more areas. The affected berries 

become watery, soft, and flabby when ripe. In 

California, this disorder has been associated with 

a high-nitrogen-status vine, canopy shading, or 

cool weather during veraison and fruit ripening. 

Avoid overfertilization with nitrogen. Foliar 

nutrient sprays of nitrogen should be avoided in 

waterberry-prone vineyards. Removing affected 

berries during harvest and packing is a common, 

though labor-intensive, practice.

Postharvest Pathology

Gray mold. The most destructive of the 

postharvest diseases of table grapes is gray 

mold (Botrytis cinerea), primarily because it 

develops at temperatures as low as 31 oF (-0.5 o

C) and grows from berry to berry. Gray mold 

first turns berries brown, then loosens the 

skin of the berry. Its white, threadlike hyphal 

filaments erupt through the berry surface, and 

finally masses of gray-colored spores develop. 

Wounds on the berry surface near harvest provide 

opportunities for infection, though no wound 

is required for infection under wet conditions. 

Removing desiccated, infected grapes from the 

previous season can reduce gray mold infection. 

Leaf-removal canopy management, preharvest 

fungicides, and trimming visibly infected, split, 

cracked, or otherwise damaged grapes before 

packing is recommended. Prompt cooling and 

fumigation with SO2

 (100 μL L-1 for 1 h) are 

essential to control gray mold during cold storage. 

Because of increased interest in the export market, 

there is a need to use SO2

-generating pads, 

especially for long-distance export marketing in 

which grapes are in ocean transport for extended 

periods. These pads have sodium metabisulfite 

incorporated into them that releases SO2

 during 

transit and marketing.

Other pathogens. Black rot, caused by Aspergillus 

niger; blue rot, caused by Penicillium spp.; and 

rhizopus rot, caused by Rhizopus stolonifer or R. 

oryzae, become important at warmer temperatures, 

and they commonly appear sometime during 

transport or marketing after grapes are removed 

from cold storage. They are at least partially 

controlled by SO2

 fumigation, though little 

research has been done to show this (Snowdon 

1990).

Sulfur dioxide use. Botrytis rot of grapes is not 

sufficiently reduced by fast cooling alone. It is 

standard practice in California to fumigate with 

SO2

 immediately after packing and follow with 

lower-dose treatments weekly during storage. 

Formulas for calculating initial and subsequent 

weekly SO2

 fumigation dosages using the 

traditional system are available (Luvisi et al. 

1995, Nelson 1985). It was demonstrated that 

the amount of SO2

 gas needed to kill Botrytis

spores or to inactivate exposed mycelium depends 

on the concentration and length of time the 

fungus is exposed to the fumigant. A cumulative 

concentration, calculated as the product of 

concentration and time, called “CT product,” 

describes the SO2

 exposure needed to kill the 

decay organism. A CT of at least 100 μL L-1 h-1 is 

the minimum required to kill spores and mycelia 
347

of Botrytis at 0 o

C (32 oF). This finding was the 

basis for the development of the total utilization 

system (Luvisi et al. 1992). Total utilization often 

uses about half as much SO2

 as the traditional 

method and improves uniformity and effectiveness 

of SO2

 fumigant. In this total utilization system, 

the first fumigation is done in conjunction with 

forced-air cooling. The forced air flows through 

boxes and ensures good penetration of SO2 even to 

the center boxes on a pallet. In most combinations 

of boxes and packs, this system produces over 

80% penetration, measured as a percentage of the 

room air CT product. Storage fumigation is done 

every 7 to 10 days.

During ocean shipment for periods longer than 

10 days or long retail handling in which SO2

fumigation cannot be applied, the use of SO2

-

generating pads in combination with a box liner is 

advised. These SO2

-generating pads have sodium 

metabisulfite incorporated into them to allow a 

constant and slow release of SO2

 during shipping 

and marketing. In California, a slow-release 

SO2

-generating pad, combined with a perforated 

polyethylene box liner with 1/4-in (6.4-mm) holes 

at 3- to 4-in (7.6- to 10.2-cm) center, reduces 

water loss and assures gray mold control without 

enhancing SO2

 phytotoxicity (Crisosto et al. 

1994).

Quarantine Issues

Issues associated with exotic pest quarantines, 

addressing either imported or exported table 

grapes, can change rapidly. Rules regarding 

import requirements are issued by USDA Animal 

and Plant Health Inspection Service (APHIS). 

This agency provides information to assist 

exporters in targeting markets and defining what 

entry requirements a particular country might 

have for table grapes. APHIS, in cooperation with 

State plant boards, developed a database called 

“Excerpt” to track the phytosanitary requirements 

for each country. APHIS also provides 

phytosanitary inspections and certifications 

declaring grapes are free of pests to facilitate 

compliance with foreign regulatory requirements.

Grapes imported into the United States are 

fumigated with methyl bromide, following 

treatment schedules issued by APHIS, to prevent 

entry of insect pests. Cold treatments are also 

accepted by APHIS for the control of fruit flies. 

Of primary concern are the vine moth, Lobesia 

botrana; the Mediterranean fruit fly, Ceratitis 

capitata; and miscellaneous external-feeding 

insects.

Grapes exported from the United States may 

harbor pests of concern elsewhere, but they rarely 

require treatment, though this situation can change 

rapidly. Black widow spiders are occasional 

hitchhikers within grape clusters or within grape 

boxes. SO2

 fumigation, alone or combined with 

CO2

, has been used successfully to kill spiders 

before export. Omnivorous leafroller, Platnota 

stultana, is found on grapes in California and has 

the potential to be a pest of regulatory concern on 

table grapes exported to counties where this pest is 

not found. Two methods of control are insecticidal 

CA treatment (Ahumada et al. 1996) and lowtemperature storage combined with SO2

 slowrelease generators (Yokoyama et al. 1999).

Suitability as Fresh-Cut Product

Grapes are well-adapted to a stemless packaging 

system.

Special Considerations

Market life varies among table grape cultivars 

grown in California and is also strongly 

affected by temperature management and decay 

susceptibility. 

Acknowledgments

Some of the information in this chapter is from the 

University of California, Davis, website on “Fresh 

Produce Facts” at http://postharvest.ucdavis.edu/ 

produce_information.
348

References

Ahumada, M.H., E.J. Mitcham, and D.G. Moore. 

1996. Postharvest quality of ‘Thompson Seedless’ 

grapes after insecticidal controlled-atmosphere 

treatments. HortScience 31:833-836.

Cappellini, R.A., M.J. Ceponis, and G.W. 

Lightner. 1986. Disorders in table grape shipments 

to the New York market, 1972-1984. Plant Dis. 

70:1075-1079.

Crisosto, C.H., J.L. Smilanick, N.K. Dokoozlian, 

and D.A. Luvisi. 1994. Maintaining table grape 

postharvest quality for long distant markets. In

Proceedings of the International Symposium on 

Table Grape Production, Anaheim, California, 

June 28-29,1994, pp. 195-199. American Society 

for Enology and Viticulture, Davis, CA.

Harvey, J.M., and W.T. Pentzer. 1960. Market 

Diseases of Grapes and Other Small Fruits. 

Agriculture Handbook 189, U.S. Department 

of Agriculture, Agricultural Marketing Service, 

Washington, DC.

Kanellis, A.K., and K.A. Roubelakis-Angelakis. 

1993. Grape. In G.B. Seymour et al., eds., 

Biochemistry of Fruit Ripening, pp. 189-234. 

Chapman and Hall, London, U.K.

Lindsey, P.J., S.S. Briggs, K. Moulton, and 

A.A. Kader. 1989. Sulfites on grapes: issues and 

alternatives. Chemical Use in Food Processing and 

Postharvest Handling: Issues and Alternatives, pp. 

5-19. University of California, Agricultural Issues 

Center, Davis, CA.

Luvisi, D.A., H. Shorey, J. Smilanick, et al. 1995. 

Packaging California Table Grapes. DANR Pub. 

no. 1934, University of California, Oakland, CA.

Luvisi, D.A., H.H. Shorey, J.L. Smilanick, et al. 

1992. Sulfur Dioxide Fumigation of Table Grapes. 

DANR Pub. no. 1932, University of California, 

Oakland, CA.

Nelson, K.E. 1985. Harvesting and Handling 

California Table Grapes for Market. DANR Pub. 

no. 1913, University of California, Oakland, CA.

Nelson, K.E. 1978. Precooling—its significance 

to the market quality of table grapes. Int. J. Refrig. 

1:207-215.

Ryall, A.L., and J.M. Harvey. 1959. The Cold 

Storage of Vinifera Table Grapes. Agriculture 

Handbook 159, U.S. Department of Agriculture, 

Agricultural Marketing Service, Washington, DC.

Snowdon, A.L. 1990. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 1, General Introduction and Fruits. CRC 

Press, Boca Raton, FL.

Yahia, E.M., K.E. Nelson, and A.A. Kader. 1983. 

Postharvest quality and storage-life of grapes as 

influenced by adding carbon monoxide to air or 

controlled atmospheres. J. Amer. Soc. Hort. Sci. 

108:1067-1071.

Yokoyama, V.Y., G.T. Miller, and C.H. Crisosto. 

1999. Low temperature storage combined with 

sulfur dioxide slow release pads for quarantine 

control of omnivorous leafroller Platynota 

stultana (Lepidoptera: Tortricidae). J. Econ. 

Entom. 92(1):235-238.
349

Grapefruit

Jacqueline K. Burns

Burns is with the Citrus Research and Education 

Center, IFAS, University of Florida, Lake Alfred, 

FL.

Scientific Name and Introduction

Citrus paradisi Macf., a member of the Rutaceae 

family, originated in the Caribbean and was 

introduced in Florida in the early 19th century 

(Gmitter 1995). The grapefruit is classified as 

a hesperidium, a kind of berry with a leathery 

rind that is divided into segments. Each segment 

contains hundreds of individual juice vesicles 

that compose the majority of the edible portion 

of the fruit. Florida is the largest producer of 

grapefruit in the United States, followed by 

Texas, California, and Arizona. White- and redpigmented cultivars are grown. ‘Marsh’ is the 

dominant white cultivar. ‘Ruby Red,’ ‘Star Ruby,’ 

‘Henderson,’ ‘Ray Ruby,’ and ‘Flame’ are the 

most popular red-pigmented cultivars (Saunt 

2000).

Quality Characteristics

A high-quality fresh-market grapefruit will have 

a turgid, smooth peel and be relatively blemishfree. The fruit should be elliptical and firm. 

SSC:TA balance within the edible portion should 

be appropriate, and bitterness should be at a 

minimum.

Horticultural Maturity Indices

In markets that emphasize processing, grapefruit 

must achieve a minimum juice content and 

SSC:TA ratio before harvest.

Grades, Sizes, and Packaging

Marketable fresh grapefruit generally range from 

size 23 (23 fruit/carton) to 56 (56 fruit/carton). 

Grade standards for fresh grapefruit rely on 

color-break, texture, peel blemishes, shape, and 

firmness. Grapefruit are commonly packed, stored, 

and shipped in 4

/

5

-bushel cardboard cartons (Soule 

and Grierson 1986).

Optimum Storage Conditions

Grapefruit are typically stored at 12 to 15 °C (54 

to 59 °F) with 95% RH. Coatings are applied 

in the packinghouse to reduce water loss from 

the peel. However, to minimize postharvest 

pitting, grapefruit should be cooled immediately 

to <10 °C (50 °F) with 95% RH after harvest 

and maintained at 5 to 8 °C (41 to 46 °F) during 

transit and storage until distribution at retail 

outlets. High-shine water waxes will minimize 

chilling injury, and incorporated fungicides should 

control decay at these temperatures. At optimum 

storage temperatures, fruit respiration rates will 

be reduced and quality will be maintained up to 6 

weeks (ASHRAE 1998).

Controlled Atmosphere (CA) 

Considerations

Though some benefit of increased firmness 

and delayed senescence can be gained from 

CA storage, commercial use of CA storage for 

grapefruit is very limited or nonexistent (Arpaia 

and Kader 2000).

Chilling Sensitivity

Chilling injury can occur with low-temperature 

storage, typically 5 °C (41 °F) or below. Chilling 

injury is characterized by peel pitting. Pitting 

associated with postharvest pitting is targeted 

to areas of the peel surrounding oil glands, 

whereas pitting associated with chilling injury 
350

is not targeted to oil glands (Petracek et al. 

1995). Coating grapefruit with high-shine water 

waxes reduces the incidence of chilling injury. 

Conditioning fruit by intermittent warming or 

stepwise lowering of temperature can also reduce 

chilling injury.

Ethylene Production and Sensitivity

The grapefruit is a nonclimacteric fruit and does 

not exhibit a classic ripening pattern of increased 

respiration and ethylene production. The rate of 

ethylene production is typically <0.1 μL kg-1 h-1 at 

20 °C.

Degreening is necessary for marketing earlyseason fresh grapefruit in areas where night 

temperatures remain high. In these cases, 1 to 5 

μL L-1 ethylene for periods of 12 h to 3 days is 

used to cause the destruction of peel chlorophyll. 

The recommended temperature for degreening 

is 28 to 29 °C (82 to 84 °F) in Florida and 21 to 

22 °C (70 to 72 °F) in California, each reflecting 

the physiological state of the fruit grown under 

different climactic conditions. High RH of 90 to 

95% must be maintained to avoid softening and 

accentuation of existing peel injuries or blemishes. 

One complete air change per hour should enter the 

degreening room to avoid unnecessary buildup 

of CO2

 and to assist in uniform temperature and 

ethylene distribution (Wardowski 1996).

Respiration Rates

Respiration rates at optimum storage temperature 

are generally <10 mg CO2 kg-1 h-1 (Arpaia and 

Kader 2000).

Physiological Disorders

Granulation, or section-drying, affects late-season 

grapefruit dominantly on the stem or stylar end of 

the segment. Granulation can be severe in larger 

fruit stored for extended durations (Burns and 

Albrigo 1998). Granulation can be avoided by 

harvesting large fruit early in the season. 

Oleocellosis can occur during harvest when 

excessive squeezing force is used to remove fruit 

from the stem. Grapefruit harvested in the morning, 

when RH is high, are most susceptible because oil 

glands are easily broken in turgid peel. Symptoms 

of oleocellosis appear in the packinghouse or in 

storage, and can be exacerbated by degreening. 

Stem-end rind breakdown (SERB) is characterized 

by collapse and sinking of the peel in irregularly 

shaped regions near the stem end. SERB is closely 

associated with excessive water loss. Late-season 

grapefruit are most susceptible to SERB. 

Blossom-end clearing is most commonly found 

in late harvested, thin-peeled red-pigmented 

grapefruit. The wet, translucent area that develops 

dominantly on the blossom end results from the 

leaking of juice from the segments to the peel. 

Blossom-end clearing can be reduced by reducing 

pulp temperatures to <21 °C (70 °F) after harvest 

and eliminated by avoiding high-impact handling 

procedures (Echeverria et al. 1999).

Green ring is a physiological disorder that appears 

on early-season grapefruit in Florida. The disorder 

is characterized by failure of the peel to degreen in 

circular areas around fruit-to-fruit contact points. 

The remaining green ring can become necrotic as 

fruit remain in storage. The incidence of green ring 

disappears as the fruit peel matures. 

Interest in long-term storage of grapefruit has 

developed for the purposes of extending market 

availability. Grapefruit stored longer than 

6 weeks at 3 °C (37 °F) may develop physiological collapse of juice vesicles (Brown et al. 

1998).

Postharvest Pathology

Postharvest pitting is a peel disorder that affects 

waxed grapefruit stored at higher temperatures. 

Postharvest pitting can be reduced or eliminated 

by reducing fruit pulp temperature to 10 °C (50 °F) 

or less and coating fruit with highly gas-permeable 

coatings (Petracek et al. 1995, Florida Department 

of Citrus 1996). 
351

Postharvest decay can result in significant losses 

of grapefruit. Postharvest grapefruit decays 

generally fall into two categories: those that 

develop as a result of colonization or infection 

on the fruit before harvest (stem end rots, 

anthracnose, and brown rot) and those that 

develop by inoculations made through wounds 

made during harvest or subsequent handling 

(blue and green mold and sour rot). Stem end rots 

develop as latent infections on the fruit button 

(calyx and disc) and begin growth through the 

core after harvest. The decay develops unevenly 

at the stem and stylar ends resulting in wavy 

margins. Stem-end rots are a problem with 

grapefruit grown in warm humid climates such as 

Florida but are rare in Mediterranean climates.

Diplodia natalensis is prevalent in early-season 

fruit if temperatures are high and degreening is 

used. Development of Phomopsis citri is favored 

during the winter months when temperatures 

are low and degreening is no longer necessary. 

Alternaria citri is a less aggressive fungus that 

can be problematic in overmature grapefruit and 

those in extended storage. Often the symptoms of 

alternaria, internal black discoloration generally 

towards the stem end, are not visible until the fruit 

are cut. 

Anthracnose, Colletotrichum gloesporioides, 

is a minor problem that can appear on lateseason fruit. Brown rot, caused by Phytophthora 

citrophthora, appears more frequently in mature 

fruit and fruit stored for longer durations at low 

temperatures. Green and blue mold, caused by 

Penicillium digitatum and italicum, respectively, 

invade fruit through wounds made during 

harvest handling. Growth of P. digitatum is more 

favorable at temperatures above 10 °C (50 °F), 

whereas growth of P. italicum occurs more readily 

at lower temperatures. Immature fruit are resistant 

to sour rot (Geotrichum candidum) infection, 

but as the fruit mature, the disease can become 

a problem. Consequently, late-season grapefruit 

can become infected, especially since the disease 

develops more readily at temperatures above 15 

°C (59 °F) (Eckert and Brown 1986, Whiteside 

1988, Florida Department of Citrus 1996).

Drenching harvested grapefruit with 

thiabendazole (TBZ) before packinghouse arrival 

is recommended for Diplodia, Phomopsis, 

anthracnose, and Penicillium control. In addition, 

application of aqueous imazalil or TBZ in the 

wax treatment aids in control. Minimizing 

degreening time by delaying harvest will assist in 

controlling stem-end rot caused by Diplodia and 

anthracnose. Careful harvesting and handling can 

reduce injuries that allow wound pathogens to 

enter grapefruit. Good sanitation of packinghouse 

equipment and storage areas will help control 

diseases that have no effective chemical control, 

such as sour rot. Generally, precooling or storing 

fruit after packing at temperaturesof 10 °C (50 oF) 

or below will help control growth of postharvest 

pathogens.

Quarantine Issues

In areas infested with tropical fruit flies, cold 

treatment is an approved quarantine treatment. 

However, grapefruit must first be preconditioned 

at 10 to 15 °C (50 to 59 °F) to increase resistance 

to chilling injury. After 1 week, temperatures 

can be reduced to 0.6 to 2.2 °C (33 to 36 °F) for 

14 to 24 days. In areas of low fly infestation, a 

less stringent temperature-duration schedule can 

be used (Florida Department of Citrus 1996). 

The appearance of citrus canker (Xanthomonas 

axonopodis pv. citri) has restricted movement 

of grapefruit grown in affected areas in Florida. 

Compliance with the Citrus Canker Eradication 

Program (2000) is required for harvesting, packing, and shipping fruit from quarantined areas.

Suitability as Fresh-Cut Product

The potential for grapefruit as a fresh-cut 

product is great. Peeled and sectioned grapefruit 

packaged in hard plastic containers is displayed 

on refrigerated shelves of Southeastern U.S. 

retail markets. Technological developments have 

overcome various postharvest problems with 

fresh-cut citrus. However, further development of 

automated systems for efficient and economical 

peeling is essential (Pao et al. 1997).
352

References

ASHRAE [American Society of Heating, 

Refrigerating and Air-Conditioning Engineers]. 

1998. Citrus fruit, bananas, and subtropical fruit. 

In 1998 ASHRAE Handbook on Refrigeration. 

American Society of Heating, Refrigerating and 

Air-conditioning Engineers, Atlanta, GA.

Arpaia, M.L., and A.A. Kader. 2000. Grapefruit. 

Recommendations for Maintaining Postharvest 

Quality. At http://postharvest.ucdavis.edu/

produce_information. 

Brown, G.E., P.D. Petracek, M. Chambers, et al. 

1998. Attempts to extend the market availability 

of ‘Marsh’ grapefruit with storage at 2 to 3 oC. 

Proc. Fla. State Hort. Soc. 111:268-273.

Burns, J.K., and L.G. Albrigo. 1998. Time of 

harvest and method of storage affect granulation 

in grapefruit. HortScience 33:728-730.

Echeverria, E., J.K. Burns, and W.M. Miller. 1999. 

Fruit temperature and maturity affect development 

of blossom end clearing in grapefruit. HortScience 

34:1249-1250.

Eckert, J.W., and G.E. Brown. 1986. Postharvest 

diseases and their control. In W.F Wardowski, S. 

Nagy, and W. Grierson, eds., Fresh Citrus Fruits, 

pp. 315-360. AVI Publishing Co., Westport, CT.

Florida Department of Agriculture and Consumer 

Services. 2000. Citrus Canker Eradication 

Program. At http://www.freshfromflorida.com.

Florida Department of Citrus. 1996. Fact Sheets 

on Postharvest Diseases of Citrus. At http://www.

crec.ifas.ufl.edu/extension.

Gmitter, F.G. 1995. Origin, evolution, and 

breeding of the grapefruit. In J. Janick, ed., Plant 

Breeding Reviews, vol. 13, pp. 345-363. John 

Wiley & Sons, New York, NY.

Pao, S., P.D. Petracek, and M.A Ismail. 1997. 

Advances in preparing peeled fresh-cut citrus. 

Food Tech. Intl. 42:39-40.

Petracek, P.D., W.F. Wardowski, and G.E. Brown. 

1995. Pitting of grapefruit that resembles chilling 

injury. HortScience 30:1422-1426.

Saunt, J. 2000. Citrus Varieties of the World. 

Sinclair Intl. Ltd., Norwich, U.K.

Soule, J., and W. Grierson. 1986. Maturity and 

grade standards. In W.F. Wardowski, S. Nagy, and 

W. Grierson, eds., Fresh Citrus Fruits, pp. 23-48. 

AVI Publishing Co., Westport, CT.

Wardowski, W.F. 1996. Recommendations for 

Degreening Florida Fresh Citrus Fruit. Circular 

1170, pp. 1-3. Florida Cooperative Extension 

Service, University of Florida, Gainesville, FL.

Whiteside, J., S. Garnsey, and L. Timmer, eds. 

1988. Compendium of Citrus Diseases. APS Press, 

St. Paul, MN.
353

Greens for Cooking

James W. Rushing

Rushing is formerly with the Coastal Research 

and Education Center, Clemson University, 

Charleston, SC. He is now retired.

Scientific Name and Introduction

Leafy greens that are normally eaten cooked 

include collards and kale (Brassica oleraceae

L. var. Acephala DC.), rape (Brassica napus

L. var. napus), spinach (Spinacia oleraceae

L.), mustard (Brassica juncea [L.] Czerniak), 

and turnip (Brassica rapa L. var. [DC.] Metzg. 

utilis) (Maynard and Hochmuth 1997). Since the 

intended use is either cooking at a later date or 

immediate processing (canning or freezing) for 

later sale, some handlers do not give the attention 

to quality maintenance that would normally be 

given to fresh salad greens. However, managers 

should recognize that quality at the point of sale 

is of primary concern for all vegetables, whether 

they are to be cooked or eaten raw.

Quality Characteristics and Criteria

Leaves should be of similar varietal 

characteristics, fresh, fairly tender and clean, welltrimmed, of characteristic color for the variety or 

type of greens, and free from decay, discoloration, 

freezing injury, foreign material, disease, insects, 

and damage caused by coarse stalks or other 

mechanical means (AMS 1953a,b, Hurst 2000)

Horticultural Maturity Indices

Spinach leaves are typically harvested at about 

mid maturity, while other types of greens may 

be allowed to grow until the leaves have reached 

nearly full size but have not begun to senesce. 

Hand-harvesting allows a greater degree of 

selection of leaf size, whereas in mechanical 

harvesting every leaf large enough to reach the 

cutting blade is taken.

Grades, Sizes, and Packaging

All greens for cooking, except spinach, are 

classified as either U.S. No. 1 or unclassified. The 

term “unclassified” is not an official U.S. standard; 

it simply means that no specific grade has been 

assigned (AMS 1953a,b). Since spinach is often 

consumed uncooked, greater flexibility is included 

in its classification than for other leafy greens. 

Thus, the grades for spinach are U.S. Extra No. 1, 

U.S. No. 1, and U.S. Commercial (AMS 1946). 

The leaf size of the various types of greens offered 

for sale depends primarily on the requirements 

of the buyer and the physiological condition of 

the product. Obviously, large, overmature leaves 

would not be marketed.

Leaf collards, kale, turnip greens, and mustard 

are commonly bunched using rubberbands or 

twist ties. The size of the bunch may vary but 

is generally approximately 0.5 kg (1 lb). Direct 

packing of loose leaves may be done at the request 

of the buyer. Head collards are packed loose 

into cartons with 8 to 16 bunches per container. 

Waxed fiberboard cartons or wire-bound crates 

are commonly used (Hurst 1999, Sanders et al. 

1999). Spinach leaves, which are smaller and 

more tender, may be packed loose or bunched, but 

they require greater care to avoid handling injury 

(Suslow and Cantwell 2002).

Precooling Conditions

Field heat should be removed from greens as 

quickly as possible. Hydrocooling, hydrovaccooling, liquid-icing, package-icing, and top-icing 

all have been used. Water that is used for washing 

or cooling should contain approximately 200 μL 

L-1 chlorine (Kasmire and Cantwell 1999). When 

package-iced, approximately 1 kg (2.2 lb) of ice is 

recommended per 1.8 kg (4 lb) of product (Hurst 

2000; Boyhan et al. 2004).

Optimum Storage Conditions

Greens should be stored near 0 °C (32 °F) with 

95 to 98% RH. Crushed ice may be placed in 
354

baskets or boxes to help maintain low temperature 

and high RH. When properly handled, greens 

in general may be kept for about 2 weeks 

(Hardenburg et al. 1986, Sanders et al. 1999, 

Suslow and Cantwell 2002). Turnip greens are 

particularly perishable, in contrast to kale, which 

has been kept in excellent condition for up to 3 

weeks under ideal storage conditions (Hardenburg 

et al. 1986).

Controlled Atmosphere (CA) 

Considerations

Spinach benefits slightly from storage at 7 to 10% 

O2

 combined with 5 to 10% CO2 (Saltveit 1997). 

When prepackaged in plastic bags, films should 

allow the generation of 1 to 3% O2

 and 8 to 10% 

CO2

 (Suslow and Cantwell 2002). Neither CA 

nor modified atmosphere packaging (MAP) is 

commonly used commercially for leafy greens 

other than spinach.

Retail Outlet Display Considerations

Though greens are sometimes displayed on 

unrefrigerated counters, they should be placed 

on ice or on refrigerated counters. Intermittent 

misting minimizes water loss and wilting.

Chilling Sensitivity

Leafy greens are not sensitive to chilling 

temperatures and should be stored as cold as 

possible without freezing.

Ethylene Production and Sensitivity

The ethylene production rate for fresh spinach 

is <0.1 μL kg-1 h-1 at 20 oC (68 °F) (Suslow and 

Cantwell 2002). Similar data are not available 

for other greens, but their ethylene production 

rates could reasonably be expected to be in the 

same general range as that of spinach (Kader 

1992). All leafy greens are sensitive to ethylene 

in the postharvest environment, which accelerates 

senescence and leaf yellowing (Suslow and 

Cantwell 2002).

Respiration Rates

The data provided below are for spinach. Similar 

data are not available for other types of leafy 

greens.

Temperature mg CO2 kg-1 h-1

0 oC 19 to 22

5 oC 32 to 58

10 oC 82 to 138

15 oC 134 to 223

20 oC 172 to 287

Data from Hardenburg et al. (1986).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Freezing injury, which results in watersoaked tissue and decay, is the most common 

physiological disorder. Temperatures slightly 

below 0 °C (32 °F) can result in freezing (Suslow 

and Cantwell 2002).

Postharvest Pathology

Bacterial soft rots, primarily caused by Erwinina 

and Pseudomonas, are the most common types 

of postharvest decay (Suslow and Cantwell 

2002). Other market diseases may be found, but 

in general these are not of serious concern if 

appropriate disease control has been implemented 

during production and if greens are properly 

handled.

Quarantine Issues

There are no current issues. However, anyone 

exporting fresh produce should check with the 
355

appropriate agency in the importing country to 

ensure that all regulations are met.

Suitability as Fresh-Cut Product

All leafy greens have potential for fresh-cut 

marketing.

Special Considerations

Harvest workers should sanitize cutting tools 

periodically to avoid the spread of decay-causing 

microorganisms.

References

AMS [USDA Agricultural Marketing Service]. 

1946. United States Standards for Grades of 

Spinach Leaves (Fresh). U.S. Department of 

Agriculture, Agricultural Marketing Service, 

Washington, DC.

AMS [USDA Agricultural Marketing Service]. 

1953a. United States Standards for Grades 

of Collard Greens or Broccoli Greens. U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

AMS [USDA Agricultural Marketing Service]. 

1953b. United States Standards for Grades 

of Mustard Greens and Turnip Greens. U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

Boyhan, G.E., William C. Hurst, W. Terry 

Kelley, et al. 2004. Postharvest handling and 

transportation of fruits and vegetables. University 

of Georgia Fact Sheet 100. At http://pubs.caes.uga.

edu/caespubs/pubcd/FS-100.

Boyette, M.D., D.C. Sanders, and E.A. Estes. 

1999. Postharvest cooling and handling of 

cabbage and leafy greens. North Carolina State 

University Cooperative Extension Service. At

http://www.bae.ncsu.edu/programs/extension/

publicat/postharv/ag-413-5/index.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Hurst, William C. 2000. Commercial production 

and management of cabbage and leafy greens. 

University of Georgia Bull. 1181. At http://pubs.

caes.uga.edu/caespubs/pubcd/B1181.

Kader, A.A. 1992. Postharvest biology and 

technology: an overview. In A.A. Kader, ed., 

Postharvest Technology of Horticultural Crops, 

pp. 15-20. DANR Pub. no. 3311, University of 

California, Davis, CA.

Maynard, D.N., and G.J. Hochmuth. 1997. Knott’s 

Handbook for Vegetable Growers. 4th ed. John 

Wiley & Sons, New York, NY.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California Davis, 

CA.

Seelig, R.A. 1974. Collards—Fruit and Vegetable 

Facts and Pointers. United Fresh Fruit and 

Vegetable Association, Alexandra, VA.

Suslow, T.V., and Marita Cantwell. 2002. Spinach, 

recommendations for maintaining postharvest 

quality. Produce Facts. University of California, 

Davis, CA. At http://postharvest.ucdavis.edu/

produce_information.
356

Guava

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

The guava (Psidium guajava L.) is round or oval 

and can be eaten as a fresh fruit at two stages: 

mature green when it has white flesh and tastes 

like a sweet apple, or fully ripe when it has white 

to bright-red flesh, light-yellow skin, tastes very 

sweet, and is quite fragrant.

Quality Characteristics and Criteria

Skin color is used to measure maturity and 

ripeness. Size and shape are other important 

quality criteria. Fruit should be free of defects, 

decay, and insect damage. Some varieties have 

only a few seeds, while others have a large cavity 

full of seeds. Fruit range from 9 to 12 cm (3.5 to 

4.7 in) in size.

Horticultural Maturity Indices

Harvest stage depends on variety and the stage 

at which the fruit are to be eaten. If eaten green, 

guava fruit should be harvested at the mature, 

firm stage without any signs of ripening. Fruit to 

be consumed soft and ripe are harvested when 

they show some sign of color change from green 

to yellow, as well as initial softening. Later 

harvesting, when fruit are riper, can lead to a high 

number of fruit fly stings and, later, larvae in the 

flesh. Soluble solids content (SSC) can vary from 

3% in green fruit to over 10% in ripe fruit, and 

total acidity (TA) from 0.2 to 1.5%; cultivars vary 

greatly in sweetness and acidity. There is also 

seasonal variation in acidity in some cultivars.

Grades, Sizes, and Packaging

Guava fruit are commonly shipped in 4.5-kg 

(10-lb) single-layer cartons with foam sleeves or 

wrapping to prevent injury.

Precooling Conditions

Room, forced-air, or hydrocooling should be used 

to about 10 °C (50 °F).

Optimum Storage Conditions

Mature green and partially ripe fruit can be held 

for 2 to 3 weeks at 8 to 10 °C (46 to 50 °F). Ripe, 

soft fruit can be held about 1 week at 5 to 8 °C 

(41 to 46 °F). RH of 90 to 95% is recommended 

(Kader 1999). Shelf-life is about 7 days when 

stored at 20 °C (68 °F).

Controlled Atmosphere (CA) 

Considerations

Short-term treatment (24 h) with 10% O2

 in 

combination with 5% CO2

 before storage in air at 

4 °C (39 °F) for 2 weeks delays color development 

and reduces chilling injury compared with fruit 

held in air (Bautista and Silva 1997). Modified 

atmosphere packaging (MAP) in polyethylene 

bags and use of wax coatings delay ripening and 

softening. Skin blackening is a problem when 

some wax coatings are applied (McGuire and 

Hallman 1995).

Retail Outlet Display Considerations

Display guava fruit chilled if fruit are fully ripe. 

Display guava fruit at 8 to 10 °C (46 to 50 °F) if 

fruit are green and if ripening is to be avoided.

Chilling Sensitivity

Symptoms include skin scald, pitting, and a failure 

to ripen if fruit are mature green or partially ripe 
357

when chilled. Browning of the flesh can occur. 

Decay incidence and severity increase with 

chilling injury. Ripe, soft fruit can be held at 5 °C 

(41 °F), as they are less sensitive to chilling injury.

Ethylene Production and Sensitivity

Production rates vary from 1 to 20 μL kg-1 h-1 at 20 

°C and show a climacteric pattern of respiration. 

Rates vary with variety and stage of ripeness. 

Ripening is accelerated by exposure to ethylene 

(100 μL L-1, 24 h). Immature fruit do not ripen 

properly and develop a “gummy” texture (Reyes 

and Paull 1995).

Respiration Rates

Temperature mg CO2 kg-1 h-1

10 oC 8 to 60

20 oC 18 to 130

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Postharvest desiccation is a major problem, along 

with mechanical injury. Desiccation leads to a 

dull yellow, sometimes wrinkled, skin, while 

mechanical injury leads to browning that can 

extend into the flesh. Mechanically injured areas 

of the skin and flesh are very susceptible to decay.

Postharvest Pathology

Most diseases have preharvest origins and are 

sometimes latent infections such as anthracnose 

(Colletrotrichium gloeosporioides). Other 

diseases are associated with entry of pathoges 

via wounds from insect stings or mechanical 

damage; for example, aspergillus rot (Aspergillus 

niger), mucor rot (Mucor hyemalis), phomopsis 

rot (Phomopsis destructum), and rhizopus rot 

(Rhizopus stolonifer). Orchard sanitation and 

effective postharvest management, such as 

avoiding mechanical injury and prompt cooling, 

can reduce disease incidence.

Quarantine Issues

Guava is a preferred host for fruit flies. Flies begin 

to sting fruit at the mature green color break stage, 

but infestation is a problem as softening begins 

to occur. Heat treatments and irradiation are both 

potential disinfestation procedures.

Suitability as Fresh-Cut Product

Sliced mature green fruit are available in many 

Southeast Asian countries and are eaten like apple 

slices. Ripe fruit are also prepared as slices with 

both the skin and seeds removed. Both types are 

sold in trays with an overwrap.

References

Bautista, P.B., and M.E. Silva. 1997. Effects of CA 

treatments on guava fruit quality. In A.A. Kader, 

ed., 7th International Controlled Atmosphere 

Research Conference, University of California, 

Davis, July 13-18, 1997, Abstract 113. University 

of California, Davis, CA.

Kader, A.A. 1999. Guava—produce facts. 

University of California, Davis, Perishables 

Handling Quarterly 97:19-20.

McGuire, R.G., and G.J. Hallman. 1995. Coating 

guavas with cellulose- or carnaba-based emulsions 

interferes with postharvest ripening. HortScience 

30:294-295.

Reyes M.U., and R.E. Paull. 1995. Effect of 

storage temperatures and ethylene treatment 

on guava (Psidium guajava L.) fruit ripening. 

Postharv. Biol. Technol. 6:357-365.
358

Honeydew Melon

Gene Lester and Krista Shellie

Lester and Shellie are formerly with the Kika de la 

Garza Subtropical Agricultural Research Center,

Agricultural Research Service, U.S. Department 

of Agriculture, Weslaco, TX. Lester is now with 

the Office of National Programs, Agricultural 

Research Service, U.S. Department of 

Agriculture, Beltsville, MD. Shellie is now with 

the Horticultural Crops Research Laboratory, 

Agricultural Research Service, U.S. Department 

of Agriculture, Parma, ID.

Scientific Name and Introduction

Cucumis melo L. (Inodorus Group), called winter 

melons even though they are mainly grown in the 

spring in Texas and summer elsewhere, include 

honeydew, casaba, crenshaw, and canary melons 

(Bailey 1976). This melon group is an annual, 

tender, running herb of the Cucurbitaceae (gourd) 

family that is grown for its sweet, flavorful fruits 

with light-green, white, or pink flesh. Honeydew 

melons are the dominantly grown and shipped 

melon of this group and are primarily produced in 

Arizona, California, and Texas.

Quality Characteristics and Criteria

Minimum quality standards for honeydew melons 

are good internal quality of 8% soluble solids 

content (SSC) (10% in California); firm; wellformed; mature; and free of aphid stain, rust 

spot, bruises, broken skin, solar injury (sunscald 

and sunburn), hail damage, moisture loss, 

insect damage, or growth cracks (AMS 1981). 

Nonhybrid honeydew melons are ready for harvest 

(cutting) when the rind is slightly waxy and the 

color is mostly whitish with a light-green tinge. 

These fruit should be well filled out and covered 

by a fine fuzz of hairs. Superior honeydew melon 

quality at harvest is associated with a whitish 

peel, high SSC, and round fruit shape (Lester 

and Shellie 1992). Hybrid honeydew melons will 

abscise (slip) when mature and are mostly creamy 

white, slightly waxy, and may have very sparse 

netting. Full-slip hybrid honeydew melons, versus 

honeydew melons cut at harvest, are perceived by 

consumers to have superior flavor, texture, and 

sweetness.

Horticultural Maturity Indices

Honeydew melons, hybrids and nonhybrids, are 

ready to eat when the peel turns pale green to 

cream colored and the surface feels waxy. The 

blossom end gives when pressed with the thumb, 

and the melon has a pleasant aroma. Less ripe and 

cold melons have little aroma. The majority of 

honeydew melons have green flesh, but specialty 

fruit can have gold, orange, or pink flesh.

Casaba melons are ready to eat when the very 

furrowed or wrinkled peel is yellow and the 

blossom end is springy. The flesh should be soft, 

almost white, with a slight salmon cast around 

the seed cavity and subtly sweet. No aroma is 

produced except for a hint of cucumber.

Crenshaw melons are a cross between casaba 

and persian (see “Netted Melons”). Crenshaw 

melons are ready to eat when half the dark-green 

peel turns yellow, the blossom end is springy, 

and a pleasant spicy aroma is emitted at room 

temperature. The very sweet and juicy flesh should 

be salmon color and soft. Entirely yellow and soft 

fruit are overripe and unpleasant to eat.

Canary melons are ready to eat when the peel, 

generally smooth but sometimes furrowed, is 

bright canary yellow (the brighter the peel, the 

riper the melon) and the oval-shaped fruit is 

springy at the blossom end. The flesh should be 

crisp, flavorful, and white, with a hint of pink 

around the seed cavity. A fragrant aroma is emitted 

at room temperature.

Grades, Sizes, and Packaging

Grades include U.S. No. 1, U.S. Commercial, 

and U.S. No. 2, based primarily on percentage 

of honeydew fruit that meet decay, damage, 

and disease tolerance guidelines (AMS 1981). 
359

Honeydew fruit have no Federal marketing 

standard for SSC except for May 1 through June 

20, when all honeydew melons regardless of grade 

must be at 8% SSC minimum (AMS 1981). Size 

classification is the number of fruit (based on a 

uniform fruit diameter and fruit weight) per box to 

achieve a standard weight of 13.6 kg (30 lb). The 

distinct size classes are 4, 5, 6, 8, and 9.

Precooling Conditions

Honeydew melons harvested cut from the vine 

need not be precooled. Full-slip melons should be 

precooled to 10 to 15 oC (50 to 60 oF) soon after 

harvest to reduce the rate of ripening and sugar 

loss. Hydrocooling and forced-air cooling are 

acceptable methods of precooling. Hydrocooling 

is the most efficient and can reduce a 35 oC (95 oF) 

melon to at least 15 oC at the center of the flesh 

within 20 min. The larger fruit sizes take longer.

Optimum Storage Conditions

Prolonged holding (3 weeks) of fruit harvested 

cut from the vine, as well as casaba, crenshaw, 

and canary melons, should be stored at 10 oC (50 

oF) with 90 to 95% RH. Honeydew melons cut 

from the vine that have been induced to ripen with 

ethylene, as well as full-slip honeydew melons, 

should be stored at 7 oC with 95% RH; they can be 

held for 7 to 10 days.

Controlled Atmosphere (CA) 

Considerations

CA storage of honeydew melons harvested cut 

from the vine has limited commercial use. CA 

conditions for full-slip melons are not known.

Retail Outlet Display Considerations

Honeydew melons are less perishable then netted 

melons (see “Netted Melons”), while those fully 

abscised (full-slip) are highly perishable and 

should therefore be displayed promptly on arrival.

Chilling Sensitivity

Chilling injury can occur at temperatures below 

7 oC (45 °F), but the riper the melon the more 

tolerant to chilling injury. Injury is expressed as 

pitting and darkened, elongated patchy surface 

lesions.

Ethylene Production and Sensitivity

Honeydew melons harvested cut from the vine, 

as well as casabas, crenshaw, and canary melons, 

produce very low amounts of ethylene. However, 

they benefit at the time of shipping, soon after 

harvest, by exposure to 100 μL L-1 ethylene at 

12.5 to 25 oC (55 to 77 oF) for up to 24 h (Kader 

1992). Full-slip honeydew melons should not be 

gassed with ethylene.

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 oC 8

10 oC 14

15 oC 24

20 oC 30

25 oC 33

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Compression, bruising, scuffing, and cutting 

may occur during harvest and at packing sheds 

and may lead to desiccation, water-soaking, 

internal breakdown, and discoloration of the peel. 

Honeydew melons should never be dropped more 

than 60 cm (2 ft), and all harvesting and packing 

line equipment should be well-padded to reduce 

bruising, scuffing, and cuts (Ryall and Lipton 

1979). To reduce fruit crushing and bruising at 

harvest, replace the traditional deep 180-cm-bed 
360

(6-ft-bed) hauling trucks with stackable, ventilated 

plastic field boxes measuring 1.2 m × 1.2 m × 0.6 

m (48 in × 48 in × 26 in deep), and load them onto 

a flatbed truck (Kader 1992). 

Postharvest Pathology

Honeydew melons produced in the Western 

United States occasionally develop bacterial 

brown spot, infested by Pantoea ananatis

(formerly called Erwinia ananas). Alternaria 

alternata and Cladosporium cucumerinum rots 

can be found on honeydew as a result of chilling 

injury, cuts, punctures, or holding fruit too long in 

storage (Bruton 1995, Zitter et al. 1996).

Quarantine Issues

Honeydew melons entering the United States must 

be disinfested of external feeders (noctuid moths, 

thrips, and Copitarisa species) by fumigation with 

methyl bromide (APHIS 1998). Methyl bromide 

was identified as causing significant damage to the 

Earth’s protective ozone layer and was scheduled 

for global phaseout under the Montreal Protocol, 

an international treaty developed to protect the 

Earth from the detrimental effects of ozone 

depletion. Title VII of the U.S. Clean Air Act 

(Amendments of 1990) requires that production 

and importation of “Class I” substances (ozone 

depletion potential of 0.2 or greater) be phased 

out in the United States by the year 2005. Use of 

methyl bromide for preshipment and quarantine 

purposes has been declared exempt from these 

restrictions, but the limited supply and increasing 

cost of methyl bromide may make it undesirable 

for commercial use in the future.

Suitability as Fresh-Cut Product

Honeydew fruit harvested cut from the vine or 

hybrid honeydew fruit harvested at half-slip 

with 11 to 12% SSC have crisp pulp and are 

appropriate for fresh-cut processing. Cultivar 

selection is essential as there is considerable 

variation among cultivars for sugar, firmness, 

and flesh thickness—that is, piece yield. Fruit 

should be well washed and sanitized by rinsing 

in 200 μL L-1 of a 5.25% sodium hypochlorite 

solution at 5 oC (41 °F), pH 6.5 to 7.0, for 5 min, 

and cut into cubed pieces with very sharp blades. 

Cubed pieces should be rinsed with 150 μL L-1 of 

5.25% NaOCl at 5 oC (41 °F) for 30 sec. Shelflife of honeydew fruit cubes, with good eating 

quality, can be expected for 6 to 10 days when 

stored at 5 oC (41 °F). Modified atmospheres of 

5% O2

 combined with 5% CO2 are beneficial in 

retarding microbial growth and reducing loss in 

firmness and other quality degradations. Shelf-life 

of honeydew fruit cubes is not reduced by taking 

pieces from defective areas such as the ground 

spot or sunburned regions, but eating quality is 

reduced due to lower sugar content, green color, 

and firmness (Wu and Watada 1999).

Special Considerations

Product quality and shelf-life of full-slip, hybrid 

honeydew can be extended by applying an amino 

acid-chelated calcium (80 mM) rinse or soak prior 

to sizing and storage (Lester and Grusak 1999).

References

AMS [USDA Agricultural Marketing Service]. 

1981. U.S. Standards for Grades of Honey Dew 

and Honey Ball Type Melons. U.S. Department of 

Agriculture, Washington, DC.

APHIS [USDA Animal and Plant Health 

Inspection Service]. 1998. T101-o-2 MB Methyl 

bromide fumigation of melons for external 

feeders. In APHIS Plant Protection and Quarantine 

Treatment Manual, pp. 5-2-23. U.S. Department 

of Agriculture, Hyattsville, MD.

Bailey, L.H., and E.Z. Bailey. 1976. Hortus Third: 

A Concise Dictionary of Plants Cultivated in the 

United States and Canada. Macmillan Publishing 

Company, New York, NY.
361

Bruton, B.D. 1995. Etiology, epidemiology, and 

control of muskmelon fruit rots. In G.E. Lester 

and J.R. Dunlap, eds., Cucurbitaceae ’94, pp. 48-

54. Gateway Printing Co., Edinburg, TX.

Kader, A.A. 1992. Postharvest Technology of 

Horticultural Crops. University of California, 

Davis, CA. 

Lester, G., and K.C. Shellie. 1992. Postharvest 

sensory and physicochemical attributes of honey 

dew melon fruits. HortScience 27:1012-1014.

Lester, G.E., and M.A. Grusak. 1999. Postharvest 

application of calcium and magnesium to 

honeydew and netted muskmelons: effects on 

tissue ion concentrations, quality, and senescence. 

J. Amer. Soc. Hort. Sci. 124:545-552.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, Vegetables and Melons. AVI 

Pub. Co., Westport, CT.

Sholtz, W.W., H.B. Johnson, and W.R. Buford. 

1963. Heat evolution rates of some Texas-grown 

fruits and vegetables. J. Rio Grande Valley Hort. 

Soc. 17:170-175.

Wu, T.Z., and A.E. Watada. 1999. Quality changes 

of fresh-cut honeydew melons during controlled 

atmosphere storage. J. Food Qual. 22:513-521.

Zitter, T.A, D.L. Hopkins, and C.E. Thomas. 1996. 

Compendium of Cucurbit Diseases. APS Press, St. 

Paul, MN.
362

Horseradish

Franciszek Adamicki

Adamicki is with the Department of Vegetable 

Storage, Research Institute of Vegetable Crops,

Skiemiewice, Poland.

Scientific Name and Introduction

Horseradish (Armoracia rusticana, syn. 

Cochlearia armoracia Gaertn., Mey., Scherb.) 

is a perennial of the Cruciferae family. The plant 

is native to southeastern Europe, where the roots 

and leaves are used for food, condiments, and 

medicinal purposes. Horseradish is grown for its 

enlarged taproot, which is used as an appetizing 

condiment for meats and fish. The characteristic 

pungent aroma and taste come from sulfur 

compounds. Horseradish is grown worldwide, but 

especially in Europe, the United States (mainly 

southwestern Illinois), and Russia.

Quality Characteristics and Criteria

Several criteria are used for quality evaluation 

of horseradish, such as uniformity of shape and 

size, firmness, smoothness, freedom from hollow 

heart, internal color of the roots, other defects, 

and decay. The most important quality criteria are 

long, uniform roots with white flesh and pungent 

flavor.

Horticultural Maturity Indices

Horseradish is ready to harvest after the leaves 

have been killed by frost. Sometimes it is 

harvested at an early stage of development and 

the roots used for processing. Horseradish that is 

harvested when roots are actively growing does 

not store as well as roots that are conditioned by 

cold before harvest.

Grades, Sizes, and Packaging

Horseradish roots Grade I should be at least 25 

cm (10 in) long and 2.5 cm (1 in) in diameter 

measured one-third of the distance from the top. 

Grade II horseradish roots are 15 cm (6 in) long 

and 1.5 cm (0.6 in) in diameter. Smaller roots may 

be acceptable for processing. Horseradish for fresh 

harvest is commonly packed in 20- to 25-kg (44- 

to 55-lb) sacks or in small retail packages about 1 

kg (2.2 lb). Roots intended for storage are packed 

in 15-kg (33-lb) polyethylene-lined crates or large 

containers with a capacity 300 to 500 kg (660 to 

1,100 lb).

Precooling Conditions

Horseradish roots are very sensitive to wilting. 

Roots should be precooled to 4 to 5 °C (39 to 41 

°F) immediately after harvest using forced air at 0 

°C (32 °F) with 90 to 98% RH.

Optimum Storage Conditions

Roots can be stored for 8 to 12 mo at 0 °C 

(32 °F) with 98 to 100% RH (Adamicki et 

al. 1999). Pungency is rapidly lost at higher 

temperatures, and roots dry out at lower RH. 

Perforated polyethylene bags and lined crates 

or bins can maintain a high RH during storage. 

Roots can also be stored at -1 to -2 °C (28 to 30 

°F). Freshly harvested and washed roots can be 

stored for several months in polyethylene bags 

or lined polyethylene crates. In areas with mild 

winters, horseradish may be left in the ground and 

harvested in early spring. Horseradish can also be 

stored over winter in cool cellars or in outdoor pits 

(clamps) or trenches.

Controlled Atmosphere (CA) 

Considerations

There is no or only slight benefit from CA. High 

levels of CO2

 increase respiration but do not cause 

greater loss of weight, dry matter, or sugar content 
363

during storage. An increase in sucrose occurs as 

CO2

 increases up to 7.5% (Weichmann 1980).

Retail Outlet Display Considerations

Washed horseradish roots packed in polyethylene 

bags can be placed on refrigerated shelves for 

several days at temperatures below 10 °C (50 °F).

Chilling Sensitivity

Horseradish roots are not chilling sensitive and 

can survive temperatures as low as -8 °C (18 °F) 

(Bohling and Hansen 1980).

Ethylene Production and Sensitivity

Horseradish roots produce a very low amount of 

ethylene, <1 mL kg-1 h-1, and are not particularly 

sensitive to ethylene exposure.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 8

5 °C 14

10 °C 25

15 °C 32

20 °C 40

Data from Ryall and Lipton 1983.

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

There are no important physiological disorders of 

horseradish root.

Postharvest Pathology

The soilborne fungus Verticilium dahliae Kleb. 

infects the vascular tissue of the horseradish plant, 

resulting in discoloration (Eastburn and Weizierl 

1995). The discoloration often appears as black 

specks in cross section or as streaks along the root 

when the root is cut lengthwise. It is the major 

reason for loss in market quality of horseradish 

roots.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

There is no current potential.

References 

Adamicki, F., W. Macias, and E. Badełek. 

1999. Effect of temperature on the quality and 

storage ability of two cultivars of horseradish. 

Unpublished.

Bohling, H., and H. Hansen. 1980. Influence of 

controlled atmosphere on the respiration activity 

of achlorophyllous vegetable kinds. Acta Hort. 

116:165-170.

Dobrzański, A., J. Pałczyński, and F. Adamicki. 

1994. The influence and soil applied herbicides on 

weed control, yield and storage-life of horseradish 

(Cochlearia armoracia L.). Biul. Warzywniczy 

42:53-63.

Eastburn, D., and R. Weizierl. 1995. Horseradish. 

A Guide to Major Insect and Disease Problems. 

University of Illinois Cooperative Extension 

Service, Urbana, IL.
364

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Ryall, A.L., and W.J. Lipton. 1983. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1, 2nd ed. AVI Publishing Co., 

Westport, CT.

Schirmer, H., and B. Tauscher. 1999. 

Langzeitlagerung von Meerretich bei 

unterschiedlichen Temperaturen. Gemüse 7:449-

450. 

Weichmann, J. 1980. CA storage of horseradish 

(Armoracia rusticana Ph.Gärtn., B.May. et 

Scherb.). Acta Hort. 116:171-178.
365

Jerusalem Artichoke

Stanley J. Kays

Kays is with the Department of Horticulture, 

University of Georgia, Athens, GA.

Scientific Name and Introduction

Helianthus tuberosus L., the Jerusalem 

artichoke, is a perennial of the Asteraceae family 

(Compositae) that is grown as an annual. The tops 

die in the early winter, at which time the tubers 

are harvested. There are many cultivars, and 

the cultivar selected depends on the production 

location. Commercial production in the United 

States is limited and found mostly in the Northeast 

and North Central States and California. In the 

Deep South, soilborne diseases largely prevent 

commercial production (McCarter and Kays 

1984).

Interest in the crop has stemmed from the fact 

that the storage form of carbon in the Jerusalem 

artichoke is inulin, a straight chain fructan that is 

poorly digested by humans. Inulin can be used as a 

bulking agent in foods when sugar is replaced with 

an artificial sweetener. The volume previously 

occupied by sugar is replaced by the low-calorie 

inulin, allowing the total caloric content of the 

processed product to be greatly reduced. With 

little reformulation, inulin, though not sweet, has 

functions similar to sugar in many foods; that is, 

browning reactions, aroma synthesis, and textural 

properties. Likewise, inulin, whether ingested 

as Jerusalem artichoke tubers or as a bulking 

agent, is a dietary fiber and confers a number of 

health advantages. For example, it lowers blood 

cholesterol level; promotes Bifido bacteria in the 

large intestine; reduces blood sugar level, lowdensity lipoproteins, and triglycerides; and helps 

prevent certain heart diseases (Varlamova et al. 

1996).

Quality Characteristics and Criteria

Tuber size and shape are critical quality attributes 

and are strongly modulated by cultivar and 

production conditions. Many clones have 

an irregular tuber surface topography due to 

branching, an undesirable trait.

Horticultural Maturity Indices

The tubers are harvested in the late fall, generally 

after the first frost. In production areas where 

harvest can be accomplished throughout winter 

(see Storage Options section below), the crop 

can be field stored and harvested as needed. 

Elsewhere, harvest is followed by cold storage.

Grades, Sizes, and Packaging

There are no existing standard grades. Generally, 

larger tubers with smooth surfaces are preferred. 

Polyethylene bags are the typical packaging 

used, though precise recommendations are not 

established. Package physical parameters vary 

with storage temperature, product volume, and 

other factors.

Precooling Conditions

Generally, precooling is not required, though 

placing the tubers under favorable low 

temperature conditions as soon as possible after 

harvest is recommended.

Storage Options

The three primary storage options are refrigerated 

storage, common storage in root cellars, and in 

situ field storage. In common storage in root 

cellars, champs, or pits, cooling is obtained from 

the natural low temperatures of the outdoor air and 

soil (Shoemaker 1927). In the first two options 

(refrigerated and common storage), tubers are 

harvested in fall and placed in storage. With field 

storage, however, tubers are left in the ground 
366

and harvested as needed. Cold storage is highly 

effective, but costly. Regardless, refrigerated 

storage is routinely used for seed and fresh 

market tubers, especially in situations where field 

storage is not a viable alternative. Root cellars, 

champs, and pits are used when the tubers must be 

harvested in the fall, prior to the ground freezing 

or other adverse conditions occurring, and 

refrigeration is not available or is prohibitively 

expensive.

The selection of in situ field storage depends 

on several factors. Location is the primary 

determinant in the potential success of in situ field 

storage. Field storage is a viable option in northern 

hemisphere production areas where cold soil 

temperatures prevail throughout the winter, but 

freezing of the soil surface is uncommon. Sandy, 

well-drained soils are preferred because they allow 

harvest throughout the winter. Locations that do 

not meet these criteria generally require the use of 

refrigeration or some form of common storage.

Optimum Storage Conditions

Tubers can be stored for 6 to 12 mo at 0 to 2 °C 

(32 to 34 °F) and 90 to 95% RH. Some cultivars 

are much more susceptible to storage losses 

than others (Steinbauer 1932). Tubers shrivel 

readily and are more likely to decay at low 

RH. Rates of dry matter loss during storage at 

various temperatures is shown in the section on 

Respiration Rates below.

Controlled Atmosphere (CA) 

Considerations

The benefit of CA storage has not been adequately 

assessed. Storage of tubers in 22.5% CO2

 with 

20% O2

 significantly retarded the rate of inulin 

degradation, apparently through an effect on 

enzyme activity (Denny et al. 1944).

Retail Outlet Display Considerations

Water loss accounts for the majority of postharvest 

weight loss during retail sales. Product should be 

displayed in refrigerated display cases and, when 

not packaged, under high RH conditions such as 

that afforded by mist systems.

Chilling Sensitivity

Tubers can withstand low temperatures without 

damage but freeze at -2.2 °C (28 °F) (Whiteman 

1957). Freezing at -10 °C (14 °F), whether in the 

field or in storage, causes rapid deterioration, but 

nonlethal freezing at -5 °C (23 °F) causes little 

damage. As with most fleshy plant products, 

temperature at which freezing damage occurs 

and extent of damage vary with cultivar, season, 

preconditioning, rate of freezing, and other factors 

(Kays 1997).

Ethylene Production and Sensitivity

Tubers are not sensitive to ethylene. 

Respiration Rates

Temperature Respiration Rate of dry 

matter loss

mg CO2 kg-1 h-1 g kg-1 day-1

0 °C 10.2 0.162

5 °C 12.3 0.201

10 °C 19.4 0.317

20 °C 49.5 0.801

Data from Peiris et al. (1997).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 
367

Physiological Disorders

Storage losses are due primarily to desiccation, 

rotting, sprouting, freezing, and inulin 

degradation. Desiccation remains a significant 

storage problem even though losses can be 

fairly easily circumvented with proper storage 

conditions. Storage at high RH is essential 

(Shoemaker 1927, Steinbauer 1932) because 

tubers lack a corky surface layer similar to that 

found on potatoes to reduce water loss; their thin, 

easily damaged surface permits rapid water loss. 

While beneficial for some produce (Kays 1997), 

γ-irradiation greatly accelerates inulin degradation 

(Salunkhe 1959) and is of little storage value.

Postharvest Pathology

Storage rots are a serious problem (McCarter 

and Kays 1984, Barloy 1988), and higher storage 

temperatures result in greater loss. Approximately 

20 organisms causing storage rots have been 

isolated from Jerusalem artichoke tubers. The 

organisms most frequently isolated were Botrytis 

cinerea Pers. and Rhizopus stolonifer (Ehrenb.: 

Fr.) Vuill., though R. stolonifer and Sclerotinia 

sclerotiorum (Lib.) de Bary are the most 

serious organisms causing rots at low storage 

temperatures. Sclerotium rolfsii Sacc. and Erwinia 

carotovora spp. carotovora (Jones) Bergey et 

al., in contrast, are not significant pathogens at 

temperatures below 20 °C (68 °F). Storage rots 

are controlled by storage at 0 to 2 °C (32 to 34 

°F), removal of diseased tubers, minimizing 

mechanical damage, and proper RH control.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

No current potential.

Special Considerations

During storage, tubers undergo significant 

alterations in carbohydrate chemistry, which, 

depending on the intended use, can have a 

pronounced effect on quality. Inulin is not one 

compound, but a series of molecules of varying 

chain length that begin to depolymerize during 

storage (Jefford and Edelman 1963, SchorrGalindo and Guiraud 1997), whether harvested 

or left in situ. The degree of polymerization 

is critical for uses such as fat replacement or 

high-fructose syrups. With the former, as the 

chain length decreases the ability of inulin 

to mimic a lipid diminishes. Likewise, with 

progressive depolymerization, the ratio of 

fructose:glucose decreases and, upon hydrolysis, 

yields a progressively less pure fructose 

syrup. For example, during winter storage the 

fructose:glucose ratio decreases from 11 to 3 

(Schorr-Galindo and Guiraud 1997). Thus, syrups 

derived from stored tubers contain a lot more 

glucose than fructose.

References

Barloy, J. 1988. Jerusalem artichoke tuber diseases 

during storage. In G. Grassi and G. Gosse, eds., 

Topinambour (Jerusalem Artichoke). Proceedings 

of a Workshop Held in Madrid, 30 September and 

1 October 1987, pp. 145-149. Office for Official 

Publications of the European Communities, 

Luxembourg, Luxembourg.

Denny, F.E., N.C. Thornton, and E.M. Schroeder. 

1944. The effect of carbon dioxide upon the 

changes in the sugar content of certain vegetables 

in cold storage. Cont. Boyce Thompson Inst. 

13:295-311.

Jefford, T.G., and J. Edelman. 1963. The 

metabolism of fructose polymers in plants. II. 

Effect of temperature on the carbohydrate changes 

and morphology of stored tubers of Helianthus 

tuberosus L. J. Exp. Bot. 14:56-62.
368

Kays, S.J. 1997. Postharvest Physiology of 

Perishable Plant Products. Exon Press, Athens, 

GA.

McCarter, S.M., and S.J. Kays. 1984. Diseases 

limiting production of Jerusalem artichokes in 

Georgia. Plant Dis. 64:299-302.

Peiris, K.J.S., J.L. Mallon, and S.J. Kays. 1997. 

Respiratory rate and vital heat of some specialty 

vegetables at various storage temperatures. 

HortTechnology 7:46-48.

Salunkhe, D.K. 1959. Physiological and 

biochemical effects of gamma radiation on tubers 

of Jerusalem artichoke. Bot. Gaz. 120:180-183.

Schorr-Galindo, S., and J.P. Guiraud. 1997. Sugar 

potential of different Jerusalem artichoke cultivars 

according to harvest. Biores. Tech. 60:15-20.

Shoemaker, D.N. 1927. The Jerusalem Artichoke 

as a Crop Plant. Technical Bull. 33, U.S. 

Department of Agriculture, Washington, DC.

Steinbauer, C.E. 1932. Effects of temperature and 

humidity upon length of rest period of tubers of 

Jerusalem artichoke (Helianthus tuberosus). Proc. 

Amer. Soc. Hort. Sci. 29:403-408.

Varlamova, C., E. Partskhaladze, V. Oldhamovsky, 

and E. Danilova. 1996. Potential uses of Jerusalem 

artichoke tuber concentrates as food additives and 

prophylactics. In A. Fuchs, S.Schhittenhelm, and 

L. Frese, eds., Proceedings of the 6th Seminar 

on Inulin, Braunschweig, Germany, pp. 141-144. 

Carbohydrate Research Foundation, The Hague, 

Netherlands.

Whiteman, T.M. 1957. Freezing Points of Fruits, 

Vegetables and Florist Stocks. Marketing Research 

Report 196, U.S. Department of Agriculture, 

Agricultural Marketing Service, Washington, DC.
369

Jicama

Marita Cantwell

Cantwell is with the Mann Laboratory, 

Department of Plant Sciences, University of 

California, Davis, CA.

Scientific Name and Introduction

Jicama (Pachyrhizus erosus [L.] Urban) is a root 

crop of the Legume family (Leguminosae). It is 

also called “yam bean” and is a brown-skinned, 

turnip-shaped root eaten raw or cooked as a 

substitute for water chestnut. The root only forms 

under warm, short days. Therefore, most jicama in 

U.S. markets is imported from Mexico, where it is 

a native crop. Jicama is also produced, to a limited 

extent, in Hawaii. Roots are about 85% water, less 

than 1% fiber, less than 1.5% protein, less than 

0.5% ash, and about 10% carbohydrate, of which 

about 10% is sucrose.

Quality Characteristics and Criteria

Good quality jicama roots should be smooth and 

firm, be uniform in shape and size, be free from 

mechanical damage, and have a crisp, succulent, 

white, sweet-starchy flesh.

Horticultural Maturity Indices

Jicama roots can be harvested at various stages of 

development. Young, tender roots harvested from 

green plants (100 to 150 g; 3.5 to 5.3 oz) are found 

in specialty markets. Fully mature roots, however, 

weigh from 250 to 1,500 g (0.55 to 3.3 lb). Mature 

roots are characterized by size and well-developed 

periderm as well as their starchy-sweet flavor. To 

promote hardening of the periderm, plant tops are 

removed mechanically or irrigation is stopped.

Grades, Sizes, and Packaging

There are no U.S. grades for jicama. In Hawaii, 

however, two grades are recognized based on size 

and freedom from defects (dirt, discoloration, 

growth cracks, roughness, insect damage, and 

mechanical injury). 

After transport in bulk, jicama roots are typically 

packed in wooden crates of 9 kg (20 lb) or more or 

in carton boxes of about 4.5 kg (10 lb) for export 

to the United States.

Optimum Storage Conditions

Jicama can be stored for 2 to 4 mo at 12.5 to 15 

°C (54 to 59 °F) with 80 to 90% RH. However, 

leaf and stem sprouts develop after 2 mo with loss 

of weight and diminished juiciness of the pulp. 

Minimizing mechanical damage to the periderm 

during harvest will reduce decay incidence during 

storage.

Controlled Atmosphere (CA) 

Considerations

No information is available on the potential 

benefits of CA storage of intact jicama roots. 

Based on work with other root crops, however, it 

would not be expected to provide much benefit. 

Decay development and discoloration of freshcut pieces was reduced by a modified atmosphere 

containing 5 to 10% CO2

 (Aquino-Bolaños et al. 

2000).

Retail Outlet Display Considerations

Keep roots cool and dry to reduce water loss and 

superficial decay. 

Chilling Sensitivity

Depending on variety and production area, jicama 

may develop symptoms of chilling injury after 1 

to 3 weeks of storage at 10 °C (50 °F) (Cantwell 
370

et al. 1992, Mercado and Cantwell 1998). No 

chilling injury is observed on roots stored at 12.5 

°C (55 °F). Decay is the main external symptom 

of chilling injury, and discoloration and loss of 

crisp texture are the main internal symptoms. 

The roots eventually become “rubbery” in texture 

when severely chilled. Internal discoloration 

typically occurs from the skin inwards and is 

more common and more severe in moderately 

chilled roots stored at 10 °C (50 °F). At lower 

temperatures, the pulp will take on a translucent 

appearance but not necessarily develop brown 

discoloration; these roots also exhibit external 

decay.

Ethylene Production and Sensitivity

Jicama produces only very low amounts of 

ethylene, <0.1 μL kg-1 h-1, though higher rates may 

be observed after chilling at 10 °C (50 °F), about 

0.5 μL kg-1 h-1. Jicama is not sensitive to ethylene 

exposure (Cantwell 2006).

Respiration Rates

Temperature Intact roots Fresh-cut pieces

----------mg CO2 kg-1 h-1----------

0 °C 4 to 8 4 to 8

5 °C 10 to 12 8 to 12

10 °C 9.5 to 19 11 to 19

12.5 °C 4 to 8 -

20 °C 5 to 7 -

Data for intact commercial size roots from 

Cantwell et al. (1992).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

At 5 °C and 10 °C, respiration rates increase 

during storage; rates decrease during storage at 

temperatures above 10 °C. Less mature roots may 

have higher rates (Bergsma and Brecht 1992). 

Respiration rates for fresh-cut pieces were from 

2-by-3 cm cylinders (Aquino-Bolaños et al. 2000).

Physiological Disorders

See Chilling Sensitivity section above.

Postharvest Pathology

The most common decay organisms found 

externally on jicama roots are species of 

Penicillium, Rhizopus, and Cladosporium (Bruton 

1983, Cantwell et al. 1992). Most postharvest 

decay of jicama is a consequence of mechanical or 

chilling injury.

Quarantine Issues

None.

Suitability as Fresh-Cut Product

Fresh-cut jicama is incorporated in mixed 

vegetable snack trays because of its crisp texture 

and sweet-starchy flavor. Fresh-cut jicama 

should be stored below 5 °C (41 °F) to reduce 

microbial growth and discoloration. A shelf-life 

of 4 to 8 days can be expected at 5 °C (41 °F) 

in air. Modified atmosphere with 5 to 10% CO2

maintains quality and extends shelf-life of freshcut jicama (Aquino-Bolaños et al. 2000).

Special Considerations

Curing. The periderm of jicama roots is easily 

damaged during harvest and transport, and this 

leads to an unsightly appearance, high rates of 

water loss, and increased susceptibility to decay. 

Wound healing or curing can be achieved by 

holding jicama roots at 20 to 25 °C (68 to 77 °F) 

under 95 to 100% RH for at least 1 week. These 

conditions are similar to those described for curing 

sweetpotatoes and other tropical root and tuber 

crops.
371

References

Aquino-Bolaños, E.N., M.I. Cantwell, G. Peiser, 

and E. Mercado-Silva. 2000. Changes in the 

quality of fresh-cut jicama in relation to storage 

temperatures and controlled atmospheres. J. Food 

Sci. 65(7):1238-1243.

Bergsma, K.A., and J.K. Brecht. 1992. Postharvest 

respiration, moisture loss, sensory analysis and 

compositional changes in jicama (Pachyrhrizus 

erosus) roots. Acta Hort. 318:325-332.

Bruton, B.D. 1983. Market and storage diseases of 

jicama. J. Rio Grande Valley Hort. Soc. 36:29-34.

Cantwell, M. 2006. Jicama Recommendations 

for Maintaining Postharvest Quality. Perishables 

Handling. At http://postharvest.ucdavis.edu/

produce_information.

Cantwell, M., W. Orozco, V. Rubatzky, and L. 

Hernández. 1992. Postharvest handling and 

storage of jicama roots. Acta Hort. 318:333-343.

Mercado-Silva, E., and M. Cantwell. 1998. 

Quality changes in jicama roots stored at chilling 

and nonchilling temperatures. J. Food Qual. 

21:211-221.

Paull, R.E., and N.J. Chen. 1988. Compositional 

changes in yam bean during storage. HortScience 

23(1):194-196. 
372

Kiwifruit

James W. Rushing

Rushing is formerly with Coastal Research 

and Education Center, Clemson University, 

Charleston, SC. He is now retired.

Scientific Name and Introduction

The most common of the edible kiwifruit in the 

Western world is Actinidia deliciosa, a perennial 

of the Actinidiaceae. The fruit, produced on 

climbing or straggling plants, is a berry containing 

hundreds of small, dark seeds embedded in green 

flesh. Its skin is hairy and light brown. Different 

species exhibit variability in numerous attributes; 

for example, skin color (green to brown), flesh 

color (yellow to green), degree of hairiness, 

and taste (Ferguson 1990a,b). The guidelines 

presented here are based on information published 

for the ‘Hayward’ cultivar and similar types of A. 

deliciosa. A yellow-fleshed fruit of A. chinensis 

is rapidly gaining favor in the market, but little 

information is available.

It is important to note that most of the following 

information, especially that related to grades, 

sizes, and packaging, is derived from U.S. and 

California literature. In order of importance in 

the world market, Italy is the leading producer 

followed by New Zealand, Chile, and California. 

Therefore, the guidelines used by the European 

Union should be considered as well.

Quality Characteristics and Criteria

High-quality kiwifruit should not be shriveled 

and should be free from sunscald, scars, growth 

cracks, insect injury, bruises, internal breakdown, 

and decay. At table ripeness, fruit should have at 

least 14% SSC (soluble solids content) with flesh 

firmness of 2 to 3 lb (0.9 to 1.35 kg) penetration 

force, measured with a 5/16 in (8 mm) tip 

(Crisosto et al. 1999).

Horticultural Maturity Indices

Harvest maturity for kiwifruit produced in 

California is defined as a minimum of 6.5% SSC 

and flesh firmness of 14 lb (6.3 kg) force (Crisosto 

et al. 1999). In New Zealand, the index used for 

fruit destined for export is a minimum average 

SSC of 6.2% measured in 10 fruit. A general 

practice is that if 2 of the 10 fruit measured have 

below 5.8% SSC, the orchard is not considered 

acceptable for export picking. Fruit that are to be 

marketed locally with a minimum of handling may 

be held on the vine until the SSC reaches 10 to 

12% (Beevers and Hopkirk 1990).

Grades, Sizes, and Packaging

Grades include U.S. Fancy, U.S. No. 1, and 

U.S. No. 2. Criteria that define grades are 

subjective and are based primarily on the quality 

characteristics described above (AMS 1986). 

Because of the irregular shape of kiwifruit, it is 

difficult to define fruit size in terms of length or 

diameter. Since California is the most significant 

producer of kiwifruit in the United States, the size 

criteria defined by the Kiwifruit Administrative 

Committee (KAC) are generally adhered to 

throughout the United States. Size designations 

are based on number of fruit that can be placed 

on a single tray. Actual fruit size is based on 

weight and is defined as the number of uniformly 

sized fruit required to constitute an 8-lb sample. 

Current designations from the KAC (1999) are 

summarized in table 1. Handlers should note this 

information is subject to change, and the most 

recent information should be reviewed by anyone 

packing kiwifruit.
373

Table 1. 1999/2000 Kiwifruit size designation chart

_____________________________________________________________________

Tray equivalency Maximum no. of Fairly uniform

size designation fruit in 8-lb sample1 size variation2

_____________________________________________________________________

in

21 22 1/2

25 27 1/2

27/28 30 1/2

30 33 1/2

33 36 3/8

36 42 3/8

39 48 3/8

42 53 3/8

45 55 1/4

_____________________________________________________________________

1

Tolerance: Average weight of all sample units must be at least 8 lb (3.63 kg) and no 

individual sample unit may weigh less than 7 lb 12 oz (3.52 kg).

2

Tolerance: Not more than 10% of the containers in any lot and not more than 5%, by 

count, of the fruit in any container may fail to meet the diameter range, except for sizes 

42 and 45 in which the tolerance, by fruit count, may not be more than 25%.

A variety of packages are used for kiwifruit. Traypacked fruit may be placed in cartons of wood or 

fiberboard that contain one, two, or three trays. 

Appropriate padding should be placed between 

trays. Alternatively, volume-filled (typically 23 

lb; 10.4 kg) or count-filled cartons are available. 

Bagged fruit are generally placed in master 

cartons, a common arrangement being a master 

container containing twenty 1-lb (0.45 kg) bags. 

At the retail level, fruit are sometimes sold in lots 

of 6 to 10 fruit per bag with no size specifications. 

Mini wooden bins containing about 125 lb (56 kg) 

of fruit are used for some markets (KAC 1999). 

Any size carton or configuration may be used 

in the United States provided it is appropriately 

labeled.

Precooling Conditions

Early literature recommends that kiwifruit should 

be cooled to near 0 °C (32 °F) as soon as possible 

after harvest for maximum storage potential. 

Forced-air cooling is preferred. Hydrocooling 

has been used successfully but is not generally 

recommended because the hairs on the fruit 

surface tend to retain an excessive amount of 

water, which can promote the growth of decaycausing microorganisms (McDonald 1990). The 

decision to precool remains a matter of choice for 

the packer, and the process of curing (see Curing) 

is gaining acceptance. Lallu (1997) reports 

that rapid precooling may exacerbate internal 

breakdown associated with chilling injury.

Curing

Curing occurs during the delay between harvest 

and cooling and is characterized by some water 

loss from fruit and drying of the stem scar. In New 

Zealand, curing for at least 48 h has been reported 

to reduce the incidence of Botrytis decay (Lallu et 

al. 1997) and development of internal breakdown 

(Lallu 1997) during subsequent cold storage. In 

Chile, Retamales et al. (1997) reported that curing 

up to 72 h did not increase softening during cold 

storage. 
374

Optimum Storage Conditions

The recommended condition for commercial 

storage of kiwifruit is 0 °C (32 °F) with 90 to 95% 

RH. Fruit that are properly handled before storage 

may be held in good condition for 4 to 5 mo. (See 

Ethylene Production and Sensitivity).

Controlled Atmosphere (CA) Conditions

Kiwifruit respond favorably to CA. The potential 

for benefit is excellent, with extension of 

storage life up to about 6 mo. The recommended 

conditions are 1 to 2% O2

 with 3 to 5% CO2 at 

0 °C. Less than 1% O2

 may induce off flavors, 

and greater than 7% CO2 can cause internal 

breakdown of the flesh. However, the risk of such 

injuries is moderate as long as management of 

the atmosphere is given reasonable attention (see 

Physiological Disorders). There is increasing 

commercial use of CA during both storage and 

transport. Refer to Kader (1997) for selected 

references on kiwifruit CA research.

Retail Outlet Display Considerations

Kiwifruit may be displayed on unrefrigerated 

counters since it is desirable to have the fruit near 

eating ripeness at the time of sale.

Chilling Sensitivity

Lallu (1997) reports that the fruit of A. 

deliciosa cv. ‘Hayward’ are chilling sensitive at 

temperatures near 0 °C with symptoms appearing 

as a ring or zone of granular, water-soaked tissue 

in the outer pericarp at the stylar end of the fruit. 

Other symptoms may include the development of 

diffuse pitting and a dark, scaldlike appearance on 

the skin. Curing alleviated symptoms of chilling 

injury (see Curing). The terms “low temperature 

breakdown,” “senescent breakdown,” and 

“physiological pitting” all appear in the literature, 

but the differences among these disorders are 

difficult to define in fruit stored for an extended 

period.

Ethylene Production and Sensitivity

At harvest maturity, kiwifruit are low ethylene 

producers with rates of approximately 0.1 μL 

kg-1 h-1 at 0 °C (32 °F) and about 0.1 to 0.5 μL 

kg-1 h-1 at 20 °C (68 °F). Fruit that are ripe at less 

than 4 lb (1.8 kg) force produce 50 to 100 μL kg-1

h-1. Kiwifruit in storage are extremely sensitive 

to the presence of ethylene and should not be 

stored with commodities that produce significant 

amounts. As little as 5 to 10 ppb (0.005 to 0.010 

μL L-1) ethylene in the storage atmosphere can 

accelerate softening without affecting other 

ripening processes, resulting in unripe fruit that 

are excessively soft (McDonald 1990, Crisosto et 

al. 1999).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 oC 3

4 to 5 oC 5 to 7

10 oC 12

20 to 21 oC 16 to 22

Data from Hardenburg et al. (1986).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

In storage or transit, the flesh of immature fruit 

may soften rapidly and have a water-soaked 

appearance while the core remains hard and 

tough (Beevers and Hopkirk 1990). A similar type 

of hard-core disorder also has been attributed 

to exposure of the fruit to damaging levels of 

ethylene in combination with CO2

 of 8% or higher 

(Crisosto et al. 1999).

Inadvertent freezing results in flesh translucency 

(Beevers and Hopkirk 1990). If freezing injury 

occurs, it usually appears first at the stem end 
375

and progresses to the stylar end. The flesh of 

damaged fruit may become somewhat yellow with 

prolonged storage (Crisosto et al. 1999).

Pericarp granulation and pericarp translucency 

may occur independently, but both are associated 

with long-term storage. The presence of ethylene 

in storage may exacerbate symptoms. These 

disorders may simply be a consequence of 

senescence, as other causes are not well defined 

(Crisosto et al. 1999).

The presence of ethylene in CA storage can 

cause white-core inclusions, which are distinct 

white patches of core tissue that are obvious in 

ripe fruit. Symptoms may develop as early as 3 

weeks in storage, when atmospheric composition 

is favorable for development of the disorder 

(Crisosto et al. 1999).

Postharvest Pathology

Kiwifruit from all growing areas may deteriorate 

due to infection by Botrytis cinerea, which causes 

gray mold decay. This fungus may infect the fruit 

through senescent flower parts, penetrate the fruit 

directly, or enter through wounds (see Curing). 

Other types of decay of lesser commercial 

significance are blue mold, caused by Penicillium 

expansum, and phomopsis, caused by Phomopsis 

actinidiae. An appropriate fungicide application 

program in the orchard coupled with harvest 

management practices to reduce wounding is 

the primary means of reducing incidence of 

decay (Snowdon 1990). As fruit soften, they 

become more susceptible to all types of decay, so 

harvesting at the appropriate maturity and good 

temperature management in the storeroom, plus 

the use of CA, all are important in controlling 

decay (Crisosto et al. 1999).

Various types of pitting also are attributed to 

fungal infection (Manning and Beever 1992, 

Testoni et al. 1997). Symptoms typically do not 

occur until fruit have been stored for several 

months, and direct isolation of the fungi usually is 

required to distinguish between fungal pitting and 

physiological pitting.

Quarantine Issues

There are no quarantine issues in the United 

States. However, importers and exporters should 

contact APHIS or other regulatory bodies 

in receiving countries to ensure quarantine 

requirements are met.

Suitability as Fresh-Cut Product

The potential does not seem good for national 

or regional distribution of fresh-cut kiwifruit. 

However, some restaurants do serve fresh-cut 

kiwifruit on salad bars and in fruit medleys, so 

there is a degree of consumer demand for the 

product. Agar et al. (1999) reported that fresh-cut 

slices of kiwifruit could be stored for 9 to 12 days 

if calcium treatments and modified atmospheres 

were used. Emerging technologies in fresh-cut 

processing may facilitate greater availability in 

retail markets.

Special Considerations

One of the most troublesome concerns for 

storage of kiwifruit is management of ethylene 

in the atmosphere. Enormous losses are incurred 

when fruit soften prematurely in storage without 

ripening. The effectiveness of various ethylene 

removal techniques—for example, catalytic 

converters, potassium permanganate filters, ozone 

generators, and simple ventilation systems—must 

be evaluated carefully for a specific situation. For 

example, the frequency of opening the storeroom 

doors; proximity of the storeroom to sources 

of ethylene, such as the packing house itself or 

nearby roadways; and presence of decaying fruit 

in the storeroom all influence the efficacy of 

ethylene removal. Innovative managers should 

have a means of measuring ethylene in the 

storeroom and in the surrounding area.
376

References

Agar, I.T., R. Massantini, B. Hess-Pierce, and 

A.A. Kader. 1999. Postharvest CO2

 and ethylene 

production and quality maintenance of fresh-cut 

kiwifruit slices. J. Food Sci. 64:33-440.

AMS [USDA Agricultural Marketing Service]. 

1986. United States Standards for Grades of 

Kiwifruit. Effective October 15, 1986. U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

Beever, D.J., and G. Hopkirk. 1990. Fruit 

development and physiology. In I.J. Warrington 

and G.C. Weston, eds., Kiwifruit: Science and 

Management, pp. 97-126. Ray Richards Publisher, 

Auckland, New Zealand.

Crisosto, C.H., E.J. Mitcham, and A.A. Kader. 

1999. Kiwifruit. Fresh Produce Facts. University 

of California, Davis, CA. At http://postharvest.

ucdavis.edu/produce_information.

Ferguson, A.R. 1990a. The genus Actinidia. In

I.J. Warrington and G.C. Weston, eds., Kiwifruit: 

Science and Management, pp. 15-35. Ray 

Richards Publisher, Auckland, New Zealand.

Ferguson, A.R. 1990b. Botanical nomenclature: 

Actinidia chinensis, Actinidia deliciosa, and

Actinidia setosa. In I.J. Warrington and G.C. 

Weston, eds., Kiwifruit: Science and Management, 

pp. 36-57. Ray Richards Publisher, Auckland, 

New Zealand.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Kader, A.A. 1997. A summary of CA 

recommendations for fruits other than apples 

and pears. In E.J. Mitcham, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 3, pp 1-34. University of California, Davis, 

CA.

Kiwifruit Administrative Committee. 1999. 

1999/2000 Season California Kiwifruit Packing 

Regulations Bulletin. Kiwifruit Administrative 

Committee, Sacramento, California. At http://

www.kiwifruit.org.

Lallu, N. 1997. Low temperature breakdown in 

kiwifruit. Acta Hort. 444:579-585.

Lallu, N., M. Manning, and H. Pak. 1997. Best 

curing practices for the orchard and packhouse. 

New Zealand Kiwifruit Journal (March/April) pp. 

35-37.

Manning, M., and D. Beever. 1992. An update 

on storage pitting research. NZ Kiwifruit Journal 

(Feb.) pp. 5-7.

McDonald, B. 1990. Precooling, storage, and 

transport of kiwifruit. In I.J. Warrington and G.C. 

Weston, eds., Kiwifruit: Science and Management, 

pp. 429-459. Ray Richards Publisher, Auckland, 

New Zealand.

Retamales, J., T. Cooper, and J. Montealegre. 

1997. Effects of cooling and curing regime on 

ethylene production and storage behavior of 

kiwifruit. Acta Hort. 444:567-571.

Snowdon, A.L. 1990. Soft fruits and berry fruits. 

In A Color Atlas of Postharvest Diseases and 

Disorders of Fruits and Vegetables, vol. 1, General 

Introduction and Fruits, pp. 255-266. CRC Press, 

Boca Raton, FL.

Testoni, A., B. Grassi, S. Quaroni, et al. 1997. 

Pitting on kiwifruit in storage caused by 

Phialophora sp. Acta Hort. 444:751-756.
377

Kohlrabi

Peter M. A. Toivonen and Charles Forney

Toivonen is with Pacific Agri-Food Research 

Centre, Agriculture and Agri-Food Canada, 

Summerland, British Columbia, Canada; Forney 

is with Atlantic Food and Horticulture Research 

Centre, Agriculture and Agri-Food Canada, 

Kentville, Nova Scotia, Canada.

Scientific Name and Introduction

Brassica oleracea L., Gongylodes group, also 

known as kohlrabi and turnip-rooted cabbage, is a 

member of the Brassicaceae (Cruciferae) family. 

It is a native of northern Europe and grows best 

in cool climates. Kohlrabi is grown as an annual, 

with the enlarged stem being the most commonly 

used edible portion. The enlarged stem may 

have purple, white, or green skin, but the flesh is 

white. The leaves can also be eaten like collards. 

Kohlrabi is available from spring to late fall from 

various growing regions of North America.

Quality Characteristics and Criteria

Only young kohlrabi should be harvested, since 

mature product becomes woody and tough. Leaf 

stems are a good indicator of quality; they should 

be succulent and tender.

Horticultural Maturity Indices

Early- and mid-season kohlrabi are best harvested 

when they are about 5.1 to 6.4 cm (2 to 2.5 in) in 

diameter. Fall-grown kohlrabi may be grown to 

10.2 to 12.7 cm (4 to 5 in) in diameter since they 

are less prone to becoming woody.

Grades, Sizes, and Packaging

There are no grade standards for kohlrabi. Topped 

kohlrabi is usually packaged in 11.4-kg (25-lb) 

film bags, 22.7-kg (50-lb) film bags, or 11-kg (24-

lb) cartons containing 24 0.5-kg (1-lb) film bags. 

Those with tops are usually bunch-tied together 

much like beets, with 4 to 6 kohlrabi per bunch 

(Thompson and Kelly 1957).

Precooling Conditions

Hydrocooling, package-icing, and forced-air 

cooling are acceptable for kohlrabi, with tops on 

or with tops removed.

Optimum Storage Conditions

Topped kohlrabi can be stored for 2 to 3 mo at 

0 °C (32 °F) and 98 to 100% RH (Kasmire and 

Cantwell 2002). Storage life is 2 to 4 weeks if tops 

are not removed. Storage life can be improved 

with the use of perforated film bags to maintain 

high RH.

Controlled Atmosphere (CA) 

Considerations

There is no benefit of CA (Kasmire and Cantwell 

2002).

Retail Outlet Display Considerations

Kohlrabi should be displayed like root vegetables 

such as beets and carrots. They can be placed in 

iced displays.

Chilling Sensitivity

Kohlrabi are not chilling sensitive.

Ethylene Production and Sensitivity

Kohlrabi have a very low ethylene production 

rate of <0.1 μL kg-1 h-1 at 20 °C (68 °F) and a low 

sensitivity to ethylene exposure.
378

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 10

5 °C 16

10 °C 31

15 °C 46

Data were adapted from Pieh (1965).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day. 

Physiological Disorders

Kohlrabi becomes tough when stored beyond 

its expected storage life or under lower than 

recommended RH.

Postharvest Pathology

Important diseases during storage are bacterial 

soft rot (Erwinia carotovora [Jones] Bergey et al.) 

and black rot (Xanthomonas campestris [Pammel] 

Dowson) (Ramsey and Smith 1961).

Quarantine Issues

There are no quarantine issues.

Suitability as Fresh-Cut Product

Peeled and sliced kohlrabi has potential as a freshcut product.

Special Considerations

The freezing point is -1 °C (30.2 °F) (Kasmire 

and Cantwell 2002). Peeled and cut kohlrabi does 

not produce strong off odors when held in low-O2

atmospheres (Forney and Jordan 1999).

References

Forney, C.F., and M.A. Jordan. 1999. Anaerobic 

production of methanethiol and other compounds 

by Brassica vegetables. HortScience 34(4):696-

699.

Kasmire, R.E. and Marita Cantwell. 2002. 

Postharvest handling systems: flower, leafy 

and stem vegetables. At http://vric.ucdavis.edu/

postharvest/leaf.

Pieh, K. 1965. Cooling of fruits and vegetables. 

Deut. Gartenbau 13:136-140

Ramsey, G.B., and M.A. Smith. 1961. Market 

Diseases of Cabbage, Cauliflower, Turnips, 

Cucumbers, Melons, and Related Crops. 

Agriculture Handbook 184, U.S. Department 

of Agriculture, Agricultural Marketing Service, 

Washington, DC.

Thompson, H.C., and W.C. Kelly. 1957. Vegetable 

Crops, 5th ed., pp. 313-314. McGraw-Hill, New 

York, NY.
379

Leek

Jennifer R. DeEll

DeEll is with the Ontario Ministry of Agriculture 

and Food, Simcoe, Ontario, Canada.

Scientific Name and Introduction

The leek, Allium porrum L. (syn. Allium 

ampeloprasum L. var. porrum), is an onionlike 

plant belonging to the Liliaceae family. The 

edible portion consists of the elongated bases of 

the foliage leaves (a false stem) and the lower 

parts, which are blanched white from being 

underground. There are three major types of leek: 

European leek, which develops a short and thick 

pseudostem; Turkish leek, which develops a 

relatively long and thin pseudostem; and kurrat, 

which does not produce a pseudostem. The kurrat 

type is grown in the Mediterranean and the Middle 

East for its leaves.

Quality Characteristics and Criteria

High-quality leeks are firm and smooth, free of 

blemishes, and have characteristic white stems 

with dark-green leaves. The cut bottoms should 

be flat, because rounded bottoms may indicate 

prolonged storage.

Horticultural Maturity Indices

Leeks can grow as tall as 50 to 100 cm (20 to 

39 in) in height and are harvested when the base 

diameter reaches 2.54 cm (1 in).

Grades, Sizes, and Packaging

There are no established USDA quality standards 

for leeks. Leeks are commonly trimmed so that 

only a 30.5-cm (12-in) portion of the green 

top remains. They can, depending on diameter, 

be bunched in groups of three and placed in 

polyethylene film bags to prevent moisture loss. 

They are usually packaged in 4.5-kg (10-lb) 

cartons or wire-bound crates, holding ten 0.45-kg 

(1-lb) film bags. Some crates may be packed with 

18 to 24 bunches, with a net weight of up to 13.6 

kg (30 lb).

Precooling Conditions

Hydrocooling, crushed ice, and vacuum-cooling 

are the most common methods to promptly cool 

harvested leeks to 0 °C (32 °F).

Optimum Storage Conditions

Leeks can be stored for 2 to 3 mo at 0 °C (32 

°F) with 95 to 100% RH. High RH is essential 

to prevent wilting. Good refrigeration retards 

elongation and curvature that develops in leeks 

at 10 to 21 °C (50 to 70 °F). Leeks held in 

polyethylene-lined crates remain saleable for 5 

to 6 weeks at 0 °C (32 °F) under crushed ice, 4 

weeks at 0 °C without ice, more than 2 weeks 

at 4.4 °C (40 °F), and 13 days at 10 °C (50 °F). 

Leeks stored in nonlined crates keep for 3 weeks 

at 0 °C (32 °C) , 8 days at 4.4 °C (40 °F), and 1 

week at 10 °C (50 °F), with or without crushed 

ice (Hruschka 1978). Freshly harvested leeks held 

naked in consumer-unit perforated polyethylene 

bags or in nonperforated (sealed) polyethylene 

bags remain attractive and saleable for up to 

10 weeks. They can last up to 10 weeks under 

crushed ice at 0 °C (32 °F); for 10 weeks without 

ice at 0 °C (32 °F); for 12 days at 10 °C (50 °F); 

and 6 days at 21 °C (70 °F).

Controlled Atmosphere (CA) 

Considerations

Storage for 4 to 5 mo at 0 °C (32 °F) is possible 

with CA, though there will be some loss of quality. 

Recommended CA conditions are 1 to 3% O2

 in 

combination with either 2 to 5% CO2 (Saltveit 

1997) or 5 to 10% CO2

 (Kurki 1979). Such CA 

retards yellowing and decay development. Levels 

of 15 to 20% CO2

 cause tissue injury.
380

Retail Outlet Display Considerations

Leeks should be held as close to 0 °C (32 °F) as 

possible and preferably away from products that 

produce ethylene.

Chilling Sensitivity

Leeks are not sensitive to chilling and should be 

stored as cold as possible without freezing. 

Ethylene Production and Sensitivity

Leeks produce very low levels of ethylene: <0.1 

μL kg-1 h-1. Leeks are moderately sensitive to 

ethylene. Detrimental effects include softening 

and increased decay.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 10 to 20

4.4 °C 20 to 29

10 °C 50 to 70

15.6 °C 75 to 117

21 °C 110

26.7 °C 107 to 119

Data from Hruschka (1978).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Slight elongation and geotrophic curvature 

may occur, even at 0 °C (32 °F). Leeks held in 

polyethylene-lined crates elongate less than 1% 

per week at 0 °C (32 °F) under crushed ice, 3% 

per week at 0 °C (32 °F) without ice, 13% per 

week at 4.4 °C (40 °F), and 22% per week at 10 

°C (50 °F) (Hruschka 1978). No attempt has been 

made to establish a relation between elongation 

and curvature, though varying degrees of 

curvature have been observed in such treatments. 

Senescent yellowing develops more rapidly at 

warmer temperatures, and moderate wilting is 

apparent when leeks lose about 15% of their 

weight.

Postharvest Pathology

Most diseases that attack onions may also affect 

leeks.

Quarantine Issues

None are known. 

Suitability as Fresh-Cut Product

No current potential exists.

Special Considerations

Cultivar, preharvest and postharvest conditions, 

degree of trimming, and method of packing will 

all influence the storage life of leeks.

Acknowledgments

Some of the information in this chapter is from 

the University of Oregon website, “Commercial 

Vegetable Production Guides, Leeks,” at http://

horticulture.oregonstate.edu/content/vegetableproduction-guides.

References

Hruschka, H.W. 1978. Storage and Shelf 

Life of Packaged Leeks. Marketing Research 

Report 1084, U.S. Department of Agriculture, 

Agricultural Marketing Service, Washington, DC.

Kurki, L. 1979. Leek quality changes during CA 

storage. Acta Hort. 93:85-90.
381

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California, Davis, 

CA.
382

Lemon

Kenneth C. Gross and Joseph L. Smilanick

Gross is formerly with the Food Quality 

Laboratory, Henry A. Wallace Beltsville 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. He is now retired. Smilanick is 

formerly with the Horticultural Crops Research 

Laboratory, Agricultural Research Service, U.S. 

Department of Agriculture, Fresno, CA. He is 

now with the Commodity Protection & Quality 

Research Unit, Agricultural Research Service, 

U.S. Department of Agriculture, Parlier, CA.

Scientific Name and Introduction

Lemons (Citrus limon L. Burman f.) are grown 

year round in California, the major producer. 

Arizona and to a lesser extent Florida also 

produce a significant portion of the lemon crop. 

The primary varieties are ‘Eureka’ and ‘Lisbon.’ 

Both have firm, smooth skins, juicy flesh, and few 

seeds. The exact origin of the lemon is unknown, 

but some have linked it to northwestern India.

Quality Characteristics and Criteria

The primary quality characteristics are intensity 

and uniformity of yellow color, size, shape, 

smoothness, firmness, and freedom from decay 

and defects including freezing damage, drying, 

mechanical damage, rind stains, red blotch, 

shriveling, and discoloration. Lemons should be 

firm and have smooth, thin skins. Ripe lemons 

should have a pleasant citrus fragrance. Lemons 

with discolored, bruised, or wrinkled skins should 

be avoided.

Horticultural Maturity Indices

The generally accepted standard is a minimum 

juice content of 28 to 30% by volume, depending 

on the grade.

Grades, Sizes, and Packaging

Grading includes U.S. No. 1, U.S. Export No. 

1, U.S. Combination, and U.S. No. 2. Common 

packaging specifications are 40-lb (18.2-kg) 

cartons, 10-lb (4.6-kg) mini-pack cartons, 8-lb 

(3.6-kg) consumer cartons, and 2-, 3-, and 5-lb 

(0.9-, 1.4-, and 2.3-kg) bags. Sizes include 75, 95, 

115, 140, 165, 200, and 235 count.

Precooling Conditions

Most packing houses do not precool lemons 

because the anticipated benefit is too modest, or 

they may need to degreen the fruit with ethylene, 

which requires 20 °C (68 °F) pulp temperatures.

Optimum Storage Conditions

Yellow lemons harvested when dark green have 

a much longer postharvest life than those picked 

yellow, which must be marketed more rapidly due 

their shorter shelf-life. Lemons should be stored 

between 7 and 12 °C (45 and 54 °F) depending 

on the maturity-ripeness stage at harvest, season 

of harvest, storage time, and production area. 

They can be stored for up to 6 mo under the right 

conditions. Optimum RH is 85 to 95%. Because 

lemons are chilling sensitive, they should not be 

stored for prolonged periods below 10 °C (50 °F), 

though 3 to 4 weeks storage at 3 to 5 °C (37 to 41 

°F), which is typical for some receivers, is usually 

tolerated without harm. Removal of ethylene 

from storage rooms can reduce senescence and 

fungal decay. It is generally recognized that proper 

storage of lemons improves quality (juice content, 

flavor, and color).

Adequate ventilation must be maintained during 

storage. Cartons should be kept off the floor to 

prevent them becoming wet from condensation. 

Lemons should be stored away from produce 

having a strong odor. Also, decay can occur from 

skin cuts or scratches caused by rough handling. 

Lemons must be handled with care, and shipping 

containers should not be dropped on the floor. Any 
383

affected product should be removed immediately 

to prevent mold from spreading. 

Controlled Atmosphere (CA) 

Considerations

Controlled atmosphere conditions of 7.5 to 10% 

O2

 and up to 10% CO2 can delay senescence, 

including loss of green color, but the risk of injury 

to the fruit is high and CA is only rarely used. 

Levels of CO2

 sufficient to inhibit fungal growth 

(>10%) are not used because high CO2

 induces 

nonpersistent but objectionable off flavors due to 

the accumulation of volatiles from fermentation. 

Also, levels of O2

 sufficient to control fungi (<1%) 

are not used because when O2

 is <5%, persistent 

off flavors can develop.

Retail Outlet Display Considerations

Lemons should not receive a water sprinkle or top 

ice.

Chilling Sensitivity

Chilling injury can be a major disorder of lemon, 

and it is therefore important not to store lemons 

below 10 °C (50 °F). Symptoms include pitting of 

the skin (termed “peteca”), interior discoloration, 

red blotch, and loss of juice. Chilling injury 

severity depends on cultivar, production area, 

harvest time, maturity-ripeness stage at harvest, 

and time-temperature of postharvest handling 

operations. Moderate to severe chilling injury is 

usually followed by decay.

Ethylene Production and Sensitivity

Rates of ethylene production are generally <0.1 

μL kg-1 h-1 at 20 °C (68 °F). If degreening is 

desired, lemons can be treated with 1 to 10 μL L-1

ethylene for 1 to 3 days at 20 to 25 °C (68 to 77 

°F). However, it should be noted that this exposure 

may accelerate deterioration and incidence of 

decay, since lemons are sensitive to ethylene 

exposure. They should not be stored together with 

ethylene-producing produce.

Respiration Rates

Temperature mg CO2 kg-1 h-1

10 °C 10 to 12

15 °C 14 to 24

20 °C 20 to 28

Data from Arpaia and Kader (2001).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Several disorders of lemon fruit are significant. 

Oleocellosis or oil spotting, a rind blemish that 

involves the breaking of oil cells due to physical 

stress on turgid fruits, results in the release of oil 

that damages surrounding tissues. Not harvesting 

lemons when they are turgid and careful handling 

reduce the severity of this disorder. Peteca, 

another rind disorder, begins in white portion of 

peel and develops sunken brown pits. It is favored 

by low temperatures before or after harvest, 

oil applications in the grove, and an imbalance 

of calcium and potassium in the peel. Some 

reduction in peteca is obtained by gibberelic acid 

applications to trees and by avoiding storage of 

susceptible lemons below 13 °C (55 °F).

Membrane stain, an internal disorder in which the 

membranes between segments, or carpellary walls, 

show irregular brown or black areas. It is reduced 

by avoiding storage of lemons below 13 °C (55 

°F) and improving ventilation in storage.
384

Postharvest Pathology

There are three main postharvest pathological 

diseases of lemon.

Green mold and blue mold are caused by 

Penicillium digitatum and P. italicum,

respectively. Spores of these pathogens access the 

fruit rind through wounds. Symptoms begin as 

water-soaked areas at the fruit surface followed by 

growth of colorless mycelia, and then sporulation. 

Blue mold is more common when storage 

temperatures are low, and it spreads from fruit to 

fruit more readily than green mold. Fungicides 

thiabendazole, imazalil, and sodium ortho-phenyl 

phenate are used for these diseases, and partial 

control can be obtained with biological control 

agents and the immersion of fruit in soda ash or 

sodium bicarbonate. Incidence of these diseases is 

reduced by careful handling to minimize wounds.

Sour rot is caused by Geotrichum citri-aurantii,

which enters lemons initially through wounds 

made by insects. Then infected fruit is digested by 

the pathogens, which spread rapidly from fruit to 

fruit. Sour rot is associated with cool, wet growing 

conditions. Partial control can be obtained by 

immersing fruit in soda ash, sodium bicarbonate, 

or sodium ortho-phenyl phenate after harvest and 

using minimal storage temperatures.

Other pathogens are occasionally troublesome in 

lemon storage, including Alternaria citri and the 

stem-end rot fungi Diplodia natalensis, as well as 

Phomopsis citri, Botrytis cinerea, Trichoderma

spp., Sclerotinia sclerotiorum, and Phytopthora

spp. Additional strategies to minimize postharvest 

decay include prompt cooling to the proper 

temperature range, maintaining optimum ranges 

of temperature and RH; excluding ethylene during 

transport and storage; using gibberelic acid before 

harvest to delay senescence of the fruit after 

harvest; and providing sanitation throughout the 

handling system.

Quarantine Issues

Most quarantine concerns for lemons address 

eliminating fruit flies, such as the Caribbean, 

Oriental, Mediterranean, and Mexican fruit flies. 

Heat, cold, and methyl bromide treatments are 

certified for this purpose, but they all pose risk 

of injury to lemons. Harvest and export of fruit 

from certified pest-free zones is another option 

to control fruit flies that eliminates risks of fruit 

injury, and this approach has also been employed 

against citrus black fly and Fuller rose beetle. 

Quarantine authorities are concerned that citrus 

black spot, an unsightly rind blemish caused 

by Guignardia citricarpa that occurs in South 

Africa and parts of Asia and South America, could 

potentially become established in Mediterranean 

countries and in North America.

Suitability as Fresh-Cut Product

Lemon sections, prepared by both manual and 

automatic processors, are distributed for use in the 

food service industry.

Acknowledgments

Some of the information in this chapter is from 

the Produce Marketing Association’s “Fresh 

Produce Manual” and the University of California, 

Davis, website “Fresh Produce Facts” at http://

postharvest.ucdavis.edu/produce_information. 

We express our appreciation to Laurie Houck, 

University of California, Davis, as well as to Bob 

Elliott and Chuck Orman, Sunkist Growers Fruit 

Sciences Division, for their helpful review of this 

chapter.

References

Arpaia, M.L., and A.A. Kader. 2001. Lemon. 

Recommendations for Maintaining Postharvest 

Quality. At http://postharvest.ucdavis.edu/

produce_information.
385

Eaks, I.L. 1961. Effect of temperature and holding 

periods on physical and chemical characteristics 

of lemon fruit. J. Food Sci. 26:593-599.

Eckert, J.W., and I.L. Eaks. 1989. Postharvest 

disorders and diseases of citrus fruits. In W. 

Reuther, E.C. Calavan, and G.E. Carman, 

eds., The Citrus Industry, vol. 5, pp. 179-260. 

University of California Press, Oakland, CA.

Houck, L.G., and J.W. Snider. 1969. Limitations 

of modified atmospheres for decay control of 

citrus fruits. Phytopathology 59:1031-1032.

Rygg, G.L., and E.M. Harvey. 1959. Storage of 

Lemons From the Desert Areas of Arizona and 

California. Marketing Research Report 310, U.S. 

Department of Agriculture, Agricultural Marketing 

Service, Washington, DC.

Rygg, G.L., and A.W. Wells. 1962. Experimental 

Storage of California Lemons in Controlled 

Atmospheres. Marketing Research Report 475, 

U.S. Department of Agriculture, Agricultural 

Marketing Service, Washington, DC.

Timmer, L.W., and L.W. Duncan, eds. 1999. 

Citrus Health Management. APS Press, St. Paul, 

MN.

Wild, B.L., W.B. McGlasson, and T.H. Lee. 

1976. Effect of reduced ethylene levels in 

storage atmospheres on lemon keeping quality. 

HortScience 11:114-115.
386

Lettuce

Mikal E. Saltveit

Saltveit is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Four distinct types of lettuce are produced in 

the United States: crisphead or iceberg (Lactuca 

sativa L. var. capitata); butterhead, bib, or Boston 

(L. sativa, var. capitata); cos or romaine (L. 

sativa, var. longifolia); and leaf (L. sativa, var. 

crispa). Two others types, stem or celtuce (L. 

sativa var. asparagina) and Latin are rarely found 

outside local or ethnic communities. 

Crisphead lettuce produces large, heavy, compact 

folded heads with crisp, brittle, prominently 

veined leaves. Butterhead lettuce forms open 

heads with softer leaves having a smooth texture. 

Cos lettuce does not form a true head, but is 

composed of upright, large, elongated, and often 

coarser leaves. Leaf lettuce also does not produce 

a head, and the leaves are more spreading, 

delicate, smaller, and less elongate than cos.

Crisphead lettuce is the main type grown in the 

United States and is best adapted for long distance 

shipment. A greater percentage of all types of 

lettuce are being processed into fresh-cut salad 

mixes for commercial and home use. With proper 

vacuum-cooling and packaging, refrigerated 

transportation under controlled atmosphere can 

supply whole and packaged lettuce to national and 

international markets. 

Quality Characteristics and Criteria

Head lettuce should be solid with no seed-stem, 

defects, or decay. In general, high-quality lettuce 

should be clean, free of browning, crisp and 

turgid, and bright light green. 

Horticultural Maturity Indices

Head lettuce is harvested when the heads are 

well formed and solid (Ryall and Lipton 1979). 

Maturity is based on head compactness, and the 

firmness of the head is related to its susceptibility 

to certain postharvest disorders. Soft heads are 

easily damaged, while fairly firm heads have 

higher respiration rates. Firm heads have maximal 

storage life, while hard and extra-hard heads are 

more prone to develop russet spotting, pink rib, 

and other physiological disorders. 

Grades, Sizes, and Packaging

Head lettuce is graded by size and firmness, while 

leafy types are graded by size (Hardenburg et al. 

1986). Lettuces, as with other leafy vegetables, 

must be kept clean and free of soil and mud. 

This is easier when grown on mineral soils than 

on muck (organic) soils. A strong bitter taste 

and toughness develops if harvest is delayed or 

if lettuce is overmature, and then the product 

becomes unmarketable. 

Because lettuce is very fragile, it should be 

handled as little as possible. Field packing and 

palletizing eliminate a major source of mechanical 

damage, but they require specialized handling 

equipment and vacuum-cooling facilities to be 

practical. The stem is cut at ground level and the 

head trimmed of unusable leaves. Harvesting 

and field packing by hand is assisted by various 

equipment including conveyors and mobile 

packing stations. Heads can be wrapped or bagged 

in plastic film by the cutter or the packer. Wrapped 

or loose heads are then placed in cardboard 

containers that are stapled closed and palletized. 

Leaf, butterhead, and cos types are cut, trimmed, 

and tied into compact bundles before being placed 

in cartons. 

Crisphead or iceberg lettuce is usually packaged 

in 20- to 22-kg (43- to 48-lb), 24-count cartons. 

Cos or romaine lettuce is commonly packaged in 

24-count cartons. Leaf lettuce is usually packaged 

in 9- to 11-kg (20- to 25-lb) or 24-count cartons. 

Butterhead or Boston lettuce is usually packaged 
387

in 9-kg (20-lb) cartons. Bibb and greenhousegrown lettuce are commonly packaged in 4.5-kg 

(10-lb) cartons. 

Lettuce harvested for processing is placed in large 

bulk bins for transportation to the precooling or 

processing facility. Lettuce may be cored in the 

field or at a local or regional processing facility. 

At the processing facility, heads are cut, washed 

in cold water, and centrifuged to remove excess 

water. Cut lettuce is often mixed with other types 

of lettuce or greens, shredded carrot, and red 

cabbage to produce a salad bag mix. The mix 

may be treated with a processing aid composed 

of a chlorine-containing compound and/or an 

antioxidant or preservative during washing or 

before packaging. The package is made from 

special films that are selected to maintain a desired 

lower O2

 and higher CO2 concentration than in air. 

The bags are then placed in cartons for temporary 

cold storage or for immediate shipment to market. 

Since gas composition in bags results from a 

dynamic interplay between tissue respiration 

and film permeability, it is important to maintain 

proper temperature and to know the respiratory 

characteristics of the enclosed tissue. 

Precooling Conditions

Vacuum-cooling is the preferred method for 

precooling all lettuces (Ryall and Lipton 1979, 

Hardenburg et al. 1986). For effective vacuumcooling, containers and film wraps are perforated 

or readily permeable to water vapor. If heads 

of lettuce are dry and warmer than 25 °C (77 

°F), clean water is sprinkled on them the before 

closing the cartons to aid cooling. A modification 

called hydrovacuum reduces water loss during 

cooling. Thorough precooling is essential because 

mechanically refrigerated trucks do not have 

enough cooling capacity to cool warm lettuce 

during transit. Field heat retained in the densely 

packed cartons can be removed by forced air 

where vacuum-cooling facilities are not available, 

but it is much less effective. Hydrocooling is 

effective for nonheading lettuce types but should 

not be used with head lettuce since the water 

retained in the head fosters decay. 

Optimum Storage Conditions

Lettuce should be quickly cooled and maintained 

as close to 0 °C (32 °F) as possible with 98 

to 100% RH. Head types are better adapted 

to prolong storage than are the other types, 

but none keep longer than 4 weeks, and about 

half that time at 5 °C (41 °F). Film liners or 

individual polyethylene head wraps are desirable 

for attaining high RH; however they should 

be perforated or be permeable to maintain a 

noninjurious atmosphere and to avoid 100% 

RH on removal from storage. Lettuce is easily 

damaged by freezing, so all parts of the storage 

room must be kept above the highest freezing 

point of lettuce, -0.2 °C (31.6 °F). 

Though most lettuce is hand-harvested, some 

mechanical harvesters are available for product 

destined for processing into bag mixes. The 

attendant greater damage to the tissue and the 

induced higher rates of respiration and water 

loss requires greater attention to maintaining the 

optimal storage conditions of temperature and RH.

Controlled Atmosphere (CA) 

Considerations

Lettuce, especially crisphead and fresh-cut, 

respond favorably to CA (Saltveit 1997a). Levels 

of 1 to 3% O2

 at temperatures of 0 to 5 °C (32 to 

41 °F) reduce russet spotting in susceptible lots. 

Intact heads do not benefit from elevated CO2

, 

and injury—brown stain—may develop when 

lettuce is transferred from storage in >2% CO2

to air at 10 °C (50 °F) (Ke and Saltveit 1989). A 

2 to 5% O2

 atmosphere maintains appearance of 

lettuce and inhibits pink rib and butt discoloration 

compared to air. Brown stain is intensified when 

O2

 is reduced to 2 to 3%, but the effect differs by 

cultivar. If lettuce needs to be in transit overseas 

for a month, an atmosphere of 2% CO2

 and 3% O2

is recommended because the reduction in decay 

achieved by 2% CO2

 outweighs the danger of 

injury. Romaine and leaf lettuce appear to tolerate 

a slightly higher CO2

 level when packaged than 

head lettuce. Browning is a major problem with 

fresh-cut lettuce, and is controlled by packaging in 
388

<1% O2

 and 10% CO2 (Lopez-Galvez et al. 1996, 

Smyth et al. 1998). The elevated level of CO2

 is 

more effective at reducing browning of the cut 

surfaces than it is at inducing brown stain.

Retail Outlet Display Considerations

Lettuce should be maintained under cold 

conditions to maximize storage and shelflife. Periodic sprays of cold water minimize 

dehydration. Avoid storage with commodities that 

produce ethylene such as apples and tomatoes. 

All lettuces are very susceptible to water loss and 

to ethylene-induced disorders, and they rapidly 

deteriorate at elevated temperatures.

Chilling Sensitivity

Not chilling sensitive, but freezing at -0.2 °C (31.6 

°F) must be avoided.

Ethylene Production and Sensitivity

Ethylene production is very low, but exposure 

to ethylene can result in damage such as russet 

spotting and leaf yellowing. 

Respiration Rates

Temperature Head lettuce Leaf lettuce

-------mg CO2 kg-1 h-1-------

0 °C 6 to 17 19 to 27

5 °C 13 to 20 24 to 35

10 °C 21 to 40 32 to 46

15 °C 32 to 45 51 to 74

20 °C 51 to 60 82 to 120

25 °C 73 to 91 120 to 173

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Some of the more common disorders of head 

lettuce include tipburn, russet spotting, brown 

stain, and pink rib (Ryall and Lipton 1979, Saltveit 

1997b). Hard heads are more susceptible to these 

disorders than firm lettuce. Tipburn is of field 

origin, but occasionally increases in severity after 

harvest. Leaves with tipburn have brown, often 

necrotic leaf margins. Russet spotting, which is 

caused by exposure to ethylene and its induction 

of the synthesis, accumulation, and oxidation of 

phenolic compounds at temperatures around 5 °C 

(41 °F), occasionally causes serious losses. Russet 

spots appear as dark brown, oval lesions on the 

midribs, and on the green leaf tissue in severe 

cases. It is easily controlled by making sure the 

storage atmosphere is free of ethylene and that the 

temperature is below 2 °C (36 °F). 

Lettuce should not be stored with ethyleneproducing commodities such as apples, 

cantaloupes, pears, and peaches. Storage in a 

low-O2

 atmosphere (1 to 8%) is very effective 

in controlling russet spotting. Brown stain is 

causedby exposure to >2.5% CO2

 and appears 

as large, irregularly shaped brown spots or 

streaks mostly on the midrib. Pink rib occurs in 

overmature heads stored at elevated temperatures 

and appears as a diffuse pink discoloration of the 

midrib; the cause of this disorder is unknown. 

Postharvest Pathology

Bacterial soft rot, the most serious disease of 

lettuce, often starts on bruised leaves and results in 

a slimy breakdown of the tissue (Saltveit 1997b). 

A similar breakdown of tissue follows fungal 

infection by Sclerotinia and gray mold rot caused 

by Botrytis cinerea. Trimming and storage at 0 

°C (32 °F) greatly reduce the severity of these 

disorders. 

Quarantine Issues

None are known.
389

Suitability as Fresh-Cut Product

Suitability is very high, especially in salad mixes 

with other leafy greens.

Special Considerations

Lettuce is fragile and must be handled with care 

to avoid mechanical damage and to minimize 

discoloration and pathological problems. 

Temperatures must be kept low and RH high to 

prevent loss of turgor and wilting. Ethylene must 

be avoided.

Acknowledgments

Some of the information in this chapter, notably 

the respiration data, was taken from the University 

of California, Davis, website “Fresh Produce 

Facts” at http://postharvest.ucdavis.edu/produce_

information and from the Produce Marketing 

Association’s “Fresh Produce Manual.”

References

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agriculture Handbook 66, U.S. Department 

of Agriculture, Agricultural Research Service, 

Washington, DC.

Ke, D., and M.E. Saltveit. 1989. Carbon dioxideinduced brown stain development as related to 

phenolic metabolism in iceberg lettuce. J. Amer. 

Soc. Hort. Sci. 114(5):789-794.

Lopez-Galvez, G., M.E. Saltveit, and M. Cantwell. 

1996. The visual quality of minimally processed 

lettuce stored in air or controlled atmospheres with 

emphasis on romaine and iceberg types. Postharv. 

Biol. Technol. 8:179-190.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transporation and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1, Vegetables and 

Melons. AVI Pub. Co., Westport, CT.

Saltveit, M.E. 1997a. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

vol. 4, pp. 98-117. University of California Davis, 

CA.

Saltveit, M.E. 1997b. Postharvest diseases. In

R.M. Davis, K.V. Subbarao, R.N. Raid, and E.A. 

Kurtz, eds., Compendium of Lettuce Diseases, pp. 

57-59. APS Press, St. Paul, MN.

Smyth, A.B., J. Song, and A.C. Cameron. 1998. 

Modified atmosphere packaged cut iceberg 

lettuce: Effect of temperature and O2

 partial 

pressure on respiration and quality. J. Agric. Food 

Chem. 46:4556-4562.
390

Lime

Jacqueline K. Burns

Burns is with the Citrus Research and Education 

Center, Institute of Food and Agricultural 

Sciences, University of Florida, Lake Alfred, FL.

Scientific Name and Introduction

Limes are thought to have originated in northeast 

India. Persian lime (also known as Bearss or 

Tahiti, Citrus latifolia Tan.) is the principal type 

grown in the United States. Commercial Persian 

lime production in the United States is now less 

than 2,000 ha and is limited to south Florida and 

southern California (Saunt 2000). Persian lime 

and key lime (Citrus aurantifolia Swing.) trees 

are popular in backyard settings, where they are 

commonly placed in large pots that are easily 

moved indoors during cold weather. Persian 

limes are seedless or nearly so, whereas key limes 

contain numerous seeds. 

Quality Characteristics and Criteria

High-quality limes should be oval and firm with 

smooth peel and deep green (Persian) or green and 

yellow (key lime) color. Limes should be turgid 

and free from decay, splitting, and blemishes.

Horticultural Maturity Indices

High quality, mature limes have a juice content 

of 30% or higher, by volume (Arpaia and Kader 

2000). U.S. consumers prefer a mature, green 

lime; these have a significantly longer postharvestlife than those picked when yellow. In some other 

countries, yellow limes are preferred because 

of their higher juice content (Arpaia and Kader 

2000).

Grades, Sizes, and Packaging

Persian limes must attain a size of 4.76 cm (1.87 

in) in diameter and a juice content of 42% by 

volume. There are no size requirements for key 

lime, but juice content must be 42% by volume 

(Wardowski et al. 1995). Persian limes are packed 

in 10-lb (4.5-kg), 20-lb (9.1-kg) , and 40-lb (18.2-

kg) cartons for storage and shipping (Roy et al. 

1996).

Ethylene Production

The typical rate of ethylene production is very low 

at <0.1 μL kg-1 h-1 at 20 °C.

Respiration Rate

Under optimal storage conditions, respiration rate 

of limes is <10 mg CO2

 kg-1 h-1 (Arpaia and Kader 

2000). 

Optimum Storage Conditions

Limes should be cooled and stored at 10 °C (50 

°F) with 95% RH. Under optimal conditions, 

limes can be stored up to 8 weeks. CA storage 

can retard senescence, but commercial use is very 

limited.

Physiological Disorders

Stylar-end breakdown can be a significant problem 

with limes. Stylar-end breakdown begins as an 

apparent breakdown of tissues at the stylar end 

of the fruit. Typically the stylar end takes on a 

wet appearance. Large, mature fruit are more 

susceptible. Incidence of the disorder can be 

aggravated by high field heat and rough handling 

(Davenport and Campbell 1977, Malo and 

Campbell 1994). Exposing limes to temperatures 

below the optimum storage temperature can 

result in chilling injury characterized by peel 
391

pitting. Oleocellosis can develop on the peel 

if hand-harvest begins early in the morning or 

immediately after rainfall, when the peel is turgid.

Postharvest Pathology and Control

Key lime is very susceptible to stem-end rot 

caused by Diplodia natalensis and anthracnose 

(Colletotricum). Stem-end rot caused by D. 

natalensis, Phomopsis citri, and Alternaria citri

are important postharvest diseases in Persian lime. 

In addition, green and blue mold (Penicillium 

digitatum and P. italicum, respectively) can enter 

through wounds made during harvesting and 

handling and appear in storage. Careful handling 

to minimize mechanical damage can help reduce 

blue and green mold. Proper sanitation of packing 

line equipment and use of postharvest fungicides 

reduce postharvest diseases.

Quarantine Issues

Appearance of citrus canker (Xanthomonas 

axonopodis pv. citri) has restricted movement 

of limes grown in south Florida. Compliance 

with the Citrus Canker Eradication Program 

(Florida Department of Agriculture and Consumer 

Services 2000) is required to market limes from 

quarantined areas.

Suitability as Fresh-Cut Product

No current potential exists.

References

Arpaia, M.L., and A.A. Kader. 2000. Lime. 

Recommendations for Maintaining Postharvest 

Quality. At http://postharvest.ucdavis.edu/

produce_information. 

Florida Department of Agriculture and Consumer 

Services. 2000. Citrus Canker Eradication 

Program. At http://www.freshfromflorida.com/pi/

canker/pdf/cankerflorida.pdf.

Davenport, T.L., and C.W. Campbell. 1977. Stylarend breakdown in ‘Tahiti’ lime: Aggravating 

effects of field heat and fruit maturity. J. Amer. 

Soc. Hort. Sci. 102:484-486.

Malo, S.E., and C.W. Campbell. 1994. The Tahiti 

Lime. Fruit Crops Department Fact Sheet FC-8, 

IFAS, Florida Cooperative Extension Service, 

University of Florida, Gainesville, FL

Roy, M., C.O. Andrew, and T.H. Spreen. 1996. 

Persian Limes in North America: An Economic 

Analysis of Production and Marketing Channels. 

Florida Science Source, Inc., Lake Alfred, FL.

Saunt, J. 2000. Citrus Varieties of the World. 

Sinclair International Ltd., Norwich, England, 

U.K.

Wardowski, W., J. Whigham, W. Grierson, and 

J. Soule. 1995. Quality Tests for Florida Citrus. 

Bull. SP66, University of Florida Cooperative 

Extension Service. University of Florida, 

Gainesville, FL.
392

Litchi

Robert E. Paull, Ching Cheng Chen, and Nancy 

Jung Chen

Paull, Chen, and Chen are with the Department of 

Tropical Plant and Soil Sciences,

University of Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Litchi (Litchi chinensis Sonn.), also spelled 

lychee, originated in southern China where it 

has been cultivated for at least 2,000 years. The 

tree has somewhat exacting requirements that 

vary with cultivar for flowering, hence there 

is substantial year-to-year variation in supply 

(Nakasone and Paull 1998). The round to eggshaped fruit, about 2.5 cm (1 in) in diameter, has 

a thin leathery red skin with blunt or sharp spines. 

The edible, translucent-opaque flesh (aril) encloses 

a large (occasionally small), black seed.

Quality Characteristics and Criteria

Skin color and fruit size are external quality 

criteria. Internal criteria are seed size and flesh 

sweetness and juiciness. A bright-red fruit with no 

browning is preferred, along with freedom from 

bird, insect, and mechanical damage; cracking; 

and decay.

Horticultural Maturity Indices

Red skin color and flesh have the optimum range 

of sugar-to-acid ratio for the cultivar. During litchi 

maturation, acid levels decline and sugar levels 

increase (Paull et al. 1984). Fruit do not continue 

to ripen after harvest.

Grades, Sizes, and Packaging

There are no U.S. or international standards. Onepiece fiberboard boxes holding 2.25 kg (5 lb) or 

4.5 kg (10 lb) with polyethylene film liners are 

used. Fruit are also packed into 0.5-pint (0.12-L) 

styrene containers.

Precooling Conditions

Room-cooling is used for precooling.

Optimum Storage Conditions

Storage at 2 to 5 °C (36 to 41 °F) with 90 to 95% 

RH should result in 3 to 5 weeks of storage life. At 

20 °C (68 °F) with 60% RH, fruit will last only 3 

to 5 days. Fruit need to be carefully sorted before 

storage to remove any damaged or decayed fruit 

or fruit with insect stings (Campbell 1959, Paull 

and Chen 1987).

Controlled Atmosphere (CA) 

Considerations

An atmosphere of 3 to 5% O2

 and 5% CO2 at 5 

to 7 °C (41 to 45 °F) is recommended (Kader 

1994, 1998, Vilasachandran et al. 1997). Higher 

levels of CO2

 (10 to 15%) can lead to off flavors 

(Vilasachandran et al. 1997). MAP has been 

tried with sealed polyethylene bags either with 

(Ragnoi 1989) or without SO2

 pads or treatment 

(Scott et al. 1982, Paull and Chen 1987). Using 

polyethylene film bags probably prevents 

dehydration that leads to rapid skin browning 

(Akamine 1960, Paull and Chen 1987).

Retail Outlet Display Considerations

Litchi should be displayed refrigerated, preferably 

in polystyrene containers or plastic bags. If litchi 

are left directly exposed to ambient air, the skin 

will rapidly brown.
393

Chilling Sensitivity

Litchi have low sensitivity to chilling. However, 

dehydration during storage often leads to loss 

of skin color and browning and is referred to as 

chilling injury.

Ethylene Production and Sensitivity

Litchi have a low rate of ethylene production: <1 

nL kg-1 h-1. There are no reports on the response 

of this nonclimacteric fruit to ethylene exposure. 

Ethylene may lead to early aril deterioration.

Respiration Rates

Fruit do not continue to ripen after harvest 

(Joubert 1986), and respiration rate declines 

during storage (Akamine and Goo 1973). 

Temperature mg CO2 kg-1 h-1

5 °C 10 to 16

10 °C 19 to 29

20 °C 46 to 74

25 °C 75 to 128

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

The major disorder is the rapid browning of the 

shell from a bright red color (Paull and Chen 

1987, Holcroft and Mitcham 1997). The browning 

is associated with water loss and injury (insect 

stings). The browning associated with insect stings 

may go through to the pinkish-white inner surface 

of the shell. A breakdown (softening and loss of 

turgidity) of flesh occurs in senescent fruit after 

prolonged storage and overmaturity. The condition 

starts at the blossom end. Field and sometimes 

postharvest skin cracking can occur. Cracked fruit 

should be culled.

Postharvest Pathology

Numerous postharvest diseases can occur, but 

most have their origins preharvest. Good field 

sanitation and culling of fruit that show damage 

from fruit-piercing insects, cracks, and sunscorch 

are effective in minimizing losses (Prasad and 

Bilgrami 1973, Scott et al. 1982). Disease 

organisms include Aspergillus spp. (Roth 1963, 

Prasad and Bilgrami 1973, Scott et al. 1982), 

Pestalotiopsis spp. (Prasad and Bilgrami 1973), 

Peronophythora spp. (Ho et al. 1984), sour rot 

caused by Geotrichum candidum, and yeasty rots 

(Roth 1963). Other organisms found to cause rots 

include Botryodiplodia theobroma, Colletotrichum 

gloesporioides, and Rhizopus oryzae (Roth 1963, 

Prasad and Bilgrami 1973, Scott et al. 1982).

Quarantine Issues

Litchi is a fruit fly host and requires treatment 

before entry into the United States from fruitfly-infected areas. Potential treatments include 

irradiation, heat, and cold treatments.

Suitability as Fresh-Cut Product

There are no published data. The skin and seed 

can be removed with little damage to the aril flesh. 

The aril can be placed on trays and overwrapped.

Special Considerations

Fumigation with SO2

 followed by a dip in 

hydrochloric acid can preserve red skin color 

(Paull et al. 1994). Careful application can avoid 

an increase in aril sulfite residues and avoid 

off flavors (Paull et al. 1998). Sulfites are not 

approved on fresh produce in the United States, 

except for grapes. Most other countries have 

sulfite residue limits for edible portions (Tongdee 

1994).
394

References

Akamine, E.K. 1960. Preventing the darkening 

of fresh lichees prepared for export. Technical 

Progress Report 127, Hawaii Agricultural 

Experiment Station, Honolulu, HI.

Akamine, E.K., and T. Goo. 1973. Respiration and 

ethylene production during ontogeny of fruits. J. 

Amer. Soc. Hort. Sci. 98:381-383.

Campbell, C.W. 1959. Storage behavior of fresh 

‘Brewster’ and ‘Bengal’ lychees. Proc. Florida St. 

Hort. Soc. 72:356-360.

Ho, H.H., J.Y. Lu, and L.Y. Gong. 1984. 

Observation on asexual reproduction by 

Peronophythora litchii. Mycologia 76:745-747.

Holcroft, D.M., and E.J. Mitcham. 1997. 

Postharvest physiology and handling of litchi 

(Litchi chinesis Sonn.). Postharv. Biol. Technol. 

9:265-281.

Joubert, A.J. 1986. Litchi. In S.P. Monselise, ed., 

CRC Handbook of Fruit Set and Development, pp. 

233-246. CRC Press, Boca Raton, FL.

Kader, A.A. 1994. Modified and controlled 

atmosphere storage of tropical fruits. In B.R. 

Champ, E. Highley, and G.I. Johnson, eds., 

Postharvest Handling of Tropical Fruits. 

International Conference on Postharvest Handling 

of Tropical Fruits, Chiang Mai, Thailand, July 

1993, pp. 239-249. ACIAR Proceedings no. 50, 

ACIAR, Canberra, Australia.

Kader, A.A. 1998. Produce facts—lychee. 

Perishables Handling Quarterly, no. 94, University 

of California, Davis, CA.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Paull, R.E., and J.N. Chen. 1987. Effect of 

storage temperature and wrapping on quality 

characteristics of litchi fruit. Sci. Hort. 33:223-

236.

Paull, R.E., N.J. Chen, J. Deputy, et al. 1984. 

Litchi growth and compositional changes during 

fruit development. J. Amer. Soc. Hort. Sci. 

109:817-821.

Paull, R.E., M.E. Reyes, and M. Reyes. 1994. 

Litchi and rambutan insect disinfestation: 

treatments to minimize induced pericarp 

browning. Postharv. Biol. Technol. 6:139-148.

Paull, R.E., M.E. Reyes, and M. Reyes. 1998. 

Sulfite residues on litchi fruit with sulfur dioxide. 

Postharv. Biol. Technol. 14:229-233.

Prasad, S.S., and R.S. Bilgrami. 1973. 

Investigations on diseases of ‘Litchi.’ vol. 3, Fruit 

rots and their control by postharvest treatments. 

Indian Phytopath. 26:523-527.

Roth, G. 1963. Postharvest decay of litchi fruit 

(Litchi chinesis Sonn.). Technical Communication, 

Department of Agricultural Technical Services, 

Pretoria, South Africa.

Ragnoi, S. 1989. Controlled Atmosphere 

Storage of Fruits and Vegetables, pp. 179. CAB 

International, Wallingford, U.K.

Scott, K.J., B.I. Brown, G.R. Chaplin, et al. 1982. 

The control of rotting and browning of litchi 

fruit by hot benomyl and plastic film. Sci. Hort. 

16:253-262.

Tongdee, S.C. 1994. Sulfur dioxide fumigation 

in postharvest handling of fresh longan and 

lychee for export. In B.R. Champ, E. Highley, 

and G.I. Johnson, eds., Postharvest Handling 

of Tropical Fruits. International Conference on 

Postharvest Handling of Tropical Fruits, Chiang 

Mai, Thailand, July 1993, pp. 186-195. ACIAR 

Proceedings no. 50, ACIAR, Canberra, Australia.

Vilasachandran, T., S.A. Sargent, and F. Maul. 

1997. Controlled atmosphere storage shows 

potential for maintaining postharvest quality of 

fresh litchi. In A.A. Kader, ed., 7th International 

Controlled Atmosphere Research Conference, 

University of California, Davis, July 13-18, 1997, 

Abstract 54, University of California, Davis, CA.
395

Longan

Saichol Ketsa and Robert E. Paull

Ketsa is with the Department of Horticulture, 

Kasetsart University, Bangkok, Thailand; Paull 

is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI.

Scientific Name and Introduction

This small fruit (Dimocarpus longan [Lour.] 

Steud.), a relative of the litchi, is 2.5 to 3 cm 

(1 to 1.2 in) in diameter with a smooth, thin, 

yellowish-brown shell and a sweet translucent 

flesh (aril) surrounding a large hard nonedible 

seed (Nakasone and Paull 1998). The pulp comes 

away cleanly from the shell and seed.

Quality Characteristics and Criteria

Shell color, size, and shape; seed size; and 

sweetness are criteria. Fruit should be free of 

insect damage and skin blemishes; defective fruit 

are culled while being sorted for size. See Jiang et 

al. (2002) for further information.

Horticultural Maturity Indices

Maturity is judged by shape, skin color, and flavor 

of each cultivar. Most fruit can be picked from a 

tree with one harvest, unless multiple flowerings 

have occurred. No definite harvest index exists for 

longan, but growers usually note changes in skin 

appearance—mature fruit develop a smooth and 

relatively darker skin (Wong and Ketsa 1991).

Grades, Sizes, and Packaging

One-piece fiberboard crates are used, holding 

either 4.5 kg (10 lbs) or 2.25 kg (5 lbs), with 

plastic liners if fruit are not already packed in 

polystyrene containers. Fruit are clipped from 

the stem, as hand removal often leads to some 

inadvertent skin removal.

Precooling Conditions

Room or forced-air cooling is used for precooling. 

Longan in plastic baskets can be hydrocooled, 

though hydrocooled longan should not be treated 

with SO2

. SO2 fumigation damages hydrocooled 

fruit skin by producing brown spots on both 

the inner and outer skin surfaces. It also results 

in greater SO2

 residue remaining on the fruit 

(Suwanagul 1992). SO2

 treatment of fruit to be 

sold as fresh is not approved in the United States.

Optimum Storage Conditions

The recommendation storage conditions are 4 to 

7 °C (41 to 46 °F) with 90 to 95% RH (Paull and 

Chen 1987). Fruit can be held for 2 to 3 weeks, 

though the skin loses it yellowish coloration, 

becoming brown. At lower temperatures, there 

is rapid loss of eating quality, and above 10 °C 

(50 °F), postharvest diseases are a concern. The 

expected storage life of longan held at high RH 

(Suwanagul 1997) is—

-----------Storage life-----------

Temperature Untreated SO2-treated

--------------days-----------------

0 oC 14 to 28 21 to 42

4 oC 14 14 to 28

10 oC 7 to 14 14

20 oC 3 to 5 7

30 oC 1 to 2 3 to 5

Controlled Atmosphere (CA) 

Considerations

No controlled atmosphere studies have been 

reported, though modified atmosphere packaging 

in 0.03 mm (1/1000 in) polyethylene bags was 

tested for 7 days at room temperature, followed by 

35 days at 4 °C (39 °F). A modified atmosphere 
396

of 1 to 3% O2

 delays browning and maintains 

SSC and vitamin C content (Zhang and Quantick 

1997). Treatment with 1% O2

 results in a slight off 

flavor.

Retail Outlet Display Considerations

Longan should be displayed refrigerated. Misting 

is not recommended so as to avoid microbial 

growth.

Chilling Sensitivity

At storage temperatures, <5 °C (41 °F), a slight 

off flavor can develop after about 1 week. The 

peel of longan stored at 0 °C (32 °F) turns dark 

brown, while SO2

-fumigated longan remain 

yellowish-brown. The dark brown peel of longan 

that develops at very low temperatures is regarded 

as chilling injury (La-Ongsri et al. 1993).

Ethylene Production and Sensitivity

Longan fruit have a low rate of ethylene 

production: <1 nL kg-1 h-1. There are no reports on 

ethylene sensitivity.

Respiration Rates 

Temperature mg CO2 kg-1 h-1

5 °C 3.5 to 11.3

10 °C 16.0 to 25.0

20 °C 30.0 to 53.0

Data from Liao et al. (1983).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Desiccation is a major problem that leads to a 

rapid loss of bright yellowish color of the skin, 

which turns to a dull brown (Jiang et al. 2002).

Postharvest Pathology

Longan suffers similar postharvest diseases 

to litchi. Fungi associated with skin browning 

and darkening of the skin along with mycelium 

include Lasiodiplodia theobromae, Pestalotiopsis

sp., Cladosporium sp., Fusarium sp., and 

Aspergillus niger (Sardsud et al. 1994).

Quarantine Issues

Longan is a fruit fly host. Suitable treatments 

include hot air, vapor heat treatment, and 

irradiation.

Suitability as Fresh-Cut Product

Peeled, deseeded fruit aril can be used as a freshcut product.

Special Considerations

Longan are fumigated with SO2

 in Thailand and 

other countries to prevent skin browning and 

to control postharvest disease (Tongdee 1994). 

Though very effective, SO2

 fumigation is not 

approved for use in the United States for fruit to 

be sold as fresh. Asian consumers prefer longan in 

bunches. They assume that single fruit have fallen 

from the bunch because it has been dropped or 

that fruit are not fresh. Individual fruit may also 

have a higher rate of weight loss.
397

References

Jiang, Y.M, Z.Q. Zhang, D.C. Joyce, and S. Ketsa. 

2002. Postharvest biology and handling of longan 

(Dimocarpus longan Lour.) fruit. Postharv. Biol. 

Technol. 26:241-252.

La-Ongsri, S., S. Gomolmanee, and O. WaraAswapati. 1993. Reducing chilling injury 

symptoms in sulfur dioxide fumigated longan 

fruits. In B.R. Champ, E. Highley, and G.I. 

Johnson, eds., Postharvest Handling of Tropical 

Fruits. International Conference on Postharvest 

Handling of Tropical Fruits, Chiang Mai, 

Thailand, July 1993, pp. 20. ACIAR Proceedings 

no. 50, ACIAR, Canberra, Australia.

Liao, M.L., M.S. Liu, and J.S. Yang. 1983. 

Respiration measurement of some important fruits 

in Taiwan. Acta Hort. 138:227-246.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Paull, R.E., and N.J. Chen. 1987. Changes in 

longan and rambutan during postharvest storage. 

HortScience 22:1303-1304.

Sardsud, V., U. Sardsud, C. Sittigul, and T. 

Chaiwangsri. 1994. The effects of post-fumigation 

washing treatments and storage temperature on 

disease development in fresh longan. In G.I. 

Johnson and E. Highley, eds., Development of 

Postharvest Handling Technology for Tropical 

Tree Fruits. A Workshop Held in Bangkok, 

Thailand, 16-18 July 1992, pp. 77. ACIAR 

Proceedings no. 58, ACIAR, Canberra, Australia.

Suwanagul, A. 1997. Postharvest management 

of lychee and longan. In Proceedings of the 

Workshop on New Technology for Lychee and 

Longan Production, Chiang Mai, Thailand, pp. 

105-120. Thailand Institute of Scientific and 

Technological Research, Bangkok, Thailand.

Tongdee, S.C. 1994. Sulfur dioxide fumigation 

in postharvest handling of fresh longan and 

lychee for export. In B.R. Champ, E. Highley, 

and G.I. Johnson, eds., Postharvest Handling 

of Tropical Fruits. International Conference on 

Postharvest Handling of Tropical Fruits, Chiang 

Mai, Thailand, July 1993, pp. 186-195. ACIAR 

Proceedings no. 50, ACIAR, Canberra, Australia.

Wong, K.C., and S. Ketsa. 1991. Dimocarpus 

longan Lour. In E.W.M. Verheij and R.E. 

Coronel, eds., Plant Resources of South-East 

Asia, vol. 2, Edible Fruits and Nuts, pp. 146-151. 

Pudoc Scientific Publishers, Wageningen, The 

Netherlands.

Zhang, D., and P.C. Quantick. 1997. Preliminary 

study on the effects of modified atmosphere 

packaging on postharvest storage of longan fruit. 

In A.A. Kader, ed., 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, CA, July 1997, vol. 3, pp. 90-

96. University of California, Davis, CA.
398

Longkong

Robert E. Paull

Paull is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI.

Scientific Name and Introduction

There are at least two major types, with a 

number of intermediate types, of Lansium 

domesticum Jack.: langsat (Malay, Thailand), 

longkong (Thailand, intermediate type), and duku 

(Malay, Thailand). Other names include lanson 

(Philippines), and intermediate types are referred 

to as duku-langsat in Malaysia (Nakasone and 

Paull 1998). There is considerable inconsistency 

in the naming of the different types (Yaacob and 

Bamroongrugsa 1992). Peninsular Thailand to 

Borneo is the major area of cultivation. Besides 

the Philippines, L. domesticum is also cultivated 

in Vietnam, Burma, India, Sri Lanka, Australia, 

Surinam, and Puerto Rico.

Quality Characteristics and Criteria

Langsat fruit are more ovoid, roughly 30 to 60 

mm (1.2 to 2.4 in) in diameter, while duku are 

rounder and 40 to 50 mm (1.6 to 2 in) in diameter; 

longkong is intermediate, nearly seedless, has a 

brittle skin, and is the same size as langsat. There 

are 15 to 25 fruit per longkong raceme and 4 to 

12 in duku. The skin of young fruit is pale green 

and turns yellow when ripe, frequently with 

brown blemishes. The langsat has a thin skin 

that contains a milky white sticky sap. Duku has 

a thicker—up to 6 mm (0.25 in)—skin and no 

latex. Longkong has a slightly thicker skin than 

langsat and less sap that is not sticky. The green 

seed is covered by a white translucent flesh that 

is slightly sour in langsat. Langsat tends to vary 

from sweet to sour; duku is sweet. Both fruit have 

five separate segments with one to five seeds in 

langsat and one or two in duku. During ripening, 

astringency in the flesh declines while sugars 

increase six-fold (Paull et al. 1987). The skin 

bruises very easily, leading to brown discoloration.

Horticultural Maturity Indices

Fruit are harvested at the full ripe stage indicated 

by the skin color change from light to dark 

yellow, dryness of the sepals, and the peduncle 

(stem) losing most of its green color. The flesh 

is transparent when ripe. Fruit on the bunch 

generally ripen together over a very short period. 

Four to five harvests per tree are necessary. It is 

essential to harvest as soon as possible before 

over-ripe fruit abscise from the peduncle. Fruit to 

be shipped long distances are harvested when 70 

to 80% ripe to avoid excessive fruit drop. Fruit 

should be picked when dry, as they can become 

moldy if packed wet.

Grades, Sizes, and Packaging

There are no U.S. or international standards. 

Fruit are generally graded by size and color and 

normally sold in single-layer fiberboard cartons 

holding 2.25 kg (5 lb) of fruit, with padding, or 

sometimes in trays with liners.

Precooling Conditions

Room cooling is used because forced-air cooling 

causes moisture loss.

Optimum Storage Conditions

The most recent recommendation for storage is 

18 °C (46 °F) with 90% RH (Piyasaengthong et 

al. 1997), giving about 21 days of storage life. 

Previously, 11 to 14.4 °C (34 to 58 °F) with 85 to 

90% RH for 2 weeks was recommended, which 

gave 24.3% weight loss (Pantastico 1975). Others 

have recommended 11 to 13 °C (52 to 55 °F) with 

85 to 90% RH for 14 days (Srivastava and Mathur 

1955).
399

Controlled Atmosphere (CA) 

Considerations

Fruit stored at 14 °C (58 °F) in 3% O2

 and 0% 

CO2

 had 16 days of postharvest life, compared to 

9 days for fruit held in air (Pantastico et al. 1975). 

High CO2

 aggravated postharvest skin browning, 

especially at 10% O2

; browning can also occur in 

fruit held in polyethylene film bags. Holding in 

plastic bags (0.08 mm thickness) reduces weight 

loss but increases surface browning (Brown and 

Lizada 1984). Preliminary recommendations are 

5% O2

 and 0% CO2 (Yahia 1998).

Retail Outlet Display Considerations

Fruit are commonly displayed in overwrapped 

trays or closed styrene clam shell containers with 

no holes at 15 °C (59 °F). They should not be 

misted.

Chilling Sensitivity

Chilling leads to skin browning; at 15 °C 

symptoms develop after 21 days (Piyasaengthong 

et al. 1997). 

Ethylene Production and Sensitivity

Fruit produce low amounts of ethylene, with 

internal concentrations of 2 to 6 μL kg-1. There 

are no reported responses to ethylene treatment; it 

may lead to premature senescence.

Respiration Rates

Respiration rates decline after harvest, and small 

fruit have a higher rate than large fruit (Srivastana 

and Mathur 1955, Pantastico et al. 1968). 

Temperature mg CO2 kg-1 h-1

9 °C 40 to 50

20 °C 50 to 90

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Abrasion and impact injury, water loss, and 

chilling injury are the three major disorders. 

Mechanical injury (abrasion, impact, and 

compression) leads to skin darkening and 

browning. Chilling injury symptoms are pitting 

and brown scalding of the skin.

Postharvest Pathology

Anthracnose, aspergillus, and rhizopus surface 

rots on the skin have been reported. Packing dry 

fruit and using fungicides can minimize losses.

Quarantine Issues

Longkong is a fruit fly host; irradiation at 300 

grays has potential for disinfestation.

Suitability as Fresh-Cut Product

No current potential. 

References

Brown, B.I., and M.C.C. Lizada. 1985. Modified 

atmospheres and deterioration of lanzones 

(Lansium domesticum Correa.). Postharvest 

Research Notes 1(2):36.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Pantastico, E.B. 1975. Postharvest Physiology, 

Handling and Utilization of Tropical and 

Subtropical Fruits and Vegetables. AVI Pub. Co., 

Westport, CT.
400

Pantastico, E.B., D.B. Mendoza, and R.M. Abilay. 

1968. Some chemical and physiological changes 

during storage of lanzones (Lansium domesticum

Correa.). The Philippines Agriculturist 52:505-

517.

Paull, R.E., T. Goo, and N.J. Chen. 1987. Growth 

and compositional changes during development of 

lanzone fruit. HortScience 22:1252-1253.

Piyasaengthong, Y., S. Suanpairoj, P. Pakamat, and 

C. Ruensamran. 1997. The optimum for storaging 

longkong (Aglaia dookoo Griff). In 35th Kasetsart 

University Conference, Bangkok, Thailand. 

(English summary.)

Srivastana, H.C., and P.B. Mathur. 1955. Studies 

in the cold storage of langsat. J. Sci. Food Agric. 

6:511-513.

Yaacob, O., and N. Bamroongrugsa. 1992. 

Lansium domesticum Correa. In E.Verheij and 

R.E. Coronel, eds., Plant Resources of SouthEast Asia, vol. 2, Edible Fruits and Nuts. 

Pudoc Scientific Publishers, Wageningen, The 

Netherlands.

Yahia, E. 1998. Modified and controlled 

atmospheres for tropical fruits. Hort. Rev. 22:123-

183.
401

Loquat

Changkui Ding

Ding is formerly with the Food Quality 

Laboratory, Henry A. Wallace Beltsville 

Agricultural Research Center, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. He is currently with DuPont 

Agricultural Biotechnology, Johnston, IA.

Scientific Name and Introduction

Loquat (Eriobotrya japonica L.) belongs to the 

rose family and is a subtropical evergreen fruit 

tree. Fruits grow in loose clusters and are round 

or oval, weighing about 20 to 80 g (0.7 to 2.8 oz). 

Fruit have a thin but tough skin. Ripe fruit flesh 

is soft and juicy, varying in color from white to 

deep orange. Loquat originated in midwestern 

China and is widely cultivated in the subtropical 

regions of southern China, Japan, Israel, and the 

Mediterranean area. In the United States, loquats 

grow in Hawaii, California, and the Gulf States.

Quality Characteristics and Criteria

High-quality loquat have SSC >12%, moderate 

TA (0.3 to 0.6%), and low flesh firmness. Loquat 

cultivars have a rapid rate of fruit softening.

Horticultural Maturity Indices

The quality of loquats is highly dependent on the 

degree of ripening. Loquats harvested at the fully 

ripe stage have optimum quality. However, in 

commercial situations where transport and shelflife are involved, loquats are generally harvested 

at the eating-ripe stage before becoming fully ripe. 

In most cultivars, harvest date is determined by 

skin color changes described for each cultivar. 

Grades, Sizes, and Packaging

Size grades of the cultivar ‘Tanaka’ are large, 

>60 g (2.1 oz); medium, 50 to 59 g (1.9 oz); 

small, 40 to 49 g (1.6 oz); and SS, 30 to 39 g (1.2 

oz). Packages commonly employ soft materials 

because of the fruit’s susceptibility to bruising.

Precooling Conditions

In order to maintain quality and storage life, 

loquat should be precooled to <5 °C (41 °F) 

within 20 h of harvest (Shinbori and Nakai 1991). 

Optimum Storage Conditions

Recommended conditions for commercial storage 

are 0 to 5 °C (32 to 41 °F) with >90% RH. Loquat 

fruit can be kept in good condition for 3 to 4 

weeks at 0 °C (32 °F) and 2 weeks at 10 °C (50 

°F) (Guelfat-Reich 1970, Ding et al. 1998). Use 

of polyethylene bags retards weight loss and 

minimizes decreases in organic acids (Ding et al. 

1997).

Controlled Atmosphere (CA) Conditions

No information is available.

Retail Outlet Display Considerations

A refrigerated shelf at 5 to 12 °C (41 to 54 oF) is 

good.

Chilling Sensitivity

Loquat fruit are not sensitive to chilling.

Ethylene Production and Sensitivity

Loquat fruit produce relatively low amounts of 

ethylene and are not particularly sensitive to 

ethylene exposure after harvest.
402

Respiration Rates

Respiration rates of loquat are influenced by 

temperature and decrease rapidly over the first 

4 days of storage. By the fourth day of storage, 

respiration rates of stored fruit were— 

Temperature mg CO2 kg-1 h-1

1 °C 11.2

5 °C 12.4

10 °C 30.6

20 °C 80.0

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Fruit are easily bruised and scratched, and the 

damaged areas usually turn brown or black, so 

careful handling and packaging during and after 

harvest are important. Also, internal browning and 

brown surface spotting occur during long-term or 

high-CO2

 storage (Ding et al. 1999).

Postharvest Pathology

Cooling fruit and holding them at <5 °C (41 °F) 

are effective at controlling spoilage.

Quarantine Issues

None are known.

Suitability as Fresh-Cut Product

No current potential exists.

Special Considerations

Loquats must be handled with care to avoid 

mechanical damage, and low-temperature storage 

is essential for extending postharvest life.

References

Ding, C.-K., K. Chachin, Y. Hamauzu, et al. 1998. 

Effects of storage temperatures on physiology and 

quality of loquat fruit. Postharv. Biol. Technol. 

14:309-315.

Ding, C.-K., K. Chachin, and Y. Ueda. 1997. 

Effects of polyethylene bag packing and lowtemperature storage on physical and chemical 

characteristics of loquat fruit. In A.A. Kader, ed., 

7th International Controlled Atmosphere Research 

Conference, University of California, Davis, July 

13-18, 1997, vol. 3, pp. 177-184. University of 

California, Davis, CA.

Ding, C.-K., K. Chachin, Y. Ueda, et al. 1999. 

Effects of high CO2

 concentration on browning 

injury and phenolic metabolism in loquat fruits. J. 

Jap. Soc. Hort. Sci. 68:275-282.

Guelfat-Reich, S. 1970. Storage of loquat 

(Eriobotrya japonica). Fruits 250(3):169-173.

Shinbori, F., and S. Nakai. 1991. Qualitative 

changes during maturation and keeping qualities 

of loquats fruits. J. Jap. Soc. Hort. Sci. 60(Suppl. 

2):590-591.
403

Luffa

Stephen Morris and Jenny Jobling

Morris and Jobling are with the Sydney 

Postharvest Laboratory, Food Science Australia, 

North Ryde, New South Wales, Australia.

Specific Name and Introduction

There are two main species of cultivated luffa 

(loofah). Angled luffa or Chinese okra (Luffa 

acutangula), a green, immature fruit with 

longitudinal ridges, is consumed like summer 

squash. Smooth luffa or sponge gourd (Luffa 

aegyptiaca Mill) is sometimes eaten as a 

vegetable, but mature fruit are mainly used 

to make sponges for cosmetics and cleaning 

(Ellington and Wehner 1996). Both are members 

of the Cucurbitaceae family.

Quality Characteristics and Criteria

Edible fruit are harvested while immature. If 

angled luffa are left to mature, blossom-end 

enlarges, stem-end shrinks, and bitter flavor 

develops (Zong et al. 1993). Quality loss is most 

often associated with loss of green color.

Grades, Sizes, and Packaging

There are no U.S. grades for luffa. 

Horticultural Maturity Indices

Luffa are harvested immature and selected based 

on size.

Optimum Storage Conditions

Angled luffa can be stored for up to 2 weeks at 10 

to 12 °C (50 to 54 °F) with 90 to 95% RH (Zong 

et al. 1992, 1993, Cantwell 1997).

Controlled Atmosphere (CA) 

Considerations

There is no published information on CA for luffa.

Retail Outlet Display Considerations

Top-icing is not acceptable due to luffa’s chilling 

sensitivity. Water sprays are acceptable.

Chilling Sensitivity

Fruit are sensitive to chilling at <10 °C (50 

°F) (Zong et al. 1993). Symptoms include skin 

discoloration, watery lesions under the skin, and 

enhanced decay.

Ethylene Production and Sensitivity

Angled luffa produce very low levels of ethylene: 

<0.1 μL kg-1 h-1 at 20 °C (68 °F). However, luffa is 

sensitive to ethylene during postharvest handling, 

which results in a loss of green color and reduced 

quality (Zong et al. 1993).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 14

5 °C 27

10 °C 36

15 °C 63

20 °C 79

Data from Zong et al. (1992, 1993).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 
404

Physiological Disorders

Luffas should be handled with care; damage 

to longitudinal ribs leads to water loss and 

decay. Fruit are susceptible to dehydration and 

toughening of the peel.

Postharvest Pathology

No specific information is available.

Quarantine Issues

None are known.

Suitability as Fresh-Cut Product

No current potential exists.

Special Considerations

Care must be taken with selection of the correct 

immature stage; damage to the ribs must be 

carefully controlled as it leads to water loss and 

decay.

References

Cantwell, M. 1997. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu/

produce_information.

Ellington, T.L., and T.C. Wehner. 1996. 

Postharvest treatments for producing sponges 

from immature fruits of luffa gourds. Cucurbit 

Genet. Coop. Rpt. 19:85-86.

Zong, R., M.I. Cantwell, and L.L. Morris. 1993. 

Postharvest handling of Asian specialty vegetables 

under study. Calif. Agric. 47(2):27-29.

Zong, R., M.I. Cantwell, L.L. Morris, and V. 

Rubatzky. 1992. Postharvest studies on four fruittype Chinese vegetables. Acta Hort. 318:345-354. 
405

Mandarin (Tangerine)

Jacqueline K. Burns

Burns is with the Citrus Research and Education 

Center, Institute of Food and Agricultural 

Sciences, University of Florida, Lake Alfred, FL.

Scientific Name and Introduction

Mandarin originated in China and southeast 

Asia. The names “tangerine” and “mandarin” 

have often been used synonymously. The term 

“tangerine” was first used in the 19th century to 

describe mandarins with deep orange-red external 

color. The mandarin/tangerine citrus group is 

very diverse, and attempts have been made to 

assign members into different categories and 

species. Citrus unshiu (satsuma), C. deliciosa

(Mediterranean mandarin), C. nobilis (king 

mandarin) and C. reticulata (common mandarin) 

are known worldwide, but only C. reticulata and 

associated hybrids are of economic importance in 

the United States (Saunt 2000). ‘Dancy,’ ‘Fallglo,’ 

‘Robinson,’ ‘Sunburst,’ and ‘Clemantine’ are 

popular varieties in the United States. Mandarinlike varieties, either tangors (mandarin × orange 

hybrids) such as ‘Temple’ and ‘Murcott’ or 

tangelos (mandarin × grapefruit hybrids) such as 

‘Minneola’ and ‘Orlando,’ are also grown.

Quality Characteristics and Criteria

High-quality mandarin have a turgid, deep orangered peel relatively free of blemishes. The fruit 

should be elliptical and firm. The peel should be 

easily removed from the flesh. The edible portion 

should be juicy and contain few or no seeds.

Horticultural Maturity Indices

Maturity standards require that mandarin have a 

set minimum SSC:TA ratio and have at least 50% 

peel surface color break. 

Grades, Sizes, and Packing

Mandarin are packed in 4/5-bushel cartons for 

shipping and storage. Marketable mandarin range 

from size 56 (56 fruit per carton) to size 210 (210 

fruit per carton).

Optimum Storage Conditions

Mandarin are stored at 5 to 8 °C (41 to 46 °F) with 

95% RH for periods up to 4 weeks. Chilling injury 

can occur in storage if temperatures fall below 5 

°C (41 °F). Storage duration depends on variety, 

maturity, and decay control. Thiabendazole (TBZ) 

can be incorporated into fruit coatings and used to 

control postharvest decays during storage.

Ethylene Production and Sensitivity

Mandarin are nonclimacteric and do not exhibit 

a rise in respiration and ethylene associated with 

ripening. Ethylene production is typically <0.1 μL 

kg-1 h-1 at 20 °C (68 °F).

Respiration Rates

Respiration rates at optimum storage temperatures 

are generally <10 mg CO2 kg-1 h-1 (Arpaia and 

Kader 2000).

Temperature mg CO2 kg-1 h-1

5 oC 4 to 8

10 oC 6 to 10

15 oC 12 to 20

20 oC 20 to 30

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.
406

Degreening

Some mandarin-growing areas, such as Florida, 

have persistent high temperatures that prevent 

natural color break in the peel. In these cases, 

ethylene is used to degreen (cause the destruction 

of chlorophyll) early-season mandarin. Ethylene 

is used at 1 to 5 μL L-1 at 28 to 29 °C (82 to 84 

°F) with 95% RH. Duration of ethylene exposure 

ranges from 12 h to 3 days. One complete air 

change per hour should enter the degreening 

room to avoid buildup of CO2

, which can 

inhibit ethylene action, and to assist in uniform 

temperature and ethylene distribution (Wardowski 

1996).

Physiological Disorders

Mandarin have thin peels that are readily injured 

under conditions that promote high peel-water 

content. Excessive soil moisture before harvest 

predisposes mandarin to zebra-skin. Normal 

handling on packing-line machinery causes 

peel epidermal cells to rupture in areas over the 

fruit segment. Zebra-skin can be exacerbated by 

degreening. Oleocellosis can occur on the peel 

when excessive squeezing force is used to harvest 

fruit by hand. Cells encircling oil glands die when 

oil from ruptured glands leak into the surrounding 

tissues. Generally fruit are more susceptible to 

oleocellosis when peel turgidity is high. Puffiness 

is characterized by separation of the peel from the 

pulp on the tree or in storage. Fruit of advancing 

maturity appear to be most susceptible to 

puffiness.

Stem-end rind breakdown, SERB, is characterized 

by collapse and sinking of the peel in irregularly 

shaped regions near the stem end. SERB is 

closely associated with excessive water loss. Lateseason mandarin are most susceptible to SERB. 

Chilling injury is characterized by peel pitting 

followed by increased susceptibility to postharvest 

decay. Severity of chilling injury increases with 

temperatures below 5 °C (41 °F) and longer 

durations. Mandarin are susceptible to granulation, 

or section-drying. Susceptibility is influenced by 

variety and overmaturation (Grierson 1986).

Postharvest Pathology

Stem-end rot (Diplodia natalensis and Phomopsis 

citri) is a significant problem on mandarin, 

especially where degreening is required in early 

season fruit. Stem-end rots develop as latent 

infections on the fruit button (calyx and disc) 

before harvest and begin to grow through the core 

after harvest. Decay develops unevenly at the stem 

and stylar ends, resulting in uneven margins.

Anthracnose, caused by Colletotrichum 

gloesporiodes, is a major decay of mandarin. 

Characterized by brown peel lesions, anthracnose 

appears on early-season mandarin that have 

undergone lengthy degreening periods.

Brown rot (Phytophthora citrophthora) develops 

from infections that take place in the grove before 

harvest. Brown rot has a characteristic rancid 

odor and is characterized by tan lesions that 

quickly overtake the entire fruit under optimum 

conditions.

Green and blue mold (Penicillium digitatum and 

P. italicum, respectively) develop on mandarin as 

a result of wounds made during harvesting and 

handling (Eckert and Brown 1986, Whiteside et al. 

1988).

Drenching harvested mandarins with TBZ before 

they arrive at the packinghouse is recommended 

for controlling Diplodia, Phomopsis, anthracnose, 

and Penicillium. Application of aqueous imazalil 

or TBZ in the coating treatment aids in control. 

Minimizing degreening time by delaying harvest 

will assist in controlling stem-end rot caused by 

Diplodia and anthracnose. Brown rot is most 

effectively controlled by preharvest treatment with 

copper-containing fungicides. Careful harvesting 

and handling can reduce injuries that allow 

entrance of wound pathogens such as Penicillium. 

Good sanitation of packinghouse equipment 

and storage areas will help control the spread of 

postharvest pathogens.
407

Quarantine Issues

The appearance of citrus canker (Xanthomonas 

axonopodis pv. citri) has restricted movement 

of mandarin grown in affected areas in Florida. 

Compliance with the Citrus Canker Eradication 

Program (Florida Department of Agriculture 

and Consumer Services 2000) is required for 

harvesting, packing, and shipping mandarin from 

quarantined areas to domestic markets. 

Cold treatment is an approved quarantine 

treatment for citrus grown in areas infested with 

tropical fruit flies. In Florida, the Caribbean 

fruit fly (Anastrepha suspensa) may be found 

in citrus groves during late spring and summer. 

Cold treatment involves storage of fruit below 

2 oC (36 °F) for specified periods to ensure their 

freedom from fly infestation. However, because 

of susceptibility to chilling injury, fruit may be 

stored at higher temperatures of 10 to 15 °C (50 to 

59 °F) for about 1 week prior to cold treatment to 

increase resistance to chilling injury.

Suitability as Fresh-Cut Product

Some potential exists for separated segments.

References

Arpaia, M.L., and A.A. Kader. 2000. Mandarin/

Tangerine. Recommendations for maintaining 

postharvest quality. University of California, 

Davis, CA. At http://postharvest.ucdavis.edu/

produce_information.

Florida Department of Agriculture and Consumer 

Services. 2000. Citrus Canker Eradication 

Program. At http://www.freshfromflorida.com/pi/

canker/pdf/cankerflorida.pdf.

Eckert, J.W., and G.E Brown. 1986. Postharvest 

diseases and their control. In W.F. Wardowski, S. 

Nagy, and W. Grierson, eds., Fresh Citrus Fruits, 

pp. 315-360. AVI, Westport, CT.

Grierson, W. 1986. Physiological disorders. In

W.F. Wardowski, S. Nagy, and W. Grierson, eds., 

Fresh Citrus Fruits, pp. 361-378. AVI, Westport, 

CT. 

Saunt, J. 2000. Citrus Varieties of the World. 

Sinclair International, Norwich, England.

Wardowski, W.F. 1996. Recommendations for 

degreening Florida fresh citrus fruit. Circular 

1170, University of Florida, Institute of Food and 

Agricultural Science, Gainesville, FL.

Whiteside, J.O., S.M. Garnsey, and L.W. Timmer, 

eds. 1988. Compendium of Citrus Diseases. APS 

Press, St. Paul, MN.
408

Mango

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Mango (Mangifera indica L.) is cultivated 

throughout the tropics and warmer subtropics. Of 

the numerous varieties, Florida’s ‘Tommy Atkins,’ 

‘Kent,’ ‘Keitt,’ and ‘Haden’ are the most common 

in the United States. The fruit’s skin is yellow or 

green with a golden to red blush, depending on 

the variety. Fruit can be round, oval, or kidney 

shaped. Some varieties have a turpentine-like 

smell and taste.

Quality Characteristics and Criteria

Skin coloration, size, appropriate shape for 

the variety, appearance, freedom from defects 

and decay, absence of fiber in the flesh, and 

a turpentine-like flavor are the most common 

quality parameters. Wilted, grayish discoloration 

and pitting are undesirable. Some fruit varieties 

(‘Haden’) have pinhead-sized black spotting that 

is not regarded as a defect.

Horticultural Maturity Indices

The general criteria for maturity of most cultivars 

of mango are (1) the fruit “shoulders” have risen 

above the stem-end and (2) there is a slight skin 

color break on the first fruit of a crop. Early fruit 

from a single flowering should only be harvested 

after a slight skin color change; 2 weeks later all 

full-sized fruit can be harvested, even if there is 

no apparent change in skin color. Other indices 

include SSC and TA, specific gravity, and days 

from blooming. These indices depend on cultivar 

and season (Hatton et al. 1965, Kanes et al. 1982).

Grades, Sizes, and Packaging

There are no U.S. or international grade standards. 

Fruit are sold in 16-kg (35-lb) cartons as well as 

6-kg (14-lb) flat single-layer cartons and 4.5-kg 

(10-lb) single-piece fiberboard boxes with various 

counts.

Precooling Conditions

Fruit are normally forced-air cooled or roomcooled, preferably within 24 h of harvest (Mattern 

et al. 1972).

Optimum Storage Conditions

Storage at 10 to 13 °C (50 to 55 °F) with 85 to 

90% RH should give a shelf-life of 14 to 28 days 

for mature green fruit, depending on variety. 

Ripe fruit can be stored at 7 to 8 °C (45 to 46 °F). 

Diseases are the principal factor limiting storage 

life. Optimum ripening temperature is 20 to 23 °C 

(68 to 73 °F) for best appearance, palatability, and 

decay control (Jobin-Decor 1988).

Controlled Atmosphere (CA) 

Considerations

Different cultivars show various responses to CA. 

The optimum storage atmosphere for prolonging 

storage and shipping is 3 to 5% O2

 and 5 to 10% 

CO2

 at 7 to 9 °C (45 to 48 °F) with 90% RH 

(Yahia 1998). Ripening delays are minor and may 

not be economic in all situations. Polyethylene 

or other film bags, with and without an ethyleneabsorber, give some delay in ripening. However, 

some film bags can also result in off flavor and 

abnormal skin coloration.

Retail Outlet Display Considerations

Mangoes can be displayed at store temperature 

and should not be misted. Bruised and diseased 

fruit should be removed from display.
409

Chilling Sensitivity

Chilling susceptibility varies with cultivar; 

‘Haden’ and ‘Keitt’ are particularly susceptible. 

Most cultivars show injury below 10 °C (50 °F), 

especially if fruit have just reached maturity. 

Tolerance to chilling increases during ripening 

(Medlicott et al. 1990). The symptoms include 

grayish, scaldlike discoloration on the skin, 

followed by pitting, uneven ripening, and poor 

flavor and color development (Hatton et al. 1965, 

Medlicott et al. 1990). Heat treatment prior to 

storage reduces injury in ‘Keitt’ (McCollum et al. 

1993).

Ethylene Production and Sensitivity

Mangoes have moderate ethylene production: 

1 to 2 μL kg-1 h-1 at 20 °C (68 °F). Ethylene 

induces faster and more uniform softening 

(Lakshminarayana 1973, Barmore 1974). Ethylene 

treatment can be done prior to shipping (Barmore 

and Mitchell 1977). There is disagreement in the 

literature regarding effect of ethylene treatment 

on quality (Chaplin 1988). This may relate to 

maturity when treated. Treatment of immature 

fruit leads to softening, but the fruit have poor 

flavor.

Respiration Rates

Temperature mg CO2 kg-1 h-1

4.5 °C 10 to 22

10 °C 23 to 46

15 °C 45 to 90

20 °C 75 to 151

Data from Karmarkar and Joshi (1941) and Lam 

(1987).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Heating for insect disinfestation elevates 

respiration 3- to 5-fold; after cooling, rates remain 

higher than those of unheated fruit for 4 to 6 days 

(Mitcham and McDonald 1993).

Physiological Disorders

Some disorders, such as chilling injury and high 

CO2

 injury, are induced after harvest, while 

others are inherent. Inherent disorders occur 

intermittently and are unpredictable; for example, 

jelly seed, which results in watery, translucent 

tissue around the seed giving an over-ripe 

appearance. It does not develop after harvest 

unless it was present at harvest (Young and Miner 

1961). Some cultivars are very susceptible, such 

as ‘Tommy Atkins’ (Lelyveld and Smith 1979). 

Soft nose and internal breakdown (or spongy 

tissue) are other disorders (Lim and Khoo 1985), 

though it is possible these are the same condition. 

Sap burn is a major problem with some cultivars 

(O’Hare 1994), such as ‘Kensington,’ while ‘Irvin’ 

is less susceptible (Loney et al. 1992); washing 

with water and detergent helps avoid damage 

(Brown et al. 1986).

Postharvest Pathology

Anthracnose (Colletotrichum gloesporioides),

which is caused by preharvest infection and does 

not spread postharvest, and the postharvest stemend rots caused by several fungi that infect before 

and after harvest (often as wound invaders that 

spread postharvest) are the two most common 

diseases (Johnson and Coates 1993). Anthracnose 

appears as fruit ripen and first appears as 

superficial black spots and streaks that then 

become sunken (Fitzell and Peak 1984).

Alternaria rot (Alternaria alternata), a preharvest 

infection, can sometimes be a problem, while the 

postharvest wound infections can occasionally be 

severe, such as black mold (Aspergillus spp.) and 

transit rot (Rhizopus spp.). Disease control begins 

in the field followed by postharvest sanitation, 

as well as avoidance of latex burn (stain) and 

mechanical injury. Hot-water treatment (46 °C 

for 60 to 120 min) and fungicides can be used, 

depending on the cultivar (Spalding and Reeder 
410

1986). Hot-water brushing at 55 °C (131 oF) for 

20 s shows good control (Prusky et al. 1999).

Quarantine Issues

As a fruit fly host, mango must be treated prior 

to import into the United States. Hot water at 47 

°C (116 °F) for 65 to 90 min, vapor heat with 

fruit core temperature of 46 to 48 °C (115 to 

118 °F), and irradiation (300 grays) are potential 

treatments.

Suitability as Fresh-Cut Product

Fresh-cut pieces and slices are frequently found in 

markets. Browning of the flesh can be a problem.

References

Barmore, C.R. 1974. Ripening mangoes with 

ethylene and ethephon. Proc. Florida St. Hort. 

Soc. 87:331-334.

Barmore, C.R., and E.F. Mitchell. 1977. Ethylene 

pre-ripening of mangoes prior to shipment. Citrus 

Industry 58:18-19, 22-23.

Brown, B.I., I.A. Wells, and C.F. Murray. 1986. 

Factors affecting the incidence and severity of 

mango sap-burn and its control. ASEAN Food J. 

2:127-132.

Chaplin, G.R. 1988. Advances in postharvest 

physiology of mango. Acta Hort. 231:639-648.

Fitzell, R.D., and C.M. Peak. 1984. The 

epidemiology of anthracnose disease of mango: 

inoculum sources, spore production and disposal. 

Ann. Appl. Biol. 104:53-59.

Hatton, T.T. Jr., W.F. Reeder, and C.W. Campbell. 

1965. Ripening and Storage of Florida Mangos. 

Marketing Research Report 725, U.S. Department 

of Agriculture, Washington, DC.

Jobin-Decor, M.P. 1988. Mango ripening guide. 

Queensland Agric. J. 114:369-371.

Johnson, G.I., and L.M. Coates. 1993. Postharvest 

diseases of mango. Postharv. News Info. 

4:27n-34n.

Kanes, O., M. Boulet, and F. Costaigne. 1982. 

Effect of chilling-injury on texture and fungal rot 

of mangoes (Mangifera indica L.). J. Food Sci. 

47:992-995.

Karmarkar, D.V., and B.M. Joshi. 1941. 

Respiration studies of the alphonse mango. Ind. J. 

Agric. Sci. 11:993-1005.

Lakshminarayana, S. 1973. Respiration and 

ripening patterns in the life cycle of the mango 

fruit. J. Hort. Sci. 48:227-233.

Lelyveld, L.J. van, and J.H.E. Smith. 1979. 

Physiological factors in the maturation and 

ripening of mango (Mangifera indica L.) fruit in 

relation to the jelly seed physiological disorder. J. 

Hort. Sci. 54:283-287.

Lam, P.F. 1987. Respiration rates and ethylene 

production of ripening Harumanis mangoes after 

different chilling storage periods. MARDI Res. 

Bull. 95:15-19.

Lim, T.K., and K.C. Khoo. 1985. Diseases and 

Disorders of Mango in Malaysia. Tropical Press, 

Kuala Lumpur, Maylasia.

Loney, B.R., S.P. Robinson, J.J. Brophy, and E.K. 

Chacko. 1992. Mango sap-burn, components of 

the fruit sap and their role in causing skin damage. 

Austral. J. Plant Physiol. 19:449-457.

Mattern, F., W. Pennock, and L.S. Valles. 1972. 

Supplying the New York market with high quality 

Puerto Rican mangoes. J. Agric. Univ. Puerto Rico 

56:1-10.

McCollum, T.G., S. D’Aquino, and R.E. 

McDonald. 1993. Heat treatment inhibits mango 

chilling injury. HortScience 28:197-198.
411

Medlicott, A.P., J.M.M. Sigrist, and O. Sy. 1990. 

Ripening of mangoes following low temperature 

storage. J. Amer. Soc. Hort. Sci. 115:430-434.

Mitcham, E.T., and R.E. McDonald. 1993. 

Respiration rate, internal atmosphere and ethanol 

and acetaldehyde accumulation in heat-treated 

mango fruit. Postharv. Biol. Technol. 3:77-86.

O’Hare, T.J. 1994. The susceptibility of Thai 

and Australian mango cultivars to sap injury and 

possible means of control. In G.I. Johnson and 

E. Highley, eds., Development of Postharvest 

Handling Technology for Tropical Tree Fruits, 

pp. 21-24. Australian Centre for International 

Agricultural Research Proceedings 58, ACIAR, 

Canberra, Australia.

Prusky, D., Y. Fuchs, I. Kobiler, et al. 1999. 

Effects of hot water brushing, prochloraz 

treatment and waxing on the incidence of black 

spot decay caused by Alternaria alternata on 

mango fruits. Postharv. Biol. Technol. 15:165-174.

Spalding, D.H., and W.F. Reeder. 1986. Decay and 

acceptability of mangoes treated with combination 

of hot water, imazalil and γ-radiation. Plant Dis. 

70:1149-1150.

Yahia, E.M. 1998. Modified and controlled 

atmospheres for tropical fruits. Hort. Rev. 22:123-

183.

Young, T.W., and J.T. Miner. 1961. Relationship 

of nitrogen and calcium to ‘soft-nose’ disorder in 

mango fruits. J. Amer. Soc. Hort. Sci. 78:201-208. 
412

Mangosteen

Robert E. Paull and Saichol Ketsa

Paull is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI; Ketsa is with the Department of 

Horticulture, Kasetsart University, Bangkok, 

Thailand.

Scientific Name and Introduction

Mangosteen (Garcinia mangostana L.) is 

one of the most praised of tropical fruit. It is 

also known as mangostanier, mangoustanier, 

mangouste, mangostier (French), mangostan 

(Spanish), manggis, mesetor, semetah, sementah 

(Malaysian), manggustan, mangis, mangostan 

(Philippine), mongkhut (Cambodian), mangkhut 

(Thai), cay mang cut (Vietnamese), manggis, 

manggistan (Dutch), and mangostao, mangosta, 

or mangusta (Portuguese) (Nakasone and Paull 

1998). 

The globe-shaped, smooth berry is 4 to 7 cm (1.6 

to 2.8 in) across and has a persistent calyx. The 

pericarp is 6 to 10 mm (0.24 to 0.4 in) thick and 

turns purple during ripening. It contains a bitter, 

yellowish latex and purple-staining juice. The 

edible white aril has 4 to 8 segments with 1 or 2 

larger segments containing apomictic seeds; there 

is no true seed.

Quality Characteristics and Criteria

Fruit have pinkish-red skin when mature, turning 

to a dark purple skin and white flesh. The skin 

should be thick and soft, but firm, when ripe. 

Fruit have a soft, sweet, slightly acid flesh with 

a pleasant flavor. Misshapen and damaged fruit 

should be removed. Burst latex vessels leave 

a yellow dried latex on the skin that should be 

scraped off, followed by washing the fruit with a 

soft brush. Fruit are graded to remove damaged 

fruit and for size. Some Thai growers and 

exporters coat cleaned fruit with lacquer, giving 

fruit skin damaged by thrips prior to harvest a 

more attractive appearance.

Horticultural Maturity Indices

Skin color is the major criterion used to judge 

maturity. Immature fruit that have a light, 

greenish-yellow skin with scattered pinkish 

spots do not ripen to full flavor if harvested. The 

minimum harvest stage for high quality fruit is 

when the skin has distinct irregular, pink-red 

spots over the whole surface. Fruit are at the 

edible, ripe stage when the skin has darkened to 

reddish-purple, no latex remains in the skin, and 

the flesh segments separate easily from the skin 

(Tongdee and Suwanagal 1989). Careful handling 

is essential in order to avoid mechanical injury.

Grades, Sizes, and Packaging

There are no U.S. or international standards. Fruit 

are graded by size and color. Mangosteens are 

normally sold in single-layer, fiberboard cartons 

holding 2.25 kg (5 lb) with padding, or sometimes 

in trays with fruit individually wrapped to prevent 

injury (20 to 24 fruit per tray). In Southeast Asia, 

fruit are sold in baskets or strung in bundles of 10 

to 25 fruit.

Precooling Conditions

Room-cooling is normally used (Augustin and 

Azudin 1986).

Optimum Storage Conditions

Recommendations vary from 4 to 6 °C (39 to 42 

°F) with 85 to 90% RH for 7 weeks (Pantastico 

1975) to 13 °C (56 °F) with 85 to 90% RH for 14 

to 25 days. Storage at 4 °C (39 °F) or 8 °C (46 

°F) can lead to significant hardening of the skin 

(Augustin and Azudin 1986), though the flesh may 

still be acceptable after 44 days. Current practice 

is to store fruit at 12 to 14 °C (54 to 57 °F), giving 

storage life of about 20 days without chilling 
413

injury. Application of surface coatings reduces 

weight loss and prevents calyx wilting (Choehom 

1997).

Controlled Atmosphere (CA) 

Considerations

An atmosphere of 5% O2

 and 5% CO2 has been 

used for 1 mo (Yahia 1998) and resulted in best 

overall retention of peel appearance and internal 

quality (Rattanachinnakorn et al. 1996). Holding 

fruit in polyethylene film bags reduces weight 

loss and disease (Daryono and Sabari 1986); 

however, it is not clear if the effects are due to 

the prevention of water loss or to the modified 

atmosphere in the bags.

Retail Outlet Display Considerations

Fruit are commonly displayed in overwrapped 

trays or in closed styrene, clam-shell containers 

with no perforations at 10 to 14 °C (50 to 57 °F). 

They should not be misted.

Chilling Sensitivity

Storage at <10 °C (50 °F) leads to rapid hardening 

and darkening of pericarp when fruit are returned 

to ambient temperature (Uthairatanakij and Ketsa 

1996, Choehom 1997).

Ethylene Production and Sensitivity

Mangosteen is a climacteric fruit. Ethylene 

production is about 29 nL kg-1 h-1. The respiratory 

peak occurs sooner when fruit are treated with 

ethylene. Ethylene treatment triggers autocatalytic 

ethylene production (Noichinda 1992).

Respiration Rates

Respiration rate is 21 mg (12 μL) CO2

 kg-1 h-1 at 

25 °C. Heat production is 4,620 BTU ton-1 day-1

(1,281 kcal tonne-1 day-1).

Physiological Disorders

Fruit damage during harvesting and marketing can 

affect >20% of fruit. The “gamboges” disorder 

occurs where latex seeps into the flesh (aril), 

turning it yellow and giving it a bitter taste. 

“Gamboges” also moves onto the outer surface 

of the fruit. This is a preharvest disorder of 

unknown cause that makes it difficult to separate 

the aril from the surrounding tissue, even in ripe 

fruit; it causes hardening of the pericarp. This 

should not be confused with impact injury that 

leads to hardening of the pericarp at the point 

of impact and aril collapse, dehydration, pink 

color development, or browning (Tongdee and 

Suwanagul 1989). A drop of 10 cm can cause 

slight pericarp damage, indicated as hardening 

at the point of impact within 24 h. Higher drops 

causing significantly greater damage often lead to 

downgrading of the fruit (Tongdee and Suwanagul 

1989, Ketsa and Atantee 1998).

Another disorder of mangosteen fruit is 

translucent aril (nue-kaew), believed to be 

induced by heavy rain during fruit growth 

and development, even if just before harvest 

(Laywisakul 1994). The specific gravity of fruit 

with translucent aril is >1.0, while that of normal 

aril is <1.0. This allows separation of fruit by 

floating them in water (Podee 1998). Fruit with 

translucent aril have lower SSC and TA than 

normal fruit (Pankasemsuk et al. 1996).

Postharvest Pathology

Botryodiplodia theobromae, Diplodia spp., 

Pestalotia flagisettula, Phomopsis spp., and 

Rhizopus spp. have been reported; they harden the 

skin and decay the aril.

Quarantine Issues

Mangosteen is a fruit fly host. Irradiation at 

300 grays has potential for disinfestation. 

Alternatively, harvested fruit are carefully cut 

open and the aril inspected; fruit are then frozen 

whole and shipped.
414

Suitability as Fresh-Cut Product

Some potential exists.

References

Augustin, M.A., and M.N. Azudin. 1986. Storage 

of mangosteen (Garcinia mangostana, L.). 

ASEAN Food J. 2:78-80.

Choehom, R. 1997. Effect of waxing and plant 

growth regulators on quality and storage-life 

of mangosteen (Garcinia mangostana L.) fruit 

during cold storage. Graduate Special Problem, 

Department of Horticulture, Kasetsart University, 

Bangkok, Thailand. 

Daryono, M., and S. Sabari. 1986. The practical 

method of harvest time on mangosteen fruit and 

its characteristics in storage. Bull. Penelitian Hort. 

Indonesia 14(2):38-44.

Ketsa, S., and S. Atantee. 1998. Phenolics, lignin, 

peroxidase activity and increased firmness of 

damaged pericarp of mangosteen fruit after 

impact. Postharv. Biol. Technol. 14:117-124.

Laywisakul, S. 1994. Factors Influencing 

the Development of Translucent Disorder in 

Mangosteen. M.S. thesis, Kasetsart University, 

Bangkok, Thailand. 

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Noichinda, S. 1992. Effect of Modified 

Atmosphere on Quality and Storage-Life of 

Mangosteen (Garcinia mangostana L.) Fruit. M.S. 

thesis, Kasetsart University, Bangkok, Thailand. 

Pankasemsuk, T., J.O. Garner Jr., F.B. Matta, 

and J.L. Silver. 1996. Translucent flesh disorder 

of mangosteen fruit (Garcinia mangostana L.). 

HortScience 31:112-113.

Pantastico, E.B., ed. 1975. Postharvest Physiology, 

Handling and Utilization of Tropical and 

Subtropical Fruits and Vegetables. AVI, Westport, 

CT.

Podee, R. 1998. Nondestructive Methods for 

Separation of Translucent Pulp in Mangosteen 

by Specific Gravity and X-Ray Computed 

Tomography. M.S. thesis, Chiang Mai University, 

Chiang Mai, Thailand. 

Rattanachinnakorn, B., J. Phumhiran, and S.S. 

Nanthachai. 1996. Controlled atmosphere storage 

of mangosteen. In Annual Technical Conference 

and Proceedings of the Horticulture Research 

Institute, Department of Agriculture, Bangkok, 

Thailand. 

Tongdee, S.C., and A. Suwanagul. 1989. 

Postharvest mechanical damage in mangosteen. 

ASEAN Food J. 4:151-155.

Uthairatanakij, A., and S. Ketsa. 1995. Physicochemical changes of pericarp of mangosteen 

fruits after low temperature storage. In S. 

Vijaysegaran, M. Pauziah, M.S. Mohamed, and 

S. Ahmad Tarmizi, eds., Proceedings of the 

International Conference on Tropical Fruits, vol. 

1, pp. 411-422. Malaysian Agricultural Research 

and Development Institute, Serdang, Salangor, 

Maylasia.

Yahia, E.M. 1998. Modified and controlled 

atmospheres for tropical fruits. Hort. Rev. 22:123-

183.
415

Mushroom

Franciszek Adamicki

Adamicki is with the Department of Vegetable 

Storage, Research Institute of Vegetable Crops, 

Skiemiewice, Poland.

Scientific Name and Introduction

Mushrooms (Agaricus bisporus (Lange) Sing.)

(button mushrooms) are cultivated worldwide. 

Highest production is in the United States, China, 

France, Holland, United Kingdom, and Poland. 

They are eaten fresh in salads or as a cooked 

vegetable. A large volume is canned. 

Quality Characteristics and Criteria

Quality is based on maturity, size, trimming, 

freedom from open veils, disease, spots, insect 

injury and decay. A uniform, well-rounded cap 

with a smooth, glossy surface and fully intact veil 

indicate high quality. The cap should be white or 

dark brown. Lack of growth medium on caps and 

absence of browning or other discoloration are 

also quality factors. Visible open caps and absence 

of a stipe are negative factors. 

Horticultural Maturity Indices

Mushrooms are harvested by maturity, not by the 

size of the caps. Proper maturity is reached when 

the caps are well rounded and the partial veil is 

completely intact. The stipe should have a small 

length:thickness ratio and should be sufficient to 

permit some trimming without cutting caps.

Grades, Sizes, and Packaging

U.S. grades are No. 1 and No. 2. Sizes are Small 

(button), 1.9 to 3.2 cm (0.75 to 1.25 in); Medium, 

3.2 to 4.5 cm (1.25 to 1.8 in); and Large, 4.5 

cm (1.8 in), measured as cap diameter. Grades 

discriminate for maturity, shape uniformity, 

cleanliness, and trim quality. Mushrooms are 

packed in trays or cartons with a perforated 

polyethylene film overwrap (Suslow and Cantwell 

1998). 

Precooling Conditions

Mushrooms should be precooled to 2 to 4 C (32 

to 39 °F) immediately after harvest. Hydrocooling 

and forced-air cooling are often used. Freshly 

harvested mushrooms keep their quality longer 

throughout their shelf-life if immediately packed 

and vacuum-cooled and then transported at a low 

temperature. The same procedure is applied to cut 

mushrooms.

Optimum Storage Conditions

Mushrooms can be held for 7 to 9 days upon rapid 

cooling and storing at 0 to 1 °C (32 to 34 °F) 

with 95% RH. Storing at 2 °C (36 °F) shortens 

storage life to 3 to 5 days by accelerating surface 

browning, stipe elongation, and veil opening 

(Umiecka 1986). High RH is essential to prevent 

desiccation and loss of glossiness. Moisture 

loss is correlated with stipe blackening and veil 

opening. Mushrooms should be packed in cartons 

with a perforated overwrap of polyethylene film 

to reduce moisture loss. It is important to avoid 

water condensation inside packages. There are 

no chemical treatments to extend storage life of 

mushrooms intended for fresh consumption.

Controlled Atmosphere (CA) 

Considerations

Mushrooms derive a moderate benefit from 

storage under 3 to 21% O2

 and 5 to 15% CO2

(Saltveit 1997). A 3% O2

 and 10% CO2 CA 

extends storage life to 12 to 15 days at 0 C (32 

°F) (Suslow and Cantwell 1998). A 10 to 15% 

CO2

 CA reduces cap opening, browning, and stipe 

elongation. Mushroom quality was maintained 

in 8% O2

 and 10% CO2 (Zheng and Xi 1994). 

Storage under low O2

 and high CO2 inhibits 

cap opening and internal browning but causes 
416

yellowing of the cap surface. Levels of O2

 <1% 

can favor growth of Clostridium botulinum and 

the development of off odors and off flavors, as 

well as cap opening and stipe elongation. For this 

reason, CA is not commonly used (Carrier 1995). 

Retail Outlet Display Considerations

Mushrooms should be kept on refrigerated shelves 

at <4 °C (40 °F). Mushrooms absorb odors from 

green onions; they should not be transported or 

displayed together. 

Chilling Sensitivity

Mushrooms are not chilling sensitive, but they 

freeze below -0.6 °C (31 °F). Freezing injury 

appears as water-soaked and extremely soft caps 

(Suslow and Cantwell 1998). 

Ethylene Production and Sensitivity

Mushrooms produce very low amounts of 

ethylene: 0.1 L kg-1 h-1 at 20 °C (68 °F). Since 

ethylene causes browning of mushroom caps, they 

should be kept separate from ethylene-producing 

fruits and vegetables. 

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 28 to 44

5 °C 70

10 °C 97

20 °C 240 to 288

Data from Suslow and Cantwell (1998).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Low storage temperatures are needed to reduce 

continued development of mushrooms after 

harvest. Common disorders include upward 

bending of caps and opening of the veil. 

Mushrooms are easily bruised by rough handling 

and develop brown discolored tissue.

Postharvest Pathology

Disease is generally not an important source of 

postharvest loss in comparison with physiological 

senescence and improper handling or bruising. 

All diseased caps must be eliminated at harvest. 

Bacterial blotch or Pseudomonas spp. can become 

a problem during extended storage at elevated 

temperatures (Suslow and Cantwell 1998).

Quarantine Issues

None are known.

Suitability as Fresh-Cut Product

Fresh-cut mushrooms are becoming increasing 

popular at the wholesale and retail level.

References

Carrier Corporation. 1995. Controlled Atmosphere 

Handbook. A Guide for Shipment of Perishable 

Cargo in Refrigerated Containers. Carrier, 

Syracuse, NY.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

4, pp. 98-117. University of California, Davis, 

CA.
417

Salunkhe, D.K., and S.S. Kadam. 1998. Handbook 

of Vegetable Science and Technology. Marcel 

Dekker, New York, NY.

Suslow, T.V., and M. Cantwell. 1998. Mushroom. 

Recommendations for Maintaining Postharvest 

Quality. At http://postharvest.ucdavis.edu/

produce_information.

Umiecka, L. 1986. Effect of the material quality, 

treatment, package methods, and storage 

conditions on export quality of several mushroom 

races. Biul. Warzywniczy 29:271-292.

Zheng, Y.H., and Y.F. Xi. 1994. Preliminary study 

on colour fixation and controlled atmosphere 

storage of fresh mushrooms. J. Zbej. Agr. Univ. 

20:165-168.
418

Nectarine

Carlos H. Crisosto and Adel A. Kader

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA. Kader was 

with the Department of Plant Sciences, University 

of California, Davis, CA. He is deceased.

Scientific Name and Introduction

Nectarine (Prunus persica var. nectarina) has 

been described for nearly as long as the peach, but 

its origin is unknown. Because nectarine may have 

arisen from peach seeds, most peach-growing 

areas worldwide have also introduced nectarine 

cultivars.

U.S. Grades for nectarines are U.S. Fancy, U.S. 

Extra No. 1, U.S. No. 1, U.S. No. 2, and Reserved 

and can be found at the USDA, AMS website 

entitled “United States Standards for Grades of 

Nectarine” at http://www.ams.usda.gov/AMSv1.0/

getfile?dDocName=STELPRDC5050395.

California is a major producer and shipper of 

nectarines in the United States. Current shipments 

of fresh nectarines have approached 20 million 10-

kg (22-lb) packages. More than 130 cultivars are 

raised commercially. In recent years, an important 

development has been the breeding of white-flesh 

nectarine cultivars. In the San Joaquin Valley, 

harvest of early cultivars starts in mid May, and 

harvest of late cultivars of nectarines is completed 

in mid September. Nectarines are exported mainly 

to Canada, Taiwan, Hong Kong, Mexico, and 

Brazil.

Quality Characteristics and Criteria

Greater consumer acceptance is attained for fruit 

with high SSC. TA and SSC:TA are also important 

in consumer acceptance. In general, nectarines 

have more TA than peaches. No minimum 

flavor-quality standard has been established for 

nectarines. Fruit with 9 to 13.5 N (2 to 3 lb-force) 

of flesh firmness are considered ready to eat. 

Fruit with <27 N (6 lb-force) firmness are highly 

accepted by consumers.

Horticultural Maturity Indices

In California, harvest date is determined by skin 

ground color, which changes from green to yellow 

in most cultivars. A color chip guide is used to 

determine maturity of each cultivar except whitefleshed cultivars. A two-tier maturity system is 

used in California: (1) U.S. Mature (minimum 

maturity); and (2) Well-Mature or Tree Ripe. WellMature and Tree Ripe have the same definition 

according to the California Department Food and 

Agriculture Division of Inspection Services.

Measurement of fruit firmness is recommended for 

cultivars in which skin ground color is masked by 

full red color development before maturation. In 

these, a maximum maturity index can be applied. 

Maximum maturity is defined as the minimum 

flesh firmness (measured with a penetrometer 

with an 8-mm tip) at which fruit can be handled 

without bruising. Bruising susceptibility varies 

among nectarine cultivars.

Grades, Sizes, and Packaging

Fruit should be hand-picked into bags, baskets, 

or totes and then dumped into bins on trailers 

between tree rows in the orchard. If fruit are 

picked into totes, the totes are usually placed 

directly inside bins.

Nectarines should be transported from the 

orchard to a packinghouse and cooled as soon as 

possible after harvest. At the packinghouse, fruit 

are dumped (mostly using dry bin dumps) and 

cleaned. Sorting is done to eliminate fruit with 

visual defects and sometimes to divert fruit of 

high surface color to a high-quality pack. Sizing 

segregates fruit by either weight or dimension. 

Most of the yellow-flesh nectarines are packed 

into 2-layer (tray) boxes. Small yellow-flesh 

nectarines are generally volume-fill packed. Most 
419

of the white-flesh and “tree ripe” nectarines are 

packed into 1-layer (tray) boxes.

Limited volumes of partially-ripe to ripe 

nectarines are “ranch packed” at the point of 

production. In a typical “tree ripe” operation, fruit 

are picked into buckets or totes that are carried by 

trailer to the packing area. Packers work directly 

from buckets to select, grade, size, and pack fruit 

into plastic trays.

Optimum Storage Conditions

Fruit can be cooled in field bins using forced-air 

cooling or hydrocooling. Forced-air cooling in 

side-vented bins can be done by the tunnel or the 

serpentine method. Hydrocooling is normally 

done by a conveyor type hydrocooler or in place.

Fruit in field bins can be cooled to intermediate 

temperatures of 5 to 10 °C (41 to 50 °F) provided 

they are packed the next day. If packing is to 

be delayed beyond the next day, fruit should be 

thoroughly cooled in bins to near 0 °C (32 °F). 

With cultivars susceptible to internal browning, 

fast cooling (within 8 h) and maintaining fruit 

temperature near 0 °C (32 °F) are recommended. 

Nectarines in packed containers should be cooled 

to near 0 °C (32 °F). Even nectarines that were 

thoroughly cooled in bins will warm substantially 

during packing and should be thoroughly recooled 

using forced-air cooling after packing. 

Stone-fruit storage and long-distance shipments 

should be at or below 0 °C (32 °F). Maintaining 

these low temperatures requires knowledge of the 

freezing point of the fruit and of the temperature 

fluctuations in storage and transport systems. 

Temperature during truck transportation within 

the United States, Canada, and Mexico should 

be <2 °C (36 °F). Holding stone fruits at these 

low temperatures minimizes losses to rotting 

organisms, excessive softening, and water losses, 

as well as reducing severity of internal browning 

in susceptible cultivars.

Optimum Temperature

The optimum storage temperature is -1 to 0 °C (30 

to 32 °F). The freezing point varies, depending on 

SSC, from -3 to -1.5 °C (27 to 30 °F). A RH of 90 

to 95% with an air velocity of approximately 50 

ft3

 min-1 is suggested during storage. 

Controlled Atmosphere (CA) 

Considerations

The major benefits of CA (1 to 2% O2 and 3 to 5% 

CO2

) during storage and shipment are retention 

of fruit firmness, stability of color, and limiting of 

internal browning. CA of 10% O2

 and 10% CO2

is sometimes used to reduce internal breakdown 

during storage and shipment. CA with O2

 <1% 

and CO2

 >20% should be avoided because 

of associated development of off flavors and 

browning.

Retail Outlet Display Considerations

If firmness is <27 N (6 lb-force), nectarines should 

be displayed on a cold table. If firmness is >27 

N (6 lb-force), fruit should be displayed on a dry 

table.

Chilling Sensitivity

Some of the mid- and late-season cultivars 

are susceptible to chilling injury or internal 

breakdown. Chilling injury symptoms develop 

faster and more intensely when fruit are stored 

between about 2 and 8 °C (36 and 46 °F) than in 

those stored at 0 °C (32 °F) or below. Recently 

released mid- and late-season cultivars have low 

susceptibility to internal browning.
420

Ethylene Production and Sensitivity

In the following table, the lower end of the range 

is for mature but unripe fruit; higher values are for 

ripe fruit:

Temperature μL C2H4 kg-1 h-1

0 oC 0.01 to 5

5 oC 0.02 to 10

10 oC 0.05 to 50

20 oC 0.10 to 160

In general, nectarines harvested at the “wellmature” or riper stages will ripen properly without 

exogenous ethylene application. In some cultivars, 

exposure to 100 μL L-1 ethylene results in more 

uniform ripening of nectarines picked at the “U.S. 

mature” stage.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 4 to 6

10 °C 16 to 24

20 °C 64 to 110

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Internal breakdown (IB), or chilling injury, is a 

physiological problem characterized by internal 

flesh browning, flesh mealiness or leatheriness, 

flesh bleeding, failure to ripen, and flavor loss. 

In most cases, the red color development inside 

the flesh (bleeding) is not an IB symptom, and it 

does not affect taste. These symptoms develop 

during ripening after a cold-storage period, and 

thus are usually detected by consumers. However, 

there is large variability in susceptibility to IB 

among cultivars. In general, nectarines are less 

susceptible to IB than peaches. In susceptible 

cultivars, IB symptoms develop faster and more 

intensely when fruit are stored at temperatures 

between about 2 and 8 °C (36 and 46 °F) than 

when stored at 0 °C (32 °F) or below. At the 

shipping point, fruit should therefore be cooled 

and held near or below 0 °C (32 °F) if possible. 

During transportation if IB-susceptible cultivars 

are exposed to approximately 5 °C (41 °F), it 

can significantly reduce their postharvest life. 

Several treatments to delay and limit development 

of this disorder have been tested. Among them, 

preripening fruit before storage is a successful 

commercially used treatment in the United States. 

Success of CA (10% CO2 and 10% O2

) depends on 

cultivar, market life, and shipping time.

Inking (black staining) is a cosmetic problem 

affecting only the skin of nectarines. It is 

characterized by black or brown spots or stripes. 

These symptoms appear generally 24 to 48 h after 

harvest. Inking is a result of abrasion damage 

in combination with contamination by heavy 

metals (iron, copper, and aluminum). This usually 

occurs during harvesting and hauling, though it 

may occur during postharvest handling. Careful 

fruit handling, short hauling, avoiding any foliar 

nutrient sprays within 15 days before harvest, and 

following suggested preharvest fungicide spray 

guidelines are recommended to reduce inking.

Postharvest Pathology

Brown rot is caused by Monilinia fructicola and 

is the most important postharvest disease of 

stone fruits. Infection begins during flowering 

and fruit rot may occur before harvest but often 

appears postharvest. Orchard sanitation to 

minimize infection sources, preharvest fungicide 

application, and prompt cooling after harvest are 

among the control strategies. Also, postharvest 

fungicide treatment may be used. 

Gray mold is caused by Botrytis cinerea and can 

be serious during wet spring weather. It can occur 

during storage if the fruit has been contaminated 

through harvest and handling wounds. Avoiding 

mechanical injuries and good temperature 

management are effective control measures. 
421

Rhizopus rot is caused by Rhizopus stolonifer and 

can occur in ripe or near-ripe fruit at 20 to 25 °C 

(68 to 77 °F). Cooling fruit and keeping them at 

<5 °C (41 °F) is effective against this fungus.

Quarantine Issues

Because some insects such as Conotracherlus 

nenuphar (plum curculio), Cydia pomonella

(codling moth), Rhagoletis pommonella (apple 

maggot), and Tetranychus pacificus (Pacific spider 

mite) are not present in some import markets, 

phytosanitary restrictions have been established. 

Issues with exotic pest quarantine, addressing 

imported and exported nectarines, can change 

rapidly. APHIS issues rules regarding import 

requirements and provide information to assist 

exporters in targeting markets and defining what 

entry requirements a particular country might have 

for nectarines. APHIS, in cooperation with the 

State plant boards, developed a database called 

“Excerpt” to track phytosanitary requirements 

for each country. APHIS provides phytosanitary 

inspections and certifications that declare 

nectarines free of pests to facilitate compliance 

with foreign regulatory requirements.

For nectarines, there are three main ways to deal 

with these phytosanitary requirements: inspection 

prior to shipment (including use of screened crates 

transported in sealed containers), methyl bromide 

fumigation, and a systems approach.

A phytosanitary certificate is required to import 

California nectarines into Taiwan. Nectarines must 

be free of Anarsia ineatella (peach twig borer), 

Conotracherlus nenuphar (plum curculio), Cydia 

pomonella (codling moth), Erwinia amylovora

(fire bright), Rhagoletis pomonella (apple 

maggot), Tetranychus pacificus (Pacific spider 

mite), and Ceratitis capitata (Mediterranean fruit 

fly). If these conditions cannot be met, then fruit 

must be treated with an appropriate treatment 

prior to shipment. Details of the treatment must be 

recorded on the phytosanitary certificate.

Suitability as Fresh-Cut Product

The optimal ripeness for preparing fresh-cut 

nectarines slices is the partially ripe (>27 to 49 

N, >6 to 11 lb-force) or ripe (>13 to 27 N, >3 to 6 

lb-force) flesh firmness stages. These slices can be 

kept at 0 °C (32 °F) with 90 to 95% RH for 2 to 

12 days, depending on cultivar and ripeness, while 

retaining good eating quality. 

Special Considerations

Because nectarines are a climacteric fruit, they are 

harvested at a minimum or higher maturity but 

are not fully ripe; that is, they are not ready to eat. 

Nectarines must be ripened before consumption to 

satisfy consumers.

Acknowledgments

Some of the information in this chapter is from the 

University of California, Davis, website “Produce 

Facts” at http://postharvest.ucdavis.edu/produce_

information.

Further Reading

Ceponis, M.J., R.A. Cappellini, J.M. Wells, and 

G.W. Lightner. 1987. Disorders in plum, peach 

and nectarine shipments to the New York market, 

1972-1985. Plant Dis. 71:947-952.

Crisosto, C.H. 1994. Stone fruit maturity indices: 

a descriptive review. Postharv. News Info.

5(6):65N-68N.

Crisosto, C.H., F.G. Mitchell, and S. Johnson. 

1995. Factors in fresh market stone fruit quality. 

Postharv. News Info. 6(2):17N-21N.

Crisosto, C.H., F.G. Mitchell, and Z. Ju. 1999. 

Susceptibility to chilling injury of peach, 

nectarine, and plum cultivars grown in California. 

HortScience 34:1116-1118.
422

Kader, A.A., and F.G. Mitchell. 1989. Postharvest 

physiology. In J.H. LaRue and R.S. Johnson, 

eds., Peaches, Plums, Nectarines: Growing and 

Handling for Fresh Market, pp. 154-164. Pub. no. 

3331, University of California, Davis, CA.

Gorny, J.R., B. Hess-Pierce, and A.A. Kader. 

1998. Effect of fruit ripeness and storage 

temperature on the deterioration rate of fresh-cut 

peach and nectarine slices. HortScience 33:110-

113.

Gorny, J.R., B. Hess-Pierce, and A.A. Kader. 

1999. Quality changes in fresh-cut peach and 

nectarine slices as affected by cultivar, storage 

atmosphere and chemical treatments. J. Food Sci. 

64:429-432.

Lurie, S. 1992. Controlled atmosphere storage to 

decrease physiological disorders in nectarines. 

Intl. J. Food Technol. 27:507-415.

Lill, R.E., E.M. O’Donoghue, and G.A. King. 

1989. Postharvest physiology of peaches and 

nectarines. Hort. Rev. 11:413-452.
423

Netted Melon

Krista C. Shellie and Gene Lester

Shellie and Lester are formerly with the Kika de la 

Garza Subtropical Agricultural Research Center, 

Agricultural Research Service, U.S. Department 

of Agriculture, Weslaco, TX. Shellie is now with 

the Horticultural Crops Research Laboratory, 

Agricultural Research Service, U.S. Department 

of Agriculture, Parma, ID; Lester is now with 

the Office of National Programs, Agricultural 

Research Service, U.S. Department of Agriculture, 

Beltsville, MD. 

Scientific Name and Introduction

Cucumis melo L. (Reticulatus group), commonly 

called cantaloupe or muskmelon, is a member 

of the Cucurbitaceae family (Bailey et al. 1976). 

True cantaloupes, members of the Cantaloupensis 

group, are nonnetted fruit common to Cantaluppi, 

Italy, and are seldom grown in the United States. 

Western Shipper melons (grown in Arizona, 

California, and Texas) are grown principally 

for domestic and export markets, while Eastern 

Choice melons (grown in the eastern United 

States) are more perishable and are used 

principally for local consumption. A heavy, 

uniform, tan-colored net and bright orange flesh 

characterizes the external appearance of Western 

Shipper and Eastern Choice melons. Eastern 

Choice melons are often deeply sutured, while 

Western Shipper melons usually lack sutures. 

Charentais, galia, ananas, and Persian melons 

are not commonly grown in the United States, 

but are gaining popularity as specialty melons. 

The French Charentais is a round, sparsely netted 

melon with a grey-green rind having pronounced 

dark-green longitudinal tracts; it has a sweet, 

highly-scented, orange flesh. Galia melons from 

Israel are characterized by a fine, uniform net, 

round shape, and green flesh (Karchi and Govers 

1977). Ananas melons have a sparse, cracked net 

and white, very sweet flesh. The shape and netting 

of Persian melons are similar to those of Western 

Shipper type melons, but Persian melons are 

larger, about 6 lb (2.7 kg) each, and have a bright, 

orange-pink flesh. 

Quality Characteristics and Criteria

To meet U.S. grade standards, melons must 

have sufficient maturity to ensure completion of 

ripening, sufficient firmness (not soft or wilted), 

shape and netting characteristic for their type, 

a stem scar not wet and slippery (wet slip), no 

sunscald (solar injury), flesh and rind free of 

decay by fungi or bacteria, and absence of damage 

(USDA 1981). Damage includes liquid in the seed 

cavity, hail injury, surface mold, aphid honeydew, 

scars, cracks, ground spot rind disorders, bruises, 

and mechanical damage. A minimum SSC of 11% 

and 9% is required for U.S. grades Fancy and U.S. 

No. 1, respectively. State market-order quality 

standards may exceed Federal grade requirements.

Horticultural Maturity Indices

Stem separation and background rind color are 

used to indicate acceptable maturity for harvest. 

As netted melons begin to ripen, a separation 

layer, or abscission zone, develops at the point 

where the stem attaches to the fruit. Most netted 

melons are commercially harvested when half of 

the stem has separated from the melon (referred 

to as half-slip) (Kasmire et al. 1970). Abscission 

zone development often corresponds to a change 

from green to yellow in rind background color. 

If picked at proper maturity, netted melons will 

continue to soften and become more aromatic after 

harvest (Shellie 1995, Ayub et al. 1996). Netted 

melons harvested prematurely by cutting the 

stem prior to abscission-zone development may 

produce little aroma, have low SSC, and do not 

properly ripen (Lyons et al. 1962).

Grades, Sizes, and Packaging

U.S. Grades for cantaloupes (USDA 1981) include 

U.S. Fancy, U.S. No. 1, U.S. Commercial, and 

U.S. No. 2. The difference among grades reflects 

levels of tolerance for quality criteria. A minimum 
424

SSC of 11% is required for U.S. Fancy and 9% 

for U.S. No 1. There are six common size classes 

(9, 12, 15, 18, 23, and 30) based on the number 

of fruit of uniform size and weight that fit into a 

standard 40-lb (18-kg) cardboard shipping box.

Precooling Conditions

Precooling to a fruit center temperature of 10 

to 15 °C (50 to 59 °F) soon after harvest is 

recommended to delay ripening and retain sugar 

content. Hydrocooling, forced-air cooling, and 

top-icing are acceptable, but hydrocooling is most 

efficient (Kader 1992). 

Optimum Storage Conditions

Optimum is 2 to 7 °C (36 to 45 °F) with 95% RH 

(Saltveit 1997). The expected shelf-life at these 

recommended conditions is 10 to 14 days. 

Controlled Atmosphere (CA) 

Considerations

CA in transit or storage has some potential for 

extending shelf-life. The recommended level of O2

is 3 to 5% for reducing respiration and ethylene 

production. The recommended level of CO2

 is 10 

to 20% for reducing loss of sugar and inhibiting 

surface mold. Storage in an atmosphere containing 

>10% CO2

 may result in a carbonated taste that is 

lost during subsequent storage in air. Off flavors, 

odors, and impaired ripening may develop if 

netted melons are stored in <1% O2

 or >20% CO2

(Kader 1992, Saltveit 1997).

Retail Outlet Display Considerations

The shelf-life of netted melons can be maximized 

by storage under refrigeration and by avoiding 

postharvest exposure to ethylene.

Chilling Sensitivity

Sensitivity decreases as fruit mature. Full-slip, 

netted melons may be stored for 5 to 14 days at 

0 to 2 °C (32 to 36 °F). Less mature melons may 

be damaged by storage at <2 °C (36 °F). Injury 

symptoms include pitting, surface decay, and 

failure to ripen (Wang 1990).

Ethylene Production and Sensitivity

Netted melons are climacteric fruit that produce 

10 to 100 μL kg-1 h-1 ethylene (Kader 1992) from 4 

days prior to stem separation to as late as 10 days 

after harvest (Shellie and Saltveit 1993, Shellie 

1995). Postharvest exposure to ethylene reduces 

shelf-life and should be avoided. Exogenous 

ethylene application after harvest will not ripen 

netted melons harvested prematurely, nor will it 

prevent normal postharvest decline in SSC. 

Respiration Rates

Netted melons have a moderate rate of respiration 

(Kader 1992).

Temperature mg CO2 kg-1 h-1

0 °C 5 to 6

4 to 5 °C 9 to 10

10 °C 14 to 16

15 to 16 °C 34 to 39

20 to 21 °C 45 to 65

25 to 27 °C 62 to 71

Data from Sholz et al. (1963).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Solar injury causes patchy ground color, or 

“bronzing,” and net discoloration. Severely injured 

tissue becomes sunken or wrinkled (Snowdon 
425

1992). Vein track browning, a darkening of the 

longitudinal tracts between netted areas, is caused 

by exposure to sun or high temperature at harvest 

(Snowdon 1992). Netted melons are easily injured 

and should never be dropped more than 60 cm 

(2 ft). Harvest and packing equipment should be 

padded to reduce scuffing of netting (Ryall and 

Lipton 1979). Avoidance of wounding during 

handling (compression, bruising, or scuffing) and 

storage under recommended conditions provides 

protection against physical injury and decay. 

Postharvest Pathology

Fusarium rot is the most common disease 

(Zitter et al. 1996). Symptoms vary depending 

on Fusarium species, but large fissures and an 

enlarged or thickened, dark-tan net at the lesion 

site is common. A distinct delineation is apparent 

between diseased and healthy tissue. There is 

often no sign of infection before harvest, but 

numerous spongy white lesions may develop 

internally postharvest. Fungicide application in 

a hot-water dip, 1 min at 57 °C (135 °F), can 

suppress fusarium fruit rot. Other less common 

diseases include black rot incited by Didymella 

bryoniae or Phomopsis cucurbitae, rhizopus soft 

rot (Rhizopus stolonifer), bacterial brown spot 

(Erwinia ananas), bacterial soft rot (Erwinia 

carotovora), and alternaria rot (Alternaria 

alternata).

Quarantine Issues

Melons entering the United States must be 

disinfested of external feeders (noctuid moths, 

thrips, and Copitarsia species) by fumigation 

with methyl bromide (APHIS 1998). Methyl 

bromide was identified in 1987 as having an 

ozone-depleting potential of 0.4 and is scheduled 

for global phase-out under the Montreal Protocol. 

Title VII of the U.S. Clean Air Act required 

phasing out production and importation of 

substances with ozone-depleting potentials of 0.2 

or greater. Use of methyl bromide for preshipment 

and quarantine is exempt from these restrictions, 

but limited supply and increased costs may make 

methyl bromide undesirable in the near future.

Suitability as Fresh-Cut Product

Harvest maturity, cultivar, growing location, 

cultural practices, and postharvest handling 

influence quality of the processed product. Netted 

melons destined for fresh-cut sale should be 

harvested at the earliest maturity acceptable for 

minimum sugar content and proper ripening and 

be precooled immediately after harvest. Firm 

cultivars should be selected that have a high sugar 

content, bright orange flesh, and small cavity—

that is, a high piece yield. Melons should be rinsed 

in 200 μL L-1 of 5.25% NaOCl at 5 °C (41 °F) 

at pH 6.5 to 7.0 for 5 min. The whole melon is 

cut into cubed pieces with sharp blades. Pieces 

should then be rinsed with 150 μL L-1 of the above 

chloride solution at 5 °C (41 °F) for 30 sec prior 

to packaging. A shelf-life of 6 to 10 days can be 

expected for orange-fleshed melon cubes stored 

at 0 to 5 °C (32 to 41 °F). A modified atmosphere 

of 8 to 10% CO2

 in air is beneficial for retarding 

microbial growth, as well as slowing softening 

and other quality changes.

Special Considerations

Use of liners in cardboard shipping boxes may 

reduce fruit moisture loss and extend storage life 

(Lester and Bruton 1986). 

References

APHIS [USDA Animal and Plant Health 

Inspection Service]. 1998. T101-o-2 MB Methyl 

bromide fumigation of melons for external 

feeders. In Treatment Manual, http://www.hsdl.

org/?view&did=28976, U.S. Department of 

Agriculture, Animal and Plant Health Inspection 

Service, Plant Protection and Quarantine, 

Hyattsville, MD.
426

Ayub, R., M. Guis, M. Ben Amor, et al. 1996. 

Expression of ACC oxidase antisense gene 

inhibits ripening of cantaloupe melon fruits. Nat. 

Biotech. 14:862-866.

Bailey, L.H., and E.Z. Bailey. 1976. Hortus Third. 

Macmillan, New York, NY.

Kader, A.A., ed. 1992. Postharvest Technology of 

Horticultural Crops, 2nd ed., p. 192. DANR Pub. 

no. 3311, University of California, Oakland, CA.

Karchi, Z., and A. Govers. 1977. Galia melon—a 

new F1

 hybrid for export and the local market. 

Hassadeh 57:630-634 (In Hebrew; English 

Summary).

Kasmire, R.F., L. Rappaport, and D. May. 1970. 

Effects of 2-chloroethylphosphonic acid on 

ripening of cantaloupes. J. Amer. Soc. Hort. Sci. 

95:134-137.

Lester, G.E., and B.D. Bruton. 1986. Relationship 

of netted muskmelon fruit water loss to 

postharvest storage-life. J. Amer. Soc. Hot. Sci. 

111:727-731.

Lyons, J.M., W.B. McGlasson, and H.K Pratt. 

1962. Ethylene production, respiration, and 

internal gas concentrations in cantaloupe fruits at 

various stages of maturity. Plant Physiol. 37:31-

36.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, vol. 1. AVI Pub. Co., Westport CT.

Saltveit, M.E. 1997. A summary of CA and MA 

requirement and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

4, pp. 98-117. University of California, Davis CA.

Shellie, K.C. 1995. Enhancing ripening 

characteristics of ‘Netted, Orange-flesh’ and 

‘Smooth, Green-flesh’ type melons (Cucumis 

melo L.). In G.E. Lester and J.R. Dunlap, eds., 

Cucurbitacae ’94: Evaluation and Enhancement 

of Cucurbit Germplasm, pp. 101-103. Gateway 

Printing, Edinburg, TX.

Shellie, K.C., and M.E. Saltveit. 1993. The lack of 

a respiratory rise in muskmelon fruit ripening on 

the plant challenges the definition of climacteric 

behaviour. J. Exp. Bot. 44:1403-1406.

Scholz, E.W., H.B. Johnson, and W.R. Buford. 

1963. Heat evolution rates of some Texas-grown 

fruits and vegetables. J. Rio Grande Valley Hort. 

Soc. 17:170-175.

Snowdon, A. 1992. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables. 

CRC Press, Boca Raton FL.

USDA [U.S. Department of Agriculture]. 

1981. United States Standards for Grades of 

Cantaloupes. U.S. Department of Agriculture, 

Washington, DC.

Wang, C.Y. 1990. Chilling Injury of Horticultural 

Crops. CRC Press, Boca Raton FL.

Zitter, T.A, D.L. Hopkins, and C.E. Thomas. 1996. 

Compendium of Cucurbit Diseases. American 

Phytopathological Society, St. Paul MN.
427

Nopalitos

Marita Cantwell

Cantwell is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Cactus stems (“nopalitos” in Spanish) are the 

rapidly growing succulent stems (cladodes) of 

the prickly pear cactus (Opuntia spp.). They are 

a warm-season vegetable but are available yearround, being grown in California as a specialty 

vegetable or imported from Mexico where they 

are a traditional vegetable. Though the young 

stems of many Opuntia species can be eaten, most 

commercial plantings of nopalitos are from O. 

ficus-indica and O. inermis. Nopalitos are mostly 

water (92%) and carbohydrates, as well as fiber 

(4 to 6%), and a little protein (1 to 2%). They also 

contain some minerals, principally calcium (1%), 

and moderate amounts of vitamin C and vitamin 

A. They are similar in composition to dark-green 

leaf lettuces (Rodríguez-Felix and Cantwell 1988). 

Quality Characteristics and Criteria

Good-quality nopalitos are fresh, turgid, and 

a brilliant green color. In the early stages of 

growth, vestigial true leaves, usually subtended by 

spines, are present on the stems. The leaves often 

abscise by the time nopalitos reach commercial 

size; however, green true leaves on the stem are 

an additional indication of freshness. Nopalitos 

should be harvested when young and tender, but 

not early in the morning so as to avoid a high acid 

content (see Special Considerations).

Horticultural Maturity Indices

Nopalitos are harvested based on size and can be 

Small (<10 cm [4 in] long) or Medium (<20 cm 

[8 in] long). Medium weigh about 100 g (0.2 lb). 

Overmature nopalitos are thick with lots of spongy 

white tissue and are acidic in flavor. 

Grades, Sizes, and Packaging

There are no grades. Nopalitos are packed 

according to size and quality. The fruit are 

typically loose-packed in 4.5- to 9.0-kg (10- or 

20-lb) cartons or boxes. 

Precooling conditions

Nopalitos should be cooled to about 5 °C (41 °F) 

to reduce loss of visual appearance (shiny surface) 

that results from water loss. They are usually 

room-cooled, but also may be forced-air cooled. 

Hydrocooling should be avoided as it favors 

discoloration in damaged areas (especially where 

spines have penetrated the surface) and decay. 

Optimum Storage Conditions

Good quality can be maintained for 3 weeks at 5 

°C (41 °F) and 2 weeks at 10 °C (50 °F) with 95 

to 99% RH (Cantwell et al. 1992). Major factors 

limiting storage life of nopalitos are decay and 

dehydration (Cantwell, 1995). Nopalitos stored 

under ambient conditions rapidly lose their 

brilliant shiny appearance, become dull green 

and may begin to yellow and curve inward due to 

water loss. Some discoloration (chilling injury) 

occurs if stored longer than 3 weeks at 5 °C (41 

°F) (Cantwell et al. 1992). 

Controlled Atmosphere (CA) 

Considerations

No information is available on the potential 

benefits of CA or MAP for nopalitos. For 

diced product, 5 to 10% CO2

 may be beneficial 

(Cantwell, 2002, unpublished). 

Retail Outlet Display Considerations

Nopalitos should be kept in a refrigerated display 

case to reduce water loss and curvature. They 

should not be sprinkled or top-iced. 
428

Chilling Sensitivity

Nopalitos are chilling sensitive when stored below 

10 °C (50 °F). Chilling damage may be manifested 

as a superficial bronzing or discoloration and 

increased susceptibility to decay. Symptoms may 

appear after 3 weeks at 5 °C (41 °F) (Cantwell et 

al. 1992) or sooner (Ramayo-Ramirez et al. 1978).

Ethylene Production and Sensitivity

Ethylene production rates are very low: 0.05, 0.1 

and 0.22 nL kg-1 h-1 at 5, 10 and 20 °C (41, 50, 

and 68 °F), respectively (Cantwell et al. 1992). 

Nopalitos are not sensitive to ethylene exposure, 

but exposure at warm temperatures will enhance 

yellowing. 

Respiration Rates

The following are average rates for 10-cm (4-in) 

nopalitos over a 7-day period at the indicated 

temperatures. Initial rates are about 50% higher. 

Respiration rates of 20-cm (8-in) stems are about 

50% lower than rates of 10-cm (4-in) stems. 

Temperature mg CO2 kg-1 h-1

5 °C 16 to 19

10 °C 38 to 42

15 °C 52 to 59

20 °C 68 to 79

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

See above section on Chilling Sensitivity.

Postharvest Pathology

Decay at the cut stem end may be a problem if 

nopalitos are stored for more than 2 weeks. Decay 

can be avoided by insuring that nopalitos are not 

damaged when cut from the plant. Fungicide dips 

reduce postharvest decay of nopalitos but are not 

used commercially (Ramayo-Ramírez et al. 1978). 

Quarantine Issues

None are known.

Suitability as Fresh-Cut Product

Some types of nopalitos are spiny, and therefore a 

cleaned and diced product is an attractive option. 

Reducing brown discoloration at cut surfaces 

and preventing fluid (mucilage) loss are the main 

problems in handling diced cactus stems. Cut 

nopalitos cannot be washed before marketing, 

because washing will cause mucilage to exude 

and enhance discoloration of cut surfaces. 

Notwithstanding the chilling sensitivity of intact 

nopalitos, they should be stored between 0 and 5 

°C (32 and 41 °F) (Cantwell, 2002, unpublished). 

Shelf-life of diced nopalitos was 1 day at 20 °C 

(68 °F) and 6 days at 5 °C (41 °F) (RodríguezFelix and Soto-Valdez 1992). Moderate CO2

 (5 to 

10%) CA may be useful to reduce discoloration 

and other visual defects of cut nopalitos (Cantwell, 

2002, unpublished). 

Special Considerations

Cactus stems should be harvested and handled 

with care to avoid mechanical damage, especially 

from spines on one stem penetrating the 

neighboring stem. Spine damage leads to a rustybrown discoloration and pathological problems

Because the prickly pear plant is a crassulacean 

acid metabolism (CAM) plant and fixes CO2

 at 

night as malic acid before converting it to sugars 

during the day, the acid content of nopalitos 

may fluctuate greatly and affect their flavor 
429

(Rodríguez-Felix and Cantwell 1988). Therefore, 

it is recommended that stems be harvested 2 to 3 

h after sunrise. Small nopalitos, however, are not 

CAM-active. Also, low temperature storage at 5 

°C (41 °F) maintains acid levels, while warmer 

storage conditions of 15 to 20 °C (59 to 68 °F) 

result in decreased acid (Cantwell et al. 1992). 

References

Cantwell, M. 1995. Postharvest management 

of fruits and vegetable stems. In G. Barbera, 

P. Inglese, and E. Pimienta-Barrios, eds., 

Agroecology, Cultivation and Uses of Cactus 

Pear, pp. 120-136. Plant Production and Protection 

Paper 132, United Nations, Food and Argiculture 

Organization, Rome, Italy.

Cantwell, M., A. Rodriguez-Felix, and F. RoblesContreras. 1992. Postharvest physiology of prickly 

pear cactus stems. Sci. Hort. 50:1-9.

Ramayo-Ramírez, L., C. Saucedo-Veloz, and S. 

Lakshminarayana. 1978. Prolongación de la vida 

de almacenamiento del nopal hortaliza (Opuntia 

inermis Coulter) por refrigeración. Chapingo, 

Nuevo Epoca 10:30-32. 

Rodríguez-Felix, A., and M. Cantwell. 1988. 

Developmental changes in composition and 

quality of prickly pear cactus cladodes (nopalitos). 

Plant Foods for Human Nutrition 38:83-93. 

Rodríguez-Felix, A., and H. Soto-Valdez. 1992. 

Quality changes of diced nopal during storage in 

polyethylene bags. In P. Felker, and J.R. Moss, 

eds., Proceedings of the 3rd Annual Texas Prickly 

Pear Conference, Kingsville, TX, pp. 22-25.
430

Okra

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, NC Research Campus, Kannapolis, 

NC.

Scientific Name and Introduction

Okra (Abelmoschus esculentus (L.) Moench, also 

known as Hibiscus esculentus L.) is a member of 

the mallow (Malvaceae) family and can be found 

as an annual (primarily in the United States) or as 

a perennial in India and Africa (Lamont 1999). In 

the United States, Mexico, and Japan, the young 

fruiting pods are the edible portion, while young 

leaves and mature seeds may be consumed in 

other countries (Duzyaman 1997). Other names 

include quingumbo, bhendi, bhindi, gumbo, 

gombo, quaio, and lady’s finger. 

In the United States, most fresh market okra is 

from California and the Southern United States 

and Mexico. ‘Clemson Spineless’ is the bestknown fresh market cultivar; while low-mucilage, 

low-fiber, high-chlorophyll types such as 

‘Emerald’ and ‘Louisiana Green Velvet’ are grown 

for processing. A few fresh-market hybrids—

‘Annie Oakley,’ ‘North and South,’ and ‘Cajun 

Delight’—are now available. 

Most okra cultivars produce green pods, but a 

few varieties produce yellow (‘Blondy’) or dark 

red (‘Burgundy’) pods. Usually, pods have 4 to 

10 distinct ribs or ridges (‘Emerald’ is completely 

round, with no ribs). Pods are prized for their 

unique flavor and high mucilaginous content 

(being used as a thickening agent).

Quality Characteristics and Criteria

High quality pods are 5 to 15 cm (2 to 6 in) long, 

flexible, bright-green, and turgid. Seeds should not 

be protruding through the epidermis, and ridges 

should be free of blackening and bruising.

Horticultural Maturity Indices

Okra pods are harvested when immature and high 

in mucilage but before becoming highly fibrous—

generally within 2 to 6 weeks after flowering 

(Ramaswamy and Rangana 1982).

Grades, Sizes, and Packaging

Okra is graded by size; absence of defects, decay, 

insects, and dirt; shape; and tenderness. Fancy 

pods are <9 cm (3.5 in); Choice are 9 to 11 cm 

(3.5 to 4.25 in); and Jumbo are >11 cm (4.25 in). 

Fresh okra is most commonly presented in 0.45-

kg (l-lb) clamshell boxes or as bulk weight or 

volume-filled 11.4-kg (25-lb) bins.

Precooling Conditions

Okra should be marketed within 36 h of harvest 

and shipped under refrigeration. Storage in 

unventilated containers without refrigeration can 

cause degradation of color. Some growers use 

hydrocooling or forced-air cooling. 

Optimum Storage Conditions

Okra pods lose weight readily and are chilling 

sensitive. Pods can be stored for 7 to 14 days at 7 

to 10 °C (45 to 50 °F) with >90% RH. 

Controlled Atmosphere (CA) 

Considerations

There is a slight benefit from storage at 7 to 12 

°C (45 to 54 °F) in 4 to 10% CO2

 (Saltveit 1997). 

Other combinations have also shown some benefit, 
431

including 5 to 10% CO2

 at 5 to 8 °C (41 to 46 °F) 

and 3 to 5% O2

 and 0% CO2 (Baxter and Waters 

1986). Levels of CO2

 >20% can cause off flavors.

Retail Outlet Display Conditions

Okra should be kept dry, refrigerated, and 

humidified.

Chilling Sensitivity

Okra pods are highly sensitive to chilling, 

especially very young (more mucilaginous) pods. 

As little as 2 days at 2 °C (36 °F) can cause 

chilling injury. Chilling injury shows up within 

24 h at 20 °C (68 °F) after pods have been held 7 

days at 2 or 5 °C (36 to 68 °F). Symptoms include 

presence of water-soaked areas, exuding lesions, 

and appearance of mold or mildew, especially if 

held at 5 °C (41 °F) (Perkins-Veazie and Collins 

1992). Green pods turn a brown-olive-green, 

yellow varieties turn brown, and burgundy 

varieties become a dull brown-red. 

Ethylene Production and Sensitivity

Okra produce small amounts of ethylene during 

storage: 0.5 μL kg-1 h-1 (Baxter and Waters 1986). 

Okra pods exposed to >1 μL L-1 ethylene for 3 or 

more days show yellowing (Perkins-Veazie, 2002, 

unpublished).

Respiration Rates

Temperature mg CO2 kg-1 h-1

2 to 3 °C 10 to 321

4 to 5 °C 211 to 55

10 °C 86 to 95

15 to 16 °C 138 to 153

20 to 21 °C 248 to 274

25 to 27 °C 328 to 362

1

Data from Perkins-Veazie (2002 unpublished) for 

‘Annie Oakley,’ ‘Blondy,’ and ‘Clemson Spineless 

80’ pods 4 to 12 cm (1.5 to 4.75 in) long; other 

data from Scholz et al. (1963).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Pods are susceptible to chilling injury, yellowing, 

shrivel from weight loss, and warty pods (nitrogen 

deficiency).

Postharvest Pathology

Cladosporium, gray mold (Botrytis cinerea),

mildew, yeasts, Rhizopus stolonifer, Rhizoctonia 

solani, and Psuedomonas pv syringae (Snowdon 

1992) can all be problematic in okra.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Suitability is unknown. Okra is generally 

consumed after cooking.

Special Considerations

The ridges on okra pods damage easily. Avoid 

storing okra with melons, onions, and potatoes, 

since pods will trap their odors and develop off 

flavors. 

References

Baxter, L., and L. Waters Jr. 1986. Controlled 

atmosphere effects on physical changes and 

ethylene evolution in harvested okra. HortScience 

25:92-95.
432

Duzyaman, E. 1997. Okra: botany and 

horticulture. Hort. Rev. 29:41-72.

Lamont, W. 1999. Okra—a versatile vegetable 

crop. HortTechnology 9:179-184.

Perkins-Veazie, P.M., and J.K. Collins. 1992. 

Cultivar, packaging, and storage temperature 

differences in postharvest shelf life of okra. 

HortTechnology 2:350-352.

Ramaswamy, H.S., and S. Rangana. 1982. 

Maturity parameters for okra (Hibiscus esculentus

(L) Moench var Posa Cawani). Can. Inst. Food 

Sci. Technol. J. 15(2):140-143.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., Proceedings 

of the 7th International Controlled Atmosphere 

Research Conference, vol. 4, pp. 98–117. 

University of California Postharvest Horticulture 

Series no. 18, University of California, Davis, CA.

Scholz, E.W., H.B. Johnson, and W.R. Buford. 

1963. Heat evolution rates of some Texas-grown 

fruits and vegetables. J. Rio Grande Valley Hort. 

Soc. 17:170-175.

Snowdon, A.L. 1992. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables, pp. 94-95. CRC Press, Boca 

Raton, FL.
433

Olive

Carlos H. Crisosto and Adel A. Kader

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA. Kader was 

with the Department of Plant Sciences, University 

of California, Davis, CA. He is deceased.

Scientific Name and Introduction

A member of the Oleaceae family (Olea europaea

L.), the olive is a small tree native to the eastern 

Mediterranean region. The ancient Egyptians, 

Greeks, Romans, and other Mediterranean nations 

cultivated olives for their oily drupes. The part 

used for consumption is the fleshy mesocarp, 

from which edible oil is extracted, or fruit may be 

pickled and the mesocarp and exocarp eaten.

Olives are a drupe, botanically similar to cherry 

and other stone fruits. It consists of carpel, and the 

wall of the ovary has both fleshy and dry portions. 

The skin (exocarp) is free of hairs and contains 

stomata. The flesh (mesocarp) is the tissue eaten, 

and the pit (endocarp) encloses the seed. Fruit 

shape, size and pit size, and surface morphology 

vary greatly among cultivars.

Quality Characteristics and Criteria

For green olives, criteria are color and freedom 

from mechanical damage, shriveling, surface 

blemishes, scale and other insect injury, and decay. 

These are processed according to California blackripe style or Spanish green style fermented olives. 

For black olives, criteria are color, freedom from 

defects, and oil content of 12 to 25% (depending 

on cultivar). These are processed (Greek or Italian 

style) or used for oil extraction.

Horticultural Maturity Indices

For green olives, size and color (even coloration 

of pale green with a minimum of whitish spots 

[lenticels] through a straw color) indicate when 

to harvest. An olive is considered mature if it 

exudes a characteristic white juice when squeezed. 

For black olives, skin color and removal force 

are used; fruit reach this stage 3 to 4 mo after the 

green stage.

Grades, Sizes, and Packaging

Harvesting of olives represents 50 to 70% of the 

total production labor cost and 30 to 40% of the 

gross returns from the crop. Harvested fruit begin 

to lose moisture immediately. When harvested 

during hot, sunny weather, olives should be put 

in the shade until hauled away. Sun-exposed 

fruit gets sunburn and will grade as culls. Rough 

handling causes bruises and grade reduction.

A few growers harvest their fruit mechanically, 

using tree shakers and catching frames. The use 

of mechanical harvesting is likely to increase in 

the future. Olives are harvested for pickling in 

California from mid September to mid November, 

depending on cultivar, local conditions, and needs 

of the canneries. Optimum harvesting time is 

determined by the color and texture of the olive. 

Overmature or badly bruised fruit frequently 

spoils during processing. To get the best return, 

fruit should be delivered to the cannery as soon as 

possible after harvest.

Optimum Storage Conditions

Olives should be stored at 5 to 7.5 °C (41 to 46 

°F) with 90 to 95% RH. Temperatures <5 °C 

(41oF) cause chilling injury of fresh olives.

Controlled Atmosphere (CA) 

Considerations

Optimum CA is 2 to 3% O2

 and 0 to 1% CO2, 

which delays senescence and softening for up to 

12 weeks at 5 °C (41 oF) and 9 weeks at 7.5 °C 

(46 °F). Atmospheres with <2% O2

 can cause off 

flavors, and CO2

 >5% may increase severity of 

chilling injury if olives are stored below 7.5 oC 
434

(46 oF). This information is for fresh green olives. 

Fresh black olives should be processed as soon 

after harvest as possible, but if necessary black 

olives can be kept in 2% O2

 at 5 °C (41 °F) for up 

to 4 weeks.

Chilling Sensitivity

Olives are sensitive to temperatures <5 °C (41 °F). 

Symptoms in ‘Ascolano,’ ‘Manzanillo,’ ‘Mission,’ 

and ‘Sevillano’ fruit are a slight, tannish to brown 

discoloration which develops in the flesh adjacent 

to the pit. Over time, the discoloration becomes 

more intense and progresses through the flesh 

into the skin, at which time the olive has the 

appearance of having been boiled.

Chilling injury becomes visible on olives stored 

for >2 weeks at 0 °C (32 °F), 5 weeks at 2 °C 

(35 °F), or 6 weeks at 3 °C (38 °F). The order 

of susceptibility to chilling injury, from most 

to least susceptible, is ‘Sevillano,’ ‘Ascolano,’ 

‘Manzanillo,’ and ‘Mission.’

Ethylene Production and Sensitivity

Green olives produce <0.1 μL kg-1 h-1 ethylene,

and black olives produce 0.5 μL kg-1 h-1 at 20 °C 

(68oF). Though olives produce very little ethylene, 

they are moderately sensitive to ethylene at 

concentrations >1 μL L-1, which causes a loss of 

green color and flesh firmness.

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 °C 10 to 20

7.5 °C 16 to 24

10 °C 24 to 32

20 °C 40 to 80

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Nailhead is characterized by surface pitting and 

spotting. It results from death and collapse of 

epidermal cells, creating air pockets underneath 

the skin. Symptoms are observed on olives kept 

at 10 °C (50 °F) for >6 weeks or at 7.5 °C (46 °F) 

for >12 weeks. CO2

 injury is evidenced by internal 

browning and increased incidence and severity of 

decay. It results from exposure to >5% CO2

 for 

more than 4 weeks.

Postharvest Pathology

Postharvest diseases occur if olives have been 

chilled at temperatures below 5 °C (41 °F), 

mechanically damaged, not cooled promptly after 

harvest to 5 to 7.5 °C (41 to 46 °F), or exposed to 

undesirable atmospheres (>5% CO2

 or <2% O2).

Quarantine Issues

Since olive fruit fly (Bactrocera oleae) is present 

in many California olive-growing areas, a limited 

amount of fresh olives is imported from Mexico 

and Argentina. A very limited amount is exported 

to Canada. These exported and imported fresh 

olives are not fumigated with methyl bromide. 

Issues associated with exotic pest quarantines 

addressing either imported or exported fresh olives 

can change rapidly. APHIS issues rules regarding 

import requirements. This agency provides 

information to assist exporters in targeting markets 

and defining what entry requirements a particular 

country might have for fresh olives. APHIS, in 

cooperation with the State plant boards, developed 

a database called “Excerpt” to track phytosanitary 

requirements for each country. APHIS provides 

phytosanitary inspections and certifications that 

declare fresh olives free of pests to facilitate 

compliance with foreign regulatory requirements. 
435

Suitability as Fresh-Cut Product

Fresh olives are not edible or suitable as a freshcut product.

Special Considerations

Olives for pickling are harvested either unripe, in 

which case they remain green, or ripe, when they 

are purple and turn black during pickling. Olives 

for oil extraction can be harvested from the strawcolor stage through the black-ripe stage.

Acknowledgments

Most of the information in this chapter is from 

the University of California, Davis, website on 

“Produce Facts” at http://postharvest.ucdavis.edu/

produce_information.

Further Reading

Agar, I.T., B. Hess-Pierce, M.M. Sourour, and 

A.A. Kader. 1998. Quality of fruit and oil of 

black-ripe olives is influenced by cultivar and 

storage period. J. Agr. Food Chem. 46:3415-3412.

Ferguson, L., G.S. Sibbett, and G. Martin. 1994. 

Olive production in California. DANR Pub. no. 

3353, University of California, Davis, CA.

Fernandez, A.G., M.J. Fernandez-Diez, and 

M.R. Adams. 1997. Table Olive Production and 

Processing. Chapman & Hall, London, U.K.

Kader, A.A., G. Nanos, and E. Kerbel. 1990. 

Storage potential of fresh ‘Manzanillo’ olives. Cal. 

Agric. 44(3):23-24. 

Maxie, E.C. 1963. Storing olives under controlled 

temperature and atmospheres. Cal. Olive Assoc. 

Ann. Tech. Rpt. 42:34-40.

Maxie, E.C. 1964. Experiments on cold storage 

and controlled atmosphere. Calif. Olive Assoc. 

Ann. Tech. Rpt. 43:12-15.

Maxie, E.C., P.B. Catlin, and H.T. Hartmann. 

1960. Respiration and ripening of olive fruits. 

Proc. Amer. Soc. Hort. Sci. 75:275-291.

Olias, J.M., and J.M. Garcia. 1997. Olive. In S. 

Mitra, ed., Postharvest Physiology and Storage 

of Tropical and Subtropical Fruits, pp. 229-243. 

CAB Intl., Wallingford, U.K. 
436

Onion

Franciszek Adamicki

Adamicki is with the Department of Vegetable 

Storage, Research Institute of Vegetable Crops, 

Skiemiewice, Poland.

Scientific Name and Introduction

Onions (Allium cepa L., Cepa group) is a biennial 

of the Alliaceae family. The edible portions of 

the bulb are the enlarged leaf bases and compact 

stem. Green onions, also called scallions, are 

eaten for their immature bulb and green foliage. 

The predominant flavor component results 

from activity of the enzyme alliinase in broken 

or crushed tissue, yielding the volatiles propyl 

disulfide and methyl propyl disulfide. Major onion 

producers are China, India, United States, Turkey, 

Japan, Spain, Holland, Poland, and Ukraine. 

Quality Characteristics and Criteria

High-quality onions have mature bulbs with 

good firmness and compactness of fleshy scales. 

Size, shape, and the color of the dry skin should 

be typical for the variety. They should be free of 

mechanical or insect damage, decay, sunscald 

injury, greening of fleshy scales, sprouting, 

bruising, doubles, bottlenecks (onions which 

have abnormally thick necks with only fairly well 

developed bulbs), and any other defects. 

Horticultural Maturity Indices

Harvest maturity depends on the purpose for 

which the onions are grown. Onions intended for 

storage should be harvested when 50 to 80% of 

the tops have fallen over and bulbs are mature 

with a thin neck. Yields are higher if they are 

harvested after the tops are completely dry, but 

then bulbs tend to have a shorter storage life. To 

hasten maturity, tops can be rolled with a light 

roller when 10% of them have fallen. About 7 

days before lifting, bulbs can be undercut by 

a blade; such onions should not be used for 

long-term storage. Onions for bunching can be 

harvested from the time they are pencil-sized until 

they have proper bulb size.

Grades, Sizes, and Packaging

Grades for green onions include U.S. No. 1 and 

U.S. No. 2 based on external appearance and 

size. For U.S. No. 1, the overall length (excluding 

roots) must be 20 to 61 cm (8 to 24 in), and the 

diameter of the bulb 6.4 to 25.4 mm (0.25 to 1 in). 

Sizes are based on bulb diameter: Small, <12.7 

mm (0.5 in); Medium, 12.7 to 25.4 mm (0.5 to 1 

in); and Large, >25.4 mm (>1 in). Trimmed green 

onions are bunched and marketed as bulb-type in 

9.1 and 12.7 kg (20 and 28 lb) cartons, and as 24, 

36 and 48 count, bunched in 9.1, 5.0 and 5.9 kg 

(20, 11 and 13 lb) containers, respectively. 

Grades of Bermuda-Granex-Grano type onions 

include U.S. No. 1, U.S. No. 2, and U.S. 

Combination and are based on external appearance 

and size. U.S. Combination consists of a mixture 

of U.S. No. 1 and U.S. No. 2 onions in which at 

least 50% (by weight) of the onions in each lot 

meet the requirements of U.S. No. 1 grade. Bulb 

diameters are defined as follows:

Small, 2.5 to 5.7 cm (1 to 2.25 in); Prepacker, 

4.5 to 7.6 cm (1.75 to 3 in); Medium, 5.1 to 8.3 

cm (2 to 3.25 in.); Large or Jumbo, 7.6 to 9.5 cm 

(3 to 3.75 in); and Colossal, >9.5 cm (3.75 in). 

Containers vary from 2.3 to 22.7 kg (5 to 50 lb) 

with 9.1 kg (20 lb) being the most common size. 

For onions other than Bermuda-Granex-Grano and 

Creole types, there are five Grades:

U.S. No. 1, U.S. Export No. 1, U.S. Commercial, 

U.S. No. 1 Boilers, U.S. No. 1 Picklers, and U.S. 

No. 2. The sizing of onions in this group is the 

same as above. Containers are usually 9.1 kg (20 

lb), except for export onions, which are packed in 

25-kg (56-lb) containers.
437

Precooling Conditions

In order to maintain high quality, bunched 

green onions should be precooled to <4 °C (39 

°F) within 4 to 6 h of harvest. Hydrocooling, 

forced-air cooling, and vacuum-cooling are used 

with crushed ice over the product to maintain 

temperature and moisture.

Dry onion bulbs for long-term storage should 

be precooled to 0 °C (32 °F) immediately after 

drying, or within 1 mo using cool outside air. 

The precooling method affects storability. Rapid 

precooling inhibits rooting and sprouting during 

storage. Natural cooling (slow) has a positive 

effect on storability when onions have a long rest 

period and weather conditions are good for curing. 

Gradual cooling at 1 °C (1.8 °F) per day in storage 

is less effective at inhibiting sprouting and rooting 

than rapid cooling (Grzegorzewska 1999). 

Optimum Storage Conditions

Bunched green onions can be stored 3 to 4 

weeks at 0 °C (32 °F) with 95 to 98% RH. 

Under these conditions, bunched onions stored 

in polyethylene-lined containers and top-iced 

maintain excellent quality for 1 mo. Storage life 

decreases to 1 week if the temperature is 5 °C 

(41 °F), and rapid yellowing and decay of leaves 

occurs at higher temperatures. 

Pungent dry onions can be stored for 6 to 9 mo 

at 0 °C (32 °F) with 65 to 75% RH. High RH 

induces root growth, while high temperature 

induces sprouting. A combination of high 

temperature and high RH increases rotting and 

decreases quality. Storage below the freezing point 

of -1 to -2 °C (28 to 30 °F) is recommended in 

Europe. Mild type or sweet onions can be kept for 

1 to 3 mo; they are stored in common storage with 

cool, circulating ambient air or in refrigerated cold 

rooms. Onions grown from seed store better than 

those grown from sets or transplants. 

After harvest, onion bulbs enter a state of rest for 

4 to 6 weeks, depending on cultivar and weather 

conditions during growth. Maleic hydrazide, a 

sprouting inhibitor, is often used to prevent root 

growth and sprouting during long-term storage. 

It is applied 2 weeks before harvest, when bulbs 

are mature and 50% of tops are down, but onion 

plants must still have five to eight green leaves in 

order to absorb and translocate the sprout inhibitor 

to bulbs.

Onions intended for storage should be dried well 

and cured in the field, under sheds, or in storage. 

After 2 weeks of field drying, onions can be 

transferred to storage rooms for final drying and 

curing. Forced-air ventilation at 25 to 27 °C (77 

to 81 °F) using outside or heated air is commonly 

used to dry onions. Onions can be stored and 

dried on the floor in bulk 3 to 4 m deep or in 500 

to 1,000 kg (1,100 to 2,200 lb) boxes. Drying 

is complete when the onion neck is tight, outer 

scales are dry and make a rustling noise when 

touched, and the skin color is uniform. Weight loss 

of 3 to 5% can occur during drying. Losses from 

neck rot are reduced by rapid drying immediately 

after harvest. After drying and curing, the 

temperature should be lowered gradually to the 

normal seasonal temperature, or bulbs can be 

precooled in cold storage at 0 °C (32 °F). In 

either case, condensation should be avoided as it 

encourages rot and changes the color of the dry 

skin. 

In most European countries and in the Northern 

United States, onions are stored in common 

storage, using cool, ambient air to maintain 

optimum temperature and RH. In this condition, 

onions are usually stored only until the end of 

March or beginning of April, since further storage 

can cause losses to sprouting and rotting. 

Refrigerated storage is used for onions that are 

to be marketed in late April to early July. For 

cold storage, onions are usually packed in crates 

or containers. Air circulation must be sufficient 

to maintain a constant temperature and remove 

moisture from inside storage containers. Onions 

packed in sacks can only be stored for a limited 

period, about 1 mo, since air movement through 

sacks is insufficient to maintain proper storage 
438

conditions. When stored below -1 to -2 °C (28 to 

30 °F), onions should be thawed at 5 °C (41 °F) 

for 1 to 2 weeks before they are removed from 

storage. Rapid thawing damages onion bulbs.

Mild and sweet onions can be stored for only 1 

to 4 mo, even in optimal cold storage. CA may 

extend the storage period. Onions tolerate storage 

at 30 to 35 °C (86 to 95 °F) for short periods 

before marketing or processing, but their quality 

and external color is less attractive than that of 

cold-stored onions. 

Controlled Atmosphere (CA) 

Considerations

Bunched green onions can be stored for 6 to 8 

weeks in 2% O2

 and 5% CO2 at 0 °C (32 °F). They 

can tolerate 1% O2

 and up to 5% CO2, but off 

flavor may develop if they are stored at >5 °C (41 

°F) (Suslow and Cantwell 1998).

Low-O2

 atmospheres reduce respiration and 

extend storage life, while elevated CO2

 reduces 

sprouting and root growth. CA has been used 

for storage of pungent onions in England, 

Switzerland, and Poland (Adamicki 1998). 

An atmosphere of 3% O2

 and 5% CO2 inhibits 

rooting, sprouting ,and disease development 

(Adamicki and Kepka 1974, Smittle 1988). 

However, onions stored in 3% O2

 and 10% CO2

showed physiological disorders; high CO2

 caused 

injury, but neck rot (Botrytis spp.) was reduced 

(Sitton et al. 1997).

CA can have also residual effects. After storage 

for up to 226 days in 3% O2

 and 5% CO2, 

sprouting of ‘Wolska’ onions at 20 °C (68 °F) 

was delayed for 10 days, compared to air-stored 

controls (Adamicki and Kepka 1974). It is 

possible to store onions in low O2

 (1 to 2%) with 

2% CO2

 (Adamicki 1998, Tanaka et al. 1996). 

There is some commercial use of 3% O2

 and 5 to 

7% CO2

 for sweet onion cultivars (Smittle 1989, 

Mikitzel et al. 1993, Sitton et al. 1997). 

Retail Outlet Display Considerations

Onion bulbs can be displayed in small packages 

or in bulk at <5 °C (41 °F). This temperature 

effectively retards sprouting for up to 7 mo. 

Onions should not be stored with fruits and 

vegetables that tend to absorb odors.

Chilling Sensitivity

Onions are not sensitive to chilling and can be 

stored at -2 to -3 °C (28 to 27 °F), since the 

highest freezing point is -0.8 °C (31.6 °F). Storage 

at <-4 °C (25 °F) may cause freezing injury. 

Ethylene Production and Sensitivity

Ethylene production is very low: < 0.1 μL 

kg-1 h-1 at 20 °C (68 °F) (Suslow and Cantwell 

1998). Sensitivity to ethylene is also low, but 

concentrations of >1,500 μL L-1 encourage 

sprouting of onion bulbs.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 3 

5 °C 5

10 °C 7

15 °C 7

20 °C 8

Data from Robinson et al. (1975).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Onion bulbs are affected by several physiological 

disorders. Freezing injury causes soft, watersoaked, fleshy scales and rapid decay after 
439

transfer from cold storage to higher temperature, 

which results in microbial growth. Translucent 

scales resemble freezing injury and are prevented 

by prompt cold storage following curing. 

Translucent scales occur with loss of or changes 

in carbohydrate content. Storage of onions at >7% 

CO2

 can also lead to development of translucent 

scales. Late harvesting and a long drying period at 

high temperatures produce the highest incidence 

of translucent scales.

Watery scales is a thick leathery skin with watery, 

glassy, fleshy scales below. The watery scales 

may later be affected by fungal or bacterial 

growth. Late harvesting and prolonged field 

drying produce the highest occurrence of leathery 

skin. Scale greening, a green coloration of outer 

scales, is caused by exposure to light after curing. 

Ammonia injury is indicated by brown-black 

blotches resulting from leakage of ammonia 

during storage (Adamicki and Kepta 1974, Smittle 

1988, Hoftun 1993, Suslow and Cantwell 1998, 

Solberg 1999).

Postharvest Pathology

A number of microorganisms attack onions 

postharvest.

Botrytis neck rot is indicated by watery decay, 

which begins at the neck and then attacks the 

entire bulb. A gray fungal mold then covers the 

neck of the bulb and later the whole bulb surface. 

Neck rot can be slowed after harvest, but it cannot 

be stopped, even during storage under optimum 

conditions. Proper drying in the field and during 

storage can decrease this postharvest fungal decay 

disease. 

Black mold rot presents a black discoloration and 

shriveling at the neck and on outer scales caused 

by Aspergillus niger van Tiegh. Infection usually 

occurs in the field, but the disease spreads from 

bulb to bulb postharvest. The surface of bulbs 

must be dry during and after harvest to avoid 

infection. Storage at 0 °C (32 °F) with moderate 

RH prevents the spread of this disease.

Blue mold rot also produces watery soft rot of 

neck and outer scales, followed by formation of 

blue to blue-green mold of the fungus Penicillium

spp. Harvest of mature bulbs, proper curing, 

and storage at 0 °C (32 °F) with 60 to 70% RH 

minimizes blue mold problems.

Bacterial soft rot, caused by Erwinia carotovora 

Jones, develops water-soaked individual scales, 

or the entire onion, with foul smelling, viscous, 

liquid-covered rotted areas. The disease progresses 

rapidly under warm, humid conditions. Harvesting 

at full maturity, proper drying, minimizing 

bruising, and maintaining optimum storage 

conditions prevent bacterial soft rot (Ryall and 

Lipton 1983, Suslow and Cantwell 1998).

Quarantine Issues

Onions intended for export should be free from 

Ditylenchus dipsaci Kühn.

Suitability as Fresh-Cut Product

Demand for fresh-cut onions (ready-to-eat) is 

increasing.

References

Adamicki, F. 1998. Effect of controlled 

atmosphere on storage and quality of onions. 25th 

International Horticulture Congress, Brussels, 

Belgium, vol. 1, pp. 365. International Society for 

Horticultural Science, Leuven, Belgium.

Adamicki, F., and A. Kepka. 1974. Storage of 

onions in controlled atmosphere. Acta Hort. 

38:53-75.

Grzegorzewska, M. 1999. The Influence of 

Weather Conditions, Harvest Maturity and 

Cooling Methods on the Quality and Storage 

Ability of Onions. Ph.D. thesis, Research Institute 

of Vegetable Crops, Instytut Warzywnictwa, 

Skierniewice, Poland. 
440

Hoftun, H. 1993. Internal atmosphere and watery 

scales in onion bulbs (Allium cepa L.). Acta Hort. 

343:135-140.

Mikitzel, L.J., M.E. Patterson, and H. Waelti. 

1993. The effect of CA storage on the postharvest 

life of sweet onions. In 6th International 

Controlled Atmosphere Research Conference, 

Ithaca, NY, June 1993, NRAES-71, vol. 2, 

pp. 789-796. Northeast Regional Agricultural 

Engineering Service, Cornell University, Ithaca, 

NY.

Robinson, J.E., K.M. Browne, and W.G. Burton. 

1975. Storage characteristics of some vegetables 

and soft fruits. Ann. Appl. Biol. 81:399-408.

Sitton, J.W., J.K. Fellman, and M.E. Patterson. 

1997. Effects of low-oxygen and high-carbon 

dioxide on postharvest quality, storage and decay 

of “Walla Walla” sweet onions. In M.E. Saltveit, 

ed., 7th International Controlled Atmosphere 

Research Conference, July 13-18, 1997, 

University of California, Davis, vol. 4, pp. 20-25. 

University of California, Davis, CA.

Solberg, S.O. 1999. Effects of harvesting and 

drying methods on internal atmosphere, outer 

scale appearance, and storage of bulb onions. J. 

Veg. Crop Prod. 42:23-35. 

Ryall, A.L., and W.J. Lipton. 1983. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1. AVI, Westport CT. 

Smittle, D.A. 1988. Evaluation methods for 

‘Granes’ onions. J. Amer. Soc. Hort. Sci.113:877-

880. 

Smittle, D.A. 1989. Controlled atmosphere 

storage of vidalia onions. In J.K. Fellman, ed., 

Proceedings of the 5th International Controlled 

Atmosphere Research Conference, Wenatchee, 

WA, pp.171-177.

Suslow, T., and M. Cantwell. 1998. Onions: dry. 

Recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.

Tanaka, K., Y. Matsuo, and J. Egashira. 1996. 

Controlled atmosphere storage for onions. In

T. Kozai, ed., Proceedings of the International 

Symposium on Plant Products in Closed 

Ecosystems, Narita, Japan, 1996, pp. 669-674. 

Acta Hort., Leuven, Belgium.
441

Orange

Mark A. Ritenour

Ritenour is with the Indian River Research 

and Education Center, Institute of Food and 

Agricultural Sciences, University of Florida, Fort 

Pierce, FL.

Scientific Name and Introduction

The sweet orange (Citrus sinensis L. Osbeck) 

is a dicotyledonous, perennial evergreen of the 

Rutaceae family that leads other Citrus species 

in both production area and value. Fruit vary 

from spherical to oblong and are seedless (0 

to 6 seeds) to seeded (>6 seeds). Peel color at 

maturity ranges from light to deep orange but may 

remain green under warm conditions. Late season 

‘Valencia’ oranges may turn from orange to green 

(“regreen”) under warm conditions. 

Sweet oranges are generally classified into one of 

four groups: (1) round oranges such as ‘Valencia,’ 

‘Hamlin,’ ‘Pineapple,’ and ‘Shamouti’; (2) navel 

oranges such as ‘Washington Navel’; (3) blood or 

pigmented oranges such as ‘Moro’ and ‘Tarocco’; 

and (4) acidless oranges such as ‘Succari.’ In the 

United States, the leading orange-growing States 

are Florida, California, Texas, and Arizona. Of 

these, Florida is the largest producer of oranges; 

over 90% go for processing. California is the 

largest producer of oranges for the fresh market. 

Like other citrus fruits, oranges are nonclimacteric 

with no postharvest ripening phase. 

Quality Characteristics and Criteria

A high-quality orange is mature, with good color 

intensity that is uniformly distributed over the 

surface. Fruit must be firm with a fairly smooth 

texture and shape that is characteristic of the 

variety. Fruit should be free from decay, defects, 

and blemishes.

Horticultural Maturity Indices

Maturity indices are based on percentage color 

break, SSC, TA, SSC:TA, and juice content. 

Specific regulations are established for different 

growing regions. 

Florida: Minimum maturity indices for fresh fruit 

shipments change according to harvest date and 

are based on SSC and SSC:TA:

SSC SSC:TA ratio

Date Minimum Minimum

------------------%-------------

Aug. 1 to Oct. 31 9.0 10.00

Nov. 1 to Nov. 15 8.7 10.15

Nov. 16 to July 31 8.5 10.25

Florida oranges also have minimum requirements 

for TA (0.4%) and juice content (4.5 gal per 1.6-bu 

box).

California and Arizona: For fruit with yelloworange color on ≥25% of the surface, SSC:TA 

must be 8 or higher; and for fruit with greenyellow color on ≥25% of the surface, SSC:TA 

ratio must be 10 or higher.

Texas: To meet minimum maturity, fruit must have 

8.5 to 8.9% SSC with a SSC:TA ratio of 10 or 

higher, or must have SSC of 9% or higher with a 

SSC:TA of 9 or higher. Texas oranges also have a 

minimum juice content of 4.5 gal per 1.6-bu box.

Grades, Sizes, and Packaging

U.S. grade standards for sweet oranges are based 

on maturity, color intensity and uniformity, 

firmness, shape, size, smoothness, and freedom 

from decay, as well as freedom from defects 

(bruises and abrasions), insects, fungal attack (for 

example, cake melanose), growth cracks, chemical 

burns, and physiological disorders. See http://

www.ams.usda.gov/AMSv1.0/standards for more 

details on State-specific grade standards. 

U.S. grades for Florida oranges (AMS 1997): U.S. 

Fancy, U.S. No. 1 Bright, U.S. No. 1, U.S. No. 1 

Golden, U.S. No. 1 Bronze, U.S. No. 1 Russet, 
442

U.S. No. 2 Bright, U.S. No. 2, U.S. No. 2 Russet, 

U.S. No. 3. Standard packed sizes used in Florida 

include 64, 80, 100, 125, and 163 fruit per 28.2-L 

(4/5 bu) container (Florida Department of Citrus 

1999).

U.S. grades for California and Arizona oranges 

(AMS 1999): U.S. Fancy, U.S. No. 1, U.S. 

Combination, U.S. No. 2. Standard packed sizes 

used in California include 24, 32, 36, 40, 48, 56, 

72, 88, 113, 138, 163, 180, 210, 245, and 270 

fruit per 28.5-L (4/5 bu) container (California 

Department of Food and Agriculture 1990).

U.S. grades for Texas and States other than 

Florida, California, or Arizona (AMS 1969): U.S. 

Fancy, U.S. No. 1, U.S. No. 1 Bright, U.S. No. 1 

Bronze, U.S. Combination, U.S. No. 2, U.S. No. 2 

Russet, U.S. No. 3. Standard packed sizes used in 

Texas and States other than Florida, California and 

Arizona include 48 or 50, 64, 80, 100, 125, 144, 

and 162 fruit per 24.7-liter (7/10-bushel) container 

(AMS 1969).

Well-vented polyethylene and plastic mesh bags 

of various sizes are also used to market oranges. 

Oranges may be individually seal-packaged 

(wrapped with various plastic films), but this 

practice has not been widely adopted.

Precooling Conditions

Rapid cooling is often neglected in many citrus 

packinghouses but should be seriously considered 

as a means of improving fruit quality at 

destination markets. Cooling reduces respiration, 

slows pathogen growth, reduces water loss, and 

increases shelf-life. Common cooling methods 

for oranges include room-cooling and forced-air 

cooling. Oranges can also be hydrocooled, but this 

practice is seldom used because of the increased 

risk of spreading decay organisms. For roomcooling and forced-air cooling, maintaining good 

airflow through cartons is important to rapidly 

remove heat from the product. To facilitate this, 

carton design should include at least 5% side 

venting, designed to line up with adjacent carton 

vents and allow airflow through the entire load. 

Optimum Storage Conditions

Under normal weather conditions, fruit store 

better on the tree than in cold storage. Cold 

storage should not be attempted if the fruit storage 

potential has been expended by prolonged tree 

storage. Once harvested, fruit quality will not 

improve. Before being placed into storage, fruit 

should be precooled to slow respiration and 

treated with an approved fungicide to reduce 

decay. Oranges can be stored for up to 12 weeks 

under optimum storage conditions. Ultimate 

storage life depends on cultivar, maturity, 

preharvest conditions, and postharvest handling. 

Oranges begin to freeze in storage at about -1 °C 

(30 °F) (Whiteman 1957). During storage, fruit 

should be inspected often for signs of decay or 

disorders. Such problems will advance rapidly 

once the fruit are removed from cold storage. 

Recommended storage conditions are—

Growing Region Temperature Relative 

 Humidity

Florida & Texas 0 to 1 °C 85 to 90%

California & Arizona 3 to 8 °C 90 to 95%

Controlled Atmosphere (CA) 

Considerations

CA of 5 to 10% O2 and 0 to 5% CO2 may aid in 

retaining quality of oranges. Decreased O2

 levels 

help maintain firmness and retard senescence, 

while high CO2

 levels can inhibit the development 

of chilling injury. However, CA is not commonly 

used because tolerable O2

 and CO2 levels do not 

significantly inhibit decay (Hatton and Cubbedge 

1977), which limits shelf-life the most. Addition 

of 5 to 10% CO to CA may improve decay control 

but is dangerous because it is lethal to humans. 

Maintaining low ethylene (<1 μL L-1) during CA 

storage may improve flavor retention and reduce 

stem-end decay (McGlasson and Eaks 1972).
443

Retail Outlet Display Considerations

Oranges should be displayed on nonrefrigerated 

shelves and inspected often to remove damaged or 

decaying fruit.

Chilling Sensitivity

California and Arizona oranges may develop 

chilling injury when held at temperatures below 

about 3 to 5 oC (37 to 41 oF). Oranges produced 

in Florida or Texas rarely show chilling injury. 

Symptoms of chilling injury include pitting, 

brown staining, increased decay, internal 

discoloration, off flavors, and watery breakdown 

that may take 60 days to develop at 5 °C (41 °F) 

or become evident 1 to 2 days after moving to 

room temperature (about 72 °F). After removing 

fruit from chilling temperatures, respiration and 

ethylene production both increase.

The development and severity of chilling injury 

in citrus is influenced by both preharvest and 

postharvest factors. Preharvest factors include 

cultivar, weather conditions, and even location 

of fruit on the tree (sun-exposed fruit are more 

susceptible to chilling injury). Postharvest 

development of chilling injury symptoms can 

be reduced by temperature conditioning before 

storage, use of high-CO2

 atmospheres (for 

example, in CA or through the use of wax coatings 

or plastic film wraps), intermittent warming, 

and use of benzimidazole fungicides (such as 

thiabendazole and benomyl). The best means 

of preventing chilling injury is storing fruit at 

nonchilling temperatures.

Ethylene Production and Sensitivity

Citrus produce very little ethylene: <0.1 μL kg-1

h-1 at 20 °C (68 °F). Ethylene is used to degreen 

oranges, especially early in the season when 

natural degreening has been delayed because of 

warm night temperatures. Degreening usually 

takes 1 to 3 days to complete and does not 

affect internal quality (SSC, TA, etc.). However, 

ethylene stimulates decay, such as anthracnose 

(Brown 1992) and stem-end rot (Barmore and 

Brown 1985), especially at >10 μL kg-1 h-1. 

Ethylene also increases respiration in citrus. 

Conditions for degreening (Kader and Arpaia 

1992, Wardowski 1996) are—

Florida California

Temperature 28 to 29 oC 20 to 25 oC 

Ethylene 5 μL L-1 5 to 10 μL L-1

RH 90 to 96% 90%

Ventilation

 (<0.1% CO2) 1 air change 1 to 2 air changes 

 per hour per hour 

Air Circulation 100 ft3 min-1 1 room volume 

 per 900-lb bin per min

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 2 to 6

5 °C 4 to 8

10 °C 6 to 10

15 °C 11 to 22

20 °C 20 to 31

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Creasing (albedo breakdown) results from the 

irregular deterioration of albedo cells (white 

spongy tissue) and the collapse of the overlaying 

flavedo (colored portion of the rind) into irregular 

grooves over the fruit surface. Such areas are 

weaker and often split, providing entry for 

pathogenic fungi and subsequent decay. This 

disorder is usually more common on thin-skinned, 

fully mature fruit. Conditions giving rise to 

creasing are complex and not well understood, 

but appear to be related to cultivar, potassium 

nutrition deficiencies, high levels of nitrogen, 

rootstock, water status, and temperature during 
444

fruit expansion. Because the disorder is associated 

with advanced fruit maturity, earlier fruit 

harvesting may also reduce the problem.

Granulation is caused by gel formation within 

juice vesicles that greatly reduces extractable 

juice content. It may occur primarily at the stem 

end (in ‘Valencia’ oranges), or extend through the 

center of the fruit (in navel oranges). In the United 

States, this is considered a preharvest disorder 

that appears more in fruit exposed to the sun, fruit 

from young or water-stressed trees, overmature 

fruit, or fruit from vigorously growing trees. In 

other parts of the world, the disorder also develops 

after harvest.

Oil spotting (oeocellosis) arises when mechanical 

damage releases oil from the oil glands. When 

fruit are very turgid, even slight pressure from 

bumps and abrasions can result in oil release and 

spotting. The oil is toxic to surrounding tissue and 

will inhibit degreening of that tissue. Symptoms 

appear as irregularly shaped green, yellow, or 

brown spots that darken over time and make the 

glands more prominent. The most effective means 

of prevention is not harvesting turgid fruit early in 

the morning, when dew is present, during foggy 

conditions, or immediately after rain or irrigation 

(Wardowski et al. 1997).

Postharvest pitting is characterized by clusters 

of collapsed oil glands (often 5 to 20) scattered 

over the fruit surface. It can begin to develop 

2 days after packing. Collapsed regions turn 

bronze-brown or brown-black over time. This 

disorder is associated with low O2

 levels in fruit 

following application of wax coating having low 

O2

 permeability and holding at warm temperatures 

>10 °C (50 °F; Petracek et al. 1998).

Rind staining is associated with physiologically 

overmature fruit that are easily injured by 

mechanical abrasions, particularly navel oranges. 

Brown or reddish-brown blemishes develop 12 

to 24 h after washing and waxing (Eaks 1964). In 

California, fruit are sprayed with gibberellic acid 

to delay peel senescence and reduce incidence of 

this disorder.

Stem-end rind breakdown (SERB) is characterized 

by the irregular collapse and darkening of rind 

tissue around the stem end of the fruit. A narrow 

ring of unaffected tissue immediately around 

the stem (button) is a distinctive symptom of 

SERB. In some growing regions, SERB has been 

correlated with a preharvest imbalance in nitrogen 

and potassium. Postharvest, SERB is primarily 

associated with drying conditions and fruit water 

loss, particularly between harvest and waxing. 

Postharvest practices that minimize water loss, 

such as maintaining high RH during degreening, 

rapid handling, avoiding excessive brushing, 

and promptly applying an even coat of wax, are 

currently the best means of reducing SERB. 

Postharvest Pathology

Postharvest decay is the most important factor 

limiting shelf-life of oranges. Oranges are 

susceptible to a wide variety of fungal diseases, 

including green mold (Penicillium digitatum),

blue mold (Penicillium italicum), diplodia 

stem-end rot (Diplodia natalensis), phomopsis 

stem-end rot (Phomopsis citri), brown rot 

(Phytophthora citrophthora), sour rot (Geotrichum 

candidum), and anthracnose rot (Colletotrichum 

gleosporioides).

Factors such as growing region, production 

practices, cultivar, rootstock, and postharvest 

practices influence susceptibility to each of these 

pathogens. For example, stem-end rots are more 

prevalent under environmental conditions found 

in Florida and Texas. Green mold predominates 

in Florida, but blue mold does so in California. 

Postharvest decay can be reduced by harvesting 

at optimum maturity, gently handling fruit during 

harvest and postharvest operations, maintaining 

sanitary facilities and water handling systems, 

prompt cooling, storing at optimum temperature 

and RH, and using approved fungicides or 

biological control agents.
445

Quarantine Issues

Oranges are a fruit fly host, and when produced 

in areas where any fruit fly is found, must be 

treated for insect control before shipment to 

some markets. Approved disinfestation for 

oranges include methyl bromide fumigation, 

cold treatments, and vapor heat treatments. Use 

of methyl bromide is being phased out and will 

no longer be available by the year 2005. Cold 

treatments are commonly used but may result 

in chilling injury. Irradiation and controlled 

atmospheres are potential alternative disinfestation 

treatments. 

All disinfestation treatments can result in 

phytotoxic injury to the fruit, with the degree of 

injury depending on preharvest factors such as 

cultivar and stage of maturity. As an alternative to 

disinfestation treatments, some production areas 

have established protocols that are accepted by 

receiving markets for certifying “fly-free” areas. 

Oranges grown in these areas do not have to be 

treated before shipment.

Suitability as Fresh-Cut Product

Consumers’ preference for peeled, sectioned, or 

cubed oranges that are ready to eat has driven 

research and development of new technologies 

and equipment to help meet this demand. Freshcut oranges can maintain quality for about 12 

days, but mechanically removing the peel has 

been problematic. Though there are several 

different peeling technologies developed or under 

development, none is yet widely adopted. 

Acknowledgments

Some information in this chapter is from the 

University of California, Davis, website “Fresh 

Produce Facts” at http://postharvest.ucdavis.edu/

produce_information. 

References

AMS [USDA Agricultural Marketing Service]. 

1969. United States Standards for Grades of 

Oranges (Texas and States Other Than Florida, 

California and Arizona). U.S. Department of 

Agriculture, Washington, DC.

AMS [USDA Agricultural Marketing Service]. 

1997. United States Standards for Grades of 

Florida Oranges and Tangelos. U.S. Department of 

Agriculture, Washington, DC.

AMS [USDA Agricultural Marketing Service]. 

1999. United States Standards for Grades 

of Oranges (California and Arizona). U.S. 

Department of Agriculture, Washington, DC.

Barmore, C.R., and G.E. Brown. 1985. Influence 

of ethylene on increased susceptibility of oranges 

to Diplodia natalensis. Plant Dis. 69:228-230.

Brown, G.E. 1992. Factors affecting the 

occurrence of anthracnose on Florida citrus. Proc. 

Intl. Soc. Citricult. 3:1044-1048.

California Department of Food and Agriculture. 

1990. Administrative Code, Title 3. State of 

California, Sacramento, CA.

Eaks, I.L. 1964. The effect of harvesting and 

packing house procedures on rind staining of 

central California ‘Washington’ navel oranges. 

Proc. Am. Soc. Hort. Sci. 85:245-256.

Florida Department of Citrus. 1999. Official rules 

affecting the Florida citrus industry: pursuant to 

Chap. 601. Florida Statutes, Lakeland, FL.

Hatton, T.T., and R.H. Cubbedge. 1977. Status of 

controlled-atmosphere storage research of citrus 

fruit. In D.H. Dewey, ed., 2nd National Controlled 

Atmosphere Research Conference, pp. 250-259. 

Hort. Rpt. 28., Michigan State University, East 

Lansing, MI.
446

Kader, A.A., and M.L. Arpaia. 1992. Postharvest 

handling systems: subtropical fruits. In

A.A. Kader, ed., Postharvest Technology of 

Horticultural Crops, 2nd ed., pp. 233-240. DANR 

Pub. no. 3311, University of California, Davis, 

CA.

McGlasson, W.B., and I.L. Eaks. 1972. A role for 

ethylene in the development of wastage and offflavors in stored valencia oranges. HortScience 

7:80-81.

Petracek, P.D., H. Dou,, and S. Pao. 1998. 

The influence of applied waxes on postharvest 

physiological behavior and pitting of grapefruit. 

Postharv. Biol. Technol. 14:99-106.

Wardowski, W.F. 1996. Recommendations for 

degreening Florida fresh citrus fruits. Circular 

1170, University of Florida, Institute of Food and 

Agricultural Science, Gainesville, FL.

Wardowski, W.F., P.D. Petracek, and W. Grierson. 

1997. Oil spotting (oleocellosis) of citrus fruit. 

Circular 410, University of Florida, Institute of 

Food and Agricultural Science. 

Whiteman, T.M. 1957. Freezing points of fruits, 

vegetables and florist stocks. Marketing Research 

Report 196, U.S. Department of Agriculture, 

Washington, DC.
447

Papaya

Lili Zhou, Robert E. Paull, and Nancy Jung Chen

Zhou, Paull, and Chen are with the Department 

of Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Papaya, papaw, or paw paw (Carica papaya L.) 

is cultivated throughout the tropics for its fruit 

(Nakasone 1986). Fruit are eaten green or ripe, in 

salads or fresh. The related Ecuadorian babaco (C. 

pentagonia) is also eaten fresh. 

Fruit are pyriform (pear-shaped), spherical, or 

cylindrical. The pyriform, hermaphroditic fruit 

is the most common in commerce. These belong 

to the ‘Solo’ group and includes the cultivars 

‘Kapoho,’ ‘Rainbow,’ ‘Sunup,’ ‘Sunrise,’ and 

‘Sunset’; these varieties weigh 300 to 700 g (10 

to 25 oz). Other varieties range from 200 g to 10 

kg (0.4 to 22 lbs), with flesh 1.5 to 4 mm (0.06 to 

0.16 in) thick. Flesh is greenish-white in immature 

fruit to pale orange-yellow, salmon pink, or red, 

depending on cultivar, when ripe.

Quality Characteristics and Criteria

Size, shape, a smooth skin, and absence of 

blemishes are major quality characteristics. 

Consumers in Western countries also prefer 

fruit without a heavy musky, sweaty odor found 

in some Southeast Asian cultivars. Small, 

dry, brown-black “freckles” on the skin are 

nonpathogenic and do not detract from ripening or 

flavor (Reyes and Paull 1994).

Horticultural Maturity Indices

In Hawaii, minimum grade standard requires 

11.5% SSC (Hawaii Department of Agriculture 

1990), so fruit should have started ripening 

before harvest, indicated by some skin yellowing 

(Akamine and Goo 1971). Less mature fruit are 

lower in sugar and ripen poorly.

Grades, Sizes, and Packaging

The most common package size is a 4.5-kg 

(10-lb) carton; larger 10-kg (22-lb) cartons are 

also used. Cartons from areas requiring insect 

disinfestation are fully sealed to meet regulatory 

requirements, while fruit from other areas can be 

in open-topped cartons. Count size ranges from 

6 to 18, depending on fruit and carton size. Fruit 

are marketed as color break, quarter, half, or 

three-quarters ripe and are normally ready to eat 

when there is 75% or more skin color. Foam mesh 

sleeves, foam padding on the bottom of cartons, or 

paper wrapping prevents abrasion injury, a major 

problem in fruit still having green areas of skin 

(Quintana and Paull 1993).

Precooling Conditions

Room-cooling and forced-air cooling are 

commonly used. Hydrocooling is possible. 

However, rapid cooling after insect disinfestation 

treatments can lead to skin scalding.

Optimum Storage Conditions

Store at 7 to 13 °C (45 to 55 °F) with 90 to 95% 

RH. At 7 to 10 °C (45 to 50 °F), storage life is 

limited by chilling injury, while at 10 to 13 °C 

(50 to 55 °F) fruit ripens slowly (Chen and Paull 

1986). Papaya fruit at color-turning (break) stage 

can be stored at 7 °C (45 °F) for 14 days and 

will ripen normally when transferred to room 

temperature (Thompson and Lee 1971, Chen and 

Paull 1986). Ripe, full-color fruit can be held for 

>1 week at 1 to 3 °C (34 to 37 °F).

Controlled Atmosphere (CA) 

Considerations

Shelf-life was extended 1 to 1.5 days when 

papaya were stored at 12 °C (54 °F) in 1 to 1.5% 
448

O2

 for 6 days (Akamine and Goo 1969). Low O2

(1 to 5%), with or without high CO2

 (2 to 10%), 

reduces decay (Hatton and Reeder 1969) and 

delays ripening (Akamine 1959, Chen and Paull 

1986). High CO2

 (30%) adversely affects internal 

color, aroma, and flavor, while there is no residual 

effect of 10% CO2

 on decay control, though skin 

degreening is delayed.

At 10 °C (50 °F), fruit can be stored for 36 days 

in 8% CO2

 and 3% O2 and still have 5 days 

at 25 °C (77 °F) for retail (Cenci et al. 1997). 

Ethylene removal prior to storage has shown 

variable results (Nazeeb and Broughton 1978). 

CA recommendations are 2 to 5% O2

 plus 5 to 

8% CO2

. However, no commercial use has so 

far been reported (Yahia 1998). Fruit stored at 

10 °C (50 °F), 98% RH, and low pressure of 20 

mm Hg ripened more slowly than fruit at normal 

atmospheric pressure. Low-pressure storage 

appears to suppress disease development (Alvarez 

1980, Chau and Alvarez 1983).

Retail Outlet Display Considerations

The optimum temperature for fruit ripening is 23 

to 28 °C (73 to 82 °F), with fruit taking 10 to 16 

days to reach full skin yellowing from the colorbreak stage (An and Paull 1990). Severe weight 

loss and external abnormalities become significant 

at temperatures higher than 28 °C (82 °F). Display 

temperatures should not be less than 10 °C (50 

°F) if fruit are not fully ripe. Fully ripe fruit at the 

edible stage can be held at 1 to 3 °C (34 to 37 °F). 

Fruit should not be stacked more than two or three 

deep in racks, and wicker baskets with uneven 

bottoms and sides should be avoided; or at least a 

layer of protection should be placed between racks 

and fruit (Paull et al. 1997). Loss of about 8% of 

weight from color break produces rubbery, lowgloss, unmarketable fruit (Paull and Chen 1989). 

Diseased and bruised fruit should be removed 

from display and used immediately, if possible, in 

salads or mixed fruit cocktails. Papaya should not 

be misted.

Chilling Sensitivity

Chilling injury symptoms include skin scald, hard 

lumps in the pulp around vascular bundles, and 

water-soaking of flesh (Thompson and Lee 1971, 

El-Tomi et al. 1974, Chen and Paull 1986). Fruit 

become progressively less susceptible to chilling 

stress as they ripen (Chen and Paull 1986). 

Symptoms of chilling injury occur after 14 days 

at 5 oC (41oF) in mature green fruit and 21 days 

in 60% yellow fruit. Skin scald can be induced in 

color-break fruit after chilling at 1 oC (34 oF) for 

24 h. At a storage temperature of 7 oC (45 oF) for 

14 days, storage decay is less than when fruit are 

held at 12 to 13 oC (54 to 55 oF) (Arisumi 1956, 

El-Tomi et al. 1974).

Ethylene Production and Sensitivity

Ethylene rates in ripening fruit are 6 to 10 μL kg-1

h-1 (Paull and Chen 1983, Paull 1993). Ethylenetreated papaya ripen faster and more uniformly 

in terms of skin degreening, softening, and flesh 

color (An and Paull 1990). Since papaya ripen 

from the inside outwards, the effect of ethylene 

treatment is to accelerate the rate of ripening of 

the mesocarp tissue nearer the skin that has not 

started to soften. Ethylene is not recommended 

commercially, as rapid softening severely limits 

available marketing time (An and Paull 1990).

Respiration Rates

Papaya are climacteric and begin to yellow from 

the blossom end (Akamine 1966).

Temperature mg CO2 kg-1 h-1

5 °C 4 to 6

15 °C 15 to 22

20 °C - color break 9 to 18

20 °C - ripe 70 to 90

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.
449

Physiological Disorders

A number of nonpathological disorders are seen 

in marketed fruit (Paull et al. 1997). Green, 

slightly sunken areas on ripe yellow fruit are 

caused by abrasion injury when fruit were still 

green (Quintana and Paull 1993). Unsightly skin 

freckles (small, brown, slightly raised areas) 

that are more common on the side of the fruit 

exposed to the sun is seasonal, developing when 

rainfall and low temperatures occur 2 mo before 

harvest (Reyes and Paull 1994). This disorder is 

nonpathogenic and does not influence ripening or 

flavor. Sunscald, a dark-olive-brown discoloration, 

occurs on fruit developing on trees with very 

sparse foliage, on trees that are leaning over 

with fruit directly exposed to the sun, and where 

harvested fruit are left exposed to the sun.

Blossom end defect can be severe at some times 

of the year (Zee et al. 1989). It leaves an open 

channel at the blossom end to the fruit seed cavity. 

Fruit with this disorder are prone to bacterial 

diseases in the fruit seed cavity before harvest. 

Hard lumps in the flesh occur infrequently in 

otherwise ripe, non-heat-treated fruit (Magalona 

1963, Cavaletto 1989). The lumps are thought to 

be associated with insect injury, disease, or other 

foreign material in the flesh. The condition can 

also occur in heat-treated fruit. Premature ripening 

of fruit, referred to as “soft fruit,” is related to low 

calcium content. This condition is more common 

following periods of heavy rainfall 2 to 3 mo 

before harvest, at the start of the final phase of 

fruit growth (Qiu et al. 1995). 

Intra-ovarian ovaries are common in some strains 

of papaya (Nakasone and Arkle 1971). These 

ovaries occur as a proliferation of tissue in the 

seed cavity and can be a threadlike appendage to 

round or elongated structures of various sizes and 

shapes. A few fill the entire seed cavity of the fruit 

and have their own seed cavity.

Sunken, dry, brownish-grey areas are caused by 

mites feeding on skin during early fruit growth. 

The red and black mite (Brevipalpus phoenicis

[Geijskes]) generally causes this damage in 

Hawaii.

Postharvest Pathology

The major postharvest diseases are anthracnose 

and stem end rot. Postharvest diseases, especially 

anthracnose, become a problem when fruit have 

25% or more skin yellowing (Wardlaw et al. 

1939, Alvarez and Nishijima 1987). Papaya 

diseases greatly increase in severity and incidence 

following 4 weeks storage at 10 °C (50 °F). 

Mechanical injury and chilling injury can enhance 

development of postharvest diseases (Somner 

and Mitchell 1978, Alvarez and Nishijima 1987, 

Nishijima et al. 1990). Rhizopus requires breaks 

in the cuticle for the disease to develop (Nishijima 

et al. 1990). Cuticle disruption occurs as latex 

vessels break down, when the fruit is 40 to 60% 

yellow (Paull and Chen 1989). Fruit fly punctures 

can also increase Rhizopus rot (Hunter and 

Buddenhagen 1972), as can mechanical injuries 

and lesions caused by fungi such as anthracnose 

and Cercospora black spot (Nishijima et al. 1990). 

Postharvest diseases are effectively controlled by 

hot water at 49 °C (120 °F) for 20 min (Akamine 

and Arisumi 1953, Couey et al. 1984, Glazener 

et al. 1984) and fungicide treatment (Couey and 

Farias 1979).

Quarantine Issues

Fruit fly infestation becomes a problem with 

papaya after fruit have 25% skin yellowing (Seo et 

al. 1982). The damage caused by fruit flies include 

small surface blemishes, destruction of the edible 

flesh, and spoilage from decay. Heat treatments 

and irradiation are used for

 fruit fly disinfestation (Couey 1989, Paull 1990, 

Armstrong 1994). Occasionally, heat treatment 

can cause internal injury and scald (Paull 

1995), limit postharvest life, and reduce quality 

(Paull 1990). Papaya can tolerate insecticidal 

atmospheres (0.17 to 0.35% O2

, balance N2) at 20 

°C (68 °F) for up to 5 days (Yahia et al. 1989), 

though its disinfestation potential has not been 

shown.
450

Suitability as Fresh-Cut Product

Fruit are prepared as deseeded, halved fruit, slices, 

and chunks. Fresh-cut products made from 60 

to 80% yellow-skinned fruit, overwrapped with 

plastic film, can be held for up to 3 weeks at 0 to 

4 °C (32 to 39 °F) (Paull and Chen 1997). Powrie 

et al. (1990) patented a procedure in which pieces 

dipped in citric acid held in multilayer bags with 

15 to 20% O2

 and 3% helium had little loss in taste 

and texture after 16 weeks at 1 oC (34 °F).

References

Akamine, E.K. 1959. Effects of carbon dioxide 

on quality and shelf life of papaya. Tech. Progr. 

Rpt. 120, Hawaii Agricultural Experiment Station, 

Honolulu, HI.

Akamine, E.K. 1966. Respiration of fruits 

of papaya (Carica papaya L. var. Solo) with 

reference to effect of quarantine disinfestation 

treatments. Proc. Amer. Soc. Hort. Sci. 89:231-

236.

Akamine, E.K., and T. Arisumi. 1953. Control 

of postharvest storage decay of papaya (Carica 

papaya L.) with special reference to the effect of 

hot water. Proc. Amer. Soc. Hort. Sci. 61:270-274.

Akamine, E.K., and T. Goo. 1969. Effects of 

controlled atmosphere storage of fresh papaya 

(Carica papaya, L. var. Solo) with special 

reference to shelf life extension of fumigated fruit. 

Res. Bull. 144, Hawaii Agricultural Experiment 

Station, Honolulu, HI.

Akamine, E.K., and T. Goo. 1971. Relationship 

between surface color development and total 

soluble solids in papaya. HortScience 6:567-568.

Alvarez, A.M. 1980. Improved marketability of 

fresh papaya by shipment in hypobaric containers. 

HortScience 15:517-518.

Alvarez, A.M., and W.T. Nishijima. 1987. 

Postharvest diseases of papaya. Plant Dis. 71:681-

686.

An, J.F., and R.E. Paull. 1990. Storage 

temperature and ethylene influence on ripening of 

papaya fruit. J. Amer. Soc. Hort. Sci. 115:949-953.

Arisumi, T. 1956. Test shipments of papaya with 

special reference to storage decay control. Tech. 

Bull. 29, Hawaii Agricultural Experiment Station, 

Honolulu, HI.

Armstrong, J.W. 1994. Tropical and subtropical 

fruits. In R.E. Paull and J.W. Armstrong, eds., 

Insect Pests and Fresh Horticultural Products: 

Treatments and Responses, pp. 275-290. CAB 

Intl., Wallingford, U.K.

Cavaletto, C.G. 1989. Quality of high temperature 

forced air treated papaya. In Proceedings of 

the 25th Annual Papaya Industry Association 

Conference, Sept. 1989, Hilo, HI, pp. 10-15.

Cenci, S.A., A.G. Soares, J.M.S. Bibino, and 

M.L.M. Soiya. 1997. Study of the storage of 

‘Sunrise’ and ‘Solo’ papaya fruits under control 

atmospheres. Abstract no. 112. In M.E. Saltveit, 

ed., 7th International Controlled Atmosphere 

Research Conference, July 13-18, 1997, 

University of California, Davis, vol. 4, University 

of California, Davis, CA.

Chau, K.F., and A.M. Alvarez. 1983. Effects 

of low-pressure storage on Colletotrichum 

gloeosporioides and postharvest infection of 

papaya. HortScience 18:953-955.

Chen, N.M., and R.E. Paull. 1986. Development 

and prevention of chilling injury in papaya fruit. J. 

Amer. Soc. Hort. Sci. 111:639-643.

Couey, H.M. 1989. Heat treatment for control 

of postharvest diseases and insect pests of fruits. 

HortScience 24:198-202.

Couey, H.M., A.M. Alvarez, and M.G. Nelson. 

1984. Comparison of hot-water spray and 

immersion treatments for control of postharvest 

decay of papaya. Plant Dis. 68:436-437.
451

Couey, H.M., and G. Farias. 1979. Control of 

postharvest decay of papaya. HortScience 14:719-

721.

El-Tomi, A.L., A.B. Abon-Aziz, A.S. AbdelKader, and F.K. Abdel-Wahab. 1974. The effect of 

chilling and non-chilling temperatures on quality 

of papaya fruit. Egypt. J. Hort. 1:179-185.

Glazener, J.A., H.M. Couey, and A. Alarez. 1984. 

Effect of postharvest treatments on stemphyllium 

rot of papaya. Plant Dis. 68:986-988.

Hatton, T.T., and W.F. Reeder. 1969. Controlled 

atmosphere storage of papaya. Proc. Trop. Reg. 

Amer. Soc. Hort. Sci. 13:251-256.

Hawaii Department of Agriculture. 1990. 

Standards for Hawaii-Grown Papaya. Hawaii 

Department of Agricuture, Marketing Division, 

Honolulu, HI.

Hunter, J.E., and I.W. Buddenhagen. 1972. 

Incidences, epidemiology and control of fruit 

disease of papaya in Hawaii. Trop. Ag. 49:61-71.

Magalona, N. 1963. Artificial Induction of Lumps 

in the Fruit of Papaya (Carica papaya L.) M.Sc. 

Thesis, University of Hawaii, Honolulu, HI.

Nakasone, H.Y. 1986. Papaya. In S.P. 

Monselise, ed., CRC Handbook of Fruit Set and 

Development, pp. 277-301. CRC Press, Boca 

Raton, FL.

Nakasone, H.Y., and T.D. Arkle. 1971. 

Development of intra-ovarian ovaries in Carica 

papaya L. J. Amer. Soc. Hort. Sci. 96:550-553.

Nazeeb, M., and W.J. Broughton. 1978. Storage 

conditions and ripening of papaya ‘Bentong’ and 

‘Taiping.’ Sci. Hort. 9:265-277.

Nishijima, W.T., S. Ebersole, and J.A. Fernandez. 

1990. Factors influencing development of 

postharvest incidence of Rhizopus soft rot of 

papaya. Acta Hort. 269:495-502.

Paull, R.E. 1990. Postharvest heat treatments and 

fruit ripening. Postharv. News Info. 1:355-363.

Paull, R.E. 1995. Preharvest factors and the heat 

sensitivity of field grown ripening papaya fruit. 

Postharv. Biol. Technol. 6:167-175.

Paull, R.E. 1993. Pineapple and papaya. In

G. Seymour, J. Taylor, and G. Tucker, eds., 

Biochemistry of Fruit Ripening, pp. 291-323. 

Chapman & Hall, London, U.K.

Paull, R.E., and N.J. Chen. 1983. Postharvest 

variation in wall degrading enzymes of papaya 

fruit during ripening. Plant Physiology 72:131-

138.

Paull, R.E., and N.J. Chen. 1989. Waxing and 

plastic wraps influence water loss from papaya 

fruit during storage and ripening. J. Amer. Soc. 

Hort. Sci. 114:937-942.

Paull, R.E., and N.J. Chen. 1997. Minimal 

processing of papaya (Carica papaya L.) and 

the physiology of halved fruit. Postharv. Biol. 

Technol. 12:93-99.

Paull, R.E., W. Nishijima, M. Reyes, and C. 

Cavaletto. 1997. A review of postharvest handling 

and losses during marketing of papaya (Carica 

papaya L). Postharv. Biol. Tech. 11:165-179.

Powrie, W.D., R. Chiu, H. Wu, and B.J. Skura. 

1990. Preservation of cut and segmented fresh 

fruit pieces. U.S. Patent No. 4,895,729.

Qiu, Y., M.S. Nishina, and R.E. Paull. 1995. 

Papaya fruit growth, calcium uptake and fruit 

ripening. J. Amer. Soc. Hort. Sci. 120:246-253.

Quintana, M.E.G., and R.E. Paull. 1993. 

Mechanical injury during postharvest handling 

of ‘Solo’ papaya fruit. J. Amer. Soc. Hort. Sci. 

118:618-622.

Reyes, M.E.Q., and R.E. Paull. 1994. Skin 

freckles on ‘Solo’ papaya fruit. Sci. Hort. 58:31-

39.
452

Seo, S.T., G.B. Farias, and E.J. Harris. 1982. 

Oriental fruit fly: ripening of fruit and its effect on 

index of infestation of Hawaiian papayas. J. Econ. 

Ent. 75:173-178.

Sommer, N.F., and F.G. Mitchell. 1978. Relation 

of chilling temperatures to postharvest Alternaria

rot of papaya fruit. Proc. Trop. Reg. Amer. Soc. 

Hort. Sci. 22:40-47.

Thompson, A.K., and G.R. Lee. 1971. Factors 

affecting the storage behaviour of papaya fruit. J. 

Hort. Sci. 46:511-516.

Wardlaw, C.W., R.E.D. Baker, and S.H. Crowdy. 

1939. Latent infections in tropical fruits. Trop. Ag. 

16:275-276.

Yahia, E. 1998. Modified and controlled 

atmospheres for tropical fruits. Hort. Rev. 22:123-

183.

Yahia, E., F. Medina, and M. Rivera. 1989. 

Tolerance of mango and papaya to atmospheres 

containing very high levels of CO2

 and/or very 

low levels of O2

 as a possible insect control 

treatment. In E. Kupferman, and M. Patterson, 

eds., 5th International Controlled Atmosphere 

Research Conference, Wenatchee WA, June 14-16, 

1989, vol. 2, pp. 77-89. 

Zee, F.T., M.S. Nishina, H.T. Chan, and K.A. 

Nishijima. 1989. Blossom end defects and fruit 

fly disinfestation in papayas following hot water 

quarantine treatment. HortScience 24:323-325.
453

Parsley

Julian A. Heyes

Heyes is formerly with the New Zealand Institute 

for Crop and Food Research, Palmerston North, 

New Zealand. He is now with the Department of 

Food Science and Technology, Massey University, 

Palmerston North, New Zealand.

Scientific Name and Introduction

Petroselinum crispum (Mill.) Nyman ex A.W. 

Hill—parsley—is a member of the Apiaceae 

family. The edible foliage is grown as an annual 

and used as a garnish and food ingredient. Both 

curly-leaved (such as ‘Deep Green,’ ‘Forest 

Green,’ and ‘Moss Curled’) cultivars and flatleaved (such as Plain, Plain Italian Dark Green, 

and Deep Green Italian) types are available. 

There is a subspecies, P. crispum subsp. 

tuberosum, Hamburg parsley, that has an edible 

root. Parsley has very high vitamin and nutrient 

content. It is highest in calcium, iron, and folate 

of all vegetables studied (Athar et al. 1999) and 

has among the highest contents of β-carotene, 

thiamin, riboflavin, and vitamins C and E. A high 

proportion of the carotene is 9-cis β-carotene, 

possibly active against cancer and cardiovascular 

disease (Benamotz and Fishler 1998).

Quality Characteristics and Criteria

The quality criteria for parsley are freshness, 

green color, freedom from defects or seed stems, 

and freedom from decay (AMS 2002). 

Horticultural Maturity Indices

Parsley can be harvested progressively or cut 

all at one time. Long petioles are desirable for 

bunching. Most of the U.S. crop is harvested by 

hand.

Grades, Sizes, and Packaging

Only one grade is available (U.S. No. 1), which 

consists of parsley that meet quality criteria and 

have similar varietal characteristics; that is, curlyleaf and flat-leaf varieties are not mixed. Parsley is 

usually packaged in cartons or jumbo crates of 60 

bunches, 9 to 11 kg (20 to 25 lb).

Precooling Conditions

Rapid removal of field heat without excessive 

drying helps retain green color and freshness. 

Parsley can be precooled with ice (package icing 

or liquid-icing [Cantwell and Reid 1992]) or by 

vacuum-cooling (Aharoni et al. 1989). Forced-air 

cooling or hydrocooling are commonly practiced 

(Joyce et al. 1986). 

Optimum Storage Conditions

The recommended conditions for commercial 

storage of parsley are 0 °C (32 °F) with 95 to 

100% RH (Cantwell 2002). Parsley can be stored 

for 1 to 2 mo under these conditions, compared to 

only 3 days at 18 to 20 °C (64 to 68 °F) with 85 to 

90% RH (Lisiewska et al. 1997). The endpoint of 

storage at 0 °C (32 °F) occurs when parsley wilts, 

at around 20% weight loss (Hruschka and Wang 

1979). MAP is effective in extending storage 

life, but temperature changes and condensation 

must be avoided. Aharoni et al. (1989) showed 

that nonperforated polyethylene liners delayed 

yellowing and decay at low temperature. Park 

et al. (1999) achieved 77 days of storage at 0 °C 

(32 °F) and 35 days at 5 °C (41 °F) with good 

retention of firmness and vitamin C content by 

using a 40 μm-thick ceramic film. A preharvest 

spray with gibberellic acid may extend storage life 

(Lers et al. 1998). Hamburg parsley roots (without 

leaves) can be stored at 0 °C (32 °F) for several 

months (Bakowski et al. 1994, Elkner et al. 1998).
454

Controlled Atmosphere (CA) 

Considerations

Parsley can tolerate 8 to 10% O2

 and 8 to 10% 

CO2

 (Saltveit 1997), but this may be of little 

benefit at 0 °C (32 °F). An atmosphere of 10% O2

and 11% CO2

 was optimal for delaying yellowing 

in parsley stored at 5 °C (41 °F) (Apeland 1971). 

Storage in 10% O2

 and 10% CO2 (Yamauchi and 

Watada 1993) or 10% CO2

 (Lers et al. 1998) 

delayed yellowing at room temperature. 

Retail Outlet Display Considerations

Parsley is often sold in unsealed bunches. Light 

reduces yellowing, but levels in retail shelves 

are too low to have a significant effect. Use of 

ice or water sprays is acceptable. If MAP is used 

during storage, care must be taken to prevent 

condensation during the retail period. 

Chilling Sensitivity

Parsley is not chilling sensitive. It should be stored 

as cold as possible without freezing, which occurs 

at -1.1 °C (30 °F).

Ethylene Production and Sensitivity

Parsley leaves produce very little ethylene but are 

very sensitive to it (Joyce et al. 1986, Tsumura et 

al. 1993). Cantwell and Reid (1993) observed that 

parsley leaves produced 0.08, 0.44 and 0.80 μL 

kg-1 h-1 at 0, 10 and 20 °C (32, 50, 68 °F). As little 

as 0.4 μL L-1 is enough to accelerate yellowing 

if parsley is stored above 0 °C (32 °F) (Cantwell 

and Reid 1993). Ethylene application does not 

stimulate respiration in parsley (Inaba et al. 1989). 

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 22 to 38

5 °C 49 to 70

10 °C 78 to 150

15 °C 131 to 168

20 °C 176 to 221

25 °C 259 to 289

Data from Apeland (1971), Hruschka and Wang 

(1979), and Cantwell and Reid (1986).

Rates were measured 3 days after harvest.

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Wilting and yellowing signal the end of shelf-life. 

No particular disorders are described for parsley.

Postharvest Pathology

Both Erwinia and Botrytis can cause postharvest 

damage from rots and mold (Ryall and Lipton 

1979).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Parsley’s flavor and aroma were retained better 

in perforated film packages than in sealed film 

packs (Manzano et al. 1995). Food safety is a 

major concern. Chlorinated water is somewhat 

beneficial in reducing contamination (Park and 

Sanders 1992), but personal hygiene of the 
455

staff is paramount. Parsley has been implicated 

as a source of the infectious Shigella (Crowe 

et al. 1999) and Citrobacter freundii, causing 

gastroenteritis and hemolytic uremic syndrome 

(Tschape et al. 1995), and thermotolerant 

campylobacters (Park and Sanders 1992).

Special Considerations

Parsley has an extremely high respiration rate. 

Young leaves respire at a higher rate than old 

leaves at harvest, but the respiration rate does not 

decrease as much after harvest in older leaves as 

in younger leaves, so younger leaves store better 

(Apeland 1971). 

Parsley contains furocoumarins, including 

psoralen (Manderfeld et al. 1997), which are 

effective antimicrobial agents but can act as 

phototoxins, inducing dermatitis (Lagey et al. 

1995). Parsley is used as a medicinal plant to treat 

hypertension in Morocco (Ziyyat et al. 1997) and 

diabetes in Turkey (Tunali et al. 1999).

References

Aharoni, N., A. Reuveni, and O. Dvir. 1989. 

Modified atmospheres in film packages delay 

senescence and decay of fresh herbs. Acta Hort. 

258:255-262.

Apeland, J. 1971. Factors affecting respiration and 

color during storage of parsley. Acta Hort. 20:43-

52.

Athar, N., T.W. Spriggs, and P. Liu. 1999. The 

Concise New Zealand Food Composition Tables, 

4th ed. New Zealand Institute for Crop & Food 

Research, Palmerston North, N.Z.

Bakowski, J., H. Michalik, and L. Umiecka. 

1994. Effect of sowing and harvest date on the 

quality of root parsley and its storability. Biuletyn 

Warzywniczy 41:157-167.

Benamotz, A., and R. Fishler. 1998. Analysis of 

carotenoids with emphasis on 9-cis β-carotene 

in vegetables and fruits commonly consumed in 

Israel. Food Chem. 62:515-520.

Cantwell, M. 2002. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu/

produce_information/storagefreshproduce.

Cantwell, M.I., and M.S. Reid. 1986. Postharvest 

handling of fresh culinary herbs. II. Respiration 

and ethylene production. Perishables Handling 

Quarterly 60:2-5.

Cantwell, M.I., and M.S. Reid. 1992. Postharvest 

handling systems: fresh herbs. In A.A. Kader, ed., 

Postharvest Technology of Horticultural Crops, 

2nd ed., pp. 211-213. DANR Pub. no. 3311, 

University of California, Oakland, CA.

Cantwell, M.I., and M.S. Reid. 1993. Postharvest 

physiology and handling of fresh culinary herbs. J. 

Herbs, Spices and Medicinal Plants 1:93-127.

Crowe, L., W. Lau, and L. McLeod. 1999. 

Outbreaks of Shigella sonnei infection associated 

with eating fresh parsley—United States and 

Canada, July-August 1998. J. Amer. Med. Assoc. 

281:1785-1787.

Elkner, K., M. Horbowicz, and R. Kosson. 1998. 

Effect of storage on contents of dietary fibre and 

its composition in some cultivars of red beet, root 

parsley and carrot. Veg. Crops Res. Bull. 49:107-

120.

Hruschka, H.W., and C.Y. Wang. 1979. Storage 

and shelf life of packaged watercress, parsley 

and mint. Marketing Research Report 1102, U.S. 

Department of Agriculture, Washington, DC.

Inaba, A., Y. Kubo, and R. Nakamura. 1989. Effect 

of exogenous ethylene on respiration in fruits and 

vegetables with special reference to temperature. 

J. Jap. Soc. Hort. Sci. 58:713-718.
456

Joyce, D., M.S. Reid, and P. Katz. 1986. 

Postharvest handling of fresh culinary herbs. 

Perishables Handling Quarterly 58:1-4.

Lagey, K., L. Duinslaeger, and A. Vanderkelen. 

1995. Burns induced by plants. Burns 21:542-543.

Lers, A., W.B. Jiang, E. Lomanies, and N. 

Aharoni. 1998. Gibberellic acid and CO2

 additive 

effect in retarding postharvest senescence of 

parsley. J. Food Sci. 63:66-68.

Lisiewska, Z., W. Kmiecik, and A. Budnik. 

1997. Effect of conditions and time of storage on 

technological quality changes of parsley leaves. 

Folia Hort. 9:21-29.

Manderfeld, M.M., H.W. Schafer, P.M. Davidson, 

and E.A. Zottola. 1997. Isolation and identification 

of antimicrobial furocoumarins from parsley. J. 

Food Protect. 60:72-77.

Manzano, M., B. Citterio, M. Maifreni, et al. 

1995. Microbial and sensory quality of vegetables 

for soup packaged in different atmospheres. J. Sci. 

Food Agric. 67:521-529.

Park, C.E., and G.W. Sanders. 1992. Occurrence 

of thermotolerant campylobacters in fresh 

vegetables sold at farmers outdoor markets and 

supermarkets. Can. J. Microbiol. 38:313-316.

Park, K.W., H.M. Kang, E.M. Yang, and J.C. 

Jung. 1999. Effects of film package and storage 

temperature on quality of parsley in modified 

atmosphere storage. Acta Hort. 483:291-298.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1. AVI, Westport CT.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

4, pp. 98-117. University of California, Davis CA.

Tschape, H., R. Prager, W. Streckel, et al. 1995. 

Verotoxinogenic Citrobacter freundii associated 

with severe gastroenteritis and cases of hemolytic 

uraemic syndrome in a nursery school—green 

butter as the infection source. Epidem. Inf. 

114:441-450.

Tsumura, F., Y. Ohsako, Y. Haraguchi. 1993. 

Rapid changes in parsley leaves during storage in 

controlled or ethylene-containing atmosphere. J. 

Food Sci. 58:619-625.

Tunali, T., A. Yarat, R. Yanardag, et al. 1999. 

Effect of parsley (Petroselinum crispum) on the 

skin of STZ-induced diabetic rats. Phytotherapy 

Res. 13:138-141.

AMS [USDA Agricultural Marketing Service]. 

2002. Quality Standards—Fresh Fruits and 

Vegetables. At http://www.ams.usda.gov/

AMSv1.0/standards.

Yamauchi, N., and A.E. Watada. 1993. Pigment 

changes in parsley leaves during storage in 

controlled or ethylene-containing atmosphere. J. 

Food Sci. 58:616-618, 637.

Ziyyat, A., A. Legssyer, H. Mekhfi, et al. 1997. 

Phytotherapy of hypertension and diabetes in 

oriental Morocco. J. Ethnopharmacol. 58:45-54.
457

Parsnip

Peter M.A. Toivonen

Toivonen is with the Pacific Agri-Food Research 

Centre, Agriculture and Agri-Food Canada, 

Summerland, British Columbia, Canada.

Scientific Name and Introduction

The parsnip (Pastinaca sativa L.) is a native 

of Europe and Asia. The plant is a biennial, 

belonging to the Apiaceae (Umbelliferae), or 

parsley, family. The crop is grown as an annual, 

and the thickened, cream-colored root is the edible 

portion. It is a long-season crop (~100 days) and 

thrives best in cool growing climates. Parsnips are 

generally available from mid August to March.

Quality Characteristics and Criteria

A high-quality parsnip will be firm, reasonably 

clean, and fairly smooth-surfaced (not deeply 

ridged, no secondary rootlets). Parsnips are topped 

after harvesting but should not be trimmed into the 

crown.

Horticultural Maturity Indices

Parsnips are harvested when root diameter 

is between 2.5 and 7.6 cm (1 and 3 in) at the 

shoulder.

Grades, Sizes, and Packaging

There are two grades, U.S. No. 1 and U.S. No. 

2, based on shape, external appearance, and size. 

Parsnips are commonly packaged in 11.4-kg (25-

lb) perforated polyethylene bags or 5.5-kg (12-lb) 

cartons holding 12 cello bags of 0.5 kg (1 lb) each.

Precooling Conditions

Parsnips are similar to carrots in requirements and 

should be cooled using hydrocooling or packageicing. Rapid cooling to 5 °C (41 °F) or below 

immediately after harvest is essential to minimize 

decay and moisture losses during extended 

storage.

Optimum Storage Conditions

Parsnip roots can be stored 4 to 6 mo at 0 to 1 °C 

(32 to 34 °F) with 98% RH (van den Berg and 

Lentz 1973). Only healthy roots with no damage 

should be placed in storage.

Controlled Atmosphere (CA) 

Considerations

Little work has been done, but limited results 

suggest that there are no benefits to controlledatmosphere storage (Stoll and Weichmann 1987).

Retail Outlet Display Considerations

Water sprinklers and top-icing are acceptable for 

nonpackaged product. Packaged products should 

be held in a cold display case with no ice or water 

sprinklers.

Chilling Sensitivity

Parsnips are not chilling sensitive.

Ethylene Production and Sensitivity

Parsnips produce very little ethylene: <0.1 μL 

kg-1 h-1 at 20 °C (68 °F). Exposure to low levels 

of ethylene in cold storage causes bitterness, 

likely due to accumulation of xanthotoxin 

(8-methoxypsoralen) (Johnson et al. 1973, 

Shattuck et al. 1988).
458

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 8 to 16

5 °C 8 to 18

10 °C 19 to 25

15 °C 30 to 43

Data from Smith (1957) and van den Berg and 

Lentz (1972).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Surface browning is a significant problem that 

is largely associated with bruising and abrasion 

injury during harvest (Kaldy et al. 1976, Toivonen 

1992). Crops grown on coarse sandy soils are 

more susceptible, and there are cultivars resistant 

to browning (Kaldy et al. 1976, Toivonen 1992). 

Surface browning also increases with length of 

storage (Kaldy et al. 1976). Postharvest dips 

reduce browning during storage (Toivonen 1992). 

Waxing parsnips, to reduce moisture loss, will 

increase browning (Plantenius 1939).

Postharvest Pathology

Diseases of importance during storage, transit, 

and marketing are parsnip canker (Itersonilia 

perplexans Derx.), gray mold rot (Botrytis cinerea

Pers.:Fr.), bacterial soft rot (Erwinia carotovora

(Jones) Bergey et al.) and watery soft rot 

(Sclerotinia sclerotiorum [Lib.] de Bary) (Smith et 

al. 1982). Some cultivars are resistant to parsnip 

canker (Davis et al. 1989).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

No potential exists.

Special Considerations

The highest freezing temperature is -0.9 °C (30.4 

°F). An important component of parsnip quality 

is sweetness, which is enhanced if exposed to fall 

frosts before harvest. However, early-harvested 

parsnips can also be induced to sweeten using 

short-term cold storage (Shattuck et al. 1989).

Acknowledgments

Some information in this chapter is from the 

Oregon State University website “Commercial 

Vegetable Production Guides” (http://horticulture.

oregonstate.edu/content/vegetable-productionguides) and the British Columbia Vegetable 

Marketing Commission website (http://www.

bcveg.com).

References

Davis, D.W., F.L. Pfleger, and M.A. Shehata. 

1989. ‘Andover’ parsnip. HortScience 24:521-522.

Johnson, C., D.R. Brannon, and J. Kuc. 1973. 

Xanthoxin: A phytoalexin of Pastinaca sativa

root. Phytochemistry 12:2961-2962.

Kaldy, M.S., J.F. Dormaar, S.A. Molnar, and P. 

Ragan. 1976. Browning of parsnips as related to 

varieties, soil conditions and length of storage. In

55th Annual Report of the Canadian Horticultural 

Council, pp. 101-102.

Plantenius, H. 1939. Wax emulsions for 

vegetables. Bull. 723, New York University 

Agricultural Experiment Station, Geneva, NY.

Shattuck, V.I., Y. Kakuda, and R. Yada. 1989. 

Sweetening of parsnip roots during short-term 

cold storage. Can. Inst. Food Sci. Technol. J. 

22(4):378-382.
459

Shattuck, V.I., R. Yada, and E.C. Lougheed. 1988. 

Ethylene-induced bitterness in stored parsnips. 

HortScience 23:912.

Smith, H. 1957. The production of carbon dioxide 

and metabolic heat by horticultural produce. 

Modern Refrig. 60:493-496.

Smith, M.A., L.P. McColloch, and B.A. Friedman. 

1982. Market Diseases of Asparagus, Onions, 

Beans, Peas, Carrots, Celery, and Related 

Vegetables. Agriculture Handbook 303, U.S. 

Department of Agriculture, Washington, DC.

Stoll, K., J. Weichmann. 1987. Root vegetables. 

In J. Weichmann, ed., Postharvest Physiology of 

Vegetables, pp. 541-553. Marcel Dekker, New 

York, NY.

Toivonen, P.M.A. 1992. The reduction of 

browning in parsnips. J. Hort. Sci. 67:547-551.

van den Berg, L., and C.P. Lentz. 1972. 

Respiratory heat production of vegetables during 

refrigerated storage. J. Amer. Soc. Hort. Sci. 

97:431-432.

van den Berg, L., and C.P. Lentz. 1973. High 

humidity storage of carrots, parsnips, rutabagas 

and cabbage. J. Amer. Soc. Hort. Sci. 98:129-132.
460

Passion Fruit

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Purple passion fruit (Passiflora edulis Sim.) and 

yellow passion fruit (P. edulis f. flavicarpa Deg.) 

should more correctly be referred to as the passion 

flower fruit, but the trade more commonly uses 

passion fruit. Hybrids of the two subspecies form 

freely and have characteristics between the two 

parents. A tough outer skin surrounds a fleshy, 

acidic, yellow pericarp and aril surrounding small 

edible black seeds (Pruthi 1963). The yellow, eggshaped type of passion fruit is 6 to 8 cm (2.5 to 

3 in) wide by 7 cm (2.7 in) long and weighs 50 

to 150 g (1.8 to 5.3 oz). The smaller purple fruit 

weighs 25 to 50 g (1 to 2 oz).

Quality Characteristics and Criteria

Size, shape, skin color, acidity, and SSC are 

the major criteria used to evaluate quality. Fruit 

should be free of blemishes. SSC is 10 to 18% in 

yellow fruit and 10 to 20% in the purple type, with 

the yellow type having a more acidic flavor.

Horticultural Maturity Indices

Fruit are harvested when ≥75% are turning yellow 

or purple (Chan 1980). Purple passion fruit at 

the light-purple stage is more suitable for long 

distance transport. Normally, the respiratory 

climacteric occurs on the vine. Fruit harvested 

earlier have an unripe flavor (Campbell and 

Knight 1983). In some cases, fruit are allowed to 

abscise and fall and are then picked up from the 

ground.

Grades, Sizes, and Packaging

Fruit should have a diameter of 5 to 8 cm (2 to 

3 in) for purple and 6 to 8 cm (2.5 to 3 in) for 

yellow. Skin color should be full yellow or purple, 

unless a hybrid. Fruit are packed in 6-kg (13.2-lb) 

and 4.5-kg (9.9-lb) fiberboard cartons, sometimes 

in one- or two-layer trays or cell packs.

Precooling Conditions

Room-cooling or forced-air cooling to 10 °C (50 

°F) is desirable.

Optimum Storage Conditions

Yellow passion fruit should be stored at 7 to 10 °C 

(45 to 50 °F) with 90 to 95% RH. They will have 

a potential storage life of 2 weeks (Arjona et al. 

1992). Purple passion fruit are chilling tolerant 

and can be stored at 3 to 5 °C (37 to 41 °F) for 3 

to 5 weeks.

Controlled Atmosphere (CA) 

Consideration

Modified atmospheres (MA) have been tested on 

yellow passion fruit, and a fungicide treatment 

before storage is desirable. Film-bagging and 

various coatings reduce water loss in yellow 

and purple passion fruit (Arjona et al. 1992, 

Mohammed 1993, Bepete et al. 1994). Response 

to coatings and film bagging may be associated 

with control of water loss, rather than MA effects.

Retail Outlet Display Considerations

Fruit should be displayed at ambient temperature 

and not misted or iced.
461

Chilling Sensitivity

Symptoms of chilling injury on yellow passion 

fruit are skin discoloration, pitting, water-soaked 

areas, uneven ripening, and increased decay. 

Discoloration can penetrate skin into the exocarp.

Ethylene Production and Sensitivity

Passion fruit produce very high levels of ethylene: 

160 to 400 μL kg-1 h-1 at 20 °C (68 °F) at their 

climacteric peak (Shiomi et al. 1996). Exposure to 

100 μL L-1 ethylene for 24 h accelerates ripening 

(Akamine et al. 1957, Arjona and Matta 1991).

Respiration Rates

The climacteric of this fruit normally occurs on 

the vine (Biale 1975).

Temperature mg CO2 kg-1 h-1

5 °C 29 to 58

10 °C 39 to 78

20 °C 87 to 194

25 °C 175 to 349

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Shrivel, pulp fermentation, and fungal attack are 

the major postharvest problems (Pruthi 1963). 

Shrivel is caused by moisture loss without initially 

significantly affecting pulp quality.

Postharvest Pathology

Postharvest disease is normally a minor problem. 

Most common is brown spot (Alternaria 

passiflorae), whose symptoms include circular, 

sunken, light-brown spots on ripening fruit (Inch 

1978). This disease is most severe following 

warm, wet periods. Septoria spot (Septoria 

passiflorae) infects fruit in the field and leads to 

uneven ripening of the skin. Phytophthora fruit rot 

(Phytophthora spp.) causes water-soaked, darkgreen patches that dry up on the skin. Orchard 

sanitation, reduction of high RH by pruning to 

open the canopy, and application fungicides can 

minimize these diseases.

Quarantine Issues

Fruit are a fruit fly host and may require treatment. 

Irradiation has been successful.

Suitability as Fresh-Cut Product

No potential currently exists.

References

Akamine, E.K., R.E. Young, and J.B. Biale. 1957. 

Respiration and ethylene production in the purple 

passion fruit. Proc. Amer. Soc. Hort. Sci. 69:221-

225.

Arjona, H.E., and F.B. Matta. 1991. Postharvest 

quality of passion fruit as influenced by harvest 

time and ethylene treatment. HortScience 

26:1297-1298.

Arjona, H.E., F.B. Matta, and J.O. Garner. 1992. 

Temperature and storage time affect quality of 

yellow passion fruit. HortScience 27:809-810.

Biale, J.B. 1975. Synthetic and degrading 

process in fruit ripening. In N.F. Haard and D.K. 

Salunkhe, eds., Symposium: Postharvest Biology 

and Handling of Fruits and Vegetables, pp. 5-18. 

AVI, Westport, CT.

Bepete, M., N. Nenguwo, and J.E. Jackson. 

1994. The effect of sucrose coating on ambient 

temperature storage of several fruits. In B.R. 

Champ, E. Highley and G.I. Johnson, eds., 

Proceedings of the International Conference 
462

on Postharvest Handling of Tropical Fruits, pp. 

427-429. Chiang Mai, Thailand, July 1993. The 

Australian Centre for International Agricultural 

Research Proceedings no. 50, Canberra, Australia

Campbell, C.W., and R.J. Knight. 1983. 

Production de Gandadilla, pp. 223-231. Ministerio 

de Agricultura, Pesca y Alimentacion, Canary 

Islands, Spain.

Chan, H.T. 1980. Passion fruit. In S. Nagy and 

P.E. Shaw, eds., Tropical and Subtropical Fruits: 

Composition, Properties and Uses, pp. 300-315. 

AVI, Westport, CT.

Inch, A.J. 1978. Passion fruit diseases. Queensland 

Ag. J. 104:479-484.

Mohammed, M. 1993. Storage of passion fruit in 

polymeric films. Proceedings of the Interamerican 

Society for Tropical Horticulture 37:85-88.

Pruthi, J.S. 1963. Physiology, chemistry, and 

technology of passion fruit. Adv. Food Res. 

12:203-282.

Shiomi, S., L.S. Wamocho, and S.G. Agong. 1996. 

Ripening characteristics of purple passion fruit on 

and off the vine. Postharv. Biol. Technol. 7:161-

170. 
463

Pea

Stephen Morris and Jenny Jobling

Morris and Jobling are with the Sydney 

Postharvest Laboratory, Food Science Australia, 

North Ryde, New South Wales, Australia.

Specific Name and Introduction

There are three types of edible peas (Pisum 

sativum L.) from the family Fabaceae (also called 

Leguminosae). The most common is the garden 

or green pea P. sativum var. sativum L. This pea 

has a tough pod that is discarded prior to eating 

(Basterrechea and Hicks 1991, Snowdon 1991). 

Most often these peas are frozen or processed. The 

success of the frozen pea industry in the United 

States has resulted in a decline in the sale of peas 

sold in the pods (Basterrechea and Hicks 1991). 

The other two types of peas have soft, edible 

pods and belong to the subspecies P. sativum var. 

macrocarpon Ser. The snow or sugar pea has a flat 

pod with minimal development of the seeds, while 

the sugar snap pea or snap pea has well developed 

seeds and is fully rounded (Hocking 1997, Suslow 

and Cantwell 1998). The sugar snap pea is the 

result of a cross between the snow pea and an 

unusual tightly podded pea with thick walls. All of 

these peas grow best under cool, moist conditions. 

Quality Characteristics and Criteria

Good-quality peas are uniformly bright green, 

fully turgid, and free from defects and mechanical 

damage. Stems and calyxes should be green.

Grades, Sizes, and Packaging

Grades include U.S. No. 1 and U.S. Fancy, based 

primarily on external appearance. They should 

exhibit similar varietal characteristics and be 

not overmature or excessively small, not badly 

misshapen or water-soaked, fairly well filled, 

fresh, and free from decay and from damage 

caused by black calyxes, freezing, splitting, hail, 

dirt, leaves or other foreign matter, mildew or 

other diseases, insects, or mechanical or other 

means. There are no USDA grades for snow or 

snap peas, but best-quality snow peas are 7.6 to 9 

cm (3 to 3.5 in) long and 1.9 cm (0.75 in) wide, 

while snap peas should be 6.4 to 7.6 cm (2.5 to 3 

in) long. Green peas are shipped in 13.6-kg (30-

lb) bushel baskets, or crates. Snow and sugar snap 

peas are shipped in 4.5-kg (10-lb) cartons.

Harvest Maturity Indices

For best quality, both edible podded peas 

and green peas should be harvested before 

physiological maturity; that is, before peas 

deform the hull (Basterrechea and Hicks 1991). 

Snow peas should be harvested when the pods 

are maximum size but before any visible seed 

development; frequent harvesting is necessary. 

Sugar snap peas should be harvested after they 

have developed seeds, as with garden peas 

(Hocking 1997). 

Precooling Conditions

Sugar content and flavor decrease rapidly after 

harvest unless green peas are promptly cooled to 

0 °C (32 °F). Therefore, they must be promptly 

precooled after harvest by forced-air cooling, 

hydrocooling, or vacuum-cooling. If vacuumcooling is used, it is important that the peas are 

prewet to ensure rapid cooling (Ryall and Lipton 

1979). Forced-air cooling is the preferred method 

of cooling for edible podded peas (NWREC 

1998).

Optimum Storage Conditions

All three types of peas can be stored for 1 to 2 

weeks at 0 °C (32 °F) with 95 to 98% RH (Wager 

1964, Suslow and Cantwell 1998). Garden peas 

store better unshelled than shelled, possibly 

because shelling damages the peas (Basterrechea 

and Hicks 1991). If there is surface moisture on 

peas, it is essential that they be stored below 2 °C 

(36 °F). 
464

Controlled Atmosphere (CA) 

Considerations

Little work has been done on CA storage of peas. 

Green pea quality was maintained better for 20 

days in 5 to 7% CO2

 at 0 °C (32 °F) than in air 

(Tomkins 1957). Snow and snap peas respond 

moderately to CA of 2 to 3% O2

 and 2 to 3% 

CO2

, though not all research has found CA to be 

beneficial (Suslow and Cantwell 1998).

Retail Outlet Display Considerations

Storage with crushed ice can be beneficial, and 

water sprays are acceptable for garden and snow 

peas, but these methods should be avoided for 

snap peas (Suslow and Cantwell 1998).

Chilling Sensitivity

Peas are not sensitive to low temperature and 

should be stored as close to 0 °C (32 °F) as 

possible without freezing.

Ethylene Production and Sensitivity

Peas produce very low levels of ethylene: <0.1 

μL kg-1 h-1 at 20 °C (68 °F). However, they are 

moderately sensitive to ethylene after harvest, 

which results in yellowing and increased decay. 

The calyx is more sensitive to ethylene than the 

pod (Suslow and Cantwell 1998).

Respiration Rates

Temperature Garden Peas Edible-pod 

peas (estimated)

-----------mg CO2 kg-1 h-1-----------

0 °C 30 to 46 30 to 48

5 °C 55 to 72 53 to 74

10 °C 63 to 108 65 to 112

15 °C 165 to 185 165 to 187

20 °C 220 to 322 221 to 324

25 °C 298 to 327 —

Data from ASHRAE (1985) and Suslow and 

Cantwell (1998).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Freezing may start at -0.6 °C (31 °F). Freezing 

causes water-soaked areas followed by rapid 

decay from soft rot bacteria (Suslow and Cantwell 

1998). Edible podded peas are susceptible to 

premature senescence resulting in yellowing, color 

changes in the calyx, and loss of tenderness and 

flavor (Suslow and Cantwell 1998). Storage at >5 

°C (41 °F) and exposure to ethylene can accelerate 

this problem. 

Postharvest Pathology

Because of high respiration rate, the heat 

generated by unrefrigerated peas will promote 

decay. Blemishes that reduce quality can be 

caused by alternaria blight (Alternaria alternata),

anthracnose (Colletotrichum), ascochyta pod 

spot (Ascochyta pisi Lib), and powdery mildew 

(Erysiphe spp.) (Snowdon 1991). Common 

diseases for edible podded peas are gray mold 

(Botrytis cinerea), watery soft rot (Sclerotinia 

sclerotiotorum), rhizopus rot, and bacterial soft 

rot. Botrytis gray mold can be a problem at the 

blossom-end of fresh-cut pods.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Edible podded peas are suitable for use in freshcut mixtures.
465

Special Considerations

Keeping peas cold is critical for retaining quality. 

Surface moisture should be avoided unless the 

marketing chain is short and temperatures are kept 

<2 °C (<36 °F). 

References

ASHRAE [American Society of Heating, 

Refrigerating, and Air-Conditioning Engineers]. 

1985. ASHRAE Handbook—1985 Fundamentals. 

ASHRAE, Atlanta, GA.

Basterrechea, M., and J.R. Hicks. 1991. Effect 

of maturity on carbohydrate changes in snap pea 

pods during storage. Sci. Hort. 48:1-8.

Hocking, D.F. 1997. Snow peas and sugar 

snap peas. Agfact H8.1.35, New South Wales 

Agriculture, Sydney, Australia.

NWREC [North Willamette Research and 

Extension Center]. 1998. Edible pod peas. At

http://horticulture.oregonstate.edu/content/

vegetable-production-guides.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transport and Storage of Fruits and Vegetables, 

2nd ed., vol. 1, Vegetables and Melons. AVI Pub., 

Westport, CT.

Snowdon, A.L. 1991. A Colour Atlas of 

Postharvest Diseases and Disorders of Fruit and 

Vegetables, vol. 2, Vegetables, pp. 97-138. Wolfe 

Scientific, London, U.K.

Suslow, T.V., and M. Cantwell. 1998. Peas—

Snow and Snap Pod Peas. Perishables Handling 

Quarterly 93:15-16 

Tomkins, R.G. 1957. Peas kept for 20 days in gas 

store. Grower (U.K.) 48:226-227.

Wager, H.G. 1964. Physiological studies of the 

storage of green peas. J. Sci. Food Agr. 15:245- 

252. 
466

Peach

Carlos H. Crisosto and Adel A. Kader

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA. Kader was 

with the Department of Plant Sciences, University 

of California, Davis, CA. He is deceased. 

Scientific Name and Introduction

The peach, Prunus persicae, is native to China and 

Persia (Iran); at one time it was called “Persian 

apple.” Chinese literature dates its cultivation in 

China to 1,000 B.C. Carried from China to Persia, 

the peach quickly spread from there to Europe. 

In the 16th century, it was established in Mexico, 

probably by the Spanish. Spanish missionaries 

introduced the peach to California in the 18th 

century. 

California is a major producer and shipper of 

peaches in the United States. The development of 

white-fleshed peach cultivars is important. Current 

fresh peach shipments approach 19 million 10-kg 

(22-lb) packages from more than 155 cultivars. In 

the San Joaquin Valley, harvest of early cultivars 

starts in mid May, and harvest of late cultivars 

is completed in early October. The United States 

exports mainly to Canada, Taiwan, Hong Kong, 

Mexico, and South America.

Quality Characteristics and Criteria

There is high consumer acceptance of peaches 

with high SSC. TA and SSC:TA are also important 

factors in consumer acceptance. For mid-season 

peaches, a minimum of 11% SSC with TA ≤0.7% 

is required to satisfy about 80% of consumers. 

Fruit with 9 to 13.5 N (2 to 3 lb-force) flesh 

firmness are considered ready to eat. Fruit with 

firmness below about 30 N (7 lb-force) measured 

on the fruit cheek have high consumer acceptance.

Horticultural Maturity Indices

In California, harvest date of most cultivars is 

determined by change in skin ground color from 

green to yellow. A color chip guide is used to 

determine maturity of each cultivar except whitefleshed cultivars. A two-tier maturity system is 

used in California: (1) U.S. Mature (minimum 

maturity) and (2) Well-Mature or Tree Ripe. WellMature and Tree Ripe are the same according 

to the California Department of Food and 

Agriculture, Division of Inspection Services.

Measurement of fruit firmness is recommended 

for cultivars in which skin ground color is masked 

by full red color development before maturation. 

In these cases, a maximum maturity index can 

be applied. Maximum maturity is defined as 

the minimum flesh firmness (measured with a 

penetrometer with an 8-mm tip) at which fruit can 

be handled without bruising damage. Bruising 

susceptibility varies among cultivars.

Grades, Sizes, and Packaging

Fruit are hand-picked into bags, baskets, or 

totes. Fruit are then dumped into bins on trailers 

between tree rows in the orchard. If fruit are 

picked into totes, the totes are usually placed 

directly inside the bins. Peaches are transported 

from orchard to packinghouse and cooled as soon 

as possible after harvest.

At the packinghouse, fruit are dumped (mostly 

using dry bin dumps) and cleaned. Sorting is 

done to eliminate fruit with visual defects and 

sometimes to divert fruit of high surface color 

to a high-quality pack. Attention to details in 

sorting line efficiency is especially important with 

peaches, which have a range of colors, sizes, and 

shapes. Sizing segregates fruit by either weight or 

dimensions.

Most yellow-flesh peaches are packed into 2-layer 

(tray) boxes. Small yellow-flesh peaches are 

generally volume-fill packed. Most white-flesh 

and tree-ripe peaches are packed into 1-layer 

(tray) boxes. Limited volumes of high-maturity 
467

fruit are “ranch-packed” at the point of production. 

In a typical tree-ripe operation, high-maturity or 

high-quality fruit are picked into buckets or totes 

that are carried by trailer to the packing area. 

Packers work directly from buckets to select, 

grade, size, and pack fruit into plastic trays.

Precooling Conditions

Fruit can be cooled in field bins using forced-air 

cooling or hydrocooling. Forced-air cooling in 

side-vented bins can be accomplished by either 

the tunnel or the serpentine method. Hydrocooling 

is normally done by a conveyor-type hydrocooler 

or in situ. Fruit in field bins can be cooled to 

intermediate temperatures of 5 to 10 °C (41 to 50 

°F), provided packing will occur the next day. If 

packing is to be delayed beyond the next day, fruit 

should be thoroughly cooled in the bins to near 

0 °C (32 oF). In cultivars susceptible to internal 

breakdown, fast cooling (within 8 h), as well as 

maintaining fruit temperature near 0 °C (32 °F), 

is recommended. Peaches in packed containers 

should be cooled by forced-air cooling to near 0 

°C (32 °F). Even peaches that were thoroughly 

cooled in the bins will warm substantially during 

packing and should be thoroughly recooled after 

packing.

Optimum Storage Conditions

Optimum temperature for storage is -1 to 0 °C (31 

to 32 °F). The freezing point varies, depending on 

SSC, from -3 to -1.5 °C (27 to 30 °F). RH should 

be 90 to 95%, and an air velocity of approximately 

50 ft3

 min-1 is recommended during storage. 

Controlled Atmosphere (CA) 

Considerations

The major benefits of CA during storage and 

shipment are retention of fruit firmness and 

ground color. CA of 6% O2

 and 17% CO2 at 0 °C 

is recommended for reducing internal breakdown 

during shipping, but the efficacy is related to 

cultivar, preharvest factors, temperature, market 

life, and shipping time. Large-sized ‘Elegant 

Lady’ and ‘O’Henry’ peaches stored at 0 °C 

benefit from an atmosphere of 6% O2

 and 17% 

CO2

.

Fruit size, storage atmosphere, and temperature 

all affect development of chilling injury. Small 

peaches stored in air at 0 °C have a longer market 

life than large fruit. At both temperatures, largesized ‘Elegant Lady’ and ‘O’Henry’ fruit have 

a longer market life under CA than under air 

storage. However, at 3 °C (38 oF) small-sized 

‘Elegant Lady’ in CA showed flesh browning. 

Retail Outlet Display Considerations

If fruit firmness is <27 N (6 lb-force), fruit should 

be displayed on a cold table. If firmness is >27 

N (6 lb-force), fruit should be displayed on a dry 

table.

Chilling Sensitivity

Most mid-season and late peach cultivars 

are susceptible to chilling injury or internal 

breakdown. Chilling injury develops faster and 

more intensely in fruit stored at 2 to 7 °C (36 to 45 

°F) than in those stored at 0 °C (32 °F) or below.

Ethylene Production and Sensitivity

The lower end of this range is for mature but unripe 

fruit; higher values are for ripe fruit:

Temperature μL C2H4 kg-1 h-1

0 °C 0.01 to 5

5 °C 0.02 to 10

10 °C 0.05 to 50

20 °C 0.10 to 160

In general, peaches harvested at Well Mature 

(higher than U.S. Mature) will ripen properly 

without exogenous ethylene application. In most 

cultivars, ethylene application to fruit harvested 

at U.S. Mature will ripen the fruit more uniformly 

without speeding up the rate of ripening. 
468

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 4 to 6

10 °C 16 to 24

20 °C 64 to 110

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

The major physiological cause of deterioration 

is a low-temperature or chilling injury problem 

generically called “internal breakdown” (IB).

The disorder can manifest itself as dry, mealy, 

woolly, or hard-textured fruit; flesh or pit cavity 

browning; or flesh translucency usually radiating 

through the flesh from the pit. An intense red 

color development of the flesh (“bleeding”) 

usually radiating from the pit may be associated 

with this problem in some peach cultivars. In all 

cases, flavor is lost before visual symptoms are 

evident. However, there is large variability in IB 

susceptibility among peach cultivars. In general, 

peach cultivars are more susceptible to IB than 

nectarine and plum cultivars. At the shipping 

point, fruit should be cooled and held near or 

below 0 °C (32 °F). If IB-susceptible cultivars 

are exposed to 5 °C (41 °F) during transportation, 

their postharvest life can be significantly reduced. 

Several treatments to delay and limit IB have 

been tested. Among them, preripening fruit before 

storage is being used successfully in California. 

The success of CA (17% CO2 and 6% O2

) depends 

on cultivar market life, shipping time, and fruit 

size.

Inking (black staining) is a cosmetic problem 

affecting only the skin. This disorder is 

characterized by black-brown spots or stripes. 

These symptoms appear generally 24 to 48 h 

after harvest. Inking occurs as a result of abrasion 

damage in combination with contamination by 

heavy metals (iron, copper, and aluminum). It 

occurs usually during harvesting and hauling, 

though it may occur in other steps of postharvest 

handling. Gentle handling of fruit, short hauling, 

avoiding foliar nutrient sprays within 15 days of 

harvest, and following suggested guidelines for 

preharvest fungicide spray intervals will reduce 

inking.

Postharvest Pathology

Brown rot, caused by Monilinia fructicola, is the 

most important postharvest disease of peaches. 

Infection begins during flowering. Fruit rot may 

occur before harvest but often appears after 

harvest. Orchard sanitation to minimize infection 

sources, preharvest fungicide application, and 

prompt cooling after harvest are among the control 

strategies. Also, postharvest fungicide treatment 

may be used.

Gray mold is caused by Botrytis cinerea. It can 

be a serious problem during wet spring weather. 

It can occur during storage if fruit have been 

contaminated through harvest and handling 

wounds. Avoiding mechanical injuries and good 

temperature management are effective controls.

Rhizopus rot is caused by Rhizopus stolonifer. It

can occur in ripe or near-ripe peaches kept at 20 

to 25 °C (68 to 77 °F). Cooling and keeping fruit 

below 5 °C (41 °F) is an effective control.

Quarantine Issues

Because some insects, such as Conotracherlus 

nenuphar (plum curculio), Cydia pomonella

(codling moth), Rhagoletis pommonella

(apple maggot), and Tetranychus pacificus are 

not present in some of our import markets, 

phytosanitary restrictions have been established. 

Issues associated with exotic pest quarantines, 

addressing either imported or exported peaches, 

can change rapidly. APHIS issues rules regarding 

import requirements. This agency provides 

information to assist exporters in targeting markets 

and defining countries’ entry requirements. 

APHIS, in cooperation with State plant boards, 
469

developed a database called “Excerpt” to track 

phytosanitary requirements for each country. 

APHIS also provides phytosanitary inspections 

and certifications that declare peaches free of pests 

to facilitate compliance with foreign regulatory 

requirements.

For peaches, there are three main ways to deal 

with these phytosanitary requirements: inspection 

prior to shipment (including use of screened 

crates transported in sealed containers), methyl 

bromide fumigation, and a systems approach. A 

phytosanitary certificate (PC) is required to import 

California peaches into Taiwan. Peaches must 

be free of Anarsia ineatella (peach twig borer), 

Conotracherlus nenuphar (plum curculio), Cydia 

pomonella (codling moth), Erwinia amylovora 

(fire bright), Rhagoletis pomonella (apple 

maggot), Tetranychus pacificus (Pacific spider 

mite), and Ceratitis capitata (Mediterranean fruit 

fly). If these conditions are not met, fruit must 

receive an appropriate treatment prior to shipment. 

Details of the treatment must be recorded on the 

PC.

A phytosanitary certificate is required to import 

California peaches into British Columbia. The PC 

should state that fruit are free of Cydia molesta

(oriental fruit moth). Also, it should clearly 

state that fruit were produced and inspected in 

accordance with the systems approach guidelines 

agreed to by APHIS and the Canadian Food 

Inspection Agency. Fruit imports are unrestricted 

to all other Canadian provinces.

A similar program between APHIS and several 

Mexican agencies exists to facilitate import 

and assure that peaches and nectarines are 

free of Cydia molesta (oriental fruit moth), 

Conotracherlus nenuphar (plum curculio), 

Rhagoletis pomonella (apple maggot), and fruit 

flies (Tephritdae). Peaches imported into the 

United States from other parts of the world are 

sometimes fumigated with methyl bromide, at 

shipping or arrival point, following treatment 

schedules issued by APHIS, to prevent entry of 

insect pests.

Suitability as Fresh-Cut Product

The optimal ripeness for preparing fresh-cut peach 

slices is a flesh firmness of 13 to 27 N (3 to 6 lbforce). These slices can be kept while retaining 

good eating quality for 2 to 8 days (depending 

on cultivar) at 5 °C (41 °F) with 90 to 95% RH. 

Postcutting dips in ascorbate and calcium lactate, 

or use of MAP, may slightly prolong shelf-life.

Special Considerations

Because peaches area a climacteric fruit, they are 

harvested after they reach a minimum maturity 

but before they are completely ripe (that is, 

ready to eat). Ripening must be initiated before 

consumption in order to satisfy consumers. 

Detailed ripening protocols for shippers, retail 

handlers, warehouse managers, and produce 

managers have been developed.

Acknowledgments

Some of the information in this chapter is from 

the University of California, Davis, website on 

“Produce Facts” at http://postharvest.ucdavis.edu/

produce_information.

Further Reading

Ceponis, M.J., R.A. Cappellini, J.M. Wells, and 

G.W. Lightner. 1987. Disorders in plum, peach 

and nectarine shipments to the New York market, 

1972-1985. Plant Dis. 71:947-952.

Crisosto, C.H. 1994. Stone fruit maturity indices: 

a descriptive review. Postharv. News Info. 

5(6):65N-68N.

Crisosto, C.H., F.G. Mitchell, and S. Johnson. 

1995. Factors in fresh market stone fruit quality. 

Postharv. News Info. 6(2):17N-21N.
470

Crisosto, C.H., F.G. Mitchell, and Z. Ju. 1999. 

Susceptibility to chilling injury of peach, 

nectarine, and plum cultivars grown in California. 

HortScience 34:1116-1118.

Kader, A.A., and F.G. Mitchell. 1989. Postharvest 

physiology. In J.H. LaRue and R.S. Johnson, 

eds., Peaches, Plums, Nectarines: Growing and 

Handling for Fresh Market, pp. 154-164. Pub. no. 

3331, University of California, Davis, CA.

Gorny, J.R., B. Hess-Pierce, and A.A. Kader. 

1998. Effect of fruit ripeness and storage 

temperature on the deterioration rate of fresh-cut 

peach and nectarine slices. HortScience 33:110-

113. 

Gorny, J.R., B. Hess-Pierce, and A.A. Kader. 

1999. Quality changes in fresh-cut peach and 

nectarine slices as affected by cultivar, storage 

atmosphere and chemical treatments. J. Food Sci. 

64:429-432. 

LaRue, J.H., and R.S. Johnson, eds., 1989. 

Peaches, plums, nectarines: growing and handling 

for fresh market. Pub. no. 3331, University of 

California, Davis, CA. 

Lill, R.E., E.M. O’Donoghue, and G.A. King. 

1989. Postharvest physiology of peaches and 

nectarines. Hort. Rev. 11:413-452.

Mitchell, F.G. 1987. Influence of cooling and 

temperature maintenance on the quality of 

California grown stone fruit. Intl. J. Refrig. 10:77-

81.
471

Pear

Paul M. Chen

Chen is with the Mid-Columbia Agricultural 

Research and Extension Center, Oregon State 

University, Hood River, OR

Scientific Name and Introduction

Pyrus communis L., the pear, is a member of 

the family Rosaceae. The fleshy part of pear 

fruit consists of the fused base of the calyx 

(sepals), corolla (petals), and stamens, which are 

interpreted by one school of anatomists as being 

the “receptacle.” Therefore, pears are also a pome 

fruit (Hulme and Rhodes 1971). Commercial 

pear production on the Pacific Coast is largely 

confined to nine districts including the Wenatchee 

and Yakima Valley areas in central Washington, 

the Hood River Valley in north central Oregon, 

and the Rogue River Valley around Medford in 

southern Oregon. In California, production is 

mainly in the foothill district of Eldorado, Placer, 

and Nevada counties; the Sacramento River 

district; the coast district north of San Francisco 

Bay known as the Santa Clara Valley district; 

and the southern California acreage mostly in the 

Antelope Valley in Los Angeles County (Childers 

1949). 

Pears rank third among the most important tree 

fruits grown in the world and fourth among all 

fruits for which statistics are available (Childers 

1949). All important pear varieties grown in the 

United States belong to the European species, 

and commercial pear production is confined to 

six main varieties—‘Bartlett,’ ‘Beurré d’Anjou,’ 

‘Beurré Bosc,’ ‘Beurré Hardy,’ ‘Doyenne’ du 

Comice,’ and ‘Seckel.’ Other minor varieties 

include ‘Winter Nelis,’ ‘El Dorado,’ ‘Kieffer,’ and 

‘Packham’s Triumph.’

Quality Characteristics and Criteria

A properly ripened pear is buttery with juicy 

texture and the aroma and taste distinct to each 

cultivar. Pear fruit require a period of cold storage 

at -1 °C (30 °F) to induce normal ripening and 

develop high dessert quality upon ripening. When 

pear fruit meet the chilling requirement after a 

period of cold storage, they should be ripened at 

20 °C (68 °F) in air for 4 to 7 days depending on 

the variety for the development of high dessert 

quality.

Horticultural Maturity Indices

Pear fruit are capable of developing good dessert 

quality upon ripening only if they are harvested at 

proper maturity. Pear fruit harvested at improper 

maturity are more susceptible to physiological 

disorders and have a shorter storage life. Immature 

pear fruit are more susceptible to superficial 

scald, shriveling, and friction discoloration, while 

overmature fruit tend to have higher incidence 

of core breakdown and CO2

 injury (Hansen and 

Mellenthin 1962, Fidler et al. 1973, Mellenthin 

and Wang 1974). 

One of the most satisfactory and easiest ways of 

determining proper harvest maturity is to measure 

fruit firmness. A pressure test using a penetrometer 

on the pear surface gives an indication of flesh 

firmness. Firmness decreases with maturation. 

Different varieties have different firmness at 

maturity. Recommended ranges of firmness for 

harvesting different pear varieties as measured 

using a 8-mm plunger tip are as follows (Williams 

et al. 1978, Hansen and Mellenthin 1979):

 N

‘d’Anjou’ 57.8 to 66.7

‘Bartlett’ 66.7 to 84.3

‘Bosc’ 62.7 to 71.6

‘Comice’ 49.0 to 57.8

‘Hardy’ 41.2 to 49.0

‘Kiefer’ 52.9 to 66.7

‘Seckel’ 57.8 to 66.7

‘Packham’ 57.8 to 66.7

‘El Dorado’ 57.8 to 66.7

‘Winter Nelis’ 57.8 to 66.7

(1 N = 0.225 lb-force)
472

Heat units accumulated during the 9 weeks 

following full bloom provide an accurate 

prediction of maturity and harvest date. The 

equation (for Fahrenheit) can be expressed as—

Daily Heat Unit = [(Maximum Temp. + Minimum 

 Temp.)/2] - 45

Heat units accumulated during the 9 weeks 

following full bloom have been developed at 

the Mid-Columbia Agricultural Research and 

Extension Center to provide an accurate prediction 

of the commercial harvest date for ‘d’Anjou’ and 

‘Bartlett’ pear cultivars. The 50-yr record (1944 

to 1994) at this Center has shown that correlation 

coefficients between the number of days from full 

bloom (DFFB) until harvest and the accumulated 

heat units (AHU) are -0.9213 for ‘d’Anjou’ 

pears and -0.8300 for ‘Bartlett’ pears. The linear 

equations between DFFB and AHU are—

‘d’Anjou’ DFFB = 177.5472 - 0.0481 × AHU 

‘Bartlett’ DFFB = 147.5377 - 0.0353 × AHU

In Oregon’s Hood River Valley district, the entire 

pear-producing area covers elevations between 

500 ft (152 m) and 2,000 ft (610 m). The dates of 

full bloom or the dates of first commercial harvest 

between the lower and higher elevations could be 

as much as 3 weeks apart. Predictive models for 

the harvest maturity of ‘d’Anjou’ and ‘Bartlett’ 

pears grown in 14 orchards representing the entire 

Hood River Valley district have been developed 

(Varga and Chen 1995). Other predictive methods 

such as days from full bloom, SSC, and starchiodine test are quite variable from season to season 

and have not been adopted for routine practice by 

the pear industry.

Grades, Sizes, and Packaging

Grades include Extra Fancy, U.S. No. 1, Fancy, 

and Unclassified (or Third Grade) for all winter 

pear cultivars, and U.S. No. 1 and Fancy for 

‘Bartlett.’ Grading is based primarily on external 

appearance. Size categories are 50, 60, 70, 80, 90, 

100, 110, 120, 135, 150, 165, and 180 fruit per 

standard 20-kg box.

Precooling Conditions

Rapid removal of field heat and prompt cooling of 

harvested pears are essential for long-term storage. 

During the pull-down period, room temperatures 

of -3.5 to -2.0 °C (26 to 28 °F) can be used, but 

the environment should be raised to -1 °C (30 °F) 

as the fruit temperatures approach this temperature 

(Hansen and Mellenthin 1979). Delay in cooling 

shortens storage life. It has been suggested that 

the core temperature should be reduced to near 

the holding temperature in 4 days (Porritt 1965). 

When pears are packed in cartons before cooling, 

cartons should be stacked to provide exposure 

of the sides to airflow (Sainsbury and Schomer 

1957).

Optimum Storage Conditions

Pears are very sensitive to temperature. The 

storage life of ‘d’Anjou’ and ‘Bartlett’ pears has 

been reported to be 35 to 40% longer at -1 °C 

(30 °F) than at 0 °C (32 °F) (Porritt 1964). Most 

pears in the Pacific Northwest are stored at -1 

°C (30 °F) with RH of 90 to 94% (Hansen and 

Mellenthin 1979). Many operators of pear storage 

rooms use thermocouples in the air and in fruit 

to determine temperatures at selected areas in the 

storage. Precise temperature control is needed to 

prevent freezing when pears are stored at these 

low temperatures (Hartman 1931). Intermediate 

temperatures of 2.5 to 10 °C (37 to 50 °F) are 

harmful to some pear cultivars. ‘Bartlett’ pears 

stored at this temperature have dry texture and 

inferior flavor (Porritt 1964). Pears lose moisture 

rapidly; hence, it is advisable to hold RH at >90%. 

Polyethylene liners are effective in controlling 

moisture loss.

Controlled Atmosphere (CA) 

Considerations

CA storage has been used successfully to extend 

the storage life of pears and to maintain greater 

capacity for ripening. The optimum and safe CA 

for commercial use is 2 to 2.5% O2

 and 0.8 to 1% 

CO2

 (Hansen and Mellenthin 1979). Use of short-
473

term high-CO2

 treatment improves keeping quality 

of ‘d’Anjou’ pears (Wang and Mellenthin 1975). 

Treatment with 12% CO2

 for 2 weeks immediately 

after harvest has a beneficial effect on retention 

of ripening capacity. Keeping ‘d’Anjou’ pears in 

a low-O2

 atmosphere (1.0%) with ≤0.1% CO2 can 

also maintain higher dessert quality and reduce 

incidence of superficial scald after long-term cold 

storage (Hansen 1957, Mellenthin et al 1980).

Pear Ripening in Storage

Most pear cultivars require a period of cold 

storage before they will ripen normally at room 

temperature (Leblond and Ularic 1973, Drouet 

and Hartmann 1979, Blankenship and Richardson 

1985, Morin et al. 1985, Knee 1987). Most 

cultivars do not soften appreciably during cold 

storage; hence, they require a period of ripening 

at warm temperature to develop good flavor and 

texture for eating. The best ripening temperature 

after storage is about 15 to 21 °C (59 to 70 oF). 

Higher temperatures may result in poor quality 

or decay. Most cultivars fail to soften at 30 °C 

(86 oF). It is generally recognized that ethylene 

induces ripening.

A striking characteristic of climacteric fruits 

is their autocatalytic ethylene production; that 

is to say, ethylene stimulates its own synthesis 

(Pech et al. 1994). During storage at -1 °C (30 

°F), 1-aminocyclopropane-1-carboxylic acid 

(ACC; the immediate ethylene precursor) starts 

to accumulate; as a consequence, pear fruit begin 

to produce ethylene and ripen normally upon 

exposure to room temperature. Exposure of pear 

fruit to a storage temperature of -1 to 0 °C (30 to 

32 oF) stimulates synthesis of ACC and ethylene 

because low temperature induces biosynthesis of 

ACC oxidase and ACC synthase (Blankenship 

and Richardson 1985, Wang et al. 1985, Leliévre 

at al. 1997, Agar et al. 2000). The duration of 

chilling required for proper ripening is cultivardependent (Wang et al. 1985) and varies with 

storage temperature (Sfakiotakis and Dilley 1974, 

Gerasopoulos and Richardson 1995). Storage 

duration at -1 °C (30 °F), which is required to 

induce normal ripening of pear fruit, is 2 to 4 

weeks for ‘Bartlett’ (Puig et al. 1996, Agar et al. 

1999), 2 to 3 weeks for ‘Bosc’ (Chen et al. 1982), 

and 7 to 8 weeks for ‘d’Anjou’ (Chen et al. 1982).

Exogenous ethylene, at 100 μL L-1, has been 

used commercially to precondition underchilled 

‘Bartlett’ and ‘d’Anjou’ pears at 20 °C (68 °F) 

for 2 to 3 days before shipment. Preconditioned 

pear fruit are capable of ripening normally and 

uniformly upon reaching the retail markets or for 

the canning process (Chen et al. 1996, Puig et al. 

1996, Agar et al. 1999, 2000).

Ethylene Production and Sensitivity

Ethylene production rates are low at harvest: <0.1 

mL kg-1 h-1; but rates gradually increase during air 

storage at -1.1°C (30 °F). After 3 mo of air storage 

at -1.1 °C (30 °F) and 1 day at 20 °C (68 °F), 

ethylene production of ‘d’Anjou’ was 0.5 mL kg-1

h-1; of ‘Bosc,’ 30 mL kg-1 h-1; and of ‘Comice,’ 30 

mL kg-1 h-1.

Most pear cultivars will exhibit climactericlike ethylene production during the ripening 

period at 20 °C (68 °F) when optimally mature 

fruit have satisfied their chilling requirement 

at -1.1 °C (30 °F). The chilling requirement of 

optimally mature pears stored at -1.1 °C (30 

°F) for induction of normal ripening capacity is 

about 60 days for ‘d’Anjou,’ 30 days for ‘Bosc,’ 

30 days for ‘Comice,’ and 15 days for ‘Bartlett.’ 

The magnitude of ethylene production at the 

climacteric-like peak is 10 to 20 mL kg-1 h-1 for 

‘d’Anjou,’ 40 to 80 mL kg-1 h-1 for ‘Bosc,’ 80 to 

200 mL kg-1 h-1 for ‘Bartlett,’ and 60 to 80 mL kg-1

h-1 for ‘Comice.’

Unripe pear fruit are somewhat sensitive to 

ethylene, depending on the cultivar. ‘Bartlett’ 

pears are most sensitive to ethylene, ‘Bosc’ and 

‘Comice’ fruit are moderately sensitive, and 

‘d’Anjou’ fruit are least sensitive to ethylene for 

induction of ripening. Nevertheless, it is best to 
474

avoid storing pear fruit near ripe fruit or other 

fresh produce that produces appreciable levels of 

ethylene. Preconditioning of pear fruit with 100 

μL L-1 ethylene at 20 °C (68 °F) for 72, 48, or 24 h 

will induce ripening within 3 to 6 days, depending 

on the cultivar (Wang and Mellenthin 1972, Chen 

et al. 1982, Elgar et. al. 1997).

Respiration Rates

‘d’Anjou’ ‘Bartlett’

Temperature Days in Storage Days in Storage

°C 1 25 50 100 150 200 1 10 20 90 120

-------------------------------------mg CO2 kg-1 h-1--------------------------------------

-2 5.0 2.0 2.0 2.3 2.4 2.7 — 1.5 2.2 3.2 3.8

-1 5.0 2.0 2.0 2.4 2.5 2.8 — 2.2 2.4 3.6 4.2

0 5.0 2.4 2.5 3.2 4.1 4.5 — 2.5 2.6 5.6 5.9

2 5.0 3.1 3.6 5.1 — — — 3.2 4.5 — —

10 9.0 6.0 7.0 — — — 16.0 8.1 24.0 — —

21 17.0 7.0 7.0 — — — 16.0 38.0 — — —

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 1.8 at 

20 °C (68 °F). To calculate heat production, multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1 or by 61 to 

get kcal tonne-1 day-1.

Physiological Disorders

Superficial scald, also called storage scald, is a 

cosmetic condition of surface browning affecting 

only a few layers of cells beneath the skin. Eating 

quality of fruit is not affected. Frequently, fruit 

appear normal after several months in cold storage 

but then develop scald symptoms after a few 

days at room temperature. The unpleasant brown 

appearance makes fruit difficult to market.

Superficial scald affects ‘d’Anjou’ pears and other 

pear cultivars. The cause of superficial scald is 

conjugated trienes, the oxidative products of the 

naturally occurring terpene α-farnesene, which are 

toxic to the epidermal and endodermic cells of the 

fruit peel (Chen et al. 1990b). Factors that usually 

increase the severity of the disorder include 

immaturity, high fruit nitrogen, low fruit calcium, 

warm preharvest weather, delayed cold storage, 

high storage temperatures, and high RH during 

cold storage.

Conventional control method: The primary 

method of controlling superficial scald on 

‘d’Anjou’ pears at present is a postharvest 

treatment of ethoxyquin, an antioxidant 

(Hansen 1964, Hansen and Mellenthin 1967, 

1979). Ethoxyquin is recommended at a 

concentration of 2,700 μL L-1, which can be 

applied to the fruit either as a drench, as a line 

spray, or by impregnating it into paper wraps 

(Hansen and Mellenthin 1979). Drenching 

fruit is done as soon as possible after harvest, 

usually no later than 2 days. Unfortunately, 

this treatment often causes considerable 

phytotoxicity when the ethoxyquin solution 

becomes more concentrated at contact points 

between fruit or between fruit and wooden 
475

bins. Fruit at these contact points develop 

pinkish (or blackened) ring markings during 

storage (Porritt et al. 1982), and the injured 

fruit become unmarketable. Ethoxyquin 

treatment as a line spray or a paper wrap 

is carried out during commercial packing. 

Because it usually takes about 3 mo to pack all 

fruit stored in air, fruit may receive ethoxyquin 

protection as early as 1 week after harvest or 

as late as 3 mo after storage using either of 

these methods. Though neither method causes 

any phytotoxicity to fruit, delay in ethoxyquin 

application has resulted in significant 

incidence of scald disorder at terminal 

markets. Current recommended ethoxyquin 

treatments are inadequate.

Split application of ethoxyquin control method: 

Drenching ‘d’Anjou’ fruit with 1,000 μL 

L-1 ethoxyquin within 2 days after harvest 

controlled scald development for 4 mo in air 

storage without causing phytotoxicity to fruit. 

Drenching fruit with 1,000 μL L-1 ethoxyquin 

within 2 days after harvest plus an additional 

line spray of 1,700 μL L-1 ethoxyquin within 3 

mo of harvest controlled scald development for 

5 mo in air storage (Chen et al. 1990a).

Nonchemical control method: A short-term 

(3- to 4-mo) CA storage of ‘d’Anjou’ pears at 

-1 oC in 0.8% O2

 and <0.1% CO2 (denoted as 

low O2

) effectively controls development of 

superficial scald without inducing black speck 

and pithy brown core (Chen and Varga 1997a, 

1997b). Fruit stored in a short-term low-O2

regime remain free from scald after 8 weeks in 

air at -1 oC. These fruit can be safely packed 

without antioxidant treatment and marketed 

after 2 mo of air storage.

Combined ethoxyquin/CA control method

(Chen and Varga 1997a): For ‘d’Anjou’ fruit 

destined for mid-term (5- to 6-mo) or longterm (7- to 8-mo) CA storage, a prestorage 

drench of fruit with 1,000 μL L-1 ethoxyquin 

within 2 days after harvest was necessary in 

order to control superficial scald disorder. The 

concentrations of O2

 and CO2 in CA storage 

must be kept at 1.5% and <0.5%, respectively, 

throughout the entire storage period to 

minimize development of black speck and 

pithy brown core. An alternative method would 

be to store field-run ‘d’Anjou’ pears in low O2

(0.8% O2

 and <0.03% CO2) at -1 °C (30 °F) for 

90 days until qualified. Low-O2

 stored fruit can 

be either presized or packed with in-line spray 

of 2,700 μL L-1 ethoxyquin within 2 weeks 

after being returned to air storage. Treated fruit 

can be further stored in regular CA storage 

(2% O2

 and 1% CO2) for another 3 to 4 mo at 

-1 °C (30 °F) for late season marketing.

Pithy brown core (PBC) affects ‘d’Anjou’ pears 

stored in either sealed polyethylene box liners or 

CA storage with elevated CO2

. It is characterized 

by pithy, brown areas in the core region of the 

fruit. It may be restricted to brown flecks between 

the carpels, or it may encompass the entire core 

and extend into the surrounding flesh. In some 

instances, the tissues collapse, producing cavities. 

The affected tissues are dry and pithy, in contrast 

to the soft, watery texture resulting from core 

breakdown. The disorder is associated with 

high CO2

 in atmospheres of sealed box liners 

or CA storage and is considered to be a form of 

CO2 injury. It is aggravated by the combination 

of low O2

 and high CO2 levels in CA storage. 

Susceptibility to PBC increases with factors that 

induce fruit senescence, such as late harvesting, 

delayed storage, slow cooling, high storage 

temperatures, and extended CA storage (Hansen 

and Mellenthin 1962). Fruit from trees with low 

vigor and fruit grown in cool seasons are more 

susceptible to PBC (Hansen and Mellenthin 1962).

For fruit stored loose in bins—field-run fruit—

CO2

 should be maintained at <0.03% when O2

in CA storage is 0.8 to 1.0% (Chen and Varga 

1997b). The maximum storage length of ‘d’Anjou’ 

fruit stored under low O2

 should be no more than 

120 days. For fruit stored loose in bins, CO2

should be maintained at <0.5% when O2

 in CA 

storage is 1.5 to 1.8%. The maximum storage 

time of fruit stored in the CA regime described 

above should be no longer than 8 mo. For fruit 

stored loose in bins, CO2

 should be maintained at 

<1.0% when O2

 in CA storage 2.0 to 2.5%. The 

maximum storage time of fruit stored in the CA 
476

regime described above should also be no longer 

than 8 mo (Chen and Varga 1997b).

For fruit stored in packed boxes, only the CA 

regime with 2.0 to 2.5% O2

 and <1.0% CO2 gives 

minimal risk for ‘d’Anjou’ pears to develop PBC 

after prolonged CA storage (6 to 8 mo) (Chen and 

Varga 1997b).

Black speck (BS), or “skin speckling,” of 

‘d’Anjou’ pears becomes an economic problem 

after prolonged CA storage. It has been observed 

frequently in commercial CA storage. It is a 

physiological disease and is suspected to be 

closely associated with PBC. Kupferman (1988) 

reported that BS could develop on ‘d’Anjou’ 

pears with or without PBC. Similarly to PBC, 

‘d’Anjou’ fruit develop BS only in CA storage. 

The unbalanced O2 :CO2 ratio in CA storage 

must be an initial factor in causing skin injury of 

fruit. It was confirmed that BS was induced by 

≤1.0% O2

 in CA storage for longer than 4 mo and 

was not affected by <1% CO2

 (Chen and Varga 

1989). Each BS spot consists of several hundred 

epidermal cells discolored to dark brown. The 

distinct specks scatter randomly on the peel tissue 

and are not restricted to around the lenticels. It 

affects only five to six layers of hypodermal cells 

of the skin (Kupferman 1988, Chen and Varga 

1989, Lee et al. 1990).

Since BS is associated with low O2

 (≤1%), a CA 

regime with O2 at 1.5% or higher will alleviate 

the disorder after prolonged CA storage. For 

‘d’Anjou’ pears, low-O2

 (0.8 to 1.0% O2) storage 

should not exceed 120 days (Chen and Varga 

1997b).

Black end of ‘d’Anjou’ pears begins with 

symptoms appearing when fruit are one-third 

to one-half full size. It is a protrusion of the 

calyx due to the retarded development of tissues 

around the calyx. As the disorder progresses, the 

calyx lobes turn black, the tissues surrounding 

the calyx opening become hard, and a brownish 

discoloration forms. This discoloration may 

appear first in separate spots, which later coalesce; 

or there may be a large area completely and 

uniformly discolored from the beginning. The 

final color of affected tissues is black, and cracks 

up to 3 cm in length may appear in the blackened 

area. The affected area is usually confined to 

approximately 1 to 2 cm around the calyx, but it 

may cover the entire lower half of fruit in severe 

cases. Discoloration usually does not extend deep 

into the flesh, sometimes only affecting the skin.

Black end is believed to be caused by water 

imbalance stemming from a restricted root 

system. Excessive subsoil moisture in spring 

damages feeder roots, inducing development 

of the disorder. Fruit grown on trees with Asian 

rootstocks (Pyrus serotina Rehder) are highly 

susceptible to black end. Fruit grown on trees 

with French rootstocks (Pyrus communis L.) are 

generally free from the disorder (Heppner 1928, 

Davis and Tufts 1932).

Core breakdown has been referred to in different 

investigations as “internal breakdown,” “core rot,” 

“brown heart,” and “mealy core.” As the names 

imply, this disorder of pears is characterized 

by the softening and browning of tissues in the 

region of the core. The breakdown may be closely 

confined to the core or may extend into the 

surrounding flesh. In the early stages, the affected 

tissues are soft and watery; they later become dark 

brown. The disorder is often associated with an 

external skin discoloration resembling senescent 

scald.

Overmature fruit are more susceptible to core 

breakdown in storage and in the market. Lateharvested pears are unable to slow their metabolic 

activities sufficiently for successful storage at 

-1 °C (30 oF). Serious breakdown can occur in 

storage or after pears are removed to ripen at 20 

°C (68 oF). Late-harvested pears show an increase 

in CO2

 in the tissues around the core area until 

the onset of core breakdown. Such fruit produce 

an abnormally high amount of acetaldehyde until 

core breakdown is advanced. ‘Bartlett,’ ‘Bosc,’ 

and ‘Comice’ pears are highly susceptible to 

core breakdown, whereas ‘d’Anjou’ pears are 

somewhat resistant. Harvesting fruit at optimum 

maturity and rapidly precooling fruit before 

storage are essential to reduce core breakdown 

(Hartman 1925, Harley 1929). 
477

Senescent scald occurs differently in various 

pears. Pears can be classified broadly into two 

groups based on their storage behavior. One 

group, including ‘d’Anjou,’ ‘Winter Nelis,’ 

‘Packham’s Triumph,‘ and ’Hardy,‘ senesce 

very slowly in cold storage and generally do not 

lose their capacity for normal ripening at room 

temperature as a result of extended storage. These 

pears are subject to storage scald, called “Anjou 

scald” or “superficial scald.” The other group of 

pears, which includes ‘Bartlett,’ ‘Bosc,’ ‘Howell,’ 

‘Comice,’ ‘Sierra,’ and ‘Flemish Beauty,’ show 

a higher rate of senescence during cold storage; 

fruit lose their ability for normal ripening at room 

temperature after prolonged storage. As storage 

length is extended, fruit become yellow and 

ultimately develop a dark brown discoloration of 

the skin called “senescent scald.” This may occur 

in cold storage or after fruit are removed from 

cold storage and subjected to higher temperatures. 

Fruit remain firm, but the skin sloughs off easily 

(Porritt et al. 1982).

Methods of treating senescent scald are similar 

to those used to reduce core breakdown disorder, 

with overmature fruit more susceptible in storage 

and in the market. Pears that are harvested late 

do not exhibit a decrease in metabolic activity 

necessary for storage at -1 °C (30 oF). There are 

no control measures other than harvesting pears 

at optimum maturity, reducing the storage period, 

and improving postharvest handling with methods 

such as fast cooling of pears immediately after 

harvest and maintaining constant temperature at -1 

°C (30 oF) throughout storage (Porritt et al. 1982). 

Postharvest Pathology

A detailed description of pear diseases and control 

measures can be found in “Compendium of Apple 

and Pear Diseases” (Jones and Aldwinckle 1990). 

The cause of postharvest decay in pear fruit is 

often difficult to identify through symptoms alone. 

Many decay pathogens do not sporulate on fruit 

in cold or CA storage. The only reliable method 

for identifying the cause of decay is to isolate 

and identify the causal agent. Isolations are easily 

accomplished by removing the fruit skin over the 

margin of a decayed area and plating some of the 

decayed flesh on potato-dextrose agar.

Fungi causing postharvest decay in pome fruits 

can be subdivided into two broad groups: those 

that cause primarily postharvest decay and those 

that also cause fruit decay in the field. Postharvest 

decay attributable to fungi in the latter group 

usually result from infections that occurred in 

the field but were quiescent or otherwise escaped 

notice at harvest. Control measures for these 

diseases are based on the protection of fruit from 

preharvest infections. Control measures broadly 

applicable to many postharvest diseases include 

both sanitation and harvesting, as well as handling 

methods that maintain the integrity of harvested 

fruit. Sanitation measures are especially important 

for reducing exposure of fruit to spores of wound 

pathogens, such as Penicillium and Botrytis. 

Harvesting and handling methods are important 

because wounded, bruised, or overmature fruit 

are more susceptible to many postharvest decay 

fungi. Rapid cooling after harvest reduces the 

incidence of decay in storage, because low 

temperatures reduce both the rate of fungal growth 

and fruit senescence. Low temperature prevents 

development of incipient infections by some fungi 

in storage, such as those causing white rot and 

brown rot.

Postharvest decay pathogens infecting pears in 

the field and causing symptoms in stored pears 

as a result of incipient or quiescent infections 

are Botryosphaeria dothidea (white rot), B. 

obtusa (black rot), Glomerella cingulata (bitter 

rot), Monilinia fructicola (brown rot), M. 

fructigena (brown rot), M. laxa (brown rot), and 

Phytophthora cactorum (phytophthora fruit rot).

Postharvest diseases commonly found in pears 

after storage are blue mold (Penicillium spp.),

gray mold (Botrytis cuberea Per.), bull’s-eye 

rot (Pezicula malicorticis [H. Jacks.] Nannf.), 

alternaria rot (Alternaria alternata [Fr.] Keissler), 

mucor rot (Mucor piriformis E. Fischer), side 

rot (Phialophora malorum [Kidd & Beaumont] 

McColloch), cladosporium rot (Cladosporium 

herbarum [Pers.] Link), coprinus rot (Coprinus 

psychromorbidus Redhead & Traquair), fisheye rot 
478

(Butlerelfia eustacei Weresub & Illman), pink rot 

(Trichothecium roseum [Pers.] Link), and rhizopus 

rot (Rhizopus stolonifer [Ehrenb.] Vuill.).

References

Agar, I.T., W.V. Biasi, and E.J. Mitcham. 

1999. Exogenous ethylene accelerates ripening 

responses in ‘Bartlett’ pears regardless of maturity 

or growing region. Postharv. Biol. Technol. 17:67-

68.

Agar, I.T., W.V. Biasi, and E.J. Mitcham. 2000. 

Cold storage duration influences ethylene 

biosynthesis and ripening of ‘Bartlett’ pears. 

HortScience 35:687-690.

Blankenship, S.M., and D.G. Richardson. 1985. 

Development of ethylene biosynthesis and 

ethylene induced ripening in ‘d’Anjou’ pears 

during the cold requirement for ripening. J. Amer. 

Soc. Hort. Sci. 110:520-523.

Chen, P.M., S.R. Drake, D.M. Varga, and L. Puig. 

1996. Precondition of ‘d’Anjou’ pears for early 

marketing by ethylene treatment. J. Food Qual. 

19:375-390.

Chen, P.M., D.G. Richardson, and W.M. 

Mellenthin. 1982. Differences in biochemical 

composition between ‘Beurre d’Anjou’ and ‘Bosc’ 

pears during fruit development and storage. J. 

Amer. Soc. Hort. Sci. 107:807-812.

Chen, P.M., and D.M. Varga. 1989. Black speck. 

A superficial disorder of ‘d’Anjou’ pears after 

prolonged CA storage. In J.K. Fellman, ed., 5th 

International Controlled Atmosphere Research 

Conference, vol 1, Wenatchee, WA, pp. 145-156.

Chen, P.M., and D.M. Varga. 1997a. CA regimes 

for control of superficial scald of ‘d’Anjou’ pears. 

In G. Kupferman, ed., 13th Annual Washington 

Tree Fruit Postharvest Conference, Wenatchee 

WA, pp, 17-26. 

Chen, P. M., and D.M. Varga. 1997b. 

Determination of optimum controlled atmosphere 

regimes for the control of physiological disorders 

of ‘d’Anjou’ pears after short-term, mid-term 

or long-term storage. In E.J. Mitcham, ed., 7th 

International Controlled Atmosphere Research 

Conference, July 13-18, 1997, University of 

California, Davis, vol. 2, pp. 85-90. University of 

California, Davis CA.

Chen, P.M., D.M. Varga, E.A. Mielke, et al. 

1990a. Control of superficial scald on ‘d’Anjou’ 

pears by ethoxyquin: effect of ethoxyquin 

concentration, time and method of application, 

and a combined effect with controlled atmosphere 

storage. J. Food Sci. 55:167-170.

Chen, P.M., D. Varga, E. Mielke, et al. 1990b. 

Control of superficial scald on ‘d’Anjou’ pears 

by ethoxyquin: oxidation of α-farnesene and its 

inhibition. J. Food Sci. 55:171-175, 180.

Childers, N.F. 1949. Pear and quince culture. 

In R.W. Gregory, ed., Fruit Science, Orchard 

and Small Fruit Management, pp. 248-273. J.B. 

Lippincott, New York, NY.

Davis, L.D., and W.P. Tufts. 1932. Black end and 

its occurrence in selected pear orchards. Proc. 

Amer. Soc. Hort. Sci. 28:634-638.

Drouet, A., and C. Hartmann. 1979. 

Ployribosomes from pear fruit. Plant Physiol. 

64:1104-1108.

Elgar, H.J., C.B. Watkins, S.H. Murray, and F.A. 

Gunson. 1997. Quality of ‘Buerre Bosc’ and 

‘Doyenne du Comice’ pears in relation to harvest 

date and storage period. Postharv. Biol. Technol. 

10:29-37.

Fidler, J.G., B.G. Wilkinson, K.L. Edney, and R.O. 

Sharples. 1973. The Biology of Apple and Pear 

Storage. Commonwealth Agricultural Bureaux, 

Farnham Royal, U.K.
479

Gerasopoulos, D., and D.G. Richardson. 1995. 

Changes in fatty acids of ‘d’Anjou’ pears in 

relation to storage temperature and calcium. Acta 

Hort. 379:459-466. 

Hansen, E. 1957. Reactions of anjou pears to 

carbon dioxide and oxygen content of the storage 

atmosphere. Proc. Amer. Soc. Hort. Sci. 69:110-

115.

Hansen, E. 1964. Control of anjou pear scald 

improves market appeal and quality. Oreg. State 

Hort. Soc. Ann. Rpt. 56:29.

Hansen, E., and W.M. Mellenthin. 1962. Factors 

influencing susceptibility of pears to carbon 

dioxide injury. Proc. Amer. Soc. Hort. Sci. 80:146-

153.

Hansen, E., and W.M. Mellenthin. 1967. Chemical 

control of superficial scald on Anjou pears. Proc. 

Amer. Soc. Hort. Sci. 91:860-864.

Hansen, E., and W.M. Mellenthin. 1979. 

Commercial handling and storage practices for 

winter pears. Spec. Rpt. 550, Oregon Agricultural 

Experiment Station, Corvallis, OR.

Harley, C.P. 1929. Relation of picking time to 

acetaldehyde content and core breakdown of 

‘Bartlett’ pears. J. Agric. Res. 39:483-493.

Hartman, H. 1925. The control of core breakdown 

in pears. Bull. 216, Oregon State University 

Agricultural Experiment Station, Corvallis, OR. 

Hartman, H. 1931. A peculiar freezing trouble 

of pears in cold storage. Bull. 282, Oregon State 

University Agricultural Experiment Station, 

Corvallis, OR.

Heppner, M.J. 1928. Pear black-end and its 

relation to different rootstocks. Proc. Amer. Soc. 

Hort. Sci. 24:139-142.

Hulme, A.C., and M.J.C. Rhodes. 1971. Pome 

fruits. In A.C. Hulme, ed., The Biochemistry of 

Fruits and Their Products, vol. 2, pp. 333-373. 

Academic Press, New York, NY.

Jones, A.L., and H.S. Aldwinckle, eds. 1990. 

Compendium of Apple and Pear Diseases. Amer. 

Phytopath. Soc. Press, St. Paul, MN.

Knee, M. 1987. Development of ethylene 

biosynthesis in pear fruit at -1 °C. J. Exp. Bot. 

38:1724-1733.

Kupferman, E.M. 1988. Research on skin 

speckling and pithy brown core of ‘d’Anjou’ pears 

reported. Good Fruit Grower 39(16):17-18.

Leblond, C., and R. Ularich. 1973. Controle de 

l’evolution de la maturation par divers traitements 

theriques et gazeux chez la poire “PasseCrassane.” Bull. Inst. Intl. Froid. 3:69-74.

Lee, S.P., P. Chen, T.H.H. Chen, et al. 1990. 

Differences of biochemical components between 

the skin tissues of normal and black-speckled 

‘d’Anjou’ pears after prolonged low oxygen 

storage. J. Amer. Soc. Hort. Sci. 115:784-788.

Leliévre, J.M., L. Tichit, P. Dao, et al. 1997. 

Effects of chilling on the expression of ethylene 

biosynthetic genes in ‘Passe-Crassane’ pear (Pyrus 

communis L.) fruit. Plant Mol. Biol. 33:847-855.

Mellenthin, W.M., P.M. Chen, and S.B. Kelly. 

1980. Low oxygen effects on dessert quality, scald 

prevention, and nitrogen metabolism of ‘d’Anjou’ 

pear fruit during long-term storage. J. Amer. Soc. 

Hort. Sci. 105:522-527.

Mellenthin, W.M., and C.Y. Wang. 1974. Friction 

discoloration of ‘d’Anjou’ pears in relation to fruit 

size, maturity, storage and polyphenoloxidase 

activities. HortScience 9:592-593.

Morin, F., C. Rigault, and C. Hartmann. 

1985. Consequences d’un sejour au froid sur 

le metabolisme de l’ethylene au cours de la 

maturation de la poire Passe Crassane apres 

recolte. Physiol. Veg. 23:353-359.

Pech, J., C. Balagué, A. Latche, and M. Bouzayen. 

1994. Postharvest physiology of climacteric fruits: 

recent developments in the biosynthesis and action 

of ethylene. Sci. Des Aliment. 14:3-15.
480

Porritt, S.W. 1964. The effect of temperature on 

postharvest physiology and storage-life of pears. 

Can. J. Plant Sci. 44:568-579.

Porritt, S.W. 1965. Effect of cooling rate on 

storage-life of pears. Can. J. Plant Sci. 45:90-97.

Porritt, S.W., M. Meheriuk, and P.D. Lidster. 

1982. Postharvest disorders of apples and pears. 

Agric. Can. Pub. no. 1737/E.

Puig, L., D.M. Varga, P.M. Chen, and E.A. 

Mielke. 1996. Synchronizing ripening in 

individual ‘Bartlett’ pears with ethylene. 

HortTechnology 6:24-27.

Sainsbury, G.F., and H.A. Schomer. 1957. 

Influence of carton stacking patterns on pear 

cooling rates. Marketing Research Report 171, 

U.S. Department of Agriculture, Washington, DC.

Sfakiotakis, E.M., and D.R. Dilley. 1974. 

Induction of ethylene production in ‘Bosc’ pears 

by postharvest stress. HortScience 9:336-338.

Varga, D.M., and P.M. Chen. 1995. Predicting 

optimum maturity essential for pears. Good Fruit 

Grower 46:39-40.

Wang, C.Y., and W.M. Mellenthin. 1972. 

Induction period and threshold temperatures for 

premature ripening in ‘Bartlett’ pears. J. Amer. 

Soc. Hort. Sci. 97:557-560.

Wang, C.Y., and W.M. Mellenthin. 1975. Effect of 

short-term high CO2

 treatment on storage response 

of ‘d’Anjou’ pears. J. Amer. Soc. Hort. Sci. 

100:492-495.

Wang, C.Y., C.E. Sams, and K.C. Gross. 1985. 

Ethylene, ACC, soluble polyuronide, and cell wall 

noncellulosic neutral sugar content in ‘Eldorado’ 

pears during cold storage and ripening. J. Amer. 

Soc. Hort. Sci. 110:687-691.

Williams, M.W., H.M. Couey, H. Moffitt, and 

D.L. Coyier. 1978. Pear Production. Agriculture 

Handbook 526, U.S. Department of Agriculture, 

Washington, DC.
481

Pepper

Gustavo Adolfo González-Aguilar

González-Aguilar is with the Centro de 

Investigación en Alimentación y Desarrollo, 

Hermosillo, Sonora, Mexico.

Scientific Name and Introduction

Pepper (Capsicum annul L.), also called bell 

pepper, chili, chilies, aji, pimiento, paprika, and 

capsicum, is a warm-season crop that is a member 

of the Solanaceae family. Sweet bell peppers are 

green at the immature stage (when most are sold) 

and turn red, gold, purple, orange, or brown as 

they ripen. Because sugar content increases as 

they ripen, colored peppers tend to be sweeter 

than green peppers. The most notable feature of 

peppers is flavor, which can be sweet, mild, or 

strongly pungent. Sweet bell peppers are available 

year round, with ‘California Wonder’ being the 

most common cultivar.

Chili peppers include a number of varieties: 

ancho, anaheim, cayenne, cherry hot pepper, 

cheese, fresno (red and green), habanero (red, 

green, and orange), jalapeno, poblano, serrano 

(green and red), yellow, chiltepin, cuban, long 

wax, new mexican, tabasco, thai, etc. Chili 

peppers vary greatly from mild to very hot. Heat 

is determined by capsaicin content. Some chili 

peppers are dried and sold individually or tied 

together in ornamental arrangements.

Peppers are eaten raw in salads and salsa; 

processed by canning, freezing, or pickling; and 

dehydrated and powdered to produce paprika 

and chili powder. Unlike in the United States, 

most European paprika is mildly pungent. Chili 

powder prepared at different levels of pungency 

is usually composed of ground, dried, pungent 

peppers mixed with other spices, such as oregano, 

cumin, and garlic. Various pepper forms, usually 

chili types, are extensively used in combination 

with other spices such as turmeric, cumin, and 

coriander to produce curry powder, the pungency 

of which depends on the pepper cultivars used. 

For instance, cayenne powder is a high-pungency 

condiment produced from dried mature fruit of 

cayenne-type cultivars

Quality Characteristics and Criteria

Good-quality sweet bell peppers are uniform 

in shape and are the size and color typical of 

the variety. The flesh (pericarp) should be firm 

and relatively thick with a bright skin color and 

sweet flavor; it should be free from defects such 

as cracks, decay, and sunburn. Peppers should 

not be shriveled and dull-looking or pitted. The 

same quality criteria apply to fresh chili peppers. 

Dry lines or striations across the skin are not an 

indication of poor quality—they indicate a hotter 

pepper.

Horticultural Maturity Indices

Criteria for the maturity of green peppers include 

fruit size, firmness, and color. For colored peppers 

the additional criteria of having a minimum of 

50% coloration is important. 

Chili peppers are harvested by hand. They are 

generally picked when ripe and then dried and 

allowed to equilibrate in moisture content in 

covered piles. The major dried peppers are hot red 

peppers for cayenne and occasionally pimientos 

for paprika. The pods may be sliced before drying 

to shorten drying time and improve color and 

flavor. Seeds may be removed by screening and 

water sprays.

Grades, Sizes, and Packaging

Grades for fresh sweet bell peppers include 

U.S. Fancy, U.S. No.1, and U.S. No. 2. Not all 

sweet peppers are graded; ungraded peppers are 

“unclassified.” Differences between grades are 

based primarily on external appearance. Sizes 

include Small, Medium, Large, and Extra Large/

Jumbo. Cardboard boxes commonly hold 6.8 to 
482

15.9 kg (15 to 35 lb) of randomly packed peppers. 

Very high quality peppers are often marketed in 

5-kg (11-lb) flat cartons with one or two layers of 

fruit. 

There are no U.S. grades for chili peppers. 

Precooling Conditions

After harvest, fresh market peppers should be 

rapidly cooled to no lower than 7 °C (45 °F) 

at high RH to reduce water loss and shrivel. 

Precooling can be done using forced-air cooling, 

hydrocooling, or vacuum-cooling. Properly 

vented cartons are required to facilitate forcedair cooling. If hydrocooling is used, care should 

be taken to prevent development of decay. High 

RH is necessary to avoid desiccation. Waxing has 

been used to reduce desiccation, but it tends to 

increase bacterial soft rot. Shelf-life varies among 

different pod types. Deterioration is often due to 

moisture loss, with some pod types more prone to 

desiccation than others.

Optimum Storage Conditions

Fresh peppers can be kept for 2 to 3 weeks at 7 °C 

(45 °F) with 90 to 95% RH. Storage life can be 

extended another week by packaging in moistureretentive films at 7 to 10 °C (45 to 50 °F). Peppers 

are subject to chilling injury when stored below 

7 °C (45 °F) and to accelerated ripening and 

bacterial soft rot when stored above 13 °C (55 

°F). Storage at 5 °C (41 °F) reduces water loss 

and ripening, but after 2 weeks chilling injury will 

appear. Some pepper cultivars can be sensitive to 

chilling if stored at 7 °C (45 °F), so a good storage 

temperature range is 7 °C (45 °F) to 13 °C (55 °F).

Controlled Atmosphere (CA) 

Considerations

Peppers derive a slight benefit from CA storage 

(Saltveit 1997). Low-O2

 atmospheres (2 to 5% 

for bell peppers and 3 to 5% for chilies) retard 

ripening and respiration during transit and storage 

and benefit quality slightly. At 10 °C (50 °F), 

high CO2

 (>5%) can cause calyx discoloration, 

skin pitting, and discoloration and softening in 

both bell and chili peppers. An atmosphere of 

3% O2

 and 5% CO2 is more beneficial for red 

than for green peppers stored at 5 to 10 °C (41 

to 50 °F) for 3 to 4 weeks. Before processing, 

chili peppers can be stored under 3 to 5% O2

 and 

15 to 20% CO2

 for up to 3 weeks at 5 °C (41 °F) 

without appreciable chilling injury or quality loss. 

Freshly harvested chili or other hot peppers should 

be stored under the same temperature and RH 

conditions as sweet peppers.

Retail Outlet Display Considerations

Fresh bell and chili peppers should be displayed at 

7 °C (45 °F). They should not be sprinkled or top 

iced. Dried chili peppers should be kept dry. 

Chilling Sensitivity

Peppers are sensitive to chilling injury when 

stored below 7 °C (45 °F). Symptoms include 

surface pitting, water-soaked areas, decay 

(especially Alternaria), and discoloration of the 

seed cavity. Symptoms can appear after a few days 

at 0 °C (32 °F) or a few weeks at 5 °C (41 °F). 

Sensitivity varies with cultivar; ripe or colored 

peppers are less chilling sensitive than green 

peppers.

Ethylene Production and Sensitivity

Peppers are nonclimacteric and produce very low 

levels of ethylene: 0.1 and 0.2 μL kg-1 h-1 at 10 

and 20 °C (50 and 68 °F), respectively. The use 

of ethylene to enhance ripening or color change is 

not recommended because it stimulates respiration 

and softening more than coloration. The most 

effective way to color peppers is to hold partially 

colored fruit at 20 to 25 °C (68 to 77 °F) with RH 

>95%. To maintain quality, store them away from 

ethylene-producing fruits and ripening rooms.
483

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 °C 7 to 8

10 °C 10 to 15

15 °C 24 to 30

20 °C 32 to 36

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Blossom end rot is characterized by a slightly 

discolored or dark sunken lesion at the blossom 

end of the fruit. It is caused by calcium deficiency 

during growth. Pepper speck appears as spotlike 

lesions that penetrate the fruit wall. The cause is 

unknown; some varieties are more susceptible. 

Chilling injury is described above.

Postharvest Pathology

The most common decay microorganisms are 

Botrytis, Alternaria, and soft rots of fungal 

and bacterial origin. Botrytis (grey mold) is a 

common organism on peppers. Field sanitation 

and prevention of wounds on the fruit reduce 

its incidence. Botrytis grows well at the 

recommended pepper storage temperatures. 

High CO2

 levels (>10%) can control Botrytis

but damages peppers. Hot water dips at 53 to 

55 °C (126 to 130 °F) for 4 min can effectively 

control botrytis rot without causing fruit injury. 

The presence of alternaria black rot, especially 

on the stem end, is a symptom of chilling injury. 

The best control is to store peppers at 7 °C 

(45 °F). Bacterial soft rot is caused by several 

bacteria that attack damaged tissue. Soft rots can 

occur on washed or hydrocooled peppers when 

water sanitation is inadequate. Peppers are also 

affected by many of the disease, virus, insect, and 

nematode pests that affect tomato.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Before cutting, peppers should be stored at 7 to 10 

°C (45 to 50 °F). After cutting, fresh-cut peppers 

should be held at 0 to 5 °C (32 to 41 °F). Pepper 

slices (red and green) can be stored for up 12 days 

at 5 °C (41 °F) using a CA of 3% O2 and 10% 

CO2

.

Special Considerations

Mechanically harvested peppers are usually 

unsuitable for fresh market because of extensive 

injuries but can be used for processing. Peppers 

must be handled with care to avoid mechanical 

damage that may cause discoloration and 

pathological problems. Before packaging, peppers 

can be washed with 300 μL L-1 chlorine to reduce 

disease. Waxing with fungicides reduces water 

loss and disease.

After drying, chili peppers are packaged tightly 

into sacks holding ≥200 lb (≥91 kg) and are 

generally stored in nonrefrigerated warehouses 

for up to 6 mo. The temperature of the warehouse 

depends on its construction and the way it 

is managed, but mainly on ambient outdoor 

temperature. Insect infestation is a major storage 

problem. In Southern States, chili and other hot 

peppers are dried, packaged, and stored at 0 to 

10 °C (32 to 50 °F). Storage at low temperature 

retards loss of red color and slows insect activity.

Moisture content of chili and other hot peppers 

during storage should be low (10 to 15%) to 

prevent mold growth. A RH of 60 to 70% is 

desirable. With a high moisture content, pods 

may be too pliable for grinding and may have 

to be redried. With lower moisture content 

(<10%), pods may be so brittle they shatter during 

handling, causing loss and release of dust, which 

is irritating to the skin and respiratory system.
484

The use of polyethylene film liners within bags 

allows better storage and reduces dust. The liners 

ensure that the pods maintain constant moisture 

content during storage until the time of grinding. 

Thus, they permit successful storage or shipment 

under a wide RH range. Peppers can be stored 6 to 

9 mo at 0 to 4 °C when packed in this manner.

Manufacturers of hot-pepper products hold part of 

their raw material in cold storage at 0 to 10 °C but 

prefer to grind peppers immediately and store the 

dried product in air-tight containers.

Whole peppers are also dried until they are brittle 

and the seeds and pulp are completely dry. The 

dried product is used in flavoring and improving 

the appearance of various products, including 

canned products. Some sliced peppers are partially 

dried and mixed with salt for preservation for 

ultimate use in various processed products.

References

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

4, pp. 98-177. University of California, Davis, 

CA.

Further Reading

Ben-Yehoshua, S., B. Shapiro, J. Chen, and S. 

Lurie. 1983. Mode of action of plastic film in 

extending life of lemon and bell pepper fruits by 

alleviation of water stress. Plant Physiol. 73:87-

93.

Brackett, R.E. 1990. Influence of modified 

atmosphere packaging on the microflora and 

quality of fresh bell peppers. J. Food Prot. 53:255-

257.

Cantwell, M. 1998. Bell peppers. 

Recommendations for maintaining postharvest 

quality. University of California, Davis, CA. 

At http://postharvest.ucdavis.edu/produce_

information.

Gonzalez-Aguilar, G.A., and M. Tiznado. 1993. 

Postharvest physiology of bell peppers stored in 

low density polyethylene bags. Lebensm-Wiss. 

U-Thechnol. 26(5):450-455.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agricultural Handbook 66, U.S. Department of 

Agriculture, Washington, DC.

Miller, W.R., and L.A. Risse. 1986. Film wrapping 

to alleviate chilling injury of bell peppers during 

cold storage. HortScience. 21:467-468.

Miller, W.R., L.A. Risse, and R.E. McDonald. 

1986. Deterioration of individually wrapped 

and non-wrapped bell peppers during long term 

storage. Trop. Sci. 26:1-8.

Meir, S., Y. Rosenberger, Z. Aharon, et al. 1995. 

Improvement of the postharvest keeping quality 

and color development of bell pepper (cv. ‘Maor’) 

by packaging with polyethylene bags at reduced 

temperature. Postharv. Biol. Technol. 5:303-309.

Mercado, J.A., M.A. Quesada, V. Valpuerta, et al. 

1995. Storage of bell peppers in CA at chilling and 

non-chilling temperatures. Acta Hort. 412:134-

142.

Rodov, V., S. Ben-Yehoshua, T. Fierman, and 

F. Fang. 1995. Modified-humidity packaging 

reduces decay of harvested red bell pepper fruit. 

HortScience 30:299-302.

Wang, C.Y. 1977. Effect of CO2

 treatment on 

storage and shelf life of sweet peppers. J. Amer. 

Soc. Hort. Sci. 102:808-812. 
485

Perennial Culinary Herbs

Kimberly P. Wright

Wright is with Dole Fresh Vegetables, Salinas, 

CA.

Scientific Names and Introduction

Perennial culinary herbs include chives (Allium 

schoenoprasum L.), Chinese chives (A. tuberosum

Rottler), marjoram (Origanum hortensis), oregano

(O. vulgare L.), peppermint (Mentha piperita L.), 

spearmint (M. spicata L.), rosemary (Rosmarinus 

officinalis L.), sage (Salvia officinalis L.), tarragon

(Artemesia dracunculus L.), and thyme (Thymus 

vulgaris L.). The leaves are the part primarily used 

in foods and cooking. Due to their strong flavors 

and aromas, these culinary herbs are generally 

used in small quantities.

Quality Characteristics and Criteria

Herbs should appear fresh and green, with no 

yellowing, decay, insect damage, or mechanical 

damage. Leaves should be uniform in size. Flavor 

and aroma should be strong and characteristic of 

the herb. 

Horticultural Maturity Indices

Most herbs for fresh culinary use are best if 

harvested before flowering. Exceptions are 

marjoram and oregano (sometimes sold with 

flower buds) and chive blossoms (sometimes used 

in salads or as edible garnishes).

Grades, Sizes, and Packaging

There are no market grades or sizes for fresh 

herbs. They are bunched and tied with twist-ties or 

rubberbands, packaged in plastic bags or clamshell 

containers, and then packed in corrugated cartons. 

Perforated polyethylene liners should be used.

Precooling Conditions

Herbs should be cooled to just above 0 °C (32 °F) 

immediately after harvest.

Optimum Storage Conditions

Chives and mint can be stored for 2 to 3 weeks at 

0 °C (32 °F) with 95 to 100% RH; Chinese chives 

last for 1 to 2 weeks. Top icing is sometimes used 

for mint. Marjoram, oregano, and tarragon can be 

stored at 0 °C (32 °F) with 90 to 95% RH for 1 to 

2 weeks; rosemary, sage, and thyme will last for 

2 to 3 weeks (Hruschka and Wang 1979, Cantwell 

1997).

Controlled Atmosphere (CA) and Modified 

Atmosphere Packaging Considerations

Because of their short postharvest life, CA is 

generally not used for fresh herbs. MAP has been 

shown to retard yellowing in chives (Aharoni et al. 

1993).

Retail Outlet Display Considerations

Use of water sprinklers is acceptable. 

Chilling Sensitivity

These perennial herbs are not chilling sensitive 

and should be stored as close to 0 °C (32 °F) as 

possible without freezing.

Ethylene Production and Sensitivity

Ethylene production is low, but sensitivity is 

high. Low levels of ethylene can result in leaf 

abscission, epinasty, and yellowing. Storage at 0 

°C (32 °F) minimizes effects of ethylene on visual 

quality (Cantwell and Reid 1993, Cantwell 1997).
486

Respiration Rates

0 °C 10 °C 20 °C

 mg CO2 kg-1 h-1

Chives 22 110 540

Chinese chives 54 99 432

Marjoram 28 68 —

Mint 20 76 252

Oregano 22 101 176

Sage 36 103 157

Tarragon 40 99 234

Thyme 38 82 203

Data from Cantwell and Reid (1993) and Peiris et 

al. (1997).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Yellowing and leaf abscission may occur due to 

ethylene exposure, especially if held at ≥10 °C 

(≥50 °F).

Postharvest Pathology

Molds and bacterial decay may develop, 

especially on mechanically damaged leaves or cut 

ends of stems. Mints are subject to rust caused 

by Puccinia menthae Pers., which causes small 

brown pustules to form on leaves (Snowdon 

1992). It is important that low temperatures be 

maintained during storage and distribution to slow 

the rate of decay.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Perennial herbs are not currently used in fresh-cut 

products.

References

Aharoni, N., O. Dvir, D. Chalupowicz, and 

Z. Aharon. 1993. Coping with postharvest 

physiology of fresh culinary herbs. Acta Hort. 

344:69-78. 

Cantwell, M. 1997. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu/

produce_information/storagefreshproduce.

Cantwell, M.I., and M.S. Reid. 1993. Postharvest 

physiology and handling of fresh culinary herbs. J. 

Herbs, Spices and Medicinal Plants 1:93-127.

Hruschka, H.W., and C.Y. Wang. 1979. Storage 

and shelf life of packaged watercress, parsley and 

mint, p. 19. Marketing Research Report 1102, 

U.S. Department of Agriculture, Washington, DC.

Peiris, K.H.S., J.L. Mallon, and S.J. Kays. 1997. 

Respiratory rate and vital heat of some specialty 

vegetables at various storage temperatures. 

HortTechnology 7:46-49.

Snowdon, A.L. 1992. A color atlas of post-harvest 

diseases and disorders of fruits and vegetables, 

vol. 2, Vegetables. CRC Press, Boca Raton, FL.
487

Persimmon

Carlos H. Crisosto

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Persimmon is the species Diospyros kaki, a tree 

belonging to the family Ebenaceae and native to 

the Far East. Originally cultivated in China and 

Japan, it is also known as Chinese date plum. Fruit 

are grown throughout warmer parts of the world, 

including southern France, other Mediterranean 

countries, and the United States. Fruit are a good 

source of carotenoids, dietary fiber, and vitamins 

A and C.

The fruit is a berry, but the seeds are large, 

almond-shaped, and few in number. The epidermis 

is thin, and an enlarged calyx adheres to the base 

of the fruit. Persimmon has a delicious flavor 

and may be eaten fresh as a dessert or may be 

consumed dried or candied. In the United States, 

a native species—Diospyros virginiana—occurs, 

but its fruit are inferior to D. kaki. Another well 

known species is D. lotus, which yields fruit 

called date plums and is grown in Asia and Italy.

Quality Characteristics and Criteria

High-quality persimmons are medium to large 

in size, with uniform skin color from yellow to 

orange. Fruit should be firm, (penetration force 

[8-mm tip] >22.2 N [5 lb-force] for ‘Fuyu’ and 

similar cultivars). Fruit should be free from 

growth cracks, mechanical injuries, and decay. 

Recommended SSC is 21 to 23% in ‘Hachiya’ 

and 18 to 20% in ‘Fuyu’ and similar nonastringent 

cultivars. Astringent cultivars must be treated to 

remove astringency by polymerizing tannins.

Horticultural Maturity Indices

Minimum maturity is based on change in skin 

color from green to orange or reddish-orange 

(‘Hachiya’) or to yellow or yellowish-green 

(‘Fuyu,’ ‘California Fuyu,’ ‘Jiro’). In California, 

the minimum maturity indicators for ‘Hachiya’ 

persimmon are a blossom-end color of orange 

or reddish equal to or darker than Munsell color 

chart 6.7YR 5.93/12.7 on at least one-third of 

the fruit’s length with the remaining two-thirds a 

green color equal to or lighter than Munsell 2.5GY 

5/6. For other varieties, fruit must have attained 

a yellowish-green color equal to or lighter than 

Munsell 10Y 6/6.

Optimum Storage Conditions

The optimum temperature for storing persimmons 

is 0±1 °C (32±2 °F). The freezing point is -2 °C 

(28.4 °F), but may vary depending on SSC. RH 

should be maintained at 90 to 95%.

Controlled Atmosphere (CA) 

Considerations

Low O2

 of 3 to 5% delays ripening; CO2 at 5 to 

8% helps retain firmness and can reduce chilling 

injury symptoms on ‘Fuyu’ and similar cultivars. 

Postharvest life under optimum temperature and 

RH in ethylene-free air is 3 mo, whereas fruit can 

be stored up to 5 mo using ethylene-free CA (3 to 

5% O2

 and 5 to 8% CO2).

Retail Outlet Display Considerations

Cold-table display is recommended.

Chilling Sensitivity

Sensitivity varies by cultivar. ‘Hachiya’ 

is not chilling sensitive while ‘Fuyu’ and 

similar nonastringent cultivars are sensitive at 

temperatures between 5 oC and 15 oC (41 oF 
488

and 59 oF); they will exhibit flesh browning 

and softening. Exposure to ethylene aggravates 

chilling injury at these temperatures. 

Ethylene Production and Sensitivity

Persimmons produce <0.1 μL kg-1 h-1 at 0 °C (32 

°F) and 0.1 to 0.5 μL kg-1 h-1 at 20 °C (68 °F). 

They are very sensitive to ethylene. Exposure to 1 

and 10 μL L-1 ethylene at 20 °C (68 °F) accelerates 

softening to less than 4 lb-force (17.8 N), the limit 

of marketability, after 6 and 2 days, respectively. 

Thus, removing or excluding ethylene from 

transport and storage facilities is recommended.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 4 to 8

20 °C 20 to 24

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Chilling injury is the main physiological 

disorder. The incidence and severity depend on 

temperature, cold temperature duration, and the 

cultivar. For example, ‘Fuyu’ is chilling sensitive 

while ‘Hachiya’ is not. Chilling injury can be a 

major cause of deterioration of ‘Fuyu’ persimmons 

during marketing. Symptom development is 

greatest at 5 to 7 °C (41 to 45 °F) and slowest at 

0 °C (32 °F), which is the recommended storage 

and transport temperature for persimmons. ‘Fuyu’ 

fruit exhibit symptoms if held between 2 °C 

(36 °F) and 15 °C (59 °F). On transfer to higher 

temperatures, symptom severity (flesh softening, 

browning, and water-soaked appearance) increases 

and renders fruit unmarketable. Respiration 

and ethylene production rates of chilled ‘Fuyu’ 

persimmons are higher than those of nonchilled 

fruits. Exposure to ethylene at 0.1 μL L-1 or 

higher aggravates chilling symptoms of ‘Fuyu’ 

persimmons, while CA ameliorates symptoms. 

Chilling injury is controlled by avoiding exposure 

of ‘Fuyu’ fruit to temperatures between 2 °C (36 

°F) and 15 °C (59 °F). The optimum storage and 

transport temperature is 0 °C (32 °F). Exposure 

to ethylene >1 μL L-1 during postharvest handling 

should also be avoided. CA of 3 to 5% O2

 and 5 to 

8% CO2

 at temperatures <5 °C (<41 °F) reduces 

chilling injury.

Exposure to O2 levels <3% during storage for 

longer than 1 mo can result in failure of fruit to 

ripen and development of off flavors. Exposure to 

CO2

 >10% during storage for longer than 1 mo 

can cause brown discoloration of the flesh and 

lead to development of off flavors.

Calyx separation is a problem with some 

cultivars. It has caused losses in New Zealand. 

Growing conditions are all-important, and 

excessive nitrogen fertilization should be avoided. 

Thinning trees early in the season will enhance 

calyx growth and help prevent this disorder.

Postharvest Pathology

Alternaria rot is caused by Alternaria alternata,

which attacks developing fruits. Infections remain 

quiescent until after harvest, when black spots 

become apparent during ripening. Wound infection 

results in earlier appearance of symptoms. Other 

causes of decay in persimmons include species of 

Botrytis, Cladosporium, Colletotrichum, Mucor, 

Penicillium, Phoma, and Rhizopus.

Quarantine Issues

Currently, there is a limited trade exchange 

for persimmons. The United States exports 

persimmons to the Middle East and Mexico and 

imports persimmons from Chile without specific 

requirements. APHIS issues rules regarding 

import requirements and provides information to 
489

assist exporters in targeting markets and defining 

what entry requirements a particular country has. 

APHIS, in cooperation with State plant boards, 

developed a database called “Excerpt” to track 

phytosanitary requirements for each country. 

APHIS also provides phytosanitary inspections 

and certifications that declare fruit are free of pests 

to facilitate compliance with foreign regulatory 

requirements.

Suitability as a Fresh-Cut Product

Nonastringent persimmon cultivars can be 

prepared as fresh-cut wedges or slices. Wright and 

Kader (1997) reported that the shelf-life of ‘Fuyu’ 

persimmon slices was 7 days in air and 8 days in 

a CA of 2% O2

 and 12% CO2 at 5 °C (41 °F). A 

longer shelf-life can be expected at 0 to 2 °C (32 

to 36 °F). Protecting slices from ethylene helps 

firmness retention.

Special Considerations

The best method of harvesting fruit is to cut them 

from the tree, leaving the calyx attached to the 

fruit. It is possible to snap fruit from the tree by 

hand, but this practice is not recommended as it 

can injure the fruit and adjoining shoot. Fruit must 

be handled very carefully to avoid bruising, which 

is likely to become unsightly as fruit ripen. Two 

or three harvests are usually required, depending 

on fruit size and color. A desirable size for ‘Fuyu’ 

is 230 to 250 g; 200 g is the minimum marketable 

size.

Astringency can be removed from ‘Hachiya’ 

persimmons using 10 μL L-1 ethylene at 20 °C (68 

oF), but the excessive softening that results can 

make marketing the fruit difficult. Exposure to air 

enriched with 80% CO2

 for 24 h at 20 °C (68 oF) 

is also effective, and fruit maintain firmness.

References

Wright, K.P., and A.A. Kader. 1997. Effect of 

slicing and controlled-atmosphere storage on the 

ascorbate content and quality of strawberries and 

persimmons. Postharv. Biol. Technol. 10:39-48.

Further Reading

Beede, R.H. 1983. The Storage Performance 

of the Fuyu Persimmon and Its Susceptibility 

to Chilling Injury. M.S. thesis, Department of 

Pomology, University of California, Davis, CA.

Collins, R.J., and J.S. Tisdell. 1995. The influence 

of storage time and temperature on chilling injury 

in ‘Fuyu’ and ‘Suruga’ persimmon (Diospyros 

khaki L.) grown in subtropical Australia. Postharv. 

Biol. Technol. 6:149-157.

Crisosto, C.H., E.J. Mitcham, and A.A. Kader. 

1995. Produce Facts: Persimmons. Perishables 

Handling Quarterly 84:19-20. At http://

postharvest.ucdavis.edu/produce_information. 

Glucina, P.G. 1987. Calyx separation: a 

physiological disorder of persimmons. Orchardist 

of New Zealand 60:161-163.

Ito, S. 1971. The persimmon. In A.C. Hulme, ed., 

The Biochemistry of Fruits and Their Products, 

vol. 2, pp. 281-301. Academic Press, New York, 

NY.

Ito, S. 1980. Persimmon. In S. Nagy and P.E. 

Shaw, eds., Tropical and Subtropical Fruits: 

Composition, Properties and Uses, pp. 442-468. 

AVI, Westport, CT.

Kitagawa, H., and P.G. Glucina. 1984. Persimmon 

Culture in New Zealand, ch. 6-7. Science 

Information Publishing Center, Wellington, N.Z.

MacRae, E.A. 1987. Development of chilling 

injury in New Zealand grown ‘Fuyu’ persimmon 

during storage. N.Z. J. Exp. Agric. 15:333-344.
490

Prusky, D., R. Ben-Arie, and S. Guelfat-Reich. 

1981. Etiology and histology of Alternaria rot of 

persimmon fruits. Phytopathology 71:1124-1128.

Snowdon, A.L. 1990. A Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 1, General Introduction and Fruits. CRC 

Press, Boca Raton, FL.
491

Pineapple

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of Plant 

and Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI.

Scientific Name and Introduction

Pineapple (Ananas comosus L. Merr.) is a 

terrestrial member of the diverse Bromeliaceae

family. The pineapple fruit has the distinction of 

being selected, developed, and domesticated by 

peoples in tropical America in prehistoric times 

(Collins 1968). Of the many pineapple cultivars, 

‘Smooth Cayenne’ is the major commercial 

cultivar. Other cultivars grown on a smaller scale 

include ‘Red Spanish,’ ‘Queen,’ ‘Pernambuco,’ 

‘Sugarloafs,’ and ‘Cabaiani.’ Low acid ‘Smooth 

Cayenne’ varieties are also available (Nakasone 

and Paull 1998).

Quality Characteristics and Criteria

Pineapple fruit must have a desirable size and 

shape, with flat “eyes” (individual fruitlets) and 

deep-green crown leaves that look fresh. High 

shell color is not always a good measure of 

sweetness. Negative characteristics include dry, 

brown crown leaves; dull, yellow skin; presence 

of mold on the surface or cut stem; and an unfirm 

feel.

Horticultural Maturity Indices

Pineapple fruit maturity is evaluated on the 

extent of fruit “eye” flatness and skin yellowing. 

Consumers similarly judge fruit quality by 

skin color and aroma. A minimum of 12% SSC 

is required for fresh fruit in Hawaii (Hawaii 

Department of Agriculture 1968). A SSC:TA 

ratio of 0.9 to 1.3 is recommended (Soler 1992b). 

Fruit do not continue to ripen or sweeten after 

harvest. Fully ripe yellow fruit are unsuitable 

for transporting to distant markets, so slightly 

less mature fruit are selected for this purpose 

(Akamine 1963, Cancel 1974). Immature fruit 

should not be shipped, since they do not develop 

good flavor, have low Brix, and are more prone to 

chilling injury (Rohrbach and Paull 1982).

Grades, Sizes, and Packaging

Pineapples are graded by degree of skin 

coloration, size (weight), absence of defects and 

disease, and uniformity of these characteristics 

before packing. Other characteristics include 

maturity, firmness, nice shape, flat eyes, wellcured broken stem (peduncle), and a minimum 

SSC of 12% in Hawaii (Hawaii Department of 

Agriculture 1968). Crown size is a crucial grade 

component, with a minimum size and minimum 

ratio of crown:fruit length (0.33 to 1.5) for higher 

grades. Crowns developed during summer in 

Hawaii tend to be larger and may require gouging 

(removal of the crown center) at harvest to meet 

the standard.

Pineapples are normally packed into cartons of 

two different sizes and on the basis of color and 

size: (1) a large telescoping fiberboard carton 

holding 18 kg (40 lb) and containing 8 to 10 fruit 

in two layers, flat or upright, for surface and air 

shipment and (2) a smaller container of 9 kg (20 

lb) with five to six fruit in a single layer laid flat 

for air shipment. Tourist packs of two to four fruit 

are also prepared. Absorbent pads are used at the 

bottom of the carton and between layers if fruit 

are placed horizontally within the carton. In other 

packs, fruit are placed vertically.

Precooling Conditions

Room-cooling or forced-air cooling should be 

used.

Optimum Storage Conditions

Temperatures of 7 to 12 °C (45 to 55 °F) are 

recommended for storage of pineapples for 14 to 

20 days, provided fruit are at the color break stage 
492

(Paull 1993). RH of 85 to 95% is recommended; 

high RH significantly reduces water loss. Ripe 

fruit can be held at 7 °C (45 °F) for about 7 to 10 

days. Pineapples may be stored at 0 to 4 °C (32 

to 39 °F) for weeks, but upon removal fruit fail 

to continue ripening and show severe chilling 

injury. Quarter-yellow fruit at harvest gain about 1 

additional week of storage for every 6 °C (11 °F) 

decrease in storage temperature (Dull 1971). The 

maximum storage life at 7 °C (45 °F) is about 4 

weeks (Paull and Rohrbach 1985); however, when 

the fruit are removed, chilling-injury-induced 

internal browning develops within 2 to 3 days.

Controlled Atmospheres (CA) 

Consideration

Modifying O2

 levels is only minimally effective 

at extending pineapple shelf-life (Dull et al. 1967, 

Akamine and Goo 1971). Some benefit is gained 

from CA (4% O2

) treatments in reducing chilling 

injury development (Paull and Rohrbach 1982). 

The fruit waxes currently used generate high 

internal concentrations of CO2

 (up to 5%) and 

reduced O2

 (Paull and Rohrbach 1982). Low O2

has no effect on crown condition or decay but 

does delay shell color development and reduce 

superficial mold growth (Akamine and Goo 1971). 

Subjecting fruit to 1 to 2% O2

 and 0 to 10% CO2

after shipment from Mexico to England at 8 oC did 

delay chilling injury (Haruenkit and Thompson 

1994). Polyethylene bagging, though difficult to 

perform commercially on individual fruit, results 

in atmosphere of 8 to 10% O2

 and 7% CO2, and 

fruit waxing delays appearance of chilling-induced 

internal browning (Paull and Rohrbach 1982, 

Rohrbach and Paull 1982, Abdullah et al. 1985). 

The tentative recommendation is 2 to 5% and 5 to 

10% CO2

 (Yahia 1998).

Retail Outlet Display Considerations

Whole fruit should be displayed refrigerated at 10 

to 13 °C (50 to 55 °F) and should not be misted or 

iced.

Chilling Sensitivity

Symptoms of chilling injury include wilting, 

drying and discoloration of crown leaves, failure 

of green-shelled fruit to yellow, browning and 

dulling of yellow fruit, and internal flesh browning 

(Lim 1985, Paull and Rohrbach 1985). Preharvest 

shading, as well as preharvest and postharvest 

low temperature, are the major factors increasing 

symptom intensity (Akamine et al. 1975, Akamine 

1976, Keetch and Balldorf 1979, Smith 1983). 

Chilling injury symptoms include endogenous 

brown spot, physiological breakdown, blackheart, 

and internal browning. Symptoms develop after 

fruit are returned to physiological temperatures 

of 15 to 30 °C (59 to 86 °F) (Paull and Rohrbach 

1985). Susceptible fruit are generally lower in 

ascorbate and sugar and are opaque (Abdullah 

and Rohaya 1983, Abdullah et al. 1985, Paull and 

Rohrbach 1985, Swete Kelly and Bragshaw 1993).

Ethylene Production and Sensitivity

The ethylene production rate of this 

nonclimacteric fruit is low: 0.1 to 1.0 μL kg-1 h-1. 

Postharvest use of ethephon to degreen the shell 

has been tested in the Ivory Coast (Poignant 1971, 

Crochon et al. 1981), Hawaii (Paull 1985), and 

Australia (Smith 1991). Treated fruit show more 

rapid uniform skin degreening and little change in 

quality. However, shelf-life is slightly shortened 

(Paull 1985, unpublished data; Smith 1991, Soler 

1992a). There is no recommendation for use of 

ethephon; it is not approved for postharvest use.

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 °C 2

10 °C 4 to 7

15 °C 10 to 16

20 °C 19 to 29

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.
493

Physiological Disorders

Flesh translucency, also called porosity, is 

associated with greater fruit sensitivity to 

mechanical injury, indicated by leakage and 

oozing of cellular fluids. This condition begins 

before harvest and continues after (Bowden 

1969, Rohrbach and Paull 1982, Paull and Reyes 

1996). Fruit with increased translucency also have 

increased pH, a higher SSC:acid ratio, higher 

fruit weight, higher total esters, and lower acidity. 

SSC, flesh pigments, and palatability increase to a 

maximum at about 60% translucency, then decline 

in fruit with higher translucency (Bowden 1969).

Bruising by impact damage is a major problem 

during harvesting, packing, and shipping of 

pineapple. Mechanical injury of translucent fruit 

can lead to leakage of cell contents and loss of 

marketable fruit. Injury can be avoided by careful 

handling and avoiding impacts and bruising.

Sunburned, or sun-scorched, pineapples show 

a bleached, yellow-white skin that turns pale 

gray-brown with damage to the flesh underneath. 

Damaged areas are more susceptible to disease. 

It is common during hot periods (>35 °C [95 oF]) 

(Keetch and Balldorf 1979).

Malformations, or pineapple fruit with pronounced 

eyes or fruitlets, are normally not acceptable in 

Fancy grades of fruit, and the thicker skin results 

in lower flesh recovery. This condition is common 

in fruits that flower during cool weather. Some 

Spanish varieties are susceptible to broken core, 

in which the central core has a transverse break 

leading to the upper part of the fruit ripening 

ahead of the bottom (Lim 1985).

Postharvest Pathology

Black rot, also called thielaviopsis fruit rot, water 

blister, soft rot, or water rot, is a universal fresh 

pineapple problem characterized by a soft watery 

rot (Rohrbach 1983). Diseased tissue turns dark 

in the later stages of the disease because of the 

dark mycelium and spores. Black rot is caused 

by the fungus Chalara paradoxa (De Seynes) 

Sacc. Red Spanish types are more resistant than 

‘Smooth Cayenne.’ Infection occurs within 8 to 

12 h following harvest and enters through the 

point of detachment or wounds. The severity of 

the problem depends on the degree of bruising or 

wounding during harvesting and packing, the level 

of inoculum on the fruit, and storage temperature 

during transportation and marketing (Rohrbach 

and Schmitt 1994). The rot is commercially 

controlled by minimizing bruising of fruit during 

harvest and handling, refrigerating the fruit, and 

applying postharvest fungicides (Rohrbach and 

Phillips 1990).

Fruitlet core rot, black spot, fruitlet brown rot,

and eye rot describe the brown to black color of 

the central part of an individual fruitlet. Epidemic 

levels are rare in the major commercial pineappleproducing areas of the world (Rohrbach and 

Schmitt 1994). Low-acid cultivars being grown 

commercially are most susceptible (Rohrbach 

and Schmitt 1994). This disease is caused by a 

complex of fungi (Rohrbach and Schmitt 1994). 

Infection frequently can lead to misshapen fruit 

that are culled before packing and shipping.

Yeasty fermentation arises due to the fact that 

fruit are not sterile inside, containing many 

nongrowing but viable yeasts and bacteria. In 

damaged, overripe fruit and fruit with interfruitlet 

cracking, resident yeasts begin to grow or new 

yeasts invade. This growth leads to fermentation 

and bubbles of gas and juice through cracks in the 

skin. The skin turns brown and leathery and fruit 

become spongy with bright yellow flesh.

Saprophytes (Penicillium sp.) growing on the 

broken end of the peduncle and fruit surface are 

nonpathogenic but are unsightly and therefore 

a marketing problem (Rohrbach 1989). The 

condition is more common on highly translucent 

fruit.

Quarantine Issues

Pineapple fruit that are >50% ‘Smooth Cayenne’ 

are not regarded a host for tephritid fruit flies. 
494

Thus, insect disinfestation is not required for 

import into fly-free countries (Armstrong 1994).

Pineapple caterpillars (Thecla basilides Geyer,

Metamasius ritchiei Marchall, Batrachedre 

methesoni Busch, and Paradiophorus crenatus

Billbarg) are exotic and limited to Central 

America, South America, and the Caribbean 

(Harris 1927, Rohrbach 1983). The adult oviposits 

on the inflorescence prior to anthesis. Larvae then 

infest fleshy parts of the bracts and feed inside 

the developing inflorescence, exuding gum from 

the feeding chambers. Control with insecticides is 

relatively easy if flowering is induced uniformly 

with forcing agents. T. basilides is a tropical 

species that could cause problems if imported 

into Southern States such as Florida, as it can 

feed on corn, cacao, heliconia, and several other 

bromeliads (Rohrbach 1983).

Pineapple scale, Diaspis bromeliea Kerner, occurs 

wherever pineapple is grown. Normally, in Hawaii 

pineapple scale is not a major problem in fields, 

probably because of scale parasites and predators. 

However, because of the quarantine requirement 

to have fruit insect-free, even low levels of 

pineapple scale at harvest present quarantine 

problems. Scale are controlled by preharvest 

insecticide applications, taking into account “lastapplication-to-harvest” time.

The pineapple fruit mite, Steneotarsonemus 

ananas Tryon, occurs universally on the growing 

plant, developing in the inflorescence, fruit, and 

crown. Fruit mites feed on developing trichomes 

on the white basal leaf tissue and flower bracts and 

sepals, causing light brown necrotic areas. The 

pineapple red mite, Dolichotetranychus floridanus

Banks, feeds on the white basal leaf tissue, 

particularly of the crown. Severe damage occurs 

when the fruit mature under drought conditions. 

Red mites may cause death of basal crown leaves, 

affecting quality (Rohrbach and Schmitt 1994).

Mealybugs are removed from the surface by 

brushing. Preharvest insecticide and ant control 

almost eliminate mealybugs (Soler 1992b). 

Crickets and locusts may feed on bracts before 

harvest.

Suitability as Fresh-Cut Product

Fresh-cut pineapple is readily prepared at a 

central plant or in-store for ready-to-use consumer 

pack. Packs contain fresh-cut cylinders with the 

core removed or spears, chunks, or wedges. The 

product has a shelf-life of at least 7 days at proper 

temperature. A patent has been issued for the 

use of pouches flushed with 15 to 20% O2

 and 

3% argon and held at 1 °C (34 °F) for 10 weeks 

(Powrie et al. 1990) for fresh-cut pineapple pieces.

Special Considerations

Ease of removal of crown leaves, full skin 

yellowing, or the sound produced by tapping the 

fruit are not signs of ripeness or quality. Fruit are 

picked at the ripe stage and are ready-to-eat, even 

if there is a little skin yellowing.

References

Abdullah, H., and M.A. Rohaya. 1983. The 

development of black heart disease in Mauritius 

pineapple (Ananas comosus cv. Mauritius) during 

storage at lower temperatures. MARDI Res. Bull. 

11:309-319.

Abdullah, H., M.A. Rohaya, and M.Z. Zaipun. 

1985. Effect of modified atmosphere on black 

heart development and ascorbic acid contents 

in ‘Mauritius’ pineapple (Ananas comosus cv. 

‘Mauritius’) during storage at low temperature. 

ASEAN Food J. 1:15-18.

Akamine, E.K. 1963. Fresh pineapple storage. 

Hawaii Farm Sci. 12:1-4.

Akamine, E.K. 1976. Postharvest control of 

endogenous brown spot in fresh Australian 

pineapples with heat. HortScience 11:586-588.

Akamine, E.K., and T. Goo. 1971. Controlled 

atmosphere storage of fresh pineapples (Ananas 

comosus [L.] Merr. ‘Smooth Cayenne’). Res. Bull. 

152, Hawaii Agricultural Experiment Station, 

Honolulu, HI.
495

Akamine, E.K., T. Goo, T. Steepy, et al. 1975. 

Control of endogenous brown spot of pineapple 

in postharvest handling. J. Amer. Soc. Hort. Sci. 

100:60-65.

Armstrong, J.W. 1994. Tropical and subtropical 

fruits. In R.E. Paull and J.W. Armstrong, eds., 

Insect Pests and Fresh Horticultural Products: 

Treatments and Responses, pp. 275-290. CAB 

Intl., Wallingford, U.K.

Bowden, R.P. 1969. Further studies on ripeness in 

pineapple. Food Tech. Australia. 21:160-163.

Cancel, H.L. 1974. Harvesting and storage 

conditions for pineapples of the ‘Red Spanish’ 

variety. J. Agric., Puerto Rico 58:162-169.

Collins, J.L. 1968. The Pineapple. Leonard Hill, 

London, U.K.

Crochon, M., R. Tisseau, C. Teisson, and R. Huet. 

1981. Effet d’une application d’Ethrel avant la 

recolte sur la qualite gustative de ananas de Cote 

d’Ivoire. Fruits 36:409-415.

Dull, G.G. 1971. The pineapple: general. In A.C. 

Hulme, ed., The Biochemistry of Fruits and Their 

Products, vol. 2, pp. 303-331. Academic Press, 

London, U.K.

Dull, G.C., R.E. Young, and J.B. Biale. 1967. 

Respiratory patterns in fruit of pineapple, 

Ananas comosus, detached at different stages of 

development. Physiol. Plant. 20:1059-1065.

Harris, W.V. 1927. On a lycaenid butterfly 

attacking pineapple in Trinidad, British West 

Indies. Bull. Ent. Res. 18:183-188.

Haruenkit, R., and A.K. Thompson. 1994. 

Storage of fresh pineapple. In B.R. Champ, E. 

Highley and G.I. Johnson, eds., Proceedings 

of the International Conference on Postharvest 

Handling of Tropical Fruits, pp. 422-426. Chiang 

Mai, Thailand, July 1993. Australian Centre for 

International Agricultural Research, Proceedings 

no. 50, Canberra, Australia.

Hawaii Department of Agriculture. 1968. 

Wholesale standards for Hawaiian-grown 

pineapple. Hawaii Department of Agriculture, 

Marketing Division, Honolulu, HI.

Keetch, D.P., and D. B. Balldorf. 1979. The 

incidence of certain pineapple fruit blemishes in 

the eastern cape and border. Citrus Subtrop. Fruit 

J. 551:12-15.

Lim, W.H. 1985. Diseases and Disorders of 

Pineapples in Peninsular Malaysia. Report 97, 

MARDI, Kuala Lumpur, Malaysia.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

Paull, R.E. 1993. Pineapple and papaya. In

G. Seymour, J. Taylor, and G. Tucker, eds., 

Biochemistry of Fruit Ripening, pp. 291-323. 

Chapman & Hall, London, U.K.

Paull, R.E., and K.G. Rohrbach. 1982. Juice 

characteristics and internal atmosphere of waxed 

‘Smooth Cayenne,’ pineapple fruit. J. Amer. Soc. 

Hort. Sci. 107:448-452.

Paull, R.E., and K.G. Rohrbach. 1985. Symptom 

development of chilling injury in pineapple fruit. 

J. Amer. Soc. Hort. Sci. 110:100-105.

Paull, R.E., and M.E.Q. Reyes. 1996. Preharvest 

weather conditions and pineapple fruit 

translucency. Sci. Hort. 66:59-67.

Poignant, A. 1971. La maturation controlee de 

l’ananas II-L’ethrel et son action au cours des 

phases ascendante et descendarte de la maturite. 

Fruits 26:23-35.

Powrie, W.D., R. Chiu, H. Wu, and B.J. Skura. 

1990. Preservation of cut and segmented fresh 

fruit pieces. U.S. Patent 4,895,729.

Rohrbach, K.G. 1983. Exotic pineapple diseases 

and pests and their potential for spread. In K.G. 

Singh, ed., Exotic Plant Quarantine Pests and 

Procedures for Introduction of Plant Materials, pp. 

145-171. ASEAN Plant Quarantine Centre and 

Training Institute, Selangor, Malaysia.
496

Rohrbach, K.G. 1989. Unusual tropical fruit 

diseases with extended latent periods. Plant Dis. 

73:607-609.

Rohrbach, K.G., and R. E. Paull. 1982. Incidence 

and severity of chilling induced browning of 

waxed ‘Smooth Cayenne’ pineapple. J. Amer. Soc. 

Hort. Sci. 107:453-457.

Rohrbach, K., and D.J. Phillips. 1990. Postharvest 

diseases of pineapple. Acta Hort. 269:503-508.

Rohrbach, K., and D.P. Schmitt. 1994. Pineapple. 

In R.C. Ploetz, G.A. Zentmyer, W.T. Nishijima, et 

al., eds., Compendium of Tropical Fruit Diseases, 

pp. 45-55. Amer. Phytopath. Soc., St. Paul, MN.

Smith, L.G. 1983. Causes and development of 

black heart in pineapples. Trop. Agric. (Trinidad) 

60:31-35.

Smith, L.G. 1991. Effects of ethephon on ripening 

and quality of fresh market pineapples. Austr. J. 

Exp. Agric. 31:123-127.

Soler, A. 1992b. Metabolism de l’ethephon dans 

l’epiderme de l’ananas (Ananas comosus, L. 

Merr). Fruits 47:471-477.

Soler, A. 1992a. Pineapple. CIRAD-IRFA, Paris, 

France.

Swete Kelly, D., and J. Bragshaw. 1993. Effect 

of fruit handling and fruit coatings on black heart 

(internal brown spot) and other aspects of fresh 

pineapple quality. Acta Hort. 334:305-316.

Yahia, E. 1998. Modified and controlled 

atmospheres for tropical fruits. Hort. Rev. 22:123-

183.
497

Plum and Fresh Prune

Carlos H. Crisosto and Adel A. Kader

Crisosto is with the Department of Plant Sciences, 

University of California, Davis, CA. Kader was 

with the Department of Plant Sciences, University 

of California, Davis, CA. He is deceased.

Scientific Name and Introduction

Plums (Prunus salicina) are mainly marketed for 

fresh consumption and not for drying. They are 

also used for canning, freezing, and making jam 

and jelly. The Japanese plum (P. salicina) is native 

to China but was domesticated in Japan 400 years 

ago. It was first brought to California from Japan 

in 1870 by John Kelsey. In 1885, Luther Burbank 

imported about 12 seeds from Japan and used 

them to breed many cultivars. The plum industry 

has increased throughout California (mainly in the 

central San Joaquin Valley) where most Japanese 

plums in the United States are grown.

Prunes are cultivars of the European plum (Prunus 

domestica, L.) that can be dried whole. Like 

plums, prunes can be eaten fresh (if a very sweet 

fruit is desired), but they also have the high sugar 

content necessary for successful drying. The 

European plum, believed to have originated in the 

Near East, has been grown in parts of Europe for 

many centuries. Through its culture in France, the 

prune ‘d’Agen’ was introduced to California from 

France by Louis Pellier, a French horticulturist 

who had come to California seeking gold.

Quality Characteristics and Criteria

Consumer acceptance is high for fruit with 

high SSC. Fruit TA, SSC:TA, and phenolic 

content (astringency) are also important factors 

in consumer acceptance. However, there is no 

established minimum quality standard based on 

these factors. Plums with about 10 N (1 kg-force) 

flesh firmness (8-mm tip) are considered ready to 

eat.

Horticultural Maturity Indices

In most of the plum cultivars grown in California, 

harvest date is determined by skin color changes 

specific to each cultivar. A color chip guide is 

used to determine maturity for some cultivars. 

Firmness, measured by squeezing fruit in the palm 

of the hand (“spring”), is also a useful maturity 

index for a few cultivars.

A two-tier maturity system is currently used in 

California: U.S. Mature (minimum maturity) 

and California Well-Mature. Measurement 

of fruit firmness is recommended for plum 

cultivars in which skin ground color is masked 

by development of full red or dark color before 

maturation. Flesh firmness, measured using a 

penetrometer (8-mm tip), can be used to determine 

a maximum maturity index, which is the stage 

at which fruit can be harvested without suffering 

bruising damage during postharvest handling. 

Plums are less susceptible to bruising than most 

peach and nectarine cultivars at comparable 

firmness.

Fresh prunes are picked on the basis of color: 

at least 50% of the fruit surface is red or purple 

and SSC is at least 16% in ‘Moyer’ and 19% in 

‘French’ prunes.

Grades, Sizes, and Packaging

Plums and fresh prunes are hand-picked into 

bags, then dumped in bins that are moved on 

trailers between tree rows in the orchard. At the 

packinghouse, plums are dumped (mostly using 

dry bin dumps) and washed. Sorting is done to 

eliminate fruit with visual defects and sometimes 

to divert fruit of high surface color to a highquality pack. Sizing segregates fruit either by 

weight or dimension. In general, plums and fresh 

prunes are packed into 12.6-kg (28-lb) volumefilled containers.
498

Precooling Conditions

Plums and fresh prunes can be cooled in field bins 

using forced-air cooling, hydrocooling, or roomcooling prior to packing. Packed plums and fresh 

prunes should be cooled by forced-air cooling to 

near 0 °C (32 °F).

Optimum Storage Conditions

A storage temperature of -1.1 to 0 °C (30 to 32 

°F) with 90 to 95% RH should be used. An air 

circulation velocity of approximately 15 m3

 min-1

is suggested. The freezing point varies from -2 to 

-1 °C (28 to 30 °F) depending on SSC.

In late-season plums and in fresh ‘French’ and 

‘Moyer’ prunes, internal breakdown (IB) has been 

delayed by storing IB-susceptible cultivars at -1.1 

°C (30 °F). However, to store fruit at this low a 

temperature, high SSC and excellent thermostatic 

control are essential to avoid freeze damage.

Controlled Atmosphere (CA) 

Considerations

The major benefits of CA during storage and 

shipment are retention of fruit firmness and delay 

of changes in ground color. Decay incidence is 

reduced by CA of 1 to 2% O2

 and 3 to 5% CO2. 

Currently, CA has a limited use for storage longer 

than 1 mo of some cultivars such as ‘Angeleno,’ 

‘Casselman,’ ‘Santa Rosa,’ ‘Laroda,’ and ‘Queen 

Ann.’

Retail Outlet Display Considerations

If fruit firmness is <22 N (2.3 kg-force [5 lbforce]), plums should be displayed on a cold table. 

If fruit firmness is >22 N (2.3 kg-force [5 lbforce]), they should be displayed on a dry table.

Chilling Sensitivity

Postharvest life varies among cultivars and is 

strongly affected by temperature management. 

Most plum and fresh prune cultivars are 

susceptible to chilling injury when stored at 5 °C 

(41 °F). Market-life of ‘Blackamber,’ ‘Fortune,’ 

and ‘Angeleno’ plums at 0 °C (32 °F) was >5 

weeks. ‘Show Time,’ ‘Friar,’ and ‘Howard Sun’ 

plums developed chilling injury symptoms within 

4 weeks, even when stored at 0 °C (32 °F). In all 

plum cultivars, a much longer market life was 

achieved when stored at 0 °C (32 °F) than at 5 °C 

(41 °F).

Ethylene Production and Sensitivity

Ethylene production rates are 0.01 to 5 μL kg-1 h-1

at 0 °C, 0.02 to 15 μL kg-1 h-1 at 5 °C, 0.04 to 60 

μL kg-1 h-1 at 10 °C, and 0.1 to 200 μL kg-1 h-1 at 

20 °C. The lower end of this range is for mature 

but unripe fruit; higher values are for ripe fruit.

Most plums harvested at the California WellMature stage (higher than U.S. Mature stage) 

will ripen properly without exogenous ethylene. 

However, for slow-ripening cultivars, such as 

‘Black Beaut,’ ‘Casselman,’ ‘Late Santa Rosa,’ 

‘Kelsey,’ ‘Nubiana,’ ‘Queen Ann,’ and ‘Roysum,’ 

application of 100 μL L-1 for at least 24 h at 20 

°C (68 °F) is needed for faster and more uniform 

ripening.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 2 to 3

10 °C 8 to 12

20 °C 16 to 24

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.
499

Physiological Disorders

Chilling injury (CI) is a concern with most plum 

and fresh prune cultivars. It is expressed as flesh 

translucency associated with flesh browning. 

Late plum cultivars also develop lack of juiciness 

in addition to these symptoms. In previous 

publications from South Africa, flesh translucency, 

specifically in some plum cultivars, has been 

called “gel breakdown” (Dodd 1984). In the 

United States, these symptoms are reported under 

“internal breakdown,” or CI (Kader and Mitchell 

1989, Crisosto et al. 1999). CI symptoms normally 

appear after placing fruit at ripening temperatures 

following cold storage at 2 to 8 °C (36 to 46 °F).

Internal browning is a physiological disorder 

of ‘Italian’ and other cultivars of prunes. It 

originates before harvest. It is associated with high 

temperatures during fruit maturation and delayed 

harvest.

Postharvest Pathology

Brown rot is caused by Monilia fructicola and is 

the most important postharvest disease of stone 

fruits. Infection begins during flowering. Fruit 

rot may occur before harvest but often develops 

during postharvest handling. Orchard sanitation to 

minimize infection sources, preharvest fungicide 

application, and prompt precooling after harvest 

are control strategies. Fruit cracking makes late 

season cultivars more prone to decay. Postharvest 

fungicide treatments may be used to limit decay.

Gray mold is caused by Botrytis cinerea. This 

rot can be serious during wet spring weather. 

It can develop during storage if fruit have been 

contaminated through harvest and handling 

wounds. Avoiding mechanical injuries, effective 

temperature management, and postharvest 

fungicide treatments are effective control 

measures.

Rhizopus rot is caused by Rhizopus stolonifer. 

This rot can occur in ripe or near-ripe stone fruits 

kept at 20 to 25 °C (68 to 77 °F). Precooling fruit 

and storing them below 5 °C (41 °F) is effective in 

controlling this fungus.

Quarantine Issues

A phytosanitary certificate is required to import 

California plums into Taiwan. Plums must be 

free of Anarsia lineatella (peach twig borer), 

Conotracherlus nenuphar (plum curculio), Cydia 

pomonella (codling moth), Erwinia amylovora

(fire blight), Rhagoletis pomonella (apple 

maggot), Tetranychus pacificus (Pacific spider 

mite), and Ceratitis capitata (Mediterranean 

fruit fly). If these conditions cannot be met, fruit 

must be treated appropriately prior to shipment. 

Details of the treatment must be recorded on the 

phytosanitary certificate.

A phytosanitary certificate is required to import 

California plums into British Columbia. The 

certificate should state that fruit are free of Cydia 

molesta (oriental fruit moth), and it should 

clearly advertise that the fruit in the shipment 

were produced and inspected in accordance 

with the “systems approach guidelines” agreed 

to by APHIS and the Canadian Food Inspection 

Agency. Fruit imports to all of the other Canadian 

provinces are unrestricted.

A similar systems approach, between APHIS and 

Mexican agencies, facilitates import and assures 

plums are free of Cydia molesta (oriental fruit 

moth), Conotracherlus nenuphar (plum curculio), 

Rhagoletis pomonella (apple maggot), and fruit 

flies (Tephritidae).

Suitability as Fresh-Cut Product

Fresh-cut plums are best kept at 0 °C (32 °F) in 

packages that minimize water loss. Marketing 

life of fresh-cut plums ranges from 2 to 5 days, 

depending on cultivar and stage of ripeness 

(firmness) at the time of slicing.
500

Acknowledgments

Some of the information in this chapter is from 

the University of California, Davis, website on 

“Produce Facts” at http://postharvest.ucdavis.edu/

produce_information.

References

Crisosto, C.H., F.G. Mitchell, and Z. Ju. 1999. 

Susceptibility to chilling injury of peach, 

nectarine, and plum cultivars grown in California. 

HortScience 34:1116-1118.

Dodd, M.C. 1984. Internal breakdown in plums. 

Deciduous Fruit Grower, August, pp. 255-256.

Kader, A.A., and F.G. Mitchell. 1989. Postharvest 

physiology. In J.H. LaRue and R.S. Johnson, 

eds., Peaches, Plums, Nectarines: Growing and 

Handling for Fresh Market, pp. 154-164. Pub. no. 

3331, University of California, Davis, CA.

Further Reading

Ben, J., and M. Gaweda. 1992. Effect of 

increasing concentrations of CO2

 in controlled 

atmosphere storage on the development of 

physiological disorders and fungal diseases in 

plums (Prunus domestica L.). Folia Hort. 4:87-

100.

Ceponis, M.J, R.A. Cappellini, J.M. Wells, and 

G.W. Lightner. 1987. Disorders in plum, peach 

and nectarine shipments to the New York market, 

1972-1985. Plant Dis. 71:947-952.

Combrink, J.C. 1996. Integrated Management of 

Postharvest Quality. INFRUITEC, Stellenbosch, 

South Africa.

Couey, H.M. 1960. Effect of temperature and 

modified atmosphere on the storage-life, ripening 

behavior, and dessert quality of ‘El Dorado’ 

plums. Proc. Amer. Soc. Hort. Sci. 75:207-215.

Couey, H.M. 1965. Modified atmosphere storage 

of ‘Nubiana’ plums. Proc. Amer. Soc. Hort. Sci. 

86:166-168.

Crisosto, C.H. 1994. Stone fruit maturity indices: 

a descriptive review. Postharv. News Info. 

5(6):65N-68N.

Eksteen, G.J., T.R. Visagie, and J.C. Laszlo. 1986. 

Controlled atmosphere storage of South African 

grown nectarines and plums. Deciduous Fruit 

Grower 36(4):128-132.

Gerdts, D., F.G. Mitchell, and G. Mayer. 1987. 

Extended storage of late season plum varieties. 

California Tree Fruit Agreement Report, CTFA, 

Sacramento CA.

Mitchell, F.G. 1987. Influence of cooling and 

temperature maintenance on the quality of 

California grown stone fruit. Intl. J. Refrig. 10:77-

81.

Mitchell, F.G., G.S. Sibbett, and G. Mayer. 1981. 

Cold storage of ‘French’ prunes may expand 

dehydrator capacity. Calif. Agr. 35(1&2):20-22.

Proebsting, E.L. Jr., G.H. Carter, and H.H. Mills. 

1974. Interaction of low temperature storage and 

maturity on quality of ‘Early Italian’ prunes. J. 

Amer. Soc. Hort. Sci. 99:117-121.

Streif, J. 1989. Storage behaviour of plum fruits. 

Acta Hort. 258:177-183.

Truter, A.G., J.C. Combrink, and L.J. von 

Mollendorff. 1994. Controlled-atmosphere storage 

of plums. Deciduous Fruit Grower 44:373-375.

Wells, J.M., J.E. Butterfield, and M.J. Ceponis. 

1994. Diseases, physiological disorders, and 

injuries of plums marketed in metropolitan New 

York. Plant Dis. 78:642-644.
501

Pomegranate

M. Pekmezci and M. Erkan

Pekmezci and Erkan are with the Department 

of Horticulture, Faculty of Agriculture, Akdeniz 

University, Turkey.

Scientific Name and Introduction

Punica granatum L., the pomegranate, belongs 

to the Punicacea family and is one of the 

oldest known edible fruits. It is sometimes 

called Chinese apple and has been cultivated 

extensively in Mediterranean countries (Tunisia, 

Turkey, Israel, Egypt, Spain, and Morocco), 

Iran, Afghanistan, India, and to some extent in 

the United States (California), China, Japan, and 

Russia. The pomegranate requires a long, hot 

summer for fruit to mature, but it can withstand 

low temperatures in winter and is drought- and 

salt-tolerant. 

Pomegranate fruit is nearly round with a 

prominent attached calyx and a hard, leathery 

skin. Surface color varies among commercial 

cultivars from yellow with a crimson cheek to 

solid brownish-red and also bright-red. The edible 

portion is the bright-red pulp (aril) surrounding 

the individual seed. The fruit is consumed fresh, 

or it can be processed into juice, syrup, jams, or 

wine. Fruit of the wild-type pomegranate is acidic, 

but cultivated cultivars bear fruit with a sweetsour or sweet flavor. There are several types of 

edible pomegranate, and there are ornamental 

types with double flowers, largely sterile, which 

are not grown for edible fruit. Several cultivars are 

grown commercially around the world, including 

‘Wonderful’ in California and Israel, ‘Mollar’ and 

‘Tendral’ in Spain, ‘Schahvar’ and ‘Robab’ in Iran, 

‘Hicaznar’ and ‘Beynar’ in Turkey, and ‘Zehri’ 

and ‘Gabsi’ in Tunisia (LaRue 1980, Onur and 

Kaşka 1985, Morton 1987, Patil and Karale 1990, 

Llacer et al. 1994, Mars 1994).

Quality Characteristics and Criteria

Fruit quality depends largely on sugar and acid 

content of the juice. A high-quality pomegranate 

should also have an attractive skin and small 

seeds in the aril and should be free from sunburn, 

growth cracks, cuts, bruises, and decay. Skin color 

and smoothness are also quality indices. Sour 

and sour-sweet pomegranates have reddish skin, 

in contrast to sweet pomegranates which have 

yellowish-green skin. Skin thickness varies from 

1.5 to 4.24 mm (Küpper 1995). Skin contains 

30% tannin, which is used in medical and dye 

industries.

Pomegranates are low in vitamin C, an important 

nutritional quality component, compared to many 

other fruits. Vitamin C content ranges from 0.49 

to 30 mg per 100 g juice depending on cultivar 

(Hussein and Hussein 1972, Küpper 1995). Juice 

content of pomegranates is 45 to 65% of the whole 

fruit or 76 to 85% of the aril.

Horticultural Maturity Indices

Pomegranates can be harvested when they reach a 

certain size and skin color. Other maturity indices 

are TA and SSC. Each pomegranate type requires 

a certain TA:SSC at harvest. TA of pomegranates 

varies between 0.13 and 4.98% at harvest (Küpper 

1995). The TA is <1% in sweet cultivars, 1 to 2% 

in sweet-sour cultivars, and >2% in sour cultivars 

(Onur and Kaşka 1985). SSC of pomegranates 

varies from 8.3 to 20.5% at harvest (Küpper 

1995). Thus, maturity indices depend on cultivar. 

For example, TA <1.85% and SSC ≥17% are 

recommended for California-grown ‘Wonderful’ 

fruit (Ben-Arie et al. 1984, Elyatem and Kader 

1984). Juice tannin content <0.25% is preferred, 

and red juice color equal to or darker than Munsell 

color chart 5R 5/12 is desirable (Crisosto et al. 

1996).
502

Grades, Sizes, and Packaging

There are no U.S. grades. Only a small number of pomegranates have been grown historically in the U.S., 

mostly in California and Arizona. Therefore, most fruit are imported for the U.S. market. Pomegranates 

are classified into four groups based on size. Under Turkish standards, sizes are defined as— 

Small 150 to 200 g 65 to 74 mm diameter 25 to 34 fruit per 5-kg carton

Medium 201 to 300 g 75 to 84 mm diameter 17 to 25 fruit per 5-kg carton

Large 301 to 400 g 85 to 94 mm diameter 13 to 17 fruit per 5-kg carton

Extra large 401 to 500 g 94 to 104 mm diameter 10 to 13 fruit per 5-kg carton 

Fruit are generally packed into two-layer tray packs or bulk cartons.

Optimum Storage Conditions

Optimum storage temperature varies by cultivar, 

production area, and postharvest treatment 

(Mercantilia 1989, Hardenburg et al. 1990, Köksal 

1989, Snowdon 1990, SeaLand 1991, Onur et al. 

1995). The recommended conditions for storage of 

‘Hicaznar’ are 6 °C (43 °F) with 90% RH (Onur et 

al. 1992, 1995, Pekmezci et al. 1998). Storage of 

‘Wonderful’ at <5 °C (41 °F) resulted in chilling 

injury, and severity of symptoms increased with 

time and temperature below 5 °C (Elyatem 

and Kader 1984). Control of RH is critical in 

storage because skin desiccates readily at low 

RH, resulting in hard, darkened rinds, which are 

unattractive and reduce marketability. RH of 90 to 

98% is preferred for storage (Salunkhe and Desai 

1984). Waxing fruit and storage in plastic liners 

can reduce weight loss (Küpper 1995). 

Controlled Atmosphere (CA) 

Considerations

CA storage has the advantage of reducing loss of 

TA and vitamin C (Küpper et al. 1995). Optimal 

CA levels for pomegranate storage are 3% O2

 and 

6% CO2

 (Küpper et al. 1995). ‘Hicaznar’ fruit 

can be stored for 6 mo at 6 °C (43 °F) under CA 

(Pekmezci et al. 1998).

Retail Outlet Display Considerations

Pomegranates should not be water-sprinkled or 

top-iced.

Chilling Sensitivity

Pomegranates are susceptible to chilling 

injury and should not be stored at <5 °C (41 

°F). External symptoms include rind pitting, 

brown discoloration of the skin, and increased 

susceptibility to decay. Internal symptoms include 

a pale aril color and brown discoloration of the 

white segments separating the arils (Elyatem and 

Kader 1984). 

Ethylene Production and Sensitivity

Pomegranates produce very low amounts of 

ethylene: <0.1 μL kg-1 h-1 at up to 10 °C (50 °F) 

and <0.2 μL kg-1 h-1 from 10 to 20 °C (50 to 68 

°F) (Elyatem and Kader 1984). Fruit are not 

particularly sensitive to ethylene exposure, though 

ethylene at ≥1 μL L-1 stimulates respiration and 

autocatalytic ethylene. Ben-Arie et al. (1984) 

reported that ethylene treatment of ‘Wonderful’ 

pomegranates caused a rapid but transient rise in 

CO2

 but no change in SSC, TA, or fruit and juice 

color. Pomegranates do not ripen after harvest and 

must be picked fully ripe.
503

Respiration Rates

Pomegranate is a nonclimacteric fruit and has a 

very low respiration rate that declines with time in 

storage.

Temperature mg CO2 kg-1 h-1

5 °C 4 to 8

10 °C 8 to 16

20 °C 16 to 36

Data from Crisisto et al. (1996).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Chilling injury (CI) is the most common 

physiological disorder during storage. Incidence 

and severity of CI depend on temperature and 

duration. Symptoms are especially apparent 

upon removal of fruit from cold storage to 20 °C 

(68 °F). External CI symptoms include surface 

pitting, skin discoloration, scald, and dead skin 

tissues. Internal symptoms include dead tissues, 

brown discoloration of the white segments 

separating the arils, and pale aril color (Elyatem 

and Kader 1984). Husk scald (brown superficial 

discoloration) is another manifestation of CI in 

pomegranate; it is a restricted to the husk. At 

advanced stages, scalded areas became moldy. 

Scald symptoms become evident after 8 weeks of 

storage at 2 °C (36 °F).

Splitting and cracking occur in fruit on the tree. 

The rind shows various degrees of cracking, which 

often serves as entry points for decay organisms 

(Salunkhe and Desai 1984). Splitting and cracking 

can be prevented by using regular irrigation; the 

last irrigation must be done 15 to 20 days before 

harvest. 

Internal breakdown is another physiological 

disorder in pomegranate fruit. The pulp-bearing 

seeds (arils) do not develop their typical red color 

and are somewhat flattened rather than plump 

(Ryall and Pentzer 1974).

Postharvest Pathology

Gray mold rot (Botrytis cinerea), green mold rot

(Penicillium digitatum), and Cladosporium spp. 

are the main postharvest diseases of pomegranate 

fruit. Gray mold usually starts at the calyx. As it 

progresses, the skin becomes light-brown, tough, 

and leathery. Heart rot is another disorder; it may 

be caused by Aspergillus spp. and Alternaria spp. 

Affected fruit show slightly abnormal skin color 

and a mass of blackened arils; disease develops 

while fruit are on the tree (Salunkhe and Desai 

1984). 

Quarantine Issues

There are no known quarantine issues.

Suitability as a Fresh-Cut Product

Possibly, but none are fresh-cut at this time.

Special Considerations

Pomegranates do not ripen after harvest and must 

be picked fully ripe to ensure the best eating 

quality.

References

Ben-Arie, R., N. Segal, and S. Guelfat-Reich. 

1984. The maturation and ripening of the 

‘Wonderful’ pomegranate. J. Amer. Soc. Hort. Sci. 

109:898-902.

Crisosto, C.H., E.J. Mitcham, and A.A. Kader. 

1996. Pomegranates. Perishables Handling 

Quarterly 85:17-18. At http://postharvest.ucdavis.

edu/pffruits/pomegranate.
504

Elyatem, M.S., and A.A. Kader. 1984. Postharvest 

physiology and storage behavior of pomegranate 

fruit. Sci. Hort. 24:287-298.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1990. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks, rev. 

Agricultural Handbook 66, U.S. Department of 

Agriculture, Washington, DC.

Hussein, M.A.H., and M.A.S. Hussein. 1972. 

Suitability of pomegranate varieties for 

processing. Assuit J. Ag. Sci. 3:303-307.

Köksal, I. 1989. Research on the storage of 

pomegranate cv. ‘Gökbahçe’ under different 

conditions. Acta Hort. 258:295-302.

Küpper, W. 1995. Wirkungen von Temperatur 

und CO2

-Konzentration in der Langfristigen CALagerung auf Verschiedene Qualitaetsmerkmale 

und die Respiration Waehrend der 

Nachlagerungsphase des Granatapfels (Punica

Granatum L.) der Sorte ‘Hicaznar.’ Ph.D. 

thesis, Institut für Obstbau und Gemüsebau der 

Rheinschen, Friedrich-Wilhelms-Univertat., Bonn, 

Germany.

Küpper, W., M. Pekmezci, and J. Henze. 1995. 

Studies on CA-storage of pomegranate (Punica 

granatum L., cv. ‘Hicaz’). Acta Hort. 398:101-

108.

LaRue, J.H. 1980. Growing pomegranates in 

California. Leaflet 2459, University of California, 

Division of Agricultural Science, Davis, CA.

Llacer, G., R. Martinez Valero, P. Melgarejo, et 

al. 1994. Present status and future prospects of 

underutilized fruit tree crops in Spain. pp. 63-75. 

In First Meeting CIHEAM Coop. Res. Network 

Underutilized Fruit Trees, 1994, Zaragoza, Spain.

Mars, M. 1994. La culture du granadier (Punica 

granatum L.) et du figuier (Ficus carica L.) en 

tunisie. pp. 76-83. In First Meeting CIHEAM 

Coop. Res. Network Underutilized Fruit Trees, 

1994, Zaragoza, Spain.

Mercantila. 1989. Guide to Food Transport. 

Fruit and Vegetables. Mercantilia, Copenhagen, 

Denmark.

Morton, J. F. 1987. Fruits of Warm Climates. Julia 

F. Morton, Miami, FL.

Onur, C. 1989. Nar muhafazasında bir yenilik 

[News on pomegranate storage]. Derim 6:88-93. 

Onur, C., and N. Kaska. 1985. Akdeniz bölgesi 

narlarının (Punica granatum L.) seleksiyonu 

[Selection of pomegranate of Mediterranean 

region]. Turkish J. Agric. For., D2, 9, 1:25-33.

Onur, C., M. Pekmezci, H. Tibet, et al. 1992. 

Hicaznarının soğukta muhafazası üzerinde 

bir araştırma [Research on cold storage of 

pomegranate cv. Hicaznar]. In Proceedings of 

Turkey 1st National Horticulture Congress, 

October 13-16, 1992, Ege University Agricultural 

Faculty, pp: 209-212. 

Onur, C., M. Pekmezci, H. Tibet, et al. 1995. 

Nar (Punica granatum L.) muhafazası üzerinde 

araştırmalar [Investigations on pomegranate 

storage]. In Proceedings of 2nd National 

Horticulture Congreess, 3-6 October, 1995, Adana, 

Turkey, vol 1, pp. 696-700. Çukurova University, 

Patil, A.V., and A.R. Karale. 1990. Pomegranate. 

In T.K. Kose and S.K. Mitra, eds., Fruits: Tropical 

and Subtropical, pp. 614-631. Naya Prokash, 

Calcutta, India.

Pekmezci, M., M. Erkan, H. Gübbük, and S. 

Gözlekçi. 1998. Effect of modified atmosphere on 

storage of pomegranate fruits (cv. Hicaznar). 25th 

International Horticultural Congress, Brussels, 

Belgium. Acta Hort. PP2/04/A10:368

Ryall, A.L., and W.T. Pentzer. 1974. Handling, 

Transportation and Storage of Fruit and 

Vegetables, vol. 2. AVI, Westport, CT.

Salunkhe, D.K., and B.B. Desai. 1984. Postharvest 

Biotechnology of Fruits, vol. 2. CRC Press, Boca 

Raton FL.
505

SeaLand Service. 1991. Shipping guide to 

perishables. SeaLand Service, Iselim, NJ.

Snowdon, A.L. 1990. A Colour Atlas of 

Postharvest Diseases and Disorders of Fruits 

and Vegetables, vol. 1, General Introduction and 

Fruits. Wolfe Scientific, London, U.K. 

Further Reading

Artes, F., J.G. Marin, and J.A. Martinez. 1996. 

Controlled atmosphere storage of pomegranate. Z. 

Lebensm. Unters. Forsch. 203:33-37. 

Ben-Arie, R., and E. Or. 1986. The development 

and control of husk scald on ‘Wonderful’ 

pomegranate fruit during storage. J. Amer. Soc. 

Hort. Sci. 111:395-399.

Gil, M., F. Artes, and F. Tomas-Barberan. 1996. 

Minimal processing and modified atmosphere 

packaging effects on pigmentation of pomegranate 

seeds. J. Food Sci. 61:161-164. 

Gil, M.I., R. Sanchez, J.G. Marin, and F. Artes. 

1996. Quality changes in pomegranates during 

ripening and cold storage. Z. Lebensm. Unters. 

Forsch. 202:481-485.

Kader, A.A., A. Chordas,, and S. Elyatem. 1984. 

Responses of pomegranates to ethylene treatment 

and storage temperature. Calif. Agri. 38(748):14-

15.
506

Potato

Ronald E. Voss

Voss is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

The white, or Irish, potato, Solanum tuberosum L., 

is an annual of the Solanaceae family. The edible 

portion is the tuber, an underground stem that 

forms at the end of stolons. Potato is a cool-season 

plant. It is native to the Americas, with many close 

relatives in the Andean region of South America. 

New varieties commonly have one or more wild 

Solanum species included in their pedigree. Potato 

is grown throughout the world in temperate zones, 

with planting in spring and harvest in fall. 

There are many skin colors (brown russet, white, 

red, pink, yellow) and flesh colors (white, cream, 

yellow, blue/purple/red, and striated). Tuber 

shapes vary from round to oblate to oblong to 

long. Stored potatoes are available year-round; 

fresh potatoes are harvested year-round, albeit 

in small quantities during winter, spring, and 

summer. Processed potatoes (frozen french fries, 

potato chips, flakes, etc.) are manufactured yearround from fresh and stored tubers.

Quality Characteristics and Criteria

A high-quality fresh-market potato tuber is 

turgid, well shaped, uniform, and brightly colored 

(especially reds, whites, and yellows), as well 

as free from adhering soil, mechanical damage, 

greening, sprouts, diseases, and physiological 

defects.

Horticultural Maturity Indices

The ability of potato tuber skin to resist abrasion 

(skinning) during harvest is a common index for 

maturity. Sugar content is a maturity index for 

processing potatoes, with both immaturity and 

overmaturity resulting in higher sugar levels. Vine 

senescence is used as a preharvest maturity index, 

but the correlation between vine senescence and 

tuber skin-set varies among cultivars.

Grades, Sizes, and Packaging

USDA market grades (established in 1991) are 

Extra No. 1, No. 1, Commercial, and No. 2; grade 

is distinguished primarily on external condition 

and appearance. Grades vary among tuber shapes. 

The minimum diameter for U.S. No. 1 or No. 2 

is 4.8 to 5.1 cm (1 7/8 to 2 in) for round potatoes 

with a weight minimum of 118 g (4 oz) for long 

potatoes. At times, an additional requirement that 

≥60% of the tubers must be a minimum of 148 g 

(5 oz) is imposed. A “B-size” grade is becoming 

more common, primarily for round red and white 

potatoes. B-size grade tubers are <5.1 cm (2 in).

Oblong and long russets are commonly wholesale 

marketed in “count” boxes of 60, 70, 80, 90 or 100 

tubers in a 22.5-kg (50-lb) carton, thus averaging 

approximately 380, 325, 296, 266, or 237 g each 

(13, 11, 10, 9, or 8 oz), respectively. These are 

retailed bulk for consumers to select individual 

tubers. Common retail packages of 2.27 and 4.55 

kg (5 and 10 lbs) plastic and paper bags generally 

contain 150- to 240-g (5- to 8-oz) tubers. B-size 

tubers are sold in pint “strawberry” baskets or in 

bulk. Prepeeled tubers are generally packaged in 

plastic trays covered with plastic wrap.

Potatoes for processing into such products as 

french fries or chips are graded using the U.S. 

grade and size standards in combination with 

individual quality and size requirements of each 

processing company. The company requirements 

vary with the type of product to be manufactured 

and the purchaser. Tubers are delivered to 

processing plants in bulk trucks or bins holding 

about 2,000 lb (910 kg).

Optimum Storage Conditions

Long-term storage of potato tubers—up to 

12 mo—requires that they be cured. Curing 
507

stimulates suberization and wound healing and 

reduces respiration. Optimal curing conditions 

are approximately 20 °C (68 °F) with RH of 80 to 

100%. Curing is markedly slower at temperatures 

<12 °C (54 °F) and >25 °C (77 °F). Similarly, 

RH <80% delays curing. Curing at 15 °C (59 °F) 

is commonly recommended to minimize decay. 

Frequently, potatoes harvested in fall in temperate 

climates are colder than the optimal curing 

temperatures. However, respiration in storage 

will heat the tubers and raise RH. Temperature 

and RH control during this “sweating” or curing 

time is managed using fans to bring outside air 

into the storage room, depending on the need 

during the night or day. Once cured, a process 

requiring 1 to 2 weeks, the tuber temperature is 

lowered by 1 to 2 °C per day until the desired 

maintenance temperature and RH are reached. 

In some cases, two additional steps must be 

employed: drying of wet potatoes upon entry into 

storage, and heating of tubers before removal 

from storage. Forced movement of air is used to 

ensure uniform temperature throughout the storage 

pile. Maintaining 95 to 99% RH is required at all 

times to minimize shrink and pressure bruising in 

storage. 

Desired maintenance temperature depends on the 

desired end use of the tubers. Respiration rate 

of potato tubers is lowest at 2 to 3 °C (36 to 37 

°F). Storage at 0 to 2 °C (32 to 36 °F) increases 

the risk of freezing or chilling injury. Sprouting 

accelerates at temperatures >4 °C (40 °F), so seed 

tubers are commonly stored at 4 to 5 °C (40 °F). 

Tubers for fresh consumption are stored at 7 to 

10 °C (45 to 50 °F), to minimize conversion of 

non-reducing sugars such as starch to reducing 

sugars such as glucose, which darken during 

cooking. Tubers for frying are stored at 10 to 15 

°C (50 to 59 °F), depending on the cultivar and its 

respective sugar conversion characteristics. Many 

chipping cultivars accumulate excessive sugar if 

stored <15 °C (59 °F). Thus, chipping cultivars are 

stored at 15 to 20 °C (59 to 68 °F); new cultivars 

are being developed that will not accumulate sugar 

at temperatures as low as 5 to 10 °C (41 to 50 °F).

Quality tubers can be stored for 2 to 12 mo, 

depending on quality at harvest, quality of storage 

facilities, variety, and whether or not sprout 

inhibitors are used. Sprout inhibitor may be 

applied in the field before senescence begins, on 

the tubers as they are graded and packaged, or in 

storage after curing is completed.

Controlled Atmosphere (CA) Conditions

The usefulness of CA storage is minimal, and 

economic justification doubtful. Periderm 

development and wound healing are delayed at 

atmospheres with <5% O2

. Injury from <1.5% 

O2

 or >10% CO2 includes induced off odors and 

flavors, internal discoloration, and increased 

decay. While higher CO2

 levels tend to inhibit 

formation of reducing sugars, they also increase 

sucrose content.

Retail Outlet Display Considerations

Cured and new potatoes, whether displayed in 

bulk or in cellophane or paper bags are displayed 

dry. New potatoes that are displayed in bulk 

are commonly included with other cool-season 

vegetables that receive periodic water misting or 

sprinkling.

Chilling Sensitivity

Potatoes freeze at approximately -1 °C (30 °F). 

Internal mahogany browning can occur at 1 to 

2 °C (34 to 36 °F), while temperatures of 3 to 

4 °C (37 to 39 °F) typically result in increased 

reducing sugar levels that are not reversible with 

reconditioning.

Ethylene Production and Sensitivity

Potatoes produce very low levels of ethylene: 

<0.1 μL kg-1 h-1 at 20 °C (68 °F). Cut, bruised, 

or wounded tubers have greatly increased 

ethylene production rates. Potato tubers are not 

very sensitive to external ethylene. Low levels 

of ethylene elevate respiration, especially in 

immature potatoes, and result in weight loss and 
508

mild shriveling. After 2 to 3 mo at >5 °C (41 °F) 

without sprout inhibitor, low levels of ethylene 

may retard sprouting, while high amounts may 

induce sprouting.

Respiration Rates

Immature potato tubers usually have higher 

respiration rates than mature or cured tubers. 

Cooler temperatures and increased air movement 

are effective at controlling effects of a high rate of 

respiration. Increased air movement in the absence 

of high RH, however, will cause desiccation.

Temperature Immature Mature (cured)

--------mg CO2 kg-1 h-1---------

5 °C 24 6 to 18

10 °C 30 to 40 13 to 19

15 °C 25 to 57 11 to 22

20 °C 32 to 81 14 to 29

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

The most common and serious physiological 

disorders affecting potatoes include black spot, 

blackheart, freezing injury, greening, hollow heart, 

sugar end browning, and internal necrosis. 

Black spot results from a physical impact to the 

tuber; the stem end is most sensitive. Following 

severe bruising or cutting, the affected tissue turns 

reddish, then blue, becoming black in 24 to 72 

h. Severity increases with time. Cultivars differ 

significantly in their susceptibility and symptom 

expression. Soil conditions can predispose tubers 

to blackspot; poor aeration is the most common 

cause. Proper fertilization (particularly potassium), 

water management, careful handling, and high RH 

to maintain turgidity are important in minimizing 

black spot. Use of compost and manure helps 

prevent blackspot.

Blackheart is a storage- or transportation-induced 

disorder caused by low O2

. Typically, blackheart 

is induced at >30 °C (86 °F), which increases 

respiration. If air exchange around tubers is 

insufficient, low-O2

 conditions develop in the 

interior of the tuber, and the cells suffocate 

and turn black. Blackheart is rare in early crop 

potatoes because of typical marketing practices.

Freezing at -1 °C (30 °F), whether in the field or in 

storage, typically results in a distinct demarcation 

between affected and unaffected tissue. Symptoms 

include a water-soaked appearance, glassiness, 

and tissue breakdown on thawing. Chilling injury 

can occur after a few weeks at 0 °C (32 °F) and 

result in a mahogany discoloration of internal 

tissue in some varieties. Much longer periods of 

storage are generally required for chilling injury. 

Greening may occur in part of a tuber exposed 

to light. Affected tubers are easily culled at 

grading and rarely proceed to marketing channels. 

Darkness is essential for long-term storage 

because greening can occur during storage 

or marketing. Exposure to bright light during 

postharvest handling, or longer periods (1 to 2 

weeks) of low light, can result in development 

of chlorophyll (greening) and bitter, toxic 

glycoalkaloids such as solanine. Solanine also 

forms in response to bruising and wounding 

(including fresh processing followed by storage) 

and during sprouting. Glycoalkaloids are heat 

stable and minimally degraded by cooking. Tubers 

in market displays should be replaced daily or 

more frequently to minimize greening. 

Enlarged lenticels are a common disorder in 

early potatoes where excessive irrigation is often 

applied to maintain cooler soil temperatures in 

warm or hot climates. These lenticels are subject 

to pathological infection in the soil or during 

packing. Infections may remain innocuous; or 

if transportation conditions are not properly 

maintained, they can increase rapidly in severity. 

Tubers that appear sound at the packing shed can 

become unmarketable during transit.
509

Skinning is a common disorder in early crop or 

“new” potatoes (harvested immature). Soil drying 

and vine death enhance skin set, and thus decrease 

skinning. Cultivars vary in ability to set-skin, in 

skin thickness, and thus in skinning susceptibility. 

“New” potatoes must be kept at a very high RH, 

near 100%, and must be handled with special care.

Hollow heart, sugar end accumulation, and 

internal necrosis are all production problems 

related to irregular growth, inadequate water 

availability, or widely fluctuating temperatures. 

These conditions do not change during harvest and 

postharvest handling.

Postharvest Pathology

Diseases are an important source of postharvest 

loss, particularly in combination with rough 

handling and poor temperature control. Three 

major bacterial diseases and a greater number of 

fungal pathogens are responsible for occasional, 

serious postharvest losses. The major bacterial 

and fungal pathogens that cause postharvest 

losses in transit, in storage, and after-market are 

bacterial soft rot (Erwinia carotovora subsp. 

carotovora and subsp. atroseptica), Ralstonia (ex 

Pseudomonas, ex Burkholderi) solanacearum,

late blight (Phytophthora infestans), fusarium 

dry rot (Fusarium spp.), pink rot (Phytophthora

spp.), water rot (Pythium spp.), and silver scurf 

(Helminthosporium solani). Occasionally serious 

diseases of immature tubers include pink eye 

(Pseudomonas fluorescens) and grey mold 

(Botrytis cinerea).

In addition to careful sorting before placing 

tubers into storage, management of air, RH, 

and temperature during storage and transit of 

potatoes with potential problems can be effective. 

Lower RH, shortened curing time, and lower 

temperatures can minimize spread of rot diseases. 

Quarantine Issues

Export and import of potato tubers can involve 

numerous quarantine issues related to grade, 

diseases, and nematodes. Each country has its 

own phytosanitary requirements. Inspections 

and appropriate authorizations are required. 

Among the most common diseases and nematodes 

included in quarantine or zero-tolerance 

requirements are cyst nematode (Globodera spp.), 

viruses and viroids, brown rot (Pseudomonas 

solanacearum), ring rot (Corynebacterium 

sepedonicum), and powdery scab (Spongospora 

subterranean). Similarly, these diseases and 

nematodes are restricted on potato tubers to be 

imported. Currently, potato tubers may not be 

imported into the United States from any country 

except Canada.

Suitability as Fresh-Cut Product

Potatoes are relatively new as a lightly processed 

product. Fresh-cut potatoes are not marketed, 

but par-boiled whole tubers can be prepared and 

marketed in plastic trays with sealed plastic wrap 

with low O2

-transmission characteristics. Storage 

requirements for tubers to be processed in this 

manner have not been well defined.

Special Considerations

Potatoes may impart an “earthy” odor to apples 

and pears if held in storage with low air exchange. 

Potatoes may acquire an off flavor from odor 

volatiles released by other produce items. 

Postharvest handling and storage of late-crop 

potatoes is very complex and depends on growing 

conditions, environment at harvest, variety, 

intended use, and many other factors.
510

Further Reading

Kader, A.A., ed. 2002. Postharvest Technology of 

Horticultural Crops, 3rd ed. DANR Pub. no. 3311, 

University of California, Oakland, CA.

Kleinkopf, G.E. 1979. Translucent end of 

potatoes. Cur. Info. Ser. 488, University of Idaho, 

Moscow, ID.

Kleinkopf, G.E. 1995. Dynamics of the stored 

potato—a management approach. Early season 

storage. Amer. Potato J. 72:449-462. 

Lewis, M.D., M.K. Thornton, and G.E. Kleinkopf. 

1997. Commercial application of CIPC sprout 

inhibitor to storage potatoes. Curr. Info. Ser 059, 

University of Idaho, Moscow, ID.

Rastovski, A. 1987. Storage of Potatoes: 

Postharvest Behavior, Store Design, Storage 

Practice, Handling. Pudoc, Wageningen, 

Netherlands.

Secor, G.A., N.C. Gudmestad, D.A. Preston, 

and H.A. Lamey. 1997. Disease Control 

Guidelines for Seed Potato Selection, Handling, 

and Planting. North Dakota State University 

Extension Publication PP-877, North Dakota State 

University, Fargo, ND.

Shetty, K.K. 1998. Potato storage. At http://www.

kimberly.uidaho.edu/potatoes.

Shetty, K.K., M.J. Frazier, G.E. Kleinkopf, and P. 

Nolte. 1997. Silver scurf of potatoes. Curr. Info. 

Ser. 1060, University of Idaho, Moscow, ID.

Sieczka, J.B., and R.E. Thornton, eds. 1993. 

Commercial Potato Production in North America, 

rev. Amer. Potato J. Suppl., vol. 57, and USDA 

Handbook 267, Potato Assoc. Amer. 1993 Official 

Pub. Potato Assoc. Amer., Orono, Maine.

Stevenson, W.R., R. Loria, G.D. Franc, and D.P. 

Weingartner, eds. 2001. Compendium of potato 

diseases, 2nd ed. American Phytopathological 

Society Press, St. Paul, MN.

Strand, L., G. Bishop, G. Kleinschmidt, et al., eds. 

1992. Integrated pest management for potatoes in 

the western United States, rev. DANR Pub. no. 

3316 and Western Regional Res. Pub. no. 011, 

University of California, Oakland, CA.

Suslow, T., and R. Voss. 2000. Potato (immature 

early crop). Recommendations in maintaining 

postharvest quality. Postharvest Technology 

Research & Information Center, University of 

California, Davis, CA.
511

Prickly Pear

Marita Cantwell

Cantwell is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Prickly pear fruit are harvested from various 

species of the prickly pear cactus, genus Opuntia

of the cactus family (Cactaceae). Fruit are also 

called cactus pears or cactus fruit, though these 

names can result in confusion with fruits from 

other cactus species. The fruit is a berry, typically 

weighs 100 to 200 g (0.2 to 0.4 lb), and consists of 

a thick fleshy skin or rind surrounding a juicy pulp 

that contains many hard-coated seeds. Fruit vary 

considerably in color, size, and flavor. Prickly pear 

fruit are produced in California or are imported 

from Mexico (“tunas”) and Chile. 

Quality Characteristics and Criteria

Fruit of high quality need to be harvested near 

full ripeness to have color and flavor typical of 

each variety. They should have a high percentage 

of pulp, low seed content, and peel that is easy to 

remove. Fruit typically have high sugar content 

(12 to 17% SSC) and low acidity (0.03 to 0.12% 

TA). Cactus pears contain considerable amounts 

of vitamin C (200 to 400 μg g-1). If harvested at 

maturity from good varieties, fruit have a delicate 

sweet flavor that differs by variety. 

Horticultural Maturity Indices

Stage of maturity or ripeness at harvest is very 

important for fruit quality since sugar content and 

sweetness do not increase after harvest. Maturity 

indices include fruit size and fullness, changes 

in peel color, abscission of the small spines 

(glochids), fruit firmness, and flattening of the 

floral cavity or receptacle. Peel color is the single 

most important index for commercial harvest. 

Grades, Sizes, and Packaging

There are no U.S. grades. Fruit are packed 

according to color, size, and condition in 4.5 kg 

(10 lb) cartons or may be packed in single- or 

double-layer tray cartons. Large fruit may be 

wrapped in tissue paper to reduce scuffing and 

other physical injury. Fruit may also be packaged 

in cartons with perforated plastic liners to reduce 

water loss under dry storage conditions. 

Precooling Conditions

Fruit should be cooled to 5 °C (41 °F) to reduce 

loss of visual appearance (shiny surface) resulting 

from water loss. Fruit are usually room-cooled, 

but may also be forced-air cooled. Cooling may 

be delayed if fruit undergo curing treatment (see 

Special Considerations).

Optimum Storage Conditions

Depending on variety, ripeness stage, and harvest 

season, fruit can be kept for 2 to 5 weeks at 5 to 

8 °C (41 to 46 °F) with 90 to 95% RH. Factors 

limiting storage life are decay, dehydration, and 

chilling injury.

Controlled Atmosphere (CA) 

Considerations

Limited research indicates that holding cactus pear 

at 5 °C (41 °F) in 2% O2

 and 2 to 5% CO2 delays 

ripening and extends storage life (Kader 2000). 

Retail Outlet Display Considerations

Fruit should be kept cold to reduce dehydration. 

At retail, the surface of cactus fruit may appear 

dull due to water loss. 
512

Chilling Sensitivity

Cactus pear fruit are especially chilling sensitive 

when stored at <5 °C (41 °F), but chilling injury 

may occur in some varieties at <10 °C (50 °F). 

Symptoms include pitting, surface bronzing and 

dark spots on the peel, and increased susceptibility 

to decay. Chilling occurred in a red-fruit variety 

after only 2 weeks at 6 °C (43 °F), but fruit 

from other varieties were held for several weeks 

without signs of chilling. Summer-harvested fruit 

are more chilling sensitive than autumn-harvested 

fruit (Schirra et al. 1999). Application of calcium 

chloride, conditioning, and intermittent warming 

have had variable success in reducing chilling 

injury.

Ethylene Production and Sensitivity

Prickly pear fruit produce very low amounts of 

ethylene, about 0.2 μL kg-1 h-1 at 20 °C (68 °F). 

They are not sensitive to ethylene exposure.

Respiration Rates

Fruit are nonclimacteric and respiration rates are 

low during storage. The respiration rate at 20 oC 

(68 oF) is 27 to 36 mg (15 to 20 μl) CO2

 kg-1 h-1. 

Heat production is about 7,000 BTU ton-1 day-1 or 

1,900 kcal tonne-1 day-1.

Physiological Disorders

See section above on Chilling Sensitivity.

Postharvest Pathology

Harvest damage to the peel and stem-end of cactus 

fruit will lead to attack by numerous pathogens 

and result in fruit decay. Common postharvest 

pathogens on cactus fruit are mostly fungi and 

include Fusarium spp., Alternaria spp., and 

Penicillium spp., but yeasts and bacteria also 

cause decay. Hot water dips at 53 to 55 °C (127 

to 131 °F) for 5 min and fungicide-containing 

waxes may reduce surface decay, but are not 

effective when there is damage to the stem-ends. 

For control of decay on stem-ends, see Special 

Considerations. Preharvest calcium sprays result 

in less postharvest decay (Schirra et al. 1999). 

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Even after brushing and washing, the peel of intact 

cactus fruit may have irritating small spines, and 

a peeled packaged fruit product could be a useful 

option. A mixture of cactus fruit of different colors 

and types could be a potentially attractive product. 

Special Considerations

Fruit can be bruised easily by finger compression 

during harvest, but damage at the stem-end is by 

far the most serious mechanical injury. Damage 

at the stem-end can be eliminated by careful 

harvesting (twisting fruit from the stem or cutting 

fruit with a small piece of stem attached). Fruit 

harvested with a bit of stem may be packed that 

way or cured under moderate temperature of 15 

to 20 °C (59 to 68 °F) with airflow so that the bit 

of stem dries and falls off before fruit are packed. 

This prevents damage to the stem end and greatly 

reduces decay incidence. High-gloss fruit waxes 

are often used to improve appearance and reduce 

dehydration. This is especially important if fruit 

are dry-brushed to remove small tufts of spines or 

glochids.

References

Kader, A. 2000. Cactus (prickly) pear. 

Recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.
513

Schirra, M., P. Inglese, and T. La Mantia. 1999. 

Quality of cactus pear [Opuntia ficus-indica (L.) 

Mill.] fruit in relation to ripening time, CaCl2 

preharvest sprays and storage conditions. Sci. 

Hort. 81:425-436.

Further Reading

Cantwell, M. 1995. Postharvest management 

of fruits and vegetable stems. In G. Barbera, 

P. Inglese, and E. Pimienta-Barrios, eds., 

Agroecology, Cultivation and Uses of Cactus 

Pear, pp. 120-136. Plant Production and Protection 

Paper 132, Food and Agriculture Organization of 

the United Nations, Rome, Italy.

Lakshminarayana, S., L. Alvarado y Sosa, and 

F. Barrientos-Pérez. 1979. The development and 

postharvest physiology of the fruit of prickly pear 

(Opuntia amyclaea Tenore). In G.E. Inglett and 

G. Charalambous, eds., Tropical Foods, vol. 1, 

Chemistry and Nutrition, pp. 69-93. Academic 

Press, New York, NY.

Piga, A., S. D’Aquino, M. Agabbio, and M. 

Schirra. 1996. Storage-life and quality attributes of 

cactus pears cv. “Gialla” as affected by packaging. 

Agr. Med. 126:423-427.

Schirra, M., M. Agabbio, S. D’Aquino, and T.G. 

McCollum. 1997. Postharvest heat conditioning 

effects on early ripening ‘Gialla’ cactus pear fruit. 

HortScience 32:702-704.
514

Pumpkin and Winter Squash

Jeffrey K. Brecht

Brecht is with the Horticultural Sciences 

Department, University of Florida, Gainesville, 

FL.

Scientific Name and Introduction

Three species of the Cucurbitaceae family 

produce edible fruit that are harvested when 

physiologically mature. These are pumpkin or 

acorn squash (Cucurbita pepo L.); winter squash 

or giant pumpkin (Cucurbita maxima Duchesne 

ex Lam.); and crookneck squash, tropical pumpkin 

(calabaza), or butternut squash (Cucurbita 

moschata [Duchesne ex Lam.] Duchesne ex 

Poir.). Mature fruit are harvested in fall, and some 

can be stored for many months. The distinction 

between pumpkins and winter squash is culinary 

rather than taxonomical. Pumpkins have coarser, 

stronger-flavored flesh and are used for pies. In 

the United States they are also used for decoration 

as Halloween jack-o’-lanterns or for their edible 

seeds. Winter squash have finer-textured and 

milder-flavored flesh. They are cooked and served 

as vegetables, but they are also commonly used 

for “pumpkin” pies. The C. moschata tropical 

pumpkin, or calabaza, is a staple food in the 

American tropics and is prepared in many ways 

that overlap the above definitions of pumpkin and 

squash (Daniel 1995).

Quality Characteristics and Criteria

Pumpkins and winter squash should be fully 

mature, with hard rinds and, except for some 

striped varieties, solid external color. Good-quality 

pumpkins and winter squash have bright-yellow 

or orange flesh with fine, moist texture and high 

solids, sugars, and starch (Cantwell and Suslow 

1998). Overmature flesh can become dry and 

stringy.

Horticultural Maturity Indices

Horticultural maturity coincides with 

physiological maturity and is recognized 

externally by corking of the stem (initiation of 

abscission), loss of rind surface sheen or gloss, 

groundspot yellowing, and die-back of the tendril 

nearest the fruit. The rind should resist thumbnail 

pressure. Development of intense yellow or orange 

flesh color (due to synthesis of carotenoids) and 

accumulation of sugars and solids are indicators 

of maturity that are highly correlated with sensory 

quality (Daniel et al. 1995, Harvey et al. 1997). 

Delaying harvest is not recommended: It increases 

occurrence of storage rot (Hawthorne 1990), and 

sensory quality improves more in storage than 

on the plant (Edelstein et al. 1989, Harvey et al. 

1997).

Grades, Sizes, and Packaging

Grades are U.S. No. 1 and U.S. No. 2 and are 

based on similar varietal characteristics (shape, 

texture, and color), maturity, and freedom from 

damage and decay. There are no standard sizes for 

pumpkins and winter squashes, though minimum 

and maximum weights of individual fruit 

within packages may be specified. Packages are 

commonly mesh or burlap bags and one- or twopiece fiberboard cartons containing 23 kg (50 lb). 

Pumpkins and winter squash are also shipped in 

19-kg (42-lb, 1 1/9 bushel) crates and 360- to 410-

kg (800- to 900-lb) bulk bin cartons.

Precooling Conditions

Pumpkins and winter squash should be roomcooled or loaded directly into refrigerated trucks 

and containers.

Optimum Storage Conditions

All pumpkins and winter squashes should be 

well matured, carefully handled, and free from 

injury or decay. Pumpkins and winter squashes 

are placed on racks, in bulk bins, or in baskets and 
515

are often held in ventilated or common storage in 

production areas. Recommended conditions for 

storage of pumpkins and winter squashes are 10 to 

13 °C (50 to 55 °F). At higher temperatures of 15 

to 20 °C (59 to 68 °F), green varieties will become 

undesirably yellow and acquire a stringiness of 

the flesh. Fruit are chilling sensitive (see Chilling 

Sensitivity). The RH should be 50 to 70%. Higher 

RH promotes decay while lower RH causes excess 

weight loss and texture deterioration (Ryall and 

Lipton 1979). The fruit surface should be kept 

dry, and storage rooms should have good air 

circulation (Holmes 1951).

Pumpkins generally do not keep as well as hardshelled winter squashes. Most cultivars of winter 

squash and pumpkins, as well as the tropical 

pumpkins, cannot be stored for more than 2 

to 3 mo. Acorn-type squashes, such as ‘Table 

Queen,’ can be kept 5 to 8 weeks at 10 °C (50 

°F). The popular butternut squash can be kept 2 

to 3 mo at 10 °C (50 °F). It is often stored longer, 

but spoilage and shrinkage increase. Weight 

loss should be kept below 15% to minimize 

development of hollow neck (Francis and 

Thomson 1965). Turban and buttercup squashes 

can be kept 3 mo. Good quality Hubbard squash 

can be stored 6 mo at 10 to 13 °C (50 to 55 °F) 

and 70% RH. A 15% loss in weight after 6 mo is 

about average (Guba 1950).

Controlled Atmosphere (CA) 

Considerations

CA of 1% O2

 and 7% CO2 was recommended for 

buttercup squash (Prange and Harrison 1993). 

Reduced O2 and elevated CO2 maintained green 

color, while elevated CO2

 reduced “white mealy 

breakdown”; decay was lower in 7% CO2

 than 

in other CA treatments. There were no beneficial 

effects of 5% O2 or either 5% or 10% CO2 on 

decay of spaghetti squash (Lin and Saltveit 1997). 

Decay was actually greater in CA than air in both 

cases because RH was higher; decay was reduced 

when CaCl2

 was used to absorb moisture. Control 

of RH is critical in CA storage.

Retail Outlet Display Considerations

Pumpkins and winter squash can be displayed in 

ambient conditions.

Chilling Sensitivity

Both pumpkins and winter squashes develop 

chilling injury at <10 °C (50 °F). Storage at 

0 to 4 °C (32 to 39 °F) inhibits yellowing but 

causes sunken pits on the fruit surface and loss 

of flavor. Alternaria rot develops on chilled 

squashes after removal from storage (McColloch 

1962). Depending on the cultivar, chilling injury 

symptoms develop after 1 mo at 5 °C (41 °F) or 

several months at 10 °C (50 °F) (Cantwell and 

Suslow 1998). 

Ethylene Production and Sensitivity

Pumpkins and winter squash produce only trace 

amounts of ethylene, but wounding greatly 

increases ethylene production (Hyodo et al. 1993). 

Hubbard squash and other dark-green-skinned 

squashes should not be stored near apples, as the 

ethylene from apples may cause the skin to turn 

orange-yellow (Yeager et al. 1945). Ethylene 

may also cause stem abscission, especially in less 

mature fruit (Cantwell and Suslow 1998).

Respiration Rates

Temperature mg CO2 kg-1 h-1

12 °C 88 to 110 (buttercup)

25 °C 61 to 121 (butternut)

Data for buttercup from Irving et al. (1997); data 

for butternut from L.L. Morris (unpublished).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 
516

Physiological Disorders

Damaged areas on fruit turn brown, detracting 

from their appearance. Pumpkins and winter 

squash are susceptible to water loss at the 

recommended 50 to 70% RH, but low RH is 

necessary to minimize decay. Yellowing can be 

a problem for green winter squash varieties and 

is exacerbated by overmaturity, high storage 

temperatures, and ethylene exposure.

Postharvest Pathology

Decay is the primary cause of storage losses 

of pumpkins and winter squash. Numerous 

fungi cause storage rots, including species of 

Aspergillus, Colletotrichum (anthracnose), 

Didymella, Fusarium, Mycosphaerella (black 

rot), Rhizopus, and Sclerotinia (Guba 1950, 

Abdel-Rahim 1988, Hawthorne 1988, Rath 

et al. 1990, Vigliola 1993, Arvayo-Ortiz et al. 

1994). Alternaria rot develops on chill-damaged 

fruit (McColloch 1962). Delaying harvest of 

buttercup squash 2 weeks increased fungal 

storage rots (Hawthorne 1990). Infection starts 

through wounds and natural openings in the 

surface. Therefore, careful handling to minimize 

mechanical damage is recommended to minimize 

storage rots (Guba 1950). Less rot will develop in 

Hubbard squash if stems are completely removed 

before storage (Yeager et al. 1945). Hot water 

at 60 °C (140 °F) for 2 min reduces storage rots 

(Francis and Thomson 1965); lower temperatures 

were not effective (Hawthorne 1989, Arvayo-Ortiz 

et al. 1994).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Some large winter squash are cut into sections and 

seeds removed for retail sale.

Special Considerations

A 10- to 20-day curing period at 24 to 27 °C (75 

to 81 °F) before storage can harden the rind of 

pumpkins and winter squashes (Gorini and Testoni 

1978). However, in New York, curing for 3 weeks 

at 27 °C (81 °F) to heal mechanical injuries and 

to ripen immature specimens proved unnecessary 

(Platenius et al. 1934, Schales and Isenberg 1963). 

Curing butternut, Hubbard, and quality squashes 

was of no value but not harmful, whereas curing 

‘Table Queen’ was detrimental to skin color, 

texture, and taste (Schales and Isenberg 1963). 

Cured ‘Table Queen’ also decayed more rapidly 

than noncured fruit.

References

Abdel-Rahim, A.M. 1988. Postharvest fungal 

diseases of some vegetables in Kuwait. Arab J. 

Plant Protect. 6:83-87.

Arvayo-Ortiz, R.M., S. Garza-Ortega, and E.M. 

Yahia. 1994. Postharvest response of winter 

squash to hot-water treatment, temperature and 

length of storage. HortTechnology 4:253-255.

Cantwell, M., and T.V. Suslow. 1998. Pumpkins 

and winter squashes. Recommendations for 

maintaining postharvest quality. Perishables 

Handling Quarterly 94:15-16.

Daniel, A.L. 1995. Tropical Pumpkin Cultigen 

Postharvest Quality Evaluation and Maturity 

Studies. M.Sc. thesis, University of Florida, 

Gainesville, FL.

Daniel, A.L., J.K. Brecht, C.A. Sims, and D.N. 

Maynard. 1995. Sensory analysis of bush and 

vining types of tropical pumpkin. Proc. Fla. State 

Hort. Soc. 108:312-316.

Edelstein, M., H. Nerson, and H.S. Paris. 1989. 

Quality of spaghetti squash as affected by fruit 

maturity, storage period, and cooking duration. 

Acta Hort. 258:543-545.
517

Francis, F.J., and C.L. Thomson. 1965. Optimum 

storage conditions for butternut squash. Proc. 

Amer. Soc. Hort. Sci. 86:451-456.

Gorini, F.L., and A. Testoni. 1978. Long-term 

storage of pumpkins. Ann. Ist. Sper. Valoriz. 

Technol. Prod. Agr. 9:131-135. 

Guba, E.F. 1950. Spoilage of squash in storage. 

Massachusetts Agricultural Experiment Station 

Bull. no. 457, University of Massachusetts, 

Amherst, MA.

Harvey, W.J., D.G. Grant, and J.P. Lammerink. 

1997. Physical and sensory changes during 

development and storage of buttercup squash. 

N.Z. J. Crop Hort. Sci. 25:341-351.

Hawthorne, B.T. 1988. Fungi causing storage 

rots on fruit of Cucurbita spp. N.Z. J. Exp. Agr. 

16:151-157.

Hawthorne, B.T. 1989. Effects of cultural 

practices on the incidence of storage rots in 

Cucurbita spp. N.Z. J. Crop Hort. Sci. 17:49-54.

Hawthorne, B.T. 1990. Age of fruit at harvest 

influences incidence of fungal storage rots on fruit 

of Cucurbita maxima D. hybrid ‘Delica.’ N.Z. J. 

Crop Hort. Sci. 18:141-145.

Holmes, A.D. 1951. Factors that affect the storage 

life of butternut squashes. Food Technol. 5(9):372-

373.

Hyodo, H., C. Hashimoto, S. Morozumi, et al. 

1993. Induction of wound ethylene production and 

lignin formation in wounded mesocarp tissue of 

Cucurbita maxima. Acta Hort. 343:264-269.

Irving, D.E., P.L. Hurst, and J.S. Ragg. 1997. 

Changes in carbohydrates and carbohydrate 

metabolizing enzymes during development, 

maturation, and ripening of buttercup squash 

(Cucurbita maxima D. ‘Delica’). J. Amer. Soc. 

Hort. Sci. 122:310-314.

Lin, W.C., and M.E. Saltveit. 1997. Quality of 

winter squash affected by storage air composition 

and temperature. In M.E. Saltveit, ed., 7th 

International Controlled Atmosphere Research 

Conference, July 13-18, 1997, University of 

California, Davis, vol. 4, pp. 78-83. University of 

California, Davis, CA.

McColloch, L.P. 1962. Alternaria rot following 

chilling of acorn squashes. Marketing Research 

Report 518, U.S. Department of Agriculture, 

Washington, DC.

Platenius, H., F.S. Jamison, and H.C. Thompson. 

1934. Studies on cold storage of vegetables. New 

York (Cornell) Agricultural Experiment Station, 

Bull. no. 602, Cornell University, Ithaca, NY.

Prange, R.K., and P.A. Harrison. 1993. Effect 

of controlled atmosphere and humidity on 

postharvest physiology of buttercup winter squash, 

Cucurbita maxima Duch. hybrid ‘Sweet Mama.’ 

In 6th International Controlled Atmosphere 

Research Conference, June 1993, vol. 2, pp. 759-

766. Ithaca, NY.

Rath, G.C., D. Mishra, and N.C. Nayak. 1990. 

A note on fungi causing rotting of cucurbits in 

Orissa markets. Orissa J. Agr. Res. 3:161-162.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1. AVI, Westport, CT.

Schales, F.D., and F.M. Isenberg. 1963. The effect 

of curing and storage on chemical composition 

and taste acceptability of winter squash. Proc. 

Amer. Soc. Hort. Sci. 83:667-674.

Vigliola, I. 1993. Postharvest diseases and 

storage conditions in butternut squash (Cucurbita 

moschata Duch.) in Argentina. Acta Hort. 368:33-

36.

Yeager, A.F. 1945. The Storage of Hubbard 

Squash. New Hampshire Agricultural Experiment 

Station Bulletin, The University of New 

Hampshire Bull. no. 356, Durham, NH.
518

Quince

Paul M. Chen

Chen is with the Mid-Columbia Agricultural 

Research and Extension Center, Oregon State 

University, Hood River, OR.

Scientific Name and Introduction

Quince (Cydonia oblonga Mill.) is a manyseeded pome, pyriform type of fruit. Its genus 

consists of a single species, native to the warmer 

regions of southeastern Europe and Asia Minor 

(Childers 1949, Westwood 1978). Few studies 

have been made of this minor crop (Michelesi et 

al. 1973, Jankowiak 1976, Muller and Husistein 

1979). It is used mostly as a dwarfing rootstock 

for pear, but is also used for preserves, jams, and 

jellies. The main cultivars of quince are ‘Orange,’ 

‘Champion,’ ‘Pineapple,’ ‘Angers,’ ‘Smyrna,’ 

‘Van Deman,’ ‘Rea,’ and ‘Meech’ (Childers 1949, 

Westwood 1978). About 200 acres is grown in the 

United States, but it is an important crop of 20,000 

tons annual production in Argentina (Westwood 

1978).

Quality Characteristics and Criteria

Quince are climacteric fruit (Kader 1992) and 

require a proper ripening process at 20 °C (68 

oF) for high quality fruit for processing. Properly 

ripened quince of high quality are used chiefly 

for jellies, marmalades, and preserves and to 

some extent for baking, canning, and adding 

flavor to other processed fruit products. Much 

scientific research has centered on the chemical 

nature of texture and flavor quality of quince fruit. 

Literature regarding quality includes Andrade et 

al. (1972), Gumbaridze (1972a,b), Kozenko et 

al. (1976) , Rozmyslova and Papunov (1977) , 

Shimizu and Yoshihara (1977), Strandzhev et al. 

(1978), Iocheva (1979), Sharova and Illarionova 

(1980), Tsuneya et al. (1980, 1983), Kornatskaia 

(1981), Lobachev and Gavrishova (1982), Umano 

et al. (1986), Guldner and Winterhalter (1991), 

Lutz and Winterhalter (1992a,b, 1993).

Horticultural Maturity Indices

Quince fruit harvesting criteria and methods are 

similar to most winter pear cultivars. There is no 

specific maturity index for quince fruit. Harvest 

begins when fruit change ground color from deep 

green to a lighter green (Auchter and Knapp 

1929). Green, immature fruit scald readily in 

storage, and fruit affected with scab do not store 

well.

Grades, Sizes, and Packaging

There are no official standard grades, sizes, or 

packaging for quince. According to the California 

Food and Agricultural Code for quality standards, 

quince fruit should be marketed at optimum 

maturity and free from insect damage, mechanical 

damage, and decay (Kader 1992). Since fruit 

are rather tender and bruise easily, the shipping 

container should be lined with soft pads on both 

ends. The blossom end is turned upwards (Auchter 

and Knapp 1929). Fruit should be handled 

carefully to avoid mechanical injury.

Precooling Conditions

No precooling of quince fruit is done 

commercially.

Optimum Storage Conditions

Optimum storage temperature is -0.5 °C to 0 °C 

(31 to 32 °F) with about 90% RH. Storage life in 

air at -0.5 °C (31 °F) is 2 to 3 mo, similar to early 

apple cultivars, such as ‘Jonathan’ and ‘Grimes 

Golden’ (Williams 1935).

Controlled Atmosphere (CA) 

Considerations

There is no recommendation for CA storage.
519

Ethylene Production and Sensitivity

The best ripening temperature for quince fruit 

after storage is 20 °C (68 oF). Since quince is a 

climacteric fruit (Kader 1992), the acceleration 

of ethylene production during ripening may be 

expected. However, literature regarding ethylene 

biosynthesis in quince fruit is lacking.

Postharvest Pathology

Though the skin of quince has a thick coat of fuzz, 

the fruit is tender and bruises easily (Auchter and 

Knapp 1929). Quince is subject to decays similar 

to those found on apples and pears (Halsted, 1892, 

Tafradzhiiski and Angelov 1977). Treatment with 

fungicides is necessary to prevent decay during 

storage and marketing (Pierson et at. 1971).

References

Andrade, P.B., A.R.F. Carvalho, R.M. Seabra, and 

M.A. Ferreira. 1998. A previous study of phenolic 

profiles of quince, pear, and apple purees by 

HPLC diode array detection for the evaluation of 

quince puree genuineness. J. Agric. Food Chem. 

46:968-972.

Auchter, E.C., and H.B. Knapp. 1929. Harvesting, 

storing and marketing, pp. 1-132, and Establishing 

the orchard, pp. 138-176. In A.K. Getman and 

C.E. Ladd, eds., Orchard and Small Fruit Culture. 

John Wiley & Sons, New York, NY.

Childers, N.F. 1949. Pear and quince culture. 

In R.W. Gregory, ed., Fruit Science, Orchard 

and Small Fruit Management, pp. 248-273. J.B. 

Lippincott, New York, NY.

Durmishidze, S.V., and N.P. Gumbaridze. 1972. 

Catechins and leucoanthocyanidins of quince fruit. 

Soobshch. Akad. Nauk. Gruz. Ssr. 67:449-451.

Guldner, A., and P. Winterhalter. 1991. Structures 

of two new ionone glycosides from quince fruit 

(Cydonia oblonga Mill.). J. Agric. Food Chem. 

39:2142-2146.

Gumbaridze, N.P. 1972a. Chlorogenic acid from 

quince fruit. Soobshch. Akad. Nauk. Gruz. Ssr. 

68:729-731.

Gumbaridze, N.P. 1972b. Flavonols of quince 

fruit. Soobshch. Akad. Nauk. Gruz. Ssr. 65:701-

704.

Halsted, B.D. 1892. Some fungous diseases of the 

quince fruit. Bull. no. 91, New Jersey Agricultural 

College Experiment Station, New Brunswick, NJ.

Iocheva, E. 1979. Change of catechins in pome 

fruit during technological processing [quince]. 

Khranitelna promishlenost 28:33-35.

Jankowiak, J. 1976. Quince is a “new” oldfashioned fruit. Org. Gard. Farming 23(8):114-

115.

Kader, A.A., ed. 1992. Postharvest Technology of 

Horticultural Crops, 2nd ed. DANR Pub. no. 3311, 

University of California, Oakland, CA.

Kornatskaia, N.M. 1981. Chemical-technological 

evaluation of some common quince varieties 

and hybrids fruit processing. Konservnaia I 

ovoshchesushil’naia promyshlennost’ 2:28-29.

Kozenko, S.I., G.A. Kleshchunova, and A.N. 

Goren’kova. 1976. Amino acid composition of 

quince fruit and its change caused by canning. 

Konservn Ovoshchesushil Prom-St’ 2:32-34.

Lobachev, A.I.A., and I.F. Gavrishova. 1982. 

Chemical composition and technological qualities 

of quince fruit under conditions of the lower Volga 

River area (varieties and hybrids, RSFSR-inEurope). Trudy Po Prikladnoi Botanike, Genetike i 

Selektsii. 74:98-104.

Lutz, A., and P. Winterhalter. 1992a. Bio-oxidative 

cleavage of carotenoids: important route to 

physiological active plant constituents. Tetra. Lett. 

33:5169-5172.

Lutz, A., and P. Winterhalter. 1992b. Isolation of 

additional carotenoid metabolites from quince 

fruit (Cydonia oblonga Mill.). J. Agric. Food 

Chem. 40:1116-1120.
520

Lutz, A., and P. Winterhalter. 1993. Abscisic 

alcohol glucoside in quince. Phytochem. 32:57-60.

Michelesi, J.C., J. Brossier, and J.D. Flick. 1973. 

Premieres observations sur plusieurs varietes de 

cognassiers a fruits [First observations on several 

quince fruit varieties]. Arboric. Fruit 233/234:36-

38.

Muller, W., and A. Husistein. 1979. Quitte—eine 

zu beachtende obstart [Quince—a fruit species of 

interest]. Schweizerische Zeitschrift for Obst- und 

Weinbau 115(1):4-8.

Pierson, C.F., M.J. Ceponis, and L.P. McColloch. 

1971. Market Diseases of Apples, Pears and 

Quinces. Agriculture Handbook 376, U.S. 

Department of Agriculture, Washington, DC.

Rozmyslova, A.G., and N.N. Papunov. 1977. 

Chemical characteristics of quince fruit. Sadovod 

Vinograd Vinodel Mold 4:55-56.

Sharova, N.I., and Illarionova, N.P. 1980. Value 

of quince fruit chemical composition, varieties. 

Sadocodstvo 12:39.

Shimizu, S., and S. Yoshihara. 1977. The 

constituents of the essential oil from Japanese 

quince fruit, Cydonia oblonga Miller. Agric. Biol. 

Chem. 41:1525-1527.

Strandzhev, A., M. Krusteva, and D. Kosturkova. 

1978. Determination of pectin substances in 

quince and their transformations during cold 

storage. Khranitelna Promishlenost 27:26-27.

Tafradzhiiski, I., and T. Angelov. 1977. Study 

on the control of fruit rot of quince (caused by 

Sclerotinia cydoniae). Gradinar Lozar Nauka 

14(6):16-21.

Tsuneya, T., M. Ishihara, H. Shiota, and M. Shiga. 

1980. Isolation and identification of novel terpene 

lactones from quince fruit (Cydonia oblonga Mill., 

Marmelo). Agric. Biol. Chem. 44:957-958.

Tsuneya, T., M. Ishihara, H. Shiota, and M. 

Shiga. 1983. Volatile components of quince fruit 

(Cydonia oblonga Mill.). Agric. Biol. Chem. 

47:2495-2502.

Umano, K., A. Shoji, Y. Hagi, and T. Shibamoto. 

1986. Volatile constituents of peel of quince fruit, 

Cydonia oblonga Miller. J. Agric. Food Chem. 

34:593-596.

Westwood, M.N. 1978. Fruit and nut species. In

M.N. Westwood, ed., Temperate-Zone Pomology, 

pp. 41-76. W.H. Freeman, San Francisco, CA.

Williams, W.J. 1935. Cold storage of figs, raisins, 

persimmons, quinces, and tobacco. Ice Refrig. 

89:367-368. 
521

Radicchio

Fabio Mencarelli

Mencarelli is formerly with the Istituto Tecnologie 

Agroalimentari, University of Tuscia, Viterbo, 

Italy. He is now with the Department of Food 

Science and Technology, University of Viterbo, 

Italy.

Scientific Name and Introduction

Radicchio (Cichorium intybus L.) is a member 

of the Asteraceae (Compositae) family. Plants 

are characterized by variegate leaves (var. 

silvestre Bishoff) or red leaves (consequence of 

spontaneous crossings). Plant shape also differs 

among varieties, including long conical shape 

with tight red leaves, completely open with red or 

green-red leaves, or ball-shaped with red leaves. 

Head and leaves are crisp with a bittersweet 

flavor similar to Belgian endive and escarole. 

Some varieties—for example ‘di Treviso’ and 

‘Verona’—are held in the dark for 7 to 15 days at 

10 to 15 °C (50 to 68 °F) after harvest to promote 

production of new, very tender leaves; this is 

called “whitening” (Pimpini 1990). Radicchio is 

available year-round from California, New Jersey, 

Mexico, and Italy. 

Quality Characteristics and Criteria

Plants and leaves should be very turgid and crisp 

with bright white midribs. There should be no 

cracking, splitting, dark spots from mechanical 

damage, or necrosis on the leaf margins. 

Compactness is important but depends on the 

variety; for example, ‘Treviso’ and ‘Chioggia’ 

should have a compact head and very tight leaves, 

whereas ‘Verona’ and ‘Castelfranco’ should have 

an open, regularly shaped head. The root must be 

cleanly cut with no secondary roots or evidence of 

decay and cannot exceed 4 cm (1.5 in). 

Horticultural Maturity Indices

Plants are hand-harvested when they reach 

appropriate size or when the center of the plant 

has formed a compact “grumolo” (Pimpini 1990). 

The same variety can be harvested very early (45 

days), early (75 to 90 days), or late (120 to 150 

days). Varieties that need whitening are harvested 

with their roots. 

Grades, Sizes, and Packaging

There are no USDA grades. Head size is based 

on weight: 30 g (1 oz) for forced radicchio and 

60 g (2 oz) for normal production. Extra fancy 

radicchio has the quality criteria given above. 

Fancy radicchio can have some light browning 

on leaves due to freezing or forcing treatment. 

Radicchio can be packed in trays with shrinkable 

plastic film or in corrugated containers with plastic 

liners to avoid water loss (Suslow and Cantwell 

1999).

Precooling Conditions

Radicchio is usually placed directly in a cold room 

before shipping.

Optimum Storage Conditions

Radicchio can be stored for 20 to 30 days at 3 to 5 

°C (37 to 41 °F) with 90% RH. Varieties that are 

whitened can only be stored 1 to 2 weeks under 

these conditions. Storage life is reduced to 11 days 

at 6 °C (43 °F) (Botondi et al. 1996), while storage 

at -2 to -3 °C (27 to 28 °F) can prolong storage to 

3 mo by controlling decay (Bertolini and Pratella 

1993).

Controlled Atmosphere (CA) 

Considerations

Good results were obtained with 3% O2

 and 5% 

CO2

. Low O2 promotes internal browning (Suslow 

and Cantwell 1999), and high CO2

 controls decay 

(Foschi and Mari 1987).
522

Retail Outlet Display Considerations

Radicchio can be displayed in the same manner 

as lettuce. Water sprays are acceptable, but water 

remaining on the leaves at elevated temperatures 

promotes bacterial growth. 

Chilling Sensitivity

Radicchio is not chilling sensitive. However, there 

have been reports of metabolic disorders after 

storage at 0 °C (32 °F) (Botondi et al. 1996).

Ethylene Production and Sensitivity

Radicchio produces very low amounts of ethylene: 

0.1 to 0.3 μL kg-1 h-1 at 0 to 6 °C (32 to 43 °F) and 

0.6 to 1.0 μL kg-1 h-1 at 20 °C (68 °F). Exposure 

to 10 μL L-1 ethylene for 6 days at 7.5 °C (46 °F) 

with 95% RH increased leaf browning, decay, 

and pigmentation of midribs (Botondi et al. 1996, 

Suslow and Cantwell 1999).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 6 to 10

6 °C 10 to 16

7.5 °C 23

25 °C 45

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Desiccation can lead to necrosis of the leaf 

margins. Wilting can occur after a few days of 

display if plants are not misted. Leaf abscission is 

common for some varieties, and reconditioning is 

often required. Rough handling during harvest or 

packing causes cracking of leaves or, in the case 

of abrasion, appearance of browning stains on the 

white midribs. 

Postharvest Pathology

Radicchio is susceptible to bacterial soft rot 

caused by Erwinia carotovora at warmer 

temperatures and pectolytic Pseudomonas at lower 

temperatures. Botrytis cinerea can be frequent, 

even with good temperature control (Suslow and 

Cantwell 1999)

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

There is growing interest in fresh-cut lettuceradicchio mixes.

References

Bertolini, P., and G. Pratella. 1993. Protezione 

postraccolta del radicchio. I Radicchi Veneti: 20 

Anni di Esperienze Produttive e Commerciali, p. 

39. ICE, Verona, Italy.

Botondi, R., R. Massantini, G. Anelli, and F. 

Mencarelli. 1996. Postharvest physiology of red 

cicory stored at 0° and 6°C. Ital. J. Food Sci. 

4:273-282.

Foschi F., and M. Mari. 1987. Controlled 

atmosphere storage techniques of red chicory. In

Proc. 17th International Congress on Refrigeration, 

vol. C, pp. 290-295. Vienna, Austria. International 

Institute of Refrigeration, Paris, France.

Pimpini, N. 1990. Il radicchio. In V.V. Bianco and 

F. Pimpini, eds., Orticoltura, pp. 320-338. Patron 

Press, Bologna, Italy. 
523

Suslow, T., and M. Cantwell. 1999. Radicchio. 

Recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.
524

Radish

Richard LaMar Hassell

Hassell is with the Coastal Research and 

Education Center, Clemson University, 

Charleston, SC.

Scientific Name and Introduction

The radish, Raphanus sativus, is a member of 

the Cruciferae family, native to Europe or Asia. 

It was once grown on a small scale in all areas 

of the United States and also as a greenhouse 

vegetable. However, mechanization of harvesting 

and handling has resulted in more centralized 

production. The word “raphanus” comes from a 

Greek word meaning “quick-appearing” or “easily 

grown.” 

The roots are of many shapes, sizes and colors—

round, turnip-shaped, oval, olive-shaped, halflong, long. Colors include white, pink-red, purple, 

yellow, or even black. However, the most common 

radish is oval with a dark red skin and white 

flesh (Thompson and Kelly 1957, Maynard and 

Hochmuth 1997).

Quality Characteristics and Criteria

Radishes should be fresh, well-colored, tender, 

firm, crisp, smooth with no ridges, free from soil 

or other foreign material, and free from harvest 

cuts, abrasions, and insect damage. They should 

not be stringy or woody, soft, flabby, or wilted. 

Bunched radishes should have fully intact tops 

that are dark-green with no yellowing; they may 

be slightly wilted. Size varies depending on 

market demand, but larger roots are more likely to 

be pithy (Thompson and Kelly 1957, Carione and 

Lucas 1972, USDA 1975).

Horticultural Maturity Indices

Harvest maturity is based on size and market 

demand. The diameter of oval types should be 

between 2 and 3 cm (0.75 to 1.25 in). Bunched 

radishes are harvested in either regular or big 

bunch size, and roots for cello packages are pulled 

at regular or jumbo size (Nonnecke 1989). 

Grades, Sizes, and Packaging

There are two USDA grades for topped 

and bunched radishes: U.S. No. 1 and U.S. 

Commercial. Bunched radishes have full-length 

tops tied in bunches, while topped radishes have 

clipped tops no more than 1 cm (0.38 in) long. 

Root diameter is termed Small, 1.9 cm (0.75 in); 

Medium, 1.9 to 2.5 cm (0.75 to 1.0 in); Large, 2.5 

to 3.2 cm (1 to 1.25 in); and Very Large, 3.2 cm 

(>1.25 in). U.S. No.1 roots have similar varietal 

characteristics and are clean, well formed, smooth, 

firm, and tender. They are also free from decay, 

cuts, pithiness, disease, and damage caused by 

freezing, growth cracks, insects, or other means. 

Bunched radishes have tops that are fresh and free 

from decay and damage caused by freezing, seed 

stem, yellowing or other discoloration, diseases, 

insects, or other means. In order to allow for 

variation in grading and handling, a 5 to 10% 

variation by count is acceptable tolerance for a 

U.S. No. 1 grade product. If the variation is >10% 

but <20%, they are designated U.S. Commercial 

(AMS 1968, Maynard and Hochmuth 1997). 

Radishes are available in many sizes of container. 

Topped radishes are packed in perforated plastic 

bags holding 168 g (6 oz), 224 g (8 oz), 454 g (1 

lb), 2.3 kg (5 lb), 11 kg (25 lb), or 18 kg (40 lb). 

Commonly, 30 168-g (6-oz), 24 224-g (8-oz), 

or 14 454-g (1-lb) bags are boxed together for 

retail, while 11-kg (25-lb) bags are used for the 

foodservice industry (L. Buurma, 1999, personal 

communication).

Radishes are first graded according to diameter 

to eliminate spikes that are <1.9 cm (0.75 in) and 

to accumulate Jumbos that are >3.8 cm (1.25 

in). The radishes are then conveyed over grading 

tables to remove products below acceptable grade 

standards. After being graded, they are packaged 

in cellos using vertical form fill machines. These 

machines form the breathable poly bag, weigh 
525

the specific amount of desired radishes, and seal 

the bag or provide a zipper locking system. These 

bags are then hand-packed into wax cartons and 

temporarily stored at 2 °C (36 °F) until shipment.

Precooling Conditions

Hydrocooling at 0 to 4.5 °C (32 to 40 °F) is the 

preferred method. Cello packs are hydrocooled 

to restore crispness, bulk stored in bins, and then 

placed in refrigerated coolers before grading. 

Bunched radishes are dipped in chlorinated water 

at 2 °C (26 °F) to restore crispness and freshness 

to the tops and roots, as well as to remove field 

debris. They are then packed into cartons, usually 

24 bunches per carton, and hydrocooled; and the 

carton is topped with an ice slurry before shipping 

(Brooker and Pearson 1970, Ryall and Lipton 

1972a).

Optimum Storage Conditions

Topped radishes can be held 3 to 4 weeks at 0 °C 

(32 °F) with 90 to 95% RH and at least 7 days at 

7 °C (45 °F). Bunch radishes are harder to keep 

fresh due to the perishability of the tops. However, 

they can be held at 0 °C (32 °F) and 90 to 95% 

RH for 1 to 2 weeks. Winter or black radishes can 

be stored under the same conditions for 2 to 4 mo. 

Addition of top ice aids in keeping the tops fresh 

(Ryall and Lipton 1972b).

Controlled Atmosphere (CA) Conditions

An atmosphere of 1 to 2% O2

 and 2 to 3% CO2 at 

0 to 5 °C (32 to 41 °F) slightly extends storage life 

(Ryall and Lipton 1972a, Saltveit 1997).

Retail Outlet Display Considerations

Packaged radishes should be placed in a 

refrigerated rack. Bunch radishes should be 

refrigerated and can be iced or misted to help 

preserve quality.

Chilling Sensitivity

Radishes are not sensitive to chilling. Store them 

as cold as possible without freezing.

Ethylene Production and Sensitivity

Radishes produce small amounts of ethylene and 

are not particularly sensitive to ethylene exposure.

Respiration Rates

Temperature Topped Roots Bunched Roots 

with Tops

°C -----------mg CO2 kg-1 h-1-----------

0 14 to 17 3 to 9

4 to 5 19 to 21 6 to 13

10 31 to 36 15 to 16

15 to 16 70 to 78 22 to 42

20 to 21 124 to 136 44 to 58

25 to 27 158 to 193 60 to 89

Data from Hardenburg et al. (1986).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Freezing injury can cause softening and 

shriveling, as well as leakage of pigment for red 

radishes. Growth cracks or air cracks reduce 

quality when they are >6 mm (0.25 in) deep and 

associated with discolored tissue. Overmaturity 

or stress during growth can induce dry, cottony 

voids, called pithiness, in roots. Yellowing of 

tops can result from overmaturity, exposure to 

ethylene, or elevated storage temperature (Murry 

1977, Nonnecke 1989).
526

Postharvest Pathology

The initial lesions of bacterial black spot 

(Xanthomonas vesicatoria) are brown and have a 

diameter of 1.0 to 2.5 mm (0.04 to 0.1 in). They 

eventually turn black and coalesce. Protective 

measures include washing in water with 100 

to 200 μL L-1 of chlorine. Downy mildew 

(Peronospora parasitica) produces purplish-red 

to brown surface lesions that become rough and 

cracked in advanced cases, while the internal 

tissue can become grayish brown to black. 

Rhizoctonia root rot (Rhizoctonia solani) produces 

lesions that are initially round and light brown 

and can become slightly sunken. The tissue can 

become spongy. This disease favors high RH. 

Avoid bruising, hydrocool to 4 °C (40 °F), and 

store at 0 to 2 °C (32 to 35 °F) to control these 

diseases (Ryall and Lipton 1972a).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Currently radishes are cut or diced in packaged 

salad mixes and for food service, particularly for 

incorporation into salad bars. 

References

AMS [USDA Agricultural Marketing Service]. 

1968. United States standards for grades of 

radishes. At http://www.ams.usda.gov/AMSv1.0/

standards.

Brooker, J., and J. L. Pearson. 1970. Planning 

data for marketing selected fruits and vegetables 

in the south, part III, Fresh Vegetable Packing 

Handbook. Southern Cooperative Ser. Bull. 152, 

Southern Association of Agricultural Experiment 

Station Directors, Raleigh, NC.

Carcione, J., and B. Lucas. 1972. The Greengrocer: 

The Consumer’s Guide to Fruits and Vegetables.

Chronicle Books, San Francisco, CA.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agricultural Handbook 66, U.S. Department of 

Agriculture, Washington, DC.

Maynard, D.N., and G.J. Hochmuth 1997. Knott’s 

Handbook for Vegetable Growers, 4th ed. Wiley, 

New York, NY. 

Nonnecke, I.L. 1989. Vegetable Production/Radish, 

pp. 339-346. Van Nostrand Reinhold, New York, 

NY.

Murry J. 1977. Fruit and vegetable facts and 

pointers (radish). United Fresh Fruit and Vegetable 

Association, Washington, DC. 

Ryall, A.L., and W.J. Lipton. 1972a. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, vol. 1. AVI, Westport, CT.

Ryall, A.L., and W.J. Lipton. 1972b. Longer 

storage-life for radishes. Agric. Res., vol. 20, no. 7.

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

4, pp. 98-117. University of California, Davis, CA.

Thompson, H.C., and W.C. Kelly. 1957. Vegetable 

Crops. McGraw-Hill, New York, NY.

USDA [U.S. Department of Agriculture]. 1975. 

How To Buy Food for Economy and Quality: 

Recommendations of the United States Department 

of Agriculture. Dover, New York, NY.
527

Rambutan

Saichol Ketsa and Robert E. Paull

Ketsa is with the Department of Horticulture, 

Kasetsart University, Bangkok, Thailand; Paull 

is with the Department of Tropical Plant and 

Soil Sciences, University of Hawaii at Manoa, 

Honolulu, HI.

Scientific Name and Introduction

Rambutan fruit (Nephelium lappacium L.) are 

large ovoid or globose fruit about 4.5 cm (1.8 in) 

long and 2.5 to 3.7 cm (1 to 1.5 in) wide that grow 

on woody stalks in clusters of 10 to 18. The outer 

skin is 2 to 4 mm (0.1 to 0.2 in) thick and covered 

with soft, long spines (spinterns) that turn red or 

yellow when ripe. The edible aril flesh is attached 

to a single, large seed. The fruit is related to litchi 

and longan (Nakasone and Paull 1998).

Quality Characteristics and Criteria

Quality criteria include fruit size, shape, and 

weight; bright skin and spine color; uniformity; 

absence of defects; and freedom from disease and 

insects. High SSC and low TA are desirable (Ketsa 

and Klaewkasetkorn 1992). Mechanical injury and 

dehydration are major causes of appearance loss.

Horticultural Maturity Indices

Skin and spine coloration is the main horticultural 

maturity index. Fruit having green skin and 

greenish-red spines are sour. Ripe fruit have both 

skin and spines red or yellow, depending on the 

variety. Between these two stages, sugar content 

increases about 20% and acid level decreases by 

half (Mendoza et al. 1982). The acceptable stage is 

16 to 28 days after color break, at which time skin 

and spines are brightly colored (O’Hare 1992). 

Over-ripe fruit have a watery texture (Somboon 

1984) which may be a senescence-induced tissue 

breakdown.

Grades, Sizes, and Packaging

There are no U.S. or International grade standards. 

Fruit are sold in 2.25-kg (5-lb) and 4.5-kg (10-lb) 

one-piece fiberboard cartons. Sometimes fruit are 

prepacked in punnets. In Southeast Asia, clusters 

of fruit are sold in bunches still attached to the 

stem.

Precooling Conditions

Only room-cooling is recommended.

Optimum Storage Conditions

Store at 8 to 15 °C (46 to 59 °F) with 90 to 95% 

RH to achieve a storage life of 14 to 16 days. 

There may be changes in the skin and spine 

coloration after storage, but the flesh is unaffected. 

Temperature recommendations vary for different 

cultivars (O’Hare 1992). Fruit held at 20 °C (68 

°F) with 60% RH last about 3 to 5 days.

Controlled Atmosphere (CA) 

Considerations

CA of 7 to 12% CO2

 and 3 to 5% O2 at 10 °C (50 

°F) is recommended (Kader 1993). At 9 to 12% 

CO2

, color loss is reduced and shelf-life extended 

by 4 to 5 days, while low O2

 (3%) has little effect 

(O’Hare et al. 1994, O’Hare 1995). Raising 

CO2

 levels above 12% has no additional effect, 

and decay can begin after a few weeks’ storage. 

The MA/CA effect appears to derive more from 

CO2

 elevation and minimizing water loss than 

through any effect of low O2

. Storage in sealed 

polyethylene film bags or plastic containers is 

effective in reducing water loss (Mendoza et al. 

1972, Mohamed and Othman 1988, Ketsa and 

Klaewkasetkorn 1995), while wax coatings are 

less effective (Mendoza et al. 1972, Lam and Ng 

1982, Brown and Wilson 1988). A shelf-life of 14 

to 21 days can be expected.
528

Retail Outlet Display Considerations

Rambutan should be displayed in trays with a 

clear film overwrap or in clam shell containers 

with no perforations at 10 to 12 °C (50 to 55 °F). 

Fruit should not be misted or iced.

Chilling Sensitivity

If maintained at 5 °C (41 °F), fruit can be stored 

for up to 3 weeks, but the skin and spines change 

from red to brownish-red; the edible aril is white 

and remains in good condition (Lam and Ng 

1982). Somboon (1984) reported that after 3 

days at 5 °C (41 °F), the aril turned from white 

(translucent) to being more transparent and juicier.

Ethylene Production and Sensitivity

This nonclimacteric fruit has a very low rate of 

ethylene production: <0.04 μL kg-1 h-1 (O’Hare et 

al. 1994). Higher rates of up to 3 μL kg-1 h-1 can 

occur if there is a fungal infection. The presence 

of 5 μL L-1 ethylene in CA (9 to 12% CO2

) or 

the presence of an ethylene absorber does not 

influence rate of skin color loss (O’Hare 1995).

Respiration Rates

Respiration is 40 to 100 mg (about 23 to 57 

μL) CO2 kg-1 h-1 at 25 oC (77 oF). This is a 

nonclimacteric fruit and the rates are for mature 

fruit; immature fruit respiration rates are 

higher (Mendoza et al. 1972). To calculate heat 

production, multiply mg kg-1 h-1 by 220 to get 

BTU ton-1 day-1 or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Chilling injury and darkening of spines and skin 

are major postharvest disorders. Darkening is 

caused by dehydration and mechanical injury 

(Landrigan et al. 1996). Preharvest disorders 

include skin splitting and poor filling of fruit 

(O’Hare 1992). Skin splitting occurs in thinskinned cultivars often following heavy rains 

during the last phase of fruit growth. Poor filling 

has been associated with poor nutrition and dry 

conditions just after flowering.

Postharvest Pathology

Postharvest losses to disease are low (Ketsa and 

Klaewkasetkorn 1992), though stem end rot 

and fruit rots are found. Sangchote et al. (1992) 

found that the spectrum of fungi associated 

with rambutan decay varied with storage 

temperatures. Collectotrichum gloeosporioides

and Botryodiplodia theobromae are considered the 

most serious pathogens. Other pathogens recorded 

include Pestalotiopsis spp. and Phomopsis spp. 

(Farungasang et al. 1991).

Quarantine Issues

Rambutan is a fruit fly host, and the available 

treatments are irradiation and heat treatment. Heat 

treatment leads to rapid loss of skin color. Mealy 

bugs are often found on the fruit, but they do not 

damage the flesh (Ketsa and Klaewkasetkorn 

1992).

Suitability as Fresh-Cut Product

Suitability is limited, since it is difficult to 

separate aril and seed.

References

Brown, B.I., and P.R. Wilson. 1988. Exploratory 

study of postharvest treatments on rambutan 

(Nephelium lappaceum) 1986/1987 season. Rare 

Fruit Counc. Austral. Newsletter 48:16-18.

Farungsang, U., N. Farungsang, and S. Sangchote. 

1991. Postharvest diseases of rambutan during 

storage at 13 or 25 °C. In 8th Australasian Plant 

Pathology Society Conference, 7-11 October, 

1991, Sydney, Australia. Sydney University, 

Sydney, Australia.
529

Kader, A.A. 1993. Modified and controlled 

atmosphere storage of tropical fruits. In B.R. 

Champ, E. Highley and G.I. Johnson, eds., 

Proceedings of the International Conference on 

Postharvest Handling of Tropical Fruits, Chiang 

Mai, Thailand, July 1993, pp. 239-249. ACIAR 

Pub. no. 50. Australian Centre for International 

Agricultural Research, Canberra, Australia.

Ketsa, S., and O. Klaewkasetkorn. 1992. 

Postharvest quality and losses of ‘Rongrein’ 

rambutan fruits in wholesale markets. Acta Hort. 

321:771-777.

Ketsa, S., and O. Klaewkasetkoan. 1995. Effect 

of modified atmosphere on chilling injury and 

storage-life of rambutan. Acta Hort. 398:223-231.

Lam, P.F., and K.H. Ng. 1982. Storage of waxed 

and unwaxed rambutan in perforated and sealed 

polyethylene bags. Report no. 251, Malaysian 

Agricultural Research and Development Institute, 

Food Technology Division, Selangor, Malaysia.

Landrigan, M., S.C. Morris, D. Eamus, and W.B. 

McGlasson. 1996. Postharvest water relationships 

and tissue browning of rambutan fruits. Sci. Hort. 

66:201-208.

Mendoza, D.B., E.B. Pantastico, and F.B. 

Javier. 1972. Storage and handling of rambutan 

(Nephelium lappaceum L.). The Philippines 

Agriculturist 55:322-332.

Mendoza, D.B., P.T. Ramos, G.R. del Mundo, 

et al. 1982. Maturity and ripening guide for 

rambutan cultivars. Tech. Bull. 5. ASEANPHTRC, University of the Philippines, Los Banos, 

Philippines.

Mohamed, S., and E. Othman. 1988. Effect 

of packaging and modified atmosphere on the 

shelf life of rambutan (Nephelium lappaceum).

Pertanika 11:217-228.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K.

O’Hare, T.J. 1992. Rambutan: postharvest 

physiology and storage. Trop. Fruit News 26:4-6.

O’Hare, T.J. 1995. Postharvest physiology and 

storage of rambutan. Postharv. Biol. Technol. 

6:189-199.

O’Hare, T.J., A. Prasad, and A.W. Cooke. 1994. 

Low temperature and controlled atmosphere 

storage of rambutan. Postharv. Biol. Technol. 

4:147-157.

Sangchote, S.,U. Farungsang, and N. Farungsang. 

1992. Rambutan diseases. In G.I. Johnson and 

E. Highley, eds., Proceedings of the Workshop 

on Development of Postharvest Handling 

Technology for Tropical Tree Fruits, July 1992, 

Bangkok, Thailand, p. 51-59. Australian Center 

for International Agricultural Research, Canberra, 

Australia.

Somboon, Y. 1984. Effect of Temperature and 

Maturity Stages on Biochemical Changes During 

Storage of Rambutan (Nephelium lappaceum

Linn.) cv. Seechompoo and cv. Rongrien. M.S. 

thesis. Kasetsart University, Bangkok, Thailand.
530

Raspberry

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, NC Research Campus, Kannapolis, 

NC.

Scientific Name and Introduction

Raspberries (Rubus ideaus L.) are a member of 

the Rosaceae family, grown as a perennial crop. 

Raspberries are available commercially in red, 

yellow, purple, and black forms. The red or yellow 

raspberry is classified into two subspecies: R. 

idaeus subsp. vulgatus Arrhen. (European red 

raspberry) and R. idaeus subsp. strigosus Michx. 

(American red raspberry). Black raspberries found 

in eastern North America are R. occidentalis L.; 

R. glaucus L. is a South American tetraploid black 

raspberry. Purple raspberries (R. neglectus Peck.) 

result from crosses of black and red raspberries. 

All commercially important raspberry species are 

prized for their unique and delicate fruit flavor 

and are often used in fresh desserts. The berries 

are compound fruits, made up of many drupelets 

and a hollow center where the fruit detaches 

from the receptacle. Berries are soft, juicy, and 

have a distinct aroma. Important cultivars include 

‘Meeker,’ ‘Heritage,’ ‘Tulameen,’ ‘Willamette,’ 

‘Chilliwack,’ and ‘Munger.’

Quality Characteristics and Criteria

High-quality raspberries are free of injury, decay, 

and sunscald; are uniformly colored; and appear 

turgid.

Horticultural Maturity Indices

For fresh market, raspberries are best harvested 

when bright red (red raspberries) or fully colored 

(black, purple, or yellow raspberries). Berries 

should pull or shake easily from the receptacle 

yet be firm, not mushy. Color development after 

harvest is highly cultivar-dependent; ‘Heritage’ 

berries turn purple-red quickly while ‘Nova’ retain 

a full red color. Cultivars known to change color 

rapidly are sometimes picked when pink, though 

acid levels are higher and flavor low or lacking at 

this color stage. 

Grades, Sizes, and Packaging

Raspberries are graded as U.S. No. 1 or No. 2 

based on freedom from mold, decay, sunscald, 

over-ripeness, and injury. A limit of 1% of berries 

for mold and 10% total for defects separates 

No. 1 grade from No. 2. No. 2 fruit can have no 

more than 2% berries with decay. Trays holding 

12 half pints (125 g), usually vented plastic 

clamshell containers, are the standard package. 

No minimum berry size is required.

Precooling Conditions

Raspberries should be forced-air cooled to 1 °C 

(34 oF) within 12 h of harvest (Moore and Robbins 

1992).

Optimum Storage Conditions

Raspberries should be held no more than 2 to 5 

days, depending on cultivar, at -0.5 to 0 oC (31 to 

32 oF) with >90% RH.

Controlled Atmosphere (CA) 

Considerations

Raspberries benefit from 10 to 20% CO2

 and 

5 to 10% O2

 (Kader 1997). CA storage slows 

respiration, ethylene production, softening, color 
531

change, and growth of molds. Levels of CO2

>20% can cause discoloration, softening, and off 

flavor (Agar and Streif 1996). 

Retail Outlet Display Conditions

Raspberries should be stored and displayed at the 

coldest refrigeration temperature possible without 

freezing. As little as 1 day at 20 °C (68 °F) can 

result in growth of gray mold (Botrytis cinerea 

Pers.).

Chilling Sensitivity

Raspberries are not known to be chilling sensitive. 

Ethylene Production and Sensitivity

The presence of ethylene can stimulate growth of 

Botrytis cinerea (gray mold) on raspberries; also, 

color can be adversely affected, darkening to a 

purple-red in red raspberries. Ethylene production 

is cultivar-dependent, from 1 to 12 μL kg-1 h-1 at 

20 °C (68 °F) (Burdon and Sexton 1990, PerkinsVeazie and Nonnecke 1992).

Respiration Rates

Temperature mg CO2 kg-1 h-1

2 °C 16 to 18

4 to 5 °C 18 to 27

10 °C 31 to 39

15 to 16 °C 28 to 55

20 to 21 °C 74 to 175

Data from Haller et al. (1941), Perkins-Veazie 

and Nonnecke (1992), and Perkins-Veazie 

(unpublished).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Shriveling (water loss), leakers (berries with 

leakage of juice), and UV damage (white 

drupelets) are the primary disorders found in 

raspberries.

Postharvest Pathology

The most common postharvest diseases are gray 

mold (Botrytis cinerea Pers.) and rhizopus rot 

(Rhizopus stolonifer Ehrenb.:Fr.) (Ellis et al. 

1991).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Raspberries are incorporated into mixed fruit cups.

Special Considerations

Raspberries damage easily; they are one of the 

most fragile and perishable of all fruits.

Acknowledgments

Some information in this chapter is from the 

University of California, Davis, website on 

“Produce Facts” at http://postharvest.ucdavis.edu/

produce_information. 

References

Agar, I.T., and J. Streif. 1996. Effect of high CO2

and controlled atmosphere (CA) storage on the 

fruit quality of raspberry. Gartenbauwissenschaft 

61:261-267.
532

Burdon, J.N., and R. Sexton. 1990. Fruit 

abscission and ethylene production in red 

raspberry cultivars. Sci. Hort. 43:95-102.

Ellis, M.A., R.H. Converse, R.N. Williams, and B. 

Williamson, eds. 1991. Compendium of Raspberry 

and Blackberry Diseases and Insects. APS, St. 

Paul, MN.

Haller, M.H., D.H. Rose, and P.L. Harding. 1941. 

Studies on the respiration of strawberry and 

raspberry fruits. Circular 613, U.S. Department of 

Agriculture, Washington, DC.

Kader, A.A. 1997. A summary of CA requirements 

and recommendations for fruits other than apples 

and pears. In A.A. Kader, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

3, pp. 1-34. University of California, Davis CA.

Moore, P. P., and J. Robbins. 1992. Fruit quality 

of stored, fresh red raspberries after a delay in 

Precooling. HortTechnology 2:468-470.

Perkins-Veazie, P., and G. Nonnecke. 1992. 

Physiological changes during ripening of 

raspberry fruit. HortScience 27:331-333.
533

Rhubarb

Donald N. Maynard

Maynard is formerly with the Gulf Coast Research 

and Education Center, University of Florida, 

Wimauma, FL. He is now retired.

Scientific Name and Introduction

Rhubarb, or “pie plant,” (Rheum rhabarbarum

L.) is a perennial of the Polygonaceae family. 

Fleshy petioles are the edible portion. Petioles 

may be green, pink, or white depending on the 

variety. Field production in North America is 

mainly in Washington, Oregon, Michigan, and 

Ontario. Rhubarb is forced in heated structures 

in Washington, Michigan, and Ontario. Fresh 

rhubarb is mostly available in late winter through 

spring (Foust and Marshall 1991), but limited 

supplies are available at other times.

Quality Characteristics and Criteria

Petiole color is associated with quality. The order 

of preference is red, pink, and green. Petioles 

should appear fresh with no signs of desiccation or 

decay whether presented for sale intact or cut into 

sections.

Grades, Sizes, and Packaging

U.S. grades for field-grown rhubarb include U.S. 

Fancy, U.S. No. 1, U.S. No. 2, and Unclassified 

(USDA 1966). Grade is based primarily on petiole 

color, frequency of defects, and appearance. State 

and provincial grades have been developed for 

forced rhubarb. For example, Washington rhubarb 

is marketed as Fancy and Extra Fancy (McGregor 

1987), while Michigan rhubarb is classed as 

Choice, Small Fancy, or Fancy (Pennell 1976). 

Rhubarb is packed in 4.5-, 6.8-, or 9.0-kg (10-, 

15-, or 20-lb) cartons (Anon 1995).

Precooling Conditions

Rhubarb petioles should be precooled to 0 °C 

(32 °F) by hydrocooling or forced-air cooling 

(McGregor 1987).

Optimum Storage Conditions

Rhubarb petioles can be stored for 2 to 4 weeks 

at 0 °C (32 °F) with 95 to 100% RH (McGregor 

1987).

Controlled Atmosphere Considerations

CA storage has not yet been used for rhubarb.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 9 to 13

5 °C 11 to 18

10 °C 25

15 °C 31 to 48

20 °C 40 to 57

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Petioles lacking small leaf lamina are subject to 

splitting when exposed to moisture. Overmature 

petioles become pithy. Abrasion of petioles 

by sand or rough handling adversely affects 

appearance.

Postharvest Pathology

Several diseases may cause postharvest losses 

of rhubarb (Snowdon 1992). Anthracnose 

(Colletotrichum erumpens) causes oval, soft, 
534

watery lesions on petioles. Bacterial soft rot 

(Pseudomonas marginalis, Erwinia caratovra)

causes a soft, slimy decay. Gray mold (Botrytis 

cinerea) causes soft, brown lesions on petioles. 

Postharvest decay is usually traced to poor 

sanitation of hydrocooling water, so proper 

sanitation with recommended storage temperature 

is essential to avoid infection. 

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Suitability has not been evaluated.

References

Anonymous. 1995. Packer Sourcebook. Vance, 

Lenexa, KS

Faust, C.M., and D.E. Marshall. 1991. Culinary 

rhubarb production in North America: history and 

recent statistics. HortScience 26:1360-1363.

McGregor, B.M. 1987. Tropical Products 

Transport Handbook. Agriculture Handbook 668, 

U.S. Department of Agriculture, Washington, DC.

Pennell, J.T. 1976. Rhubarb production. Leaflet 

555, U.S. Department of Agriculture, Washington, 

DC.

Snowdon, A.L. 1992. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. CRC Press, Boca Raton, FL.

AMS [USDA Agricultural Marketing Service]. 

1966. United States standards for grades of 

rhubarb (field grown). U.S. Department of 

Agriculture, Agricultural Marketing Service, 

Washington, DC. 
535

Rutabaga

Maria Cecilia do Nascimento Nunes 

Nunes is formerly with the Air Cargo 

Transportation Research Group, Department of 

Soils and Agrifood Engineering, Laval University, 

Quebec, Canada. She is now with the Food 

Science and Human Nutrition Department, 

University of Florida, Gainesville, FL.

Scientific Name and Introduction

Rutabaga (Brassica napus L.; Napobrassica 

group), also referred to as swedes, Swedish 

turnips, and turnip-rooted cabbage, is a member 

of the Cruciferae. The edible portion is the large, 

usually yellow-fleshed storage root. The three 

main commercial varieties of rutabagas include 

‘American Purple Top,’ ‘Laurentian,’ and the 

‘Thomson strain’ of ‘Laurentian.’ Rutabaga is a 

cool-season vegetable that withstands frost and 

mild freezing. In North America, rutabaga is 

primarily grown in Canada, California, Colorado, 

Wisconsin, and Minnesota. 

Quality Characteristics and Criteria

A high-quality rutabaga is a well-shaped, purpletopped root having a smooth, small neck and 

a well-defined taproot with a minimum of side 

roots. It is free of blemishes and bruises. The root 

should be firm, fresh looking, sweet and not bitter, 

and heavy for its size. Lightweight rutabagas may 

be “woody” (Gardner and Nonnecke 1987). 

Horticultural Maturity Indices

Rutabagas should be harvested when fully 

mature, since immature rutabagas can have a 

bitter taste. Good quality rutabagas are harvested 

at maximum sugar accumulation. Winter crops 

should be harvested before weather becomes hot 

or roots will become pithy and woody. Harvesting 

fall crops after the first frost can sweeten flavor 

(Suzuchi and Cutcliffe 1981).

Grades, Sizes, and Packaging

Grades include U.S. No. 1 and U.S. No. 2, based 

on subjective external appearance. Sizes are 

defined as Small, diameter of 5.1 to10.2 cm (2 to 

4 in); Small-Medium, 8.9 to 14 cm (3.5 to 5.5 in); 

Medium, 10.2 to 15.2 cm (4 to 6 in); and Large, 

13 to 17.8 cm (5 to 7 in). Common packaging is 

23-kg (50-lb) bushel cartons or bags (about 20 

roots) and 11-kg (25-lb) 0.5-bushel cartons (about 

10 roots). 

Precooling Conditions

Roots should be cooled as quickly as possible in 

order to avoid excessive moisture loss. Brown 

surface discoloration called “storage burn” can be 

largely controlled by rapid cooling at 0 °C (32 °F) 

together with adequate air circulation (Franklin 

and Lougheed 1975). If harvested when the soil 

or air is above 25 °C (77 °F), rutabagas should 

be cooled within 3 to 4 h to avoid loss of quality 

during storage. Room-cooling is most commonly 

used; however, forced-air cooling, hydrocooling, 

and package-icing can also be used to retard 

development of skin discoloration, weight loss, 

and decay.

Optimum Storage Conditions

Rutabagas can be kept for 4 to 6 mo at 0 °C 

(32 °F) with 98 to 100% RH (van den Berg and 

Lentz 1973). They should be stored unwrapped, 

in a cool, moist, dark area with good ventilation. 

If held 6 mo at 2 °C (36 °F) with 95% RH or 

5 °C (41 °F) with 90% RH, weight loss can be 

as high as 6 and 11%, respectively (Cutcliffe 

and Anderson 1989). Rutabagas for immediate 

marketing are often waxed to enhance appearance 

and protect against excessive moisture loss. 

Waxed roots will keep well under refrigerated 

conditions for 1 to 2 mo. Roots for long-term 

storage should not be waxed, since wax coatings 

become unsightly during storage and may impede 

gas exchange.
536

Controlled Atmosphere (CA) 

Considerations

There are no indications that rutabagas stored 

in CA have superior quality or longer shelf-life 

than roots stored at normal atmosphere at 0 °C 

(32 °F) with high RH (Tomkins 1959, Franklin 

and Lougheed 1975). Furthermore, CO2

 >8% is 

injurious to rutabagas.

Retail Outlet Display Considerations

Rutabagas should be held in a refrigerated 

display. Use of top ice is accepted; misting is not 

recommended.

Chilling Sensitivity

Rutabagas are not sensitive to chilling and should 

be stored as cold as possible. They can stand slight 

freezing without injury.

Ethylene Production and Sensitivity

Rutabagas produce very low amounts of ethylene: 

<0.1 μL kg-1 h-1 at 20 °C (68 °F). Exposure to 

ethylene is not an important factor.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 4 to 6

5 °C 8 to 12 

10 °C 9.5 to 19

15 °C 20 to 31

20 °C 34 to 40

Data from International Institute of Refrigeration 

(1967).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Rutabagas freeze at about -1 °C (30 °F), and 

freezing may be initiated at -0.5 °C (31 °F). 

Symptoms include small, water-soaked spots 

on the surface and light browning of the flesh. 

Injured tissue appears tan or gray and gives off a 

fermented odor.

Brown heart or water-core of rutabagas is caused 

by boron deficiency. Stored roots with brown heart 

may suffer tissue breakdown and moisture loss, 

becoming spongy. They may also develop brown 

spots and cracks (Ryall and Lipton 1983).

Postharvest Pathology

Rot diseases are promoted by storage at higherthan-recommended temperatures. Brown soft rot 

caused by Botrytis cinerea is a major pathogen. 

Mold growth typically begins at sites of tissue 

damage and then spreads to adjacent roots, 

creating a dense surface growth of mycelium and 

conidia. Black rot caused by Phoma lingam causes 

restricted dry, corky, dark brown or blackish 

lesions with a sparse superficial growth of white 

mycelia. Phoma lesions can occur both at cut 

surfaces, where discoloration frequently spread 

into the vascular tissue, and as small craters on 

undamaged skin (Geeson et al. 1989). Bacterial 

soft rot caused by Erwinia carotovora has also 

been associated with postharvest deterioration 

of roots during storage (Shattuck and Proudfoot 

1990).

Quarantine Issues

Rutabagas must be completely free of soil because 

many plant pests are soil-borne. A permit to 

import rutabagas into Canada is required for 

areas of New York State (because of the possible 

presence of golden nematode, Heterodera 

rostochiensis), off-continent United States, and all 

other countries.
537

Suitability as Fresh-Cut Product

Rutabagas are good candidates for sale in 

consumer-size packages. Prepeeled rutabagas 

packaged in consumer film bags keep in good 

condition for 3 weeks at 0 °C (32 °F). Fresh-cut 

rutabagas stored in 15% O2

 will keep for 

10 days at 10 °C (50 °F) and 20 days at 1 °C 

(34 °F). Fermentation may occur at lower 

O2

 levels (Alexander and Francis 1964). Storage 

of cubed, shredded, or peeled rutabaga in 5% O2

and 5% CO2

 at 0 to 5 °C (32 to 41 °F) reduces 

respiration rate and has a moderate potential 

(Gorny 1997).

Special Considerations

Strong odors may be transferred to fruits and leafy 

vegetables if they are held in the same storage area 

with rutabagas.

Acknowledgments

Some of the information in this chapter is from the 

Agriculture Canada, Canadian Food Inspection 

Agency website at http://www.cfia-acia.agr.ca; 

the USDA-Animal and Plant Health Inspection 

Service, Plant Protection and Quarantine website 

at http://www.aphis.usda.gov/plant_health/index; 

and the USDA-Agricultural Marketing Service 

website at http://www.ams.usda.gov/AMSv1.0/

standards.

References

Alexander, B., and F.J. Francis. 1964. Packaging 

and storage of pre-peeled rutabagas. Proc. Amer. 

Soc. Hort. Sci. 85:457-464.

Cutcliffe, J.A., and J.B. Anderson. 1989. Effects 

of added nitrogen and potassium on yield and 

storability of rutabagas. Can. J. Plant Sci. 

69:1359-1363.

Franklin, E.W., and E.C. Lougheed. 1975. Storing 

rutabagas. Factsheet 75-068, AGDEX 258/64, 

Ministry of Agriculture and Food Ontario, Guelph, 

Ontario, Canada.

Gardner, J., and I.L. Nonnecke. 1987. Rutabagas 

(table turnips). Factsheet 87-032, AGDEX 258/20, 

Ministry of Agriculture and Food Ontario, Guelph, 

Ontario, Canada.

Geeson, J.D., K.M. Browne, and H.P. Everson. 

1989. Long-term refrigerated storage of swedes. J. 

Hort. Sci. 64(4):479-483.

Gorny, J.R. 1997. A summary of CA and MA 

requirements and recommendations for freshcut (minimally processed) fruits and vegetables. 

In J.F. Gorny, ed., 7th International Controlled 

Atmosphere Research Conference, July 13-18, 

1997, University of California, Davis, vol. 5, pp. 

30-66. University of California, Davis, CA.

International Institute of Refrigeration. 1967. 

Recommended conditions for cold storage of 

perishable produce, 2nd ed. International Institute 

of Refrigeration, Paris, France.

Ryall, A.L., and W.J. Lipton. 1983. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, 2nd ed., vol. 1. AVI, Westport, CT.

Shattuck, V.I., and K.G. Proudfoot. 1990. 

Rutabaga breeding. Plant Breeding Rev. 8:217-

248.

Suzuki, M., and J.A. Cutcliffe. 1981. Sugars and 

eating quality of rutabagas. Can. J. Plant Sci. 

61:167-169.

Tomkins, R.G. 1959. The biological effects of 

sealed plastic containers by prepacked fresh 

fruit and vegetables. International Institute of 

Refrigeration Bull. 40, annex 3. International 

Institute of Refrigeration, Paris, France.

van den Berg, L., and C.P. Lentz. 1973. High 

humidity storage of carrots, parsnips, rutabagas, 

and cabbage. J. Amer. Soc. Hort. Sci. 98:129-132. 
538

Salad Greens

Kimberly P. Wright

Wright is with Dole Fresh Vegetables, Salinas, 

CA.

Scientific Names and Introduction

Various greens other than lettuce are used in raw 

salads. These include corn salad; lamb’s lettuce; 

field salad; mâche (Valerianella locusta [L.] 

Latterrade em. Betcke [V. olitoria]); dandelion 

(Taraxacum officinale Wiggers); French or round 

sorrel (Rumex scutatus); garden sorrel (R. acetosa

L.); miner’s lettuce; winter purslane; claytonia 

(Montia perfoliata [Claytonia perfoliata]); 

mizuna (Brassica rapa L. subsp. japonica group 

Japonica); purslane (Portulaca oleracea L.); and 

rocket salad, roquette, arugula, rucola, or rugula 

(Eruca vesicaria [L.] Cav. subsp. sativa [Mill.] 

Thell). Young leaves are generally used. 

Quality Characteristics and Criteria

Greens used in raw salads must be fresh, tender, 

and turgid with no yellowing, decay, or insect 

or mechanical damage. Whole plants of rocket 

and lamb’s lettuce are sometimes sold with roots 

attached, which lengthens postharvest life.

Horticultural Maturity Indices

Greens are harvested as individual leaves, leaf 

clusters, or whole plants and should be young, 

tender, and mild flavored. Plants that have 

flowered are usually too strong in flavor and tough 

in texture for use in raw salads.

Grades, Sizes, and Packaging

These crops are not graded or sized in the United 

States. Salad greens may be packed in fiberboard 

cartons lined with perforated polyethylene bags 

or in small sealed plastic bags, trays, or clamshell 

containers. These greens may also be packed 

as bunches of leaves or plants (Rubatzky and 

Yamaguchi 1997, Péron and Rees 1998). 

Precooling Conditions

Greens for salads should be cooled to 0 °C (32 °F) 

as soon as possible after harvest. Vacuum-cooling 

is effective for removing field heat.

Optimum Storage Conditions

Salad greens should be stored at 0 to 2 °C (32 

to 36 °F) with 95 to 100% RH. Rocket salad 

typically lasts 7 to 10 days and other leafy greens 

10 to 14 days (Cantwell 1997). Top icing can be 

used.

Controlled Atmosphere (CA) 

Considerations

CA is generally not beneficial. MAP is mostly 

beneficial for controlling RH. However, lamb’s 

lettuce retains acceptable quality after 28 days in 

sealed plastic bags with reduced O2

 and elevated 

CO2

 at <4 °C (39 °F) (de Leiris 1987). MAP 

reduces yellowing and decay of sorrel (Aharoni et 

al. 1993).

Retail Outlet Display Considerations

Use of water sprinklers is acceptable. Leafy greens 

are highly susceptible to water loss and wilting.

Chilling Sensitivity

Salad greens are not sensitive to chilling and 

should be stored as cold as possible without 

freezing.
539

Ethylene Production and Sensitivity

Salad greens have very low ethylene production 

but are highly sensitive to ethylene exposure 

(Cantwell 1997), which typically results in loss of 

chlorophyll leading to yellowing of leaves.

Respiration Rates

Temperature Rocket salad Lamb’s lettuce

----------mg CO2 kg-1 h-1----------

0 °C 42 12

5 °C 113 -

7 °C - 67

10 °C - 81

20 °C - 139

Data from Cantwell and Reid (1993), Cantwell 

(1997), Peiris et al. (1997), Rubatzky and 

Yamaguchi (1997), and Piergiovanni et al. (1999). 

Respiration rates for other greens are not reported, 

but would be expected to be similar.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day 1 

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Because of the delicate texture of the leaves, 

greens are highly susceptible to mechanical 

damage, which may result in discoloration and 

decay.

Postharvest Pathology

Low temperatures must be maintained throughout 

the cold chain to minimize pathological disorders 

and prolong shelf-life. Salad greens are typically 

susceptible to the same bacterial soft rot and 

fungal decay as lettuce.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Intact leaves are sometimes included in packaged 

salad mixes.

Special Considerations

Greens must be handled carefully to avoid 

mechanical damage and water loss.

References

Aharoni, N., O. Dvir, D. Chalupowicz, and 

Z. Aharon. 1993. Coping with postharvest 

physiology of fresh culinary herbs. Acta Hort. 

344:69-78.

Cantwell, M. 1997. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu/

produce_information/storagefreshproduce.

Cantwell, M.I., and M.S. Reid. 1993. Postharvest 

physiology and handling of fresh culinary herbs. J. 

Herbs, Spices and Medicinal Plants 1:93-127.

de Leiris, J. 1987. The packaging of fresh 

vegetables in barrier films and modified 

atmospheres. In Proceedings of the 1st 

International Conference on Packaging Advances, 

pp. 135-162. Nova-Pack, Dusseldorf, Germany.

Peiris, K.H.S., J.L. Mallon, and S. J. Kays. 1997. 

Respiratory rate and vital heat of some specialty 

vegetables at various storage temperatures. 

HortTechnology 7:46-49.

Péron, J.Y., and D.C. Rees. 1998. High-tech 

production of corn salad (Valerianella locusta (L.) 

Laterr.), a local, French vegetable crop. Acta Hort. 

467:259-268.
540

Piergiovanni, L., P. Fava, and S. Ceriani. 1999. A 

simplified procedure to determine the respiration 

rate of minimally processed vegetables in flexible 

permeable packaging. Ital. J. Food Sci. 11:99-110.

Rubatzky, V.E., and M. Yamaguchi. 1997. World 

Vegetables: Principles, Production and Nutritive 

Values, 2nd ed. Chapman & Hall, London, U.K.
541

Salsify

Fabio Mencarelli

Mencarelli is formerly with the Istituto Tecnologie 

Agroalimentari, University of Tuscia, Viterbo, 

Italy. He is now with the Department of Food 

Science and Technology, University of Viterbo, 

Italy.

Scientific Name and Introduction

Salsify (Tragopogon porrifolius var. sativus 

[Gaterau] Br.-Bl.) belongs to the Compositae 

family. It is also called vegetable oyster and oyster 

plant. It is a biennial that produces an edible 

taproot. The root is light yellow outside and white 

inside and 15 to 30 cm (6 to 12 in) long with 

a diameter of 2 to 2.5 cm (0.75 to 1 in). Black 

salsify (Scorzonera hispanica L.) belongs to the 

same family. Its taproot is larger, more cylindrical 

in shape, brown-black on the outside, and white 

inside. Both are rich in iron, vitamins (B1, B2, and 

E) and inulin, asparagin, and the glycoside laricin. 

Inulin is poorly digested by humans and can be 

used as a bulking ingredient in foods formulated 

with artificial sweeteners (see “Jerusalem 

Artichoke” chapter) and as a source of fructose 

(Kierstan 1978).

Quality Characteristics and Criteria

There are no U.S. or international standards. 

Taproots must be sound, clean, fresh, and without 

any foreign smell or taste. They must be fullbodied, straight, and unbranched. They should not 

be woody. Color must be uniform light-yellow or 

brown-black.

Horticultural Maturity Indices

Harvest is based on root size and time from 

seeding—usually after 150 to 210 days.

Grades, Sizes, and Packaging

No official grades exist; sizing is based on length 

and diameter. Salsify is packaged in plastic liners 

or trays wrapped with plastic film to minimize 

water loss.

Precooling Conditions

Precooling is not necessary.

Optimum Storage Conditions

Under refrigerated conditions, salsify roots can 

be stored for 3 to 4 mo at 0 oC (32 oF) with 95 to 

98% RH (Hardenburg et al. 1986). In the absence 

of refrigeration, roots are also commonly stored in 

clamps (Hak 1993).

Controlled Atmosphere (CA) 

Considerations

Black salsify can be stored in 3% CO2

 and 3% 

O2

 for 6 mo at 0 oC (32 oF) with excellent results 

(Stoll 1974).

Retail Outlet Display Considerations

The skin is very delicate, and salsify easily loses 

water if not in plastic-lined trays. Misting with 

water is beneficial.

Chilling Sensitivity

Salsify is not chilling sensitive. It should be stored 

as cold as possible without freezing. 

Ethylene Production and Sensitivity

Salsify produces very little ethylene and has low 

sensitivity to ethylene.
542

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 oC 22 to 28

5 oC 33 to 53

10 oC 40 to 57

20 oC 193

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 oC (32 oF), 1.9 at 10 oC (50 oF), and 

1.8 at 20 oC (68 oF). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Freezing is a risk during storage.

Postharvest Pathology

The most frequent diseases in the field are Albugo 

tragopogonis, causing russet spotting on leaves, 

and powdery mildew (Erysiphe cichoriacearum 

DC.), which compromises quality.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Salsify is not currently marketed as fresh-cut 

product.

References

Hak, P.S. 1993. Kuilbewaring van 

fabrieksaardappelen, suikerbieten, rode bieten, 

schorseneren en winterpeen. Bedrijfsontwikkeling 

14:799-801.

Hardenburg, R.E., A.E. Watada, and C.Y. Wang. 

1986. Salsify. In R.E. Hardenburg, A.E. Watada, 

and C.Y. Wang, The Commercial Storage of 

Fruits, Vegetables, and Florist and Nursery Stocks, 

p. 69. Agricultural Handbook 66, U.S. Department 

of Agriculture, Washington, DC.

Kierstan, M.P.J. 1978. Production of fructose 

syrups from inulin-containing plants [Jerusalem 

artichokes, chicory, salsify extracts]. Biotech. 

Bioeng. 20:447-450.

Stoll, K. 1974. Storage of vegetables in modified 

atmospheres. Acta Hort. 38:13.
543

Sapodilla and Related Fruits

Elhadi M. Yahia

Yahia is with the Facultad de Química, 

Universidad Autónoma de Querétaro, Querétaro, 

Mexico.

This chapter discusses black sapote, lucuma, 

mamey apple, sapodilla, sapote, star apple, and 

white sapote. 

Note regarding respiration data for Sapodilla and 

related fruit:

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1.

Black Sapote

Scientific Name and Introduction

Black sapote (Diospyros dignya) resembles a 

large, round, green tomato. It weighs 200 to 250 g, 

is 5 to 12 cm in diameter, and has a thin skin. The 

green color changes to brown or black when ripe. 

During ripening, pulp becomes soft and black.

Optimum Storage Conditions and Chilling 

Sensitivity

Black sapote is chilling sensitive. Fruit held at 

15, 20, or 25 °C (59, 68, or 77 °F) for up to 7, 10, 

or 15 days and then transferred to 25 °C (77 °F) 

ripened normally (Miller et al. 1997). Fruit held 

at 10 °C (50 °F) for 7 days and then transferred 

to 25 °C (77 °F) also ripened normally. However, 

some fruit held at 10 °C (50 °F) for 10 or 15 days 

showed abnormal ripening, and most fruit stored 

at 1 to 5 °C (34 to 41 °F) did not ripen normally or 

failed to ripen regardless of storage duration. 

Black sapote will tolerate irradiation at 0.15 kGy, 

but abnormal ripening of some fruit is likely when 

treated at 0.3 kGy (Miller et al. 1997).

Lucuma

Scientific Name and Introduction

The lucuma (lucumo, lucmo, lucma, rucma, or 

mamon) (Lucuma obovata, HBK) is round or 

ovate with a green surface and yellow, mealy 

flesh. Fruit are about 7 cm long. The lucuma is a 

climacteric fruit. It has a low water content (64 

to 72%) and higher amounts of riboflavin, niacin, 

and ascorbate than apples or bananas (Wenkam 

and Miller 1965, Lopez 1984). 

Horticultural Maturity Indices

The maturity index commonly used is a change 

of peel color from green to yellow. However, 

variability exists in peel and pulp color, ranging 

from green to yellowish-green peel and lightyellow to orange-yellow pulp (Lizana 1980). 

SSC can be used as a harvest index, but fruit 

have a dense and dry pulp. To measure SSC, it is 

necessary to disrupt pulp by mechanical means 

and dilute with water. Otherwise apparent SSC 

content will appear lower than the true value 

(Lizana et al. 1986).

A classification of five stages of maturity was 

developed according to peel and pulp color, 

texture, SSC, and respiration (Lizana 1980). The 

classes in relation to peel and pulp color are—

Class Peel color Pulp color

1 light-yellow light-yellow

2 light-green creamy-yellow

3 yellow-green yellow

4 green-yellow dark-yellow

5 green-yellow orange-yellow

Fruit ripened on the tree usually become soft 

and very fragile (Lizana 1980). The pulp is very 

dry when ripe (Lizana 1980). Intense respiratory 

activity and sugar accumulation occur during 

ripening (Lizana et al. 1986). 
544

Mamey Apple

Scientific Name and Introduction

Mamey apple, also know as mamey and zapote, 

(Mammea americana) is a fruit of about 300 

to 500 g having a peachlike flavor. The fruit is 

a drupe about the shape and size of an orange, 

with a russet surface covered with small spots. 

It is round with a thick, brown, leathery skin 

containing one large single seed surrounded by a 

thin layer of flesh. The tough rind is about 4 mm 

thick. The flesh, or endocarp, is yellow, about 2 to 

5 mm thick, and fused with the testa.

Chilling Sensitivity

Chilling injury symptoms include failure to ripen, 

accelerated softening, development of brown 

spots in pulp, and development of off flavors and 

aromas. 

Ethylene Production

Ethylene production at 27 °C (81 °F) is as much 

as 400 μL kg-1 h-1, among the highest of all fruits 

(Akamine and Goo 1978). 

Respiration Rates

Mamey apple is a climacteric fruit. The respiration 

rate at 27 °C (81 °F) is 28 to 40 mg (14 to 20 μL) 

CO2

 kg-1 h-1 (Akamine and Goo 1978).

Sapodilla

Scientific Name and Introduction

Sapodilla (Manilkara achras [Mill] Fosb., syn 

Achras sapota, L.) is the fruit of the chicle 

tree and is also known as sapota, chiku, ciku, 

dilly, nasberry, sapodilla plum, chico zapote, 

zapote, chico, néspero, and sapota plum. The 

fruit is a fleshy berry—ellipsoidal, conical, or 

oval—and contains one or several shiny black 

seeds. It weighs about 70 to 300 g and has a 

dull brown color, thin skin, and yellowish, light 

brown, or red pulp. Sapodilla fruit are prized for 

a pleasant aroma and sweet taste. Fruit growth 

follows a sigmoid pattern (Lakshminarayana and 

Subramanyam 1966). Fruit are very susceptible to 

mechanical injury.

Horticultural Maturity Indices

The erratic flowering habit of sapodilla and the 

presence of fruit at all stages of development on 

the tree make it difficult to determine optimum 

harvest time (Lakshminarayana 1980). Fruit 

harvested later than optimum time usually soften 

very rapidly and become very difficult to handle. 

Fruit harvested earlier than physiological maturity 

may not soften, are usually low in sweetness 

and high in astringency when ripe with a rather 

unappealing alcoholic aftertaste, and form pockets 

of coagulated latex that lower quality. Unripe fruit 

are highly astringent and contain large amounts 

of leucoanthocyanidins. The sucrose content and 

pulp-to-peel ratio increase during maturation 

(Pathak and Bhat 1953). 

Fruits shed brown scaly external material and 

become smooth when reaching physiological 

maturity (Lakshminaryana 1980). Fruit ready for 

harvest do not show green tissue or latex when 

scratched with a fingernail. Fully mature fruit 

have brown skin and separate easily from the stem 

without leaking latex. Extent of scurfiness is also a 

good indicator of maturity (Kute and Shete 1995). 

A fruit with a smooth surface, shining potato 

color, and rounded stylar end is considered mature 

(Kute and Shete 1995). 

Grades, Sizes, and Packaging

Fruit are commonly cell-packed in fiberboard or 

wood flats with 25 to 49 fruit (4.5 kg; 10 lb) per 

flat (McGregor 1987). 
545

Optimum Storage Conditions

Postharvest life is 2 to 3 weeks at 12 to 16 °C (54 

to 61 °F) with 85 to 90% RH. Storage life is about 

13 days at 25 °C (77 °F), 15 days at 20 °C (68 

°F), and 22 days at 15 °C (59 °F) (Broughton and 

Wong 1979). Short-term holding of fruit—less 

than 10 h at 4 °C (39 °F)—before storage at 20 

°C (68 °F) extends storage life up to 24 days with 

satisfactory quality (Broughton and Wong 1979). 

Exposure of fruit to gamma irradiation at 0.1 

kGy extended storage life by 3 to 5 days at 27 °C 

(80 °F) and 15 days at 10 °C (50 °F) without any 

effect on ascorbate content (Salunkhe and Desai 

1984). 

Modified Atmosphere (MA) and Controlled 

Atmosphere (CA) Considerations

Storage life of sapodilla is extended by use of 

MA and removal of ethylene (Broughton and 

Wong 1979, Yahia 1998). Storage life at room 

temperature increased from 13 days to 18 days in 

5% CO2

, 21 days in 10% CO2, and to 29 days in 

20% CO2

. However, fruit held in 20% CO2 failed 

to ripen, and this level of CO2

 is deleterious.

‘Kalpatti’ fruit treated with 6% Waxol, with 250 

or 500 μL L-1 Bavistin, or with hot water at 50 °C 

(122 °F) for 10 min and wrapped in 150 gauge 

polyethylene film with 1% ventilation ripened 

later than the controls, but fungal rot was high 

(Bojappa and Reddy 1990). Fruit treated with 

6% wax emulsion and packed in 200-guage 

polyethylene covers containing ethylene and CO2

absorbents had a shelf-life of 45 days at 12 °C 

(54 °F), 10 days more than controls (Chundawat 

1991).

‘Jantuang’ fruit were successfully stored using 

MAP for 4 weeks at 10 °C (50 °F) and 3 weeks 

at 15 °C (59 °F), a week longer than fruit without 

MAP (Mohamed et al. 1996).

Chilling Sensitivity

Sapodilla fruit are highly susceptible to chilling 

injury. Storage of fruit at 6 to 10 °C (43 to 50 °F) 

causes irreversible damage and results in poor 

flavor (Broughton and Wong 1979, Salunkhe and 

Desai 1984). Chilling injury also occurred in fruit 

stored for 21 days at 10 °C (50 °F). However, fruit 

waxed with a fatty acid sucrose ester kept for 40 

days at 10 °C (50 °F).

Ethylene Production and Sensitivity

Ethylene production is 2.8, 3.7 and 6.1 μL 

kg-1 h-1 at 15, 20 and 25 °C (59, 68 and 77 °F), 

respectively (Broughton and Wong 1979). 

Treatment of sapodilla fruit with etherel at 1 to 3 

mL L-1 accelerated ripening and reduced pectin 

content, phenolic content, SSC, sugar content, and 

vitamin C content (Shanmugavelu et al. 1971, Das 

and Mahapatra 1977, Ingle et al. 1982). Removing 

ethylene delays ripening (Chundawat 1991). 

Respiration Rates

Sapodilla is a climacteric fruit (Lakshminaryana 

and Subramanyam 1966, Broughton and Wong 

1979) but does not reach the climacteric while 

on the tree (Lakshminaryana and Subramanyam 

1966). The respiration rate at 24 to 28 °C 

(75 to 82 °F) was 16 mg (9 μl) CO2

 kg-1 h-1

(Lakshminaryana and Subramanyam 1966). 

Preharvest sprays of isopropyl n-phenylcarbamate 

(IPC) at 100 μL L-1 retard respiration, while 

maleic hydrazide at 0.5 to 1.0 mL L-1 accelerates it 

(Lakshminarayana and Subramanyam 1966).

Postharvest Pathology

Diseases and pests are rare. Phytophthora

palmivora and species of Pestalotiopsis and 

Phomopsis can cause fruit rot (Snowdon 1990). 

Some species of bacteria are associated with fruit 

latex (Pathak and Bhat 1952).
546

Insects that infest sapodilla fruit include 

Nephopteryx engraphella Rag., fruit flies, and an 

unidentified borer (Kute and Shete 1995). The 

most troublesome fruit flies are the Mediterranean 

(Ceratitis capitata, Wied.) and Mexican 

(Anastrepha ludens, Loew.) species.

Sapote

Scientific Name and Introduction

The sapote (zapote, mamey, mamey colorado, 

mamey sapote, chico-mamey, marmalade-fruit, 

marmalade-plum, or grosse sapote) (Pouteria

sapota Jacq., H.E. Moore & Stearn; syn. 

Colocarpum sapota Jacq. Merr., Calocarpum

mammosum Pierre., Achras mammosa L., Lucuma

mammosa Gaertn., Vitellaria mammosa Radlk., 

and Achradelpha mammosa Cook) is ovoid to 

ellipsoid in shape, 7 to 15 cm long, and 10 to 15 

cm in diameter. The skin is thick and woody with 

a russet-brown and somewhat scurfy surface. The 

pulp of mature fruit is soft and smooth to finely 

granular in texture and salmon pink, orange, and 

red or reddish-brown in color. The pulp has a 

rich, sweet, almondlike flavor; low fiber content; 

and creamy texture. Fruit weigh 0.3 to 3 kg and 

contain a large elliptical seed that has a shiny, 

hard, dark-brown surface with a light-brown hilum 

on the ventral side. 

Quality Characteristics and Criteria

Inferior or improperly ripened mamey sapotes will 

develop a pronounced squashlike flavor.

Horticultural Maturity Indices and 

Harvesting

Fruit are harvested when the flesh begins to turn 

red and are mature when the newly exposed layer 

has turned from green to pinkish-brown, orange, 

or red. Immature fruit fail to soften, and their pulp 

will turn dark-brown and inedible. Harvesting 

must be done carefully to avoid mechanical 

damage. The fruit should be twisted until it breaks 

from the stem. Poles with knifes at the end are 

also used to harvest fruit. Fruit should not be 

allowed to fall on the ground. 

Grades, Sizes, and Packaging

Fruit are packed in 3-kg-capacity flat fiberboard 

boxes using sleeves or excelsior (McGregor 

1987). 

Optimum Storage Conditions

Storage life is 2 to 6 weeks at 13 to 18 °C (55 to 

64 °F) with 85 to 90% RH. 

Ethylene Production and Sensitivity

The fruit is climacteric and is one of the most 

prolific producers of ethylene: >100 μL kg-1 h-1 at 

20 °C (68 °F) (Kader 1992).

Physiological Disorders

Fruit are chilling sensitive. Symptoms include 

brown spots on the skin, poor color development, 

and off flavor. 

Star Apple

Scientific Name and Introduction

The star apple (caimito, sweetsop, or anon) 

(Chrysophyllum cainito L.) is an apple-sized fruit, 

commonly round but sometimes ovate, heartshaped, or conical. It has a smooth, waxy skin. 

The fruit appears as a star when cross-sectioned. 

Fruit have a soft flesh and are yellowish green in 

color with a mild, sweet flavor. The pulp is white 

or creamy white with numerous embedded small, 

shiny, dark-brown seeds. 
547

Harvesting

Fruit should be matured on the tree but picked 

before fully ripe. Fruit picked immature will be 

astringent and contain a sticky white latex. Fruit 

left to ripen on the tree often split open, especially 

during the rainy season.

Packaging

Fruit are tray-packed in fiberboard boxes of 4.5 kg 

(10 lb) capacity (McGregor 1987). 

Precooling

Precooling should be done by hydrocooling or 

forced-air cooling.

Optimum Storage Conditions

Star apple intended for cold storage are picked at 

the half-ripe stage, cured in a well-ventilated room 

for 2 days, and held at 3 to 6 °C (37 to 43 °F) with 

90% RH for about 3 weeks.

Chilling Sensitivity

This fruit is slightly sensitive to chilling injury. 

Ethylene Production and Sensitivity

Ethylene production at 20 °C (68 °F) is 10 to 

100 mL kg-1 h-1. The fruit does not respond 

significantly to treatment with ethylene (Pratt and 

Mendoza 1980).

Respiration Rates

The star apple is a nonclimacteric fruit. The 

respiration rate at 20 °C (68 °F) is 25 to 50 mg (13 

to 25 μL) CO2

 kg-1 h-1. Heat evolution is 1,600 to 

4,400 BTU ton-1 day-1, equivalent to a respiration 

rate of 7 to 20 mg CO2

 kg-1 day-1 at 3 to 6 °C (37 

to 43 °F) (Pratt and Mendoza 1980). 

Postharvest Pathology

The most important pests include the annona seed 

borer and the ambrosia beetle. The annona seed 

borer lays eggs in the seeds of very young fruits. 

Insects develop in the seeds and emerge as adults 

when the fruit matures. 

White Sapote

Scientific Name and Introduction

White sapote, or zapote blanco, (Casimiroa

edulis llave & Lex) is also known as matasano in 

Spanish, meaning “killing healthy person” because 

of the presence of the glucoside casimirosine, 

mainly in seeds but also in bark and leaves. This 

compound has sedative effects, induces sleep, and 

can also calm rheumatic pains. The fruit is dullgreen to greenish-yellow, subglobose to oblate, 

and 5 to 10 cm in diameter. The fruit is round, 

oval, or ovoid. The skin is very thin and the flesh 

is cream-colored to yellowish, soft, and very 

sweet, with 1 to 5 large, hard, ovoid seeds. Greenskinned varieties have white flesh, and yellowskinned varieties have yellow flesh. The skin is 

thin and smooth and the flesh has a custardlike 

texture and sweet flavor.

Quality Characteristics and Criteria

Quality fruit are yellow to yellowish-green and 60 

to 120 mm in diameter (McGregor 1987).

Horticultural Maturity Indices

White sapote fruit ripen 6 to 9 mo after bloom. 

Fruit color at maturity ranges from apple-green 

to orange-yellow, depending on the cultivar. 

Overripe fruit are commonly pungent with an 

unpleasant flavor. Fruit taste best when treeripened, but should be picked before ripening. 

Fruit should be handled very carefully during 

harvesting because they are easily bruised, turning 

the skin black and the flesh bitter. 
548

Optimum Storage Conditions

Storage life is 2 to 3 weeks at 19 to 21°C (66 to 70 

°F) and 85 to 90% RH.

Postharvest Pathology

White sapote is resistant to phytophthora and to 

armillaria, but some cultivars can be attacked by 

fruit flies.

Acknowledgments

Some of the information in this chapter is from the 

University of Florida website at http://ifas.ufl.edu.

References

Akamine, E.K., and T. Goo. 1978. Respiration and 

ethylene production in Mammee apple (Mammea

americana L.). J. Amer. Soc. Hort. Sci. 103:308-

310. 

Bojappa, K.K.M., and T.V. Reddy. 1990. 

Postharvest treatments to extend the shelf life of 

sapota fruit. Acta Hort. 269:391.

Broughton, W.J., and H.C. Wong. 1979. Storage 

conditions and ripening of chiku fruits Achras

sapota L. Sci. Hort. 10:377-385.

Chundawat, B.S. 1991. Postharvest handling and 

marketing of sapota fruits. National Seminar on 

Optimizing Production and Utilization of Sapota, 

October 1991, Navsari, Gujarat, India.

Das, R.C., and S.K. Mahapatra. 1977. Effect of 

growth substances and fungicidal wax emulsion 

on ripening of sapota. Prog. Hort. 8:75.

Ingle, G.S., D.M. Khedkar, and R.S. Dabhade. 

1982. Ripening studies in sapota fruit. Indian Food 

Packer 36:72-77.

Kader, A.A., ed. 1992. Postharvest Technology of 

Horticultural Crops, 2nd ed. DANR Pub. no. 3311, 

University of California, Oakland, CA.

Kute, L.S., and M.B. Shete. 1995. Sapota 

(Sapodilla). In D.K. Salunkhe and S.S. Kadam, 

eds., Handbook of Fruit Science and Technology, 

pp. 475-484. Marcel Dekker, New York, NY.

Lakshminarayana S. 1980. Sapodilla and prickly 

pear. In S. Nagy and P.E. Shaw, eds., Tropical and 

Subtropical Fruits: Composition, Properties and 

Uses, pp. 415-441. AVI, Westport, CT.

Lakshminarayana S., and H. Subramanyam. 

1966. Physical, chemical and physiological 

changes in sapota fruit (Achras sapota L.) during 

development and ripening. J. Sci. Food Sci. 

Technol. (Mysore) 3:15-154. 

Lizana, L.A. 1980. Lucuma. In S. Nagy, P.E. 

Shaw, and W.F. Wardowski, eds., Fruits of 

Tropical and Subtropical Origin, pp. 373-380. 

Florida Science Source, Lake Alfred, FL.

Lizana, L.A., G. Reginato, and J.C. Lavanderos. 

1986. Characterization of the maturation of the 

lucuma (Lucuma bifera Mol., L. Obovata H.B.K.). 

Proc. Interam. Soc. Trop. Hortic. 30:105-10. 

Lopez, C. 1984. Cultivation of the lucumo and its 

industrialization. Rev. Campesino 115:38-53. 

McGregor, B.M. 1987. Tropical Products 

Transport Handbook. Agriculture Handbook 668, 

U.S. Department of Agriculture, Washington, DC.

Miller, W.R., J.L. Shari, and E. Baldwin. 1997. 

Quality of irradiated and non-irradiated black 

sapote (Diospyros digyna Jacq.) after storage and 

ripening. Proc. Fla. State Hort. Soc. 110:215-218.

Mohamed, S., B. Taufik, and M.N.A. Karim. 

1996. Effects of modified atmosphere packaging 

on the physiological characteristics of ciku (Arcas

sapota L.) at various storage temperatures. J. Sci. 

Food Agric. 70:231-240. 
549

Pathak, S., and J.V. Bhat. 1952. Studies on the 

microorganisms associated with Achras sapota. J. 

Univ. Bombay 20(5):14-18.

Pathak, S., and J.V. Bhat. 1953. The carbohydrate 

metabolism of Acras sapota fruit. J. Univ. 

Bombay 21(5):11-16, Section A.

Pratt, H.K., and D.B. Mendoza Jr. 1980. Fruit 

development and ripening of the star apple 

(Chrysophyllum cainito L.). HortScience 15:721-

722.

Salunkhe, D.K., and B.B. Desai. 1984. Postharvest 

Biotechnology of Fruits, vol. 2, pp. 387-396. CRC 

Press, Boca Raton, FL.

Shanmugavelu, K., G. Srinivasan, and V.N.M. 

Rao. 1971. Influence of etherel (2-chloroethyle 

phosphonic acid) on ripening of sapota (Achras

zapota L.). Hortic Adv. 8:33-36.

Snowdon, A.L. 1990. Postharvest disease and 

disorders of fruits and vegetables, vol. I. General 

introduction and fruits. CRC Press, Boca Raton 

FL.

Wenkam, N.S., and C.D. Miller. 1965. 

Composition of Hawaii fruits. Bull. 135, Hawaii 

Agricultural Experimental Station, Honolulu, HI.

Yahia, E.M. 1998. Modified/controlled 

atmospheres for tropical fruits. Hort. Rev. 22:123-

183.
550

Southern Pea

Penelope Perkins-Veazie and Blair Buckley

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, NC Research Campus, Kannapolis, 

NC. Buckley is formerly with the Louisiana 

State University Research Station, Calhoun, LA. 

He is now with the Red River Research Station, 

Lousiana State University, Bossier City, LA.

Scientific Name and Introduction

Southern pea, or cowpea, (Vigna unguiculata [L.] 

Walp.) is a native of Africa and is adapted to hot, 

dry climates. The southern pea is not actually a 

pea, and thus differs considerably from the green 

or English pea (Pisum sativum) (Peirce 1987). 

Prized in the southern United States, southern 

peas are rich in folic acid, fiber, and calcium. 

Peas are distinguished by pod color, pea color and 

pattern, and hilum color. Five groups of cultivars 

are recognized on the basis of seed and pod 

coloration and seed packing in pod. They include 

black-eyed (‘California Blackeye No. 5’), cream 

(‘Elite’), purplehull (‘Pinkeye Purple Hull’), 

crowder (‘Mississippi Silver’), and miscellaneous 

other colored, noncrowder peas (‘Dixielee’). 

‘Bettersnap’ was developed specifically for edible 

pods (Fery and Dukes 1995).

Quality Characteristics and Criteria

Some cultivars have edible pods (similar to green 

beans) and should be harvested when the pods 

are 10 to 16 cm (4 to 6 in) long, flexible, and dark 

green. Shelled peas should be a mature size, have 

smooth skin, and exhibit characteristic color. 

Horticultural Maturity Indices

Fresh-market southern peas are harvested when 

the pods are at the mature-green stage (peas are 

fully developed and the majority of the pods have 

undergone a color change). It is acceptable to have 

some pods that have not undergone a complete 

color change (green with some purpling in the 

case of purplehulls) provided the peas are mature 

size. Shelled peas should be light green in color. 

Pea color is affected both by maturity and cultivar. 

Tan or white peas are perceived to be too mature 

(except for cream types). Blackeye cultivars 

exhibit the most difficulty in determining when 

to harvest for fresh use because the color of the 

black hilum does not fully develop until peak 

maturity. The color will be purple to chocolatebrown if harvested early. If southern peas are to be 

harvested for edible pod use, they must be selected 

when quite young and tender—no more than half 

of the expected diameter of mature green pods—

unless it is a cultivar specifically developed for 

edible pod use. 

Grades, Sizes, and Packaging

USDA grades of southern peas are U.S. No. 

1 (95% of pods must be at least 12.5 cm [5 

in] long), and U.S. Commercial (no minimum 

length). Shelled peas are marketed in 4.5- to 

5.4-kg (10- to 12-lb) plastic bags (considered 

the equivalent of a shelled bushel) or in 0.45-kg 

(1-lb) bags. Some large operations package peas 

in vacuum-packed 0.45- and 4.5-kg (1- and 10-

lb) bags. No grades exist for southern peas used 

as snap beans. Fresh southern peas may also be 

sold in the hull by the bushel. A USDA bushel 

is 11.4 kg (25 lbs); however, at the local market 

level the bushel weight varies widely from region 

to region or from 7.3 to 13.6 kg (16 to 30 lbs). 

Pods for shelling are packed primarily in mesh 

bags (cabbage sacks) or wooden bushel baskets 

(becoming less common). 
551

Precooling Conditions

In both shelled and unshelled states, peas are 

very prone to decay if held at room temperature. 

Unshelled peas are best cooled using a forced-air 

system. Contact with water greatly accelerates 

their deterioration. Shelled peas should be blown 

free of foreign material and then hydrocooled in 

a solution of 100 μL L-1 chlorine to remove heat 

quickly, preserve green color, and slow microbial 

growth. Peas to be trucked for processing are 

shelled into field bins where temperatures may 

reach 38 °C (100 °F) (Hardenburg et al. 1986). 

Peas start to yellow and decay after a few hours 

at 25 °C (77 °F). Flavor deterioration and off 

flavor in shelled peas may be a problem if they 

are held for as much as 7 h at 30 °C (86 °F) before 

processing. 

Optimum Storage Conditions

Southern peas in the pod can be held for 6 to 8 

days at 4 to 5 °C (39 to 41 °F) with 95% RH. 

Without refrigeration, they remain edible only 

about 2 days and show extensive decay in 4 to 

6 days. Shelled peas should be held for no more 

than 24 to 48 h at 4 to 5 °C (39 to 41 °F) (Jenkins 

1954).

Controlled Atmosphere (CA) 

Considerations

Effects of CA are unknown.

Retail Outlet Display Conditions

Peas should be kept under high RH and 

refrigerated to slow decay and color loss.

Chilling Sensitivity

Unknown. Southern peas are probably sensitive 

when held at 5 °C (41 °F) or below.

Ethylene Production and Sensitivity

Ethylene production rate is unknown. Southern 

peas are probably sensitive to ethylene with 

effects characterized by yellowing of pods.

Respiration Rates

Temperature Whole pods Shelled peas

------mg CO2 kg-1 h-1--------

2 °C 13 to 36 26 to 33

5 °C 16 to 33 -

20 °C 145 to 151 90 to 161

Data from P. Perkins-Veazie (unpublished) 

from pods 15 to 23 cm long of cultivars ‘Excel,’ 

‘BetterSnap,’ ‘Early Scarlet,’ and ‘Pinkeye Purple 

Hull BVR.’ 

Higher respiration values are for less mature 

(more green) peas and pods.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Brown spots, cracking, and seed-coat splitting are 

problems with pods and peas.

Postharvest Pathology

Very little research has been done on postharvest 

pathogens of southern pea. Botrytis cinerea (gray 

mold) can quickly develop on pods and shelled 

peas (Roland E. Roberts, Texas A&M, 2002, 

personal communication).

Quarantine Issues

There are no known quarantine issues.
552

Suitability as Fresh-Cut Product

Snap pea or yard-long cowpea cultivars, such as 

‘Bettersnap,’ can be used as a fresh-cut product. 

These types must be harvested at the immature 

pod stage.

Special Considerations

Failure to precool shelled peas prior to packaging 

results in condensation in the bags and rapid 

souring and spoiling of the peas. Insect damage 

can create major postharvest grading problems 

due to feeding damage and misshaped peas caused 

by stinkbugs and due to the presence of punctures 

and larvae inside peas as a result of cowpea 

cucurlio. 

References

Fery, R.L., and P.D. Dukes. 1995. ‘Bettersnap’ 

southernpea. HortScience 30:1318-1319.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agricultural Handbook 66, U.S. Department of 

Agriculture, Washington, DC. 

Jenkins, W.F. 1954. Postharvest changes in 

refrigerated and non-refrigerated southern peas. 

Proc. Amer. Soc. Hort. Sci. 64:327-330.

Peirce, L.C. 1987. Legumes-southern pea. In L.C. 

Peirce, Vegetables: Characteristics, Production, 

and Marketing, pp. 345-347. J. Wiley and Sons, 

New York, NY.
553

Sprouts

Jennifer R. DeEll

DeEll is with the Ontario Ministry of Agriculture 

and Food, Simcoe, Ontario, Canada.

Scientific Name and Introduction

Sprouts are young seedlings just after seed 

germination. The most common marketed 

sprout is mung bean (Vigna radiata L. Wilczek; 

syn., Phaseolus aureus Roxb.). Other sprouts 

include alfalfa (Medicago sativa L.); buckwheat 

(Fagopyrum esculentum Moench); green pea 

(Pisum sativum L.); kidney, pinto, and navy bean 

(Phaseolus vulgaris L.); lentil (Lens culinaris

Medik.), mustard (Brassica nigra L. Koch; 

Sinapis alba L.); onion (Allium cepa L.); radish 

(Raphanus sativus L.); red clover (Trifolium 

partense L.); soybean (Glycine max L. Merr.); 

watercress (Nasturtium officinale R.Br.); and 

wintercress (Barbarea vulgaris R.Br.).

Quality Characteristics and Criteria

Fresh mung bean sprouts have crisp white 

hypocotyls and yellow or green cotyledons. 

Symptoms of deterioration include darkening 

of the root and cotyledons, development of 

dark streaks on the hypocotyl, and eventual 

development of sliminess, decay, and a musty 

odor. Sprouts vary in texture and taste: Some are 

spicy (such as radish and onion sprouts); others 

are hardy and often used in Asian foods (such 

as mung bean sprouts); while others are more 

delicate and used in salads and sandwiches to add 

texture and moistness (such as alfalfa sprouts).

Horticultural Maturity Indices

Sprouts are harvested after 1 to 8 days of growth, 

depending on the type and desired plant height 

and width. For example, mung bean sprouts are 

normally harvested after 3 to 8 days when length 

is 1.3 to 7.6 cm (0.5 to 3 in), alfalfa sprouts are 

harvested after 1 to 2 days when length is 2.5 to 

3.8 cm (1 to 1.5 in), and radish sprouts after 2 to 4 

days when length is 1.3 to 2.5 cm (0.5 to 1 in).

Grades, Sizes, and Packaging

There are no established USDA quality standards 

for sprouts. Perforated film packaging helps 

maintain the quality of fresh sprouts by reducing 

water loss. Alfalfa sprouts are marketed in 112- or 

168-g (4- or 6-oz) containers with 12 containers 

per case. Mung bean sprouts are marked in the 

same size containers and in 2.3-kg (5-lb) open 

flats. 

Precooling Conditions

Sprouts should be cooled immediately and held at 

0 °C (32 °F). Vacuum-cooling, hydrocooling, and 

forced-air cooling are common methods.

Optimum Storage Conditions

Sprouts are highly perishable and most last 5 to 10 

days at 0 °C (32 °F) with 95 to 100% RH. Mung 

bean sprouts stored at 0, 2.5, 5 or 10 °C (32, 37, 

41 or 50 °F) reach the lower limit of marketability 

after 8.5, 5.5, 4.5 and 2.5 days, respectively 

(Lipton et al. 1981). The shelf-life of bean sprouts 

held at 0 °C (32 °F), but exposed daily to 20 °C 

(68 °F) for 30 min can be reduced by 50%. Alfalfa 

and radish sprouts stored at 0 °C (32 °F) with 

>95% RH had a shelf-life of 7, and 5 to 7 days, 

respectively (Cantwell 1997).

Controlled Atmosphere Considerations

The shelf-life of mung bean sprouts can be 

increased by storage under MA in which O2

 is 

reduced and CO2

 is increased (Varoquaux et al. 

1996). For instance, they can be held for 4 to 5 

days at 8 °C (46 °F) in packages containing 5% 

O2

 and 15% CO2. Darkening of sprouts is reduced 

and development of sliminess is delayed.
554

Retail Outlet Display Considerations

Sprouts should be held close to 0 °C (32 °F). They 

should not be misted.

Chilling Sensitivity

Sprouts are highly perishable and should be stored 

as cold as possible without freezing. In some 

cases, the cotyledons of mung bean sprouts darken 

more at lower temperatures. However, due to 

faster deterioration at higher temperatures, storage 

at 0 °C (32 °F) is recommended.

Ethylene Production and Sensitivity

Sprouts produce little ethylene. Mung bean 

sprouts produce 0.15, 0.05, 0.24, and 0.90 μL kg-1

h-1 at 0, 2.5, 5, and 10 °C (32, 37, 41 and 50 °F), 

respectively (Lipton et al. 1981).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 23

2.5 °C 29

5 °C 42

10 °C 96

Data from Lipton et al. (1981).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Mung bean sprout hypocotyls darken with age, 

becoming beige to light tan. However, some 

develop light-tan to rusty-brown streaks, mainly 

along the lower portion of the axis (Lipton et al. 

1981). Such streaks may be present at harvest and 

are thought to arise from a group of cells that were 

injured before or during germination. 

Darkening of the radicles and browning of the 

cotyledons are other changes associated with the 

deterioration of mung bean sprouts. Cotyledon 

color in mung bean sprouts may blacken at low 

temperatures, and this may be a symptom of 

chilling injury (DeEll et al. 2000).

Postharvest Pathology

Development of decay, sliminess, and musty odors 

are symptoms of deterioration.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

No current potential exists.

Special Considerations

Sprouts have been associated with human 

pathogenic bacteria, such as Aeromonas 

hydrophila, Escherichia coli O157:H7, Listeria 

monocytogenes, Salmonella spp., and Bacillus 

cereus (Brackett 1999). Therefore, the importance 

of proper storage and handling, along with good 

worker hygiene and sanitation, cannot be stressed 

enough.

Acknowledgments

Some information in this chapter is from the 

International Sprout Growers Association website 

at http://www.isga-sprouts.org. 

References

Brackett, R.E. 1999. Incidence, contributing 

factors, and control of bacterial pathogens in 

produce. Postharv. Biol. Technol. 15:305-311.
555

Cantwell, M. 1997. Properties and recommended 

conditions for storage of fresh fruits and 

vegetables. At http://postharvest.ucdavis.edu/

produce_information/storagefreshproduce.

DeEll, J.R., C. Vigneault, F. Favre, et al. 2000. 

Vacuum cooling and storage temperature 

influence the quality of stored mung bean sprouts. 

HortScience 35(5):891-893.

Lipton, W.J., W.K. Asai, and D.C. Fouse. 1981. 

Deterioration and CO2

 and ethylene production of 

stored mung bean sprouts. J. Amer. Soc. Hort. Sci. 

106:817-820.

Varoquaux, P., G. Albagnac, C. Nguyen-The, 

and F. Varoquaux. 1996. Modified atmosphere 

packaging of fresh bean sprouts. J. Sci. Food. Agr. 

70:224-230.
556

Squash

T. Gregory McCollum

McCollum is with the U.S. Horticultural Research 

Laboratory, Agricultural Research Service, U.S. 

Department of Agriculture, Fort Pierce, FL.

Scientific Name and Introduction

Summer squash are the young fruit of Cucurbita 

pepo. They are members of the Cucurbitaceae 

family. There are six horticultural groups of 

summer squash: cocozelle, crookneck, scallop, 

straightneck, vegetable marrow, and zucchini 

(Paris 1986). Summer squash are cultivated 

throughout the world and is available yearround. Zucchini is the most widely grown and 

economically important summer squash.

Quality Characteristics and Criteria

Tenderness and firmness are the major quality 

characteristics. The surface of summer squash 

should be shiny; dullness is a sign of senescence. 

Fruit should be firm and free of physical injury. 

Dark green types should be entirely green; 

yellowish areas are a sign of senescence. Water 

loss results in a dull surface and loss of firmness.

Horticultural Maturity Indices

Summer squash are harvested up to 1 week after 

anthesis, when they are still shiny. Small fruit 

are more desirable than large fruit because small 

fruit’s flesh and seeds are more tender and slightly 

sweet.

Grades, Sizes, and Packaging

Summer squash are graded U.S. No. 1 and U.S. 

No. 2 (AMS 1984). Summer squash can be 

harvested over a wide range of sizes, from <50 g 

to >400 g (<2 oz to >0.9 lb). Acceptable size is a 

function of the type of squash and market demand. 

Squash may be field-packed directly into shipping 

containers or transported to the packinghouse in 

field boxes or bulk bins for washing and sizing 

before packing. Squash are packed in a variety of 

containers including bushel baskets, wire-bound 

wooden crates, and fiberboard boxes (McGregor 

1987). A plastic liner should be used in all wooden 

containers to prevent abrasion and retard water 

loss.

Precooling Conditions

Room-cooling, forced-air cooling, and 

hydrocooling are acceptable methods for 

removing field heat from summer squash (Lill 

and Read 1982). Prompt precooling after harvest 

reduces the rate of water loss and is essential for 

maximum postharvest life. 

Optimum Storage Conditions

Summer squash are highly perishable and 

not suited for storage longer than 2 weeks 

(Hardenburg et al. 1986). For maximum shelf-life, 

summer squash should be held at 5 to 10 °C (41 to 

50 °F) with 95% RH.

Controlled Atmosphere (CA) 

Considerations

Storage in low-O2

 atmospheres appears to be of 

little or no value for zucchini squash (Mencarelli 

et al. 1983, Leshuk and Saltveit 1990).

Retail Outlet Display Considerations

Summer squash should not be stacked more than 

four layers deep and should be arranged carefully 

so they do not fall off the rack. The display should 

be refrigerated, but direct contact with ice should 

be avoided as it can cause physical damage as well 

as lead to chilling injury.
557

Chilling Sensitivity

Summer squash are chilling sensitive and should 

not be exposed to temperatures below 5 °C (41 

°F) (Ryall and Lipton 1979). However, variation 

in chilling tolerance among summer squash 

types is great (Sherman et al. 1987, Suslow and 

Cantwell 1998). Chilled summer squash show 

surface pitting and decay rapidly at nonchilling 

temperatures, though damage may be absent 

during refrigeration. Chilled fruit have increased 

rates of water loss upon transfer to nonchilling 

temperatures (McCollum 1989).

Ethylene Production and Sensitivity

Summer squash produce low to moderate amounts 

of ethylene: 0.1 to 1.0 μL kg-1 h-1 at 20 °C (68 

°F). The rate of ethylene evolution is greatly 

increased in fruit that have been held at chilling 

temperatures (McCollum 1989). Increased 

yellowing may result if green-skinned summer 

squash are exposed to ethylene (Ryall and Lipton 

1979).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 24 to 26

5 °C 27 to 37

10 °C 65 to 68

15 °C 139 to 167 

20 °C 153 to 175

Data from Hardenburg et al. (1986).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Summer squash are very susceptible to water loss. 

Shriveling may become evident with as little as 

3% weight loss. Precooling and storage at high 

RH minimize weight loss. Squash can be waxed, 

but only a thin coating should be applied. Waxing 

provides some surface lubrication that reduces 

chafing in transit. Summer squash skin is very 

tender; skin breaks and bruises can be a serious 

source of water loss and microbial infection.

Postharvest Pathology

Decay caused by fungal and bacterial pathogens 

can cause significant postharvest losses in summer 

squash. The incidence of decay increases in 

fruit that have physical injury or chilling stress. 

Common postharvest diseases include alternaria 

rot, bacterial soft rot, cottony leak, fusarium rot, 

phythopthora rot, and rhizopus rot. Alternaria rot 

can be especially pronounced following chilling 

injury.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Summer squash is frequently sliced and marketed 

in foam trays overwrapped with polyethylene.

Special Considerations

All types of summer squash are extremely tender 

and are injured by the slightest scratch, bruise, or 

scuff. Yellow and scalloped squash show scuffing 

clearly because the ensuing darkening is obvious 

on a light background. Summer squash should 

be handled gently throughout marketing; sorters 

and packers should wear cotton gloves to prevent 

fingernail cuts.
558

References

AMS [USDA Agricultural Marketing Service]. 

1984. United States Standards for Grades of 

Summer Squash. U.S. Department of Agriculture, 

Agricultural Marketing Service, Washington, DC. 

At http://www.ams.usda.gov/AMSv1.0/standards.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks. 

Agricultural Handbook 66, U.S. Department of 

Agriculture, Washington, DC.

Leshuk, J.A., and M.E. Saltveit. 1990. Controlled 

atmospheres and modified atmospheres for the 

preservation of vegetables. In M. Calderon, ed., 

Food Preservation by Modified Atmospheres, pp. 

315-352. CRC Press, Boca Raton, FL.

Lill, R.E., and A.J. Read. 1982. Storage conditions 

for zucchini. N.Z. Comm. Grow. 37:26.

McCollum, T.G. 1989. Physiological changes in 

yellow summer squash at chilling and nonchilling 

temperatures. HortScience 24:633-635.

McGregor, B.M. 1987. Tropical Products 

Transport Handbook. Agriculture Handbook 668, 

U.S. Department of Agriculture, Washington, DC.

Mencarelli, F., W.J. Lipton, and S.J. Peterson. 

1983. Response of ‘zucchini’ squash to storage in 

low-O2

 atmospheres at chilling and non-chilling 

temperatures. J. Amer. Soc. Hort. Sci. 108:884-

890.

Paris, H.S. 1996. Summer squash: history, 

diversity, and distribution. HortTechnology 6:6-

13.

Ryall, A.L. and W.J. Lipton. 1979. Handling, 

Transportation, and Storage of Fruits and 

Vegetables, vol. 1. AVI, Westport CT.

Sherman, M., H.S. Paris, and J.J. Allen. 1987. 

Storability of summer squash as affected by gene 

B and genetic background. HortScience 22:920-

922.

Suslow, T.V., and M. Cantwell. 1998. Squash 

(soft rind). Recommendations for maintaining 

postharvest quality. At http://postharvest.ucdavis.

edu/produce_information.
559

Strawberry

Elizabeth J. Mitcham

Mitcham is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

Strawberry, Fragaria × ananassa, is a perennial 

of the Rosaceae family. The edible portion, not a 

true berry, is a multiple fruit comprised of many 

achenes (seeds) and receptacle tissue. Fruit are 

produced on short-day and day-neutral plants 

in many growing areas. However, the major 

production in the United States is in California, 

Oregon, and Florida.

Quality Characteristics and Criteria

A high-quality strawberry is uniformly red, firm, 

flavorful, and free of defects and disease. Sugar 

content does not increase after harvest; therefore, 

harvest when fully ripe for best flavor. For 

acceptable flavor, a minimum SSC of 7% and a 

maximum TA of 0.8% are recommended (Kader 

1999).

Horticultural Maturity Indices

Maturity is based on surface color. The U.S. 

minimum is half or three-fourths of the berry’s 

surface showing red or pink color, depending on 

grade. The California minimum is two-thirds of 

the berry’s surface showing red or pink. 

Grades, Sizes, and Packaging

U.S. No. 1 grade consists of strawberries with 

calyx (cap) attached which are firm, not overripe 

or undeveloped, of uniform size, and free of decay 

and damage. Each fruit must have at least threefourths of its surface showing pink or red color. 

U.S. No. 2 grade consists of strawberries free 

from decay or serious damage and with at least 

half of each fruit showing pink or red color. U.S. 

Combination grade is a mixture of U.S. No. 1 and 

2, with at least 80% meeting U.S. No. 1 grade. 

Strawberries are often packaged by pickers in the 

field either into open-mesh baskets or into clear 

clamshell containers of 1 dry pint or 1 dry quart 

capacity. The mesh baskets or clamshells are held 

in a corrugated fiberboard tray holding about 4 to 

5 kg (9 to 11 lb).

Precooling Conditions

Strawberries are extremely perishable, and it is 

important to begin cooling within 1 h of harvest to 

avoid loss of quality and reduction in amount of 

marketable fruit (Maxie et al. 1959). Temperature 

management is the single most important factor 

in minimizing strawberry deterioration and 

maximizing postharvest life. Forced-air cooling 

is highly recommended, though room-cooling is 

used in some cases (Mitchell et al. 1996).

Optimum Storage Conditions

Store at 0 °C (32 °F) with 90 to 95% RH. 

Strawberry fruit can be stored for up to 7 days at 0 

°C (32 °F), depending on disease pressure.

Controlled Atmosphere (CA) 

Considerations

MAP for shipment with 10 to 15% CO2

 reduces 

growth of Botrytis cinerea (Wells and Uota 1970) 

and reduces respiration rate (Li and Kader 1989), 

thereby extending postharvest life. Use of whole 

pallet covers for MA is the most common method 

(Mitchell et al. 1996). Off flavors can develop if 

higher levels of CO2

 are used.

Retail Outlet Display Considerations

Refrigerated display greatly extends shelf-life 

and maintains quality. Covered baskets maintain 

higher RH around berries, reducing water loss and 

shrivel.
560

Chilling Sensitivity

Strawberry fruit are not sensitive to chilling and 

should be stored as cold as possible without 

freezing.

Ethylene Production and Sensitivity

Strawberries produce very low amounts of 

ethylene: <0.1 μL kg-1 h-1 at 20 °C (68 °F). They 

do not respond to ethylene (Mason and Jarvis 

1970). Removal of ethylene from storage air may 

reduce disease development (El-Kazzaz et al. 

1983).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 12 to 20

10 °C 50 to 100

20 °C 100 to 200

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Perhaps because of rapid marketing and very short 

storage, few physiological disorders occur after 

harvest. CO2

 injury, particularly when >15% CO2

is used, is manifested as a bluing of the skin (Ke 

et al. 1991), whitening of inner fruit tissues (Gil et 

al. 1997), and fermentative off flavors.

Postharvest Pathology

Disease is the greatest cause of postharvest loss. 

The most common decay is botrytis rot, also called 

gray mold, caused by Botrytis cinerea (Ceponis 

et al. 1987). This disease can begin preharvest, 

remaining as a latent infection; or it can begin 

postharvest. The fungus continues to grow at 0 °C 

(32 °F), but growth is slow at this temperature. 

Rhizopus rot, caused by Rhizopus stolonifer, is 

another important disease of strawberry. This 

fungus cannot grow at temperatures <5 °C (41 

°F). Postharvest fungicides are not used on 

strawberries; therefore, prompt cooling, storing at 

0 °C (32 °F), preventing injury, and shipping at 0 

°C (32 °F) under high CO2

 are the best methods 

for disease control. Damaged fruit should be 

eliminated from baskets to prevent spread of the 

disease to healthy berries (nesting) (Sommer et al. 

1973). 

Quarantine Issues

Methyl bromide fumigation is routinely used for 

strawberries shipped from the United States to 

Japan and Australia to eliminate live insects. For 

California, two-spotted spider mites and western 

flower thrips are the main pests of quarantine 

concern in exported fruit.

Suitability as Fresh-Cut Product

Strawberries are suitable, and slices have a shelflife of about 7 days at 2.5 °C (37 °F) and 5 days at 

5 °C (41 °F) (Rosen and Kader 1989, Wright and 

Kader 1997). 

Special Considerations

Strawberry fruit are very delicate and easily 

damaged. Since the harvest crew is responsible 

for grading, packing, and gentle handling, their 

training is critical to packing a quality product.

References

Ceponis, M.J., R.A. Cappellini, and G.W. 

Lightner. 1987. Disorders in sweet cherry and 

strawberry shipments to the New York market, 

1972-1984. Plant Dis. 71:472-475.
561

El-Kazzaz, M.K., N.F. Sommer, and R.J. 

Fortlage. 1983. Effect of different atmospheres 

on postharvest decay and quality of fresh 

strawberries. Phytopathology 73:282-285.

Gil, M.I., D.M. Holcroft, and A.A. Kader. 1997. 

Changes in strawberry anthocyanins and other 

polyphenols in response to carbon dioxide 

treatments. J. Agric. Food Chem. 45:1662-1667.

Kader, A.A. 1999. Fruit maturity, ripening, and 

quality relationships. Acta Hort. 485:203-208.

Ke, D., L. Goldstein, M. O’Mahony, and A.A. 

Kader. 1991. Effects of short-term exposure to low 

O2

 and high CO2 atmospheres on quality attributes 

of strawberries. J. Food Sci. 56:50-54.

Li, C., and A.A. Kader. 1989. Residual effects of 

controlled atmospheres on postharvest physiology 

and quality of strawberries. J. Amer. Soc. Hort. 

Sci. 114:629-634.

Mason, D.T., and W.R. Jarvis. 1970. Postharvest 

ripening of strawberries. Hort. Res. 10:125-132.

Maxie, E.C., F.G. Mitchell, and A. Greathead. 

1959. Quality study on strawberries. Calif. Agric. 

13:6,15.

Mitcham, E.J., C.H. Crisosto, and A.A. Kader. 

1996. Strawberry. Recommendations for 

maintaining postharvest quality. At http://

postharvest.ucdavis.edu/produce_information.

Mitchell, F.G., E.J. Mitcham, J.F. Thompson, and 

N. Welch. 1996. Handling strawberries for fresh 

market. Pub. no. 2442, University of California, 

Division of Agriculture and Natural Resources, 

Davis, CA.

Rosen, J.C., and A.A. Kader. 1989. Postharvest 

physiology and quality maintenance of sliced pear 

and strawberry fruits. J. Food Sci. 54 (3):656-659.

Sommer, N.F., R.F. Fortlage, F.G. Mitchell, and 

E.C. Maxie. 1973. Reduction of postharvest losses 

of strawberry fruits from gray mold. J. Amer. Soc. 

Hort. Sci. 98 (3):285-288.

Wells, J.M., and M. Uota. 1970. Germination and 

growth of five fungi in low-oxygen and highcarbon dioxide atmospheres. Phytopathology 

60:50-53.

Wright, K.P., and A.A. Kader. 1997. Effect of 

slicing and controlled-atmosphere storage on the 

ascorbate content and quality of strawberries and 

persimmons. Postharv. Biol. Technol. 10:39-48.
562

Sweet Corn

Jeffrey K. Brecht

Brecht is with the Horticultural Sciences 

Department, University of Florida, Gainesville, 

FL.

Scientific Name and Introduction

Sweet corn (Zea mays L. var. rugosa Bonaf.) is 

an annual grass of the Poaceae (grass) family. 

Traditional varieties are su1 (sugary1) mutants 

that contain about twice the sugar (primarily 

sucrose) content of field corn, as well as 8 to 

10 times more water-soluble polysaccharide. 

The latter imparts a creamy consistency to su1

sweet corn. Other mutants with increased sugar 

content have more recently been used, primarily 

sh2 (shrunken 2), which has at least double the 

sugar content of su1 but almost no water-soluble 

polysaccharide. Less commonly used is su1/se

(sugary-enhancer); se modifies su1 to also double 

the sugar content, but with no loss of watersoluble polysaccharide content (Wann et al. 1997). 

The sh2 mutation inhibits starch biosynthesis 

while se does not. These newer varieties are 

referred to as “supersweet” and have become 

the dominant type in all major U.S. sweet corn 

production regions. The high initial sugar content, 

coupled with inhibited starch synthesis in sh2

varieties, doubles the potential postharvest life 

of sweet corn. However, all supersweet varieties 

remain extremely perishable.

Quality Characteristics and Criteria

High-quality sweet corn has uniform size and 

color (yellow, white, or bicolor); sweet, plump, 

tender, well-developed kernels; and fresh, 

tight, green husks. It is free from insect injury, 

mechanical damage, and decay. Sweetness is the 

most important factor in consumer satisfaction 

(Evensen and Boyer 1986). All sweet corn 

varieties lose sweetness and aroma during storage, 

but the taste of su1 and su1/se varieties becomes 

starchy while sh2 varieties eventually taste watery 

and bland.

Horticultural Maturity Indices

Sweet corn harvest maturity is determined by 

a combination of ear fill, silk drying, kernel 

development, kernel sweetness, and kernel 

tenderness. The appearance of the juice, or 

endosperm, is a good indicator of maturity for su1

and se varieties, in which a milky (not watery or 

doughy) consistency represents proper maturity, 

but not for sh2 varieties, which always have a 

watery endosperm.

Grades, Sizes, and Packaging

Grades include U.S. Fancy; U.S. Fancy, Husked; 

U.S. No. 1; U.S. No. 1, Husked; and U.S. No. 2. 

Grade is based primarily on maturity, freshness, 

and cob length, as well as freedom from various 

injuries and decay. Sweet corn is commonly 

handled in wire-bound wooden crates and less 

commonly in waxed fiberboard cartons or in 

returnable plastic containers. All contain 54 to 

60 ears with a weight of about 19 kg (42 lb). 

Some is prepackaged in polyvinylchloride (PVC) 

film-wrapped trays (Risse and McDonald 1990, 

Aharoni et al. 1996) with the ends of ears trimmed 

and husks partially removed to expose some 

kernels. PVC film is highly permeable to O2

 and 

CO2

 while acting as a moisture barrier.

Precooling Conditions

Sweet corn is often >30 °C (86 °F) when 

harvested, and rapid removal of field heat is 

critical to retard deterioration. Maximum quality 

is retained by precooling corn to 0 °C (32 °F) 

within 1 h of harvest and holding it at 0 °C (32 

°F) during marketing. In practice, cooling to this 

extent is rarely achieved. However, cooling is 

the first step in a good temperature-management 

program. Sweet corn has a high respiration rate, 

which results in a high rate of heat generation. 

Supersweet varieties have respiration rates equal 
563

to that of traditional sweet corn varieties and lose 

sugar as rapidly (Evensen and Boyer 1986, Olsen 

et al. 1991), so cooling is still critical with these 

newer varieties. Sweet corn should not be handled 

in bulk unless copiously iced because it tends to 

heat throughout the pile.

Vacuum-cooling can adequately precool sweet 

corn, but the corn must be first wetted (and topiced after cooling) to minimize water loss from 

husks and kernels (Showalter 1957, Stewart and 

Barger 1960). Crated sweet corn can be vacuumcooled from about 30 °C (86 °F) to 5 °C (41 °F) 

in 30 min. Hydrocooling by spraying, showering, 

or immersion in water at 0 to 3 °C (32 to 38 °F) 

is effective, though it takes longer than vacuumcooling if the sweet corn is packed. Bulk sweet 

corn takes about 60 min to cool from 30 to 5 °C 

(86 to 41 °F) in a well-managed hydrocooler, 

while crated sweet corn takes about 80 min 

(Talbot et al. 1991)—and few if any operators 

leave it in that long. Periodic monitoring of sweet 

corn temperature is needed to ensure proper 

cooling to at least 10 °C (50 °F). Hydrocooling 

nomographs for bulk and crated sweet corn are 

available (Stewart and Couey 1963).

After hydrocooling, top-icing is desirable during 

transport or holding to continue cooling, remove 

the heat of respiration, and keep the husks fresh. 

When precooling facilities are not available, 

sweet corn can be cooled with package ice and 

top ice. Injection of an ice-water slurry (slush ice) 

into cartons was as effective as hydrocooling and 

better than vacuum-cooling in maintaining quality 

(Talbot et al. 1991), probably due to residual ice in 

the cartons, since the cooling rate was slower than 

for the other methods.

Optimum Storage Conditions

Traditional sweet corn varieties are seldom stored 

for more than a few days because of the resulting 

serious deterioration and loss of tenderness and 

sweetness. The loss of sugar is about 4 times as 

rapid at 10 °C (50 °F) than at 0 °C (32 °F). At 30 

°C (86 °F), 60% of the sugar in su1 sweet corn 

can be converted to starch in a single day, while 

only 6% is converted at 0 °C (32 °F). While 

sh2 varieties lose sugar at the same rate as su1

varieties, their higher initial sugar levels keep 

it sweet-tasting longer. For sh2 varieties, water 

loss and pericarp toughening supplant loss of 

sweetness in limiting postharvest life (Brecht et 

al. 1990). The former is minimized by prompt 

cooling, trimming flag leaves and long shanks, and 

maintaining high RH, usually by icing. Denting 

of kernels is promoted by water loss from husk 

leaves (Showalter 1967). A loss of 2% moisture 

may result in objectionable kernel denting. 

Pericarp toughening can also be minimized by 

prompt cooling and by maintaining sweet corn at 

0 °C (32 °F). Under optimum storage conditions, 

the potential postharvest life of sh2 sweet corn is 

>2 weeks.

Controlled Atmosphere (CA) 

Considerations

Increased attention for CA and MAP was spurred 

by an interest in marine transport to export sweet 

corn from the United States to Europe and the Far 

East, which can involve transit times of >2 weeks. 

Injurious atmospheres at 2 °C (35 °F) contain <2% 

O2

 or >15% CO2 (Spalding et al. 1978), resulting 

in fermentation, off flavors, and odors. Reduced 

O2

 and elevated CO2 reduce respiration and slow 

sucrose loss; elevated CO2 also reduces decay and 

maintains green husk color (Spalding et al. 1978, 

Schouten 1993, Aharoni et al. 1996).

Retail Outlet Display Considerations

Sweet corn should be displayed in refrigerated 

cases or with ice.

Chilling Sensitivity

Sweet corn is not chilling sensitive. It should be 

stored as cold as possible without freezing.
564

Ethylene Production and Sensitivity

Sweet corn produces only trace ethylene, and 

exogenous ethylene is not a problem, though high 

ethylene amounts can lead to husk yellowing 

given sufficient exposure time.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 30 to 51

5 °C 43 to 83

10 °C 90 to 120

15 °C 142 to 175

20 °C 210 to 311

25 °C 282 to 435

Data from Tewfik and Scott (1954), Scholz et al. 

(1963), and Robinson et al. (1975).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

There are no significant disorders.

Postharvest Pathology

Decay is not usually a serious problem, but when 

present it typically occurs on the husk and silks. 

Trimming ears can promote decay development on 

the cut kernels and other damaged tissues mainly 

caused by Alternaria alternata (Fr.) Keissler, 

Fusarium moniliforme Sheldon, and Mucor 

hiemalis Wehmer (Aharoni et al. 1996). Thus, 

proper sanitation and temperature management 

are important to minimize decay in trimmed sweet 

corn.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Fresh-cut sweet corn kernels are extremely 

perishable. Their respiration rate is very high, 

several times that of intact ears. Thus, temperature 

control is extremely critical if the kernels are 

to have acceptable shelf-life. Problems during 

handling can include off flavors, microbial 

survival and growth, and discoloration if the 

temperature is not maintained near 0 °C (32 °F). 

Especially troublesome is browning when the 

kernels are cooked. This browning is greater in 

kernels from more mature ears and is correlated 

with temperature, storage duration, and extent of 

physical damage.

References

Aharoni, Y., A. Copel, M. Gil, and E. Fallik. 1996. 

Polyolefin stretch films maintain the quality of 

sweet corn during storage and shelf life. Postharv. 

Biol. Technol. 7:171-176.

Brecht, J.K., S.A. Sargent, R.C. Hochmuth, 

and R.S. Tervola. 1990. Postharvest quality of 

supersweet (sh2) sweet corn cultivars. Proc. Fla. 

State Hort. Soc. 103:283-288.

Evensen, K.B., and C.D. Boyer. 1986. 

Carbohydrate composition and sensory quality of 

fresh and stored sweet corn. J. Amer. Soc. Hort. 

Sci. 111:734-738.

Olsen, J.K., R.E. Giles, and R.A. Jordan. 1991. 

Postharvest carbohydrate changes and sensory 

quality of three sweet corn cultivars. Sci. Hort. 

44:179-189.

Risse, L.A., and R.E. McDonald. 1990. Quality 

of supersweet corn film-overwrapped in trays. 

HortScience 25:322-324.
565

Robinson, J.E., K.M. Browne, and W.G. Burton. 

1975. Storage characteristics of some vegetables 

and soft fruits. Ann. Appl. Biol. 81:339-408.

Scholz, E.W., H.B. Johnson, and W.R. Buford. 

1963. Heat evolution rates of some Texas-grown 

fruits and vegetables. J. Rio Grande Valley Hort. 

Soc. 17:170-175.

Schouten, S.P. 1993. Effect of temperature and 

CA storage on visual quality aspects, sugars, and 

ethanol content of sweet corn. In 6th International 

Controlled Atmosphere Research Conference, 

Ithaca, NY, June 1993, vol. 2, pp. 797-799. 

Northeast Regional Agricultural Engineering 

Service, Cornell University, Ithaca, NY.

Showalter, R.K. 1957. Effect of wetting and top 

icing upon the quality of vacuum cooled and 

hydro-cooled sweet corn. Proc. Fla. State Hort. 

Soc. 70:214-219.

Showalter, R.K. 1967. Sweet corn shelf life as 

affected by trimming and packaging. Proc. Amer. 

Soc. Hort. Sci. 91:881-884.

Spalding, D.H., P.L. Davis, and W.F. Reeder. 

1978. Quality of sweet corn stored in controlled 

atmospheres or under low pressure. J. Amer. Soc. 

Hort. Sci. 103:592-595.

Stewart, J.K., and W.R. Barger. 1960. Effects of 

cooling method and top-icing on the quality of 

peas and sweet corn. Proc. Amer. Soc. Hort. Sci. 

75:470-475.

Stewart, J.K., and H.M. Couey. 1963. Hydrocooling vegetables—a practical guide to 

predicting final temperatures and cooling times. 

Market Research Report 637, U.S. Department of 

Agriculture, Washington, DC.

Talbot, M.T., S.A. Sargent, and J.K. Brecht. 1991. 

Cooling Florida sweet corn. Circular 941, Florida 

Extension Service, Gainesville, FL.

Tewfik, S., and L.E. Scott. 1954. Respiration of 

vegetables as affected by postharvest treatment. J. 

Agr. Food Chem. 2:415-417.

Wann, E.V., C.Y. Lee, M.C. Bourne, and D.L. 

Downing. 1997. Sweet corn. In D. Smith, J. Cash, 

W. Nip, and Y. Hui, eds., Processing Vegetables: 

Science and Technology, pp. 325-354. Technomic, 

Lancaster, PA. 
566

Sweetpotato

Stanley J. Kays

Kays is with the Department of Horticulture, 

University of Georgia, Athens, GA.

Scientific Name and Introduction

The sweetpotato, Ipomoea batatas (L.) Lam., 

is a member of the Convolvulaceae family that 

is grown for its fleshy storage roots. Though 

a perennial, the crop is grown as an annual. 

Sweetpotato is the seventh most important food 

crop in the world. However, in the United States 

it is used primarily as an occasional vegetable. 

Sweetpotato confers a wide range of health 

benefits (Kays and Kays 1998) that have enhanced 

its popularity. The traditional North American 

type of sweetpotato, typified by the cultivars 

‘Beauregard’ and ‘Jewel,’ are deep orange in 

color, moist (soft) in texture, and very sweet when 

cooked. The orange/moist types, however, are not 

preferred in most other areas of the world, nor by 

certain ethnic groups within the United States.

Quality Characteristics and Criteria

Sweetpotato cultivars vary in color (white to 

cream to orange to purple), flavor (sweet to 

nonsweet; mild to intensely flavored), and textural 

properties (firm to very soft). In the United States, 

postharvest conditions that favor a very sweet, 

moist-textured cooked product are desirable.

Horticultural Maturity Indices

The storage roots of sweetpotato do not have a 

developmental stage at which they are mature. 

Rather the roots continue to grow and under 

favorable conditions will enlarge until the 

interior of the root becomes anaerobic or rots. As 

a consequence, the crop is harvested when the 

majority of roots have reached the desired size.

Grades, Sizes, and Packaging

Sweetpotatoes are graded into U.S. Extra No. 1, 

U.S. No. 1, U.S. Commercial, U.S. No. 2, and 

Unclassified. Grading is based largely on size, 

condition, and absence of defects. Desired sizes 

are 8.3 to 8.9 cm (3.25 to 3.5 in) in diameter and 

0.53 to 0.59 kg (18 to 20 oz). During storage, roots 

are handled in 360-kg (800-lb) bulk bins but are 

generally marketed in 18-kg (40-lb) boxes. At the 

retail level, roots are typically displayed loose.

Curing

Roots should be cured immediately after harvest 

at 29±1 °C (84±2 °F) and 90 to 97% RH for 4 to 7 

days (Kushman 1975). During curing, ventilation is 

required to remove CO2

 and replenish O2 because 

roots consume about 63 L tonne-1 day-1 (2 ft3

 ton-1

day-1) of O2

 and release equivalent amounts of CO2. 

Curing heals wounds from harvest and handling, 

helping reduce moisture loss during storage and 

decreasing the potential for microbial decay. 

In addition, curing facilitates the synthesis of 

enzymes that are operative in flavor development 

during cooking (Wang et al. 1998). The effect of 

temperature and RH on the rate of wound healing 

has been extensively investigated (Morris and 

Mann 1955).

During curing, initially the outermost parenchyma 

cells at the wound site desiccate. The subtending 

parenchyma cells subsequently become suberized 

(Walter and Schadel 1983), which is followed by 

formation of a ligninlike wound periderm beneath 

the suberized layer. Roots are adequately healed 

when the wound periderm is 3 to 7 cells thick, the 

status of which can be assessed using a relatively 

simple color test (Walter and Schadel 1982). The 

structure and chemical composition of suberin and 

lignin in both the epidermis and healed wounds 

have been characterized (Walter and Schadel 

1983).
567

Radiation Treatments

Extension of sweetpotato shelf-life via treatment 

with gamma irradiation in general offers no 

advantage over proper storage temperature 

management. 

Optimum Storage Conditions

Following curing, sweetpotatoes should be 

carefully moved, usually in palletized containers, 

to a separate storage room and held at 14±1 °C 

(57±2 °F) with 90% RH (Kushman 1975). Longterm storage experiments have shown that roots 

can be stored successfully under these conditions 

for up to 1 year without sprouting (Picha 1986), 

though sensory quality declines with extended 

storage. Storage room air flow should be 1,125 L 

min-1 tonne-1 (36 ft3

 min-1 ton-1) of roots at optimal 

temperature and RH. Storage at 19 °C (66 °F) 

or above results in considerable sprouting after 

several months of storage and an associated loss in 

root quality and marketability. Storage of roots at 

<12 °C (55 °F) results in chilling injury.

Controlled Atmosphere (CA) 

Considerations

Sweetpotatoes can be stored under CA conditions 

that reduce the rate of respiratory losses and 

increase total sugars (Chang and Kays 1981). 

However, additional research on O2

 and CO2

concentrations, timing, and cultivar requirements 

are needed. Uncured roots have been shown to 

decay rapidly when stored in low O2

; though after 

curing, 2 and 4% O2

 did not appear to be harmful 

(Delate and Brecht 1989). To date, the beneficial 

effects of CA storage have not been shown to 

outweigh the additional expense.

Retail Outlet Display Considerations

Sweetpotatoes are typically displayed loose 

(unpackaged) in unrefrigerated display cases at 

approximately 21°C (70 °F).

Chilling Sensitivity

Sweetpotato roots freeze at -1.9 °C (28.6 °F) 

(Whiteman 1957) and are susceptible to chilling 

injury when stored at <12 °C (55 °F) (Lewis and 

Morris 1956, Picha 1987). Symptoms of chilling 

injury include root shriveling, surface pitting, 

abnormal wound periderm formation, fungal 

decay, internal tissue browning, and hardcore 

formation (Buescher et al. 1975a, Daines et al. 

1976). Synthesis of chlorogenic acid and other 

phenolic compounds has been associated with 

tissue browning symptoms (Walter and Purcell 

1980). 

Hardcore is a physiological disorder in which 

various areas within the root become hard, 

apparently due to cold-induced alterations in 

cellular membranes (Yamaki and Uritani 1972). 

The disorder is not apparent in fresh roots but 

appears after cooking or processing. All cultivars 

appear to be susceptible to hardcore; however, 

there is substantial variation in susceptibility 

among cultivars, and noncured roots appear to be 

more susceptible than cured roots.

The severity of chilling injury depends on the 

temperature and length of exposure below 12 

°C (54 oF). The respiratory rate of roots at 16 °C 

(61 °F), after holding at chilling temperatures, 

increased in relation to the duration of the holding 

period. Lower storage temperature also increased 

respiratory rate after removal from the cold 

storage (Lewis and Morris 1956, Picha 1987). 

Total sugar content of roots stored at 7 °C (45 °F) 

was significantly greater than in those stored at 16 

°C (61 °F), though the effect was highly cultivardependent.

Ethylene Production and Sensitivity

Exposure of sweetpotatoes to ethylene should 

be avoided. Roots exposed to 10 μL L-1 ethylene 

had reduced β-amylase activity (Buescher et al. 

1975b). In addition, ethylene enhances synthesis 

of phenolic compounds and phenolic oxidizing 

enzymes, resulting in increased discoloration. 

The effect, however, requires exposure of roots 
568

to ambient ethylene that would normally not 

be encountered during storage with proper 

ventilation. Therefore, ethylene exposure under 

normal storage conditions is a relatively minor 

concern.

Physiological Disorders

In addition to chilling-induced hardcore, the 

sweetpotato is susceptible to other physiological 

disorders. Roots may be lost during curing 

or storage because of exposure to anaerobic 

conditions before harvest caused by excessive 

moisture (Ahn et al. 1980, Chang et al. 1982). 

Roots may appear sound, only to decompose 

rapidly once in storage, emitting a distinctive 

sour, fermented odor. Pithiness is another 

disorder found in apparently sound roots; it is 

characterized by reduced density and a spongy 

feel when squeezed. Curing and storage conditions 

that promote a high metabolic rate facilitate 

development, as do sprouting in storage and 

exposure to low soil temperatures of 5 to 10 °C 

(41 to 50 °C) before harvest.

Postharvest Pathology

Storage rots are caused by a number of 

microorganisms. Among the more commonly 

encountered are Lasiodiplodia theobromae (Java 

black rot) (synomyous with Botryodiplodia 

theobromae and Diplodia gossypina), Ceratocystis 

fimbriata (black rot), Erwinia chrysanthemi

(bacterial soft rot), Fusarium oxysporum (surface 

rot), Fusarium solani (root rot), Macrophomina 

phaseolina (charcoal rot), Monilochaetes 

infuscans (scurf), and Rhizopus stolonifer (soft 

rot) (for details on etiology, see Clark and Moyer 

1988). Timing of infection varies with the 

organism and field, harvest, and storage conditions 

(Moyer 1982). Black rot, fusarium root rot, scurf, 

and bacterial soft rot can occur preharvest, during 

harvest, and postharvest. In contrast, soft rot 

infections tend to occur at harvest or postharvest, 

while charcoal rot, dry rot, surface rot, and root 

rot occur during harvest. Harvest and postharvest 

pathogens are typically opportunistic pathogens 

that require wounds to gain entry into the root.

Internal cork is a virus-mediated disorder in 

which root tissue develops necrotic lesions during 

storage (Kushman and Pope 1972). The number 

and size of lesions varies widely and increases 

with storage duration and elevated storage 

temperature. Lesions are found primarily in the 

interior, but may also be present on the surface.

Control of postharvest diseases centers on 

prevention, since little can be done once the 

root is infected. During harvest, care must be 

taken to minimize damage to roots and exercise 

proper sanitation. After harvest, roots should 

be cured immediately and then stored at the 

proper temperature. Creating entry wounds via 

mechanical damage during movement from the 

curing room to storage areas should be judiciously 

avoided, as well as after storage during washing, 

sorting, and grading prior to marketing. Washwater should be frequently changed to prevent 

accumulation of inoculum, and the use of calcium 

hypochlorite in the water is recommended. 

Postharvest pesticides, if used, must be applied in 

accordance to State and Federal laws.

Postharvest Entomology

The sweetpotato weevil (Cylas formicarius [F.]) 

(Coleoptera:Brentidae) is a serious storage insect 

pest. Infested roots should not be stored, because 

adequate control measures are unavailable. Fruit 

flies (Drosophila spp.) and soldier flies (Hermetia 

illucens) (Diptera:Stratiomyidae) can be problems 

when there are diseased, soured, or damaged roots 

in storage. Both can be controlled with sanitation 

or appropriate insecticide treatment.

Quarantine Issues

Viruses and the sweetpotato weevil are serious 

quarantine issues. Viral diseases are of concern if 

roots are used for propagation material because 

the disease is transferred in roots and transplants 

(slips) produced from them. Roots from most 
569

production areas can be shipped throughout the 

continental United States, but they may not be 

imported because of the risk of viral diseases.

The sweetpotato weevil is the single most 

devastating insect pest of the crop worldwide and 

is a pest in both field and storage. To date, there 

are no adequate field or storage control measures, 

though CA storage treatments may have promise 

(Delate and Brecht 1989). Roots should not be 

shipped from weevil-infested production sites to 

other areas of the country.

Suitability as Fresh-Cut Product

No current potential.

References

Ahn, J.W., W.W. Collins, and D.M. Pharr. 1980. 

Gas atmosphere in submerged sweet potato roots. 

HortScience 15:795-796.

Buescher, R.W., W.A. Sistrunk, J.L. Bowers, and 

C.F. Boettinger. 1975a. Susceptibility of sweet 

potato lines to development of hardcore, a chilling 

disorder. Ark. Farm Res. 24(6):2.

Buescher, R.W., W.A. Sistrunk, and P.L. Brady. 

1975b. Effects of ethylene on metabolic and 

quality attributes in sweet potato roots. J. Food 

Sci. 40:1018-1020.

Chang, L.A., and S.J. Kays. 1981. Effect of low 

oxygen on sweet potato roots. J. Amer. Soc. Hort. 

Sci. 106:481-483.

Chang, L.A., L.K. Hammett, and D.M. Pharr. 

1982. Ethanol, alcohol dehydrogenase and 

pyruvate decarboxylase in storage roots of four 

sweet potato cultivars during simulated flood 

damage and storage. J. Amer. Soc. Hort. Sci. 

107:674-677.

Clark, C.A., and J.W. Moyer. 1988. Compendium 

of Sweet Potato Diseases. American 

Phytopathological Society, St. Paul, MN.

Daines, R.H., D.F. Hammond, N.F. Haard, and 

M.J. Ceponis. 1976. Hardcore development 

in sweet potatoes. A response to chilling and 

its remission as influenced by cultivar, curing 

temperatures and time and duration of chilling. 

Phytopathology 66:582-587.

Delate, K.M., and J.K. Brecht. 1989. Quality of 

tropical sweetpotatoes exposed to controlledatmosphere treatment for postharvest insect 

control. J. Amer. Soc. Hort. Sci. 114:963-968.

Kays, S.J., and S.E. Kays. 1998. Sweetpotato 

chemistry in relation to health. In Sweetpotato 

Production Systems toward the 21st Century, 

pp. 231-272. Kyushu National Agricultural 

Experiment Station, Miyakonojo, Japan.

Kushman, L.J. 1975. Effect of injury and relative 

humidity during curing on weight and volume 

loss of sweet potatoes during curing and storage. 

HortScience 10:275-277.

Kushman, L.J., and D.T. Pope. 1972. Causes 

of pithiness in sweet potatoes. Tech. Bull. 207, 

North Carolina Agricultural Experiment Station, 

Raleigh, NC. 

Lewis, D.A., and L.L. Morris. 1956. Effects of 

chilling storage on respiration and deterioration 

of several sweet potato varieties. Proc. Amer. Soc. 

Hort. Sci. 68:421-428.

Morris, L.L., and L.K. Mann. 1955. Wound 

healing, keeping quality and compositional 

changes during curing and storage of sweet 

potatoes. Hilgardia 24:143-183.

Moyer, J.W. 1982. Postharvest disease 

management for sweet potatoes. In Proceedings 

of the First International Symposium of the Asian 

Vegetable Research and Development Center, pp. 

177-184. AVRDC, Shanhua, Tainan, Taiwan. 

Picha, D.H. 1986. Weight loss in sweet potatoes 

during curing and storage: contribution of 

transpiration and respiration. J. Amer. Soc. Hort. 

Sci. 111:889-892.
570

Picha, D.H. 1987. Chilling injury, respiration and 

sugar changes in sweet potatoes stored at low 

temperature. J. Amer. Soc. Hort. Sci. 112:497-502.

Walter, W.M. Jr., and A.E. Purcell. 1980. Effect of 

substrate levels and polyphenol oxidase activity 

on darkening in sweet potato cultivars. J. Agric. 

Food Chem. 28:941-944.

Walter, W.M. Jr., and W.E. Schadel. 1982. A rapid 

method for evaluating curing progress in sweet 

potatoes. J. Amer. Soc. Hort. Sci. 107:1129-1133.

Walter, W.M. Jr., and W.E. Schadel. 1983. 

Structure and composition of normal skin 

(periderm) and wound tissue from cured sweet 

potatoes. J. Amer. Soc. Hort. Sci. 108:909-914.

Wang, Y., R.J. Horvat, R.A. White, and S.J. Kays. 

1998. Influence of postharvest curing treatment on 

the synthesis of the volatile flavor components in 

sweetpotato. Acta Hort. 464:207-212.

Whiteman, T.M. 1957. Freezing points of fruits, 

vegetables and florist stocks. Marketing Research 

Report 196, U.S. Department of Agriculture, 

Washington, DC.

Yamaki, S., and I. Uritani. 1974. The mechanism 

of chilling injury in sweet potato. XI. 

Irreversibility of physiological deterioration. Plant 

Cell Physiol. 15:385-388. 
571

Swiss Chard

Fabio Mencarelli

Mencarelli is formerly with the Istituto Tecnologie 

Agroalimentari, University of Tuscia, Viterbo, 

Italy. He is now with the Department of Food 

Science and Technology, University of Viterbo, 

Italy.

Scientific Name and Introduction

Swiss chard (Beta vulgaris L. var. cycla) is a 

biennial plant belonging to Chenopodiacae family. 

The edible parts are the elongated, oval, smooth or 

wrinkled leaves, which can reach 50 cm (20 in) in 

length including the petiole. The prominent petiole 

is white or dark-red. It is a good source of folacin 

(Gami and Chen 1985), vitamin C, and flavonoids 

(Gil et al. 1998).

Quality Characteristics and Criteria

Leaves must be turgid and dark green, with 

the midrib and petiole completely white or red 

depending on the variety. Leaves must not show 

any symptoms of yellowing or browning or have 

soil residue. Harvested leaves with petioles can be 

20 to 50 cm (7.5 to 20 in) long.

Horticultural Maturity Indices

Leaves are periodically hand-harvested beginning 

about 60 days after seeding. The harvest season 

can last 2 to 3 mo in spring and 4 to 6 mo in 

fall and winter. Sometimes the whole plant is 

harvested.

Grades, Sizes, and Packaging

There are no U.S. grade standards for Swiss chard. 

Leaves of similar size and quality are banded 

together and packed loose in waxed cardboard, 

wooden, or plastic boxes. Using plastic film to 

cover packaging reduces water loss.

Precooling Conditions

Room-cooling is often used, but hydrocooling and 

vacuum-cooling result in faster cooling.

Optimum Storage Conditions

Can be stored for 1 to 2 weeks at 0 °C (32 °F) 

with 95 to 98% RH.

Controlled Atmosphere (CA) 

Considerations

Storage can be increased to 1 mo using 2 to 3% 

CO2

 and 10% O2 at -0.5 °C (31 °F) (Tesi 1990).

Retail Outlet Display Considerations

Leaves are very delicate and lose water easily 

if not in plastic liners. Misting with water and 

refrigerated storage are recommended.

Chilling Sensitivity

Swiss chard is not chilling sensitive and should be 

stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Ethylene production is very low: 0.13 to 0.14 μL 

kg-1 h-1 at 20 °C (68 oF). Sensitivity, however, 

is very high. Exposure results in yellowing and 

senescence.

Respiration Rates

Temperature mg CO2 kg-1 h-1

2 °C 18 to 20

20 °C 29

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 
572

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal per tonne per day.

Physiological Disorders

Freezing is a risk during refrigerated storage, 

as are yellowing and browning of leaf margins 

caused by ethylene exposure.

Postharvest Pathology

The most frequent field pathogens are 

Peronospora schachtii Fuckel and Cercospora 

beticola Sacc.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

No current potential exists.

References

Gami, D.B., and T.S. Chen. 1985. Kinetics of 

folacin destruction in Swiss chard during storage. 

J. Food Sci. 50:447-449.

Gil, M.I., F. Ferreres, and F.A. Tomas-Barberan. 

1998. Effect of modified atmosphere packaging on 

the flavonoids and vitamin C content of minimally 

processed Swiss chard. J. Agric. Food Chem. 

46:2007-2012.

Tesi, R. 1990. Bietola da costa. In V. Bianco and 

F. Pimpini, eds., Orticoltura, pp. 323-328. Patron 

Press, Bologna, Italy.
573

Tamarillo

Marita Cantwell

Cantwell is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

The tamarillo or “tree tomato” (Cyphomandra 

betacea [Cav.], or as renamed by Sendtner, 

Solanum betaceum [Cav.]) is a fruit-bearing 

subtropical tree of the Solanaceae family. Fruit are 

smooth-skinned, oval berries capped with a calyx 

and stem. The three main fresh market types are 

based on peel and pulp color: red, dark-red, and 

yellow. The mucilaginous, juicy, seedy pulp has a 

sweet-acid taste reminiscent of the tomato, and the 

fruit are sometimes eaten raw; usually, however, 

they are cooked. Tamarillos can be produced in 

California, but most dark-red tamarillos in U.S. 

markets are imported from New Zealand. 

Quality Characteristics and Criteria

Fruit should be firm and heavy with no decay or 

discoloration. Color should be characteristic of the 

variety. Good quality tamarillos are juicy when 

ripe with moderate sugar content (8 to 10%) and 

TA no higher than 1 to 2%. 

Horticultural Maturity Indices

The best maturity index for tamarillo is peel and 

pulp color. Other indices correlated with skin color 

are changes in firmness, juice content, and SSC. 

For dark-red-skinned types, which progress from 

green to dark purple (color due to chlorophyll and 

anthocyanins) to red, harvesting at the dark purple 

stage is considered best. If fruit are harvested 

green, flavor score, juice content, SSC, and 

color of ripened fruit are inferior to those of fruit 

harvested at the dark-purple stage (Heatherbell et 

al. 1982, El-Zeftawi et al. 1988). 

Grades, Sizes, and Packaging

There are no U.S. grade standards. Fruit are 

typically packed into tray packs in single cartons 

based on four or five fruit size categories.

Precooling Conditions

Room-cooling to storage temperature appears 

to be the only way tamarillo fruit are precooled. 

No guidelines are available regarding maximum 

allowable cooling delays.

Optimum Storage Conditions

Tamarillo fruit can be stored for 4 to 8 weeks 

(plus an additional week for marketing) at 3 to 

5 °C (37 to 40 °F) with 90 to 95% RH (Harman 

and Patterson 1982). Chilling injury occurs if fruit 

are stored below 3 °C (37 °F), and fungal decay 

occurs on the stem and calyx if stored above 

5 °C (40 °F). Storage at 7 °C (45 °F) was superior 

to storage at 0 °C (32 °F) for 35 days, with more 

discoloration of the calyx and stem at 0 °C (32 °F) 

but more decay and firmness loss at 7 °C (45 °F) 

(Espina and Lizana 1991). 

Controlled Atmosphere (CA) 

Considerations

No considerations can be reported at this time.

Retail Outlet Display Considerations

Fruit should be kept cool and dry throughout 

marketing.

Chilling Sensitivity

Tamarillos are sensitive to chilling injury if stored 

below 3 °C (37 °F). Symptoms include pitting and 

a scaldlike browning of the skin, calyx, and stem. 

Discoloration on the peel is observed within 15 

days of storage at 0 °C (32 °F) (Espina and Lizana 

1991).
574

Ethylene Production and Sensitivity

Ethylene production is very low (<0.1 μL kg-1 h-1) 

until fruit begin to senesce (Pratt and Reid 1976). 

Green and partially ripe fruit respond to ethylene 

with increased respiration (Pratt and Reid 1976) 

and accelerated red color development (Prohens 

et al. 1996). Green fruits, however, have less color 

development and lower SSC:TA ratio when ripe 

than fruit harvested partially ripe (Prohens et al. 

1996).

Respiration Rates

The respiration rate is 18 to 36 mg (10 to 20 μL) 

CO2

 kg-1 h-1 at 18 to 20 oC (64.4 to 68.0 oF). Heat 

production is 3,960 to 7,920 BTU ton-1 day-1 or 

1,098 to 2,196 kcal tonne-1 day-1. Data from Pratt 

and Reid (1976) and Espina and Lizana (1991).

Physiological Disorders

Viral diseases attacking tamarillo plants may 

cause mottling on the fruit surface.

Postharvest Pathology

Decay is the single most important cause of 

postharvest losses in tamarillo. The most common 

decay is bitter rot caused by Colletotrichum 

acutatum and C. gloeosporioides. This fungus 

attacks fruit on the tree, but decay does not 

develop until fruits start to ripen or are stored for 

several weeks. A good orchard control program 

with postharvest applications of fungicides can 

control development of the disease (Blank et al. 

1987). Hot water dip of 50 °C (122 °F) for 10 min, 

followed by waxing, is also effective (Yearsley 

et al. 1988). With good decay-control measures, 

storage life may be extended to 10 to 12 weeks at 

3.5 °C (38 °F) (Harman and Patterson 1982).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

No current potential exists.

References

Blank, R.H., H.M. Dance, R.E. Hampton, et al. 

1987. Tamarillo (Cyphomandra betacea): effect of 

field-applied fungicides and postharvest fungicide 

dips on storage rots of fruit. N.Z. J. Exp. Agric. 

15:191-198.

El-Zeftawi, B.M., L. Brohier, L. Dooley, et al. 

1988. Some maturity indices for tamarillo and 

pepino fruits. J. Hort. Sci. 63:163-169.

Espina, S., and L.A. Lizana. 1991. 

Comportamiento de tamarillo (Cyphomandra 

betacea (Cav.) Sendtner) en almacenaje 

refrigerado. Proc. Interamer. Soc. Trop. Hort. 

35:285-290.

Harman, J.E., and K.J. Patterson. 1982. Kiwifruit, 

tamarillos and feijoas. Maturity and storage. 

AgLink HPP 103, Ministry of Agriculture and 

Fisheries, Wellington, N.Z. 

Heatherbell, D.A., M.S. Reid, and R.E. Wrolstad. 

1982. The tamarillo: chemical composition during 

growth and maturation. N.Z. J. Sci. 25:239-243.

Pratt, H.K., and M.S. Reid. 1976. The tamarillo: 

fruit growth and maturation, ripening, respiration, 

and the role of ethylene. J. Sci. Fd. Agric. 27:399-

404.

Prohens, J., J.J. Ruiz, and F. Nuez. 1996. 

Advancing the tamarillo harvest by induced 

postharvest ripening. HortScience 31:109-111.

Yearsley, C.W., B.Y. Huang, H.J.W. McGrath, et 

al. 1988. Red tamarillos (Cyphomandra betacea): 

comparison of two postharvest dipping strategies 

for the control of fungal storage disorders. N.Z. J. 

Exp. Agric.16:359-356.
575

Tamarind

Elhadi M. Yahia

Yahia is with the Facultad de Quimica, 

Universidad Autonoma de Queretaro, Queretaro, 

Mexico.

Scientific Name and Introduction

Tamarind fruit (Tamarindus indica L.; synonyms 

T. occidentalis Gaertn., T. officinalis Hook.) 

are indehiscent, beanlike, curved pods 3 to 

20 cm (1.2 to 7.9 in) long weighing 15 to 20 

g (0.5 to 0.7 oz). Fruit have a scurfy brown, 

woody, fragile shell with brown pulp and 8 to 10 

blackish-brown, hard, shiny seeds (HernandezUnzon and Lakshminarayana 1982a). Fruit are 

about 30% shell, 30% pulp, and 40% seeds. The 

color of the pulp comes from the presence of 

several anthocyanins, of which vitexene is the 

most important (Lewis and Neelakantan 1964). 

There are also fruit with red pulp; these are not 

commonly cultivated. However, the reddish-flesh 

types are distinguished in some regions and are 

regarded as superior in quality. Fruit are eaten at 

the green-mature stage or when the shell pod has 

become brittle and the pulp brown. Tamarind is 

a good source of calcium, phosphorous, and iron 

and an excellent source of riboflavin, thiamin, 

and niacin; but it contains only small amounts of 

vitamins A and C (Bueso 1980). 

Tamarind is of minor importance in the United 

States. The two major types are “sweet-fruited” 

and “acid-flavored.” Tamarind is considered to be 

both the sweetest and the most sour of all fruits—

on a fresh weight basis, mature tamarind pulp 

has 30 to 35% sugar and 12 to 24% TA. Some 

cultivars have sweeter pulp, such as ‘Makham 

Waan’ in Thailand and ‘Manila Sweet’ in Florida 

(Morton 1958). 

Quality Characteristics and Criteria

Both green immature pods and brown ripe pods 

are normally marketed when 5 to 20 cm (2.0 to 7.9 

in) long. 

Horticultural Maturity Indices

Tamarind fruit take about 8 mo from fruit set 

to harvest, and growth is a typical sigmoid type 

(Hernandez-Unzon and Lakshminarayana 1982a). 

As pods mature, skin develops into a brown, 

brittle shell, the pulp turns brown or reddishbrown, and seeds become covered with dry and 

sticky pulp. When fully ripe, the shells are brittle 

and easily broken. Mature fruit can be left on the 

tree for more than 6 mo after ripening without 

significant spoilage; however, birds and insects 

become pests. Fruit should be harvested when the 

moisture content is <20% to facilitate separation 

of the shell from the pulp.

Harvesting

Ripe fruit should be harvested so as to prevent 

improper ripening and difficulties in separation of 

the peel after harvest. Fruit can be pulled off the 

peduncle or cut using scissors (Hernandez-Tuzon 

and Lakshminarayana 1982b). Fruit for immediate 

processing are harvested by pulling pods away 

from the stalk. Some can be harvested by shaking 

the branches, leaving the remaining fruit to fall 

naturally when ripe. In humid climates, fruit are 

readily attacked by beetles and fungi and should 

therefore be harvested before they are fully ripe. 

Dry, ripe fruits are easily cracked, and the pulp 

and fibers separated from the broken shell.

Optimum Storage Conditions

The high SSC:TA and the low water content 

contribute to a long storage life. Tamarind can be 

stored with the skin or as a separated dry pulp. 

Tightly packaged pods can be stored at about 20 

°C (68 °F) for several weeks. The pulp of mature 

tamarind is commonly compressed and packed in 
576

palm leaf mats or plastic bags and stored at 20 °C 

(68 °F). It can be stored for a significant length of 

time when processed into a paste. It can be frozen 

and stored for 1 year, or refrigerated for up to 6 

mo. During storage, the dry, dark-brown pulp 

becomes soft, sticky, and almost black. The pulp 

can be stored for a longer period after drying or 

steaming.

Respiration Rates

Tamarind fruit are nonclimacteric. Maximum 

CO2

 production occurs 4 weeks after fruit set and 

then gradually declines (Hernandez-Unzon and 

Lakshminarayana 1982b).

Postharvest Pathology

Tamarind fruit are very tolerant to pathogens 

and insects, except for occasional incidence of 

scab. This resistance may be due to the low water 

content and high acid and sugar content, as well as 

high polyphenol content in the peel. Ripe fruit are 

susceptible to mold, insects, and birds.

Quarantine Issues

Various weevils and borers can infest the ripening 

pods or stored fruits. Pulp separated from the peel 

is highly susceptible to molds. Tamarind beetle

(Pacymerus [Coryoborus] gonogra) and tamarind 

seed borer (Calandra [Sitophilus] lineris) can 

infest ripening pods and persist in the stored fruits. 

The rice weevil (Sitophilus oryzae), rice moth 

(Corcyra cepholonica), and fig moth (Ephestia 

cautella) can infest fruit in storage.

Suitability as Fresh-Cut Product

Tamarind is not suitable as a fresh-cut product at 

this time.

Special Considerations

Fruit are commonly processed into juices, nectars, 

fruit punch, concentrates, and glaceéd and 

crystallized fruit. The pulp can withstand thermal 

processing without affecting the original flavor 

profile (Bueso 1980).

References

Bueso, C.E. 1980. Soursop, tamarind and chironja. 

In S. Nagy and P.E. Shaw, eds., Tropical and 

Subtropical Fruits: Composition, Properties and 

Uses, pp. 375-406. AVI, Westport, CT.

Hernadez-Unzon, H.Y., and S. Lakshminarayana. 

1982a. Biochemical changes during development 

and ripening of tamarind fruit (Tamarindus indica

L.). HortScience 17:940-942.

Hernadez-Unzon, H.Y., and S. Lakshminarayana. 

1982b. Developmental physiology of tamarind 

fruit (Tamarindus indica L.). HortScience 17:938-

940.

Lewis, Y.S., and S. Neelakantan. 1964. The 

real nature of tamarind anthoxanthin. Curr. Sci. 

15:460.

Morton, J.F. 1958. The tamarind, its food, 

medicinal and industrial uses. Proc. Fla. State 

Hort. Soc. 79:355-366.
577

Taro

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Taro (Colocasia esculenta [L.] Schott) is one 

of the oldest of food crops, widely distributed 

throughout Asia and the Pacific. The plant is also 

known as tannier, malanga, dasheen, eddoe, and 

cocoyam. There is also substantial production in 

Egypt and the Caribbean (O’Hare and Asokan 

1986). There are up to 600 varieties. The root (also 

called a corm or tuber) is consumed, as are the 

petioles and leaves. Corm flesh varies from white 

to yellow and red to purple. The corm is high in 

starch and low in protein and fat. All parts of the 

plant must be cooked prior to eating because of 

the presence of acridity substance(s) associated 

with raphides, needle-shaped crystals of calcium 

oxalate (Paull et al. 1999).

Quality Characteristics and Criteria

There are two main types of taro: the smaller 

segmented root up to 14 cm (5.5 in) long and the 

larger cylindrical root upwards of 35 cm (14 in) 

long and 10 to 15 cm (4 to 6 in) in diameter. Both 

are brown. The corm should have no sprouts and 

be free from cuts, insects, and disease damage. 

The smaller eddoe possesses some degree of 

dormancy, while there is no dormancy in the 

larger taro corms.

Horticultural Maturity Indices

Roots are harvested when they are the size desired 

by the market. Most often this is after they have 

stopped growing and leaves have begun to die 

back 8 to 12 mo after planting. The main corm is 

harvested and smaller coromels removed; diseased 

areas on main corms are excised. In eddoe, the 

coromels are also harvested. Young taro leaves are 

also harvested, bunched, and marketed as a leafy 

vegetable.

Grades, Sizes, and Packaging

There are no U.S. or international standards. 

Corms are graded by size, skin color, shape, and 

flesh texture. They are packed in 22.5-kg (50-lb) 

cartons, crates, or sacks. The small root (dasheen) 

may also be sold in 4.5-kg (10-lb) cartons. 

Precooling Conditions

Taro should be room-cooled to 10 to 14 °C (50 to 

57 °F).

Optimum Storage Conditions

Good ventilation is essential for storage. The 

storage recommendation is 7 to 10 °C (45 to 

50 °F) with 80 to 95% RH for up to 18 weeks. 

However, roots must be eaten within 2 days of 

removal to ambient temperature (Snowdon 1992). 

At 11 to 13 °C (52 to 55 °F), storage life is up to 8 

weeks. At 20 °C (68 °F), storage life is from 2 to 4 

weeks.

Controlled Atmosphere (CA) 

Considerations

There are no published reports on CA and taro. 

However, MAP in polyethylene film bags of the 

related xanthosoma and taro at 27 to 32 °C (81 to 

90 °F) reduces weight loss (Passam 1982).

Retail Outlet Display Considerations

Taro should be displayed dry and should not be 

misted.
578

Chilling Sensitivity

Chilling injury leads to pitting and increased 

postharvest disease.

Ethylene Production and Sensitivity

Taro roots have a very low ethylene production. 

There is no known response of taro roots to 

ethylene application.

Respiration Rates

Respiration rates of taro have not been 

documented.

Physiological Disorders

Chilling injury is a common problem with large 

taro roots. Variation in cooked texture sometimes 

occurs; the cause is unknown.

Postharvest Pathology

Pythium root rot can be a major problem in 

wetland taro. Corm rots can also be associated 

with a complex of microorganisms, including 

Fusarium, Sclerotinia, Erwinia, Botryodiplodia,

and Ceratocystis. These decay organisms are 

associated with field infection through wounds. 

After washing roots to remove soil and then 

cutting out diseased tissue, corms should be dried 

(cured) so that wounds can heal. Curing is best 

done at 20 to 30 °C (68 to 86 °F), followed by 

cooling to control further disease development 

(Snowdon 1992).

Quarantine Issues

Aphids can be a major problem on taro leaves.

Suitability as Fresh-Cut Product

Taro must be cooked before eating.

Special Considerations

Corms are roasted, baked, boiled, or deep-fried. 

Grated, cooked corm is sometimes mixed with 

coconut milk. Corms are boiled, mashed, and 

sieved for poi.

References

O’Hare, S.K., and M.P. Asokan. 1986. Edible 

aroids: botany and horticulture. Hort. Rev. 8:43-

99.

Passam, H.C. 1982. Experiments on the storage of 

eddoes and tannias (Colocasia and Xanthosoma

spp) under ambient conditions. Trop. Sci. 24:39-

46.

Paull, R.E., C.S. Tang, K.C. Gross, and G. Uruu. 

1999. The nature of the taro acridity factor. 

Postharv. Biol. Technol. 16:71-78.

Snowdon, A.L. 1992. Tropical roots and tubers—

cocoyams (tannias and taros). In A.L. Snowdon, 

Color Atlas of Postharvest Diseases and Disorders 

of Fruits and Vegetables, vol. 2, Vegetables, pp. 

350-357. CRC Press, Boca Raton FL.
579

Tomatillo

Marita Cantwell

Cantwell is with the Department of Plant Sciences, 

University of California, Davis, CA.

Scientific Name and Introduction

The tomatillo, or husk tomato, (Physalis ixocarpa

Brot. ex Hornem) is a warm-season vegetable 

of the Solanaceae family. The small, spherical, 

green or green-purple fruit is surrounded by an 

enlarged calyx, or “husk.” As the fruit matures, 

it fills the husk and can split it open by harvest 

time. Tomatillo is the key ingredient in fresh and 

cooked green salsas and other Latin American 

dishes. Tomatillos are available year-round. In the 

United States tomatillo are produced mainly on 

small acreages in California, but large volumes are 

imported from Mexico (Smith et al. 1999). 

Quality Characteristics and Criteria

The freshness and greenness of the calyx (husk) 

are quality criteria. Fruit should be firm and 

bright green, since the color and acidic flavor 

are the main culinary contributions of tomatillos 

(Moriconi et al. 1990, Bock et al. 1995). 

Horticultural Maturity Indices

Tomatillos can be harvested at various stages of 

development. For commercial marketing, they 

should be harvested when fruit are well formed 

and have substantially filled the husk but are still 

bright green. Overmature fruit that are light green 

or yellowing should be avoided, since they are 

sweeter and undesirable for most uses. 

Grades, Sizes, and Packaging

There are no U.S. Grades. Fruit are not usually 

sized before packing. They are packed in 18-kg 

(40-lb) crates (Mexican fruit) or in 4.5-kg (10-lb) 

cartons (U.S. fruit). 

Precooling Conditions

Forced-air cool or room-cool to retain fresh 

appearance of the husk. 

Optimum Storage Conditions

Tomatillos can be stored under a wide range 

of conditions. At ambient temperatures, the 

husks will dry, but the fruit will remain in good 

condition for about 1 week. The freshness of fruit 

and husk can be extended by storage at 5 to 10 °C 

(41 to 50 °F) with 80 to 90% RH. Chilling injury 

can occur after 3 weeks at 5 °C (41 °F).

Controlled Atmosphere (CA) 

Considerations

No information is available. 

Retail Outlet Display Considerations

Tomatillos should be kept cool to reduce water 

loss and minimize superficial decay. They should 

not be misted.

Chilling Sensitivity

Tomatillos can be stored for 1 mo at 10 °C (50 

°F) without developing chilling injury symptoms. 

Fruit begin to show symptoms (surface pitting and 

decay) after 3 weeks at 5 °C (41 °F); symptoms 

become more pronounced at 2.5 °C (37 °F).
580

Ethylene Production and Sensitivity

Immature tomatillos produce low amounts of 

ethylene: 0.5 to 2.0 μL kg-1 h-1 at 10 to 20 °C 

(50 to 68 °F). More mature fruit produce greater 

amounts: 1 to 10 μL kg-1 h-1. Ethylene production 

can be high, 20 to 40 μL kg-1 h-1 at 20 °C (68 °F), 

in overmature fruit (that is, fruit showing color 

changes due to ripening). Exposure of mature 

fruit to ethylene causes undesirable color changes 

(Cantwell et al. 1992). 

Respiration Rates

Respiration rates remain relatively constant during 

storage at 5 and 10 °C (41 to 50 °F); rates decrease 

during storage at 20 °C (68 °F). Respiration rates 

of developing fruit are about 25% higher than 

those of mature fruit.

Temperature mg CO2 kg-1 h-1

5 °C 12 to 14

10 °C 13 to 19

20 °C 27 to 36

Data for mature-green fruit from Cantwell et al. 

(1992).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

See Chilling Sensitivity.

Postharvest Pathology

Chilling injury can encourage the development 

of black mold caused by Alternaria alternata, the 

same organism often found on chill-injured red 

tomatoes. Superficial molds occur on the husk 

during storage under high RH, but they have not 

been identified. Washing in chlorinated water 

reduces superficial mold growth, but this may be 

difficult to implement commercially since it is 

difficult to remove all moisture inside the husk. 

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Not suitable for fresh-cut product at this time. 

References

Bock, M.A., J. Sanchez-Pilcher, L.J. McKee, and 

M. Ortiz. 1995. Selected nutritional and quality 

analyses of tomatillos (Physalis ixocarpa). Plant 

Foods Human Nutr. 48:127-133.

Cantwell, M., J. Flores-Minutti, and A. TrejoGonzález. 1992. Developmental changes and 

postharvest physiology of tomatillo fruits 

(Physalis ixocarpa Brot.). Sci. Hort. 50:59-70.

Moriconi, D.N., M.C. Rush, and H. Flores. 

1990. Tomatillo: a potential vegetable crop for 

Louisiana. In J. Janick and J.E. Simon, eds., 

Advances in New Crops: Research, Development, 

Economics, pp. 407-413. Timber Press, Portland, 

OR.

Smith, R., M. Jimenez, and M. Cantwell. 1999. 

Tomatillo production in California. Pub. no. 7246, 

University of California, Division of Agriculture 

and Natural Resources, Davis, CA.
581

Tomato

Steven A. Sargent and Celso L. Moretti

Sargent is with the Horticultural Sciences 

Department, University of Florida, Gainesville, 

FL; Moretti is with EMBRAPA, National 

Vegetable Crop Research Center, Brasilia, Brazil.

Scientific Name and Introduction

Tomato (Solanum lycopersicum L.) is a warmseason crop with origins in elevated regions of 

Peru and Ecuador. A member of the Solanaceae 

family, tomato is the second most produced 

vegetable in the United States, behind the potato. 

The round, red-fleshed tomato predominates in the 

fresh market, but red- and yellow-fleshed round, 

plum (roma), cluster, cherry, grape, and minipear 

types are also available. Domestic production is 

year round, though winter and spring imports from 

Mexico are increasing. Most tomatoes are grown 

in the field, but the use of protected culture is on 

the rise around the world. Dominant suppliers of 

greenhouse-grown tomatoes to U.S. markets are 

Holland, Spain, Israel, and Canada.

Quality Characteristics and Criteria

High-quality fruit have a firm, turgid appearance; 

uniform and shiny color; and no signs of 

mechanical injury, shriveling, or decay. Principal 

causes for postharvest losses are decay, external 

damage incurred during harvest and handling, and 

harvest at an improper maturity stage. 

Horticultural Maturity Indices

Depending on the market and production area, 

tomatoes are harvested at stages of maturity 

ranging from physiological maturity (maturegreen stage) through full-ripe. Immature tomatoes 

are available for certain regional dishes. It is 

difficult to accurately determine the completion 

of physiological maturity. Depending on the 

growing area and time of harvest, the percentage 

of immature tomatoes (M-1) in lots of greenharvested tomatoes can range from 20 to 80% 

(Sargent and VanSickle 1996). Tomatoes harvested 

at the mature-green stage (M-3 or M-4) will ripen 

to high quality if handled properly (Maul et al. 

1998). Tomatoes harvested at the M-2 stage will 

ripen to moderate quality, while those harvested 

at M-1 stage will not ripen to acceptable levels of 

quality.

Maturity Internal appearance

 stage (equatorial section)

M-1 Seeds immature (white) and can be 

cut when the tomato is sliced; no 

 gel in the locule.

M-2 Seeds mature (tan); gel formation in 

at least two locules.

M-3 Seeds pushed aside when tomato 

sliced; all locules have gel; internal 

color is still green.

M-4 Appearance of red color in gel and 

pericarp tissue.

Adapted from Kader and Morris (1976).

Ripeness stages are defined according to the 

following standards for red-fleshed tomatoes 

(AMS 1991):

Ripeness External color

 stage

(1) Green Fruit surface is completely green; 

the shade of green may vary from 

light to dark.

(2) Breaker There is a definite break in color 

from green to tannish-yellow, pink, 

or red on not more than 10% of the 

surface.

(3) Turning 10 to 30% of the surface is not 

 green; in the aggregate, shows a 

definite change from green to 

 tannish-yellow, pink, red, or a 

combination thereof.

(4) Pink 30 to 60% of the surface is not 

green; in the aggregate, shows pink 

or red color.
582

(5) Light red 60 to 90% of the surface is not 

 green; in the aggregate, shows 

 pinkish-red or red.

(6) Red More than 90% of the surface is not 

 green; in the aggregate, shows red 

 color.

Tomato Color Standards are based on the USDA 

Visual Aid TM-L-1, which consists of a chart 

containing twelve color photographs illustrating 

the color classification requirements.

Grades, Sizes, and Packaging

Grades for field-grown tomatoes include U.S. 

No. 1, U.S. , No. 2, U.S. Combination, and No. 3, 

with tolerances established for defects at shipping 

point and en route or at destination (AMS 1991). 

Fruit within a grade should have similar varietal 

characteristics and be uniformly mature, not 

overripe or soft, clean, well developed, fairly 

well formed, fairly smooth, and uniform in 

color. Fruit should be free from decay, freezing 

injury, sunscald, and damage caused by bruising, 

discoloration, sunken scars, cuts and broken 

skins, puffiness, catfaces, other scars, radial or 

concentric growth cracks, and hail or insect injury. 

Tomatoes are rigorously sized with a 0.8 mm 

(1/32-in) overlap permitted between sizes, 

according to the following dimensions (AMS 

1991):

Size Minimum Maximum 

 diameter1 diameter2

Small 5.40 cm (2 4/32 in) 5.79 cm (2 9/32 in)

Medium 5.72 cm (2 8/32 in) 6.43 cm (2 17/32 in)

Large 6.35 cm (2 16/32 in) 7.06 cm (2 25/32 in)

Extra 7.00 cm (2 24/32 in)

 large

1

 Will not pass through a round opening of the 

designated diameter when tomato is placed 

with the greatest transverse diameter across the 

opening.

2

 Will pass through a round opening of the 

designated diameter in any position.

Field-grown tomatoes are typically packed in 

lidded, 11.4-kg (25-lb) cartons, 30×40×24 cm 

(12×16×9.5 in) (W×L×H), that stack 10 cartons 

per layer on a 100×120 cm (40×48 in) pallet. 

Grades for greenhouse tomatoes include U.S. No. 

1 and No. 2 (AMS 2007). Ripeness stages and 

defects are similar to field-grown tomatoes. These 

fruit are sized as follows:

Size Weight

Small <99.4 g (<3.5 oz)

Medium 99.4 to 256 g (3.5 to 9 oz)

Large >256 g (>9 oz)

Greenhouse-grown tomatoes are generally 

harvested at turning stage or later and packed 

according to ripeness and size (count) in singleor double-layer cartons, with or without bottom 

trays. Cluster tomatoes are usually picked when 

the least mature tomato begins to show red 

color. Uniformity of fruit color, stem freshness, 

and fruit attachment to the stem are important 

quality characteristics for this tomato type. 

Cluster tomatoes are usually packed in singlelayer cartons but sometimes in netted bags. Foam 

bottom pads may be inserted to reduce abrasion 

and bruising.

There are currently no U.S. grade standards for 

other types of tomatoes. They are all typically 

harvested once ripening has started and are sorted 

by defect and color. Roma-type tomatoes are 

normally packed in 11.4-kg (25-lb) cartons by 

color, while cherry, grape, and minipear tomatoes 

are packed in 227- to 454-g (8- to 16-oz) baskets 

or clamshell containers and placed in larger master 

cartons to facilitate palletizing.

Precooling Conditions

Following commercial packing, tomatoes are 

routinely palletized and cooled to 20 °C (68 °F) 

for ripening or to 12 °C (54 °F) for storage. While 

room-cooling is common, forced-air cooling is 

more uniform and produces better quality fruit. 

Packed, palletized tomatoes with pulp temperature 

of 28 °C (83 °F) actually increased 2 °C (4 °F) 
583

immediately after being stored at 20 °C (68 

°F), and only cooled to 23 °C (73 °F) after 24 

h using room-cooling (Brecht 1996). However, 

with forced-air cooling, tomatoes cooled to 20 

°C (68 °F) in 2.5 h and ripened more uniformly 

throughout the pallet than those room-cooled.

Optimum Storage Conditions

Optimal storage temperatures depend on the 

maturity stage of the tomatoes. Ideal conditions 

for ripening are 19 to 21 °C (66 to 70 °F) with 90 

to 95% RH. Storage at temperatures >27 °C (81 

°F) reduces intensity of red color, while storage 

at <13 °C (55 °F) retards ripening and can lead 

to development of chilling injury, particularly in 

tomatoes at the mature-green stage. Red tomatoes 

can be stored at 7 °C (45 °F) for a couple of days, 

though tomatoes stored at 10 °C (50 °F) were 

rated lower in flavor and aroma than those held at 

13 °C (55 °F) (Maul et al. 2000).

Controlled Atmosphere (CA) 

Considerations

Tomatoes can be stored under CA to extend 

product quality (see below). The exact 

combination of CO2

 and O2 varies among maturity 

stages and cultivars; but a satisfactory CA is 

3% O2

 and 2% CO2 (Wills et al. 1998). Storage 

under CA delays quality loss as measured by 

several factors, such as lycopene synthesis and 

sugar and chlorophyll degradation (Goodenough 

and Thomas 1980, Nakhasi et al. 1991). Storage 

in 3% O2

 and 97% N2 extended postharvest life 

of mature-green tomatoes for 6 weeks at 13 °C 

(55 °F) without the development of off flavors 

(Parsons et al. 1970). Storage under CA may 

reduce development of undesirable symptoms 

caused by mechanical injury (Kader 1986). 

However, Moretti et al. (1999) observed that CA 

storage did not alleviate development of internal 

bruising (disruption of locular gel ripening) 

following impacts. 

Retail Outlet Display Considerations

Tomatoes are normally displayed at the retail 

level in single-layer, corrugated cartons or in 

plastic clamshell containers at about 20 °C (68 

°F). Grading, sizing, and packing fruit adds 

value and convenience to the final product. An 

important issue in the marketing of high-quality 

tomatoes is uniformity of size, grade, firmness, 

and color. Consumers tend to avoid packages 

of fruit with different colors, decay, or external 

blemishes. Some distributors also offer tomatoes 

in bulk containers, giving the consumer the option 

to choose among different maturities, sizes, and 

types of tomato. However, since tomato fruit are 

sensitive to compression stress, care must be taken 

to avoid overloading the display.

Chilling Sensitivity

Tomato fruit are chilling sensitive, and the 

recommended storage temperature varies with 

the maturity stage. Mature-green fruit will ripen 

normally at 13 to 21 °C (55 to 70 °F). On the other 

hand, ripe tomato fruit can be stored at 10 °C (50 

°F) without visible symptoms of chilling injury, 

though flavor and aroma are negatively affected 

(Maul et al. 2000). Visual symptoms of chilling 

injury include pitting, nonuniform ripening, and 

storage decays (see Postharvest Pathology) (Wills 

et al. 1998).

Ethylene Production and Sensitivity

Tomato fruit produce moderate amounts of 

ethylene: 1 to 10 μL kg-1 h-1 at 20 °C (68 °F). 

Tomatoes are sensitive to ethylene exposure: As 

little as 0.5 μL L-1 ethylene is sufficient to trigger 

Ripeness stage Temperature O2(%) CO2(%) Benefit

Mature green 12 to 20 °C 3 to 5 2 to 3 slight

Red 10 to 15 °C 3 to 5 3 to 5 moderate

Data from Saltveit (1997).
584

ripening and other associated metabolic processes 

(Abeles et al. 1992). For commercial ripening, 

green tomatoes should be held at 20 to 21 °C (50 

to 52 °F) with 90% RH and 50 μL L-1 ethylene; 

this will promote uniform ripening. Upon reaching 

breaker stage, tomatoes produce sufficient 

ethylene and no longer require gassing. Highest 

quality tomatoes are those reaching the breaker 

stage within 3 days of ethylene exposure. These 

fruit were harvested at the mature green stage 

and will ripen with quality similar to tomatoes 

harvested at the breaker stage or later (Maul et al. 

1998).

Respiration Rates

Tomatoes are climacteric and show a pronounced 

increase in respiration during ripening. The 

intensity and duration of the climacteric varies 

among cultivars (Wills et al. 1998). Respiration 

also varies with temperature and atmospheric 

composition.

Temperature Air* 3% O2 /97% N2

†

mg CO2 kg-1 h-1

10 °C 13 to 16 6

15 °C 16 to 28 -

20 °C 28 to 41 12

25 °C 35 to 51 -

*Data from Scholz et al. (1963). Storage at 10 

°C (50 °F) is only recommended for red-ripe 

tomatoes.

†Data from Robinson et al. (1975).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Blotchy ripening is characterized by randomized 

development of green or green-yellowish areas 

on the surface of red tomato fruit. Apparently 

the development of this disorder is related to the 

availability of potassium and inorganic nitrogen 

in the soil. Areas showing blotchy ripening have 

less organic acids, SSC, and starch (Moretti et al. 

2000).

Sunburn is associated with excessive exposure 

to sunlight and the resultant elevated tissue 

temperature during fruit development, disrupting 

lycopene synthesis and resulting in the appearance 

of yellow areas that remain during ripening.

Blossom-end rot involves a calcium deficiency 

caused by either poor uptake or poor translocation 

into the fruit. Symptoms begin in the green fruit 

as a small discoloration at the blossom end that 

increases in size and becomes dry and dark brown. 

Occurrence increases dramatically when calcium 

levels in the soil system drop below 0.08% 

(Moretti et al. 2000). Eventually, secondary decay 

organisms colonize weakened tissues.

Graywall is noticeable as necrotic vascular tissue 

in the pericarp fruit wall (Jones et al. 1999). It 

begins developing at the green stage and has been 

associated with marginal growing conditions such 

as cool weather, low light levels, poor nutrition, 

saturated soils, tobacco mosaic virus, and bacteria; 

however, the cause is still undetermined. Graywall 

can be a serious disorder in both field and 

greenhouse production systems.

Irregular ripening is characterized by the 

appearance of nonuniform ripening and white 

internal tissue. It has been associated with feeding 

of sweetpotato whitefly (Bemisia argentifolii) on 

tomato fruit (Hanif-Khan et al. 1997).

Internal bruising is recognized by the appearance 

of yellow to green locular gel in ripe tomatoes. 

It is caused by an impairment of normal ripening 

of the locular gel following a physical impact at 

the green or breaker stage of ripeness (MacLeod 

et al. 1976). Fruit with internal bruising show 

significant reductions in vitamin C content, TA, 

consistency, and total carotenoids (Moretti et al. 

1998). Besides altering quality attributes, internal 

bruising also affects flavor (Moretti et al. 2002). 

Breaker-stage tomatoes are more sensitive to 

internal bruising than those handled at the green 

stage (Sargent et al. 1992).
585

Postharvest Pathology

Tomatoes are susceptible to numerous fruit decays 

from the field through postharvest handling. 

Postharvest decay often develops in wounds and 

bruised tissue and during fruit softening. Sound 

tomatoes can be inoculated by plant pathogens 

via cross-contamination from diseased fruit, dirty 

harvest containers, and poorly sanitized water 

handling systems and packing line components. 

Populations of decay pathogens can be adequately 

controlled through a regular sanitation program 

in the field and during handling, packing, and 

ripening-storage operations. 

Causes of bacterial decay include soft rot (Bacillus 

spp., Erwinia carotovora ssp., Pseudomonas spp., 

and Xanthomonas campestris) and lactic acid 

decay (bacterial sour rot) (Lactobacillus spp. and 

Leuconostoc mesenteroides) (Bartz et al. 1995, 

Conn et al. 1995). 

Fungal decay sources include alternaria rot (black 

rot) (Alternaria alternata), fusarium rot (Fusarium

spp.), gray mold rot (Botrytis cinerea), mucor 

rot (Mucor mucedo), phoma rot (Phoma ssp.), 

phomopsis rot (Diaporthe spp.), phytophthora rot 

(buckeye rot) (Phytophthora spp.), pleospora rot 

(Pleospora herbarum, Stemphylium botryosum 

imp. stage), rhizopus rot (Rhizopus stolonifer, 

R. oryzae), ring rot (Myrothecium roridum),

sclerotium rot (Sclerotium rolfsii), sour rot 

(Geotrichum candidum), target spot (Corynespora 

cassiicola), and watery soft rot (Sclerotinia 

minor, S. sclerotiorum). Tomato spotted wilt virus 

induces a mottled coloration at red stage. 

(Information adapted from Jones et al. [1991] and 

Snowdon [1992].)

Quarantine Issues

Tomato fruit are a host for fruit flies and are 

subject to inspection in quarantined areas. Methyl 

bromide has been employed on a wide range of 

fruits and vegetables; however, its use is being 

phased out. Tomatoes have a phytotoxic response, 

characterized by delayed ripening and reduced 

sensitivity to exposure to ethylene (Brecht 1994). 

Vapor heat and hot water treatments are effective 

alternatives to treatment with methyl bromide.

Suitability as Fresh-Cut Product

Despite efforts to commercialize fresh-cut 

tomatoes, such products are still only available 

in limited quantities to the food-service industry, 

particularly fast-food restaurants and catering 

services. After processing, loss of the gel-like 

locule tissue, desiccation, water-soaking, and the 

development of decay are the principal constraints 

challenging the worldwide fresh-cut industry. 

Crossing commercial varieties with mutants that 

express delayed softening and slicing less ripe 

tomatoes (in the breaker stage, for instance) for 

subsequent application of ethylene are strategies 

being researched in different parts of the world 

to obtain a fresh-cut tomato with sufficient 

postharvest life to be readily commercialized. 

Mature-green sliced tomatoes ripen normally at 20 

°C (68 °F) (Mencarelli and Saltveit 1988). Sliced 

red tomatoes maintain good quality for 14 days 

when stored in MAP at 5 °C (Hong and Gross 

2001).

Special Considerations

Ethylene used to ripen tomatoes can be 

catalytically generated from ethanol using 

commercially available units or supplied from 

compressed cylinders. Because air mixtures of 

3 to 32% ethylene are explosive (Abeles et al. 

1992), ethylene for ripening rooms is supplied 

from a compressed cylinder containing a <3% 

ethylene in N2

. A metered flow of ethylene from 

either a catalytic unit or compressed cylinder is 

used to produce a diluted, active concentration of 

ethylene in the ripening room.

Acknowledgments

The authors wish to thank Jerry A. Bartz, Plant 

Pathology Department, University of Florida, 

Gainesville, for assistance with the Postharvest 

Pathology section.
586

References

Abeles, F.B., P.W. Morgan, and M.E. Saltveit. 

1992. Ethylene in Plant Biology, 2nd ed. Acad. 

Press, Waltham, MA.

AMS [USDA Agricultural Marketing Service]. 

2007. United States standards for grades of 

tomatoes on the vine. At http://www.ams.usda.

gov/AMSv1.0/getfile?dDocName=STELPR

DC5065392

AMS [USDA Agricultural Marketing Service]. 

1991. United States standards for grades of fresh 

tomatoes. At http://www.ams.usda.gov/standards/

tomatfrh.pdf.

Bartz, J.A., N.C. Hodge, Y. Perez, and D. 

Concelmo. 1995. Two different bacteria cause 

a decay in tomatoes that is similar to sour rot. 

Phytopathology 85:1123.

Brecht, J.K. 1994. Vegetables. In R.E. Paull and 

J.W. Armstrong, eds., Insect Pests and Fresh 

Horticultural Products: Treatments and Responses, 

pp. 309-328. CAB International, Wallingford, 

U.K.

Brecht, J.K. 1996. Tomato response to ethylene 

at high temperatures: are pressure ripening 

systems worth considering? In C.S. Vavrina, ed., 

Proceedings of the Florida Tomato Institute, pp. 

11-13. Pub. no. PRO 108, University of Florida, 

Institute of Food and Agricultural Science, 

Gainesville, FL.

Conn, K.E., J.M. Ogawa, B.T. Manji, and J.E. 

Adaskaveg. 1995. Leuconostoc mesenteroides

subsp. mesenteroides, the first report of a coccoid 

bacterium causing a plant disease. Phytopathology 

85:593-599.

Goodenough, P.W., and T.H. Thomas. 1980. 

Comparative physiology of field grown tomatoes 

during ripening on the plant or retard ripening in 

controlled atmospheres. Ann. Appl. Biol. 94:445-

455.

Hanif-Khan, S., R.C. Bullock, P.J. Stoffella, et al. 

1997. Possible involvement of altered gibberellin 

metabolism in the induction of tomato irregular 

ripening in dwarf cherry tomato by silverleaf 

whitefly. J. Plant Growth Reg. 16(4):245-251.

Hong, J.H., and K.C. Gross. 2001. Maintaining 

quality of fresh-cut tomato slices through modified 

atmosphere packaging and low temperature 

storage. J. Food Sci. 66(7):960-965.

Jones, J.B., J. Jones, R. Stall, and T. Zitter. 1991. 

Compendium of Tomato Diseases. APS, St. Paul, 

MN.

Kader, A.A. 1986. Biochemical and physiological 

basis for effects of controlled and modified 

atmospheres on fruits and vegetables. Food 

Technol. 40(5):99-104.

Kader, A.A., and L.L. Morris. 1976. Correlating 

subjective and objective measurements of 

maturation and ripeness of tomatoes. In

Proceedings of the 2nd Tomato Quality Workshop. 

Vegetable Crop Series no. 178, University of 

California, Davis, CA.

MacLeod, R.F., A.A. Kader, and L.L. Morris. 

1976. Stimulation of ethylene and CO2

 production 

of mature-green tomatoes by impact bruising. 

HortScience 11(6):604-606.

Maul, F., S.A. Sargent, M.O. Balaban, et al. 1998. 

Aroma volatile profiles from ripe tomato fruit are 

influenced by physiological maturity at harvest: 

an application for electronic nose technology. J. 

Amer. Soc. Hort. Sci. 123(6):1094-1101. 

Maul, F., S.A. Sargent, C.A. Sims, et al. 2000. 

Recommended commercial storage temperatures 

affect tomato flavor and aroma quality. J. Food 

Sci. 65(7):1228-1237.

Mencarelli, F., and M.E. Saltveit. 1988. Ripening 

of mature-green tomato fruit slices. J. Amer. Soc. 

Hort. Sci. 113(5):742-745. 
587

Moretti, C.L., E.A. Baldwin, S.A. Sargent, 

and D.J. Huber. 2002. Internal bruising alters 

aroma volatile profiles in tomato fruit tissues. 

HortScience 37(2):378-382.

Moretti, C.L., A.G. Calbo, and G.P. Henz. 2000. 

Postharvest physiology and handling. In J.B.C. 

Silva and L.B. Giordano, eds., Processing 

Tomatoes, p.136-143. Embrapa/SCT, Brasilia, 

Brazil.

Moretti, C.L., S.A. Sargent, D.J. Huber, et 

al. 1998. Chemical composition and physical 

properties of pericarp, locule and placental tissues 

of tomatoes with internal bruising. J. Amer. Soc. 

Hort. Sci. 123(4):656-660.

Moretti, C.L., S.A. Sargent, D.J. Huber, et 

al. 1999. Delayed ripening does not alleviate 

symptoms of internal bruising in tomato fruit. 

Proc. Fla. State Hort. Soc. 112:169-171.

Nakhasi, S., D. Schlimme, and T. Solomos. 1991. 

Storage potential of tomatoes harvested at the 

breaker stage using modified atmosphere storage. 

J. Food Sci. 56(1):55-59.

Parsons, C.S., R.E. Anderson, and R.W. Penney. 

1970. Storage of mature-green tomatoes in 

controlled atmospheres. J. Amer. Soc. Hort. Sci. 

95:791-794.

Robinson, J.E., K.M. Browne, and W.G. Burton. 

1975. Storage characteristics of some vegetables 

and soft fruits. Ann. Appl. Biol. 81:399-408. 

Saltveit, M.E. 1997. A summary of CA and MA 

requirements and recommendations for harvested 

vegetables. In M.E. Saltveit, ed., 7th International 

Controlled Atmosphere Research Conference, July 

13-18, 1997, University of California, Davis, vol. 

4, pp. 98-117. University of California, Davis, 

CA. 

Sargent, S.A., J.K. Brecht, and J.J. Zoellner. 

1992. Sensitivity of tomatoes at mature-green 

and breaker ripeness stages to internal bruising. J. 

Amer. Soc. Hort. Sci. 117(1):119-123.

Sargent, S.A., and J.J. VanSickle. 1996. Premiumquality tomato program for Florida. In C.S. 

Vavrina, ed., Proceedings of the Florida Tomato 

Institute, pp. 8-9. Pub. no. PRO 108, University of 

Florida, Institute of Food & Agricultural Science, 

Gainesville, FL.

Scholz, E.W, H.B. Johnson, and W.R. Buford. 

1963. Heat-evolution rates of some [Lower Rio 

Grande Valley] Texas-grown fruits and vegetables. 

J. Rio Grande Valley Hort. Soc. 17:170-175.

Snowdon, A.L. 1992. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. CRC Press, Boca Raton FL.

Wills, R.B.H., B. McGlasson, D. Graham, and D. 

Joyce. 1998. Postharvest: An Introduction to the 

Physiology and Handling of Fruits, Vegetables 

and Ornamentals. University of New South Wales 

Press, Sydney, Australia.
588

Truffle

Fabio Mencarelli

Mencarelli is formerly with the Istituto Tecnologie 

Agroalimentari, University of Tuscia, Viterbo, 

Italy. He is now with the Department of Food 

Science and Technology, University of Viterbo, 

Italy.

Scientific Name and Introduction

“Truffle” is the common name for several 

hypogous fungi—the most highly prized white 

truffle (Tuber magnatum Pico:Fr.), the black 

truffle (Tuber melanosporum Pico), and the least 

prized summer truffle (Tuber æstivum Vitt.). The 

market is concentrated in France, Italy, and Spain; 

but truffles are now being produced all over the 

world, with China as one of the biggest producers.

Quality Characteristics and Criteria

A high-quality truffle is characterized by a strong 

odor. No commercial standards exist, and only 

the kind of truffle and its geographical origin 

influence market price. The size (larger is more 

appreciated), soundness, regular shape, and 

uniform distribution of color are important quality 

characteristics.

Horticultural Maturity Indices

Maturity indices do not exist for truffles, but 

truffles harvested for immediate sale should be 

collected during the normal season because they 

are bigger and develop stronger smell. Truffles 

harvested at the beginning of the season store 

better because they have lower water content and 

are less prone to superficial mold development.

Grades, Sizes, and Packaging

No standards exist for grading, sizing, or 

packaging.

Precooling conditions

Only summer truffles or truffles grown in hot areas 

need precooling because of their higher metabolic 

rates. Hydrocooling at 0 °C (32 °F) is best, and 

must be done by immersion, which can be part 

of the washing procedure. After washing, excess 

water should be removed in a well-ventilated 

room at 4 to 5 °C (39 to 41 °F). Lowering the 

temperature helps maintain the characteristic 

aroma. 

Optimum Storage Conditions

Truffles can be kept in good condition for 20 to 30 

days at 0 oC (32 °F) with 90 to 95% RH. Storage 

life is slightly reduced at 5 °C (41 °F) (Mencarelli 

et al. 1997). Attention must be paid to fluctuation 

of the refrigeration temperature around 0 °C (32 

°F) that could freeze truffles and completely 

destroy their texture.

Controlled Atmosphere (CA) 

Considerations

Textural characteristics were maintained similar 

to fresh when stored in 60% CO2

 for 35 days at 

5 °C (41 °F) (Massini and Landucci 1988). High 

CO2

 maintains aroma better than low O2 and 

controls development of superficial molds. Quality 

characteristics and aroma can be maintained in 

low permeability plastic film packages. High CO2

should be combined with low O2

 to avoid anoxic 

conditions.

Retail Outlet Display Considerations

The aroma compounds produced by truffles can 

contaminate other produce. Only those truffles 

that can be sold that day should be displayed 

unwrapped; the others should be kept sealed in 

impermeable plastic trays in the cold section. 
589

Chilling Sensitivity

Truffles are not chilling sensitive and should be 

stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Truffles produce only very low amounts of 

ethylene and are not sensitive to ethylene exposure 

(Mencarelli et al. 1997). Production of ethylene 

in storage can therefore be a good indicator of 

internal decay.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 20 to 36

5 °C 24 to 45

10 °C 30 to 60

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Drying of the epicarp caused by low RH can 

be a problem. Internal browning of whitefleshed truffles can be caused by overmaturity, 

while worms and growing conditions can cause 

sponginess.

Postharvest Pathology

Bacteria are present inside and on the surface, 

but they usually do not cause decay. The frequent 

presence of worms inside truffles is often 

undetectable from the outside.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

No current potential exists.

Special Considerations

Truffles need brushing during washing. Excess 

water must be removed before storage to avoid 

growth of superficial mold. Special care must used 

with mixed loads because truffles can significantly 

affect the aroma of other commodities.

References

Massantini, R., and A. Landucci. 1988. 

Trattamento e commercializzazione dei tartufi 

freschi e in conserva. Problemi normativi e 

sviluppo tecnologico. Proceedings of the 2nd 

International Symposium on Truffle, Spoleto, 

Italy, pp. 645-651.

Mencarelli, F., R. Massantini, and R. Botondi. 

1997. Physiological and textural response of 

truffles during low-temperature storage. J. Hort. 

Sci. 72(3):407-414.
590

Turnip

Penelope Perkins-Veazie

Perkins-Veazie is formerly with the South Central 

Agricultural Laboratory, Agricultural Research 

Service, U.S. Department of Agriculture, 

Lane, OK. She is now with the Department 

of Horticultural Science, North Carolina State 

University, NC Campus, Kannapolis, NC.

Scientific Name and Introduction

Turnip (Brassica campestris, Rapaceum group) is 

often confused with rutabaga or swede (B. napus, 

Napobrassica group). Turnips have a small, whitefleshed root, often with the surface of the top half 

purple. Leaves are hairy. Roots can be grown in 

warm soils, >25 °C (>77 °F) (Peirce 1987). (In 

contrast, rutabagas have large, yellow-fleshed 

roots and large, smooth leaves, and they grow in 

cool soils.) There are also yellow-fleshed turnips. 

Common turnip varieties are ‘Purple Top,’ ‘White 

Globe,’ ‘White Egg,’ and ‘Golden Ball.’

Quality Characteristics and Criteria

High-quality turnips are firm and are free of 

growth cracks, woodiness, rot, injury, and 

pithiness. 

Horticultural Maturity Indices

Root diameter and freedom from woodiness are 

maturity indices for turnips. If sold as topped 

turnips, roots should be at least 4.4 cm (1.75 in) in 

diameter.

Grades, Sizes, and Packaging

Grades of U.S. No. 1 and U.S. No. 2 are based 

primarily on external appearance, size, and 

defects. U.S. Grade 1 roots are well trimmed, firm, 

fairly smooth and clean, and free from injury, 

growth cracks, woodiness, water core, dry rot, 

and soft rot. The roots should have a minimum 

diameter of 4.4 cm (1.75 in). Turnips are sold 

bunched with tops not less than 15 cm (6 in) 

long, short-trimmed roots with tops not more than 

10 cm (4 in) long, and topped turnips with tops 

removed to not more than 2 cm (0.75 in). Some 

roots are waxed, but most are packaged as fresh 

roots and leaves or topped, and packed in vented 

plastic film or mesh 11.4- or 22.7-kg (25- or 50-lb) 

bags or 0.45-kg (1-lb) bags packed 12 per carton. 

Precooling Conditions

Turnips can be cooled in the wash water, but a 

temperature differential of 10 °C (50 °F) or more 

should be avoided to prevent cracking.

Optimum Storage Conditions

Turnips can be held 4 to 5 mo at 0 °C (32 °F) with 

90 to 95% RH. 

Controlled Atmosphere (CA) 

Considerations

Unknown.

Retail Outlet Display Conditions

Turnips should be stored and displayed under high 

RH and refrigerated to slow shrivel. They can be 

misted.

Chilling Sensitivity

Turnips are not sensitive to chilling and should be 

stored as cold as possible without freezing.

Ethylene Production and Sensitivity

Turnips produce no detectable ethylene and are 

insensitive to ethylene.
591

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 6 to 9

5 to 6 °C 10

10 °C 13 to 19

15 to 16 °C 21 to 24

20 to 21 °C 24 to 25

Data from Smith (1957) and Scholz et al. (1963).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU per ton per 

day or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Turnips can develop growth cracks from 

overmaturity or boron deficiency, brown heart 

from boron deficiency, and pithiness from water 

stress (Snowdon 1992). Root shriveling and loss 

of firmness can occur from storage at >2 °C (36 

°F) or at low RH.

Postharvest Pathology

Dry rot or phoma rot (Leptospharia maculans),

watery soft rot (Sclerotina minor or S. 

scerotiorum), alternaria rot (Alternaria brassicae),

rhizoctonia rot (Thanatephorus cucumeris), gray 

mold (Botrytis cinerea), and bacterial soft rot 

(Erwinia crotovora ssp. carotovora) can occur 

in harvested roots, generally resulting from field 

infection.

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Turnips may be peeled and diced as a fresh market 

pre-cut product (Snowdon 1992).

Special Considerations

Turnips are susceptible to freezing damage 

when held at 0 °C (32 °F). Storage at warmer 

temperatures, >5 °C (41 °F), accelerates weight 

loss and development of soft rot. Waxing roots 

with a water-miscible, carnauba-based wax 

slightly delays weight loss and intensifies the 

purple color of the roots (Perkins-Veazie and 

Collins 1991).

References

Peirce, L.C. 1987. Root crops. In L.C. Peirce, 

Vegetables: Characteristics, Production, and 

Marketing, pp. 251-269. J. Wiley & Sons, New 

York, NY.

Perkins-Veazie, P., and J.K. Collins. 1991. Color 

changes in waxed turnips during storage. J. Food 

Qual. 14:313-319.

Scholz, E.W., H.B. Johnson, and W.R. Buford. 

1963. Heat evolution rates of some Texas-grown 

fruits and vegetables. J. Rio Grande Valley Hort. 

Soc. 17:170-175.

Smith, W.H. 1957. The production of carbon 

dioxide and metabolic heat by horticultural 

produce. Modern Refrig. 60:493-496.

Snowdon, A.L. 1992. Diseases of swedes 

(rutabagas) and turnips. In A.L. Snowdon, Color 

Atlas of Postharvest Diseases and Disorders of 

Fruits and Vegetables, vol. 2, Vegetables, pp. 339-

343. CRC Press, Boca Raton, FL. 
592

Waterchestnut

Jeffrey K. Brecht

Brecht is with the Horticultural Sciences 

Department, University of Florida, Gainesville, 

FL.

Scientific Name and Introduction

Waterchestnut or matai (Eleocharis dulcis [Burm.] 

Trin. ex Hens.) is a member of the sedge family 

(Cyperaceae). It is primarily cultivated throughout 

tropical Asia for its edible corms. The plant is a 

hydrophyte (water-loving) and is grown under 

flooded conditions similar to paddy rice. There 

are two types: the sweet hon matai and the starchy 

sui matai, with the former more popular in the 

United States. Eleocharis dulcis corms differ from 

fruit of the dicot Trapa species (T. bicornis and T. 

natans), which are also called water chestnut, in 

that they are toxic when eaten raw (Rubatzky and 

Yamaguchi 1997).

Quality Characteristics and Criteria

High-quality hon matai waterchestnuts are tender, 

crisp, and somewhat sweet with a white interior 

tissue. The corms may be eaten raw, but they 

maintain their crispness when cooked and are 

usually consumed cooked. 

Horticultural Maturity Indices

Corms mature after plant tops have died or been 

killed by frost. Mature corms are recognized by 

their well-developed, lignified, dark, shell-like 

epidermis. Corms keep well underground, and 

harvest can be delayed for up to 4 mo after tops 

senesce (Hodge 1956). Sugar content is more than 

double in corms harvested in December versus 

October in the southeastern United States (Twigg 

et al. 1957). However, corms became less tender 

and more fibrous when harvest is delayed (Brecht 

et al. 1992).

Grades, Sizes, and Packaging

There are no USDA grade standards. However, 

mature, dark-skinned corms over 30 mm (1.25 

in) in diameter with no physical injury from 

harvesting are considered marketable (DeRigo and 

Winters 1964), but corms over 40 mm (1.5 in) in 

diameter are more desirable (McGregor 1989). 

Corms are usually packed and stored in film bags 

with moist sphagnum moss. 

Precooling Conditions

Though amenable to faster cooling methods 

such as hydrocooling and forced-air cooling, 

waterchestnuts are usually room-cooled for 

storage and prior to shipping. Immersion in cold, 

chlorinated water (see “Special Considerations” 

section) may be an effective precooling treatment.

Optimum Storage Conditions

When stored and packed in moist sphagnum moss, 

waterchestnuts can be stored for 1 to 2 mo at 0 

to 2 °C (32 to 36 °F) with 98 to 100% RH (Ryall 

and Lipton 1979). They can be stored at least 

10 mo at 0 °C (32 °F) and 8 mo at 5 °C (41 °F) 

if corms are free from damage and submerged 

in NaOCl solution soon after harvest. An initial 

concentration of about 1,000 μL L-1 falls to 

essentially zero within 3 to 5 days. Anaerobiosis 

was not a problem when 23 kg (50 lb) lots were 

stored in open containers with the solution 60 cm 

(24 in) deep (Kanes and Vines 1977). However, 

the storage life of mechanically harvested corms 

was <2 mo in either aerated water or 1,000 μL 

L-1 NaOCl at 1.5 °C (35 °F) (Kays and Sanchez 

1984).

Controlled Atmosphere (CA) 

Considerations

There is no documented information on the use of 

CA.
593

Retail Outlet Display Considerations

Waterchestnuts should be displayed in refrigerated 

units with water spray or mist to keep them from 

shriveling.

Chilling Sensitivity

Chilling injury is only a concern with immature 

corms. Symptoms are water-soaking, internal 

browning, and external decay. Immature corms 

can become injured within 10 days at 1 °C (34 °F); 

by 21 days, they shrivel and become discolored 

(Brecht et al. 1992).

Ethylene Production and Sensitivity

There is no information on ethylene production or 

ethylene sensitivity of waterchestnuts.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 10.1

5 °C 25.4

10 °C 41.6

15 °C 78.7 (estimated by extrapolation)

20 °C 114.4

Data from Peiris et al. (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Damaged areas on corms turn brown, which 

detracts from their appearance and must be 

trimmed when the corms are peeled. Corms are 

susceptible to water loss, which causes loss of 

crispness and tenderness, but texture changes are 

minimal in refrigerated storage if water loss is 

minimized (Kays and Sanchez 1984, Brecht et al. 

1992).

Postharvest Pathology

Decay, caused mainly by Fusarium and 

Geotrichum spp., is a problem at storage 

temperatures of >5 °C (41 °F) and in immature 

corms with chilling injury (Brecht et al. 

1992). Black rot (Cerastomella paradoxa) and 

trichoderma rot (Trichoderma viride) have been 

reported, with black rot being controlled by curing 

at 30 to 32 °C (86 to 90 °F) with 100% RH for 3 

days (Ryall and Lipton 1979).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Fresh, peeled corms could be marketed if 

consumer demand is sufficient. A method has been 

developed to mechanically peel waterchestnut 

corms that involves cutting off the apical and basal 

ends, removing the peel with hot alkali followed 

by wet brushing, and bleaching with hydrogen 

peroxide (Leeper and Williams 1976).

Special Considerations

Following washing with water to remove adhering 

soil, corms should be treated with chlorinated 

water (1,000 μL L-1, pH 7.0) to reduce decay. 

Waterchestnuts sweeten during low temperature 

storage, much like potato (Solanum tuberosum

L.) tubers and parsnip (Pastinaca sativa L.) roots 

(DeRigo and Winters 1964). Starch to sugar 

conversion can result in doubling or tripling 

of sugar levels within 1 mo of storage, with 

no further increase over longer storage times; 

maximum sugar levels are reached at 10 °C (50 

°F) and in early harvested, larger corms (Brecht et 

al. 1992), but decay can limit storage at 10 °C (50 

°F) to 1 mo.
594

References

Brecht, J.K., K.A. Bergsma, C.A. Sanchez, and 

G.H. Snyder. 1992. Harvest maturity and storage 

temperature effects on quality of chinese water 

chestnuts (Eleocharis dulcis). Acta Hort. 318:313-

319.

DeRigo, H.T., and H.F. Winters. 1964. Effects 

of storage temperatures on physiological and 

chemical changes in chinese waterchestnut corms. 

Proc. Amer. Soc. Hort. Sci. 85:521-525.

Hodge, W. 1956. Chinese water chestnut or 

matai—a paddy crop of China. Econ. Bot. 10:49-

65.

Kanes, C.A., and A.K. Vines. 1977. Storage 

conditions for chinese water chestnuts (Eleocharis 

dulcis). Acta Hort. 62:151-160.

Kays, S.J., and M.G.C. Sanchez. 1984. Storage of 

chinese water chestnut (Eleocharis dulcis [Burm. 

F.] Trin.) corms. Acta Hort. 157:149-159.

Leeper, G.F., and A.K. Williams. 1976. Peeling of 

chinese waterchestnuts. J. Food Sci. 41:86-88.

McGregor, B.M. 1989. Tropical Products 

Transport Handbook. Agriculture Handbook 668, 

U.S. Department of Agriculture, Washington, DC.

Peiris, K.H.S., J.L. Mallon, and S.J. Kays. 

1997. Respiratory rate and vital heat of some 

specialty vegetables at various temperatures. 

HortTechnology 7:46-49.

Rubatzky, V.E., and M. Yamaguchi. 1997. World 

Vegetables: Principles, Production, and Nutritive 

Values, 2nd ed. Chapman & Hall, New York, NY.

Ryall, A.L., and W.J. Lipton. 1979. Handling, 

Transportation and Storage of Fruits and 

Vegetables, vol. 1. AVI, Westport, CT.

Twigg, B.A., F.C. Stark, and A. Kramer. 1957. 

Cultural studies with matai (chinese water 

chestnut). Proc. Amer. Soc. Hort. Sci. 70:266-272.
595

Water Convolvulus

Ching Cheng Chen and Robert E. Paull

Chen and Paull are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Water convolvulus (Ipomoea aquatica Forsk.) is 

also called ung choi and kang kong. It is a member 

of the morning-glory family (Convolvulaceae) and 

is in the same genus as sweetpotato. It is thought 

to be native of India and is now widely consumed 

as a vegetable throughout Southeast Asia. Young 

stems and leaves are consumed after frying 

or boiling. It has high protein and carotenoid 

contents. It is grown both in ponds and in moist 

soil. Common varieties include types with large 

or small leaves, green or greenish-yellow leaves, 

and stems that are white or green. There are many 

common names besides the three given above: 

kong xin cai, water spinach, water cabbage, and 

pake boong.

Quality Characteristics and Criteria

Plants should have tender tips, and the diameter in 

the middle of the stem should be 8 mm (0.3 in) or 

more. There should be no insect or disease injury 

or blemishes; leaves should be uniformly darkgreen, smooth, healthy, and turgid with no black 

streaks from folding or mechanical injury; and 

stems should be tender (Tisbe and Cadiz 1967). 

Plants should be free of dirt and residue, and 

stems should have a minimum of fibers.

Horticultural Maturity Indices

Young plants are either up-rooted or cut near the 

water surface (flooded culture) or ground level 

(moist soil culture) when about 30 cm (12 in) 

long. Then they are tied into bundles. Plants with 

roots attached are less perishable (Cornelis et al. 

1985).

Grades, Sizes, and Packaging

There are no U.S. or international grades. Plants 

are sold in 0.45- to 0.9-kg (1- to 2-lb) bunches 

packed in fiberboard cartons holding 9 to 18 kg 

(20 to 40 lb).

Precooling Conditions

Room-cooling is normally used. Vacuum-cooling 

is possible.

Optimum Storage Conditions

Tentative data suggest a storage life of 10 to 12 

days at 12 to 14 °C (54 to 57 °F) with 90 to 95% 

RH.

Controlled Atmosphere (CA) 

Considerations

Tissue browning is promoted by 3% CO2

 at 

1 °C (33 °F) but is prevented by higher CO2

concentrations at 20 °C (68 °F) (Ose et al. 1999).

Retail Outlet Display Considerations

Water convolvulus should be displayed at 10 to 14 

°C (50 to 57 °F) with misting. Placing on ice or 

top-icing is not recommended.

Chilling Sensitivity

Water convolvulus is injured below 10 to 14 

°C (50 to 57 °F). Symptoms include darkening 

and wilting of leaves, darkening of the stems, 

and increased susceptibility to bacterial disease. 

Darkening symptoms develop after about 4 days at 

1 °C (34 °F).
596

Ethylene Production and Sensitivity

Water convolvulus produces about 2 μL kg-1

h-1 ethylene at harvest; the rate declines during 

storage. Production can then increase to about 

the same level when leaves senesce and turn 

yellow. Ethylene exposure induces premature leaf 

senescence and yellowing.

Respiration Rates

Respiration rate is 50 to 150 mg (28 to 85 μL) 

CO2 kg-1 h-1 at 27 °C (81 °F). Heat production is 

11,000 to 33,000 BTU ton-1 day-1 or 3,050 to 9,150 

kcal tonne-1 day-1.

Physiological Disorders

Chilling injury is the main disorder. 

Postharvest Pathology

White rust can be a problem in Southeast Asia, 

as occasionally can alternaria rot (Alternaria 

ipomoeae-aquaticae). Cercospora leaf spots 

are also found (Ho and Edie 1969). Postharvest 

diseases are not generally a problem, though 

bacterial rot does occur. Rapid cooling, good 

temperature management, and sanitation reduce 

the problem significantly.

Quarantine Issues

Peach aphid is sometimes found. Though 

sweetpotato weevil may not be able to complete 

its life cycle in this vegetable, larvae have been 

found in the hollow stems, and therefore it is 

regarded as a host (Austin 1991).

Suitability as Fresh-Cut Product

Water convolvulus is sold in Southeast Asian 

markets as part of a meal pack for stir-frying.

References

Austin, D.F. 1991. Associations between the plant 

family Convolvulaceae and cylas weevils. In R.K. 

Jansson and K.V. Raman, eds., Sweet Potato Pest 

Management: A Global Perspective, pp. 45-78. 

Westview, Boulder, CO.

Cornelis, J., J.A. Nugteren, and E. Westphal. 

1985. Kang kong (Ipomoea aquatica Forsk.): an 

important leaf vegetable in South-East Asia. Abst. 

Trop. Agric. 10:9-21.

Ho, B.W.C., and H.H. Edie. 1969. White rust 

(Albergo ipomoeae-aquatica) on Ipomoea 

aquatica in Hong Kong. Plant Dis. Rep. 53:959-

962.

Ose, K., K. Chachin, and Y. Ueda. 1999. 

Relationship between the occurrence of chilling 

injury and the environmental gas concentration 

during storage of water convolvulus (Ipomoea 

aquatica Forsk.). Acta Hort. 483:303-310.

Tsay, L.M. 1987. Effects of holding posture on the 

respiration and ethylene production of eggplant 

and water convolvulus. J. Chinese Soc. Hort. Sci. 

33:34-37.

Tisbe, V.O., and T.G. Cadiz. 1967. Convolvulus 

or kang kong. In J.E. Knott and J.R. Dean, eds., 

Vegetable Production in South-East Asia, pp. 285-

289. University of the Philippines, Los Banos, 

Philippines.
597

Watercress

Stephen Morris and Jenny Jobling

Morris and Jobling are with the Sydney 

Postharvest Laboratory, Food Science Australia, 

North Ryde, New South Wales, Australia.

Specific Name and Introduction

Watercress (Nasturtium officinale R.Br.) has been 

known in Europe and Asia for thousands of years, 

and it is now grown in many countries worldwide. 

It is a member of the Brassicaceae (Cruciferae) 

family and is used as a leafy salad vegetable. It 

has attractive dark green leaves, a strong flavor 

and is rich in vitamins. Watercress is typically 

grown in running water (Snowdon 1991).

Horticultural Maturity Indices

Leaves should be harvested when full size and still 

bright-green.

Quality Characteristics and Criteria

Watercress should be bright green and not limp. 

The leaves of watercress quickly become yellow 

and slimy when improperly handled.

Grades, Sizes, and Packaging

There are no U.S. grade standards. Watercress 

is sold in bunches and can be packed in waxed 

cartons with top ice (Hruschka and Wang 1979). It 

can also be packaged in boxes with plastic liners. 

Precooling Conditions

Watercress should be precooled promptly after 

harvest either by hydrocooling or vacuum-cooling 

(Hruschka and Wang 1979).

Optimum Storage Conditions

Watercress can be stored for 2 to 3 weeks at 0 

°C (32 °F) with >95% RH (Hruschka and Wang 

1979). Shelf-life is reduced to 2 to 3 days if stored 

under low RH. 

Controlled Atmosphere (CA) 

Considerations

The rate of yellowing can be reduced by storing in 

atmospheres >7% CO2

 with not less than 5% O2

(Aharoni et al. 1989).

Retail Outlet Display Considerations

Contact with melting ice and water sprays help 

in preventing dehydration. Careful handling 

is necessary to avoid crushing or bruising the 

delicate leaves.

Chilling Sensitivity

Watercress is not sensitive to low temperature 

and should be stored as cold as possible without 

freezing. 

Ethylene Production and Sensitivity

Watercress produces only low amounts of ethylene 

in response to wounding: <0.1 μL kg-1 h-1 at 20 °C 

(68 °F). However, exposure to ethylene reduces 

shelf-life due to increased rate of yellowing 

(Philosoph-Hadas et al. 1989).

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 16 to 28

5 °C 47 to 53

10 °C 95 to 125

15 °C 139 to 210

20 °C 300 to 344

25 °C 334 to 420
598

Data from Smith (1957) and Hruschka and Wang 

(1979).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Watercress is very susceptible to dehydration and 

crushing of leaves.

Postharvest Pathology

Harvested watercress is highly perishable. 

In warm conditions, the stems can become 

slimy as a result of bacterial soft rot caused by 

Erwinia carotovora. It is therefore important 

that watercress be cooled promptly after harvest 

(Snowdon 1991).

Quarantine Issues

There are no known quarantine issues.

Suitability as Fresh-Cut Product

Watercress can be used as part of mixed salads.

Special Considerations

Care must be taken to maintain high RH or storage 

life is substantially shortened.

References

Aharoni, N., A. Reuveni, and O. Dvir. 1989. 

Modified atmospheres in film packages delay 

senescence and decay of fresh herbs. Acta Hort. 

258:255-263.

Hruschka, H.W., and C.Y. Wang. 1979. Storage 

and shelf life of packaged watercress, parsley 

and mint. Market Research Report 1102, U.S. 

Department of Agriculture, Washington, DC.

Philosoph-Hadas, S., E. Pesis, S. Meir, et al. 

1989. Ethylene-enhanced senescence of leafy 

vegetables. Acta Hort. 258:37-45.

Smith, W.H. 1957. The production of carbon 

dioxide and metabolic heat by horticultural 

produce. Modern Refrig. 60:493-496.

Snowdon, A.L. 1991. A Colour Atlas of 

Postharvest Diseases and Disorders of Fruits 

and Vegetables, vol. 2, Vegetables, p. 219. Wolfe 

Scientific, London, U.K.
599

Watermelon

James W. Rushing

Rushing is formerly with the Coastal Research 

and Education Center, Clemson University, 

Charleston, SC. He is now retired.

Scientific Name and Introduction

Watermelon, Citrullus lanatus (Thunb.) Matsum. 

and Nakai, is an annual plant of the Cucurbitaceae 

family. The edible fruit is produced on trailing 

vines that may reach 15 ft. (4.6 m) or more in 

length. Fruit vary in shape from globular to 

oblong. The color of the hairless skin varies in 

shades of green from pale yellowish to almost 

black and may be solid, striped, or marbled. Fruit 

have a thin, firm outer rind, a layer of whitefleshed inner rind that may be up to about one inch 

thick, and an interior edible pulp containing seeds 

unless the variety is triploid. Pulp color of most 

commercial varieties is some shade of yellow or 

red (Sackett 1974).

Quality Characteristics and Criteria

High-quality watermelons are well formed, 

symmetrical, and uniform in shape and have a 

waxy, bright appearance. The rind should be free 

of scars, sunburn, and abrasions with no bruising 

or other physical injury; free from anthracnose or 

other decay; and not overripe (AMS 1978, Suslow 

1999).

Horticultural Maturity Indices

As watermelons reach horticultural maturity, the 

ground spot changes from white to pale yellow, 

tendrils nearest the fruit may turn brown and dry, 

and the fruit surface may become irregular and 

dull rather than bright or glossy. Experienced 

harvest managers may note that when the fruit is 

thumped or rapped with the knuckles, immature 

fruit gives off a metallic ringing sound while 

mature fruit sounds dull or hollow. The most 

reliable method of determining maturity within 

a given field is to visually examine the fruit for 

the changes described above, then cut some fruit 

in random sectors of the field to check flavor and 

internal color development. Some buyers require 

that fruit have some minimum SSC, which is 

easily measured with a refractometer (Sackett 

1974, Rushing et al. 2000).

Grades, Sizes, and Packaging

Watermelon grades are U.S. Fancy, U.S. No. 1., 

and U.S. No. 2. Grade is subjectively based on 

the quality characteristics and criteria described 

above. Size may be specified in terms of average 

weight, minimum weight, or minimum and 

maximum weight (AMS 1978). Watermelons may 

be shipped in bulk, placed on corrugated bins with 

a capacity of approximately 1,000 lb (454 kg), or 

packed into cartons containing 3 to 6 watermelons 

depending on fruit size. Cartons should have 

specially designed inserts to help support the 

weight of the fruit (Close et al. 1971).

Precooling Conditions

Watermelons generally are not precooled and 

some are shipped in unrefrigerated trucks (Suslow 

1999). If precooling is implemented, forcedair cooling would be the method of choice. In 

common room-cooling, good air circulation 

between palletized boxes is essential. Fruit that 

are placed in bulk fiberboard bins will cool slowly 

because of poor air circulation within the bin.

Optimum Storage Conditions

Some variability is noted in watermelon varieties 

and types, such as seeded vs. seedless; but in 

general none are suited to very-long-term storage. 

The ideal storage temperature is in the range of 10 

to 15 °C (50 to 59 °F) with approximately 90% 

RH. Fruit should be consumed within 2 to 3 weeks 

following harvest (Hardenburg et al. 1986).
600

Controlled Atmosphere (CA) Conditions

Watermelons generally do not respond well to CA 

or to MAP. Studies with shrink-wrap packaging 

of individual fruits, a form of MAP, was not 

beneficial, and in some cases decay in MAP was 

higher (Biglete 1992).

Retail Outlet Display Considerations

Watermelons are usually sold from unrefrigerated 

displays. Bulk fiberboard bins with colorful 

graphics have been a popular method of 

displaying watermelons for retail sale.

Chilling Sensitivity

Watermelons develop chilling injury when stored 

below about 10 °C for more than a few days. 

Lower temperatures will hasten the onset of 

injury. Symptoms appear as brown-staining of 

the rind, surface pitting, deterioration of flavor, 

fading of flesh color, and increased incidence of 

decay after being returned to room temperatures 

(Hardenburg et al. 1986, Suslow 1999, Rushing et 

al. 2000). Conditioning fruit at 30 °C (86 °F) for 

about 4 days prior to cooling has been shown to 

induce some tolerance to chilling, but it does not 

completely alleviate the problem (Picha 1986).

Ethylene Production and Sensitivity

Watermelons are classified as low-ethylene 

producers, with production rates in the range of 

0.1 to 1.0 μL kg-1 h-1 at 20 °C. Though production 

rates are low, fruit are extremely sensitive to 

ethylene. Exposure to as little as 5 μL L-1 ethylene 

causes softening, rind thinning, fading of flesh 

color, and over-ripeness (Elkashif et al. 1989, 

Suslow 1999). Interactions between ethylene 

concentration, temperature, and duration of 

exposure are not well defined. The recommended 

management protocol is to avoid any exposure to 

ethylene in storage.

Respiration Rates

Temperature mg CO2 kg-1 h-1

4 to 5 oC 3 to 4

10 oC 6 to 9

20 to 21 oC 17 to 25

Data from Hardenburg et al. (1986).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Physiological Disorders

Refer to above sections on “Chilling Injury” 

and “Ethylene Sensitivity.” A disorder of 

preharvest origin that can have serious postharvest 

consequences for marketing is hollowheart.

Postharvest Pathology

A variety of pathogens may cause postharvest 

decay of watermelon, but in the absence of any 

approved chemical control measures, the primary 

defense against decay is the exclusion of diseased 

fruit from the marketing chain through careful 

selection at harvest and appropriate grading before 

shipment. Postharvest rot caused by Fusarium spp. 

and Phytophthora capsici are of concern because 

control measures for these fungi in the field often 

are inadequate. With good disease control in the 

field, anthracnose (Colletotrichum orbiculare) and 

black rot (Didymella bryoniae) rarely develop on 

watermelon (Snowdon 1992, Rushing et al. 2001). 

In production areas with high RH and temperature, 

an extensive list of rind lesions, stem-end or 

blossom-end rots, and surface lesions may be 

caused by Erwinia or an assortment of fungi 

(Snowdon 1992, Suslow 1999). Watermelon fruit 

blotch (Acidovorax avenae subsp. citrulli) was a 

postharvest problem for several years, but research 

demonstrated the disease is not easily transmitted 

from fruit to fruit after harvest. Appropriate 

grading and temperature management can 
601

virtually eliminate its presence in the marketing 

chain (Rushing et al. 1999).

Quarantine Issues

Watermelons destined for export must be free 

of disease, insects, soil, or vegetative debris. 

Phytosanitary requirements in the receiving 

country should be reviewed prior to shipment.

Suitability as Fresh-Cut Product

The fresh-cut market for watermelon cubes and 

slices has grown dramatically, but most processing 

is done near the point of sale. Some benefits may 

be derived from MAP. Fresh-cut watermelon 

is badly damaged by rough handling during 

distribution (Sargent 1998).

Special Considerations

Special care should be given to avoid rough 

handling injury of watermelon fruit during 

harvesting and handling. Fruit that are 

inadvertently dropped during harvest or handling 

should not be shipped. Injury that may not be 

obvious at the moment it occurs can develop into 

bruised areas and damage to the flesh in transit.

References

AMS [Agricultural Marketing Service]. 1978. 

United States standards for grades of watermelons. 

At http://www.ams.usda.gov/AMSv1.0/standards.

Biglete, N.A. 1992. Packaging And Storage 

of Watermelon Using Different Shrink-Wrap 

Techniques. M.S. thesis, Clemson University, 

Clemson, SC.

Close, E.G., J. Varick, and L.A. Risse. 1971. 

Comparative methods of handling watermelons—

bulk and cartons. Series MA 1-71, Florida 

Department of Agriculture and Consumer 

Services, Tallahassee, FL.

Elkashif, M.E., D.J. Huber, and J.K. Brecht. 1989. 

Respiration and ethylene production in harvested 

watermelon fruit: evidence for non-climacteric 

respiratory behavior. J. Amer. Soc. Hort. Sci. 

114:81-85.

Hardenburg, R.E., A.E. Watada, and C.Y. 

Wang. 1986. The Commercial Storage of Fruits, 

Vegetables, and Florist and Nursery Stocks, 

pp. 12,62. Agricultural Handbook 66, U.S. 

Department of Agriculture, Washington, DC.

Picha, D.H. 1986. Postharvest fruit conditioning 

reduces chilling injury in watermelons. 

HortScience 21:1407-1409.

Rushing, J.W., J.M. Fonseca, and A.P. Keinath. 

2001. Harvesting and postharvest handling, pp. 

156-164. In Watermelons - Characteristics, 

Production, and Marketing, D.N. Maynard, ed., 

American Society for Horticultural Science Press, 

Alexandria, VA.

Rushing, J.W., A.P. Keinath, and W.P. Cook. 1999. 

Postharvest development and transmission of 

watermelon fruit blotch. HortTechnology 9:33-35.

Sackett, C. 1974. Watermelons. Fruit and 

Vegetable Facts and Pointers. United Fresh Fruit 

and Vegetable Association, Alexandria, VA.

Sargent, S.A. 1998. Fresh-cut watermelon. Citrus 

and Veg. Mag. 62:26-28,44.

Snowdon, A.L. 1992. Color Atlas of Postharvest 

Diseases and Disorders of Fruits and Vegetables, 

vol. 2, Vegetables. pp. 18,51. CRC Press, Boca 

Raton, FL.

Suslow, T.V. 1999. Watermelon. 

Recommendations for maintaining postharvest 

quality. At http://postharvest.ucdavis.edu/produce_

information.
602

Wax Apple

Robert E. Paull and Ching Cheng Chen

Paull and Chen are with the Department of 

Tropical Plant and Soil Sciences, University of 

Hawaii at Manoa, Honolulu, HI.

Scientific Name and Introduction

Wax apple (Syzygium samarangense [Blume] 

Merrill & L. M. Perry) is the main species in this 

Southeast Asian genus that is consumed fresh. 

Other species with similar fruits are S. aqueum, 

rose water apple; S. aimini, java plum; S. jambos, 

rose apple; and S. malaccense, Malay apple. The 

spice clove is S. aromaticum. 

The fruit is broad, bell-shaped or sometimes oval, 

5 to 6 cm (2 to 2.5 in) long, and 4 to 5 cm (1.5 to 

2 in) wide. It has one to four seeds. The skin can 

be green to light red to dark red and has a waxlike 

high gloss sheen. The low-acid flesh is white and 

juicy (Nakasone and Paull 1998).

Quality Characteristics and Criteria

Criteria are skin color; waxy glossy appearance; 

large size with small seeds; crunchy, watery, sweet 

taste; and subtle flavor.

Horticultural Maturity Indices

Wax apples are ready for harvest when the 

blossom-end is fully expanded and the skin shows 

desired market color. Green-skin varieties are 

harvested when they reach full size.

Grades, Sizes, and Packaging

There are no U.S. or international standards. Fruit 

are generally graded by size and color. They are 

generally marketed in single-layer fiberboard 

cartons of 2.25 kg (5 lb) with padding, sometimes 

in trays.

Precooling Conditions

Room-cooling is normally used because of the risk 

of excessive moisture loss with forced-air cooling.

Optimum Storage Conditions

Storage at 2 to 10 °C (36 to 50 °F) is 

recommended. However, chilling injury is a 

problem at these temperatures. A conservative 

recommendation would be 12 to 14 °C (54 to 57 

°F) with 90 to 95% RH, which should result in a 

shelf-life of 10 to 14 days.

Controlled Atmospheres (CA) 

Consideration

No CA studies have been reported. MAP in sealed 

polyethylene film bags reduces chilling injury 

and decay (Horng and Peng 1983). Waxing is less 

effective, partly due to RH control.

Retail Outlet Display Considerations

Fruit should be displayed in overwrapped trays or 

closed polystyrene clamshell containers with no 

perforations at 10 °C (50 °F). They should not be 

misted.

Chilling Sensitivity

Wax apples show pitting and skin scald after 4 

days at 2 °C (36 °F), while slight injury occurs 

after 4 days at 10 °C (50 °F) (Horng and Peng 

1983).

Ethylene Production and Sensitivity

Wax apples produce very low ethylene. It is a 

nonclimacteric fruit (Akamine and Goo 1979). 

There are no reported responses to ethylene, 

but ethylene treatment may lead to premature 

senescence.
603

Respiration Rates

Respiration declines after harvest (Liao et al. 

1983). 

Temperature mg CO2 kg-1 h-1

10 °C 4 to 5

20 °C 8 to 11

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Physiological Disorders

Chilling injury, mechanical injury, and water 

loss are the three major disorders. Chilling injury 

symptoms are pitting and scalding of the skin, 

while mechanical injury (impact and abrasion) 

leads to development of sunken areas and some 

darkening of affected flesh. Though fruit have a 

bright waxy coating, water loss is rapid, leading to 

shriveling on the skin and loss of crisp texture. At 

2% moisture loss, fruit become slightly shriveled; 

and at 6%, fruit are shrunken and lose turgidity 

(Horng and Peng 1983).

Postharvest Pathology

There are no published reports. Wax apple may be 

susceptible to anthracnose.

Quarantine Issues

Wax apple is a fruit fly host; irradiation at 300 Gy 

may have potential for disinfestation.

Suitability as Fresh-Cut Product

Wax apple is often available as a fresh-cut product 

in Southeast Asian markets in trays with overwrap. 

It has some potential as a fresh-cut product.

References

Akamine, E.K., and T. Goo. 1979. Respiration 

and ethylene production of fruits of species and 

cultivars of Psidium and species of Eugenia. J. 

Amer. Soc. Hort. Sci. 104:632-635.

Horng, D., and C. Peng. 1983. Studies on package, 

transportation and storage of wax apple fruits 

(Syzygium samarangense). Natl. Chung Hsing 

Univ. Hort. J. 8:31-39.

Liao, M.L., M.S. Liu, and J.S. Yang. 1983. 

Respiration measurement of some important fruits 

in Taiwan. Acta Hort. 138:227-246.

Nakasone, H.Y., and R.E. Paull. 1998. Tropical 

Fruits. CAB Intl., Wallingford, U.K
604

Fresh-Cut Fruits

John C. Beaulieu and James R. Gorny

Beaulieu is with the Southern Regional Research 

Center, Agricultural Research Service, U.S. 

Department of Agriculture, New Orleans, LA. 

Gorny is formerly with the International Fresh-cut 

Produce Association, Alexandria, VA. He is now 

with the Produce Marketing Association, Newark, 

DE.

Introduction and Overview

Fresh-cut fruit products for both retail and food 

service applications have enjoyed an increasing 

presence in the marketplace due to demand by the 

consumer. In the coming years, it is commonly 

perceived that the fresh-cut fruit industry will 

have unprecedented growth. For this reason, 

many leading fresh-cut salad manufacturers have 

targeted development of fresh-cut fruit products as 

part of their long-term business plans. However, 

processors of fresh-cut fruit products face 

numerous challenges not commonly encountered 

during fresh-cut vegetable processing. The 

difficulties encountered with fresh-cut fruit, while 

not insurmountable, require a new and higher 

level of technical and operational sophistication.

Fresh-Cut Defined for Fruits

The USDA and FDA definitions for “fresh” and 

“minimally processed” fruits and vegetables 

imply that fresh-cut (precut) products have been 

freshly cut, washed, packaged, and maintained 

with refrigeration. Fresh-cut products are raw, 

and even though processed (physically altered 

from the original form), they remain in a fresh 

state, ready to eat or cook, without freezing, 

thermal processing, or treatments with additives 

or preservatives (AMS 1998, Anonymous 1998). 

The United Fresh Produce Association defines a 

fresh-cut product as fruits or vegetables that have 

been trimmed and/or peeled and/or cut into 100% 

usable product that is bagged or prepackaged 

to offer consumers high nutrition, convenience, 

and flavor while still maintaining freshness. 

Several commodities, although botanically fruits 

(for example, cucumber, pepper, and tomato), 

will not be covered in this section since they are 

commonly classified as vegetables.

Fresh-Cut Physiology and Physiological 

Concerns

Once harvested, fruits are removed from their 

source of water, minerals, and sustenance. Fruit 

tissues continue to respire, using available and 

stored sugars and organic acids, and they begin 

to senesce rapidly. Postharvest quality loss is 

primarily a function of respiration, onset or 

progression of ripening (climacteric fruit), water 

loss (transpiration), enzymatic discoloration of 

cut surfaces, decay (microbial), senescence, and 

mechanical damage suffered during preparation, 

shipping, handling, and processing (Schlimme 

and Rooney 1994, Watada et al. 1996). Fruits 

destined for fresh-cut processors should be 

harvested as ripe as possible. This makes it critical 

that temperature-dependent events related to 

respiration, water loss, pathological decay, and 

ethylene production be strictly regulated during 

shipment (or storage) of the fruit.

During the climacteric ripening stage of many 

fruits, there is a dramatic increase in respiratory 

production of CO2

 and ethylene. Non-climacteric 

fruit, leafy vegetables, non-fruit vegetables, and 

roots and tubers do not have a surge in ethylene 

production and generally have only slightly 

increased respiration as senescence approaches. 

However, if severely wounded (for example, 

by fresh-cut processing), significant stressinduced production of CO2

, and often ethylene, 

occurs (Abeles et al. 1992, Brecht 1995). Freshcut processing increases respiration rates and 

causes major tissue disruption as enzymes and 

substrates, normally sequestered within the 

vacuole, become mixed with other cytoplasmic 

and nucleic substrates and enzymes. Processing 

also increases wound-induced ethylene, water 

activity, and surface area per unit volume, which 

may accelerate water loss and enhance microbial 

growth since sugars also become readily available 
605

(King and Bolin 1989, Watada et al. 1990, Wiley 

1994, Watada and Qi 1999). 

These physiological changes may be accompanied 

by flavor loss, cut surface discoloration, color 

loss, decay, increased rate of vitamin loss, rapid 

softening, shrinkage, and a shorter storage 

life. Increased water activity and mixing of 

intracellular and intercellular enzymes and 

substrates may also contribute to flavor and 

texture loss during and after processing. 

Therefore, proper temperature management during 

product preparation and refrigeration throughout 

distribution and marketing are essential for 

maintenance of quality.

Physical alterations and potential low-O2

atmospheres in packages may create significant 

negative changes in flavor, aroma, and “mouthfeel.” There are also synergistic interactions 

between numerous factors such as variety, source, 

season, initial maturity, optimum processing 

maturity, slicing and cutting equipment, sanitation 

and GRAS chemical treatments, packaging 

(including MAP), temperature management, 

shipping, handling, and length of shelf-life. 

The combined effect of these factors may have 

negative consequences on postharvest shelflife and sensory quality. Therefore, improperly 

preparing, packaging, and handling fresh-cut fruit 

may compromise overall quality and decrease 

consumer acceptability.

Defining Fresh-Cut Fruit Quality

Postharvest quality and post-cutting quality are 

unfortunately ambiguous or confused terms. 

Harvest indices used to deliver optimum quality 

whole fruits to storage facilities, terminal markets, 

and the fresh markets oftentimes may not be 

appropriate for fruits destined to be processed 

(see also Factors Affecting Fresh-Cut Fruit 

Quality). Growers often destructively sample fruit 

before making a decision to harvest. Processor 

assessment of fruit maturity before cutting either 

upon receipt or after in-house storage is also 

advisable. For example, a lot of peaches that are 

optimally mature for fresh market may be shipped 

to a processor and rejected because the fruit are 

too soft or ripe for cutting. Determination of 

optimum maturity depends on the commodity 

and the use. The processor must understand the 

physiology of the fruit and the finished product 

(and packaging) to accurately determine when 

fruit is at the appropriate maturity stage to process. 

Choice of variety, harvest condition, maturity, 

storage, and shelf-life for various fresh-cut fruits 

are active areas of research.

Proper initial maturity of fruit is essential. 

However, once processed, quality is most 

commonly, and sometimes only, assessed visually. 

Visual appearance is generally the determinant for 

commercial shelf-life. Although some studies have 

found that vitamin C and carotene degrade very 

little during short-term (about 1 week) refrigerated 

storage in some fresh-cut fruits (Wright and Kader 

1997a,b), other researchers are attempting to retain 

fresh-cut quality for 3 to 4 weeks. Although some 

quality attributes may still be acceptable, overall 

quality in terms of aroma, taste, and texture may 

be jeopardized (Anonymous 2000a).

Firmness and Texture

Tissue softening is a very serious problem with 

fresh-cut fruit products and can limit shelf-life. 

Fresh-cut fruit firmness is an important quality 

attribute that can be affected by cell softening 

enzymes present in the fruit tissue (Varoquaux et 

al. 1990) and by decreased turgor due to water 

loss. For example, there was 26 to 49% firmness 

loss in four varieties of fresh-cut cantaloupe 

processed from three-quarters to full-slip maturity 

fruit when stored in air at 4 °C (39 °F) (Beaulieu 

2002, unpublished data). Unwrapped watermelon 

slices lost 47% of their firmness after 4 days at 

5 °C (41 °F) (Abbey et al. 1988), and firmness 

decreased in stored cantaloupe cubes (12 days 

in air at 5 °C) by more than 25% (Cantwell and 

Portela 1997).

Flesh firmness of fresh-cut fruit products can 

be maintained by application or treatment with 

calcium compounds. Dipping fresh-cut products in 

solutions of 0.5 to 1.0% calcium chloride is very 
606

effective in maintaining product firmness (Ponting 

et al. 1971, 1972). However, calcium chloride may 

leave bitter off flavors on some products. Firmness 

of slices from 12 untreated apple cultivars stored 

at 2 °C (36 °F) decreased steadily for 7 days 

and more rapidly thereafter (Kim et al. 1993). 

However, mild heat treatment of whole apples 

before processing maintained firmness during 

storage in some fresh-cut apple cultivars (Kim et 

al. 1994).

Firmness can sometimes be maintained by CA 

storage. Firmness loss averaged 2.2 lb (10 N) in 

honeydew cylinders after 12 days of storage in 

air at 5 °C (41 °F), while CA storage (air + 15% 

CO2

) reduced the loss significantly in one of four 

cultivars tested (Portela and Cantwell 1998). CA 

treatments (2% O2

 + 10% CO2 at 5 °C [41 °F] 

and 4 % O2

 + 10% CO2 at 10 °C [50 °F]) were 

more beneficial than air storage in maintaining 

honeydew cube quality for up to 6 days at 5 °C 

(41 °F) (Qi et al. 1999).

Color at the Cut Surface

An important issue in fresh-cut fruit processing is 

the control of discoloration (pinking, reddening, 

or blackening) or browning on cut surfaces. 

Oxidative browning is usually caused by the 

enzyme polyphenol oxidase (PPO), which in the 

presence of O2

 converts phenolic compounds in 

fruits and vegetables into dark-colored pigments. 

Outlined below are a number of strategies that 

may be used to reduce PPO-mediated cut-surface 

discoloration.

Reduced O2

Because PPO requires O2 to induce cut surface 

discoloration, reducing the amount of O2

 in a 

package of fresh-cut product by vacuum MAP or 

gas flushing may reduce cut surface discoloration, 

but not completely stop it. Careful design of a 

fresh-cut package is essential to assure that the 

proper amount of O2

 is present. Excessive levels 

of O2

 in a package may allow for cut surface 

discoloration to occur, while too little O2

 may 

cause anaerobic metabolism and production of off 

flavors and odors.

Acidification

PPO most effectively catalyzes cut surface 

discoloration at a neutral pH of approximately 7. 

Therefore, browning can be slowed by dipping 

products in mildly acidic food grade solutions 

of acetic, ascorbic, citric, tartaric, fumaric, or 

phosphoric acid. However, these acids may leave 

off flavors and promote tissue softening and 

therefore must be used with care.

Reducing Agents

Ascorbic acid or erythorbate (an isomer of 

ascorbic acid) are two common compounds used 

in the food industry to prevent PPO-mediated 

cut-surface discoloration. Ascorbic acid and 

erythorbate reduce PPO-induced discoloration at 

the cut surface by converting quinones (formed 

by PPO from phenolics) back to phenolic 

compounds. Unfortunately, once all the ascorbic 

acid or erythorbate is exhausted, PPO browning 

will proceed uninhibited. Ascorbic acid or 

erythorbate are commonly used as 1% solutions 

to prevent browning and discoloration of cut 

surfaces. These compounds are organic acids, so 

they may also reduce surface pH of commodities, 

further slowing browning.

Sensory Aspects

Fresh-cut vegetable salads have great consumer 

appeal because of their convenience, flexibility 

of use, and probably the fact that their desirable 

flavor often comes about via condiments 

(croutons, spices, or dressing) or because 

numerous products make up a medley mixture. 

However, consumer acceptance of fresh-cut 

fruits most often relies on the inherent flavor 

and texture quality of the product, seldom with 

accompaniments. It is generally and unfortunately 

assumed that “if it looks good, it tastes good.” 

Improving consistency in fresh-cut fruit product 
607

flavor and texture may enhance consumers desire 

to repeatedly purchase such products.

Soluble Solids Content (SSC) and Titratable 

Acidity (TA)

Sweetness, flesh firmness, and taste are very 

important characteristics for fresh-cut melon 

quality. In a midseason trial of 17 western 

cantaloupe varieties, there was an average 5% 

decrease in SSC (range 0 to 11%) and an average 

8% decrease in sugar (range 0 to 21%) when 

cubes were stored 12 days (in air) at 5 °C (41 

°F) (Cantwell and Portela 1997). After 9 days at 

10 °C (50 °F) or 15 days at 5 °C (41 °F), SSC 

in CA-stored melon pieces were higher than in 

air: 10.3 vs. 9.5% and 10.2 vs. 9.1% at 10 and 

5 °C (50 and 41 °F), respectively (Cantwell and 

Portela 1997). Cantaloupe balls prepared from 

four eastern varieties stored 8 days at 0 °C (32 

°F) had an average SSC decrease of 9.7% with a 

range of 2.3 to 13% (Lange 1998). SSC remained 

somewhat constant for 7 days storage at 4 °C (39 

°F) in fresh-cut cantaloupe when harvest maturity 

was at least half-slip, and cubes prepared from 

fruit harvested at quarter-slip had significantly 

lower initial SSC, which rapidly declined after 

only 5 days storage (Beaulieu and Baldwin 

2002). It is well established in the food industry 

that sugar content (SSC) is generally positively 

correlated with desirable flavor quality. However, 

occasionally too much sugar is perceived 

negatively. The best sugar range for storage of 

fresh-cut cantaloupe was 10 to 13 °Brix. However, 

some judged the 13 °Brix fruit as too sweet 

(Anonymous 2000b).

TA and SSC have also been used to assess quality 

via the SSC:TA ratio in some fresh-cut fruits.

Changes in TA, pH, and SSC in apple slices from 

12 cultivars that were stored at 2 °C (36 °F) for 

12 days were small and varied by cultivar (Kim 

et al. 1993). Likewise, there were changes in SSC 

in fresh-cut strawberries stored under various 

CA for 7 days at 5 °C (41 °F). However, pH 

increased over time (Wright and Kader 1997b). 

Fresh-cut persimmons stored under various CA 

had increased SSC for 3 days, then decreased SSC 

by day 8; pH tended to increase through storage 

(except when stored under 2% O2

) (Wright and 

Kader 1997b). In cantaloupe slices, a 17% loss 

in SSC and a 2-fold increase in TA occurred 

after only 2 days storage at 20 °C (68 °F), but 

the acidity change was attributed to lactic acid 

bacteria (Lamikanra et al. 2000). TA in fresh-cut 

oranges stored 8 days at 4 °C (39 °F) decreased 

36% (Rocha et al. 1995).

Aroma and Flavor

An acceptable post-cutting visual appraisal 

does not necessarily imply that a product has 

satisfactory flavor quality. Excellent visual quality 

and acceptance by retailers and consumers often 

occur with fruits processed when immature. For 

example, immature peaches and nectarines will 

process and hold visual quality for extended 

periods, but rehardening and poor eating-quality 

limit their use (Gorny et al. 1998b, Beaulieu 

et al. 1999). A mature green cantaloupe at less 

than half-slip delivers a fresh-cut product with 

optimum visual shelf-life but insufficient sugar or 

volatile composition compared to a desirable ripe 

whole melon (Pratt 1971, Beaulieu and Grimm 

2001, Beaulieu and Baldwin 2002). ‘Makdimon’ 

melons harvested 2 days before fully-ripe (fullslip) developed only about 25% the total volatiles 

as 3 day-old, fully-ripe fruit (Wyllie et al. 1996). 

Volatiles increased with harvest maturity, and 

cubes prepared from quarter-slip fruit contained 

only 25 to 33% of the total volatiles of full-slip 

fruit (Beaulieu and Baldwin 2002). Furthermore, 

these trends were conserved during 10 days at 4°C 

(39 °F) in fresh-cut products.

Flavor and aroma quality are important attributes 

for consumers, and these attributes should be 

seriously examined when determining the shelflife of fresh-cut fruit products. Nevertheless, 

the quality of intact vegetables and fruits is 

often determined almost exclusively based 

on appearance, sometimes to the exclusion of 

flavor and texture (Sapers et al. 1997). Much 

variability exists in the literature regarding 

acceptability based on sensory evaluations, and 

this variability oftentimes can be attributed to 
608

different experimental designs or sensorial analyses 

and cultural bias. For example, sensory evaluation 

determined that fresh-cut honeydew, kiwi fruit, 

papaya, pineapple, and cantaloupe stored at 4 

°C (39 °F) were unacceptable after 7, 4, 2, about 

7, and 4 days, respectively (O’Connor-Shaw 

et al. 1994). However, fruit were not sanitized, 

nor were gloves worn during preparation and 

subsequent microbial decay and associated 

texture loss most likely limited post-cutting life. 

Sterilized, diced cantaloupe stored at 4 °C (39 °F) 

in various controlled atmospheres were acceptable 

from a sensory quality standpoint after 28 days 

(O’Connor-Shaw et al. 1996). Cantaloupe pieces 

stored at 2 °C (36°F) in ready-to-serve tray-packs 

were visually acceptable after 19 days, but flavor 

scores fell after 13 days storage (Silva et al. 1987). 

An informal taste panel determined that fresh-cut 

honeydew melon stored in air at 5 °C (41 °F) for 6 

days lacked acceptable textural characteristics and 

were flat in flavor (Qi et al. 1998). 

Fresh-cut pineapple stored at 4 °C (39 °F) had 

excellent visual appearance after 7 to 10 days 

storage; however, fruit in the lower portion of 

containers developed off flavors associated with 

microbial fermentation (Spanier et al. 1998). 

Fresh-cut orange segments that had acceptable 

appearance after 14 days storage were found to 

have unacceptable flavor quality after only 5 days 

at 4 °C (39 °F) (Rocha et al. 1995). Likewise, 

undesirable flavor was the limiting factor in sliced 

wrapped watermelon stored 7 days at 5 °C (41 

°F), even though aroma was still acceptable and 

microbial populations were not problematic until 

after 8 days (Abbey et al. 1988).

Establishing overall shelf-life limits for fresh-cut 

fruit, taking flavor quality into consideration, is 

difficult since initial product variability, potential 

post-cutting treatments, and packaging affect flavor 

attributes differently. Washing whole products prior 

to processing and other proper sanitation practices, 

in combination with optimum storage temperature, 

are critical to maintaining quality and prolonging 

product life. Little is known concerning what effect 

storage temperature has on volatile production and 

little flavor and sensory work has been performed 

on fresh-cut fruits.

Microbiology

Microbial decay can be a major source of spoilage 

of fresh-cut produce (Brackett 1994). Microbial 

decay of fresh-cut fruit may occur much more 

rapidly than in vegetable products because of 

the high levels of sugars found in most fruit. 

The acidity of fruit tissue usually helps suppress 

bacterial growth but not growth of yeast and 

molds. There is no evidence to suggest that lower 

aerobic plate counts (APC) or total plate counts 

(TPC) immediately after processing correlate 

with increased shelf-life in fresh-cut vegetables. 

However, for fresh-cut fruit, very low APC, TPC, 

and especially yeast and mold counts correlate 

with increased shelf-life.

The dominant microorganisms associated with 

spoilage of fresh-cut vegetables are bacteria 

(for example, Pseudomonas spp.), whereas the 

dominant microorganisms associated with the 

spoilage of fresh-cut fruit products are yeasts and 

molds. In fresh-cut vegetables the proliferation 

of bacteria may be a symptom associated with 

tissue senescence and may not be a true cause of 

spoilage except in a few rare exceptions when 

pectinolytic Pseudomonas are present. However, 

in acidic fresh-cut fruit products, yeasts and molds 

are typically associated with product spoilage. 

Reducing initial yeast and mold counts, as well as 

slowing growth by low temperature storage at <5 

°C (41 °F), affects product shelf-life (O’ConnorShaw et al. 1994, Qi et al. 1999). In fresh-cut fruit 

with a neutral pH, such as cantaloupe, bacteria 

were the main source of spoilage (Lamikanra 

et al. 2000), and bacterial development was 

inhibited in fresh-cut watermelon by CA (3% O2

and 15 or 20% CO2

). However, visual quality was 

compromised (Cartaxo et al. 1997).

Little research has been performed on foodborne 

human pathogens on fresh-cut fruits. Conway et 

al. (2000) determined that Listeria monocytogenes

survived and proliferated on ‘Delicious’ apple 

slices stored at 10 or 20 °C (50 or 68 °F) in air 

or CA (0.5% O2

 + 15% CO2) but did not grow 

at 5 °C (41 °F). CA had no significant effect on 

the survival or growth of L. monocytogenes at 

elevated temperatures. Botulinal toxin was not 
609

recovered in fresh-cut cantaloupe or honeydew 

inoculated with a 10-strain mixture of proteolytic 

and nonproteolytic Clostridium botulinum after 

21 days at 7 °C (45 °F). However, toxin was 

recovered in some inoculated honeydew samples 

stored 9 days at 15 °C (59 °F) in hermetically 

sealed packages (Larson and Johnson 1999).

Factors Affecting Fresh-Cut Fruit Quality

Major factors affecting fresh-cut fruit quality are 

cultivar (Kim et al. 1993, Romig 1995), preharvest 

cultural practices (Romig 1995), harvest maturity 

(Gorny et al. 1998b), physiological status of the 

raw product (Brecht 1995), postharvest handling 

and cold storage (Watada et al. 1996), processing 

technique (Bolin et al. 1977, Saltveit 1997, Wright 

and Kader 1997b), sanitation (Hurst 1995), and 

packaging (Solomos 1994, Cameron et al. 1995).

General Fresh-Cut Physiology and Physiological 

Concerns

Most fruit are very susceptible to bruising and 

mechanical injury. This is very different from 

most fresh-cut vegetables, which may be derived 

from very durable root tissues (carrots, radishes) 

or pliable leaf tissue (iceberg lettuce, cabbage). 

Fresh-cut processing removes the fruit’s natural 

cuticle, or skin barrier, to gas diffusion and 

microbial invasion, and severe disruption of 

the tissue often provokes increased respiration, 

ethylene production, and enhanced susceptibility 

to water loss and microbial decay. All of these 

factors may contribute to decreased shelf-life via 

browning, off color, softening, or decay. 

Subsequently, methods for cutting and peeling 

fruit differ from those for vegetables. Therefore, 

mechanical size reduction (trimming, peeling, 

deseeding, etc.) by high-speed cutting equipment 

may not be appropriate for some fresh-cut fruit 

products. Knife sharpness has a significant effect 

on shelf-life of fresh-cut lettuce products (Bolin 

et al. 1977, Bolin and Huxsoll 1991), and this also 

applies to fresh-cut fruits. Pear slices cut with a 

freshly sharpened knife retained visual quality 

longer than fruit cut with a dull hand-slicer (Gorny 

and Kader 1996). Sharpening of machine and 

hand knives as often as possible prolongs shelflife of fresh-cut fruit because there is less tissue 

injury.

Chilling Injury and Holding Temperatures

A significant number of fresh-cut fruits are not as 

chilling injury (CI) sensitive as the corresponding 

intact fruit before processing. Examples include 

pineapple, cantaloupe, honeydew, watermelon, 

peach, nectarine, and mango. If these intact fruits 

are stored at chilling temperatures, typically <12 

°C (54 °F), accelerated physiological breakdown 

and increased incidence of pathological decay 

occurs. CI symptoms are often manifested when 

fruit are subsequently placed at non-chilling 

temperatures and may not be visible if maintained 

at chilling temperatures (Saltveit and Morris 

1990). Nonetheless, precooling whole cantaloupe 

to below their optimal long-term storage 

temperature shortly before cutting is effective at 

increasing product shelf-life (Cantwell and Portela 

1997, Lange 1998).

Fruit tissues normally damaged by storage at 

chilling temperatures are the inedible outer rind 

or skin portions. During fresh-cut processing, 

these tissues are normally removed and discarded. 

Although the optimal storage temperature for 

many whole CI-sensitive fruit is above 10 °C 

(50 °F), after processing storage at 0 °C (32°F) 

is almost always the temperature that provides 

optimal shelf-life by reducing growth of spoilage 

microorganisms. However, the edible flesh of CIsensitive fruits may still be susceptible to chilling 

injury, and no studies have indicated if flavor 

biosynthesis is inhibited or negatively affected by 

chilling.

Variety, Growing Region, and Season

Seed companies and numerous fresh-cut 

processors are already aware that a given variety 

performs optimally in certain growing regions 

and oftentimes has variable postharvest quality 
610

attributes depending on cultural practices, climate, 

season, and harvest maturity. For example, the 

desirable volatile oil content of pineapple flesh 

is higher in summer fruit (Haagen-Smit et al. 

1945), and the proportions of dominant apple 

volatiles vary by season (López et al. 1998). 

The aforementioned interactions, in concert with 

breeding against or for specific traits to optimize 

shelf-life, must be considered when developing 

cultivars tailored for the fresh-cut industry (Romig 

1995). Several reports have documented that 

certain cultivars out-perform others with regard to 

fresh-cut shelf-life and quality (Kim et al. 1993, 

Cantwell and Portela 1997, Lange 1998, Gorny et 

al. 1999, Anonymous 2000b). However, no single 

study can encompass all desirable varieties, and 

singling out a “winner” can be compromised by 

seed source and seasonal/climactic variations. 

Furthermore, the industry may also be historically 

driven toward specific varieties (such as western 

cantaloupes) when indeed optimum alternatives 

exist for local seasonal production (such as eastern 

cantaloupes) (Lange 1998).

Gorny et al. (1999) determined the shelf-life of 

peach and nectarine slices made from 13 cultivars 

of peaches and eight cultivars of nectarines that 

had been ripened to between 4 to 7 lb (18 to 31 

N) firmness, cut, and then held at 0 °C (32 °F) 

with 90 to 95% RH. Shelf-life was 2 to 12 days 

among the cultivars tested. Of the peach cultivars 

tested, ‘Cal Red,’ ‘Red Cal,’ and ‘Elegant Lady’ 

had the longest marketable shelf-life of 7.4, 7.2, 

and 6.7 days, respectively; while ‘Summer Lady’ 

and ‘Ryan Sun’ had the shortest (<2 days). Among 

nectarines, ‘Sparkling Red,’ ‘Arctic Queen,’ and 

‘Zee Grand’ had the longest shelf-life of 12, 8, 

and 8 days, respectively, while the other cultivars 

had a shelf-life of 4 to 6 days. White-flesh peaches 

and nectarines had a comparable shelf-life to 

yellow-fleshed cultivars, with similar browning 

characteristics.

Based on visual quality, fresh-cut pear slices 

prepared from partially ripened ‘Bosc’ and 

‘Bartlett’ fruit had the longest shelf-life in air at 

10 °C (50 °F), being 3 and 4 days, respectively 

(Gorny et al. 1998a). d‘Anjou’ and ‘Red Anjou’ 

pear slices had a very short shelf-life of <2 days 

each, due to severe enzymatic browning on cut 

surfaces (Gorny et al. 1998a). However, ‘Bartlett’ 

and ‘Bosc’ pear slices experienced a much greater 

loss in firmness after slicing and storage in air at 

10 °C (50 °F) than d‘Anjou’ and Red d’Anjou’ 

slices.

Fruit Size and Yield

Typically, fresh-cut fruit processors will use 

either very large or very small fruit to maximize 

yields or to reduce the cost of raw ingredients. For 

example, fresh-cut melon processors will typically 

use very large 9-count-per-box fruit. This is 

because large melons are often available at lower 

prices in the marketplace, the yield from larger 

melon fruits is almost always higher, and the 

labor to process one large fruit is often less than 

processing many smaller fruit. Very little research 

has been done to document the effects of fruit 

size on post-cutting shelf-life and quality. One 

study by Gorny et al. (2000) found that ‘Bartlett’ 

pear fruit size did not have a significant effect on 

fresh-cut slice shelf-life, based on flesh color and 

firmness, if slices were treated after cutting with 

2% ascorbate + 1% calcium lactate + 0.5% (w/v) 

cysteine, pH 7. However, if slices were not treated, 

smaller fruit discolored at their cut surface more 

rapidly than slices from large fruit. Small fruit also 

had lower SSC than large fruit, which may affect 

eating quality. These findings demonstrate that, 

in some cases, smaller whole fruit, which often 

receive lower prices in the marketplace, should be 

avoided for value-added fresh-cut products.

Physical Treatments

Many physical and chemical techniques have 

been studied as alternatives or adjuncts to MAP, 

especially for fresh-cut fruit: edible coatings 

(Baldwin et al. 1995a,b, 1996, Howard and Dewi 

1996, Li and Barth 1998), disinfection (Hong and 

Gross 1998, Sapers and Simmons 1998), natural 

plant products (Kato-Noguchi and Watada 1997, 

Leepipattanawit et al. 1997, Buta et al. 1999, 

Moline et al. 1999), ethylene absorbents (Abe and 

Watada 1991), gamma irradiation (Chervin and 
611

Boisseau 1994, Hagenmaier and Baker 1997), 

heat treatments or heat shock (Loaiza-Velarde 

et al. 1997), microbial competition (Liao 1989, 

Breidt and Fleming 1997), non-thermal physical 

treatments (Hoover 1997), and pulsed-microwave 

irradiation (Shin and Pyun 1997).

Storage Time, Temperature, and Atmosphere

The beneficial effects of CA storage for whole 

fruit have been well documented, and CA is 

widely employed throughout the industry. 

However, CA storage markedly inhibits apple 

volatile production (Yahia 1991, 1994, Mattheis 

et al. 1995). Furthermore, fruit maturity at harvest 

has been shown to be important in terms of 

volatile production in melons (Pratt 1971, Wyllie 

et al. 1996, Beaulieu and Grimm 2001, Beaulieu 

and Baldwin 2002) and in apples (Hansen et al. 

1992, Brackmann et al. 1993, Yahia et al. 1990), 

especially once apple fruit were removed from CA 

and ripened 10 days at 20 °C (68 °F) (Mattheis 

et al. 1995). In fresh-cut ‘Gala’ apples stored for 

14 days at 1 °C (34 °F) in sealed pouches, sugars 

remained constant during storage, pH decreased, 

and TA, sweetness, and sweet aromatic flavor all 

increased and then decreased (Bett et al. 2001). 

Therefore, certain packaged fresh-cut products 

may require active modification of the atmosphere 

to ensure desirable flavor during consumption.

Gorny et al. (2002) determined that, compared 

to air storage, CA (2% O2

 + 98% N2) storage 

at -1 °C (30 °F) of whole mature-green pears 

extended shelf-life of slices 1 to 2 days. There was 

a significant reduction in shelf-life of pear slices 

stored at -1 °C (30 °F) in air or CA compared to 

slices from freshly harvested pears. Therefore, it 

seems beneficial to use CA for off-season pears 

(as opposed to air-stored) to maximize postcutting life of slices. However, research is needed 

to determine if volatile synthesis is impaired, as in 

CA-stored apples.

Modified Atmosphere Packaging (MAP) 

MAP is widely used for fresh-cut vegetables, but 

with fruits occasionally undesirable atmospheres 

can reduce quality due to off flavor and 

discoloration (Gil et al. 1998).

Heat Treatment

Slices prepared from heat-treated apples at 45 

°C (113 °F) for 105 min, that did not display 

browning after treatment (‘Delicious,’ ‘Empire,’ 

‘Golden Delicious,’ ‘McIntosh’ and ‘New York 

674’), were firmer (differences ranging from 12% 

for ‘McIntosh’ to 48% for ‘Delicious’) after 8 days 

storage at 2 °C (36 °F) than those prepared from 

untreated apples (Kim et al. 1994). However, heat 

treatments often led to undesirable flesh browning 

in many other cultivars tested (Kim et al. 1994).

Irradiation

Irradiation of fresh-cut fruit products may be 

beneficial in reducing the number of bacteria 

present on the product. The current FDA limit 

for irradiation on fresh produce is 1.0 kGy, but 

to destroy yeasts and molds that may exist as 

spores, irradiation levels of 1.5 to 20 kGy are 

necessary (Brackett 1987); and these levels are 

damaging to fruit tissues. Irradiation reduced 

ethylene production of all pre- versus postclimacteric apple slices and irradiation doses of up 

to 2.4 kGy had minimal effect on the respiratory 

physiology of tissues (Gunes et al. 2000). 

However, tissue softening occurred at doses 

above 0.4 kGy. Therefore, the use of irradiation 

to extend the shelf-life of fresh-cut fruit products 

has only limited benefits since the main spoilage 

microorganisms on fresh-cut fruit products are 

yeasts and molds.
612

Chemical Treatments

Retention of fresh-cut product firmness and 

inhibition of browning are common measures 

used to determine efficacy of chemical treatments. 

Calcium has been used as an agent for maintaining 

firmness of whole produce (Poovaiah 1986), and 

its use in fresh-cut was inevitable. Other chemical 

treatments have also been explored, and most 

GRAS applications used today involve chlorine, 

ascorbic acid, or calcium salts for preservation.

Chlorination and Washes

In general, fresh-cut fruit should be rinsed just 

after cutting with cold (0 to 1°C, 32 to 34 °F) 

chlorinated water at pH 7.0. This may help extend 

product shelf-life by reducing microbial load, 

removing cellular juices at cut surfaces that may 

promote cut surface discoloration, and actually 

inhibiting the enzymatic reactions involved in fruit 

browning (Brecht et al. 1993, Hurst 1995).

Chlorination, as commonly used for fresh-cut 

salad sanitation (not exceeding 200 μL L-1 total 

chlorine), may not be desirable for all freshcut fruits. Post-cutting washing or dipping may 

have negative consequences regarding increased 

water activity and “washing away” of desirable 

flavor attributes. Processors may or may not 

wash freshly cut commodities that develop little 

or no browning (cantaloupe and honeydew, for 

example), since chemical treatments are seldom 

applied and because removal of free surface water 

(centrifugation or spinning) from the cut fruit can 

be damaging. On the other hand, honeydew and 

cantaloupe pieces dipped in hypochlorite (pH 6, 

50 μL L-1) prior to packaging in 95% N2

 + 5% 

O2

 at 2 °C (36 °F) had no deleterious effect and 

microbial counts were lowered throughout storage 

(Ayhan et al. 1998).

Hydrogen peroxide (H2

O2) is a strong oxidizing 

agent and a powerful surface-contact sterilizer. It 

has been shown experimentally to reduce microbe 

populations on the surface of many produce items 

with minimal to no residue (Bolin and Huxsoll 

1989, Sapers and Simmons 1998). However, the 

GRAS status regarding use on fresh-cut products 

is currently unclear.

Calcium Compounds and Firmness Retention

Application of aqueous calcium compounds 

(generally 1% CaCl2

 dips) helps maintain firmness 

of fresh-cut apples, pears, and strawberries 

(Ponting et al. 1971, 1972, Morris et al. 1985, 

Rosen and Kader 1989, Gorny et al. 1998a). 

Softening of muskmelon sections was affected 

differently depending on calcium concentration 

(Lester 1996). Softening was the major factor in 

quality loss in kiwifruit slices. However, these 

slices had a shelf-life of 9 to 12 days if treated 

with 1% CaCl2

 or 2% calcium lactate and stored 

at 0 to 2 °C with >90% RH in 2 to 4% O2

 and/or 5 

to 10% CO2 (Massantini and Kader 1995, Agar et 

al. 1999). Cantaloupe cylinders treated with 1, 2.5, 

and 5% CaCl2

 for 1 to 5 min and stored 10 days 

at 5 °C (41 °F) generally increased in firmness 

(Luna-Guzmán et al. 1999).

Calcium lactate has been shown to be as effective 

as the chloride form without imparting a bitter 

flavor at higher concentrations (Luna-Guzmán 

and Barrett 2000). A 1% calcium lactate dip was 

an effective alternative to ascorbate in fresh-cut 

‘Bartlett’ pears stored 1 to 2 days at 20 °C (68 °F), 

and 1% calcium lactate with 2% ascorbate was 

most effective (Gorny et al. 1998a).

Antibrowning Compounds

Many fruits brown rapidly after cutting, and 

extensive work has been performed to address 

this quality loss. Cut surface discoloration or 

enzymatic browning, caused by formation of 

quinones in the presence of O2

 and PPO, has been 

the subject of much research (Vámos-Vigyázó 

1981, Sapers 1993). Since sulfite use as an antibrowning agent in the United States requires 

labeling for fresh produce, alternative GRAS and 

experimental compounds have been investigated. 

Nevertheless, enzymatic browning still represents 

a major challenge with fresh-cut fruit (Weller et al. 

1997, Sapers and Miller 1998).
613

Ascorbate, citrate, isoascorbate, and sodium 

erythorbate are some of the most commonly 

used agents to reduce or eliminate cut-surface 

discoloration. Ascorbate was more effective 

than erythorbate in preventing surface browning 

in ‘Winesap’ and ‘Red Delicious’ apple plugs 

stored 24 h, and 1% citric acid enhanced their 

effectiveness (Sapers and Zoilkowski 1987). Cut 

surface discoloration was restricted in vacuumpacked carambola slices stored at 4 °C (39 °F) 

that were treated with 1 or 2.5% citrate plus 

0.25% ascorbate (Weller et al. 1997). Ascorbate2-phosphate and ascorbate-2-triphosphate also 

decreased cut surface discoloration in ‘Red 

Delicious’ apple plugs for 24 h (Sapers et 

al. 1989). ‘Fuji’ apple slices treated with 2% 

ascorbate had no browning or loss of visual 

quality for up to 15 days when stored at 10 °C 

(50 °F) in 0.25% O2

 (Gil et al. 1998). Calcium, 

in combination with ascorbate, was effective 

in preventing discoloration of fresh-cut apples 

(Ponting et al. 1972) and pears (Rosen and Kader 

1989, Gorny et al. 1998a). Browning was also 

reduced in fresh-cut ‘Carnival’ peaches treated 

with 1% calcium lactate plus 2% ascorbate (Gorny 

et al. 1999). 

Browning was retarded in slightly under-ripe 

‘Bartlett’ and ‘d’Anjou’ pears treated with a 

combination of sodium erythorbate, CaCl2

, and 

4-hexylresorcinol after 14 days storage at 4 °C 

(39 °F). However, fresh-cut ‘Bosc’ pears browned 

severely irrespective of inhibitor treatment 

(Sapers and Miller 1998). On the other hand, a 

combination dip with 0.01% 4-hexylresorcinol, 

0.5% ascorbate, and 1% calcium lactate extended 

shelf-life of ‘Anjou,’ ‘Bartlett,’ and ‘Bosc’ pear 

slices for 15 to 30 days (Dong et al. 2000). 

Furthermore, combined treatments with 1 mM 

4-hexylresorcinol, 0.5 M isoascorbate, 50 mM 

potassium sorbate, and 25 mM N-acetylcysteine 

decreased browning in fresh-cut ‘Anjou,’ 

‘Bartlett,’ and ‘Bosc’ pears for 14 days. The 

preservative effect was unaffected by initial 

firmness (4.7 to 11.7 lb, 21 to 52 N) for ‘Anjou’ 

slices (Buta and Abbott 2000).

‘Red Delicious’ apple slices treated with a 

combined antibrowning dip (4-hexylresorcinol, 

isoascorbic acid, N-acetylcysteine, and calcium 

propionate) and held at 5 °C (41 °F) maintained 

visual quality for 5 weeks, yet microbial decay 

was evident after 4 weeks (Buta et al. 1999). 

Analyses of organic acids and sugars revealed that 

slices treated with combinations of antibrowning 

compounds retained higher levels of malate and 

had no decrease in sugar levels at 5 and 10 °C 

(41 and 50 °F), indicating that higher quality was 

maintained during storage. Fresh-cut mangoes 

treated with 1 mM 4-hexylresorcinol, 50 mM 

potassium sorbate, and 500 mM ascorbic acid 

in MAP at 10 °C (50 °F) maintained color and 

sensory characteristics, with low microbial 

growth, for 14 days (Gonzalez-Aguilar et al. 

2000). Cut-surface discoloration was significantly 

reduced in fresh-cut banana slices treated with 

500 mM citrate and 50 mM N-acetylcysteine and 

stored at 5 °C (41 °F) or 15 °C (59 °F) for 7 days, 

and no microbial decay was observed (Moline 

et al. 1999). A combination of 0.5% carrageenan 

and 0.5% citrate also inhibited browning in diced 

‘Granny Smith’ and ‘Red Delicious’ apples for 7 

to 9 days at 3 °C (37 °F) (Tong and Hicks 1991).

Cysteine inhibits PPO-mediated enzymatic 

browning (Joslyn and Ponting 1951, Molnar-Perl 

and Friedman 1990, Gunes and Lee 1997). Three 

mechanisms have been proposed to explain how 

thiol compounds inhibit enzymatic browning: 

reduction of o-quinone back to o-dihydroxyphenol 

(Kahn 1985); direct inhibition of PPO (Dudley 

and Hotchkiss 1989, Robert et al. 1996); and 

formation of a colorless cys-quinone adduct 

(Richard et al. 1991).

When cysteine is used as an inhibitor of 

enzymatic browning on sliced apples (Walker and 

Reddish 1964) or pears (Sapers and Miller 1998), 

pinkish-red off-colored compounds are formed 

due to phenol regeneration with deep 

color formation (Richard-Forget et al. 1992). If 

off-color formation can be prevented, cysteine 

may prove to be an effective replacement to 

bisulfites. Cysteine is a naturally occurring 

amino acid that has GRAS status for use as a 

dough conditioner (Code of Federal Regulations 

21:184.1271 and 21:184.1272). Development of 

cut surface discoloration was reduced for only 
614

1 day at 0 °C (32 °F) in ‘Golden Delicious’ freshcut apples treated with 0.1% cysteine (Nicoli et al. 

1994). Ineffectiveness of the cysteine treatment 

was attributed to oxidation in the package and 

likely was due to the low concentration applied. 

Gorny et al. (2002) reported that a post-cutting 

dip (pH 7.0) of 2% ascorbate, 1% calcium 

lactate, plus 0.5% (weight by volume) cysteine 

significantly extended shelf-life of ‘Bartlett’ 

pear slices by inhibiting loss of firmness and 

preventing browning. Consumer panelists could 

not distinguish between pear slices treated with 

the preservative and controls. After 10 days in air 

at 0 °C (32 °F), 82 and 70% of consumers judged 

treated pear slices to be acceptable in appearance 

and flavor, respectively.

When used in combination with ascorbic acid, 

4-hexylresorcinol is an effective inhibitor of cut 

discoloration on many fresh-cut fruit, including 

apples and pears especially ( Monslave-Gonzalez 

et al. 1993, Luo and Barbosa-Cánovas 1996, 1997, 

Sapers and Miller 1998, Moline et al. 1999, Buta 

and Abbott 2000, Dong et al. 2000). Between 1 

and 7 μL L-1 of residual 4-hexylresorcinol was 

necessary to prevent browning on fresh-cut pear 

slices stored up to 14 days at 2 to 5 °C (36 to 41 

°F) (Dong et al. 2000). Although it is effective in 

preventing cut surface browning, it is not currently 

considered GRAS by the FDA and may not be 

used on fresh-cut fruit. It may also impart an 

unacceptable off flavor on fruit products.

Antimicrobials, Edible Coatings, and Other 

Treatment Compounds

Hexanal is a natural aroma precursor in apples that 

is readily converted to aroma volatiles in vivo by 

fresh-cut apple slices (Song et al. 1996). Hexanal 

can not only enhance aroma, but it also reduced 

enzymatic browning at cut surfaces, as well as 

inhibiting molds, yeasts, and mesophilic and 

psychrotrophic bacteria in ‘Granny Smith’ slices 

stored at 15 °C (59 °F) (Lanciotti et al. 1999). The 

inclusion of hexanal and (E)-hexenal in the MAP 

(70% N2

 + 30% CO2) of sliced ‘Granny Smith’ 

apples reduced spoilage microbe populations 

and increased color stability for up to 16 days at 

abusive storage temperatures (Corbo et al. 2000). 

Research is currently in the initial stages for the 

use of volatile compounds on fresh-cut products; 

hexanal is not currently approved for use.

Methyl jasmonate is a naturally occurring 

volatile compound, found in many plants, that 

has hormonelike activity at low concentrations. 

Exogenously applied methyl jasmonate is effective 

in reducing mold growth on fresh-cut celery and 

peppers and may have applications as a naturally 

derived fungicide (Buta and Moline 1998).

Edible coatings have been used in an attempt to 

preserve fresh-cut products because the coatings 

act as barriers to water loss and gas exchange, 

creating a micromodified atmosphere around 

products, and can serve as carriers for other GRAS 

compounds (Baldwin et al. 1995a). Ethylene 

production and CO2

 evolution were reduced in 

apple slices coated with double layers of buffered 

polysaccharide/lipid, stored at 23 °C (73 °F) 

(Wong et al. 1994). Use of a cellulose-based 

edible coating on fresh-cut apple cylinders stored 

in overwrapped trays at 4 °C (39 °F) increased 

shelf-life by about 1 week (Baldwin et al. 1996). 

The effectiveness of ascorbate to reduce browning 

and potassium sorbate to decrease microbial 

growth was superior when incorporated into this 

edible coating. A commercially available sucrose 

ester edible coating also inhibits browning of 

fresh-cut fruit by acting as an O2

 barrier.

Peeled, packaged citrus products have a shelf-life 

of approximately 17 to 21 days, but fluid leakage 

can be problematic. Edible wax microemulsion 

coatings (up to 12% SSC) reduced leakage of drypacked grapefruit segments by 80% after 2 weeks 

and by 64% after 4 weeks (Baker and Hagenmaier 

1997). Coatings could be made with polyethylene, 

candelilla, or carnauba wax with lauric, stearic, 

palmitic, oleic, or myristic acids. Carnauba wax 

was most effective, and coatings were not detected 

by informal taste panels (Baker and Hagenmaier 

1997).
615

Compendium of Recommendations and 

Data Related to Fresh-Cut Fruit Products

Proper storage temperature and atmosphere are 

the two most important factors that influence 

post-cutting shelf-life of fresh-cut fruit. Tables 

1 and 2 identify optimum storage atmospheres, 

temperatures, and respiration rates for a range of 

fresh-cut fruits. This information may be used as 

a starting point for design and testing of MAP for 

fresh-cut fruit products. Fresh-cut fruit respiration 

rates, as well as responding to atmospheric 

modification, will vary depending on many 

factors, including variety and maturity of fruit at 

cutting.

Table 1. Respiration rates for fresh-cut fruits in air at various storage temperatures

________________________________________________________________________________

Fresh-cut product Temperature (oC)

________________________________________________________________

0 to 2.5 4 to 5 10 15 20 to 23

________________________________________________________________________________

mg CO2 kg-1 h-1

Apple, sliced 

 ‘Fuji’ — — 6.7-19.0 — —

Cantaloupe, cubed 4.0-16.0 5.9-31.2 11.4 — 54.0

Honeydew, cubed 3.6-10.2 — — 18.9-85.1 —

Kiwifruit, sliced 2.0-6.0 — — — 32.4-46.8

Orange, sliced — 5.3-5.7 — — 30.8-32.9

Peach, sliced 6.0-12.0 11.7-44.9 32.3-100.7 — —

Pear, sliced 

 ‘Bartlett’ 0.0-10.0 — 22.8-30.4 — 90.0

 ‘Bosc’ — — 15.2-26.6 — —

 ‘d’Anjou’ — — 13.3-26.6 — —

 ‘Red d’Anjou’ — — 11.4-26.6 — —

Pineapple, cubed 

 mature green 4.0-5.0 — 6.7-15.2 — —

 Golden 11.0-14.0 — 24.7-30.4 — —

Pomegranate, arils 1.0-4.0 2.9-5.9 5.7-11.4 — —

Strawberry, sliced — 11.1 — — 315.0

________________________________________________________________________________

From Gorny (1998), updated based on references cited in this chapter. 

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.
616

Table 2. Storage atmosphere recommendations for selected fresh-cut fruits

________________________________________________________________________

 Atmosphere

 

Fresh-cut product Temperature O2 CO2 Efficacy

________________________________________________________________________

oC %

Apple, sliced 0-5 <1 — moderate

Cantaloupe, cubed 0-5 3-5 6-15 good

Honeydew, cubed 0-5 2 10 good

Kiwifruit, sliced 0-5 2-4 5-10 good

Mango, cubed 5 2-4 10 moderate

Orange, sliced 0-5 14-21 7-10 moderate

Peach, sliced 0 1-2 5-12 poor

Pear, sliced 0-5 0.5 <10 poor

Persimmon, sliced 0-5 2 12 poor

Pomegranate, arils 0-5 - 15-20 good

Strawberry, sliced 0-5 1-2 5-10 good

Watermelon, sliced 3 3 10-20 poor

____________________________________________________________________________

From Gorny 1998, updated based on references cited in this chapter such as Rattanapanone and 

Watada 2000.

References

Abbey, S.D., E.K. Heaton, D.A. Golden, and 

L.A. Beuchat. 1988. Microbiological and sensory 

quality changes in unwrapped and wrapped sliced 

watermelon. J. Food Prot. 51:531-533.

Abe, K., and A.E. Watada. 1991. Ethylene 

absorbent to maintain quality of lightly processed 

fruits and vegetables. J. Food Sci. 56:1589-1592.

Abeles, F.B., P.W. Morgan, and M.E. Saltveit. 

1992. Ethylene in Plant Biology, 2nd Edition, 

Academic Press, San Diego.

Agar, I.T., B. Hess-Pierce, and A.A. Kader. 1999. 

Postharvest CO2

 and ethylene production and 

quality maintenance of fresh-cut kiwifruit slices. J. 

Food Sci. 64(3):433-440.

AMS [U.S. Department of Agriculture, 

Agricultural Marketing Service]. 1998. Quality 

through verification program for the fresh-cut 

produce industry. Federal Register 63:47220-

47224.

Anonymous. 1998. Food and Drugs. Food 

labeling. Code of Federal Regulations, 

21CFR101.95.

Anonymous. 2000a. No substitute for flavor in 

fresh-cut. Fresh Cut, May, pp. 22-28.

Anonymous. 2000b. Supplying quality cantaloupe 

for fresh-cut processing. Fresh Cut, Jan, pp. 6-12.

Ayhan, Z., G.W. Chism, and E.R. Richter. 1998. 

The shelf-life of minimally processed fresh cut 

melons. J. Food Qual. 21:29-40.
617

Baker, R.A., and R.D. Hagenmaier. 1997. 

Reduction of fluid loss from grapefruit segments 

with wax microemulsion coatings. J. Food Sci. 

62:789-792.

Baldwin, E.A., M.O. Nisperos, X. Chen, and R.D. 

Hagenmaier. 1996. Improving storage-life of cut 

apple and potato with edible coating. Postharv. 

Biol. Technol. 9:151-163.

Baldwin, E.A., M.O. Nisperos-Carriedo, and 

R.A. Baker. 1995a. Edible coatings for lightly 

processed fruits and vegetables. HortScience 

30:35-38.

Baldwin, E.A., M.O. Nisperos-Carriedo, and 

R.A. Baker. 1995b. Use of edible coatings to 

preserve quality of lightly (and slightly) processed 

products. CRC Crit. Rev. Food Sci. Nutr. 35:509-

524.

Beaulieu, J.C., and E.A. Baldwin, 2002. Flavor 

and aroma of fresh-cut fruits and vegetables. In O. 

Lamikanra, ed., Fresh-Cut Fruits and Vegetables. 

Science, Technology and Market, pp. 391-425. 

CRC Press, Boca Raton, FL.

Beaulieu, J.C., K.L. Bett, E.T. Champagne, et al. 

1999. Flavor, sensory and postharvest evaluations 

of commercial versus tree-ripe fresh-cut ‘Bounty’ 

peaches. HortScience 34:504.

Beaulieu, J.C., and C.C. Grimm. 2001. 

Identification of volatile compounds in cantaloupe 

at various developmental stages using solid phase 

microextraction. J. Agric. Food Chem. 49:1345-

1352.

Bett, K.L., D.A. Ingram, C.C. Grimm, et al. 2001. 

Flavor of fresh-cut ‘Gala’ apples in modified 

atmosphere packaging as affected by storage time. 

J. Food Qual. 24:141-156.

Bolin, H.R., and C.C. Huxsoll. 1989. Storage 

stability of minimally processed fruit. J. Food 

Proc. Preserv. 13:281-292.

Bolin, H.R., and C.C. Huxsoll. 1991. Effect of 

preparation procedures and storage parameters on 

quality retention of salad-cut lettuce. J. Food Sci. 

56:60-62,67.

Bolin, H.R., A.E. Stafford, A.D. King Jr., and 

C.C. Huxsoll. 1977. Factors affecting the storage 

stability of shredded lettuce. J. Food Sci. 42:1319-

1321.

Brackett, R.E. 1987. Microbiological 

consequences of minimally processed fruits and 

vegetables. J. Food Qual. 10:195-206.

Brackett, R.E. 1994. Microbiological spoilage and 

pathogens in minimally processed refrigerated 

fruits and vegetables. In R.C. Wiley, ed., 

Minimally Processed Refrigerated Fruits and 

Vegetables, pp. 269-312. Chapman and Hall, 

London, U.K.

Brackmann, A., J. Streif, and F. Bangerth. 1993. 

Relationship between a reduced aroma production 

and lipid metabolism of apples after long-term 

controlled-atmosphere storage. J. Amer. Soc. Hort. 

Sci. 118:243-247.

Brecht, J.K. 1995. Physiology of lightly processed 

fruits and vegetables. HortScience 30:18-22.

Brecht, J.K., A.U.O. Sabaa-Srur, S.A. Sargent, 

and R.J. Bender. 1993. Hypochlorite inhibition of 

enzymatic browning of cut vegetables and fruit. 

Acta Hort. 343:341-344.

Breidt, F., and H.P. Fleming. 1997. Using lactic 

acid bacteria to improve the safety of minimally 

processed fruits and vegetables. Food Technol. 

51:44-46, 48-51.

Buta, J.G., and J.A. Abbott. 2000. Browning 

inhibition of fresh-cut ‘Anjou’, ‘Bartlett’, and 

‘Bosc’ pears. HortScience 35:1111-1113.

Buta, J.G., and H.E. Moline. 1998. Methyl 

jasmonate extends shelf-life and reduces microbial 

contamination of fresh-cut celery and peppers. J. 

Agric. Food Chem. 46:1253-1256.
618

Buta, J.G., H.E. Moline, D.W. Spaulding, and C.Y. 

Wang. 1999. Extending storage-life of fresh-cut 

apples using natural products and their derivatives. 

J. Agric. Food Chem. 47:1-6.

Cameron, A.C., P.C. Talasila, and D.W. Joles. 

1995. Predicting film permeability needs for 

modified-atmosphere packaging of lightly 

processed fruits and vegetables. HortScience 

30:25-34.

Cantwell, M., and Portela, S. 1997. Comparing 

varieties and storage method. FreshCut, Oct., pp. 

14-18.

Cartaxo, C.B.C., S.A. Sargent, and D.J. Huber. 

1997. Controlled atmosphere storage suppresses 

microbial growth on fresh-cut watermelon. Proc. 

Fla. Sta. Hort. Soc. 110:252-257.

Chervin, C., and P. Boisseau. 1994. Quality 

maintenance of “ready-to-eat” shredded carrots by 

gamma irradiation. J. Food Sci. 59:359-361.

Conway, W.S., B. Leverentz, R.A. Saftner, 

et al. 2000. Survival and growth of Listeria 

monocytogenes on fresh-cut apple slices and 

its interaction with Glomerella cingulata and 

Penicillium expansum. Plant Dis. 84:177-181.

Corbo, M.R., R. Lanciotti, F. Gardini, et al. 2000. 

Effects of hexanal, trans-2-hexenal, and storage 

temperature on shelf-life of fresh sliced apples. J. 

Agric. Food Chem. 48:2401-2408.

Dong, X., R.E. Wrolstad, and D. Sugar. 2000. 

Extending shelf-life of fresh-cut pears. J. Food 

Sci. 65:181-186.

Dudley, E.D., and J.H. Hotchkiss. 1989. Cysteine 

as an inhibitor of polyphenol oxidase. J. Food 

Biochem. 13:65-75.

Gil, M.I., J.R. Gorny, and A.A. Kader. 1998. 

Responses of ‘Fuji’ apple slices to ascorbic 

acid treatments and low-oxygen atmospheres. 

HortScience 33:305-309.

Gonzalez-Aguilar, G.A., C.Y. Wang, and J.G. 

Buta. 2000. Maintaining quality of fresh-cut 

mangoes using antibrowning agents and modified 

atmosphere packaging. J. Agric. Food Chem. 

48:4204-4208.

Gorny, J.R. 1998. A summary of CA and MA 

requirements and recommendations for fresh-cut 

(minimally processed) fruits and vegetables. In

J.R. Gorny, ed., Fresh-cut Fruits and vegetables 

and MAP, vol. 5, 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, July 13-18, 1997, pp. 30-66. 

University of California Postharvest Horticulture 

Series no. 19, University of California, Davis, CA.

Gorny, J.R., R.A. Cifuentes, B. Hess-Pierce, and 

A.A. Kader. 2000. Quality changes in fresh-cut 

pear slices as affected by cultivar, ripeness stage, 

fruit size, and storage regime. J. Food Sci. 65:541-

544.

Gorny, J.R., M.I. Gil, and A.A. Kader. 1998a. 

Postharvest physiology and quality maintenance 

of fresh-cut pears. Acta Hort. 464:231-236.

Gorny, J.R., B. Hess-Pierce, R.A. Cifuentes, and 

A.A. Kader. 2002. Quality changes in fresh-cut 

pear slices as affected by controlled atmospheres 

and chemical preservatives. Postharv. Biol. 

Technol. 24(3):271-278.

Gorny, J.R., B. Hess-Pierce, and A.A. Kader. 

1998b. Effects of fruit ripeness and storage 

temperature on the deterioration rate of fresh-cut 

peach and nectarine slices. HortScience 33:110-

113.

Gorny, J.R., B. Hess-Pierce, and A.A. Kader. 

1999. Quality changes in fresh-cut peach and 

nectarine slices as affected by cultivar, storage 

atmosphere and chemical treatments. J. Food Sci. 

64:429-432.

Gorny, J.R., and A.A. Kader. 1996. Fresh-cut 

fruit products. In M. Cantwell, ed., Fresh-Cut 

Products: Maintaining Quality and Safety. 

Postharvest Horticulture Series no. 10, University 

of California, Davis, CA.
619

Gunes, G., and C.Y. Lee. 1997. Color of 

minimally processed potatoes as affected by 

modified atmosphere packaging and antibrowning 

agents. J. Food Sci. 62:572-575,582.

Gunes, G., C.B. Watkins, and J.H. Hotchkiss. 

2000. Effects of irradiation on respiration and 

ethylene production of apple slices. J. Sci. Food 

Agric. 80:1169-1175.

Haagen-Smit, A.J., J.G. Kirchner, A.N. Prater, and 

C.L. Deasy. 1945. Chemical studies of pineapple 

(Ananas sativa Lindl). I. The volatile flavor and 

odor constituents of pineapple. J. Amer. Chem. 

Soc. 67:1646-1652.

Hagenmaier, R.D., and R.A. Baker. 1997. Lowdose irradiation of cut iceberg lettuce in modified 

atmosphere packaging. J. Agric. Food Chem. 

45:2864-2868.

Hansen, K., L. Poll, and M.J. Lewis. 1992. The 

influence of picking time on the postharvest 

volatile ester production of ‘Jonagold’ apples. 

Lebensm. Wiss. Technol. 25:451-456.

Hong, J.H., and K.C. Gross. 1998. Surface 

sterilization of whole tomato fruit with sodium 

hypochlorite influences subsequent postharvest 

behavior of fresh-cut slices. Postharv. Biol. 

Technol. 13:51-58.

Hoover, D.G. 1997. Minimally processed fruits 

and vegetables: reducing microbial load by nonthermal physical treatments. Food Technol. 51:66-

69,71.

Howard, L.R., and T. Dewi. 1996. Minimal 

processing and edible coating effects on 

composition and sensory quality of mini-peeled 

carrots. J. Food Sci. 61:643-645,651.

Hurst, W.C. 1995. Sanitation of lightly processed 

fruits and vegetables. HortScience 30:22-24.

Joslyn, M.A., and J.D. Ponting. 1951. Enzymecatalyzed oxidative browning of fruit products. 

Adv. Food Res. 3:44.

Kahn, V. 1985. Effect of proteins, protein 

hydolyzates and amino acids on o-diphenolase 

activity on polyphenol oxidase of mushroom, 

avocado and banana. J. Food Sci. 50:111-115.

Kato-Noguchi, H., and A.E. Watada. 1997. Citric 

acid reduces the respiration of fresh-cut carrots. 

HortScience 32:136-136.

Kim, D.M., N.L. Smith, and C.Y. Lee. 1993. 

Quality of minimally processed apple slices from 

selected cultivars. J. Food Sci. 58:1115-1117,1175.

Kim, D.M., N.L. Smith, and C.Y. Lee. 1994. 

Effect of heat treatment on firmness of apples and 

apple slices. J. Food Proc. Preserv. 18:1-8.

King, A.D. Jr., and H.R. Bolin. 1989. 

Physiological and microbiological storage stability 

of minimally processed fruits and vegetables. 

Food Technol. 43:132-135.

Lamikanra, O., J.C. Chen, D. Banks, and P.A. 

Hunter. 2000. Biochemical and microbial changes 

during the storage of minimally processed 

cantaloupe. J. Agric. Food Chem. 48:5955-5961.

Lanciotti, R., M.R. Corbo, F. Gardini, et al. 1999. 

Effect of hexanal on the shelf-life of fresh apple 

slices. J. Agric. Food Chem. 47:4769-4776.

Lange, D. 1998. Eastern cantaloupe varieties 

and their potential for fresh-cut melon products. 

FreshCut, Aug., pp. 17-18.

Larson, A.E., and E.A. Johnson. 1999. Evaluation 

of botulinal toxin production in packaged freshcut cantaloupe and honeydew melons. J. Food 

Prot. 62:948-952.

Leepipattanawit, R., R.M. Beaudry, and R.J. 

Hernandez. 1997. Control of decay in modified 

atmosphere packages of sliced apples using 

2-nonanone vapor. J. Food Sci. 62:1043-1047.

Lester, G.E. 1996. Calcium alters senescence rate 

of postharvest muskmelon fruit disks. Postharvest 

Biol. Technol. 7:91-96.
620

Li, P., and M.M. Barth. 1998. Impact of edible 

coatings on nutritional and physiological changes 

in lightly processed carrots. Postharvest Biol. 

Technol. 14:51-60.

Liao, C.H. 1989. Antagonism of Pseudomonas 

putida strain PP22 to phytopathogenic bacteria 

and its potential use as a biocontrol agent. Plant 

Dis. 73:223-226.

Loaiza-Velarde, J.G., F.A. Tomas-Barberan, 

and M.E. Saltveit. 1997. Effect of intensity and 

duration of heat-shock treatments on woundinduced phenolic metabolism in iceberg lettuce. J. 

Amer. Soc. Hort. Sci. 122:873-877.

López, M.L., M.T. Lavilla, M. Riba, and 

M. Vendrell. 1998. Comparison of volatile 

compounds in two seasons in apples: Golden 

Delicious and Granny Smith. J. Food Qual. 

21:155-166.

Luna-Guzmán, I., and D.M. Barrett. 2000. 

Comparison of calcium chloride and calcium 

lactate effectiveness in maintaining shelf stability 

and quality of fresh-cut cantaloupes. Postharv. 

Biol. Technol. 19:61-72.

Luna-Guzmán, I., M.I. Cantwell, and D.M. 

Barrett. 1999. Fresh-cut cantaloupe: effects 

of CaCl2

 dips and heat treatments on firmness 

and metabolic activity. Postharv. Biol. Technol. 

17:201-213.

Luo, Y., and G.V. Barbosa-Cánovas. 1996. 

Preservation of apple slices using ascorbic acid 

and 4-hexylresorcinol. Food Sci. Technol. Int. 

2:315-321.

Luo, Y., and G.V. Barbosa-Cánovas. 1997. 

Enzymatic browning and its inhibition in new 

apple cultivar slices using 4-hexylresorcinol 

in combination with ascorbic acid. Food Sci. 

Technol. Int. 3:195-201.

Massantini, R., and A.A. Kader. 1995. 

Conservazione e mantenimento qualitativo delle 

fette de kiwi [Storability and quality preservation 

of sliced kiwifruits]. Industrie Alimentari. 34:357-

360. Italian.

Mattheis, J.P., D.A. Buchanan, and J.K. Fellman. 

1995. Volatile compound production by Bisbee 

Delicious apples after sequential atmosphere 

storage. J. Agric. Food Chem. 43:194-199.

Moline, H.E., J.G. Buta, and I.M. Newman. 1999. 

Prevention of browning of banana slices using 

natural products and their derivatives. J. Food 

Qual. 22:499-511.

Molnar-Perl, I., and M. Friedman. 1990. Inhibition 

of browning by sulfur amino acids. Apples and 

potatoes. Agric. Food Chem. 38:1652-1656.

Monslave-Gonzalez, A., G.V. Barbosa-Cnovas, 

R.P. Cavallieri, et al. 1993. Control of browning 

during storage of apple slices by combed methods. 

4-Hexylresorcinol as an anti-browning agent. 

Food Sci. 58:797-800.

Morris, J.R., W.A. Sistrunk, C.A. Sims, and 

G.L. Main. 1985. Effects of cultivar, postharvest 

storage, preprocessing dip treatment and style of 

pack on the processing quality of strawberries. J. 

Amer. Soc. Hort. Sci. 110(2):172-177.

Nicoli, M.C., M. Anese, and C. Severini. 1994. 

Combined effects in preventing enzymatic 

browning reactions in minimally processed fruit. 

J. Food Qual. 17:221-229.

O’Connor-Shaw, R.E., R. Roberts, A.L. Ford, and 

S.M. Nottingham. 1994. Shelf-life of minimally 

processed honeydew, kiwifruit, papaya, pineapple 

and cantaloupe. J. Food Sci. 59:1202-1215.

O’Connor-Shaw, R.E., R. Roberts, A.L. Ford, 

and S.M. Nottingham. 1996. Changes in sensory 

quality of sterile cantaloupe dice stored in 

controlled atmospheres. J. Food Sci. 61:847-851.
621

Ponting, J.D., R. Jackson, and G. Walters. 1971. 

Refrigerated apple slices: effects of pH, sulfites 

and calcium on texture. J. Food Sci. 36:449-450.

Ponting, J.D., R. Jackson, and G. Watters. 1972. 

Refrigerated apple slices: preservative effects of 

ascorbic acid, calcium and sulfites. J. Food Sci. 

37:434-435.

Poovaiah, B.W. 1986. Role of calcium in 

prolonging the storage-life of fruits and 

vegetables. Food Technol. 40:86-89.

Portela, S.I., and M.I. Cantwell. 1998. Quality 

changes of minimally processed honeydew melons 

stored in air or controlled atmosphere. Postharv. 

Biol. Technol. 14:351-357.

Pratt, H.K. 1971. Melons. In A.C. Hulme, ed., The 

Biochemistry of Fruits and Their Products, pp. 

207-232. Academy Press, New York, NY.

Qi, L., A.E. Watada, and J.R. Gorny. 1998. 

Quality changes of fresh-cut fruits in CA storage. 

Fresh-Cut Fruits and Vegetables and MAP. In

M.E. Saltveit, ed., 7th International Controlled 

Atmosphere Research Conference, University of 

California, Davis, July 13-18, 1997, vol. 4, pp. 98-

117. University of California, Davis, CA.

Qi, L., T. Wu, and A.E. Watada. 1999. Quality 

changes of fresh-cut honeydew melons during 

controlled atmosphere storage. J. Food Qual. 

22:513-521.

Rattanapanone, N., and A.E. Watada. 2000. 

Respiration rate and respiratory quotient of freshcut mango (Mangifera indica L.) in low oxygen 

atmosphere, pp. 471-478. In S. Subhadrabandhu, 

and A. Pichakum, Proceedings of the 6th 

International Symposium on Mango, International 

Society for Horticultural Science, Working Group 

on Mango, April 6-9, Leuven, Belgium 

Richard, F.C., P.M. Goupy, J.J. Nicolas, et al. 

1991. Cysteine as an inhibitor or enzymatic 

browning. 1. Isolation and characterization of 

addition compounds formed during oxidation of 

phenolics by apple polyphenol oxidase. J. Agric. 

Food Chem. 39:841-847.

Richard-Forget, F.C., P.M. Goupy, and J.J. 

Nicholas. 1992. Cysteine as an inhibitor of 

enzymatic browning. 2. Kinetic studies. J. Agric. 

Food Chem. 40:2108-2114.

Robert, C., F. Richard-Forget, C. Rouch, et al. 

1996. A kinetic study of the inhibition of palmito 

polyphenol oxidase by L-cysteine. Int. J. Biochem. 

Cell Biol. 28:457-463.

Rocha, A.M.C.N., C.M. Brochado, R. Kirby, and 

A.M.M.B. Morais. 1995. Shelf-life of chilled 

cut orange determined by sensory quality. Food 

Control. 6:317-322.

Romig, W.R. 1995. Selection of cultivars 

for lightly processed fruits and vegetables. 

HortScience 30:38-40.

Rosen, J.C., and A.A. Kader. 1989. Postharvest 

physiology and quality maintenance of sliced pear 

and strawberry fruits. J. Food Sci. 54:656-659.

Saltveit, M.E. 1997. Physical and physiological 

changes in minimally processed fruits and 

vegetables. In F.A. Tomas-Barberan and R.J. 

Robins, eds., Phytochemistry of Fruits and 

Vegetables, pp. 205-220. Claredon Press, Oxford.

Saltveit, M.E., and L.L. Morris. 1990. Overview 

on chilling injury of horticultural crops. In Wang, 

C.Y., ed., Chilling Injury of Horticultural Crops, 

pp. 4-15. CRC Press, Boca Raton, FL.

Sapers, G.M. 1993. Browning of foods: control by 

sulfites, antioxidants, and other means. Scientific 

status summary. Food Technol. 47:75-84.

Sapers, G.M., P.H. Cooke, A.E. Heidel, et al. 

1997. Structural changes related to texture of prepeeled potatoes. J. Food Sci. 62:797-803.
622

Sapers, G.M., K.B. Hicks, J.G. Phillips, et al. 

1989. Control of enzymatic browning in apple 

with ascorbic acid derivatives, polyphenol oxidase 

inhibitors, and complexing agents. J. Food Sci. 

54:997-1002,1012.

Sapers, G.M., and R.L. Miller. 1998. Browning 

inhibition in fresh-cut pears. J. Food Sci. 63:342-

346.

Sapers, G.M., and G.F. Simmons. 1998. Hydrogen 

peroxide disinfection of minimally processed 

fruits and vegetables. Food Technol. 52:48-52.

Sapers, G.M., and M.A. Ziolkowski. 1987. 

Comparison of erythorbic and ascorbic acids as 

inhibitors of enzymatic browning in apple. J. Food 

Sci. 52:1732-1733.

Schlimme, D.V., and M.L. Rooney. 1994. 

Packaging of minimally processed fruits and 

vegetables. In R.C. Wiley, ed., Minimally 

Processed Refrigerated Fruits and Vegetables, pp. 

135-182. Chapman and Hall, New York, NY.

Shin, J.K., and Y.R. Pyun. 1997. Inactivation of 

Lactobacillus plantarum by pulsed-microwave 

irradiation. J. Food Sci. 62:163-166.

Silva, J.L., T. Chanrittisen, C.W. Shannon, and 

G.R. Ammerman. 1987. Shelf-life of refrigerated 

cantaloupe and watermelon pieces. Res. Rep. 

Miss. Agric. Forestry Expt. Stat. 12:1-4.

Solomos, T. 1994. Some biological and physical 

principles underlying modified atmosphere 

packaging. In R.C. Wiley, ed., Minimally 

Processed Refrigerated Fruits and Vegetables, pp. 

183-225. Chapman and Hall, New York, NY.

Song, J., R. Leepipattanawit, W. Deng, and 

R.M. Beaudry. 1996. Hexanal vapor is a natural, 

metabolizable fungicide: inhibition of fungal 

activity and enhancement of aroma biosynthesis in 

apple slices. J. Amer. Soc. Hort. Sci. 121:937-942.

Spanier, A.M., M. Flores, C. James, et al. 1998. 

Fresh-cut pineapple (Ananas sp.) flavor. Effect of 

storage. In E.T. Contis et al., eds., Developments 

in Food Science. Food Flavors: Formation, 

Analysis, and Packaging Influences, pp. 331-343. 

Elsevier, Maryland Heights | MO.

Tong, C.B.S., and K.B. Hicks. 1991. Sulfated 

polysaccharides inhibit browning of apple juice 

and diced apples. J. Agric. Food Chem. 39:1719-

1722.

Vámos-Vigyázó, L. 1981. Polyphenol oxidase 

and peroxidase in fruits and vegetables. CRC Crit. 

Rev. Food Sci. Nutr. 15:49-127.

Varoquaux, P., I. Lecendre, F. Varoquaux, and M. 

Souty. 1990. Changes in firmness of kiwifruit after 

slicing. Sci. Aliment. 10:127-139.

Walker, J.R.L. and C.E.S. Reddish. 1964. Note on 

the use of cysteine to prevent browning in apple 

products. J. Sci. Food Agric. 15:902-904.

Watada, A.E., K. Abe, and N. Yamauchi. 1990. 

Physiological activities of partially processed 

fruits and vegetables. Food Technol. 44:116, 118, 

120-122.

Watada, A.E., N.P. Ko, and D.A. Minott. 1996. 

Factors affecting quality of fresh-cut horticultural 

products. Postharv. Biol. Technol. 9:115-125.

Watada, A.E., and L. Qi. 1999. Quality of freshcut produce. Postharv. Biol. Technol. 15:201-205.

Weller, A., C.A. Sims, R.F. Matthews, et al. 

1997. Browning susceptibility and changes in 

composition during storage of carambola slices. J. 

Food Sci. 62:256.-260.

Wiley, R.C. 1994. Minimally Processed 

Refrigerated Fruits and Vegetables. Chapman and 

Hall, London, U.K.
623

Wong, D.W.S., S.J. Tillin, J.S. Hudson, and A.E. 

Pavlath. 1994. Gas exchange in cut apples with 

bilayer coatings. J. Agric. Food Chem. 42:2278-

2285.

Wright, K.P., and A.A. Kader. 1997a. Effect of 

controlled-atmosphere storage on the quality and 

carotenoid content of sliced persimmons and 

peaches. Postharv. Biol. Technol. 10:89-97.

Wright, K.P., and A.A. Kader. 1997b. Effect of 

slicing and controlled-atmosphere storage on the 

ascorbate content and quality of strawberries and 

persimmons. Postharv. Biol. Technol. 10:39-48.

Wyllie, S.G., D.N. Leach, and Y. Wang. 1996. 

Development of flavor attributes in the fruit of 

C. melo during ripening and storage. In G.R. 

Takeoka, R. Teranishi, P.J. Williams, and A. 

Kobayashi, eds., Biotechnology for Improved 

Foods and Flavors, pp. 228-239. American 

Chemical Society, Washington, DC.

Yahia, E.M. 1991. Production of some odoractive volatiles by ‘McIntosh’ apples following 

low-ethylene controlled-atmosphere storage. 

HortScience 26:1183-1185.

Yahia, E.M.. 1994. Apple flavor. Hort. Rev. 

16:197-234.

Yahia, E.M., T.E. Acree, F.W. Liu. 1990. The 

evolution of some odor-active volatiles during 

the maturation and ripening of apples on the tree. 

Lebensmitt. Wissensch. Technol. 23:488-493.
624

Fresh-Cut Vegetables

M. Margaret Barth, Hong Zhuang, and Mikal E. 

Saltveit

Barth and Zhuang are with Redi-Cut Foods, Inc., 

Franklin Park, IL; Saltveit is with the Department 

of Plant Sciences, University of California, Davis, 

CA.

Introduction

Wounds inflicted during the preparation of 

fresh-cut vegetables promote many physical and 

physiological changes that hasten loss of product 

quality (Brecht 1995, Saltveit 1997). Foremost 

among these are the removal of the protective 

epidermal layer and exposure of internal cells. 

These changes not only facilitate water loss but 

also provide easy entry for microbial pathogens 

and chemical contaminants. Packaging or 

application of edible films can lessen water loss 

by maintaining a high RH near the cut surface 

and providing a physical barrier that protects the 

product from contamination.

Water loss and collapse of injured cells at the 

cut surface can alter the appearance of the freshcut product. As the cut surface loses water, 

adhering cellular debris may impart a white 

blush to the surface that masks varietal color; for 

example, white blush on “baby” carrots decreases 

the intensity of the underlying orange color. 

Differential dehydration of exposed cortex and 

vascular tissue may produce an uneven surface, 

as with formation of vascular strands projecting 

a few millimeters from the cut end of celery 

petioles. Consumers associate both of these 

surface changes with the loss of freshness.

Physiological processes devoted to wound repair 

can be beneficial (such as curing potatoes) or 

detrimental to quality retention. Physiological 

changes following wounding include increased 

respiration and ethylene production, promotion of 

the ripening of climacteric fruit vegetables (such 

as melons and tomatoes), and enhanced synthesis 

and accumulation of phenolic compounds that 

contribute to tissue browning. These changes are 

managed by the use of low temperatures, creation 

of reduced O2

 or elevated CO2 atmospheres, and 

application of inhibitors of specific chemical 

reactions or metabolic pathways.

Wound-enhanced respiration and ethylene 

production can deplete carbohydrate storage 

reserves and stimulate tissue softening associated 

with fruit ripening (melons, squash, tomatoes) 

or chlorophyll loss associated with leaf or 

tissue senescence (spinach, broccoli). In many 

tissues, wounding produces a signal that induces 

the increased synthesis and accumulation of 

phenolic compounds. Tissue browning can 

result from the oxidation or polymerization of 

accumulated phenolic compounds. Lignification 

and toughening of tissue are others way in which 

the metabolism of phenolic compounds can reduce 

quality.

Sanitation, implementation of Good Agricultural 

Programs (GAPs) in the field, use of Good 

Manufacturing Programs (GMPs) and Hazard 

Analysis and Critical Control Point (HACCP) 

monitoring plans during all steps of processing, 

and proper temperature control, are all needed to 

ensure that an initial low microbial load on freshcut vegetables is maintained during marketing. 

The current industry standard washing and 

disinfection procedures used on whole produce 

are rather ineffective with fresh-cut vegetables 

once they have been contaminated with microbial 

pathogens. Overall microbial load relative to 

spoilage organisms usually remain below levels 

of concern as long as visual quality remains 

acceptable. However, postharvest treatments 

that maintain visual quality under abusive 

temperatures may allow microbial loads to reach 

dangerous levels before quality is reduced below 

acceptable levels.

Many vegetables are sensitive to nonfreezing 

temperatures below about 10 °C (50 °F) and 

suffer physiological damage if held at these 

chilling temperatures beyond a specific period. 

These vegetables include jicama, pepper, sweet 

potato, tomato, and zucchini. In contrast to the 

whole commodity, which should not be chilled, 
625

the increased susceptibility of fresh-cut products 

to spoilage often means that the product has a 

longer market life at 0 °C (32 °F) than at higher, 

nonchilling temperatures. Development of chilling 

injury symptoms is less pronounced in riper 

tissue and takes some time to develop. Since 

most fresh-cut vegetables are consumed soon 

after purchase and fruit vegetables are fully ripe 

when processed, chilling injury symptoms usually 

do not develop to a significant extent because 

the rate of deterioration due to chilling is slower 

than the rate of spoilage that is inhibited by low 

temperatures. The two most important fresh-cut 

commodities, lettuce and carrots, are not chilling 

sensitive and should be stored as close to 0 °C (32 

°F) as possible without freezing: 1 to 3 °C (34 to 

38 °F) in a commercial setting.

The imposed physical damage done to the 

product during preparation and its increased 

vulnerability to deleterious internal and external 

changes requires that fresh-cut vegetables be 

handled with a greater degree of care than the 

whole product. Storage requirements for intact 

produce may be inadequate to handle increased 

physiological activity and susceptibility to water 

loss encountered with fresh-cut vegetables.

The highest quality that is available (usually 

USDA No. 1) and that is compatible with an 

economic return should be used for processing. 

Although poor quality pieces of fresh-cut product 

can be discarded to upgrade quality (an example 

is culling discolored pieces of cut lettuce leaves 

or broccoli florets), the associated cost usually 

adversely affects quality and yields and greatly 

outweighs the differential cost of using higher 

quality raw material.

The remainder of this chapter provides 

information on the commercial packaging and 

storage of a number of fresh-cut vegetables.

Beets, Red (Grated, Cubed, Whole Peeled)

Fresh-cut beets should be stored at 1 to 3 °C (34 to 

38 °F) before and after processing. Respiration is 

slightly reduced during storage in 5% O2

 and 5% 

CO2

 at 5 °C (41 °F).

Respiration Rates

Temperature Whole Cubed Grated

peeled 1 cm cubes 2 mm

 mg CO2 kg-1 h-1

2 °C 4 10 12

5 °C 6 12 16

10 °C 19 27 38

23 °C 54 117 162-207

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Broccoli (Florets)

Fresh-cut broccoli florets should be tight, firm, 

turgid, and dark green without blooming buds. 

There should be no sulfur odor or discoloration 

along the stems and cut ends. The core 

temperature of raw material should be <1.5 °C 

(35 °F). Raw and processed material should be 

stored at 1 to 3 °C (34 to 38 °F) to ensure quality 

and reduce potential for freezing of product during 

handling, distribution, and storage. Yellowing is 

a common problem caused by either chlorophyll 

loss or blooming of the buds. The cut surface 

and damaged floret stems can turn black during 

storage. Development of off odors can be a major 

concern when MAP is used. Temperature abuse 

promotes soft rot and mold growth.

Whole broccoli heads are hand-cut into florets that 

are between 2.5 cm (1 in) and 5 cm (2 in) long. 

They are washed in water containing up to 200 μL 

L-1 total chlorine to wash residual material from 

the florets as well as reduce aerobic plate counts. 

Repeated daily washing did not maintain lower 

microbial counts for >2 days.
626

The benefit of CA (5% O2

 and 4% CO2) may be 

marginal for storage up to 14 days at 0 to 5 °C 

(32 to 41 °F) compared to air. Lowering O2

 to 

0.25% or increasing CO2

 to 10% at 0 to 5 °C (32 

to 41 °F) reduces respiration by about 50%. Use 

of appropriate polymeric film in MAP maintained 

green color at 0 to 5 °C (32 to 41 °F) for more 

than 21 days (Cabezas and Richardson 1997). 

Severe off odors and discoloration at cut ends 

can develop during MAP storage at 10% CO2

 and 

2.5% or less O2

 (Makhlouf et al. 1989). Perforated 

and microperforated polymeric packages reduce 

off odor (Izumi et al. 1996a). Reducing ethylene 

below 1 to 10 μL L-1 did not significantly reduce 

color loss at 1 °C (34 °F), but did have an effect at 

higher temperatures.

No foodborne disease outbreak has been reported 

associated with fresh-cut broccoli, although the 

aerobe population is usually high (>100,000 cfu 

g-1 fresh weight). Florets stored in 5% O2

 and 

8% CO2

 at 8 °C (46 °F) have lower aerobic plate 

counts, total coliform plate counts, and yeast/mold 

plate counts compared to storage in air.

Respiration Rates

Temperature mg CO2 kg-1 h-1

0 °C 26

5 °C 44

10 °C 78

Data from Watada et al. (1996) and Izumi et al. 

(1996a).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Cabbage, Green and Red (Shredded, 

Diced)

Fresh-cut green cabbage should be light green 

with a moderately pungent flavor and no sulfur 

aroma. Raw and processed material should have 

typical cabbage flavor with no off notes and 

should be stored at 1 to 3 °C (34 to 38 °F) to 

ensure quality and reduce potential for freezing of 

product during handling, distribution, and storage. 

Fresh-cut cabbage includes diced and shredded 

product with cut size varying from 0.63 cm (1⁄4 in) 

to 0.95 cm (3/8 in). Heads are trimmed to remove 

wrapper leaves and cored, cut, and washed using 

chlorinated water (100 μL L-1 of total chlorine) 

for about 1 min before being spun-dried and 

packaged. For coleslaw, cut cabbage (shredded 

or diced) can be preblended with carrots or plainpackaged.

A CA of 5 to 7.5% O2

 and 15% CO2 is 

recommended (Hiroaki et al. 1993). Lowering 

O2

 below 5% caused rapid proliferation of 

fermentative bacteria and off odors within 6 days 

at 5°C (41 °F). The fermentation induction point 

of coleslaw mixes in low density polyethylene 

bags varied with the cabbage to carrot ratio and 

with temperature. At 5 °C (41 °F), a 70:30 mix 

went anaerobic at 1.8% O2

, while 3% O2 was the 

limit for aerobic respiration at 10°C (50 °F).

Off odors forming in cut cabbage bags with 

low OTR film (<3,000 mL/m2

 atm-1 d-1) and 

discoloration of cabbage leaf packed in high OTR 

film (>12,000 mL/m2

 atm-1 d-1) bags are the major 

quality deterioration during storage (Pirovani et 

al. 1997). At 11 °C (52 °F), Listeria spp. grew 

faster in fresh-cut cabbage packages that had an 

atmosphere of <1.8% O2

 and >20% CO2 than in 

air (Omary et al. 1993).

Respiration Rates

Temperature 3/8 in (9.6 mm) 1/4 in (6.4 mm)

mg CO2 kg-1 h-1

2 °C 16-18 18-24

5 °C 22-33 25-39

10 °C 42-48 51-57

23 °C 117-153 153-171

Data from Watada et al. (1996).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 
627

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Cabbage, Chinese (Sliced, Sticks, 

Shredded)

Fresh-cut Chinese cabbage should be handled 

like green cabbage and stored at 1 to 3 °C (34 to 

38 °F). The recommended CA is 5% O2

 and 

5% CO2

; benefits are moderate compared to air 

storage at 0 °C (32 °F).

Carrots (Diced, Shredded, Sticks, Peeled, 

Grated, Sliced, Cubed)

Fresh-cut carrots are orange without a white brush 

or slimy surface. Raw and processed product 

should be kept at 1 to 3 °C (34 to 38 °F) to ensure 

quality and reduce potential for freezing of 

product during handling, distribution, and storage. 

Most quality loss in cut carrots results from 

formation of either white blush or off odor and 

slimy surface generated by bacteria (Carlin et al. 

1989).

Fresh-cut carrots include whole peeled (baby), 

sticks, sliced, shredded, grated, and diced. 

Whole carrots are washed with water to remove 

undesirable field material. The stems and tips are 

excised and the trimmed carrots are peeled, cut, 

and washed in 100 μL L-1 NaOCl for less than 

1 min. Washed carrot cuts are centrifuged to 

remove excess water and packaged in plastic bags.

Dehydration of surface debris on cut and peeled 

carrots imparts a whitish translucent appearance to 

the surface (Tatsumi et al. 1991, Cisneros-Zevallo 

et al. 1995), which is undesirable because consumers associate it with the loss of freshness 

(Bolin and Huxsoll 1991). Applying an edible 

coating (Howard and Dewi 1995, 1996, Li and 

Barth 1998), such as sodium caseinate-stearic 

acid (Avena-Bustillos et al. 1994), or heating and 

raising the pH (Bolin and Huxsoll 1991) may be 

helpful in reducing white blush. Treatments that 

modify the water-retaining capacity of the cut 

surface also prevent white blush development 

(Cisneros-Zevallos et al. 1997).

Fresh-cut carrots derive slight benefit from 2 to

5% O2

 and 15 to 20% CO2 atmospheres (Izumi 

et al. 1996b). Lower O2

 or increased CO2 levels 

promoted slimy appearance, increased lactic acid 

bacteria growth, and accelerated microbial decay 

and excessive alcohol production. Grated carrots 

retain good quality for up to 10 days at 2 to 10 °C 

(36 to 52 °F) in MAP with high O2

 permeability 

films of 10,000 to 20,000 mL m2

 atm-1 d-1 at 25°C 

(Carlin et al. 1990). Low permeability films of 950 

mL m2

 atm-1 day-1 resulted in low O2 damage.

The quality and headspace composition of sliced 

carrots (0.5 cm) treated with 1% ascorbic acid 

before packing in MAP was unaffected during 

14 days at 4 °C (39 °F) (Galetti et al. 1997). 

Growth of aerobic mesophilic bacteria on sticks 

was suppressed by a 0.5% O2

 and 10% CO2

atmosphere at both 0 and 5 °C (32 and 41 °F); 

but total microbial count on slices and shreds was 

unaffected.

The mean microbial population after 9 days 

storage was much lower (1,300 cfu g-1) for 

irradiated shredded carrots (0.5 kGy) than for nonirradiated, chlorinated controls (87,000 cfu g-1) 

(Hagenmaier and Baker 1998). Ethanol and O2

content of the headspace were not affected.

Respiration Rates

Temperatures Whole Sliced Sticks Shredded

peeled

 mg CO2 kg-1 h-1

0 °C — 5 11 15

5 °C 9-12 13 19 24

10 °C 17-21 25 42 46

23 °C 54 72-81 — 108-126

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.
628

Celery (Diced, Sliced, Sticks)

Fresh-cut celery petioles have no leaves or brown 

spots and should not have cracked, flared, or 

white-blush ends. Raw material should arrive at 

<7 °C (38 °F) and be stored at 2 to 4 °C (36 to 40 

°F) before processing and at 1 to 3 °C (34 to 38 

°F) after processing to ensure quality and reduce 

potential for freezing of product during handling, 

distribution, and storage. Atmospheres of 5% 

O2

 and 4% CO2 were slightly beneficial. Water 

loss is the main factor affecting eating quality 

(Gariepy et al. 1986). Small amounts of water 

loss (2.5 to 5%) can result in litheness, flaccidity, 

shriveling, and wrinkling. Moisture loss can 

be reduced 75% by the application of an edible 

coating (Avena-Bustillos et al. 1997). Differential 

dehydration of exposed cortex and vascular tissue 

caused the stronger vascular strands to project 

a few millimeters from the cut end of celery 

petioles. Development of pithiness is associated 

with water stress during growth and wounding 

during processing (Saltveit and Mangrich 

1996). Heat-shock treatments prevented tissue 

browning without adversely affecting other quality 

parameters (Loaiza-Velarde et al. 2003).

Sliced celery can only be maintained for 6 

days at 4°C (40 °F) without notable quality 

change (Johnson and von Elbe 1974). Major 

pathogens are Pseudomonas fluorescens and P. 

marginalis, which cause water soaking, soft rot, 

and discoloration (Robbs et al. 1996). Low-dose 

irradiation (1.0 kGy) delayed microbial spoilage 

in fresh, diced celery stored at 4 °C (40 °F) for 

3 weeks without affecting sensory attributes. 

In contrast, blanching and chlorine rinsing had 

little effect on microbial count. Sensory results 

indicated the 1 kGy sample was preferred over 

all other treatments in terms of taste, texture and 

color.

Garlic (Peeled)

Quality problems with peeled garlic include 

sprouting and discoloration of areas damaged 

during peeling. Garlic cloves can be peeled 

manually or mechanically with compressed air. 

Acid treatments and edible coatings can improve 

preservation. Excellent visual quality was 

maintained for 21, 16, 12, or 8 days of storage 

in air at 0, 5, 10, or 15 °C (32, 41, 50, or 59 °F), 

respectively. Decay was not observed at 0 and 5 

°C (32 or 41 °F) and was slight at 10 and 15 °C 

(50 and 59 °F). At 5 and 10 °C (41 and 50 °F), 

a 1% O2

 and 10% CO2 CA gave the best quality 

(lack of decay and least discoloration). Respiration 

rates in manually peeled garlic were 50% higher 

than unpeeled cloves. Mechanically peeled garlic 

has rates of respiration 5 to 10% higher at 5 °C 

(41 °F) and 20 to 30% higher at 10 °C (50 °F) than 

hand-peeled cloves.

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 °C 35

10 °C 57

Data from Burlo-Carbonell et al. (2000).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Jicama (Sticks, Cubes)

Fresh-cut jicama should be white with a crisp 

texture. Raw material should be received at <7 

°C (44 °F), and processed product should be 

stored at 1 to 3 °C (34 to 38 °F) to ensure quality 

and reduce potential for freezing of the product 

during handling, distribution, and storage. Tuber 

size does not affect visual quality or color. 

Browning can be a significant cause of quality 

loss after 9 days at 5 °C (41 °F). Increased storage 

temperature results in accelerated discoloration. 

The best treatment to control browning is a 2-min 

dip in water at 50 °C (122 °F) and then storage at 

2 °C (36 °F).

Quality loss during storage at 0 or 5 °C in air is 

also attributable to yeast and bacterial growth. A 

10% CO2

 atmosphere retards brown discoloration, 
629

maintains crisp texture, and delays microbial 

growth. However, acetaldehyde and ethanol 

concentrations are higher after 8 days at 5 °C (41 

°F) in 10% CO2

 atmospheres and 3% O2 or air. 

Atmospheres of 20% CO2

 can damage jicama if 

stored longer than 8 days.

Kale (Shredded)

Fresh-cut kale should be dark green and crisp 

without yellow or discolored leaf pieces. Raw 

material should be received at <7 °C (45 °F) and 

stored at 1 to 3 °C (34 to 38 °F) after processing to 

ensure quality and reduce potential for freezing of 

product during handling, distribution, and storage. 

Washing shredded kale with 0.1% NaOCl results 

in a 10-fold reduction in aerobic plate count 

compared to unwashed products. Fresh-cut kale in 

perforated (5.96 ± 0.35 mm2

 diameter holes with 

6.68 cm2

 total surface area per sack) polyethylene 

bags (38 mm thick) become unacceptable due to 

yellowing and microbial spoilage after 3 days at 4 

°C (39 °F). Desiccation, yellowing, and spoilage 

were unacceptable after 1 or 2 days at 20 or 10 °C 

(68 or 50 °F), respectively (Beaulieu et al. 1997).

Leek (Sliced)

Raw material should be received at, and processed 

leeks stored at, 1 to 3 °C (34 to 38 °F) to ensure 

quality and reduce potential for freezing of 

product during handling, distribution, and storage. 

A CA of 5% O2

 and 5% CO2 is moderately 

beneficial, and slightly reduces respiration at 5 °C 

(41 °F). A non-perforated film led to unacceptable 

quality after a few days at 4 °C (39 °F) with high 

CO2

, ethanol, and acetaldehyde concentrations 

(Keteleer et al. 1993).

Respiration Rates

Temperature Whole leaf Rings 

2 mm thick

 mg CO2 kg-1 h-1

2 °C 24 32

5 °C 29 49

10 °C 38 57-67 

23°C 117 252-288 

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Lettuce: Butterhead, Crisphead, Greenleaf, 

Iceberg, and Romaine (Chopped, 

Shredded, Whole Leaf)

The quality of the fresh-cut product is very 

dependent on the initial raw product quality. The 

raw product should be the best quality available 

and should be <2 °C (36 °F) when received as 

whole or cored heads. It should be stored at 1 to 

3 °C (34 to 38 °F) before and after processing to 

ensure quality and reduce potential for freezing of 

product during handling, distribution, and storage.

Browning (enzymatic) of the cut edges is the main 

defect of fresh-cut lettuce pieces during storage. 

The best way to prevent the discoloration is to 

reduce O2

 to <3%. Antioxidant treatment and 

heat-shock can inhibit discoloration, but these 

treatments may result in loss of visual quality. 

Unless stressed in the field, lettuce has low levels 

of phenolic compounds and tissue browning 

occurs after the induction of synthesis and 

accumulation of phenolics by wounding. A 90-sec 

heat-shock at 45 °C (104 °F) prevented woundinduced browning of iceberg (Loaiza-Velarde et 

al. 1997, Loaiza-Velarde and Saltveit 2001) and 

romaine (Saltveit 2000) lettuce.
630

Butterhead Lettuce

Browning of the cut edges of butterhead lettuce is 

reduced by modified atmospheres rapidly created 

by flushing with N2

 to get 1 to 3% residual O2 with 

CO2

 levels of 5 to 10%. Tissue in atmospheres 

of <1% O2

 and >10% CO2 develop CO2 injury 

or brown stain (Stewart and Ceponis 1968). The 

incidence of brown stain increased from 16 to 38 

to 81% as CO2

 increased from 2.5 to 5 to 10%, 

respectively, and was enhanced when combined 

with low O2

 atmospheres (Steward and Uota 

1971).

The physiological behavior of butterhead lettuce 

is modified by cultural practices such as irrigation, 

climate, and fertilization (Poulsen et al. 1994, 

1995, Sorensen et al. 1994). Susceptibility to 

brown stain varies among cultivars and position of 

leaves within the head (Krahn 1977). Shelf-life of 

butterhead lettuce was negatively correlated with 

respiration rate and susceptibility to CO2

. High 

O2

 and low CO2 enhanced enzymatic browning. 

Off odors and flavors developed (ethanol, 

acetaldehyde, and ethyl acetate aroma), crispness 

was lost, and the tissue became translucent when 

fresh-cut lettuce was stored in <0.5% O2

 or >15% 

CO2

.

Necrosis of butterhead lettuce may be associated 

with microbial growth, such as pectolytic 

Pseudomonas (Nguyen-The and Prunier 1989) and 

other epiphytic bacteria.

Respiration Rates (Chopped)

Temperature mg CO2 kg-1 h-1

2 °C 12-14

4.5 °C 20-25

10 °C 38-48

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Greenleaf Lettuce

A 0.5 to 3% O2

 and 5 to 10% CO2 CA reduced cutedge browning of greenleaf lettuce (Lopez-Galvez 

et al. 1996).

Iceberg Lettuce

The raw product should have <6% pink rib 

discoloration, while russet spotting, hooked core, 

and tipburn should be <1%. Moisture content of 

lettuce is extremely important for maintaining 

texture and reducing microbial growth. Excess 

moisture can be removed in a forced-air tunnel or 

by spinning. Lettuce that was air dried for 10 to 

15 min or spin dried for 30 min had less browning 

during storage than control samples. Consumer 

sensory panelists indicated that after 4 days of 

storage, only 15% would purchase control lettuce 

while 40% would purchase lettuce spin- or airdried for 15 min. Slicing methods can influence 

ascorbic acid retention in with the order: manual 

tearing > manual slicing > machine slicing.

In clamshell trays, market-life of fresh-cut lettuce 

was <24 h at 23 °C (73 °F), >24 h at 10 °C (50 

°F), and >48 h at 2 °C (36 °F) (Zhuang and Barth 

1999). Fresh-cut lettuce packages commonly have 

<1% O2

 to effectively slow browning and >10% 

CO2

 to inhibit microbial growth (Gorny 1997). An 

atmosphere of 0.5 to 3% O2

 and 10 to 15% CO2

reduces cut edge browning, retains visual quality, 

and reduces psychrophilic bacterial counts. 

Flushing with 100% N2

 increases retention over 

MAP. On the basis of ethanol appearance in the 

headspace, the fermentation induction point was 

0.3 to 0.4% O2

 at 5 °C (41 °F) and 0.6 to 0.8% 

at 10 °C (50 °F). Acetaldehyde and ethyl acetate 

were detected when O2

 was <0.4% at 5 to 20 °C 

(41 to 68 °F). The extent of browning increased 

with O2

 level but not with CO2 level (Smyth-Anne 

et al. 1998). Fresh-cut iceberg should be stored at 

1 to 3 °C (34 to 38 °F) before and after processing 

to ensure quality and reduce potential for freezing 

during handling, distribution, and storage.

Shelf-life of fresh-cut lettuce at 5 °C (41 °F) was 6 

days in air, 8 days in 3% O2

, and 12 days in 0.2% 
631

O2

 (Peiser et al. 1997). Increasing CO2 enhances 

the beneficial effect of low O2

. A combination 

of 0.2% O2

 with 7 to 15% CO2 gave a 16-day 

shelf-life. A 14-day shelf-life was obtained when 

shredded iceberg lettuce was stored in 1 to 3% O2

and 5 to 6% CO2

 at 5 °C (41 °F). However, CO2

>15% causes brown stain. Reduced O2

 or elevated 

CO2

 may induce formation of fermentation and 

off odor (fermentative volatiles, ethanol, and 

acetaldehyde) in the packages (McDonald et al. 

1990, Mateos et al. 1993, Peiser et al. 1997).

Although gram-negative bacteria are numerically 

dominant, a large yeast population may also 

be found. Species of Pseudomonas, Erwinia, 

and Serratia were the most frequently isolated 

bacteria. Cryptococcus, Pichia, Torulaspora, and 

Trichosporon spp. were the most common yeasts. 

Beuchat and Brackett (1990) studied the effects 

of shredding, chlorine treatment, and MAP on 

survival and growth of Listeria monocytogenes, 

mesophilic aerobes, psychrotrophs, yeasts, and 

molds. They found that no significant changes in 

populations of L. monocytogenes were detected 

during the first 8 days of incubation at 41 °F (5 

°C); there was a significant increase between 8 

and 15 days. Significant increases occurred within 

3 days when lettuce was stored at 50 °F (10 °C). 

Chlorine treatment, MAP of 3% O2

, and shredding 

did not influence growth of L. monocytogenes.

Respiration Rates (Shredded)

Temperature mg CO2 kg-1 h-1

2.5 °C 12.0-15.0

5 °C 15.6-27.3

7.5 °C 23.1-32.7

10 °C 30.4-39.9

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Lollo Rosso (Red) Lettuce

The beneficial storage atmosphere is 0.5 to 3% 

O2

 and 5 to 10% CO2. MAP storage (2 to 3% O2

and 12 to 14% CO2

) was useful in preventing 

brown discoloration. However, MAP storage was 

not beneficial for preserving quality of red tissues 

and, in fact, their overall visual quality, texture, 

aroma, and macroscopic breakdown under MAP 

conditions were worse than those of air-stored 

tissues (Gil-Maria et al. 1998). Castaner et al. 

(1997) found that after 14 days of storage at 5 

°C (41 °F), the overall visual quality of freshcut white and green tissue of Lollo Rosso (red) 

lettuce is better in MAP than in air. Green tissue 

had the lowest overall quality after air storage. 

In addition, there were no significant overall 

quality differences for red tissue stored under 

either condition. Texture and aroma were excellent 

for green tissue held in MAP, while it was 

unacceptable in air. Both atmospheres maintained 

texture of red and white tissues. Aroma was 

excellent for white tissue in both air and MAP. In 

contrast, aroma was only acceptable for red tissue 

stored in air.

Romaine Lettuce

Fresh-cut romaine should be stored at 1 to 3 

°C (34 to 38 °F) before and after processing to 

ensure quality and reduce potential for freezing of 

product during handling, distribution, and storage. 

MAP exerted a beneficial effect on sensory quality 

by preventing pink discoloration. Compared to 

air, 3% O2

 and 6, 10, or 14% CO2 MAP delayed 

development of tissue discoloration and increased 

shelf-life by about 50%. Of the three CO2

 levels, 

10% was slightly more effective than 6 and 14% 

(Hamza et al. 1996, Lopez-Galvez et al. 1996, 

Segall and Scanlon 1996).

The aerobic plate counts of fresh-cut Romaine 

lettuce in MAP were decreased by 0.15 and 0.35 

kGy gamma irradiation (Prakash et al. 2000). The 

0.35 kGy treatment decreased aerobic plate counts 

by 1.5 logs and yeast and mold counts by 1 log. 

A combination of MAP and 0.35 kGy resulted 

in a 2-log reduction in microbial counts. These 
632

differences were maintained through 22 days of 

storage. Irradiation at 0.15 kGy caused smaller 

reductions in microbial counts. A 10% loss in 

firmness was observed at 0.35 kGy, while other 

sensory attributes such as color, generation of off 

flavor, and appearance of visual defects were not 

affected. The control sample reached microbial 

counts of 107

 in 14 days compared to the MAP 

samples, which reached the same level in 17 

days, and the combination samples (0.35 kGy and 

MAP), which took 28 days. Color, flavor, and odor 

were unaffected by irradiation, although an off 

odor was obvious in MAP samples after 21 days 

(17% CO2

 and <1% O2). Low-dose irradiation 

increased shelf-life of cut romaine lettuce by 2 to 

5 days (Prakash et al. 2000)

Mushrooms (Sliced)

Fresh-cut mushroom slices are white with no 

darkening and wrinkling. Mushroom slices should 

be stored at 1 to 3 °C (34 to 38 °F). Wrinkling and 

brown surface patches are caused by excessive 

moisture loss (Roy et al. 1996). A CA of 10% CO2

and 3% O2

 maintains quality, while 5% O2 and 

5% CO2

 at 5 °C slightly reduces respiration. More 

than 20% CO2

 accelerates tissue darkening, while 

<3% O2

 may result in potential botulinum toxin 

production. Inoculation studies have demonstrated 

that C. botulinum type A will sporulate and 

produce endotoxin in 0.9 to 2% O2

 after 6 days 

at 75 to 79 °F (24 to 26 °C) (Sugiyama and Yang 

1975, Sugiyama and Rutledge 1978). It is not 

recommended to use low O2

 MAP due to the 

inherent food safety risk.

Respiration Rates (Sliced)

Temperature mg CO2 kg-1 h-1

0 °C 20-60

5 °C 39-88

10 °C 86-124

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Onions (Diced, Slivered, Rings, Chunks)

Fresh-cut onions should have no discoloration, 

skin and core. Bulbs should be dry, free of 

decay, firm, and 7.5 to 10 cm (3 to 4 in) in 

diameter. The core of whole onions should be 

1.5 °C (35 °F) at receiving and 1 to 3 °C (34 to 

38 °F) before and after processing to ensure 

quality and reduce potential for freezing of 

product during handling, distribution, and storage. 

The seed stems and new internal growth should 

be less than 10%; double centers and translucent 

scale should be less than 5%.

Whole onions are peeled and trimmed by machine 

or hand. Washing with chlorinated water can be 

done before or after processing. Bulbs for onion 

rings are washed with cold water at 0 °C (32 °F) 

before processing. However, diced and slivered 

onions are washed using chlorinated water after 

processing.

Browning, yellowing, and development of 

translucence are major factors affecting the 

visual quality of diced onion (Blanchard et al. 

1996). Cutting causes important biochemical 

changes in tissues, including development of 

sulfur aromatic volatiles. These compounds are 

produced enzymatically by hydrolysis of alliins 

(odorless derivatives of amino acids) by alliinase 

(Schwimmer and Weston 1961, MacLoed 1970). 

Among the volatiles present in the aromatic profile 

of onion are oxides of disulfide, thiosulfinates, and 

propene disulfide, known bacteriostats (Davidson 

et al. 1983). Their action on microorganisms 

may be due to the inhibition of respiratory 

enzymes containing thiol groups (Augusti 1990). 

Thiopropanal-S-oxide, a lacrimogenous factor, has 

antifungal properties (Sharmon et la. 1979) and 

may be involved in development of bitterness and 

browning of onion puree (Howard et al. 1994).

CA of 2 to 5% O2

 and 10 to 15% CO2 decreases 

respiration and microbial proliferation and retains 

sucrose and pungency of cut onions. Lowering 
633

the O2

 level can be beneficial for visual quality 

but has no effect on aroma. Enrichment in CO2

improves both qualities. Rapid reduction of O2

 in 

the package reduces discoloration. Browning can 

be slowed slightly by lowering O2

, and more so 

by CO2

 enrichment. Langerak (1975) reported that 

freshly cut onion became brown and unacceptable 

after cooking when wrapped in perforated film, 

in comparison with onion wrapped in film 

that achieved MAP conditions more rapidly. 

Atmospheres containing 1 to 2% O2

 prevent the 

loss of pyruvic acid, an indicator of onion flavor 

intensity, and reduce the rate of respiration of the 

fresh-cut tissue (Mencarelli et al. 1990).

The inclusion of potassium permanganate (as an 

ethylene scrubber) and sulfur volatiles in packages 

of diced onions improves sensory quality. A 

storage life of 10 days is possible for fresh-cut 

onions packaged in polymeric bags without a 

gas flush and stored at 2 °C (36 °F). Addition of 

absorbents, potassium permanganate and clay, in 

packages increased shelf-life up to 18 days at 1 °C 

(34 °F) (Howard et al. 1994, Toivonen 1997).

Yeasts and molds were virtually absent on diced 

onion. When present, their count did not increase 

beyond 100 cfu g-1 (Garg et al. 1990, Blanchard 

et al. 1996). Psychrotrophic and mesophilic flora 

increased throughout storage under all treatments. 

Their growth in diced onion was slowed under CA 

as compared to air (Blanchard et al. 1996).

Respiration rates vary significantly depending on 

how long whole onions were in cold storage prior 

to processing. CA (5% O2

 and 5% CO2) at 5 °C 

(41 °F) reduces respiration rate by 25%.

Respiration Rates

Temperature Sliced Diced

2 mm thick rings 1 cm cubes

 mg CO2 kg-1 h-1

2 °C 14.0 12.0

5 °C 23.4 15.6

10 °C 38.0 22.8

23 °C 126-131 90-99

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Pepper, Bell (Diced, Sliced)

Fresh-cut bell pepper should have no discoloration 

(darkening) or water soaking. Raw material should 

be received at <7 °C (45 °F) and stored at 7 to 

10 °C (45 to 50 °F), but stored at 1 and 4 °C (34 

to 40 °F) after processing to ensure quality and 

reduce potential for freezing of product during 

handling, distribution, and storage. Defects that 

reduce overall visual quality include darkening of 

the green or red pulp, brown discoloration of the 

cut surfaces, and decay. Whole peppers should 

be spray-washed before processing and washed 

after being cored and cut to reduce microbial 

population. Alternatively, cut pepper can be 

washed using a combination of open-flume and 

close-flume systems.

Although intact peppers are chilling sensitive, 

it is necessary to store fresh-cut red and green 

pepper at 0 to 5 °C (32 to 41 °F) to maintain visual 

quality (El-Bassuoni and Cantwell 1994). Visual 

quality was maintained and few compositional 

changes occurred during 15 days of storage at 1 

°C (34 °F) (Abe et al. 1991, Zhou et al. 1992). 

Full ripe or red peppers are less chilling sensitive 

than mature-green fruits of the same cultivar.

The recommended CA is 3% O2

 and 5 to 10% 

CO2

. Levels of CO2 >10% can result in tissue 

darkening and softening. Shelf-life and sensitivity 

to CO2

 injury vary significantly among cultivars. 

CA using air with 10% CO2

 maintains quality 

at both 5 and 10 °C (41 and 50 °F). Aroma and 

texture decrease after 6 days in 10% CO2

 but were 

maintained in air at 0°C. Storage in high CO2

 at 

5 °C (41 °F) and air at 0 °C (32 °F) retard decay 

development. Atmospheres with 5% CO2

 help 

maintain quality but are not as effective as 10% 

CO2

. Fresh-cut pepper pieces that were ripening 
634

or were already fully red ripe had better shelflife than pieces from mature-green fruit (LopezGalvez et al. 1997). They also found that visual 

quality was best maintained in air or CA at 0 °C 

(32 °F), with important quality loss observed by 

day 9 at 5 °C (41 °F) and by day 3 at 10 °C (50 

°F). Decay is caused by both fungi (Alternaria and 

Botrytis spp.) and soft-rot-causing bacteria. Diced 

tissue was more susceptible to decay than slices 

(Lopez-Galvez et al. 1997).

Respiration Rates

Temperature Sliced Diced

5 cm 1 cm cubes

 mg CO2 kg-1 h-1

0 °C 2-6 2-9

5 °C 4-7 6-12

10 °C 6-13 11-18

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Potato (Sticks, Diced, Sliced, Peeled)

Fresh-cut potatoes should be firm and without 

brown discoloration. Enzymatic browning is a 

major problem in the discoloration of peeled or 

fresh-cut potatoes. Hand-peeling and lye-peeling 

result in good quality, while abrasion-peeling is 

undesirable for fresh potatoes. Anti-browning 

dips such as 0.5% L-cysteine and 2% citrate, in 

combination with MAP, are needed to prevent 

browning of whole peeled potatoes. Pretreatment 

with heated ascorbate and citrate solutions, 

prior to a browning inhibitor dip containing 

4% ascorbate, 1% citrate, and 1% sodium 

pyrophosphate, has greatly extended storage life 

over that after the dip alone (Sapers and Miller 

1995, Sapers et al. 1997). However, under some 

conditions, such pretreatment-induced changes 

in the cooked product that result in surface 

firming (case hardening) and partial separation 

of the case-hardened superficial layer from 

underlying tissue during slicing. Furthermore, 

case-hardened potatoes form large lumps during 

mashing (Martin et al. 1999). The recommended 

storage temperature is 0 °C (32 °F). Shelf-life of 

minimally processed products can be extended to 

3 weeks under CA and refrigeration.

Dipping potato strips in chlorine solutions 

(100 and 300 μL L-1) result in higher microbial 

populations during storage, while potatoes 

treated with antibrowning solutions combined 

with MAP showed only a slight increase. 

MAP had no significant effect on microbial 

populations compared to nonpackaged samples. 

The predominant organism was Pseudomonas 

fluorescens (Gunes et al. 1997).

The recommended CA is 1 to 3% O2

 and 6 to 9% 

CO2

. Reducing O2 level to 10% or 3%, with 10% 

CO2

, at 2 °C (36 °F) reduces respiration of potato 

sticks by 50 to 75%. However, 5% O2

 and 5% 

CO2

 at 5°C (41 °F) increases respiration of sticks 

during storage.

Active modification of package atmospheres 

is necessary to prevent browning and achieve 

extended shelf-life. MAP alone will not prevent 

browning (Gunes and Lee 1997). Vacuum 

packaging of fresh-cut potatoes may create 

anaerobic conditions that allow growth of 

Clostridium botulinum.
635

Respiration Rates

Temperature Whole Halves Slices Sticks

peeled 2 mm 0.95 cm 

 cross-section

 mg CO2 kg-1 h-1

2 °C 6.0-8.0 8.0 10.0-12.0 12.2

5 °C 7.8 7.8-9.8 11.7-15.6 -

10 °C 17.1-19.0 21-22.8 38.0 -

23 °C 54-63 81 - 117-126

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate by 2.0 at 0 °C 

(32 °F), 1.9 at 10 °C (50 °F), and 1.8 at 20 °C (68 °F). To calculate 

heat production, multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Rutabaga (Cubed, Shredded, Peeled)

Fresh-cut rutabaga should have uniform yellow 

flesh without decay, bruises, or discoloration. Raw 

material should arrive at <7 °C (45 °F), while raw 

and fresh-cut product should be stored at 1 to 3 °C 

(34 to 38 °F) before and after processing to ensure 

quality and reduce potential for freezing during 

handling, distribution, and storage. A CA of 5% 

CO2

 and 5% O2 is slightly beneficial and reduces 

respiration at 5 °C (41 °F).

Respiration Rates

Temperature Quarters Shredded Diced

peeled 2 mm 1 cm cubes

 mg CO2 kg-1 h-1

2 °C 8 16 18

5 °C 12 20 25

10 °C 15 42 42-48

23 °C 45 72-81 153-162

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

Spinach (Whole Leaves, Cut Leaves)

Fresh-cut spinach should be green without any 

decay or bruise. Raw material should arrive at 

1.5 °C (35 °F). Fresh and processed products 

should be stored at 1 to 3 °C (34 to 38 °F) before 

and after processing to ensure quality and reduce 

potential for freezing of product during handling, 

distribution, and storage.

Storage in 0.8 to 3% O2

 and 8 to 10% CO2 is 

beneficial. Spinach stored in 0.8% O2

 at 20°C 

(68 °F) had a lower respiration rate, superior 

appearance, and better taste than spinach leaves 

stored in air (Izumi et al. 1997). Atmospheres of 

0.8% O2

 or 0.8% O2 and 10% CO2 reduced the 

number of aerobic mesophilic and psychrotrophic 

microorganisms on fresh-cut spinach leaves by 

10- to 100-fold, compared to air-stored leaves at 

5 °C (41 °F); however, there was no effect at 10 

°C (50 °F). These atmospheres had no effect on 

texture changes during storage at 5 °C (41 °F) for 

9 days or at 10 °C (50 °F) for 7 days (Babic and 

Watada 1996).

An atmosphere of 4% O2

 and 9% CO2 reduced 

the loss of ascorbic acid by 50% compared to 

air (Burgheimer et al. 1967). Increasing CO2

concentrations up to 13% caused a rapid decrease 

in ascorbic acid and development of off odors that 
636

were not acceptable after 1 week storage at 7 °C 

(45 °F) (McGill et al. 1966). Chlorophyll loss can 

be reduced by 50% with ethylene scrubbing. Low 

O2

 (0.8%) results in a slightly reduced respiration 

rate of cleaned spinach leaves.

Microbiological and sensory changes occur 

in all packaged spinach samples, being 

more pronounced at 10 °C (50 °F) than at 

4 °C (40 °F). Spinach leaves harbor high 

numbers of mesophilic, psychrotrophic, and 

Pseudomonadaceae bacteria (Babic and Watada 

1996). The pectinolytic species Pseudomonas 

fluorescens is probably the major spoilage agent of 

fresh-cut spinach. Microbial populations on freshcut spinach leaves increase during storage in air 

and CA at 5 and 10 °C (41 and 50 °F). Populations 

of Enterobacteriaceae and Micrococcaceae are not 

greatly affected by storage atmosphere.

Respiration Rates (Whole Leaves)

Temperature mg CO2 kg-1 h-1

0 °C 6.0-14.0

5 °C 11.7-23.4

Data from Gorny (1997).

To get mL CO2

 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1 

or by 61 to get kcal tonne-1 day-1. 

Sweet Potato (Shredded, Sliced)

Fresh-cut sweet potatoes should be firm and 

without discoloration. Whole sweet potatoes are 

washed with water before peeling and shredding. 

Cut sweet potatoes are then washed with 100 μL 

L-1 sodium hypochlorite, rinsed, and centrifuged 

to remove excess water. Product quality remains 

acceptable during 2 weeks storage at 0 to 4 °C (32 

to 40 °F) in polymeric bags. Color of shredded 

sweet potato darkens and firmness declines during 

storage. β-Carotene remains stable at 7.8 mg per 

100 g at 4 °C (40 °F). Vitamin C remains stable 

at 7 mg per 100 g for 1 week and then decreases. 

A 6.5% CO2

 and 12% O2 atmosphere is slightly 

beneficial.

Tomato (Sliced, Diced)

Fresh-cut tomatoes should have consistent red 

color and firm texture. Sliced tomatoes have no 

gel loss from the seed cavities. Diced tomatoes 

have no seeds or stem pieces. ‘Roma’ tomatoes 

are often used for diced tomatoes; the ripening 

stage should be 5 or higher (USDA standard). 

The ripening stage of round tomatoes for slicing 

should be 5.5 or higher. Fruit should be firm 

and have small seed cavities. For diced tomato 

products, ‘Roma’ tomatoes should be spraywashed with chlorinated water before cutting. 

After cutting, an open fluming system with 0.25% 

CaCl2

 and 100 μL L-1 chlorine is used to wash and 

remove seeds. For sliced tomato products, whole 

tomatoes are dipped in 200 μL L-1 chlorinated 

water for more than 1 min before slicing. Various 

automated slicing machines have been developed 

for tomatoes. Sliced tomatoes can be packed in 

stacking, shingling, or soldier style.

Although tomatoes are chilling sensitive, they can 

be stored at 0 to 5 °C (32 to 41 °F) for a few days 

before processing to retard softening. A CA of 

3% O2

 and 3% CO2 will delay ripening as well as 

SSC and TA losses (Mencarelli and Saltveit 1988). 

Water soaking that produces translucent tissue, 

textural changes, and softening reduces the quality 

of diced tomatoes during storage. In addition to 

these deleterious changes, quality of tomato slices 

can be reduced by seed germination and loss of 

locular gel. The high acidity of tomato products 

suppresses microbial growth, but growth of yeasts 

and molds can reduce quality in storage.

Respiration Rates

Temperature mg CO2 kg-1 h-1

20 °C 57.6-93.6

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 
637

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1.

Zucchini (Slices)

Fresh-cut zucchini should have a dark green peel, 

white tissue, and a crisp texture. Raw material 

should be received at <13 °C (55 °F) and stored at 

5 to 10 °C (41 to 50 °F). Storage should be at 0 to 

5 °C (32 to 41 °F) after processing. A CA of 0.25 

to 1% O2

 is beneficial. Lowering O2 to <0.5% at 5 

°C (41 °F) reduces respiration by 50%; respiration 

is reduced by 80% at 10 °C (50 °F). Sliced 

zucchini develops water-soaked areas (chilling 

injury) at 0 °C (32 °F) and brown discoloration 

at 5 to 10 °C (41 to 50 °F), which increases with 

storage duration. Zucchini slices can be dipped in 

solutions of CaCl2

 alone or with NaOCl. Calcium 

treatments reduce development of decay, total 

microbial growth, and ascorbate loss.

Respiration Rates

Temperature mg CO2 kg-1 h-1

5 °C 21.1

10 °C 19.4-49.4

Data from Gorny (1997).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rate 

by 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and 

1.8 at 20 °C (68 °F). To calculate heat production, 

multiply mg kg-1 h-1 by 220 to get BTU ton-1 day-1

or by 61 to get kcal tonne-1 day-1. 

References

Abe, K., K. Yoshimura, Y.-F. Zhou, and T. Iwata. 

1991. Studies on physiological and chemical 

changes of partially processed sweet pepper 

fruit. II. Changes of chemical compounds in cut 

surface of sweet pepper in relation to difference 

of storability by shredding direction. J. Jap. Soc. 

Cold Preserv. Food 17:146-151.

Augusti, K.T. 1990. Therapeutic and medicinal 

values of onions and garlic. In J.L. Brewser and 

H.D. Rabinowitch, eds., Onions and Allied Crops, 

vol. III, Biochemistry, Food Science, and Minor 

Crops, pp. 93-108. CRC Press, Boca Raton, FL.

Avena-Bustillos, R.D.J., J.M. Krochta, and M.E. 

Saltveit. 1997. Water vapor resistance of red 

delicious apples and celery sticks coated with 

edible caseinate-acetylated monoglyceride films. 

J. Food Sci. 62:351-354.

Avena-Bustillos, R.J., L.A. Cisneros-Zevallos, 

J.M. Krochta, and M.E. Saltveit. 1994. 

Application of casein-lipid edible film emulsions 

to reduce white blush on minimally processed 

carrots. Postharv. Biol. Technol. 4:319-329.

Babic, I., and A.E. Watada. 1996. Microbial 

populations of fresh-cut spinach leaves affected by 

CAs. Postharv. Biol. Technol. 9:187-193.

Beaulieu, J.C., F.A.R. Oliveira, T.D. Fernandes, 

et al. 1997. Fresh-cut kale: quality assessment 

of Portuguese store-supplied product for 

development of a MAP system. In J. Gorny, ed., 

vol. 5, Fresh-Cut Fruits and Vegetables and MAP, 

pp. 145-151. Proceedings of the 7th International 

Controlled Atmosphere Conference, University of 

California, Davis CA.

Beuchat, L.R., and R.E. Brackett. 1990. Survival 

and growth of Listeria monocytogenes on lettuce 

as influenced by shredding, chlorine treatment, 

modified atmosphere packaging and temperature. 

J. Food. Sci. 55: 755-758.

Blanchard, M., F. Caistaingne, C. Willemot, 

and J. Makhlouf. 1996. Modified atmosphere 

preservation of freshly prepared diced yellow 

onions. Postharv. Biol. Technol. 9:173-185.

Bolin, H.R., and C.C. Huxsoll. 1991. Control 

of minimally processed carrot (Daucus carota)

surface discoloration caused by abrasion peeling. 

J. Food Sci. 56:416-418.

Brecht, J.K. 1995. Physiology of lightly processed 

fruits and vegetables. HortScience 30:18-21.
638

Burgheiner, F., J.N. Macgill, A.I. Nelson, and M.P. 

Steinberg. 1967. Chemical changes in spinach 

stored in air and CA. Food Technol. 21:109-111.

Burlo-Carbonell, F.M., A.A. CarbonellBarrachina, D. Valero, et al. 2000. Acid treatment 

and edible coatings can improve preservation 

of fresh garlic. Institute of Food Technologists, 

Annual Meeting 2000, Technical Program and 

Book of Abstracts, pp. 133. Institute of Food 

Technologists, Chicago, IL.

Cabezas, A., and D.G. Richardson. 1997. Modified 

atmosphere packaging of broccoli florets of 

temperature and package type. In J. Gorny, ed., 

vol. 5, Fresh-Cut Fruits and Vegetables and MAP, 

pp. 8-15. Proceedings of the 7th International 

Controlled Atmosphere Conference, University of 

California, Davis CA.

Carlin, F., C. Nguyen-The, Y. Cudennec, and M. 

Reich. 1989. Microbial spoilage of fresh, “readyto-use” grated carrots. Sciences des Alinents. 

9:371-386.

Carlin, F., C. Nguyen-The, G. Hilbert, and Y. 

Chambroy. 1990. Modified atmosphere packaging 

of fresh, “ready-to-use” grated carrots in 

polymeric films. J. Food. Sci. 55:1033-1038.

Castaner, M., M.I. Gil, F. Ferreres, et al. 1997. 

Effect of modified atmospheres on anthocyanin 

stability and other phenolic metabolites during 

storage of minimally processed red lettuce. In J. 

Gorny, ed., vol. 5, Fresh-Cut Fruits and Vegetables 

and MAP, pp. 134-138. Proceedings of the 7th 

International Controlled Atmosphere Conference, 

University of California, Davis CA.

Cisneros-Zevallos, L., M.E. Saltveit, and J.M. 

Krochta. 1995. Mechanism of surface white 

discoloration of peeled (minimally processed) 

carrots during storage. J. Food Sci. 60:320-

323,333.

Cisneros-Zevallos, L.A., M.E. Saltveit, and J.M. 

Krochta. 1997. Hygroscopic coatings control 

surface white discoloration of peeled (minimally 

processed) carrots during storage. J. Food Sci. 

62:363-366.

Davidson, P.M., L.S. Post, A.L. Branen, and 

A.R. McCordy. 1983. Naturally occurring and 

miscellaneous food antimicrobials. In A.L. Bradeo 

and P.M. Davidson, eds., Antimicrobials in Foods, 

pp. 275-276. Marcel Dekker, New York, NY.

El-Bassuoni, R., and M. Cantwell. 1994. Low 

temperatures and CAs maintain quality of fresh 

cut bell pepper. HortScience 29:448.

Galetti, L., H. Berger, V. Escalona, et al. 1997. 

Modified atmospheres and ascorbic acid for 

minimum process of carrot slices. In J. Gorny, ed., 

vol. 5, Fresh-Cut Fruits and Vegetables and MAP, 

pp. 139-144. Proceedings of the 7th International 

Controlled Atmosphere Conference, University of 

California, Davis CA.

Garg, N., J.I. Churey, and D.F. Splinsioester. 1990. 

Effect of processing conditions on the microflora 

of fresh-cut vegetables J. Food Prot. 53:701-703.

Gariepy, Y., G.S.V. Raghavan, and R. Theriault. 

1986. CA storage of celery with the silicone 

membrane system. Int. J. Refrig. 9:234-239.

Gil-Maria. I., M. Castaner, F. Ferreres, et al. 

1998. Modified-atmosphere packaging of 

minimally processed “Lollo Rosso” (Lactuca 

sativa): phenolic metabolites and quality changes. 

Zeitschrift Lebensmittel Untersuchung Forschung. 

206:350-354.

Gorny, J.R., ed. 1997. A summary of CA and MA 

requirements and recommendations for fresh-cut 

(minimally processed) fruits and vegetables. In J. 

Gorny, ed., vol. 5, Fresh-Cut Fruits and Vegetables 

and MAP, pp. 30-67. Proceedings of the 7th 

International Controlled Atmosphere Conference, 

University of California, Davis CA.

Gunes, G., and C.Y. Lee. 1997. Color of 

minimally processed potatoes as affected by 

modified atmosphere packaging and anti-browning 

agents. J. Food Sci. 62:572-575.

Gunes, G., D.F. Splittstoesser, and C.Y. Lee. 1997. 

Microbial quality of fresh potatoes: effect of 

minimal processing. J. Food Prot. 60:863-866.
639

Hagenmaier, R.D., and R.A. Baker. 1998. 

Microbial population of shredded carrot in 

modified atmosphere packaging as related to 

irradiation treatment. J. Food Sci. 63:162-164.

Hamza, F., F. Castaigne, C. Willemot, et al. 1996. 

Storage of minimally processed romaine lettuce 

under CA. J. Food Qual. 19:177-188.

Hiroaki, K., U. Masayuki, and O. Yutaka. 1993. 

Storage of shredded cabbage under dynamically 

CA of high O2

 and high CO2. Biosci. Biotech. 

Biochem. 57:1049-1052.

Howard, L.R., and T. Dewi. 1995. Sensory, 

microbiological and chemical quality of minipeeled carrots as affected by edible coating 

treatment. J. Food Sci. 60:142-144.

Howard, L.R., and T. Dewi. 1996. Minimal 

processing and edible coating effects on 

composition and sensory quality of mini-peeled 

carrots. J. Food Sci. 61:643-646,651.

Howard, L.R., K.S. Yoo, L.M. Park, and G.H. 

Miller Jr. 1994. Quality changes in diced onions 

stored in film packages. J. Food Sci. 59:110-112. 

Izumi, H., T. Nonaka, and T. Muraoka. 1997. 

Physiology and quality of fresh-cut spinach 

stored in low O2

 CAs at various temperature. In J. 

Gorny, ed., vol. 5, Fresh-Cut Fruits and Vegetables 

and MAP, pp. 130-133. Proceedings of the 7th 

International Controlled Atmosphere Conference, 

University of California, Davis CA.

Izumi H., A.E. Watada, and W. Douglas. 1996a. 

Optimum O2

 or CO2 atmosphere for storing 

broccoli florets at various temperatures. J. Amer. 

Soc. Hort. Sci. 121:127-131.

Izumi, H., A.E. Watada, N.P. Ko, and W. Douglas. 

1996b. CA storage of carrot slices, sticks and 

shreds. Postharvest Biol. Technol. 9:165-172.

Johnson, C.E., and J.H. von Elbe. 1974. Extension 

of postharvest storage-life of sliced celery. J. Food 

Sci. 39:678-680.

Keteleer, A., C. De Mulder, A. Hermans, and 

P. Tobback. 1993. Biplot presentation of the 

physiological-biochemical characterization and 

the sensorial quality of minimally processed leek 

stored under modified atmosphere. Acta Hort. 

343:345-346.

Krahn, T.R. 1977. Improving the keeping quality 

of cut head lettuce. Acta Hort. 62:79-92.

Langerak, D.I. 1975. The influence of irradiation 

and packaging on the keeping quality of prepared 

cut endive, chicory and onions. Acta Alim. 4:123-

138.

Li, P., and M.M. Barth. 1998. Impact of edible 

coatings on nutritional and physiological changes 

in lightly-processed carrots. Postharvest. Biol. 

Technol. 14:51-60.

Loaiza-Velarde, J.G., M.E. Mangrich, R. CamposVargas, and M.E. Saltveit. 2003. Heat-shock 

reduces browning of fresh-cut celery petioles. 

Postharv. Biol. Technol. 27:305-311.

Loaiza-Velarde, J.G., and M.E Saltveit. 2001. Heat 

shocks applied either before or after wounding 

reduce browning of lettuce leaf tissue. J. Amer. 

Soc. Hort. Sci. 126:227-234.

Loaiza-Velarde, J.G., F.A. Tomás-Barberá, and 

M.E. Saltveit. 1997. Effect of intensity and 

duration of heat-shock treatments on woundinduced phenolic metabolism in iceberg lettuce. J. 

Amer. Soc. Hort. Sci. 122:873-877.

Lopez-Galvez, G., R. El-Bassuoni, X. Nie, and N. 

Cantwell. 1997. Quality of red and green freshcut peppers stored in CAs. In J. Gorny, ed., vol. 

5, Fresh-Cut Fruits and Vegetables and MAP, pp. 

152-157. Proceedings of the 7th International 

Controlled Atmosphere Conference, University of 

California, Davis CA.

Lopez-Galvez, G., M. Saltveit, and M. Cantwell. 

1996. The visual quality of minimally processed 

lettuces stored in air or CA with emphasis on 

romaine and iceberg types. Postharv. Biol. 

Technol. 8:179-190.
640

MacLoed, A.L. 1970. The chemistry of vegetable 

flavor. Flav. Ind., October, pp. 665-672.

Makhlouf, J., F. Castaign, J. Arul, et al. 1989. 

Long-term storage of broccoli under CA. 

HortScience 24:637-639.

Martin, S.T., G.M. Sampers, and R.L. Miller. 

1999. Process for inhibiting enzymatic browning 

and maintaining textural quality of fresh peeled 

potatoes. U.S. Patent No. 5912034.

Mateos, M., D. Ke, M. Cantwell, and A.A. 

Kader. 1993. Phenolic metabolism and ethanolic 

fermentation of intact and cut lettuce exposed 

to CO2

-enriched atmospheres. Postharv. Biol. 

Technol. 3:225-233.

McDonald, R.E., L.A. Risse, and C.R. Barmore. 

1990. Bagging chopped lettuce in permeability 

films. HortScience 25:671-673.

McGill, J.N., A.I. Nelson, and M.P. Steinberg. 

1966. Effects of modified storage atmospheres on 

ascorbic acid and other quality characteristics of 

spinach. J. Food Sci. 31:510-517.

Mencarelli, F., D. De Santic, R. Massantini, and 

M. Contini. 1990. Low O2

 concentrations use 

for the short-term onion slice storage. Industrie 

Alinentari. 29:982-984.

Mencarelli, F., and M.E. Saltveit Jr. 1988. 

Ripening of mature-green tomato fruit slices. J. 

Amer. Soc. Hort. Sci. 113:742-745.

Nguyen-The, C., and J. Prunier. 1989. 

Involvement of Pseudomonas in ‘ready-to-use’ 

salad deterioration. Int. J. Food Sci. Technol. 

24:47-56.

Omary, M., R. Testin, S. Barefoot, and J. Rushing. 

1993. Packaging effects on growth of Listeria

innocula in shredded cabbage. J. Food Sci. 

58:623-626.

Peiser, G., G. Lopez-Galvez, and M. Cantwell. 

1997. Changes in aromatic volatiles during storage 

of packed salad products. In J. Gorny, ed., vol. 5, 

Fresh-Cut Fruits and Vegetables and MAP, pp. 23-

28. Proceedings of the 7th International Controlled 

Atmosphere Conference, University of California, 

Davis CA.

Pirovani, M.E., D.R. Guenes, A.M. Piagentini, 

and J.H.D. Pentima. 1997. Storage quality of 

minimally processed cabbage packaged in plastic 

films. J. Food Qual. 20:381-389.

Poulsen, N., A.S. Johnson, and J.N. Sorensen. 

1995. Influence of growth conditions on the value 

of crisphead lettuce, 4: Quality changes during 

storage. Plant Foods Hum. Nutr. 47:157-162.

Poulsen, N., J.N. Sorensen, and A.S. Johnson. 

1994. Influence of growth conditions on the value 

of crisphead lettuce, 2: weight losses during 

storage as affected by nitrogen, plant age and 

cooling system. Plant Foods Hum. Nutr. 46:13-18.

Prakash, A. A.R. Guner, F. Caporaso, and 

D.M. Foley. 2000. Effects of low-dose gamma 

irradiation on the shelf-life and quality 

characteristics of cut romaine lettuce packaged 

under modified atmosphere. J. Food Sci. 65:549-

553.

Robbs, P.G., J.A. Bartz, G. McFie, and N.C. 

Hodge. 1996. Causes of decay of fresh-cut celery. 

J. Food Sci. 61:444-448.

Roy, S., R.C. Anantheswaran, and R.B. Beelman. 

1996. Modified atmosphere and modified 

humidity packaging of fresh mushrooms. J. Food 

Sci. 61:391-397.

Saltveit, M.E. 1997. Physical and physiological 

changes in minimally processed fruits and 

vegetables. In F.A. Tomas-Barberan and R.J. 

Robins, eds., Phytochemistry of Fruit and 

Vegetables, pp. 205-220. Clarendon Press, Oxford, 

U.K.
641

Saltveit M.E. 2000. Wound induced changes in 

phenolic metabolism and tissue browning are 

altered by heat shock. Postharv. Biol. Technol. 

21:61-69.

Saltveit, M.E., and M.E. Mangrich. 1996. Use 

of density measurements to study the effect of 

excision, storage, abscisic acid and ethylene on 

the development of pithiness in celery (Apium 

graveolens L.) petioles. J. Amer. Soc. Hort. Sci. 

121:137-141.

Sapers, G.M., P.H. Cooke, A.E. Heidel, et al. 

1997. Structural changes related to texture of prepeeled potatoes. J. Food Sci. 62:797-803.

Sapers, G.M., and R.L. Miller. 1995. Heated 

ascorbic citric acid solution as browning inhibitor 

treatment for pre-peeled potatoes. J. Food Sci. 

60:762-766.

Schwimmer, S., and W.J. Weston. 1961. 

Enzymatic development of pyruvic in onion as a 

measure of pungency. Ag. Food Chem. 9:301-304.

Segall, K.I., and M.G. Scanlon. 1996. Design and 

analysis of a modified-atmosphere package for 

minimally processed romaine lettuce. J. Amer. 

Soc. Hort. Sci. 121:722-729.

Sharmon, A., G.M. Tewari, A.J. Shrikhande, et al. 

1979. Inhibition of aflatoxin-producing fungi by 

onion extract. J. Food Sci. 44:1545-1547.

Smyth-Anne, B., J. Song, and C. Cameron-Authur. 

1998. Modified atmosphere packaged cut iceberg 

lettuce: effect of temperature and O2

 partial 

pressure on respiration and quality. J. Ag. Food. 

Chem. 46:4556-4562.

Sorensen, J.N., A.S. Johnnsen, and N. Poulsen. 

1994. Influence of growth conditions on the value 

of crisphead lettuce, 1: marketable and nutritional 

quality as affected by nitrogen supply, cultivar and 

plant age. Plant Foods Human Nutr. 46:1-12.

Stewart, J.K., and M.J. Ceponis. 1968. Effect of 

transit temperatures and modified atmospheres 

on market quality of lettuce shipped in nitrogenrefrigerated trailers. Agricultural Marketing 

Research Report 832, U.S. Department of 

Agriculture, Washington, DC.

Stewart, J.K., and M. Uota. 1971. Carbon dioxide 

injury and market quality of lettuce held in CAs. J. 

Amer. Soc. Hort. Sci. 96:27-30.

Sugiyama, H., and K.S. Rutledge. 1978. Failure 

of Clostridium botulinum to grow in fresh 

mushrooms packaged in plastic film overwraps 

with holes. J. Food Prot. 41:348-350.

Sugiyama, H., and K.H. Yang. 1975. Growth 

potential of Clostridium botulinum in fresh 

mushrooms packaged in semi-permeable plastic 

film. App. Microbiol. 30:964-969.

Tatsumi, Y., A.E. Watada, and W.P. Wergin. 1991. 

Scanning electron microscopy of carrot stick 

surface determines cause of white translucent 

appearance. J. Food Sci. 56:1357-1359.

Toivonen, P.M.A. 1997. Quality changes in 

packaged, diced onions (Alliumcepa L.). In J. 

Gorny, ed., vol. 5, Fresh-Cut Fruits and Vegetables 

and MAP, pp. 1-6. Proceedings of the 7th 

International Controlled Atmosphere Conference, 

University of California, Davis CA.

Watada, A.E., N.P. Ko, and D.A. Minott. 1996. 

Factors affecting quality of fresh-cut horticultural 

products. Postharv. Biol. Technol. 9:115-125.

Zhou, Y.F., K. Abe, and T. Iwata. 1992. Effect 

of shredding modes on the deterioration of the 

quality of partially processed pepper fruits. 

Nippon Shokuhin Kogyo Gakkaishi 39:161-166.

Zhuang, H., and M.M. Barth. 1999. Control of 

browning discoloration in tray-packed freshcut iceberg lettuce. In 1999 Institute of Food 

Technologists Annual Meeting, Technical Program 

and Book of Abstracts, pp. 226. Institute of Food 

Technologists, Chicago, IL.
642

Bedding Plants and Seedlings

Hyeon-Hye Kim, Kevin Kern, and William H. 

Carlson

Kim, Kern, and Carlson are with the Department 

of Horticulture, Michigan State University, East 

Lansing, MI.

Introduction

Storage of vegetable and flower bedding plants 

may be necessary if adverse weather conditions, 

seasonal availability, or extension of the time 

of availability makes it essential. There are two 

stages of plants in bedding plant production and 

storage: plugs and finished plants. Generally, 

finished bedding plants are hardier and can 

withstand greater environmental changes than the 

plug stage of the same plant. However, storage is 

easier when the plant is in the more compact plug 

stage.

Plug Storage

Most bedding plants are produced as plugs. 

Research on plug storage is mainly limited 

to that published in recent years. Heins et al. 

(1995) found that the duration a species could 

be stored without plant death or flowering 

delay was influenced by storage temperature 

and irradiance. Plant quality improved with the 

addition of light compared to that of plants in dark 

storage, especially as the duration of storage and 

storage temperature increased (Heins and Lange 

1992a,c,d, Heins and Wallace 1993a,d). The effect 

of storage on plugs may vary depending on the 

specific storage conditions, age, species, cultivar, 

and physiological state of the plugs. The optimum 

storage temperatures and maximum storage 

durations for selected species are shown in table 1. 

Shipping plugs in boxes or trucks is in fact a 

form of short-term storage. As the duration of 

shipping increases, cooling plugs prior to shipping 

becomes more important and will improve their 

postharvest condition when they reach their 

final destination (Lange et al. 1991b, Heins et al. 

1994b, Kaczperski et al. 1996). 

Growers who only have one or two coolers may 

need to store plugs of several species at one time. 

Researchers in Michigan (Heins and Lange 1992d, 

Heins et al. 1992) showed how to identify a 

compromise temperature—one that is collectively 

acceptable, although maybe not individually 

optimal. If only short-term storage is necessary, 

a temperature warmer than the optimum may be 

more economical (Heins et al. 1994b). Also, the 

environmental conditions before and after storage 

can influence the growth of the plugs following 

storage (Heins et al. 1991, 1994b, Heins and 

Lange 1992c, Kaczperski et al. 1996). 

A major disease problem associated with plug 

storage is botrytis (Lange et al. 1991a,b, Heins et 

al. 1992, 1994b, 1995). Maintaining a high RH 

in a cooler decreases the frequency of watering 

but favors the growth of botrytis. The disease is 

generally not a problem on pansies but does affect 

many species including impatiens, geraniums, and 

petunias. Those crops should be stored under low 

RH conditions and irrigated if plugs are stored 

longer than 1 week (Heins et al. 1991). 

Low RH in coolers with significant air velocity 

causes plugs to dry out quickly. The frequency of 

irrigations will vary, depending on the temperature 

and RH of the cooler. Contact between the 

foliage and water should be minimized to avoid 

fungal infection. Plugs can be subirrigated with 

clear water as needed during storage because the 

plants’ nutritional needs are minimal under low 

temperatures (Heins and Lange 1992c, Heins 

et al. 1994b). Heins et al. (1994b) recommend 

applications of certain fungicide tank mixtures for 

controlling botrytis blight and sporulation during 

plug storage.
643

Table 1. Optimal storage temperatures and maximum storage durations for plugs of selected bedding plant species and cultivars either in the dark or under a minimum of 5 footcandles of lightSpecies Cultivars evaluated Optimal storage temperature Maximum weeks storage References

°C °F In the dark In the light

Ageratum ‘Blue Danube’ 7.5 45.0 6 6 Heins et al. 1992

Heins et al. 1994aHeins et al. 1995Heins and Lange 1992a

Alyssum ‘New Carpet of Snow’ 2.5 36.0 5 6 Heins et al. 1994a

Heins et al. 1995

Begonia, fibrous ‘Vodka’ 5.0 41.0 6 6 Heins et al. 1994a

Heins et al. 1995

5.0-7.5 41.0-45.0 Heins et al. 1992

Heins and Lange 1992c

Begonia, tuberous ‘Nonstop Scarlet’ 5.0 41.0 3 6 Heins et al. 1994a

Heins et al. 1995

5.0-7.5 41.0-45.0 Heins & Wallace 1993d

Celosia ‘Cherry Red’ 10.0 50.0 2 3 Heins et al. 1994a

Heins et al. 1995

Dahlia ‘Amore / Figaro’ 5.0 41.0 2 5 Heins et al. 1994a

Heins et al. 1995

5.0-7.5 41.0-45.0 — — Heins and Wallace 1993c
644Table 1. Optimal storage temperatures and maximum storage durations for plugs of selected bedding plant species and cultivars either in the dark or under a minimum of 5 footcandles of light—continued

Species Cultivars evaluated Optimal storage temperature Maximum weeks storage References

°C °F In the dark In the light

Geranium ‘Pinto Red’ 3.0 37.5 — — Heins et al. 1991

Lange et al. 1991b

2.5 36.0 4 4 Heins et al. 1994a

Heins et al. 1995

Impatiens ‘Accent Orange’ 7.5 45.0 6 6 Heins et al. 1991

Heins et al. 1994aHeins et al. 1995Lange et al. 1991a

Lobelia ‘Blue Moon’ 5.0 41.0 6 6 Heins et al. 1994a

Heins et al. 1995Heins and Wallace 1993e

Marigold, French ‘Hero Yellow’ 5.0 41.0 3 6 Heins et al. 1992

Heins et al. 1994a, Heins and Lange 1992cHeins et al. 1995

New Guniea impatiens ‘Kientzler Agua’ 12.5 55.0 2 3 Heins et al. 1994a

‘Kientzler Anaea’ Heins et al. 1995

‘Kientzler Apollon’‘Kientzler Celerio’‘Kientzler Celsia’‘Kientzler Eurema’‘Kientzler Marpesia’‘Kientzler Melissa’‘Kientzler Octavia’‘Kientzler Saturnia’‘Kientzler Sesia’
645

‘Paradise Antigua’‘Paradise Aruba’‘Paradise Barbados’‘Paradise Bora-Bora’‘Paradise Lanai’‘Paradise Maui’‘Paradise Papete’‘Paradise Samoa’‘Paradise Tahiti’‘Paradise Tobago’‘Paradise Tonga’‘Paradise Trinidad’

Pansy ‘Majestic Yellow’ 2.5 36.0 6 6 Heins et al. 1991

Heins et al. 1994aHeins et al. 1995

0-2.5 32.0-36.5 — — Heins and Lange 1992d

Lange et al. 1991a

Petunia ‘Ultra Red’ 3.0 37.5 — — Heins et al. 1991

Lange et al. 1991b

2.5 36.0 6 6 Heins et al. 1994a

Heins et al. 1995

Portulaca ‘Fuchsia’ 7.5 45.0 5 5 Heins et al. 1994a

Heins et al. 1995

5.0-7.5 41.0-45.0 — — Heins & Wallace 1993e

Table 1. Optimal storage temperatures and maximum storage durations for plugs of selected bedding plant species and cultivars either in the dark or under a minimum of 5 footcandles of light—continuedSpecies Cultivars evaluated Optimal storage temperature Maximum weeks storage References

°C °F In the dark In the light
646

Salvia ‘Red Hot Sally’ 5.0 41.0 6 6 Heins et al. 1994a

Heins et al. 1995

7.5 45.0 — — Heins et al. 1992

Heins and Lange 1992a

Tomato ‘Rutgers’ 7.5 45.0 3 3 Heins et al. 1994a

Heins et al. 1995Heins and Wallace 1992

Verbena ‘Romance Mix’ 7.5 45.0 1 1 Heins et al. 1994a

Heins et al. 1995

Vinca ‘Peppermint Cooler’ 10.0 50.0 5 6 Heins et al. 1994a

Heins et al. 1995

Table 1. Optimal storage temperatures and maximum storage durations for plugs of selected bedding plant species and cultivars either in the dark or under a minimum of 5 footcandles of light—continuedSpecies Cultivars evaluated Optimal storage temperature Maximum weeks storage References

°C °F In the dark In the light
647

because of reductions in fertility prior to storage 

are more resistant to botrytis (Heins et al. 1995). 

In addition, hardening of these plugs will aid in 

resistance to drought stress. A hardened plug will 

resist drought damage better than a plug grown 

with high levels of phosphorus (Borch et al. 

1999).

Plug storage has the potential to become a viable 

grower management tool (Heins and Lange 1992a) 

if cooler space is available. However, as with any 

new technique, growers should experiment with 

just a few plug trays before they commit a large 

volume to storage (Heins et al. 1991, Lange et 

al. 1991a,b, Heins and Lange 1992c, Heins and 

Wallace 1993b). See table 1 for specific species 

storage temperatures and light levels.

Finished Plant Storage

Finished bedding plants are those that are in 

a state ready for sale to the general public. 

Generally, finished plants are not stored in 

coolers because of the difficulty in moving large 

quantities of plants from greenhouse to cooler. 

To reduce plant growth, greenhouse temperatures 

are dropped while waiting for the crop to sell. 

Finished plants should be held at temperatures low 

enough to reduce growth but not to cause damage 

or impair future growth. Table 2 lists certain 

cultivars of popular bedding plants and suggested 

holding temperatures.

According to Nelson (1983), a general greenhouse 

holding temperature of 13 °C (55 °F) is applicable 

for many of the common types of bedding 

plants. Alyssum, begonia, geranium, impatiens, 

marigold, petunia, and salvia all keep well at 

this temperature. Impatiens plants were still 

marketable after 36 days at this temperature. 

Bedding plants hold better at a higher light level 

(7,500 lux) than at a lower light level (500 to 

2,700 lux).

Table 2. Short-term greenhouse-holding 

temperatures for finished bedding plants1

Hold at or above Reference

15 °C (60 °F)

Balsam Ross and Aldrich 1976

Begonia (fibrous) Ross and Aldrich 1976

Celosia Ross and Aldrich 1976

Coleus Ross and Aldrich 1976

Kochia Ross and Aldrich 1976

Vinca rosea Ross and Aldrich 1976

Zinnia (dwarf & tall) Ross and Aldrich 1976

 

10-13 °C (50-55 °F)

Ageratum Ross and Aldrich 1976

Aster Ross and Aldrich 1976

Browallia Ross and Aldrich 1976

Centaurea cyanus Ross and Aldrich 1976

Dahlia Ross and Aldrich 1976

Dianthus Ross and Aldrich 1976

Dusty Miller Ross and Aldrich 1976

Geranium Ross and Aldrich 1976

Impatiens Ross and Aldrich 1976

Marigold Ross and Aldrich 1976

Nierembergia Ross and Aldrich 1976

Petunia Ross and Aldrich 1976

Phlox Ross and Aldrich 1976

Portulaca Ross and Aldrich 1976

Salvia Ross and Aldrich 1976

Verbena Ross and Aldrich 1976

7-10 °C (45-50 °F)

Alyssum Ross and Aldrich 1976

Calendula Ross and Aldrich 1976

Carnation Ross and Aldrich 1976

Larkspur Ross and Aldrich 1976

Lobelia Ross and Aldrich 1976

Pansy Ross and Aldrich 1976

Snapdragon (tall & dwarf) Ross and Aldrich 1976

1

Temperatures are the lowest recommended 

growth temperatures after transplant. At lower 

temperatures, plant quality may be adversely 

affected by chilling injury. Refer to the plug 

storage table for temperatures and lengths of time 

the plants may be stored without damage.
648

Conifer and Hardwood Seedling Storage

Storage of conifer and hardwood forest seedlings 

is possible at a low temperature and high RH 

(Duffield and Eide 1959, Aldhous 1964, Camm 

et al. 1994). Loosely tied bundles of seedlings, 

as well as containerized seedlings, may be 

stored in conditions that lower the metabolic 

activity of the plants. For most species, however, 

temperatures should be kept above freezing to 

avoid injury (Lantz et al. 1989, Camm et al. 

1994). Top and root growth capacity of certain 

seedlings are affected by the cold storage, and 

these are dependent on seed source and lifting date 

of the seedlings (Jenkinson et al. 1993). A coldhardened seedling will store more successfully 

and for longer time than a nonhardened seedling. 

Maximum stress resistance occurs in late fall to 

early winter. Therefore, lifting dates for seedlings 

being put into cold storage should be delayed as 

long as possible (Camm et al. 1994).

Warehouses or sheds can be used for storage 

of seedlings at a variety of temperatures. 

Refrigerated storage rooms or coolers are also 

used for storing seedlings at cooler temperatures 

(1 to 4 °C, 34 to 40 °F). High RH and good air 

circulation, as well as daily photoperiod control 

if possible, are important factors that influence 

the success of seedling storage (Lantz et al. 1989, 

Camm et al. 1994).

Storage of seedlings may be done in polyethylene 

bags to facilitate high RH, but spacing between 

the bags must be enough to allow for adequate air 

movement in order to prevent fungal pathogens. 

Loosely tied bundles of seedlings may be packed 

with slightly wet peat surrounding the roots 

and then wrapped in film-coated paper with 

the tops exposed and placed in a container for 

storage. With prolonged storage (>6 mo), root 

growth capacity can decline, as well as lead 

to a disruption of naturally occurring seasonal 

progression events. 

The following species may be stored for up to

3 mo at 1 to 4 °C (34 to 40 °F): 

Norway spruce Sycamore

Sitka spruce Sweetgum

Douglas-fir Green ash

Lodgepole pine Oak

Scotch pine Birch

Loblolly pine Yellow poplar

Ponderosa pine Hybrid poplar*

Western hemlock Eastern cottonwood*

Lawson cypress

* hardwood cuttings

References

Aldhous, J.R. 1964. Cold storage of forest nursery 

plants: an account of experiments and trials, 1958-

1963. Forestry (Great Britain) 37:47-63.

Ross, D.S., and R.A. Aldrich. 1976. Production 

Operations Analysis. In J.W. Mastalerz, 

ed., Bedding Plants, 2 edition, pp. 386-397. 

Pennsylvania Flower Growers. University Park, 

PA.

Barrett, J., et al. 1999. Tips on Growing Bedding 

Plants. OFA Serv., Inc., Columbus, OH.

Borch, K., T. Bouma, J.P. Lynch, and K.M. 

Brown. 1999. Interactions of ethylene and 

phosphorus nutrition on root growth. Plant Cell 

Environ. 22:425-431.

Camm, E.L., D.C. Goetze, S.N. Silim, and D.P. 

Lavender. 1994. Cold storage of conifer seedlings: 

an update from the British Columbia perspective. 

Forestry Chronicle 70:311-316.

Duffield, J.W., and R.P. Eide. 1959. Polyethylene 

bag packaging of conifer planting stock in the 

Pacific Northwest. J. Forestry, 57:578-579.

Heins, R.D., W. Carlson, and N. Lange. 1991. 

Plug into storage. Greenhouse Grower’s Plug 

Guide, Fall, pp. 72-73.
649

Heins, R.D., M.P. Kaczperski, T.F. Wallace Jr., 

et al. 1995. Low-temperature storage of bedding 

plant plugs. Acta Hort. 396:285-296.

Heins, R.D., and N. Lange. 1992a. Development 

of systems for storage of bedding-plant plugs. 

Bedding Plants Foundation, no. F-056, February, 

pp. 1-8.

Heins, R.D., and N. Lange. 1992b. How to store 

begonia and marigold plugs. Greenhouse Grower, 

March, pp. 34-38.

Heins, R.D., and N. Lange. 1992c. How to store 

salvia and ageratum plugs. Greenhouse Grower, 

February, pp. 76-82.

Heins, R.D., and N. Lange. 1992d. One temp can 

fit all. Greenhouse Grower, April, pp. 30-36.

Heins, R.D., N. Lange, and T.F. Wallace Jr. 

1992. Low-temperature storage of bedding-plant 

plugs. In K. Kurata and T. Kozai, eds., Transplant 

Production Systems, pp. 45-64. Kluwer Academic 

Publishers, Dordrecht, The Netherlands.

Heins, R.D., N. Lange, T.F. Wallace Jr., and 

W. Carlson. 1994a. Plug Storage. Greenhouse 

Grower.

Heins, R.D., Y. Si, and M. Hausbeck. 1994b. 

Control of Botrytis during storage of beddingplant plugs. Bedding Plants Foundation, no. 

F-9406, November, pp. 1-8. 

Heins, R.D., and T.F. Wallace Jr. 1993a. How to 

store alyssum plugs. Greenhouse Grower, March, 

pp. 32-33.

Heins, R.D., and T. Wallace Jr. 1993b. How to 

store New Guinea impatiens. Greenhouse Grower, 

Fall, pp. 55-58.

Heins, R.D., and T.F. Wallace Jr. 1993d. How to 

store vinca plugs. Greenhouse Grower, April, pp. 

44-45.

Jenkinson, J. L., J. A. Nelson, and M. E. 

Huddleston. 1993. Improving planting stock 

quality—The Humboldt experience. General 

Technical Report PSW-GTR-143. U.S. 

Department of Agriculture, Forest Service, Pacific 

Southwest Research Station, Albany, CA.

Kaczperski, M.P., A.M. Armitage, and P. M. 

Lewis. 1996. Performance of plug-grown 

geranium seedlings preconditioned with nitrogen 

fertilizer or low-temperature storage. HortScience 

31:361-363.

Lange, N., R. Heins, and W. Carlson. 1991a. 

Another look at storing plugs. Greenhouse 

Grower, February, pp. 18-24.

Lange, N., R. Heins, and W. Carlson. 1991b. Store 

plugs at low temperatures. Greenhouse Grower, 

January, pp. 22-28.

Lantz, C.W., 1989. A guide to the care and 

planting of southern pine seedlings. Management 

Bull. R8-MB39, U.S. Department of Agriculture, 

Forest Service, Atlanta, GA.

Nelson, L.J. 1983. Correct conditions extend 

bedding plant marketability. The Great Lakes 

Vegetable Growers News, October, pp. 8-9.
650

Christmas Trees

Eric Hinesley and Gary Chastagner

Hinesley is with the Department of Horticultural 

Science, North Carolina State University, Raleigh, 

NC; Chastagner is with the Department of Plant 

Pathology, Washington State University, Puyallup, 

WA.

Introduction

Approximately 33 million natural Christmas 

trees were used in the U.S. in 1998. Given a 

conservative wholesale value of $10.00 per tree, 

the value of the trees alone approaches $330 

million. When associated products are added 

to the picture, total value is well above $500 

million. The National Christmas Tree Association 

estimated the average retail price for Christmas 

trees in 1998 at $3.45 to $6.30 per ft. Based on a 

standard 6- to 7-ft tall (2 m) tree, the retail value 

of natural Christmas trees approaches $1.5 billion.

About 25% of the live Christmas trees consumed 

in the U.S. are sold on choose-and-cut farms. This 

means that 75% of the trees experience some form 

of storage and shipment after harvest. Storage 

and shipment times can be several weeks for trees 

shipped between countries or less than one day for 

trees sold in local markets.

Natural Christmas trees quickly lose quality if 

handled improperly. People who grow, sell, handle 

or use Christmas trees should know something 

about tree keepability. This is true of the consumer 

who may use only one tree each year, as well as 

brokers or growers who handle thousands of trees.

Many publications have been written concerning 

postharvest physiology, handling, and keepability 

of Christmas trees. Despite this, there is often 

ignorance of the subject, resulting in wasted trees, 

reduced tree quality, erroneous information, or 

dissatisfied consumers. In this chapter, we provide 

a summary of information concerning Christmas 

tree keepability. 

Moisture Status of Cut Trees

A Christmas tree is a perishable product that 

contains a finite amount of water when cut. 

Postharvest quality and fire safety are closely tied 

to moisture status. When a tree is cut, it begins 

to dry. Rate of drying is affected by species as 

well as environmental conditions (vapor pressure 

deficit, temperature, wind) and cold hardiness.

The two most common methods for determining 

moisture status are twig moisture content (MC) 

and water potential (ψ). The second method uses 

a pressurized chamber to extrude water from 

the cut end of a twig encased in a heavy-walled 

metal chamber. The drier the twig, the greater the 

pressure required to force water out of the end of 

the twig. Freshly harvested trees normally have ψ 

= -0.2 to -0.8 MPa. (1 MPa = 10 atmospheres or 

about 10 bars.)

The temporal change in moisture content has 

several inflection points. Initially, the tree dries 

quickly to an inflection point, V1

, which varies 

considerably by species. For example, V1

 is about 

-1.8 MPa (-18 bar) in eastern red cedar, -2.2 MPa 

(-22 bar) in eastern white pine, and -2.8 MPa (-28 

bar) in Fraser fir. At that point, the rate of drying 

slows noticeably, presumably because stomata 

close to reduce water loss under increasing stress. 

Eventually, another value is reached, V2

, at which 

the drying rate accelerates again, presumably 

when increasing drying stress exceeds the capacity 

of guard cells to limit water loss. V2

 probably 

corresponds to the “damage threshold,” a term 

first used by Montano and Proebsting (1986). 

Further drying results in irreversible damage 

(needle abscission, discoloration, failure to 

rehydrate when placed in water) to the tree. The 

damage threshold for Douglas-fir and Fraser fir 

is between -3.5 and -4.0 MPa (-35 to -40 bar), 

compared to -3.0 to -3.2 MPa (-30 to -32 bar) for 

eastern white pine. Spruces typically experience 

very heavy needle loss when they dry to a certain 

MC, making it important to handle these species 

in a way that minimizes moisture loss after harvest 

and to display them in water before they reach that 

threshold.
651

The values of V1

 and V2 vary by species. In 

addition, a pressure potential of -3.0 MPa (-30 

bar) does not correspond to the same value of MC 

in various species. The time required to reach a 

particular MC also varies by species. For example, 

eastern red cedar and Atlantic white cedar dry 

very fast when displayed under room conditions, 

whereas Fraser fir and noble fir dry much slower. 

The latter species are regarded as long-lasting 

trees, whereas the former have a short shelf-life.

The moisture status of the tree determines its 

ability to rehydrate when recut and displayed in 

water. Fresh-cut trees typically have an MC in 

excess of 100%. When a fresh tree is recut and 

displayed in water, it typically gains weight, 

reaching a MC 5 to 10% above the initial value. 

Trees without water gradually lose moisture 

and can readily rehydrate at moisture levels 

approaching V2

. Beyond that, the degree of 

rehydration may decrease; or if rehydration 

occurs, there may be adverse changes in quality 

(needle abscission, discoloration). For example, 

eastern red cedar rehydrates when V2

 = -4.5 to -5.0 

MPa (-45 to -50 bar), but not without subsequent 

abscission of foliage. 

The moisture status during display also varies 

among species. Species that endure for a long time 

during the display period, such as noble fir and 

Fraser fir, tend to maintain MC and ψ close to the 

initial value for at least 4 weeks. Species that have 

a short shelf-life, such as eastern red cedar and 

Atlantic white cedar, maintain a high water level 

for about 1 wk and then begin to slowly dry even 

while displayed in water. This process is reflected 

by a decrease in ψ (more negative), a decrease in 

twig MC, and a reduction in water consumption.

Water Use

When supplied with water, cut Christmas trees 

generally consume about 1 qt (about 1 L) of water 

per day per inch (2.54 cm) of stem diameter. Thus, 

a tree with a 4-in diameter trunk would use about 

4 qt (about 4 L) of water per day. The biggest 

mistake by consumers is using a stand with too 

little capacity, resulting in trees drying up between 

waterings. If this happens, the tree might not 

rehydrate when rewatered.

Water use changes during the display period and 

also varies among species. Compared to other 

species, true firs tend to use large quantities of 

water over extended display periods. For example, 

a 6-ft (about 2 m) Fraser fir can easily use 4 qt of 

water per day during the first 5 to 7 days and 2 to 

3 qt (about 2 to 3 L) per day thereafter for the next 

3 to 4 weeks. In contrast, water use by an eastern 

red cedar might decrease noticeably after a week. 

In general, if the tree continues to use a relatively 

constant amount of water, it indicates that the 

tree is maintaining its initial water status. On the 

other hand, if there is a marked reduction in water 

consumption, it probably indicates that the tree is 

beginning to dry.

Additives

Many chemicals and home concoctions have 

been tested in hopes of prolonging the life of cut 

Christmas trees. Additives are of little benefit and 

sometimes produce adverse effects. Additives 

can undesirably increase water consumption by 

displayed trees. Because people often use stands 

that are too small, increased water consumption 

would increase the likelihood of a tree “going dry” 

in the stand. Some additives can induce heavy 

needle loss. The best tree preservative is plain 

water, without additives. 

Cold Hardiness

Cold-hardened Christmas trees keep better after 

harvest and better withstand exposure to low 

temperatures. Induction of cold hardiness requires 

photosynthesis, reduced temperatures, and shorter 

days. In this context, it will not occur in darkness, 

as in a refrigerator. When trees are harvested too 

early, heavy needle loss is possible, even with 

proper care. It is not known why cold-hardened 

trees keep better than nonhardened trees. Foliar 

raffinose increases during fall, although the 

absolute amount is small compared to sucrose. 

The increase in raffinose is mostly a response 
652

to lower temperatures. The role of raffinose is 

not clear, although in other plants it can reduce 

the ice crystallization temperature in cell sap. 

Nonhardened trees also transpire more and thus 

dry faster than hardened trees.

Tree species and seed sources also differ in their 

ability to tolerate exposure to cold temperatures. 

Coastal types of Douglas-fir are genetically not 

as cold-hardy as intermountain types. If coastal 

types of Douglas-fir are shipped into coldweather market areas and not protected from 

exposure to cold temperatures, they can exhibit 

severe needle loss due to cold injury. The level 

of damage depends on the level of cold hardiness 

of the trees, the rate of temperature drop, and 

the lowest temperatures the trees are exposed 

to. People should be aware that tree species, the 

environmental conditions prior to harvest, and the 

environmental conditions that trees are exposed to 

during transit and on retail lots can have a bearing 

on postharvest quality.

Diseases and Pests

Christmas trees can be damaged by a variety of 

diseases and pests. Although trees and branches 

can be killed, most of the damage results in 

cosmetic needle discoloration or loss of needles 

prior to harvest. Little information is available 

concerning the direst impact of various diseases 

and pests on the postharvest keepability of trees. 

Swiss needle cast on Douglas-fir Christmas trees 

can accelerate moisture loss and needle loss when 

trees are displayed indoors. 

Quarantine Issues

Live Christmas trees sometimes harbor plant 

pathogens, insects, and other arthropods. Most are 

only an annoyance; but some, if exported to places 

that have no natural enemies, could potentially 

cause serious problems. States and countries 

impose various quarantines in an effort to prevent 

the introduction or further spread of potentially 

harmful pests. For example, trees grown in areas 

infested with the gypsy moth, European pine 

shoot moth, or pine shoot beetle are frequently 

prevented from being shipped out of these areas 

unless they have been certified to be free of these 

pests. Many quarantine problems can be avoided 

by appropriate scouting, trapping, management 

practices, and certification programs. Mechanical 

shakers can be used to remove old dead needles 

and certain types of insects. The failure to meet 

quarantine requirements can result in entire 

shipments being rejected, causing great loss and 

inconvenience to producers and importers.

Fumigation. In some instances trees are required 

to be treated prior to entry, especially in some 

foreign countries. Fumigation is a common 

method used to meet quarantine requirements 

for a number of horticultural products. Although 

methyl bromide is one of the most common 

materials used to fumigate horticultural products, 

information on the tolerance of various types of 

Christmas trees to methyl bromide is limited. 

Chastagner (1990) fumigated several species 

typically grown in the Pacific Northwest with 

methyl bromide at rates up to 6 lb per 1,000 ft3

for 2 h at 10 °C (50 °F). Douglas-fir and noble 

fir were not damaged, Fraser fir and grand fir 

experienced only slight damage, Scotch pine 

showed moderate damage, and Shasta fir was 

severely damaged. Use of methyl bromide will 

diminish in the future, and alternatives are needed. 

Increasing development of international markets 

will increase the demand for procedures to ensure 

that exported trees are pest-free.

Irradiation. Gamma radiation can be used to 

sterilize or kill insects at all stages of the life 

cycle, including larvae and pupae within the 

wood. Little information is available for Christmas 

trees, but balsam fir is sensitive to chronic, lowlevel doses of gamma radiation. The cumulative 

lethal dose (LD50) is about 0.1 kGy over a period 

of years. Dormant branches of Fraser fir, when 

subjected to single doses of gamma radiation, 

experienced significant needle loss at 0.10 kGy. 

Massive needle loss occurred within 2 days for 

branches that receive higher doses of radiation. In 

addition, there was great intertree variation; for 

example, for the 0.1 kGy treatment, needle loss 

ranged from 5 to 100% for branches displayed 
653

for 2 weeks in water (average 42%). Irradiation 

discolored foliage and accelerated drying.

If Fraser fir is representative of other Christmas 

tree species, irradiation does not appear to be a 

viable way to meet insect quarantine requirements. 

Sterilizing insect pests would probably require 

irradiation doses of 0.5 to 1.0 kGy, and levels 

needed to outright kill insects would be higher. 

These levels of radiation would result in virtually 

complete defoliation of Fraser fir within a few 

days after exposure. 

Controlled Atmosphere (CA) and Modified 

Atmosphere (MA) Storage

Information is limited, but short-term CA or MA 

storage at low temperature (5 °C, 41 °F) appears 

to be of little benefit with Fraser fir. CO2

 >5%, as 

well as O2

 <3%, can lead to increased needle loss. 

The respiration rate at 21 °C (70 °F) is about four 

times that at 5 °C (41 °F). 

Fire Safety

Fresh Christmas trees, if properly watered and 

maintained, are not a fire hazard and are very 

difficult to ignite with a point source of flame. But 

problems can arise when trees become too dry. 

Several factors are important in assessment of fire 

risk, including ignition time, peak heat release rate 

(PHRR), total heat released, peak smoke release 

rate, and total smoke released. Dry trees produce 

extremely high PHRR in short periods. A PHRR 

of 500 kW is enough to cause flashover. Although 

limited PHRR data is limited, very dry Douglas‐fir 

can produce PHRR up to 3,000 kW within 1 min 

of exposure to an open flame.

Experiments (Chastagner 2002, unpublished) 

tested 21 conifer species to determine the MC at 

which branches initially begin to fail an ignition 

test and the MC for consistent failure. Branches 

were exposed to a flame from a small alcohol 

lamp for 5 sec. If the sample failed to burn or selfextinguished without any additional spread when 

removed from the flame, it passed the test. If there 

was any spread of the flame after the sample was 

removed from the flame, it failed the test. There 

is considerable interspecific variation in the MC 

for ignition. In addition, there is often a large 

transition zone of MC from the point of initially 

failing the flammability test to the point of flash 

ignition. For example, Douglas‐fir begins to fail 

the flammability test at about 68% MC, but is 

totally consumed only when dried to about 30% 

MC.

There is a close relationship between twig MC 

and water potential (ψ), which also varies among 

species. With noble fir, twig MC must reach about 

37% before it begins to fail the flammability test. 

This corresponds to a pressure potential below -6 

MPa (-60 bars), well beyond its damage threshold. 

Based on this and other postharvest display data, 

one can estimate how long it would take for trees 

to dry to moisture levels at which they would fail 

the test. With proper care, winter-hardened noble 

fir and Fraser fir can easily be displayed in water 

for 6 to 8 wk without becoming a fire hazard.

The use of flame retardants on trees is not 

recommended unless required by law. Flame 

retardants can damage needles and increase 

moisture loss from trees. The best way to 

minimize any potential fire hazard associated with 

cut Christmas trees is to display them in waterholding stands.

Colorants, Stickers, and Antitranspirants

Many conifers naturally fade to a yellow-green 

color in fall. Colorants, similar to latex paint, 

mask this effect if applied prior to the change, 

increasing consumer acceptability. Needle 

stickers, which dry to a clear, shiny film on the 

surface of foliage, supposedly cause better needle 

retention, but this has not been confirmed by 

research.

Antitranspirants form a thin film on the surface of 

foliage. Although it would seem that such products 

should greatly reduce the drying process, this is 

usually not the case. Under moderate to strong 

drying conditions, they do little to retard drying 
654

Table 1. Postharvest quality ratings for Christmas trees, displayed dry or in water

(Trees are assumed to be cold-hardened.)

 Rating

Species Scientific name Displayed—

Dry† Wet

Arizona corkbark fir Abies lasciocarpa (Hook.) Nutt. ssp. 

arizonica (Merriam) E. Murray F E

Arizona cypress Cupressus arizonica Green var. glabra

(Sudw.) Little ‘Carolina sapphire’ P/F F/G

Atlantic white cedar Chamaecyparis thyoides (L.) BSP. P P/F

Balsam fir Abies balsamea L. F G/E

California red fir Abies magnifica A. Murray G E

Canaan fir Abies balsamea (L.) Mill. var. phanerolepis Fern. F G/E

Colorado blue spruce Picea pungens Engelm. F G/E

Concolor fir Abies concolor (Gordon & Glend.) Lindl. ex Hildebr. P/G* P/E*

Douglas-fir (coastal) Pseudotsuga menziesii ssp. glauca (Beissn.) E. Murray P/F G

Douglas-fir (intermountain) Pseudotsuga menziesii (Mirb.) Franco ssp. menziesii F/G* G/E

Eastern red cedar Juniperus virginiana L. P F

Eastern white pine Pinus strobus L. G G/E

European silver fir Abies alba Mill. P G/E

Fraser fir Abies fraseri (Pursh) Poir. G E

Grand fir Abies grandis (Douglas ex D. Don) Lindl. P G/E

Greek fir Abies cephalonica Loud. P G/E

Korean fir Abies koreana Wils. G G/E

Leyland cypress × Cupressocyparis leylandii (Dallim. & 

A. B. Jackson) Dallim. F G/E

Monterey pine Pinus radiata F G

Noble fir Abies procera Rehd. G E

Nordmann fir Abies nordmanniana (Steven) Spach. P/G* E

Norway spruce Picea abies (L.) Karst. P G

Pacific silver fir Abies amabilis Douglas ex Forbes F G/E

Scotch pine Pinus sylvestris L. F/G G

Shasta fir Abies magnifica A. Murray var. shastensis Lemmon P/F F/G

Turkish fir Abies nordmanniana ssp. equitrojani

(Asch. & Sint. Ex Boiss.) Coode & Cullen 

(syn. Abies x bornmuelleriana Mattf.) P/G* E

Veitch fir Abies veitchii Lindl. G E

Virginia pine Pinus virginiana Mill. F F

Western white pine Pinus monticola Douglas ex D. Don G G/E

White spruce Picea glauca (Moench) Voss P G

Scientific names from Griffiths (1994).

Ratings: Excellent (E) has potential to last 4-6 wk under typical household conditions. Good (G) can 

last 3-4 wk. Fair (F) can last 10 d to 3 wk. Poor (P) lasts only 7-10 d. 

* Results vary greatly among seed sources. 

†

 It is never a good practice to display Christmas trees dry.
655

unless applied at levels sufficiently high to render 

trees qualitatively less acceptable to consumers by 

making them sticky. However, minor differences 

sometimes occur. For example, drying of eastern 

red cedar was slowed by latex colorant, but the 

overall drying rate of trees was so fast that the 

difference was of little practical significance.

Species Comparisons

Some Christmas tree species maintain postharvest 

quality better than others. Based on various 

experiments and observations by the authors, a 

rating of the postharvest quality of 30 species 

of Christmas trees is given in table 1. Ratings in 

this table should be used as a guide, given that 

the postharvest quality of cut Chrismas trees 

can be affected by preharvest and postharvest 

environmental factors and can vary between 

different seed sources within a species. 

The postharvest period has two phases: the period 

between cutting and placement back in water and 

the period after placement in water. Some trees 

endure well in both phases, such as noble fir and 

Fraser fir. Others do poorly when displayed dry 

but endure well in water, such as white spruce 

and grand fir. Some species have a short shelf-life 

whether displayed wet or dry, such as eastern red 

cedar, and are not suited for wholesale marketing 

or long-term display in the home. Many of the true 

firs have excellent quality when displayed in water 

but tend to shed needles when displayed dry, such 

as Nordmann fir.

Tree Handling Recommendations for 

Growers and Retailers

Cut Christmas trees can deteriorate under the 

effects of heat, wind, sunlight, and extreme 

changes in temperature. Thus, reducing exposure 

to these elements should be the goal of every 

grower and retailer. Below is a series of 

recommendations that should ensure consumers 

get the freshest tree possible:

•	 In warm climates, harvest trees as late in 

the season as possible to allow for cold 

hardening, which will improve keepability 

after harvest.

•	 Bale trees soon after cutting, especially if the 

weather is sunny and warm. Drying can be 

very rapid in the first 24 h.

•	 Temporarily store trees in areas that are 

shaded and cool. Trees can be stored either 

vertically (standing on the end of the trunk) 

or horizontally (piles or pallets). It is not 

clear if one method is better than the other; 

however, under some conditions horizontal 

stacking can lead to increased mold problems 

and damage to foliage and branches. 

Limiting the height of storage piles and 

thus reducing the compaction of trees helps 

minimize these problems. 

•	 Avoid baling wet trees under warm 

temperatures because doing so can lead to 

premature needle loss.

•	 Ship or sell trees on a “first in, first out” 

basis. 

•	 Avoid piling baled trees on hot parking lots 

or against south-facing brick or concrete 

walls.

•	 The best storage condition is low temperature 

of 33 °F to 50 °F (1 °C to 10 °C), high RH of 

85 to 95%, and darkness.

•	 Use refrigerated trucks, if possible, especially 

on hauls exceeding 400 miles or when 

moving trees into warm regions. For longdistance shipment and storage in refrigerated 

trucks and containers, trees should be loaded 

and baffled to allow for air circulation on top, 

bottom and sides and refrigeration systems 

should be run on wet cycles so they do not 

dehydrate the trees.

•	 Never allow closed vans or flatbeds to sit idle 

in the sun for extended periods because it 

quickly leads to overheating.

•	 In warm marketing areas, trees should be 

displayed under shade, protected from the 

wind, and standing in water.

•	 On retail lots, store trees upright or in 

shallow piles in a shady, cool place out 

of high traffic areas. If permanent shade 

is unavailable, use a tarp or shade cloth 
656

suspended above the trees and down the 

sides with at least a 2-ft (61 cm) air-space for 

ventilation.

•	 Minimize or eliminate walking on baled 

trees because it breaks limbs and leaders 

and crushes foliage. Be especially careful 

handling frozen trees: They are very brittle.

•	 Trees on display in retail lots in warm market 

areas can be misted or sprayed with water 

at night to reduce the moisture lost during 

daylight hours. Misting trees on the surface 

of storage piles may also be beneficial, but 

soaking trees can result in severe mold and 

deterioration problems. 

•	 Trees hauled long distances on open trucks 

should be smoke-tarped on the front and 

covered with shade cloth on the top and sides 

to prevent windburn and damage from diesel 

smoke.

•	 Avoid temperatures above 10 °C (50 °F) in 

closed storage.

•	 In cold-weather market areas, protect trees 

from drying winds. Do not attempt to sell 

trees such as coastal Douglas-fir in these 

types of markets unless they can be protected 

from exposure to potentially damaging 

temperatures.

References

Chastagner, G.A. 1990. Insect contaminants—a 

problem that is limiting the market for Pacific 

Northwest trees. Pacific Northwest Christmas Tree 

Association., Northwest Lookout 23(3):72-74.

Montano, J.M., and W.M. Proebsting. 1986. 

Storage of cut Douglas-fir: relationship to the 

damage threshold. HortScience 21:1174-1175.

Further Reading

AMS [U.S. Department of Agriculture, 

Agricultural Marketing Service]. 1989. United 

States standards for grades of Christmas trees. 

U.S. Department of Agriculture, Washington, DC. 

Ahrens, J.F., and G.R. Stephens. 1975. Effect 

of harvest date or dry storage on moisture 

content and flammability of white spruce. Amer. 

Christmas Tree J. 19(4):13-16.

Ahrens, J.F., and G.R. Stephens. 1975. The 

effects of additives on freshness and flammability 

of Christmas trees. Connecticut Agricultural 

Experiment Station Bull. no. 760, New Haven, 

CT.

Blankenship, S.M., and L.E. Hinesley. 1990. 

Tolerance of controlled atmosphere storage 

of cut Fraser fir and its respiration rate in air. 

HortScience 25:941-943.

Chastagner, G.A. 1984. Moisture levels in 

Douglas-fir Christmas trees on retail lots in 

Washington and California. Pacific Northwest 

Christmas Tree Assoc., Northwest Lookout 

17(3):10-14.

Chastagner, G.A. 1985. Research on Christmas 

tree keepability. Amer. Christmas Tree J. 29(4):31-

35.

Chastagner, G.A. 1986. Effect of postharvest 

moisture stress on the keeping qualities of 

Douglas-fir Christmas trees. HortScience 21:485-

486.

Chastagner, G.A. 1987. Trees of the future: tree 

keepability research needs. Amer. Christmas Tree 

J. 31(2):30-34.

Chastagner, G.A. 1989. Maximizing your sales by 

keeping cut trees fresh. California Christmas Tree 

Assoc. Bull. 35:12-19. 

Chastagner, G.A. 1991. How were these superior 

trees developed? Pacific Northwest Christmas 

Tree Assoc., Northwest Lookout 24(2):36.

Chastagner, G.A., and R.S. Byther. 1984. 

Postharvest moisture stress and the keeping 

qualities of Douglas-fir Christmas trees. Pacific 

Northwest Christmas Tree Assoc., Northwest 

Lookout 17(3):29-34.
657

Chastagner, G.A., and R.S. Byther. 1984. Impact 

of Swiss needle cast on postharvest hydration and 

needle retention of Douglas-fir Christmas trees. 

Plant Dis. 68:192-195.

Chastagner, G.A., and K. Riley. 1990. Effect 

of water additives on the postharvest quality of 

Douglas-fir Christmas trees. California Christmas 

Tree Assoc. Bull. 141(Oct):6-11.

Chastagner, G.A., and K. Riley. 1991. Effect of 

foliar sprays of antitranspirants on the postharvest 

quality of Douglas-fir Christmas trees. California 

Christmas Tree Assoc. Bull. 143:36-40.

Davis, T.S., and T.A. Fretz. 1972. The antitranspirant effect on harvested Christmas trees. 

Amer. Christmas Tree J. 16(1):3-5.

Dugle, J.R. 1986. Growth and morphology in 

balsam fir: effects of gamma radiation. Can. J. 

Bot. 64:1484-1492.

Griffiths, M. 1994. Index of Garden Plants: The 

New Royal Horticultural Society Dictionary. 

Timber Press, Portland, OR.

Hinesley, L.E. 1984. Measuring freshness of 

cut Fraser fir Christmas trees. HortScience 

19:860-862.

Hinesley, L.E. 1988. Water relations of cut eastern 

redcedar Christmas trees. HortScience 23:589-

591.

Hinesley, L.E. 1990. Grower postharvest handling 

of Christmas trees. Christmas Tree Notes, CTN015, North Carolina Cooperative Extension 

Service, Raleigh, NC.

Hinesley, L.E. 1990b. Latex colorant slows drying 

of redcedar Christmas trees. HortScience 25:673-

674.

Hinesley, L.E., and S.M. Blankenship. 1991. 

Attributes of water additives affect postharvest 

needle retention of Fraser fir. HortScience 26: 

569-570.

Hinesley, L.E., and S.M. Blankenship. 1991. 

Effect of water additives on Fraser fir needle 

retention. HortTechnology 1:90-91. 

Hinesley, E., and G. Chastagner. 1993. Common 

myths and questions: the handling and care of cut 

Christmas trees. Amer. Christmas Tree J. 37(4):16-

19.

Hinesley, L.E., and W.T. Huxster Jr. 1991. Retail 

merchandising of North Carolina Fraser fir. 

Christmas Tree Notes, CTN-017, North Carolina 

Cooperative Extension Service, Raleigh, NC.

Hinesley, L.E., and L.K. Snelling. 1991. Vapor 

pressure deficit, temperature and light affect 

postharvest drying of Fraser fir and eastern white 

pine. HortScience 26:402-405.

Hinesley, L.E., and L.K. Snelling. 1993. “CropLife” does not slow postharvest drying of Fraser 

fir and eastern redcedar. HortScience 28:1054.

Hinesley, L.E., and L.K. Snelling. 1993. Gamma 

radiation unpromising as insect quarantine 

treatment for Fraser fir branches. HortScience 

28:1109-1110.

Hinesley, L.E., and L.K. Snelling. 1994. 

Postharvest drying of Leyland cypress, eastern red 

cedar, and Fraser fir Christmas trees. HortScience 

30:1427-1428.

Hinesley, L.E., and L.K. Snelling. 1997. 

Postharvest drying and rehydration of Leyland 

cypress, Atlantic white cedar, Virginia pine, 

Arizona cypress and eastern white pine Christmas 

trees. HortScience 32:1252-1254.

Hinesley, L.E., L.K. Snelling, and S. Goodman. 

1992. Rehydration of Fraser fir Christmas trees: 

effect of time since cutting. HortScience 27:930.

Hummel, R.L. 1996. Cold hardiness and 

dormancy. Amer. Christmas Tree J. 40(2):24-26.

Koelling, M. 1998. Christmas trees do not 

cause fires: some facts! Amer. Christmas Tree J. 

42(4):4,6,8,10,12,14,16,18-21.
658

Kubiske, M.E., M.E. Abrams, and J.C. Finley. 

1990. Keepability of Pennsylvania versus 

West Coast grown Douglas-fir Christmas trees: 

genotypic variation in relation to subfreezing 

temperatures. Northern J. Appl. For. 7:86-89.

McKinley, C.R., and L.E. Hinesley. 1995. 

Handling Christmas trees on retail lots. Christmas 

Tree Notes, CTN-026, North Carolina Cooperative 

Extension Service, Raleigh, NC.

Miller, D.R., and W.T. Bagley. 1970. Christmas 

tree flammability. Amer. Christmas Tree J. 

14(4):9-12.

Mitcham-Butler, E.J., L.E. Hinesley, and D.M. 

Pharr. 1988. Effects of harvest date and storage 

temperature on the postharvest needle retention of 

Fraser fir branches. J. Environ. Hort. 6(1):1-4.

Seiler, J.R., T.J. Nichols, and D.J. Paganelli. 1988. 

Rehydration characteristics of cut white pine and 

Norway spruce Christmas trees. HortScience 

23:164-166.

Tilton, E.W., and A.K. Burditt Jr. 1983. Insect 

disinfestation of grain and fruit. In E.S. Josephson 

and M.S. Peterson, eds., Preservation of Foods 

by Ionizing Radiation, vol. 3, pp. 215-229. CRC 

Press, Boca Raton, FL.
659

Cut Flowers and Greens

Michael S. Reid

Reid is with the Department of Plant Sciences, 

University of California, Davis, CA.

Botany and Introduction

Plant materials from a wide range of taxa are 

grown and harvested as cut flowers or florist 

greens; these include ferns and lycopods, 

gymnosperms, and angiosperms. Because of 

this diversity, these guidelines include a general 

review of postharvest requirements for cut 

ornamentals, followed by brief summaries of the 

requirements of a selection of the most common 

materials used in commercial floriculture. The 

references cited are usually the most recent report 

on a particular crop and therefore provide an 

entree to the literature that is the basis for the 

recommendations.

Quality Characteristics and Criteria

Cut ornamentals are complex plant organs, in 

which loss of quality of stems, leaves, or flower 

parts may result in rejection in the marketplace. 

In some ornamentals, loss of quality may result 

from one of several causes, including wilting or 

abscission of leaves or petals, yellowing of leaves, 

and geotropic or phototropic bending of scapes 

and stems. In evaluating factors that affect the life 

of ornamentals and how to maximize their market 

life, it is important first to understand the diverse 

causes of quality loss.

Growth, Development, and Aging

The whole plant and its individual organs are an 

integral part of the plant’s life cycle. Even when 

there is no senescence of floral organs or leaves, 

continued growth can result in quality loss; 

for example, in spike-type flowers that bend in 

response to gravity.

Flower Senescence

The early death of flowers and greens is a common 

cause of quality loss and reduced vase life for 

many ornamentals. Flowers can be divided into 

several categories on the basis of their senescence. 

Some flowers are extremely long-lived, especially 

in the Asteraceae and Orchidaceae families, while 

others are short-lived, including many of the bulb 

crops such as tulip, iris, and narcissus.

Wilting

Extended life for cut ornamentals depends 

absolutely on a continuing and adequate supply 

of water. Rapid wilting of shoot tips, leaves, and 

petals results from an obstruction of the water 

supply through the cut stems. 

Leaf Yellowing and Senescence

Yellowing of leaves and other organs (buds, 

stems) is commonly associated with the end of 

display life in some flowers; alstroemeria being 

an important example (Hicklenton 1991). Leaf 

yellowing is a complex process that may be 

caused by a range of different environmental 

factors.

Shattering

Abscission and loss of leaves, buds, petals, 

flowers, or even branchlets is a process called 

“shattering,” and it is a common problem in cut 

flowers and potted plants (van Doorn and Stead 

1997). Very often, this problem is associated 

with the presence of ethylene in the air, but other 

environmental factors may also be involved. 

Factors Affecting Postharvest Quality

Maintaining the freshness of cut flowers and other 

ornamentals requires an understanding of the 

factors that lead to their deterioration. A number 

of these factors are different from those that apply 
660

to the edible crops covered in this handbook. 

Nevertheless, understanding these factors allows 

us to develop and implement optimum postharvest 

handling technologies.

Variety

Many commercial cut flowers and cut greens 

are patented cultivars, characterized by specific 

attributes such as color, form, disease resistance, 

and size. Sometimes, breeders fail to consider 

other commercially important attributes. For 

example, some of the modern alstroemeria 

cultivars have wonderful flowers, but their display 

life is short because of rapid leaf yellowing under 

commercial conditions. There is relatively little 

published information comparing the postharvest 

life of different ornamental cultivars (Van Der 

Meulen-Muisers et al. 1999).

Preharvest Factors

What goes on in the greenhouse or field is an 

important determinant of the quality and life of cut 

flowers and foliage (Celikel and Karaaly 1995). 

Disease-free plants that were properly irrigated 

and fertilized will produce flowers that look better 

and perform better in the vase. However, the large 

leaves on roses grown under supplementary light 

with CO2 fertilization make them more susceptible 

to postharvest wilting. 

Food Supply

Starch and sugars stored in the stem, leaves, 

and petals provide much of the food needed for 

cut‐flower opening and maintenance. The levels 

of these carbohydrates are highest when plants 

are grown in high light with proper cultural 

management. Carbohydrate levels are, in fact, 

generally highest in the late afternoon—after 

a full day of sunlight. However, flowers are 

preferably harvested in the early morning, because 

temperatures are lower, plant water content is 

higher, and a whole day is available for processing 

the cut flowers.

The quality and vase life of many cut flowers can 

be improved by pulsing them immediately after 

harvest with a sugar solution. Pulsing is done 

by standing the cut flowers in the solution for 

a short period, usually less than 24 h, and often 

at low temperature. Typical examples include 

tuberose, for which storage life and opening are 

dramatically improved; gladiolus, for which 

flowers open further up the spike, are bigger, and 

have a longer vase life; and sweet peas, for which 

vase life was improved (Ichimura and Suto 1999). 

Sugar is also an important part of the bud-opening 

solution used to open bud‐cut flowers before 

distribution (Kuiper et al. 1995) and as part of the 

vase solution used at the retail and domestic level. 

Potted plants are able to provide their own food 

supply through photosynthesis if they are held in 

adequate light conditions.

Light

The presence or absence of light during storage 

is generally not a concern except in cases where 

yellowing of foliage is a problem. The leaves of 

certain cultivars of chrysanthemum, alstroemeria, 

marguerite daisy, and other crops can yellow if 

stored in darkness at warm temperatures. The 

blackening of leaves of cut Protea nerifolia 

flowers can be prevented by maintaining them 

in high light or by giving them a sugar pulse. 

This suggests that the problem is induced by low 

carbohydrate status in the harvested inflorescence 

(Bieleski et al. 1992). 

Water Supply

Cut flowers, especially those with large leaf areas, 

lose water and wilt very rapidly. They should be 

stored above 95% RH to minimize water loss, 

particularly during long-term storage. Water loss 

is dramatically reduced at low temperatures, 

another reason for prompt and efficient cooling

of cut flowers and potted plants. Even after 

flowers have lost considerable water (for example, 

during transportation or storage) they can be fully 

rehydrated using proper techniques. Cut flowers 

will absorb solutions without difficulty providing 
661

there is no obstruction to water flow in the stems. 

Air embolism, plugging with bacteria, plant debris 

or dirt, and poor water quality reduce solution 

uptake (van Doorn 1999).

Air embolism. Air embolisms occur when small 

bubbles of air (emboli) are drawn into the stem at 

the time of cutting. These bubbles cannot move far 

up the stem, so the upward movement of solution 

to the flower may be restricted. Emboli may be 

removed in many ways; for instance, recutting 

the stems under water (removing about 2 cm), 

ensuring that the solution is acid (pH 3 or 4), 

placing the stems in a vase solution heated to 40 

°C (104 °F; warm, but not hot) or in an ice-cold 

solution (0 °C), placing the stems in deep (>20cm) 

water, or treating the flowers with a detergent 

“pulse.”

Bacterial plugging. The cut surface of a flower 

stem releases the contents of the cut cells 

(proteins, amino acids, sugars, and minerals) 

into the vase water. These are ideal food for 

bacteria, yeasts, and fungi, which grow rapidly 

in the anaerobic environment of the vase. Slime 

produced by the bacteria, and the bacteria 

themselves, can obstruct the water-conducting 

system. This problem must be addressed at every 

step of the postharvest chain by—

•	 Using clean water to make postharvest 

solutions 

•	 Cleaning and disinfecting buckets

•	 Using white buckets—dirt is easier to see in 

a white bucket.

Include a biocide in all bucket and vase 

solutions. Ca(OCl)2

, NaOCl, Al2(SO4)3, and 

salts of 8-hydroxyquinoline are commonly used 

bactericides. An acidic solution also inhibits 

bacterial growth.

Hard water. Hard water frequently contains 

minerals that make the water alkaline (high pH). 

Water movement in flower stems is drastically 

reduced when the water is of high pH. This 

problem can be overcome either by removing 

minerals from the water (by using a deionizer, 

still, or reverse osmosis system) or by making the 

water acid (pH ~3.5). Citric acid is commonly 

used as a safe acidulant. 

Water Quality

Chemicals commonly found in tap water are toxic 

to some ornamentals. Sodium, present in high 

concentrations in soft water, is toxic to carnations

and roses and will cause salt burn (burning of the 

leaf tips and margins) in potted plants. Fluoride 

is very toxic to gaillardia (Rajitha et al. 1999), 

gerbera, gladiolus, roses, and freesia. Fluoridated 

drinking water contains enough flouride (about 1 

μL L-1) to damage these flowers. 

Growth Tropisms

Certain responses of cut flowers to environmental 

stimuli (tropisms) can result in quality loss. Most 

important is geotropism (bending away from 

gravity) and phototropism (bending towards light). 

Geotropism often reduces quality in spike‐flower 

crops like gladiolus, snapdragon, lisianthus, 

and gerbera because the flowers and spike bend 

upward when stored horizontally (Philosoph et al. 

1995). These flowers should be handled upright 

whenever possible. 

Mechanical Damage

Physical abuse of cut flowers and foliage results 

in torn petals, damaged leaves, and broken stems. 

Obvious injuries are undesirable for aesthetic 

reasons, and disease organisms can more easily 

infect plants through injured areas. Additionally, 

respiration and ethylene evolution are generally 

higher in injured tissues, further reducing storage 

and vase life. 

Horticultural Maturity Indices

Minimum harvest maturity for most cut flowers 

is the stage at which harvested buds can be 

opened fully and have satisfactory display 

life after distribution. Many flowers are best 

cut in the bud stage and opened after storage, 
662

transport, or distribution. This technique has many 

advantages, including reduced growing time for 

single-harvest crops, increased product packing 

density, simplified temperature management, 

reduced susceptibility to mechanical damage, and 

reduced desiccation. Many flowers are presently 

harvested when the buds are starting to open (rose, 

gladiolus), although others are normally fully 

open or nearly so (chrysanthemum, carnation). 

Flowers for local markets are generally harvested 

much more open than those intended for storage 

or long-distance transport. Cut foliage is harvested 

when the uppermost leaves are fully expanded to 

avoid postharvest wilting of the shoot tips.

Grades, Sizes, and Packaging

The designation of grade standards for cut flowers 

is one of the most controversial areas in their care 

and handling. Objective standards such as stem 

length, which is still the major quality standard 

for many flowers, may bear little relationship to 

flower quality, vase life, or usefulness. Weight 

of the bunch for a given length is a method that 

has been shown to strongly reflect flower quality. 

Straightness of stems, stem strength, flower 

size, vase life, freedom from defects, maturity, 

uniformity, and foliage quality are among the 

factors that should also be used in cut flower 

grading. If used, mechanical grading systems 

should be carefully designed to ensure efficiency 

and to avoid damaging the flowers. 

Flowers are normally bunched, except for 

anthuriums, orchids, and some other specialty 

flowers. The number of flowers in the bunch 

varies according to growing area, market, and 

flower species. Groups of 10, 12, and 25 are 

common for single‐stemmed flowers. Spray‐type 

flowers are bunched by the number of open 

flowers, by weight, or by bunch size. Bunches are 

held together by string, paper-covered wire, or 

elastic bands and are frequently sleeved soon after 

harvest to unitize the bunch, protect the flower 

heads, prevent tangling, and identify the grower or 

shipper. Materials used for sleeving include paper 

(waxed or unwaxed), corrugated card (smooth 

side towards the flowers), and polyethylene 

(perforated, unperforated, and blister). Sleeves can 

be preformed (although variable bunch size can 

be a problem), or they can be formed around each 

bunch using tape, heat-sealing (polyethylene), or 

staples. 

There are many shapes of packing containers for 

cut flowers, but most are long and flat. This design 

restricts the depth to which the flowers can be 

packed in the box, and this may reduce physical 

damage. In addition, flower heads can be placed 

at both ends of the container for better use of 

space. With this kind of flower placement, whole 

layers of newspaper are often used to prevent 

the layers of flowers from injuring each other. 

The use of small pieces of newspaper to protect 

only the flower heads, however, is probably the 

better practice, since it allows for more efficient 

cooling of flowers after packing. It is critically 

important that containers be packed in such a 

way that transport damage is minimized. Some 

packers anchor the product by using enough 

flowers and foliage in the box so that flowers in 

the package, after banding, are immobilized by 

the surrounding material. To avoid longitudinal 

slip, packers in many flower-producing countries 

use one or more “cleats.” These are normally 

foam- or newspaper-covered wood pieces that are 

placed over the product, pushed down, and stapled 

into each side of the box. Padded metal straps, 

elastic bands, high density polyethylene blocks, 

and cardboard tubes can also be used as cleats. 

The heads of the flowers should be placed 6 to 10 

cm (2.4 to 4 in) from the end of the box to allow 

effective precooling and to eliminate the danger of 

petal bruising should the contents of the box shift. 

Gladioli, snapdragons, and some other species 

are often packed in vertical hampers to 

prevent geotropic curvature that reduces their 

acceptability. Cubic hampers are used for upright 

storage of daisies and other flowers. A new 

packaging system uses “proconas”—plastic bases 

and a cardboard sleeve—to allow transport of 

flowers upright in water. This system is more 

expensive than traditional boxes, and less can 

be packed in it. However, the presence of water 

may improve flower quality when they are not 

transported under proper temperature conditions. 
663

Specialty flowers such as anthurium, orchid, 

ginger, and bird of paradise are packed in 

various ways to minimize friction damage

during transport. Frequently, flower heads are 

individually protected by paper or polyethylene 

sleeves. Cushioning materials such as shredded 

paper and paper or wood wool may be placed 

between packed flowers to further reduce damage. 

Precooling Conditions

By far the most important part of maintaining the 

quality of harvested flowers is ensuring that they 

are cooled as soon as possible after harvest and 

that optimum temperatures are maintained during 

distribution. Most flowers should be held at 0 

to 1 °C (32 to 34 °F). Chilling‐sensitive flowers 

(anthurium, bird of paradise, ginger, tropical 

orchids) should be held at temperatures above 10 

°C (50 °F). 

Once packed, cut flowers are difficult to cool. 

Their high rate of respiration and the high 

temperatures of most greenhouses and packing 

areas result in heat build‐up in packed flower 

containers unless measures are taken to ensure 

temperature reduction. It is therefore necessary to 

cool the flowers as soon as possible after packing. 

Individually, flowers change temperature rather 

rapidly, with half-cooling times of a few minutes. 

However, individual flowers brought out of cool 

storage into a warmer packing area will warm 

quickly and water will condense on the flower. 

The simplest method of ensuring that packed 

flowers are adequately cooled and dry is to pack 

them in the cool room. Although this method is 

not always popular with packers, and may increase 

labor cost and slow down packing somewhat, it 

will ensure a cooled, dry product. 

Forced-air cooling of boxes with end holes or 

closeable flaps is the most common and effective 

method for precooling cut flowers. Cool air is 

sucked or blown through the boxes. Care must be 

taken to pack them so that air can flow through the 

box and not be blocked by the packing material or 

flowers. In general, packers use less paper when 

packing flowers for precooling. The half-cooling

time for forced-air cooling ranges from 10 to 

40 min, depending on product and packaging. 

Flowers should be cooled for three half-cooling

times, by which time they are 7/8 cool.

If the packages are to remain in a cool 

environment after precooling, vents may be left 

open to assist removal of the heat of respiration. 

Flowers that are to be transported at ambient 

temperatures can be packed in polyethylene 

caskets, foam-sprayed boxes, or boxes with the 

vents resealed. Ice that is used after precooling is 

only effective if placed to intercept heat entering 

the carton (that is, it must surround the product), 

and care must be taken to ensure that the ice 

does not melt onto flowers or cause chilling 

damage. Precooling of vertical hampers or 

proconas presents a particular challenge, but can 

be achieved using a “tunnel” forced-air cooling 

system. 

Chilling Sensitivity

Some tropical crops such as anthurium, bird of 

paradise, some orchids, ginger, and many foliage 

plants are injured at temperatures below 10 °C 

(50 °F). Symptoms of chilling injury include 

darkening of the leaves and petals, water soaking 

of the petals, and in severe cases collapse and 

drying of leaves and petals. Special care needs to 

be taken with tropical flowers shipped in a mixed 

load. The flowers should be packed in plenty of 

insulating material (an insulated box packed with 

shredded newsprint, for example). These flowers 

should not be precooled. If they are to be shipped 

by refrigerated truck, they should be placed in the 

middle of the load, away from direct exposure to 

cooling air.

Ethylene Production and Sensitivity

A number of flowers, especially carnations, 

gypsophila, and some rose cultivars, senesce 

rapidly if exposed to minute concentrations 

of ethylene gas. A number of flowers (such as 

carnations and sweet peas) produce ethylene 

as they age, and this endogenous ethylene 
664

is involved in the death of the flower. Other 

flowers, such as snapdragon and delphinium, 

produce little ethylene themselves, but exogenous 

ethylene causes flower abscission (or shattering). 

Concentrations of ethylene above 100 ppb (nL 

L-1) in the vicinity of sensitive ornamentals can 

cause damage and therefore should be avoided. 

Storage and handling areas should be designed 

not only to minimize contamination of the 

atmosphere with ethylene, but should also have 

adequate ventilation to remove any ethylene 

contamination that may occur. Treatment with 

the anionic thiosulfate complex of silver (STS) or 

with 1-methylcyclopropene (1-MCP) inhibits the 

deleterious effects of ethylene whether a product 

of atmospheric contaminant (exogenous) or 

produced by the flower (endogenous) (Macnish et 

al. 2000). Finally, refrigerated storage is beneficial 

in that both ethylene production and sensitivity are 

reduced greatly when temperatures are low.

Optimum Storage Conditions

The vase life of flowers that are stored even 

for a few days is closely correlated with their 

respiration during storage. Rapid cooling 

and proper refrigeration are thus essential to 

maintaining quality and satisfactory vase life 

of cut flowers and foliage. The recommended 

conditions for commercial storage of most cut 

flowers are 0 to 1 °C (32 to 34 °F) at 95 to 99% 

RH. Although flowers are commonly held in 

water for short-term storage, better vase life after 

longer storage is achieved by storing the flowers 

dry. Under these conditions, stable temperatures 

(to reduce condensation and Botrytis infection) 

and high RH are essential. Flowers for longerterm storage are typically wrapped in newsprint 

(to absorb any condensation) and perforated 

polyethylene (to reduce water loss). Storage 

life varies by species but is typically less than 3 

weeks.

Controlled Atmosphere (CA) 

Considerations

There have been relatively few reported benefits 

of CA storage for cut flowers. Any consideration 

of the use of CA must follow achievement of 

proper temperature control and elimination of the 

effects of Botrytis during storage. Recommended 

atmospheres vary from pure nitrogen (daffodils) to 

more conventional atmospheres (carnations).

Retail Outlet Display Considerations

The simple way to ensure rapid rehydration of all 

but the most difficult or desiccated flowers is to 

recut the stems and place them in a clean bucket 

of water containing a quality flower preservative 

solution in the cooler. The pH of the preservative 

solution should be below 5. For badly wilted 

flowers a rehydration solution may be helpful, 

since the sugar in vase preservatives reduces 

the flow of water in stems. Flowers with woody 

branches respond particularly well to low pH (3.5 

is optimal), and some flowers (sunflowers, astilbe) 

respond well to a 10-min “pulse” with a 0.02% 

detergent solution. Flower coolers should be <5 

°C (41 °F); flowers should be placed in the coolers 

when not on display or being used for preparing 

arrangements.

Respiration Rates

Cut flowers have extremely high rates of 

respiration that increases exponentially with 

temperature (Cevallos 1998). Various cultivars 

of the same species may have quite different 

respiration rates and may respond differently to 

temperature.
665

Physiological Disorders

There are relatively few recognized physiological 

disorders in the postharvest life of cut flowers and 

foliage. “Topple” of tulips, a collapse of the scape, 

is a disorder associated with low calcium status 

of the flowers. Petal blackening in some red roses 

has been suggested also to be associated with 

inadequate calcium and perhaps boron nutrition. 

Postharvest Pathology

Flowers are very susceptible to disease, not only 

because their petals are fragile but also because 

the secretions of their nectaries often provide an 

excellent nutrient supply for even mild pathogens. 

Transfer from cold storage to warmer handling 

areas often results in condensation of water 

on the harvested flowers. The most commonly 

encountered disease organism, gray mold (Botrytis

cinerea), can germinate wherever free moisture is 

present. In the humid environment of the flower 

head, it can even grow, albeit more slowly, at near 

freezing. Proper greenhouse hygiene management 

(Hammer and Evensen 1996), temperature control, 

and minimized condensation on harvested flowers 

reduce losses caused by this disease. 

Quarantine Issues

Export of cut flowers to other markets requires 

phytosanitary certification. A number of pests 

on cut flowers are the subject of quarantine 

regulations in a number of overseas markets. 

Disinfestation of quarantine insects in cut flowers 

is the subject of active research. 

Suitability as Fresh-Cut Product

There is a small market for edible flowers, and 

some high-value fresh-cut salads include petals in 

the mix. Obviously chemicals not registered for 

food use may not be used in postharvest handling 

of flowers intended as food.

Special Considerations

Many special considerations that arise from the 

unique physiology, handling, and marketing of cut 

flowers and foliage are addressed in the following 

section for individual crops.

Guidelines for Individual Crops

The following section contains guidelines for 

individual crops. The content is organized 

by scientific name and introduction, quality 

characteristics and criteria, grading and bunching, 

ethylene sensitivity, pretreatments, storage 

conditions, packing, and special considerations. 

The following individual crops are discussed:

Alstroemeria

Anemone, windflower

Anthurium, flamingo flower

Asparagus fern, lace fern, Sprengeri

Aster, Michaelmas daisy

Baby’s breath, gypsophila

Bird of paradise

Bouvardia

Calla lily

Carnation, miniature carnation

Chrysanthemum, florist mum

Daffodil

Delphinium, larkspur

Emerald palm

Eucalyptus, silver dollar tree

Fir, spruce, pine

Freesia

Gerbera, Transvaal daisy

Ginger, shell ginger, torch ginger

Gladiolus, glad

Heliconia, parrot flower

Holly, ilex

Huckleberry

Iris, fleur-de-lis

Leatherleaf fern

Lemonleaf, salal

Liatris, gay feather

Lily of the Nile, agapanthus
666

Lily, Asiatic lily, Oriental lily

Lisianthus, prairie gentian

Marguerite daisy, Boston daisy

Orchids

Protea, pincushion

Rose, spray rose, sweetheart rose

Snapdragon

Statice, German statice

Stock

Sunflower

Sweet pea

Sweet William

Tuberose

Tulip

Waxflower, Geraldton waxflower

Yellow aster

Alstroemeria

Scientific Name and Introduction

Alstroemeria cvs., hybrids. In the last 30 yr, 

flowers of various hybrids of species of the genus 

Alstroemeria, variously called alstroemeria, 

Peruvian lily, or lily of the Incas, have become 

an increasingly important part of commercial 

cut flower trade. Flowers come in a variety of 

types and colors. All have a long postharvest life, 

typically terminated by petal wilting or drop and 

yellowing of the leaves. The Swedish Consul in 

Spain, Klas Alstroemer, had seeds of this species 

brought to Europe in 1754. The famous plant 

taxonomist Carl Linnaeus, a friend of Alstroemer, 

subsequently named the species after him. 

Quality Characteristics and Criteria

For long-distance markets, flowers are harvested 

when the buds are about to open and start to color. 

For local market, harvest is delayed until the first 

three flowers have opened. Flowers are pulled off 

or cut, depending on the variety. Where pulling 

may damage the underground parts of the plant (as 

in young plants of ‘Regina’), the stem should be 

cut. If flowers are cut, the remaining stem should 

be removed later. At least one flower per stem 

should be open at time of purchase. Purchase only 

by cultivar name. 

Grading and Bunching

There are no grade standards for alstroemeria, 

but in addition to the common characters of 

freedom from damage, stem length, strength, and 

straightness, it is suggested that the flowers in a 

bunch should be uniform. The flower head should 

be symmetrical, and leaves should be bright green. 

The minimum acceptable number of florets per 

stem varies with cultivar, but is typically 7 to 10. 

Ethylene Sensitivity

Alstroemeria flowers are ethylene sensitive. 

Pretreatments

Although untreated alstroemeria flowers have a 

long vase life, petal drop (particularly a problem 

if there is ethylene in the environment) can be 

delayed by pretreatment with 1-MCP or STS. 

In some cultivars, leaf yellowing occurs before 

flower senescence; it can be delayed by a pulse 

treatment with preservative containing growth 

regulators (gibberellins [Kappers et al. 1998] or 

cytokinins).

Storage Conditions

Alstroemeria should be stored at 0 to 1 °C (32 

to 34 °F). Present information suggests that 

alstroemeria can readily be stored for up to 1 week 

at 1 °C (34 °F). 

Packing

Alstroemeria are normally bunched in groups 

of 10, sleeved, and packed in horizontal boxes. 

Flower pedicels are affected by gravity and will 

bend upwards if temperature control during 

storage is poor. 
667

Special Considerations

When recutting, remove the whitish or blanched 

bottom portion of the stem, if present, for 

maximum solution uptake and life. Leaf removal 

will reduce vase life if enough flowers are not 

present for solution uptake. Since Alstroemeria

is a member of the Amaryllidaceae, a botanical 

family from which many pharmaceutical products 

are derived, it’s not surprising that some humans 

get allergic dermatitis from this species. 

Anemone, Windflower

Scientific Name and Introduction

Anemone spp. Brightly colored in deep reds, 

blues, purples, and white, anemones have rather 

short stems and are typically a spring flower. New, 

improved tetraploid varieties have been introduced 

into commerce (Jacob et al. 1997). Anemone is an 

ancient Greek name meaning windflower, from 

anemos for wind. 

Quality Characteristics and Criteria

Flowers should be harvested when the buds are 

fully colored and 25 to 50% open, but before 

the petals have expanded and the pollen is shed. 

Purchase when true colors are showing. 

Grading and Bunching

Anemones are normally sold in bunches of 10 

stems. 

Ethylene Sensitivity

Ethylene exposure causes petal shatter and 

reduced vase life. 

Pretreatments

Pretreatment with STS or MCP prevents the 

deleterious effects of ethylene. 

Storage Conditions

Anemones should be stored in a vertical position 

at 0 to 1 °C (32 to 34 °F), and may be dry-stored 

for at least 1 week.

Packing

Flowers are usually packed in standard horizontal 

fiberboard boxes.

Special Considerations

The anemone’s prominence and beauty in 

arrangements is a double-edged sword because 

of the flower’s relatively short vase life. It is 

preferable not to use anemones as focal points. 

Keep stems wrapped during rehydration to help 

keep them straight. There is no scientific basis for 

the practice of piercing a hole through the flower 

base to extend life. Placing anemones in vases 

with freshly cut daffodils can reduce their life 

because of the harmful juices exuded from the 

daffodils.

Anthurium, Flamingo Flower 

Scientific Name and Introduction

Anthurium andraeanum. With their brilliant glossy 

spathes (the brightly colored ornamental part of 

the flower) and slender spadices, anthuriums are 

classic tropical flowers. New cultivars provide 

a wide range of colors and forms, and their vase 

life can be very long. The elegant blooms of this 

tropical aroid are produced and sold throughout 

the world. The true flowers are found on the 

spadix, the upright organ in the center of the 

spathe, which is the decorative petallike organ 

surrounding the spadix. Although anthuriums are 
668

sensitive to low temperatures, they have a long 

vase life when properly handled. The end of their 

vase life is usually the result of inability to draw 

water from the vase solution and is associated 

with loss of glossiness and then blueing of the 

spathe. Most of the water lost by the flower 

evaporates from the spadix. Application of wax 

to prevent this water loss or pulsing with silver 

nitrate to improve water relations of the flower can 

extend their vase life considerably. Anthurium is 

also known as “tailflower.”

Quality Characteristics and Criteria

Maturity of anthurium flowers is determined by 

the proportion of open flowers on the spadix. 

In immature anthuriums, the spadix is smooth. 

Flower opening starts at the base of the spadix and 

proceeds upwards. Spadices with open flowers 

are noticeably rough. Although producers in some 

countries harvest anthuriums when as little as 

20% of the spadix is rough, Hawaiian growers 

harvest flowers when only 25% of the spadix is 

still smooth (75% of the flowers are therefore 

open). Harvesting anthuriums when more mature 

increases overall vase life. Avoid flowers that 

show any signs of chilling injury (purpling of the 

spathe, browning or wilting of the spadix). For 

maximum life, flowers should be purchased when 

the spadix, the slender “tail” of the flower, is 50 to 

75% rough. The spadix is the true inflorescence of 

the anthurium, and the rough mature flowers are 

easily distinguished from the smooth, immature 

flowers. 

Grading and Bunching

Although there are no formal grade standards 

for anthuriums, top quality implies long stems, 

uniformity of color and size, proper maturity, 

glossiness of the spathe, and freedom from any 

damage or disease. Anthuriums are normally 

packed individually. 

Ethylene Sensitivity

Anthuriums are not affected by exposure to 

ethylene, and anti-ethylene treatments provide no 

benefit. 

Pretreatments

Some researchers recommend pretreatment to 

increase the vase life of anthuriums, but some 

cultivars (such as ‘Osaki’) achieve maximum 

vase life with DI alone. It seems probable that 

vase-life problems are associated with bacterial 

contamination of the cut stem bases. If anthuriums 

are placed in water after harvest, a biocide such as 

50 μL L-1 hypochlorite should be added. One of 

the following methods should be used:

•	 Pulse the recut stems for 10 to 20 min in 

1,000 μL L-1 silver nitrate. Rinse stems with 

fresh water after treatment. 

•	 Dip the whole flower in an emulsion of 

carnuba wax. Use a 3% dilution of the wax. 

After dipping, place flower stems in water 

while the wax dries. 

Storage Conditions

Anthuriums should be stored at 12.5 to 20 °C 

(55 to 68 °F) because they are very sensitive to 

chilling injury (Pritchard et al. 1991). Holding 

the flowers for any length of time at temperatures 

below 10 °C (50 °F) will induce purpling, 

then browning, and then death of the flowers. 

Anthuriums should therefore never be precooled 

with other flowers nor held in low-temperature 

cool-rooms. Anthuriums shipped in mixed loads 

at low temperatures should be protected from 

chilling exposure by appropriate insulation (for 

example, wrapping the flowers in newsprint and 

packing them in an insulated box). Anthurium 

flowers can be stored for at least 1 week if packed 

in moist shredded newsprint and held at 15 °C 

(59 °F). They also respond favorably to storage in 

controlled atmosphere. Vase life after storage was 

increased by 50% when flowers were stored at 

12.5 °C (55 °F) in 2% O2

 for up to 2 weeks. 
669

Packing

Anthuriums are commonly packed in moist 

shredded newsprint or other shredded paper. 

Major damage during transportation is the result 

of spadices puncturing the spathe of neighboring 

flowers in the pack. Many producers now sheathe 

the flowers in small plastic bags and pack the 

anthuriums more densely in the box. 

Special Considerations

Anthuriums can have a vase life of up to 3 weeks 

if properly treated. Even after storage, vase life 

can be adequate if proper techniques are used 

to handle the flowers. They are very susceptible 

to stem blockage and easily bruised because of 

mechanically induced injuries, especially during 

packing and unpacking. Keep holding solutions 

clean by using an effective preservative solution. 

Asparagus Fern, Lace Fern, Sprengeri 

Scientific Name and Introduction

Asparagus spp. Asparagus fern (A. setaceus and 

other species in the genus Asparagus) is probably 

better known in the floral trade as A. plumosus

or plumosus fern. It provides an interesting 

foliage and filler for arrangements. These species 

are not true ferns but are members of the lily 

family, in the same genus as edible asparagus. 

The Asparagus densiflorus “Sprengeri” group is 

another common foliage used as a filler.

Quality Characteristics and Criteria

As with other foliage, asparagus fern should 

be harvested when the fronds are fully mature; 

immature tips are very likely to wilt after 

harvest. Make sure that the fronds are mature and 

uniformly green, that there are no yellow leaves, 

and that leaves do not fall from the fronds when 

they are shaken. 

Grading and Bunching

There are no formal grade standards for asparagus 

fern, but fronds should be intact and of uniform 

length, maturity, and color. Fronds are frequently 

bunched in groups of 20 and not normally placed 

in sleeves. 

Ethylene Sensitivity

Exposure to ethylene will cause leaf-fall in 

some species of asparagus fern, and therefore 

pretreatment with 1-MCP or STS is beneficial.

Pretreatments

Because ethylene exposure will cause accelerated 

leaf fall, treatment with 1-MCP or STS is 

recommended. 

Storage Conditions

Store asparagus ferns at 0 to 1 °C (32 to 34 °F), 

wrapped in polyethylene to reduce drying during 

storage. The fern should be cooled before being 

wrapped in polythene. 

Packing

Because of their relatively low value, asparagus 

and other ferns are packed densely in boxes—

usually horizontal boxes that are filled as full as 

possible. This places an additional emphasis on 

the importance of precooling; but no paper or 

plastic is used, which permits reasonably effective 

forced air cooling. 

Special Considerations

Asparagus fern suffers from premature leaf fall. 

Induced primarily by water stress, this can be a 

serious problem. To avoid yellowing and leaf fall, 

avoid prolonged storage. Certain preservative 

solutions aggravate premature leaf yellowing. 
670

However, preservative should be used in all 

arrangements containing this fern, as other items 

in the arrangement will benefit. 

Aster, Michaelmas Daisy 

Scientific Name and Introduction

Aster spp. The family Asteraceae and the genus 

Aster include numerous species and cultivars used 

in horticulture. A. ericoides ‘Monte Casino’ is 

particularly important in the florist trade. Another 

important aster for florists is the China aster, 

Callistephus chinensis. 

Quality Characteristics and Criteria

As with most members of the Asteraceae, 

immature flowers (ones harvested too early) will 

generally not open properly. Purchase as you 

would purchase chrysanthemums, more open 

(at least 75% open) than in a bud stage. Avoid 

specimens with yellowing leaves as this is an 

indication of improper storage and/or growing 

conditions. 

Grading and Bunching

There are no grade standards as such, apart from 

the standard quality attributes of stem length, 

foliage quality, uniformity, and freedom from 

defects. Depending on species and cultivar, 

bunches may be prepared by stem number (China 

aster, for example) or by bunch size (‘Monte 

Casino’ aster, for example). 

Ethylene Sensitivity

Members of the Asteraceae are generally 

unaffected by exposure to moderate concentrations 

of ethylene. 

Pretreatments

The vase life of asters is often limited by poor 

water relations, demonstrated by wilting of the 

flower or buds. Their vase life has been shown 

experimentally to be extended by a 10-sec 

pretreatment with a high concentration (1,000 

μL L-1) of silver nitrate, which is a very effective 

germicide. 

Storage Conditions

Store asters at 0 to 1 °C (32 to 34 °F). 

Packing

Asters are packed in traditional flower boxes, 

hampers, or proconas. 

Special Considerations

It is very difficult to make broad flower care 

recommendations for asters because of the large 

number of species and cultivars. Keep stems and 

vase solution clean. It is especially important with 

asters to remove leaves that might be in the water 

since bacteria grow quickly on leaves that are 

underwater, contaminating the vase solution and 

leading to early wilting. Treat with a hydrating 

solution, and prepare the preservative solution 

properly to minimize contamination by debris and 

microorganisms.

Baby’s Breath, Gypsophila 

Scientific Name and Introduction

Gypsophila paniculata. A favorite for use 

in bouquets and dried flower arrangements, 

gypsophila is most often field-grown. The flowers 

are sensitive to water deficit and intense sunlight 

and will brown and shrivel easily if subjected to 

these stress conditions. On the other hand, damp 

or rainy conditions increase the risk of gray mold

(Botrytis) and Phytophthora root rot. Gypsophila
671

is Greek for “gypsum-loving,” in reference to this 

species’ good growth performance in high-calcium 

soils. 

Quality Characteristics and Criteria

Gypsophila plants produce flowers on large 

panicles whose individual flowers open over a 

considerable time period. Flowering stems are 

usually cut 20 to 40 cm (8 to 16 in) long. The 

degree of maturity at harvest is determined by 

whether the flowers are intended for the fresh 

market or for dried arrangements. Stems are cut 

when 50% of the flowers are open if they are to 

be placed in a drying solution immediately or 

marketed within 24 h. Stems are cut when 20 to 

30% of the flowers are open if they are to be dried 

later or held longer than 24 h. Purchase gypsophila 

that has plenty of unopened buds and shows no 

signs of water stress, wilting, or disease (brown 

florets). 

Grading and Bunching

Stems are gathered into field bunches using rubber 

bands or ties to secure the cut ends. Bunches from 

California are sold as growers’ bunches with 5 to 

25 stems, whereas gypsophila from South America 

comes in bunches weighing 300 g. 

Ethylene Sensitivity

Exposure to ethylene causes wilting of open 

flowers and sleepiness of opening buds. 

Pretreatments

Gypsophila responds best to pretreatment with 

STS, which protects not only open florets but 

also the developing buds (Newman et al. 1998). 

Gypsophila flowers treated with STS and held in a 

solution containing Physan will maintain excellent 

display life for several weeks as new buds open on 

the panicle. However, STS sometimes is of little 

benefit because stem blockage prevents uptake. Be 

sure stems are rinsed and recut underwater before 

placement in STS.

Storage Conditions

Store at 0 to 1 °C (32 to 34 °F) in high (90%) RH 

to reduce flower and stem desiccation. Because 

botrytis can be a serious problem, florists should 

ask suppliers (or be prepared themselves) to 

treat with appropriate fungicides. Stems with 

about 50% of their flowers open can be kept in a 

preservative solution (200 μL L-1 Physan) at 1 °C 

(34 °F) for up to 3 weeks. 

Packing

Gypsophila may be packed in horizontal boxes or 

hampers. Thirty bunches are packed in a standard 

box. 

Special Considerations

Gypsophila harvested in the bud stage (5% of 

flowers open) can be opened to excellent quality 

in a bud-opening solution containing 200 μL L-1

Physan-20 and 5 to 10% sucrose. Flowers should 

be held at about 20 °C (68 °F) and 50% RH and 

with light levels of about 15 mmol m-2 sec-1 PAR 

(use cool-white fluorescent lamps). For drying 

gypsophila, a solution containing 1 part glycerine 

to 2 parts water should be used. Cut stems are then 

dried by hanging bunches upside down in a warm 

dry environment. 

Bird of Paradise 

Scientific Name and Introduction

Strelitzia reginae. The bird of paradise 

inflorescence consists of a boat-shaped bract 

containing a series of four or five flowers, so when 

an exposed flower withers, another one can be 

pulled out. Few cut flowers have this capability. 

Traditionally, Southern California growers bag 
672

the inflorescence a few weeks before harvest. 

Slender, elongated waxed paper bags are placed 

over the expanding bracts a week or more before 

the orange flowers are ready to emerge. The bags 

protect the brittle flowers by holding them inside 

or next to the bracts. The bag also helps prevent 

Botrytis mold, rain and hail damage, aphid attacks, 

and sunburn of the flowers. The specific epithet 

“reginae” means “queen.” 

Quality Characteristics and Criteria

Inflorescences bend as they reach maturity, 

assuming a 90° angle to the stem. The first 

emerging orange flowers can barely be seen 

through the paper bags. The stems are pulled at 

this point. Stems can also be harvested in the tight 

bud stage before the first flowers emerge. At this 

stage the inflorescence is swollen, and there is 

a slight orange crack on the upper surface. The 

inflorescence is mature at the tight bud stage, 

and this is the optimum stage for harvest from 

the point of view of ease of handling and flower 

longevity. Flower stems are generally pulled off 

rather than cut. A side to side pulling motion is 

often necessary to loosen the stem at the base of 

the plant, although the inflorescences can break off 

if jerked too vigorously. Make sure flower heads 

are dry at time of purchase. If flowers are wet or 

have excessive nectar exudation upon unpacking, 

then the possibility of subsequent disease 

problems is increased.

Grading and Bunching

Strelitzia stems are sorted into at least three grades 

according to stem length and inflorescence size. 

For premium grade flowers, the field bags are 

replaced with new bags. Five stems are firmly 

tied together at two points, with the inflorescences 

facing in the same direction. The stem ends are 

evenly trimmed. A paper wrapper is placed around 

the bunched inflorescences to further protect the 

flowers. 

Ethylene Sensitivity

Strelitzia flowers are insensitive to ethylene and 

their life is not improved by treatment with STS or 

1-MCP. 

Pretreatments

Flower longevity can be substantially increased 

by pulsing buds or flowers for 24 h (48 h is even 

better) with a solution containing 10% sucrose, 

250 μL L-1 8-hydroxyquinoline citrate (8-HQC), 

and 150 μL L-1 citrate (Halevy et al. 1978). 

Storage Conditions

The optimum long-term storage temperature range 

for this species is 6 to 7 °C (43 to 45 °F), which is 

different from most other flowers. Storage below 

this recommended range can result in chilling 

disorders, the appearance of brown lesions on the 

flowers and bracts, and the failure of the flower 

to open properly. For short-term storage, hold 

the flowers at room temperature or in a tropical 

storage room at 12.5 °C (55 °F). Strelitzia flowers 

harvested in the tight bud stage will open and have 

satisfactory vase life after 4 weeks in storage if 

pretreated with a fungicide, wrapped to prevent 

desiccation, and stored at 7 °C (45 °F) and 85 to 

90% RH. 

Packing

Waxed paper bags on each inflorescence and 

the paper wrapper on each bunch give ample 

protection from handling injury and desiccation. 

Because they are very heavy, Strelitzia stems 

should be packed in shallow cartons. 

Special Considerations

If flowers do not emerge from the spathe 

(modified leaf below the flower), the first flower 

can be gently eased out by hand and will normally 

provide good display life. 
673

Bouvardia 

Scientific Name and Introduction

Bouvardia spp. Bouvardia flowers are a relatively 

recent addition to the florist’s palette. Their bright 

salmon, red, and white color range and interesting 

flower form offer interesting design possibilities. 

The genus is named after Charles Bouvard (1572-

1658) who was physician to Louis XIII and 

superintendent of the Royal Gardens in Paris. 

Quality Characteristics and Criteria

Bouvardia flowers are normally harvested with 

two to three outer flowers open. Purchase when 

one or two flowers are open on each stem. 

Avoid flowers that have yellowed foliage or are 

showing signs of wilting. If the flowers have been 

pretreated to prevent the effects of ethylene, there 

should be little shattering when the flower bunch 

is shaken. 

Grading and Bunching

There are no formal grade standards for 

bouvardia, but top quality flowers will be uniform 

in maturity and color, free of defects, and have 

good quality foliage and long stems. Flowers are 

normally bunched; bunches contain 10 stems and 

are sleeved prior to packing. 

Ethylene Sensitivity

Accelerated wilting and abscission result from 

exposure of flowers to ethylene. 

Pretreatments

Because of their ethylene sensitivity, bouvardia 

flowers should be pretreated with 1-MCP or 

STS. Research has shown STS to be the superior 

pretreatment because it protects not only open 

flowers but also the developing buds from the 

effects of ethylene. Treatment for 4 to 24 h with 

water containing detergents such as Agral LN or 

Nonoxynol-8.5 prior to dry storage prevents early 

wilting of the flowers (van Doorn et al. 1993). 

Storage Conditions

Although previous recommendations have been 

to store bouvardia at 7 to 10 °C (45 to 50 °F), 

this species is not chilling sensitive and therefore 

should be stored, like most temperate cut flowers, 

at 0 to 1 °C (32 to 34 °F). 

Packing

Bouvardia may be packed in horizontal boxes or 

proconas. 

Special Considerations

Bouvardia exhibits leaf yellowing and is wilt 

sensitive. In some markets a special preservative 

formulation is sold that can reduce leaf yellowing. 

Recut stems underwater and use good sanitation 

procedures to reduce the frequency of wilted 

flowers. Postharvest performance differs greatly 

among the many cultivars marketed. 

Calla Lily 

Scientific Name and Introduction

Zantedeschia spp. The striking white blooms 

of Zantedeschia aethiopica have long been an 

important cut flower, and new green-tinged 

and differently shaped variants are increasingly 

important. The hybrid “minicallas,” with their 

elegant shape and wide range of colors, continue 

to increase in importance as cut flowers and 

potted plants. The showy spathe is a leaflike 

organ that surrounds the true flowers—the thick, 

fleshy spadix. The genus is named for Francesco 

Zantedeschia, who wrote about Italian plants 

around 1825. Although often called calla lilies, 

these flowers are not related to the true lily.
674

Quality Characteristics and Criteria

Callas should be harvested when the spathe 

has opened enough that the spadix can be seen. 

Flowers harvested more mature will be more 

susceptible to damage and may have reduced 

vase life. The flowers are normally pulled from 

the rhizome and recut to ensure adequate water 

uptake. The spadix (the thick fleshy inflorescence 

inside the showy spathe) should be visible at the 

time of purchase. Watch for bruising of the fleshy 

stems due to packaging. If cut too tight, flowers 

will usually not open properly. 

Grading and Bunching

Quality callas have long stems, are uniform in 

maturity and color, and have no defects such as 

damage to the spathe or spadix. Both large and 

mini callas are normally bunched in groups of 

10. Minicallas are sometimes sleeved to provide 

additional protection. 

Ethylene Sensitivity

Calla flowers are not ethylene sensitive, although 

some researchers have shown positive effects of 

STS pretreatment. Contrary to popular belief, 

callas do not produce significant quantities of 

ethylene. 

Pretreatments

Callas do not require any pretreatments. 

Storage Conditions

Callas should be stored at 0 to 1 °C (32 to 34 °F). 

Packing 

The flowers may be packed horizontally or in 

upright hampers or water packs. If they are packed 

horizontally, avoid direct contact with cleats, 

which may damage the fleshy stems. Standard 

callas may bend in response to gravity unless held 

at the proper storage temperature. 

Special Considerations

The minicallas have fewer postharvest problems 

and are generally easier to handle and use because 

of their smaller size. 

Carnation, Miniature Carnation 

Scientific Name and Introduction

Dianthus caryophyllus. Long one of the most 

important of the commercial cut flowers, the 

carnation has benefited enormously from the 

use of STS, which can increase its vase life 2- 

to 3-fold. The wide range of colors and forms, 

especially for miniatures, allows florists and 

consumers to use and enjoy them in many ways. 

The genus name, Dianthus, derives from the 

Greek for “flower of love.” Carnations used to be 

called “clove gilly-flowers” in reference to their 

intense clovelike aroma. Some modern cultivars 

are very fragrant and are used to make perfumes. 

Carnations can be stored longer than any other 

flower and can be opened to high quality flowers 

from very tight buds. Miniature carnations are also 

referred to as spray carnations. 

Quality Characteristics and Criteria

The maturity at which carnations are harvested 

depends on the proposed marketing procedure. 

Star-stage buds are too immature for most 

purposes except long-term storage. Buds at the 

“paint-brush” stage, with petals straight up, will 

open quickly. Flowers for immediate use are 

normally harvested with the outer petals between 
675

vertical and horizontal. To minimize spread of 

disease, avoid harvesting from plants with obvious 

disease symptoms. Many pickers place cut flowers 

on top of wires for later collection into bunches. 

Flowers collected into canvas slings can be taken 

to the shed by mechanical devices ranging from 

overhead cables to tractor-hauled trailers designed 

to hold slings. Standard carnations ship better and 

last longer if purchased in the bud stage, while 

miniature carnations should be purchased when 

at least one flower per stem is open. Fragrant 

cultivars have more consumer appeal. 

Grading and Bunching

Both standard and miniature carnations are graded 

by stem strength, stem length, bloom diameter, 

and freedom from defects. Stem strength is 

determined by holding the stem horizontally 

at a point one inch above the minimum length 

for the grade. If the deviation of the flower 

head is more than 30° from horizontal (with 

the natural curvature down), the flower is 

considered defective. Other defects include 

slabsides, bullheads, blown heads, singles, sleepy 

appearance, splits, discoloration, and damage 

from insects and diseases. Standard carnations are 

bunched and tied at the base and at least one other 

place below the flower heads. Instead of different 

colored labels, some growers indicate different 

grades by color or number of rubber bands on 

the bunches. Standards for miniature carnation 

bunches vary; a bunch normally contains a 

minimum of 30 buds total, at least 7 of which are 

open. With standard carnations, flower heads may 

be alternated (five high and five low) at the top of 

the bunch to produce a neat and compact bunch 

and reduce the risk of the neck breaking. 

Ethylene Sensitivity

Carnations are ethylene sensitive, and exposure to 

ethylene causes premature petal wilting referred 

to as “sleepiness.” Some newer cultivars are less 

sensitive to ethylene than the standard ‘Sim’ 

types, and carnations have now been genetically 

modified by the addition of a mutation of the 

ethylene-binding site that makes them insensitive 

to ethylene (Bovy et al. 1999).

Pretreatments 

Carnation flowers must be pretreated with 1-MCP 

or STS. Research shows that the effectiveness of 

1-MCP is lost within a week at room temperature 

but is retained for extended periods when 

carnations are held at low temperatures. Pulsing 

the treated flowers overnight with a preservative 

containing 10% sucrose improves flower opening, 

and quality carnation buds can be opened at room 

temperature and under normal room lighting in 

a solution containing 7% sucrose and 200 μL L-1

Physan. The buds should have been treated first 

with 1-MCP or STS. 

Storage Conditions

Carnations should be stored at 0 to 1 °C (32 to 34 

°F). Bud-harvested flowers perform best in storage 

because they are less sensitive to ethylene than 

mature flowers. Flowers or buds for storage should 

be of the highest quality and absolutely free of 

pests and diseases. They should be treated with 

1-MCP or STS and a fungicide for botrytis control 

then packed in a box lined with polyethylene and 

newspaper. Open flowers can be stored 2 to 4 

weeks, while bud-cut flowers can be safely stored 

up to 4 to 5 weeks. There are methods available 

for storing buds for up to 4 mo. 

Packing

Carnations are usually packed in standard 

horizontal fiberboard boxes. 

Special Considerations 

Spray carnations do not always respond well to 

STS because the different flower maturities do not 

take up the STS solution equally. It is difficult to 

recognize water-stressed carnations, but severe 
676

reduction in vase life is the result; so keep them 

hydrated when held above 0 to 1 °C (32 to 34 °F). 

Chrysanthemum, Florist Mum 

Scientific Name and Introduction

Dendranthema × grandiflorum. Less important 

than formerly, but still an important cut flower, 

chrysanthemums (which come in a wide range 

of colors and forms, including standard and 

spray, or pompon) have a long postharvest life 

when properly handled. The chief postharvest 

problems in these flowers are failure to draw water 

(which results in premature leaf wilting) and leaf 

yellowing. Chrysanthemum is Greek for “golden 

flower.” 

Quality Characteristics and Criteria 

Standard chrysanthemums are normally harvested 

fully open, or nearly so, and pompons are 

harvested with the most mature flowers fully 

open. Harvesting too early may result in failure 

of the flowers to open. However, chysanthemums 

can be harvested as quite tight buds and opened 

satisfactorily with simple bud-opening solutions. 

Bud-cut standards can be harvested when the 

inflorescence is about 5 cm (2 in) across or greater 

and opened into full-sized flowers. Spray varieties 

can be harvested when most of the petals on the 

most mature flower are still upright. The flowers 

can be opened after storage or transportation. 

Stems should be cut (with a knife or shears) 

at least 10 cm (4 in) above the soil line to 

avoid taking woody plant tissue. Pinched 

spray chrysanthemums can be pulled from the 

soil and then cut to correct length. Leaves are 

removed from the lower third of the stems. 

Proper rehydration is vital for good vase life of 

chrysanthemums that have been stored or shipped 

long distances. Remove chrysanthemum bunches 

from the boxes, recut stems to remove about 

2.5 cm (1 in), and place in a good rehydration 

solution. Educate workers and customers to accept 

flowers that are from two-thirds to three-quarters 

open, as these flowers will last longer than ones 

harvested when tighter. 

Grading and Bunching

Standard chrysanthemums are graded by length 

and packed individually. Spray types are graded 

by length and bunched. Standards or disbuds of 

equal sizes are graded into groups of 10 or 12. 

Each bunch of 5 to 8 spray chrysanthemums 

should be sleeved with plastic to prevent flowers 

from becoming entangled. Standards and spider 

mums can be wrapped individually with thin wax 

paper to avoid bruising and entangling florets. 

Some growers place nets over spider mums in the 

greenhouse before the buds open.

Ethylene Sensitivity

Chrysanthemums are not sensitive to ethylene. 

Pretreatments

Stems should be placed in a rehydration solution 

or in water containing a germicide soon after 

harvest if they are not to be packed immediately 

(van Meeteren and van Gelder 1999). Immersion 

in solutions of the cytokinin 6-benzyl adenine 

has been shown to be effective in preventing 

premature leaf yellowing in some spray cultivars 

that are prone to this problem. This treatment is 

not yet used commercially. Bud-harvested flowers 

can be opened in fresh-flower solutions containing 

2 to 3% sugar (higher concentrations damage 

leaves) at 15 to 20 °C (59 to 68 °F) with 16 h per 

day of normal room-intensity light. Physan is a 

common, effective germicide, but it discolors the 

stem portion in the solution; therefore, only 3 to 

8 cm (1.2 to 3.2 in) of solution should be used. 

After the buds are open, the injured portion of the 

stem can be removed. Silver nitrate at 25 μL L-1

plus citric acid at 75 μL L-1 is very effective but 

more expensive to use than Physan. Silver nitrate 

is, however, absorbed into the stem and becomes a 

lasting germicide throughout the life of the flower.
677

Storage Conditions

Chrysanthemums should normally be stored 

at 0 to 1 °C (32 to 34 °F). Bud-cut standard 

chrysanthemums harvested when the bud is 1.2 

cm (3 in) across can be stored up to 2 weeks, and 

1.6-cm (4-in) buds for up to 3 weeks, at 0 to 1 

°C (32 to 34 °F). Bud-cut stems that are held in 

cold storage beyond the recommended time can 

develop flat-topped flowers. Fully mature blooms 

can be stored dry (wrapped in polyethylene) 

for 3 to 4 weeks at 0 °C (32 °F). Storage at 0 to 

1 °C (32 to 34 °F) should not exceed 2 weeks. 

Yellowing of leaves can occur at 5 °C (41 °F) in 

the dark, but is less likely at 1 °C (34 °F). 

Packing

Chrysanthemums are normally packed in standard 

horizontal fiberboard boxes. Standards are packed 

individually, and a layer of wax paper often 

separates each row of flowers. 

Special Considerations

The main postharvest problems for 

chrysanthemums are premature foliage yellowing, 

wilting, and the failure of the flowers to fully 

open. Yellow foliage is cultivar specific and is 

caused by poor production, excessive or improper 

storage, and preservative solutions used at higher 

than recommended concentrations. The bottom 

portion of some mum stems can be woody; make 

sure these stems are cut above this woody tissue in 

order to facilitate water uptake, delay wilting, and 

extend end-user life. 

Daffodil

Scientific Name and Introduction

Narcissus cvs. daffodils—symbol of spring and 

known for their bright yellow, orange, red, pink, 

and white colors—are garden favorites world 

wide. Unfortunately, these flowers have relatively 

short vase life that cannot as yet be increased 

substantially with standard postharvest treatments. 

Narcissus is a classical Latin name, from the 

Greek; perhaps, as the origin suggests, an allusion 

to narcotic properties. It is not clear whether it was 

named after the youth Narcissus in mythology. 

Quality Characteristics and Criteria

Daffodils are normally harvested at the “gooseneck” stage. Jonquils are often harvested at the 

“one-bell” stage, when only one flower is open on 

the spike. Harvesting is normally done by cutting 

the flower from the foliage and bulb, although the 

whole plant may be removed and the bulb and 

leaves then cut from the flower spike. Flowers 

should be purchased in the pencil to goose-neck 

stages. These terms refer to flower position 

relative to the stem; pencil being straight up and 

gooseneck bent downwards to about a 45° angle. 

Grading and Bunching

As with a number of other spike-type flowers, 

narcissus will bend upwards away from gravity 

if laid down flat. For this reason, flowers should 

be kept vertical when they are not cooled to the 

proper storage temperature. Although there are 

no formal grade standards for these flowers, the 

most important quality attributes are maturity, 

uniformity of color, and freedom from damage or 

disease. Flowers are normally bunched in groups 

of 10 or 25, tied with twist-ties, and sleeved in 

paper or plastic. 

Ethylene Sensitivity

Senescence of these flowers is accelerated 

by exposure to ethylene, although their 

natural senescence does not involve ethylene. 

Pretreatment with 1-MCP or STS may extend 

flower life where flowers are handled in ethylenepolluted environments such as mass market 

outlets. 
678

Pretreatments 

Pretreatment with 1-MCP or STS can help extend 

vase life of flowers that are likely to be exposed to 

ethylene. 

Storage Conditions

Daffodils and jonquils should be stored at 0 to 1 

°C (32 to 34 °F). Store upright as these flowers 

will bend upwards from gravity. Narcissus can 

be stored at 1 °C (34 °F) and 90% RH for up to 

2 weeks with only slight reduction in vase life. 

They may also be stored for several weeks in an 

atmosphere of 100% N2

. Narcissus stored in this 

way have as long a vase life as fresh-cut flowers 

and nearly double the vase life of air-stored 

flowers. Flowers are best stored upright and dry in 

containers that permit rapid cooling of the flowers, 

such as fiberboard boxes. 

Packing

Because of their sensitivity to gravity, daffodils 

are often packed in hampers; although they may 

be packed in horizontal fiberboard boxes if they 

are properly precooled and maintained at the 

correct storage temperature. 

Special Considerations

Daffodils exude a gelatinous (slimy) substance 

that, when transferred through a common holding 

solution to other flowers like tulips and anemone, 

can result in premature death for the other species 

(van Doorn 1998). Therefore, place freshly cut 

or recut flowers into a separate holding bucket 

for a few hours. Later they can be placed with 

other flowers and used (even recut if required) 

in arrangements without affecting the life of the 

other flowers. 

Delphinium, Larkspur 

Scientific Name and Introduction

Delphinium, Consolida spp. The tall spikes of 

delphinium and the smaller spikes of larkspur are 

important accent flowers with colors ranging from 

white through pink, purple, and blue. 

Quality Characteristics and Criteria

Delphiniums and larkspur are normally harvested 

with one or two open flowers on the spike. Avoid 

flowers with mildew-infected leaves. At least one 

or two flowers per stem should be fully opened at 

the time of purchase with no sign of flower fall. 

Make sure stems are rinsed prior to recutting and 

arranging to remove dirt and debris.

Grading and Bunching

There are no formal grade standards for larkspur 

and delphinium. Flower number per spike, stem 

length, stem straightness, and foliage quality 

are important quality attributes in these flowers. 

Larkspur are normally bunched by size with an 

average of 10 stems per bunch. 

Ethylene Sensitivity

Delphiniums are very sensitive to ethylene, which 

causes rapid loss of all of the flowers on the spike. 

Pretreatments

Flower spikes should be pretreated with 1-MCP 

or STS to extend their vase life and protect them 

from exposure to ethylene. Because flowers are 

on spikes and are therefore at different maturity 

stages at the time of anti-ethylene treatment, STS 

may be more effective than 1-MCP. 
679

Storage Conditions

Delphinium and larkspur should be stored at 0 to 

1 °C (32 to 34 °F). For longer term storage, they 

should be wrapped in perforated polyethylene to 

reduce water loss. 

Packing

These flowers are often packed in hampers with 

or without water, but they may also be packed in 

standard horizontal boxes. They are somewhat 

sensitive to gravity, so horizontally packed flowers 

should be precooled and maintained at proper 

holding temperatures. 

Special Considerations

Flowers called larkspur or delphinium often are 

named incorrectly. 

Emerald Palm 

Scientific Name and Introduction

Chamaedorea spp. Chamaedorea is a smallleaved member of the palm family with leaves that 

perform well in the vase. Three other members 

of the palm family (coconut, date-palm, and 

oil-palm) make up the commercially important 

species for food consumption in North America. 

Quality Characteristics and Criteria

Chamaedorea palms are harvested in the wild as 

well as being produced in plantations. Fronds are 

harvested when fully expanded, mature, and dark 

green. Fronds of Chamaedorea should be dark 

green, clean, and uniform. Avoid fronds whose 

leaf tips show marginal necrosis or dead areas and 

fronds that are beginning to turn yellow. 

Grading and Bunching

There are no formal grade standards for 

Chamaedorea, but uniformity, size, color, and 

absence of defects are important criteria of quality. 

Bunches of emerald palm contain 25 stems. 

Ethylene Sensitivity

Exposure to ethylene has no deleterious effects on 

Chamaedorea fronds. 

Pretreatments

No pretreatments are recommended for 

Chamaedorea fronds.

Storage Conditions

Because Chamaedorea is a tropical foliage, it 

is sensitive to chilling damage if stored at low 

temperatures for extended periods. Fronds may be 

stored for 1 to 2 weeks at 12.5 °C (55 °F) and high 

RH. 

Packing

Fronds are packed densely, usually without 

sleeves of paper, in standard horizontal fiberboard 

boxes. 

Special Considerations

Early death of the fronds, drying, and inrolling of 

individual leaves (pinnae) result from water stress. 

Make sure that stems are recut before arranging 

them as this can quadruple their life. The species 

is chill sensitive, so hold at proper temperatures. 
680

Eucalyptus, Silver Dollar Tree 

Scientific Name and Introduction

Eucalyptus spp. The silvery-green leaves of the 

juvenile form of Eucalyptus pulverulenta are a 

very popular foliage item, used in fresh and dried 

form. A number of other species of Eucalyptus

also are used as cut foliage. Eucalyptus is Greek 

for well and lid, referring to the sepals and petals, 

which are united to form a cap that is shed when 

the flower opens, revealing the showy, colored 

stamens. 

Quality Characteristics and Criteria

As with other foliage, eucalyptus performs better 

in the vase if leaves are mature. Branches are 

harvested to provide long stems but leave growing 

points behind for development of new branches. 

Stem tips should not be wilted when purchased. 

Grading and Bunching

Quality foliage is bright blue-green in color, has 

undamaged leaves, and is uniform in length. 

Eucalyptus branches are sold in grower bunches 

by weight, usually as 454 g (1 lb) bunches. 

Ethylene Sensitivity

Eucalyptus branches are not sensitive to ethylene, 

but if the foliage is poorly handled, warm, and 

water-stressed, it can produce concentrations of 

ethylene that could damage ethylene-sensitive 

flowers that have not been treated with 1-MCP or 

STS. 

Pretreatments

No pretreatments are required. 

Storage Conditions

Eucalyptus foliage should be stored at 0 to 1 °C 

(32 to 34 °F). 

Packing

Eucalyptus is normally packed in horizontal 

fiberboard boxes without additional packing 

materials. 

Special Considerations

Handle this species with gloves to prevent hands 

from becoming sticky. Eucalyptus is native 

to areas like Australia and Tasmania, but over 

200 species have been introduced elsewhere. 

As a result, this species predominates in certain 

woodlands in California. Many florists believe 

eucalyptus gives off a lot of ethylene because 

of its strong fragrance. In fact, most species 

and cultivars do not produce excessive amounts 

of ethylene gas, although some will produce 

potentially detrimental quantities of ethylene if 

they become water-stressed. Hence, make sure 

this species is properly hydrated. Eucalyptus 

can be treated with various colored glycerinbased solutions, which result in preserved 

specimens. Australian and Israeli researchers are 

investigating the possible use of eucalyptus as 

flowering branches, and we may expect to see 

this interesting item increasing in the trade in the 

future. 

Fir, Spruce, Pine 

Scientific Name and Introduction

Abies, Picea, and Pinus spp. Fir, spruce, and pine 

are all members of the pine family (Pinaceae). 

The 200+ species are noted for producing resins, 

lumber, and numerous ornamental landscape 

species. As foliage, mature branches are long 

lasting, provide a piney fragrance, and are often 

used in arrangements during the Christmas season. 
681

Quality Characteristics and Criteria

Branches should be harvested when tips and 

needles are mature. Soft green growth is more 

likely to wilt in the vase. Branches should be 

mature, with uniform dark green foliage. Avoid 

bunches with fungal growth or whose needles are 

falling off. 

Grading and Bunching

There are no grade standards for conifer branches 

and Christmas greens. Quality foliage is dark 

green and well hydrated and shows no abscission 

or fungal infection. 

Ethylene Sensitivity

Conifer branches are not usually affected by 

exposure to ethylene and contrary to what 

is commonly suggested, do not produce any 

ethylene. 

Pretreatments

No pretreatments are required for conifer 

branches. 

Storage Conditions

Store at 0 to 1 °C (32 to 34 °F). These foliages 

store very well when held around 0 °C (32 °F), 

wrapped in plastic to reduce water loss. Make 

sure the branches are cooled prior to wrapping in 

plastic to avoid condensation and rots. 

Packing

Because of the low value and relative hardiness 

of these materials they are usually packed loose 

in horizontal fiberboard boxes without any 

protection. 

Special Considerations

Antitranspirant dips have not been shown to 

reduce water stress or to extend user life. Despite 

their strong aroma, these foliage materials have 

not been demonstrated to produce ethylene. If they 

are infected by fungi, it is possible that they may 

produce ethylene, but otherwise they are safe to 

store with ethylene-sensitive flowers. 

Freesia 

Scientific Name and Introduction

Freesia × cvs. Native to South Africa, the single 

or double flowers range in color from yellow, 

orange, red, and bronze to purple. Some cultivars 

retain the delightful fragrances that are common 

in garden freesias. The genus was named for Dr. 

Freese (1785-1876), a native of Kiel, Germany, 

and a student of South African plants. 

Quality Characteristics and Criteria

Stems are harvested when the first flower 

colors and opens. Several flowering stems may 

be harvested from one plant. In that case, the 

uppermost flower stem should be cut just above 

the junction of the desired lateral flowering stem. 

When the lateral stem reaches maturity, it too is 

harvested. The upper flowering stem will have 

more flowers per stem and better postharvest life 

than lateral flowering stems. One or two florets 

per stem should be just beginning to open at the 

time of harvest and hence, at the time of purchase. 

If harvested too tight, many florets may not open 

unless preservative solutions are used properly. 

Learn cultivar names and market those that have 

good postharvest characteristics. 

Grading and Bunching

There are no standard grades for freesias, but they 

may be graded according to maturity, number of 

flowers per stem, and the length of stem. Quality 

freesias have at least seven florets per spike and 
682

have long, straight stems. Flowers are sold in 

bunches of 10 stems, usually of the same color. 

Ethylene Sensitivity

The open florets on freesia inflorescences are not 

affected by exposure to ethylene, but the effects 

of this gas are seen in young buds, which fail to 

develop. 

Pretreatments

A 1-MCP or STS pulse pretreatment is effective 

in preventing abortion of small buds on the 

inflorescence. Freesias can be pulsed for 18 h in 

the dark with a preservative solution containing 

25% sucrose. Pulsing should be carried out at 

about 20 °C (68 °F) with 85% RH. This treatment 

will increase flower size, percentage of flowers 

that open, and vase life (van Meeteren et al. 1995). 

Storage Conditions

Freesia should be stored at 0 to 1 °C (32 to 34 °F). 

Packing

Freesias are packed in horizontal boxes or upright 

hampers. 

Special Considerations

The species is ethylene sensitive, but it responds 

well to STS, which inhibits premature flower 

fading and the appearance of translucent petals. 

STS helps open more flowers per stem, and more 

open flowers absorb more STS, protecting against 

ethylene-induced disorders. Water stress can cause 

significant ethylene production and reduce life. 

Gerbera, Transvaal Daisy 

Scientific Name and Introduction

Gerbera jamesonii and hybrids. Cut gerbera 

flowers, known for their remarkable variety in 

coloration and form, are an increasingly important 

part of the florists’ palette. Their postharvest 

life can be substantial if they are given proper 

postharvest conditions, but they are sensitive to 

gravity, to light, and to bacterial contamination of 

the vase solution. Originally spelled “Gerberia,” 

the genus was named after Traug Gerber, a 

German naturalist. 

Quality Characteristics and Criteria

Most gerbera varieties should be harvested when 

the two outer rows of disk florets have begun to 

open; but some cultivars can be harvested later, 

particularly those types that close at night. Flowers 

are harvested by twisting the stems off near the 

point of attachment to the rhizome; this is thought 

to encourage subsequent flower production. 

If flower stems are pulled from the ground, 

immediately cut 10 cm (4 in) from the bottom to 

remove the “woody” base of the stem, which does 

not draw water readily. Place soon after harvest 

in a solution containing 40 μL L-1 hypochlorite. 

Make sure that at least one or two rows of disk 

flowers (tubular flowers in the center of the head) 

are showing pollen. With well over 300 cultivars 

in commerce that vary greatly in vase life (Wernett

et al. 1996), it is important that florists order 

gerberas by cultivar name. Unfortunately, the large 

number of cultivars makes it difficult to learn the 

names of better ones. 

Grading and Bunching

Maturity; freedom from defects; and stem length, 

strength, and straightness are important quality 

criteria for gerberas. Some producers bunch the 

flowers, but most pack them individually. Some 

producers place each flower into a firm plastic 

sleeve and may insert the stem into a plastic tube 

to reduce stem-bending. 
683

Ethylene Sensitivity

Gerberas are unaffected by exposure to ethylene. 

Pretreatments

Present industry practice is to place cut gerbera 

stems in a 40 μL L-1 sodium hypochlorite solution 

immediately after harvest to improve vase life. 

A rapid pulse treatment with 100 μL L-1 silver 

nitrate is sufficient to greatly alleviate postharvest 

problems with gerbera cultivars that are relatively 

short-lived. The silver nitrate presumably guards 

against bacterial contamination of the stem and 

vase water. After the dip, rinse the flowers in 

good-quality water. This treatment causes only 

minimum phytotoxicity (brown damage to the 

stem). The use of 6% sugar plus 200 μL L-1

8-HQC as a preservative has shown to be of some 

benefit but can cause stem elongation during 

storage and may reduce overall flower quality. 

Storage Conditions

Gerberas should be stored at 0 to 1 °C (32 to 

34 °F); the widely-held opinion that gerberas 

are sensitive to chilling injury has not been 

scientifically substantiated. Generally, gerberas 

should not be stored longer than 1 week; even this 

short storage period can reduce subsequent vase 

life. 

Packing

Most commonly, producers pack individual 

flowers horizontally in shallow cardboard 

containers especially designed to support gerberas. 

Flower stems are passed through slits in the 

bottom of a cardboard tray so that the flower heads 

face up showing their colors while the stems pass 

under the box. Several rows of flowers can be 

arranged in each box. The boxes are then hung so 

that the stems dangle downward and can be placed 

in a rehydration solution (hypochlorite is most 

commonly used). Afterward, two trays of flowers 

are packed horizontally into a fiberboard box in 

such a way that the flowers are facing upward and 

easily seen while the stems are underneath the 

flower cards. 

Special Considerations

Stem bending is primarily in response to gravity 

and is greatly reduced if flowers are held at the 

proper storage temperature. One of the major 

problems in postharvest handling of these flowers 

is their tendency to “conk”: the stem folds 10 to 

15 cm (4 to 6 in) below the flower head, resulting 

in an unmarketable flower. This bending has been 

variously attributed to harvesting of the flower 

before the stem has hardened sufficiently and to 

microbial plugging of the stem and subsequent 

water stress. The tendency to conk varies with 

variety and also varies throughout the year for any 

given variety. Be sure to enhance water uptake 

by keeping holding solutions and buckets clean 

and including hypochlorite in the water. Since 

more water is lost through the flower stem (scape) 

than through the flower petals, the scapes should 

be handled with as much care as the flowers 

themselves. Hang flower heads through a meshed 

support or shipping tray when first hydrating to 

keep stems straight. 

Ginger, Shell Ginger, Torch Ginger 

Scientific Name and Introduction

Alpinia zerumbet, A. purpurata. The ginger 

flowers represent a range of species and genera 

from the tropics that include the plants producing 

the edible ginger rhizome. One of the common 

lei flowers used in Hawaii is white ginger. Torch 

ginger flowers are spectacular spikes of red 

flowers that give an especially tropical effect in 

arrangements. The genus is named after the Italian 

botanist Prosper Alpinus. 
684

Quality Characteristics and Criteria

No specific maturity standards have been 

developed for these flowers. They are normally 

harvested when all of the flowers on the spike 

are open. Make sure flowers do not exhibit chill 

damage symptoms such as off-colored (grayish/

bluish) blooms. 

Grading and Bunching

There are no specific grade standards for gingers. 

Proper maturity and freedom from flower and 

foliage defects would be important indicators of 

quality. Gingers are large flowers and are therefore 

normally packed individually. Some species may 

be individually sleeved to protect the delicate 

petals. 

Ethylene Sensitivity

These flowers do not appear to be particularly 

sensitive to ethylene. 

Pretreatments

There is no evidence that pretreatments provide 

any benefit to ginger flowers. 

Storage Conditions

Store at 12.5 to 15 °C (55 to 59 °F). Gingers are 

chilling sensitive, so they must be held at warmer 

temperatures. 

Packing

Gingers are packed flat in standard or insulated 

fiberboard boxes. 

Special Considerations

Their large size makes gingers difficult to manage. 

Since insects sometimes make the trip from 

grower to wholesaler to retailer, make sure flowers 

are inspected and any insects removed. 

Gladiolus, Glad 

Scientific Name and Introduction

Gladiolus cvs., hybrids. Still an important 

commercial cut flower despite a substantial 

decline in production in recent years, gladiolus 

responds well to proper postharvest management. 

The smaller flowered and “butterfly” cultivars, as 

well as modern standards in a variety of colors 

and forms, have helped transform this often 

stereotypic funeral flower into a contemporary 

favorite that can be an important accent flower 

in arrangements. Gladiolus is Latin for “small 

sword,” in reference to the sword-shaped 

leaves. Modern day gladioli are the results of 

hybridization programs that commenced in 

Belgium around 1841 using South African species. 

Quality Characteristics and Criteria

Normal harvest is at the stage when the bottom 

two or three florets on the spike are showing 

color. For long-distance transportation, an even 

earlier harvest stage can be recommended if it 

is combined with sugar pulsing to ensure proper 

opening of the flowers at their destination. Local 

market flowers are cut when the first floret is 

open. Harvesting is carried out so as to leave as 

many leaves on the plant as possible. A knife is 

run down between the leaves with the back of 

the knife down. When the knife blade is as low 

as the cutter believes it should go, it is pulled 

upward and out, severing the stem, which can 

then be pulled out of the leaves. It is possible to 

open almost all florets on flower spikes if they 

are harvested in the green bud stage and handled 

properly. However, it is recommended that 

color be visible in one to three florets at time of 

purchase to help ensure that most florets will open. 
685

Grading and Bunching

Gladioli, like most spike-type flowers, are 

very sensitive to gravity and will always tend 

to grow away from the ground, particularly at 

warm temperatures. This can result in permanent 

deformation of the upper part of the spike and 

consequent reduction of flower quality. To avoid 

deformation, gladioli should be held upright 

throughout postharvest procedures. This rule may 

be relaxed only while the flowers are held at low 

temperature during storage and transportation. 

Quality factors for gladiolus include stem 

straightness and strength, freedom from damage 

and disease, and maturity. The flowers are 

bunched by color and maturity in groups of 10. 

Ethylene Sensitivity

Although exposure to ethylene does not affect the 

life of open florets, it can reduce the flower life by 

causing abortion of unopened buds (Serek et al. 

1995). 

Pretreatments

Gladioli respond very well to pulsing with a 

preservative containing 20% sugar (sucrose or 

glucose). Pulse overnight at room temperature 

or in the cooler. The flowers can be pulsed in the 

dark. Treatment with 1-MCP or STS provides 

some protection against the effects of exposure to 

ethylene, which causes young buds to abort. 

Storage Conditions

Although earlier recommendations were to store 

gladiolus at 5 °C (41 °F) to prevent chill damage 

to tips, we now know they can safely be stored 

for a week at 0 to 1 °C (32 to 34 °F). Flowers are 

negatively geotropic (they bend away from the 

force of gravity), so they are commonly stored 

and shipped upright. One beneficial aspect of 

low temperature handling and transportation is 

that this negative geotropic response is inhibited, 

allowing gladioli to be packed in the standard 

horizontal flower box. For longer storage, gladioli 

are best stored upright at the lowest safe storage 

temperature. 

Packing

Gladioli are traditionally packed in tall “glad 

hampers” clearly marked for upright stacking. 

Since the advent of precooling, some shippers 

have packed gladioli in normal flower boxes. 

This practice is fairly safe if the flowers will 

remain refrigerated throughout the marketing 

chain and will be removed from the box on 

arrival. Excessive moisture on the foliage should 

be avoided so as to minimize the risk of Botrytis

infection. 

Special Considerations

Some cultivars are sensitive to fluoride, which 

can result in deterioration of the petal margin 

(bleaching, water soaking, then necrosis), failure 

of florets to open and develop normally, burning 

of the floret sheath, and marginal leaf scorch. 

Heliconia, Parrot Flower 

Scientific Name and Introduction

Heliconia humilis, H. psittacorum. The varied 

and fantastic forms and rich colors of the different 

species of Heliconia make them an important 

florist item, particularly prized for large and 

signature arrangements. Heliconia is named 

after Mount Helicon, the seat of the Muses, 

the nine goddesses of the arts and sciences in 

Greek mythology. Like their god Apollo, the 

Muses supposedly remained young and beautiful 

forever like the long-lasting and elegant flowers 

of heliconia. Lobster claw and crab’s claw are 

additional common names for flowers in this 

genus. 
686

Quality Characteristics and Criteria

Heliconia are normally harvested fully mature: 

The flowers will not open past the stage at which 

they are harvested. While flowers last longer if 

the bracts are less open compared to more open, 

they generally do not open further after harvest 

and that may reduce their visual appeal. Therefore, 

the openness of the flower at purchase often is 

the most it ever will open. Consumer life varies 

greatly among species and cultivars; thus, learn 

species and cultivar differences. 

Grading and Bunching

Quality flowers of heliconia are fully mature, 

free of defects (damage or discoloration) on the 

flowers, and have good quality foliage (when 

present). Both the smaller, hanging species 

and the larger, more upright species are packed 

individually by stem. 

Ethylene Sensitivity

There is no evidence of any deleterious effects of 

ethylene exposure on the vase life of heliconias. 

Pretreatments

No pretreatments have proved beneficial for 

heliconias. Some species may benefit from the 

flowers being dipped in an antitranspirant, such 

as those sold in garden centers for use on woody 

plants. However, no antitranspirant product is 

presently sold for this use. 

Storage Conditions

Heliconias are native to the tropical Americas, and 

they are therefore very sensitive to chilling injury. 

They should never be held at temperatures below 

10 to 12.5 °C (50 to 55 °F). Flowers may be stored 

in moist shredded newsprint or in water at 12.5 °C 

(55 °F). 

Packing

Heliconias are normally packed in horizontal 

fiberboard boxes. 

Special Considerations

Heliconias most often die early due to poor water 

uptake. They can last for up to 2 weeks in plain 

tap water if the water is free of microorganisms. 

Larger diameter and longer stemmed specimens 

last longer. Since insects sometimes make the trip 

from grower to retailer, make sure flowers are 

inspected and any insects removed. 

Holly, Ilex 

Scientific Name and Introduction

Ilex spp. Evergreen shrubs, hedges and small trees 

prized for their holiday-season dark green leaves 

and bright red fruits. The plants carry female and 

male flowers on separate trees, and are therefore 

termed “dioecious.” Only female plants are 

harvested for specimens possessing fruit.

Quality Characteristics and Criteria

Holly is harvested when the fruits are already 

fully red. Avoid purchasing holly in packages 

if condensation is visible. This indicates poor 

temperature management and possible fungal 

growth and ethylene production. Also, avoid 

specimens showing berry or leaf fall. 

Grading and Bunching

Quality holly branches have uniform dark green 

leaves, are free of blemishes, and have bright red 

berries. They are seldom gathered into bunches 

but may be grouped and placed in polyethylene 

bags. 
687

Ethylene Sensitivity

Exposure to ethylene results in loss of berries and 

leaves and is a common problem in holly handled 

through mass-market outlets. 

Pretreatments

Because of its ethylene sensitivity, holly should 

be pretreated with STS or 1-MCP, which prevents 

bud and leaf loss during marketing (Joyce et al. 

1990). 

Storage Conditions

Holly should be stored at 0 to 1 °C (32 to 34 °F) 

and may even be held for longer periods at lower 

but nonfreezing temperatures. 

Packing

Holly may be packed in hampers or horizontal 

boxes. In the past, the branches were treated with 

various solutions (containing naphthalene acetic 

acid, NAA) to reduce their sensitivity to ethylene 

and were therefore sometimes packed (wet) in 

wax-treated cartons. The use of 1-MCP should 

greatly simplify the marketing of this product. 

Special Considerations

There are major differences among holly types 

in their sensitivity to ethylene. For example, 

‘Burford’ is essentially insensitive to ethylene, 

while Chinese and English types are very 

sensitive. Therefore, know the type of holly being 

marketed. Some producers will dip holly into 

various solutions in an attempt to reduce fruit 

and leaf fall or to package the product in such a 

way as to extend life. However, at wholesale or 

retail levels there is not presently a product to 

retard fruit loss other than STS. Treating with STS 

does reduce fruit and leaf fall. Do not pregreen 

arrangements with holly, as it will not last. 

Huckleberry 

Scientific Name and Introduction

Vaccinium ovatum. Huckleberry is native to the 

West Coast in areas from northern California 

to British Columbia. Vaccinium is the ancient 

Latin name for blueberry, and the specific epithet 

ovatum refers to the oval leaf shape of this species. 

Quality Characteristics and Criteria

Harvest branches when fully mature, without soft 

tips. This species is very long lasting with few 

postharvest problems. Thus, if it is of good quality 

at the time of purchase, it should perform well. 

Grading and Bunching

N/A.

Ethylene Sensitivity

Huckelberry is not sensitive to ethylene. 

Pretreatments

No pretreatments are required for huckleberry. 

Storage Conditions

Huckleberry can be stored for an extended period 

by enclosing precooled bunches in a plastic vapor 

barrier and holding them near 0 °C (32 °F). 

Special Considerations

Watch for excessive storage as depicted by 

fungal growth (fuzziness) and watersoaked or 

discolored leaves. The woody stems sometimes 

make huckleberry difficult to recut. Recutting this 

species is less critical than for other floral crops. 
688

Iris, Fleur-de-Lis

Scientific Name and Introduction

Iris cvs., hybrids. Because of their intense yellow, 

blue, and purple colors, and the elegant shape 

of their flowers and foliage, bulbous (Dutch) 

iris are in considerable demand as cut flowers. 

Unfortunately, they are also one of the shortestlived of the commercial cut flowers, and may 

not open if handled improperly or held too long 

before sale. In recent years, other iris species; for 

example the “flag” or German iris, which have 

even shorter vase life, have been used in the trade. 

Iris is Greek for “rainbow” in reference to the 

range of flower colors. 

Quality Characteristics and Criteria

Iris grown at low temperature should be 

harvested more open than those grown in warmer 

conditions. Iris flowers are normally harvested at 

the “pencil stage.” This term describes flowers that 

exhibit a line of color vertically, as the sheathing 

leaves covering them unfurls, but before the 

flower petals reflex. The ‘Blue Ribbon’ cultivar 

should be harvested more mature, when the edge 

of one petal is unfurled. Iris are pulled from the 

field at the correct stage of maturity. The bulb is 

cut off and the lower foliage removed. The flower 

stems are then placed in water. Wholesale and 

retail florists should purchase iris in the pencil 

stage. A major exception is the cultivar ‘Blue 

Ribbon,’ which should be more open at the time of 

purchase. 

Grading and Bunching

There are no formal grade standards for iris 

flowers. Flowers should be uniform in variety, 

color, and maturity. Foliage should be relatively 

undamaged and free from disease. Stems should 

be strong and straight. Flowers are normally 

bunched in groups of 10 and tied with rubber 

bands or twist-ties. 

Ethylene Sensitivity

Iris are not affected by exposure to ethylene. 

Pretreatments

There are no recommended pretreatments for iris 

flowers. 

Storage Conditions

Store iris dry, upright, at 0 °C (32 °F) for no more 

than 1 week. Some growers store iris with the 

bulb attached. Prolonged storage may result in 

failure of flowers to open (especially the ‘Blue 

Ribbon’ cultivar). Storage at warmer temperatures 

will result in “popping” of the flower when it is 

rehydrated. 

Packing

Iris are normally packed in upright hampers. 

Special Considerations

Some increase in vase life has been realized by 

including a high concentration of benzyladenine 

in the vase solution, and pretreatments with 

gibberellins have been shown to overcome the 

negative effects of dry storage (Celikel and van 

Doorn 1995).

Leatherleaf Fern

Scientific Name and Introduction

Rumohra adiantiformis. By far the most popular 

cut foliage for use in arrangements, with 

year-round availability and good display life, 

leatherleaf fern is grown in shade-houses under 

subtropical conditions. The specific epithet 

adiantiformis indicates the similarity to the fronds 

of Adiantum, the maidenhair fern. The Greek 
689

adianton means unwettable—a reference to the 

fact that fern fronds shed water. It is probably the 

most commonly used floral green. 

Quality Characteristics and Criteria

Avoid wilted or yellow fronds. 

Grading and Bunching

None.

Ethylene Sensitivity

None.

Pretreatments

None.

Storage Conditions

1 to 6 °C (34 to 42.8 °F)

Packing

N/A

Special Considerations

Frond curl or postharvest wilt is a disorder that 

occurs more frequently from July to November. 

The precise cause of this disorder is not known, 

and it cannot be prevented at grower, wholesale, 

or retail levels. Water stress can make the frond 

curl worse; however, leatherleaf is very tolerant 

to water stress conditions when frond curl is 

not a problem. The use of some postharvest 

antitranspirant (wax-type) dips can enhance 

vase life but does not reduce frond curl. Dipping 

leatherleaf in plain tap water can reduce vase life. 

The brown bumps (sori or fruit-dots) found on 

the back of some fronds have not been reported to 

reduce life. 

Lemonleaf, Salal 

Scientific Name and Introduction

Gaultheria shallon. A hardy, long-lived cut 

foliage, salal was named for Jean-François 

Gaultier, a naturalist and physician from Quebec, 

Canada, about 1750.

Quality Characteristics and Criteria

Branches should be harvested when the leaves are 

mature, without tender young growth at the tips. 

Salal is very long-lasting and has few postharvest 

problems. If foliage is of good quality at time 

of purchase, it should provide satisfaction in the 

vase. 

Grading and Bunching

Quality foliage has uniform mature green leaves 

with no damage, defects, or disease. Salal is 

usually sold 20 stems per bunch. 

Ethylene Sensitivity

Salal is not affected by exposure to ethylene. 

Pretreatments

Salal does not require any pretreatments to 

perform satisfactorily in the vase. 

Storage Conditions

Salal should be stored at -0.5 to 1 °C (31 to 34 °F). 

Once harvested, bunched and cooled, lemonleaf 

is normally stored at or slightly below freezing in 
690

large bins lined with plastic to reduce water loss. 

Packing

Salal is normally packed in horizontal fiberboard 

boxes. 

Special Considerations

Even though the stems are woody, salal is adapted 

to standard florists’ procedures for rehydration and 

use in arrangements. 

Liatris, Gay Feather

Scientific Name and Introduction

Liatris pycnostachya, L. spicata. Native to prairies 

of North America, liatris was developed as a cut 

flower in Israel. The bright purple spikes provide 

interesting texture and line in arrangements, and 

can open fully if properly treated after harvest. 

Members of the Asteraceae (chrysanthemum or 

aster family), these species are also unusual in that 

flowers open from the top of the stem downwards; 

delphinium, gladiolus, snapdragon, and most 

other spiked-type flowers open from the bottom 

up. L. spicata is the taller of the two species. The 

specific epithet pycnostachya means thick-spiked 

in reference to flowers, while spicata means spike.

Quality Characteristics and Criteria

Liatris spikes should be harvested with no more 

than 25% to 33% of the flowers in the spike open. 

They may be harvested with only the top buds 

showing color and will open fully if provided with 

an effective preservative. However, if preservative 

solution is properly used, flowers can be harvested 

with no color showing and subsequently opened. 

Grading and Bunching

Quality liatris flowers are of proper maturity (no 

more than one-third of the flowers on the spike 

open), are free from defects and damage, and have 

good quality foliage. They are normally bunched 

in groups of 10 and sometimes sleeved. 

Ethylene Sensitivity

Liatris flowers are not affected by exposure to 

ethylene. 

Pretreatments

Pulsing with preservative containing additional 

sugar (10 to 20%; about 100 g of sugar per quart 

or liter of water) will improve opening of tight-cut 

flowers (Han 1992). 

Storage Conditions

Store liatris at 0 to 1 °C (32 to 34 °F). 

Packing

Liatris are normally packed in horizontal 

fiberboard boxes but may also be packed in 

hampers. 

Special Considerations

Be careful of fungal problems such as Botrytis

(especially for flowers grown outdoors) as well 

as water stress. Leaf yellowing and reduced life 

are common when these problems exist and are 

not easily controlled. Using preservative solution 

helps open more flowers per stem but doesn’t 

make individual flowers last longer. 
691

Lily of the Nile, Agapanthus

Scientific Name and Introduction 

Agapanthus africanus. The globose heads of 

agapanthus are a pleasing accent for spring 

and early summer arrangements, providing an 

alternative source of blue. The most common 

flower color is blue, but white cultivars are 

also available. Miniature, dark blue (‘Storm 

Cloud’), and reduced-shatter cultivars have been 

developed. Agapanthus is Greek for “love flower.”

Quality Characteristics and Criteria

Agapanthus flowers are normally harvested when 

the bud bract has fallen off and no more than three 

florets are open. Stalks are cut near their base with 

a sharp knife. Ensure that flowers are of proper 

maturity. If the neck of flowers is bent upward, 

they have been transported at warm temperatures 

and have responded to gravity. 

Grading and Bunching

No formal grade standards have been established. 

Agapanthus flowers are bunched in groups of 5 or 

10 stems. 

Ethylene Sensitivity

Ethylene exposure results in loss of florets from 

agapanthus. 

Pretreatments

The vase life of freshly cut agapanthus flowers 

was shown to be significantly extended by 

pretreatment with a 3 h pulse in 4 mM STS, 

followed by spraying (to runoff) with 30 μL L-1

NAA, followed by a 48 h pulse in a solution 

containing 10% sucrose, 300 μL L-1 citric acid, 

and 300 μL L-1 Physan-20 (Mor et al. 1984). 

This pretreatment is not sufficient to counteract 

the decrease in vase life due to even short-term 

storage and is of no apparent benefit to flowers 

harvested immature. 

Storage Conditions

Store at 0 to 1 °C (32 to 34 °F). Even when 

pretreated to prevent flower abscission, 

agapanthus flower stalks stored dry at 1 °C (34 

°F) suffer significant decrease in vase life after 

only 4 days and are frequently unable to achieve a 

minimally acceptable number of open florets. 

Packing

Agapanthus flowers are normally packed in 

horizontal fiberboard boxes. 

Special Considerations

Premature flower fall is caused mainly by 

ethylene, especially for immature flower buds. 

The common blue cultivar ‘Mooreanus’ is much 

less prone to premature flower fall than the white 

flowering ‘Aldidus.’ 

Lily, Asiatic Lily, Oriental Lily 

Scientific Name and Introduction 

Lilium spp. Lilies have long been popular as 

garden flowers, prized for their stately beauty; 

and potted white lilies are a tradition in countries 

that celebrate Easter or Christmas. The brightly 

colored flowers of hybrid lily cultivars have 

become increasingly popular as cut flowers and 

have excellent vase life, especially if pretreated 

to prevent effects of ethylene. Buds open well if 

provided with preservative. “Lilium” is from the 

Greek word lirion, used in the naming of certain 

subdivisions of the genus. 
692

Quality Characteristics and Criteria

Lilies are normally cut when one or two buds 

are just beginning to “crack.” Tight-bud-stage 

flowers take some time to open, and petals of open 

flowers are likely to be damaged during transport. 

Most species and cultivars should be purchased 

with color showing on at least one flower. Avoid 

bunches with a number of open flowers, since they 

probably have been held at warmer temperatures 

during marketing. 

Grading and Bunching

Although there are no grade standards for 

lilies, the number of buds per stem, the stage of 

maturity, and the color and quality of the foliage 

are all important quality parameters. Flowers are 

normally bunched in groups of 5 or 10. 

Ethylene Sensitivity

Exposure of lilies to ethylene results in petal 

abscission, leaf yellowing, and abortion of young 

buds.

Pretreatments

After harvest, lilies should be treated with STS 

or 1-MCP to extend their vase life. Pulsing with a 

preservative solution containing 10% sucrose can 

improve subsequent bud opening, and it is also 

possible to reduce postharvest leaf yellowing in 

susceptible cultivars by pretreating them overnight 

with 2,000 μL L-1 GA3. 

Storage Conditions

Lilies should be stored at 0 to 1 °C (32 to 34 °F). 

If flowers are to be stored for any length of time, 

they should be treated prior to storage with STS 

or 1-MCP and an appropriate fungicide, the latter 

to protect against Botrytis. Lilies can be stored 

for up to 4 weeks if they are pulsed for 24 h with 

1.6 mM STS plus 10% sucrose and then stored 

dry at 1 °C (34 °F). Flowers should be properly 

precooled, and they must be packaged so that 

water loss during storage is minimized (wrap 

precooled flowers in polyethylene film). However, 

some problems with leaf browning or yellowing 

can occur even after 2 weeks storage. 

Packing

Lilies are normally packed in horizontal fiberboard 

boxes. 

Special Considerations

Proper cultivar selection (van der MeulenMuisers et al. 1997) and the use of antiyellowing 

postharvest chemical treatments (available 

commercially in some markets) can diminish 

leaf yellowing. STS or 1-MCP only reduce leaf 

yellowing caused by exposure to ethylene. Lily 

pollen can stain almost anything; removing 

stamens containing the pollen does not affect 

flower life. Some new cultivars do not shed 

pollen. 

Lisianthus, Prairie Gentian 

Scientific Name and Introduction

Eustoma grandiflora. Introduced into cultivation 

from Texas, production of lisianthus has increased 

dramatically, spurred by development, mostly in 

Japan, of excellent cultivars with a wide range of 

colors and single and double forms.

Quality Characteristics and Criteria

Stems are harvested when at least one flower is 

open. Although requiring extra labor, removal of 

immature shoots, whose buds will not develop, 

improves display quality. Choose stems with at 

least one open flower and several large buds. 
693

Grading and Bunching

There are no grade standards for lisianthus, but 

obvious leaf miners and damage to the flower 

are quality defects. Bunches consist of 10 flower 

stems. 

Ethylene Sensitivity

Lisianthus is slightly sensitive to ethylene. 

Exposure of mature flowers to ethylene will 

decrease their ultimate vase life, but the effect is 

relatively slight and does not warrant treatment 

with 1-MCP or STS. 

Pretreatments

Lisianthus flowers benefit from sugar in the vase 

solution and can respond to pretreatment for 24 

h with a preservative containing 5 to 10% sugar 

(Halevy and Kofranek 1984). 

Storage Conditions

Lisianthus should be stored at 0 to 1 °C (32 to 34 

°F). 

Packing

Lisianthus flowers are sensitive to gravity, and 

their stems will bend upwards if the flowers are 

held horizontal at ambient temperatures. For this 

reason, lisianthus flowers that will be transported 

at warmer temperatures are often packed and 

transported in vertical hampers. 

Special Considerations

Lisianthus is sensitive to some of the biocides 

in preservatives, which may cause browning of 

the stems. Aluminum sulfate (200 μL L-1) and 

hypochlorite (50 μL L-1) are excellent bactericides 

to use with lisianthus. 

Marguerite Daisy, Boston Daisy 

Scientific Name and Introduction

Argyranthemum frutescens. The white or yellow 

flowers of Margeurite daisies are produced yearround outdoors in frost-free areas of California. 

Borne on a perennial bush, flowers have long been 

an inexpensive staple for florists, often dip-dyed 

to provide different colors for special holiday 

occasions. Their postharvest life is relatively long 

but often limited by wilting or yellowing of the 

foliage. The specific epithet frutescens means 

bushy. 

Quality Characteristics and Criteria

Flowers are considered to be of proper maturity 

from the time elongating petals are beginning 

to reflex back from the vertical position until 

the elongated petals are fully open and the outer 

ring of stamens (“fuzz”) is showing. Marguerites 

are harvested with shears, and harvesting is an 

important part of management of the bushlike 

plants. Flowers are often bunched in the field. 

The practice of laying finished bunches on the 

ground after harvest should be discouraged, as it 

may lead to rotting of flowers and foliage. Quality 

Marguerites have strong stems, healthy dark green 

foliage, and several flowers and buds on each 

stem. Purchase when at least two to three flowers 

per stem are fully open with no yellow foliage 

present. 

Grading and Bunching

Marguerites are usually bunched in the field, and 

the bunch will contain flowers of varying maturity 

and size. The cost of grading flowers in a packing 

shed precludes this practice in such a low-return 

crop. Each bunch has 20 stems, or sometimes 

10 stems when sold to supermarkets. Quality 

marguerites have strong stems, healthy dark green 

foliage, and several flowers and buds on each 

stem. 
694

Ethylene Sensitivity

Margeurite daisies, like other members of the 

Asteraceae, are not affected by exposure to 

moderate concentrations of ethylene. 

Pretreatments

Research has shown improved performance with 

flowers that are pulsed overnight at 20 °C (68 °F) 

with 25 μL L-1 silver nitrate and 0.5% sucrose 

before storage or transport. Sucrose concentrations 

above 0.5% can accelerate leaf yellowing and 

cause leaf injury. 

Storage Conditions

Margeurites may be stored at 0 to 1 °C (32 to 34 

°F) for 3 days in water or more than 1 week if dry. 

If flowers are well cooled, dry storage can be in 

standard daisy hampers. 

Packing

Marguerites are normally packed in special “daisy 

hampers.” Flowers are jammed tightly together 

to increase the number in each package. With 

present cooling systems, it is almost impossible to 

cool flowers packed in this way. Poor postharvest 

temperature management may explain the 

development of yellow foliage and foliar disease 

in marguerites. 

Special Considerations

Water in which Margeurites are held often 

develops a bad odor. Keep solutions fresh and 

buckets clean. Remove dirt and debris from stems 

prior to cutting them. Preservative solutions 

offer varying degrees of benefit depending on 

brand. Avoid preservative solutions containing 

8-hydroxyquinoline citrate or sulfate (generally 

ones that turn the water slightly yellow). 

Lower foliage often turns yellow, which can be 

accelerated by improper storage or precooling 

and excessive or ineffective preservative solution. 

White flowers often are submerged in dye to get 

pink, green, red, or blue colors. 

Orchids 

Scientific Name and Introduction

Cattleya, Cymbidium cvs., and hybrids. 

Additional genera in the plant family Orchidaceae 

are Dendrobium, Phalaenopsis, Vanda, and 

Paphiopedilum. In addition to their exotic forms 

and colors, one of the principal attractions of 

cut orchid flowers is their outstanding longevity. 

Even out of water, an orchid flower will last for an 

evening in a corsage. Spikes of cymbidiums will 

often last a month in a vase. 

Quality Characteristics and Criteria

Orchid flowers are usually harvested 3 to 4 days 

after opening because flowers cut prematurely 

will fail to develop normally off the plant. Early 

and late in the season, individual flowers are cut 

from the spike as they develop because prices 

are high at these times. In mid season, the whole 

spike is cut. Virus diseases can be spread from 

plant to plant during harvest, so cutting tools 

should be sterilized before being used on the next 

plant, or disposable razor blades should be used. 

As individual flowers, purchase when fully open. 

Spikes should be purchased when at least two 

flowers per spike are open. 

Grading and Bunching

There are no grade standards for orchids. Freedom 

from defects is a primary measure of quality. 

Ethylene Sensitivity

Some genera such, as Cymbidium and 

Phalaenopsis, are very sensitive to ethylene; 

others, such as Dendrobium, are less sensitive. 
695

Pretreatments

Pretreatment with 1-MCP is very effective in 

preventing the effects of ethylene (Heyes and 

Johnston 1998) and increasing the life of orchid 

flowers and should be standard practice for these 

flowers. 

Storage Conditions

Temperature can range from 0 to 12.5 °C (32 

to 55 °F) depending on cultivar. Many cultivars 

are not chilling sensitive and therefore can be 

stored as other cut flowers at 0 to 1 °C (32 to 34 

°F). If feasible, leaving flowers on the plants at 

room temperature is a good storage procedure. 

Be careful not to remove or knock off the pollinia 

(anthers) as this causes an immediate surge 

in ethylene production, which in turn causes 

premature death. 

Packing

Because of their fragility and relatively high value, 

most orchids are packed as individual flowers or 

spikes, frequently in shredded paper to cushion 

and protect them from mechanical injury to the 

blooms. They are then packed 12 to 24 flowers 

in each carton. Box inserts hold individual water 

tubes stationary. Shredded wax paper is tucked 

around and between the flowers for additional 

protection. 

Special Considerations

Only some species and cultivars are ethylene 

sensitive, which explains why anti-ethylene 

treatments like STS and 1-MCP work only some 

of the time. The two most common ethyleneinduced symptoms are flower discoloration and 

premature wilting and flower fall. Demand has 

increased for this species prepared as a corsage 

and sold through mass market outlets at Easter and 

Mothers’ Day. When sold for corsages the use of 

water picks filled with fresh-flower solution (not 

plain tap water) is beneficial. 

Protea, Pincushion 

Scientific Name and Introduction

Proteaceae family. The family Proteaceae includes 

a diverse range of species of trees and shrubs in 

the genus Protea from southern Africa and of 

other genera from Australia whose branches and 

flowers are used for foliage and as cut flowers. 

The flowers are normally pollinated by birds and 

produce copious amounts of nectar, explaining 

the old Afrikaans name of “sugar bush.” The 

family name refers to the diversity of forms 

of the flowers. Additional genera are Banksia,

Leucospermum, and Leucodendron.

Quality Characteristics and Criteria

Foliage is cut when mature (no soft tips), and the 

flowers when at least the outer florets are fully 

expanded. Banksias may be harvested when at 

least half of the flowers on the cylindrical spike 

are open. Make sure leaves are not black. 

Grading and Bunching

Quality protea flowers and foliage are free 

of blemishes and have reasonably long, 

straight stems. Foliage such as ‘Safari Sunset’ 

leucodendron is bunched in groups of 10, 15, or 

25. Flowers are handled individually or in bunches 

of 5 or 10, depending on quality, size, and market 

demand. 

Ethylene Sensitivity

Neither foliage nor flowers of the proteas are 

affected by exposure to ethylene. 

Pretreatments

Species that are susceptible to leaf blackening may 

be pretreated by pulsing overnight at 20 to 25 °C 

(68 to 77 °F) with 5% sugar (sucrose or glucose) 

(Dai and Paull 1995). Higher concentrations may 

cause leaf blackening. 
696

Storage Conditions

Flowers and foliage from the Proteaceae should 

be stored at 0 to 1 °C (32 to 34 °F). Rapid 

precooling and maintenance of the proper storage 

temperature are important tools in preventing leaf 

blackening, a common postharvest problem in 

proteas. Care must be taken to ensure that there 

is no condensation or free water on leaves during 

storage as this greatly increases the incidence of 

blackening. 

Packing

Proteas are normally packed in horizontal 

fiberboard boxes. 

Special Considerations

Leaves turn black due to lack of carbohydrate 

(food) and warm temperatures. Use preservative 

solutions and proper low temperature management 

to prevent leaf blackening. In addition, this 

disorder can be reduced if the flowers are held 

under lighted conditions. Leaf blackening is not 

due to low temperature (chilling disorder), nor 

is it due to poor water relations. Many species 

and cultivars can be easily dried or preserved by 

just allowing them to dry under warm, low-RH 

conditions. 

Rose, Spray Rose, Sweetheart Rose 

Scientific Name and Introduction

Rosa cvs., hybrids. The rose undoubtedly remains 

the queen of the cut flowers. The historical 

association of this flower with romance and beauty 

ensures that roses will continue to be a highly 

desired cut flower in the future. Properly handled, 

most of the commercial cut roses will easily last 

in the vase for 10 days. Unfortunately, many 

consumers consider roses to have a very short 

vase life. This is partly because poor water uptake 

by certain cultivars of purchased roses all too 

often results in the symptom called “bent neck” 

in which the flower neck wilts and the bud fails 

to open. We also found that many commercial 

cultivars are quite sensitive to ethylene gas. The 

cut-flower industry has an important stake in 

overcoming the poor postharvest reputation of cut 

roses. All that is required is proper postharvest 

care for those cultivars susceptible to bent neck 

and appropriate pretreatment of those that are 

sensitive to ethylene, especially if they are to be 

sold in supermarkets or other ethylene-polluted 

areas.

Quality Characteristics and Criteria

Roses are harvested at different levels of maturity, 

depending on marketing and cultivar. For longdistance transport or storage, roses should usually 

be harvested with some of the sepals reflexed. 

Flowers harvested before the sepals reflex may fail 

to open or may be more susceptible to bent neck. 

Fast-opening roses, like some yellows and whites, 

should be harvested just before the sepals start to 

separate from the bud. The marketing life of roses 

harvested later will be reduced unless extra care is 

taken with their postharvest handling. 

Harvesting is most convenient using shears 

provided with auxiliary jaws to hold the bloom 

after harvest. The cut is normally made so as to 

leave two five-foliate leaves below the cut. When 

stem length is an important consideration, the cut 

may be made below. Roses should be purchased 

and sold by cultivar name. Avoid blooms that are 

already open; flowers should normally have some 

or all of their sepals (the green protective leaves at 

the base of the flower) folded back, but the petals 

should not have started unfolding. Brown spots or 

patches on the outer petals may be an indication of 

Botrytis infection. 

Grading and Bunching

Objective grading is based on stem length; 

subjective grading is based on flower maturity, 

stem straightness, stem caliper, and quality of 
697

flower and foliage. Defects on the outer “guard” 

petals are not normally a cause for down-grading, 

because these petals are removed by the retail 

florist. Leaves and thorns may be removed 

manually or mechanically if desired. This 

operation has little effect on vase life if flowers are 

placed in an effective preservative. The number 

of stems per bunch and bunch pattern (single 

layer, staggered two-layer) depend on market 

preferences. 

Ethylene Sensitivity

Some cultivars are ethylene sensitive. Treat 

with 1-MCP or STS if they are being distributed 

through the mass markets, especially if being 

shipped through distribution centers, and also treat 

to prevent the effects of the ethylene prior to dry 

storage. 

Pretreatments

Roses should be pretreated with 1-MCP or STS 

to prevent the effects of ethylene, especially if 

they will be sold through a supermarket. Sugarcontaining pretreatments are not particularly 

useful for roses. Rehydrate after cutting, 

storage, and on arrival at the retail outlet with a 

rehydration solution. Commercial rehydration 

solutions are effective, as is clean water containing 

50 μL L-1 hypochlorite, preferably below pH 5.0. 

This solution has proved safe and is inexpensive, 

so the buckets can be filled to the desired 20 to 30 

cm (8 to 12 in) depth (Reid et al. 1996). 

Storage Conditions

Roses should be stored dry at 0 to 1 °C (32 to 34 

°F). Roses intended for long-term storage should 

be packed in polyethylene-lined cartons and 

precooled. They may be held for up to 2 weeks in 

dry storage if the temperature is maintained close 

to the freezing point. 

Packing

Rose bunches are routinely sleeved in plastic, 

waxed paper, or soft corrugated card sleeves. The 

“spiral” bunch used by many off-shore producers 

increases the difficulty of precooling the flowers, 

as well as the opportunity for condensation 

collecting on the outer petals. Botrytis infection is 

a common result of the presence of free moisture 

on the petals of cut roses. 

Special Considerations

Removal of those leaves and thorns below the 

water line should not reduce vase life if stems are 

placed into a preservative solution. The fungus 

Botrytis represents a major problem for roses. 

Symptoms of Botrytis infection include brown 

blotches on petals and gray, fuzzy growth on 

leaves, stems, or flowers. Postharvest fungicide 

dips can be helpful—use only registered products 

according to label instructions. Petal blackening 

on some red cultivars is due to growing conditions 

and cannot be corrected at wholesale or retail 

levels. 

Snapdragon 

Scientific Name and Introduction

Antirrhinum majus cvs. The many pastel flower 

colors of the tall spikes of snapdragons allow 

florists and consumers innumerable design 

options. Snapdragons used to be considered very 

sensitive to ethylene, but the newer cultivars have 

been selected for ethylene resistance, and ethylene 

normally causes a problem only when present in 

moderate concentrations. Flower drop (shattering) 

occurs in 24 h if ethylene is present in air at 

≥0.5 μL L-1. Antirrhinum is Greek for “like” and 

“nose,” in reference to the flower shape. 
698

Quality Characteristics and Criteria

For local sales, snapdragons are typically 

harvested when flowers on the lower half to twothirds of the spike are open. A less mature stage 

is desirable for shipping and short-term storage. 

Purchase those cultivars that are less sensitive 

to ethylene. At least two to five florets per stem 

should be open. Avoid flowers with excessive stem 

bending and yellowing foliage, which indicate 

poor temperature management after harvest. 

Grading and Bunching

Snapdragons are bunched in groups of 10 by color. 

Flowers must have straight stems and healthy 

foliage. Foliage on the lower third of the stem 

should be removed.

Ethylene Sensitivity

Most snapdragon cultivars are sensitive to 

ethylene. Older flowers on a stem are more 

susceptible to ethylene than younger ones. 

However, some cultivars are naturally ethylene 

resistant and, therefore, respond little to treatment 

with 1-MCP or STS.

Pretreatments

Treatment with 1-MCP or pulsing with STS 

protects snapdragon flowers from ethyleneinduced shattering. Snapdragons also benefit 

from an overnight pulse at 20 °C (68 °F) with 

a preservative fortified with 7% sucrose. Upper 

flowers on spikes treated in this way open with 

better color than control flowers. Snapdragons are 

best stored with only a few flowers open, but this 

often results in poor development of the flowers 

on the spike and fading of color at the tip. Spikes 

cut with only one or two flowers open should 

be opened in a solution containing 300 μL L-1

8-hydroxyquinoline citrate (8-HQC) and 1.5% 

sucrose. This bud-opening solution can also be 

used as a vase solution. Addition of 25 μL L-1 of 

the growth regulator n-dimethylamino succinamic 

acid increases flower quality and also counteracts 

the excess spike length that sometimes results 

from placing snapdragons in 8-HQC and sucrose. 

Pulse treatments with naphthylpthalamic acid or 

calcium antagonists (Philosoph-Hadas et al. 1996) 

can reduce geotropic curvature that results from 

horizontal storage at warmer temperatures.

Storage Conditions

Snapdragons can be stored at 0 to 1 °C (32 

to 34 °F) for 7 to 10 days if they are wrapped 

in polyethylene film to retard moisture loss. 

Snapdragons have been satisfactorily stored for 

up to 3 weeks at -1 °C (30 °F). For long-term 

storage, bud-harvested flowers should be used. 

Bud-harvested flowers are ones in which the 

bottom two or three florets have colored petals 

emerging about one-quarter of an inch above 

the calyx. Snapdragons are relatively sensitive 

to ethylene gas. Flowers on harvested spikes 

assume a permanent upward bend, thus reducing 

quality, if held at warmer temperatures for even a 

short time in a nonvertical position. Snapdragons 

should always be stored and shipped upright 

in snapdragon hampers at low temperatures. 

Pretreatment with naphthyphthalamic acid can 

overcome this bending, but it is not registered for 

this purpose. 

Packing

Snapdragons are usually packed upright in 

hampers or proconas, which reduce the likelihood 

of geotropic bending. If flowers are properly 

precooled and transported at optimal temperature 

of 0 to 1 °C, (32 to 34 °F), they can be packed in a 

normal horizontal flower box. 

Special Considerations

Do not remove more leaves than necessary, as this 

can stimulate flower-fall. Do not use any home 

brews, such as antifreeze, as replacements for 
699

preservative solutions. The many pastel flower 

colors allow florists and consumers innumerable 

options. The flower can be made to snap shut after 

separating and releasing the two-lipped corolla 

(fused petals). When grown as a garden plant, 

treat the flowers as an annual, although many will 

respond as a perennial, depending on location and 

cultivar. 

Statice, German Statice

Scientific Name and Introduction

Limonium spp., Goniolimon. A traditional filler 

flower, the standard statice (Limonium sinuatum)

comes in a range of pastel colors and is widely 

used both fresh and dried. Other species of 

Limonium are sold in the trade as German, 

latifolia, sea foam, and caspia statice. Hybrid 

Limonium cultivars, grown from tissue culture, 

have become very popular in recent years. Their 

vase life is greatly improved by pretreatments to 

prevent the effects of ethylene and to improve bud 

opening. 

Quality Characteristics and Criteria

Standard statice is harvested fully open but before 

the true flowers (small white flowers within the 

brightly colored bracts) senesce. Hybrid statice 

cultivars should be harvested when the first flower 

on each spike is open. Avoid bunches where 

flowers have yellowing stems and leaves and 

bunches with obvious fungal growth or wilted 

flowers. Remove from shipping boxes and recool 

flowers immediately. Also remove stem ties and 

separate stems to improve air circulation and 

reduce the likelihood of Botrytis infection. 

Grading and Bunching

Quality statice is of the correct maturity and is 

free of defects and disease. Standard statice is 

normally bunched in groups of 25. Sleeves help 

prevent tangling of the delicate branchlets. 

Ethylene Sensitivity

Statice flowers are sensitive to ethylene, which 

causes accelerated wilting. In standard statice, 

this effect is not apparent since the “flowers” are 

papery bracts surrounding the true flowers. In 

hybrid statice cultivars, effective treatments to 

inhibit action of ethylene improve flower quality 

and vase life.

Pretreatments

Hybrid statice benefits enormously from 

pretreatment with STS or 1-MCP and pulse 

pretreatment with a solution containing 10% 

sugar and 200 μL L-1 Physan-20 for 12 h. Sucrose 

present in the preservative extends the life of 

individual florets and promotes flower opening, 

resulting in up to 3-fold increases in longevity of 

inflorescences (Burge et al. 1998). 

Storage Conditions

Store all statice at 0 to 1 °C (32 to 34 °F); when 

flowers are infected with Botrytis, even short-term 

storage can greatly reduce life. 

Packing

Statice is normally packed in horizontal fiberboard 

boxes. 

Special Considerations

Many statice species can be dried and used for 

years in permanent flower arrangements. Yet 

when used as a fresh flower, they may last only 

a few days before leaf yellowing (on statice 

only, not German statice) or Botrytis infestation 

occurs. Storing statice under lights can retard 

leaf yellowing, but this may be hard to do in 

commercial practice. 
700

Stock 

Scientific Name and Introduction

Matthiola incana. A very traditional field flower 

with spikes of aromatic flowers in a wide range 

of colors, stock continues to be a staple floristry 

item. Somewhat sensitive to ethylene and prone to 

bacterial contamination of the vase solution, stock 

flowers respond to proper postharvest care. The 

genus is named after Dr. Peter Andrew Matthioli, 

an Italian physician and botanist, 1500-1577. The 

specific epithet incana means hoary (hairy) in 

reference to the plant’s whitish fuzz or hair. 

Quality Characteristics and Criteria

Stock should be harvested with no fewer than 

six open florets on each spike. To increase stem 

length, growers may pull the plants from the 

ground and remove the roots later. Flowers 

harvested and sold with at least six flowers open 

per stem generally perform better than ones 

harvested and sold with fewer open flowers. Avoid 

spikes with bruised, brown, or infected florets or 

yellowed leaves. 

Grading and Bunching

Quality stock has long straight spikes of uniform 

unblemished flowers and free of defects. 

Ethylene Sensitivity

Exposure to ethylene results in water-soaking of 

the petals, accelerated senescence of the florets, 

and epinasty (downward curvature) of the leaves. 

Pretreatments

To prevent deleterious effects of ethylene, stock 

should be pretreated with 1-MCP or STS. 

Storage Conditions

Stock should be stored at 0 to 1 °C (32 to 33.8 °F). 

Packing

Stock are frequently packed in hampers or 

aquapacks but may also be packed in horizontal 

fiberboard boxes. 

Special Considerations

Water uptake can be reduced in flowers harvested 

with the roots. Use a preservative solution to 

keep the growth of microorganisms in check. 

As with baby’s-breath and Marguerite daisy, the 

vase and bucket solutions can develop a very 

unpleasant smell if the correct amount and type of 

preservative solution is not used and if buckets are 

not properly sanitized. 

Sunflower 

Scientific Name and Introduction

Helianthus annuus. Smaller cultivars of sunflower 

have become a very popular florist item, and 

a range of forms and colors are now widely 

available. “Helianthus” is derived from the Greek 

helios, the sun, and anthos, a flower. 

Quality Characteristics and Criteria

Sunflowers are normally harvested when the 

petals (the outer flowers or ligules) have unfolded 

and are at least vertical. For local market, flowers 

are harvested with ligules fully expanded and 

horizontal. No yellow, wilted leaves should be 

present. Storage life is often determined more 

by leaf yellowing or desiccation than by flower 

problems. 
701

Grading and Bunching

Quality sunflowers are of uniform maturity, are 

free from defects, and have straight stems and 

good quality foliage. Small-flowered cultivars 

may be bunched in groups of 10 or 12, and largeflowered types are normally packed individually. 

Ethylene Sensitivity

Prolonged exposure of sunflowers to low 

concentrations of ethylene results in abscission of 

ligules. 

Pretreatments

The tendency for sunflowers to wilt prematurely in 

the vase can be avoided by pretreating flowers for 

15 to 30 min with clean water containing 0.02% 

detergent (Jones et al. 1993). 

Storage Conditions

Sunflowers can safely be stored at 0 to 1 °C (32 to 

34 °F). 

Packing

Sunflowers are normally packed in standard 

horizontal flower boxes. 

Special Considerations

Sunflowers are also somewhat sensitive to gravity. 

If held horizontally at warmer temperatures, the 

flower heads will be permanently bent down; so it 

is important to maintain cool temperatures during 

transport and storage. 

Sweet Pea 

Scientific Name and Introduction

Lathyrus odoratus. Once important cut flowers, 

prized for their aroma and range of colors, sweet 

peas benefit substantially from anti-ethylene 

pretreatments. Combined with a sugar pulse, 

treatment with STS or 1-MCP enables these 

delicate flowers to be harvested at an earlier stage 

when the flowers are less susceptible to damage 

and can give as much as 1 week of display life. 

Quality Characteristics and Criteria

Sweet peas are traditionally harvested when the 

last bud on the stem is about half open. “Budstage” flowers are harvested when the petals on 

the first bud are colored and near full size but have 

not yet opened. Flowers are harvested by holding 

the stem between the thumb and forefinger near 

the base (supporting the vine with two fingers 

behind and one in front) and then pulling the 

flower backwards and upwards from the axil of 

the leaf. Sweet peas should have five flowers per 

stem, with only one flower open at the time of 

purchase. Avoid bunches with wilting flowers or 

from which buds or flowers have fallen. 

Grading and Bunching

There are no grade standards for sweet peas, but 

quality flowers have long, straight stems and at 

least five buds on each spike. Flowers can be 

bunched by color, or in mixed colors, in bunches 

of 10. 

Ethylene Sensitivity

Exposure to ethylene results in accelerated wilting 

of petals, abscission of flowers, and failure of 

developing buds to open. 
702

Pretreatments

Proper pretreatment greatly improves the vase 

life of sweet peas. Flowers should be treated with 

1-MCP or STS (Sexton et al. 1995), then placed in 

a preservative solution containing 4% sucrose at 

20 °C (68 °F) overnight. 

Storage Conditions

Sweet peas should be stored at 0 to 1 °C (32 to 

34 °F). Flowers that have been pretreated with 

1-MCP and sucrose will open well and have a 

satisfactory vase life after storage for up to 1 week 

at 1 °C (34 °F). 

Packing

Sweet peas are packed in horizontal boxes or 

hampers. 

Special Considerations

Cultivars vary in the intensity of their aroma, one 

of the characteristic and appealing features of 

sweet peas. 

Sweet William 

Scientific Name and Introduction

Dianthus barbatus. A close relative of the 

carnation, normally grown in the field, sweet 

william flowers are borne on a short-stemmed 

inflorescence. Colors range from white through 

intense red and purple and provide strong accents 

in an arrangement. The specific epithet barbatus

means bearded or barbed in reference to the 

beardlike growth emerging from the petals. 

Quality Characteristics and Criteria

Flowers in the sweet william inflorescence 

continue developing after harvest, and they should 

be harvested with the outer ring of flowers open. 

Flowers should have at least the outer whorl 

of florets open. Avoid flowers with withered or 

sleepy florets, as this indicates ethylene-induced 

problems. 

Grading and Bunching

Quality sweet william flowers are of uniform 

maturity, are free from damage and evidence of 

pests and diseases, and have reasonable stem 

length and good quality foliage. Flowers are sold 

in a grower’s bunch of at least 12 stems. 

Ethylene Sensitivity

Flowers are ethylene-sensitive. 

Pretreatments

Flowers should be pretreated with 1-MCP or STS 

to prevent effects of ethylene. 

Storage Conditions

Like carnation, flowers should be stored at 2 to 3 

°C (36 to 37 °F). 

Packing

Sweet william flowers are normally packed in 

horizontal fiberboard boxes. 

Special Considerations

As with many flowers grown in the field, fungal 

infections resulting from the wet foliage and 

flower conditions sometimes experienced at 

harvest can be a problem. Make sure flowers are 

rapidly unpacked and aerated to reduce possible 

disease spread. 
703

Tuberose 

Scientific Name and Introduction

Polianthes tuberosa. Spikes of ivory flowers 

much prized in the East for their fragrance 

and by western florists for accents and bridal 

bouquets, tuberose flowers bear as many as 50 

florets, in pairs, on a tall spike. The postharvest 

life of these flowers typically is limited by failure 

of developing buds to open, so that the life is 

determined by the life of the flowers that were 

open at harvest. Proper pretreatments can greatly 

extend the life of tuberose and should routinely be 

carried out with flowers intended for storage and 

transport. 

Quality Characteristics and Criteria

The flowers are normally harvested with two to 

four open blooms on the spike. Although earlier 

harvest provides a spike that is more resistant to 

transportation, the buds are unlikely to open after 

transport unless properly pretreated. Flowers for 

the local market may be harvested with more open 

flowers on the spike. It is unfortunately difficult 

to determine whether tuberose flowers have been 

effectively pretreated prior to purchase. Look for 

straight stems and unblemished blooms and work 

with suppliers to ensure that the flowers have been 

properly pretreated. 

Grading and Bunching

Tuberose are sold in bunches of 10 stems. 

Ethylene Sensitivity

Floret opening is reduced in spikes exposed to 

high concentrations of ethylene; but this effect is 

probably not normally of commercial significance, 

so 1-MCP or STS treatments are not warranted for 

tuberose. 

Pretreatments

Tuberose flowers should be pulsed for 24 h at 

20 to 25 °C (68 to 77 °F) with a preservative 

solution augmented with 20% sucrose (Naidu and 

Reid 1989). This pretreatment will significantly 

improve vase life and opening of buds on the 

flower spikes. Flowers to be pretreated in this 

way should preferably be harvested dry; graded, 

bunched, and recut; then placed immediately in 

the pulsing solution. 

Storage Conditions

The optimal temperature for cooling and storage 

of tuberose is 0 °C (32 °F), but after only short 

periods the buds on the spike fail to open. 

Pulse pretreatment with sucrose overcomes this 

problem, and after 6 days storage, flowers open as 

well as on freshly cut spikes. 

Packing

Tuberose may be packed in hampers or 

in horizontal fiberboard boxes. If packed 

horizontally, they should be held at the proper 

temperature to avoid geotropic curvature. 

Special Considerations

Florists often use individual tuberose blooms in 

corsages and boutonnieres. Proper pretreatment 

of the spikes will ensure continued opening of the 

blooms in the florists’ workroom and consequent 

increased utility of each spike. 

Tulip

Scientific Name and Introduction

Tulipa cvs., hybrids. Tulips, one of the classical 

cut flowers, were the source of tremendous interest 

when they were first brought to Holland from the 

Mediterranean countries where they are native. 
704

The most common species, Tulipa gesnerana, was 

named after C. Gesner, a botanist who lived from 

1516 to 1565. 

Quality Characteristics and Criteria

The entire tulip plant, with bulb attached, is 

harvested when the tepals show 50% color. It is 

preferable to harvest in the early morning when 

temperatures are lower and to cool the harvested 

flowers immediately. Purchase when flower color 

is just visible and only by cultivar name since 

postharvest characteristics vary greatly. 

Grading and Bunching

Tulip blooms are graded for uniform maturity 

(degree of opening), stem length, and freedom 

from defects. Defects include flower bud blasting, 

greening of flower buds, and toppling. Bulbs are 

then removed and the bases of stems are cut to 

ensure adequate water uptake. Tulips are typically 

bunched in groups of 10.

Ethylene Sensitivity

Tulips show no response to ethylene nor any 

response to inhibitors of ethylene actions or 

synthesis (Sexton et al. 2000).

Pretreatments

No pretreatments are required for tulips. 

Storage Conditions

Tulips should be stored at 0 to 1 °C (32 to 34 °F) 

with 85% RH, upright to prevent stem bending, 

and with bulbs attached. It has been reported 

that flowers stored dry in bunches can keep up 

to 7 weeks if sealed in polyethylene bags or 

kept in boxes overwrapped with polyethylene. 

Desiccation of tulips can be a serious problem, 

causing collapse of the stem below flowers. 

Control of RH and proper rehydration following 

storage can minimize the problem.

Packing

Tulips may be packed in hampers or in regular 

fiberboard flower boxes. Stems and blooms should 

be securely wrapped to prevent bruising and 

breakage. Tulips packed horizontally must be held 

at proper temperature of 0 to 1 °C (32 to 34 °F) to 

avoid gravity-induced bending. 

Special Considerations

End-user life is very species- and cultivardependent, as is the flower maturity stage when 

sold. Preservative solutions are recommended; 

benefits vary from 0 to 150% increase in vase life, 

depending on cultivar, flower food brand, and 

water quality. Do not place in the same bucket 

with daffodils that have been just recut, as the 

mucilage exuded by daffodils can reduce the vase 

life of tulips. Tulip flower stems (scapes) often 

continue to elongate after harvest and will often 

grow out of the arrangement. Stems should be 

maintained in an upright position during handling 

to prevent stem bending. 

Some people may get dermatitis from continual 

handling of tulip flowers.

Waxflower, Geraldton Waxflower 

Scientific Name and Introduction

Chamelaucium uncinatum. A native of western 

Australia, the ‘Geraldton’ waxflower is available 

in shades of white through deep purple and has 

become an important filler material. It is produced 

in substantial quantities in Israel and more recently 

in Australia and California. Various techniques 

have been developed to manipulate the flowering 

season, and the availability of substantial volumes 

from the Southern Hemisphere makes waxflower 

an item that is commonly available in the trade. 

The specific epithet uncinatum means “hooked 
705

at the point,” in reference to the leaves which are 

hooked at their ends. The crushed leaves give a 

pleasing citrus aroma.

The major postharvest problems are the shattering 

of flowers and petals, an ethylene-related problem 

that can be controlled by pretreating the flowers 

with 1-MCP or STS, and Botrytis infection, 

particularly an issue for growing areas with 

erratic rainfall. Fungicide dips have been used 

successfully as a control measure. 

Quality Characteristics and Criteria

Waxflowers are normally harvested with a 

mixture of open flowers and mature buds on each 

branchlet. Branches are harvested to maximize 

stem length without compromising the following 

year’s crop. Avoid buying if leaves or flowers 

have fallen off or are turning yellow. 

Grading and Bunching

There are no grade standards for the flowers, 

which are sold in field bunches. Quality 

waxflowers have numerous flowers on long stems 

and dark-green unblemished foliage. Waxflower 

bunches from Australia weigh 300 g per bunch, 

whereas California bunches usually weigh 400 g. 

Ethylene Sensitivity

Waxflowers are very sensitive to ethylene, which 

causes loss of flowers, buds, and leaves (Joyce 

1993). 

Pretreatments

Harvested wax flower bunches should be 

treated with 1-MCP or STS in the same way as 

carnations. 

Storage Conditions

Store waxflower at 0 to 1 °C (32 to 34 °F). If 

properly precooled and subsequently wrapped in 

plastic to reduce water loss, flowers can be stored 

dry for up to 2 weeks at 1 °C (34 °F). There is no 

benefit of wet over dry storage, and dry storage is 

therefore the method of choice. The main problem 

during storage is from growth of Botrytis on 

flowers. Dipping in 1% Rovral (Ipridione) solution 

prior to storage can prevent Botrytis infection. 

Packing

Waxflowers are packed in bunches that contain 

variable numbers of stems (around 10) to provide 

a satisfactory bunch. 

Special Considerations

The major storage problems are flower shatter 

(flowers fall off) and premature leaf yellowing 

and desiccation. Treat with anti-ethylene 

treatments like STS. Leaf yellowing cannot be 

controlled with STS or other commonly available 

preservatives. 

Yellow Aster 

Scientific Name and Introduction

× Solidaster luteus. The “×” prior to the generic 

name indicates that this species is an intergenetic 

hybrid, the result of crossing two different genera 

(Aster and Solidago). The specific epithet luteus

means yellow. The hybrid originated in 1910 at 

the Leonard Lille Nursery in Lyon, France. 

Quality Characteristics and Criteria

At least 50% of the flowers should be open. Avoid 

old product, as leaf yellowing and desiccation can 

be troublesome. 
706

Grading and Bunching

As with other filler flowers, bunches are made by 

size or weight. 

Ethylene Sensitivity

Like other Asteraceae, solidaster flowers are not 

sensitive to ethylene. 

Pretreatments

Like Solidago, solidaster flowers probably would 

benefit from a cytokinin pulse treatment to delay 

leaf yellowing (Philosoph et al. 1995). 

Storage Conditions

Solidaster should be stored at 0 to 1 °C (32 to 34 

°F). 

Special Considerations

If flowers are too immature when harvested, they 

may not develop to their maximum beauty. Treat 

like most other members of the chrysanthemum 

family. Leaves should be stripped from the stem 

as they rot underwater and will foul the vase 

solution. Make sure that buckets, vases, and 

solution are kept clean. 

Acknowledgments

Much of the information included is based on 

the recommendations of the Society of American 

Florists.

References

Bieleski, R.L., J. Ripperda, J.P. Newman, and 

M.S. Reid. 1992. Carbohydrate changes and leaf 

blackening in cut flower stems of Protea eximia. J. 

Amer. Soc. Hort. Sci. 117:124-127.

Bovy, A.G., G.C. Angenent, H.J.M. Dons, and 

A.C. van Altvorst. 1999. Heterologous expression 

of the Arabidopsis etr1-1 allele inhibits the 

senescence of carnation flowers. Molec. Breed. 

5:301-308.

Burge, G.K., E.R. Morgan, I. Konczak, and 

J.F. Seelye. 1998. Postharvest characteristics of 

Limonium ‘Chorus Magenta’ inflorescences. NZ. 

J. Crop Hort. Sci. 26:135-142.

Celikel, F.G., and Y. Karaaly. 1995. Effect of 

preharvest factors on flower quality and longevity 

of cut carnations (Dianthus caryophyllus L.). Acta 

Hort. 405:156-163.

Celikel, F.G., and W.G. van Doorn. 1995. Effects 

of water stress and gibberellin on flower opening 

in Iris × hollandica. Acta Hort. 405:246-252.

Cevallos, J.C. 1998. Temperature and the 

Postharvest Biology of Cut Flowers. M.S. 

Dissertation, University of California, Davis, CA.

Dai, J., and R.E. Paull. 1995. Source-sink 

relationship and Protea postharvest leaf 

blackening. J. Amer. Soc. Hort. Sci. 120:475-480.

Halevy, A.H., and A.M. Kofranek. 1984. 

Evaluation of lisianthus as a new flower crop. 

HortScience 19:845-847.

Halevy, A.H., A.M. Kofranek, and S.T. Besemer. 

1978. Postharvest handling methods for bird-ofparadise flowers (Strelitzia reginae Ait.). J. Amer. 

Soc. Hort. Sci. 103:165-169.

Hammer, P.E., and K.B. Evensen. 1996. Effects of 

the production environment on the susceptibility 

of rose flowers to postharvest infection by Botrytis 

cinerea. J. Amer. Soc. Hort. Sci. 121:314-320.
707

Han, S.S. 1992. Role of sucrose in bud 

development and vase-life of cut Liatris spicata

(L.) Willd. HortScience 27:1198-2000.

Heyes, J.A., and J.W. Johnston. 1998. 

1-Methylcyclopropene extends Cymbidium orchid 

vase-life and prevents damaged pollinia from 

accelerating senescence. New Zealand J. Crop 

Hort. Sci. 26:319-324.

Hicklenton, P.R. 1991. GA3 and 

benzylaminopurine delay leaf yellowing in cut 

Alstroemeria stems. HortScience 26:1198-1199.

Ichimura, K., and K. Suto. 1999. Effects of the 

time of sucrose treatment on vase-life, soluble 

carbohydrate concentrations and ethylene 

production in cut sweet pea flowers. Plant Growth 

Regul. 28:117-122.

Jacob, Y., R. Barrade, M.J. Marquier, and E. 

Botton. 1997. Breeding of Anemone coronaria

tetraploid hybrids. Acta Hort. 430:503-508.

Jones, R.B., M. Serek, and M.S. Reid. 1993. 

Pulsing with Triton X-100 improves hydration and 

vase-life of cut sunflowers (Helianthus annuus

L.). HortScience 28:1178-1179.

Joyce, D.C. 1993. Postharvest floral organ fall in 

Geraldton waxflower (Chamelaucium uncinatum

Schauer). Austral. J. Exp. Agric. 33:481-487.

Joyce, D.C., M.S. Reid, and R.Y. Evans. 1990. 

Silver thiosulfate prevents ethylene-induced 

abscission in holly and mistletoe. HortScience 

25:90-92.

Kappers, I.F., W. Jordi, F.M. Maas, et al. 1998. 

Gibberellin and phytochrome control senescence 

in alstroemeria leaves independently. Physiologia 

Plantarum 103:91-98.

Kuiper, D., S. Ribot, H.S. van Reenen, and N. 

Marissen. 1995. The effect of sucrose on the 

flower bud opening of ‘Madelon’ cut roses. Sci. 

Hort. 60:325-336.

Macnish, A.J., D.C. Joyce, P.J. Hofman, et al. 

2000. 1-Methylcyclopropene treatment efficacy in 

preventing ethylene perception in banana fruit and 

grevillea and waxflower flowers. Austral. J. Exp. 

Agric. 40:471-481.

Mor, Y., A.H. Halevy, A.M. Kofranek, and M.S. 

Reid. 1984. Postharvest handling of lily of the nile 

flowers. J. Amer. Soc. Hort. Sci. 109:494-497.

Naidu, S.N., and M.S. Reid. 1989. Postharvest 

handling of tuberose (Polianthes tuberosa L.). 

Acta Hort. 261:313-317.

Newman, J.P., L.L. Dodge, and M.S. Reid. 

1998. Evaluation of ethylene inhibitors for 

postharvest treatment of Gypsophila paniculata L. 

HortTechnology 8:58-63.

Philosoph-Hadas, S., S. Meir, I. Rosenberger, 

and A.H. Halevy. 1995. Control and regulation of 

the gravitropic response of cut flowering stems 

during storage and horizontal transport. Acta Hort. 

405:343-350.

Philosoph-Hadas, S., S. Meir, I. Rosenberger, 

and A.H. Halevy. 1996. Regulation of the 

gravitropic response and ethylene biosynthesis 

in gravistimulated snapdragon spikes by calcium 

chelators and ethylene inhibitors. Plant Physiol. 

110:301-310.

Pritchard, M.K., C.S. Hew, and H. Wang. 1991. 

Low-temperature storage effects on sugar content, 

respiration and quality of anthurium flowers. J. 

Hort. Sci. 66:209-214.

Rajitha, B.S., S.G. Rao, Y.B.N. Rao, and D. Singh. 

1999. Post harvest effect of fluoride and other 

chemicals on the vase-life of Gaillardia pulchella

cut flowers. J. Phyto. Res. 12:107-108.

Reid, M.S., M. Mokhtari, J.H. Lieth, et al. 1996. 

Modeling the postharvest life of cut roses. Acta 

Hort. 424:137-144.

Serek, M., R.B. Jones, and M.S. Reid. 1995. 

Physiology of flower senescence in gladiolus. Acta 

Hort. 455-459:16-21.
708

Sexton, R., A.E. Porter, S. Littlejohns, and S.C. 

Thain. 1995. Effects of diazocyclopentadiene 

(DACP) and silver thiosulfate (STS) on ethylene 

regulated abscission of sweet pea flowers 

(Lathyrus odoratus L.). Ann. Bot. 75:337-342.

Sexton, R., G. Laird, and W.G. van Doorn. 2000. 

Lack of ethylene involvement in tulip tepal 

abscission. Physiol. Plant. 108:321-329.

van der Meulen-Muisers, J.J., J.C. van Oeveren, J. 

Jansen, and J.M. van Tuyl. 1999. Genetic analysis 

of postharvest flower longevity in Asiatic hybrid 

lilies. Euphytica 107:149-157.

van der Meulen-Muisers, J.J., J.C. van Oeveren, 

and J.M. van Tuyl. 1997. Breeding as a tool for 

improving postharvest quality characters of lily 

and tulip flowers. Acta Hort. 430:569-575.

van Doorn, W.G. 1998. Effects of daffodil flowers 

on the water relations and vase-life of roses and 

tulips. J. Amer. Soc. Hort. Sci. 123:146-149.

van Doorn, W.G. 1999. Water relations of cut 

flowers. II. Some species of tropical provenance. 

Acta Hort. 482:65-69.

van Doorn, W.G., R.R.J. Perik, and P.J.M. Belde. 

1993. Effects of surfactants on the longevity of 

dry-stored cut flowering stems of rose, Bouvardia, 

and Astilbe. Postharv. Biol. Technol. 3:69-76.

van Doorn, W.G., and A.D. Stead. 1997. 

Abscission of flowers and floral parts. J. Exp. Bot. 

48:821-837.

van Meeteren, U., and H. van Gelder. 1999. Effect 

of time since harvest and handling conditions on 

rehydration ability of cut chrysanthemum flowers. 

Postharv. Biol. Technol. 16:169-177.

van Meeteren, U., H. van Gelder, and A.C. van 

de Peppel 1995. Aspects of carbohydrate balance 

during floret opening in Freesia. Acta Hort. 

405:117-122.

Wernett, H.C., T.J. Sheehan, G.J. Wilfret, et 

al. 1996. Postharvest longevity of cut-flower 

Gerbera. I. Response to selection for vase-life 

components. J. Amer. Soc. Hort. Sci. 121:216-221.
709

Flower Bulbs

August A. De Hertogh and Marcel Le Nard

De Hertogh is formerly with the Department 

of Horticultural Science, North Carolina State 

University, Raleigh, NC. He is now retired. Le 

Nard is with Station d’Amélioration de la Pomme 

de Terre et des Plantes à Bulbes, Institut National 

de la Recherche Agronomique, Ploudaniel, France.

Introduction

“Flower bulbs” refers to all taxa of ornamental 

flowering “bulbs” having true bulbs, corms, 

tubers, rhizomes, tuberous roots, or enlarged 

hypocotyls as underground storage organs (De 

Hertogh and Le Nard 1993b). All of them are 

geophytes (Raunkiaer 1934), a term that not only 

includes flower bulbs but also most herbaceous 

perennials, some fruits such as strawberries, and 

some vegetables such as asparagus. Commercially, 

over 60 taxa and thousands of cultivars of flower 

bulbs are grown on approximately 32,000 hectares 

(De Hertogh and Le Nard 1993a). However, six 

genera make up over 90% of the total acreage of 

bulbs produced. In 2000 (Anonymous 2000), the 

world production of flower bulbs was: Tulipa,

39%; Narcissus, 20%; Lilium, 19%; Gladiolus,

8.5%; Hyacinthus, 4%; and Iris, 3%. This review 

provides the basic guidelines for postharvest 

storage of only these six genera. Because of 

the number of cultivars and their varied usage, 

details cannot be provided because the precise 

requirements for all taxa are complex. For 

example, can a tulip cultivar be “precooled” for 

very early forcing and based on the growing 

season should the cultivar be given 34 °C 

immediately after harvest or placed at 17 to 20 

°C? For detailed postharvest information of this 

nature, users must consult the articles cited.

Commercially, flower bulb usage can be divided 

into two groups. The first group is “planting 

stock.” These are the propagation materials and 

are generally grown by specialized bulb growers. 

Thus, they will only be covered briefly in this 

review. For additional information, consult De 

Hertogh and Le Nard (1993a) and specific articles 

cited. The second group is the “commercial 

bulbs,” which are primarily used for forcing 

either as fresh-cut flowers or as potted growing 

and flowering plants, indoor or outdoor container 

plants, outdoor fresh-cut flower production, and 

gardens and landscapes (De Hertogh and Le Nard 

1993c).

Horticultural Objectives

Optimum postharvest storage conditions in 

combination with ideal bulb growing conditions 

and procedures are required to control (prevent, 

retard, or accelerate) the flowering process from 

floral initiation to anthesis (Hartsema 1961, 

Le Nard and De Hertogh 1993a, Theron and 

De Hertogh 2001) assist in controlling certain 

diseases and insects (Baker 1993, Byther and 

Chastagner 1993, Van Aartrijk 1995, 2000) and 

prevent physiological disorders (De Hertogh and 

Le Nard 1993e). For each species, it is important 

to know—

•	precisely when flower initiation occurs, which 

can be before harvest (for example, Hardy 

Narcissus), during postharvest storage (tulips 

and hyacinths), or after planting (Easter lily);

•	length of time required for floral development 

from initiation to anthesis, which can be a few 

weeks to several months;

•	optimal temperatures required to control the 

entire flowering process, which can range from 

-2 to 34 °C, depending on the species etc.;

•	sensitivity of the bulb species and cultivar 

to ethylene, which ranges from none to very 

sensitive;

•	ventilation requirements, which range from 

none to high;

•	moisture requirements, which range from none 

to high; and

•	specific diseases and insects that can be 

controlled during the postharvest storage 

period, which can range from none to several. 

These and other aspects have been reviewed by 

De Hertogh and Le Nard (1993a) and Hartsema 

(1961).
710

Table 1. Packing and storage temperature requirements of ornamental flower bulbs

 Requirements

Taxon Storage Packing Storage 

temperature

 °C

 

Achimenes Prevent from drying Peat 10 to 15

 

Acidanthera Dry and ventilated None 20

 

Allium 

 giganteum Dry and ventilated None 25 to 28 

 Other alliums Dry and ventilated None 20 to 23

 

Alstroemeria Prevent from drying Peat 1 to 3

 

Amaryllis 

 belladonna Prevent from drying Peat 13 to 23

 

Anemone 

 

 blanda & Dry and ventilated None 9 to 17

 fulgens 

 coronaria

 (summer) Dry and ventilated None 15 to 25 

 (winter) Dry and ventilated None 10 to 13

Anigozanthos Prevent from drying Not reported 2 to 20

 

Begonia Prevent from drying Peat 2 to 5

 (Tuberous 

 hybrids)

Caladium Dry and ventilated None 23 to 25

 

Camassia Prevent from drying Wood shavings 17 to 20

 

Canna Prevent from drying Peat 5 to 10

 

Chionodoxa Prevent from drying Wood shavings 20

 

Clivia Prevent from drying Peat 13

 

Colchicum Prevent from drying Wood shavings 17 to 23

 
711

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—

continued

 Requirements

Taxon Storage Packing Storage 

temperature

 °C

Convallaria Keep frozen-in Peat -2

 

Crocosmia Prevent from drying Plastic 2 to 5

 

Crocus Dry and ventilated None 17 to 20

 

Cyclamen Prevent from drying Peat 9

 

Dahlia Prevent from drying Peat 5 to 10

 

Endymion Prevent from drying, Wood shavings 20

 (Scilla store in paper bags

 campanulata) 

Eranthis Prevent from drying Peat 5

 

Eremurus Prevent from drying Peat 5 to 7

 

Erythronium Prevent from drying Peat 5 to 9

 

Eucharis Prevent from drying Peat 20

 

Eucomis Dry and ventilated None 13 to 20

 

Freesia Dry and ventilated None 

 Preshipping 30

 Postshipping 9 to 13

 

Fritillaria

 imperialis Prevent from drying Wood shavings 23 to 25

 persica & Peat 2 to 5

 meleagris

Galanthus Prevent from drying Peat 17

 

Galtonia Prevent from drying Wood shavings 17 to 20

 
712

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—

continued

 Requirements

Taxon Storage Packing Storage 

temperature

 °C

Gladiolus Dry and ventilated None 2 to 10

 

Gloriosa Prevent from drying Peat 10 to 18

 

Gloxinia Prevent from drying Peat 5 to 9

 

Haemanthus Dry and ventilated None 10 to 15

 

Hemerocallis Prevent from drying Peat 7 to 10

 

Hippeastrum Prevent roots from drying Peat or wood shavings 2 to 13

 

Hyacinthus Dry and ventilated None 17 to 20

 

Hymenocallis Prevent from drying Peat 7 to 10

 

Iris 

 Dutch hybrids Dry and ventilated None 20 to 25

 English Dry and ventilated None 17

 hybrids 

 Germanica Prevent from drying Peat 0 to 5

 hybrids 

 reticulata & Dry and ventilated None 20 to 23

 danfordiae 

Ixia Dry and ventilated at None 20 to 25

 65-70% RH

Ixiolirion Dry and ventilated None 20

 

Lachenalia Dry Peat 9 to 25

 

Leucojum

 aestivum Dry and ventilated None 20

 vernum Dry and ventilated None 2 to 5

Liatris Prevent from drying None 2 to -2

 
713

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—

continued

 Requirements

Taxon Storage Packing Storage 

temperature

 °C

Lilium 

 longiflorum Prevent from drying Peat 2 to 7

 Hybrids & Prevent from drying Peat and polyethylene 2 to -2

 other species

Lycoris Dry and ventilated None 13 to 17

 

Montbretia Prevent from drying Plastic 2 to 5

 

Muscari Dry and ventilated None 20

 

Narcissus

 Hardy cultivars Dry and ventilated None 17

 Paperwhites Dry and ventilated None 2 to 30

 

Nerine Prevent from drying 

 Short-term storage Peat 17 to 21

 Long-term storage Peat 5 to 9

 

Ornithogalum

 dubium Dry and ventilated None 9 to 30

 thyrsoides Prevent from drying Wood shavings 23 to 25

 umbellatum & Prevent from drying Wood shavings 20

 nutans

Oxalis

 adenophylla Prevent from drying Wood shavings 17 to 20

 deppei Dry and ventilated None 2 to 5

 

Polianthes Dry and ventilated None 20

 

Puschkinia Dry and ventilated Wood shavings 20 to 23

 

Ranunculus 

 Summer Dry and ventilated None 17 to 20

 Winter Dry and ventilated None 10 to 13

 
714

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—

continued

 Requirements

Taxon Storage Packing Storage 

temperature

 °C

Scadoxus Dry and ventilated None 10 to 15

 

Scilla siberica Dry and ventilated Wood shavings 20 to 23

 

Sparaxis Dry and ventilated None 25

 

Tigridia In closed boxes Peat 2 to 5

 

Triteleia Dry and ventilated None 17 to 20

 (Brodiaea) laxa

Tulipa Dry and ventilated None 17

 

Zantedeschia Dry and ventilated Wood shavings 7 to 10

 

Zephyranthes Dry and ventilated Polystyrene 17 to 20

Adapted from De Hertogh and Le Nard (1993c).
715

About 75% of the flower bulbs used in the 

United States are imported, and the remainder 

are domestically produced. In addition, all 

production areas are distant from the sites of 

use, and essentially 99% must be transported 

for a few days to several weeks. Thus, all 

trucks and shipping containers must be able to 

provide the proper temperature, ventilation, and 

moisture requirements for the bulbs (table 1). The 

normal rate of air exchange for bulbs requiring 

ventilation during transport is 150 m3

 h-1 (De 

Hertogh and Le Nard 1993c). In addition, for 

bulbs like hyacinths and dutch iris, the RH must 

be controlled to minimize the development of 

diseases such as Penicillium. Therefore, on arrival, 

all bulb shipments must be carefully inspected 

for serious diseases and insects, ventilated as 

needed, and then properly stored (table 1). Also, 

stage of development of the apical meristem must 

be determined. De Hertogh (1996) summarized 

packing, transportation, and storage requirements 

for forcing bulbs.

Major Postharvest Storage Factors

Temperature

Blaauw and his coworkers (Hartsema 1961) 

clearly demonstrated that temperature was the 

most important factor controlling the growth and 

development and flowering processes of flower 

bulbs. They demonstrated that precise control was 

required and that the specific temperature optima 

varied for each bulb species and the desired time 

of flowering. The optimal temperatures can range 

from -2 to 34 °C (28 to 93 °F) depending on the 

bulb species, use, growing season, and cultivar. 

Examples for the six major taxa are provided 

below. 

Subsequently, De Hertogh and Le Nard (1993d) 

classified the hardiness of flower bulbs into 

seven groups (table 2). This classification is very 

important for the storage of nonplanted bulbs 

(table 1) because they have limited protection 

against extremes in temperatures. If they are 

stored or transported at temperatures lower or 

higher than the required temperatures, even for 

short periods, most bulbs will be physiologically 

injured (Van Aartrijk 1995 and 2000).

Table 2. Hardiness classifications for 

ornamental flower bulbs

Hardiness Injured at 

classification temperatures below

Tender I 20 °C

Tender II 10 °C

Tender III 2 °C

Semi-hardy -2 °C

Hardy I -5 °C

Hardy II -10 °C

Hardy III -15 °C

Ventilation

When the taxa require ventilation (table 1), it 

is essential that the flower bulbs receive proper 

air circulation and exchange during all periods 

of postharvest storage. Thus, the application 

of these requirements must begin immediately 

after the grower harvests the bulbs and continue 

during transportation and subsequent handling 

by the wholesaler, forcer, and retailer. The exact 

ventilation requirement is generally very specific. 

It can be very low (Eremurus and Liatris, which 

must be prevented from drying out) or very high 

(tulips, in which ventilation assists in preventing 

flower abortion and abnormalities and in removing 

ethylene). In general, ventilation rates must be 

adapted to the storage temperature; that is, higher 

temperatures require higher rates of ventilation.

Moisture

There are two basic considerations for the 

moisture level used for bulb storage (table 1). The 

first is to provide the optimum moisture level, 

which will prevent desiccation of susceptible 

bulbs. Thus, materials such as moist peat or 

wood shavings are used in combination with the 

various packaging materials such as polyethylene. 

The second is the control of RH during storage 

or transportation, which can minimize root 
716

development and prevent the development 

of diseases such as Penicillium on hyacinths, 

Narcissus, tulips, and dutch iris. In addition, this 

approach is an important technique to minimize 

the use of fungicides either prior to or after 

shipping. Since the registration of fungicides 

varies with each country and is always subject to 

change, users must consult with their appropriate 

governmental agency to determine which 

pesticides are approved.

Ethylene

With the exception of dutch iris (see information 

below), nonplanted flower bulbs must not 

be exposed to ethylene. Most bulbs are 

physiologically sensitive to ethylene levels of 0.1 

μL L-1 and higher. In general, when the flower has 

been formed and is immature, this plant growth 

regulator causes either floral abnormalities or 

complete flower abortion. For very sensitive 

bulbs, such as tulips, it is advisable to have the 

storage rooms analyzed for ethylene. Commercial 

ethylene services are available to monitor the level 

of ethylene in all floriculture facilities. 

Modified Atmospheres

Research on the modification of the O2

, N2, and 

CO2

 levels of the storage atmosphere has been 

reported for gladioli, lilies, and tulips (De Hertogh 

and Le Nard 1993d). In Europe, this system is 

referred to as “ultra-low oxygen” (ULO) and is 

used commercially in the Netherlands for lily and 

tulip bulb storage (Anonymous 1996). However, 

the specific procedures used and the results have 

not been published in refereed journals. 

Diseases and Insects

All users of flower bulbs must be familiar with 

the diseases and insects that affect each species 

(Baker 1993, Byther and Chastagner 1993, Van 

Aartrijk 1995, 2000). There are many pests, but 

usually there are only a few major ones for each 

species. Knowledge of the major pests and the 

conditions controlling their development can 

assist in either eliminating and/or minimizing their 

effects during postharvest storage.

Major Flower Bulb Taxa

Gladiolus (Gladioli) 

Cohat (1993) reviewed the physiology, pests, and 

other aspects of Gladiolus. Many diseases can 

affect gladioli in storage, and prestorage fungicidal 

dips are generally used. Current registrations must 

be consulted for approved fungicides. Corms for 

commercial uses should be transported at 2 to 5 °C 

(36 to 41 °F) under highly ventilated conditions, 

about 2 m3

 h-1 per 100 L of corms. With the 

exception of a hot water treatment (see below), 

unplanted corms should never be stored at <0.5 °C 

or >30 °C (Cohat 1993, Van Aartrijk 1995).

Planting stock. After being harvested, cleaned, 

and then graded, corms and cormlets used as 

planting stock are initially given 2 to 3 weeks 

at 15 to 23 °C (59 to 73 °F) followed by 2 °C 

(24 °F) under highly ventilated conditions for a 

minimum of 8 to 10 weeks. The latter is required 

to break the rest period (dormancy) of the corms 

and cormlets. Prior to planting, they are given 4 

to 8 weeks at 20 to 30 °C (68 to 86 °F) to promote 

sprouting. To control Fusarium, cormlets are 

stored at 20 to 25 °C (68 to 77 °F) for 8 to 12 

weeks, then soaked in running water for 1 to 2 

days at 20 °C (68 °F), and then given a hot water 

treatment of 55 to 56 °C (131 to 133 °F) for 30 

min.

Commercial bulbs for outdoor use. Horticulturally, the major uses for gladioli corms are 

outside either for use as commercial fresh cut 

flowers or in gardens and landscapes. The large 

flowering corms for these uses must be provided 

with the same storage temperatures and conditions 

as the planting stock. Corms used for very long 

storage and thus for very late flowering must be 

stored at 2 °C (36 °F) until planted.
717

Hyacinthus (Hyacinths) 

Nowak and Rudnicki (1993) reviewed the 

physiology, pests, and other aspects of hyacinths. 

Commercially, the Netherlands produces almost 

all of the bulbs used world wide. The major 

storage disease for commercial sized hyacinth 

bulbs is Penicillium. It can be controlled with 

optimum ventilation conditions and a RH of 85 

to 90%. Hyacinth bulbs should be transported 

and subsequently stored at 17 °C under highly 

ventilated conditions. With the exception of the 

heat treatment to control Xanthomonas hyacinthii

(see below), unplanted bulbs are never stored at 

<0 °C or >25.5 °C (78 °F) (Nowak and Rudnicki 

1993, Van Aartrijk 2000).

Planting stock. The postharvest handling and 

storage of small hyacinth bulbs require precise 

conditions to control the bacterium Xanthomonas 

hyacinthii (yellow disease). After harvest, the 

bulbs are stored at 30 °C under highly ventilated 

and dry conditions until September 1; they are 

then given 2 weeks at 38 °C, followed by 3 days 

at 44 °C, and subsequently 25.5 °C (78 °F) until 

planted. Bulbs used for scooping and scoring and 

other large planting stock bulbs are stored under 

dry and highly ventilated conditions at 25.5 °C (78 

°F) from harvest until planted.

Commercial bulbs for forcing. Two types of 

commercial bulbs are available for greenhouse 

forcing as either potted plants or fresh cut flowers. 

The first is “prepared bulbs,” which are used for 

very early forcing. After being harvested in early 

June, the bulbs are stored under dry and highly 

ventilated conditions for 2 weeks at 30 °C (86 °F), 

followed by 3 weeks at 25.5 °C (78 °F), and then 

23 °C (73 °F) until the uppermost floret reaches 

stage A2. Subsequently, they are stored at 17 °C 

(63 °F) until planted. “Regular bulbs,” which are 

used for medium and late forcing, are given 25.5 

°C (78 °F) followed by 4 weeks at 17 °C (63 °F) 

prior to planting. De Hertogh (1996) provided 

detailed forcing programs for hyacinths in North 

America.

Commercial bulbs for gardens and landscaping.

After being harvested, bulbs for these uses are 

stored dry and under highly ventilated conditions 

at 25.5 °C (78 °F). They are shipped and 

subsequently stored at 17 °C (63 °F).

Iris hollandica (Dutch Iris)

De Munk and Schipper (1993) reviewed the 

physiology, pests, and other aspects of dutch iris. 

The two major storage diseases of dutch irises are 

Fusarium and Penicillium. To assist in controlling 

these diseases, it is essential to always handle the 

bulbs carefully to minimize mechanical damage, 

which provides sites for disease development. 

Prestorage and preplanting fungicidal dips are 

generally used for dutch iris. Current registrations 

must be consulted for approved fungicides. 

After harvest and up to planting, dutch iris bulbs 

should be stored at 50 to 60% RH to minimize 

root growth and development of Penicillium. In 

general, unplanted bulbs should never be stored 

at <0 °C (32 °F) or >30 °C (86 °F) (De Munk and 

Schipper 1993, Van Aartrijk 1995).

Planting stock. The primary objective during 

postharvest storage of the bulbs is to prevent 

flower formation in order to produce round, 

commercial-sized bulbs in the field. In addition, 

the conditions should prevent the development of 

diseases. The control of flower initiation is very 

critical in 7/8-cm circumference planting stock 

bulbs. This size group is known as “the in-between 

size,” since larger bulbs flower readily and smaller 

ones do not. These bulbs should be provided with 

the following postharvest temperatures: 23 °C 

(73 °F) from harvest to 1 September, followed by 

2 weeks at 30 to 35 °C (86 to 95 °F), and then, 

depending on the cultivar and bulb size, 5 to 9 °C 

(41 to 48 °F). Bulbs that are smaller than 7/8 cm 

in circumference should be stored at 18 to 20 °C 

(64 to 68 °F).

Commercial bulbs for forcing. Generally, bulbs 

for very early forcing are stored at 30 °C for a 

few days after being harvested. This is necessary 

for bulb drying, cleaning, and grading. They are 
718

subsequently exposed to 500 μL L-1 ethylene for 

24 h. This treatment stimulates flower initiation, 

especially with small bulbs of some cultivars and 

bulbs not receiving sufficient heat in the field 

before being harvested. Bulbs for late and retarded 

(up to 1 year) forcing are placed at 30 °C (86 °F) 

to suppress their growth and development. Prior 

to planting, they are “precooled” at 5 to 9 °C (41 

to 48 °F) for 6 to 11 weeks, depending on the 

cultivar. After being precooled, bulbs should be 

planted as quickly as possible and, if transported, 

the period should be as short as possible. De 

Hertogh (1996) provided forcing programs for 

dutch iris used as fresh cut flowers in North 

America.

Commercial bulbs for outdoor uses. Dutch irises 

are grown outdoors as commercial fresh cut 

flowers and in gardens and landscapes. After being 

harvested, these bulbs are initially stored at 30 °C 

(86 °F) and then shipped and stored at 17 °C (63 

°F) until planted. When necessary, bulbs can be 

precooled for 3 to 4 weeks at 5 to 9 °C (41 to 48 

°F).

Lilium (Lilies) 

In North America two basic types of commercial 

lilies are generally used: the Easter lily (L. 

longiflorum), which is mainly used as a flowering 

potted plant, and a wide range of hybrid and 

species lilies, which are used either as fresh-cut 

flowers, as flowering potted plants, or in gardens 

and landscapes. When properly packed in moist 

peat, unplanted lily bulbs can be stored at -1 to -2 

°C (28 to 30 °F), but are normally never stored 

above 17 °C (63 °F) (Beattie and White 1993, 

Miller 1993, Van Aartrijk 2000).

Easter lily. Miller (1993) reviewed the physiology 

of forcing and bulb production, pests, and 

other aspects of the Easter lily. These bulbs 

are produced in the coastal areas of Northern 

California and Southern Oregon. Immediately 

after being harvested and graded, the “planting 

stock” is planted in the field. The “commercialsized bulbs” are immediately packed in moist peat 

in wooden cases and then sent to either the forcer 

or commercial bulb jobber. To flower properly, 

the bulbs must receive 6 weeks at 2 to 7 °C (36 

to 45 °F) either by case precooling in moist peat 

or by being controlled-temperature forced in pots 

in a moist planting medium. De Hertogh (1996) 

provided forcing schedules for Easter lily in North 

America. 

Hybrid lilies. Beattie and White (1993) reviewed 

the physiology, pests, and other aspects of the 

hybrid and species lilies. Breeding of these lilies 

is expanding rapidly and many new cultivars 

are continuously being released. After being 

harvested, the bulbs are graded and cleaned. To 

properly flower them, the bulbs must be packed in 

moist peat, wrapped in polyethylene, and packed 

in trays for storage and shipping. Subsequently, 

they require at least 6 to 8 weeks at 2 °C (36 °F) 

before being planted for early forcing. For late 

and year-round forcing the bulbs are “frozen-in” 

at -1 to -2 °C (28 to 30 °F) after being precooled 

for 6 to 8 weeks. Modified atmospheres (ULO) 

systems, although not new (Stuart et al. 1970), 

are being used for long storage of some hybrids 

(Anonymous 1996). This system is being used 

because there are fewer negative effects of the 

long-term period of being frozen-in (Van Aartrijk 

2000). An alternative to this system is to produce 

the bulbs in the Southern Hemisphere for fall 

planting in the Northern Hemisphere (Anonymous 

2001). Planting stock is stored at 2 °C (36 °F) 

in moist peat until planted. De Hertogh (1996) 

provided forcing guidelines for Asiatic and 

Oriental lilies in North America.

Narcissus (Hardy Daffodils and Paperwhites)

There are two basic groups of Narcissus, the 

“Hardy Narcissus” (daffodils) and the nonhardy 

“Paperwhite Narcissus.” Hanks (1993) reviewed 

the physiology, pests, and other aspects of these 

groups. With the exception of the hot water 

treatment (see below), nonplanted hardy Narcissus

bulbs are never stored at >34 °C (93 °F) (see early 
719

forcing below), while paperwhites are not stored 

at >30 °C (86 °F) (Hanks 1993). Neither group 

of bulbs is stored at <0 °C (32 °F) (Van Aartrijk 

1995).

Hardy Narcissus. By far, the largest group of 

Narcissus comprisesthe hardy cultivars, and 

hundreds are grown in many countries. The major 

storage diseases are Fusarium and Penicillium

(Byther and Chastagner 1993, Van Aartrijk 

1995). To control Fusarium in the planting 

stock, approved fungicides are added during a 

hot water treatment (HWT) of 1 to 2 h at 44 °C 

(112 °F). This treatment also controls nematodes 

and bulb flies. Penicillium can be controlled by 

use of proper ventilation conditions and a RH of 

85 to 90%. Except for the HWT, planting stock 

bulbs are stored at 17 to 20 °C (63 to 68 °F). 

Commercial bulbs for early forcing are given 

1 week at 34 °C (93 °F) followed by 17 °C (63 

°F). All of the other bulbs are provided 17 to 20 

°C (63 to 68 °F). De Hertogh (1996) provided 

forcing programs for hardy Narcissus cultivars in 

North America. Transportation of hardy daffodils 

either for forcing or garden and landscape use 

should be at 17 °C (63 °F) under highly ventilated 

conditions.

Paperwhite Narcissus. Most cultivars of 

paperwhite Narcissus bulbs are produced in Israel. 

They are not considered to be hardy bulbs but can 

be planted outdoors in USDA Climatic Zones 9 to 

11 (Cathey 1990). Planting stock and commercial 

bulbs are stored at 25 to 30 °C (77 to 86 °F) after 

being harvested. Commercial bulbs should be 

shipped at 25 to 30 °C (77 to 86 °F) under highly 

ventilated conditions. After arrival, bulbs should 

be stored at 25 to 30 °C (77 to 86 °F) until shoots 

begin to emerge. Subsequently, they should be 

placed at 2 °C (36 °F). Prior to planting, they 

require 2 weeks at 9 to 17 °C (48 to 63 °F). De 

Hertogh (1996) provided forcing programs for 

Israeli-grown paperwhites in North America.

Tulipa (Tulips)

Le Nard and De Hertogh (1993b) reviewed the 

physiology, pests, and other aspects of tulips. 

Without question, tulips are the largest taxa of 

flower bulbs grown and used throughout the 

world. Hundreds of cultivars are produced for 

forcing as fresh cut flowers, as potted growing 

plants, and in gardens and landscapes. The major 

storage diseases are Fusarium and Penicillium. 

Normally, Fusarium infections begin in the field 

and continue during postharvest storage. There are 

substantial differences in cultivar susceptibility, 

but it is important to reduce the number of 

infected bulbs in storage because of the ethylene 

they produce. This can lead to flower abortion and 

abnormalities. Thus, the bulbs must be routinely 

inspected and the rooms monitored for ethylene; 

levels in the storage rooms must not exceed 0.1 

μL L-1. In storage, Penicillium can be controlled 

with high rates of ventilation and RH of 85 to 

90%. Regardless of the horticultural use, tulip 

bulbs should be shipped at 17 °C (63 °F) under a 

ventilation rate of 150 m3

 h-1. With the exception 

of the 34 °C (93 °F) treatment for early forcing 

(see below), nonplanted bulbs are never stored at 

>25 °C (77 °F) or <0 °C (32 °F) (Le Nard and De 

Hertogh 1993b, Van Aartrijk 2000).

Planting stock. After being harvested, bulbs are 

initially placed at 23 to 25 °C (73 to 77 °F) for 

3 to 4 weeks. Subsequently, depending on the 

cultivar, they are stored at progressively lower 

temperatures, from 23 to 20 °C (73 to 68 °F) down 

to 17 to 15 °C (63 to 59 °F), until just before being 

planted. These temperatures are used to encourage 

enhanced production of large sized bulbs from the 

planting stock.

Forcing bulbs. For very early forcing, most 

cultivars are given 34 °C (93 °F) for 1 week 

immediately after lifting. Subsequently, they are 

stored under dry and well-ventilated conditions at 

17 to 20 °C (63 to 68 °F). It is very important to 

be able to identify the stages of flower initiation 

(Hartsema 1961), since most cultivars must reach 

stage G prior to being precooled at 5 to 9 °C (41 

to 48 °F). For medium and late forcing, bulbs 

are placed at 17 to 23 °C (63 to 73 °F) prior to 
720

planting at low temperatures. De Hertogh (1996) 

provided forcing programs for cut and potted 

tulips in North America. However, bulbs are also 

grown in the Southern Hemisphere for planting in 

the fall in the Northern Hemisphere (Anonymous 

2001). As with the hybrid lilies, this eliminates the 

need for and effects of long storage periods.

Garden and landscaping bulbs. The key to use 

of tulip bulbs in North America is the USDA 

Climatic Zone (Cathey 1990). In northern 

climatic zones, they naturally receive adequate 

cold exposure to satisfy their low temperature 

requirement. In warm climatic zones, they must be 

precooled at 5 °C (41 °F) for 8 to 10 weeks prior 

to planting. Normally after being harvested, tulip 

bulbs for gardens and landscape use are stored at 

20 to 23 °C (68 to 73 °F) and then shipped and 

stored at 17 °C (63 °F) prior to being planted.

References

Anonymous. 1996. Resultaten ULO-bewaring 

lelies hoopvol. CNB INFO 551:19.

Anonymous. 2000. Inventarisatie 

wereldbollenareaal. Bloembollencultuur 21:4.

Anonymous. 2001. Bollenareaal: Wereldwijde 

groei. Bloembollencultuur 21:7,17-19.

Baker, J. 1993. Insects. In A. De Hertogh and 

M. Le Nard, eds., The Physiology of Flower 

Bulbs, pp. 101-153. Elsevier Science Publishers, 

Amsterdam, Netherlands.

Beattie, D.J., and J.W. White. 1993. Lilium—

Hybrids and Species. In A. De Hertogh and M. Le 

Nard, eds., The Physiology of Flower Bulbs, pp. 

423-454. Elsevier Science Publishers, Amsterdam, 

Netherlands.

Byther, R., and G. Chastagner. 1993. Diseases. 

In A. De Hertogh and M. Le Nard, eds., The 

Physiology of Flower Bulbs, pp. 71-99. Elsevier 

Science Publishers, Amsterdam, Netherlands.

Cathey, M. 1990. USDA Plant Hardiness Zone 

Map. Miscellaneous Publication 1475, U.S. 

Department of Agriculture, Washington, DC.

Cohat, J. 1993. Gladiolus. In A.A. De Hertogh, 

and M. Le Nard, eds. The physiology of flower 

bulbs. pp. 297-320. Elsevier Science Publishers, 

Amsterdam, Netherlands.

De Hertogh, A.A. 1996. Holland Bulb Forcer’s 

Guide, 5th ed. Intl. Flower Bulb Centre, Hillegom, 

Netherlands.

De Hertogh, A.A., and M. Le Nard. 1993a. The 

Physiology of Flower Bulbs. Elsevier Science 

Publishers, Amsterdam, Netherlands.

De Hertogh, A.A., and M. Le Nard. 1993b. 

Botanical aspects of flower bulbs. In A. De 

Hertogh and M. Le Nard, eds., The Physiology 

of Flower Bulbs, pp. 7-20. Elsevier Science 

Publishers, Amsterdam, Netherlands. 

De Hertogh, A.A., and M. Le Nard. 1993c. World 

production and horticultural utilization of flower 

bulbs. In A. De Hertogh and M. Le Nard, eds., The 

Physiology of Flower Bulbs, pp. 21-28. Elsevier 

Science Publishers, Amsterdam, Netherlands.

De Hertogh, A.A., and M. Le Nard. 1993d. 

Physiological and biochemical aspects of flower 

bulbs. In A. De Hertogh and M. Le Nard, eds., The 

Physiology of Flower Bulbs, pp. 53-69. Elsevier 

Science Publishers, Amsterdam, Netherlands.

De Hertogh, A.A., and M. Le Nard. 1993e. 

Physiological disorders. In A. De Hertogh and 

M. Le Nard, eds., The Physiology of Flower 

Bulbs, pp. 155-160. Elsevier Science Publishers, 

Amsterdam, Netherlands.

De Munk, W.J., and J. Schipper. 1993. Iris—

bulbous and rhizomatous. In A. De Hertogh and 

M. Le Nard, eds., The Physiology of Flower 

Bulbs, pp. 349-379. Elsevier Science Publishers, 

Amsterdam, Netherlands. 
721

Hanks, G.R. 1993. Narcissus. In A. De Hertogh 

and M. Le Nard, eds., The Physiology of Flower 

Bulbs, pp. 463-558. Elsevier Science Publishers, 

Amsterdam, Netherlands. 

Hartsema, A.M. 1961. Influence of temperatures 

on flower formation and flowering of bulbous and 

tuberous plants. In W. Ruhland, ed., Handbuch 

der Pflanzenphysiologie, pp. 123-167. SpringerVerlag, Berlin. 

Le Nard, M., and A.A. De Hertogh. 1993a. Bulb 

growth and development. In A. De Hertogh and 

M. Le Nard, eds., The Physiology of Flower 

Bulbs, pp. 29-43. Elsevier Science Publishers, 

Amsterdam, Netherlands. 

Le Nard, M., and A.A. De Hertogh. 1993b. Tulipa. 

In A. De Hertogh and M. Le Nard, eds., The 

Physiology of Flower Bulbs, pp. 617-682. Elsevier 

Science Publishers, Amsterdam, Netherlands. 

Miller, W.B. 1993. Lilium longiflorum. In A. De 

Hertogh and M. Le Nard, eds., The Physiology 

of Flower Bulbs, pp. 391-422. Elsevier Science 

Publishers, Amsterdam, Netherlands.

Nowak, J. and R.M. Rudnicki. 1993. Hyacinthus. 

In A. De Hertogh and M. Le Nard, eds., The 

Physiology of Flower Bulbs, pp. 335-347. Elsevier 

Science Publishers, Amsterdam, Netherlands. 

Raunkiaer, C. 1934. Life Forms of Plants and 

Statistical Plant Geography. Clarendon Press, 

Oxford, U.K.

Stuart, N.W, S. Parsons, and C.J. Gould. 1970. 

The influence of controlled atmospheres during 

cold storage on the subsequent flowering of Easter 

lilies and bulbous Iris. HortScience 5:356.

Theron K.I., and A.A. De Hertogh. 2001. 

Amaryllidaceae: geophytic growth, development 

and flowering. Hort. Rev. 25:1-70.

Van Aartrijk, J. 1995. Ziekten en Afwijkingen bij 

Bolgewassen. Deel 2: Amaryllidaceae, Araceae, 

Begoniaceae, Cannaceae, Compositae Iridaceae, 

Oxalidaceae, Ranunculaceae. Tweede Druk. 

Laboratorium voor Bloembollenonderzoek, Lisse, 

Netherlands.

Van Aartrijk, J. 2000. Ziekten en Afwijkingen 

bij Bolgewassen. Deel 1: Liliaceae. Derde Druk. 

Laboratorium voor Bloembollenonderzoek, Lisse, 

Netherlands.
722

Flowering Potted Plants

Terril A. Nell

Nell is with the Environmental Horticulture 

Department, University of Florida, Gainesville, 

FL.

Transporting and storing flowering potted plants 

challenges commercial growers’ continuing ability 

to provide a high quality product. Quality suffers 

when plants are exposed to adverse shipping and 

storage conditions, such as exclusion from light 

in closed containers and sleeves, exposure to 

harmful gases and temperature extremes, poor 

air ventilation, high RH, and vibration. These 

conditions can lead to deterioration of even the 

highest quality plants. Further, the environmental 

and physical stresses imposed on plants during 

transit are worsened if plants are improperly 

produced, incorrectly packaged, or mishandled 

during shipping or upon receipt.

Flowering potted plants represent a significant 

portion of floriculture production in the United 

States (20.3% of production), with 53% of the 

production in six States: California, Florida, 

Texas, Pennsylvania, North Carolina, and New 

York. Plants are often produced at locations distant 

from the point of marketing; Thus shipping, often 

for long distances, has become commonplace in 

the industry. The extended shipping or storage 

times may result in loss of quality and reduced 

longevity.

Flowering potted plants range from cold tolerant 

to chilling sensitive and from ethylene insensitive 

to ethylene sensitive. Quality and longevity are 

based on flower longevity and leaf quality. A 

flowering potted plant with yellow leaves has 

little value even if the flowers last for a long 

period. Likewise, plant quality is diminished 

when the flower dies rapidly though the leaves 

remain green. Problems with shipping may not be 

apparent immediately following shipping: Buds or 

flowers may drop several days after unboxing, or 

leaves may turn yellow or flowers die prematurely 

1 to 2 weeks after shipping. Research over the last 

25 years has concentrated on factors providing for 

retention of leaf color while maximizing flower 

longevity. 

Cultivar selection and production conditions 

affect the response of flowering potted plants 

to shipping conditions. Chrysanthemum and 

poinsettia cultivars vary considerably in their 

ability to withstand shipping. Hibiscus cultivars 

drop buds and flowers as a result of improper 

shipping conditions. It is likely that differences 

in cultivar response of other flowering potted 

plants to shipping conditions exist, but extensive 

research has not been conducted to elucidate these 

responses.

Production conditions can play a major role 

in the ability of potted flowering plants to 

withstand shipping conditions. High fertilizer 

levels during production decreases the quality 

of chrysanthemums, campanula, poinsettia, and 

other plants during and following shipping. In 

chrysanthemum, terminating fertilizer at flower 

color (3 weeks prior to marketing) resulted in 

a 7- to 11-day increase in longevity, depending 

on cultivar and fertilizer rate. With potted roses, 

overwatering of the plants during the final 1 to 2 

weeks of production results in rapid losses in plant 

and flower quality following shipping as a result 

of damage to the root system.

Four factors—disease, improper temperature, 

extended shipping duration, and exposure to 

ethylene—result in either rapid loss of quality 

during shipping or reduced longevity and quality 

following shipping. All of these factors can be 

interrelated in their effects. For instance, packing 

flowering potted plants in a warm greenhouse or 

packing area then placing the box into a cooler 

will result in condensation on the flowers and 

leaves, providing ideal conditions for botrytis, 

powdery mildew, or other diseases. Similarly, use 

of optimum temperatures may cause problems 

during long shipping times. 

Production and shipping practices should 

minimize the potential incidence of diseases. For 

instance, calcium sprays and reduced fertilizer 
723

have been shown to minimize the incidence of 

poinsettia bract edge burn in the greenhouse, 

during shipping, and in the retail setting. In most 

cases, diseases, especially botrytis and powdery 

mildew, will become worse during shipping 

because of the high RH microclimate created in 

the closed shipping box. 

Temperature management is one of the best 

methods of maintaining quality during shipping. 

Reduced temperatures lead to lower respiration, 

conservation of carbohydrate reserves, and 

minimize problems associated with ethylene. 

Optimum shipping temperature varies with 

species, but plants should be shipped at the lowest 

possible temperature (table 1). Chilling-sensitive 

crops are generally shipped at 50 to 53 °F (10 to 

12 °C), while those that are not chilling sensitive 

are shipped at 35 °F (2 °C) to maximize plant and 

flower quality. 

Ethylene can adversely affect quality. Plants 

may produce ethylene, or plants may be exposed 

to ethylene from external sources, such as 

combustion engines and dead and decaying 

organic matter (fruit, vegetables, or flowers). 

Ethylene is a colorless, odorless gas that can cause 

many undesirable effects on flowering potted 

plants at very low levels—25 to 100 nL L-1 (ppb). 

Typical ethylene injury symptoms include leaf and 

bud drop, premature aging, and leaf yellowing, but 

other disorders have also been identified (table 2).

Regardless of concentration, ethylene becomes 

more damaging as temperature increases during 

the exposure period. Of course, injury is worse 

with higher concentrations and longer exposure 

periods. For example, open carnations are 1,000-

fold more sensitive to ethylene at 21 °C (70 °F) 

than at 2 °C (36 °F). One of the most effective 

means of minimizing ethylene damage is to reduce 

temperature, being cautious not to ship chillingsensitive crops at too low temperatures. Also, open 

flowers are often more sensitive to ethylene than 

buds.

Table 1. Recommended shipping 

temperatures for flowering potted plants

Shipping temperature

35 to 40 °F 50 to 60 °F

(2 to 5 °C) (10 to 15 °C)

Amaryllis Africian violet

Azalea Begonia-elatior

Calceolaria Bougainvillea

Chrysanthemum Browallia

Cineraria Christmas cactus

Crocus Clereodendron

Cyclamen Crossandra

Daffodil Cymbidium

Easter lily Easter cactus

Freesia Exacum

Grape hyacinth Gloxinia

Hyacinth Hibiscus

Hydrangea Poinsettia

Kalanchoe Streptocarpus

Oxalis

Regal geranium

Rose

Tulip

Adapted from Sterling and Molemaar (1985) and 

Nell (1993).
724

Table 2. Response of flowering potted 

plants to ethylene1

Crop Symptoms

Achimenes Flower/bud drop

African violet Flower wilting

Azalea Leaf drop

Begonia-elatior Flower drop

Bougainvillea Flower/bract drop

Browallia Flower/bud drop

Carnation Failure of flower to open

Calceolaria Flower/bud drop

Clereodendron Flower/bract drop; leaf drop

Crossandra Flower drop

Cyclamen Flower drop; flower wilting

Cymbidium Wilting of the sepal

Exacum Flower wilting

Geranium Floret drop

Gardenia Flower/bud drop

Gloxinia Flower drop

Hibiscus Flower/bud drop

Kalanchoe Failure of flowers to open; 

 petal drying

Pachystachus Petal wilting; bud blasting; 

 leaf yellowing

Poinsettia Petiole droop2

Streptocarpus Flower drop

Adapted from Woltering (1987).

1 The degree of sensitivity to ethylene varies with 

plant species, variety, ethylene concentration, 

 and temperature during exposure and duration of 

exposure.

2 Petiole droop (epinasty) of poinsettia is caused 

by upward bending of leaf and bract petioles

 during sleeving.

Several chemicals are available commercially that 

will minimize the detrimental effects of ethylene. 

Application procedures and effectiveness on 

ethylene-sensitive crops vary, but these chemicals 

can be a valuable tool for crops that exhibit 

ethylene injury. The use of anti-ethylene chemicals 

is especially valuable on chilling-sensitive crops, 

since temperature cannot be reduced.

Flowering potted plant quality can be maintained 

during shipping provided that production practices 

and cultivar are selected properly and optimum 

shipping conditions are maintained, including 

temperature management and prevention of 

injury from ethylene. However, regardless of the 

conditions, shipping and storing flowering potted 

plants for extended periods will lead to decreased 

longevity. Ideally, flowering potted plants should 

be stored and shipped for brief periods at optimum 

conditions.

References

Nell, T.A. 1993. Flowering Potted Plants: 

Prolonging Shelf Performance. Ball Publishing 

Co., Batavia, IL

Sterling, E.P., and W.H. Molemaar. 1985. 

The influence of time and temperature during 

simulated shipment on the quality of potplants. 

Rapport Sprenger Instituut no. 2286, Springer 

Institute, Wageningen, The Netherlands

Woltering, E.J. 1987. Effects of ethylene on 

ornamental pot plants: classification. Scientia 

Hort. 31:283-294
725

Foliage Plants

Terril A. Nell

Nell is with the Environmental Horticulture 

Department, University of Florida, Gainesville, 

FL.

Foliage plant production and sales represent a 

significant part of ornamental plant production 

in the United States. In 1998, sales were $509 

million, with the greatest production in Florida 

(61%), California (18%), and Texas (4%). 

Consequently, foliage plants are shipped long 

distances to supply retail markets throughout 

North America and Europe. 

Temperature control is critical to successful 

shipping and quality retention in the darkness of 

transport vehicles. The shipping environment is 

not conducive to maintaining foliage plant quality. 

Although it is difficult to generalize, the best 

shipping temperature is in the range of 15 to 18 °C 

(59 to 64 °F) with 85 to 90% RH. Temperatures 

of 10 to 13 °C (50 to 55 °F) are the lowest that 

should be considered for shipping, and even at this 

range some chilling injury may occur with some 

plants. 

Foliage plants should be acclimatized by growers 

prior to shipment. Acclimatization is the process 

of making plants more tolerant to environmental 

changes during or after shipment. Growers 

acclimatize plants using lower fertilizer levels and 

temperatures or reduced light and water during the 

last 2 to 4 weeks before shipment. Acclimatized 

plants are better adapted to dark storage in transit 

and reduced light in stores than nonacclimatized 

plants. Requirements and length of shipping 

tolerated vary because of the wide diversity 

of foliage plants. Shipping temperatures have 

been identified for some acclimatized plants in 

temperature-controlled containers (table 1). These 

guidelines are based on simulated shipping tests in 

darkness. 

In simulated shipping tests at 10, 13, 16, and 

19 °C (50, 55, 61, and 66 °F) for 1 to 4 weeks 

in the dark, Scheffiera arboricola shipped best 

at 19 °C, Ficus benjamina at 10 or 13 °C, and 

Dracaena marginata equally well at 13, 16, and 

19 °C. These plants withstood shipment for 3 

weeks without a significant loss of quality and for 

4 weeks, at some temperatures, without severe 

quality reduction. Shefflera plants recovered 

from dark storage within 17 days after transfer 

to light. Ficus plants are damaged by holding at 

4 °C (39 °F) for 6 or more days. Similar chilling 

injury can occur on many foliage plaints at 

temperatures of 7 °C (45 °F) for long periods or 

2 to 5 °C (36 to 41 °F) for even short periods. 

Although 1 day at 5 °C (41 °F) may not damage 

most foliage plants, severe damage can occur 

when plants are subjected to cool temperatures 

over a 3- to 5-day transit time. Coleus is very cold 

sensitive. Dracaena sanderana and Spathiphyllum 

clevelandii are severely injured after 1 day at 2 

°C (36 °F) and slightly after 1 day at 10 °C (50 

°F). Aglaonema is very intolerant of temperatures 

<10 °C (<50 °F). Exposure to 4.4 °C (40 °F) for 2 

days causes severe damage to Scindapsus pictus

(satin pothos) and Maranta leuconeura (prayer 

plant). Fittonia verschaffeitii (silvernerve plant) is 

severely damaged within 8 h at 2 °C (36 °F).

Foliage plants should be turned over rapidly in 

marketing and should not be overordered. Plants 

should not be stored in back rooms for extended 

periods or in severe drafts of heat or cold. Foliage 

plants should not be transported with fruits, 

vegetables, or cut flowers, most of which emit 

ethylene and are shipped at low temperatures. 

Plants such as scheffleras, crassulas, fittonias, and 

ficuses are very sensitive to ethylene.
726

Table 1. Suggested shipping temperatures for acclimatized foliage plants to 

maintain quality in refrigerated vans1

Plant name 1-15 days shipment 16-30 days shipment2

°C °F °C °F

Aglaonema, cv. ‘Fransher’ 13-16 55-60 16-18 60-65

Aglaonema, cv. ‘Silver Queen’ 16-18 60-65 16-18 60-65

Ardisia crispa 10-13 50-55 — —

Aspidistra elatior 10-13 50-55 — —

Brassaia actinophylla 10-13 50-55 10-13 50-55

Chamaedorea elegans 13-16 55-60 — —

Chamaedorea seifrizii 13-16 55-60 — —

Chrysalidocarpus lutescens 13-18 60-65 16-18 60-65

Codiaeum variegatum 16-18 60-65 16-18 60-65

Cordyline terminalis 16-18 60-65 — —

Dieffenbachia picta 16-18 60-65 — —

Dracaena deremensis 16-18 60-65 — —

Dracaena fragrans 16-18 60-65 — —

Dracaena marginata 13-18 55-65 16-18 60-65

Ficus benjamina 13-16 55-60 13-16 55-60

Ficus nitida 13-16 55-60 — —

Howeia forsteriana 10-18 50-65 10-18 50-65

Nephrolepis exaltata 16-18 60-65 — —

Peperomia bicolor 16-18 60-65 — —

Philodendron selloum 13-16 55-60 — —

Philodendron oxycardium 16-18 60-65 — —

Phoenix roebelenii 10-13 50-55 — —

Pleomele reflexa 16-18 60-65 — —

Rhapis excelsa 10-13 50-55 — —

Schefflera arboricola 10-13 50-55 10-13 50-55

Scindapsus aureus 16-18 60-65 — —

Spathiphyllum, Mauna Loa 10-13 50-55 13-16 55-60

Yucca elephantipes 10-13 50-55 10-13 50-55

1 Data are for plants in containers in the dark. Some plants stored without lights for 10 to 14 days 

will show slight to severe leaf loss and/or yellowing but will recover.

2 Blanks indicate that plant’s tolerance to shipping beyond 15 days is unknown.
727

Herbaceous Perennials

Arthur C. Cameron

Cameron is with the Department of Horticulture, 

Michigan State University, East Lansing, MI.

Introduction

Herbaceous (nonwoody) perennials are a 

diverse group of plants grown primarily for 

their ornamental value in gardens throughout 

the world. Storage of herbaceous perennial plant 

material may be required at several steps during 

the production and marketing of the final product, 

which is often a containerized flowering plant 

for retail sales. Some herbaceous perennials such 

as strawberry, rhubarb, potato, and asparagus 

are grown as food crops, but the storage of their 

underground organs is discussed separately in 

this handbook. Many herbaceous perennials have 

succulent stems and leaves that, in cold or dry 

climates, die back in fall to an overwintering 

crown or root structure, while others cease growth 

but do not go dormant in response to inclement 

weather. 

Herbaceous perennials include species in just 

about every plant family and vary greatly in 

adaptability, growth patterns, and tolerance to 

heat and cold. In fact, it is the great diversity 

that presents the most problems, including that 

of postharvest storage. Some nurseries carry 

hundreds if not thousands of species, and methods 

of production vary greatly. 

Storage of Bare-Root Crowns

Seedlings, rooted cuttings, or divisions can be 

field-planted, grown, and harvested as bare-root 

(crowns and roots with soil removed) plants in 

fall. Storage of the bare-root plants is convenient, 

since they can be trimmed, processed, and 

packaged during winter when harvest may not be 

practical because of snow, ice, or rain. Throughout 

winter and spring, bare-root plants are removed 

from storage and shipped to wholesale and retail 

nurseries.

Grower experience and research results have 

established that many hardy herbaceous perennials 

will retain excellent regrowth quality after 

several months of storage when properly packed 

to control moisture loss and stored at -2 °C (28 

°F) (Walters 1983). Mahlstede and Fletcher 

(1960) published an excellent and comprehensive 

summary of the requirements for storage of 

nursery stock (unfortunately out of print).

Field Conditions and Harvesting of BareRoot Crowns

Rain and excess moisture in the field can cause 

serious problems during storage, particularly 

if any free water from the harvested plants is 

not removed before storage. Crowns and roots 

can be difficult to dry and can quickly develop 

surface molds and rots. Many growers prefer to 

grow plants on sandy soils so that harvesting is 

interrupted as little as possible during wet periods 

(Walters 1983).

Field-grown herbaceous perennials should be 

harvested after the crowns are fully mature for 

optimum storage success. Peony, iris, mertensia, 

and poppy can be harvested even before the first 

freeze, since they tend to mature early in the fall. 

However, many other hardy herbaceous perennials 

enter dormancy later in the season or not at all 

and should be harvested as late in fall as possible 

for best storage success (Mahlstede and Fletcher 

1960, Hanchek and Cameron 1995). For most 

hardy herbaceous perennials, sugars and nutrients 

accumulate in the roots, crowns, and other 

underground organs, while leaves and aboveground tissues senesce in response to short days, 

low temperatures, or both in a process similar to 

that in potato, sugar beet, and certain other edible 

herbaceous perennials. 

If harvested before complete maturation, 

bare-root plants will have a much shorter 

storage life because of various factors such 

as incomplete carbohydrate accumulation, 
728

insufficient suberization of the roots and crowns, 

lack of overwintering buds, and ultimately the 

development of molds and rots (Hanchek and 

Cameron 1995). In practice, however, growers 

often harvest prematurely in fall, especially in 

northern regions, since snow can quickly end the 

harvest season. Growers must accept the extra 

risk of reduced storage life imposed by the earlier 

harvest. 

When possible, plants should be harvested after 

tops have at least begun to die back, often after 

the first hard freeze. Some species never really 

go dormant and do not completely die back to the 

ground except in the coldest of winters. In some 

instances, the tops can be cut with a rotary mower 

to remove excess leaves and stems before harvest 

to reduce postharvest cleaning and grading and 

potentially increase storage success. However, 

most species that do not attain full dormancy are 

difficult to store for long periods, since many have 

wounded green tops with a high respiration rate, 

fibrous roots, and insufficient carbohydrate storage 

reserves. Also, the more green tissue removed, the 

more likely that the crowns are not fully mature.

Classification of Perennials by Root 

Characteristics

Mahlstede and Fletcher (1960) suggested 

several categories of perennials based primarily 

on structural or physical characteristics of 

the overwintering underground structures. 

Considering the diversity of herbaceous 

perennials, the overwintering root structure can 

provide one additional piece of information that 

can be used to develop storage recommendations. 

Greentops are one group of herbaceous perennials 

that overwinter with at least some aboveground leaf and stem tissue remaining. Green 

tissue increases the storage difficulty for a great 

percentage of the plants in this category. Difficultto-store greentops include ajuga, arabis, alyssum, 

creeping phlox, coreopsis, dianthus, and gaillardia. 

Numerous difficult-to-store herbaceous perennials 

have fibrous roots. During the natural cycle of 

growth, it is not uncommon for plants to recycle 

fibrous roots, meaning that most small roots die 

during winter and are replaced the following 

spring as growth commences. The dead and dying 

roots do not usually create problems outdoors but 

can feed numerous surface molds while in storage. 

The molds are unsightly and can lead to loss of 

product (Hanchek et al. 1990). Fungicides are 

seldom used to control molds, in part because of 

the great diversity of plant types and sensitivity.

Some herbaceous perennials such as Dicentra 

spectabilis (bleeding hearts) have more 

specialized crowns and roots. These enlarged 

roots hold substantial food reserves and can be 

successfully stored for several months when 

harvested mature. However, when harvested 

immature, bleeding hearts are very susceptible 

to surface molds (Hanchek et al. 1990). In many 

respects, this process is similar to maturation and 

storability of potato tubers.

Postharvest Grading and Packaging

Ideally, harvested roots and crowns should be 

processed, packed, and immediately cooled 

for long-term storage. In practice, herbaceous 

perennials are often harvested in fall faster 

than they can be processed. Crowns, roots, 

and remaining above-ground tissue are rapidly 

respiring immediately after harvest because of 

wounding, and to prevent fermentation it is critical 

to keep plants cool and to provide adequate 

ventilation for the tissue. Initial plant temperature 

depends on soil and air temperatures during 

harvest. Harvested plants should be quickly cooled 

to 0 °C (32 °F) to reduce respiration and moisture 

loss, though precooling seldom occurs in practice. 

Temperatures of harvested material should be 

monitored closely with hand-held or automated 

thermometers. There is a real possibility of 

fermentation when O2

 movement is restricted 

in large piles or tightly packed crates of plants, 

particularly those with green tops or fibrous root 

systems. If temperatures rise in stacks of plant 

material, then it is critical to add refrigeration, 

improve ventilation, or both.
729

Excess green tissue is usually removed during 

grading, and plants may be cut into smaller 

divisions for propagation. The wounds caused 

during division can be a source of subsequent 

infection if not properly healed before storage. 

Even typically easy-to-store plants such as 

hosta and daylily can be lost during long-term 

storage because of fungal and bacterial wound 

infection. Conditions favoring wound healing 

could be useful for these crops after grading. No 

studies have been published on wound healing 

of harvested herbaceous perennials, but wound 

healing and suberization of potato tubers occurs 

most rapidly at 15 to18 °C (60 to 65 °F) and <90% 

RH.

Packaging depends on the intended means of 

storage. Unsealed polyethylene liners (1.5 to 3 

mils thick) are used for -2 °C (28 °F) storage. 

At below-freezing storage temperatures, these 

liners permit O2

 movement adequate to supply 

the needs of respiration and protect against water 

loss (Cameron 1988). These same liners can lead 

to fermentation and loss of product at higher 

temperatures, since they may limit air movement 

to such an extent that the supply of O2

 can not 

meet the increased demands of respiration. Many 

herbaceous perennials are packaged in multiples 

of 25 with the liners in a cardboard box ready 

for shipping later in the season. It is important to 

match box size to crown size since overpacking 

can also lead to fermentation and loss of product, 

particularly for plants with green tops, fibrous 

roots, or both. Wood fibers or other dry fillers 

(such as shredded paper) should be added inside 

the polyethylene liner to absorb free moisture 

(condensation etc.) and improve gas exchange 

inside the package.

In some cases, bare-root plants are stored in bulk 

bins (often the same as bins used for storage of 

apples). Although appropriate for some otherwise 

difficult-to-store plants, bulk bins can lead to 

problems if extra care is not taken to ensure 

that the entire contents are cooled quickly. 

Temperatures at the center of the bin need to be 

monitored closely, especially for the first 2 to 3 

weeks. Heating, fermentation, and eventually 

decay will start at the middle of the piles. Boxes, 

crates, or bins should be placed into cold storage 

in rows that maximize air movement and cooling 

rate. They can be restacked closer together after 

they reach storage temperature.

Optimum Storage Conditions

The optimum storage temperature for most 

hardy herbaceous perennials is between -2.8 and 

-2.2 °C (27 to 28 °F) (Mahlstede and Fletcher 

1960, Maqbool and Cameron 1994). At these 

temperatures, tissues are generally not frozen, 

and respiration and water activity are minimized. 

However, not all herbaceous perennials can 

withstand subfreezing temperatures, and the 

following are best stored at 0 to 2 °C (32 to 34 

°F) (Mahlstede and Fletcher 1960, Maqbool and 

Cameron 1994): aconitum, agapanthus, althaea, 

anchusa, aentranthus, helleborus, hibiscus, malva, 

shasta daisy.

Some perennials have very poor regrowth 

following storage, regardless of pretreatments and 

storage conditions, and are best overwintered as 

potted plants. These plants, such as gaillardia and 

coreopsis, can be stored as small containerized 

plants packed into polyethylene-lined boxes up 

to several months. Hibiscus, alcea, sidalcea, and 

other malvaceous plants are sensitive to low 

temperature storage, even in minimally heated 

greenhouses. Short-term storage of these genera 

should be at warmer temperatures. Herbaceous 

perennials considered very difficult to store for 

extended durations (Mahlstede and Fletcher 1960) 

are alcea rosea, anemone, anthemis, asclepias, 

clematis, coreopsis, epimedium, gaillardia, 

helleborus, hibiscus, lavender, lithospermum, 

malva, primula, sidalcea.

Problems During Storage of Bare-Root 

Perennials

Some herbaceous perennials are difficult to 

store as bare-root plants for extended periods. 

Even closely related plants can have different 

overwintering capacities. Much depends on the 

species, overall plant vigor, and size in the field 
730

before harvest. Problems encountered during 

storage of bare-root plants include development 

of rots and surface molds, desiccation, and growth 

of fragile buds after the dormancy requirement 

has been met. Each of these problems increases 

with storage duration and temperature. Hourly 

or daily temperature fluctuations can increase 

tissue desiccation, condensation on the package, 

and ultimately surface molds and rots, so it is 

important to maintain constant temperature into 

spring. 

Molds and bacteria can establish on dead roots or 

wounded tissue early during storage, especially if 

plants are not cooled rapidly. Some surface molds 

do not seriously harm the regrowth capacity of the 

crowns (Maqbool and Cameron 1994). However, 

they are unsightly and often cause rejection of a 

shipment, which can represent a substantial loss 

of revenue, considering the time and effort spent 

producing and storing the plants up to the time 

they are sold. Molds are invariably more severe at 

elevated temperatures or when there is significant 

condensation, particularly if packages are poorly 

ventilated or stacked without sufficient air 

circulation. Free water must be absorbed or it will 

increase mold and rot development. Limited trials 

with fungicides for control of surface molds have 

been inconclusive (Hanchek et al. 1990).

Bud-break can occur on many perennials such as 

asters, shasta daisies, geums, lupines, bleeding 

hearts, and astilbes kept at 1 °C (34 °F) after their 

dormancy requirement has been satisfied. New 

growth is usually etiolated and extremely fragile 

(Maqbool and Cameron 1994). Bud-break can 

occur during shipping, since lack of temperature 

control is common. Astilbes and bleeding heart, 

often shipped from the Netherlands, commonly 

have new shoot growth in the packages, 

presumably because of long shipping times at 

elevated temperatures. Storage temperatures 

below 0 °C (32 °F) completely prevented budbreak for all herbaceous perennial species tested 

(Maqbool and Cameron 1994). In some instances, 

refrigerated storage facilities do not have adequate 

cooling capacity, so temperatures can rise in 

spring as the cooling requirement increases. 

Premature bud-break can be a serious problem in 

these storage facilities.

Storage of Herbaceous Perennials in 

Plug Trays

There has been a complete transition in 

herbaceous perennial production over the past 

two decades. Most herbaceous perennials are now 

propagated, from either seeds or cuttings, in plug 

trays with anywhere from 32 to 516 small plugs 

(one plug is an individual cell with one plant) per 

30×60 cm (12×24 in) tray by using techniques 

borrowed largely from the bedding plant industry. 

The shift to plug production has been hastened 

by improved uniformity of seed-propagated 

herbaceous perennials and increased demand 

for large numbers of plants. Typically, plugs 

are finished within 6 to 12 weeks of seeding or 

placement of the cutting. Producers often sell their 

product to finishers—greenhouse growers who 

pot plugs into larger containers and grow them for 

retail sale. Traditionally, plugs are purchased and 

containerized in fall, and finished plants are sold 

the following spring or summer. 

When started from seeds or cuttings, many young 

herbaceous perennial plants require a period of 

cold, or vernalization, before they can achieve 

optimum regrowth potential (Whitman et al. 1996, 

Runkle et al. 1998). A cold period of 10 to 15 

weeks may be needed to fulfill the vernalization 

requirement for some herbaceous perennials 

(Whitman et al. 1996), though 6 to 8 weeks is 

more common (Cameron et al. 2000). The cold 

requirement is delivered to containerized plants 

in overwintering greenhouses with supplemental 

heating to prevent severe cold damage. Bedding 

plants are sometimes stored as plugs, though 

most traditional bedding plants do not have a cold 

requirement. It is becoming increasingly common 

to store plugs at low temperatures to economize 

on the amount of controlled temperature space 

required. Plugs can be stored for convenience (as 

when the finish date precedes the marketing date) 

or to provide a physiological requirement for 

subsequent flowering. Cooled plugs can be sold at 

a premium price when there is no need for further 

cooling.

Many species of perennials can be stored as plugs 

for more than 3 mo at 5 °C (41 °F), but only when 
731

provided with sufficiently intense light to perform 

photosynthesis. Photosynthesis supplements 

carbohydrate supplies, which can be depleted 

during storage, particularly in small plugs. Engle 

(1994) studied storage of plugs at -2.5 °C (28 

°F) in a manner analogous to that described 

for bare-root plants. Plug trays were packed in 

polyethylene liners and stored in the dark without 

any additional water. Many perennial species 

grown as plugs did not survive direct transfer 

from the greenhouse to subfreezing temperatures. 

However, 3 to 6 weeks of hardening at 0 or 5 °C 

(28 or 41°F) improved storage success for many. 

As for bare-root storage, plugs with significant 

green tissue were more difficult to store.

Several growers are experimenting with plug 

storage under controlled conditions, though most 

storage still takes place in minimally heated 

greenhouses. If growers rent storage facilities, 

they should ensure that refrigeration capacity is 

adequate to reduce storage temperatures to at least 

2 °C (35 °F). Insufficient cooling will increase 

respiration and plant demand for photosynthetic 

light. Lighting the plugs will improve success.

References

Cameron, A.C. 1988. Postharvest handling of 

bareroot plants: desiccation control of bare root 

stock. Perennial Plants 16:16–18.

Cameron, A.C., B. Fausey, R. Heins, and W. 

Carlson. 2000. Firing up perennials—beyond 

2000. Greenhouse Grower 18(8):74-78.

Engle, B.E. 1994. The Use of Hardening 

Temperatures and Lighting of Herbaceous Plugs 

Prior to Storage at -2.5 °C. M.S. Thesis, Michigan 

State University, East Lansing, MI.

Hanchek, A.M., and A.C. Cameron. 1995. Harvest 

date and storage quality of herbaceous perennials. 

HortScience. 30:573-576.

Hanchek, A.M., K. Everts, M. Maqbool, and A.C. 

Cameron. 1990. Storage molds of herbaceous 

perennials. J. Environ. Hort. 8(1):29–32.

Mahlstede, J.P., and W.E. Fletcher. 1960. Storage 

of Nursery Stock. Amer. Assn. Nurserymen, 

Washington, DC.

Maqbool, M., and A.C. Cameron. 1994. Regrowth 

performance of field-grown herbaceous perennials 

following bare-root storage between -10 and +5 

°C. HortScience 29:1039–1041.

Runkle, E.S., R.D. Heins, A.C. Cameron, and 

W.H. Carlson. 1998. Flowering of Leucanthemum

× superbum ‘Snowcap’ in response to photoperiod 

and cold treatment. HortScience 33:1003–1006.

Walters, J. 1983. Overwintering in the field 

and in storage. In E.M. Smith, and S.M. Still, 

eds., Proceedings of the Herbaceous Perennial 

Symposium, July 1983, Columbus, OH. Ohio 

Cooperative Extension Service Bull. no. 717, Ohio 

State University, Columbus, OH.

Whitman, C.M., R.D. Heins, A.C. Cameron, and 

W.H. Carlson. 1996. Cold treatment, photoperiod, 

and forcing temperature influence flowering of 

Lavandula angustifolia. HortScience 31(7):1150–

1153.
732

Orchids

Yin-Tung Wang

Wang is with the Agricultural Experiment Station, 

Department of Horticultural Sciences, Texas A&M 

University, Weslaco, TX.

Introduction

For years, potted orchids were produced 

mainly for hobbyists. They are usually shipped 

in containers and arrive in buyers’ hands by 

overnight delivery or within a few days. Many 

orchid growers do not ship orchids during winter 

months to avoid chilling or freezing injury to the 

plants. However, during the past decade, there 

has been a tremendous worldwide boom in orchid 

production for sale as potted blooming plants 

for the public, particularly the Phalaenopsis and 

Dendrobium orchids. Potted, blooming orchids 

represent a $100 million industry in the United 

States alone (NASS 2001). However, for the most 

part, research in proper postharvest handling 

of orchids has lagged behind the increase in 

production and demand.

Ethylene Sensitivity

Orchid flowers are extremely sensitive to ethylene, 

even at very low levels (Davison 1949, Beyer 

1976, Goh et al. 1985). Pollination and removal 

of pollen caps (emasculation) trigger ethylene 

production by flowers and result in rapid wilting. 

Blooming orchids should be handled carefully so 

that accidental pollination and emasculation do 

not occur. Accelerated flower wilting as a result 

of ethylene evolution following pollination in 

Cymbidium, Dortitaenopsis, Dendrobium, and 

Phalaenopsis orchids is induced by a loss of water 

from cells of the upper layer of the petals, leading 

to their in-folding and water-soaked appearance 

(Lee and Lin 1992, Porat et. al. 1994). Treating 

orchid flowers with the ethylene biosynthesis 

inhibitor aminooxyacetic acid (AOA) did not alter 

their sensitivity to ethylene. Research also showed 

that pulsing excised Dendrobium flowers with 0.5 

mM AOA for 24 h before exposing them to 0.2 μL 

L-1 ethylene did not prolong their life (Wang and 

Wang 2000); all treated flowers wilted within 3 

days after exposure. Thus, AOA has no effect on 

longevity when wilting is triggered by exogenous 

ethylene.

Treatments for Extending Shelf-Life

It was found that shelf-life of Oncidium Goldiana 

cut sprays increased after pulsing with silver 

nitrate for 30 min (Ong and Lim 1983). Pulsing 

Arranda cut inflorescences for a short 10 min 

with a 4 mM solution of STS prolonged their 

display-life (Hew et al. 1987). Exposing excised 

Dendrobium and Phalaenopsis flowers to 0.1 μL 

L-1 1-methylcyclopropene (1-MCP, an ethylene 

action ihibitor) for 12 h, or pulsing them with 0.5 

mM silver thiosulfate (STS, an ethylene inhibitor) 

for 24 h completely blocked the deleterious effect 

of ethylene (Wang and Wang 2000). Phalaenopsis

flowers that were treated with 0.1 to 0.4 μL L-1

of 1-MCP are protected against ethylene as high 

as 10 μL L-1. However, the protective effect of 

1-MCP lasts for no longer than 7 days at room 

temperature. Commercially, cut Phalaenopsis

inflorescences are pulsed with 0.5 mM STS 

immediately following cutting.

When used at 50 to 100 mg L-1, 

8-hydroxiquinoline sulfate (8-HQS) extended 

shelf-life of Dendrobium Pompadour cut flowers 

(Kesta and Amutiratana 1986). Conflicting results 

were reported on the effect of sucrose in keeping 

solutions as a carbon source for extending vase 

life of cut orchid flowers. 

Sprays of tropical orchids should be stored and 

transported at 12 to 18 °C (54 to 64 °F) (Akamine 

1976), whereas flowers of temperate orchids such 

as Cymbidium may be stored at temperatures as 

low as 5 °C (41 °F) (Sheehan 1954).
733

Optimum Storage Conditions

Minimal research has been conducted on optimum 

orchid storage conditions. In one study (Wang 

1997a), bare-root Phalaenopsis plants were 

packed in boxes and subjected to temperatures of 

15, 20, 25, or 30 °C (59, 68, 77, or 86 °F) for 4, 

7, or 14 days. Weight loss from plants increased 

with increasing temperature and storage duration. 

Symptoms of chilling injury were inversely related 

to 15 and 20 °C storage temperatures. Chilling 

injury became more severe as storage duration 

increased. Plants had little or no chilling injury at 

25 or 30 °C, regardless of the duration. Leaf loss 

was most severe on plants stored at 15 °C for 7 

or 14 days or 30 °C for 14 days. Plants that have 

severe leaf loss after storing at 30 °C have delayed 

spiking and flowering.

Preconditioning greenhouse-grown potted 

Phalaenopsis plants at 25 °C (77 °F ) for 10 

days, followed by another 10 days at 20 °C (68 

°F), reduced severity of chilling injury after 

storage at 15 °C (59 °F) for 2 weeks. Therefore, 

Phalaenopsis orchids harvested during the warm 

period of the year should be held above 20 °C (68 

°F), and preferably closer to 25 °C (77 °F), during 

shipping. Under such conditions, plants can lose 

as much as 20% of their fresh weight at harvest 

without subsequent performance being adversely 

affected. While most Phalaenopsis species and 

hybrids need relatively cool air to initiate the 

flowering process, plants do not respond to cool 

air while being shipped in the absence of light 

(Wang 1995).

Although prolonged duration in complete darkness 

is not recommended for keeping plants in bloom 

(Wang and Blessington 1989), Phalaenopsis

orchids tolerate low light levels once they have 

started flowering. One study show that exposing 

them to irradiance levels between 10 and 50 

μmol m-2 sec-1 for 12 h daily produced orchids 

with similar longevity (individual flowers lasting 

over 120 days) and flower size (Wang 1997b). 

Therefore, most retail stores have adequate light 

levels to maintain blooming Phalaenopsis while 

they are being marketed.

Shipping Information

Because of quarantine regulations, internationally 

shipped orchids are often removed from their 

potting medium. The bare-root plants are allowed 

to dehydrate slightly before packing. This is 

done for several reasons. Slight dehydration 

allows for packing more plants per box, avoids 

breaking leaves, and reduces the chances of 

moisture buildup to weaken shipping boxes. Dryer 

plants also reduce incidence of rotting before 

boxes are opened. Plants are usually packed in 

layers alternating with shredded paper or other 

material. Often, plants are individually wrapped in 

newspaper, particularly those that have developed 

inflorescences.

Millions of bare-root Phalaenopsis orchids are 

shipped domestically and internationally each 

year. After the orchids are planted in pots and 

placed on greenhouse benches, yellow spots 

occasionally develop on either side of the midrib near the base of leaves due to chilling injury. 

Irregular yellow blotches also occur on other parts 

of leaf blades. Other times, leaves turn yellow 

and fall off, resulting in weak plants that do not 

produce flowers.

References

Akamine, E.K. 1976. Postharvest handling 

of tropical ornamental cut crops in Hawaii. 

HortScience 11:125-126.

Beyer, E.M. 1976. A potent inhibitor of ethylene 

action in plants. Plant Physiol. 58:268-271.

Davison, O.W. 1949. Effect of ethylene on orchid 

flowers. Proc. Amer Soc Hort Sci. 53:440-446.

Hew, C.S., K.H. Wee, and F.Y. Lee. 1987. Factors 

affecting the longevity of cut Aranda flowers. Acta 

Hort. 205:195-202.

Goh, C.J., A.H. Halevy, R. Engel, and A.M. 

Kofranek. 1985. Ethylene evolution and 

sensitivity in cut orchid flowers. Sci. Hort. 26:57-

67.
734

Kesta, S., and D. Amutiratana. 1986. Effect of 

sucrose, silver nitrate, and 8-hudroxyquinoline 

sulfate on postharvest behavior of Dendrobium

Pompadour flowers. In Proceedings of the 6th 

ASEAN Orchid Congress, Bangkok, Thailand, pp. 

124-129. Association of Southeast Asian Nations, 

Bangkok, Thailand.

Lee, N., and Y.S. Lin. 1992. Respiration of 

Phalaenopsis flowers. J. Chinese Soc. Hort. Sci. 

38:228-240. 

NASS [USDA National Agricultural Statistics 

Service]. 2001. Floriculture Crops, 2000 

Summary. National Agricultural Statistics Service, 

Washington, DC. 

Ong, H.T., and L.L. Lim. 1983. Use of silver 

nitrate and citric acid to improve shelf-life of 

Oncidium Golden Showers flowers. Orchid Rev. 

90:264-266.

Porat, P., A. Borochov, H. Halevy, and S.D. 

O’Neill. 1994. Pollination-induced senescence of 

Phalaenopsis petals. Plant Growth Regul. 15:129-

136.

Sheehan, T.J. 1954. Orchid flower storage. Amer. 

Orchid Soc. Bul. 23:579-584. 

Wang, Y.T. 1995. Phalaenopsis orchid light 

requirement during the induction of spiking. 

HortScience 30:59-61.

Wang, Y.T. 1997a. Effect of postharvest 

temperature and storage duration on growth 

and flowering of the Phalaenopsis orchids. 

HortScience 32:517.

Wang, Y.T. 1997b. Phalaenopsis light 

requirements and scheduling of flowering. Orchids 

66:934-939.

Wang, Y.T., and T.M. Blessington. 1989. Darkstorage temperature and duration influences 

flowering and quality retention of hibiscus. 

HortScience 24:646-647. 

Wang, M.K., and Y.T. Wang. 2000. 1-MCP and 

STS counteract ethylene effects on cut orchid 

flowers. HortScience 35(3):349.
735

Seeds and Pollen

Chris Walters and Leigh Towill

Walters and Towill are with Preservation of Plant 

Germplasm Research, National Center for Genetic 

Resources Preservation, Agricultural Research 

Service, U.S. Department of Agriculture, Fort 

Collins, CO.

Introduction

Seeds of all of the species covered in this handbook must be stored for some length of time 

after harvest. Some seeds are used as food (for 

example, cereals and legumes) and stored before 

consumption, while others are stored to maintain 

viability and used to produce the next season’s crop. 

This section describes basic procedures to maintain 

seed and pollen viability. More detailed descriptions 

or procedures to maintain seed viability for 

extended periods (for example, for genetic stocks) 

are published in Agriculture Handbook 506, 

Principles and Practices of Seed Storage (Justice 

and Bass 1978) or review articles (Priestley 1986, 

Hong and Ellis 1996, Walters 1998a).

Classification of Seed Storage Behavior

Mature seeds generally have higher tolerance for 

low moisture levels or temperatures than fresh 

fruits, vegetables, or flowers. They acquire this 

tolerance during maturation on the parent plant, 

presumably as a strategy to survive adverse climatic 

conditions such as drought and winter. The degree 

of tolerance varies among species, but three 

general categories exist: orthodox, recalcitrant, and 

intermediate. 

Orthodox seeds are produced by most annual or 

biennial crops and horticultural species. Some 

examples are grains, pulse crops, vegetables, floral 

crops, and temperate tree fruit, as well as many 

temperate forest tree and shrub species. Orthodox 

seeds can survive complete water removal and 

can be easily stored for many years by drying and 

cooling. 

Recalcitrant seeds are produced by herbaceous 

plants from aquatic habitats (for example, 

wildrice, watercress, and wasabi), perennials 

from tropical areas (examples include avocado, 

mango, coconut, cocoa, and jackfruit), and some 

deciduous forest trees from temperate areas (such 

as oak, chestnut, buckeye, and silver and sycamore 

maple). As the name implies, recalcitrant seeds are 

difficult to store and have shelf-lives usually <1 

year unless they are cryopreserved. 

Intermediate seeds are produced by perennials 

of tropical and subtropical origin (such as coffee, 

citrus, macadamia, and papaya) and by some 

tree nut species (such as walnut, hickory, pecan, 

hazelnut, and pistachio). (Hazelnut and pistachio 

may belong to the recalcitrant category.) With 

proper handling and excellent quality seeds, 

the viability of seeds with intermediate storage 

behavior can be maintained for a few years. These 

seeds can be stored over a single winter with a 

stratification treatment such as damp media at 

5 °C (41 °F).

The best way to identify whether a seed is 

recalcitrant or not is to monitor survival while 

drying (Hong and Ellis 1996). Seeds that are 

recalcitrant lose viability within minutes of 

drying below 85 to 90% RH. Intermediate seeds 

lose viability within days of drying below 20% 

RH. Seeds that are orthodox can survive many 

months or even years when dried to 5% RH. The 

ability of orthodox seeds to survive drying is 

acquired during development, so seeds harvested 

prematurely will appear to be recalcitrant 

(Vertucci and Farrant 1995). Mature seeds must 

be dried sufficiently rapidly—within a few 

days—to avoid deterioration at intermediate water 

contents (Pammenter and Berjak 1999). Often 

drying experiments are inconvenient to perform, 

and growers resort to anecdotal information or 

guidelines (table 1) to identify storage behavior of 

their seeds. Guidelines exist to help identify seed 

storage behavior, but there are no hard and fast 

rules. A compendium listing storage guidelines for 

over 7,000 species is now available (Hong et al. 

1996). Also, useful information on woody species 

grown in the United States can be gleaned from 

Agricultural Handbook 450 (Schopmeyer 1974).
736

Table 1. Guidelines to identify storage behavior of seeds

Trait Guideline Some exceptions

Growth habit Most herbaceous plants produce orthodox seeds Aquatic species

Habitat Many aquatic species, tropical rainforest species, Most native Hawaiian species, 

and temperate climax forest species produce temperate conifers, some

recalcitrant seeds maples

Water content Most orthodox seeds dry naturally on the All immature seeds, 

at harvest parent plant Solanaceae, Cucurbitae

 

Seed size Recalcitrant seeds are often large Some aquatic species, 

Rutaceae, some Rubiaceae

 

Desiccation Orthodox seeds can survive complete water loss; Orthodox seeds dried very

sensitivity recalcitrant seeds cannot slowly (for >2 weeks) can be 

severely damaged

Seed Storage Behavior and General 

Storage Principles

Because they are sensitive to drying, recalcitrant 

seeds must be stored at 92 to 98% RH. The best 

storage temperature depends on the chilling 

sensitivity of the species. Seeds from many 

tropical fruits (mango, avocado, cocoa, jackfruit) 

are sensitive to chilling and should be stored at 

≥15 °C (59 °F). These seeds have the shortest 

potential shelf-life, remaining viable for 2 weeks 

to 3 mo. Seeds produced from temperate species 

such as oaks, buckeye, or chestnut can survive 

for 0.5 to possibly 2 years by storing them at 2 

to 5 °C (36 to 41 °F). Microbial contamination 

is always a problem at high RH, and seeds often 

survive longer if a fungicide is applied. Storage 

in damp peatmoss is often beneficial. The RH 

required for safe storage of recalcitrant seeds often 

allows seeds to germinate. Once this has occurred, 

procedures for storage of seedlings should be 

adopted. 

Seeds with intermediate storage behavior are 

more amenable to drying and consequently can 

be preserved for longer periods than recalcitrant 

seeds. RH of 40 to 60% appears to provide 

maximum longevity. Intermediate seeds survive 1 

to 6 mo if stored at 25 °C (77 °F) and 2 to 5 years 

if stored at 5 °C (41 °F). These seeds rapidly lose 

viability if frozen (stored at -18 °C [0 °F]).

Seeds that exhibit orthodox behavior are easily 

stored by drying and cooling. The extent to which 

drying and cooling extends shelf-life is best 

described by Harrington’s “Thumb rules” which 

state that the life of a seed is doubled for every 1% 

decrease in water content or every 5 °C (41 °F) 

decrease in temperature (Harrington 1963, Justice 

and Bass 1978). The “100s Rule” states that 

adequate longevity for commercial seed storage 

purposes (<5 yr) can be achieved by ensuring that 

the sum of the RH and temperature in °F during 

storage does not exceed 100. 

These rules were developed as guidelines for 

commercial seed storage. They are not valid for 

extremely dry conditions, and their applicability 

at extremely cold temperatures has not been 

adequately tested. 

A relatively new rule is that seeds store optimally 

at 15 to 25% RH. Storing seeds with RH <15% 

will not increase shelf-life and may actually 
737

accelerate deterioration (Walters 1998b). Seed 

water content achieved at 15 to 25% RH varies 

from about 2 to 10%, depending on seed lipid 

composition and storage temperature. 

Storage at -18 °C (0 °F) (the temperature of a 

standard freezer) enhances shelf-life 4- to 5-fold 

over that of seeds stored at 5 °C (41 °F) (Walters 

1998a). Storage temperature should be dictated by 

the required longevity for the seed: Storage at 15 

°C (59 °F) may be adequate for most species to 

maintain quality for 3 to 5 years; longevities of 5 

to 10 years may require refrigeration at 5 °C (41 

°F); while storage at -18°C (0 °F) is required if 

seeds are to be maintained for 15 to 20 years.

Seed Quality Factors Influencing 

Longevity of Orthodox Seeds

Harrington’s rules are approximations and give 

relative, rather than absolute, longevities. Absolute 

longevity depends on initial seed quality. Seed 

quality is controlled by genetic and environmental 

factors such as seed structure and composition, 

maturity, dormancy, purity, mechanical damage, 

and initial viability and vigor (Justice and Bass 

1978). Field conditions during seed development 

and harvest and postharvest treatment, such as 

drying temperature, cleaning procedures, and 

priming, affect overall seed quality and hence 

seed longevity (Walters 1998a). Infestations of 

storage fungi, insects, and rodents significantly 

curtail seed quality and lifespan. Reducing RH or 

temperature can ameliorate the deleterious effects 

of infestations. For example, insect activity is 

retarded at <10 °C (<50 °F) and almost ceases at 

0 °C (32 °F). Exposure of seeds to -18 °C (0 °F) 

kills most insects and their eggs.

Numerous factors during seed development and 

maturation affect the potential longevity of seeds. 

Seeds harvested prematurely may have shorter 

shelf-life than seeds harvested fully mature 

(defined as having completed maturation drying). 

Shelf-life may be shorter because immature 

embryos are not fully tolerant of desiccation and 

are damaged when dried, or because maximum 

seed quality is acquired during the final stages 

of development on the parent plant. The high 

temperatures, >40 °C (>104 °F), frequently 

used to rapidly dry immature seeds can severely 

damage them. Some drying procedures call for 

exposure to 35 °C (95 °F) for several days. This 

treatment can initiate seed aging processes. An 

initial treatment that dries immature seeds slowly 

enhances seed desiccation tolerance (Vertucci 

and Farrant 1995, Pammenter and Berjak 1999) 

and potentially seed longevity. If seeds must be 

harvested prematurely, holding them for 2 to 5 

days in their fruiting structures can simulate slow 

drying. Once immature seeds receive a slight and 

slow desiccation treatment, they can be threshed 

with less damage. 

While a brief period of slow drying of <5 days 

at 20 °C (68 °F) enhances quality of prematurely 

harvested orthodox seeds, prolonged exposure 

of fully mature seeds to RH >75% promotes 

deterioration, encourages microbial infection, 

and at RH >95% allows precocious germination 

(Pammenter and Berjak 1999). Seeds may 

be exposed to high RH in the field if harvest 

is delayed by rain or if, after harvest, there is 

inadequate RH control. Generally, exposure of 

seeds to high RH first results in a reduction of seed 

vigor (slower germination) and then a reduction 

in germination percentage. The higher the RH or 

temperature, the faster seeds deteriorate (refer to 

Harrington’s rules). Germination percentages of 

vegetables and grains may decline to 0% within 

3 to 6 mo of storage at 20 °C (68 °F) with 90% 

RH. It is generally assumed that reduction in 

seed quality leads to a reduction in shelf-life once 

seeds are placed under more favorable storage 

conditions. Preharvest and postharvest treatments 

may explain the variability in longevity among 

seed lots of the same cultivar (Walters 1998a). 

Seed priming is a procedure used to accelerate 

germination rates of planted seeds. Seeds are 

usually held at <10 °C (<50 °F) with water 

potentials close to -1 MPa for a few days. While 

this treatment gives the appearance of improving 

seed vigor—seeds germinate faster or more 

uniformly—it exposes mature seeds to high RH 

and likely reduces their shelf-life if they are 

redried and then stored (Walters 1998a). 
738

Anecdotal evidence suggests that seeds harvested 

from the wild have a shorter shelf-life than 

seeds harvested from cultivated plants. There 

are numerous possible explanations. Through 

agricultural practices, humans may have selected 

for seeds with superior quality. Cultivated plants 

may have received optimum growth conditions—

irrigation, fertility, and pest management—and 

are therefore more robust. Seeds collected from 

the wild are often highly immature because 

maturation of uncultivated seeds is less uniform 

and mature fruits often dehisce. 

Seed dormancy is often linked to seed longevity. 

Seeds with hard seed coats store longer (Justice 

and Bass 1978), probably because the seed 

coats restrict the movement of air and water. 

Seeds of Leguminosae and Malvaceae have a 

tendency toward hard-seededness. The linkage 

between embryo dormancy and longevity is 

difficult to verify since seed dormancy confounds 

measurements of viability for longevity tests. 

Clearly, dormant seeds survive longer in the 

soil, but this is more likely because they fail to 

germinate under moist conditions than because 

they have more efficient mechanisms to survive in 

the dry state. 

Given similar storage and harvest conditions, 

seeds from orthodox species exhibit different 

inherent longevities. For example, lettuce and 

onion seeds are fairly short-lived, whereas tomato 

and barley seeds show substantial longevities. 

Generally, orthodox species from Leguminosae 

and Malvaceae are long lived, while many species 

in Asteraceae or Umbelliferae produce short-lived 

seeds. Longevity of seeds from annual crops is 

better described than that from herbaceous or 

woody perennials. Sample longevities of different 

seed species are listed in table 2. More exhaustive 

species lists and detailed storage conditions can 

be found in Justice and Bass (1978) and Priestley 

(1986). 
739

Table 2. Approximate longevity for various seed storage behaviors and seed species

Storage type Species Optimum Optimum moisture Time to 50% loss

RH content of seed1 in viability2

 % g H2O per g dw

Recalcitrant Tea (Camellia sinensis) 95 to 98 0.6 to 0.8 2 weeks to 2 months 

Buckeye (Aesculus 

hippocastanum) 95 to 98 0.5 to 0.7 6 to 8 months

Trifoliate orange 

 (Poncirus trifoliata) 90 to 95 0.5 to 0.7 6 to 14 months

Wildrice (Zizania 

palustris) 90 to 95 0.35 to 0.45 9 to 18 months

Intermediate Coffee (Coffea 40 to 60 0.10 to 0.13 2 to 4 years at 5 °C; 

arabica) damage at <0 °C

Papaya (Carica 40 to 60 0.09 to 0.11 3 to 6 years at 5 °C;

papaya) damage at <0 °C.

Hickory (Carya spp.) 80 to 90 3 to 5 years

Citrus (Citrus limon) 6 to 18 months

Orthodox Lettuce (Lactuca 20 0.04 to 0.05 >4 years at 5 °C,

sativa) >20 years at -18 °C

Onion (Allium cepa) 20 0.06 to 0.08 >4 years at 5 °C,

 >20 years at -18 °C

Peanut (Arachis 

hypogeae) 20 0.04 to 0.05 >4 years at 5 °C,

 >20 years at -18 °C

Soybean (Glycine max) 20 0.07 to 0.08 >5 years at 5 °C,

 >20 years at -18 °C

Sunflower (Helianthus

annuus) 20 0.03 to 0.04 >6 years at 5 °C,

 >25 years at -18 °C

Corn (Zea mays) 20 0.07 to 0.09 >8 years at 5 °C,

 >25 years at -18 °C

Chickpea (Cicer 

arietinum) 20 0.07 to 0.08 >8 years at 5 °C,

 >25 years at -18 °C

Pea (Pisum sativum) 20 0.09 to 0.12 >10 years at 5 °C,

 >25 years at -18 °C

Barley (Hordeum 

vulgare) 20 0.09 to 0.12 >10 years at 5C,

 >25 years at-18C

Tomato (Lycopersicum

esculentum) 20 0.05 to 0.06 >12 years at 5 °C,

 >25 years at -18 °C
740

1

 For orthodox seeds, the lower value in the water content range is more appropriate for 5 °C 

(41 °F) storage, and the higher value approximates optimum water contents for constant 

storage at -18 °C (0 °F). Water content on a percentage dry weight or fresh weight basis are 

often used in the seed industry. To calculate percentage water content on a dry weight basis, 

multiply water contents in the table by 100. 

2

 Values for approximate longevity are given for 5 °C (41 °F) storage for all species except 

Camellia sinensis, which is chilling sensitive and should be stored at 15 °C (59 °F). 

While species have characteristic longevities, 

variability among cultivars and among lots of the 

same cultivar may be so great that it precludes 

prediction of shelf-life. For example, germination 

of sesame seeds with initial germination rates 

of 70 to 80% ranged from 0 to 80% after 18 

years storage at the National Center for Genetic 

Resources Preservation. Similar results were 

obtained for potato, pepper, sorghum, onion, and 

tomato: initial rates of germination from 90 to 

100% and rates after 18 years of 0 to 100%. The 

source of this variability is unknown. Suppliers 

should monitor seed viability periodically to 

ensure quality. 

Additional Storage Factors Affecting 

Shelf-Life

In addition to RH and temperature, the gas 

composition of the storage environment may be 

important, but evidence for a clear relationship 

is lacking. Low O2

 should enhance longevity 

since aging reactions are either oxidative or 

linked to respiration. Storage under higher O2

tensions causes rapid deterioration (Ohlrogge 

and Kernan 1982), but the converse has not been 

demonstrated. Freeze-drying or vacuum packaging 

may be beneficial (Woodstock et al. 1976, Justice 

and Bass 1978, Ellis et al. 1993), but it is not 

clear whether these treatments control moisture 

level or O2

 level. Reducing the RH is a far more 

effective method of limiting respiratory processes 

than lowering O2

. The time and expense of using 

low O2

 is probably not worthwhile for short-term 

storage of orthodox seeds.

Exposure to light, even at low intensities, appears 

to damage dry seeds. Seeds intended for nursery 

stock should not be dried under the sun and 

should not be stored in a lighted room without a 

protective container. 

Procedures to Dry Orthodox Seeds

At storage temperatures >0 °C (32 °F), seed water 

content or RH are the most important factors 

determining seed longevity. Seed producers must 

consider two factors when drying seeds: the rate 

at which seeds are dried and the level to which 

they are dried. With the exception of immature 

seeds that benefit from a short, slow, drying 

period, orthodox seeds with high water content, 

>18%, should be dried to about 12% as rapidly 

as possible. Temperatures >35 °C (95 °F) can be 

damaging, so lower temperatures and high air flow 

are recommended. Seeds should be spread out in 

a thin layer to allow air to circulate through the 

seed mass and gently mixed daily to ensure even 

drying. 

In temperate or cold climates, no special storage 

conditions are required if seeds are to be planted 

the next season, that is, within 6 mo. Storage of 

dried seeds in open bins with no RH control is 

called “open storage,” and the water content of 

the seed will fluctuate according to the RH and 

temperature in the warehouse. Open storage is not 

recommended in warm humid regions or if seeds 

will be planted several years after harvest.

The water content of seeds must be controlled 

if seeds are to retain high quality for >2 years. 

This is easily accomplished by placing seeds 

at a known RH once they have been dried to 

a safe water content of <12%. There are two 

strategies: Dried seeds can be packed in moisturepermeable bags and stored in rooms where the 

RH is controlled, or they can be equilibrated at 
741

the desired RH and then packaged in moistureimpermeable containers (for example, glass, 

foil laminate, or aluminum cans). The RH in the 

moisture-proof containers is a function of the 

water content of the seeds and the temperature at 

which they are stored. 

A RH of 20 to 25% produces optimal seed water 

content for storage of most orthodox species 

(Walters 1998a,b). The equilibrium water content 

varies among seeds according to lipid composition 

and storage temperature. For example, peanut 

seeds with 45% lipid will contain 2 to 5% water, 

while pea seeds with 2% lipid will contain 8 to 

12% water. When RH during storage is controlled, 

water content of seeds need not be monitored. 

The simplicity of this method may cause some 

producers to use it exclusively; however, constant 

dehumidification, especially in conjunction with 

refrigeration, may be prohibitively expensive 

(Walters-Vertucci and Roos 1996). Depending on 

volume of seeds handled and risk of mechanical 

failure, it may be safer and more cost-effective to 

store seeds in moisture-proof containers.

When seed producers opt to store seeds 

in moisture-proof bags, they increase the 

complexity of water content adjustments but 

also the flexibility in choosing drying and 

storage conditions. The interested reader may 

refer to more in-depth literature on water 

sorption isotherms of seeds (Walters 1998a,b). 

The guiding principle is that 20 to 25% RH 

provides optimum storage. However, since 

RH is a function of temperature, both the 

drying and storage temperature need to be 

considered. Generally, seeds are dried at ambient 

temperatures or slightly higher to speed up the 

drying process and to reduce refrigeration costs 

(Walters-Vertucci and Roos 1996). The greater 

the temperature differences between drying and 

storage temperatures, the higher the allowable 

RH for drying. For instance, if seeds are dried at 

25 °C (77 °F) and stored at 15, 5, or -18 °C (59, 

41, or 0 °F), they should be equilibrated to about 

30, 38, or 45% RH, respectively. Table 3 gives a 

brief summary of recommended drying conditions 

for given storage temperatures. To date, these 

guidelines have proven reliable for all species 

tested. 

Table 3. Recommended drying conditions for seeds subsequently stored in 

moisture-proof containers at various temperatures*

 Drying RH for storage at—

Drying temperature 15 °C (59 °F) 5 °C (41 °F) -18 °C (0 °F)

°C %

25 30 38 45

15 22 30 38

 5 15† 22 30

*The given drying temperature and RH combinations give storage RH of 20-25% at the 

indicated storage temperature.

†

Drying seeds at temperatures less than the storage temperature is not cost effective and 

therefore is strongly discouraged; dehumidification is more difficult at lower temperatures, 

and the refrigeration costs used during drying might be more effectively spent during storage.
742

Cost-Benefit Analyses

Drying and storage conditions used by seed 

producers and suppliers largely depend on a 

balance between the cost of seed preservation and 

the necessity to maintain high quality seeds for 

a certain period. The three main questions that 

should be considered when deciding appropriate 

storage conditions are—

•	 What is the required longevity of the seed?

•	 What is the volume of seed to be produced, 

processed, and stored?

•	 Are the resources available? 

The answer to the first question is the major 

determinant of seed storage procedures.

Maintaining seed quality for ≥5 years usually 

requires storage at ≤5 °C (41 °F). Refrigeration is 

expensive, but only moderately so if the quality 

of the seed would be destroyed by substandard 

storage conditions. Generally, dehumidification 

requires less energy than refrigeration, making 

controlled RH environments a less expensive 

alternative to refrigeration for the short term 

(Walters-Vertucci and Roos 1996). However, 

because there is a limit to beneficial effects of 

drying at 20 to 25% RH, extended longevity can 

only be achieved through refrigeration (Walters 

1998b). Moisture-proof packaging may be 

expensive, but it may be more cost-effective over 

the long term than constant dehumidification in a 

warm, humid climate. Seeds equilibrate faster at 

ambient temperatures, allowing more seeds to be 

processed in a shorter period if labor is available 

to package seeds for low-temperature storage. 

Alternatively, seeds can be equilibrated at lower 

temperatures, thereby increasing energy costs 

but allowing a longer processing period without 

compromising quality.

Assessing Changes in Seed Quality

No storage procedure guarantees that seeds will 

remain viable forever. Seeds eventually lose vigor 

and then viability with time. The extent to which 

aging occurs can be monitored with initial and 

subsequent germination assays. Different seed 

species have different germination requirements 

that are cataloged in Rule Books published by 

the Association of Official Seed Analysts (1999). 

Assessments of seed vigor are more difficult than 

assessments of germination percentage but usually 

provide an early warning of deterioration. 

Pollen

Pollen can be stored for facilitating seed 

production and breeding. Pollen from some 

families is desiccation-tolerant—Liliaceae and 

Solanaceae, for example—and fairly easy to 

store, but pollen from other families is desiccation 

sensitive and is more difficult to store—for 

example, Cucurbitaceae, Gramineae (Poaceae), 

and Compositae (Asteraceae) (Hanna and Towill 

1995, Hoekstra 1995, Barnabas and Kovacs 1997). 

As with seed, the major factors affecting longevity 

are water content, storage temperature, and storage 

atmosphere. Desiccation-tolerant pollens are best 

stored at moisture levels of ≤10%, obtained by 

either air-drying or by equilibration at known RH. 

Greater longevities occur at lower temperatures, 

with more than 2 years often feasible with -18 °C 

(0 °F) storage. Cryogenic storage at -80 to -196 °C 

(-112 to -320 °F) greatly increases longevity.

Storage in a vacuum or with a N2

 atmosphere also 

enhances longevity. 

Storage of desiccation-sensitive pollen is more 

problematic, but some can be desiccated to 10 to 

15%. Reports of storage at 4 °C (39 °F) and -20 

°C (-4 °F) are sparse, and the expected longevities 

are short: from hours to a few days. If the pollen is 

not over-dried, cryogenic storage is possible.

References

Association of Official Seed Analysts. 1999. Rules 

for Testing Seeds. Association of Official Seed 

Analysts, Lincoln, NE.
743

Barnabas, B., and G. Kovacs. 1997. Storage of 

pollen. In K.R. Shivanna and V.K. Sawhney, eds., 

Pollen Biotechnology for Crop Production and 

Improvement, pp. 293-314. Cambridge University 

Press,Cambridge, U.K.

Ellis, R.H, T.D. Hong, M.C. Martin, et al. 1993. 

The long term storage of seeds of seventeen 

crucifers at very low moisture contents. Plant Var. 

Seeds 6: 75-81.

Hanna W.W., and L.E. Towill. 1995. Long-term 

pollen storage. In J. Janick, ed., Plant Breeding 

Reviews, vol. 13, pp. 179-207. Wiley & Sons, 

New York, NY.

Harrington, J.F. 1963. Practical advice and 

instructions on seed storage. Proc. Intl. Seed Test. 

Assoc. 28:989-994.

Hoekstra, F.A. 1995. Collecting pollen for genetic 

resources conservation. In L. Guarino, V.R. 

Rao, and R. Reid, eds., Collecting Plant Genetic 

Diversity: Technical Guidelines, pp. 527-550. 

CAB Intl., Oxfordshire, U.K.

Hong, T.D., and R.H. Ellis. 1996. A protocol to 

determine seed storage behaviour. IPGRI Tech. 

Bull. 1, International Plant Genetic Resources 

Institute, Rome, Italy.

Hong, T.D., S. Linnington, and R.H. Ellis. 

1996. Seed Storage Behaviour: A Compendium. 

Handbooks for Genebanks no. 4, International 

Plant Genetic Resources Institute, Rome, Italy.

Justice, O.L., and and L.N. Bass. 1978. Principles 

and Practices of Seed Storage. Agriculture 

Handbook 506, U.S. Department of Agriculture, 

Washington, DC.

Ohlrogge, J.B., and T.P. Kernan. 1982. Oxygendependent aging of seeds. Plant Physiol. 70: 791-

794.

Pammenter, N.W., and P. Berjak. 1999. A review 

of recalcitrant seed physiology in relation to 

desiccation-tolerance mechanisms. Seed Sci. Res. 

9:13-37.

Priestley, D.A. 1986. Seed Aging: Implications for 

Seed Storage and Persistance in the Soil. Cornell 

University Press. Ithaca, NY.

Schopmeyer, C.S. 1974. Seeds of Woody Plants in 

the United States. Agriculture Handbook 450, U.S. 

Department of Agriculture, Washington, DC.

Vertucci, C.W., and J.M. Farrant. 1995. 

Acquisition and loss of desiccation tolerance. In J. 

Kigel and G. Galili, eds., Seed Development and 

Germination, pp. 237-271. Marcel Dekker, New 

York, NY.

Walters, C. 1998a. Understanding the mechanisms 

and kinetics of seed aging. Seed Sci. Res. 8:223-

244.

Walters, C., ed., Recent Advances on Ultra-dry 

Research. In Seed Science Research, vol. 8, 

Supplement 1, International Society for Seed 

Science, Cambridge UniversityPress, Cambridge, 

U.K.

Walters-Vertucci, C., and E.E. Roos. 1996. Seed 

moisture, seed drying and energy costs of a seed 

bank. In Report of the 50th Annual Corn and 

Sorgham Research Conference, pp. 243-255. 

American Seed Trade Association, Alexandria, 

VA.

Woodstock, L.W., J. Simkin, and E. Schroeder. 

1976. Freeze drying to improve seed storability. 

Seed Sci. Technol. 4: 301-311.
744

Almond

John M. Labavitch

Labavitch is with the Department of Plant 

Sciences, University of California, Davis, CA.

Scientific Name and Introduction

Prunus amygdalus is a member of the family 

Rosaceae. The sweet cultivated almond originated 

from bitter-seeded species that evolved in the 

deserts and foothills of central and southwest Asia. 

Almonds have been cultivated for over 4,000 

years, and starting about 450 BC were cultivated 

around the Mediterranean coastline from Turkey 

to Tunisia. Almonds were first introduced to 

California through the missions, but the large 

commercial industry was built with trees brought 

by settlers from the Eastern United States that 

have thrived in the Mediterranean climate of the 

Central Valley of California (Kester and Ross 

1996).

The edible kernel (primarily two cotyledons 

whose cells are filled with oil bodies and a small 

embryo) is surrounded by a shell and hull tissue. 

Almonds are relatively high in oil: 36 to 60% of 

kernel dry mass (Guadagni et al. 1978, Abdallah 

et al. 1998). Most of the fatty acids in almond 

oil (about 90%) are unsaturated, with the ratio of 

monounsaturated to diunsaturated ranging from 

2:1 to almost 5:1 (Abdallah et al. 1998). There 

are hard- and soft-shell varieties; the soft-shell 

varieties are the basis of the industry. Nuts are 

dislodged from the tree by shaking and allowed 

to dry on the ground before being swept into 

windrows, picked up, and transported to the huller. 

Some harvested nuts are dried after removal 

from the orchard (Thompson et al. 1996). This 

is common if late season rains threaten a delay 

in harvest. If limited huller capacity leads to 

stockpiling of nuts, they will likely be covered and 

subjected to periodic fumigation to limit insect 

damage. Nuts must be dried to <10% moisture 

prior to stockpiling. 

Quality Characteristics and Criteria

In-shell almonds should have hulls that are 

uniform, with a bright color, and be free of 

adhering hull material or debris. The hull should 

be intact and free of damage caused by the hulling 

operation, insects, or fungi. Kernels should be 

fully formed rather than shriveled. Kernels of 

larger size are preferred. The “skin” of the kernel 

should be unbroken (free of damage caused 

during shelling or by insects or pathogens) and of 

uniform dark brown color. Almond flavor should 

display a combination of sweet and oily notes. 

There should be no stale or rancid flavors. Optimal 

kernel texture is from crisp to chewy. Kernels 

should have <8% moisture, but kernels with <4% 

moisture tend to be brittle and hard (Kader 1996). 

Currently over 95% of the California almond crop 

is sold as shelled products, but developing export 

markets include substantial interest in in-shell 

product. 

Caveletto et al. (1985) used an assortment of 

physical, chemical, and sensory methods to 

evaluate the quality attributes of 23 almond 

varieties in terms of their use as in-shell, raw, 

roasted, and blanched nuts. They determined 

composition of fats and sugars, described flavor 

notes and textural characteristics, and evaluated 

the ability to tolerate processing procedures and 

suitability for various products.

Horticultural Maturity Indices

Almond maturation can be monitored externally 

by evaluating the extent of hull dehiscence. In 

the absence of pressure from insects such as the 

naval orangeworm (Amyelois transitella), harvest 

can be delayed until the two halves of the hull are 

fully bent back to expose the shell. At this point, 

hulls readily separate and moisture content is 

low enough that nuts can be immediately picked 

up from the orchard floor. Yield is maximized 

because the kernel’s dry weight is no longer 

increasing and nut removal is close to 100%. 

Nut maturation on a given tree is not uniform; 

development tends to be most rapid on the south 

and southwestern faces of the tree higher in the 

canopy. 
745

The California industry favors a timely (early) 

harvest that limits naval orangeworm egg-laying 

in split hulls. Thus, harvest should be matched 

to the time that the last nut on a tree has begun 

to split. Nut removal can be near maximum, and 

minor decreases in kernel size are acceptable due 

to reductions in insect damage (Connell et al. 

1996, Reil et al. 1996). Early harvested nuts (hulls 

and kernels) contain more water than is acceptable 

and must be dried on the orchard floor for 1 to 2 

weeks before they are picked up and hulled.

Grades, Sizes, and Packaging

In-shell and shelled grades are defined by USDA 

standards. For the in-shell product, emphasized 

characteristics include the integrity, shape, and 

hardness of the shell as well as the brightness and 

uniformity of its color. Freedom from foreign 

material and signs of insect damage or decay are 

also important. Shelled almonds should be free of 

shell debris and foreign material and from insect 

or fungal damage. The kernel skin should be intact 

and should show no shriveling or discoloration. 

Double, split, or broken kernels are negative 

factors. There should be no indication of rancid 

flavor. A complete description of Federal quality 

standards can be found at http://www.ams.usda.

gov/AMSv1.0/standards.

Optimum Storage Conditions

The low water and high fat contents of the kernel 

make it relatively stable metabolically and able to 

tolerate low temperatures. The primary objectives 

of storage regimes are to maintain the low water 

content. Federal regulations define a safe moisture 

level for nuts as a water activity <0.7 at 25 °C (77 

°F) to retard microbial growth. The recommended 

storage RH is 65% because too low a water 

content negatively affects flavor, color, and texture 

(Kader 1996). Cold storage is useful to minimize 

lipid oxidation (rancidification). In-shell almonds 

can be stored for up to 20 mo at 0 °C (32 °F), 16 

mo at 10 °C (50 °F), and 8 mo at 20 °C (68 °F). 

Shelled nuts can be stored for about half as long 

as nuts in the shell (about 6 mo), and pieces for 

even less. Almonds should not be stored with 

commodities that have strong odors because their 

high lipid content allows them to readily absorb 

odors. 

Modified Atmosphere Considerations

Kernels are less stable than in-shell almonds, 

and better fresh almond flavor is maintained in 

a low O2

 and elevated CO2 atmosphere. Flavor 

was maintained for 12 mo at 18 and 27.5 °C (64.5 

and 81.5 °F) in insect-controlling atmospheres 

of <1% O2

 and 9 to 9.5% CO2 (Guadagni et al. 

1978). Reduction in the O2

 content of the storage 

atmosphere will improve oil stability. The stability 

difference between in-shell nuts and shelled 

kernels was eliminated in 0.5% O2

 (Kader 1996).

Chilling Sensitivity

Almonds are not sensitive to chilling. 

Ethylene Production and Sensitivity

Almonds produce very little ethylene. There are 

no documented responses to ethylene that might 

directly affect kernel quality.

Respiration Rates

The low water content of properly stored kernels 

makes them relatively inert metabolically. 

Respiratory rates are very low.

Physiological Disorders

Two important quality problems of almond 

kernels are influenced by failure to maintain low 

water content. Harvested nuts are often stockpiled 

and fumigated to control naval orangeworm prior 

to hulling and shelling. Temperatures in covered 

stockpiles that are open to the sun can reach 60 

°C (140 °F). If nuts have not been dried to <10% 

moisture in the orchard, or have been wetted by 
746

late-season rains, they should not be fumigated. 

The combination of elevated moisture and 

temperature leads to a problem called concealed 

damage, which is marked by inversion of sucrose, 

lipid oxidation, and internal kernel darkening. 

Elevated temperature alone does not cause the 

problem. Wetting of freshly harvested almonds 

followed by heating can cause the problem, and 

forced-air drying of rain-wetted kernels can 

prevent it. However, almonds that have been held 

in dry storage for several months and then wetted 

and heated do not develop the problem (Reil et al. 

1996). 

Another kernel quality problem is premature 

sprouting (growth of the embryo between the 

unopened cotyledons). 

While the almond kernel’s content of 

polyunsaturated fatty acids is much less 

than walnuts or pecans, failure to maintain 

proper storage lead to rancidification. Factors 

contributing to rancidification were studied by 

Zacheo et al. (1998).

Postharvest Pathology

Most infections with pathogens are initiated in the 

orchard, and because clean-up following harvest is 

not absolute, the potential problems are transferred 

to the postharvest environment. In-shell product 

is relatively protected unless the shell has been 

broken or penetrated by insects. The most serious 

pathogens are fungi such as Aspergillus flavus

and A. parasiticus, which can produce aflatoxins 

that are both toxic and carcinogenic. Damaged 

kernels must be discarded prior to storage and 

low temperature and RH conditions must be 

maintained. Phillips et al. (1979) and King et 

al. (1983) have described the variety of fungi 

(primarily Aspergillus spp., but also Alternaria, 

Rhizopus, Cladosporium, and Penicillium spp.) 

that are found on almonds, and the latter work and 

King and Schade (1986) have described the effect 

of various water activities and temperatures on the 

competition between these fungi on stored kernels. 

Because of the relationship between insect damage 

and pathogen presence, sorting to eliminate whole 

kernels with insect damage will reduce the number 

of whole kernels with excess levels (>1 ng/g) of 

aflatoxins. However, lower grades and broken 

kernels or kernels sold as animal feed or processed 

for oil can still present problems (Schatzki 1996). 

Sampling of kernels to test for aflatoxin presents 

statistical problems because contamination is 

centered in individual kernels.

Quarantine Issues

The most serious almond postharvest insect 

problem is with naval orangeworm. The insect 

lays its eggs in newly split nuts just before harvest, 

and the resulting larvae can cause substantial 

losses. Fumigation with methyl bromide, which 

has a limited future, or phosphine is used to 

control the insect. In-home control of insects can 

use treatment at freezing temperatures of -5 to 

-10 °C (14 to 23 °F) for a few days. Irradiation 

can also be used (30 kilorad). The most useful 

nonchemical insect control approach appears 

to be a <1% O2

 and 9 to 9.5% CO2 CA regime 

(Guadagni et al. 1978).

References

Abdallah, A., M.H. Ahumada, and T.M. Gradziel. 

1998. Oil content and fatty acid composition of 

almond kernels from different genotypes and 

California production regions. J. Am. Soc. Hort. 

Sci. 123:1029-1033.

Cavaletto, C.G., A.A. Kader, and D.E. Kester. 

1985. Quality in relation to marketability of 

almond varieties. Report to the California Almond 

Board. Pomology Department, University of 

California, Davis, CA.

Connell, J.H., G.S. Sibbett, J.M. Labavitch, and 

M.W. Freeman. 1996. Preparing for harvest. In

W.C. Micke, ed., Almond Production Manual, pp. 

254-259. Pub. no. 3364, Division of Agriculture 

and Natural Resources, University of California, 

Davis, CA.
747

Guadagni, D.G., E.L. Soderstrom, and L. Storey. 

1978. Effect of controlled atmosphere on flavor 

stability of almonds. J. Food Sci. 43:1077-1080.

Kader, A.A. 1996. In-plant storage. In W.C. 

Micke, ed., Almond Production Manual, pp. 

274-277. Pub. no. 3364, Division of Agriculture 

and Natural Resources, University of California, 

Davis, CA.

Kester, D.E., and N.W. Ross. 1996. History. In

W.C. Micke, ed., Almond Production Manual, 

pp. 1-2. Pub. no. 3364, Division of Agriculture 

and Natural Resources, University of California, 

Davis, CA.

King, A.D. Jr., W.U. Halbrook, G. Fuler, and L.C. 

Whitehand. 1983. Almond nutmeat moisture and 

water activity and its influence on fungal flora and 

seed composition. J. Food Sci. 48:615-617.

King, A.D., Jr., and J.E. Schade. 1986. Influence 

of almond harvest, processing and storage on 

fungal population and flora. J. Food Sci. 51:202-

205, 215.

Phillips, D.J., B. Mackey, W.R. Ellis, and T.N. 

Hansen. 1979. Occurrence and interaction of 

Aspergillus flavus with other fungi on almonds. 

Phytopathology 69:829-831.

Reil, W., J.M. Labavitch, and D. Holmberg. 

1996. Harvesting. In W.C. Micke, ed., Almond 

Production Manual, pp. 260-264. Pub. no. 3364, 

Division of Agriculture and Natural Resources, 

University of California, Davis, CA.

Schatzki, T.F. 1996. Distribution of aflatoxin in 

almonds. J. Ag. Food Chem. 44:3595-3597. 

Thompson, J.F., T.R. Rumsey, and J.H. Connell. 

1996. Drying, hulling and shelling. In W.C. 

Micke, ed., Almond Production Manual, pp. 

268-273. Pub. no. 3364, Division of Agriculture 

and Natural Resources, University of California, 

Davis, CA.

Zacheo, G., A.R. Cappello, L.M. Perrone, and 

G.V. Gnoni. 1998. Analysis of factors influencing 

lipid oxidation of almond seeds during accelerated 

ageing. Lebensm.-Wiss. Technol. 31:6-9.
748

Hazelnut

Niels Maness

Maness is with the Department of Horticulture 

and Landscape Architecture, Oklahoma State 

University, Stillwater, OK.

Scientific Name and Introduction

Corylus avellana L., the filbert or hazelnut, is a 

member of the birch family (Betulaceae). The 

edible seed is surrounded by a round to slightly 

oblong shell that must be separated from a husk 

during or after harvest. All important world 

cultivars originated from human selections of wild 

C. avellana in Europe and Turkey. The common 

name “filbert” originated in England and was 

originally applied to the long-husked types of 

Corylus avellana to distinguish them from the 

short-husked types and has since been used in the 

U.S. to distinguish the cultivated Corylus avellana

from other native wild species of Corylus. The 

common name “hazelnut” is more commonly 

applied worldwide for nuts produced by all 

Corylus species.

Whatever the chosen common name, nuts from 

this genera represent one of the world’s major 

nut crops, second only to almonds (Thompson 

et al. 1996). Turkey produces most of the world 

supply (70%), followed by Italy (22%), Spain 

(5%), and the United States (3%). By far the 

largest production area in the United States is the 

Pacific Northwest, with 99% of production in the 

Willamette Valley of Oregon (Mehlenbacher and 

Olsen 1997). Market uses for the U.S. crop have 

been roughly evenly divided between in-shell and 

kernel markets, but trends are shifting towards 

kernel markets. The major variety in the U.S. 

is Barcelona, followed by Davinia, Ennis, and 

Willamette.

Two wild species, C. americana and C. cornuta, 

are found in the United States. C. americana has 

been used in breeding programs for crossing with 

C. avellana in attempts to provide genotypes with 

sufficient cold hardiness and eastern filbert blight 

tolerance or resistance to allow production east of 

the Rocky Mountains with some success. 

Quality Characteristics and Criteria

In-shell hazelnuts should be properly sized 

to meet the stated market type and should be 

properly filled with at least 50% of the shell cavity 

occupied by nutmeat. Shells should be free of 

cracks and noticeable mechanical injury and clean 

and brightly colored; coloring patterns should be 

characteristic of the stated variety. The pellicle 

should be smooth and devoid of husk attachments. 

Kernels should meet the stated market type, be 

free of any misshapen or underdeveloped kernels, 

and be free of any shell or foreign material and 

off odor, off flavor, or mold. Water content of 

kernels should not exceed 6% if shelled or 7% if 

in-shell, and the total water content of unshelled 

nuts should not exceed 10 to 12%. Size is 

specified with grade as a determinant of quality, 

and minimum sizes are used for specification 

of classes “Extra” and “Class I” in international 

trade. 

For in-shell markets, larger and particularly 

rounded types are preferred. Shelled markets 

accommodate both rounded and oblong types, and 

size preference depends on the intended end use. 

Hazelnut kernel oil content ranges from 57 to over 

70%, and total sugars average about 4%; both 

vary with variety and growing location (Botta et 

al. 1994). Hazelnuts are highest among tree nuts in 

α-tocopherol content (366 μg/g oil) and are also a 

rich source of vitamin B6

 (0.54 to 0.89 mg per 100 

g) (Richardson 1997).

Horticultural Maturity Indices

In areas where hazelnuts are mechanically 

harvested, nuts are usually allowed to naturally 

drop from trees prior to sweeping from the orchard 

floor, and harvesting may commence after 90% of 

the nuts have dropped (Lagerstedt 1979). Kernels 

are considered mature after oil accumulation is 

complete and when the nut detaches from the base 
749

of the husk (Thompson et al. 1996). In the United 

States, most nuts are mature during or by the end 

of August but may be prevented from dropping by 

an immature, clasping husk. In production areas 

where hand harvesting from trees is still practiced, 

or for varieties in which husks fail to open and 

allow nut drop, nuts are considered mature 

when they will rattle inside the husk, indicating 

detachment of the nut from the base of the husk.

Grades, Sizes, and Packaging

U.S. standards exist for hazelnuts in the shell and 

for importation of in-shell or shelled hazelnuts, 

and international UN/ECE standards exist for 

both in-shell and shelled hazelnuts. Grades are 

primarily determined by size, degree of kernel 

fill, color, and freedom from defects and foreign 

material. U.S. No. 1 filberts must contain no more 

than 20% filberts of a different type (round shaped 

versus long type); no more than 10% defective 

nuts, provided that no more than 5% are poorly 

filled (blanks), no more than 5% are rancid, 

decayed, moldy or insect injured, and no more 

than 3% are insect injured; and not more than 

15% filberts that fail to meet the specified size 

and of which no more than 10% are undersized. 

Furthermore, shells are free from surface moisture 

and the combined shell and kernel moisture 

content is not greater than 10%; shells are well 

formed, unbroken, not discolored, have adhering 

husk covering not more than 5% of the shell area 

and are practically free of adhering dirt and other 

foreign material.

Size is specified in connection with the grade in 

terms of minimum and maximum diameters that 

will pass through round openings of a screen and 

are specified separately for round-type varieties 

and long-type varieties. See following:

______________________________________________________________________

Size Round-type Long-type

Minimum Maximum Minimum Maximum

______________________________________________________________________

 in. (mm)

Jumbo 56/64 (22.2) — 47/64 (18.6) —

Large 49/64 (19.4) 56/64 (22.2) 48/64 (19.0) 44/64 (18.6)

Medium 45/64 (17.9) 49/64 (19.4) 45/64 (17.9) 34/64 (13.5)

Small — 45/64 (17.9) — 35/64 (13.9)

______________________________________________________________________
750

All hazelnuts imported into the United States in 

lot quantities which exceed 115 lb (52.2 kg) net 

weight must meet minimum grade standards as 

specified under section 8e of the Agricultural 

Marketing Agreement Act. In-shell hazelnuts must 

meet U.S. No. 1 grade and be at least medium size 

with a tolerance for insect injury of 2% or less. 

Shelled hazelnuts must be well dried and clean; 

free from foreign material, mold, rancidity, decay, 

or insect injury; and free from serious damage 

caused by serious shriveling or other means. 

Stated tolerances for shelled hazelnuts include not 

more than 0.0002% foreign material; not more 

than 5% of kernels or pieces of kernels which 

are below grade, including not more than 2% for 

mold, rancidity, decay, or insect injury; and no 

more than 1% with rancidity or insect injury. 

International grade standards are exercised at the 

export control stage and are specified for both inshell and shelled hazelnuts. For in-shell nuts, UN/

ECE classifications of Extra, Class I, and Class 

II exist in which the shell of all nuts must be well 

formed, intact, sound, and clean and the kernels 

must be sound, clean, sufficiently developed, and 

free from mold, visible damage from insects or 

pests, presence of live or dead insects or pests, 

rancidity, foreign smell or taste, and blemishes. 

All hazelnuts must contain less than 12% moisture 

and kernels not more than 7% moisture, and 

foreign material may not exceed 0.25% of the 

total in-shell weight. Sizing and statement of 

variety, commercial type, or shape is compulsory 

for Extra and Class I but is optional for Class II. 

For specified sizes in nuts of all classes, a total 

tolerance by count of 5% for rounded types and 

10% for oblong types for nuts not meeting the 

specified size is allowed. 

Extra hazelnuts must be 16 mm in diameter 

or more and be of superior quality, must be 

characteristic of the variety and/or commercial 

type, and must be practically free from defects 

with the exception of very slight superficial 

defects, provided they do not affect general 

appearance, quality, or keeping quality. They must 

contain no more than 4% empty nuts on a count 

basis; not more than 3% of the weight of in-shell 

nuts may contain shell defects; and not more than 

5% of the kernels may be defective, of which not 

more than 3% may be moldy, rotten, rancid, or 

damaged by insects. 

Class I hazelnuts must be 14 mm or more 

in diameter and be of good quality, must be 

characteristic of the variety and/or commercial 

type, and may contain only slight defects that 

do not affect the general appearance, quality, or 

keeping quality. They must contain not more than 

6% empty nuts on a count basis; not more than 5% 

of the weight of in-shell nuts may contain shell 

defects; and not more than 8% of the kernels may 

be defective, of which not more than 5% may be 

moldy, rotten, rancid, or damaged by insects. 

Class II hazelnuts may be of any size (if size is 

specified, tolerances apply) and be of marketable 

quality; they may contain defects provided that the 

in-shell nuts retain their essential characteristics as 

regards general appearance, quality, and keeping 

quality. They must contain not more than 8% 

empty nuts on a count basis; not more than 7% 

of the weight of in-shell nuts may contain shell 

defects; and not more than 12% of the kernels 

may be defective, of which not more than 6% may 

be moldy, rotten, rancid, or damaged by insects. 

Sizing or screening is used to specify market size 

in 2 mm increments from 22 mm to 14 mm or 

less. Sizing for nuts less than 22 mm in diameter 

must include the maximum and minimum size 

range, mention the minimum size followed by 

the words “and over,” or mention the maximum 

size followed by the words “and less.” For nuts 

for final consumers under the classification 

“screened,” the size “and less” is not allowed. 

For hazelnut kernels, UN/ECE classifications 

of Extra, Class I, and Class II also exist; and 

requirements are similar to those stated for kernels 

of in-shell nuts with the addition of provisions 

for intactness of kernels and a slightly reduced 

tolerance for kernel moisture content from not 

more than 7% for in-shell kernels to not more than 

6% for shelled kernels. Foreign material may not 

exceed 0.25% for kernels in any classification. 

Sizing and statement of variety is also compulsory 

for Extra and Class I kernels but optional for Class 
751

II. For kernels in all classes, a total tolerance of 

10% is allowed for kernels other than the specified 

variety and/or type, and a size tolerance by weight 

of 5% is allowed for rounded types and 10% for 

oblong types. To be designated either Extra or 

Class I, hazelnut kernels must have a minimum 

diameter of 9 mm, with the exception of hazelnuts 

of the piccolo type or hazelnuts having a similar 

designation for which a diameter of 6 to 9 mm is 

allowed. 

Extra hazelnut kernels must be of superior 

quality, must be characteristic of the variety and/

or commercial type, and must be practically 

free of defects with the exception of very slight 

superficial defects provided they do not affect the 

general appearance, quality, or keeping quality. 

Total tolerances for defects are 5% by weight or 

6% if the lot is specified as “Old Crop.” Of the 

total tolerance, no more than 1% may be rancid, 

rotten, moldy, have off odor or off flavor, or be 

damaged by insects or rodents; no more than 2% 

may be not fully developed, including shrunken 

and shriveled, stained, and yellowish kernels; and 

not more than 3% may be mechanically damaged 

and pieces. Not included in the total tolerance is 

that not more than 2% may be twin hazelnuts. 

Class I hazelnut kernels must be of good quality, 

must be characteristic of the variety and/or 

commercial type, and may have slight defects of 

form and color provided that these do not affect 

the general appearance, quality, or keeping quality. 

Total tolerances for defects are 12 to 13% if the lot 

is specified as “Old Crop.” Of the total tolerance, 

no more than 1.5% may be rancid, rotten, moldy, 

have off odor or off flavor, or be damaged by 

insects or rodents; no more than 4% may be not 

fully developed, including shrunken and shriveled, 

stained, and yellowish kernels; and not more than 

8% may be mechanically damaged and pieces. 

Not included in the total tolerance is that not more 

than 5% may be twin hazelnuts. 

Class II hazelnut kernels may be of any size (if 

size is specified, tolerances apply) and be of 

marketable quality; they may contain defects 

provided that kernels retain their essential 

characteristics as regards general appearance, 

quality, and keeping quality. Total tolerances for 

defects are 16 to 18% if the lot is specified as 

“Old Crop.” Of the total tolerance, no more than 

3% may be rancid, rotten, moldy, have off odor 

or off flavor, or be damaged by insects or rodents; 

no more than 8% may be not fully developed, 

including shrunken and shriveled, stained, and 

yellowish kernels; and not more than 10% may be 

mechanically damaged and pieces. Not included 

in the total tolerance is that not more than 8% may 

be twin hazelnuts. 

Hazelnut kernels may be sized or screened, 

with the size expressed in increments of 2 mm. 

All sizes are allowed, subject to the minimum 

designations for Extra and Class I hazelnut 

kernels. For kernels for final consumers under the 

classification “screened,” the size “and less” is not 

allowed.

Optimum Storage Conditions

Soon after harvest, nuts should be dried to below 

10 to 12% moisture, with kernels below 6 to 

7% moisture to deter mold growth. In-shell and 

unroasted kernels may be stored for 24 mo with 

minimal loss in quality at temperatures up to 10 

°C (50 °F). Roasted kernels may only be held 

for 6 mo prior to development of detectable 

rancidity stored at 0, 5, or 10 °C (32, 41, or 50 °F). 

However, reduced temperature may be effective in 

combination with other protective measures such 

as vacuum packaging in extending roasted kernel 

shelf-life to 1 year or more (Ebraheim et al. 1994).

Retail Outlet Display Considerations

Hazelnuts are normally marketed at ambient 

temperature. Use of vacuum or low-O2

 MAP 

is recommended to extend shelf-life. In-shell 

hazelnuts may be marketed in bulk containers. 

Exposure to moisture and high RH should be 

avoided.
752

Chilling Sensitivity

Hazelnuts are not sensitive to chilling and are 

commonly stored at temperatures at or below 

freezing for long term storage.

Ethylene Production and Sensitivity

Ethylene may be used as a harvest aide to enhance 

maturation of husks for earlier harvest (Lagerstedt 

1979). During storage hazelnuts produce very low 

levels of ethylene.

Respiration Rates

Properly dried hazelnuts exhibit very low 

respiration rates during storage.

Physiological Disorders

Black tips on kernels appears to be associated with 

nuts having split or weak sutures. It appears to be 

caused by an oxidation process that occurs on the 

pellicle only and may or may not be associated 

with moldy kernels (Thompson et al. 1996). 

Twin kernels occur when two kernels develop 

within one nut shell, and is an undesirable trait 

because of the small size and irregular shape of 

affected kernels. 

Blank nuts are in-shell hazelnuts devoid of normal 

kernels. It results from defective embryo sacs, 

unviable eggs, failure of fertilization, or embryo 

abortion at varying stages of development. Owing 

to the alternate bearing cycles for hazelnuts, 

poorly filled nuts may also result during an 

overproduction year, and poor kernel fill appears 

to be a heritable trait (Thompson et al. 1996).

Postharvest Pathology

The most common decay found in hazelnuts 

is molds, with Romularia spp. most prevalent 

throughout nut development. It is the major 

pathogen associated with kernel tip mold 

(Ebraheim et al. 1997, p. 483). Although 

Romularia spp. appear to infect hazelnuts during 

nut development and may be quiescent prior 

to maturity and storage, many molds require 

breakage of the shell to contaminate the nut; thus, 

intactness of the shell offers some natural defense 

against mold infestation. 

The dominant flora during storage are Penicillium

and Aspergillus spp. A. flavus, capable of 

producing aflatoxin, has been isolated from 

hazelnuts in storage (Eke and Goktan 1987). 

Reduction of in-shell moisture content to below 

10% and nutmeat moisture content to less than 6% 

is an effective means of deterring mold growth. 

Sanitation with chlorine dips may also be effective 

in reducing the incidence of mold infestation by 

reducing the amount of innoculum carried into 

postharvest storage. Because of the high amounts 

of organic material on the surface of shells, 

chlorine concentrations should be monitored and 

replenished as necessary to maintain chlorine at 

concentrations necessary to kill microorganisms.

Quarantine Issues

To prevent spread of eastern filbert blight 

(Anisogramma anomala), all trees, plants, 

cuttings, and scions of all species and varieties 

of the wild and cultivated filbert or hazelnut, 

Corylus spp., may not be transported into Oregon 

from States and districts of the U.S. east of and 

including the States of Montana, Wyoming, 

Colorado, and New Mexico; the entire State of 

Washington; and all provinces, districts, and 

territories of Canada east of and including the 

province of Alberta.

Special Considerations

Hazelnuts marketed in-shell should be sampled 

periodically to assess nutmeat quality. Although 

the most common nut causing allergy in children 

and adults is peanut, hazelnuts may also be an 

allergenic food additive (Ewan 1996), and the 

presence of hazelnut in foods must be declared. 
753

An ELISA test can be used to detect hazelnut 

presence in complex food mixtures (Holzhauser 

and Vieths 1999). Shelling, blanching, or roasting 

decreases hazelnut shelf-life compared to 

storage in-shell (Ebraheim et al. 1994). Roasting 

temperature and duration interact to decrease 

shelf-life with increasing roasting temperature 

and duration (Richardson and Ebraheim 1997). 

Hazelnuts absorb lipophilic compounds that can 

induce off flavor. Although frozen storage may 

be used to increase shelf-life, once out of storage 

hazelnuts should be used as soon as possible due 

to reduced shelf-life at room temperature.

References

Botta, R., C. Gianotti, D. Richardson, et al. 1994. 

Hazelnut variety, organic acids, sugars and total 

lipid fatty acids. Acta Hort. 351:693-699.

Ebraheim, K.S., D.G. Richardson, and R.M. 

Tetley. 1994. Effects of storage temperature, 

kernel intactness and roasting temperature on 

vitamin E, fatty acids and peroxide value of 

hazelnuts. Acta Hort. 351:677-684.

Ebraheim, K., D.G. Richarson, J. Stone, and R. 

Tetley. 1997. Hazelnut mold identification and 

timing of infestation. Acta Hort. 445:483-484.

Eke, D., and D. Goktan. 1987. Aflatoxin 

production in hazelnuts. Ege Univeritesi Ziraat 

Fakultesi Dergisi 24:289-297.

Ewan, P.W. 1996. Clinical study of peanut and nut 

allergy in 62 consecutive patients: new features 

and associations. Brit. Med. J. 312:1074-1078.

Holzhauser, T., and S. Vieths. 1999. Quantitative 

sandwitch ELISA for determination of traces of 

hazelnut (Corylus avellana) protein in complex 

food mixtures. J. Agric. Food Chem. 47:4209-

4218.

Lagerstedt, H.B. 1979. Filberts. In R.A. Jaynes, 

ed., Nut Tree Culture in North America, pp. 128-

147. Northern Nut Growers Association, Hamden, 

CT.

Mehlenbacher, S.A., and J. Olsen. 1997. The 

hazelnut industry in Oregon, USA. Acta Hort. 

445:337-346.

Richardson, D.G. 1997. The health benefits of 

eating hazelnuts: implications for blood lipid 

profiles, coronary heart disease and cancer risks. 

Acta Hort. 445:295-300.

Richardson, D.G., and K. Ebraheim. 1997. 

Hazelnut kernel quality as affected by roasting 

temperatures and duration. Acta Hort. 445:301-

304.

Thompson, M.M., H.B. Lagerstedt, and S.A. 

Mehlenbacher. 1996. Hazelnuts. In J. Janick and 

J.N. Moore, eds., Fruit Breeding, vol. 3, Nuts, pp. 

125-184. John Wiley and Sons, New York, NY.
754

Macadamia Nut

Catherine G. Cavaletto 

Cavaletto is with the Department of Tropical Plant 

and Soil Science, University of Hawaii at Manoa, 

Honolulu, HI.

Scientific Name and Introduction

The family Proteaceae includes about 10 species 

of the genus Macadamia, 2 of which produce 

edible nuts: M. integrifolia and M. tetraphylla or 

hybrids of these. The major species of commerce 

is M. integrifolia. Macadamia nuts are native to 

Australia and are produced there as well as in 

Hawaii, Central and South America, and parts of 

Africa. Nearly all production consists of grafted 

trees of cultivars developed in Hawaii or Australia. 

The edible kernel is enclosed in a thick, hard shell 

that, in turn, is enclosed in a husk that separates 

from the tree at about the time the seed is mature. 

The kernel is nearly spherical, consisting of joined 

equal-sized halves (cotyledons).

Quality Characteristics and Criteria

Kernels should be a light cream color, nearly 

spherical in shape, and free of blemishes, 

rancidity, mold, decay, insect damage, extraneous 

material, hollow centers, discoloration, and 

adhering shell. Fully developed macadamia 

kernels should contain ≥72% oil; the highest 

quality kernels contain 72 to 78% oil and 1.5% 

moisture. Kernels of M. tetraphylla typically 

contain less oil. Oil content is a major quality 

factor that varies with cultivar and maturity and is 

inversely related to sugar content (Ripperton et al. 

1938). 

Horticultural Maturity Indices

Following a prolonged flowering season, 

macadamia nuts mature over a long period 

from late summer until late spring. Kernels 

are mature when oil accumulation is complete. 

Shortly after this time, the nuts fall to the 

ground and are harvested. Sometimes shakeharvesting is employed to facilitate the harvest 

while minimizing the amount of immature nuts 

harvested. Recommended harvest interval for 

ground-harvested nuts is 1 mo. Damage by the 

tropical nut borer (Hypothenemus obscurus [F.]) 

can begin to increase rapidly after 3 weeks on the 

ground (Jones 1992). 

Grades, Sizes, and Packaging

No U.S. grades are established for macadamia 

nuts, but the State of Hawaii has standards and 

grades for shelled macadamia nuts, in-shell 

macadamia nuts, and roasted macadamia nuts 

(Hawaii Department of Agriculture 1984). 

The minimum export grade for shelled nuts is 

Hawaii No. 1, which defines defects and damage, 

development, and cleanliness as well as maximum 

moisture content of 1.5% by weight. Off-grade is 

not a grade, but is a descriptive term applicable 

to shelled nuts which have a market value 

and designates a quality lower than the lowest 

applicable Hawaii grade for shelled nuts. The 

standards also define eight styles: Style I (wholes), 

Style II (wholes and halves), Style III (cocktail), 

Style IV (halves and pieces), Style V (large diced), 

Style VI (chips), Style VII (bits, diced), and Style 

VIII (fines). There are also standards for in-shell 

nuts and for roasted kernels. Shelled nuts are 

usually packaged in 11.4 to 22.7 kg (25 to 50 lb) 

vacuum-packed or nitrogen-flushed foil bags for 

the wholesale market. Larger nitrogen-flushed 

containers are sometimes used.

Optimum Storage Conditions

Macadamia nuts should be husked within 24 h of 

harvest, after which the drying process should be 

initiated. Freshly fallen nuts contain about 25% 

kernel moisture, although nuts that have remained 

on the ground for extended periods may have as 

little as 10 to 15% moisture. Drying should begin 

with ambient air, followed by a gradual increase 

in temperature that will not exceed 60 °C (140 

°F) in the final stage of drying. Drying may be 
755

completed in-shell (to 1.5% kernel moisture); or 

the nuts can be dried partially in-shell (to about 5 

to 6% kernel moisture), followed by cracking and 

finish drying of kernels alone to 1.5% moisture. 

It is important to protect the dry kernels from 

moisture and O2

, so packaging in a material that 

is impervious to moisture is important. Vacuum 

packaging or nitrogen flush offers protection 

from O2

. Exposure to moisture results in loss 

of crispness and shelf-life. Likewise, prolonged 

exposure to O2

 results in rancidity. Cold storage is 

normally not necessary for short-term storage but 

might be desirable for extended periods. Frozen 

storage (-18 °C, 0 °F) can be very effective in 

extending shelf-life.

Retail Outlet Display Considerations

Packaging should protect kernels from moisture 

and O2

. Storage temperature is less critical. 

Nuts are rarely sold in-shell due to difficulty in 

cracking. 

Chilling Sensitivity

Macadamia nuts are not sensitive to chilling 

provided they have been dried. Dry kernels 

are commonly stored below 15 °C (59 °F) for 

bulk storage and can successfully be frozen to 

extend shelf-life. Care must be taken in thawing 

frozen nuts to prevent condensation and resulting 

moisture gain. 

Physiological Disorders

Nuts that fail to develop properly will produce 

kernels that are low in oil content and may appear 

shriveled or small. If too immature, kernels 

are very small and become hard upon drying. 

Immature kernels also have high sugar content 

and will brown excessively when roasted. Highmoisture kernels dried at higher temperatures 

develop brown centers when roasted as a result 

of high reducing sugar levels. It is necessary to 

begin the drying process at ambient temperature 

or with circulating air heated to no more than 

38 °C (100 °F) when the kernels are very wet. 

Minimum reducing-sugar levels can be obtained 

if kernel moisture content is reduced to 8% before 

increasing the temperature to 52 °C (126 °F) and 

to 6% before increasing the temperature to 60 °C 

(140 °F) (Prichavudhi and Yamamoto 1965). 

Postharvest Pathology

Extended harvest intervals may result in mold, 

yeast, or bacterial contamination in the field, as 

well as insect damage. Southern green stinkbug 

(Nezara viridula [L.]), tropical nut borer 

(Hypothenemus obscurus [F.]) koa seed worm 

(Cryptophlebia illepida [Butler]), and litchi fruit 

moth (C. ombrodelta) are the major insect pests 

causing damage to macadamia nuts in Hawaii, 

resulting in an unmarketable kernel (Jones and 

Aihara-Sasaki 1999). Delay in husking the nuts 

following harvest can also result in mold growth 

and fermentation. Husking should occur within 24 

h of harvest. The thick shell provides considerable 

protection for the kernel, but cracked shells and 

open micropyles can provide entry of fungi and 

bacteria as well as ants. When the nuts fall from 

the tree, the kernels contain about 25% moisture. 

At harvest, moisture level can range from about 

10 to 25%. Once the nuts have been dried to 1.5% 

kernel moisture, the water activity is 0.3 (Beuchat 

1978), insufficient to support the growth of mold 

or bacteria.

Quarantine Issues

There are no significant quarantine issues. A 

possible issue is the occasional presence of storage 

insects such as almond moth (Ephestia cautella),

merchant grain beetle (Oryzaephilus mercatur

[Fauvel]), and the dried fruit beetle (Carpophilus 

hemipterus [Linnaeus]) (Cavaletto 1983).
756

Special Considerations

Kernel stability is related to moisture content 

and to oxidative rancidity. Of these, moisture 

content is the most critical. Raw kernels with 

moisture content exceeding 2% have poor 

stability (Cavaletto et al. 1966). These kernels 

brown excessively when roasted and have poor 

texture. Likewise, roasted kernels must be well 

protected from moisture to ensure preservation of 

texture and flavor. Protection from O2

 is usually 

accomplished with vacuum or nitrogen packing. 

References 

Beuchat, L.R. 1978. Relationship of water activity 

to moisture content in tree nuts. J. Food Sci. 

43:754-755,758. 

Cavaletto, C.G. 1983. Macadamia nuts. In H.T. 

Chan Jr., ed., Handbook of Tropical Foods, pp. 

361-397. Marcel Dekker Inc, New York, NY.

Cavaletto, C.G., A. Dela Cruz, E. Ross, and H.Y. 

Yamamoto. 1966. Factors affecting macadamia 

nut stability. I. Raw kernels. Food Technol. 

20(8):108-111. 

Hawaii Department of Agriculture. 1984. 

Standards for roasted macadamia nuts. In

Standards for Processed Foods, ch. 44. SS 4-44-

13.

Jones, V.P. 1992. Effect of harvest interval and 

cultivar on damage to macadamia nuts caused by 

Hypothenemus obscurus (Coleoptera:Scolytidae). 

J. Econ. Ent. 85(5):1878-1883. 

Jones, V.P., and M. Aihara-Sasaki. 1999. 

Macadamia insect pests. In Proceedings of the 

Hawaii Macadamia Nut Association Annual 

Conference, 39:23-28. Hawaii Macadamia Nut 

Association, Hilo, HI.

Prichavudhi, K., and H.Y. Yamamoto. 1965. Effect 

of drying temperature on chemical composition 

and quality of macadamia nuts. Food Technol. 

19(5):129-132. 

Ripperton, J.C., R.H. Moltzau, and D.W. Edwards. 

1938. Methods of evaluating the macadamia nut 

for commercial use and the variation occurring 

among seedling plantings in Hawaii. Bull. 

79, Hawaii Agricultural Experiment Station. 

Honolulu, HI.
757

Peanut

Niels Maness

Maness is with the Department of Horticulture 

and Landscape Architecture, Oklahoma State 

University, Stillwater, OK.

Scientific Name and Introduction

Arachis hypogaea L., the peanut or groundnut, is 

an annual herb of the Leguminosae family. Two 

subspecies are grown commercially, and four 

market types are of greatest economic importance. 

A. hypogaea subsp. hypogaea includes the market 

types “runner” and “Virginia,” and A. hypogaea

subsp. fastigata includes the market types 

“Spanish” and “Valencia.” In the United States 

in the 1980s, 70% of the peanuts grown were 

runners, while 20, 10, and <1% were Virginia, 

Spanish, and Valencia market types, respectively 

(Knauft and Gorbet 1989). According to the 

USDA national peanut tonnage report, U.S. 

production in 1999 included 78% runners, 18% 

Virginia, 3% Spanish, and 3% Valencia. 

The edible portion is a seed which develops 

underground inside a pod containing two to four 

seeds. Peanuts originated in South America and 

are now cultivated worldwide, with the majority 

of production in India, Asia, and the United 

States. In the United States, about 60% of peanuts 

are used in a variety of food products, with the 

reminder used in approximately equal proportions 

for export and for production of edible oil. 

Major chemical constituents of peanuts are oil 

(44 to 56%) and protein (22 to 33%), with large 

influences by environment, genotype, and maturity 

on their concentrations (Holaday and Pearson 

1974).

Quality Characteristics and Criteria

Shelled peanuts should be properly sized to 

meet market type, be free of misshapen or 

underdeveloped kernels, and be free of any shell 

or foreign material and off odor or flavor. Raw 

peanuts should be surrounded by a tan, pink, or 

red seedcoat (testa) that fully encapsulates the 

seed, and the interior color of each half-seed 

should be ivory. Moisture content for in-shell 

peanuts should be <10% to prevent mold growth 

(Diener and Davis 1977). Prior to shelling, 

peanuts should contain 7 to 10% moisture to 

reduce splitting and kernel breakage during 

milling. After milling, moisture content for 

maximum shelf-life is ≤7%. Seed may be stored 

at ambient temperature for up to 11 years with 

good viability if seed moisture content is <3.3% 

(Cheng et al. 1997). Peanuts marketed without 

seedcoats (blanched) should have an ivory-colored 

raw kernel. Peanuts are most commonly consumed 

following roasting, which may be accomplished 

in-shell or after shelling. Roasted peanut kernels 

should be light yellow in color, free of external 

oil, contain <6% moisture, and be free of darkcolored kernels. 

Peanut seed, and particularly peanut seedcoats, are 

a source of resveratrol, a compound that reduces 

cardiovascular disease and cancer incidence. 

Resveratrol ranges from 0.02 to 1.79 μg g-1, 

compared to 0.6 to 8.0 μg mL-1 in red wines 

(Sanders et al. 2000). Fatty acid composition of 

peanut oil is predominantly oleic and linoleic 

acids, found in roughly equal amounts and making 

up 80% of total fatty acids. Certain genotypes 

may contain substantially more oleic than linoleic 

acid, with ratios as high as 40:1 (oleic:linoleic). 

Peanuts with a high oleic:linoleic ratio are less 

susceptible to oxidative deterioration and off 

flavor development caused by oxidative cleavage 

of polyunsaturated fatty acids. The ratio of oleic 

to linoleic is influenced primarily by genotype, 

but interactions exist between genotype and the 

environment.

Horticultural Maturity Indices

Peanuts are an indeterminant plant, with flowering 

followed by underground seed development over 

a range of time. Assessment of peanut maturity 

should be conducted using multiple plants at 
758

Table 1. Comparison of screen sizes and tolerances (by weight) for American Peanut 

Shellers Association (APSA) and USDA Grades for shelled Spanish peanuts

Grade and minimum Fall-through Other Splits Damage Damage Foreign Moisture

screen size prescribed types and minor material

screens defects

%

No. 1 (15/64 x 3/4” slot)

APSA 2.00 1.00 3.00 0.75 1.25 0.10 9.00

US 2.00 1.00 3.00 1.50 2.00 0.10 -----

Splits (16/64” round)

APSA * 2.00 ---- 1.50 2.00 0.20 9.00

US ** 2.00 ---- 2.00 2.00 0.20 ----

No. 2 (16/64” round)

APSA 6.00*** 2.00 ---- 1.00 2.00 0.20 9.00

US 6.00*** 2.00 ---- ---- 2.50 0.20 ----

* (APSA) 2.00% sound portions of peanuts which pass through the prescribed screen; and 4.00% 

for sound whole kernels, not over 3.00% which will pass through a 13/64×3/4 in screen. This fallthrough combined with percentage of sound portions shall not exceed 4.00%.

** (US) 2.00% sound portions of peanuts which will pass through the prescribed screen; and 4.00% for 

sound whole kernels.

*** Combined fall-through of sound portions through a 16/64 in round screen and sound whole kernels 

through a 13/64×3/4 in screen shall not exceed 4.00%
759

Table 2. Comparison of screen sizes and tolerances (by weight) for American Peanut Shellers Association (APSA) and USDA Grades for shelled runner peanutsGrade and Fall-through Fall-through Other Splits Damage Damage Foreign Moistureminimum prescribed 16/64 x 3/4” types and minor materialscreen size screens slot screen defects

%

Jumbo38-42 ct. per oz.***or 21/64 x 3/4” slot 5.00 3.00 1.00 3.00 1.00 2.00 0.10 9.00Medium40-50 ct. per oz.*** or 18/64 x 3/4” slot (Report % riding 21/64 x 3/4” slot) 5.00 3.00 1.00 3.00 1.00 2.00 0.10 9.00Select16/64 x 3/4” slot(Report % riding 21/64 x 3/4” slot) ---- 3.00 1.00 3.00 1.00 2.00 0.10 9.00No. 116/64 x 3/4” slot(Report % riding 18/64 x 3/4” slot)

APSA ---- 3.00 1.00 3.00 1.00 2.00 0.10 9.00US ---- 3.00 1.00 3.00 1.50 2.00 0.10 ----

Mill run16/64 x 3/4” slot ---- 3.00 1.00 3.00 1.00 2.00 0.10 9.00
760Table 2. Comparison of screen sizes and tolerances (by weight) for American Peanut Shellers Association (APSA) and USDA Grades for shelled runner peanuts—continued

Grade and Fall-through Fall-through Other Splits Damage Damage Foreign Moistureminimum prescribed 16/64 x 3/4” types and minor materialscreen size screens slot screen defects

%

Splits17/64” round

APSA * * 2.00 ---- 1.50 2.00 0.20 9.00US ** ** 2.00 ---- 2.00 2.00 0.20 ----

* (APSA) 2.00% sound portions pass through 17/64 in round screen. 4.00% for sound whole kernels, not over 3.00% which 

will pass through 14/64×3/4 in slot screen. This fall-through combined with sound portions passing 17/64 in round not to exceed 4.00%.

** (US) 2.00% sound portions pass through 17/64 in round. 4.00% for sound whole kernels.*** American count per ounce shall be within the specified range.Each of the above grades may be certified “with splits” providing all requirements of the grade are met, except that a tolerance of 15% is allowed for split kernels of which not more than 3% will pass through 17/64 in round screen.
761

Table 3. Comparison of screen sizes and tolerances (by weight) for American Peanut Shellers Association (APSA) and USDA Grades for shelled Virginia peanutsGrade and Fall-through Other Sound Split Damage Damage Foreign Moisture Count perminimum prescribed types or broken and minor material poundscreen size screens kernels defects maximum

%

Extra large20/64 x 1” slot

APSA & US 3.00 0.75 3.00 1.00 1.75 0.10 ---- **512

Medium Virginia18/64 x 1” slot

APSA & US 3.00 1.00 3.00 1.25 2.00 0.10 ---- **640

No. 1 Virginia15/64 x 1” slot APSA & US 3.00 1.00 3.00 1.25 2.00 0.10 ---- **864Virginia splits20/64” round APSA & US *3.00 2.00 Not less ---- 2.00 0.20 ---- ----

than 90.00

No. 2 Virginia17/64” round APSA & US *6.00 2.00 As graded ---- 2.50 0.20 ---- ----* (APSA & US)—includes both sound split and broken and sound whole kernels which pass through prescribed screens.** Unless otherwise specified.Each of the above APSA whole grades may be certified as “with splits” providing all requirements of the grade are met, except that a tolerance of 15% is allowed for split kernels of which not more than 3% will pass through 17/64 in round screen.
762

Table 4. Comparison of screen sizes and tolerances (by weight) for American Peanut 

Shellers Association (APSA) and USDA Grades for in-shell Virginia peanuts

Grade Fall-through Cracked or Damaged Count per pound

and minimum prescribed broken shells, kernels

screen size screen pops, paper, and

foreign material

 

 % 

Jumbo 

37/64 x 3”

APSA 5.00 *10.00 3.50 **176 (U.O.S.)

US 5.00 *10.00 3.50 **176 (U.O.S.)

Fancy

32/64 x 3”

APSA 5.00 *11.00 4.50 **225 (U.O.S.)

US 5.00 *11.00 4.50 **225 (U.O.S.)

* (APSA & US)—not more than 0.5% shall be allowed as dirt or other foreign material.

** Unless otherwise specified.
763

various locations within a field. Peanut maturity 

may be judged by the shell-out procedure, 

involving separation of peanut seed into mature 

or immature categories. Using the shell-out 

procedure, a peanut is considered mature if the 

inner hull is brown and the seed coat is pink to 

red. Optimum maturity is reached for runner 

and Spanish types when 75 to 80% of the inner 

hull has turned brown and for Virginia types 

when 65% of the seed coat has turned deep pink. 

Runner peanut maturity can be determined by a 

hull-scrape method, in which maturity profiles for 

samples are estimated based on degree of change 

in pod mesocarp from white to brown to black 

(Williams and Drexler 1981).

Grades, Sizes, and Packaging

U.S. grade standards and industry grade standards 

from the American Peanut Shellers Association 

exist for shelled Spanish, shelled runner, 

shelled Virginia, and in-shell Virginia peanuts. 

A comparison of tolerances as provided by the 

American Peanut Shellers Association fficial 

Trade Rules for shelled peanuts based primarily 

on size, peanuts of other types, amount of split or 

broken kernels, freedom from foreign material, 

damage, minor defects, and in some cases 

moisture percentage are presented in tables 1 to 

4. Tolerances for in-shell Virginia peanuts based 

on maturity; freedom from loose shelled peanuts; 

discoloration of shell; presence of dirt, shell, and 

other foreign material; and degree of kernel fill 

inside the shell are compared.

Raw in-shell peanuts are typically stored 

as “farmer stock peanuts” in flat, ventilated 

warehouses or grain bins in bulk or, less 

commonly, in 50-lb (23 kg) burlap bags for a 

week to 10 mo prior to shelling (Smith et al. 

1995). After shelling, raw peanuts are often 

shipped in bulk containers but may be packaged in 

burlap or nylon tote bags of various sizes. Peanuts 

for human consumption must be free of visible 

Aspergillus flavus mold, containing less than 15 

ppb (nL L-1) aflatoxin. Lots imported into the 

United States may be designated “segregation 1” 

or “segregation 2” depending on degree of kernel 

damage and concealed damage from rancidity, 

mold, or decay. Segregation 1 peanuts may 

not contain more than 2.00% damaged kernels 

nor more than 1.00% concealed damage, while 

segregation 2 peanuts may contain more than 

2.00% damaged or more than 1.00% concealed 

damage. Segregation 3 peanuts are those which 

contain visible Aspergillus flavus mold or 15 ppb 

(nL L-1) or more aflatoxin. 

Optimum Storage Conditions

In-shell farmers-stock peanuts should be dried 

to about 7.5% moisture. If stored at 10 °C (50 

°F), these can be stored for up to 10 mo without 

significant quality loss (Davidson et al. 1982). 

High losses in milling quality may occur if 

peanuts are dried to below 7% moisture or if 

kernel temperature is below 7 °C (44.6 oF) during 

shelling (McIntosh and Davidson 1971). Peanut 

moisture content >10% should be avoided to 

prevent mold growth (Diener and Davis 1977). 

Adequate ventilation in a warehouse storage 

facility, preferably providing one air change every 

3 min, is also desirable to prevent excess moisture 

and heat from accumulating in the storage facility 

(Smith and Davidson 1982). 

Quality of raw shelled peanuts can be maintained 

for at least 1 year at 1 to 5 °C (34 to 41 °F) with 

moisture content of <7%, or for 2 to 10 years at 

-18 °C (0 °F) and <6 % moisture. Maintaining 

RH between 55 and 70% at 1 to 5 °C (34 to 41 

°C) will maintain peanut moisture content at 7 to 

7.5%. Careful handling of peanuts equilibrated 

to <5 °C (41 °F) is necessary to prevent bruising 

and subsequent oil seepage from damaged 

cells within the cotyledon. Upon removal of 

raw shelled peanuts from refrigerated or frozen 

storage, equilibration to ambient temperature 

should be gradual in conditioning rooms, with 

RH, temperature, and air-flow adjusted to prevent 

moisture condensation onto peanuts.
764

Controlled Atmosphere Considerations

Low-O2

 storage shows promise for delaying 

rancid flavor development and insect infestation 

(Slay et al. 1985). High-CO2

 storage appears 

to limit growth of Aspergillus flavus in shortduration storage of high-moisture, noncured 

peanuts. Peanuts at 20% moisture stored at 0.6 

to 3 °C (33 to 37 °F) in a high-CO2

 environment 

had acceptable quality for 4 days but deteriorated 

after 8 days of storage (Moseley et al. 1971). For 

longer-term storage of high-moisture, shelled 

peanuts under ambient temperature conditions, 

<1.5% O2

 was required to slow Aspergillus flavus

growth; but no CA totally eliminated aflatoxin 

production (Wilson and Jay 1976).

Retail Outlet Display Considerations

Peanuts are normally marketed at ambient 

temperature. Using low O2

 and preventing 

excessive exposure to light is recommended. Inshell peanuts may be displayed and marketed in 

bulk containers. Exposure to moisture or high RH 

should be avoided.

Chilling Sensitivity

Prior to or during harvest and prior to postharvest 

drying, exposure to chilling temperatures of 0.9 

to 1.6 °C (33.6 to 35 °F) caused increased ethanol 

production, and the effect was greater for small 

seeds than for large seeds within a genotype. This 

was accompanied by increased seed leachate, 

suggested by the authors to be indicative of 

induction of anaerobic respiration and cell 

membrane damage (Singleton and Pattee 1989). 

Following postharvest drying and during storage, 

peanuts do not appear to be sensitive to chilling 

and may be stored at or below freezing. 

Ethylene Production and Sensitivity

Peanut seeds exhibit dormancy periods following 

harvest of 63 to 84 days, varying with genotype 

and temperature during pod maturation and 

storage. Soaking seeds in GA3 or ethephon at 

50 to 200 μg mL-1 was effective in breaking 

dormancy (Kapur et al. 1990). Nondormant 

peanuts exhibit a climacteric-like rise in ethylene 

production during seed germination (Whitehead 

and Nelson 1992). 

Respiration Rates

Properly cured peanuts in storage exhibit a 

relatively low rate of respiration. During harvest 

and prior to curing, especially for high-moisture 

peanuts, respiration rates may be substantial and 

significant losses in quality can ensue. Freshly 

harvested peanuts should be dried soon after 

harvest to <10% moisture to assure optimum 

quality.

Physiological Disorders

Shriveled seed trait has been identified as a 

heritable condition for peanuts. Seed mature 

normally but appear shriveled and thus appear 

to have been harvested while immature. Seeds 

of shriveled lines exhibit up to 67% less oil and 

double the amount of sucrose, and defatted meal 

contained less protein (Jakkula et al. 1997). 

Improper curing of peanuts results in loss of 

quality and off-flavor development. 

Fermented, fruity off flavor is caused by freezing 

temperatures during harvest while peanuts are still 

windrowed (Singleton and Pattee 1991) or by too 

high a temperature during curing (Sanders et al. 

1989). Effects of improper curing are greatest on 

smaller seed, perhaps indicating greater effect on 

immature seed (Sanders et al. 1990). 

Postharvest Pathology

Peanuts are susceptible to infection by various 

molds and fungi, and a combination of storage 

at 1 to 5 °C (33.8 to 41 °F) and reduction of 

moisture content to <7.5% may be effective in 

reducing mold and fungi growth in storage. The 
765

presence of toxic fungal metabolites (mycotoxins) 

are a particular concern. The name “aflatoxin” 

refers to four metabolites found in contaminated 

peanuts and designated aflatoxin B1, B2, G1, 

and G2. Aflatoxins B1 and B2 are metabolites of 

Aspergillus flavus, and all four aflatoxins may be 

produced by Aspergillus parasiticus (Cole et al. 

1995). A fifth mycotoxin, cyclopiazonic acid, is 

somewhat less toxic than aflatoxin and is produced 

by Aspergillus flavus, other Aspergillus species, 

and several species of Penicillium (Dorner et al. 

1985). 

Preharvest conditions favoring aflatoxin 

contamination are high temperatures and 

drought stress during the last 3 to 6 weeks of 

the growing season (Cole et al. 1989). Lateseason irrigation may be effective in reducing 

aflatoxin contamination (Dorner et al. 1989). 

When aflatoxin contamination occurs, it is 

common for most of the harvested seed to be 

free of contamination with only a few highly 

contaminated seeds. Although monitoring at the 

point of sale for Aspergillus flavus is mandated 

by the USDA Peanut Marketing Agreement, and 

detection of ≥15 ppb (nL L-1) aflatoxin leads to 

positive aflatoxin identification, the irregular 

distribution of infection may lead to false negative 

designations. 

Storage conditions to deter growth of the causal 

organisms and subsequent metabolic production 

of the mycotoxins primarily involve prevention 

of rehydration during storage. Decontamination 

of contaminated lots is most effectively done with 

electronic color sorting, although size and density 

separation may also be effective in removal of the 

most susceptible underdeveloped seed.

Quarantine Issues

Importation of peanut seed into the United States 

for planting is prohibited from Burkino Faso, 

the People’s Republic of China, Cote d’Ivoire, 

India, Indonesia, Japan, the Phillipines, Senegal, 

Thailand, and Taiwan because of peanut stripe 

virus. During import of peanuts, all lots must 

be labeled with a positive lot identification and 

must meet the requirements for segregation 1 

peanuts if used for human consumption. Peanuts 

with visible Aspergillus flavus mold, or those 

containing ≥15 ppb aflatoxin, may not be used for 

edible purposes; they may be used for oil stock. 

Such peanuts may be blanched and reseparated 

into aflatoxin-negative lots, which may be used for 

edible purposes. 

Special Considerations

Peanuts are a major allergenic food among adults 

and children in the United States (Taylor 1992). 

Allergen activity has been identified for at least 

six allergens by phage display technology and is 

known to be in association with the two major 

storage proteins, arachin and conarachin, and in 

profilin (Kleber et al. 1999). Allergens may also 

be present in refined peanut oil (Olszewski et al. 

1998). Due in large part to allergenicity, any food 

product containing peanuts or peanut oil must be 

labeled as such. 

Careful handling of cured farmers-stock peanuts 

to prevent breakage of shells reduces the risk for 

spread of fungal contamination and maintains 

the grade. Conveyors, cleaners, sizers, and 

other handling equipment should be padded 

where appropriate and properly maintained to 

prevent excessive breakage during handling. 

Once shelled and roasted, peanuts should be 

handled carefully to prevent separation of the 

half kernels and breakage since splits and pieces 

are more susceptible to oxidative deterioration 

and rancidity development. Peanuts will absorb 

lipophilic volatiles from their surroundings or 

from inappropriate packaging that can induce 

off flavors. Absorption of ammonia can cause 

darkening of nutmeats.
766

References

Cheng, H.Y., G.H. Zheng, X.M. Jing, et al. 1997. 

Storage of peanut seeds with low moisture content 

for 11 years in ambient temperature. Plant Gen. 

Resour. Newsletter 110:35-40.

Cole, R.J., J.W. Dorner, and C.C. Holbrook. 

1995. Advances in mycotoxin elimination and 

resistance. In H.E. Pattee and H.T. Stalker, 

eds., Advances in Peanut Science, pp. 456-474. 

American Peanut Research and Education Society, 

Stillwater, OK.

Cole, R.J., T.H. Sanders, J.W. Dorner, and P.D. 

Blankenship. 1989. Environmental conditions 

required to induce preharvest aflatoxin 

contamination of groundnuts: summary of 

six years research. In Proceedings of the 

ICRISAT International Workshop on Aflatoxin 

Contamination of Groundnut, 1989, pp. 279-287. 

International Crops Research Institute for the 

Semi-Arid Tropics Center, Patancheru, Peru.

Davidson, J.I., T.B. Whitaker, and J.W. Dickens. 

1982. Grading, cleaning, storage, shelling and 

marketing of peanuts in the United States. In

H.E. Pattee and C.T. Young, eds., Peanut Science 

and Technology, pp. 571-623. American Peanut 

Research and Education Society, Yoakum, TX.

Diener, U.L., and N.D. Davis. 1977. Aflatoxin 

formation in peanuts by Aspergillus flavus. Bull. 

493, Auburn University Agricultural Experiment 

Station, Auburn, AL.

Dorner, J.W., R.J. Cole, and L.G. Lomax. 1985. 

The toxicity of cyclopiazonic acid. In J. Lacey, 

ed., Trichothecenes and Other Mycotoxins, pp. 

529-535. John Wiley and Sons, New York, NY.

Dorner, J.W., R.J. Cole, T.H. Sanders, and P.D. 

Blankenship. 1989. Interrelationship of kernel 

water activity, soil temperature, maturity and 

phytoalexin production in pre-harvest aflatoxin 

accumulation of drought-stressed peanuts. 

Mycopathalogia 105:117-128.

Holaday, C.E., and J.L. Pearson. 1974. Effects of 

genotype and production area on the fatty acid 

composition, total oil and total protein in peanuts. 

J. Food Sci. 39:1206-1209.

Jakkula, L.R., S.F. O’Keefe, D.A. Knauft, and 

K.J. Boote. 1997. Chemical characterization of a 

shriveled seed trait in peanut. Crop Sci. 37:1560-

1567.

Kapur, A., J. Kaur, H.L. Sharma, and H. Singh. 

1990. Preconditioning of peanut (Arachis 

hypogaea) seeds to release dormancy. Ann. Biol. 

Ludhiana 6:141-145.

Kleber, J.T., R. Crameri, U. Appenzeller, et al. 

1999. Selective cloning of peanut allergens, 

including profilin and 2S albumins, by phage 

display technology. Int. Arch. Allergy Immun. 

119:265-274.

Knauft, D.A., and D.W. Gorbet. 1989. Genetic 

diversity among peanut cultivars. Crop Sci. 

29:1417-1422.

McIntosh, F.P., and J.I. Davidson. 1971. Effect 

of temperature on shelling runner- and spanishtype peanuts. Rep. 52-65, U.S. Department of 

Agriculture, Agricultural Research Service, 

Washington, DC.

Moseley, Y.C., H.B. Manbeck, G.L. Barnes, and 

G.L. Nelson. 1971. Controlled atmosphere for 

short duration storage of peanuts before drying. 

Trans. Amer. Soc. Agr. Eng. 14:206-210.

Olszewski, A., L. Pons, F. Moutete, et al. 1998. 

Isolation and characterization of proteic allergens 

in refined peanut oil. Clin. Exper. Allergy 28:850-

859.

Sanders, T.H., P.B. Blankenship, J.R. Vercellotti, 

and K.L. Crippen. 1990. Interaction of curing 

temperature and inherent maturity distribution in 

descriptive flavor of commercial grade sizes of 

Florunner peanuts. Peanut Sci. 17:85-89.
767

Sanders, T.H., R.W. McMichael, and K.W. 

Hendrix. 2000. Occurrence of resveratrol in edible 

peanuts. J. Agric. Food Chem. 48:1243-1246.

Sanders, T.H., J.R. Verecellotti, P.B. Blankenship, 

et al. 1989. Interaction of maturity and curing 

temperature on descriptive flavor of peanuts. J. 

Food Sci. 54:1066-1069.

Singleton, J.A., and H.E. Pattee. 1989. Effect of 

chilling injury on windrowed peanuts. Peanut Sci. 

16:51-54.

Singleton, J.A., and H.E. Pattee. 1991. Peanut 

moisture/size, relation to freeze damage and effect 

of drying temperature on volatiles. J. Food Sci. 

56:579-581.

Slay, W.O., W.G. Ferguson, and J.A. Pomplin. 

1985. Some effects of conventional and lowoxygen atmosphere storage and processing 

methods on Florunner peanut seed. Peanut Sci. 

12:8-11.

Smith, J.S., P.D. Blankenship, and F.P. McIntosh. 

1995. Advances in peanut handling, shelling and 

storage from farmer stock to processing. In H.E. 

Pattee and H.T. Stalker, eds., Advances in Peanut 

Science, pp. 500-527. American Peanut Research 

and Education Society, Stillwater, OK.

Smith, J.S., and J.I. Davidson. 1982. 

Psychometrics and kernel moisture content as 

related to peanut storage. Trans. Amer. Soc. Agric. 

Eng. 25:231-236.

Taylor, S.L. 1992. Chemistry and determination of 

food allergens. Food Tech. 46:146-152.

Whitehead, C.S., and R.M. Nelson. 1992. 

Ethylene sensitivity in germinating peanut seeds: 

the effect of short-chain fatty acids. J. Plant 

Physiol. 139:479-483.

Williams, E.J., and J.S. Drexler. 1981. A nondestructive method for determining peanut pod 

maturity. Peanut Sci. 8:134-141.

Wilson, D.A., and E. Jay. 1976. Effect of 

controlled atmosphere storage on aflatoxin 

production in high moisture peanuts (groundnuts). 

J. Stored Prod. Res. 12:97-100.
768

Pecan

Niels Maness

Maness is with the Department of Horticulture 

and Landscape Architecture, Oklahoma State 

University, Stillwater, OK.

Scientific Name and Introduction

Carya illinoinsis L. is a member of the hickory 

family (Jugulaceae). The edible seed is surrounded 

by a shuck that opens (dehisces) when the seed is 

mature. Nuts are harvested in late fall and early 

winter by mechanically shaking the trees and 

gathering the nuts from the orchard floor. Nuts 

are covered by a shell that is divided into two 

relatively equal-sized halves. Pecans are native 

to the southern United States and Mexico and 

are classified for marketing either as seedling 

(primarily natives) or cultivars. Seedling pecans 

have typically thicker shells with smaller kernels, 

lower shellout percentage, and higher oil content 

than cultivars. The majority of commercial 

production is in cultivars such as ‘Western,’ 

‘Desirable,’ ‘Stuart,’ ‘Wichita,’ and ‘Pawnee.’

Quality Characteristics and Criteria

Pecan kernels should be yellow-golden to lightbrown in color, be of roughly equal width from 

one end to the other, and be free of any shell or 

other foreign material as well as off odor or flavor. 

Water content should be <4% to prevent mold 

growth and retard rancidity development. Water 

content <2% increases brittleness that induces 

greater kernel breakage during handling and 

enhances cracking of the testa, which increases O2

permeation of the nutmeat, favoring rancidity. Oil 

content of pecan kernels inversely affects shelflife, and oil content varies from 55 to 75% (by 

weight) and is influenced by cultivar, geographic 

location, and year of production (Wells and 

McMeans 1978).

Horticultural Maturity Indices

Kernels are considered mature after oil 

accumulation is complete, which coincides with 

shuck split (Eddy and Storey 1988). Maturation of 

fruit within a tree occurs nonuniformly and can be 

influenced by cultivar and weather conditions.

Grades, Sizes, and Packaging

In-shell and shelled grades exist and are primarily 

determined by size, degree of kernel fill, color, 

and freedom from defects and foreign material. 

Grades for in-shell pecans include U.S. No. 1 and 

U.S. No. 2, based primarily on uniformity of shell 

color, absence of shell defects, kernel defects, and 

extraneous or foreign material. Sizes of in-shell 

pecans are based on number of nuts per 0.45 kg (1 

lb) and include Oversize (≤55), Extra Large (56 

to 63), Large (64 to 77), Medium (78 to 95), and 

Small (96 to 120). In-shell pecans are packaged in 

bags containing 36.4 to 54.5 kg (80 to 120 lb) or 

in palletized containers. 

Grades for shelled pecans include U.S. No. 1 and 

U.S. Commercial for halves, halves and pieces, 

and pieces based primarily on testa color, degree 

of kernel fill, moisture content, freedom from shell 

or extraneous material, and freedom from damage. 

When the color of kernels in a lot conforms to 

the “light” or “light amber” classification, these 

color designations may be used to describe the lot 

in connection with the grade. Size classifications 

for halves are based on number of halves per 0.45 

kg (1 lb) and include Mammoth (≤250), Junior 

mammoth (251 to 300), Jumbo (301 to 350), Extra 

large (351 to 450), Large (451 to 550), Medium 

(551 to 650), Small or Topper (651 to 750), and 

Midget (≥751). Size classification for pieces are 

based on the maximum and minimum round 

diameter in inches through which the pieces will 

or will not pass and include Mammoth (>1.3 cm, 

1/2 in), Extra large (1.4 to 1.1 cm, 9/16 to 7/16 in), 

Halves and pieces (>0.8 cm, 5/16 in), Large (1.3 

to 0.8 cm, 1/2 to 5/16 in), Medium (1.0 to 0.5 cm, 

3/8 to 3/16 in), Small (0.6 to 0.3 cm, 1/4 to 1/8 

in), Midget (0.5 to 0.2 cm, 3/16 to 1/16 in), and 

Granules (0.3 to 0.2 cm, 1/8 to 1/16 in). Shelled 
769

pecans are packaged in 13.6-kg (30-lb) greaseproof boxes, either loose or vacuum-sealed inside 

plastic bags.

Optimum Storage Conditions

Mechanically harvested in-shell pecans should be 

dried to 4.5% moisture prior to storage to preserve 

quality and prevent mold growth (Heaton et al. 

1977). Pecan nutmeats contain 7 to 9% moisture 

after shelling and should be dried to 3 to 4% 

moisture to maintain quality. Drying temperatures 

greater than 38 °C (100 °F) should be avoided 

because they cause darkening of nutmeats. 

Recommended conditions for storage of pecans 

is <2 °C (36 °F) at 70% RH. Long-term storage 

should be near -18 °C (0 °F) with 70% RH. Inshell pecans can be stored for 6 mo at 22 °C (72 

°F), 12 mo at 0 °C (32 °F), or 24 mo at -18 °C (0 

°F); whereas shelled pecans can only be stored for 

3 mo at 22 °C (72 °F), 9 mo at 0 °C (32 °F), or 18 

mo at -18 °C (0 °F) (Woodroof and Heaton 1962). 

Frozen pecans are brittle and should be handled 

with care to prevent excessive breakage. Pecans 

may be thawed and refrozen without damage, 

provided they are properly tempered. Tempering 

involves slowly raising the temperature of pecans 

at low RH and high airflow, with each 10 °C (18 

oF) increase in temperature occurring over 48 h. 

This can be accomplished by placing pecans from 

frozen storage sequentially into two rooms for 

several days each. The first room should be at 5 

°C (41 °F) and the second room at 16 °C (61 °F) 

(Santerre 1994). Tempering prevents moisture 

condensation onto nutmeats during thawing that 

could induce a soggy texture and promote mold 

growth. 

Modified Atmosphere Considerations

Shelf-life of pecans may be increased by storage 

in 2 to 3% O2

 in N2, and less frequently in CO2 as 

the balance gas. Storage at <2% O2

 for 52 days 

can cause a fruity flavor to develop (Santerre et 

al. 1990). O2 transmission rates for packaging 

materials should be >0.08 mL per 100 cm per 24 

h (Dull and Kays 1988). Vacuum packaging can 

offer a further benefit of protection from breakage.

Retail Outlet Display Considerations

Use of packaging to reduce O2

 concentration and 

prevent excessive light exposure is recommended 

for shelled pecans. In-shell pecans may be 

displayed in bulk containers. Exposure to moisture 

should be prevented.

Chilling Sensitivity

Pecans are not sensitive to chilling and are 

commonly stored at temperatures at or below 

freezing.

Ethylene Production and Sensitivity

Pecans produce very low amounts of ethylene. 

Prolonged exposure to ethylene may cause pecans 

to darken and shorten their shelf-life. 

Respiration Rates

Pecans have a low respiration rate of <5 mg CO2

kg-1 h-1 at 5 °C (41 °F), or about 2.5 mL CO2

 kg-1

h-1. Heat production is about 1,100 BTU ton-1 day-1

or 305 kcal tonne-1 day-1.

Physiological Disorders

Wafering is characterized by asymmetric width 

of halves along the longitudinal axis. It is caused 

by poor kernel fill during development. This 

condition is most prevalent during a year in which 

the crop load on trees is excessive (Smith et al. 

1993). 

Stink bug and pecan weevil feeding during pecan 

development results in round or irregularly 

shaped black discoloration of the testa that is only 

evident after shelling. Pecan weevils lay eggs in 

developing pecans; larvae hatch soon after kernel 
770

maturity, consume the nutmeat, and exit the pecan 

leaving a small round hole in the shell. Pecans 

containing pecan weevil larvae can sometimes be 

identified by an oil-soaked or reddish appearance.

Opalescence, a condition characterized by 

an opaque or oil-stained appearance of all or 

a portion of the nutmeat, has been identified 

and attributed to breakdown of oil bodies and 

subsequent leakage of oil within the cotyledon. 

This leakage increases O2

 exposure of oil and 

decreases shelf-life by accelerating oxidative 

rancidity development.

Sticktights are nuts that fail to shed the shuck at 

harvest. Insufficient moisture in fall, or insect 

feeding on the shuck, may cause this condition 

because shuck splitting is an active process that 

requires the shucks to remain turgid and for 

abscission layers to form at the sutures and at 

the peduncle (Worley 1982). Early fall freeze 

or potassium insufficiency may also increase 

prevalence of sticktights. Kernels from sticktight 

pecans are often of lower quality due to premature 

death of the vascular system feeding the 

developing kernels.

Vivipary (sprouting of nuts on the tree) renders 

affected pecans unmarketable and may be reduced 

by late season irrigation (Stein et al. 1989) or by 

fruit thinning (Sparks et al. 1995).

Postharvest Pathology

The most common decay found in pecans is 

caused by molds, with Penicillium and Aspergillus

most prevalent (Huang and Hanlin 1975). The 

intact shell provides some defense against mold. 

Some strains of A. flavus and A. parasiticus that 

have been isolated from pecans can produce 

aflatoxins, a heat-resistant carcinogenic and 

toxic byproduct. Storage at refrigerated or frozen 

temperatures prevents or slows mold growth. 

Reduction of nutmeat moisture content to <4.5% 

and storage at RH <70% provide a water activity 

of 0.65 to 0.70, which will not support growth of 

most molds. 

E. coli is a common shell contaminant, especially 

for nuts harvested in orchards where animal 

grazing is practiced (Marcus and Amling 1973). 

Contamination of nutmeats may occur if shells are 

broken during harvest or if shells are not properly 

sanitized by addition of chlorine to heated soakwater just prior to cracking. Because of high 

amounts of organic material on the surface of 

pecan shells, chlorine should be monitored and 

replenished as needed to maintain the desired 

concentration.

Quarantine Issues

Pecan shucks, shells, and nuts in the shell, as 

well as containers, equipment, and vehicles used 

in association with them, must be free of pecan 

casebearer, pecan weevil, and hickory shuckworm 

prior to transportation into California.

Special Considerations

Pecans marketed in-shell should be cracked and 

sampled periodically to assess nutmeat quality. 

Pecan halves and pieces marketed in plastic 

bags should be handled with care to prevent 

excessive breakage and grade change. Since 

most bags for marketing shelled pecans are clear, 

care in prevention of exposure to direct sunlight 

or excessive UV radiation should be exercised 

to prevent darkening of the testa. Increased 

temperature during handling can also enhance 

darkening and promote development of rancid 

flavor. Pecans will absorb lipophilic volatiles in 

the environment that can introduce off flavors. 

Absorption of ammonia will cause darkening of 

nutmeats. Although frozen storage increases shelflife, once out of storage pecans should be used 

quickly because of their short shelf-life at room 

temperature compared to never-frozen pecans. 
771

References

Dull, G.G., and S.J. Kays. 1988. Quality and 

mechanical stability of pecan kernels with 

different packaging protocols. J. Food Sci. 53:565-

567.

Eddy, M., and J.B. Storey. 1988. The influence 

of harvest date on oil and flavor development 

in Desirable and Whichita pecans. HortScience 

23:782.

Heaton, E.K., A.L. Shewfelt, A.E. Badenhop, and 

L.R. Beuchat. 1977. Pecans: handling, storage, 

processing and utilization. Research Bull. 197, 

University of Georgia, Georgia Experiment 

Station, Athens, GA.

Huang, L.H., and R.T. Hanlin. 1975. Fungi 

occurring in freshly harvested and in-market 

pecans. Mycologia 67:689-700.

Marcus, K.A., and H.J. Amling. 1973. Escherichia 

coli field contamination of pecan nuts. Appl. 

Microbiol. 26:279-281.

Santerre, C.R. 1994. Pecan processing. In C.R. 

Santerre, ed., Pecan Technology, pp. 49-67. 

Chapman and Hall, New York, NY.

Santerre, C.R., A.J. Scouten and M.S. Chinnan. 

1990. Room temperature of shelled pecans: 

control of oxygen. Proc. Southeastern Pecan 

Growers’ Assoc. 83:113-121.

Sparks, D., W. Reid, I.E. Yates, et al. 1995. 

Fruiting stress induces shuck decline and 

premature germination in pecan. J. Amer. Soc. 

Hort. Sci. 120:43-53.

Smith, M.W., W. Reid, B. Carroll, and B. Cheary. 

1993. Mechanical fruit thinning influences fruit 

quality, yield, return fruit set and cold injury of 

pecan. HortScience 28:1081-1084.

Stein, L.A., G.R. McEachern, and J.B. Storey. 

1989. Summer and fall moisture stress and 

irrigation scheduling influence pecan growth and 

production. HortScience 24:607-611.

Wells, J.M., and J.L. McMeans. 1978. Rancidity, 

iodine values and oil content of 21 pecan cultivars. 

Proc. Southeastern Pecan Growers’ Assoc. 71:159-

162.

Woodroof, J.G., and E.K. Heaton. 1962. Storage 

of pecans. Research Bull. 149, University of 

Georgia, Georgia Experiment Station, Athens, GA.

Worley, R.E. 1982. Tree yield and nut 

characteristics of pecan with irrigation under 

humid conditions. J. Amer. Soc. Hort. Sci. 107:30-

34. 
772

Pistachio

John M. Labavitch

Labavitch is with the Department of Plant 

Sciences, University of California, Davis, CA.

Scientific Name and Introduction

Pistacia vera L. is the only species of the 11 in 

the genus Pistacia that produces edible nuts. It is 

a native of western Asia and Asia Minor, and wild 

representatives are still found in hot, dry locations 

in these areas. The pistachio was introduced to 

Europe at the beginning of the Christian Era. 

The USDA plant exploration service introduced 

the pistachio to the United States in 1890. It was 

introduced to California in 1904 at the Plant 

Introduction Station in Chico, CA (Hendricks and 

Ferguson 1995).

The pistachio tree is dioecious; thus orchard 

plantings must include the appropriate ratio 

of females and males (8:1 in older plantings, 

but up to 25:1 in more recently established 

orchards [Kallsen et al. 1995]). At present the 

California industry is dominated by one male 

cultivar (‘Peters’) and one female (‘Kerman’), 

although other cultivars are being tested. The 

reliance on single cultivars poses the potential 

for catastrophic problems for the industry with 

pests and diseases, and efforts to evaluate existing 

alternative germplasm and develop new cultivars 

are underway (Parfitt 1995a,b). There are also 

a limited number of rootstocks in use. While 

the Verticillium-tolerant Pistacia integerrima

is currently the dominant rootstock in use, P. 

atlantica × P. integerrima is increasingly being 

planted in California (Krueger and Ferguson 

1995). An important problem for pistachio 

growers is the strong tendency toward alternate 

bearing.

Quality Characteristics and Criteria

In-shell and shelled pistachios are marketed 

extensively. An important aspect of quality of the 

in-shell product is a shell that is free of staining. 

This is not only for cosmetic reasons. Shell 

staining is also an indicator of development, 

pathogen, and insect problems prior to harvest. 

Kernel quality criteria include a firm, crisp texture 

(which is degraded by insufficient drying after 

harvest or storage at too high an RH), a sweet 

and oily flavor, and freedom from rancidity 

(Kader et al. 1982). Kernels are high in fat 

content (approximately 45% by weight) and crude 

protein (approximately 30%). Total levels of lowmolecular-weight sugars are 3 to 4%, but reducing 

sugars (primarily glucose and fructose) make up 

only about 10% of the total sugar (Kader et al. 

1982, Labavitch et al. 1982).

Horticultural Maturity Indices

The pistachio nut is a drupe; an exocarp and fleshy 

mesocarp surround the hard, but relatively thin, 

shell, which encloses the edible seed. Ideally the 

harvest is timed to the full accumulation of fat and 

sugar in the kernels. This is roughly coincident 

with the splitting of the shell. Shell split is not 

visible due to the fact that the fleshy mesocarp 

masks the shell in developing nuts. However, 

evidence of maturation can be seen in the color 

change of the hull (exocarp), which is green when 

the nut is not mature and then progresses through 

ivory to rose with full maturation. Activity in 

the abscission zones between the nuts and the 

rachis (assessed by a measurable decrease in 

“fruit removal force”) also indicates maturation. 

When fully mature, the nut with its shell will be 

ejected from the hull when pressure is applied 

with the thumb and forefinger at the hull’s distal 

end (Ferguson et al. 1995). Nuts at full maturity, 

as judged by the preceding criteria, will have full 

accumulation of fat and simple sugars (Labavitch 

et al. 1982). 

Harvest should not be delayed past full maturation 

of the crop because this will increase losses to 

navel orangeworm (Amyelois transitella Walker), 

birds, and fungi (particularly Aspergillus flavus), 

as well as late season weather (rain and wind). 

Furthermore, delayed harvest can lead to shell 

staining because of breakdown of the phenolic-
773

compound-rich hull tissues. When harvested the 

nuts are split and moisture content is high (40 to 

50%). Trees are shaken (by hand for young trees, 

mechanically for mature trees) and the nuts are 

caught on tarps or a catching frame and transferred 

to bins in order to eliminate problems caused by 

contact with the soil. 

Delays between harvest and further processing 

should be minimized because they only 

exacerbate problems caused by hull breakdown or 

contamination of hull tissues. Problems caused by 

unavoidable delays in hulling and drying (below) 

can be reduced by cold storage of bins at 0 oC 

(32 oF) and <70% RH without increasing shell 

staining (Kader et al. 1980, Thompson 1997). At 

the processor, the bins of nuts are dumped, and 

debris is removed by passage over an air leg. 

Hulls are removed, blanks are removed in a float 

tank, and the in-shell nuts are dried to 5 to 7% 

moisture. Most large handlers now use a two-stage 

process: Nuts are dried in a column dryer to 12 to 

13% moisture with forced hot air at 82 oC (180 oF) 

before the drying is completed more slowly (24 to 

48 h) with air heated to no more than 49 oC (120 

oF) (Ferguson et al. 1995).

Grades, Sizes, and Packaging

In-shell and shelled grades exist and are 

determined primarily by kernel size, degree of 

dryness, absence of foreign material, and freedom 

from defects caused by insects and mold. For the 

in-shell product, additional grading criteria include 

absence of shell pieces and free kernels, shells 

without stains and adhering hull material, and 

absence of unsplit shells and blanks. A complete 

description of U.S. quality standards, grades, and 

sizes for pistachios in the shell can be found at 

http://www.ams.usda.gov/AMSv1.0/getfile?dDoc

Name=STELPRDC5050502.

Shell staining is usually caused by dehiscence 

of the hull along its suture at the same time as 

the shell within is splitting. This premature hull 

dehiscence increases “early” problems with 

insects and molds (Doster and Michailaides 1999). 

Pearson (1996) and Pearson and Slaughter (1996) 

described testing of a machine vision system that 

might prove useful in sorting of nuts in processing 

streams to reduce the incidence of staining in the 

marketed product. The simultaneous splitting of 

shell and hull is generally caused by too tight an 

adherence of the hull to the shell. The absence of a 

tissue gap between the two pericarp-derived parts 

of the nut makes it impossible for the shell to split 

without triggering hull split. This often leads to 

shells with adhering hull material (Pearson et al. 

1996), considered a defect.

Optimum Storage Conditions

Once they have been dried (see above), nuts can 

be held at 20 oC (68 oF) and 65 to 70% RH for 

up to a year (Ferguson et al. 1995). Pistachios 

are considerably less prone to rancidification 

(precipitated by oxidation of polyunsaturated fatty 

acids) than are almonds and, particularly, pecans 

and walnuts. These commodities are also high in 

fat content, but walnut and pecan oils have a much 

higher content of polyunsaturated fatty acids than 

pistachio oil.

Controlled Atmosphere Considerations

While relatively stable when stored in air at 20 

oC (68 oF), storage under high CO2

 (Maskan and 

Karatus 1998), reduced O2

 (<0.5%), and lower 

temperature (0 to 10 oC) further improve flavor 

stability with the added benefit of providing insect 

control. Vacuum packaging or N2

 flushing of 

packages also provides benefits.

Chilling Sensitivity

Pistachios are not sensitive to chilling and can be 

stored at or below freezing.

Ethylene Production and Sensitivity

Pistachio production of ethylene is very low. 

There are no documented responses to ethylene 

that might affect nut quality.
774

Respiration Rates

The low water content of properly stored, 

dried pistachios makes them relatively inert 

metabolically. Respiratory rates are very low.

Physiological Disorders

Rancidification and shell staining have been 

discussed in previous sections. 

Developmental and physiological problems that 

occur before full maturity can have particularly 

important consequences for nut quality. Because 

nuts are only useful when they have split, failure 

of hull split as nuts reach full maturity can 

cause substantial yield losses. While splitting is 

maturation-dependant, it will be reduced by water 

stress late in the growing season (mid-August 

through September) and failure to maintain 

adequate boron (120 ppm [mg kg-1] leaf dry 

weight). Early in postharvest drying, the split on 

partially split nuts tends to widen (Freeman and 

Ferguson 1995). 

Blank nuts result when the embryo fails to 

develop. This can be caused by promotion of 

shell development from ovary tissues without 

successful fertilization. Blank development also 

occurs later in the season and has been explained 

as the result of the inability of the tree to provide 

sufficient assimilate to complete development of 

its entire crop. Inadequate boron and water stress 

are also indicated as causes of blank formation 

(Freeman and Ferguson 1995). 

Pistachios are strongly alternate-bearing and 

failure of hull split and blank formation are 

correlated with “on” and “off” crop years. Studies 

indicate that blanking tends to be much higher 

in “off” years and nonsplit nuts are much more 

common in “on” years. Of course, crop load is 

much higher in “on” years, and this has a large 

effect on assimilate partitioning.

Insect Problems

Several insects that are field pests of pistachios 

are able to cause superficial damage (“epicarp 

lesion”) to developing nuts. If insects are able 

to probe deeply or introduce fungal pathogens, 

these pests can cause damage to the kernels. The 

navel orangeworm (Amyelois transitella Walker), 

a primary field pest, is the major insect problem 

after harvest. Methyl bromide fumigation has been 

used to control navel orangeworm in harvested 

pistachios (Hartsell et al. 1986), but this fumigant 

is being phased out. Laboratory tests of navel 

orangeworm survival during pistachio processing 

indicate that very few of the insects survive nutdrying (Johnson et al. 1996). Projections indicate 

that survival of navel orangeworms is insufficient 

to be a problem in stored nuts, particularly 

because reinoculation of nuts due to insect 

reproduction within the dried, stored nuts is likely 

to be virtually nonexistent (Johnson et al. 1996).

Postharvest Pathology

Several fungi are capable of infecting growing 

pistachio nuts and causing damage to hulls and 

kernels. Infection is often facilitated by early 

splitting of hulls, which leads to infestations by 

a number of hemipteran insects that feed on the 

nuts and serve as nonspecific vectors for diseases. 

Alternaria and Cladosporium species are also 

colonizers of early split nuts. Late season rains 

will promote activity of Botryosphaeria dothidea

on pistachio hulls and kernels (Michailides et 

al. 1995). Because mold counts on nuts going 

into storage can be high (Heperkan et al. 1994), 

it is important that proper storage conditions 

(especially low RH and absence of standing water) 

be maintained to avoid serious problems. 

The greatest postharvest disease threats are from 

Aspergillus flavus and A. parasiticus. The danger 

is particularly serious because these fungi can 

produce aflatoxin. As with many disease problems 

of pistachio, vectoring by insects attracted to 

early split nuts (such as navel orangeworm) is 

an important contributing factor. In Doster and 

Michaelides’ (1994) study of Aspergillus molds 
775

in California pistachios, early split nuts had 

over 99% of the aflatoxin detected and navelorangeworm-infected nuts had substantially more 

infection by several Aspergillus species, as well 

as over 84% of the aflatoxin detected. The close 

association of contamination with early split nuts 

suggests that the potential aflatoxin problem can 

be reduced by following procedures for reducing 

early splitting or sorting out nuts with shells 

stained because of early splitting (discussed above 

and Michaelides et al. 1995). In theory, nuts 

with aflatoxin contamination could be sorted out 

based on aflatoxin fluorescence; however, Steiner 

et al. (1992) concluded that this approach may 

have limited value because of limited sensitivity 

of detection and inconsistent presentation of 

fluorescence in contaminated nuts. Further 

complicating the detection problem is the fact that 

substantial contamination in a large sample of nuts 

may be due to the initial contamination and spread 

by only a few individual nuts.

Quarantine Issues

Insect infestation is a potentially important 

problem, as are the fungal infections that often 

accompany insect damage. Fumigation with 

methyl bromide or phosphine has been used for 

disinfestation, but the former is being curtailed 

and insect resistance to phosphine has been 

reported (Zettler et al. 1990). New fumigants are 

being developed and tests of efficacy, including 

effects on flavor, are being performed (E.J. 

Mitcham, Univ. of California, Davis, 2002, 

personal communication). Thus far, the newer 

fumigants are not registered for pistachio nuts. 

References

Doster, M.A., and T.J. Michailides. 1994. 

Aspergillus molds and aflatoxins in pistachio nuts 

in California. Phytopathology 84:583-590.

Doster, M.A., and T.J. Michailides. 1999. 

Relationship between shell discoloration of 

pistachio nuts and incidence of fungal decay and 

insect infestation. Plant Dis. 83:259-264.

Ferguson, L., A. Kader, and J.Thompson. 1995. 

Harvesting, transporting, processing and grading. 

In L. Ferguson, ed., Pistachio Production, pp. 

110-114. University of California, Pomology 

Department, Center for Fruit and Nut Crop 

Research and Information, Davis, CA.

Freeman, M., and L. Ferguson. 1995. Factors 

affecting splitting and blanking. In L. Ferguson, 

ed., Pistachio Production, pp. 106-109. University 

of California, Pomology Department, Center for 

Fruit and Nut Crop Research and Information, 

Davis, CA.

Hartsell, P.L., H.D. Nelson, J.C. Tebbets, and P.V. 

Vail. 1986. Methyl bromide fumigation treatments 

for pistachio nuts to decrease residues and 

control navel orangeworm (Amyelois transitella)

(Lepidoptera: Pyralidae). J. Econ. Entomol. 

79:1299-1302.

Hendricks, L., and L. Ferguson. 1995. The 

pistachio tree. In L. Ferguson, ed., Pistachio 

Production, pp. 7-9. University of California, 

Pomology Department, Center for Fruit and Nut 

Crop Research and Information, Davis, CA.

Heperkan, D., N. Aran, and M. Ayfer. 1994. 

Mycoflora and aflatoxin contamination in shelled 

pistachio nuts. J. Sci. Food Agric. 66:273-278.

Johnson, J.A., R.F. Gill, K.A. Valero, and S.A. 

May. 1996. Survival of navel orangeworm 

(Lepidoptera: Pyralidae) during pistachio 

processing. J. Econ. Entomol. 89:197-203.

Kader, A.A., C.M. Heintz, J.M. Labavitch, and 

H.L. Rae. 1982. Studies related to the description 

and evaluation of pistachio nut quality. J. Amer. 

Soc. Hort. Sci. 107:812-816.

Kader, A.A., J.M. Labavitch, F.G. Mitchell, 

and N.F. Sommer. 1980. Quality and safety 

of pistachio nuts as influenced by postharvest 

handling procedures. In Pistachio Association 

Annual Report, pp. 44-52.
776

Kallsen, C., G.S. Sibbett, and C. Fanucchi. 

1995. Planning and designing the orchard. In L. 

Ferguson, ed., Pistachio Production, pp. 36-40. 

University of California, Pomology Department, 

Center for Fruit and Nut Crop Research and 

Information, Davis, CA.

Krueger, B., and L. Ferguson. 1995. Pistachio 

rootstocks. In L. Ferguson, ed., Pistachio 

Production, pp. 41-42. Center for Fruit and Nut 

Crop Research and Information, University of 

California, Pomology Department, Davis, CA.

Labavitch, J.M., C.M. Heintz, H.L. Rae, and A.A. 

Kader. 1982. Physiological and compositional 

changes associated with maturation of ‘Kerman’ 

pistachio nuts. J. Amer. Soc. Hort. Sci. 107:688-

692. 

Maskan, M., and S. Karatas. 1998. Fatty acid 

oxidation of pistachio nuts stored under various 

atmospheric conditions and different temperatures. 

J. Sci. Food Agric. 77:334-340.

Michailides, T., D.P. Morgan, and M.A. Doster. 

1995. Foliar and fruit fungal diseases. In L. 

Ferguson, ed., Pistachio Production, pp. 148-159. 

University of California, Center for Fruit and Nut 

Crop Research and Information, Davis, CA.

Parfitt, D. 1995a. Genetic improvement. In L. 

Ferguson, ed., Pistachio Production, pp. 47-53. 

University of California, Pomology Department, 

Center for Fruit and Nut Crop Research and 

Information, Davis, CA.

Parfitt, D. 1995b. Pistachio cultivars. In L. 

Ferguson, ed., Pistachio Production, pp. 43-46. 

University of California, Pomology Department, 

Center for Fruit and Nut Crop Research and 

Information, Davis, CA.

Pearson, T. 1996. Machine vision system for 

automated detection of stained pistachio nuts. 

Lebensm.-Wiss. u.-Technol. 29:203-209.

Pearson, T., and D.C. Slaughter. 1996. Machine 

vision detection of early split pistachio nuts. 

Trans. Am. Soc. Agric. Eng. 39:1203-1207.

Pearson, T., D.C. Slaughter, and H.E. Studer. 

1996. Hull adhesion characteristics of early-split 

and normal pistachio nuts. Appl. Eng. Agric. 

12:219-221.

Steiner, W.E., K. Brunschweiler, E. Leimbacher, 

and R. Schneider. 1992. Aflatoxins and 

fluorescence in brazil nuts and pistachio nuts. J. 

Agric. Food Chem. 40:2453-2457. 

Thompson, J.F. 1997. Maintaining quality of 

bulk-handled, unhulled pistachio nuts. Appl. Eng. 

Agric. 13:65-70.

Zettler, J.L., W.R. Halliday, and F.H. Arthur. 1990. 

Phosphine resistance in insects infesting stored 

peanuts in the southeastern United States. J. Econ. 

Entomol. 82:1508-1511.
777

Walnut

John M. Labavitch

Labavitch is with the Department of Plant 

Sciences, University of California, Davis, CA.

Scientific Name and Introduction

Persian (English) walnut (Juglans regia and a 

few related species) is a member of the family 

Juglandaceae and is by far the most important 

commercial walnut. The genus Juglans contains 

three other groups (butternut, east asian species, 

and black walnut species) that produce edible 

kernels. Persian walnuts evolved in central and 

eastern Asia and were introduced into California 

in the late 1700s. About 95% of U.S. production 

is in California. The most important cultivars 

are ‘Hartley,’ followed by ‘Chandler,’ ‘Serr,’ 

and ‘Vina.’ Recent cultivars such as ‘Tulare’ and 

‘Howard’ will become more important.

Nuts are mechanically shaken from trees during 

an extended harvest period from late August to 

early November. The edible kernel is surrounded 

by a husk that dehisces as the kernel nears 

maturity. The husk, which should be well split and 

relatively dry at harvest, is generally lost when 

the nuts fall to the ground. Harvested nuts (the 

shell and kernel) may be 35% or more water. Nuts 

are quickly swept from the orchard floor to avoid 

damage to the fragile nut and are then dehydrated 

in forced-air dryers to 8% water content. The 

temperature of the drying air is kept low, <43 

°C (110 °F), to avoid damage leading to kernel 

rancidity. 

Quality Characteristics and Criteria

The primary quality criterion is a high oil content 

(55 to 65% dry weight) and lack of off flavors 

caused by oxidation of polyunsaturated fatty acids. 

Thus, an important criterion is maintaining kernel 

water content below 4%. Not only does this retard 

the progression of events that lead to rancidity, 

it also prevents mold growth and maintains the 

kernel’s crispness. If water content drops too low, 

however, damage to the kernel’s covering can 

enhance O2

 penetration and rancidity. 

The skin covering the kernel contains chemicals 

that protect fatty acids in the kernel from 

becoming rancid. Light-colored kernels earn a 

higher price because the light color indicates that 

the kernel still has a relatively long shelf-life. An 

important criterion for evaluating new varieties 

is yield of light-colored kernels (Hendricks et al. 

1998). Retention of light color is influenced by 

the integrity of the seal between the two halves of 

the shell, because the shell is an important barrier 

to O2

 entry. Shell strength and seal integrity are 

also important in protecting kernels from insect 

damage and fungi infections that often follow 

insect damage. Two-thirds of the California 

production is sold as shelled products (see Siebert 

1998); therefore, additional characteristics of 

processing quality are ease of shelling and yield of 

intact kernel halves.

Horticultural Maturity Indices

Kernels are considered mature when oil 

accumulation is complete. This is generally 

indicated by browning of the internal packing 

tissue. However, harvest should not begin until the 

husk is well split and separated from the shell. In 

the hottest growing regions of California, kernels 

may be mature 3 weeks prior to husk “maturation” 

(dehiscence). Low temperatures and high RH, as 

occurs in some growing regions and can occur at 

night, advance dehiscence. Ethephon applications 

are used to advance the harvest and make nut 

maturation more uniform throughout the tree/

orchard (Olson et al. 1998).

Grades, Sizes, and Packaging

In-shell and shelled grades exist and are 

primarily determined by size, degree of kernel 

fill, color, and freedom from defects and foreign 

material. Freedom from off flavors (rancidity) 

is important. Shelled kernels held for a long 

period are particularly susceptible. A complete 
778

description of Federal quality standards can be 

found at http://www.ams.usda.gov/AMSv1.0/ams.

fetchTemplateData.do?template=TemplateN&pag

e=FreshNutandSpecCropStandards.

In-shell walnut kernels derive protection against 

oxidative changes from the intact shell and kernel 

skin. Packaging should be moisture-proof. Shelled 

products should be packaged in airtight, moistureproof, opaque or foil packages to maximize shelflife. Unroasted kernels are less likely to take up 

moisture than roasted kernels. FDA-approved 

antioxidants such as butylated hydroxyanisole 

(BHA) and butylated hydroxytoluene (BHT) 

can be applied to the kernels in vegetable oil to 

enhance stability. Edible coatings may be used as 

O2

 barriers to retard kernel rancidity (Maté et al. 

1996). 

Optimum Storage Conditions

Low water content and high fat content of the 

kernel make it relatively stable metabolically and 

able to tolerate low temperatures. The primary 

objectives of storage are to maintain the low 

water content attained after preliminary drying 

(to suppress enzyme activity, retain texture, and 

reduce microbial activity) and to limit exposure 

to O2

 (to minimize rancidity). The optimum 

temperature range for storage is 0 to 10 °C (32 to 

50 °F), with the lower temperature being better. 

Within this temperature range, a 50 to 65% RH 

will maintain walnuts at 4% moisture (Beuchat 

1978). Lopez et al. (1998) modeled sorption 

of walnut kernels and concluded that optimum 

stability and texture were retained in a storage 

environment of 10 °C (50 °F) and 60% RH in air.

Controlled Atmosphere Considerations

Shelf-life can be extended by storage in <1% O2

. 

O2

 <0.5% (balance N2) or CO2 >80% in air can be 

effective in insect control. 

Chilling Sensitivity

Walnuts are not sensitive to chilling. They may be 

stored at or below freezing.

Ethylene Production and Sensitivity

Walnuts produce very low levels of ethylene. 

There are no documented responses of walnut to 

ethylene that might affect quality.

Respiration Rates

The low water content of properly stored walnuts 

makes them relatively inert metabolically. 

Respiration rates are very low.

Physiological Disorders

The most serious postharvest physiological 

disorder that affects walnut quality is oil rancidity. 

The problem appears to be caused by poor 

seed storage conditions: elevated temperature 

and RH and failure to use CA with reduced O2

concentration.

Insect Problems

Insect damage can contribute to handling and 

quality problems. The major insect pest is the 

codling moth (Cydia pomonella). While nuts 

attacked in mid season are likely to be rejected, 

minor early codling moth damage can lead to 

more serious infestation with navel orangeworm 

(Amyelosis transitella [Walker]), and this is more 

difficult to detect if the nut is not shelled. The 

walnut husk fly (Rhagoletis completa) is a serious 

pest in mid to late season. Larval feeding damages 

the husk tissues, leading to staining of the shell 

and failure of the husk to split. This reduces the 

harvest yield and nuts that remain in the orchard 

serve as a reservoir of insects to threaten the next 

crop cycle (van Steenwyk and Barnett 1998). 

In all cases, insect damage will tend to increase 

problems with pathogen infection.
779

Postharvest Pathology

Most infections with pathogens are initiated in 

the orchard and transferred to the postharvest 

environment. In-shell product is protected unless 

the shell has been broken or penetrated by insects. 

The most serious pathogens are fungi such as 

Aspergillus flavus and A. parasiticus, which 

can produce aflatoxins that are both toxic and 

carcinogenic. It is important that damaged kernels 

be discarded prior to storage and that the low 

temperature and RH conditions discussed above 

be maintained in order to reduce the chance for 

mold growth. Toxin-producing Penicillium sp. 

have also been found on walnuts.

Quarantine Issues

Insect infestation is a potentially important 

problem, as are the fungal infections that often 

accompany insect damage. Fumigation with 

methyl bromide or phosphine has been used for 

disinfestation, but the former is being restricted 

and insect resistance to phosphine has been 

reported (Zettler et al. 1990). Johnson et al. 

(1998) have recommended an initial disinfestation 

treatment of 0.4% O2

 for 6 days followed by 

a combination of “protective” treatments that 

includes 10 °C (50 °F) storage in 5% O2

 and 

application of the indianmeal moth granulosis 

virus for control of navel orangeworm and 

indianmeal moth (Plodia interpunctella Hübner). 

Vail et al. (1991) have reported that these same 

walnut storage pests are susceptible to the 

Bacillus thuringiensis insecticidal crystal protein. 

Researchers have successfully introduced the 

gene for the Bt protein into walnut embryos and 

demonstrated its efficacy in suppressing larval 

development (Dandekar et al. 1998). 

Special Considerations

This presentation of quality maintenance 

guidelines for walnuts has introduced some 

discussion of changes of the fundamental 

character of the nut that may be brought about by 

the use of genetic engineering. The anticipated 

changes in nut quality and stability could have 

important effects on the potential for use of 

walnuts in a variety of food products. However, 

it is not certain that the work will be successful 

or that engineered products will be acceptable, 

particularly since an important part of the crop is 

destined for export. Whether or not new walnuts 

are introduced, it is certain that the most important 

aspects of postharvest quality will be based on 

rapid harvest with minimal exposure to field heat, 

forced-air drying at relatively low temperature, 

and cold storage at an RH designed to maintain 

low nut moisture in a reduced O2

 atmosphere.

References

Beuchat, L.R. 1978. Relationship of water activity 

to moisture content in tree nuts. J. Food Sci. 

43:754-755,758.

Dandekar, A.M., G.H. McGranahan, P.V. Vail, et 

al. 1998. High levels of expression of full-length 

cryIA(c) gene from Bacillus thuringiensis in 

transegnic somatic embryos. Plant Sci. 131:181-

193.

Hendricks, L.C., W.C. Coates. R.B. Elkins, et 

al. 1998. Selection of varieties. In D.E. Ramos, 

ed., Walnut Production Manual, pp. 84-89. Pub. 

no. 3373, University of California, Division of 

Agriculture and Natural Resources, Davis, CA.

Johnson, J.A., P.V. Vail, E.L. Soderstrom, et al. 

1998. Integration of nonchemical, postharvest 

treatments for control of navel orangeworm 

(Lepidoptera: Pyralidae) and indianmeal moth 

(Lepidoptera: Pyralidae) in walnuts. J. Econ. Ent. 

91:1437-1444.

Lopez, A., M.T. Pique, A. Romero, and N. Aleta. 

1998. Modelling of walnut sorption isotherms. 

Ital. J. Food Sci. 10:67-74.

Maté, J.I., M.E. Saltveit, and J.M. Krochta. 1996. 

Peanut and walnut rancidity: effects of oxygen 

concentration and RH. J. Food Sci. 61:465-

468,472.
780

Olson, W.H., J.M. Labavitch, G.C. Martin, and 

R.H. Beede. 1998. Maturation, harvesting and nut 

quality. In D.E. Ramos, ed., Walnut Production 

Manual, pp. 273-276. Pub. no. 3373, University 

of California, Division of Agriculture and Natural 

Resources, Davis. CA.

Seibert, J.B. 1998. Marketing California walnuts. 

In D.E. Ramos, ed., Walnut Production Manual, 

pp. 23-30. Pub. no. 3373, University of California, 

Division of Agriculture and Natural Resources, 

Davis, CA.

Vail, P.V., J.S. Tebbets, D.F. Hoffmann, and A.M. 

Dandekar. 1991. Responses of production and 

storage walnut pests to Bacillus thuringiensis

insecticidal crystal protein fragments. Biol. 

Control 1:329-333.

van Steenwyk, R.A., and W.W. Barnett. 1998. 

Insect and mite pests. In D.E. Ramos, ed., Walnut 

Production Manual, pp. 247-253. Pub. no. 3373, 

University of California, Division of Agriculture 

and Natural Resources.

Zettler, J.L., W.R. Halliday, and F.H. Arthur. 1990. 

Phosphine resistance in insects infesting stored 

peanuts in the southeastern United States. J. Econ. 

Ent. 82:1508-1511.