United States Department of Agriculture

Agricultural
Research
Service
Agriculture Handbook
Number 66
Revised February 2016

The Commercial Storageof Fruits, Vegetables, andFlorist and Nursery Stocks

United States Department of Agriculture

Agricultural
Research
Service
Agriculture Handbook
Number 66

The Commercial Storageof Fruits, Vegetables, andFlorist 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 ofPlant Sciences, University of California, Davis, CA.

Abstract
Gross, Kenneth C., Chien Yi Wang, and Mikal
Saltveit, eds. 2016. The Commercial Storage ofFruits, Vegetables, and Florist and Nursery Stocks.
Agriculture Handbook 66, U.S. Departmentof 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, presentssummaries of current storage requirementsof fresh fruits, vegetables, cut flowers, andother 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, andsuitability as fresh-cut product. A large numberof fruits and vegetables were added, as well
as sections on food safety, nutritional quality,
texture, and fresh-cut produce. The purpose ofstoring plant material is to lengthen the time it
can be consumed or utilized. In doing so, it iscritical to provide an environment that minimizes
deterioration, maintains microbial safety, andretains other quality attributes. AH-66 provides
guidelines and other important information forstoring 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, heatload, 1-methylcyclopropene, microbial safety,
minimally processed, modified-atmospherepackaging, potted plants, nutritional quality, nuts,
orchids, packaging film, perishable, postharvest
biology, precooling, respiration, sensory
evaluation, shelf-life, texture.
ii

The information contained in AH-66 has beenassembled from material prepared by nearly ahundred authors from around the world. All of theinformation contained herein was peer reviewed
and edited for scientific content. Every effort wasmade to provide the most accurate and current
information available.
The contributors’ professional affiliations
and addresses were up-to-date at the time ofsubmission 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 inconceivablethat some of the contributors may have changed
organizations in the interim and thus are nolonger at the addresses given in this handbook. In
cases where the editors received specific addresschanges or death notices, all such updates arereflected in this volume.
Mention of trade names or commercial productsin 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 havebeen 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 thispublication 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 purchasedin 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.

This publication in its entirety is freely accessibleon the Internet at http://www.ars.usda.gov/is/np/
indexpubs.

ARS Mission
The Agricultural Research Service conducts
research to develop and transfer solutions toagricultural problems of high national priorityand provides information access and dissemination to—ensure high-quality, safe food and otheragricultural products; assess the nutritional needsof Americans; sustain a competitive agricultural
economy; enhance the natural resource baseand the environment; and provide economic
opportunities for rural citizens, communities, andsociety as a whole.
The U.S. Department of Agriculture (USDA)
prohibits discrimination in all its programs andactivities 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 partof an individual’s income is derived from any
public assistance program. (Not all prohibitedbases apply to all programs.) Persons withdisabilities who require alternative means forcommunication 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
iii

Acknowledgments
The editors gratefully acknowledge the generous
assistance and helpful contributions of thefollowing reviewers: Douglas Adams, Leo Gene
Albrigo, Douglas Archbold, Reginaldo BaezSanudo, Elizabeth Baldwin, Randolph Beaudry,John Beaulieu, Shimshon Ben-Yehoshua, PaulBlankenship, 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.

iv

Abbreviations
APHIS
ARS
BTU
bu
CaCl2
CDC
CO2
cm
cfu
CA
CFM
ed., eds.
EPA
FDA
ft
GC
GRAS
h
HAT
Hg
HHS
HWB
HWT
in
J
kg
L
MS
m
mL
MA
MAP
µL
min
mo
N
N2
nL
oz
O2
OTR
ppb
ppm
%

Animal and Plant Health Inspection
Service, USDA
Agricultural Research Service, USDA
British thermal unit
bushelcalcium chloride
Centers for Disease Control
and Prevention
carbon dioxide
centimetercolony forming units
controlled atmospherecubic feet per minuteeditor; editors
Environmental Protection Agency
Food and Drug Administration, HHS
feetgas chromatographgenerally recognized as safehourhigh temperature forced-air treatment
mercury
United States Department of Healthand Human Services
hot water brushing
hot water treatment
inch
Jouleskilogram
liter
mass spectrometer
meter
milliliter
modified atmospheremodified atmosphere packaging
microliter
minutemonth
Newtons
nitrogennanoliter
ounce, Avoirdupois
oxygenoxygen transmission rateparts per billion
parts per million
percent

lb
RH
sec
T
STS
NaOCl
SSC
SO2
TA
SSC
U.S.
USDA
VHT

pound, avoirdupois
relative humidity
secondshort tonsilver thiosulfate
sodium hypochlorite
soluble solids content
sulfur dioxide
total acidity
total soluble solids
United States
United States Departmentof Agriculture
vapor heat treatmentv

vi

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
vii

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
viii

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

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. Thisversion—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 andexpanded 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, andsuitability 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 tolengthen the time it can be stored and marketedprior to consumption or other use. In doing so, it iscritical to provide an environment that minimizes
deterioration and maintains microbial safety andquality. 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, andthe recommendations should not be consideredabsolute, 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 toperiodically 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 ensurethat 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, thehandbook was revised by J.M. Lutz and R.E.
Hardenburg, also from USDA-ARS. A majorrevision by R.E. Hardenburg, A.E. Watada, andC.Y. Wang, at USDA-ARS Horticultural Crops
Quality Laboratory (now Food Quality Laboratory) in Beltsville, MD, was published in1986. 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 andto increase its availability.
Most temperatures are given in both ºC and ºF.
Nevertheless, a “Temperature Conversion Chart”
is included in this volume. Though temperaturesare sometimes expressed to the first decimal place
due to conversion, this does not mean that thislevel 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 culturesand geographical locations.

“In this work, when it shall be found that much isomitted,let it not be forgotten that much likewise isperformed.”
Dr. Samuel Johnson,
English lexicographer and essayist, 1775

1

Temperature Conversion Chart°C = 5/9 (°F - 32)°F = (9/5 × °C) + 32
°C
-2
-1
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

2

°F
28.4
30.2
32.0
33.8
35.6
37.4
39.2
41.0
42.8
44.6
46.4
48.2
50.0
51.8
53.6
55.4
57.2
59.0
60.8
62.6
64.4
66.2
68.0
69.8
71.6

°C
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
45
50
55
60
65
70
75

°F
73.4
75.2
77.0
78.8
80.6
82.4
84.2
86.0
87.8
89.6
91.4
93.2
95.0
96.8
98.6
100.4
102.2
104.4
113.0
122.0
131.0
140.0
149.0
158.0
167.0

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
Length1 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)Volume1 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)

3

Commodity Cross-Reference
To find...
See...
AbogadoAvocadoAlligator pear
AvocadoAlfalfa sprouts
Sprouts
Anon
Sapodilla
Apple cactus
Dragon fruit
Apple pear (misleading) Asian pear
Araçá boi
Arazá
AvocatAvocado
Basil
Annual culinary herbs
Bean sprouts
Sprouts
Beets
Beet
Belgian endive
Chicory
Bell pepper
PepperBhendi
Okra
BhindiOkra
Boy-toyo
Bok choyCactus fruit
Prickly pear
Cactus pad
Nopalitos
Cactus pear
Prickly pear
Caimito
Sapodilla
Calabaza
PumpkinCalabrese
Broccoli
Canary melon
Honeydew melon
Cantelope
Netted melon
Casaba melon
Honeydew melon
Cassave
Cassava
Cay mang cut
Mangosteen
ChervilAnnual culinary herbs
Chico mamey
Sapodilla
Chico zapote
Sapodilla
Chiku
Sapodilla
Chile pepper
PepperChinese 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 greens4

To find...
Crenshaw melon
Custard apple
DaikonDandelion
DasheenDate Plum
Dill
Dilly
Duku
Dulian
Duren
Duyin
Eddoe
Elderberry
Escarole
Field salad
FilbertFire dragon fruit
Flat bean
French bean
French sorrel
Garden sorrel
Gooseberry
Globe artichoke
Collard greens
Gombo
Green bean
Green cabbage
Green onion
Grosse sapote
Groundnut
Gumbo
Hamburg parsley
Husk tomato
Japanese pear
Java plum
Kadu
Kale
Kang kong
Kong xin cai
La pitahaya rouge
Lady’s finger
Lamb’s lettuce
LangsatLansonLycheeLong bean
LucumaSee...
Honeydew melon
AvocadoRadishSalad greens
Taro
Persimmon
Annual culinary herbs
Sapodilla
Longkong
DurianDurianDurianTaro
Currant
Endive and Escarole
Salad greensHazelnut
Dragon fruit
Bean
Bean
Salad greens
Salad greens
Currant
Artichoke
Greens for Cooking
Okra
Bean
Cabbage
Onion
Sapodilla
PeanutOkra
Parsley
Tomatillo
Asian pear
Wax apple
DurianGreens for cooking
Water convolvulus
Water convolvulus
Dragon fruit
Okra
Salad greens
Longkong
Longkong
LitchiBean
SapodillaTo find...
See...
Malanga
Taro
Malay apple
Wax apple
Mamey
Sapodilla
Mandioca
Cassava
Manggistan
Mangosteen
MangisMangosteen
Mangkhut
Mangosteen
Mangostan
Mangosteen
Mangostanier
Mangosteen
Mangostao
Mangosteen
Manggustan
Mangosteen
ManiocCassava
Marjoram
Perennial culinary herbs
Marmalade fruit
Sapodilla
Matai
Waterchestnut
Melon, Honeydew melon Honeydew melon
Melon, Netted
Netted melon
MesetorMangosteen
Miner’s lettuce
Salad greens
Mongkhut
Mangosteen
Mung bean sprouts
Sprouts
Muskmelon
Netted melon
Mustard cabbage
Bok choyMustard greens
Greens for cooking
Nachi
Asian pear
Nasberry
Sapodilla
Néspero
Sapodilla
Noplaes
Nopalitos
OreganoPerennial culinary herbs
Oriental pear
Asian pear
Oxheart cabbage
Cabbage
Oyster plant
Salsify
Pak-choyBok choy
Pake boong
Water convolvulvus
Pak-tsoi
Bok choy
Palta
AvocadoPaprikaPepperPeppermint
Perennial culinary herbs
Pichi
Arazá
PitahayaDragon fruit
Pitaya roja
Dragon fruit
Pod bean
Bean
Quaio
Okra
Quingumbo
Okra
Rape
Greens for cooking
Red beet
Beet
Rian
DurianRocket salad
Salad greens

To find...
Roquette
Rose apple
Rose water apple
Rosemary
Round sorrel
RucolaRugulaRunner bean
Rupina caspi
Sage
Salad chervil
Salad pear
Sand apple
SapotaSapoteSaurieng
SavorySavoy cabbage
Sementah
Semetah
Sha Li pear
Shalea pear
Shallot
Snap bean
Sororia
SorrelSpearmint
SpinachSponge gourd
Spring onion
Sprouting broccoli
Star apple
Star fruit
Stinkvrucht
Stinky rose
Strawberry pear
String bean
Sugar pea
Summer savory
Summer squash
Sunchokes
SwedesSwedish turnips
Sweetsop
Sweet cherry
Sweet pepper
Table beetTaisaiSee...
Salad greens
Wax apple
Wax apple
Perennial culinary herbs
Salad greens
Salad greens
Salad greens
Bean
Arazá
Perennial culinary herbs
Annual culinary herbs
Asian pear
Asian pear
Sapodilla
Sapodilla
DurianAnnual culinary herbs
Cabbage
Mangosteen
Mangosteen
Asian pear
Asian pear
Onion
Bean
Arazá
Salad greens
Perennial culinary herbs
Greens for cooking
Luffa
Onion
Broccoli
Sapodilla
Carambola
DurianGarlicDragon fruit
Bean
Pea
Annual culinary herbs
SquashJerusalem artichoke
Rutabaga
Rutabaga
Sapodilla
Cherry, sweet
PepperBeet
Bok choy5

To find...
Tamarindo
TangerineTannier
TarragonThang loy
ThureenThurian
Thyme
Tree tomato
Turnip-rooted cabbage
Turnip greens
Vegetable oyster
Water cabbage
White celery mustard
White sapote
Whitloof
Winter purslane
Winter spinach
Yard-long bean
Yellow pitaya
Yellow wax bean
Yuca
ZapoteZucchini

6

See...
TamarindMandarin and Tangerine
Taro
Perennial culinary herbs
Dragon fruit
DurianDurianPerennial culinary herbs
Tamarillo
Kohlrabi or Rutabaga
Greens for cooking
Salsify
Water convolvulvus
Bok choy
Sapodilla
Chicory
Salad greens
Water convolvulvus
Bean
Dragon fruit
Bean
Cassava
Sapodilla
SquashRespiration and Ethylene Production Rates
The values in table 1 are approximations or the average rates of a range; see individual sections on eachcommodity for more specific information and references. Values in parentheses after ethylene rates are thetemperatures 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 heatproduction, 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 greatly2
Asparagus
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 low7

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
Chinese Cabbage
Chinese Chive
Chive
Coconut
Coriander
Cranberry
CucumberCurrant, Black
Dill
Dragon Fruit
DurianEggplant
AmericanJapanese
White egg
Endive/Escarole
FennelFig		
GarlicBulbs
Fresh peeled
GingerGinseng
Gooseberry
Grape, American
Grape, Muscadine
Grape, Table
Grapefruit
Guava
Honeydew Melon
Horseradish
Jerusalem Artichoke
JicamaKiwifruit (ripe)
Kohlrabi
Leek
Lemon
Lettuce
Head
Leaf
8

3
10
54
22
nd
22
4
nd
16
22
nd
nd

6
12
nd
nd
nd
30
5
nd
28
nd
nd
nd

13
18
99
110
nd
nd
8
26
42
103
nd
nd

21
26
nd
nd
nd
nd
nd
29
96
324
nd
nd

37
39
432
540
nd
nd
16
31
142
nd
105
2654

nd
nd
nd
nd
50
nd
nd
37
nd
nd
nd
nd

<0.1 (0 °C)<0.1 (20 °C)
very low
very low
very low
very low
0.6 (5 °C)
0.6 (20 °C)
nd<0.1 (20 °C)<0.1
40 (ripe)

nd
nd
nd
45
196
6

nd
nd
nd
52
nd
13

nd
nd
nd
73
nd
21

695
1315
1135
100
nd
nd

nd
nd
nd
133
32
50

nd
nd
nd
200
nd
nd

0.4 (12.5 °C)
0.4 (12.5 °C)
0.4 (12.5 °C)
very low
4.3 (20 °C)
0.6 (0 °C)

8
24
nd
6
7
3
106
3
nd
nd
nd
8
10
6
3
10
15
nd

16
35
nd
nd
12
5
13
7
nd
nd
8
14
12
11
6
16
25
nd

24
85
nd
15
23
8
nd
13
nd
34
14
25
19
14
12
31
60
11

22
nd
nd
33
52
16
nd
nd
<10
nd
24
32
50
nd
nd
46
96
19

20
nd
63
nd
81
33
51
27
nd
74
30
40
nd
6
19
nd
110
24

nd
nd
nd
95
nd
39
nd
nd
nd
nd
33
nd
nd
nd
nd
nd
115
nd

very low
very low
very low
very lownd<0.1 (20 °C)<0.1 (20 °C)<0.1 (20 °C)<0.1 (20 °C)
10 (20 °C)
very low<1.0
ndvery low		75<0.1 (20 °C)<0.1<0.1 (20 °C)

12
23

17
30

31
39

39
63

56
101

82
147

very low
very low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
LimendLitchind
Longannd
Longkongnd
Loquat119
Luffa
14
Mamey Applend
Mandarin (Tangerine) nd
Mangond
Mangosteennd
Marjoram
28
Mint
20
Mushroom
35
Nectarine (ripe)
5
Netted Melon
6
Nopalitos
nd
Okra
215
Olive
nd
Onion
3
Orange4
Oregano22
Papaya (ripe)ndParsley30
Parsnip
12
Passion Fruitnd
Pea
Garden38
Edible Pod
39
Peach (ripe)
5Peppernd
Persimmon
6
Pineapplend
Plum (ripe)
3
PomegranatendPotato (cured)ndPrickly Pearnd
Radicchio
8
RadishTopped16
Bunched with tops 6
Rambutan (mature) nd

nd
13
7
nd
12
27
nd
6
16
nd
nd
nd
70
nd
10
18
40
15
5
6
nd
5
60
13
44

,10
24
21
458
31
36
nd
8
35
nd
68
76
97
20
15
40
91
28
7
8
101
nd
114
22
59

nd
nd
nd
nd
nd
63
nd
16
58
nd
nd
nd
nd
nd
37
56
146
nd
7
18
nd
19
150
37
141

nd
60
42
nd
80
79
nd
25
113
nd
nd
252
264
87
55
74
261
60
8
28
176
80
199
nd
262

nd
102
nd
nd
nd
nd
35
nd
nd
21
nd
nd
nd
nd
67
nd
345
nd
nd
nd
nd
nd
274
nd
nd

<0.1 (20 °C)
very low
very low
4.0
very low<0.1 (20 °C)
400.0 (27 °C)<0.1 (20 °C)
1.5 (20 °C)
0.03
very low
very low<0.1 (20 °C)
5.0 (0 °C)
55.0
very low
0.5<0.5 (20 °C)<0.1 (20 °C)<0.1 (20 °C)
very low
8.0
very low<0.1 (20 °C)
280.0 (20 °C)

64
64
nd
7
nd
2
nd
6
12
nd
1310

86
89
20
12
nd
6
10
12
16
nd
2311

175
176
nd
27
nd
13
nd
nd
17
nd
nd

271
273
87
34
22
24
20
24
22
32
nd

313
nd
nd
nd
nd
nd
nd
nd
nd
nd
45

<0.1 (20 °C)<0.1 (20 °C)
5.0 (0 °C)<0.2 (20 °C)<0.5 (20 °C)<1.0 (20 °C)<5.0 (0 °C)<0.1 (10 °C)<0.1 (20 °C)
0.2 (20 °C)
0.3 (6 °C)

20
10
nd

34
16
nd

74
32
nd

130
51
nd

172
75
70

very low
very low
very low9

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 GreensRocket Salad
42
113
nd
nd
nd
nd
very low
11
Lamb’s Lettuce
12
67
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
6
Shelled Peas
29
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)
5Squash, Winter
nd
nd
99
nd
nd
nd
very lowStar 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
6
Swiss Chard
19
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_________________________________________________________________________________
1nd = Not determined.
1 day after harvest.
3
At 13 °C.
4
At 22 °C.
5
At 12.5 °C.
6At 2 °C.
2

10

7

Although not accurately measured, “verylow” 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.

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 thisrecommendation are produce, such as some
citrus fruit, that are damaged if they are handled
when they are turgid in the morning (Eckert andEaks 1989), or situations in which the produce isharvested in the late afternoon so that it can betransported to a local market during the cool night
hours. Produce should be shaded to protect it fromsolar heat gain. Reduce the time between picking
and initial cooling; this is particularly criticalbecause 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.

stem-, and flower-type vegetables; melons; andsome tree fruits (Pentzer et al. 1936, Toussaint1955, Stewart and Lipton 1960, Bennett 1963,
Perry and Perkins 1968, Mitchell 1971).
Vacuum- and water spray vacuum-coolingare 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 andmaintain product temperature and is used fora very few commodities, mainly those whosepurchasers have a strong traditional demand forthis method. It is still common for broccoli.
Room cooling is accomplished by placing warm
produce in a refrigerated room. Cooling times areat least 24 h and can be much longer if produce is
not packaged correctly or if no provision is madeto 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 andcontainers 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 initialcooling.
Table 1 is a summary comparison of the six initialcooling methods.

Forced-air cooling is the most widely adaptable
method and is commonly used for many fruits,
fruit-type vegetables, and cut flowers (Parsons etal. 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 coolingbecause some products do not tolerate watercontact and because it requires the use of waterresistant packaging. It is commonly used for root-,11

12
0.3 to 2.0		
0.1 to 0.3*		
20 to 100
No data		No data		
0.1 to 2.0
Yes			
Yes, unless bagged No
High†			Low			LowMedium		High			Low‡
Medium		Low			
Low
Yes			Yes			NoCommon		 Common		 NoNo			Rarely done		
No*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.

__________________________________________________________________________________________________________________
Source: Thompson et al. 1998

Typical cooling time (h)			
1 to 10			 0.1 to 1.0 0.3 to 2.0
Product moisture loss (%)
0.1 to 2.0		 0 to 0.5
2.0 to 4.0
Water contact with productNo				 YesNo
†Potential for decay contamination Low				 High
None
Capital cost			 Low				
Low
MediumEnergy efficiency			
Low				 HighHigh
Water-resistant packaging needed No				
Yes
No
Portable			Sometimes		
Rarely done Common
Feasibility of in-line cooling		Rarely done		 YesNo		Forced-air
Hydro
VacuumWater spray		
Ice			
Room__________________________________________________________________________________________________________________

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

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 ofairflow systems are used, but the tunnel cooler isthe most common (Thompson et al. 1998). Tworows of packages, bins, or palletized product areplaced 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 inairflow-restricting materials such as bags or paper
wraps.
The cold-wall system is adapted to coolingsmaller quantities of produce (Thompson et al.
1998). Individual pallets or cartloads of packages
are placed against a plenum wall. Usually theplenum has a slightly lower air pressure than
the room, and air is pulled through the product.
Some coolers, particularly for cut flowers, use apressurized plenum and air is pushed through the
product. Cold-wall systems do not use floor space
as efficiently as tunnel coolers and require moremanagement because each pallet iscooled 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 arelimited in dimension, which restricts airflow
and causes slow cooling. This system is used forpartially cooling product that will be packaged
later and finish-cooled after packing and forcooling 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 sec1of 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 asmall minimum diameter will cool in about 2 h,while cantaloupes with a much larger diameterrequire 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 torestrict airflow as little as possible.
Forced-air cooling causes some moisture loss.
Loss may not be detectable for produce itemswith 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 andfinal product temperatures. High initial produce
temperatures cause higher moisture loss thanlower temperatures when cooling starts. Moistureloss can be reduced at the expense of longer
cooling times by wrapping product in plastic orpacking it in bags.
Details of fan selection, air plenum design,refrigeration sizing, product cooling times, andoperational guidelines can be found in Thompson
et al. (1998). Forced-air coolers are the least
energy efficient type of cooler but are widelyused because they are adaptable to a wide rangeof 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 techniqueby moving cold water around produce with ashower system or by immersing produce directlyin cold water. Shower coolers distribute waterusing a perforated metal pan that is flooded withcold water from the refrigeration evaporator(Thompson et al. 1998). Shower-type coolers canbe built with a moving conveyor for continuous
flow operation, or they can be operated in a batchmode. Immersion coolers are suited for producethat sinks in water (Thompson et al. 1998). They13

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, likecherries, cools in less than 10 min. Large diameterproducts 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 inhydrocoolers. 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 acidfrom 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 productcooling times can be found in Thompson et al.
(1998). Hydrocoolers can be fairly energy efficientand are the least expensive cooling method topurchase (Thompson 1992).

Package Icing
Packing a product with crushed or flaked ice canquickly cool it and provides a source of cooling
during subsequent handling. It also maintains highhumidity around the product, reducing moistureloss. Its disadvantages are that it has high capitaland operating costs, requires a package that willwithstand constant water contact, and usuallyadds a great amount of weight to the package.
14

In addition, meltwater can damage neighboringproduce in a shipment of mixed commodities.
Cut flowers are sometimes cooled initially witha forced-air system, and a small amount of ice ina sealed package is secured in the container. This
greatly reduces the amount of ice needed andeliminates meltwater damage, while providing
some temperature control during subsequenttransit and handling.

Vacuum CoolingThis method achieves cooling by causing waterto rapidly evaporate from a product. Water lossof 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 theend of the cooling cycle, pressure equals 4.6 mm
Hg and water boils at 0 °C (32 °F). If the productis 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 canbe 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 etal. 1987) and are cost competitive if well utilized(Thompson 1992).

Marine Transport Cooling

Cold Storage

Perishable products should be cooled before
being loaded into a refrigerated transport vehicle.
However, some production areas do not havecooling 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 thecargo 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 fromtraveling up though spaces between pallet loads
and bypassing the load. Proper packaging andloading will allow product to cool in 1 to 2 days
(Heap 1998). Improper practices will prevent theload from cooling and the product will arrive at
destination too warm and in poor quality.

Building Design and Layout

Cooling Time Calculations
Rate of cooling is directly related to thetemperature difference between the coolingmedium 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 graphicalmethod like that in Sargent et al. (1988).

The floor area needed for refrigerated storage
can be calculated by determining the maximum
amount of product the facility will be expected tohandle 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 canbe increased by adding pallet racks or, if boxes
are strong enough, by stacking pallets up to threehigh. Pallet bins are sometimes stacked to a heightof over 3 m. Add to this area space for corridors
and space for lift truck movement.
Airflow Design
Adequate airflow is needed to distributerefrigerated 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 canthen 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 reducemoisture loss from the product (Kroca andHellickson 1993).
Airflow must be distributed uniformly throughout
the coldroom to minimize temperature variability.
For product in pallet loads, one of three systems iscommonly used (Thompson et al. 1998). All threerequire placement of pallets in lanes separated
by 10 to 15 cm (4 to 6 in). In rooms where theair must travel more than 15 m (50 ft), air isdistributed through ceiling ducts or a plenum andreturns to evaporators through a long opening
in a plenum wall. Another system distributes air
into the pallet lanes, and the air returns acrossthe ceiling. Pallet bin storage can use the same
systems, or air can be distributed through forklift
openings or with a serpentine airflow system, as isused in some forced-air coolers.
15

Refrigeration Load
Determining the refrigeration capacity needed
for a facility is based on estimating heat input tothe cold storage from the following: uncooled
product; product respiration; heat conduction
through walls, floors, and roof; air infiltration
through doors; lights; motors; equipment; andpersonnel. However these estimates cannot bedone 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 makeestimates based on methods presented in Stoecker(1998) or ASHRAE (1999) and then add perhaps
20 to 30% extra capacity as a cushion. As a ruleof thumb, refrigerated produce storage requires 10
to 14 kW of refrigeration capacity per 1,000 m3 ofstorage 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 sourceof 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 isuniformly maintaining desired temperature andrelative humidity (RH). Uniform temperature ismaintained by adequate refrigeration capacity,
uniform air distribution, minimal temperature
difference between the evaporator coil and the airtemperature, and a precise temperature control
system. High RH is needed to reduce productmoisture 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 temperatureof the room. This is done by installing a coilwith a high surface area and by using a control
system that maintains the refrigerant at its highest
possible temperature.
16

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 plasticbags that slow moisture loss. Plastic materials
with minimum amounts of venting retard moistureloss from the produce (Crisosto et al. 1994)
and may allow the cold storage to be held at alower humidity. Products with low transpiration
coefficients lose water slowly (Sastry and Baird
1978) and may not need special provision for highRH storage, especially if they are not stored for along time.
Alternative Refrigeration Options
In areas with limited capital for investment inrefrigeration, 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, thenighttime air temperature tends to be lower andproduct 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. Wellwater is also usually equal to average annual air
temperature and can sometimes be used to cool
products. Using ice formed in winter and storingproducts at high altitudes are also occasionallyused to provide cool storage temperatures.
Unfortunately, few of the above options work wellin 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. Unlessoutside temperatures are very low or very high,ventilation is an inexpensive method of reducing
ethylene levels. Ethylene can also be absorbed oncommercially available potassium permanganatepellets. A few products, especially floral andornamental crops, can be chemically treated tomake them insensitive to ethylene damage.

d’Sousa, M.C., and M. Ingle. 1989. Effect ofdelayed cooling on the poststorage flesh firmnessof apples. J. Food Sci. 54:493-494.

Controlled Atmosphere Facilities

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 andNatural Resources, Pub. no. 3326, University ofCalifornia, Davis, CA.

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-tightdoors. Tilt-up concrete, metal panels, urethanefoam, and plywood have all been successfully
used as gas barriers. These storage rooms alsoneed 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 andvegetables. ASHRAE Trans. 94:1434-1454.
Barger, W.R. 1963. Vacuum cooling: a comparisonof cooling different vegetables. Marketing
Research Report 600, U.S. Department ofAgriculture, Washington, DC.
Bennett, A.H. 1963. Thermal characteristics ofpeaches as related to hydro-cooling. TechnicalBull. 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.

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. 23012308. 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 andProfessional, 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 invarious 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.

17

Parsons, R.A. 1972. Forced-air cooling of fruit inbulk bins. SP-01-72:38-41, American Society ofAgricultural Engineers, St. Joseph, MI.
Perry, R., and R. Perkins. 1968. Hydro-coolingsweet corn. Paper 68-800, American Society ofAgricultural 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 qualityof stored fresh red raspberries after a delay incooling. HortTechnology 2(4):468-470.
Sargent, S.A., M.T. Talbot, and J.K. Brecht. 1988.
Evaluating precooling methods for vegetablepackinghouse operations. Proceedings of theFlorida 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 coolingtimes. Mkt. Res. Rpt. 637, U.S. Department ofAgriculture, 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.
18

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 ofCalifornia, 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.

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 foundin 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 heatproduction in kJ, multiply mg CO2 kg-1 h-1 by 61 to get kcal tonne-1 day-1 (1 kcal = 4,186 kJ).
Conditions________________________________
Storage size
Outside surface area (including floor)
Inside dimensions
VolumeInsulation

Ambient conditions at harvest
Fruit temperature
Storage capacity
Bin weight
Loading weight and time
Cooling rate
Air changes from door openings:
during cooling
during storage
Specific heat
Heat load to lower air:from 30 to -1.1 ºC (50% RH)
from 7.2 to -1.1 ºC (70% RH)
Miscellaneous heat loads

Example_________________________________________
15×15×4.5 m
720 m2
14.7×14.7×4.2 m
908 m3
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
30 ºC and 50% RH
at harvest, 21 ºC; in storage, -1.1 ºC
600 bins at 500 kg fruit per bin = 300,000 kg of fruit
63.5 kg; total weight of bins = 38,100 kg
200 bins (100,000 kg fruit per day); 3 days to fill
1st day, 21 to 4.5 ºC; 2nd day, 4.5 to -1.1 ºC
6 per day
1.8 per day
pears, 0.86; wood bins, 0.5
74.5 kJ m-3
15.3 kJ m-3
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

19

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
591,149
1. Building-transmission load: area (720 m2) × U (1.1 kJ) × TD (31.1 ºC) × h (24) =2. Air-change load from doors: vol (908 m3) × heat load (74.5 kJ) × air changes (6) =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) =		
Bin weight (12,700 kg) × specific heat (0.5) × TD (21 to 4.5 ºC) ×		
kJ factor (4.186) =Second day		Fruit weight (100,000 kg) × specific heat (0.86) × TD (4.5 to -1.1 ºC) ×		
kJ factor (4.186) =		
Bin weight (12,700 kg) × specific heat (0.5) × TD (4.5 to -1.1 ºC) ×		
kJ factor (4.186) =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) =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) =405,876

5,939,934
438,5882,015,977
148,854

1,220,600

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; tonnesof fruit (100) × respiration rate (812) =81,2005. Miscellaneous heat loads:
Lights: W (2,400) × kJ per W (3.6) × h (8) =Fans: HP (3) × kJ per HP (3,112) × h (24) =Forklifts: 2 × 36,920 kJ per forklift for 8 h =Labor: workers (2) × kJ per h (1,000) × h (8) =69,120224,064
73,84016,000Total heat load during cooling:
Building transmission
Air change
Product cooling
Production respiration
Miscellaneous

519,149
405,876
8,543,353
1,475,900
383,024
Subtotal
Add 10% to be cautious
Total required refrigeration

20

11,399,302
1,139,930
12,539,232

Assuming refrigeration equipment operates 18 h per day: 12,539,232 ÷ 18 h = 696,624 kJ h-1. Since atonne 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 h2
157,766
1. Building-transmission load: area (720 m ) × U (1.1 kJ) × TD (8.3 ºC) × h (24) =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) =Fans: HP (3) × kJ per HP (3,112) × h (24) =Labor: people (1) × kJ per h (1,000) × h (4) =34,560224,064
4,000

Total load during storage:
Building transmission
Air change
Product load (respiration)
Miscellaneous

157,766
25,006
243,600
262,624
Subtotal
Add 10% to be cautious
Total required refrigeration

688,996
68,899757,895

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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Patchen, G.O. 1971. Storage for apples and pears.
Marketing Research Report 924, U.S. Departmentof Agriculture, Washington, DC.
Ryall, A.L., and W.J. Lipton. 1979. Vegetables andmelons. In Handling, Transportation and Storageof Fruits and Vegetables, 2nd ed., vol. 1. AVI Pub.
Co., Westport, CT.
21

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 isdifferent from air composition (about 78% N2,
21% O2, and 0.03% CO2); generally, O2 below
8% and CO2 above 1% are used. Atmospheremodification 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 therange tolerated by each commodity reduces
their respiration and ethylene production rates;
however, outside this range respiration andethylene production rates can be stimulated,indicating a stress response. This stress cancontribute to incidence of physiological disorders
and increased susceptibility to decay. ElevatedCO2-induced stresses are additive to andsometimes synergistic with stresses caused by low
O2, physical or chemical injuries, and exposure
to temperatures, RH, and/or C2H4 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,
22

fruits and vegetables are able to recover fromthe detrimental effects of low O2 and high CO2
stresses (fermentative metabolism) and resume
normal respiratory metabolism upon transfer toair. 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 ofrecovery 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), biosynthesisof carotenoids (yellow and orange colors)
and anthocyanins (red and blue colors), andbiosynthesis and oxidation of phenolic compounds(brown color). Controlled atmospheres slow
down the activity of cell wall degrading enzymes
involved in softening and enzymes involved inlignification, leading to toughening of vegetables.
Low O2 and/or high CO2 atmospheres influence
flavor by reducing loss of acidity, starch tosugar conversion, sugar interconversions, andbiosynthesis of flavor volatiles. When produce
is kept in an optimum atmosphere, ascorbic acidand other vitamins are retained, resulting in better
nutritional quality.
Severe stress CA conditions decreasecytoplasmic pH and ATP levels and reduce
pyruvate dehydrogenase activity, while pyruvatedecarboxylase, 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,maturity and ripeness stage, storage temperatureand 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 effecton 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 degreeningof nonclimacteric commodities and ripeningof climacteric fruits, respiration and ethylene
production rates, and incidence of somephysiological disorders (such as scald on apples andrusset spotting on lettuce). At levels above 80% O2,
some commodities and postharvest pathogens sufferfrom 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 CO2induced injury.

Beneficial Effects of CA (Optimum
Composition for the Commodity)—A
Summary• Retardation of senescence (including
ripening) and associated biochemicaland physiological changes, particularly
slowing down rates of respiration, ethylene
production, softening, and compositionalchanges.
• 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 somestorage disorders, including scald of apples.
• CA can have a direct or indirect effect on
postharvest pathogens (bacteria and fungi)
and consequently decay incidence andseverity. For example, CO2 at 10 to 15%
significantly inhibits development of botrytis
rot on strawberries, cherries, and otherperishables.

• Low O2 (<1%) and/or elevated CO2 (40 to60%) can be a useful tool for insect control
in some fresh and dried fruits, flowers, andvegetables 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 stainof lettuce, and chilling injury of somecommodities.
• Irregular ripening of fruits, such as banana,mango, pear, and tomato, can result fromexposure 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 resultof anaerobic respiration) and very highCO2 levels (as a result of fermentative
metabolism).
• Increased susceptibility to decay when the
fruit is physiologically injured by too low O2or too high CO2 concentrations.
Commercial Application of CA Storage
Several refinements in CA storage have been madein recent years to improve quality maintenance.
These include creating nitrogen by separationfrom 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 levelsof 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 anddistribution, include improved technologies forestablishing, monitoring, and maintaining CA
using edible coatings or polymeric films withappropriate gas permeability to create a desired23

atmospheric composition around and within thecommodity. 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 associatedstem and leaves. Also, it is less expensive to treat
flowers with anti-ethylene chemicals than to use
CA to minimize ethylene action.

sweet onions, kiwifruits, avocados, persimmons,pomegranates, and nuts and dried fruits andvegetables (table 1). Atmospheric modification
during long-distance transport is used withapples, asparagus, avocados, bananas, broccoli,cane berries, cherries, figs, kiwifruits, mangos,
melons, nectarines, peaches, pears, plums,
and strawberries. Continued technologicaldevelopments in the future to provide CA
during transport and storage at a reasonable cost(positive benefit/cost ratio) are essential to greaterapplications on fresh horticultural commodities
and their products.

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_________________________________________________________________________________________

24

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 andVegetables and MAP, CA’97 Proceedings, vol.
5. Postharvest Hort. Ser. no. 19, University ofCalifornia, Davis, CA.
Kader, A.A. 1986. Biochemical and physiologicalbasis 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, DavisCA.
Kader, A.A., D. Zagory, and E.L. Kerbel. 1989.
Modified atmosphere packaging of fruits andvegetables. CRC Crit. Rev. Food Sci. Nutr. 28:130.
Mitcham, E.J., ed. 1997. Apples and Pears, CA’97
Proceedings, vol. 2. Postharvest Hort. Ser. no. 16,
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 atmospherestorage of fruit and vegetables. Tech. Bull 199318E, Agriculture Canada, Kentville, N.S.
Wang, C.Y. 1990. Physiological and biochemical
effects of controlled atmosphere on fruits andvegetables. 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. 8:101127.
Yahia, E.M. 1998. Modified and controlled
atmosphere for tropical fruits. Hort. Rev. 22:123183.
Zagory, D., and A.A. Kader. 1989. Quality
maintenance in fresh fruits and vegetables bycontrolled atmospheres. In J.J. Jen, ed., Quality
Factors of Fruits and Vegetables: Chemistry andTechnology, pp. 174-188. American Chemical
Society, Washington, DC

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 andTechnology, vol. 1, Biology, Principles andApplications, pp. 135-167. Technomic Pub. Co.,
Lancaster, PA.
Saltveit, M.E., ed. 1997. Vegetables andOrnamentals, CA’97 Proceedings, vol. 4.
Postharvest Hort. Ser. no. 18, University ofCalifornia, Davis, CA.

25

Temperature Preconditioning
Susan Lurie and Joshua D. Klein
Lurie is with the Department of Postharvest
Science, Volcani Center, Bet-Dagan, Israel; andKlein is with the Department of Field Crops,
Volcani Center, Bet-Dagan, Israel.

Introduction
Temperature preconditioning of fruits andvegetables 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 asa postharvest treatment for control of both insect
pests and fungal pathogens in fresh produce. Inpart, this is because of the deregistration of anumber of compounds that, until recently, havebeen 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 somecases 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 fruitand vegetables, enhancing sweetness of produce
by increasing the amount of sugars or decreasing
acidity, and prevention of storage disorders suchas superficial scald on apples and chilling injury
on subtropical fruits and vegetables (Lurie 1998).
Temperature conditioning before storage may alsomean an incubation period spent at either ambient
temperature of 16 to 25 °C (61 to 77 °F) or at atemperature below ambient but above that whichmight produce chilling injury: 5 to 12 °C (41 to
54 °F), depending on the commodity. This type26

of temperature manipulation is often referred toas a “curing” period and is used with crops suchas potatoes, onions, and carrots. Its purpose isgenerally 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 temperaturepreconditioning 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 Manualfrom 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 forparticular commodities or pests.
An example of commercial temperature
conditioning for pest control is Mexican-grownmangos, which may be infested with a varietyof 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 canvary 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 thesurface of the fruit. The water droplets transfer
heat more efficiently than air, allowing the fruit
to heat quickly; but there may also be increased

physical injury to the fruit. Papayas grown in
Hawaii are vapor-heat-treated before being
exported to Japan.

develop fewer rots after storage. Onions can be
stored longer if held at 28 °C (82 °F) for 3 days
before storage.

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 thenormal 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 fromthe subsequent disinfestation treatment.

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-waterbrush 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 machinesprays 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 anddirt, though hot water combined with brushingalso causes surface cracks to be filled in by thenatural wax of the commodity, as well as eliciting
resistance to pathogens in some cases.

Insect Disinfestation
The development and implementation of heat
treatments for insect disinfestation have beenreviewed thoroughly (Couey 1989, Paull 1993).
Table 1 includes treatment regimes that havebeen 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.

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 inhot fungicide solution have been used since the1950s 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).

Antifungal Treatments
Curing is used commercially to increase resistanceto 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 onwhether they are designated for industry or homeconsumption. 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 forwound 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

Physiological Benefits of Conditioning
Treatments
Most thermal treatments have been developed
as lethal regimes for insects or fungi. Some ofthese 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, such27

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, suchas increased firmness of apples or decreased
yellowing of broccoli, or to protect against otherabiotic stresses, such as irradiation disinfestation
treatments (table 3). The physiologicalmechanisms of these treatments were previously
reviewed by Lurie (1998).

28

29

Jang 1996

Jang 1996
Heather et al. 1997
Armstrong et al. 1995

mango

VHT

Queensland fruit fly
Bactrocera tyroni
avocadoHWT & benomyl 46 °C/3 min then				
1 °C/7 days		litchiVHT
45 °C/30 min
		
mango
VHT
47 °C/10 min
					
			
HWT then VHT
53 °C/15 min then				
47°C/15 min

Bactrocera payapae

47 °C/15 min

45 °C/30 min

Papaya fruit fly

VHT

zucchini

44 °C/2 h in 1% O2

32 °C/24 h then45-46 °C/50-60 min
47 °C at pulp for 3.5 h

HAT & CA

grapefruit

Dacus dorsalis
cucumber
HAT then HWTBactrocera dorsalis					
papayaHAT

Oriental fruit fly

Anastrepha ludens
Bactrocera cucumis

Jacobi et al. 1993
Heather et al. 1997
Jacobi et al. 1995
Jacobi & Giles 1997

Jessup 1994

Heather et al. 1997

Armstrong et al. 1995

Chan & Linse 1989

Jacobi et al. 1996

Chan & Linse 1989

Shellie et al. 1997

40 °C/24 h
47 °C/15 min
47 °C at pulp for 3.5 h

Mexican fruit fly

HAT
VHT
HAT

Armstrong et al. 1995
Jacobi et al. 1996

avocadomango
papayaDacus cucurbitae
avocadoHAT
40 °C/24 h
Bactrocera cucurbitae
		cucumber
HAT then HWT
32 °C/24 h then				45-46 °C/50-60 min		
papayaHAT
4C °C at pulp for 3.5 h		zucchini
VHT		

Melon fruit fly

Mediterranean fruit fly
Ceratitis capitata				

Fruit flies					Caribbean fruit fly
Anastrepha suspensa
grapefruit
HAT		
Sharp & Gould 1994
		
mango
HAT
52 °C/125 minMiller et al. 1991
		orangeHAT		Sharp & McGuire 1996

InsectLatin name
Fruit
Regime*Temperature/Time
Reference__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Table 1. Thermal treatment of horticultural commodities for insect disinfestation

30
Chervin et al. 1997

30 °C/30 h in 0.3% O2

Longtailed mealybug
Pseudococcus longispinus persimmon
HWT
48 °C/26 min or				
50 °C/22 min
			
HAT		
					

Lay-Yee et al. 1997
Dentener et al. 2000
Hoy & Whiting 1998

40 °C/17-20 h in
1.2% O2; 1% CO2
45 °C/13 min in
50% ethanolLight brown apple moth
Epiphyas postvittana
apple
HAT & CA							
HWT & ethanol							
HAT & CA		kiwifruit		pear
HAT & CA

Dentener et al. 1996,
1997

Lester et al. 1995

Whiting et al. 1997
Hoy & Whiting 1998

40 °C/10 h in 0.4% O2
45 °C/5 h in 0.4% O2
40 °C/5-7 h in 0.4% O2
40 °C/6 h in 2% O2;
5% CO2

Whiting et al. 1999

Soderstrom et al. 1993

Chervin et al. 1997

Neven & Mitcham 1996
Neven & Drake 2000
Neven et al. 1996

Neven et al. 1996

Cnephasia jactatanaapple
HAT & CA
Ctenopseustis 			
obliquana
kiwifruit
HAT & CA								

Leafroller

HWT

52 °C/8 minlemon

Fuller’s rose beetle
Asynonychus godmani

44 °C/120 min then
0 °C/4 weeks
47 °C/44 min in 1% O2;
15% CO2
44 °C/120 min then
0°C/4 weeks
30 °C/ 30 h in 0.3% O2

Coddling moth
Cydia pomonella
apple
HAT or VHT
						
cherryHAT & CA
				
		
pear
HAT or VHT							
HAT & CA

Other insects

InsectLatin name
Fruit
Regime*Temperature/Time
Reference__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Table 1. Thermal treatment of horticultural commodities for insect disinfestation—Continued

31

Dentener et al.
1998
Lay-Yee & Whiting
1996
Lester et al. 1997

Two spotted spider mite
Tetranychus urticae
applesHWT & ethanol
45 °C/13 min in 50%
				ethanol		kiwifruit
HAT & CA
44 °C/211 min							persimmon
HWT
47 °C/67 min* HAT: high-temperature forced-air treatment
VHT: vapor-heat treatment
HWT: hot-water treatment
CA: controlled atmosphere

White peach scale
Pseudaulacaspis pentagona papaya
VHT
47 °C/4 hFollet & Gabbard 1999_____________________________________________________________________________________________________________________

Grapholita molesta

Chervin et al. 1997

Whiting & Hoy 1997

McLaren et al. 1997

30 °C/30 h in 0.3% O2

Oriental fruit moth

HAT & CA

40 °C/10 h in 0.4% O2
45 °C/5 h in 0.4% O2

Obscure mealybug
Pseudococcus affinisapple
HAT & CA				pear

48 °C/3 min then
50 °C/2 min

New Zealand flower thrips Thrips obscuratus
apricot
HWT		nectarine				peachInsectLatin name
Fruit
Regime*Temperature/Time
Reference__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Table 1. Thermal treatment of horticultural commodities for insect disinfestation—Continued

32
carrotmango
pepperAfek et al. 1999
Prusky et al. 1999
Fallik et al. 1996bReyes et al. 1998

46 °C/6 h
59-62 °C/15 sec

Penicillium digitatum
Green moldgrapefruit
			

HAT
HWB

49 °C/20 min
42 °C/30 min then
49°C/20 min

Mycospharella spp.
Stem and surface rots
papaya
HAT
				
				

Shellie 1998
Porat et al. 2000

Nishijima et al. 1992

Diplodia natalensis
Stem end rot
mango
HAT
51.5 °C/125 minMiller et al. 1991
			
HWT		McGuire 1991

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 minMiller et al. 1991

45 °C/20 min or
50 °C/10 min

Chalara paradoxa
Crown rot
bananaHWT
				Nishijima et al. 1992

38 °C/4 days and CaCl2 dip Klein et al. 1997
50 °C/3 min
Fallik et al. 1996b
45 °C/15 min
Garcia et al. 1996
50 °C/2 minBarkai-Golan et al. 1993
38 °C/2 days
Fallik et al. 1993

100 °C/3 sec
60-70 °C/15-20 sec
50 °C/3 min

49 °C/20 min
32 °C/30 min then
49 °C/20 min

HAT & CaCl2
HWT
HWT
HWT
HAT

HWB
HWB
HWT

Botryodiplodia
Stem and surface rots
papayaHAT
theobromae								

Botrytis cinerea

Grey moldBlack moldBlack spot

apple
pepperstrawberry
tomato			

Alternaria alternata

FungusCommon nameCrop
Regime*Temperature/Time
Reference__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Table 2. Thermal treatment of horticultural commodities for eradication of and protection from fungal pathogens

33Blue mold

HAT or HWT
HWT & imazalil

cactus pearlemon

50 °C/3 min + imazalil

Schirra et al. 1997

38 °C/24 h or 55 °C/5 min Schirra et al. 1996

Sams et al. 1993
Fallik et al. 1996c

Schirra et al. 1997
Smilanick et al. 1997

Kim et al. 1991
Smilanick et al. 1997

Rhizopus stolonifer
tomatoHWT
50 °C/2 minBarkai-Golan et al. 1993_____________________________________________________________________________________________________________________* HWB: hot water brushing
HWT: hot water treatment
HAT: high-temperature forced-air treatment
VHT: vapor heat treatment

Penicillium spp.

Penicillium italicum

38 °C/4 days in 4% CaCl2
38°C/4 days

Penicillium expansum
Blue mold
apple
			

HAT & CaCl2
HAT

36 °C/3 days
45 °C/150 sec in
2% Na2CO3
53 °C/3 min
41-43 °C/1-2 min in
6% Na2CO3

lemon
HAT
			
HWT & Na2CO3
				orangeHWT			HWT & Na2CO3
				FungusCommon nameCrop
Regime*Temperature/Time
Reference__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Table 2. Thermal treatment of horticultural commodities for eradication of and protection from fungal pathogens—
Continued

Table 3. Physiological benefits of thermal treatments for horticultural crops____________________________________________________________________________________
Chilling injury____________________________________________________________________________________
Crop

Phenomenon/
Regime*Temperature/Time
ReferenceAppearance____________________________________________________________________________________
Apple
scald
HAT
			

38 °C/4 days or
42 °C/2 days

Lurie et al. 1990

Avocadoskin browning
HAT theninternal browning, HWT
pitting				HWT

38 °C/3-10 h then
40 °C/30 min
38 °C/60 min

Woolf et al. 1995
Florissen et al. 1996
Woolf et al. 1997

Cactus pear

38 °C/24 h or
55 °C/5 min

Schirra et al. 1996

rind pitting,
HAT or HWT
brown staining		

Citrusrind 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
54 °C/20 min

McCollum et al. 1993
Jacobi et al. 1995

Persimmon
gel formation
HWT
47 °C/90-120 min;			
50 °C/30-45 min;			
52 °C/20-30 min
		
HAT		

Lay-Yee et al. 1997

Green pepper

pitting

HAT

40 °C/20 h

Mencarelli et al. 1993

Cucumberpitting

HWT

42 °C/30 min

McCullum et al. 1995

Tomatopitting
HAT
38 °C/2-3 days
		
HWT
48 °C/2 min			
42 °C/60 min				Lurie & Klein 1991
Lurie et al. 1997
McDonald et al. 1998,
1999

Woolf et al. 1997

Zucchini
pitting
HWT
42 °C/30 min
Wang 1994____________________________________________________________________________________

34

Table 3. Physiological benefits of thermal treatments for horticultural crops—Continued____________________________________________________________________________________
Improved postharvest quality____________________________________________________________________________________
Commodity Parameter/Attribute Regime*
Temperature/Time
Reference____________________________________________________________________________________
Apple
increased firmnessHAT			

38 °C/4 days;
42 °C/2 days

Klein & Lurie 1992

Asparagus

47 ºC/2-5 min

Paull & Chen 1999

Broccolidecreased yellowing
HWT
			
			

50 °C/2 min
45 °C/10 min;
47 °C/7.5 min

Forney 1995
Tian et al. 1996, 1997

Collarddecreased yellowing

HAT

45 °C/30 min

Wang 1998

Green onions

inhibited elongation

HWT

55 °C/2 minHong et al. 2000

Guava

decreased softening
and yellowing

HWT

46 °C/35 min

McGuire 1997

Kale

decreased yellowing

HAT

40 °C/60 min

Wang 1998

inhibited curvature

HWT

Potatoinhibited sprouting
HWT		
Rangann et al. 1998____________________________________________________________________________________* HWT: hot water treatment
HAT: high-temperature forced-air treatment

35

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37

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38

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39

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41

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 ofsealing actively respiring produce in polymericfilm 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 toatmosphere modification, MAP vastly improves
moisture retention, which can have a greater
influence on preserving quality than O2 andCO2 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 toslow the ripening of apple fruit. The primary
limitation of MAP application in the earlystudies was technical in nature—specifically,
the lack of consistent control of O2 levels in the
package. Since then, the types and propertiesof 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 ofcommodities.
It is important to recognize that while atmospheremodification can improve the storability of somefruits and vegetables, it has the potential to induce
undesirable effects. Fermentation and off flavors
may develop if decreased O2 levels cannot sustain
42

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 forO2 (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.

Table 1. O2 limits below which injury can occur for selected horticultural crops heldat 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.

43

Table 2. CO2 partial pressures above which injury will occur for selectedhorticultural crops______________________________________________________________________
Commodities
CO2______________________________________________________________________________
kPa
2
Lettuce (crisphead), pear3
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
Papaya10		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
25Blackberry, 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 theoreticallyattainable by MAP by film permeation alone (low-density
polyethylene, LDPE, lower boundary) and via perforations
alone (upper, dashed line) or their combination (shadedarea). Data are adapted from Kader (1997) and reprinted
with permission from Beaudry (1999). Copyright 1999 by
Elsevier Science.

44

Figure 2. Recommended O2 and CO2 combinations forthe 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 withpermission from Beaudry (1999). Copyright 1999 by Elsevier
Science.

The composition of the atmosphere withina package results from the interactionof a number of factors that include thepermeability characteristics of the package,
the respiratory behavior of the plant material,
and the environment. The films making up
the package are selected to have specificpermeability characteristics, and changes inthese characteristics over time, temperature,and humidity follow known physical laws. The
environment can be controlled to provide specificconditions. In contrast to these known andcontrollable factors are the often unknown anduncontrollable responses of the plant material.
Plant species and cultivar, cultural practices,
stage of development, manner of harvest, tissue
type, and postharvest handling—all of thesefactors 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 ofthese components of the packaging process can be
examined separately to better illustrate how eachcontributes to packaging strategies.

Continuous Films: The movement of O2 and CO2
is usually directly proportional to the differencein 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 muchgreater than gas movement through the film. Gas
transmission through microperforations has beenmodeled (Fishman et al. 1996). The rate of gas
exchange through perforations in a film is so muchgreater than through continuous films that a 1-mm
perforation in a 0.0025 mm (1 mil) thick lowdensity polyethylene (LDPE) film has nearly thesame gas flux as a half a square meter area of thefilm. As might be surmised, perforated packages
are more suitable for produce having a high O2
demand.
Gas Exchange Properties of Continuous andPerforated Films

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 fromtissue respiration create gradients across the film
barrier that provide the driving force for gas
movement into and out of the package. The levelsof O2 and CO2 within a package depend on theinteraction between commodity respiration and thepermeability properties of the packaging film or
microperforations (Beaudry et al. 1992, Kader etal. 1997a).
There are two strategies for creating film. The first
employs continuous films that control movementof 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.

The relative permeability of the package to O2
and CO2 differs substantially between continuousand perforated films and results in considerable
differences in gas exchange behavior. In packages
composed of continuous films, the permeabilityof the package to CO2 is usually 2 to 8 times thatof 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 CO2that is four times that of O2. In a LDPE package
having a 10% O2 steady-state atmosphere, theCO2 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, thepermeability to CO2 is only 0.77 times that of O2.
As a result, in a package relying on perforations
45

for gas exchange, CO2 levels climb to roughly
the same extent that O2 levels decline (that is, thegradients are nearly equal) such that the sum of
O2 and CO2 concentrations is usually in the rangeof 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 apackage were designed to have a 10% O2 steadystate atmosphere using perforations as the routeof gas exchange, the CO2 level would be 0.77 ×(21 - 10%), or 8.8%, which is about 3-fold greaterthan in the continuous film package. The relative
elevation of CO2 in perforated film packages may
be critically important in package design, if CO2 isneeded to help control decay or degreening.
MAP relying on a combination of perforationand permeation has features of both systems,with attainable combinations of O2 and CO2 being
between those of packages relying on permeationand those relying on perforations (Mannapperuma
et al. 1989, Beaudry 1999) (figures 1 and 2).
The temperature sensitivity for permeation, andthe permeability of O2 and CO2, is somewhere
between those for perforated packages andcontinuous 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 diffusionof 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 throughperforations will increase only 11% across thistemperature range.
Depending on the rates of respiration andtransmission through the package, atmospheremodification can be achieved rapidly or relatively
slowly. At low temperatures, atmospheremodification can take several days, such thatsome package systems would not achieve steadystate conditions before the end of their shelf-life.
In many cases, purging the package atmosphere46

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 fruitand vegetable products undergoes a 4- to 6-foldincrease 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 and30 times the rate of perforation permeability
with increasing temperature. When respiratory
demand for O2 increases faster than O2 permeationas temperature increases, O2 levels decline andmay pose a risk to product quality, limiting theusefulness 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 andaccumulation 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, andraspberry. 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, andEnvironment
Mathematical models can integrate the film
permeability to O2, to CO2, and to H2O and therespiratory response of the commodity to O2 (andin 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-

content in the package headspace under a varietyof environmental conditions prior to constructionof the package. Additionally, they permit theidentification of limiting features of the film,
package design, and product and environment
conditions. Models typically include temperaturedependency 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 thesteady-state concentration of O2 in the package
headspace. Steady-state models incorporating
temperature effects on respiration andpermeability have been published for many
commodities. In addition, more complex dynamic
models have been developed to account for
temporal changes in package volume, productrespiration, and the humidity and temperature of
the environment (Fishman et al. 1996, Hertog etal. 1998).
Package performance can be depicted in a numberof 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 variationin 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 towhich they would be exposed. The performanceof the packages can then be predicted at lower
temperatures likely to be encountered duringstorage. 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 toprotect against fermentation.
A package model can also be used to clarify thenature of the mismatch between the temperaturesensitivity of O2 uptake and O2 flux throughthe film and denote methods to ameliorate thisproblem. One method would be to choose a filmwith permeability changes for O2 similar to thatof 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 theenclosed product and responds by increasing thepermeability to O2 (Cameron et al. 1993). Such“sense-and-respond” packaging is technicallydifficult 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 thehighest temperatures typically encountered in the
distribution and retail cool chain and, as far as
possible, maintain control over the temperatureof the packaged product, thereby adapting to thelimitations imposed by the film. Most companies
using MAP have adopted this simple solution.
Generally, the lowest temperature feasible ismaintained, since temperature has a much moresignificant influence on preserving quality than theapplication of low O2 (Kays 1997).
Variation in the respiration rate of the productand the variation in film or pore permeability can
influence package design. Variation in productrespiration and package permeability has beenmeasured for broccoli, and the effect on package
O2 modeled (Cameron et al. 1993). Cameron et al.
(1993) concluded that there is an estimable risk ofthe package O2 falling sufficiently low to promotefermentation in any product. Packages should
be designed to generate O2 levels well above thelower limit to ensure aerobic conditions.
Products such as broccoli, mushrooms, andleeks have very high rates of respiration, andmost continuous films do not have the capacity47

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 toachieve needed properties.

Only four perforations were required to achievenear-ambient O2 levels, while 40 perforations only
reduced RH to 95%

The plastic polymer can also be mixed with aninert 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 ofstretching. 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 ofmicroperforation generally ranges from 40 to
200 µm; and, by altering the size and thicknessof microperforations, gas permeability througha package can be altered to meet well-defined
product requirements. Microperforated films havealso been used to extend storage of strawberries
and nectarines (Meyers 1985) and apple (Watkins
et al. 1988).

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 havetemperature 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 virtuallyinvisible. 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 Cameron1992). 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 inmaintaining a specific humidity level in shippingand storage environments.

Water Vapor

Temperature Management

Plant tissues tend to lose moisture when RH is
below 99 to 99.5%. Generally, water loss results invisible wilting or wrinkling of the surface of mostcommodities 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 atmosphereat 20 ºC (68 ºF) has only 2.1% H2O, and mostexternal 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 H2O flow.

Product temperature affects storability more thanany other factor. Precooling and temperature
maintenance during handling and shipping are
critical in preserving quality. Temperature alsosignificantly 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 usefulin the few situations in which it would be more
important to rapidly establish the atmosphere thanto slow physiological processes—for example,
to reduce cut-surface browning. Cameron et al.
(1995) calculated that, at 25 ºC (77 ºF), a packageof blueberry fruit could attain a steady-state
atmosphere in less than 2 days, whereas it required
approximately 20 days at 0 °C (32 ºF).

48

The temperature of the produce in the package ismanaged by circulating cool air around the outsideof the package. The film and the headspaceatmosphere are barriers to heat movement, prevent
rapid cooling, and reduce the effectiveness of
refrigeration. A “safe radius” for the distance fromthe center of the package to the circulated air canbe calculated based on the heat of respirationand 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 aradius 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 aneffective radius of 50 cm.

Plant Responses to MAP
Some of the most important factors that affectshelf-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, inductionof fermentation. Fresh product quality can be
maximized more effectively by good temperature
management than by atmosphere modification.

some cases is partly mediated by ethylene, as withbroccoli (Ku and Wills 1999).
While low O2 and elevated CO2 atmospheres arecommonly 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 mosteffective at reducing ripening prior to the onsetof ripening, rather than at a later stage. However,packaged products are usually intended for
immediate consumption and an unripe productis not immediately edible or is of lesser quality
than the ripe product. Thus, the advantage ofimproved 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 (Yangand Chinnan 1988). More potential for using MAP
to control ripening may exist at the packinghouseor distributor level, as in the case of overseas
shipment of apples (Watkins et al. 1998), rather
than at the retail level.
Decay

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/highCO2 atmospheres.

Decay control is a particularly important problem
for many crops. Levels of >10% CO2 effectively
slow or stop the growth of numerous decayorganisms (Brown 1922). Low O2 has a very
limited effect on decay organism activity or
survival at levels above the fermentation thresholdof most commodities. While not all horticulturalcommodities 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%.

Chlorophyll loss, a desirable trait for many
climacteric fruits, results in quality loss for many
vegetables. Chlorophyll degradation during thesenescence of green vegetables can be inhibitedby low O2 and elevated CO2, a response that inPackaging 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

Ripening and Senescence49

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 partialpressure 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 toreduce humidity in packages using salt sachets forthe purpose of limiting decay have been explored(Shirazi and Cameron 1992). A number ofeffective 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 thebrowning of cut surfaces on lightly processed
products such as lettuce and salad mixes.
Atmosphere modification is often used inconjunction 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 partialpressure of O2 in commercial packages of lettuce
and salad products is often below the fermentationthreshold (Cameron et al. 1995, Peiser et al.
1997). However, the fermentation of lettuce, if notsevere, results in very few off flavors (Smyth et al.
1998).
Negative Responses
Respiration is reduced as O2 becomes limiting, butthere 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 outweighthe loss in flavor or other quality parameters.
Ethanol, acetaldehyde, ethyl acetate, and lactate
are products of fermentation that can contribute to50

the development of off flavors as well as physicalinjury (Kays 1997, Mattheis and Fellman 2000).
Production of compounds that contribute to
the characteristic aromas of many fruit, such asapples, 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, inpart 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 ofaroma 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 consideredin 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 thefactor 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. Elevatedhumidity prevents desiccation but can alsoenhance decay.
• Temperature control is of criticalimportance and, by itself, has a greater
impact than atmosphere modification for
most products. Temperature should benear the storage/shipping temperature assoon as possible after packaging except in
those cases for which a slightly elevatedtemperature is needed to assist in rapid
atmosphere generation.
• Heat transmission from product throughthe package, carton, and pallet stack needs
to be considered in the development ofhandling procedures.

• 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 improveunderstanding of how package, plant, andenvironmental 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.

Cameron, A.C., R.M. Beaudry, N.H. Banks,and M.V. Yelanich. 1994. Modified-atmospherepackaging of blueberry fruit: Modeling respirationand package oxygen partial pressures as a functionof temperature. J. Amer. Soc. Hort. Sci. 119:534539.
Cameron, A.C., B.D. Patterson, P.C. Talasila, andD.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.

Beaudry, R.M. 2000. Responses of horticulturalcommodities to low oxygen: limits to the
expanded use of modified atmosphere packaging.
HortTechnology 10:491-500.

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.

Beaudry, R.M. 1999. Effect of O2 and CO2 partialpressure on selected phenomena affecting fruitand vegetable quality. Postharvest Biol. Technol.
15:293-303.

Fishman, S., V. Rodov, and S. Ben-Yehoshua.
1996. Mathematical model for perforation effecton oxygen and water vapor dynamics in modifiedatmosphere packages. J. Food Sci. 61:956-961.

Beaudry, R.M., A.C. Cameron, A. Shirazi, and
D.L. Dostal-Lange. 1992. Modified-atmospherepackaging of blueberry fruit: effect of temperature
on package O2 and CO2. J. Amer. Soc. Hort. Sci.
117:436-441.

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. 3066. Postharvest Hort. Ser. no. 19, University ofCalifornia, Davis, CA.

Beaudry, R.M., and C.D. Gran. 1993. Usinga modified-atmosphere packaging approachto answer some postharvest questions: factors
affecting the lower oxygen limit. Acta Hort.
362:203-212.
Brown, W. 1922. On the germination and growthof 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. Molecularrequirements for the biological activity of
ethylene. Plant Physiol. 42: 114-152.

Herner, R.C. 1987. High CO2 effects on plantorgans. 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 andtemperature. Postharvest Biol. Technol. 14:335349.

51

Kader, A.A. 1997a. A summary of CA
requirements and recommendations for fruits otherthan 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 andCO2 effects on postharvest life of horticulturalperishables. In M.E. Saltveit, ed., Vegetables andOrnamentals, CA’97 Proceedings, vol. 4, pp. 160163. Postharvest Hort. Ser. no. 18, University ofCalifornia, Davis, CA.
Kader, A.A., D. Zagory, and E.L. Kerbel. 1989.
Modified atmosphere packaging of fruits andvegetables. Crit. Rev. Food Sci. 28:1-30.
Kays, S.J. 1997. Postharvest Physiology ofPerishable Plant Products, Van Nostrand Reinhold,
New York, NY.

Mattheis, J.P., and J.P. Fellman. 2000. Impact ofmodified atmosphere packaging and controlled
atmosphere on aroma, flavor and quality ofhorticultural produce. HortTechnology 10:507510.
Meyers, R.A. 1985. Modified atmospherepackaging 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.

Ku, V.V.V., and R.B.H. Wills. 1999. Effect of
1-methylcyclopropene on the storage-life ofbroccoli. Postharvest Biol. Technol. 17:127-132.

Reid, M.S. 1997. A summary of CA andMA requirements and recommendations forornamentals 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.

Kupferman, E. 1997. Controlled atmospherestorage of apples. In E.J. Mitcham, ed., Apples
and Pears, CA’97 Proceedings, vol. 3, pp. 1-30.
Postharvest Hort. Ser. no. 16, University ofCalifornia, Davis, CA.

Richardson, D.G., and E. Kupferman. 1997.
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Lakakul, R., R.M. Beaudry, and R.J. Hernandez.
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64:105-110.

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 ofCalifornia, Davis, CA.

Mannapperuma, J., D. Zagory, R.P. Singh, and
A.A. Kader. 1989. Design of polymeric packages
for modified atmosphere storage of fresh produce.
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225-233.

52

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
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Cornell University, Ithaca, NY.

Shirazi, A., and A.C. Cameron. 1992. Controlling
relative humidity in modified-atmospherepackages 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 O2 partialpressure on respiration and quality. J. Ag. Food
Chem. 46:4556-4562.
Smyth, A.B., P.C. Talasila, and A.C. Cameron.
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injury in modified atmosphere packages of freshcut produce. Postharvest Biol. Technol. 15:127134.
Song, J., W. Deng, L. Fan, et al. 1998. Aroma
volatiles and quality changes in modified
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(ISHS) 258:225-236.
Watkins, C.B., P.L. Brookfield, H.J. Elgar, andS.P. McLeod. 1998. Development of a modified
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Yang, C.C., and M.S. Chinnan. 1988. Modelingthe effect of O2 and CO2 on respiration and qualityof stored tomatoes. Trans. ASAE 31:920-925.

53

Wholesale Distribution Center
Storage
James F. Thompson and Adel A. KaderThompson is formerly with the Biological andAgricultural Engineering Department, Universityof California, Davis, CA. He is now retired. Kader
was with the Department of Pomology, Universityof California, Davis, CA. He is deceased.

Most produce is shipped from the point of
production to regional or local distributors, suchas terminal markets, independent wholesalers, or
chain store distribution centers. Produce orders
are assembled at these sites and then shipped toretail stores, restaurants, or institutions such as
schools or hospitals. Produce and floral items
lose quality during these marketing steps, and theamount 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 retailchain, strive to receive only the amount of producethat can be shipped the following day. A few fruits
such as mature green avocados, bananas, mangos,
and tomatoes are ripened before shipment to retailstores 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 thattemperature. Fruits and vegetables can be divided
into three categories or groups according totheir optimum temperature requirements (table1). The RH of the storage atmosphere shouldbe 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,54

nonfruit vegetables and temperate fruits andmelons. If there is enough capacity in the facility,
the fruits should be stored separately from thevegetables. This allows installing equipment tomaintain 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 andnursery items divided into the recommended three
categories or groups. If handled with produce, thefloral items in group 1 should be in the group 1A
vegetable room to minimize exposure to ethylene
produced by many fruits.

55Group 313-18 °C; 85-95% RH

Bitter melon
Amaranth†
Chinese turnipMushroom
Beans, snap, green, wax
Boniato†Anise†
Collard†Mustard greens†
Cactus leaves (nopales) †Cassava
ArtichokeCorn, sweet, baby
Parsley†Calabaza		Dry onion
Arugula†Cut vegetables
Parsnip
Chayote†		GingerAsparagus†
Daikon†Radicchio
Cowpea (Southern pea)
JicamaBeans, fava, lima
Endive†-chicory
RadishCucumber†		PotatoBean sprouts
Escarole†
Rutabaga
Eggplant†		Pumpkin
Beet
Fennel†Rhubarb
Kiwano (horned melon)
Squash, winter (hard rind) †Belgian endive†
GarlicSalsifyLong 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†
Tomatillo			
Carrot†Kale†
Swiss chard†
Winged bean			Cauliflower†
Kohlrabi
Turnip				
Celeriac
Leek†
Turnip greens†				
Celery†Lettuce†
Water chestnut				Chard†		
Watercress†						
Groups 1A and 1B				Group 2			
0-2 °C; group 1A: 90-98% RH; group 1B: 85-95% RH 7-10 °C; 85-95% RH				
Group 1A				
Vegetables Alfalfa sprouts
Chinese cabbage†
Mint†
Basil†		

Table 1. Compatible fresh fruits and vegetables during 7-day storage*

56

Avocado, ripe‡
Gooseberry
Raspberry
Cactus pear, tuna
Barbados cherry
Grape
Strawberry
Calamondin
Blackberry
Kiwifruit†‡			
Carambola
Blueberry
Loganberry			
CranberryBoysenberryLongan			Custard apple‡
CaimitoLoquat			Durian, ripe‡
Cantaloup‡
Lychee			FeijoaCashew apple
Nectarine			Granadilla‡
CherryPeach			Grapefruit†
Coconut
Pear (Asian & European)		
Guava‡
Currant
Persimmon†			Juan canary melon‡
Fresh-cut fruits‡
Plum, ripe†			
Kumquat
Date
Plumcot, ripe†			
Lemon†
DewberryPomegranate				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.
Mandarin
Mango, ripe‡
Olive
OrangePassion fruit
PepinoPineapple
Pummelo
Sugar apple
Tamarillo
Tamarind
TangeloTangerine
Ugli fruit		Groups 1A and 1B				Group 2			
0-2 °C; group 1A: 90-98% RH; group 1B: 85-95% RH 7-10 °C; 85-95% RH				
Group 1B			
Fruits andApple‡
Elderberry
Prune†
Avocado, unripe‡Lime†melonsApricot‡
Fig
Quince†BabacoLimequat

Table 1. Compatible fresh fruits and vegetables during 7-day storage*—Continued

Atemoya‡
Sapodilla‡
Banana‡Sapote‡Breadfruit‡Soursop‡
Canistel‡Watermelon
Casaba melon
Cherimoya‡
Crenshaw melon‡
Honeydew melon‡
Jaboticaba
Jackfruit‡
Mamey‡
Mangosteen‡
Papaya‡Persian melon‡
Plantain‡RambutanGroup 313-18 °C; 85-95% RH

Table 2. Compatible flowers, florist’s foliage, and nursery items during 7-day storage†
Group 1*
Group 2
Group 30-2 °C; 85-95% RH
7-10 °C; 85-95% RH
13-18°C; 85-95% RH
Flowers

AcaciaGaillardia
ProteaAnemone
Alstroemeria
Gardenia
Rannunculas
Bird of paradise
AlliumGerberaRose
Camellia
Aster
Gladiolus
Snapdragon
Eucharis
Bouvardia
Gypsophlia
Snowdrop
Gloriosa
Buddleia
Heather
SquillGodetia
Calendula
Hyacinth
StaticeSweet-william
Candytuft
Iris
Stephanotis		
Carnation
Laceflower
Stevia		Chrysanthemum Lilac
Stock		Clarkia
Lily
Strawflower		
Columbine
Lily-of-the-valley Sweet pea		
Coreopsis
LupineTulip		Cornflower
Marigolds
Violet		CosmosMignonette
Zinnia		
CrocusNarcissus
Cuttings &						 scions		
DahliaOrchid,			
cymbidium			Daisy, English, Ornithogalum
		 Marguerite,
		 Shasta				Delphinium
Poppy			Feverfew
Peony			Forget-me-not
Phlox			Foxglove
Primrose			Freesia

African violet
Anthurium
GingerHeliconia
Orchid, cattleya, vandal
Poinsettia
Bulbs, corms, rhizomes,
tubers, & roots
Nursery stock

Florist’s Adiantum
Gallax
Pittosporum
Chamaedorea
Dieffenbachia
foliage		(maidenhair)		
(greens) Asparagus
Ground pine
Rhododendron Cordyline
Staghorn fern
		 (plumose)
Buxus
HederaSalal (lemonPalm		(boxwood)				leaf)		
Camellia
Ilex (holly)
Scotch-broom Podocarpus
Cedar
Juniper
Smilax		
CrotonLeatherleaf
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.

57

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 islimited, low-temperature fruits, vegetables, andflowers can be mixed in a room; air-conditioned
space at 20 to 25 °C (68 to 77 °F) can be used forhighest-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 insteadof internal combustion-driven units (forexample, propane-powered units).
Floral products are particularly sensitive toethylene. Some distribution facilities have foundthat the previously described precautions are
inadequate in preventing damage to flowers. They
have chosen to handle flowers with dairy or meatproducts, where ethylene is low, or they requirethat all floral products be chemically treated toresist ethylene damage.
Weak fiberboard containers are usually the causeof 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 andpalletized.
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 productare placed on weak boxes. Placing only strong
58

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 reducemechanical 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 tomaintain fairly uniform product temperature.
Ethylene gas (100 to 150 µL L-1) is added to theatmosphere on a schedule appropriate for eachproduct, and CO2 levels are kept below 1% byventilating 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 orderto reduce moisture loss. The ripening of someproducts, like stone fruit and pears that weretreated with ethylene at the packing operation, canbe promoted by warming them to 13 to 18 °C (55to 64 °F).

Reference
Thompson, J., A.A. Kader, and K. Sylva. 1996.
Compatibility chart for fruits and vegetables inshort-term transport and storage. Nat. Res. Pub.
no. 21560, University of California, Division ofAgriculture and Natural Resources, Oakland, CA.

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 carefulhandling to minimize mechanical injuries, storage
and display within optimum ranges of temperature
and RH, and proper sanitation of storage anddisplay 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 dependon 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 andvegetables 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 (45to 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) andthe 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) andused 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 andethylene-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 formore 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 tominimize 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 orpallets of boxes and between them and the room
walls. Enough fresh, ethylene-free air should be
introduced into storage rooms to keep ethylene <1µL L-1 (<1 ppm), and preferably <0.1 µL L-1 (<0.1ppm) 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 forsome commodities, including produce that does
not lose water quickly and has a long shelf-life
like apple, pear, kiwifruit, and orange. Producethat is on sale (special promotion) or that will
be on display for a few hours (like grapes andstrawberries) can also be stored at ambient
temperatures.
Ideally, the display case temperature range shouldmatch the recommended range for each group ofcommodities: 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 tocool the products, it is important to ensure thatthe product is near its recommended temperature
59

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 andbecomes exposed to ambient air temperatures.
Refrigerated display cases have either ahorizontal 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 andmonitored regularly. Performance of refrigerated
display cases is influenced primarily by theirrefrigeration capacity, defrost options, and air
circulation system. Important secondary factors
include temperature, RH, and movement ofsurrounding 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 indicatedan overall mean temperature of about 9 ºC (48ºF), 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, personalcommunication, 1989). A survey of temperaturesof fresh-cut vegetable products kept in refrigerated
display cases in some grocery stores indicates anoverall 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 indicatessignificant improvements in maintaining thecold chain within the grocery stores, but more
improvements are needed to bring the temperature
range for fresh-cut products close to therecommended 0 to 2 °C (32 to 36 °F).
Water-loss reduction can be achieved byprotecting produce from excessive air movement;
packaging in perforated polymeric films(as moisture barriers); periodically adding
sanitized, clean water by misting (only useful forcommodities that tolerate wetting, such as thoselisted in table 1); and/or displaying on crushed
ice (only useful for products that tolerate directcontact with ice). If ice is used, proper drainageof the melt water should be provided. It should
be remembered that ice is not an effective way tokeep the product cold unless it is well surroundedby the ice.

Table 1. Produce that benefit from misting while displayed in refrigerated cases______________________________________________________________________________
ArtichokeCorn, sweet
Peppers
Asparagus*
Eggplant
Radishes
Beans, snap
EndiveRhubarb
Beets
Kale
Shallots, green
Broccoli
Leeks
SpinachBrussels sprouts
Lettuce
Sprouts
Cabbage
Mustard greens
Squash, summer
Carrots
Onions, green
Swiss chard
Cauliflower
Parsley
Turnips
CeleryParsnips
Watercress
Collards
Peas______________________________________________________________________________*Asparagus should be displayed vertically with cut ends on a wet absorbent pad.

60

Non-refrigerated display tables or racks are used
for most group 3 fruits and vegetables, whichshould be displayed separately. Some of the fruits
in groups 1 and 2, such as avocado, kiwifruit, andpear, 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.

Thompson, J.F., and A.A. Kader. 2009. From theFarm 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

During handling at the grocery store, allprecautions should be taken to minimize potential
chemical or microbial contamination to maintainsafety of produce. All display tables, cases,
cabinets, and other fixtures must be cleaned andsanitized 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 Departmentof 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.

61

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 lowtemperatures (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 theirfreezing 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, havelower 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 andbiochemical alterations and cellular dysfunctions
occur in chilling-sensitive species in responseto chilling stress (Wang 1982, Wang and Adams
1982, Raison and Orr 1990). When chilling stressis prolonged, these alterations and dysfunctions
will lead to the development of a variety ofchilling 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 havebeen chilled may be particularly susceptible todecay. 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 andWorthington 1952, McColloch 1962).

62

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 temperaturesa few degrees into the critical zone for a longer
time before injury becomes irreversible. Maturity
at harvest and degree of ripeness are importantfactors in determining chilling sensitivity in somefruits like avocados (Kosiyachinda and Young1976), honeydew melons (Lipton 1978), andtomatoes (McColloch et al. 1966). The effects ofchilling are cumulative in some commodities. Low
temperatures in transit, or even in the field shortly
before harvest, add to the total effects of chillingthat 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 etal. 1996).
Chilling injury is discussed more specificallyunder each commodity. Many of the commodities
susceptible to chilling injury are listed in table
1 with threshold temperatures and some of thesymptoms.

Table 1. Fresh produce susceptible to chilling injury when stored at low but
nonfreezing temperatures__________________________________________________________________
Symptoms of injury when stored
Lowest Safe Temperature 		
CommodityºCº 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
Atemoya439		
Skin darkening, failure to ripen, pulp 									
discoloration†
Avocados
4.5-1340-55		Grayish-brown discoloration of flesh
Bael
3
38		
Brown spots on skin
Bananas11.5-13† 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
Choyote5-10
41-50		Dull brown discoloration, pitting, flesh 									
darkening
Cranberries
236		
Rubbery texture, red flesh
Cucumbers
745		
Pitting, water-soaked spots, decay
Eggplants
745		
Surface scald, alternaria rot, blackening of 									
seeds
Ginger7
45		
Softening, tissue breakdown, decay
Guavas
4.5†
40		
Pulp injury, decay†
Grapefruit
1050		
Scald, pitting, watery breakdown
Jicama13-18
55-65		Surface decay, discoloration
Lemons11-13†
52-55		Pitting, membranous staining, red blotch
Limes
7-9
45-48		Pitting, turning tan with time
Lychee338		
Skin browning†
Mangos10-13
50-55		Grayish scald-like discoloration of skin, 			
						
uneven ripening
Mangosteen
4-8
39-47		Hardening and browning of the cortex
MelonsCantaloupe
2-5†
36-41		Pitting, surface decay
Honeydew
7-10
45-50		Reddish-tan discoloration, pitting, surface 									 decay, failure to ripen
Casaba7-10
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
745		
Internal browning
Oranges3†38		
Pitting, brown stain
Papayas745		
Pitting, failure to ripen, off flavors, decay
63

Table 1. Fresh produce susceptible to chilling injury when stored at low but
nonfreezing temperatures—Continued__________________________________________________________________
Symptoms of injury when stored
Lowest Safe Temperature 		
CommodityºCº F		between 0 ºC and safe temperature*__________________________________________________________________________
Passion fruit
1050		
Dark red discoloration on skin, loss of 										 flavor, decay
Peppers, sweet
745		
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†
Potatoes338		
Mahogany browning, sweetening
Pumpkins andhardshell squash 10
50		
Decay, especially alternaria rot
Rambutan
1050		
Darkening of exocarp
Sweet potatoes
1355		
Decay, pitting, internal discoloration, 			
							 hardcore when cooked
Tamarillos
3-4
37-40		Surface pitting, discoloration
Taro		
1050		
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 1050		
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.

64

Freezing Injury
The recommended storage temperatures forcommodities 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 affectthe freezing point. To be on the safe side, thehighest temperature at which freezing of a
specific commodity may occur should be used asa guide for recommending the optimum storage
temperature. More detailed discussion of freezing
points and factors affecting them can be foundin McColloch (1953), Whiteman (1957), andParsons 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 andvegetables to freezing injury varies widely. Somecommodities may be frozen and thawed a numberof times with little or no injury, whereas others arepermanently injured by even a slight freezing. All
fruits and vegetables can be categorized into threegroups based on their sensitivity to freezing: mostsusceptible—those that are likely to be injured byeven one light freezing, moderately susceptible—
those that will recover from one or two lightfreezing periods, and least susceptible—those thatcan be lightly frozen several times without serious
damage. Table 2 shows the relative susceptibilityof 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
ApplesBeets
Asparagus
Broccoli
Brussels sprouts
Avocados
Carrots
Cabbage, mature and savory
BananasCauliflower
Dates
Beans, snap
CeleryKale
Berries (except cranberries)
Cranberries
Kohlrabi
Cucumbers
Grapefruit
Parsnips
Eggplants
GrapesRutabagas
LemonsOnion (dry)Salsify
Lettuce
OrangesTurnips
Limes
Parsley
Okra
Pears
Peaches
Peas
Peppers, sweet
Radishes
Plums
SpinachPotatoes
Squash, winterSquash, summer
Sweet potatoes
Tomatoes___________________________________________________________________________

65

The freezing point of the commodity is no
indication of the damage to be expected byfreezing. 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 severityof freezing injury is influenced by a combinationof time and temperature. For example, apples
that would be injured little by exposure totemperatures slightly below the freezing point
for a few days would be severely injured by justa 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 fruitor vegetable. For example, leafy lettuce is very
susceptible to freezing injury, whereas some otherleafy vegetables, such as kale and cabbage, canwithstand 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, butthey will usually start to freeze immediately ifjarred or moved. If permitted to warm above
the freezing point, many commodities that havebeen undercooled may escape having ice crystals
form in them. For example, potatoes, which arevery sensitive to freezing damage, showed nofreezing 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 etal. 1961).
Plant tissues are very sensitive to bruising while
frozen, and this sensitivity is another reason forleaving commodities undisturbed until they havewarmed. 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 rateof thawing has suggested that thawing at 4 °C (39°F) causes the least damage for most commodities
66(Lutz 1936). Even though a number of fruits andvegetables are somewhat tolerant to freezing,
commodities recovered from freezing often haveshorter storage life and are more susceptible
to invasion by microorganisms. For example,
apples that recover from freezing are softer thannormal fruit, and carrots that have been frozen
are especially subject to decay. Therefore, it isbest 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 ofripeness 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 chillingand freezing. In Plant Diseases, the Yearbook of
Agriculture 1953, pp. 826-830. U.S. Departmentof Agriculture, Washington, DC.

McColloch, L.P. 1962. Alternaria rot following
chilling injury of acorn squashes. Marketing
Research Report 518, U.S. Department ofAgriculture, Washington, DC.

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.

McColloch, L.P., and J.T. Worthington. 1952.
Low temperature as a factor in the susceptibilityof mature-green tomatoes to Alternaria rot.
Phytopathology 42:425-427.

Wang, C.Y. 1982. Physiological and biochemical
responses of plants to chilling stress. HortScience
17:173-186.

McColloch, L.P., J.N. Yeatman, and P. Loyd.
1966. Color changes and chilling injury of pinktomatoes held at various temperatures. Marketing
Research Report 735, U.S. Department ofAgriculture, 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 Report895, U.S. Department of Agriculture, Washington,
DC.

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. 15:6395.
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.

Paull, R.E. 1990. Chilling injury of crops oftropical 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 fora better understanding of the molecular basis ofchilling 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 andVegetables, vol. 1, Vegetables and Melons, 2nd ed.
AVI Publishing Company, Westport, CT.

67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 ofthese is respiratory metabolism. The process of
respiration involves combining O2 in the air withorganic molecules in the tissue (usually a sugar)
to form various intermediate compounds andeventually CO2 and water. Energy produced by
the series of reactions making up respiration canbe captured as high-energy bonds in compounds
used by the cell in subsequent reactions, or it canbe lost as heat. The energy and organic molecules
produced during respiration are used by othermetabolic processes to maintain the health of thecommodity. Heat produced during respiration
is called “vital heat,” and it contributes to therefrigeration load that must be considered indesigning storage rooms.

There is little the postharvest physiologist can doto alter the internal factors affecting respirationof harvested commodities, because they arelargely a function of the commodity itself once
harvested. However, a major part of postharvest
technology is devoted to reducing respirationand other metabolic reactions associated withquality retention by manipulating the external
environment.
In general, the storage life of commodities varies
inversely with the rate of respiration. This isbecause 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 withlower rates of respiration. Storage life of broccoli,
lettuce, peas, spinach, and sweet corn, all of whichhave high respiration rates, is short in comparison
to that of apples, cranberries, limes, onions, andpotatoes, 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
Low
Moderate<5
5 to 1010 to 20High

20 to 40

Very High
Extremely High

40 to 60
>60

Nuts, dates
Apple, citrus, grape, kiwifruit, onion, potato
Apricot, banana, cherry, peach, nectarine, pear, plum, fig,cabbage, carrot, lettuce, pepper, tomato
Strawberry, blackberry, raspberry, cauliflower, lima bean,
avocadoArtichoke, snap bean, Brussels sprouts, cut flowers
Asparagus, broccoli, mushroom, pea, spinach, sweet corn_____________________________________________________________________________________________

68Factors Affecting Respiration
Respiration is affected by a wide range ofenvironmental 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, andphysical stress.
Temperature. The most important factor
affecting postharvest life is temperature, becausetemperature has a profound effect on the rates of
biological reactions; for example, metabolism
and respiration. Over the physiological range ofmost crops, 0 to 30 °C (32 to 86 °F), increased
temperatures cause an exponential rise inrespiration. The Van’t Hoff Rule states that thevelocity 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 becalculated by dividing the reaction rate at ahigher 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 aknown rate at another temperature. However, therespiration rate does not follow ideal behavior, andthe 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
0 to 10 °C
10 to 20 °C
20 to 30 °C
30 to 40 °C

Q10
2.5 to 4.0
2.0 to 2.5
1.5 to 2.0
1.0 to 1.5

These typical Q10 values allow us to construct atable showing the effect of different temperatureson the rates of respiration or deterioration
and relative shelf-life of a typical perishable

commodity (table 2). This table shows that, if acommodity 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 ofdeterioration________________________________________
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 normallyreduced at low but nonfreezing temperatures,certain commodities, chiefly those originatingin 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 forchilling-sensitive crops than it would be forchilling-tolerant ones. Respiration may increase
dramatically at the chilling temperatures orwhen 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 thatsignal the onset of chilling injury.
Heat stress. As the temperature rises beyond
the physiological range, the rate of increase inrespiration 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 killing69

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 whilestill permitting aerobic respiration varies among
commodities. In most crops, O2 levels at around
2% to 3% produce a beneficial reduction in therate of respiration and other metabolic reactions.
Levels as low as 1% improve the storage life ofsome 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 andpromote 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, andpackaging. Unintentional modification of theatmosphere, by packaging for example, can resultin production of undesirable fermentative products
and development of foul odors.
Increasing the CO2 level around somecommodities reduces respiration, delays
senescence, and retards fungal growth. In low
O2 environments, however, increased CO2 levels
can promote fermentative metabolism. Somecommodities tolerate brief storage in a pure N2
atmosphere (for example, a few days at low
temperatures) or in very high concentrations ofCO2. The biochemical basis for this ability towithstand these atmospheres is unknown.
Physical stress. Even mild physical stress canperturb respiration, while physical abuse cancause a substantial rise in respiration that is often
associated with increased ethylene evolution. The
signal produced by physical stress migrates fromthe site of injury and induces a wide range of70

physiological changes in adjacent, non-woundedtissue. 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 sometissues, 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 oncommodities 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 highrespiration rates. As plant organs mature, their rateof respiration typically declines. This means that
commodities harvested during active growth, suchas many vegetables and immature fruits, have highrespiration rates. Mature fruits, dormant buds, andstorage organs have relatively low rates.
After harvest, the respiration rate typicallydeclines—slowly in nonclimacteric fruits andstorage organs and rapidly in vegetative tissues
and immature fruits. The rapid decline presumablyreflects 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 ofclimacteric 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.

Significance of Respiration

Figure 1. The climacteric pattern of respiration in ripening
fruit.

The division of fruits into climacteric andnonclimacteric 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 andother 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
Apple
PapayaApricot
Passion fruit
AvocadoPeach
BananaPear
BiribaPersimmon
Breadfruit Plum
Cherimoya Sapote
FeijoaSoursop
Fig
TomatoGuava
Watermelon
Jackfruit		
Kiwifruit		
Mango		Muskmelon		
Nectarine		

Nonclimacteric Fruits
Blueberry
Cacao
Caju
CherryCucumber
Grape
Grapefruit
Lemon
Lime
Olive
OrangePepperPineapple
Strawberry
Tamarillo

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 majorrole in the postharvest life of fresh commodities
because it reflects the metabolic activity of thetissue that also includes the loss of substrate, thesynthesis of new compounds, and the releaseof 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 inthe tissue and loss of taste quality (especially
sweetness) and food value to the consumer.
For certain commodities that are stored forextended periods of time, such as onions used fordehydrated 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 producedby the commodity. The rate of dry weight loss canbe 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) andnonclimacteric fruit (for example, strawberries)
is maximal at harvest, and storage conditions are
71

optimized to prevent quality loss. In contrast,
many flowers (for example, carnations androses), nonclimacteric fruit (for example,
lemons and oranges), and climacteric fruit (forexample, bananas and tomatoes) are harvested
before they reach their best quality, and storage
conditions are optimized to permit developmentof optimum quality. In the first case, the synthesisof new compounds is unnecessary because theylead to reduced quality (for example, enzymes
that destroy chlorophyll in lettuce or promotelignification 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), andthe conversion of starch to sugar (for example,
sweetening of apples and bananas) is necessary fordevelopment of maximum quality. These synthetic
reactions require energy and organic molecules
derived from respiration.
Release of heat energy. The heat produced byrespiration (vital heat), about 673 kcal for eachmole 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 atdifferent storage temperatures can be calculated
from the respiration rates for many fruits andvegetables 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 CO2yields 2.55 cal. In the language of the refrigerationengineer, 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.

72

Some commodities have high respiration rates
and require considerably more refrigeration thanmore 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, andtomatoes.
Meaning of the respiratory quotient (RQ).
The composition of a commodity frequently
determines which substrates are used in respirationand consequently the value of the respiratory
quotient (RQ). RQ is defined as the ratio of CO2
produced to O2 consumed; CO2 and O2 can bemeasured in moles or volumes. Depending on
the substrate being oxidized, RQ values for freshcommodities 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 indicationof the shift from aerobic to anaerobic respiration.

Measuring the Rate of Respiration
The rate of any reaction can be determinedby measuring the rate at which the substrates
disappear or the products appear. Apart from thewater 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 todetermine the rate of respiration. They are lossof substrate (for example, glucose) loss of O2,
increase in CO2, and production of heat. The mostcommonly used method is to measure productionof 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 aftersufficient CO2 has accumulated to be accurately
detected by any one of a number of commerciallyavailable instruments (for example, gas
chromatograph and infrared CO2 analyzer). If thecontainer is properly sealed, CO2 should increaselinearly with time. Multiplying the change inconcentration times the container volume anddividing by weight of the commodity and durationof time between samples gives the production rate.
In the dynamic system a flow of air (or othergas mixture) is passed through the container
at a known rate. The system will come into
equilibrium (>99.3%) in about the same time ittakes for 5 times the volume to flow through thecontainer. 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 thecommodity calculates the production rate.

Biochemistry of Respiration
Respiration is the oxidative breakdown ofcomplex substrate molecules normally present inplant 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 moleculesthat are required to sustain the myriad of
metabolic reactions essential for the maintenanceof cellular organization and membrane integrityof living cells. Since respiration rate is so tightly
coupled to the rate of metabolism, measurementsof respiration provide an easy, nondestructivemeans of monitoring the metabolic andphysiological state of tissues. For example, eventsof senescence and ripening are often signaled byabrupt 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) withrelease of CO2 and H2O. If glucose is used as
substrate, the overall equation for respiration canbe written as follows:

C6H12O6 + 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 likeglucose 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 atlater stages in the overall process and as smaller,
partially metabolized molecules. The 192 g ofO2 (6 moles × 32 g mol-1) used to oxidize the
1 mole of glucose diffuses into the tissue fromthe surrounding atmosphere, while the 6 molesof CO2 (264 g) diffuses out of the tissue. The 6
moles of H2O (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 islost 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 islost to heat every time energy is transferred during
a metabolic reaction.
Aerobic respiration involves a series of threecomplex reactions, each of which is catalyzed bya 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 themolecule 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 fromeach molecule of glucose. Each of the 10 distinct,
sequential reactions in glycolysis is catalyzed by
one enzyme. Two key enzymes in glycolysis arephosphofructokinase (PFK) and pyruvate kinase73

(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 twomolecules 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 breakdownof 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 thenenters the cycle by condensation with oxaloacetate
to form citric acid. Citric acid has threecarboxyl groups from which the cycle derives
its name. Through a series of seven successive
rearrangements, oxidations, and decarboxylations,citric acid is converted back into oxaloacetatethat is then ready to accept another acetyl CoA
molecule. In addition to producing the many small
molecules that are used in the synthetic reactionsof the cell, the TCA cycle also produces one
molecule of flavin adenine dinucleotide (FADH2)
and four molecules of NADH for each moleculeof 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 ismore 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 thechemical 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. Regenerationof NAD+ is absolutely essential for the survival
74of 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 andCO2 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, priorstresses, and the current metabolic needs of thecell. Acidification of the cytoplasm enhances theactivity 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 regenerationof NAD+. Two molecules of ATP and 21 kcal ofheat energy are produced in anaerobic respiration(alcoholic fermentation) from each molecule ofglucose. 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 ofsix 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 ethanoland smaller amounts of acetaldehyde. However,glycolysis usually increases only 3- to 6-fold.
The O2 concentration at which a shift frompredominantly 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.

Further Reading
Abeles, F.B., P.W. Morgan, and M.E. Saltveit.
1992. Ethylene in Plant Biology, 2nd ed.
Academic Press, New York, NY.

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.

Biale, J.B., and R.E. Young. 1981. Respiration andripening in fruits—retrospect and prospect. In J.
Friend and M.J.C. Rhodes, eds., Recent Advancesin the Biochemistry of Fruits and Vegetables, pp
1-39. Academic Press, New York, NY.
Kays, S.J. 1991. Postharvest Physiology ofPerishable 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 minimallyprocessed lettuce. Postharv. Biol. Technol. 9:223233.
Ryall, A.L., and W.J. Lipton. 1979. Handling,
Transportation and Storage of Fruits andVegetables, 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 andVegetables, vol. 2, Fruits, pp. 4-12. AVI
Publishing Company, Westport, CT.
Saltveit, M.E. 1996. Physical and physiologicalchanges in minimally processed fruits andvegetables. In F.A. Tomás-Barberán, ed.,Phytochemistry of Fruit and Vegetables, pp. 205220. 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.

75

Mikal E. Saltveit
Saltveit is with Mann Laboratory, Department ofPlant Sciences, University of California, Davis,
CA.

Introduction
Ethylene (C2H4) is a simple, naturally occurringorganic 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 biologicaltemperatures.
• It is a naturally occurring organic compound.
• It readily diffuses from tissue.
• It is produced from methionine via
aminocyclopropane carboxylate (ACC) by ahighly regulated metabolic pathway.
• Key enzymes are ACC synthase and ACC
oxidase.
• C2H4 synthesis is inhibited by C2H4 invegetative and immature reproductive tissue.
• C2H4 synthesis is promoted (autocatalytic)
by C2H4 in mature reproductive climacterictissue.
• 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 andlow levels of CO2 to be active.
Many biotic and abiotic sources contributeto the presence of C2H4 in the postharvest
environment. Ripening and diseased plant tissues
are a significant source of C2H4, 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 amountsof C2H4 that appear to coordinate growth anddevelopment. Because it is a gas, C2H4 readily
diffuses from sites of production, and continuous
synthesis is needed to maintain biologically active
levels in the tissues. Barriers to diffusive loss
76

include not only the commodity’s epidermis but
also postharvest coatings and packaging. Underbiotic or abiotic stress or during climactericripening, C2H4 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 C2H4 but are less effective. For example,
C2H4 analogs propylene (C3H6) and acetylene(C2H2) require 100- and 2,700-fold, respectively,
the concentration of C2H4 to elicit the same effect.
Plants produce C2H4 through an actively
regulated biosynthetic pathway in which theamino acid methionine is converted to ACC(1-aminocyclopropane-1-carboxylic acid) andthen to C2H4 through a series of biochemical
reactions. O2 is required for the synthesis of C2H4
and both O2 and CO2 are required for its biologicalactivity. Each reaction in the synthesis and actionof C2H4 involves a biological catalyst, an enzymethat 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 cancreate a positive or a negative feedback of C2H4 on
its synthesis (figure 1).

Removal of
ethylene

Ethylene concentration

Ethylene Effects

Positive
feedback

Addition of
ethylene

Negative
feedback
Time

Figure 1. Effect of adding and removing ethylene from theatmosphere surrounding tissues that respond with a positive(ethylene promotes its own synthesis) or negative (ethylene
inhibits its own synthesis) feedback. Modified from Saltveit(1999).

In vegetative tissue and in nonclimacteric andimmature climacteric fruit tissue, C2H4 suppresses
its own synthesis, and in ripening climacteric fruit
C2H4 enhances its own synthesis. This positive
feedback of C2H4 on C2H4 synthesis is called
autocatalytic C2H4 production. Plants respond to
C2H4 in a number of ways.
Ethylene stimulates the following:• Synthesis of C2H4 in ripening climactericfruit• Ripening of climacteric fruit and some
nonclimacteric fruit• Anthocyanin synthesis in ripening fruit• Chlorophyll destruction and yellowing (forexample, 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 andnonclimacteric fruit• Flowering and flower development in mostplants• Auxin transport• Shoot and root elongation; that is, growth
Depending on a number of variables, C2H4
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, inpineapple)• 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 C2H4-induced change in one commodity
is viewed as beneficial, while the same change
in another commodity is viewed as detrimental.
For example, C2H4 is used to promote ripeningof bananas, melons, and tomatoes; degreeningof oranges; and synthesis of pigments in apples.
Yet the same changes are unwanted when C2H4
promotes over-ripening of fruit, yellowing ofbroccoli, development of brown russet spot lesionsin lettuce, and senescence of flowers. Because of
these diverse and often opposite effects of C2H4,
controlling its action in plants is of great economic
importance to producers, wholesalers, retailers,and consumers of fresh fruits, vegetables, andornamentals.
In most vegetative tissues, C2H4 is only producedin biologically active amounts during early stagesof development or in response to biotic or abiotic
stress. Mutant plants that do not respond to C2H4
often grow normally, with only a few insignificant
alterations in development. Most of the effects
of C2H4 on vegetative tissue are therefore theresult of the tissue’s response to a stress or to theintentional or unintentional exposure of tissue toactive levels of C2H4.
In contrast to its effects on vegetative tissue,
biologically produced C2H4 plays a crucial rolein the development of reproductive tissues and in
the ripening of certain climacteric fruit. The ratesof C2H4 production and its internal concentration
often vary by orders of magnitude during earlystages of development and during the initiationand development of reproductive structures.
Increased rates of C2H4 production are especiallypronounced during the ripening of climactericfruit such as apples, avocados, bananas,
77melons, pears, and tomatoes. In these fruit, theautocatalytic production of C2H4 heralds theonset of ripening and is required for many of thereactions associated with ripening to continue. See
section “Summary of Respiration and Ethylene
Production Rates” in the Introduction of thishandbook.
Once internal C2H4 exceeds a level characteristic
for the species, tissue, and developmental stage,
the further production of C2H4 is stimulated bypresence of previously produced C2H4. In this way,
autocatalytic positive feedback can increase ratesof C2H4 production and internal concentrationof C2H4 by 1,000-fold during ripening. External
application of C2H4 can promote the ripeningof climacteric fruit—for example, avocado,
banana, honeydew, and tomato—and beneficial
quality changes in nonclimacteric fruit; forexample, degreening of lemon and orange.
Once autocatalytic C2H4 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 aspectsof plant growth and development. Regulating
its effectiveness is commercially important for
many crops. Controlling its effectiveness canmean either increasing its beneficial effects ordecreasing its detrimental effects. There are anumber of ways to accomplish either objective.
Reducing Effectiveness of Ethylene		
Use C2H4-tolerant cultivars
Keep atmosphere free of C2H4		
Maintain at coldest possible temperature
Store under CA or MA or in MAP
Minimize time between exposure and use
Increasing Effectiveness of Ethylene
Use C2H4-sensitive cultivars
Keep an active level of C2H4 in the air
Maintain at optimum temperature
Store under adequate levels of O2 and CO2
Allow sufficient time for plant response

78

Ethylene Interactions in Plants
There are some significant interactions between
the plant and its environment that are important inunderstanding how to control biological activity of
C2H4 in plants (figure 2).
Ripening or diseased
fruit, exhaust,
pollution, etc.

EXTERNAL
INTERNALETHYLENE

PLANT
TISSUE
Ethylene
Biosynthesis

Abiotic,
Biotic Stress

Inhibitors of
ethylene action,e.g., CO2, Ag, 1-MCP

Physiologicalresponse toethylene

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 ofatmospheric 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 somecases, C2H4, whether applied as a gas or as an
C2H4-releasing compound such as ethephon, isintentionally 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 C2H4 inside plants is regulated
not only by the absolute level of C2H4 but also by
the responsiveness of tissues and the presence ofCO2, the natural antagonist of C2H4 action. The
response of plants to C2H4, therefore, depends ona number of factors, only one of which is the rateof C2H4 production by the plant. Tissue sensitivity
depends on species, cultivar, cultural practices,and stage of development.

Prior and current stresses have a significant effecton modulating the effect of C2H4. For example,
wounding stimulates C2H4 production, as well
as a host of plant defense responses such asincreased phenylpropanoid metabolism. Some ofthese responses involve C2H4, while others do not.
Increased phenolic metabolism greatly increases
the susceptibility of some crops like lettuce todevelop browning—for example, russet spotting—when exposed to C2H4 and/or mechanical injury.
The effect of tissue susceptibility is most clearlyseen in fruit tissue. Immature climacteric fruit
respond to C2H4 with increased respiration andreduced C2H4 production. Once the tissue hasreached a certain stage of maturity, however, C2H4
not only promotes increased respiration but also
increased C2H4 synthesis.
Controlling the effectiveness of C2H4 does notalways involve a reduction in its activity. There
are many beneficial effects of C2H4 that can beenhanced (see above). The techniques used toincrease the effectiveness of C2H4 are almost themirror image of techniques used to reduce its
effectiveness.
Ethylene action can be enhanced by using
cultivars that are sensitive and respond uniformly
to C2H4 rather than cultivars that are C2H4
insensitive. An effective concentration of C2H4
should be maintained around the tissue for a
sufficient time to elicit the full response. However,since the response to C2H4 is log-linear (a log
increase in C2H4 concentration results in a linear
increase in the response), there is an extremely
large range over which the concentrations are
effective. The application of C2H4 must be at
the proper stage of development and at theproper temperature for the desired effects to be
induced. Ethephon and similar C2H4-releasingchemicals permit the commercial application of
C2H4 in the field. After harvest, C2H4 gas, either
from compressed gas cylinders or catalyticallygenerated from alcohol, can be used in enclosed
storage rooms.

Controlling Ethylene Action
There are roughly three ways to control the actionof C2H4 in plants. The first is to prevent the plantfrom being exposed to biologically active levelsof C2H4. The second is to prevent the plant tissue
from perceiving the C2H4 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 C2H4 by controlling exposure to
C2H4.
Preventing Exposure to Ethylene
The following should be done to prevent exposure
to C2H4:• Keep the air around the commodity C2H4
free.
• Use fresh, C2H4-free air from outside.
• Scrub C2H4 from the storage atmosphere.
• Use sachets of C2H4 absorbers inside
packages to reduce levels.
• Segregate C2H4-producing commodities
from C2H4-sensitive ones.
• Keep exposure to a minimum (in terms ofboth duration and level).
• Inhibit C2H4 synthesis (AVG, ACC synthase,
low O2, ACC oxidase).
Risk of exposure to C2H4 is usually not much ofa problem in the field because the levels of C2H4
found even in polluted air rarely reach biologically
active levels. However, in greenhouses, coldstorage rooms, and transportation vehicles, C2H4
can frequently accumulate to reach biologically
active levels. Ethylene found in these enclosed
spaces comes from varied sources, and the twomost prominent sources are diseased, stressed,
or ripening plant tissue and the incomplete
combustion of organic fuels.
With proper ventilation of enclosed spaces andwith persistent attention to the condition of
adjacent plants and the operation of heaters andgas-powered forklifts, C2H4 can be kept below
biologically active levels. Sometimes the C2H4
that we are concerned with comes from the79

plant itself. Application of inhibitors of C2H4
biosynthesis, such as AVG and AOA, to the tissue
before or after harvest can significantly reduce
this source of C2H4 exposure. For example, tissue
can be prevented from making either stress or
autocatalytic C2H4 by blocking the biosynthetic
pathway for C2H4 synthesis. If exposure cannot be
prevented or has already occurred, then both theduration of exposure and the level of C2H4 in theatmosphere should be kept as low as possible.
Preventing Perception of Ethylene
If significant amounts of C2H4 are in theimmediate environment, certain methods can beused to block the perception of C2H4 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), and1-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 interferewith the perception event.
A gaseous inhibitor like CO2 or 1-MCP can be
introduced into the atmosphere. The tissue can bedipped or fed a nonvolatile inhibitor such as silver
thiosulfate, but this treatment is limited to nonfood
crops. Ethylene-resistant cultivars can be selectedor the tissue genetically engineered to lack thenecessary biochemical receptors for ethylene or
the signal pathway necessary to transduce thesignal 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 iscurrently available.

80

Preventing Response by the Plant
The third way to control C2H4 is to prevent theplant from responding to the perceived C2H4. Thiscan be done by interfering with the metabolic
machinery that is induced by exposure to C2H4, 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 (forexample, AIP) or genetic engineering (forexample, antisense or other gene knockout
techniques).
• Divert protein synthesis—by heat-shock, forexample.
• Minimize time before use (for example,
consumption).
Since all the effects of C2H4 on plants that weare 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 specificenzyme (for example, with a chemical or throughgenetic engineering) will prevent a response toC2H4. 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 C2H4 as a signal to induce defense
mechanisms. Interfering with synthesis or activityof phenylalanine ammonia lyase (PAL, the first
enzyme in phenolic metabolism) with chemical
inhibitors or heat treatment eliminates tissue
response to C2H4, preventing development of
postharvest disorders.

Application of Ethylene
The quality of some fruits is increased when they
are harvested at a mature but unripe stage thatcan withstand the rigors and duration of transport
and then treated with C2H4 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 C2H4
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 bymetering 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% C2H4 in N2 (“bananagas”), eliminates this problem.
Catalytic converters are instruments that use aheated metal catalyst to convert alcohol into C2H4.
They deliver a continuous flow of low C2H4 into
the storage room. Ethylene can also be applied inaqueous 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 formany food crops, but postharvest application is
not approved.
Treatment with C2H4 stimulates many metabolic
pathways, including respiration. Oxygen use isincreased, 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 respirationand excessive CO2 must be removed to maintaina proper environment. Loss of water by the crop
will be increased by the rise in respiratory heatproduction. 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 productionof high-quality fruit. Care must be exercised inventing and opening ripening rooms to prevent
release of sufficient amounts of C2H4 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 C2H4 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 moresophisticated treatments like MAP and inhibitorsof specific induced enzymes to provide conditions
that optimize both storage life and product quality.

References
Saltveit, M.E. 1999. Effect of ethylene on qualityof 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 senescenceand physiological disorders in harvested
horticultural crops. HortScience 20:54-57.
81

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 thequality of fruits and vegetables. Food Technol.
40:82-85.
Weichmann, J. 1987. Postharvest Physiology ofVegetables. Marcel Dekker, New York, NY.

82

1-Methylcyclopropene (1-MCP)
Chris B. Watkins
Department of Horticulture, Cornell University,
Ithaca, NY

Introduction
The plant hormone ethylene affects a wide rangeof physiological processes in horticultural crops,
including abscission, senescence and ripening,chlorophyll loss, softening, physiologicaldisorders, 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 focusedon 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 theyseek 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 responsesof horticultural products (Blankenship and Dole
2003). The process of discovery of the effectsof cyclopropenes and their proposed method ofaction 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 inor 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. Afterapplication, 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, andmaintaining postharvest quality (McArtney etal. 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 intoaqueous 1-MCP have been published (Choi etal. 2008), but this method is not currently usedcommercially.

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 isregistered for use on a wide variety of fruits andvegetables 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 isregistered 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.
83

Semicommercial trials have been carried out atseveral 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 andethylene-independent events during ripening andsenescence, in addition to developing practicaluses for 1-MCP. Studies have focused on theeffects of 1-MCP on quality of horticultural
crops, specific postharvest issues such as handlingand packaging, physiological and biochemical
responses, and storage disorders. A number ofdetailed reviews on the effects of 1-MCP havebeen 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 ofthe product to the molecule.
Ripening and Senescence. 1-MCP affects manyripening 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 diversityof 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 canbe highly variable, but responses to 1-MCP
are typically “concentration × exposuretime” dependent.
• Most if not all climacteric fruit are affectedby 1-MCP treatment, but the capacity tointerrupt the progression of ripening, once
initiated, varies by fruit and by attributes
studied.
84• Nonclimacteric fruit can also respondto 1-MCP; such effects are providing
interesting insights about ethylene-dependentand 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 areappropriate for the product, the final quality
attained in the ripened fruit is similar to thatof untreated product.
• Rate of loss of nutritionally importantcompounds 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 areaof postharvest responses to 1-MCP is its
effects on physiological disorders (Watkins
2007,2008a,2008b). These disorders can bedivided into categories:• Ethylene-induced disorders. Examples
include russet spotting of lettuce andisocoumarin accumulation in carrots (Fanand Mattheis 2000a), lignification of
asparagus (Liu and Jiang 2006), and watersoaking of watermelons (Mao et al. 2004).
These disorders are preventable by inhibitionof ethylene perception.
• Senescence-related disorders. Examples
include senescent breakdown of apples(Moran and McManus 2005), senescentscald and breakdown of pears (Ekman etal. 2004), and yellowing of broccoli (Fanand Mattheis 2000b). These disorders arealso prevented by inhibition of ethylene
perception.
• Controlled atmosphere-related storage
disorders. 1-MCP can increase susceptibilityof 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).

• Chilling-related disorders that are increased
by inhibition of ethylene perception.
Examples include woolliness and internal
breakdown of peaches and nectarines (Donget al. 2001), chilling injury of citrus andbananas (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; browncore (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 (Luoet al. 2008), melons (Gal et al. 2006), andpersimmon (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 thecomplex interaction between host, pathogen,and environment (Watkins 2008b). In someinstances, disease incidence can be lower because
the beneficial effects of 1-MCP on skin integrity
and flesh firmness result in greater resistance toinfection. However, ethylene is necessary for
defense systems in other plant systems (Marcos etal. 2005).

Application
For postharvest use of 1-MCP on both ornamental
plants and edible food products, material mustbe 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 byauthorized 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 productmaximize the benefits of treatment.

The apple has been an excellent crop for use of
1-MCP, which is used extensively around theworld to maintain quality through the wholemarketing 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 highquality produce through marketing channels to
the consumer. The successful use of 1-MCP on
apples is largely associated with varieties forwhich 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 textureor have major color change. For example, failure
to ripen normally has been shown in avocado,
banana, pear, and tomato after fruit were treatedat 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 toquality characteristics (texture, flavor, aroma,color) that are expected by the consumer. Despite
the challenges, successful 1-MCP treatment ofavocados, bananas, melons, persimmons, andtomatoes has resulted from careful attenuationof 1-MCP concentrations or selecting fruit at theappropriate ripening stage at harvest. Researchon 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 ofresearch 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.

85

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.

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 and1-methylcyclopropene (1-MCP) in the ‘Empire’apple. Postharv. Biol. Technol. 48:92-98.

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.

Gal, S., S. Alkalai-Tuvia, Y. Elkind, and E. Fallik.
2006. Influence of different concentrations of
1-methylcyclopropene and times of exposureon the quality of ‘Galia’-type melon harvested
at different stages of maturity. J. Hort. Sci.
Biotechnol. 81:975-982.

Choi, S.T., P. Tsouvaltzis, C.I. Lim, and D.J.
Huber. 2008. Suppression of ripening andinduction of asynchronous ripening in tomato
and avocado fruits subjected to completeor partial exposure to aqueous solutions of
1-methylcyclopropene. Postharv. Biol. Technol.
48:206-214.

Golding, J.B., D. Shearer, S.G. Wyllie, and W.B.
McGlasson. 1998. Application of 1-MCP andpropylene to identify ethylene-dependent ripening
processes in mature banana fruit. Postharv. Biol.
Technol. 14:87-98.

DeEll, J.R., D.P. Murr, L. Wiley, and M.D.
Porteous. 2003. 1-Methylcyclopropene (1MCP) increases CO2 injury in apples. Acta Hort.
600:277-280.

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 andvegetables. HortScience 43:106-111.

Dong, L., H.W. Zhou, L. Sonego, et al. 2001.
Ethylene involvement in the cold storage disorderof ‘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 physiologicaldisorders of carrots and iceberg lettuce by
1-methylcyclopropene. HortScience 35:13121314.
Fan, X.T., and J.P. Mattheis. 2000b.
Yellowing of broccoli in storage is reduced by
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88

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 andFood Research Institute of New Zealand Ltd.,
Auckland, New Zealand.

Textural attributes of fruits and vegetables are
related to the structural, physiological, andbiochemical characteristics of the living cells;
their changes over time; and their alterationby 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 offruit or vegetable texture difficult. Because of theircontinuous change, textural measurements areoften relevant only at the time of evaluation; thatis, they usually cannot be used to predict condition
much later in the storage period or marketing
chain.

Introduction
Texture is a quality attribute critical in determining
the acceptability of fruits and vegetables. It isconvenient to define quality as the composite
of intrinsic characteristics that differentiate
units of the commodity—individual pieces ofthe product—and to think of acceptability as
consumers’ perceptions of and reactions to thosecharacteristics. Though the term is widely used,
texture is not a single, well-defined attribute. It isa collective term that encompasses the structuraland mechanical properties of a food and thesensory 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 propertiesof commercial interest that may not be of directinterest to the consumer, such as resistance tomechanical damage. In this review, we will use
the term texture in the broadest sense.

Physiological Basis of Texture

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 formeasuring these attributes. In fact, there is somedisagreement among sensory, horticultural, andengineering uses of certain terms, particularly
firmness, which is discussed below.

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 isthat 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 theirprimary walls are separated by a morphologicallydistinct region known as the middle lamella,

To understand the texture of a product, it isimportant 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 toughstrands of vascular material when measuring
texture of soft tissues because the small amountof fiber produces an artificially high reading that
does not agree with the sensory assessment ofsoftness. On the other hand, it is important tomeasure the strength of fibers when determining
toughness, such as in asparagus spears andbroccoli stalks. Thus, method development and thesolution to many texture problems require a goodunderstanding of the anatomy of tissues within
the fruit or vegetable, the structure of its cells, thebiological changes that occur following harvest,
and sensory texture perception.
Parenchyma Cells

89

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

GarlicCorm		

Water chestnut

Sprouted seeds		

Bean sprouts, etc.

Stem		

Asparagus

Leaf buds		
		

Cabbage, brussels sprouts,
belgian endive (etiolated)

Petiole		Celery, rhubarb

Cinnamon (bark)

Leaf		
Collards, kale, leek, lettuce,		mustard greens, onion
		(green), spinach,		watercress						Basil, bay, chives,
cilantro, dill leaf,
marjoram, mint,
oregano, parsley,rosemary, sage,
tarragon, thyme

Flower buds		
		Capers, cloves

Artichoke (globe), broccoli,cauliflower, lily bud

Flowers		
Squash blossoms
			Floral receptacle		

Strawberry, fig

Fruit, immature		
		
		
		
		
		

Chayote (christophene,
mirliton), cucumber,
eggplant, beans (green),
snap peas, pepper(Capsicum), summer
squash, zucchini

90

Edible flowers 				(garnishes)

Gherkin (pickled)

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 (formustard, nutmeg,
		examples, squashes,
pepper (black, Piper),tomatoes, and beans)pomegranate, poppy			seed, sesame seed
Fungi		Mushrooms, truffles_____________________________________________________________________________________

which separates adjacent cells and is rich inpectic 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 importantbut seemingly incompatible properties. The firstis 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 muchmechanical support. Rather, it is the interaction
between rigidity of the wall and internalhydrostatic pressure (turgor) of cell contents thatprovides support.
The arrangement and packing of parenchyma cells
within the tissue is another factor that influences
mechanical strength of produce. In carrots, thecells are small (approximately 50 μm in diameter),isodiametric in shape, and closely packed witha high degree of contact between neighboring
cells and a small volume of intercellular gas-

filled spaces. The cells can be arranged either
as columns or as a staggered array where eachcell overlays the junction of the two lower
cells (Sørensen et al. 1999). These differencesin cell packing may, in part, explain genotypic
differences in susceptibility to harvest splitting
in carrot. In apple cortical tissue, the cells arelarge (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, thetissue stiffness (elastic modulus) is higher andthe strain at failure is lower when tissue plugs arecompressed in a radial rather than a vertical ortangential orientation (Khan and Vincent 1993,
Abbott and Lu 1996). Up to 25% of the volume ofapple tissue may be gas-filled intercellular spaces,
which indicates relatively inefficient cell packing
and a low degree of cell-to-cell contact, bothof which correlate well (negatively) with tissue
stiffness (Vincent 1989).

91

Cell Wall
From a chemical perspective, the primary cellwall 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 describedby 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 solublizationand degradation of pectin and a net loss ofthe noncellulosic neutral sugars galactose andarabinose, and there may be a decrease in themolecular weight distribution of hemicelluloses(Harker et al. 1997). Numerous enzymes havebeen suggested as being critical to these changes
in the cell wall including polygalacturonases andseveral glycosidases, including β-galactosidase,
xyloglucanase, endotransglycosylase, andcellulases (Dey and del Campillo 1984, Huber
1992, Seymour and Gross 1996, Harker et al.
1997). The possible role of expansins—proteinsthat are proposed to disrupt hydrogen bonds
within the cell wall—has been considered (Civelloet al. 1999). The use of molecular approaches,
including antisense technologies, has been apowerful tool in the search for an understanding offruit 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 ofseveral enzymes or that the key enzyme has notbeen identified.

Cooking often results in degradation of pectic
polymers via β-elimination, which is usuallyrelated to the degree of methyl esterification ofpectin (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, andbeetroot. In Chinese water chestnut, the thermal
stability of texture is associated with the presenceof ferulic acid in the cell wall (Waldron et al.
1997).
Postharvest treatments involving dipping or
infiltrating with calcium maintain firmness duringstorage 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 cellwall (pectin), it may also affect texture throughinteractions with membranes.
The cell wall may also influence perceptionof juiciness through its ability to hold andrelease 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 fruitwith 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, whichdevelops when the concentration of solutes inside92

the cell (more specifically inside the plasma
membrane) is higher than that outside the cell.
The extracellular solution fills the pores of the cellwall, sometimes infiltrates into gas-filled spaces,
and usually is continuous with vascular (waterconducting) pathways of the plant. Differences insolute concentration at the inner and outer surfaceof the plasma membrane cause water to flow into
the cell by osmosis. This net movement of wateris halted by the physical constraint of the rigid cellwall 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, andΨπ 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 andPitt 1986). When tissues are subjected to tensile
measurements, turgor tends to harden the cell wall
and a greater force is needed before cells fail (DeBelie et al. 2000a). However, turgor is unlikely
to influence tissue strength if the mechanismof failure is cell-to-cell debonding, rather thanfracturing across individual cells, unless anincreasing 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 theturgor component of texture (Greve et al. 1994).
Similarly, when produce experiences a freezethaw cycle, the membranes are damaged and thetissues become more flaccid in the case of leafy
vegetables (and softer in the case of fruits) andoften 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 toplay a central role in softening and developmentof mealiness during storage of apples (Hatfield
and Knee 1988).
Cell-to-Cell Debonding Versus Cell Rupture
The strength of the cell wall relative to theadhesion 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 andtomato 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 somefruits, cell-to-cell debonding does not result ina dry texture; rather, a layer of juice covers theintact cells exposed following cell separation(Harker et al. 1997). Furthermore, cell-to-celldebonding 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 afunction of three factors: strength of the middle
lamella, the area of cell-to-cell contact, and theextent 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 bycompressive forces known as “cell relaxation”(Peleg et al. 1976) or “exosmosis” (Jackman andStanley 1995).
Other Elements of Tissue Strength
The strength and integrity of many edible plantorgans are influenced by a number of additional
factors (Harker et al. 1997). Many fruits andvegetables contain a number of tissue zones:
periderm, pericycle, and phloem parenchyma incarrot; skin, outer pericarp, inner pericarp, andcore in kiwifruit; and outer pericarp, locular gel,seeds, and columella in tomato. These tissues
93differ in strength and biological properties andoften need to be considered individually whenmeasuring texture. For example, failure of thecore 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-likeprotuberances. 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 wallsof hypodermal cells contribute to strength ofsimple 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 inan 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 inspaghetti 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 andmuskmelons, can have a problem with stringiness(Diehl and Hamann 1979). Generally, theperception of stringiness is greater with veryripe fruit due to the contrast between the soft
melting texture of the parenchyma cells and thefibrousness of the vascular tissues. Similarly,
the gritty texture of pear and guava (Harker etal. 1997) becomes particularly noticeable when
the surrounding cells are soft. However, while
stringiness is caused by vascular tissues, grittinessis caused by sclerenchymatous stone cells (Harker
et al. 1997).

proposed a texture profile, a systematic approachto sensory texture analysis based on mechanical,
geometrical, and other characteristics. Mechanicalcharacteristics included basic parameters(hardness, cohesiveness, viscosity, elasticity,
and adhesiveness) and secondary parameters(brittleness or fracturability, chewiness, andgumminess). Geometrical properties related tosize, 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 combinationof characteristics of the product be termed“quality” and that the consumer’s perception andresponse 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 andtheir 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 andjudgments to predict quality categories. Only
people can judge quality, but instruments thatmeasure quality-related attributes are vital for
research and inspection (Abbott et al. 1997).

Sensory Evaluation of Texture

Instrumental Measurement of Texture

People sense texture in numerous ways: the lookof the product, the feel in the hand, the way it
feels as they cut it, the sounds as they bite andchew it, and, most important of all, the feel ofthe product in the mouth. Szczesniak (1963)

The ability to measure texture is critical forevaluation and control of quality. The complex
nature of texture is associated with the diversityof tissues involved, the attributes required todescribe textural properties, and changes in these94attributes as the product ripens and senesces.
Instrumental measurements are preferred oversensory evaluations for research and commercial
applications because they are less subject tohuman influences, are more precise, and canprovide a common language among researchers,companies, regulatory agencies, and customers.
It is often suggested that the relevance of
instrumental measurements depends on how wellthey predict sensory attributes (Voisey 1971), butthere 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 vegetabletexture (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 themeasurement of fruit or vegetable texture. For
example, as the parenchymal tissue of honeydew
melon softens, the perception of fibers (vascularbundles) increases (Diehl and Hamann 1979). On
the other hand, the fibrousness in asparagus isrelated to active lignification of fiber and vascularbundles (Chang 1987). Similar effects can affectinstrumental measurements. For example, fibers
are held relatively rigidly in a hard melon andthus contribute to the overall force required to cut
through the flesh, but the fibers in a soft melon canbe displaced by the instrument’s probe and alter
distribution of forces within tissue. The displaced
fibers can also effectively change the shapeof the probe as it progresses through the flesh
accumulating a “cap” of fibers.
Most instrumental measurements of texture havebeen developed empirically. While they may
provide satisfactory assessments of the qualityof produce, they often do not fulfill engineering
requirements for fundamental measurements(Bourne 1982). Fundamental material properties
measurements were developed to study thestrength of materials for construction or
manufacture. After the failure point of such amaterial is exceeded, there is little interest in thesubsequent behavior of the material. On the other
hand, scientists who study food are interested ininitial failure but they are also interested in thecontinuous 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 weaknessof materials rather than strength of materials.” Infact, 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 thatforce, distance, and time—in the form of rate,
extent, and duration of load—determine thevalue of measurements. For example, impactof 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 theforce of a carton wall against tightly packed fruit
are long-term loads. The fruit will respond quite
differently to the two forms of loading. Becauseof the viscoelastic character of fruit and vegetabletissues, every effort should be made to use aconsistent 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 thatcan 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 these95

measurements are stress, strain, modulus, andenergy, respectively.
Stress is force per unit area, of either contact orcross-section depending on the test. Strain isdeformation 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 commonlyused in food applications than stress and strain
values and are sufficient, provided that the contact
area and the distance the probe travels are constantand sample dimensions are similar from sample
to sample. (Sample here means the portion oftissue tested, not necessarily the size of the fruitor vegetable.) In many horticultural texture tests,
deformation is kept constant and the force value
is reported. For example, in penetrometer testsof fruit firmness such as the Magness-Taylor test
discussed below, the force required to insert aprobe into the flesh to an inscribed mark is readfrom a gauge. No compensation is made fordifferent probe diameters (contact areas), so thevalue 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 timeis 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 vegetablehandling systems are likely to be around 400 mm
s-1 (945 in min-1), equivalent to a drop of only 8.1mm, and sometimes much greater.

96

97

None. Uses AMETEK force gauge
and manual drill press

U.C. (University
MT
MechanicalGauge
of California)				

Other labels, such as “McCormick,” may occur on Effe-gi instruments.

‡

Universal testing
Universal
MechanicalElectronic
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.

Lake City Technical Products, Kelowna, BC,
CanadaEPT
MT
MechanicalElectronic				

Effe-gi, Ravenna, Italy

Wagner Instruments, Greenwich, CT(manufactured by Effe-gi)

Gauge

WagnerMT
ManualGauge
				

Manual

McCormick Fruit Tech Co., Yakima, WA(manufactured by Effe-gi)

MT

McCormick‡
MT
ManualGauge				

Effe-gi‡____________________________________________________________________________________________________________________
Instrument
Type*
Force†
Readout
Manufacturer____________________________________________________________________________________________________________________
Magness-Taylor
MT
ManualGauge
D. Ballauff Manufacturing Co., Laurel, MD

Table 2. Magness-Taylor fruit firmness tester and related penetrometers

A typical force/deformation (F/D) curve for acylindrical piece of apple tissue compressed atconstant 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 orelastic modulus should be measured. Beyond theelastic limit, permanent tissue damage begins.
There may be a bioyield point (b), at which cells
start to rupture or move with respect to theirneighbors, causing a noticeable decrease in slope.
Point (c) marks rupture, where major tissue failurecauses the force to decrease substantially. In someF/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 shownin figure 1 are also reported for apple and for othercommodities. 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 noteven show rupture; for example, a cylinder of
eggplant compressed like apple tissue in figure
1 may show smoothly increasing force to thepoint of maximum deformation. Samples with amixture 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 compressionof 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 metricspecification was selected to control the universal testing instrument.

98Firmness of horticultural products can bemeasured 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 destructionthat 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 ofthe 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 deformationlevel to the elastic region so that negligible
tissue damage is sustained during measurement.
It is important to recognize and understandthe fundamental properties measured by both
destructive tests and nondestructive methods, thedifferences between them, and the factors that canaffect the tests.
Numerous mechanical instruments have beendeveloped over the past century for measuring
textural attributes of horticultural products.
Despite the large variations in design, thesemechanical 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, areused to measure firmness of numerous fruits andvegetables to estimate harvest maturity or for
postharvest evaluation of firmness. There areseveral adaptations of the Magness-Taylor testerthat differ in instrument size and shape, manualor 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 andmeasure the maximum force required to insert
the probe 7.94 mm (5/16 in) into the flesh (Haller1941). 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 diameterwith a radius of curvature of 8.73 mm (11/32 in) isused 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 thinslice of skin (about 2 mm thick and slightly larger
diameter than the probe) should be removed fromthe area to be tested, except for cucumbers, which
are tested with the skin intact.
A group of U.S. researchers publishedrecommendations for making manual
penetrometer tests (Blanpied et al. 1978), statingthat steady force should be applied so that theprobe 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 bynumerous 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 todrive 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 andthe fact that firmness as measured in puncture
tests is a combination of shear and compression invariable proportions, it is not possible to convert
measurements made with one size MT probe to
the other MT size, or to accurately convert toor from values for probes of other geometries(Bourne 1982). A random sample of 20 to 30 fruitof similar size and temperature should be tested
with punches on two opposite sides, depending
on uniformity of the lot. Peaches are often morevariable around the circumference than other fruit
so a larger number is recommended (Blanpied
et al. 1978). Similar measurements are madeon cherry, grape, and strawberry using a 3-mm
99

probe and on olive using a 1.5-mm probe on
the U.C. tester (E.J. Mitcham 2000, personalcommunication). Numerous puncture tests with
flat-faced cylindrical or hemispherical probes anda few with conical probes have been conducted.
None have achieved the acceptance of theMagness-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 usedon fruits and vegetables, but shear modulus canbe obtained from compression (Mohsenin 1986),
torsion (Diehl et al. 1979), impact (Bajema andHyde 1998), extrusion, and dynamic (Ramana
and Taylor 1992) tests. Although it does notmeasure 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 bottomof a cell measuring 67×67×63 mm (approximately
2 5/8×2 5/8×2 1/2 in, internal dimensions) thatcan be used on any materials tester with sufficientload capacity. The cell is generally filled withrandomly oriented pieces of the product, either tofull 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 ofmaterial properties sensed in the mouth during
chewing, the test does not satisfy requirements
for engineering tests because of the undefinedand uncontrolled stresses and strains applied to
the food. The amount of sample and the patternof 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 orientationof pieces of fruit or vegetable, especially withregard to vascular bundles and fibers, and the100

spaces between pieces would be expected toaffect 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 resultsfrom cells of different geometries.
Compression
Though compression tests are not commonlyused by the fruit and vegetable industry, they arewidely 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 attaina specified deformation or to rupture (bruise or
burst) the product is generally measured. Modulus
of elasticity, stiffness, force, contact stress, anddeformation to bioyield and to rupture can becalculated from elastic measurements, dimensionsof the specimen, and Poisson’s ratio (the ratioof transverse strain to axial strain at less thanthe elastic limit). For convex specimens suchas 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, usuallycylindrical, excised from the fruit or vegetable arequite 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 withparallel plates significantly larger than the areaof contact (ASAE 2000). Modulus of elasticity
values from whole fruit compression represents
fruit morphology, size, shape, cellular structure,strength, and turgor. Though elastic properties canbe 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al. (1990) found that whole tomato compression
was relatively insensitive to small differences infirmness due to chilling injury. Kader et al. (1978)
compressed tomatoes between a pair of sphericalindenters as a measure of firmness.

and watermelon) usually break or rupture and cells
from ripened soft fruits (banana, nectarine, andkiwifruit) tend to separate at the middle lamellae.

If the viscous element is a significant contributor
to the texture, as it is for intact tomatoes andcitrus, measurement of continuing deformation
under a constant force (creep) (Hamson 1952,
El Assi et al. 1997) or decrease in force undera fixed deformation (relaxation) (Sakurai and
Nevins 1992, Errington et al. 1997, Kajuna etal. 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 aroundthe fruit’s circumference with a belt. The failureof creep or force-relaxation testers to be adopted
commercially is due to the time required foradequate relaxation, which can be up to 60 s.

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).

Tension Test
Tensile tests measure the force required to stretchor 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 crushingor chewing as is puncture or compression andbecause 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 holdapple 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 modeof 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

Torsion Test

Twist Test
Studman and Yuwana (1992) proposed a simple
twist tester consisting of a sharp spindle with arectangular blade that is forced into the flesh; thetorque (twisting force) required to cause crushingor yielding of the tissue is measured. Thoughcalled a “twist test,” this is not to be confusedwith a torsion test: The properties tested arelikely 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 measuredifferent mechanical properties, resulting in quite
different firmness judgments. The twist test has
the advantage of being able to measure strengthof 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 subsequentsale, so a great deal of research has gone intodeveloping nondestructive methods to estimate
the mechanical properties and the textural qualityof fruits and vegetables (Chen and Sun 1991,
101

Abbott et al. 1997, Hung et al. 2001). None ofthese nondestructive methods has attained widecommercial 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 compareddirectly with descriptive sensory analyses todevelop 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 isadvisable 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 anondestructive compression test. Under fixed airpressure, firmer products deflect less than softer
ones. Laser-puff readings correlate well withdestructive Magness-Taylor firmness values forapple, cantaloupe, kiwifruit, nectarine, orange,
pear, peach, plum, and strawberry (Fan et al. 1994,
Hung et al. 1998, McGlone et al. 1999, McGloneand 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 conductedon the impact responses of horticultural products
and a number of impact parameters have been
proposed to measure firmness, including peak
102

force, coefficient of restitution, contact time, andthe impact frequency spectrum. The coefficientof 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 oncommodity, 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 etal. 1990, McGlone and Schaare 1993, Patel etal. 1993) or striking the product with the sensor(Delwiche et al. 1989, Brusewitz et al. 1991, Chenet al. 1996, Bajema and Hyde 1998). Delwiche etal. (1989, 1991) developed a single-lane firmness
sorting system for pear and peach. Impact
measurements often do not correlate highlywith the Magness-Taylor puncture measurement(Hopkirk et al. 1996). A potential problem with
impact tests is that bruising may occur unless asoft 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 meansof measuring fruit and vegetable firmness. The
traditional watermelon ripeness test is based on
the acoustic principle: One thumps the melon andlistens 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 Belieet 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 isreferred to as resonance. Resonance measurement
can be achieved by applying an impulse or thumpthat contains a range of frequencies. Modulus ofelasticity values obtained from resonant frequency
data have correlated well with those measured byconventional compression tests, but they often
correlated poorly with MT puncture forces. Abbott
et al. (1968) proposed a stiffness coefficient, f2m,
which was based on the modulus of elasticity
using the resonant frequency (f) and mass (m) of
the specimen; this was later modified by Cookeand Rand (1973) to f2m2/3.
Farabee and Stone (1991) developed a portablesonic instrument for field determination ofwatermelon ripeness and hollow heart detection.
Kawano et al. (1994) reported a commercial
sorting machine for detecting internal voids inJapanese watermelon. Shmulevich et al. (1995)
developed a sonic instrument using a lightweightflexible 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 horticulturalindustry. 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 havebeen used with limited success for measuringphysical and chemical properties of fruits andvegetables because of the high attenuation(energy absorption) of plant tissues. The
commonly measured ultrasonic parameters arevelocity, attenuation, and frequency spectrum
composition. Bruises in apples (Upchurch et al.
1987) and hollow heart of potatoes (Cheng andHaugh 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, andmangoes, respectively.
Light Scatter Imaging. As light passes throughtissue, cellular contents such as starch granules,
cell walls, and intercellular spaces cause scatter.
The extent of scatter of collumated light such asa laser beam may change during ripening due tocompositional changes and changes in cell-tocell contact. Measurement of the scatter using
computer vision may thus provide an indirectindication of textural changes. Significant
correlations between mechanical properties andimage size have been shown in apples (Duprat etal. 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 awarenessstudies; however, there has been little progressin developing instrumental measurements ofjuiciness. Intuitively, one would expect total
moisture content to determine juiciness, but thecorrelations 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 orpercentage of juice released from a fixed weightof tissue. Juice can be extracted from tissue by
the following methods: using a press (like acider press), homogenizing and centrifuging toseparate 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 criticalindicator of nonvisual aspects of quality. The
ability to measure texture has allowed industries
to set standards for quality at pack-out and tomonitor deterioration in quality during storage
and distribution. Furthermore, the study of thechemical, physiological, and molecular changes
that control or influence texture has been103

facilitated by the development of methods forquantifying texture change.
Much of the commercial and research interest in
texture has focused primarily on the mechanicalproperties of the tissues. The diversity of tissues
involved, the variety of attributes required
to fully describe textural properties, and thechanges 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 ofassessors that have been trained to score defined
attributes against a set of standards. However,
instrumental measurements are preferred oversensory evaluations for both commercial andresearch applications because instruments are
more convenient to use, widely available, tend
to provide consistent values when used bydifferent (often untrained) people, and are lessexpensive than sensory panels. These instrumental
measurements are widely understood and canprovide a common language among researchers,
industry, and customers.
There are numerous empirical and fundamental
measurements that relate to textural attributes.
Mechanical methods measure functions offorce, deformation, and time. Some indirect
methods measure chemical constituents orphysical characteristics. Destructive mechanicalmethods 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.

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110

Postharvest Pathology
Peter L. Sholberg and William S. Conway
Sholberg is with the Pacific Agri-Food ResearchCentre, 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. Departmentof Agriculture, Beltsville, MD. He is now retired.

Introduction
Losses caused by postharvest diseases are greaterthan generally realized because the value of fresh
fruits and vegetables increases several-fold while
passing from the field to the consumer (Eckert andSommer 1967). Postharvest losses are estimated torange from 10 to 30% per year despite the use ofmodern storage facilities and techniques (Harvey1978).
Postharvest diseases affect a wide variety of crops,
particularly in developing countries that lacksophisticated 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 andmarketing; 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 internationalorganizations (Kelman 1989). The reality is that
there is a portending food crisis that will require
the concerted efforts of all who are involvedin 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, foodproduction 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 causesthat are of microbiological origin that begin as

latent infections before harvest or occur at harvest
or afterward during storage. Fungi are morecommonly found attacking fruit, and bacteria
are more common as postharvest pathogens ofvegetables. 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 toconsult the references for specific information on
the topics that are covered.

Factors that Influence Postharvest
Pathology
Postharvest losses vary each year. Prevailingweather 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. Resistanceof major apple cultivars to the fungi that cause
blue mold, gray mold, bull’s-eye rot, and Mucorrot depended on cultivar (Spotts et al. 1999).
Condition of the crop, as determined by fertilizer
and soil factors, is very important in susceptibilityof 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 inoculumthat overwinters successfully to the amount ofpesticide residue that remains on the crop at
harvest (Conway 1984). Abundant inoculum
and favorable conditions for infection during theseason 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 thesame fungus that causes apple scab and gray moldcaused by the fungus Botrytis cinerea are also111

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 instorage (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 inapparently sound condition only to decay duringtransit 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 thatdecay often has a weather component, making
thorough weather records an important sourceof information for predicting possible decay instorage.
Physiological Condition. Condition of produce
at harvest determines how long the crop can besafely stored. For example, apples are pickedmature but preclimacteric to ensure that they canbe stored safely for several months. The onsetof ripening and senescence in various fruit andvegetables renders them more susceptible toinfection 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 todisease resistance than any other cation associatedwith the cell wall (Sams 1994).
In a study on the effect of increased flesh calcium
content of apples in storage, fruit were treatedwith solutions of CaCl2 by dipping, vacuum, orpressure 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
112

and can be stored longer before they breakdown
or decay. Conversely, high nitrogen content infruit predisposes them to decay (Conway 1984).
In pears, it has been found that managementof trees for low nitrogen and high calcium inthe fruit reduced severity of postharvest fungal
decay (Sugar et al. 1992). Apple cultivars canbe 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 apreharvest 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 graymold infection in apple 3 months after it wasapplied (Sholberg and Bedford 1999). The newclass 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 maintainsanitary conditions in all areas where produce ispacked. Organic matter (culls, extraneous plantparts, and soil) can act as substrates for decaycausing pathogens. For example, in apple andpear packinghouses, the flumes and dump tankaccumulate 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 ofavailable chlorine is adequate. A level of 50 to
100 ppm of active chlorine provides excellentfungicidal activity (Spotts and Peters 1980).
Chlorine measured as hypochlorous acid canbe obtained by adding chlorine gas, sodium
hypochlorite, or dry calcium hypochlorite. Thoughchlorine 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 levelsof chlorine must be constantly monitored. The useof 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 (Dychdala1983): Hypochlorite solutions with higher pH
values (7.5 to 8.5) are more stable but lessfungicidal, whereas at lower pH values (5.5 to 6.5)
the solutions are less stable but more fungicidal.
Chlorine dioxide can replace hypochlorite insome sanitizing processes, because several
disadvantages limit the use of chlorine, including
its unpleasant odor. Chlorine dioxide is notcorrosive 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 packinghousesurfaces (Roberts and Reymond 1994). Peracetic
acid is another material that could be used (Mariet al. 1999). It has greater stability and fasterbiocidal properties than chlorine dioxide but ismore corrosive.
The search goes on for effective and economical
sanitizing agents. New and old products alike arecontinually being evaluated under present-day
packing operations. Interest in ozone has been
rekindled with development of more efficientozone 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 inpreventing 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 beselected only after proper consideration of thefollowing 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 andpossible toxic effects, the most notable being
products that contain benomyl. Other products are
no longer as effective because of development ofresistance by the target pathogen. For example,
intensive and continuous use of fungicides forcontrol of blue and green mold on citrus has led
to resistance by the causal pathogens of these
diseases (Eckert 1988). Resistance has beenreported in many other crops to several different
fungicides with different modes of action (Delp
1988). Resistance development continues tobe a major problem and has resulted in theFungicide Resistance Action Committee (FRAC),
a cooperative effort among various producers offungicides to delay resistance by recommending
specific management guidelines (FRAC 1998).
Examples of chemicals currently used forpostharvest treatments are thiabendazole,
dichloran, and imazalil. However, resistanceto 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 docontrol decay and, in some cases, are the onlymeans of control. These products include sodium
benzoate, the parabens, sorbic acid, propionicacid, SO2, acetic acid, nitrites and nitrates, andantibiotics such as nisin (Chichester and Tanner1972). In California, for example, gray mold ofstored table grapes is prevented by fumigation
113

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 registrationin 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 PacificNorthwest is not controlled by any registeredfungicide (Spotts and Dobson 1989). There is adire need for new fungicide treatments that couldin part be alleviated by using biological control
agents (Wisniewski and Wilson 1992, Utkhedeand Sholberg 1993).
Biological Control
Postharvest biological control is an approachthat offers several advantages over conventional
biological control (Wilson and Pusey 1985, Pusey
1996), such as the following:• Exact environmental conditions can beestablished and maintained.
• The biocontrol agent can be targeted much
more efficiently• Expensive control procedures are costeffective on harvested food.
Several biological control agents have beendeveloped, and a few have actually beenregistered 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 brownrot, but when a commercial formulation of thebacterium 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 moldof pome fruit (Janisiewicz and Marchi 1992).
It was subsequently registered and is now soldcommercially for postharvest disease control(Janisiewicz and Jeffers 1997).

114

Other bacterial microorganisms have beendeveloped for postharvest disease control.
For example, strains of Bacillus pumilus andPseudomonas fluorescens have been identified thatexhibit successful control of B. cinerea in fieldtrials 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 forcontrol 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 sakesuccessfully control brown rot and blue mold on
sweet cherry (Spotts et al. 1998) and on threediseases 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 ifthey are to provide acceptable disease control.
Irradiation for Postharvest Decay Control
Though ultraviolet light has a lethal effect onbacteria and fungi that are exposed to the directrays, 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 rotof peaches (Stevens et al. 1998). In this case, thelow-dose ultraviolet light treatments had two
effects on brown rot development: reduction in the
inoculum of the pathogen and induced resistancein the host. However, it has not become a practicalpostharvest 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cases, 3.0 kGy (300 krad) have been effective incontrolling decay in several products (Hardenburg
et al. 1986). A dose of 250 grays (Gy) has anadverse effect on grapefruits, increasing skinpitting, scald, and decay. Low doses of 150 Gy
for fruit flies and 250 Gy for codling moth areacceptable quarantine procedures (Meheriukand Gaunce 1994). Commercial applicationof gamma radiation is limited by the cost andsize of equipment needed for treatment and byuncertainty 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 ofmethyl 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 growthminimum of -6 to 0 ºC (21 to 32 °F). Fungi witha 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 theysignificantly 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 hotwater. 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 byexposure 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 andimproves coverage by fungicides (Couey 1989).
The primary obstacle to the widespread use ofheat to control postharvest fruit diseases or insect
infestation is the sensitivity of many fruit to thetemperatures required for effective treatment.
Both low and high RH have been related topostharvest decay control. Perforated polyethylenebags 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 withwell-developed cuticle and epidermis, such asapples and pears, tolerate lower RH levels, whichhelps prevent storage decay. Often fungal spore
germination is inhibited at low RH, and small
differences in RH can have significant effects inrelation 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 possibilityof adjusting gas composition during storage
or transportation (Sommer 1989). Because thepathogen 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 respirationand growth are reduced by the high CO2 of themodified atmosphere. For example, CO2 added toair has been widely used in the transport of ‘Bing’cherries, primarily to suppress gray mold andbrown rot. Low O2 does not appreciably suppress
fungal growth until the concentration falls below
1152%. Important growth reductions result if O2 islowered to 1% or less, though there is a danger
that the crop will start respiring anaerobically anddevelop off flavors. Other technologies that havebeen tested for lowering postharvest decay withlimited 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 areloosely classified according to their signs andsymptoms. Signs are visible growths of the causal
agents, and symptoms the discernible responses
produced by the host. In many diseases there islocal discoloration and disruption of tissue, withthe formation of obvious lesions. Postharvest
diseases are caused primarily by microscopic
bacteria and fungi, with fungi the most importantcausal agent in fruit crops.
Fungi are further subdivided into classes andare described as “lower fungi” (characterized
by the production of sporangia giving rise tonumerous sporangiospores) or “higher fungi”(described as ascomycetes, deuteromycetes, andbasidiomycetes.) Ascomycetes are exemplified
by fruiting bodies that release sexual spores whenmature. Deuteromycetes, a form of ascomycete,
only release asexual spores. They are morecommon than the sexual ascomycete stage inpostharvest 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 thehost. These fungi and the rust and smut fungi are
examples of basidiomycetes. Table 1 lists many
important diseases of fruit crops according to hostand causal agents.

116

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 microscopeas mostly single-celled rods. Bacteria are capableof very rapid multiplication under the rightconditions 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 plantparts, and the common definition is a culinary
one, denoting consumption as a savory rather
than as a dessert food (Snowdon 1992). Manyvegetables are fruits in the botanical sense, notable
examples being tomatoes, peppers, squashes, andcucumbers. Table 2 lists many of the importantdiseases of vegetable crops according to host andcausal agents.

Table 1. Important postharvest diseases of fruit______________________________________________________________________________________
Fruit
DiseaseCausal agent
Fungal class/type______________________________________________________________________________________
Avocado

Anthracnose
Cercospora spot
Dothiorella rot
Scab
Stem-end rots				

Glomerella cingulata
Pyrenomycete
Pseudocercospora purpurea Hyphomycete
Botryosphaeria ribis
Loculoascomycete
Sphaceloma persae
Coleomycete
B. theobromae,
Deuteromycetes
Phomopsis perseae,
Thyronectria pseudotrichia

BananaAnthracnose
Cigar-end rot		Crown rot				
Finger rot
Pitting disease
Sigatoka disease

Colletotrichum musae
Trachysphaera fructigena,
Verticillium theobromae
C. musae,
Fusarium pallidoroseum,V. theobromae
B. theobromae
Pyricularia grisea
Mycosphaerella spp.

Coelomycete
Hyphomycete
Loculoascomycete

Berries

Botrytis cinerea
Mucor spp.
Phytophthora spp.

Hyphomycete
Zygomycete
Oomycete

Alternaria rot
Anthracnose
Bacterial canker
Black pit
Black spot
Blue mold
Brown rot
Greasy spot
Green mold
ScabSour rot
Stem-end rots				

Alternaria spp.
C. gloeosporioides
Xanthomonas campestris
Pseudomonas syringae
Phyllosticta citricarpa
Penicillium italicum
Phytophthora spp.
Mycosphaerella citri
P. digitatum
Elsinoe fawcettii
Geotrichum candidum
D. gregaria,
Phomopsis citri,
B. theobromae

Hyphomycete
Coelomycete
Bacterium
Bacterium
Coelomycete
Hyphomycete
Oomycete
Loculoascomycete
Hyphomycete
Loculoascomycete
Hyphomycete
Coelomycete

Kiwifruit

Gray moldB. cinerea

Hyphomycete

Grape

Aspergillus rot
Blue moldGray moldRhizopus rot

Aspergillus niger
Penicillium spp.
B. cinerea
Rhizopus spp.

Hyphomycete
Hyphomycete
Hyphomycete
Zygomycete

Gray mold
Leak
Leather rot

CitrusCoelomycete
Deuteromycetes
Deuteromycetes

117Table 1. Important postharvest diseases of fruit—Continued______________________________________________________________________________________
Fruit
DiseaseCausal agent
Fungal class/type______________________________________________________________________________________
Mango
Anthracnose
C. gloeosporioides
Coelomycete
Botryodiplodia rot
B. theobromae
Coelomycete
Stem-end rots
B. theobromae,
Coelomycete		Phomopsis spp.
PapayaAnthracnoseBlack rot
Phytophthora rot
Rhizopus rot
Stem-end rot
		C. gloeosporioides
Phoma caricae-papayae
P. palmivora
R. stolonifer
B. theobromae,
Phomopsis spp.

Coelomycete
Coelomycete
Oomycete
Zygomycete
Coelomycete

Pineapple

Black rot
Fruitlet core rot		Thielaviopsis paradoxa
Fusarium moniliforme,
P. funiculosum

Hyphomycete
Hyphomycete

Pome fruit(apple, pear)

C. gloeosporioides
Sphaeropsis malorum
Penicillium expansum,
Penicillium spp.
Monilinia spp.
Cryptosporiopsis curvispora
B. cinerea
Alternaria spp., others
Mucor piriformis
D. gregaria

Coelomycete
Coelomycete
Hyphomycete

Bitter rot
Black rot
Blue mold		
Brown rot
Bull’s-eye rot
Gray mold
Moldy core
Mucor rot
White rot
Stone fruit(cherry, etc.)

Hyphomycete
Hyphomycete
Hyphomycete
Hyphomycete
Zygomycete
Coelomycete

Alternaria rot
A. alternata
Hyphomycete
Blue moldP. expansum
Hyphomycete
Brown rot
Monilinia spp.
Hyphomycete
Rhizopus rot
Rhizopus spp.
Zygomycete____________________________________________________________________________________

118

Table 2. Important postharvest diseases of vegetables__________________________________________________________________________________
Vegetable
DiseaseCausal 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
SmudgeColletotrichum circinans Coelomycete
Crucifers(cabbage, etc.)

Alternaria leaf spot
Bacterial soft rot
Black rot
Downy mildew
Rhizoctonia rot
Ring spot
Virus diseases
		Watery soft rot
White blister

Alternaria spp.
Hyphomycete
E. caratovora
Bacterium
Xanthomonas campestris Bacterium
Peronospora parasitica
Oomycete
Rhizoctonia solani
Agonomycete
Mycosphaerella brassicicola
Loculoascomycete
Cauliflower mosaic virus, Virus
turnip mosaic virus
Sclerotinia spp.
Discomycete
Albugo candida
Oomycete

Cucurbits(cucumber, etc.)

Colletotrichum spp.
Coelomycete
Erwinia spp.
Bacterium
Didymella bryoniae
Loculoascomycete
Botryodiplodia theobromae Coelomycete
Macrophomina phaseolina Coelomycete
Fusarium spp.
Hyphomycete
Pythium spp.
Oomycete
Rhizopus spp.
Zygomycete
Sclerotium rolfsii
Agonomycete
R. solani
Agonomycete

Legumes(peas, beans)

Anthracnose
Bacterial soft rot
Black rot
Botryodiplodia rot
Charcoal rot
Fusarium rot
Leak
Rhizopus rot
Sclerotium rot
Soil rot

Alternaria blight
A. alternata
AnthracnoseColletotrichum spp.
Ascochyta pod spot
Ascochyta spp.
Bacterial blight
Pseudomonas spp.,
		 Xanthomonas spp.
Chocolate spot
B. cinerea
Cottony leakPythium spp.,		
Mycosphaerella blight,		
M. pinodes
Rust
Uromyces spp.
Sclerotium rot
S. rolfsii
Soil rot
R. solaniWhite mold
Sclerotinia spp.

Hyphomycete
Coelomycete
Coelomycete
Bacteria
Hyphomycete
Oomycete
Loculoascomycete
Hemibasidiomycete
Agonomycete
Agonomycete
Discomycete

119Table 2. Important postharvest diseases of vegetables—Continued__________________________________________________________________________________
Vegetable
DiseaseCausal Agent
Fungal Class/Type__________________________________________________________________________________
Roots/tubers
Carrots
Bacterial soft rot
		Black rot
Cavity spot
Chalaropsis rot
Crater rot
Gray mold rot
Sclerotium rot
Watery soft rot

Erwinia spp.,
Pseudomonas spp.
A. radicina
Disease complex
Chalara spp.
R. carotae
B. cinerea
S. rolfsii
Sclerotinia spp.

Bacteria
Hyphomycete
Soil fungi
Hyphomycete
Agonomycete
Hyphomycete
Agonomycete
Discomycete

Potatoes

Bacterial soft rot
BlightCharcoal rot
Common scab
Fusarium rot
Gangrene
Ring rot
Sclerotium rot
Silver scurf
Watery wound rot

Erwinia spp.
Phytophthora infestans
S. bataticola
Streptomyces scabies
Fusarium spp.
Phoma exigua
Clavibacter michiganensis
S. rolfsii
Helminthosporium solani
Pythium spp.

Bacteria
Oomycete
Agonomycete
Actinomycete
Hyphomycete
Coelomycete
Bacterium
Agonomycete
Hyphomycete
Oomycete

Sweet potatoes

Black rot
Fusarium rot
Rhizopus rot
Soil rot
Scurf

Ceratocystis fimbriata
Fusarium spp.
Rhizopus spp.
Streptomyces ipomoeae
Monilochaetes infuscans

Pyrenomycete
Hyphomycete
Zygomycete
Actinomycete
Hyphomycete

Alternaria rot
Anthracnose
Bacterial canker
Bacterial speck
Bacterial spot
Fusarium rot
Gray mold rot
Late blight
Phoma rot
Phomopsis rot
Phytophthora rot
Pleospora rot
Rhizopus rot

A. alternata
Colletotrichum spp.
C. michiganensis
Pseudomonas syringae
X. campestris
Fusarium spp.
B. cinerea
P. infestans
Phoma lycopersici
Phomopsis spp.
Phytophthora spp.
Stemphylium herbarum
Rhizopus spp.

Hyphomycete
Coelomycete
Bacterium
Bacterium
Bacterium
Hyphomycete
Hyphomycete
Oomycete
Hyphomycete
Coelomycete
Oomycete
Hyphomycete
Zygomycetes

Solanaceous plants(tomato, pepper,
eggplant)

120

Table 2. Important postharvest diseases of vegetables—Continued__________________________________________________________________________________
Vegetable
DiseaseCausal 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
Watery soft rot

Botrytis cinerea
Sclerotinia sclerotiorum

Hyphomycete
Discomycete

Asparagus
Bacterial soft rot
		Fusarium rot
Phytophthora rot
Purple spot

Erwinia or Pseudomonas
spp.
Fusarium spp.
Phytophthora spp.
Stemphylium spp.

Bacteria

CeleryBacterial soft rot
		
Brown spot
Cercospora spot
Gray mold
Licorice rot
Phoma rot
Pink rot
Septoria spot

Erwinia or Pseudomonas
spp.
Cephalosporium apii
Cercospora apii
Botrytis cinerea
Mycocentrospora acerina
Phoma apiicola
Sclerotinia spp.
Septoria apiicola

Hyphomycete
Oomycete
Hyphomycete
Bacteria
Hyphomycete
Hyphomycete
Hyphomycete
Hyphomycete
Coelomycete
Discomycete
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__________________________________________________________________________________

121

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 moreenvironmentally friendly crop control materials
require a new approach to disease control.
Integrated postharvest decay control is the conceptthat 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 toreduce 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 byfecal 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 theanaerobic bacterium Clostridium botulinum.
Interest in toxins produced by fungi wasstimulated by the death of 100,000 turkey poultsin England in 1960. Aflatoxins produced by fungiin 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 andAspergillis spp. can be found in apple and pear
products. Patulin is toxic to many biologicalsystems but its role in causing animal and humandisease is unclear (Hsieh and Gruenwedel 1990).
Studies on contamination of horticultural productsby fecal coliforms has increased dramaticallybecause of documented incidences of foodpoisoning from apple juice and seed sprouts.
Definite interactions have been shown between
122

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 twicethat of healthy samples (Wells and Butterfield1997). Controlled experiments with potato,
carrot, and pepper tissues inoculated with a strainof Salmonella confirmed that bacterial soft rot
infection increased multiplication of Salmonellaby at least three- to ten-fold compared withmultiplication on uninfected tissues. Similarly,
populations of Listeria monocytogenes, inoculated
into decayed apple tissue, continually increasedon 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 frompH 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 addressedalong 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 andavoid overhead irrigation.
• Apply preharvest treatments to control
insects and diseases.
• Harvest crop at the correct maturity forstorage.
• Apply postharvest treatments to disinfest andcontrol diseases and disorders on produce.

• 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 biologicaltreatments with yeast biocontrols has beenstudied on pears (Sugar et al. 1994). It was foundthat 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 biologicalmethods 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 oC (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 thebiocontrol 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 benecessary to combine several alternative methods
to develop an integrated strategy to successfully
reduce postharvest decay.

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127

FlavorElizabeth A. Baldwin
Baldwin was with the Citrus and Subtropical
Products Laboratory, Agricultural ResearchService, U.S. Department of Agriculture, WinterHaven, FL. She is now with the U.S. Horticultural
Research Laboratory, Agricultural ResearchService, U.S. Department of Agriculture, Fort
Pierce, FL.

Introduction
The quality of fresh produce has traditionallybeen based on external characteristics of size,
color, and absence of surface defects. Fruit andvegetable 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 quantifiedtraits. Public and industry organizations are
increasingly concerned with the public’s growing
dissatisfaction over the flavor and texture of somehorticultural 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 tosugars, acids, and volatiles. Other componentsof flavor include bitterness related, for example,
to sesquiterpene lactones in chicory (Peters andAmerongen 1998), saltiness due to various naturalsalts, and astringency related to flavonoids,
alkaloids (DeRovira 1997), tannins (Taylor
1993), and other factors. The perception ofsweetness—that is, sugars—one of the mostimportant components of fruit or vegetableflavor, is modified by sourness or acid levels andaroma compounds. The contribution of aroma
to the flavor quality of fresh produce has gained
increasing attention.

128

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 (Wrightand Harris 1985), harvest maturity (Fellman etal. 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 andbananas 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 qualityof nonclimacteric fruit generally declines after
harvest, while climacteric fruit can reach theirbest flavor after harvest. Climacteric fruit develop
better quality if harvested after the start ofripening, 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 nonvolatilecompounds (in concentration of parts per hundred)by several types of receptors in the tongue forsugars 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 canbe detected in parts-per-billion concentrations andare detected by olfactory nerve endings in the nose
(DeRovira 1997). The brain processes informationfrom these senses to give an integrated flavor
experience. This integration makes it difficult todetermine the relative importance of each input
since the brain can interpret changes in aroma aschanges in taste (O’Mahony 1995) or vice versa.
For example, the levels of aroma compounds
influenced panelist perception of sweetness andsourness for tomatoes (Lycopersicon esculentum
Mill.) (Baldwin et al. 1998). Conversely, levels oftaste components influenced panelist perception ofaromatic descriptors in mango (Mangifera indica
L.) (Malundo et al. 2000a). The perception ofcertain combinations of chemicals is synergistic,
while others combinations mute our perception
in a process called masking. In contrast to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, backgroundnotes—high molecular weight, nonpolar,hydrophobic compounds (DeRovira 1997).

Sensory Evaluation
Human perception of flavor can be determinedby sensory evaluation by taste panels.
Consumer preference and acceptance vary due
to socioeconomic, ethnic, and geographicalbackground, often necessitating the segmenting of
subpopulations for a particular study (O’Mahony
1995). Generally a large number of panelists (forexample, 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 frommedical 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 decisionon 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 measuresintensities of a set of sensory attributes and isconsidered a broadband approach (O’Mahony
1995). Panelists are trained to detect a rangeof 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 ofdisinfestation 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 andvegetables. Fructose is the sweetest, and glucose
is less sweet than sucrose. A single “sucrose
equivalent” value is the weighted average of thesevarious sugars in a sample (Koehler and Kays
1991). Sugar content is commonly accepted to besynonymous with SSC (soluble solids content),
and an inexpensive refractometer can easily
measure SSC. However, the quantification ofindividual 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 tosweetness; while in others, such as tomato andmango, the relationship is not linear (Baldwin etal. 1998, 1999a, Malundo et al. 2000a).
Organic acids, such as citrate in citrus andtomatoes, tartaric acid in grapes (Vitis sp.), andmalic acid in apples (Malus pumila), give fruitand vegetables their sour flavor. Some fruits, likemelon (Cucumis melo) or banana (Musa sp.), havevery little acid (Wyllie et al. 1995). Different acids
can affect sourness perception, depending on theirchemical structure. An increase in carboxyl groups
decreased acidity, while an increase in molecularweight or hydrophobicity increased sourness(Hartwig and McDaniel 1995). For example,
acetic acid was perceived as more intensely sourthan lactic or citric acid.
Acids can be measured individually by HPLC
(Baldwin et al. 1991a,b), by titration (TA) withsodium hydroxide (Jones and Scott 1984), or by
pH (Baldwin et al. 1998). Sometimes SSC, theratio of SSC/TA, or pH relate better to sourness
than TA itself (Baldwin et al. 1998, Malundo et al.
2000a).

129

Aroma Components
Volatiles that we can perceive contribute to foodflavor. The level at which a compound can bedetected by smell (the odor threshold) can beestablished in a background similar to a foodmedium as described by the Ascending Methodof Limits of the American Society for Testingand Materials (ASTM 1991). Log odor units arecalculated from the ratio of the concentrationof a component in a food to its odor threshold.
Compounds with positive odor units contributeto food flavor. Buttery (1993), for example,

determined concentrations, odor thresholds, andlog 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, boththe thresholds and descriptors of some volatilecompounds 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_____________________________________________________________________________________
Hexanalgrassy/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/paintsweet/floral
Cis-3-hexenal
grass/tomato-like
alcohol/painttomato/citrus
2-isobutylthiazole
fermented/plastic
alcohol/tomato-likepungent/bitter
2-pentenalvine/organic solventacetone/medicine
stale/oil
Acetoneglue/alcohol
alcohol/nutty/spoilt
green
β-iononesweet/perfume-likesweet
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
alcoholalcohol/nutty
3-methylbutanal
bug spray/alcohol
fruity/green/leafy
stale/rotten
1-penten-3-one
glue/oil/pungent
nutty/glue/alcohol
fresh/sweet
Ethanolearthy/stale
pungent/rancid—
Methanolearthy/stale——_____________________________________________________________________________________
Source: Tandon et al. 2000

130

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 becleaved 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 andKint 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 bygas 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 andidentification of aroma compounds (Schamp andDirinck 1982, Teranishi and Kint 1993).
Static headspace methods are said to moreclosely 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 areconcentrated without heating that may cause
adulteration. This method has been used forquantification of orange juice volatiles (Moshonas
and Shaw 1997). The newest method is solidphase micro-extraction (SPME), a rapid samplingtechnique 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 beenused on apples, tomatoes (Song et al. 1997), andstrawberries (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 orflavor component(s) to be detected by patternrecognition. However, these instruments do notgive information that leads to identification andquantification 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 (bulkacoustic 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, anddecisions can be statistically related to chemicalcomponents in foods (Martens et al. 1994). Some
important or abundant flavor compounds inselected fruits and vegetables are shown in table
2. Correlation of physical measurements withsensory analysis gives meaning to instrumental
data, as was shown with apple and tomato(Baldwin et al. 1998). For example, linear
regression established relationships between levelsof 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), andtomato (Maul et al. 1998). Differences between
131

samples were found based on measurement ofvolatiles or other flavor compounds.
Alternatively, sniff ports (olfactometry detectors)
can be used with GCs, allowing a person todetermine if odors are detectable as well as theirrelative intensity as the volatile components are
separated by the GC column. This technique wasused on apples (Cunningham et al. 1985, Younget al. 1996). Descriptive terms can be assigned to
the respective peaks on the GC chromatogram thathave odor activity (Acree 1993). The drawback
to this method is that the interactive effects ofvolatile compounds with each other and withsugars and acids, both chemically and in terms ofhuman perception, are eliminated.

Factors That Can Affect Flavor of Fruits
and Vegetables

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 fruitwith 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 withdownregulated phytoene synthase (phytoene is aprecursor of carotenoids) had lowered levels ofcarotenoid-derived volatiles (Baldwin et al. 2000).
Effect of Preharvest Factors

Effect of Genetics on Flavor
Fruit and vegetable varieties differ in flavor basedon 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 showedthat apple aroma was not the result of the same
compounds in every cultivar, although somecommon volatile compounds were important in all
cultivars.
Important aroma-specific compounds forstrawberry included ethyl butanoate, methyl
butanoate, γ-decalactone, and 2-heptanone(Larsen et al. 1992). Strawberry cultivars differed
in flavor intensity and sweetness, according toa trained sensory panel (Podoski et al. 1997).
Concentrations of several important compounds,
including α- and ß-ionones, were higher in wildcompared 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) and132

Preharvest factors such as sunlight, water
availability, fertilization, and chemical
applications affect crop growth and can affectinternal quality characteristics of the harvested
product, including flavor. Preharvest treatment
with aminoethoxyvinylglycine (AVG) suppressed
volatile production in pears by 50%, which wasreversed 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 andshowed 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 notreatments, 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 dictatethat they are harvested at a stage that minimizes
physical damage during shipping and handlingand maximizes shelf-life. The climacteric stage at
harvest affected ester formation in apples (Fellman

et al. 1993). Harvest maturity affected both thesensory and chemical analysis of ripened tomato
fruit (Maul et al. 1998). Tomatoes harvested at
the immature green stage resulted in ripened fruitwith lower volatile levels than mature-greenharvested tomatoes. Harvest maturity also affectedconsumer 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).

apples (Fellman et al. 1993). However, whenatmospheres 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 expenseof others. Sensory analysis of CA-stored apples
revealed that intensity of fruity and floral
descriptors decreased after 10 weeks in CA, whilesourness 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).

Effect of Postharvest Handling
Various techniques are used to extend the shelflife of fruits and vegetables after harvest, tocontrol 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 importantvolatiles 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). Subjectionof fruit to heat treatments for preconditioning anddecay control (McDonald et al. 1996) resulted inaltered aroma volatile profiles. Heat treatment ofapples to reduce physiological and pathologicaldisorders 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 orsweetness between stored and freshly harvested
melons (Cohen and Hicks 1986).
CA storage altered flavor of apples, and, if
prolonged, reduced volatile emission comparedto 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

Use of packaging and edible coatings can createa modified atmosphere (MA) with reduced O2
and elevated CO2 levels, similar to that of CA.
Lowering O2 and raising CO2 can maintain thequality of many fresh fruits and vegetables forextended periods. However, exposure of fresh
produce to O2 levels below their tolerance level
can increase anaerobic respiration and lead to thedevelopment 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 ofethanol and acetaldehyde and entrapped volatiles,
including ethanol and acetaldehyde (Baldwin etal. 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 anotherstudy in which strawberry fruit stored in a CO2saturated 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 anumber of volatiles through a pathway in which
PAL is the key enzyme.

133In addition to CA, other gaseous treatments offruits and vegetables have been reported. Useof ethylene to synchronize ripening has beenpracticed 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 andproduction 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 inalcohols and a decrease in related esters (Golding
et al. 1999). Application of acetaldehyde andethanol vapors to blueberries, tomatoes, and pears
increased their sugar content, sugar-acid ratio, andhedonic sensory rating (Paz et al. 1981).

fruit ripen (Brady 1993). Aroma of peaches andnectarines is distinguished by the presence ofγ- 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 peachodor. It has been named “peach aldehyde” and isused in peach flavor formulations (Crouzet et al.
1990). Ethyl hexanoate and 3-methylbutanoate,
linalool, α-terpineol, 6-pentyl-α-pyrone (coconutodor), and benzyl alcohol are also considered
important (Crouzet et al. 1990).

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).

Strawberry. In most berry fruits sucrose, glucose,and fructose are present in roughly equivalentconcentrations (Manning 1993), and citrate is
the major organic acid. More than 200 volatilecompounds have been identified in strawberry.
C-6 aldehydes such as hexanal and trans-2hexenal are found, as well as lipoxygenase andhydroperoxide 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 isthen 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 inboth strawberry and tomato and are considered tobe glycosidically bound in both fruits (Roscher etal. 1997). Of more than 100 volatile compounds
identified from strawberry, furaneol, ethyl
hexanoate, and ethyl butanoate are considered tobe 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).

Flavor of Some Popular Fruits andVegetables
Apple. Sucrose is the major sugar in apples,though it is slowly hydrolyzed to glucose andfructose during latter ripening stages. The majororganic acid is malate, although some citrateis also present (Knee 1993). Eleven aroma
compounds contribute to apple aroma in mostof the 40 cultivars, while 27 other compounds
contributing to flavor where found only in certain
genetic types (Cunningham et al. 1985). Loss ofapple flavor after long-term CA storage is a major
problem, probably due to the reduction of volatilesynthesis during storage (Mattheis et al.1995).
Peach (Prunus persica). The main sugar inpeaches is sucrose, but cultivars differ greatly
in glucose:fructose:sorbitol ratios, which may
contribute to differences in flavor. The majororganic acids are malate and citrate, with malatelevels declining and citrate levels increasing as
134

Small Fruits

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 volatilecompounds 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, andlinalool among others (Paterson et al. 1993). The“raspberry ketone,” or character-impact volatilefor raspberry, is 4-(4-hydroxyphenyl)-butan-2one (Larsen and Poll 1990). It had the lowest
threshold (therefore the largest contribution toflavor), followed by α-ionone, β-ionone, geraniol,
linalool, and benzyl alcohol. Furaneol, linalool,and ethyl hexanoate were important generalaroma 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, andcis-3-hexenal (Roberts and Acree 1996).
Blackberry (Rubus laciniata). Freshblackberry fruit contain 245 aroma compounds(Georgilopoulos and Gallois 1987). The mostabundant 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, suchas benzyl alcohol, benzoic acid, 3-hydroxy-7,8dihydro-β-ionol, and cis-3-hexenol among others(Humpf and Schreier 1991).
Blueberry (Vaccinium). Blueberries haveglucose and fructose as their major soluble sugars
and citric, malic, and quinic acids (Eck 1986).
The odor-impact compounds for high-bushblueberry (Vaccinium myrtillus) are trans-2hexenal, trans-2-hexenol, and linalool, but also

include geraniol, citronellol, hydroxycitronellol,
farnesol, and farnesyl acetate. Most volatiles arepresent 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 thepredominant sugars in grapes, while tartaric andmalic acids account for 90% of the TA (Kanellisand 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 McCarthy1997). This process is different from that of otherberries and has been termed “engusting.” Thevolatiles in wine grapes are the most complex
and are classified into five groups, of which thefirst 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 accumulationof 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, Kanellisand 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 toaroma. 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 important135

for muscadine (V. rotundifolia) aroma ( Flora andNakayama 1981). The V. vinifera grapes exhibita mild aroma that is more desirable for wine
production (Shure and Acree 1995).
Banana (Musa). Sucrose is the predominantsugar 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 bananasarises 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 frombanana pulp by ß-glucosidase, including decan1-ol, 2-phenylethanol, 3-oxy-pentanoic acid,
3-methylbutanoic acid, and benzoic acid (Perezet al. 1997). Esters account for about 70% of thevolatile 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 and3-methylbutanoate (Engel et al. 1990). Unusual
phenol derivatives eugenol, 5-methoxyeugenol,
eugenol-methylether, and elemicin contributebackground notes for the full-bodied mellow
aroma of ripe bananas (Engle et al. 1990).
Citrus Fruits
Sweet Orange (Citrus sinensis). The major sugarin most citrus types is sucrose, with varying levelsof glucose and fructose. The major acid is citrate.
Typical orange aroma is attributed to alcohols,
aldehydes, esters, hydrocarbons, ketones, andother components, of which more than 200 havebeen 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).

136

Tangerine (Citrus reticulata). Analysis oftangerine 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 mostpotent flavor component (Shaw and Wilson 1980).
Grapefruit (Citrus paradisi). At least 126
volatile components have been identified ingrapefruit (Demole et al. 1982). Nootkatone and1-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 ofvolatile compounds present (more than 150
compounds identified), often depending on area of
production. Asian mangoes have more oxygenatedvolatile 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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 levelsof 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 ofmuskmelon 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 reminiscentof 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).

aroma of a fresh ripe tomato. Of these, cis-3hexenal 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 (hydroperoxycleavage), and alcohol dehydrogenase (Galliard etal. 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 etal. 1994). Furaneol is also reported to be important(seems it is found in every fruit). Geneticallyengineered fruit with down- or up-regulated
alcohol dehydrogenase expression exhibited
altered levels of some related volatiles (Speirs etal. 1998).

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 isno 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 the137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

138

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														

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____________________________________________________________________________________________
Muscat varieties								linalool				(V. vinifera)								geraniol										methoxyisobutylpyrazine
BananaBerger 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-pinene140

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 acetate141

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
TomatoBaldwin et al. 1991a,b
glucosecitrichexanalButtery 1993
fructosemalictrans-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____________________________________________________________________________________________

142

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 andvegetable products will be an important factor in
an increasingly competitive global market. Flavor
maintenance becomes a challenge as shelf-lifeand marketing distances increase due to new
storage, handling, and transport technologies.
However, despite these issues the bottom line forflavor quality is still genetic. Breeders need more
information and analytical tools in order to selectfor flavor quality. Use of wild material may benecessary in breeding programs to regain flavor
characteristics that have been lost from somecommodities. Use of molecular markers that relate
to flavor may help identify important enzymes inflavor pathways. The effect of harvest maturity
on flavor quality needs to be determined for eachcommodity. 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 behalfof flavor quality in fresh produce.
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Food Safety

human consumption.

James R. Gorny and Devon Zagory

Systems that ensure safety and wholesomeness offruits and vegetables during postharvest handlingand 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).

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% wereassociated with fruits and vegetables, and mostof those were due to improper home canning.
In general, produce is a low-risk food, and it isunlikely 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 theperception of acceptable risk, and if no risk is
acceptable, then nothing can ever truly be safe.
Many consumers feel that food products shouldhave no risk associated with their consumption.
Unfortunately, the reality is that reducing therisk of foodborne illness from consumption of
fresh fruits and vegetables to absolute zero is an
impossible task. It should also be kept in mind thatthe 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 cancompletely eliminate food safety risks associatedwith consumption of uncooked produce.
Therefore, preventing contamination with humanpathogens, dangerous levels of chemical residues,or physical contaminants is the only way to ensurethat these foods are wholesome and safe for

The greatest risk to human health fromconsumption 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 preventthe growth of pathogens, should they be present.
Nonpathogenic bacteria also act as indicatorsof temperature abuse and age by spoiling the
product. In the absence of spoilage, high levelsof pathogens may occur, and the item may beconsumed 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 andCyclospora)• Pathogenic viruses (hepatitis, norwalk virus,
and others)
Many of these pathogens are spread from humans
or domestic animals to food to humans. Fruits andvegetables may become contaminated by infected
field workers, food preparers, consumers, crosscontamination, use of contaminated irrigationwater, use of inadequately composted manure, or
contact with contaminated soil. To minimize risks,
growers should implement practices outlinedin the “Guide to Minimize Microbial Food
Safety Hazards for Fresh Fruits and Vegetables”
published by the Center for Food Safety and149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 beaware that agricultural practices that may havebeen 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 tominimize true food safety risks and ensure foodsafety. Microbial testing cannot guarantee theabsence of pathogens on fresh produce and, infact, is unlikely to detect pathogens even when
they are present. For example, if 5 fruit in agiven lot of 100 individual fruit are harboring
pathogens (5% contamination rate), how many
fruit would have to be sampled to be 95% surethat one of the infected fruit was found? Table 1
shows that at 5% contamination rates, it would benecessary to test 60 fruit to have a 95% chance offinding the pathogen. It is surely not practical totest 60 out of every 100 fruits or vegetables. Yet
testing fewer fruits results in a high likelihoodthat pathogens will be missed, even when they
are present. For this reason, negative results fromproduct pathogen testing have little value andcan be misleading. Microbial testing can be aneffective 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, andfood contact surfaces—and monitoring employee
hygiene practices are more effective in preventing
spread of human pathogens.

150

Table 1. Probability that a given numberof samples will fail to detect microbial
contaminants at specified contaminationlevels_____________________________________
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 ofoutbreaks. In recent years, fresh produce sourcing
has undergone significant changes, and centralized
local production has been replaced withworldwide sourcing. Agricultural practices andhygienic conditions vary greatly among growing
regions around the world, and increased global
sourcing increases consumers exposure to diverse
endemic microflora carried on fresh fruits andvegetables. Also, global sourcing means longer
transportation and handling, giving pathogenic
microorganisms additional time to proliferate andreach levels which can cause illness. Population
demographics in North America have shifted, witha greater number of individuals that are older or
who have compromised immune systems. They
are at greater risk from foodborne illness, and theconsequences of exposure can be deadly. All ofthese circumstances have resulted in increased
foodborne illness awareness.

Reported Food Borne Illness Outbreaks In the UnitedStates Due to Fruits and Vegetables

No. Of Outbreaks

30
25
20
15
10
5
0
74

76

78

80

82

84

86

88

90

92

94

96

98

Two Year Interval

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 notguarantee 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).
5

S. montevideo
Log CFU/cm 2

4
3
2
1
0

0

60

110
210
Chlorine (ppm)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, canbecome a source of microbiological contaminationfor every piece of product that passes throughthat water. It is a widespread misconceptionthat 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 microbiologicalcount in the water. In this way the water does not
become a reservoir for mold spores and bacteria toinfest produce.
Sodium or calcium hypochlorite is mostcommonly 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 temperatureof the water. Above pH 7.5, very little chlorine
occurs as active hypochlorous acid, but rather asinactive hypochlorite (OCl-). Therefore, the washwater pH should be kept between 6.0 and 7.5 toensure 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 replacingor filtering the water is important to maintaincleanliness.

320

Figure 2. The effect of wash-water chlorine concentration on
the fate of Salmonella montevideo on raw tomatoes. Adaptedfrom Zhuang et al. 1995.

151

% Chlorine present as HOCl
or OCl-Effect of pH on Chlorine Dissociation Products
100
80
60
40
20
0
0

1

2

3

4

5

6

7

8

9 10

pH

HOCl
OCl-

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 afood safety program. Understanding how different
sanitizers work and how they are measured andmonitored 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 toeliminate human pathogens from produce, similar
to current allowable practices in the meat andpoultry industry. To date this strategy has beenineffective for a number of reasons, including theexpense of irradiating produce, a lack of facilities
to treat produce, the damage susceptibility ofmany produce items to irradiation, and perceived

consumer resistance to the use of irradiation forfoods. Irradiation with a gamma source, such ascobalt 60, has been studied by many researchers.
In the 30 years preceding 1983, more than athousand published reports addressed irradiationof 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 (Brackett1987).
Killing microbes with irradiation occurs when theirradiated energy interacts with water in microbial
cells. Reactive chemicals are created that damage
the cells’ genetic material, or DNA. The ability ofirradiation 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, adosage 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 areeasily killed by irradiation. D-values for gamma
irradiation of 0.1 kGy are typical. Thus, a dosageof 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-valuesof 0.3 to 0.7 kGy are typical, depending on thebacterium. Thus, it would require 1.5 to 3.5 kGy
to achieve a 5-log reduction of bacteria. At thistime, the maximum allowable dosage for treating

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
OxidizerOzone
6.0 - 10.0
Somewhat sensitive
Oxidizer
Peroxyacetic acid
1.0 - 8.0
Somewhat sensitive
Oxidizer
UV light
Not affected
Somewhat sensitive
Disrupts DNA_______________________________________________________________________
152

fruits and vegetables is 1.0 kGy. The implicationis 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, andviruses (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 foodare 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 irradiatedfood can be recontaminated if mishandled.
Consequently, while irradiation may have a futurerole in fruit and vegetable sanitation, it will nevereffectively guarantee pathogen-free produce, norwill it ever be a substitute for proper sanitationand food safety preventative programs. Different
fruits and vegetables differ in the maximum
dose that they will tolerate without unacceptablesoftening or loss of other quality parameters.
However, the negative impacts of produce
irradiation such as accelerated softening andtechnical issues (for example, nonhomogenous
dosing) have hindered the commercialization ofthis technology.
However, it is unclear if irradiation will ever becapable of surface-sterilizing produce without
irreparably damaging produce beyond salability.
Irradiation dosages necessary to kill viruses andsome bacteria are well in excess of the levels
which induce damage to produce. Though
irradiation has specific uses in produce, suchas 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 forIndustry: 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 contaminationof their crops. This document gives guidanceon those prudent steps. A number of retailchains have begun to require independent thirdparty audits of producers based, in part, on thisdocument.
The guide identifies eight food safety principles
within the realm of growing, harvesting, andtransporting fresh produce and suggests the reader“use the general recommendations in the guideto develop the most appropriate good agriculturaland management practices for their operation.”
The application of the principles is aimed atpreventing contamination of produce with humanpathogens. 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 notincreasing 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 associatedwith produce, the major source ofcontamination is associated with human or
animal feces.
• Whenever water comes in contact with fresh
produce, its source and quality dictate thepotential for contamination.
• Practices using manure or municipal
153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 rolein minimizing the potential for microbial
contamination of fresh produce.
• All applicable local, State, and Federal laws
and regulations, or corresponding or similarlaws, 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 foodsafety program. There must be qualified
personnel and effective monitoring to ensurethat all elements of the program function
correctly and to help track produce backthrough 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 anddocumented to ensure that the production land was
not formerly used for hazardous waste disposal orfor 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 beenused 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 ofhuman pathogens. Human pathogens may persist
in animal manure for weeks or even months.
E. coli O157:H7 has been found to survive inuncomposted dairy manure incorporated into
154

soil for up to 250 days (Suslow 1999). Propercomposting via thermal treatment reduces therisk of potential foodborne illness. However, thepersistence of many human pathogens in untreatedagricultural soils is unknown. Use of inorganic
fertilizers, which have been certified to be free ofheavy metals and other chemical contaminants, isrecommended.
Irrigation Water. Irrigation water is anotherpotential vector by which contaminants may bebrought into contact with fruits and vegetables.
Deep-well water is less likely to be contaminatedwith human pathogens than surface watersupplies. 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 humanpathogens. 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 tothe 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 bedone in strict accordance with manufacturer’s
recommendations as well as Federal, State, andlocal ordinances. Monitoring and documentationof 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 ofapplication should be available and reviewed bymanagement 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 andvegetables by simply touching them with anunclean 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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 fieldcontainers. Field harvesting tools should be cleanand sanitary and should not be placed directlyin contact with soil. Field containers should becleaned and sanitized on a regular basis andshould be kept free of contaminants such as mud,industrial lubricants, metal fasteners, or splinters.
Plastic bins and containers are recommended asthey are easier to clean and sanitize than wooden
ones.
Sanitary Postharvest Handling of Produce.
Depending on the commodity, produce may befield-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 willbe transported to a packing shed. Employees,
equipment, cold storage facilities, packaging
materials, and any water that will contact theharvested produce must be kept clean and sanitary
to prevent contamination.
Employee Hygiene. Gloves, hairnets, and cleansmocks 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 andhandling must be managed to minimize the risk ofcontamination. Adequate bathroom facilities andhand-washing stations must be provided and usedproperly to prevent contamination of produce bypacking house employees. Shoe- or boot-cleaning
stations may also be in place to reduce the amountof field dirt and contamination that enters thepacking 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 andsanitized on a regularly scheduled basis withapproved cleaning compounds. A 200 ppm (200µL L-1) NaOCl solution (bleach) is an example ofa food-contact-surface sanitizer. Sanitizers should
be used only after thorough cleaning with abrasion
to remove organic material such as dirt or plantmaterials. 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 sanitizedon a regular basis. The human pathogen Listeria
monocytogenes can multiply at refrigerated
temperatures in moist conditions and may
contaminate produce if condensation fromrefrigeration units or ceilings drips on to the
produce. A common environmental pathogen, L.
monocytogenes, may get on walls, in drains, andinto cooling systems. Comprehensive sanitation
programs that target these areas are important inpreventing 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 andinto the produce. Toxic chemical residues may
be present in some packaging materials due to
use of recycled base materials. Packages, suchas 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 andtotes are preferred to wooden containers since
plastic surfaces are more amenable to cleaningand sanitizing. Field bins should be cleaned andsanitized 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.

155

Produce Wash-Water and Hydrocooling Water.
All water that comes in contact with produce forwashing, hydrocooling, or vacuum cooling must
be potable. To achieve this, water should containbetween 2 and 7 ppm (µL L-1) free chlorine andhave 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, anoxidation-reduction potential greater than 650
mV using any oxidative sanitizer will ensurethat bacteria in the water are killed on contact.
Chlorine use prevents cross-contamination of
produce in the washing or hydrocooling systembut it will not sterilize the produce. Rinsing
produce with potable water will reduce thenumber of microorganisms present on the produce
but will not remove all bacteria.
Refrigerated Transport. Produce is best shippedin temperature-controlled refrigerated trucks.
Maintaining most perishables below 5 °C (41°F), except for tropical fruit, will extend shelflife and significantly reduce the growth rateof microbes, including human pathogens. Cut
produce, including tropical fruits, should always
be stored below 5 °C (41°F). Trucks used duringtransportation should be cleaned and sanitizedon a regular basis. Trucks that have been used totransport live animals, animal products, or toxic
materials should not be used to transport produce.
Recall and Traceback Plans. Recall of product isthe 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 therequest of the FDA because of a suspectedhazard in the product. The FDA has defined threerecall 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 situationand involve a direct cause-effect relationship; forexample, C. botulinum in the product. Class II is apriority situation in which the consequences may
be immediate or long term and may be potentiallylife threatening or hazardous to health; forexample, Salmonella in food. Class III is a routine
situation in which life-threatening consequences
156(if any) are remote or nonexistent. Products arerecalled 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 themarket 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-handlingfacilities.
The Code of Federal Regulations describes theconditions under which food must be processedand handled. The regulations cover generalprovisions, buildings and facilities, equipment,
production and process controls, and defect actionlevels. 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 havethe 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 (Codeof Federal Regulations, Title 21, Food and Drugs,
Pt. 100-169). Submit a check or money order toSuperintendent of Documents, U.S. Government
Printing Office, Washington, DC 20402; ortelephone the Government Printing Office at
202-783-3238 to order by credit card.
Personnel GMPs. Personnel working in foodprocessing plants or packinghouses can be asignificant source of food contamination. This
includes production employees, maintenanceemployees, supervisors, and management. It is the
responsibility of processing plant management toeducate and train all food handlers about sanitaryhandling of foods. Employees experiencing
diarrhea, vomiting, open skin sores, boils, fever,or disease should report these symptoms to theirsupervisor and should not be allowed to work withfood products. All food handlers should have cleanouter 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 andhair restraints should be used by all personnel infood handling areas.
Physical Plant and Grounds. Food processing
plants and produce packing houses should beconstructed 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 befree 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 theprocessing plant should be kept down to preventthe formation of breeding grounds for rodents.
Rodent traps should be placed on the outside
perimeter of the grounds and be inspected andserviced regularly.
Plant Construction and Design. The mostimportant aspect of sanitary food plant andproduce packinghouse design is sufficient spacefor sanitary operations. Processing areas should
be designed for easy cleaning and sanitation.
Floors, walls, and ceilings should be made of acleanable, 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 towithstand the physical and chemical abuses frommachinery 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, andhorizontal surfaces of these items should be
minimized to reduce accumulation of dust andwater 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 notprovide horizontal surfaces for accumulation offilth. Adequate lighting should be provided andall light bulbs should be covered to ensure thatbroken glass cannot contaminate food products.
All water (rinse, flume, cleaning, ice, etc.) usedin food processing must be of proper sanitary
quality. Plumbing should be of adequate size anddesign to handle the amount of product being
processed. Produce handling environments areusually wet; therefore, sloping floors with drains
should be present to remove excess water fromthe 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-washingstations should be available to accommodate
all employees. Restroom facilities should notopen into processing areas. Hot running potablewater, soap, and hand towels should be available
at all times. Signs should be posted to instructemployees to wash their hands after using the
restroom. Employee frocks, gloves, and knives
should never be taken into the restrooms, andadequate storage space should be made available
directly outside the restroom door for temporarystorage of these items. Heating, ventilation, andair-conditioning (HVAC) systems may featurefiltered 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 andfilth. Sanitation is the application of antimicrobial
157

compounds. Sanitation cannot be effective until
surfaces are cleaned. Regular and scheduled
equipment cleaning and sanitizing ensures thatfood 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 amonitoring program.
Master Sanitation Schedule. A written mastersanitation schedule should be in place to ensurethat all areas of a food processing plant or packing
shed are cleaned and sanitized on a regular basis.
The master sanitation schedule should detail thearea to be cleaned, the sanitation method, tools,
cleaning materials, and frequency of cleaning.
There are five steps involved in cleaning andsanitizing:
1. Physical debris removal
2. Rinsing
3. Washing with detergent
4. Second rinsing
5. Sanitizing
It is critical that cleaning—that is, removal ofdebris and food particles—be done prior to any
sanitation steps, because many sanitizers areinactivated by organic materials. Once gross orlarge pieces of food are removed, equipment
should be rinsed with potable water to remove
smaller particles. Then, soaps and detergentsshould 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 foruse 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. Productmanufacturer’s directions for sanitizers andcleaning chemicals should be strictly followed.
Written sanitation standard operating procedures(SSOPs) for cleaning and sanitation should be
158

prepared for specific pieces of equipment thatare cleaned on a regular basis. This ensures thatthe equipment is cleaned properly regardless of
who does the cleaning. SSOPs should specify thefollowing:• 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 takethe following form:

Sanitation of Drains
Goal:

Prevent build-up of contaminants (especially Listeria monocytogenes) in drains that
could cross-contaminate productFrequency: 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 foruse 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

159

Table 3. Comparison of common sanitizers__________________________________________________________________________________
Chlorine
IodineQUATS
Acid-anionic				surfactants__________________________________________________________________________________
Effectiveness against:
Gram-positive bacteria,(lactics, clostridia, Bacillus,
Staphylococci)

Good

Best

Good

Good

Gram-negative bacteria (E. coli, Best
Salmonella, psychrotrophs)

Good

Poor

Good

Yeast and molds

Best

Good

Good

Good

Spores

Best

Poor

Fair

Fair

Viruses

Best

Good

Poor

Poor

Effects on property:				Corrosive
FairlySlightlyNo
Affected by hard water
No
Slightly			Type A*, No
Type B†, Yes

Slightly
Slightly

Irritating to skin
Yes, >100 µL L-1
Not at levels No
		usedYes

Maximum level permitted by
200 µL L-1
25 µL L-1
200 µL L-1
FDA without rinse				200-400 µL L-1
based on type

Affected by organic matter

Most affected

Somewhat

Least affected

Somewhat

Cost

Cheapest

Cheap

Expensive

Expensive

Tests for active residual

SimpleSimpleDifficult

Difficult

Stability in hot solution(>150 oF)

Unstable; somecompounds stable

Highlyunstable

StableStableLeaves active residue

No

Yes

Yes

Yes

160

Table 3. Comparison of common sanitizers—Continued__________________________________________________________________________________
Chlorine
IodineQUATS
Acid-anionic				surfactants__________________________________________________________________________________
Incompatible with—
Phenols, amines,
Starch, silver Anionic wetting Cationicsoft 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 usedsanitizer at 100 to 200 µL L-1. It is important thatwater 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 thechlorine is ineffective.
Monitoring Program. Before processing or
packing begins, sanitation crew performance
should be evaluated on a daily basis to ensurethat conditions are hygienic. Visual inspection
should be performed to ensure that no foodparticles or foreign matter are present on
processing equipment. In particular, areas thatare difficult to clean should be inspected, suchas the underside of conveyors and peeling
equipment. Unfortunately, visual inspection is
not enough to ensure that equipment has beensanitized properly. The number of microbes
present on processing equipment after sanitation
operations should be determined on a regular basis
to evaluate sanitation crew performance. Suchdetermination can be made using one of threemethods: petri contact plate, surface swabbing, or
bioluminescence.
Petri Contact Plate. Plastic petri plates orfilms contain sterile agar with growth media
for microbes and the type of microbes that willgrow 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 andthe location is noted. The plates are then incubatedin the laboratory; if microbes were present on thesampled surfaces, they will grow on the agar. A
low bacteria count per square centimeter meansthat the sanitation crew is doing a good job atcleaning 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 areused 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 sanitationcrew performance, but results are not available
immediately. Another microbe detection method,
called bioluminescence, is capable of detecting thepresence 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 andthus 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 isdetermined within minutes after the swab is taken.
161

In this test, equipment is swabbed and the amountof ATP present is determined by a chemical test
kit. These test kits are available from a numberof suppliers. Bioluminescence test results areavailable 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 associatedwith 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 theprocess. HACCP functions as the final stage ofan 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 safetyof 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 anindividual for formal HACCP training and to be incharge of a team responsible for implementing the
HACCP program. HACCP programs should be as
simple as possible, without an excessive number
162

of CCPs. Each HACCP program is unique andmust 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 evaluatedare growing and harvesting operations, packing
shed operations, packaging material and storage
areas, and all steps in distribution. This process isbest accomplished by a team consisting of bothmanagement and production personnel. (Example:
Hydrocooling water contamination, microbial orchemical.)
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 operationand then determine where each of the identified
hazards may be prevented. Each point that will
be monitored to control a specific hazard may bedesignated 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 andmeasurable. (Example: Hydrocooler water must

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 chlorinelevels will be monitored hourly using a test kit andcontinuously with a strip chart recorder that has
been calibrated daily; hourly pH and chlorine levelmeasurements will be recorded in writing; and therecords 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 toeliminate potential contamination. All deviations
and corrective actions must be documented inwriting. (Example: Chlorine levels are determined
to be below 25 µL L-1. Hydrocooling of productis stopped, chlorine levels are adjusted, and all
products that had been hydrocooled since the lasttime the system was verified to be within criticallimits 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 samplingmust be conducted to ensure that the HACCP
program is functioning properly.

Application of HACCPWhen 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 fromthe 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 aprocess. Furthermore, there is no way to quantify
and measure bird droppings to know if they arewithin critical limits. The same would also be trueof 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, theuse of GAPs has been identified by the FDA andthe produce industry as a more appropriate way toaddress these hazards.
Another example is a cold storage room in a
packinghouse where condensed water fromrefrigeration 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 todevelop a process to prevent water from dripping
or to quantify and monitor water dripping fromrefrigeration coils. A more appropriate way to deal
with this hazard is through SSOPs. Refrigerationcoils and drip pans should be cleaned andsanitized according to a predetermined schedule
to prevent the growth of L. monocytogenes in thecondensate. This way, the hazard is prevented
more effectively and more simply than bydesignating a CCP.
There is no minimum or maximum number of
CCPs in any given operation. What is importantis that all potential hazards be addressed throughprerequisite programs or through HACCP. Those
hazards that can be controlled or minimized
through quantitative control of a process may
163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 havesystems 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 asingle incidence of personal injury traced backto a specific food manufacturer may put thatcompany 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 costto 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 foodquality. Food safety programs simply ensure thatfood 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 throughpeeling, cutting, slicing, or shredding. These same
operations can transfer pathogenic microbes fromthe 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 offresh-cut fruits and vegetables. Low temperatures
reduce enzymatic reactions and greatly slow down
the multiplication of spoilage organisms. Low
temperatures also prevent the multiplication ofmost foodborne pathogens, with the exception of
Listeria monocytogenes and a few others that arecapable of growing, albeit slowly, at refrigerated
temperatures.
164

Emphasis should be placed on preventing
contamination by pathogens. The best way toprevent 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 andensures that those potential hazards are controlled
and monitored to enhance safety. HACCP andfood 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 isbecause 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 seedthat was contaminated with a bacterial pathogen
before sprouting began. Pathogens can survive
for months under dry conditions used for seedstorage. Though contaminated alfalfa seeds havebeen 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, andL. monocytogenes prior to harvest.

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 areintended to provide recommendations to suppliersof 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 thatsprouts are not a cause of foodborne illness andthat those in the sprout industry comply with foodsafety provisions of the Federal Food, Drug, andCosmetic Act.

Zhuang, R.Y., L.R. Beuchat, and F.J. Angulo.
1995. Fate of Salmonella montevideo on and inraw tomatoes as affected by temperature andtreatment with chlorine. Appl. Environ. Microbiol.
61: 2127-2131.

References

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 andApplied Nutrition, 200 C Street, Washington, DC.;
http://www.gpo.gov/fdsys/pkg/FR-1999-10-27/
pdf/99-27976.pdf

Brackett, R.E. 1987. Microbiologicalconsequences of minimally processed fruits andvegetables. 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. Foodand Drug Administration, Center for Food Safety
and Applied Nutrition, 200 C Street, Washington,
DC.

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

Kader, A.A., and C.M. Heintz. 1983. Gamma
irradiation of fresh fruits and vegetables - anindexed reference list (1965-1982). Postharvest
Hort Ser. no. 4, University of California,
Department of Pomology, Davis, CA.

FDA. 1998. Guide to Minimize Microbial Food
Safety Hazards for Fresh Fruits and Vegetables.
Food Safety Initiative Staff, HFS-32, U.S. Foodand 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

Katsuyama, A.M., and J.P. Strachan. 1980.
Principles of Food Processing Sanitation. The
Food Processors Institute, Washington, DC.

Beuchat, L.R. 1998. Surface Decontaminationof Fruits and Vegetables Eaten Raw: A Review.
World Health Organization, Geneva, Switzerland.

Suslow, T. 1999. Addressing animal manure
management issues for fresh vegetable production.
Perishables Handling 98:7-9.

Current Good Manufacturing Practices (GMPs)
Regulations 21 CFR 100-169. Superintendent ofDocuments, U.S. Government Printing Office, 732
North Capitol Street, NW, Washington, DC.

165

Nutritional Quality and Its
Importance to Human Health
Adel A. Kader, Penelope Perkins-Veazie, andGene 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. Departmentof Agriculture, Lane, OK. She is now with the
Department of Horticultural Science, North
Carolina State University, North Carolina
Research Campus, Kannapolis, NC. Lester isformerly 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 sourcesof dietary fiber, minerals, and vitamins—C(ascorbic acid), A, thiamine (B1), niacin (B3),
pyridoxine (B6), folacin (also known as folicacid or folate), B9, and E (Quebedeaux and Bliss
1988, Quebedeaux and Eisa 1990, Craig and Beck
1999, Wargovich 2000). Their contribution as agroup is estimated at 91% of vitamin C, 48% ofvitamin 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% ofmagnesium, 19% of iron, and 9% of calories.
Legume vegetables, potatoes, and tree nuts, suchas almond, filbert, pecan, pistachio, and walnut,
contribute about 5% of the per-capita availabilityof proteins in the U.S. diet, and their proteins areof 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 andvegetables 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 overdietary supplements because of low cost and wideavailability.
166

Dietary supplements, while advantageous forconditions in which specific nutrients are neededin abundance such as iron deficiency, may bepoorly absorbed. Climatic conditions, particularly
temperature and light intensity, have an especiallystrong 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 thesame time decrease the rate of ascorbic acidoxidation. Maximum β-carotene (vitamin A)
content in tomatoes occurs at a temperature rangeof 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 temperaturesensitivity of lycopene, the precursor to β-carotene
and lutein.
The B vitamins are crop specific when it comesto 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 lightintensity 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, therootstock 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 theharvested plant parts (Goldman et al. 1999).
Other environmental factors that affect fruit andvegetable 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 andextent of physical injuries. Delays between

harvest and consumption or processing canresult 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 (Leeand Kader 2000). Furthermore, processing andcooking 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 bestabilized or enhanced by cooking.
Fruits, nuts, and vegetables in the daily diet havebeen strongly associated with reduced risk forsome forms of cancer, heart disease, stroke, andother 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 andfunction to modify the metabolic activation anddetoxification and disposition of carcinogens oreven influence processes that alter the courseof the tumor cell (Wargovich 2000). Thoughantioxidant capacity varies greatly among fruits
and vegetables (Prior and Cao 2000, PerkinsVeazie and Collins 2001, Kalt 2002), it is betterto consume a variety of commodities rather thanlimiting consumption to a few with the highest
antioxidant capacity. The Dietary Guidelines
for Americans, 2010 (USDA and HHS 2010) inpart advises filling half your plate with fruits,
vegetables, cooked beans, and grains. Such ahealthy eating pattern also embodies food safety
principles to avoid foodborne illness. In somecountries, consumers are encouraged to eat up to
10 servings of fruits and vegetables per day.

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 dietof cancer treatment patients who were eating abalanced 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 prostatecancer, and has been thought to be due to thepresence 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 etal. 2003). Similar comparative studies are neededon other constituents of fruits and vegetables
and on the bioavailability of nutrients taken as
dietary supplements or as foods that contain thesenutrients.
Examples of the phytochemicals in fruits andvegetables that have established or proposed
positive effects on human health and theirimportant sources are shown in tables 1 and
2. Some changes in these tables are likely as
the results of additional studies on effects ofphytochemicals and their bioavailability on humanhealth become available in the next few years.
Meanwhile it is important to evaluate the validityand dependability of the results of every study
before reaching conclusions for the benefit ofconsumers.

There is increasing evidence that consumptionof whole foods is better than isolated foodcomponents such as dietary supplements
and nutraceuticals. For example, increased
consumption of carotenoid-rich fruits andvegetables was more effective than carotenoid
167

Table 1. Nutritive constituents of fruits and vegetables that have positive effects
on human health and their sources_____________________________________________________________________________
Constituent
SourcesEstablished or
proposed effects onhuman wellness_____________________________________________________________________________
Vitamin C(ascorbic
acid)

Broccoli, cabbage, cantaloupe, citrus fruits,
guava, kiwifruit, leafy greens, pepper,
pineapple, potato, strawberry, tomato,watermelon

Helps prevent scurvy
and cardiovasculardisease; aids
wound healing andimmune 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 preventnight blindness,
chronic fatigue,
psoriasis, heartdisease, stroke, andcataracts

Vitamin K

Nuts, lentils, green onions, crucifers (cabbage,broccoli, brussel sprouts, etc.), leafy greens

Aids synthesis ofprocoagulant
factors; helps
prevent
osteoporosis

Vitamin E(tocopherols)

Nuts (such as almonds, cashew nuts, filberts,
macadamias, pecans, pistachios, peanuts, andwalnuts), corn, dry beans, lentils and chickpeas,
dark-green leafy vegetables

Helps prevent heartdisease, LDL
oxidation, cancer,
and diabetes; aids
immune system

Fiber

Most fresh fruits and vegetables, nuts, cooked drybeans and peas

Helps prevent
diabetes and heartdisease

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 birthdefects, cancer, andheart 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 bloodpressure; aids
muscles, skeleton,
and teeth

168

Table 1. Nutritive constituents of fruits and vegetables that have positive effects
on human health and their sources—Continued_____________________________________________________________________________
Constituent
SourcesEstablished or
proposed effects onhuman wellness_____________________________________________________________________________
Magnesium
Spinach, lentils, okra, potato, banana, nuts, corn,
Helps prevent
cashews
osteoporosis; aids
nervous system,
teeth, and immune
systemPotassium

Baked potato or sweet potato, banana andplantain, cooked dry beans, cooked greens,dried fruits (such as apricots and prunes),
winter (orange) squash, cantaloupe

Helps prevent
hypertension (highblood pressure),stroke, andarteriosclerosis--------------------------------------------------------------------------------------------------------------------

169

Table 2. Nonnutritive plant constituents that may be beneficial to human health______________________________________________________________________________
Constituent
CompoundSourcesEstablished 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, andstrawberry)

Help prevent
heart disease,cancer initiation,
diabetes,
cataracts, andallergies; help
lower bloodpressure

Flavan-3-ols

Epicatechin,Apples, apricots,
blackberries, plums,
raspberries, strawberries

Help prevent
plateletaggregation andcancerFlavanones

Hesperetin,naringenin,
eriodictyol

Citrus (oranges, grapefruit,lemons, limes,
tangerines, etc.)

Help prevent cancer

Flavones

Luteolin, apigenin

Help prevent
Celeriac, celery, peppers,
cancer, allergies,
rutabaga, spinach,and heart disease
parsley, artichoke, guava,
pepper

Flavonols

Quercetin,kaempferol,
myricetin, rutin

Onions, snap beans,broccoli, cranberry, kale,
peppers, lettuce

Help prevent heartdisease andcancer initiation;
are capillaryprotectants

Phenolic acids

Caffeic acid,chlorogenic acid,coumaric acid,ellagic acid

Blackberry, raspberry,strawberry, apple, peach,plum, cherry

Help prevent
cancer; help
lower cholesterol

Carotenoids

170

Table 2. Nonnutritive plant constituents that may be beneficial to human health—Continued______________________________________________________________________________
Constituent
CompoundSourcesEstablished or			proposed effects on			human wellness______________________________________________________________________________
Lycopene
Tomato, watermelon,
Help prevent
papaya, Brazilian guava,
cancer, heart
autumn-olive, reddisease, and malegrapefruit
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
greensHelp prevent
maculardegeneration

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 andblood pressure_______________________________________________________________________________

171

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 storageon 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 HealthFoundation, Wilmington, DE
Kalt, W. 2002. Health functional phytochemicals
of fruits. Hort. Rev. 27:269-315.
Lee, S.K. and A.A. Kader. 2000. Preharvest andpostharvest 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.

172

Perkins-Veazie, P., and J.K. Collins. 2001.
Contribution of nonvolatile phytochemicals tonutrition and flavor. HortTechnology 11:539-546.
Prior, R.L., and G. Cao. 2000. Antioxidant
phytochemicals in fruits and vegetables: diet andhealth implications. HortScience 35:588-592.
Produce for Better Health Foundation. 1999.
Dietary Guidelines: The Case for Fruits andVegetables First. The Foundation, Wilmington,
DE.
Quebedeaux, B., and F.A. Bliss, eds., 1988.
Horticulture and Human Health. Contributionsof Fruits and Vegetables, Proceedings of the 1st
International Symposium on Horticulture andHuman 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 ofFruits and Vegetables, Proc. 2nd Intl. Symp. Hort.
and Human Health.] HortScience 25:1473-1532.
Seifried, H.E., S.S. McDonald, D.E. Anderson, etal. 2003. The antioxidant conundrum in cancer.
Cancer Res. 63:4295-4298.
Southon, S. 2000. Increased fruit and vegetableconsumption within the EU: potential healthbenefits. 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 ofAgriculture and U.S. Department of Healthand Human Services. Dietary Guidelines for
Americans, 2010. 7th Edition, U.S. Government
Printing Office, December 2010, Washington, DC.
Wargovich, M.J. 2000. Anticancer properties offruits and vegetables. HortScience 35:573-575.

Annual Culinary Herbs

Precooling Conditions

Kimberly P. WrightWith the exception of basil, herbs should becooled 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).

Wright is with Dole Fresh Vegetables, Salinas,
CA.

Scientific Names and Introduction
Culinary herbs include basil (Ocimum basilicumL.), 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.

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 dilland 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 andCameron 1994).

Quality Characteristics and Criteria
Herbs should appear fresh and green: no
yellowing, decay, insect, or mechanical damage.
Leaves should be uniform in size. Flavor andaroma should be strong and characteristic of theherb. There are purple forms of basil that shouldhave a rich color.

Horticultural Maturity Indices
Annual herbs should be harvested before
flowering. Basil still maintains its quality withsome flowers.
Grades, Sizes, and Packaging
There are no market grades or sizes for fresh
herbs. They may be tied or bunched witha rubberband, packaged in plastic bags or
clamshells, then packed in corrugated cartons.
Perforated polyethylene liners will prevent
dehydration and maintain quality.

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-lifeof coriander (Loiza and Cantwell 1997), chervil(Aharoni et al. 1993), and basil (Lange andCameron 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 notsensitive to chilling and should be stored as cold
as possible (0 °C [32 °F]) without freezing. Basil173

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).

cut ends of stems. Low temperatures should bemaintained throughout the cold chain to minimize
pathological disorders and prolong shelf-life.
Chilling increases the susceptibility of basil todecay.

Ethylene Production and Sensitivity
Quarantine Issues
Annual herbs produce very little ethylene, but arehighly 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 rateby 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 toethylene exposure, especially if herbs are held at
10 °C (50 °F) or warmer. Basil is susceptible tochilling injury if held below 12 °C (54 °F), themain symptom being necrosis and browning or
blackening of the leaves.

Postharvest Pathology
Molds and bacterial decay may develop,
especially on mechanically damaged leaves or
174

There are no quarantine issues.

Suitability as Fresh-Cut ProductAnnual 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 offresh herbs.

References
Aharoni, N., O. Dvir, D. Chalupowisz, andZ. 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 andvegetables. 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 diOrtoflorofrutticoltura 22:3-4.

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. 98117. Postharvest Hort. Ser. no. 18, University ofCalifornia, Davis, CA.

175

AppleChris 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 andExtension Center, Wenatchee, WA; Rosenberger
is with Hudson Valley Laboratory, Cornell
University, Highland, NY.

Scientific Name and Introduction
Malus × domestica Borkh., the apple, is aperennial of the Rosaceae family. The apple isthought to have arisen in the Caucasus regionof southeastern Europe, and the tree is one of
the hardiest temperate zone species. The edible
part of the fruit is composed of fleshy tissue thatsurrounds the five ovaries, as well as some ovaryor carpel tissue. The parenchyma of the fusedbases of the calyx, corolla, and stamens constitutes
the major edible part of the fruit, though thistissue is sometimes interpreted as being cortical.
The skin surrounding the fleshy parenchyma
tissue is made up of cuticle, epidermal, andhypodermal layers, with lenticels allowing gas
diffusion across the skin. Cracks in the skinsurface are also important for gaseous exchange.
The diffusion characteristics of the skin can affectthe 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 visualappearance, texture, and flavor. Modern
consumers demand impeccable appearance,
optimum texture, and firmness typical of thevariety.
176

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 anindicator 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 indicationof overmature or senescent fruit. Consumers
generally prefer ‘Golden Delicious’ apples thathave 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 marketplaceis free from blemish, though there may be agreater tolerance for defects in certain markets
such as organic outlets. Occurrences of physicallyinduced damage such as bruising or stempunctures and physiological and pathologicaldisorders are not acceptable in any market. The
prevalence of these defects can be affected greatly
by variety characteristics such as stem length, skintenderness, softness of the fruit, and genetically
based resistance to physiological and pathologicaldisorders. 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 thecommercial 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).

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.

Temperature

Summer apples Fall apples
mg CO2 kg-1 h-1
0 °C
3 to 62 to 45 °C
5 to 11
5 to 7
10 °C
14 to 20
7 to 1015 °C
18 to 31
9 to 20
20 °C
20 to 41
15 to 25
Data from Hardenburg et al. (1986).

Ethylene Production and Sensitivity
The apple is classified as a climacteric fruit,exhibiting increased respiration rates during
maturation and ripening. This rise is associatedwith 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 highethylene production rates and ripen quickly,
while late season ones have low ethylene
production rates and ripen slowly. The timingof the climacteric and ripening of apple fruit isadvanced 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 andapplication of CA storage technologies (Watkins
2002, 2003). Methylcyclopropane (1-MCP) isavailable under the commercial name SmartFresh.
1-MCP is structurally related to ethylene, has anontoxic mode of action, and is applied at very
low levels with low measurable residues in foodcommodities.

Respiration Rates
In general, early season varieties have highrespiration rates, while late season varieties have
low respiration rates. The respiration rate offruit is directly affected by temperature, and therespiratory 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 willdevelop.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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, anapple fruit harvested when less mature will havepoor color and flavor and can be more susceptible
to physiological disorders such as bitter pit andsuperficial 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 ofapples 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 thanthose 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 foreach marketing period, which can range fromimmediate on-farm sales to marketing across theglobe after 11 months of storage.
Harvest Maturity Indices. A wide range ofindices 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
177indices. Since a rise in ethylene production isassociated with initiation of ripening, it has
been suggested that ethylene production orinternal ethylene concentration (IEC) should bea major determinant of harvest decisions (Lau
1985). However, relationships between ethylene
production and optimum harvest dates can bepoor, and the timing, or presence, of increased
ethylene production is a function of cultivar.
Factors such as a growing region, orchard within aregion, 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 ofsome cultivars.
For some bicolored apples, background color isconsidered an important harvest index. In somecases, 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 areoften harvested well before autocatalytic ethylene
production occurs, and therefore this measurement
is commercially irrelevant. However, in someregions 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 ofindices.
Other indices, such as flesh firmness and soluble
sugar content, are quality indicators rather thanmaturity indicators, as they are influenced greatly
by orchard factors; for example, fruit exposure tolight. During the preharvest season, firmness falls
and sugar content continues to increase. However,these quality indicators provide informationthat can be important to fruit performance instorage. Both indices are increasingly used in themarketplace 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
178

programs in conjunction with their land grantuniversities. 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 eachvariety (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 overthe harvest period. In this way, full participationof 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 weightor 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 soldby count (fruit per carton). Apples are most often
packed on four or five soft fiberboard trays madefrom recycled newspaper. In some cases, the tray
is made of soft polystyrene. Cartons are often
unvented. However, unvented cartons on palletstacks will cool slowly, detrimentally affecting

product longevity. Venting to improve coolingrates 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 theadvantage of minimizing fruit handling as the
cartons are placed directly onto display racks atretail.
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 retailstores. Consumer packages in which two to six
apples, or a combination of fruits, are shrinkwrapped are becoming more popular in someretail outlets. Shrink-wrapped packages reduce thetime consumers spend in the produce section andalso reduce loss caused by consumer sorting andhandling of individual fruit.

Cooling Conditions
The rate of cooling of apple fruit affects retentionof 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 theearly part of the harvest season (summer varieties)
since they will soften more rapidly than those thatmature 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 asstorage length increases. Therefore, inadequate
investment of resources at harvest to ensure rapid
fruit cooling may not be apparent until late in thestorage 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 coolingof fruit, irrespective of timing of CA conditions,
are illustrated for ‘Empire’ apples in table 1.

Table 1. Effect of cooling rate on firmnessof 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 notwidely used for apples in the United States. Roomcooling, 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 andrefrigeration 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 theexisting 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 airtemperature 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 theevaporator with pallet runners oriented in thesame direction as the air flow. Additional bins offruit should be stacked, no more than two high,in unfilled refrigeration rooms to cool overnight
before loading into the CA room the nextmorning. 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 room179

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 foundin Kader (1992), Thompson et al. (1998), andBartsch and Blanpied (1990).

Optimum Storage Conditions
Apple producers have learned that apple fruit
respond dramatically to both temperature andatmosphere modification. Rapid temperature
reduction and the exacting maintenance of low
temperatures close to the chilling point of thevariety can provide good to medium quality
product following 3 to 6 mo of storage and insome cases longer. However, modern commercial
warehouses combine temperature managementwith 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 fora 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.

180

Table 2. Storage characteristics of several apple varieties______________________________________________________________________________
			
Variety
Potential months Superficial Commentsof storage
scald______________ susceptibility
0 ºC
CA*
Air
______________________________________________________________________________
Braeburn
3-4
8-10
Slight				Cortland
2-3
4-6
Very high
				
				
				
Delicious
3
12
Moderate			to very high				Empire2-3
5-10
Slight		
				
Fuji
4
12
Slight
				
Gala
2-3
5-6
Slight				Golden Delicious 3-4
8-10
Slight				Granny Smith
3-4
10-11
Very high				
Idared3-4
7-9
Slight						Jonagold25-7Moderate				Jonamac23Moderate				
Law Rome
3-4
7-9
Very high				
Macoun3
5-7Slight				
McIntosh
2-3
5-7
Moderate
				
				
				

Sensitive to CO2.
Temperature sensitive; McIntosh 			conditions preferred; scald inhibitor 		
essential.
Sensitive to CO2 >2%; scald inhibitor
essential.
Avoid late harvest; temperature sensitive;
scald inhibitor not required; CO2 sensitive.
Late harvested fruit may be CO2 sensitive.
Loses flavor during storage.
Susceptible to skin shrivel.
Sensitive to CO2.
Temperature sensitive; tolerant to orchard
freezing damage.
Avoid late harvest; may develop scald.
Loses flavor during storage.
Scald inhibitor essential.
Can be stored with McIntosh.
CO2 sensitive; normal storage is 			sometimes shortened by excessive flesh 		softening; scald inhibitors recommended.

181

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				
Spartan
3-4
6-8
SlightGreen apples have low eating quality.
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 affectedby sensitivity of the variety to low-temperaturedisorders. While lower temperatures usually resultin 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 thanseveral months, so risks of low-temperature injury
are low for fruit kept in short-term storage (2 to 3mo). 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 chillingand 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.
182

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 thermometerat the door, as temperatures within stacks andthroughout 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 coolingor developing during transport to market can
reduce quality at the consumer level. Fruittemperatures can increase during packing; failure
to remove heat may result in subsequent lossof firmness during transport (Kupferman 1994,
Watkins 1999).

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).

183

Controlled Atmosphere (CA)Considerations
Apples are the predominant horticulturalcommodity 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 theatmospheres. 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 employedby 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 tolower O2 to 2.5 to 3%. Fruit quality resulting fromthese conditions gradually became unacceptablein the marketplace. Rapid CA is now standardpractice in many apple industries. Nitrogen flushingequipment 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 topredetermined thresholds before application of CA.
Even when rooms are filled over extended periods,
O2 concentrations are usually lowered by flushingwith 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 intanks or generated on site.
An RH of 90 to 95% is recommended for apples toprevent shrivel. The major causes of dehydration
are small coil surface areas and frequent184

defrosting. When CA rooms are designed, therefrigeration engineer should demand the largest
coil size feasible for the room. Operators havebeen 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 bedesigned to prevent condensation of water dropletson 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 ofthree categories, depending on level of equipment
and technology involved.
Standard CA involves conservative atmosphereconditions 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 marginof safety is large enough so that fluctuations in
gas concentrations in manually adjusted storages
should not cause fruit injury.

Table 4. Atmospheric and temperature requirements for standard CA storageof apples__________________________________________________________________________
VarietyCO2
O2
Temperature
Low-O2*__________________________________________________________________________
			
%
%
°C
Braeburn
0.5
1.5-2
1
				
Cortland
2-3
2-3
0
2-3 for2-3
2
1 mo then 5

yes

Delicious
2
0.7-2
0
				
Empire
2-3†
2
2
				
Fuji
0.5†
1.5-2
0-1
				
Gala
2-3
1-2
0-1
				
Golden Delicious
2-3
1-2
0-1
			
Granny Smith
0.5
1.5-2
1
				
Idared2-321				Jonagold
2-3
2-3
0
				
Jonamac
2-3
2-3
0
2-3 for2-3
2
1 mo then 5		

yes

Law Rome
2-3
2
0
				
Macoun52-32				Marshall McIntosh
2-3 for
4-4.5
2
1 mo then 5			
2-3 for3
2
1 mo then 5
2-3 for2
3
1 mo then 5

no

yes
yes
yes
yes
yes
yes
yes
no

yes
no
no
no

185

Table 4. Atmospheric and temperature requirements for standard CA storageof apples—Continued__________________________________________________________________________
VarietyCO2
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 atwhich fermentation will occur. Nondescriptive
terms such as “ultralow” are sometimes used but
should be avoided in favor of describing specificO2 percentages. The safe O2 concentration varies
by variety (table 4) and region. ‘Delicious’apples from British Columbia, Canada, forexample, 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 (Lauet al. 1998). Strains within a variety can also
vary in sensitivity (Lau 1997). An extreme caseis 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 (Parket al. 1993). In general, it is necessary to increasestorage temperature when low-O2 CA storage isused. A number of guidelines have been developed
for safe operation of long-term CA storage.
Using the following techniques, it has also beenpossible 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.
186

2. Avoid apples from orchard blocks that average
fewer than five seeds per apple. Low seed countcan 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 takelonger 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 toreduce 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, forvarieties with low-O2 scald risk.
Low-ethylene CA storage is appropriate because
apple fruit are climacteric, with autocatalytic
ethylene production often beginning close toharvest. However, rates of ethylene production canvary greatly among apple varieties. An important
physiological effect of CA storage is inhibitionof either ethylene production or its action, due tolowered O2 or increased CO2.

Low-ethylene CA storage has been evaluated asa 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 forstorage of the naturally low-ethylene-producing‘Empire’ apple, but it has been replaced by low-O2
storage. In general, low-ethylene CA storage has notproven successful for maintenance of fruit quality
if levels of ethylene gas within the fruit cannot be
controlled, and generally the return on investmentin 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 controlof superficial scald (Little et al. 1982, Wang andDilley 2000). High-CO2 (15 to 20%) treatments
before application of CA storage were used formaintenance of firmness of ‘Golden Delicious’apples in northwestern North America but generally
are no longer recommended because of fruitdamage (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 toprevent false positive readings for scald.

CA and Apple Varieties
The selection of CA atmospheres and temperaturemust take into consideration the variety and, insome cases as mentioned above, the strain ofa particular variety, in addition to where it wasgrown. Experience in Washington has shown thatvarieties can be divided into two types: thosetolerant of high CO2 and those that are not.

‘Gala’ and ‘Golden Delicious’ are CO2-tolerantvarieties 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 theCO2-intolerant category. Their cells are densely
packed, and air exchange within the fruit istherefore reduced. In Washington, these apples
must have the flesh temperature close to thestorage temperature before the O2 is reduced.
These varieties have a tendency to developinternal browning, a CO2 damage symptom thatis associated with a natural predisposition of thevariety (and preharvest factors as well as storage
regime). CO2 should remain well below the O2
level at all times, and temperatures should beslightly 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 withpolyliners in CA, as this can hinder air exchange
within fruit.
‘Red Delicious’ is somewhat CO2-tolerant andis 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. Typicalregimes 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 thesafe operation and the use of the legal definitionof “controlled atmosphere” for stored apples.
Regulations include the rate of establishmentof CA conditions, the maximum level of O2
187

permitted, and the length of time fruit are in
CA. Since regulations vary from State to State,
operators need to contact their State Departmentof Agriculture.
Many precautions must be taken to assure the safe
operation of CA storage rooms. Operators must beaware 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 yourlocal 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 bycultivar 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.

Physiological Disorders
A wide variety of physiological disorders arefound 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 whichintercellular air spaces in the core and corticaltissues become filled with liquid, predominantly
sorbitol (Marlow and Loescher 1984). Usually
the occurrence of watercore is associatedwith advancing fruit maturity and low nighttemperatures prior to harvest, but a variant of
the disorder can occur as a result of heat stress.
Presence of watercore in fruit at harvest createsproblems in certain varieties such as ‘Delicious’
because fruit with moderate or severe watercore
can develop breakdown during storage. By
comparison, grade standards for ‘Fuji’ weremodified so that watercore in ‘Fuji’ apples is nota grade defect in the United States or Canada,because watercore is a desirable feature for thiscultivar due to the sweetness it imparts to thefruit. Mild or moderate watercore should not be
a problem in storage of ‘Fuji’ if fruit are cooledprior to reduction of O2. Severely watercored fruit
should not be placed in CA since breakdown willdevelop over time.

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 withincreased 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 andensures more rapid turnover of product.

188

Disorders That Develop on the Tree and During
Storage. Bitter pit is a disorder characterized bydevelopment of discrete pitting of the corticalflesh, 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, isalso observed in some varieties. The incidence
and severity of bitter pit are affected by variety,but within a variety, bitter pit is related toharvest 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conditions are at least partly related to low
calcium concentrations in the fruit. Developmentof 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 onmineral (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 thelocal extension specialist. Preharvest applicationsof calcium may be far more effective thanpostharvest drenching as a means of increasing theconcentration 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 duringstorage. 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 ofsusceptible varieties are commonly drenched withcalcium 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 physiologicaldisorder associated with long-term storage (Ingle
and D’Souza 1989). It was the major cause ofapple 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 notdiscarded when soil accumulates in the solution.
Both DPA use and DPA residues on fruit areprohibited 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 isused 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 offruit 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 ofsuperficial 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 lengthof storage is increased. Climate affects sensitivityof fruit to the disorders, with more problems
occurring after colder, wetter growing seasons.
Low-temperature breakdown is characterizedby markedly brown vascular bundles, browningof flesh, and a clear halo of unaffected tissue
189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 whenapples are cut. Internal browning and coreflush areoften associated with higher CO2, since both canoccur 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. Theseodors may disappear if storage problems are
identified soon enough and severe injury has notoccurred. Injury symptoms range from purplingor browning of the skin in a red-colored variety,to development of brown soft patches resembling
soft scald, to abnormal softening and splitting offruit. As discussed earlier, varieties vary greatly
in response to low O2, and susceptibility to injury
is influenced by a number of preharvest andpostharvest factors.
CO2 injury may be external or internal. The
external form consists of wrinkled, depressed,
colorless or colored areas restricted to the skinsurface 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 ofboth external and internal CO2 injuries.
Postharvest Pathology
The main postharvest diseases of apples thatdevelop in storage are blue mold caused by
Penicillium species and gray mold caused by
Botrytis cinerea. Blue mold is the most commonand destructive of all the rots. Most blue molddecays are caused by P. expansum, but P. solitum,P. commune, and P. crustosum are also common
postharvest pathogens of apples (Sanderson andSpotts 1995). Penicillium species enter fruit
primarily through cuts, stem punctures, andbruises (Wright and Smith 1954). However, some
190

cultivars of apples can also be invaded via thestem during long-term CA storage (Rosenberger1999).
Numerous other pathogens can also appear instored apples (Pierson et al. 1971, Snowdon
1990). Some postharvest pathogens infect fruitin the field but remain latent or quiescent until
after apples are harvested and placed into storage.
These include the Colletotrichum species thatcause 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 andthiophanate-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 asapples 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 graymold because most benzimidazole-resistantstrains of the pathogen were highly sensitive to
DPA (Rosenberger and Meyer 1985, Sharom
and Edgington 1985). During the mid 1990s, theincidence of blue mold began to increase in someapple packinghouses where the predominantstrains of P. expansum had developed resistanceto 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 toless selection pressure for fungicide resistance.

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 forcontrolling 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 developmentof 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 anddeveloped 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 theproducts are applied in a closed environment
rather than being sprayed over thousands ofacres, as are conventional fungicides used toprotect crops in the field. Furthermore, liabilities
involved in postharvest treatment of apples are
considerable, both because of the value of thestored 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 agentshas been difficult. Some currently registeredproducts must be kept frozen until used. Activityof biocontrol organisms may be compromisedby excessively high pathogen inoculum or bypresence 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 fungicidethat 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 combinationsof biocontrols and reduced rates of TBZ may be
more effective than using either product alone(Chand-Goyal and Spotts 1997). When suchcombinations are used, the chemical fungicide
may provide eradicant and short-term protectant
activity necessary to prevent decay until thebiocontrol agents become established in wounds
or other infection courts. Biocontrols provide
some protection against TBZ-resistant strainsof the pathogens for which no other controls are
currently available.
Regardless of the postharvest fungicide or
biocontrol strategies that may evolve fromcurrent 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 inrepeated 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 andabrasion 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 andcountry and guidance should be sought from thelocal Department of Agriculture.

Suitability as Fresh-Cut ProductAs with other fruit, methods to reduce senescenceand browning processes in cut apples areimportant, and commercial products are available(Lee and Smith 1995). However, potential for
improvement is large.
191

Additional Information
Many States have workshops and materials
available. Washington, Michigan, and New York
offer regular CA workshops, and proceedings areavailable from Michigan State University andCornell 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 Storagefor 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 andstorage strategies to meet the market demand for
fruit quality and condition. Proc. NY State Hort.
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Blanpied, G.D. 1990. Controlled atmospherestorage of apples and pears. In M. Calderon and
R. Barkai-Golan, eds., Food Preservation by
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Blanpied, G.D., and K.J. Silsby. 1992. Predicting
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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.
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Childers, N.F., J.R. Morris, and G.S. Sibbett.
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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 controlof Botrytis cinerea in apple by yeasts fromvarious habitats and their putative mechanisms ofantagonism. Biol. Contr. 7:212-220.
Hardenburg, R.E., and D.H. Spalding. 1972.
Postharvest benomyl and thiabendazole
treatments, alone and with scald inhibitors, tocontrol 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,
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Park Y.M., G.D. Blanpied, Z. Jozwiak, and F.W.
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194

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Apricot
Carlos H. Crisosto and Adel A. Kader
Crisosto is with the Department of Plant Sciences,
University of California, Davis, CA. Kader waswith the Department of Plant Sciences, Universityof California, Davis, CA. He is deceased.

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 orvolume-filled (about 10 kg net). Apricots should
be uniform in size, and not more than 5% ineach container may vary more than 6 mm whenmeasured at the widest part of the cross section.

Optimum Storage Conditions
Scientific Name and Introduction
The apricot is native to central and western China.
Apricots were brought to Italy about 100 BC, toEngland 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 fromdecay are all important quality criteria. Highconsumer acceptance is attained for fruit withhigh (>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 softenvery fast, making them susceptible to bruising andsubsequent decay.

Horticultural Maturity Indices
In California, harvest date is determined bychanges in skin ground color from green toyellow. The exact yellowish-green color depends
on cultivar and shipping distance. Apricots shouldbe picked when still firm because of their highbruising susceptibility when fully ripe and soft.

Grades, Sizes, and Packaging

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 andshipment are retaining fruit firmness and groundcolor. 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 becauseof apricots’ fast ripening. Ripening before
consumption should ideally be done attemperatures of 18 to 24 ºC.

Apricots are always harvested by hand, usually
into picking bags or plastic totes. Apricots are
195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 tominimize incidence and severity of chilling injury
on susceptible cultivars.

Rates of Ethylene Production andSensitivity
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 fromgreen to yellow). Also, ethylene may encourage
growth of decay-causing fungi.

Respiration Rate
Temperature
0 °C
10 °C
20 °C

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 heldat 20 to 25 °C (68 to 77 °F). Cooling fruit andholding below 5 °C (41 °F) are very effective forcontrolling this fungus.

Quarantine Issues-1-1

mg CO2 kg h
4 to 812 to 2030 to 50

Physiological Disorders

Apricots are currently exported from California
to Canada and Mexico and imported from Chileand 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 systemapproach guidelines agreed to by APHIS and theCanadian Food Inspection Agency.

Gel Breakdown or Chilling Injury. Develops
in cold storage, particularly at 2 to 7 °C (35to 45 °F) when apricots are stored for a longtime period. This physiological problem ischaracterized in early stages by the formation ofwater-soaked areas that subsequently turn brown.
Breakdown of tissue is sometimes accompaniedby sponginess and gel formation. Fruit stored atthese temperatures have short market-life and lose
flavor.

For export to Mexico, a PC stating that thefruit 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

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

196

and inspected in accordance with the Mexico work
plan. A copy of the work plan for the exportationof 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 forthe 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 dothis, the shipments must be accompanied by a
PPQ Form 203 signed by the APHIS inspector onsite in Chile.

Suitability as Fresh-Cut ProductFresh-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 nearto 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

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
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97:636-638.
Folchi, A., G.C. Pratella, S.P. Tian, and P.
Bertolini. 1995a. Effect of low oxygen stress inapricot at different temperatures. Ital. J. Food Sci.
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Guelfat-Reich, S., and R. Ben-Arie. 1967.
Different factors affecting the keeping quality
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Refrigeration, vol 3, pp. 447-457, Madrid, Spain.
Iwata, T., and M. Kinoshita. 1978. Studies on
storage and chilling injury of Japanese apricot
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temperature, cultivar, maturity, and polyethylene
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Trurter, A.B., J.C. Combrink, and L.J. vonMollendorff. 1994. Controlled-atmosphere storageof apricots and nectarines. Decid. Fruit Grower
44:421-427.
Wankier, B.N., D.K. Salunkhe, and W.F.
Campbell. 1970. Effects of controlled atmospherestorage on biochemical changes in apricot andpeach 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 Methodsof Plant Analysis, pp. 111-131. Springer-Verlag,
Berlin, Germany.

Andrich, G., and R. Fiorentini. 1986. Effectsof 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 andclingstone peaches. J. Food Sci. 47:432-436.
197

Arazá
María S. Hernández and J. Pablo FernándezTrujillo
Hernández is with the Instituto Amazónico deInvestigaciones 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 froma perennial tree of the Myrtaceae family. Two
subspecies were described by McVaugh (1956):
stipitata from Brazil and Peru (also known asaraçá-boi in Brazil or as pichi in Peru, “the wildone”) and sororia from Peru (also called rupina
caspi, “the domesticated one”). One landrace
occurs in the western Amazon (Gentil andClement 1997). Arazá is primarily grown in thewestern Amazon as well as in Costa Rica. Therecan be four flowering periods per year with 2-mo
harvest periods followed by a 1-mo break (Swiftand 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 theirhigh acidity (mostly malate, followed by succinate
and, to a lesser extent, citrate), minerals, a highascorbic acid content, and low concentrations
198of 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 ofseeds per fruit and seed length depends on thesubspecies (Swift and Prentice 1983, Morton
1987, Rodriguez 1990, Ferreira 1992,). Thirty
volatile compounds have been identified in ripearazá 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 above100°) 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, andequatorial 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), andlarge (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 chamberusing air with 90 to 95% RH to maximize
storability.

Optimum Storage Conditions

Respiration Rates

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).

Temperature Preclimacteric
Climacteric-1 -1-------mg CO2 kg h ----------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).

Controlled Atmosphere (CA)Considerations
MA reduces weight loss, shriveling, developmentof skin scald, decay, softening, and the lossof 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, andatmosphere. 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 norecommendation 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 areserious problems.

Chilling Sensitivity
Arazá fruit are sensitive to chilling below 13 °C(55 ºF). At 8 to 10 °C, fruit should be stored lessthan 5 days to avoid chilling injury.

Ethylene Production and Sensitivity
Ethylene production and sensitivity have not been
determined. The fruit are climacteric.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 toripe symptoms (blotchy green color, high flesh
firmness), lack of flesh juiciness, increase inacidity, and green skin spots (Tai Chun 1995,
Hernández et al. 2002a). CaCl2 application,
particularly at higher than 4% (w/v), can result inabnormal ripening. Green skin spots remain on
the fruit and small brown spots develop that later
expand into necrotic lesions that become sites forfungal 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 reachabout 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 pulpthat lack juice and fermentative degradation. The
incidence of rust (Puccinia psidii or Uromycessp.) has been recorded in Manaus and Costa Rica
(Moraes et al. 1994, Tai Chun 1995). Yeasts are a199

minor problem with fruit bruises and/or chemicalscalded areas caused by calcium dips of 4 to 8%(Hernández et al. 2003).

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.

Quarantine Issues

Ferreira, S.A. do N. 1992. Biometria de frutos dearaçá-boi (Eugenia stipitata Mc. Vaugh) (biometryof the araza fruit ). Acta Amazonica 22:295-302.

Quarantine pests include Anastrepha obliquaand A. striata (Diptera:Tephritidae) (Saldanha
and Silva 1999). The coleoptera Conotrachelus
eugeniae and Atractomerus immigrans havebeen 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).

Franco, M.R.B., and T. Shibamoto. 2000. Volatilecomposition 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.

Special Considerations

Galvis, J.A., and M.S. Hernández. 1993a. Análisis
del crecimiento del fruto y determinación delmomento de cosecha del Arazá [Fruit development
and harvest date in araza]. Colombia Amazónica
6:107-121.

Fruit are highly susceptible to dehydration andshriveling. A warming treatment of 18 h at 20 °C(68 ºF) with 90% RH after 6 days at 10 °C (50ºF) reduces skin scald and associated decay andextends shelf-life up to 2 weeks (Hernández et al.
1999, 2002b).

Galvis, J.A., and M.S. Hernández. 1993b.
Comportamiento fisiológico del arazá (Eugenia
stipitata) bajo diferentes temperaturas dealmacenamiento [Physiological behavior ofaraza (Eugenia stipitata) under different storage
temperatures]. Colombia Amazónica 6:123-134.

Acknowledgments

Gentil, D.F.O., and C.R. Clement 1997. The
arazá (Eugenia stipitata): results and research
directions. Acta Horticulturae 452:9-17.

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
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Research and Commercialization, pp. 367-371.
John Wiley & Sons, Indianapolis, IN.

200

Hernández, M.S., H.E. Arjona, O. Martínez, andJ.P. Fernández-Trujillo. 1999. Storage disorders ofarazá fruit (Eugenia stipitata Mc Vaugh) related topostharvest treatments. HortScience 34:512.
Hernández, M.S., J.P. Fernández-Trujillo, O.
Martínez, et al.. 2001. Modified atmospherepackaging of araza fruit (Eugenia stipitata
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Postharvest Technologies of Fruits, Vegetables,
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and Quality Evaluation, vol. 43, pp. 261-265. Sci.
Pub. Inc., Plymouth, U.K.

Saldanha, L.A., and N.M. Silva. 1999. Semiartificial bearing of the larvae of Anastrephaobliqua (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.

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 hostof Cylindrocladium scoparium]. Fitopatol. Bras.
20:488-490.
Rodriguez, S. 1990. Araza (Eugenia stipitata).
Monografia 1, Corporación Colombiana parala Amazonia Araracuara COA, San Jose delGuaviare, Colombia.

201

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 aperennial of the Asteraceae (Compositae) family.
The edible portion includes the tender immature
flower bud and fleshy central base that is protectedby a cone of short, thick-stemmed bracts. The
main types include Green Globe, Desert GlobeImperial 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 todark 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 orfeel heavy for its size. Both thorny and thornlesscultivars 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 areclassified by the number that fit into a standard
202

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 (>13cm diameter, 5.4 in), 24s (10 to 13 cm, 4.0 to 4.5in), 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 someretailers prefer 36s and 48s, since artichokes are
generally priced by bud, not by weight.
A new grade was adopted for U.S. No. 1 longstem globe artichokes in 2006. The stems mustbe smoothly cut to a minimum of at least 20 cm (8in) unless otherwise specified to a longer length inconnection 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 Stewart1963). Hydrocooling, forced‑air cooling, andpackage‑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 ofartichokes 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depends on bud maturity, cultivar, temperature,and the particular atmosphere used (Rappaportand Watada 1958, Andre et al. 1980, Ryder et al.
1983). Optimal CA conditions vary widely amongcultivars, 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 canbe 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 ofethylene and are not particularly sensitive toethylene exposure.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
16 to 445 °C
26 to 60
10 °C
44 to 98
15 °C
76 to 14420 °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 rateby 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 andscratched, so careful handling is important. The
abraded areas usually turn brown or black, which
greatly detracts from appearance and quality andprovides a route through which microorganisms
can enter. Also, violet discoloration of innerbracts occurs, the severity of which was low whenartichokes 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 isgray 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 therate of spread of the disease, fungal growth nearfreezing 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 ProductNo current potential.

203

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 issueand does not affect eating quality. In fact, thiscondition may enhance the nutty flavor. Avoid
wilted, moldy, significantly discolored, or woody(overmature) artichokes.

Acknowledgments
Some of the information included was from theProduce 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 ofpreservation of artichokes by combined utilizationof vacuum precooling, controlled atmospheres,and cold. Revue Hort. 211:33-40.
Bianco, V.V. 1979. Influence of temperature on thecoloration of interior bracts and the inflorescencecomplex 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 Operationof Refrigerating Equipment in the Storage ofFruits and Vegetables by Refrigeration, pp. 336341. Inst. Intl. du Froid, Paris, France.
Lipton, W.J., and J.K. Stewart. 1963. Effectsof Precooling on Market Quality of Globe
Artichokes. Marketing Research Report 633, U.S.
Department of Agriculture, Agricultural Marketing
Service, Washington, DC.
204

Miccolis, V., and M.E. Saltveit. 1988. Influence oftemperature and controlled atmosphere on storageof ‘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, andSweet Potatoes. Agriculture Handbook 155, U.S.
Department of Agriculture, Agricultural ResearchService, Washington, DC.
Rappaport, L., and A.E. Watada. 1958. Effect oftemperature on artichoke quality. In Proceedingsof 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 andVegetables, 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.

Asian Pear

Quality Characteristics and Criteria

Carlos H. Crisosto

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 moreresistant to mechanical damage). Flesh firmness(penetration force using an 8-mm tip) of 7 to 10
lb-force, depending on cultivar, is optimum foreating. 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.

Crisosto is with the Pomology Department,
University of California, Davis, CA.

Scientific Name and Introduction
The cultivated varieties of Chinese and Japanesepears 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’ werevarieties of P. serotina, and they were unable todistinguish ‘Tsu Li’ and ‘Ya Li’ from the Japanesevarieties.
Asian pears remain firm and are crisp and juicy
when eaten ripe, whereas ‘Bartlett’ and otherPyrus communis Linnaeus varieties become softand 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 fromthose 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 “shali,” 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 oldvariety in the group (Hu 1937).

Horticultural Maturity Indices
Change in skin color can occur from green toyellowish 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 inincreased incidence and severity of physiologicaldisorders and greater susceptibility to physicalinjury.

Grades, Sizes, and Packaging
Fruit should be held lightly in the palm of the handand 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 beremoved from the fruit.
The skin of Asian pears is very susceptible toabrasion 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 withthe stem end up, preferably in single layers andpacked 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 should205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 andnot left in direct sunlight.

Optimum Storage Conditions
Asian pears should be stored at 0 ºC (32 ºF) intrays complete with packet pack and polyliners.
It is necessary to maintain RH above 90% in thestorage atmosphere because fruit are susceptible
to water loss. When water loss has been greaterthan 5 to 7%, fruit become dehydrated and havea shriveled appearance, especially in ‘Kosui’ and‘Hosui.’ Eating quality is also affected and fruitlack a crisp and juicy texture.
The continued presence of ethylene in the storage
environment may increase the development ofskin 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 fruitor fruit with disorders produce higher levels of
ethylene than sound fruit and should not be stored
alongside sound fruit.

Respiration Rates
Temperature
0 °C
20 ºC

mg CO2 kg-1 h-1
2 to 820 to 30

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 themagnitude of CA benefits for Asian pears is
cultivar specific and is generally less than thatfor 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 firmnessand delay changes in skin color. Asian pears are
sensitive to CO2 injury (above 2% CO2 for mostcultivars) when stored longer than 1 mo.

Retail Outlet Display Considerations
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.

206

Display shelf should be kept as cold as possible
without freezing or ice.

Rates of Ethylene Production andSensitivity
Some cultivars (such as ‘Nijisseiki,’ ‘Kosui,’and ‘Niitaka’) produce very little ethylene, lessthan 0.1 µL kg-1 h-1, and have a nonclimactericrespiratory 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 andproduce 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).

Exposure of climacteric cultivars to <1 µL L-1
ethylene accelerates loss of green color andslightly 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,’ andKorean 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 duringstorage, with no visible external indication ofinternal browning.
Fruit grown under the hot conditions ofCalifornia’s San Joaquin Valley and pickedlater 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 andLakso 1985). The fruit should be picked whenmost of the pears on the tree are still green, though
it is all right if a few at the top have begun todevelop some light-yellow spots. Fruit picked
when the skin is completely yellow will developinternal browning within 1 mo after harvest. In
China, reduction of ‘Ya Li’ internal breakdown has
been accomplished using a temperature programthat decreases storage temperature gradually.
Flesh spot decay (FSD) can be a problem withJapanese pear cultivars. FSD is more frequent onlarge (<300 g) and overmature fruit. FSD limits
opportunities to grow and market Japanese pears.
Symptoms include partial browning of spots anddevelopment of cavities in the flesh. It appears
along and around the vascular bundles when thesymptoms 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 theway down to the calyx. Cavities are usually dry
and surrounded by apparently healthy tissue. Thisdisorder can occur in fruit while still on the tree.
It is more obvious, however, after 2 to 6 weeks incold 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 thisdisorder. 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 acceptablelevel. Meanwhile, whenever possible, avoid thefollowing conditions that might induce FSD: low
crop load (large fruit), later picking (advanced
maturity), extreme temperature changes during
the maturation season, sunburn, erratic irrigationor precipitation (frequency, amount, and timing),
harvesting fruit under warm temperatures, andcooling the fruit rapidly.
Low-O2 injury manifests itself as discoloredsurface depressions from exposing ‘Nijisseiki’pears to ≤1% O2 for 4 mo at 0 °C (32 ºF) and fromexposing ‘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 severecases 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 andturn slightly brown) occur in some cultivars (forexample, ‘Nijisseiki,’ ‘Shinseiki,’ and ‘Hosui’)under conditions favoring vigorous tree growth.
Avoid harvesting overmature fruit to reducewatercore incidence and severity.
Superficial scald or skin browning can occur
after long-term (>16 weeks) storage of ‘Shinsiki’and ‘Nijisseiki’ fruit. Long-term storage can207lead to the development of a skin disorder thatis characterized by the appearance of scaldlike
browning symptoms. Initially, the affected areasof the skin are light brown in color, but as thedisorder progresses the skin becomes dark brownand 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 thatmost 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, thewhole 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 offruit in a relatively ethylene-free atmosphere arerecommended.

“Excerpt” to track phytosanitary requirements foreach country. APHIS also provides phytosanitaryinspections and certifications that declare fruit are
free of pests to facilitate compliance with foreign
regulatory requirements. Issues associated withexotic pest quarantines, addressing both imported
and exported fruit, can change rapidly.

Suitability as Fresh-Cut Product
Preliminary research conducted in the laboratoryof 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 (32to 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 lessthan 5 days at 2 °C (36 °F).

Postharvest Pathology
Special Considerations
Asian pear fruit are susceptible to many
pathogens, such as Botrytis, Alternaria, andPhomopsis 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 bybirds while fruit are on the tree can provide entry
points for pathogens.

The five varieties ‘Shinsui,’ ‘Shinseiki,’‘Kosui,’ ‘Hosui,’ and ‘Nijisseiki’ all have anadequate storage life. If fruit are harvested at therecommended 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.

Quarantine Issues

Acknowledgments

Limited import (Chile) and export (Canada)
activity is occurring. If imported from Chile,
Asian pear shipments must be accompanied bya PPQ (Plant Pest Quarantine Form 203) signedby the USDA, Animal Plant Health Inspection
Service (APHIS) inspector on site in Chile. If
shipments were not precleared at origin, samplingat 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 particularcountry has. In cooperation with the State plantboards, APHIS developed a database called

Most of this information was taken from the
University of California, Davis, website “Fresh
Produce Facts” at http://postharvest.ucdavis.edu/
produce_information.

208

References
Beutel, J. 1990. Asian pears. In J. Janick and J.E.
Simon, eds., Advances in New Crops, pp. 304308. Timber Press, Portland, OR.

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., Universityof 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 ofpears in China. Nanking J. 7:103-193.
Johnson, R.S., and A.N. Lakso. 1985. Relationshipbetween stem length, leaf area, stem weight, andaccumulated growing degree-days in apple shoots.
J. Amer. Soc. Hort. Sci. 110:586-590.
Lallu, N. 1990. Fruit growth, handling andstorage. In A.G. White, ed., Nashi, Asian Pearin 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 ofCommercial 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 oxidasechanges of Duck pears (Pyrus bretschneideri
Rehder) during low-temperature storage. Acta Bot.
Sinica 29:614-619.
209

Asparagus

tightly closed. Tender, immature (that is, shorter)
asparagus may be harvested for special markets.

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 ofAgriculture, 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 perennialof 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 morecommon in Europe and Asia (Lipton 1990);
green asparagus is popular in the United Statesand is produced predominantly in California andWashington. 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 andfirm with tightly closed and compact tips (Suslow
1998a,b). Spears are straight, tender, and glossy inappearance. Spears with green butts are preferredover the spears with white butts, as the latter areassociated with increased toughness. However, asmall 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
210

Grades, Sizes, and Packaging
Harvested spears are prepared for market by
grading, sizing, and bunching. Grades are basedon freshness, length and diameter of the stalks,color of spears, tightness of the spear tips, andthe 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 diameterare considered to be superior in quality with lessfiber (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 theirlength. After trimming the butt-end, the bunches
are packed upright in trapezoidal-shaped crates tominimize geotropic bending (curving away fromgravity) in transit. The container should include a
wet pad in contact with the butt end to maintainturgidity. Headspace is provided in the carton toprevent 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 partiallycooled 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

temperature is critical to delay senescence, tissue
toughening, and flavor loss (King et al. 1993).
High RH is essential to prevent desiccation and tomaintain freshness. Typically, asparagus is packed
and shipped with water-saturated pads in thebottom of the containers to maintain high RH andto replenish water lost by the spear or water usedduring spear elongation; this practice maintains
spear turgidity. Excessive free water at elevatedstorage or shipping temperatures may lead toincreased decay.

Controlled Atmosphere (CA)Considerations
Elevated CO2 at 5 to 10% is beneficial inpreventing decay and slowing tougheningof the spears. Short exposure to higher CO2
concentration is safe and beneficial only if thetemperature 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 comparedwith 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 firstobserved 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, andmay be used as an insect disinfestation treatment(Corrigan and Carpenter 1993).

Chilling Sensitivity
Asparagus is subject to chilling injury after about
10 days at 0 °C (32 °F). Symptoms include lossof 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 and3.1 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 onwhich 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 portionsof the stems (Saltveit and Kasmire 1985, Lill etal. 1990). Listed below are respiration rates of
asparagus spears held at 20 °C for various times:

Retail Outlet Display Considerations
Temperature
Asparagus is often displayed upright in shallow
trays containing chilled water. It will also tolerate
icing on retail displays. The preferred method tomaintain freshness at retail display is refrigerated
display with light misting.

Time after harvest (days)
0.25
1.0
mg CO2 kg-1 h-1
0 ºC
80		
60
5 ºC
145
105
10 ºC
305
215
15 ºC
325
235
20 ºC
500
270
Data from Lipton (1957).

3.0
40
65
120
160
185
211

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 growthand elongation. Tip bending occurs as the resultof upward growth of the tips when the spears
are horizontal. If spears are held in an uprightposition, tip bending may still occur if the tips
reach the top of the package and are physicallydeflected. 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 andChen 1999).
Spear Toughening. Tissue lignification andfiber development, which progresses from butt
to tip, cause spear toughening. It develops at >10°C (50 °F), rapidly above 15 °C (59 °F), and isaccelerated by ethylene.
Feathering. Feathering is the appearance of bractsof spear tips, which have opened due to outgrowthof the underlying buds. Tip feathering is a sign ofsenescence, often observed following extended
storage at higher than optimal temperature or
harvesting of overmature spears.
Freezing Injury. Water-soaked appearance andtissue softening occur at temperatures below -0.5
°C (31 °F).

found on the tips or the butts (Snowdon 1992,
Suslow 2001). Spears with green butts are more
susceptible to this decay than spears with whitebutts. Storing asparagus at <5 °C (41 °F) controls
this disease. In some production areas, the fungisuch as Fusarium, Penicillium, and Phytophthora
are associated with postharvest decay or spoilageof 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 foodservice product. There is limited minimal
processing of asparagus, but consumer-oriented
packing of tips is increasing.

References
Corrigan, V.K., and A. Carpenter. 1993. Effectsof 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 isoperoxidasechanges during fiber formation in postharvest
asparagus. J. Food Sci. 39:452-456.

Postharvest Pathology
The most prominent postharvest diseaseon 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
212

Hennion, S., C.H.A. Little, and C. Hartmann.
1992. Activities of enzymes involved inlignification during the postharvest storage of
etiolated asparagus spears. Physiol. Plant. 86:74478.

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. Optimizationof 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. 44:191199.
Lipton, W.J. 1990. Postharvest biology of fresh
asparagus. Hort. Reviews. 12:69-155.
Lipton, W.J. 1957. Physiological changes inharvested 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.

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 ofCalifornia 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.

Peirce, L.C. 1987. Vegetables—Characteristics,
Production, and Marketing. John Wiley & Sons,
New York, NY.

213

Atemoya

Precooling Conditions

Robert E. Paull and Nancy Jung Chen

Room or forced-air cooling to 10 to 13 °C (50 to
55 ºF).

Paull and Chen are with the Department of
Tropical Plant and Soil Sciences, University of
Hawaii at Manoa, Honolulu, HI.

Optimum Storage Conditions

Scientific Name and Introduction

Store at 10 to 13 ºC (50 to 55 ºF) with 90 to 95%
RH.

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 andPaull 1998). Favorable characteristics from thecherimoya include being heart shaped, having
few seeds, and having smooth skin that does notbreak apart during ripening. There are about six
varieties, with ‘African Pride’ and ‘Gefner’ being
the most common. Atemoya are grown in Florida
and Hawaii.

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.

Quality Characteristics and Criteria
Atemoya fruit should be heart shaped, preferablywith 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 leadto skin blackening.

Chilling Sensitivity

Horticultural Maturity Indices

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 byexposure to 100 µL L-1 for 24 h.

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 (10lbs) 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.
214

Atemoya fruit are very chilling sensitive, suffering
skin darkening and loss of aroma and flavor.
Ethylene Production and Sensitivity

Respiration Rates
Temperature
10 ºC
15 ºC
20 ºC

mg CO2 kg-1 h-1
48 to 190
54 to 281
40 to 460

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 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 (Sanewski1988).

Quarantine Issues
Atemoya fruit are a fruit fly host. Irradiation andheat are potential treatments.
Suitability as Fresh-Cut ProductAtemoya 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. TropicalFruits. CAB Intl., Wallingford, U.K.
Paull, R.E. 1996. Postharvest atemoya splitting
during ripening. Postharv. Biol. Technol. 8:329334.
Sanewski, G.M. 1988. Growing Custard Apples.
Information Series QI 87014, Queensland
Department of Primary Industries, Brisbane,
Queensland, Australia.
215

Avocado
Allan B. Woolf, Anne White, Mary Lu Arpaia, andKenneth C. Gross
Woolf and White are with the Mt. Albert ResearchCentre, 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. Departmentof Agriculture, Beltsville, MD. He is now retired.

Scientific Name and Introduction
The avocado originated in Central America andsouthern Mexico. The Aztecs considered the
avocado an aphrodisiac and called it “huacatl.” In
Chile, Peru, and Ecuador, it is called “palta,” anIncan name. Spanish-speaking people also call it“aguacate,” “cura,” or “cupandra.” The avocado
is known as “abogado” in Spain. Historically, theavocado has also been referred to as “alligator
pear,” “vegetable butter,” “butter pear,” and“midshipman’s butter.”
The avocado is botanically classified into threeraces: (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 (Berghand Lahav 1996). Many of the commercial
cultivars are hybrids of these three races. Thereis 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 somecultivars changes from green to black or purple
with increasing maturity or ripening.
216

Avocados are available year-round in the UnitedStates and are supplied by two major producing
areas: California (90%) and Florida (10%).
Fruit (mainly ‘Hass’) are also imported from (inapproximate order by volume) Chile, Mexico, theDominican Republic, New Zealand, Bahamas, andJamaica.
There are many cultivars of avocados growncommercially in the United States, and theycome 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 othercultivars 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 Guatemalanraces and hybrids) are ‘Simmonds,’ ‘Nadir,’‘Booth 8,’ ‘Choquette,’ and ‘Lula.’

Quality Characteristics and Criteria
For avocado, the major quality criteria usedduring 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), andother contaminants on the skin. When ripe, thekey issues are absence of disease (body rot andstem end rots), physiological disorders (flesh
graying), and physical damage (bruising). Manyof these quality factors depend on the cultivar, andconsumer preference for size, shape, and color canvary 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 adesirable nutlike flavor and a richer, creamier
texture than the less oily Florida fruit, which are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 containsignificant quantities of oil; sometimes more than
30% of fresh weight, depending on cultivar andmaturity. 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 ofcholesterol, should be emphasized with consumers
since avocados are perceived by some as an
unhealthy or “fat” fruit. Extraction of oil fromreject avocados is carried out in some countries
for use in cosmetic products and for culinary
purposes.

(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; andSize 70 or smaller, January 16. Florida avocados
have lower oil content (3 to 15%) and are
generally harvested at a specific date and weightor 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 timeon the tree. Freshly harvested avocados tend tohave “green” skins, though ‘Hass’ fruit that are
harvested late in the season may have some skindarkening 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 arecultivar specific.
Grades, Sizes, and Packaging

Traditionally, fruit produced in the United States
have been “clip” harvested (peduncle cut to leavea “button” at the top of the fruit). However otherproducing countries (Australia, Israel, Spain, andSouth 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 matterat harvest for the major cultivars are ‘Bacon’(17.7%), ‘Fuerte’ (19.0%), ‘Gwen’ (24.2%),‘Hass’ (20.8%), ‘Pinkerton’ (21.6%), ‘Reed’

California avocados are packed in single-layer
12.5 lb (5.67 kg) flats or trays, 2-layer 25 lb (11.34kg) lugs, and 25 lb (11.34 kg) volume-fill boxes.
RPCs (returnable plastic containers) are used
increasingly. There is also increased usage ofprepacked 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 (12.47kg) lugs; 35 lb (15.88 kg) cartons; and 10 lb (4.54kg) 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
217

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 269g), 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 thesevalues for flats (or single-layer trays). Florida
fruit are packed by count. Regulations specify thatthe pack shall be at least fairly tight and that theweight of the smallest fruit in any container shallnot be less than 75% that of the largest fruit in thesame container. Commonly used sizes for Florida
packages are 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, and24 count.

Precooling Conditions
Ripening and associated softening of avocados
can be delayed by cooling soon after harvest. Thisis critical where long storage periods are requiredor 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 theemphasis on whether fruit should be graded withcondensation or not.

Optimum Storage Conditions
Optimum storage conditions vary by cultivar,
growing conditions, time in the season (maturity),and length of storage required. However, ingeneral, 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 achallenge.
Increased physiological disorders—for example,
chilling disorders and uneven ripening—and rots
218

result from suboptimal storage temperatures.
Therefore, it is important to maintain theappropriate temperature for unripe fruit and stack
containers to allow for proper air circulation andtemperature 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 thatof delayed softening and reduction of respirationand ethylene production from standard storage
temperatures. Elevated CO2 may delay softening
and reduce sensitivity to external chilling injury
and allow lower storage temperatures (Faubion etal. 1992). Low-O2 injury may appear as irregularbrown to dark brown patches on the skin andmay additionally cause diffuse browning offlesh beneath affected skin. CO2 atmospheres
above 10% can be detrimental by leading todiscoloration of the skin and development of off
flavor, particularly when the O2 concentration isless than 1%. Reducing ethylene levels to below 1µL 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. Applicationof 1-MCP to avocados delays ripening and thus
reduces internal chilling injury (flesh graying,vascular browning), which is associated withripening during storage if storage times are longor temperature management is poor (Pesis etal. 2002). The optimum treatment conditions
are likely to be in the area of 50 to 100 nL L-1

(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 ofinternal chilling injury at even short storage times,
1-MCP may be of more benefit. Care should betaken because applying higher concentrations
may result in excessive delays to softening andripening, 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 Africanindustry, is the use of “step-down” temperatures(Vorster et al. 1987). Temperatures are typicallydecreased 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. Thesetemperature regimes have been developed andrefined over many years and have resulted in a
protocol for each cultivar for differing times in theseason 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, unevenripening of the flesh, and off flavors. As forbananas, ethylene treatment can be used to“precondition” or “preripen” fruit. Avocados arevery susceptible to bruising during softening(Arpaia et al. 1987) and thus should be handled
carefully during transport and display. Any meansof minimizing “squeezing” by customers will
also improve quality. Since quality can decrease
rapidly during softening, it is best to checkavocado 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 andother disorders. Avocados should not receive awater 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 baseof the fruit around the seed. This can be associatedwith vascular browning, which starts at the baseof the fruit (rather than at the stem end, which isoften 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 fordifferences in internal chilling injury (Chaplin and
Scott 1980). Another low-temperature disorder,“pulp spot,” may be observed in ‘Fuerte’ fruitin 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 toapple scald) that can be observed during storage
but that generally increase slightly in intensity
after removal from cold storage. The damage isfirst seen in inner cell layers of the exocarp andthen 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 lessaffected. Fruit exposed to low temperatures may
219be of poor internal quality when ripe, with a highincidence 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 thatis 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 fromstorage.

Ethylene Production and Sensitivity
Rates of ethylene production are generally low
for unripe avocados, less than 0.1 μL kg-1 h-1 at 20ºC (68 ºF), but increase rapidly after harvest up tolevels 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 producethat produces more than trace ethylene. Ethylene
exposure during storage accelerates ripening andsoftening and can increase incidence and severityof internal chilling injury and decay.

Ethylene Treatment (“Preconditioning” or“Preripening”)
There is an increasing move at the retail leveltoward “ripe for tonight” programs that generally
result in significant increases in sales. This isachieved by treating avocados with 10 to 100µL 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). Thissignificantly reduces both the time to ripen (to 3to 6 days, depending on cultivar and maturity)and fruit-to-fruit variability in ripening. If fruit are
stored prior to ethylene treatment, the duration oftreatment required to achieve maximum rate ofripening is reduced. For ‘Hass,’ after 3 to 4 weeks
of storage, there may be relatively little benefit toethylene treatment (particularly for later-season
220

fruit), since the time to ripen decreases duringstorage. 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 bemaintained at less than 1 to 2% by either continual
venting of the atmosphere or full venting andethylene 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 highcompared 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 rateby 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 theseoccur 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, theflesh may also fail to ripen evenly and become
increasingly susceptible to pathogens. The timingof expression of internal chilling injury and its
severity depend on temperature management,initial ripeness, cultivar, production area, and fruit
maturity. External chilling injury may occur if
fruit are stored at low temperatures (0 to 3 °C [32to 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 associatedbrowning of the vascular strands (Johnson andKotze 1994). Body rots invade through the skinand 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. Rotsare rarely observed at harvest or during storage but
can increase rapidly with fruit softening. Where
infection pressure is high and physical damage tothe skin occurs prior to storage, small, soft-black
circles of infection (“measles”) can occur duringstorage. 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, andPhomopsis spp. (Smilanick and Margosan 2001).
Differences in the pathogens responsible for decay
exist among countries; for example, New Zealandversus Australia (Everett 1996, Arpaia et al. 2009).
Preharvest control methods for postharvest fungal
decay include good orchard sanitation (removalof 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, andcareful handling to minimize skin damage helps

reduce rots. Snap picking of fruit can reduce stemend rot incidence in dry periods, but it can resultin increased rots in humid growing environments
or when fruit are harvested in wet conditions.
Perhaps the most important area for reducing rotsis that of maintaining good ripe-fruit quality by
optimizing temperatures during handling, storage,transport, and ripening. It is also critical not tostore 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], andthiabendazole) are used in some countries, butthese are not registered for use in the UnitedStates (Darvas et al. 1990). Research on biologicalcontrol 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, andguidance should be sought from the Departmentof Agriculture. If avocados are grown in fruit-flyinfested areas, significant quarantine issues willarise. 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, (forexample, fruit core temperatures of 47 °C [117°F] for 20 min), low-temperature disinfestationis the most viable approach. Tolerance totemperatures 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, theonly commercial disinfestation treatment in use isfor 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.
221

2003). However, this low-temperature disinfestingtreatment may not be effective for all fruit fly
species, since cold tolerance varies.

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.

Suitability as a Fresh-Cut Product

Chaplin, G.R., and K.J. Scott. 1980. Associationof calcium in chilling injury susceptibility instored avocados. HortScience 15:514-515.

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 theprevious 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); theMichigan 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 theirappreciation 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 tomechanical damage as influenced by variety,maturity, and stage of ripeness. Proceedings ofWorld Avocado Congress, May 1987, Pretoria,
Republic of South Africa. South African Avocado
Growers’ Association Yearbook 10:149-151.

222

Chaplin, G.R., R.B.H. Wills, and D. Graham.
1983. Induction of chilling injury in storedavocados with exogenous ethylene. HortScience
18:952-953.
Darvas, J.M., J.M. Kotze, and F.C. Wehner.
1990. Effect of treatment after picking on theincidence of postharvest diseases of avocado.
Phytophylactica 22:93-96.
Everett, K.R. 1996. Postharvest diseasesof 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 atmosphereconditions. In C.J. Lovatt, and P. Holthe, eds.,
Proceedings of 2nd World Avocado Congress,
Orange, CA, April 1991, pp. 467-472. Universityof 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.

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.

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.

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. 15:6395.
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2009. The International Avocado Quality
Manual, 70 pp., University of California, Davis,
CA.
223

Banana and PlantainHorticultural Maturity Indices

Eduardo Kerbel

Commercially, bananas and plantains must be
harvested while mature green and transported todestination markets where they are ripened undercontrolled 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 yieldand harvesting it soon enough so that sufficientgreen 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 themarketable 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 ofthe 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 ofhands in a stem varies, those hands at the proximal
end of the stem being more mature than thoseat the distal end. An estimate of maturity of theentire stem is then assessed using the second handfrom the proximal end. It is usual to measurelength and diameter (caliper grade or calibration)of the middle finger on outer whorls of the second
hand on the stem before running fruit through thepacking plant processes.

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 the1940s, the cultivar ‘Gros Michel’ dominated theinternational banana trade until it succumbed toFusarium wilt (Panama disease). Since the 1940s,
the trade has adopted cultivars of the Cavendish
subgroup. Bananas are eaten mainly raw as adessert fruit because they are sweet when ripe.
Plantains, also referred to as “cooking bananas,”
are much starchier and can be eaten either ripeor unripe. The edible cultivars of bananas andplantains are seedless. The two obvious tissues
that constitute the fruit are the pulp and the peel.
The peel is the ovary wall. The pulp originatesfrom 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 thepulp continues. Consequently, peel splitting often
occurs in very mature green fruit (Turner 1997).

Quality Characteristics and Criteria
A premium quality banana is very clean (freefrom 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 andsensory attributes in flavor (sweetness and acidity)
and aroma. Attributes are defined by consumer
preference.

224

Grades, Sizes, and Packaging
Minimum acceptable size (length and diameter)
grade standards for export markets vary dependingon 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 arepacked in corrugated fiberboard boxes as wholehands, clusters, or individual fingers holding an
average weight for premium fruit between 13
and 18 kg (28 to 40 lb), depending on market

preference. Plantains are packed as individual
fingers in 18 kg boxes. Most exporters use
polyethylene film liners and paper pads to reducemoisture loss and protect fruit from physicaldamage 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 holdingof green bananas are 13 to 14 ºC (56 to 58ºF) (Thompson and Burden 1995). Because
marketing quality standards are more relaxed
for plantains, and plantains are more prone topremature 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 attainphysiological 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 ofripe fruit should be kept to a minimum.

a much fresher condition (latex flowing throughthe vascular tissues) on arrival at destination.
Shelf-life can potentially be extended twofoldto 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 levelsof CO2.
The beneficial and detrimental effects of reduced
O2 and/or elevated CO2 depend on temperatureand time of exposure. Removal of ethylene gas
can have an additional benefit on extending
green-life of bananas and plantains under bothambient and modified atmosphere conditions(Scott et al. 1970, Liu 1976, Scott 1977, Turner1997). 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 withfresh 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).

Controlled Atmosphere (CA)Considerations
Retail Outlet Display Considerations
Bananas and plantains respond well to CA. CA
is used commercially during ocean transport ofgreen bananas. Modified atmosphere packaging
using polyethylene bags (banavac) is used forboth bananas and plantains, but plantain are
physiologically more active than bananas andhave higher respiration rates and so could exhaustO2 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 benefitsof controlled atmosphere include delaying ofripening, reduction of crown rot incidence, andFruit should be displayed at retail in
nonrefrigerated areas in the produce section.
Existing refrigerated shelf space in supermarkets
normally is below the minimum safe temperaturefor bananas and plantains and chilling injury canstill occur in ripe fruit. Displaying surfaces should
be cushioned to avoid physical damage to thefruit.

225

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, Turner1997). Chilling injury is mainly a peel disorder.
Symptoms include subepidermal discoloration
visible as brown or black streaks in a longitudinalcut, 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 canturn brown and develop an off taste (John andMarchal 1995, Turner 1997). Chilled fruit are
more sensitive to mechanical injury. Ripe fruit,
if chilled, turn dull brown when later exposed tohigher temperatures and are very susceptible tohandling 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 tophysiological 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 toexternal ethylene are fruit maturity, time fromharvest when ethylene exposure began, and lengthof exposure to ethylene.
Ethylene production rates:
Temperature
μL C2H4 kg-1 h-1
13 ºC
0.04 to 2.015 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).
226

Controlled ripening. Mature bananas left to ripen
naturally will eventually soften, but the change incolor 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 byreleasing ethylene into a sealed chamber or room
and at controlled temperature and RH. Plantains
are being ripened by this controlled method inmost 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 isto provide retailers and wholesalers with fruit at astage 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 commonlyused 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 cultivarsof 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) aresometimes 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 beattained when the fruit is being packed in partiallysealed polyethylene liners. Exposure of ripebananas or plantains to temperatures higher thanthose 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 isdark green, 2 is light green, 3 is more green thanyellow, 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

1% and avoid its effects on delaying ethylene
action. Use of a forced-air system (pressurized)
in ripening rooms assures more uniform coolingor 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 isessential to allow adequate air circulation foruniform ripening. Many stacking patterns areused and the best pattern to be used depends onpallet sizes and ripening facilities. Because heatrises, the amount of box-op area exposed is mostimportant for preventing heat buildup in the stackand controlling pulp temperature during ripening.
Bananas are usually ripened to color stage 3 to 4
before delivery to distribution centers, retailers, orwholesalers.
Within certain limits, the period required forripening bananas can be shortened or extended
to meet trade requirements by adjusting thetemperature. Under average conditions, depending
on initial temperatures chosen and condition of
the fruit, the ripening cycle can be as short as 4days (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 describedas “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 thegrowing of the fruit, temperatures during handlingand transit, and maturity of the fruit. Hard-green
fruit (less full) will take longer to ripen than moreadvanced 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 theyear, 20 to 30 days before harvest (Stover andSimmonds 1987). The fruit is unacceptable formarket, although eating quality is unaffected. Thisdisorder has been associated with water deficits atbunch emergence during rapid fruit growth undervery humid and hot conditions (Daniells et al.
1987, Williams et al. 1989, 1990). If bananas andplantains are exposed to temperatures above 30 to
35 ºC, ripening can be irreversibly inhibited (hightemperature injury).

Postharvest Pathology
The main postharvest diseases of bananas andplantains are crown rot—a disease complex
caused by several fungi (Colletotrichum musae,
Fusarium semitectum, Fusarium pallidoroseum,
Lasiodiplodia theobromae, Botryodiplodia
theobroame, Ceratocystis paradoxa, Verticilliumsp., Acremonium sp., and Curvularia sp.)—andanthracnose (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 becomes227

brown, soft, and water-soaked, and cigar-endrot (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 potentialof this fungal disease is such that a flourishingbanana industry can be destroyed within a few
years. Fruit symptoms include premature ripening,buff-colored pulp, and increased susceptibility tochilling injury. Preventive and control measures toreduce decay incidence begin with strict sanitationin plantation and packing plant, postharvest
treatment with systemic fungicides, minimizing
mechanical damage during handling, prompt
cooling of fruit to lowest safe temperature, andexpediting transport to final destination.
Quarantine Issues

Acknowledgments
Some of the information in this chapter was fromthe 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 mechanicaldamage. M.Sc. (Agric) Prelim. Report, Universityof Western Australia, Perth, Australia. Unpublishedreport.
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, andJ.C. Mulder. 1987. Soil water stress at bunchemergence increases maturity bronzing of banana
fruit. Queen. J. Agric. An. Sci. 44:97-100.

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 andMarchal 1995).

Special Considerations
Mechanical damage in bananas and plantains takes
several forms that vary in importance dependingon 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 forplantains. Great care during handling is needed at
all times. Bruising of the pulp is undesirable andcannot always be detected from damage to the peel
(Akkaravessapong 1986). RH levels below 85 to
90% accentuate symptoms of mechanical damage.
228

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 andbiochemistry of the fruit. In S. Gowen, ed.,Bananas and Plantains, pp. 434-467. Chapman andHall, London, U.K.
Kader, A.A., ed. 1992. Postharvest Technology of
Horticultural Crops. Pub. no. 3311, University ofCalifornia, 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 Handlingof Tropical Fruits, Chiang Mai, Thailand, July
1993, pp. 239-249. ACIAR Proceedings no. 50,
ACIAR, Canberra, Australia.

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 theinitiation 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 ripeningof 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 thebanana fruit. Tech. Bull. 38, ASPAC Food andFertilizer 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 andDisorders 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 andHall, 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 (MusaAA). 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 theEuropean Communities, Leuven, Belgium.
Williams, M.H., M. Vesk, and M.G. Mullins.
1989. Characteristics of the surface of banana peelin 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 ofthe maturity bronzing disorder. Ann. Bot. 65:9-19.

229

Bean

Grades, Sizes, and Packaging

Marita Cantwell

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 thecharacteristics 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 forfoodservice are available in 4.5 kg (10 lb) bags.

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 longbeans (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, brightin 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 breakeasily when the pod is bent, giving off a distinct
audible snap. Poor quality is most often associatedwith 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 seeddevelopment reduces quality and the pod becomespithy and tough and loses its bright color.

230

Cooling
Snaps beans can be hydrocooled. This isespecially 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 havebeen packed. Efficient cooling is achieved withoutleaving 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 (41to 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 fora few days at temperatures below 5 °C (41 °F),
but chilling injury will be induced (see Chilling
Sensitivity). Some chilling may occur even at therecommended 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 toyellowing, seed development, and water loss.
Waxed cartons and plastic film liners reduce water
loss. The perishability and rates of water loss ofimmature beans are higher than for mature beans.
Long beans have postharvest requirements similar
to those of snap beans with similar responses tochilling (Zong et al. 1992).

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% withretention of color, reduced discoloration, andreduced 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 shortperiods (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 theentire 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 attackby 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 ofethylene (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 andhave 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 rateby 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.

231

Postharvest Pathology
Various decay organisms may attack fresh podbeans 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. andRhizopus spp), gray mold (Botrytis cinerea), andwatery soft rot (Sclerotinia spp.). Water-soaked
spots may be due to lesions caused by bacterial
infections (Pseudomonas spp. and Xanthomonasspp.) (Snowdon 1992).

Quarantine Issues
None.

Suitability as Fresh-Cut Product
Beans are snipped to remove stems and tails forfood service. Browning of the cut ends can bea problem, and high-CO2 atmospheres retard
discoloration.

Special Considerations

California, Davis, July 13-18, 1997, vol. 4, pp. 4652. 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 107:271273.
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. Departmentof 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.

Extra careful and expedited postharvest handlingare required for highly perishable, very fineFrench beans (haricot verts) to avoid physicaldamage and dehydration.

Sargent, S.A. 1995. Optimizing packing andcooling 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.

References

Snowdon, A.L. 1992. A Color Atlas of Postharvest
Diseases and Disorders of Fruits and Vegetables,
vol. 2, Vegetables. CRC Press, Boca Raton, FL.

Boyette, M.D., J.R. Schultheis, E.A. Estes,
and W.C. Hurst. 1994. Postharvest cooling andhandling 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 onchlorophylls and carotenoids changes in green
beans (Phaseolus vulgaris L., cv. Perona). In
M.E. Saltveit, ed., 7th International Controlled
Atmosphere Research Conference, University of232

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.

Watada, A.E., and L.L. Morris. 1966b. Effect ofchilling and nonchilling temperatures on snap
bean fruits. Proc. Amer. Soc. Hort. Sci. 89:368374.
Wills, R.B.H., and G.H. Kim. 1996. Effect ofethylene 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.

233

Beet
Franciszek Adamicki
Adamicki is with the Department of Vegetable
Storage, Research Institute of Vegetable Crops,
Skiermiewice, Poland.

0.5 kg (1.1 lb) and must contain at least 3 beets.
Fresh-market bunches are packed in small cratesof 10 to 15 kg (22 to 33 lb) capacity, whereas
beets intended for storage are packed in 20 kg (44lb) polyethylene-lined crates or bins of 500 to 600
kg (1,100 to 1,320 lb) capacity.

Precooling Conditions
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 earlystages of plant development, the whole plant may
be consumed. Beets are grown worldwide, the top
producers being Germany, Poland, the RussianFederation, and the United States.

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

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 withminimum zoning is the most important quality
criterion.

Horticultural Maturity IndicesFresh-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, especiallywhen 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. Unlessotherwise specified, the diameter of each beetshall 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
234

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 keepmuch 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) andtrenches is needed to avoid injurious temperaturefluctuations. The temperature in pits (clamps) andcellars should not drop below -0.5 °C (31 °F) or
exceed 5 °C (41 °F) to minimize losses caused byfreezing, sprouting, and rotting.

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).

Physiological Disorders
Death of shoots and breakdown of the top partof 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 Badełek1997).

Retail Outlet Display Considerations
Postharvest Pathology
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.

The most common decay during storage is graymold (Botrytis cinerea Pers.) (Robak and Wiech
1998). Beet roots are also affected by black rot
caused by Phoma betae Frank. Water-soaked andbrown lesions become black and affect mostly the
tip of the root. Good air circulation and optimal
storage conditions retard development of blackrot.

Quarantine Issues
Ethylene Production and Sensitivity
None.
Beet roots produce very low amounts of ethylene,(<0.1 µL kg-1 h-1) and are not particularly sensitive
to ethylene exposure.

Suitability as Fresh-Cut ProductNo current potential.

Respiration Rates
Temperature mg CO2 kg-1 h-1
0 °C
4 to 65 °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 rateby 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.

References
Adamicki, F., and E. Badelek. 1997. The effect oftemperature and size of roots on storage and shelflife of red beet. Research Report of the ResearchInstitute of Vegetable Crops, pp. 10. The Ministryof 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 46:6578.

235

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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Robak, J., and K. Wiech. 1998. Diseases and Pestsof 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 andVegetables, vol. 1, 2nd ed. AVI Publishing Co.,
Westport, CT.
Schouten, S.P., and A.C.R. Schaik. 1980. Storageof red beets. Acta Hort. 116:25-29.
Shipway, M.R. 1968. Refrigerated Storage of Fruitand 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 andtransport 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 inforced ventilated clamps in comparison with longterm storage in mechanical cooling. Acta. Hort.
267:163-168.

236

Blackberry

Horticultural Maturity IndicesPenelope Perkins-Veazie

For the fresh market, blackberry maturity canbe determined by fruit color, gloss, and easeof detachment. Fully black berries should pull
easily from the pedicel yet be firm, not mushy.
Blackberries lose acidity with ripening and arequite 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.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof 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 toa 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 theSouth Central and Northwestern United States
and are found as three plant types. Trailingblackberries and dewberries are thorny and mustbe 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 withlateral 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 blackin color, appear and feel turgid, and are of regularshape. To meet U.S. No. 1 grade standards, nomore than 1% of the lot can be affected by moldor decay and no more than 5% can have otherserious damage.

Grades, Sizes, and Packaging
Generally, containers of 1 to 2 pints are used, but
1-quart containers occasionally are used. The mostcommon packaging is vented plastic “clamshell”
boxes packed in units of 12 per carton.

Precooling Conditions
Forced-air cooling to 5 ºC within 4 h isrecommended for best shelf-life. Blackberries
should be shipped with refrigeration attemperatures under 5 ºC. A similar protocol isused 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), withhigher 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).

237

Retail Outlet Display Conditions
Blackberries should be stored and displayed at thecoldest refrigeration temperature possible and withno mist. As little as 1 day at room temperature canstimulate growth of gray mold.

juice) (Perkins-Veazie et al. 1996, Mitcham et al.
1998).

Postharvest Pathology

Chilling Sensitivity

The most common postharvest diseases are graymold (Botrytis cinerea) and rhizopus rot (Rhizopus
stolonifer) (Jennings 1988, Ellis et al. 1991).

Blackberries are not known to be chilling
sensitive.

Quarantine Issues
No known issues.

Ethylene Production and Sensitivity
Stimulation of Botrytis cinerea (gray mold)growth can occur on blackberries in the presenceof 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.

Suitability as Fresh-Cut ProductBlackberries are incorporated into fruit cups andfruit plates.

Special Considerations
Blackberries are easily damaged. They candevelop 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. Fruitabscission 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 Raspberryand Blackberry Diseases and Insects. APS Press,
St. Paul, MN.

Physiological Disorders

Jennings, D.L. 1988. Raspberries andBlackberries: Their Breeding, Diseases, and
Growth. Academic Press, New York, NY.

The major disorders are red drupelet disorder(areas of red drupelets on fully ripe berry), weightloss (shrivel), and leakers (berries with leakage ofKader, A.A. 1997. A summary of CA requirements
and recommendations for fruits other than apples
and pears. In A.A. Kader, ed., 7th International

238

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.

239

Blueberry

Quality Characteristics and Criteria

Penelope Perkins-Veazie

High-quality blueberries are free of injury, decay,and sunscald. They are are fully blue in color, withlittle or no red at the stem end, and appear and feel
turgid.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof Horticultural Science, North Carolina State
University, N.C. Campus, Kannapolis, NC.

Horticultural Maturity Indices
For fresh market, fruit should be fully blue andfirm.

Scientific Name and Introduction
Blueberries (Vaccinium sp.) are a member of theheath 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 incolor. Blueberries of commercial importanceinclude 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 than1 g) than highbush types and are prized for theiruse 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 andrequire 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 tofrost 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 orwhere 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 andmore pigment than highbush berries.

240

Grades, Sizes, and Packaging
Highbush blueberries are graded as U.S. No. 1 orare 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 percup, medium is 130 to 189 berries per cup, andsmall 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, thenmaintained under refrigeration at 0 to 3 °C (32to 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 whendelays 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 southernhighbush (Perkins-Veazie et al. 1995, Jackson etal. 1999) and up to 4 weeks for rabbiteye (Miller
et al. 1988).

Controlled Atmosphere (CA)Considerations
Rabbiteye, highbush, and lowbush blueberries
benefit from 10 to 15% CO2 + 1 to 10% O2 whenheld at or below 5 ºC (41 °F) (Smittle and Miller
1988, Prange et al. 1995). Firmness and total
acidity were maintained and decay decreased witha shelf-life up to 6 weeks.

Retail Outlet Display Considerations
Blueberries should be stored and displayed underrefrigeration with temperatures as close to 0 °C
(32 °F) as possible.

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
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 to2 µL kg-1 h-1 for northern highbush, varying withyear and cultivar (Suzuki et al. 1997), to 10 µL
kg-1 h-1 for rabbiteye blueberry (El-Agamy et al.
1982)

Blueberry maggot (Rhagoletis mendax Curran) is
the primary postharvest pest limiting shipmentsof unfumigated blueberries to Canada and Stateswest 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 ProductFruit can be incorporated into fruit cups andprepared fruit trays.

Respiration Rates
Special Considerations
Temperature
0 ºC
4 to 5 ºC
10 ºC
15 to 16 ºC
20 to 21 ºC
25 to 27 ºC-1-1

mg CO2 kg h
2 to 109 to 1223 to 35
34 to 62
52 to 87
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.

Bruising caused by improper handling or
mechanical harvesting reduces the storage lifeof fresh fruit. Mechanical harvesting can reduce
fruit storage life by half compared with hand
harvesting.

Acknowledgments
Some of the information in this chapter was fromthe Produce Marketing Association’s “Fresh
Produce Manual” and the University of California,
241

Davis, website “Fresh Produce Facts” at http://postharvest.ucdavis.edu/produce_information.

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.

References
AMS [USDA Agricultural Marketing Service].
1966. United States Standards for Grades ofBlueberries. 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 asinfluenced by weekly harvests, cultivars, andstorage 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 PhytopathologicalSociety, 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 andBlomidon lowbush blueberries: effects of storage
atmosphere, duration and fungal inoculation. Can.
J. Plant Sci. 75:479-483.
242

Smittle, D.A., and W.R. Miller. 1988. Rabbiteye
blueberry storage-life and fruit quality incontrolled 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 respirationin fruits of highbush blueberry. J. Japan. Soc.
Hort. Sci. 66:23-27.

Bok Choy

Optimum Storage Conditions

Yaguang Luo

The recommended storage conditions for bok
choy are 0 to 5 °C (32 to 41 °F) with higher than
95% RH.

Luo is with the Food Quality Laboratory, Henry A.
Wallace Beltsville Agricultural Research Center,
Agricultural Research Service, U.S. Departmentof 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 thethick, chalk-white stalks (Peirce 1987). Most U.S.
bok choy is produced in California.

Quality Characteristics and Maturity
Indices

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 senescenceduring 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

High-quality bok choy has thick, fleshy, firmstalks and glossy, dark-green leaves. Bok choywith bruised or slimy spots and wilted leaves
should be avoided.

Bok choy is not chilling sensitive and should be
stored as cold as possible without freezing. It
freezes at -0.5 °C (31 °F).

Grades, Sizes, and Packaging

Ethylene Production and Sensitivity

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.

Bok choy produces very small amounts ofethylene, 0.1 to 0.2 µL kg-1 h-1, and is not overly
sensitive to ethylene.

Respiration Rates
Precooling Conditions
Prompt precooling to near 0 °C (32 °F) is
important to maintain freshness and for extended
storage.

Temperature
mg CO2 kg-1 h-1
0 °C
5 to 65 °C
10 to 12
10 °C
19 to 2115 °C
34 to 44
20 °C
48 to 63
Data from Luo and Zheng (2001).

243

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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. Storingbok choy at 0 to 5 °C (32 to 41 °F) will mitigate
this problem.

Quarantine Issues
None.

Suitability as Fresh-Cut ProductNo 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 rateand 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 wholeand minimally processed pak choi. Australasian
Postharvest Horticulture Conference, pp. 459-462.

244

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 andchlorophyll content of Chinese mustard. In E.
Kupferman, and M. Patterson, eds., Proceedingsof the 5th International Controlled Atmosphere
Research Conference, vol. 2, pp. 9-17. Wenatchee,WA.

Breadfruit

drain from the fruit after harvest before washing inwater to avoid latex stain.

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 wholeinflorescence 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 tropicalbreadfruit 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, andmechanical damage.

Horticultural Maturity Indices
Fruit at different growth stages are harvested for
different uses. Mature green fruit are harvested asa 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 bylarger size, a slight change in the skin color to ayellowish 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

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 andrubbing 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 itleads 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 skindiscoloration of breadfruit stored at 13 ºC (55ºF) (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.

245

Chilling Sensitivity
Long-term storage is not possible. At 12 ºC (54ºF), chilling injury symptoms begin to develop
within 7 days (Marriott et al. 1979). Symptoms area brown, scaldlike discoloration of the skin, failure
to fully soften, poor flavor development, and anincrease in decay.

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 beensuccessfully treated by vapor heat treatment andirradiation.

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.

Suitability as Fresh-Cut ProductPossibly, but no products have yet beendeveloped.

Special Considerations
Respiration Rates-1-1

Temperature
mg CO2 kg h
13 ºC
94 to 564
25 ºC
362 to 597
Data from Worrell and Carrington (1997) andWorrell et al. (1998).

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 arealso eaten.

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..

References

Physiological Disorders

Bennett, F.D., and C. Nozzolillo. 1987. How many
seeds in a seeded breadfruit. Econ. Bot. 41:370374.

Mechanical injury leads to rapid deterioration,
possibly due to wound ethylene inducing
premature and more rapid ripening. No otherdisorders have been reported (Worrell and
Carrington 1997).

Bates, R.P., H.D. Graham, R.F. Matthews, and
L.R. Clos. 1991. Breadfruit chips: preparation,
stability, and acceptability. J. Food Sci. 56:16081610.

Marriot, J., C. Perkins, and B.D. Been. 1979.
Some factors affecting the storage of fresh
breadfruit. Sci. Hort. 10:177-181.

Postharvest Pathology

Nakasone, H.Y., and R.E. Paull. 1998. TropicalFruits. CAB Intl., Wallingford, U.K.

Fruit rot due to Phytophthora palmivora and pink
disease (Botryobasidium salmonicola) have been

Purseglove, J.W. 1968. Tropical Crops.
Dicotyledons. Longman, London, U.K.

246

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 andStorage of Breadfruit in Refrigerated andControlled 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 ofbreadfruit 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 ofbreadfruit, Artocarpus altilis (Park.) Fosb. Sci.
Hort. 76:17-28.

247

Broccoli

Grades, Sizes, and Packaging

Peter M.A. Toivonen and Charles Forney

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 stalkdiameter (AMS 1943). Two or three heads arenormally 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.

Toivenen is with Pacific Agri-Food ResearchCentre, Agriculture and Agri-Food Canada,
Summerland, British Columbia, Canada; Forney
is with Atlantic Food and Horticultural ResearchCentre, 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 anative of southern Europe and a member of theBrassicaceae (Cruciferae) family. The crop isannual and grows to maturity in about 75 to 95
days, depending on cultivar, season, and planting
date. The whole immature influorescence (head) isthe edible portion, with the floret tissue most often
preferred by consumers. It grows best in coolclimates and is available year-round from many
areas of North America, though a large portion isgrown in California.

Quality Characteristics and Criteria
High-quality broccoli is either a dark or brightgreen with closed flower buds (termed “beads”).
The head should be firm to hand pressure
and compact, and the stalk cleanly cut to theappropriate length for a particular grade standard
or for “crowns” (dissected portions of the wholeinfluorescence).
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.

248

Precooling Conditions
Field-packed broccoli is commonly cooled byinjecting 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 isrequired 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 transportconditions cannot maintain the recommended
temperature or RH (Shewfelt et al. 1983). Useof 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, yellowingof buds and leaves, loosening or opening of buds,
and decay.

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 maintainboth O2 and CO2 at 10% to prevent accumulationof off odors.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
20 to 225 °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 rateby 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.

Retail Outlet Display Considerations
Physiological Disorders
Bottom-icing of the refrigerated display will
prolong shelf-life (Perrin and Gaye 1986). Mistingof 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).

Bead (bud) yellowing may occur in overmaturebroccoli when stored at higher-than-optimal
temperatures or in response to exposure to
ethylene. Presence of yellow beads ends thecommercial marketability of broccoli. Thereis 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 themost commonly reported mold in shipped broccoli(Ceponis et al. 1987). Erwinia carotovora (Jones)
Bergey et al. and Pseudomonas spp. bacterial headrots are found on shipped and stored broccoli.
Injury to the bead tissue during handling may
enhance development of these rots (Liao andWells 1987). While Erwinia carotovora decay
seldom develops below 5 °C (41 °F), decay caused249

by Pseudomonas spp. can be severe (Liao andWells 1987) since it grows relatively well evenat low storage temperatures (Brocklehurst andLund 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

Barth, M.M., A.K. Perry, S.J. Schmidt, and B.P.
Klein. 1992. Misting affects market quality andenzyme 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 andvegetables. 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 ofvegetables stored at low temperature. J. Appl.
Bacteriol. 50:259-266.

Broccoli is commonly converted to fresh-cut floret
products. Stems are also shredded into a packaged
coleslaw-type product.

Canaday, C.H., J.E. Wyatt, and J.A. Mullins. 1991.
Resistance in broccoli to bacterial soft rot causedby Pseudomonas marginalis and fluorescent
Pseudomonas species. Plant Dis. 75:715-720.

Special Considerations

Cantwell, M., and T. Suslow. 1999. Broccoli:
recommendations for maintaining postharvest
quality. At http://postharvest.ucdavis.edu/produce_
information.

Some cultivars have greater storage life potential
than others (Cantwell and Suslow 1999). If
long-distance shipping or storage is integral toa marketing strategy, then consideration should
be made for appropriate cultivar selection,
especially if controlled atmospheres are notbeing used. Freezing injury may occur duringliquid-ice cooling if excessive salt is used in theslurry mixture or if the broccoli is stored below-1 ºC (30 ºF). Thawed buds will be very dark andtranslucent and can later turn brown or may serve
as sites for development of bacterial decay. Roughhandling during harvest and packing can damage
floret tissue and lead to increased levels of decay.
Hot-water dips prolong shelf-life (Forney 1995).

Ceponis, M.J., R.A. Cappellini, and G.W.
Lightner. 1987. Disorders in cabbage, bunchedbroccoli, and cauliflower shipments to the New
York market, 1972-1985. Plant Dis. 71:1151-1154.
DeEll, J., and P. Toivonen. 1998. Characterizationand control of black speck in broccoli. Agricultureand Agri-Food Canada, Horticulture Research andDevelopment Centre Research Summary 1997/98,
p. 9. Agriculture and Agri-Food Canada, Quebec,
Canada.

References

Forney, C.F. 1995. Hot-water dips extend theshelf-life of fresh broccoli. HortScience 30:10541057.

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.

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.

250

Gillies, S.L., and P.M.A. Toivonen. 1995. Coolingmethod influences the postharvest quality ofbroccoli. 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 ofpectolytic, 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 ofsimulated retail display and overnight storage
treatments on quality maintenance in freshbroccoli. J. Food Sci. 51:146- 149.
Shewfelt, R.L., K.M. Batal, and E.K.
Heaton. 1983. Broccoli storage: effect of N6benzyladenine, 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, andmicro-perforated wrap on shelf-life of broccoli(Brassica oleracea L., Italica Group). Postharv.
Biol. Technol. 10:59-65.

251

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 ResearchCentre, Agriculture and Agri-Food Canada,
Summerland, British Columbia, Canada.

decay, and damage (AMS 1954). To meet thesegrades, sprouts should be larger than 2.5 cm (1in) 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 containersof sprouts (Boyette et al. 1996). Plastic liners areoften used in cartons with loose sprouts to reducemoisture loss. In addition, polyethylene bags are
sometimes used in place of the plastic containers
for consumer units.

Scientific Name and Introduction
Precooling Conditions
Brassica oleracea L., Gemmifera group, also
known as brussels sprouts, is a tall-stemmed
cabbage in which the axillary buds in the axisof each leaf form tiny heads or “sprouts.” It
has a common origin from the wild cabbage ofsouthern Europe with other cole crops including
cabbage, broccoli, and cauliflower (all membersof the Brassicaceae [Cruciferae] family). Brussels
sprouts prefer a cool growing environment. Most
sprouts grown in the United States are from thecentral coast of California.

Quality Characteristics and Criteria
High-quality brussels sprouts are about 2.5 cm (1in) in diameter, firm with green outer leaves, anda 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 andcompactness. Sprouts should be 2.5 cm (1 in) or
more in diameter but not more than 7 cm (2.75in) 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,
252

Effective cooling methods include vacuum
cooling, hydrocooling, icing, and forced-air
cooling. Vacuum cooling is most effective whensprouts are premoistened to reduce wilting
and can be an effective method of coolingeven 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 to36°F) in about 15 min (Stewart and Barger 1963).
Package or top-icing can also be used, especially
if storage or transport conditions cannot maintainrecommended temperature or RH. Forced-air
cooling effectively cools sprouts if packaging isproperly 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 thecut 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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 andpitting of outer leaves (Lyons and Rappaport1962), while O2 at 0.5% or less can induce a
reddish-tan discoloration of the heart leaves andbitter flavor (Lipton and Mackey 1987). Brussels
sprouts do not produce severe off odors when held
in low O2 as do other Brassica vegetables such asbroccoli (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 chillingand should be stored as cold as possible without
freezing.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 arebacterial soft rots (Erwinia sp. and Pseudomonassp.), 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
Ethylene Production and Sensitivity
Brussels sprouts produce <0.25 μL kg-1 h-1ethylene 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 andabscission being the most prevalent symptoms.

None.

Suitability as Fresh-Cut ProductSome trimming of the stem-end could be done toconvert the sprouts to a ready-to-cook form.

Special Considerations
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).

Brussels sprouts can be stored attached to theirstem 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).

253

References
AMS [USDA Agricultural Marketing Service].
1954. United States Standards for Grades ofBrussels 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 andvegetables. 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 andvegetables. 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 oftemperature 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 ofcontrolled atmospheres on storage quality ofBrussels 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.

254

Ryall, A.L., and W.J. Lipton. 1979. Handling,
Transportation and Storage of Fruits andVegetables, 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 ofcooling method, prepacking and top-icing on thequality of brussels sprouts. Proc. Amer. Soc. Hort.
Sci. 83:488-494.

Cabbage

Horticultural Maturity IndicesRobert K. Prange

Determination of maturity in brassicas is not
simple and no one index of maturity is reliable(Ludford and Isenberg 1987) At maturity, acabbage head should be firm and weigh 0.5 to
3 kg (1 to 6.6 lb), depending on cabbage typeand 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 andsofter, have an excessive tendency to wilt anda less characteristic odor (Pritchard and Becker1989). Overmature heads are more susceptible tosplitting, pathogens, physiological disorders, andseed stalk formation (IOS 1991, Pritchard andBecker 1989, Boyette et al. 2008a, Cantwell and
Suslow 2008).

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 (conicalor pointed-head type) cabbage; B. oleracea var.
sabauda L. is savoy cabbage. All are biennialsof the Brassicaceae (Cruciferae) family (Munro
and Small 1997, Pritchard and Becker 1989). The
edible portion includes the leaf blades, stalks, andcore (stem) inside the head. Cabbage is grown inmost major temperate vegetable-growing areasand 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 andMadhavi 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 whenrubbed together (Ryall and Lipton 1979, Boyette
et al. 2008a, Cantwell and Suslow 2008). The
presence of a waxy bloom on the leaves isdesirable. Yellow leaves on green cultivars suggest
extensive trimming of the outer leaves. The
presence of a seedstalk is undesirable.

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 3lb), and large is over 1.4 kg (3 lb). For domestic
and Danish-type (green) cabbage, small is lessthan 0.9 kg (2 lb), medium is 0.9 to 2.3 kg (2 to5 lb), and large is over 2.3 kg (5 lb). Cabbage
heads are shipped in sacks, wax-coated corrugatedcardboard cartons, and wire-bound crates ofvarious 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).
255

Optimum Storage Conditions
Cabbage should be stored at 0 °C (32 °F) with98 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 inthe storage room reduces physiological disorders
such as leaf yellowing and weight loss (Prangeand Lidster 1991). Cabbage is stored in bins orin 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 circulationin the storage should be sufficient to maintain
constant and uniform temperature and RH aroundall cabbage heads. Bulk-stored cabbage shouldbe 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 fromdecay), and storage conditions (Pritchard andBecker 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 andHicks 1985, Pritchard and Becker 1989).

Controlled Atmosphere (CA)Considerations
Cabbage is the most common vegetable stored
under CA (Saltveit 1997, Thompson 1998). Wideranges 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 withlower than 1.5 to 2% O2 and/or higher than 8 to256

10% CO2 may injure stored cabbage. Low-O2 andhigh-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 andHicks 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 beginningin 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 (highCO2) (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 betrimmed. Trimming may expose lighter green
inner leaves, but natural or artificial light canincrease the chlorophyll content and green color(Perrin 1982). The greatest concern is loss ofmoisture, 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)

(Hardenburg et al. 1986, Pritchard and Becker1989). Even though cabbage with coretemperature of -1.1 °C (30 °F) before harvest canshow no evidence of freeze damage (Pritchard andBecker 1989), storage at -1.0 °C (30.2 °F) is notadvisable because it can produce freeze damage,especially on outer leaves (R. Prange, unpublisheddata). Temperature oscillations during cyclingof mechanical refrigeration may expose tissue tofreezing 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 ofcultivar (Meinl and Bleiss 1986).
Cabbage should not be exposed to ethylene after
harvest. Ethylene increases respiration (Inabaet al. 1989), and concentrations as low as 1 μL
L-1 accelerate senescence and quality loss (forexample, 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 browningin shredded cabbage (Takahashi et al. 1996)

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
4 to 64 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 rateby 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 somedisorders 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 cabbagesis the gray mold fungus (Botrytis cinerea)(Geeson 1983, Snowden 1991). Gray mold canbe minimized by using resistant cultivars, using
preharvest fungicides, practicing strict hygiene,
avoiding mechanical or frost damage, rapid coolingto 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 thisdisease is commonly transmitted through infected
seed, it can be minimized by using disease-free
seed, rotation with noncruciferous crops, applying
preharvest fungicides, destruction of diseasedmaterial before storage, and using rapid cooling to
0 °C (32 °F). There are other fungi (such as ringspot), 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.
257

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 atdifferent temperatures, atmospheres, and varying amounts of shredding.
Degree of shredding

mg CO2 kg-1 h-1

2 °C (35 °F)
air
		
		

quarter headrough cut (1 × 3 cm)
fine cut (0.5-1.5 cm)

8
16 to 18
18 to 24

5 °C (41 °F)
air
		
		

quarter headrough cut (1 × 3 cm)
fine cut (0.5-1.5 cm)

10 to 1222 to 34
26 to 40

5 °C (41 °F)

5 % O2+ 5 % CO2		quarter headrough cut (1 × 3 cm)
fine cut (0.5-1.5 cm)

12 to 1426 to 30
30 to 40

10 °C (50 °F)
air
		
		

quarter headrough cut (1 × 3 cm)
fine cut (0.5-1.5 cm)

19 to 2342 to 48
51 to 57

23 °C (73 °F)
air
		
		

quarter headrough cut (1 × 3 cm)
fine cut (0.5-1.5 cm)

54 to 63
117 to 153
153 to 171

Temperature

Atmosphere

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 ofCabbage. 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.
258

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)

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, bunchedbroccoli and cauliflower shipments to the New
York market, 1972-1985. Plant. Dis. 71:11511154.
Cerkauskas, R.F. 1994. Alternaria diseases. In R.J.
Howard, J.A. Garland, and W.L. Seaman, eds.,
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Gorny, J.R. 1997. A summary of CA and MA
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Guffy, S.K., and J.R. Hicks. 1985. Effect of
cultivar, maturity and storage on respiration, dryweight 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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.

Hicks, J.R., and P.M. Ludford. 1981. Effects oflow ethylene levels on storage of cabbage. Acta
Hort. 116:65-73.
Inaba, A., Y. Kubo, and R. Nakamura. 1989. Effectof exogenous ethylene on respiration in fruits andvegetables with special reference to temperature.
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guide to cold storage and refrigerated transport.
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Kader, A.A. 1992. Postharvest biology andtechnology: an overview. In A.A. Kader, ed.,Postharvest Technology of Horticultural Crops,
pp. 15-20. DANR Pub. no. 3311, University ofCalifornia, Davis, CA.
Kaji, H., M. Ueno, and Y. Osajima. 1993. Storageof shredded cabbage under a dynamicallycontrolled atmosphere of high O2 and high CO2.
Biosci. Biotech. Biochem. 57:1049-1052.
Kubo, Y., A. Inaba, and R. Nakamura.
1990. Respiration and C2H4 production invarious harvested crops held in CO2-enrichedatmospheres. J. Amer. Soc. Hort. Sci. 115:975978.
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 ofCommercial Fruits and Vegetables, pp. 29-30.
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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 fürZuchtungforschung 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 onchlorophyll 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., 7thInternational Controlled Atmosphere Research
Conference, University of California, Davis, July
13-18, 1997, vol. 2, pp. 189-192. University ofCalifornia, Davis, CA.

260

Snowden, A.L. 1991. A Colour Atlas ofPostharvest Diseases and Disorders of Fruits andVegetables, 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 andbrowning 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 ofVegetables, pp. 203-230. Marcel Dekker, New
York, NY.

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.

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 ascommercially mature. Fruit continue to develop
color after harvest, though there is little otherchange in quality.

Grades, Sizes, and Packaging
Scientific Name and Introduction
The carambola (Averrhoa carambola L.) isa star-shaped fruit that has a waxy skin withseveral smooth brown seeds. The flesh and skinare 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 tomechanical 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 isdesirable. Cultivars vary greatly in sweetness andacidity, 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 andpoor shape are culled (Campbell 1989).

Horticultural Maturity Indices
Harvesting is based on physiological andhorticultural maturity as indicated by skin color
change from green to yellowish green, thento full yellow or yellowish orange (Campbell
1989). Optimum sugars are achieved at the fullyellow color; however, ripe fruit are more fragileand easily damaged. Thus, fruit are frequently

There are no U.S. or international grades.
Carambola fruit are sold in 3.5-kg (7-lb) flats, 10kg (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 orroom 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 instorage. Lower RH results in more severe rib-edgebrowning. 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 morethan 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 (Wanand 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 andGrierson 1966).
261

Respiration rate and pattern depend on cultivar
and maturity at harvest (Shiesh et al. 1987).

Retail Outlet Display Considerations
Do not display green fruit and do not stack morethan two or three fruit high to avoid mechanicalinjury 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 withstorage time (Wan and Lam 1984). Greener fruit
are more susceptible to chilling injury (Wanand 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 C2H4 kg-1 h-1 at 20 ºC (68 ºF),
depending on maturity (Oslund and Davenport1983). Ethylene treatment (100 µL L-1 for 24 h)slightly hastens degreening but has little effecton 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 withdecay.

Physiological Disorders
The major problem is physical injury, especiallyon the rib edges, that leads to browning. Injury
due to abrasion and impact can be avoided bycareful handling. Browning due to mechanicalinjury can intensify with water loss. Fruit thathave 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, andBotryodiplodia 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 ProductSlices and pieces have been developed (Matthews
1989). Vacuum-packed slices held at 4 ºC retainedcolor, texture, and flavor for 6 weeks if dipped incitrate.

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).
-1-1

References-1-1

To get mL CO2 kg h , divide the mg kg h rateby 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.
262

Campbell, C.A. 1989. Storage and handling of
Florida carambola. Proceedings of the InterAmerican Society for Tropical Horticulture 33:7982.

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 theAnnual Meeting of the Florida State Horticultural
Society 99:222-224.

Wan, C.K., and P.F. Lam. 1984. Biochemicalchanges, 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.

Lam, P.F., and C.K. Wan. 1983. Climacteric natureof the carambola (Averrhoa carambola L.) fruit.
Pertanicka 6:44-47.
Lam, P.F., and C.K. Wan. 1987. Ethylene andcarbon dioxide production of starfuits (Averrhoa
carambola L.) stored at various temperatures andin 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. TropicalFruits. 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 andphysiological studies with carambola. Proceedingsof the Annual Meeting of the Florida State
Horticultural Society 79:350-355.

263

Carrot

Grades, Sizes, and Packaging

Yaguang Luo, Trevor Suslow, and Marita Cantwell

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 aregrouped in 11- or 22- to 22.7-kg (24- or 48- to 50lb) cartons or master poly bags. Bunched carrots
are packed loosely in 12-kg (26-lb) cartons.

Luo is with the Food Quality Laboratory, Henry A.
Wallace Beltsville Agricultural Research Center,
Agricultural Research Service, U.S. Department ofAgriculture, Beltsville, MD; Suslow and Cantwell
are with the Department of Plant Sciences, MannLaboratory, 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 highlevels 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).

Precooling Conditions
Prompt washing and hydrocooling to under 5 °C
(41 °F) are essential to maintain carrot freshness
and crispness. Typically, carrots pass throughseveral wash and flume steps that remove fieldheat and are then hydrocooled in chlorinated water
before packing.

Quality Characteristics and Criteria

Optimum Storage Conditions

Quality criteria vary with use. High-quality carrots
are firm, straight from “shoulder” to “tip,” smoothwith little residual “hairiness,” sweet with nobitter or harsh taste, and show no signs of cracking
or sprouting (Suslow and Cantwell 1998).

Storage at 0 to 1 °C (32 to 34 °F) is essential tominimize decay and sprouting during storage.
High RH is required to prevent desiccation andloss 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 anddistribution 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 tothe presence of leaves and can be maintained for
only 8 to 12 days. Bunched carrots are typicallyshipped and stored with shaved or flaked ice.

Horticultural Maturity Indices
Harvest maturity varies with the market outlet anduse. Fresh market carrots are harvested partiallymature, when the roots are about 1.8 cm (0.75 in)or larger in diameter at the upper end (Kotecha etal. 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 andsweet.

264

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% canresult in increased bacterial rot, off flavors, and off
odors (Leshuk and Saltveit 1990).

Retail Outlet Display Considerations
Carrots are often displayed loosely on a shelfwith 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 andaccumulation of isocoumarin is greatest in the peelof cut carrot sections. Exposure of peeled carrot
to ethylene does not result in development ofbitterness. Whole or sectioned carrots should not
be exposed to ethylene in storage.

Respiration Rates
Temperature Topped
Bunched-1 -1--------------mg CO2 kg h ----------------0 °C		
10 to 20
18 to 35
5 °C		
13 to 26
25 to 51
10 °C		20 to 4232 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 rateby 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 roughhandling. Nantes-type carrots are particularly
susceptible to mechanical damage (McGarry1993). The severity of shatter-cracking ispartially related to varietal background. Wilting,shriveling, and rubberiness are signs of moistureloss. Sprouting may occur on topped carrots if
the storage temperature is too high. Bitterness
can develop in storage due to the accumulationof isocoumarin, caused by disease or exposure
to ethylene. Harsh flavor may be caused by highterpenoid 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 (Rhizopusspp.), watery soft rot (Sclerotinia sclerotiorum),and sour rot (Geotrichum candidum) (Snowden
1992). Ozone is a fungistatic against Botrytis and265

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.

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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.

Quarantine Issues
None

Suitability as Fresh-Cut Product

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 andTechnology, pp.119-139. Marcel Dekker, New
York, NY.

A significant portion of fresh carrot production isused to produce fresh-cut products such as “babycarrots,” 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 (“whiteblush”) is caused by dehydration and remains a
problem for processors and shippers (CisnerosZevallos et al. 1995). Low storage temperatureand retention of surface moisture significantly
delay development of white blush. Using sharp
knives is important to reduce tissue damage andextend shelf-life (Barry-Ryan and O’Beirne 1998).

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.

References

Mazza, G. 1989. Carrots. In N.A.M. Eskin, ed.,Quality and Preservation of Vegetables, pp. 75119. CRC Press, Boca Raton, FL.

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 affectedby slicing method. J. Food Sci. 63:851-856.
Cisneros-Zevallos, L., M. Saltveit, and J. Krochta.
1995. Mechanism of surface white discolorationof peeled (minimally processed) carrots duringstorage. J. Food Sci. 60:320-323, 333.

266

Leshuk, J.A., and M.E. Saltveit. 1990.
Controlled atmosphere storage requirements andrecommendations 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 ofozone and storage temperature on postharvest
diseases and physiology of carrots (Daucus carota
L.). J. Amer. Soc. Hort. Sci. 119:5673-567.

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 andMerchandising 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.

Suojara, T. 1999. Effect of harvest time on thestorage 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.

267

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 isnative 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 (daConceição 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 climatesand has been a traditional crop for subsistence
farmers, though it is increasingly cultivated as anagronomic crop.

Quality Characteristics and Criteria
Fresh cassava roots are highly perishable underambient 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 frommechanical injury, decay, and vascular streaking.
The pulp of most common cultivars varies from268

white to light yellow. Principal causes for loss arevascular 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 desiredby the market and ranges from 6 to 18 mo after
the stem sections are planted. Sweet types usuallygrow faster than bitter types. The main stem
is often trimmed to approximately 1 m (39 in)in height a few days before harvest. Plants aremanually pulled, or the root zone mechanicallyundercut to facilitate plant removal, and individualroots 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 arefavorable, 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, andmethods used to maintain high RH during storage
include moist sawdust and plastic films (Booth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 toover 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 havebeen reported. Vascular streaking during storagein air was reduced in unwaxed cassava roots by aninitial 3-day exposure to 1% O2 at 25 °C (77 °F)(Aracena 1993).

Retail Outlet Display Considerations
Cassava is normally displayed in bulk and shouldbe 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 Humphries1972).

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 andwaxed roots, respectively (Aracena 1993).

Physiological Disorders
Vascular streaking appears as blue or purple spots
when the root is cut transversely and is the resultof oxidative processes in the vascular bundles. It
typically develops at wound sites, such as at theapical end where the root is cut at harvest or under
breaks in the peel that can occur during carelesshandling. Vascular streaking is related to oxidationof scopoletin, a phenolic compound (Wheatleyand Schwabe 1985). Storage of unwaxed cassava
roots in 1% O2 at 25 °C (77 °F) for 3 days
significantly reduced vascular streaking duringstorage in air (Aracena 1993). Exposure to 75µL L-1 ethylene increased vascular streaking, andethylene induced by wounding or water stress may
be the immediate cause of vascular streaking.

Postharvest Pathology
There are two major postharvest fungal diseasesof cassava. Botryodiplodia rot (Botryodiplodia
theobromae Pat.) invades the pulp beneath theskin, initially developing white mold that later
becomes dark grey (Snowdon 1992). Fusariumrot (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), andtrichoderma rot (Trichoderma harzianum Rifai).

269

Quarantine Issues
There are no restrictions on imports from the
major production areas.

Suitability as Fresh-Cut ProductThere 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 vascularstreaking.

References
Aracena, J.J. 1993. Mechanism of Vascular
Streaking, a Postharvest Physiological Disorderof Cassava Roots. Thesis, Horticultural Sciences
Department, University of Florida, Gainesville,
FL.
Booth, R.H. 1976. Storage of fresh cassava(Manihot esculenta). I. Postharvest deteriorationand 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 duringstorage. 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 freshcassava roots (Manihot esculenta, Crantz) for
reduction of vascular streaking. In L. Kushwaha,
R. Serwatowski, and R. Brook, eds., Harvest andPostharvest Technologies for Fresh Fruits andVegetables, pp. 331-338. American Society ofAgricultural Engineers, St. Joseph, MI.
270

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.

Cauliflower

Grades, Sizes, and Packaging

Charles Forney and Peter M.A. Toivonen

There are two grades, U.S. No. 1 and U.S.
Commercial. Grading is based on size, external
appearance, decay, damage, and trimming (AMS1968). Heads are normally well-trimmed andpacked in a single layer with 12 to 24 heads ina carton weighing 11.4 to 13.6 kg (25 to 30 lb).
Cauliflower may also be packed in 27-kg (60lb) wire-bound crates or 23-kg (50-lb) cartons/
crates (Boyette et al. 1996). Cauliflower iscommonly 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 andpacked in 2.3- and 4.6-kg (5- and 10-lb) film bags
for institutional use, or smaller units for consumer
packs.

Forney is with Atlantic Food and Horticulture
Research Centre, Agriculture and Agri-Food
Canada, Kentville, Nova Scotia, Canada;
Toivonen is with Pacific Agri-Food ResearchCentre, Agriculture and Agri-Food Canada,
Summerland, British Columbia, Canada.

Scientific Name and Introduction
Brassica oleracea L., Botrytis group of theBrassicaceae (Cruciferae) family, is also known
as cauliflower. It is derived from the wild cabbagethat is native to southern Europe. Cauliflower
produces an edible head of malformed andcondensed flowers (the curd) whose stalks areshort, fleshy, and closely crowded. Cauliflower issensitive 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 isgrown to take advantage of the cooler times of thegrowing season.

Precooling Conditions
Cauliflower is mostly vacuum-cooled orhydrocooled 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.

Quality Characteristics and Criteria
Heads of high quality are white to cream incolor, firm, and compact. The curds should befree 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 andcompactness. 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.

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 reduceweight 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; anddecay.

271

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.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 moreprevalent on certain cultivars and is most severein cauliflower produced during warm weather andrapid growth (Loughton and Riekels 1988).
Boron deficiency can result in brownish
discoloration of the curd and pith of the stems andmay result in hollow stems. In addition, blisters
and cracks may form on the midribs of leaves
and curds may taste bitter (Dearborn and Raleigh1935).
Riciness is a developmental disorder in whichelongation of flower stems causes flower clusters
to separate, making the head appear granular.
Overmaturity and storage at elevated temperaturesencourages development of riciness, which can be
reduced by timely harvest and storage at 0 °C (32°F).
Heads are susceptible to freezing injury, whichappears as water-soaked and grayish curds, if held
below 0.8 °C (30.6 °F).

Postharvest Pathology
Respiration Rates-1-1

Temperature
mg CO2 kg h
0 °C
16 to 18
5 °C
20 to 2210 °C
32 to 3615 °C
42 to 50
20 °C
74 to 84
25 °C
86 to 98
Data from Suslow and Cantwell (2008).
272

The major causes of postharvest decay arebacterial soft rot caused by Erwinia andPseudomonas 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.

Quarantine Issues
None.

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.

Cauliflower is commonly converted to fresh-cut
floret products.

Forney, C.F., and M.A. Jordan. 1999. Anaerobic
production of methanethiol and other compounds
by Brassica vegetables. HortScience 34(4):696699.

Special Considerations

Herregods, H. 1964. The storage of cauliflower.
Tuinbouwberichten. 28:486-487.

Suitability as Fresh-Cut ProductGrowing conditions can strongly influence thequality 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 browningand decay (Suslow and Cantwell 2008).

Leshuk, J.A., and M.E. Saltveit. 1990.
Controlled atmosphere storage requirements andrecommendations 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 ofstored cauliflower (Brassica oleracea L., Botrytis
group) to low-O2 atmospheres. J. Amer. Soc. Hort.
Sci. 101:208-211.

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 andvegetables. (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, bunchedbroccoli, and cauliflower shipments to the New
York market, 1972-1985. Plant Dis. 71:1151-1154.

Lipton W.J., C.M. Harris, and H.M. Couey. 1967.
Culinary quality of cauliflower stored in CO2enriched atmospheres. Proc. Amer. Soc. Hort. Sci.
91:852-859.
Loughton, A., and J.W. Riekels. 1988. Black speckin 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 storageof 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 andVegetables, 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, 1997,273

vol. 4, pp. 98-117. University of California, Davis,
CA.
Stewart, J.K., and W.R. Barger. 1961. Effects ofcooling method on the quality of asparagus andcauliflower. Proc. Amer. Soc. Hort. Sci. 78:295301.
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 ofrelative humidity on storage-life of vegetables.
Acta Hort. 62:197-208.

274

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.

Precooling Conditions
Celeriac can benefit from precooling since itretains 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
Scientific Name and Introduction
Celeriac (Apium graveolens var. rapaceum
Mill. Gaudin) is a member of the Umbelliferae(Apiaceae) family. The harvest portion is abulbous tuber with a crisp texture and a whiteflesh that has a nutty, celerylike flavor. It is also
known as celery root or apio and can be used freshor cooked. It must be peeled to remove the rough,light-brown skin if used fresh. California is theprimary 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 IndicesCeleriac 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 toprevent 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

Celeriac is harvested when it meets market needs
for size.

Water sprinkle and top ice are beneficial.

Grades, Sizes, and Packaging

Chilling Sensitivity

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 forceleriac; it is graded and packed based on relative
size.

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 should275not be stored with other fruit or vegetables that
produce high levels of ethylene.

References
Cantwell, M. 2001. Celeriac. At http://postharvest.
ucdavis.edu.

Respiration Rates-1-1

Temperature
mg CO2 kg h
0 °C
5 to 85 °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 rateby 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 theroot.

Postharvest Pathology
Decay may become a problem if celeriac is stored
in a warm, humid environment.

Suitability as Fresh-Cut ProductNo current potential is apparent.

Acknowledgments
Much of the information in this chapter was takenfrom the previous edition of this Handbook andfrom the Produce Marketing Association’s “Fresh
Produce Manual.”

276

Kurki, L. 1971. Moisture in vegetable storage.
Acta Hort. 20:146-151.
Morris, S. 2001. Fruit and vegetables storage andtransport 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.

Celery

Grades, Sizes, and Packaging

Yaguang Luo, Trevor Suslow, and Marita Cantwell

U.S. grades are U.S. Extra No. 1, U.S. No. 1, andU.S. No. 2. Celery may be sold as “unclassified”
to designate a lot that has not been gradedaccording 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 (18or 28-lb) cartons (Peirce 1987).

Luo is with the Food Quality Laboratory, Henry A.
Wallace Beltsville Agricultural Research Center,
Agricultural Research Service, U.S. Department ofAgriculture, 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, withother significant production coming from Florida
and Michigan (Schaffer 2000).

Quality Characteristics and Criteria

Precooling Conditions
Celery is typically hydrocooled or vacuum-cooledwith a chilled water spray application. Prompt
precooling to near 0 °C (32 °F) is essential tomaintain freshness and crispness, as well as forextended storage.

Optimum Storage Conditions

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 ofinsect damage and decay. Any leaves remaining
on the stalk after trimming should not be wilted,
yellow, or decayed.

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 withgood 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 duringstorage at temperatures above 0 °C (32 °F),
resulting in quality loss.

Horticultural Maturity Indices

Controlled Atmosphere (CA)Considerations

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 theplants reach full size produce stalks with highmarket quality, and the prices received may morethan compensate for lower yield.

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.
277

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 acceptableto 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).

1996). It is characterized by the appearance ofwhitish regions and air spaces within the tissues
and reduced tissue density and is caused by thebreakdown of the internal pith parenchyma tissuesof the petiole to produce aerenchyma. Pithinessmay 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 pithinessafter preharvest induction. Development ofpithiness is delayed by storage at 0 °C (32 °F).
Blackheart is a physiological disorder caused bycell death resulting from calcium deficiency andpreharvest water stress. Internal leaves develop
brown discoloration, which eventually becomesdeep black.

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.

Brown check is a disorder related to boron
deficiency. It appears as cracks on the inner petiole
surface, and exposed tissues become brown andare susceptible to pathogen infection and decay.
Crushing or cracking of the petiole are signsof mechanical damage and may lead to rapid
browning and decay. Harvesting, packing, andhandling should be done with great care to prevent
damage to the highly sensitive turgid petioles.

Respiration Rates-1-1

Temperature
mg CO2 kg h
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 rateby 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 anddecreased shelf-life (Saltveit and Mangrich
278

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), andwatery 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 (Reysand Smith 1986, Reys and Smith 1987). However,careful maintenance of atmospheric composition
is required as celery is susceptible to low-O2 andhigh-CO2 injury.

Quarantine Issues
None. However, export loads of celery may befumigated at entry ports if common insects (aphids
and thrips) are found.

Reyes, A.A., and R.B. Smith. 1987. Effect ofoxygen, carbon dioxide, and carbon monoxide oncelery 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.

Suitability as Fresh-Cut Product
The majority of fresh-cut celery is in the form ofcelery sticks (cut petioles). Fresh-cut celery canbe packed alone or in combination with othervegetables, 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). Discolorationof vascular tissue, splitting of the cut ends, andbacteria decay are major problems limiting shelflife of fresh-cut celery (Robbs et al. 1996, Saltveit
and Mangrich 1996).

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. Usingdensity measurement to study the effect of
excision, storage, abscisic acid, and ethylene onpithiness in celery petioles. J. Amer. Soc. Hort.
Sci. 121:137-141.

References
Gariepy, Y., G.S.V. Raghavan, R. Plasse, et al.
1984. Long-term storage of cabbage, celery, andleeks 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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Leshuk, J.A., and M.E. Saltveit. 1990.
Controlled atmosphere storage requirements andrecommendations for vegetables. In M. Calderon
and R. Barkai-Golan, eds., Food Preservation by
Modified Atmospheres, pp. 315-352. CRC Press,
Boca Raton FL.

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.

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. Suppressionof sclerotinia and watery soft rot of celery bycontrolled atmosphere storage. Plant Dis. 72:790792.

279

Cherimoya

Precooling Conditions

Robert E. Paull and Nancy Jung Chen

Fruit should be precooled as soon as possible after
harvest to about 12 ºC to 15 ºC (54 to 59 ºF), withroom cooling or forced-air cooling used mostoften.

Paull and Chen are with the Department of
Tropical Plant and Soil Sciences, University of
Hawaii at Manoa, Honolulu, HI.

Optimum Storage Conditions
Scientific Name and Introduction
The cherimoya (Annona cherimola Mill.) is aheart-shaped fruit having few seeds and a smoothskin that does not break apart during ripening. It isgrown in Florida, California, and Hawaii.

Quality Characteristics and Criteria
Quality is determined by fruit size, shape, andskin color, as well as the absence of defects anddecay. Fruit are very susceptible to mechanicalinjury. Sugar levels can vary from 14 to 18%, withmoderate 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 associatedwith 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. Packfruit in single layers in fiberboard cartons withfoam 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).

280

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, andthere may be varietal differences (Moreno andDela Plaza 1983). O2 levels under 1% can lead tooff 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 attemperatures below 10 ºC (50 ºF). The extent of
injury depends on duration. Symptoms include
skin darkening and a failure to fully soften anddevelop full flavor.

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
10 ºC
15 ºC
20 ºC

mg CO2 kg-1 h-1
47 to 190
84 to 280
138 to 460

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 tosoften and can be “mealy” with poor flavor (Palmaet al. 1993b). The degree of injury depends onvariety and ripeness stage. Mechanical injury isa 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 pinkspore 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, andthe flesh becomes brown and corky. These arepreharvest diseases that require good orchard

sanitation. Careful handling and sanitation withcooling, along with fungicides if approved, canminimize 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 ProductThe cherimoya is sold as a fresh-cut product,
though the shelf-life is unknown. Ripe pieces canbe held at 0 to 1 ºC (32 to 34 ºF).

References
Alique, R., and G.S. Oliveira. 1994. Changes insugars and organic acids in cherimoya (Annonacherimola Mill.) fruit under controlled atmospherestorage. 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 climactericfruit. 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 incherimoya. Postharv. Biol. Technol. 2:187-208.
			

281

Cherry (Sweet)
James Mattheis and John Fellman
Mattheis is with the Tree Fruit ResearchLaboratory, Agricultural Research Service, U.S.
Department of Agriculture, Wenatchee, WA;
Fellman is with the Department of Horticultureand 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.

purplish red (overmature). ‘Lambert’ cherries canbe 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, andthe three grading systems differ in tolerance todefects. Sizes are typically expressed as row countand 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 coolsweet cherry fruit. Of these, hydrocooling is themost rapid, and chlorine compounds can be added
to the hydrocooler water to reduce decay potential(Do et al. 1966).

Quality Characteristics and Criteria

Optimum Storage Conditions

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 ofthe stem, which should be green and free frombrown discoloration, is also critical for marketing.
Flavor is enhanced by highly soluble solids andtitratable acid content with a firm, juicy fruit
texture.

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.

Horticultural Maturity Indices
Fruit color is the most consistent and reliablematurity 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
282

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 thesetechnologies is determined in part by fruit quality
at harvest. Fruit harvested at a more advanced
stage of maturity (low acid, dark color, lowfirmness) will not realize as much benefit from CA

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 criticalbecause 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, anddevelopment of decay. Fruit should be held at 5ºC 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 andshould be stored as cold as possible without
freezing.

Ethylene Production and Sensitivity
Sweet cherries produce very low amounts ofethylene but will respond to exogenous or woundinduced ethylene with increased respiration andquality loss.

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 causedby 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 ofpits 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 coolingand storage in a high-RH environment.
Stem browning is another potential physiologicaldisorder. 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 ofchlorine dioxide in hydrocooler water can reduce
development of stem browning (Roberts 1989).

Postharvest Pathology
Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
6 to 10
5 °C
16 to 28
10 °C
20 to 3615 °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 rateby 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), andFungal pathogens including Penicillium expansum(blue mold), Botrytis cinerea (gray mold),
Alternaria sp., Monilinia fructiocola (brownrot), Rhizopus stolonifer, Cladosporium sp., andAspergillus niger are the main causes of sweet
cherry decay (Crisosto 1991, Adaskaveg andOgawa 1994, Dugan and Roberts 1997). Many ofthese 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 postharvest283

decay (Willet et al. 1989). Low-temperaturestorage, fungicide application, and MAP with highCO2 (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 withmethyl bromide to control codling moth larvae.
Fruit shipped into California must be inspected
and certified free from cherry fruit fly infestation.

Chen, P.M., W.M. Mellenthin, S.B. Kelly, andT.J. Facteau. 1981. Effects of low oxygen andtemperature 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 ofCalifornia, 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.

Suitability as Fresh-Cut ProductNo 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 whenusing 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 ofsweet cherries. Plant Dis. 78:293-296.
Brash, D.W., L.H. Chea, and W. Hunt. 1992.
Controlled atmospheres inhibit storage rot ofcherries. 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.

284

Do, J.Y., D.K. Salunkhe, D.V. Sisson, and A.A.
Boe. 1966. Effects of hydrocooling, chemical,
and packaging treatments on refrigerated life andquality of sweet cherries. Food Technol. 20:115118.
Dugan, F.M., and R.G. Roberts. 1994. Etiology
of preharvest colonization of Bing cherry fruit byfungi. 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 ofcarbon dioxide and temperature on the decay ofsweet 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 moisturestudies of sweet cherries during storage. Proc.
Amer. Soc. Hort. Sci. 41:119-123.

Gerhardt, F., H. Schomer, and T.R. Wright.
1956. Sealed Film Lug Liners for Packing Bing
Cherries. Pub. no. 121, U.S. Department ofAgriculture, Agricultural Marketing Service,
Washington, DC.
Mattheis, J.P., and N. Reed. 1994. Response of‘Bing’ sweet cherries to modified atmospherepackaging. Proceedings of the Oregon
Horticultural Society, January 1994, pp. 22-28.

Thompson, J.F., J.A. Grant, E.M. Kupferman, andJ. Knutson. 1997. Reducing sweet cherry damage
in postharvest operations. HortTechnology 7:134138.
Willett, M., G. Kupferman, R. Roberts, et al.
1989. Integrated management of postharvest
diseases and disorders of apple, pears andcherries. Washington State University Postharvest
Pomology Newsletter 7:1-15.

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 ofchlorine dioxide as a postharvest tool for the
Pacific Northwest fruit industry. In Proceedingsof the 5th Annual Warehouse Seminar andTrade 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, andmodified atmosphere packaging. Plant Disease
82:1158-1160.

285

Chicory (Belgian Endive or Witloof
Chicory)
Vince Rubatzky and Mikal E. Saltveit
Rubatzky and Saltveit are with the Department ofPlant 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 rootsof 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 endiviaL.), and radicchio (Cichorium intybus L.). The
edible portion of chicory is the young, enlarged,
compact, and etiolated terminal bud that iscomposed of young leaves and the partiallysuppressed 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, partiallydefoliated except for the apical bud, and stored
until ready for forcing.
Belgium endive is a popular vegetable innorthern 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 appreciatedby the general public. Accordingly, production isminor and supply is augmented by air shipmentsfrom Europe.

Quality Characteristics and Criteria
High-quality chicons are compact and turgid withclosely overlapping outer leaves having a motherof-pearl luster or milky-white appearance and alight yellow tinge on leaf margins. They should286

be sound, free of reddish blemish, frost damage,or traces of bruises, disease, insects, parasites,or rodent attack. A chicon should feel heavy forits size. Leaf tips should not curl back, and thebase 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 isdecreased by flower stem development in excessof 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 retailpresentation are more important than exposure tolight in inducing greening.

Horticultural Maturity IndicesDepending on temperature, optimum harvest is
20 to 30 days after forcing. Harvest delays resultin elongated chicon and loss of compaction.
Chicons are harvested when outer leaves aretightly appressed and density is maximal. The
basal portions of the outermost leaves should
be well sheathed. Leaf margins should be thinand smooth. Timely harvest maximizes potential
shelf-life compared to harvesting at a later stageof development. Deterioration is mainly due tomarginal leaf drying or browning, which can occur
rapidly (Herregods 1971).

Grades, Sizes, and Packaging
Grading is largely determined by uniformity ofshape, 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 oflength to width is 2:1 to 3:1.
U.S. grades are Extra, Standard, and Baby,
while European standards are Extra, ClassI, II, and II irregular. Extra category chicons
are uniformly shaped, meet appropriate size
dimensions, have outer leaves that measure atleast half of the chicon length, are firm, and do notexhibit 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 acold room for a day or overnight before snapping(that is, removal of chicons from the roots).
Condensation on the chicons when transferred to awarmer packing area is undesirable. Precooling inthis manner wastes energy because the entire rootsof both marketable and unmarketable chicons arecooled. 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 moistureaccounting 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 mostcommonly used method. It is the least expensive
but is relatively slow compared with otherprecooling techniques.

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 andleaf spreading.

Retail Outlet Display Considerations
Maintain cold conditions to maximize storage andshelf-life and minimize dehydration, but do notsprinkle 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
In the United States, chicons are packed inpasteboard 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 tomaintaining 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 orless at 15 ºC (59 °F). There is little greening at

Ethylene production is very low, but exposure to
ethylene can produce physiological disorders suchas russet spotting and accelerated senescence.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
2 to 35 °C
5 to 6
10 °C
12 to 1415 °C
20 to 2220 °C
35 to 38
Data from Saltveit (2002, unpublished).
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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,287

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 discolorationof 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 ofchicon deterioration are continued growth of thestem, resulting in leaf spreading and opening; leaf
greening, loss of turgor, and wilting that results
in a loss of weight, grade, and quality; and theappearance 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

Special Considerations
Chicons must be handled with care to avoid
mechanical damage to minimize discolorationand pathological problems. Temperatures must be
kept low, and light must be excluded to prevent
greening. High RH is necessary to prevent loss ofturgor 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 ofBelgian 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. Departmentof 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.

None.
Ryder, E.J. 1979. Leafy Salad Vegetables, pp. 171194. AVI Pub. Co., Westport, CT.
Suitability as Fresh-Cut Product
Potential is low, but loose leaves are occasionallymarketed in some prepackaged salad mixes. The
marketing of detached leaves is occasionally done
to recover some value from fresh market productthat is damaged or otherwise would be wasted.

288

Chinese Cabbage

Grades, Sizes, and Packaging

Robert K. Prange

There are no published U.S. standards for gradesof 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 to5 in) in diameter, and weigh 0.9 to 2.3 kg (2 to 5lb) (Kelley 1999). They are shipped in wax-coated
corrugated cardboard cartons and wire-boundcrates of various sizes.

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 anannual 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 andCerkauskas 1999). Chinese cabbage is grown insmall 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 canvary, 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 isreliable (Ludford and Isenberg 1987). Harvesting
consists of cutting the whole plant at the soil
surface when the heads are firm and the outerleaves are bright green (Munro and Small 1997).
In some cultivars, the outer leaves may be tieda few weeks before harvest to promote a tighter,
upright head. Ludford and Isenberg (1987) cite
reports that Chinese cabbage store better whenheads are more compact at harvest.

Precooling Conditions
Damaged leaves should be removed, and theheads 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, personalcommunication).

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 andoffensive odors are produced during continuous289

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 andIsenberg 1987).

Retail Outlet Display Considerations
Chinese cabbage is displayed as individual heads
with the outer leaves removed, frequently with aband around the equator to maintain a compressedhead 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.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
6 to 145 °C
8 to 16
10 °C
15 to 1915 °C
19 to 3020 °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 rateby 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 Sensitivity
Chinese cabbage may be chilling sensitive. A
physiological disorder (brown midrib) developed
after prolonged storage at 0 °C (32 °F) (Apeland1985). 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 criticaltemperature.

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 acceleratesenescence in air storage. Levels inside cartons ofChinese cabbage in wholesale markets have beenmeasured at 1.09 μL L-1 (Wills 1998). Ethyleneinduced leaf abscission can be minimized bystorage in 1% O2 (Wang 1983).

290

Brown midrib, a physiological disorder causing
significant storage losses, is a symptom of chilling
injury (Apeland 1985). Elevated levels of CO2 canincrease 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 ofleaf veins, which may be due to Xanthomonas
campestris.

Quarantine Issues
None.

Suitability as Fresh-Cut Product
Chinese cabbage is suitable as a fresh-cut productpackaged 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

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 respirationthat 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 adip, a commercially acceptable shelf-life of 21 days
at 0 °C (32 °F) or 14 days at 5 °C (41 °F) can beachieved without MA.

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 headrough cut (0.5 x 3 cm)
fine cut (0.25 - 1.5 cm)

10
18
24

5 °C
air
		
		

half headrough cut (0.5 x 3 cm)
fine cut (0.25 - 1.5 cm)

16
32
40

5 °C

5 % O2+ 5 % CO2
		half headrough cut (0.5 x 3 cm)
fine cut (0.25 - 1.5 cm)

10
22
28

10 °C
air
		
		

half headrough cut (0.5 x 3 cm)
fine cut (0.25 - 1.5 cm)

17
48
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__________________________________________________________________

291

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 oxygenon the storage and quality of some vegetables. In
M.E. Saltveit, ed., 7th International Controlled
Atmosphere Research Conference, University ofCalifornia, Davis, July 13-18, 1997, vol. 4, pp. 2633. 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 andDevelopment 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 ofCalifornia, Davis, July 13-18, 1997, vol. 5, pp. 3066. University of California, Davis, CA.
Herner, R.C. 1987. High CO2 effects on plantorgans. In J. Weichmann, ed., Postharvest
Physiology of Vegetables, pp. 239-253. Marcel
Dekker, New York, NY.
Kader, A.A. 1992. Postharvest biology andtechnology: an overview. In A.A. Kader, ed.,Postharvest Technology of Horticultural Crops,
pp. 15-20. DANR Pub. no. 3311, University ofCalifornia, Davis, CA.
292

Kasmire, R.F., and M. Cantwell. 1992.
Postharvest handling systems: flower, leafy andstem 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. Vegetablesof Canada. National Research Council, Ottawa,
Ontario, Canada.
Saltveit, M.E. 1997. A summary of requirements
and recommendations for the controlled andmodified 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 asaffected by lining. Acta Hort. 116:157-162.
van den Berg, L. 1987. Water vapor pressure. In
J. Weichmann, ed., Postharvest Physiology ofVegetables, 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.

Wang, S.L., and R.F. Cerkauskas. 1999. Recent
development of production and processing oforiental vegetables in Canada. Acta Hort. 483:429436.
Wills, R.B.H. 1998. Enhancement of senescencein nonclimacteric fruit and vegetables by low
ethylene levels. Acta Hort. 464:159-162.

293

Coconut

Horticultural Maturity IndicesRobert E. Paull and Saichol Ketsa

Young coconuts are harvested 6 to 9 mo after
flowering as they approach full size and the skinis still green (Consignado et al. 1976, Srivichai
1997) and the short stem (rachillae) on the top ofindividual 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 thearea 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 toyellow, then brown, and the “rat-tail” is entirely
brown.

Paull is with the Department of Tropical Plant andSoil 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 twostages of development. At an immature stage, thefruit (water coconut) contains mainly water and alittle 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 thenwrapped 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 ofhusked coconuts, and wet or moldy eyes. Checkfor a sloshing sound for presence of coconut waterin the nut. Coconut milk is obtained by removing
and grating the hard, white flesh and squeezing out
the milky juice. Immature, dehusked coconuts areabout 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.

294

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). Immaturecoconuts (water coconuts) are shaped, dipped inbisulphate, and film-wrapped. They are sold in
single-piece cartons containing 10 to 16 nuts. For
young coconuts, the entire husk is removed, andthe 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 areacceptable. A rapid temperature change of 8 ºC
(14 °F) or greater can cause cracking.

Optimum Storage Conditions

Retail Outlet Display Considerations

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.

Display coconuts at ambient temperatures and do
not mist. Nonwrapped or individually wrappedshaped coconuts are displayed at ambient
temperatures or at 10 °C (50 °F).

Young coconuts are normally held at 3 to 6 ºC (37to 43 ºF) with 90 to 95% RH, while wrapped andshaped 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 temperaturefor 2 days before browning occurs, while thosetreated with 2% sodium meta-bisulfite can be heldat 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 thandehusked 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, thetaste 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 toreduce water loss. Immature husked nuts can also
be film-wrapped or waxed; however, the outsidecolor changes rapidly from white to brown unlessthey are dipped in sodium bisulfite (Tongdee et al.
1992).

Chilling Sensitivity
When stored at 0 °C (32 °F), immature nuts havegreen 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 formature husked coconut. There are no reports ofsensitivity to ethylene.

Respiration Rates
Temperature mg CO2 kg-1 h-1
Immature		 10 oC
7 to 8o		20 C		 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 rateby 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 willcause the white coir (the stiff fiber from the outerhusk) 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 maturehusked coconut can lead to cracking (Burton1982), while freezing occurs at -3 °C (27 °F).
295

Moisture loss causes a loss of water in the nut; thisloss can be reduced by RH control, film wrapping,or waxing of mature nuts.

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.

Postharvest Pathology

Seelig, R.A. 1970. Coconuts: Fruits and Vegetable
Facts and Pointers. United Fresh Fruit andVegetable Association, Washington, DC.

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 theimportation into certain tropical and subtropicalcountries from regions affected by palm diseases.

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 oftender coconut. ASEAN Food J. 6:74-75.

Suitability as Fresh-Cut ProductMeat from both immature (jellylike) and mature(hard) nuts is sold in trays with overwrap or
plastic bags for use in desserts. Immaturecoconuts’ jellylike meat and water have to beheld 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 heldon ice in Southeast Asian markets and roadsidestalls. Nonshredded and shredded meat of maturecoconuts 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 instorage. Coconut J. 10(4):37-51.
296

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 TropicalFruits. International Conference on Postharvest
Handling of Tropical Fruits, Chiang Mai,
Thailand, July 1993, p. 15. ACIAR Proceedings
no. 50, ACIAR, Canberra, Australia.

Cranberry

Grades, Sizes, and Packaging

Robert K. Prange

There is only one grade standard for fresh
cranberries: U.S. No. 1. Criteria include color (noless 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 fromother 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 13.2kg) (AMS 1997). Occasionally, 9 2-lb (0.9-kg) and4 5-lb (2.3-kg) polybag cartons are used for someretail customers, and wood totes may be used forsale of bulk cranberries.

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, inorder of production, Wisconsin, Massachusetts,
New Jersey, Oregon, and Washington (NASS2005).

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
Quality Characteristics and Criteria
Color intensity, glossiness, uniformity, andfreedom 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 toachieve the maximum red color without allowing
the fruit to become too overmature (Eck 1990).
Overmaturity results in physiological breakdown(see Physiological Disorders).

The minimum recommended storage temperatureis 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 recommendationof 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: forexample, 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 byholding fruit, especially early harvested fruit, at 7
to 10 °C (45 to 50 °F) for a few weeks rather thanat the lower recommended temperatures (Levine
et al. 1941). The expected storage life is 2 to 4 mo.

297

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 comparedwith ambient air (Anderson et al. 1963, Starket 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 a2-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 havelittle decay but a high amount of physiologicalbreakdown, making them unacceptable forfresh or juice use but still acceptable for use in
cranberry sauce.

Retail Outlet Display Considerations
Water sprinkling or top-icing are notrecommended.

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).

298

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 offruit 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 redcolor 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 comparedto other berry crops, which have a moderate tohigh rate (Kader 1992).
Temperature
mg CO2 kg-1 h-1
0 °C
4
4 to 5 °C
4 to 510 °C
815 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 rateby 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 fungalorganisms are associated with this condition. It

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 thesame 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 someare 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 isno decay control at 1% (Anderson et al. 1963), but
100% N2 for 3 weeks at 3 °C (38 °F) reduced thenumber of pathogenic species and decay comparedwith air-stored fruit (Lockhart et al. 1971).

Suitability as Fresh-Cut ProductNo 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 thedevelopment of decay, shrinkage resulting frommoisture 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 orrough hand-harvesting, transport, or mechanicalcleaning, 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 physiologicalbreakdown in water-harvested than in handharvested cranberries, especially if cranberries are
kept in the water more than 1 h after detachmentfrom the plant (Mitcham et al. 1999; Blake
Johnson, 2000, personal communication).

Acknowledgments
Some of the information in this chapter wasfrom the Produce Marketing Association’s“Fresh Produce Manual” and from B. Johnsonof Bezanson and Chase Cranberry Company,
Aylesford, Nova Scotia, Canada.

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 toquarantine restrictions, depending on the countries
involved.

References
AMS [USDA Agricultural Marketing Service].
1997. United States standards
for grades of fresh cranberries. U.S. Departmentof Agriculture, Washington, DC. (http://www.ams.
usda.gov/AMSv1.0/standards)299

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 harveston 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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Hruschka, H.W. 1970. Physiological breakdown incranberries—inhibition by intermittent warming
during cold storage. Plant Dis. Rptr. 54:219-222.
Kader, A.A. 1992. Postharvest biology andtechnology: an overview. In A.A. Kader, ed.,Postharvest Technology of Horticultural Crops,
pp. 15-20. DANR Pub. no. 3311, University ofCalifornia, 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 ofAgriculture, 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, andS.W. Porritt. 1988. Commercial Storage of Fruits
and Vegetables. Pub. no. 1532/E, Agriculture andAgri-Food Canada, Ottawa, Ontario, Canada.

300

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.

Stark, R., I.V. Hall, F.R. Forsyth, and P.R. Dean.
1969. Cranberries evaluated for fresh fruit andprocessing quality after reduced O2 storage.
Cranberries 34(6):14,16 and 34(7):14,16.

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.

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 andhigh relative humidities. Can. Inst. Food Sci.
Technol. J. 7:9-10.

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.

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.

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 ofpolygalacturonase 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 ofAgriculture, 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 CropManagement, pp. 504-531. Prentice Hall, Upper
Saddle River, NJ.

301

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 tropicalorigin (Robinson and Decker-Walters 1997). The
inferior ovary has three united carpels in mostcultivars. Compact, determinate cultivars havebeen 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 oftrichome origin on the rind of some cultivars(Miller and Wehner 1989). The rind of slicing
cucumbers should be dark green and firm withno pits or wrinkled (pinched) ends. Spine color isassociated with mature fruit color and fruit netting.
Fruit of white-spined cultivars are light green toyellow 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 ofdevelopment. Immature fruit are green at theedible 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
302(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 formationof jellylike material around the seeds areindicators of proper harvest maturity. Greenhousegrown parthenocarpic (produced without
pollination) fruit are harvested 10 to 14 days after
anthesis after they turn bright green (Kanellis etal. 1988). Straight, uniformly cylindrical fruitslightly 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 gradedby 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 includesize, 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 toreduce moisture loss, while greenhouse slicers arewrapped in shrink-plastic to reduce water loss.
Pickling cucumbers are usually transported fromthe 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 cantolerate brief exposure to chilling temperatures,
they should not be maintained at chilling
temperatures for more than 6 h.

Optimum Storage Conditions
Recommended conditions for commercial storageof 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 visualand 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 storageof 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 andhigh RH after chilling can reduce symptom
expression. Intermittent warming to nonchilling

temperatures for 12 h every 2 or 3 days can reducechilling injury of fruit held at 0 to 2 °C (32 to 36°F) (Cabrera and Saltveit 1990). Development ofchilling injury symptoms can be avoided if chilled
fruit are used immediately after removal fromstorage.

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 theresponse to ethylene exposure.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
10 °C
23 to 2915 °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 rateby 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, anddevelopment 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
303responsible for postharvest losses include
Alternaria spp., Didymella black rot, Pythium
cottony leak, and Rhizopus soft rot.

Acknowledgments
Some of the information in this chapter is from theProduce Marketing Association’s “Fresh Produce
Manual.”Quarantine Issues
None.

Suitability as Fresh-Cut ProductSliced cucumbers are available for the commercial
food service industry but are not yet on the retailmarket.

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 attemperatures 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 mechanicalharvesting of pickling cultivars increases
the rate of respiration (from 6 to 20%), therate of water loss, and disease susceptibility.
Also, since pickling cucumbers are commonly
shipped in large field bins, prompt precoolingis very important to remove field heat andprevent respiratory activity from raising fruit
temperature in transit. Hydrocooling is effective
for precooling, but storage life is halved becauseof 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.

304

References
Cabrera, R.M., and M.E. Saltveit. 1990.
Physiological response to chilling temperaturesof 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 responseto 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. Departmentof 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 forpreservation 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 andVegetables, 2nd ed., vol. 1, Vegetables andMelons. AVI Publishing Co., Westport, CT.

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 andmaturation. 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.

305

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 pinkflesh. 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 fromR. uva‑crispa L. (European gooseberry) and R.
hirtellum Michx. (American gooseberry). The
European gooseberry is much larger than theAmerican gooseberry. European cultivars are fromR. 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 mostintense on fruit in full sunlight. The four countries
producing both the most currants and the mostgooseberries are Germany, Czech Republic,
Poland, and the Russian Federation. North
American production of currant and gooseberryhas been hampered by adaptation and diseaseproblems (Harmat et al. 1990). Currant andgooseberry 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.
306

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 beavailable 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 fruitfrom wild plants may in part account for thelack 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 Yorkand Nova Scotia, have resulted in a number ofcultivars (Craig 1978, Way 1981, Stang 1990), andsmall-scale production has been reported in New
York, Ohio, and Oregon (Way 1981).

Quality Characteristics and Criteria
Currant and elderberry fruit are produced on theplant in clusters, and gooseberry fruit are borne
singly or in pairs. Ideally, fruit throughout eachcluster should be firm and bright, with the proper
cultivar‑specific color, and free of decay ormechanical or insect injury. For the fresh market,
it is also important to have large and uniform
fruit throughout the cluster. A long shelf‑lifewith 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 andLareau 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 acluster. 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 thecluster: the larger ones at the base of each clustermature first (Audette and Lareau 1996, http://
www.crfg.org/pubs/ff). The entire cluster can be
harvested, or only mature berries can be pickedover 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‑blackcolor. The fruit do not mature at the same time, so
several pickings are necessary over a 1- to 2-weekperiod (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 forthese fruit. There is a U.S. grade standard forprocessing currants, based on color, attachmentof stem, and freedom from decay and insect ormechanical damage. Processors, who use most of
the commercial production, may have their own
standards. Since fresh market volumes are notlarge, container sizes and packaging for the freshmarket tend to be those used for similar but morecommon 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 andHelm (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, redcurrant, and gooseberry, respectively (Batzer andHelm 1999).

Controlled Atmosphere (CA)Considerations
As summarized by Batzer and Helm (1999) andThompson (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 respondas 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 withwater or top-iced.

307

Chilling Sensitivity

Postharvest Pathology

Currant, gooseberry, and elderberry are notchilling sensitive (Kader 1992).

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 etal. 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 etal. 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 andStemphyllum. The infection is usually confinedto 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.

Ethylene Production and Sensitivity
No data available.

Respiration Rates
Temperature

GooseberryBlack currant---------mg CO2 kg-1 h-1--------0 °C
5 to 716
4 to 5 °C
8 to 16
27
10°C
12 to 3240
15 to 16°C
28 to 6989
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 rateby 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 andfruit 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 wasincreased from 8 to 12%. Fruit turned yellow andhad an abnormal flavor. Increasing the temperaturefrom 0 to 5 °C (32 to 41 °F) eliminates thedisorder.

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 andCepaea spp.) will attack fruit (North America
and Europe) (Harmat et al. 1990). Diseases andinsects are not generally serious on elderberries(Way 1981), perhaps because of the absenceof extensive plantings. An unidentified mildew
can be a problem on ripe fruit, especially if theweather is cool during ripening and there is poor
air circulation around the plants (Way 1981).
Birds feeding on ripe currant, gooseberry, andelderberry 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 beconsidered.

Quarantine Issues
None
308

Suitability as Fresh‑Cut ProductNo current potential

Harmat, L., A Porpaczy, D.G. Himelrick, andG.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.

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 bannedin some U.S. municipalities (California Rare Fruit
Growers 1996).

References
Audette, M., and M.J. Lareau. 1996. Currants
and Gooseberries Culture Guide. Conseil desProductions Végétales du Québec, Inc., Québec
City, Québec, Canada.
Batzer, U., and H.‑U. Helm. 1999. Lagerungvon 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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.

Kader, A.A. 1992. Postharvest biology andtechnology: an overview. In A.A. Kader, ed.,Postharvest Technology of Horticultural Crops,
pp. 15-20. DANR Pub. no. 3311, University ofCalifornia, 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 andVegetables, 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 CropManagement, pp. 504‑531. Prentice Hall, Upper
Saddle River, NJ.
Smith, W.H. 1967. The storage of gooseberries.
Agricultural Research Council (U.K.) Ditton andCovent Garden Laboratories Annual Report 196566, pp. 13-14.
Stang, E.J. 1990. Elderberry, highbush cranberry,and juneberry management. In G.J. Galleta
and D.G. Himelrick, eds., Small Fruit CropManagement, pp. 363‑382. Prentice Hall, Upper
Saddle River, NJ.
Story, A., and D.H. Simons. 1989. Handling andStorage Practices for Fresh Fruit and Vegetables.
Australian United Fresh Fruit and Vegetable
Association Ltd., Victoria, Australia.
309

Thompson, A.K. 1998. Controlled Atmosphere
Storage of Fruits and Vegetables. CAB Intl.,
Wallingford, U.K.
Way, R.D. 1981. Elderberry culture in New YorkState. Food Life Sci. Bull. 91, New York State
Agricultural Experiment Station, Geneva, NY.

310

Yahia is with the Faculty of Natural Sciences,
Universidad Autónoma de Querétaro, Querétaro,
Mexico.

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 ofpoor quality.

Scientific Name and Introduction

Grades, Sizes, and Packaging

Phoenix dactylifera L., the date palm, has beena staple in the Middle East and North Africa forthousands of years. Date fruit is a drupe with asingle seed or pit. The fruit has an oblong shape,
measures about 2.5 to 7.5 cm (1 to 3 in) long, andhas thick or thin flesh. It tastes astringent whenpremature and becomes sweet when ripe. Dates
are rich in carbohydrate and other nutrients andare a high-energy food.

Dates are graded based on uniformity of colorand size and extent of defects or damage, which
include discoloration of the flesh, rupture of
the skin, deformity of the fruit, puffiness ofthe skin, scars, sunburn, insect damage, decay,
black scald, fermentation, improper ripening,mechanical damage, and presence of dirt or otherforeign material. These criteria are the bases for
Codex and U.S. grades A, B, C, standard, andsubstandard applied to whole, pitted, or dry dates.
In general, the total amounts of sugar for different
grades are usually the same when expressed as apercentage 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).

Date
Elhadi M. Yahia

Quality Characteristics and Criteria
High-quality fresh dates should be of an adequate
size and proper color and have a small pit andthick flesh. They should not be contaminated bydirt, sand, or leaf particles or exhibit damage bybirds, insects, or rodents. There should be no fungi
or mold infestation nor sugar crystal formationor 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, dependingon the cultivar.

Horticultural Maturity Indices
Fruit growth follows a sigmoidal curve and isusually 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 andcultivars. At this stage, fruit can be harvested
soft, semidry, or dry depending on destination
and use. Some varieties with low tannins but

Some dates are marketed in 15-lb (6.8-kg) flatsof fiberboard or wood, others in 5- or 10-lb (2.3or 4.5-kg) cartons. Large, reinforced cartons areused for packing dry dates, especially for export.
Consumer packages are widely used and consistof various sizes and shapes, including bags oftransparent film and trays overwrapped withfilm. Round fiberboard cans with metal tops andbottoms 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).

311

Optimum Storage Conditions
Pathological and physiological deterioration
increases with increasing moisture content andstorage temperature. Relatively small differences
in moisture content may have an important effecton 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 goodconditions up to 1 year, but some varieties may
develop sugar spots or crystals. Fully mature softand firm ‘Deglet Noor’ dates can be kept for morethan 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 atambient 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 (seeHorticultural Maturity Indices), commonly
handled in the world market, are not sensitive
to chilling and freezing temperatures. However,freezing temperatures can injure dates at earlystages 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 therutab and tamr stages. Ripe dates are not sensitive
to ethylene exposure.

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 whenmoisture content increased to 27%. (Rygg 1975).

Physiological Disorders
Darkening is a major problem in dates. Itsrate varies with cultivar, temperature, andmoisture 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 areddish color and increase the astringency and off
flavors in ‘Deglet Noor.’
Blacknose, or sugartip, is a severe checking of theskin in some cultivars, especially in ‘Deglet Noor.’
It is induced by high RH just before the beginningof the khalal stage and is characterized bydarkening, shriveling, and hardening of the flesh
at the tip of the fruit (Rygg 1975). Black scald
is characterized by blackening of the flesh and asunken area with a definite line of demarcation at
the tip or on the sides of the fruit.
Puffiness, or sunken separation, is caused by hightemperatures and/or high RH before the beginningof ripening and may increase during curing. Thisdisorder affects only soft cultivars.
Sugar spotting is characterized by light-coloredspots under the skin and is restricted to the invert
sugar dates. Almost all dry cultivars, and severalof the semidry cultivars, contain large amounts ofsucrose 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).

Respiration Rates
Respiration rates of dates are very low: <5 mg
CO2 kg-1 h-1 at 20 °C (68 °F) at the khalal stageand <2 mg kg-1 h-1 at the rutab and tamr stages.
Respiration rates increase as moisture content of
312

Freezing of dates at a higher temperature
range results in the rupture of various cellularcompartments and the appearance of bright,
yellow-brown spots of crystallized solutes(Shomer et al. 1998). Intercellular membranes

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 deteriorationof dates includes fermentation by yeast andmolding 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, Cladosporiumsp., Macrosporium sp., Citromyces ramosus,
Phomopsis diopspyri, and Penicillium spp. Thesefungi can cause significant losses before or justafter 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.

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 notintended for immediate consumption. Hydration isused to soften the texture of hard-type cultivars.

Acknowledgments
Thanks are due to Dr. A. Ait-Oubahou forreviewing the manuscript.

References
Insect Pests
Oligonychus afrasiaticus McGregor and O.
pratensis Banks are mites referred to as “BouFaroua” or “Old World date mite.” They affectdates 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 immaturegreen 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 caninfest stored dates.

Dowson, V.H.W. 1982. Date production andprotection 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, Handlingand 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 andmoisture 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 ofethylene in the regulation of fruit ripening in the
Hillawi date palm (Phoenix dactylifera). J. Sci.
Food Agric. 72:306-308.
313

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.

Rygg, G.L., J.R. Furr, R.W. Nixon, and W.W.
Armstrong. 1953. Factors affecting the spoilage ofdates at room temperature. Date Growers’ Institute
Report 30:10-14.

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. 14:710.

Shomer, I., H. Borchov-Neori, B. Luzki, andU. Merin. 1998. Morphological, structural andmembrane changes in frozen tissues of Madjhoul
date (Phoenix dactylifera L.) fruits. Postharv. Biol.
Technol. 14:207-215.

Barreveld, W.H. 1993. Date palm product.
Agric. Serv. Bull.101, United Nations, Food andAgriculture Organization, Rome, Italy.

Vandercook, C.E., S. Hasegawa, and V.P. Maier.
1980. Dates. In S. Nagy and P.E. Shaw, eds.,
Tropical and Subtropical Fruits. AVI PublishingCo., Westport, CT.

Benjamin, N.D., H.R. Shabana, A.A. Mahdi
Hassan, et al. 1976. Effect of different
temperatures and types of containers on thestorage of commercial varieties of dates in Iraq.
Technical Bull. 13, Palm and Dates ResearchCenter, 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 theirapplication in softening of tough dates andsugarwall dates. Date Growers’ Institute Report
29:6.
Hasegawa, S., and D.C. Smolensky. 1970. Dateinvertase: properties and activity associatedwith 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.

314

Dragon Fruit
Robert E. Paull
Paull is with the Department of Tropical Plant andSoil 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 theother yellow pitaya, Selenicereus megalanthus(Mizrahi et al. 1997). Dragon fruit is a selfcompatible cultivar in Vietnam (Mizrahi et al.
1997, Nerd and Mizrahi 1997).

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 (over1.1 lb or 500 g), large (0.84 lb-1.1 lb or 380-500g), 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, and16.

Quality Characteristics and Criteria

Precooling Conditions

Dragon fruit is a large, oblong fruit with a redpeel and large, green scales. The scales turnyellow on ripening. The skin begins to change
color 25 to 30 days after flowering in both H.
undatus and H. polyhizus. At about the sametime flesh firmness approaches a minimum, andeating quality approaches a maximum 33 to 37
days after flowering (Nerd et al. 1999). Fruit canbe 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).

There are no reported data. Room cooling andhydrocooling are possible.

The flesh of different species can vary from white
to various hues of red to very dark red. As thefruit matures, acidity reaches a peak just as the

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 withminimum 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 storage315

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 peeland flesh deterioration and inferior taste (Nerdet al. 1999). Thus, 10 °C (50 °F) for a maximumof 14 days may be a better recommended storage
temperature.

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 arefor mature fruit:Controlled Atmosphere (CA)Considerations

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.

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.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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
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).

Chilling injury, mechanical injury, and water loss
are the three major disorders. Mechanical injury
leads to development of sunken areas. Moremature fruit are more susceptible to mechanicalinjury (Le et al. 2000). Splitting is a problem
in fruit more than 35 days after flowering thatreceived rainfall or excessive irrigation during
ripening (Le et al. 2000).

Postharvest Pathology
Bacterial (Xanthomonas campestris) andDothiorella 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.

Ethylene Production and Sensitivity
Quarantine Issues
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 notinitiate color development (Le et al. 2002).
316

Dragon fruit are a fruit fly host. Irradiation at
300 grays has potential for disinfestation. In
Israel, no insect problems have been observed incommercial production, and the fruit’s status as afruit fly host may need to be reevaluated.

Nerd, A., and Y. Mizrahi. 1999. The effect ofripening stage of fruit quality after storage ofyellow pitaya. Postharv. Biol. Technol. 15:99-105.

Suitability as Fresh-Cut Product

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.

Dragon fruit are often available as a fresh-cut
product in Southeast Asian markets in trays withoverwrap. There is some potential, as fresh-cut
fruit can be stored at 4 °C (39 °F) for 8 days (Le etal. 2002).

Weiss, J., A. Nerd, and Y. Mizrahi. 1994.
Flowering behavior and pollination requirements
in climbing cactus with fruit crop potential.
HortScience 29:1487-1492.

Special Considerations
Fruit are very low in vitamin C but rich inpotassium (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: effectof harvesting time, use of plant growth regulatorsand 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. 18:321346.
Nerd, A., and Y. Mizrahi. 1998. Fruit development
and ripening in yellow pitaya. J. Amer. Soc. Hort.
Sci. 123:560-562.
317

DurianRobert E. Paull and Saichol Ketsa
Paull is with the Department of Tropical Plant andSoil 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 somepeople. (The fruit has a strong onion-garlic odor.)“Zibethinus” is derived from the word “zibetto,”
Italian for the civet, a catlike animal with a muskyodor. 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 tropicalworld 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 andSouth 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 2.4in) long covered by a white to yellowish, soft,
318

sweet pulp (aril). The pulp can be odorless or havea 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 IndicesAt 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 insoluble 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 andflexibility, abscission zone, or carpel sutures),number of days after flowering, and a hollow
sound when tapped with a wood or rattan stickor knife. The number of days after flowering andtapping 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 rindcharacteristics, ripen to excellent quality in under
1 week at 28 to 31 °C (82 to 88 °F). Ripening

takes longer than 1 week at 22 °C (72 °F). Fruitthat are 95% mature when harvested have alreadycommenced ripening, while 75% mature fruit
may ripen with an inferior quality. Compared withfruit picked from the tree, fruit collected from theground 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 pickedfrom 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.

Controlled Atmosphere (CA)Considerations
Ripening is inhibited by 2% O2, and fruit failto ripen when removed to air. Fruit stored in up
to 20% CO2 in air were not affected in terms ofripening 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 potentialof CA or MA is still unclear (Siriphanich 1996).

Retail Outlet Display Considerations

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 fittedwith fiberboard dividers.

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 duringstorage. The husk can be removed and the whole
pulp and seed segment can be removed and soldin trays with a plastic overwrap. Remove the husk
as soon as the fruit starts to produce aroma or ishalf-ripe and the pulp is still firm. If fruit splitting
has started, the pulp is generally too soft and has avery short shelf-life.

Precooling Conditions

Chilling Sensitivity

Use forced-air or room cooling to 15 °C (59 °F).

The pulp of half-ripe or nearly fully ripe fruit ismuch 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 thesurface (Siriphanich 1996).

Grades, Sizes, and Packaging

Optimum Storage Conditions
This climacteric fruit, when stored at 15 ºC (59ºF), has extended shelf-life (Brooncherm andSiriphanich 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 abetter eating quality and are less juicy and easier
to dehusk than fruit ripened at a higher RH (Ketsa
and Pangkool 1994).

Ethylene Production and Sensitivity
Production of ethylene varies from near zeroin immature fruit up to 40 µL kg-1 hr-1 at theclimacteric peak and varies with cultivar (Tongdee319

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 ayellowish or brownish husk are not regarded as
fresh.

Collectrichum, Fusarium, and Rhizopus cansometimes be severe (Siriphanich 1996).
Sanitation, avoidance of mechanical injury, andfungicide can be used for control (Lim 1990).

Respiration Rates

Suitability as Fresh-Cut Product

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 toget 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 thepulp (Brooncherm and Siriphanich 1991). The
climacteric rise seems to occur first in the pulp.
In ‘Chanee’ and ‘Kan Yao,’ the respiration andethylene 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).

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 1,000g vitamin C. Choice varieties fetch higher
prices than others. Roadside and market stalls
in Southeast Asia may cut open the fruit andpackage the soft aril and seed in a shrink-wrappedor stretch-wrapped tray. Ripe fruit and soft arils
are also frozen for export. Partially ripe fruit are
difficult to open without damaging the pulp.

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 highlosses during rainy weather and if fruit come incontact 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,
320

Quarantine Issues
If the skin is not broken or split, durian is nota fruit fly host. The skin must be free of otherinsects such as scales.

Special Considerations
Thailand is the largest producer, followed byIndonesia 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 fruitwith less volatiles. Others may prefer the strongflavored durian over the milder cultivars. There isa demand among ethnic groups familiar with thefruit 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 andunripe durian pulp, as the lighter-colored flesh
makes more attractive chips. Durian should not be
shipped in mixed loads.

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 ofhumidity on ripening of durians. Postharv. Biol.
Technol. 4:159-165.
Ketsa, S., and S. Pongkool. 2001. Effect ofmaturity stages and ethylene treatment on ripeningof 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.

Siriphanich, J. 1996. Storage and transportationof 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 andethylene. HortScience 29:1195-1198.
Tongdee, S.C., A. Chayasombat, and S.
Neamprem. 1987a. Effects of harvest maturity
on respiration, ethylene production, andcomposition of internal atmospheres of Durian(Durio zibethinus, Murray). Proceedings of the
Durian Workshop, Bangkok, Thailand, pp. 31-36.
Thailand Institute of Scientific and TechnologicalResearch, Bangkok, Thailand.
Tongdee, S.C., S. Neamprem, and A.
Chayasombat. 1987b. Control of postharvest
infection of phytophthora fruit rot in durian withfosetyl-Al and residue levels in fruit. Proceedingsof the Durian Workshop, Bangkok, Thailand,
pp. 55-66. Thailand Institute of Scientific andTechnological 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.

Nakasone, H.Y., and R.E. Paull. 1998. TropicalFruits. CAB Intl., Wallingford, U.K.
Nanthachai, S., ed. 1994. Durian: Fruit
Development, Postharvest Physiology, Handlingand Marketing in ASEAN. ASEAN Food
Handling Bureau, Kuala Lumpur, Malaysia.
Salakpetch, S., S. Chandraparnik, H. Hiranpradit,
and U. Punnachit. 1992. Source-sink relationshipaffecting fruit development and fruit quality
in durian, Durio zibethinus Murr. Acta Hort.
321:691-694.
321

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 anannual plant of the Solanaceae or nightshadefamily. 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 UnitedStates (mostly in Florida and New Jersey), theDominican Republic, and Jamaica.

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, andUnclassified. 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) arecommonly used. Fruit are individually wrappedwith paper to reduce desiccation and mechanicalinjury.

Precooling Conditions
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 orhandling defects, and decay. Characteristics ofother 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 andviolet), Chinese (elongated, slender, and light
purple), and Thai (small, round, and striated darkgreen).

Horticultural Maturity Indices
Eggplant fruit are harvested at a range ofdevelopmental stages. The time from flowering
to harvest depends on cultivar and temperatureand may be 10 to 40 days. Fruit are harvested
immature before seeds begin to significantly
322

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 aremost effective, but room cooling after washing orhydrocooling 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 andsensory qualities deteriorate rapidly after 14 daysof 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 retailconditions.

Controlled Atmosphere (CA)Considerations
CA storage or shipping offers little benefit. Low
O2 levels (3 to 5%) delay deterioration and theonset 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 andmaintains firmness due to the high RH, especiallyon Japanese eggplant types, which have a hightranspiration 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

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 theflesh and seeds is a conspicuous internal symptomof chilling injury, almost invariably followed bydecay caused by Alternaria sp. (Ryan and Lipton
1979). Chilling injury is cumulative and may beinitiated in the field prior to harvest. Symptom
development can be reduced by storage inpolyethylene bags or polymeric film overwrapsthat retard water loss; however, increased decay
from Botrytis is a potential risk.

Eggplants should never be held in contact withice. Odor from ginger, and possibly other odorproducing commodities such as onions, can be

Table 1. Chilling susceptablity of eggplant by type_______________________________________________________
Temperature
Days to visible chilling symptoms_______________________________________________________
AmericanJapanese
Chineseeggplant
eggplant
eggplant_______________________________________________________
0.0 °C
1 to 2
2 to 3—
2.5 °C
4 to 55 to 65 to 6
5.0 °C
6 to 78 to 910 to 12
7.5 °C12
12 to 14
15 to 16_______________________________________________________

323

Respiration Rates
Temperature

American eggplant
White eggplant
Japanese eggplant-1 -1----------------------------------(mg CO2 kg h )----------------------------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.
Ethylene Production and Sensitivity

Quarantine Issues

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 greaterthan 1 µL L-1 ethylene during distribution andshort-term storage.

None.

Suitability as Fresh-Cut ProductNo current potential.

Special Considerations
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 moldrot), Rhizopus (hairy rot), Phomopsis rot, andPhytophtora (soft rot).
324

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 reductionof 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.

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 32:7174.
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 andVegetables, 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.

325

Endive and Escarole

Grades, Sizes, and Packaging

Mikal E. Saltveit

Similar to those of leaf lettuces.

Saltveit is with the Department of Plant Sciences,
University of California, Davis, CA.

Precooling Conditions

Scientific Name and Introduction

Vacuum cooling and hydrocooling to 0 °C (32 °F)
are preferred.

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), andradicchio (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 ofendive are dark green and bitter. The inner leaves
are light green to creamy white and milder inflavor. 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 ofbrowning, crisp, and bright green. Young, tenderleaves 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 basewhen 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 thefield. The leafy heads should be kept clean ofsoil and mud. The leaves should have a spicy andmildly bitter taste. Toughness and a strong bitter
taste develop if harvest is delayed and the crop
becomes overmature. The product then becomes
unmarketable.

326

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 haveusually been hand harvested, some mechanicalharvesters are available for product destined forbag mixes. However, the greater degree of injury
produced by mechanical harvesting may shorten
shelf-life unless optimal storage conditions arestrictly maintained. Top ice or package ice isdesirable 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 andshelf-life, and minimize dehydration with periodic
sprays of cold water. Conditions should be similar
to those used for leaf lettuces.

Chilling Sensitivity

Special Considerations

Endive and escarole are not chilling sensitive, butfreezing at -0.1 °C (31.8 °F) must be avoided.

Ethylene Production and Sensitivity

Endive and escarole must be handled with careto avoid mechanical damage and to minimize
discoloration and pathological problems.
Temperatures must be kept low and RH high toprevent loss of turgor and wilting.

Production is very low, but exposure can result inleaf yellowing.

References

Respiration Rates
Temperature
0 °C
5 °C
10 °C
15 °C
20 °C
25 °C

mg CO2 kg-1 h-1
45
52
73
100
133
200

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Ryall, A.L., and W.J. Lipton. 1979. Handling,
Transportation and Storage of Fruits andVegetables, 2nd ed., vol. 1, Vegetables andMelons. AVI Publishing Co., Westport, CT.
Ryder, E.J. 1979. Endive and chicory. Leafy Salad
Vegetables, pp. 171-194. AVI Publishing Co.,
Westport, CT.

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 ProductVery high, especially in salad mixes with otherleafy greens and lettuces.
327

Fennelto avoid scratching the sheaths. Mechanical injury
produces rapid browning of the leaves.

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 sourceof green stems and fuzzy leaves. Italian production
accounts for 85% of the world market. Fennel is asource of fiber, potassium, and vitamin C.
Quality Characteristics and Criteria

Precooling Conditions
Hydrocooling is needed in the summer to reduce
field heat and water loss. Aqueous citrate solutions
control browning of cut surfaces. Avoid excesswater infiltration during packing. Forced-air
cooling can be used, but only when fennel isplastic-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

There are no published quality standards, but
extra fancy fennel is characterized by uniform andbrilliant white leafy sheaths that are turgid andcrisp, with no symptoms of cracking or darkening.

Fennel must be kept refrigerated and periodicallymoistened with water sprays. Removal of injured
sheaths and brown cut surfaces may be needed.

Horticultural Maturity Indices

Chilling Sensitivity

Fennel is harvested by hand when the plantreaches a specified size by cutting the plant fromthe taproot. Outer leaves are removed, and theremaining leaves are trimmed to 10 to 15 cm (4 to6 in) in length. It is harvested year-round, except
in June and July.

Fennel is not chilling sensitive.

Grades, Sizes, and Packaging
Fennel is sized by the packer and placed in plastic
or cardboard boxes. Careful packing is necessary
328

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 etal. 1996). No data exist on sensitivity to ethylene.

Respiration Rates

References

mg CO2 kg-1 h-1
18 to 20
24 to 40

Bianco, V.V. 1990. Il finocchio. In V.V. Bianco and
F. Pimpini, eds., Orticoltura, pp. 168-183. Patron
Press, Bologna, Italy.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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.

Physiological Disorders

Sozzi, A., and V. Ilardi. 1992. Conservazione
con film microperforato e prerefrigerazione con
vacuum del finocchio. Colture Protette 4:73-76.

Temperature
2 °C
20 °C

Growth after harvest can cause the leaf sheaths
to loosen and separate (Mencarelli et al. 1996).
Freezing results in water-soaked spots on theoutside 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 ProductBrowning of cut surfaces is a problem with freshcut fennel.

Special Considerations
Special attention must be given to mechanicalharvesting 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.
329

Fig
Carlos H. Crisosto and Adel A. Kader
Crisosto is with the Department of Plant Sciences,
University of California, Davis, CA. Kader waswith the Department of Plant Sciences, Universityof California, Davis, CA. He is deceased.

Scientific Name and Introduction
Edible figs are the multiple or compound fruitsof 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 theMediterranean 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 isin California. Figs thrive only in the hotter partsof the moderate zones, while in tropical countries
they can be cultivated only at higher altitudes.
The best-known cultivated varieties are thecommon, or Adriatic, fig and the Smyrna fig.
The common fig produces seedless fruit byparthenocarpy (production of fruit without
fertilization), while the Smyrna fig must be
pollinated in spite of the fact that it does notdevelop any male flowers. The figs are pearshaped structures formed from the rolled-up discsof the capitula so that the florets of the capitulum
occur inside the aperture and are not visible fromthe outside. The capitulum is connected to theoutside 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.

330

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 absenceof defects (such as bird-peck, sunburn, scab, skinbreak, and stem shrivel), insects, and decay.

Horticultural Maturity IndicesFresh 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% moistureusing 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 andpacked in a one-layer box. Pickers wear gloves toprotect 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) isstrongly recommended.

Controlled Atmosphere (CA)Considerations

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.

CA combinations of 5 to 10% O2 with 15 to
20% CO2 are effective in decay control, firmness
retention, and reduction of respiration andethylene production. Postharvest life at optimum
temperature and RH depends on cultivar andripeness 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.

Extended storage in CA can result in loss ofcharacteristic flavor. Figs exposed to <2% O2 or>25% CO2 develop off flavors due to fermentative
metabolism.

Retail Outlet Display Considerations

Postharvest Pathology

Figs should be displayed at 0 to 2 ºC (32 to 36 ºF)
and dried with an RH of 90 to 95%.

Alternaria rot, caused by Alternaria tenuis,
appears as small, round, brown to black spots overthe fruit surface. Any cracks on the skin make thefruit more susceptible to the rot.

Physiological Disorders

Chilling Sensitivity
Figs are not chilling sensitive.

Rates of Ethylene Production andSensitivity
Temperature
0 ºC
5 ºC
10 ºC
20 ºC

µL kg-1 h-1
0.4 to 0.8
0.8 to 1.5
1.5 to 3.0
4.0 to 6.0

Figs are climacteric fruit and are slightly sensitive
to ethylene action on stimulating softening anddecay severity, especially if kept at 5 ºC (41 ºF) or
higher temperatures.

Respiration Rates
Temperature
0 ºC
5 ºC
10 ºC
20 ºC

mg CO2 kg-1 h-1
4 to 810 to 16
18 to 2440 to 60

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), andBlack mold rot, caused by Aspergillus niger,
appears as dark or yellowish spots in the flesh withno external symptoms. At advanced stages theskin and flesh turn a slightly pink color and white
mycelia with black spore masses follow.
Endosepsis (soft rot), caused by Fusariummoniliforms, appears in the cavity of the fig
making the pulp soft, watery, and brown withsometimes an offensive odor.
Souring is a preharvest problem resulting fromyeasts 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 offungi; using effective control of preharvest
diseases; enforcing strict sanitation of picking
and transporting containers; supervising carefulhandling to minimize abrasions, cracks, and otherphysical damage; avoiding picking figs from theground for fresh market; and enforcing prompt
cooling to 0 ºC (32 ºF) and maintaining the cold
chain all the way to the consumer.

331

Quarantine Issues
Currently, there is limited export to Canada. Thereis no import of fresh figs into the United States.
Issues associated with exotic pest quarantine
addressing both imported and exported fruitchange 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 freeof pests to facilitate compliance with foreign
regulatory requirements.

Suitability as Fresh-Cut ProductFresh 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 formationof 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.
332

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 26:11931195.
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 ofAgricultural Sciences, Davis, CA.

Marita Cantwell10-, 22-, and 30-lb) cartons and may also be
packed in smaller-weight net bags or trays forretail.

Cantwell is with the Department of Plant Sciences,
University of California, Davis, CA.

Cooling

Scientific Name and Introduction

Well-cured garlic has a very low respiration rateand it is typically cooled when placed in storage.
High initial airflow may be used to bring pulp
temperature down rapidly to storage temperature.

Garlic

Garlic, Allium sativum L., is a member of theonion family (Alliaceae). It is a bulb comprisedof cloves (thickened storage leaves) individuallywrapped 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 othercolor typical of the variety), and well-cured (driedneck and outer skins). The cloves should be firm
to the touch. Cloves from mature bulbs shouldhave a high dry weight and soluble solids content(SSC)—more than 35% in both cases.

Horticultural Maturity IndicesGarlic can be harvested at different stages ofdevelopment for specialty markets, but most garlicis 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 andare based primarily on external appearance andfreedom 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-,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 otherstorage containers is necessary to prevent any
moisture accumulation. Garlic can also be held incommon 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 intermediatestorage 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 withpreharvest applications of sprout inhibitors, suchas maleic hydrazide, or be irradiated after harvest(Hardenburg et al. 1986). Garlic odor is easilytransferred to other products, so garlic should be
stored separately. High RH in storage will favormold growth and rooting. Mold growth can also
be problematic if garlic has not been well cured
before storing.
333

Controlled Atmosphere (CA)Considerations
Atmospheres with high CO2 (5 to 15%) are
beneficial in retarding sprout development anddecay 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 andis not particularly sensitive to ethylene exposure.

Respiration Rates
Temperature
Intact bulbs Fresh-peeled		cloves---------mg CO2 kg-1 h-1------0 °C
4 to 1224
5 °C
8 to 2430 to 40
10 °C
12 to 36
70 to 10015 °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 rateby 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,334

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 isoften associated with periods of high temperaturenear harvest. Early symptoms are small, lightyellow areas in the clove flesh that darken toyellow or amber. Later, the clove becomestranslucent, sticky, and waxy, but the outer dryskins 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 handlingand storage may also be contributing factors.

Postharvest Pathology
Penicillium rots (Pencillium corymbiferum andother 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 stageof decay, the cloves break down in a green orgray 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 plateand causes cloves to shatter; dry rot due toBotrytis allii; and bacterial rots (Erwinia spp.,
Pseudomonas spp.).

Quarantine Issues
None.

Suitability as Fresh-Cut Product
Whole-peeled garlic cloves are a popularconvenience product processed originally for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 damageis 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 rootand 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 outerleaf sheaths and neck tissues of the bulb are dried.
Warm temperatures, low RH, and good airflow
are conditions needed for efficient curing. Underfavorable climatic conditions in California, garlic
is usually cured in the field. After harvest andtrimming, it may remain in bins in the field to curefurther. Curing is essential to maximize storage
life and minimize decay.
The characteristic odor and flavor of fresh garlic isdue to the formation of organosulfur compounds
when the main odorless precursor alliin isconverted to allicin by the enzyme alliinase.
The content of alliin decreases during storage,
but the effect of time, storage temperature, andatmosphere has not been well documented.
Production of allicin occurs at low rates unless thegarlic cloves are crushed or damaged. Allicin isalso 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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Kwon, J.H., M.W. Byun, and H.O. Cho. 1985.
Effects of gamma irradiation dose and timing oftreatment after harvest on the storeability of garlicbulbs. J. Food Sci. 50:379-381.
Mann, L.K., and D.A. Lewis. 1956. Rest anddormancy in garlic. Hilgardia 26(3):161-189.
Shaffer, E., ed. 2000. Produce Availability andMerchandising 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 andstability of sulfur-containing compounds in thegenus Allium. In G. Charalambous, ed., Shelflife Studies of Food and Beverages. Chemical
Biological and Nutritional Aspects, pp. 501-546.
Elsevier Science, New York, NY.

335

Ginger

Precooling Conditions

Robert E. Paull and Ching Cheng Chen

Forced-air or room cooling to 12 to 14 °C (54 to
57 °F) should be used.

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) isreferred to as a “root” and is used as a spice incooking and as a pickled vegetable. The knobby,
fibrous mature root has a light yellowish-brownskin when fresh. The rhizome is also harvested at
a very early stage, before fiber development has
taken place, for use in pickles and confectionery.

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 canoccur if condensation occurs on rhizomes.

Controlled Atmosphere (CA)Considerations
There are no published recommendations.

Quality Characteristics and Criteria
Desired quality characteristics include skin color,plumpness of tuber pieces, sheen on skin, andabsence of vegetative sprouts, blemishes, soil,
and insect injury. Young ginger is bright yellow tobrown and has a high sheen with greenish-yellow
vegetative buds, but no sprouts.

Retail Outlet Display Considerations
Display fresh young ginger with misting andmature ginger at ambient temperature with no
misting.

Chilling Sensitivity
Horticultural Maturity Indices
Mature ginger rhizomes are harvested when theplant tops begin to wilt and die. These rhizomes
should be plump with a dry, bright yellow-brownskin. The sheen is soon lost and the skin darkens
after harvest.

Mature ginger is chilling sensitive if held below
12 °C (54 °F). Symptoms include loss of skincolor and pitting of the skin. In severe cases there
is internal breakdown.

Ethylene Production and Sensitivity

Grades, Sizes, and Packaging

Very low.

Rhizomes are sold in full, telescoping 13.61-kg(30-lb) and 9.06-kg (20-lb) fiberboard cartons orin 2.27-kg (5-lb) cartons with film bags.

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 rateby 2.0 at 0 °C (32 °F), 1.9 at 10 °C (50 °F), and336

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.

Haware, M.P., and L.K. Joshi. 1974. Studies onsoft rot of ginger from Madhya Pradesh. Indian
Phytopath. 27:158-161.

Physiological Disorders

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.

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 ofabout 10% of harvest weight (Paull et al. 1988).

Paull, R.E., N.J. Chen, and T.T.C. Goo. 1988.
Compositional changes in ginger rhizomes duringstorage. J. Amer. Soc. Hortic. Sci. 113:584-588.

Postharvest Pathology
Fusarium rot (Fusarium spp.) can cause serious
problems. Symptoms include pale-brown
discoloration of the vascular strands (Trujillo1963) that invades the rest of the rhizome, whichthen 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, butreasonable control is obtained if the rhizomes areadequately 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 anunsightly appearance.

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 53:13701371.

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.

337

Ginseng

Precooling Conditions

Seung Koo Lee and Sang Don Yun

Ginseng roots are commonly hydrocooled orforced-air cooled to below 5 ºC (41 °F). Cooling
generally retards subsequent deterioration such as
weight loss and decay.

Lee and Yun are with the Department of
Horticulture, Seoul National University, Suwon,
South Korea.

Optimum Storage Conditions
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 UnitedStates.

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 attenuatedcavitation 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).

Quality Characteristics and Criteria
High-quality ginseng has a firm main root without
defects. It should be clearly defined to show ahead (rhizome), body (main root), and legs (lateralroots).

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.

Retail Outlet Display Considerations
Ginseng roots are displayed with green leafy
vegetables, and water loss is controlled byhumidification or packaging.
Chilling Sensitivity
Ginseng is not chilling sensitive and should be
stored as cold as possible without freezing.

Ethylene Production and Sensitivity
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.
338

Ginseng roots produce only minute amounts ofethylene and are not sensitive to ethylene.

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 rateby 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 acommon problem caused by cultural conditions
and starch breakdown (Park et al. 1986, Yun
1998). Other disorders include discolored skin andflesh 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 bemaintained to minimize pathological disorders andprolong shelf-life.
Quarantine Issues
None.

Suitability as Fresh-Cut Productlateral roots. Damaged areas provide a route forentry 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. Officeof Monopoly, Seoul, Korea.
Oh, H.I., H.W. Noh, J.H. Do, et al. 1981. Physicochemical and microbiological changes duringstorage 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 Reportof Study in Korean Ginseng. Korean Ginseng andTobacco 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.

No current potential.
Special Considerations
Careful handling is mandatory because it is easy
to bruise the surface of main roots and break339

Grape (American)

Precooling Conditions

Penelope Perkins-Veazie

Forced-air cooling to lower the temperature to
below 2 °C (36 °F) within a day of harvest isrecommended.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof Horticultural Science, North Carolina State
University, N.C. Campus, Kannapolis, NC.

Scientific Name and Introduction
American grapes (Vitis labrusca L.) are grown inareas 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.

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 shatterand 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 incooling greatly increase shatter and decay (Lutz
1939).

Chilling Sensitivity
American grapes are not known to be chilling
sensitive.

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 ortrimmed clusters (rachis and berries) in bulk in
lugs, in quart-size vented plastic containers, or inplastic slit bags of 2 lb (0.9 kg).

340

Ethylene Production and Sensitivity
Stimulation of Botrytis cinerea (gray mold)growth can occur on berries and stems in thepresence of ethylene. Ethylene production from
American grapes is less than 0.1 µL kg-1 h-1.

Respiration Rates

Suitability as Fresh-Cut ProductTemperature
mg CO2 kg-1 h-1
0 ºC
3
4 to 5 ºC
510 ºC
815 to 16 ºC
1620 to 21 ºC
33
25 to 27 ºC
39Data from Lutz (1939).

No information at this time.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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).

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 Qualityof 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. 43:230232.
Hewitt, W.B. 1988. Berry rots and raisinmolds. In R.C. Pearson and A.C. Goheen, eds.,
Compendium of Grape Diseases and Insects, pp.
26-27. APS, St. Paul, MN.

Quarantine Issues
None.

341

Grape (Muscadine)

Grades, Sizes, and Packaging

Penelope Perkins-Veazie

No standard packaging exists; quart size is mostcommonly used. Grapes are generally packaged as
single or small clusters of berries in plastic, vented
clamshells.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof Horticultural Science, North Carolina State
University, N.C. Campus, Kannapolis, NC.

Precooling Conditions
Use forced-air to lower the temperature to 2 °C or
below within 12 h of harvest.

Scientific Name and Introduction
Muscadine grapes (Vitis rotundifolia Michx.)
are grown primarily in the Southern UnitedStates (Olien 1990). Unlike V. lambrusca andV. vinifera, muscadines are borne singly or insmall clusters of 3 to 10 berries and detach fromtheir pedicels when ripe. V. rotundifolia is moreresistant 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.

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 thecoldest refrigeration temperature possible without
freezing. As little as 2 days at room temperature
can stimulate growth of molds, especially ripe rot.

Horticultural Maturity Indices
For fresh market, muscadines are mature whenberries can be detached from their stems or when
SSC is between 14 and 18% (Smit et al. 1971,
Ballinger and McClure 1983).

342

Chilling Sensitivity
Muscadines are not known to be chilling sensitive.

Ethylene Production and Sensitivity

Special Considerations

Stimulation of Botrytis cinerea (gray mold)growth can occur on grapes and stems in thepresence of ethylene. Ethylene production frommuscadines is less than 0.1 µL kg-1 h-1 (PerkinsVeazie, unpublished).

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).

Respiration Rates

References

Temperature
mg CO2 kg-1 h-1
2 °C
6 to 145 °C
8 to 18
20 °C
33 to 68
Data from Perkins-Veazie (2002, unpublished).

Ballinger, W.E., and W.B. Nesbitt. 1982. Qualityof muscadine grapes after storage with sulfur
dioxide generators. J. Amer. Soc. Hort. Sci.
107:827-830.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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), andblue mold (Penicillium) (Ballinger and McClure
1983, Pearson and Goheen 1988).
Quarantine Issues
None.

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. 28:171173.
James, J., O. Lamikanra, G. Dixon, et al. 1997.
Shelf-life study of muscadine grapes for the freshmarket. Proc. Fla. State Hort. Soc. 110:234-237.
Lutz, J.M. 1938. Factors Influencing the Qualityof 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.

Suitability as Fresh-Cut ProductUnknown. Processing work with juice and jellies
indicates that unstable pigments may cause
browning problems if used for minimal processing(Flora 1977).
343

Grape (Table)

Horticultural Maturity Indices

Carlos H. Crisosto and Joseph L. Smilanick

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 todetermine minimum maturity for cultivars thatmeet a low minimum SSC. For red- and blackcolored cultivars, there is also a minimum color
requirement.

Crisosto is with the Pomology Department,
University of California, Davis, CA; Smilanick isformerly with the Horticultural Crops ResearchLaboratory, 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 rateof physiological activity. It is subject to serious
water loss following harvest, which can result instem drying and browning, berry shattering, andeven 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. Presentinterest 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 CriteriaHigh consumer acceptance is attained for fruitwith high soluble solids content (SSC) or a highratio 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.

344

Grades, Sizes, and Packaging
Most California table grapes are packed in thefield. 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 tothe packer, who works at a small, portable stand in
the avenue between vineyard blocks.
Shed-packed fruit are harvested by pickers andplaced 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 arepacked 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 allcases, packed lugs are subject to quality inspection
and check weighing.
After packing and lidding, grapes are palletizedon disposable or recycled pallets. Some strappingin 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

are unitized, usually by strapping or netting.
Some palletizing glue is used in shed-packing
operations. This glue bonds the corrugatedcontainers 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 toachieve seven-eighths cooling in 6 h or less. Aftercooling is complete, pallets are moved to a storage
room to await transport.

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
Optimum Storage Conditions
Table grapes are not chilling sensitive.
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 temperatureof -0.5 to 0 ºC (31 to 32 ºC) throughout theirpostharvest life.

Ethylene Production and Sensitivity
Table grapes produce less than 0.1 µL kg-1 h-1 at 20ºC (68 ºF) ethylene. They are not very sensitive toethylene.

Respiration Rates
Optimum Temperature
A storage temperature of -1 to 0 ºC (30 to 32ºF) is recommended for mature fruit. Freezing
damage may occur in less mature grapes. The
highest freezing point for berries is -3.0 ºC (27oF), 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 tablegrape 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.

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 rateby 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.

345

Physiological Disorders
Shatter is a loss of berries from the cap stem.
In general, shatter increases in severity withincreasing maturity (that is, the longer fruit remainon the vine). Berries of seedless cultivars areusually less well attached to the cap stem thanseeded cultivars. Shatter varies considerably fromseason 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 withadditional shatter occurring all the way to final
retail sale. Shatter incidence can be reducedby 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 symptomis the development of small (1- to 2-mm) dark
spots on the cap stems (pedicles) and/or otherparts 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 witha 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 inwaterberry-prone vineyards. Removing affected
berries during harvest and packing is a common,though labor-intensive, practice.

Postharvest Pathology
Gray mold. The most destructive of thepostharvest diseases of table grapes is graymold (Botrytis cinerea), primarily because it
develops at temperatures as low as 31 oF (-0.5oC) and grows from berry to berry. Gray moldfirst turns berries brown, then loosens theskin of the berry. Its white, threadlike hyphalfilaments erupt through the berry surface, and346

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 theprevious 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 andfumigation with SO2 (100 µL L-1 for 1 h) areessential 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 inwhich grapes are in ocean transport for extended
periods. These pads have sodium metabisulfite
incorporated into them that releases SO2 duringtransit and marketing.
Other pathogens. Black rot, caused by Aspergillus
niger; blue rot, caused by Penicillium spp.; andrhizopus rot, caused by Rhizopus stolonifer or R.
oryzae, become important at warmer temperatures,and they commonly appear sometime duringtransport or marketing after grapes are removed
from cold storage. They are at least partiallycontrolled 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 withlower-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 thatthe amount of SO2 gas needed to kill Botrytis
spores or to inactivate exposed mycelium depends
on the concentration and length of time thefungus is exposed to the fumigant. A cumulative
concentration, calculated as the product ofconcentration 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 isthe minimum required to kill spores and mycelia

of Botrytis at 0 oC (32 oF). This finding was thebasis 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 effectivenessof SO2 fumigant. In this total utilization system,
the first fumigation is done in conjunction withforced-air cooling. The forced air flows throughboxes and ensures good penetration of SO2 even to
the center boxes on a pallet. In most combinationsof boxes and packs, this system produces over
80% penetration, measured as a percentage of theroom 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 SO2generating pads in combination with a box liner isadvised. These SO2-generating pads have sodium
metabisulfite incorporated into them to allow a
constant and slow release of SO2 during shippingand marketing. In California, a slow-releaseSO2-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).

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 ontable 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.

Quarantine Issues
Issues associated with exotic pest quarantines,
addressing either imported or exported tablegrapes, 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.

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.

347

References
Ahumada, M.H., E.J. Mitcham, and D.G. Moore.
1996. Postharvest quality of ‘Thompson Seedless’grapes after insecticidal controlled-atmospheretreatments. 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. Departmentof 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 andalternatives. Chemical Use in Food Processing andPostharvest 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.

348

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 significanceto 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 asinfluenced by adding carbon monoxide to air orcontrolled atmospheres. J. Amer. Soc. Hort. Sci.
108:1067-1071.
Yokoyama, V.Y., G.T. Miller, and C.H. Crisosto.
1999. Low temperature storage combined withsulfur dioxide slow release pads for quarantine
control of omnivorous leafroller Platynota
stultana (Lepidoptera: Tortricidae). J. Econ.
Entom. 92(1):235-238.

Grapefruit

Grades, Sizes, and Packaging

Jacqueline K. Burns

Marketable fresh grapefruit generally range fromsize 23 (23 fruit/carton) to 56 (56 fruit/carton).
Grade standards for fresh grapefruit rely oncolor-break, texture, peel blemishes, shape, andfirmness. Grapefruit are commonly packed, stored,
and shipped in 4/5-bushel cardboard cartons (Soule
and Grierson 1986).

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 wasintroduced in Florida in the early 19th century(Gmitter 1995). The grapefruit is classified asa hesperidium, a kind of berry with a leatheryrind that is divided into segments. Each segment
contains hundreds of individual juice vesicles
that compose the majority of the edible portionof the fruit. Florida is the largest producer ofgrapefruit in the United States, followed by
Texas, California, and Arizona. White- and redpigmented cultivars are grown. ‘Marsh’ is thedominant white cultivar. ‘Ruby Red,’ ‘Star Ruby,’‘Henderson,’ ‘Ray Ruby,’ and ‘Flame’ are themost popular red-pigmented cultivars (Saunt
2000).

Optimum Storage Conditions

Quality Characteristics

Controlled Atmosphere (CA)Considerations

A high-quality fresh-market grapefruit will havea 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 aminimum.

Though some benefit of increased firmnessand delayed senescence can be gained fromCA storage, commercial use of CA storage forgrapefruit is very limited or nonexistent (Arpaia
and Kader 2000).

Horticultural Maturity Indices

Chilling Sensitivity

In markets that emphasize processing, grapefruit
must achieve a minimum juice content and
SSC:TA ratio before harvest.

Chilling injury can occur with low-temperaturestorage, 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

Grapefruit are typically stored at 12 to 15 °C (54to 59 °F) with 95% RH. Coatings are appliedin the packinghouse to reduce water loss fromthe 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) duringtransit 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).

349

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 reducechilling injury.

Oleocellosis can occur during harvest when
excessive squeezing force is used to remove fruitfrom the stem. Grapefruit harvested in the morning,when RH is high, are most susceptible because oilglands are easily broken in turgid peel. Symptomsof oleocellosis appear in the packinghouse or instorage, and can be exacerbated by degreening.

Ethylene Production and Sensitivity

Stem-end rind breakdown (SERB) is characterizedby 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.

The grapefruit is a nonclimacteric fruit and does
not exhibit a classic ripening pattern of increased
respiration and ethylene production. The rate ofethylene production is typically <0.1 μL kg-1 h-1 at
20 °C.
Degreening is necessary for marketing earlyseason fresh grapefruit in areas where nighttemperatures remain high. In these cases, 1 to 5
μL L-1 ethylene for periods of 12 h to 3 days isused 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 andaccentuation 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 andethylene distribution (Wardowski 1996).

Respiration Rates
Respiration rates at optimum storage temperatureare generally <10 mg CO2 kg-1 h-1 (Arpaia andKader 2000).

Blossom-end clearing is most commonly foundin late harvested, thin-peeled red-pigmented
grapefruit. The wet, translucent area that develops
dominantly on the blossom end results from theleaking of juice from the segments to the peel.
Blossom-end clearing can be reduced by reducing
pulp temperatures to <21 °C (70 °F) after harvestand eliminated by avoiding high-impact handlingprocedures (Echeverria et al. 1999).
Green ring is a physiological disorder that appears
on early-season grapefruit in Florida. The disorderis characterized by failure of the peel to degreen incircular areas around fruit-to-fruit contact points.
The remaining green ring can become necrotic asfruit remain in storage. The incidence of green ring
disappears as the fruit peel matures.
Interest in long-term storage of grapefruit hasdeveloped 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
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 andAlbrigo 1998). Granulation can be avoided byharvesting large fruit early in the season.
350

Postharvest pitting is a peel disorder that affects
waxed grapefruit stored at higher temperatures.
Postharvest pitting can be reduced or eliminatedby 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).

Postharvest decay can result in significant lossesof grapefruit. Postharvest grapefruit decays
generally fall into two categories: those thatdevelop as a result of colonization or infection
on the fruit before harvest (stem end rots,
anthracnose, and brown rot) and those thatdevelop 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 thecore after harvest. The decay develops unevenly
at the stem and stylar ends resulting in wavy
margins. Stem-end rots are a problem withgrapefruit 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 isused. Development of Phomopsis citri is favoredduring the winter months when temperatures
are low and degreening is no longer necessary.
Alternaria citri is a less aggressive fungus thatcan be problematic in overmature grapefruit andthose in extended storage. Often the symptoms ofalternaria, 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 morefavorable at temperatures above 10 °C (50 °F),
whereas growth of P. italicum occurs more readily
at lower temperatures. Immature fruit are resistantto sour rot (Geotrichum candidum) infection,
but as the fruit mature, the disease can becomea problem. Consequently, late-season grapefruit
can become infected, especially since the diseasedevelops more readily at temperatures above 15°C (59 °F) (Eckert and Brown 1986, Whiteside
1988, Florida Department of Citrus 1996).

Drenching harvested grapefruit withthiabendazole (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 incontrolling stem-end rot caused by Diplodia andanthracnose. Careful harvesting and handling canreduce injuries that allow wound pathogens toenter grapefruit. Good sanitation of packinghouseequipment 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 resistanceto 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, aless stringent temperature-duration schedule canbe used (Florida Department of Citrus 1996).
The appearance of citrus canker (Xanthomonas
axonopodis pv. citri) has restricted movementof 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 displayedon refrigerated shelves of Southeastern U.S.
retail markets. Technological developments haveovercome various postharvest problems withfresh-cut citrus. However, further development of
automated systems for efficient and economical
peeling is essential (Pao et al. 1997).
351

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 andAir-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 availabilityof ‘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 granulationin grapefruit. HortScience 33:728-730.
Echeverria, E., J.K. Burns, and W.M. Miller. 1999.
Fruit temperature and maturity affect developmentof 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, andbreeding of the grapefruit. In J. Janick, ed., Plant
Breeding Reviews, vol. 13, pp. 345-363. John
Wiley & Sons, New York, NY.

352

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 andgrade standards. In W.F. Wardowski, S. Nagy, andW. 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.

Greens for Cooking

Grades, Sizes, and Packaging

James W. Rushing

All greens for cooking, except spinach, areclassified 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 requirementsof the buyer and the physiological condition of
the product. Obviously, large, overmature leaves
would not be marketed.

Rushing is formerly with the Coastal Researchand 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 oleraceaeL.), mustard (Brassica juncea [L.] Czerniak),and turnip (Brassica rapa L. var. [DC.] Metzg.
utilis) (Maynard and Hochmuth 1997). Since theintended 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 begiven to fresh salad greens. However, managers
should recognize that quality at the point of saleis 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 ortype of greens, and free from decay, discoloration,
freezing injury, foreign material, disease, insects,
and damage caused by coarse stalks or othermechanical 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 reachednearly full size but have not begun to senesce.
Hand-harvesting allows a greater degree of
selection of leaf size, whereas in mechanicalharvesting every leaf large enough to reach the
cutting blade is taken.

Leaf collards, kale, turnip greens, and mustard
are commonly bunched using rubberbands ortwist ties. The size of the bunch may vary but
is generally approximately 0.5 kg (1 lb). Directpacking of loose leaves may be done at the requestof 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 andmore tender, may be packed loose or bunched, butthey 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 washingor cooling should contain approximately 200 µL
L-1 chlorine (Kasmire and Cantwell 1999). When
package-iced, approximately 1 kg (2.2 lb) of ice isrecommended 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) with95 to 98% RH. Crushed ice may be placed in353

baskets or boxes to help maintain low temperatureand high RH. When properly handled, greensin 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.

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 225 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 rateby 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.

Retail Outlet Display Considerations

Physiological Disorders

Though greens are sometimes displayed on
unrefrigerated counters, they should be placedon ice or on refrigerated counters. Intermittent
misting minimizes water loss and wilting.

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).

Chilling Sensitivity
Postharvest Pathology
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 spinachis <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 thesame general range as that of spinach (Kader
1992). All leafy greens are sensitive to ethylene
in the postharvest environment, which accelerates
354

Bacterial soft rots, primarily caused by Erwinina
and Pseudomonas, are the most common typesof 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appropriate agency in the importing country toensure that all regulations are met.

Suitability as Fresh-Cut ProductAll 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.

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. Departmentof 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 andtechnology: an overview. In A.A. Kader, ed.,Postharvest Technology of Horticultural Crops,
pp. 15-20. DANR Pub. no. 3311, University ofCalifornia, Davis, CA.

References
AMS [USDA Agricultural Marketing Service].
1946. United States Standards for Grades of
Spinach Leaves (Fresh). U.S. Department ofAgriculture, Agricultural Marketing Service,
Washington, DC.
AMS [USDA Agricultural Marketing Service].
1953a. United States Standards for Gradesof 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 Gradesof 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 andtransportation of fruits and vegetables. Universityof Georgia Fact Sheet 100. At http://pubs.caes.uga.
edu/caespubs/pubcd/FS-100.

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 andVegetable 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.

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.
355

GuavaGrades, Sizes, and Packaging

Robert E. Paull and Ching Cheng Chen

Guava fruit are commonly shipped in 4.5-kg(10-lb) single-layer cartons with foam sleeves orwrapping to prevent injury.

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 andripeness. Size and shape are other importantquality 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 tobe 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 highnumber of fruit fly stings and, later, larvae in theflesh. Soluble solids content (SSC) can vary from
3% in green fruit to over 10% in ripe fruit, andtotal acidity (TA) from 0.2 to 1.5%; cultivars vary
greatly in sweetness and acidity. There is alsoseasonal variation in acidity in some cultivars.

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 heldfor 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 whenstored 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 polyethylenebags and use of wax coatings delay ripening andsoftening. Skin blackening is a problem whensome wax coatings are applied (McGuire andHallman 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 ripe356when chilled. Browning of the flesh can occur.
Decay incidence and severity increase withchilling injury. Ripe, soft fruit can be held at 5 °C
(41 °F), as they are less sensitive to chilling injury.

rot (Phomopsis destructum), and rhizopus rot(Rhizopus stolonifer). Orchard sanitation andeffective postharvest management, such as
avoiding mechanical injury and prompt cooling,
can reduce disease incidence.

Ethylene Production and Sensitivity
Quarantine Issues
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).

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 bothpotential disinfestation procedures.
Suitability as Fresh-Cut ProductRespiration Rates
Temperature
10 ºC
20 ºC

-1

-1

mg CO2 kg h
8 to 60
18 to 130

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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, alongwith mechanical injury. Desiccation leads to adull yellow, sometimes wrinkled, skin, whilemechanical injury leads to browning that can
extend into the flesh. Mechanically injured areasof the skin and flesh are very susceptible to decay.
Postharvest Pathology
Most diseases have preharvest origins and aresometimes latent infections such as anthracnose(Colletrotrichium gloeosporioides). Other
diseases are associated with entry of pathoges
via wounds from insect stings or mechanicaldamage; for example, aspergillus rot (Aspergillus
niger), mucor rot (Mucor hyemalis), phomopsis

Sliced mature green fruit are available in many
Southeast Asian countries and are eaten like apple
slices. Ripe fruit are also prepared as slices withboth 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. Universityof 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 ofstorage temperatures and ethylene treatment
on guava (Psidium guajava L.) fruit ripening.
Postharv. Biol. Technol. 6:357-365.

357

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. Departmentof Agriculture, Weslaco, TX. Lester is now with
the Office of National Programs, Agricultural
Research Service, U.S. Department ofAgriculture, Beltsville, MD. Shellie is now with
the Horticultural Crops Research Laboratory,
Agricultural Research Service, U.S. Departmentof Agriculture, Parma, ID.

Scientific Name and Introduction
Cucumis melo L. (Inodorus Group), called wintermelons even though they are mainly grown in thespring 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, rustspot, bruises, broken skin, solar injury (sunscaldand 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 thecolor is mostly whitish with a light-green tinge.
These fruit should be well filled out and coveredby 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
358

white, slightly waxy, and may have very sparse
netting. Full-slip hybrid honeydew melons, versus
honeydew melons cut at harvest, are perceived byconsumers to have superior flavor, texture, andsweetness.

Horticultural Maturity Indices
Honeydew melons, hybrids and nonhybrids, areready 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 andcold melons have little aroma. The majority ofhoneydew 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 theblossom end is springy. The flesh should be soft,
almost white, with a slight salmon cast aroundthe 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, isbright canary yellow (the brighter the peel, theriper the melon) and the oval-shaped fruit isspringy at the blossom end. The flesh should becrisp, flavorful, and white, with a hint of pinkaround 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).

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). Sizeclassification is the number of fruit (based on a
uniform fruit diameter and fruit weight) per box toachieve a standard weight of 13.6 kg (30 lb). The
distinct size classes are 4, 5, 6, 8, and 9.

Chilling Sensitivity
Chilling injury can occur at temperatures below
7 ºC (45 °F), but the riper the melon the moretolerant to chilling injury. Injury is expressed as
pitting and darkened, elongated patchy surface
lesions.

Ethylene Production and Sensitivity
Precooling Conditions
Honeydew melons harvested cut from the vineneed not be precooled. Full-slip melons should beprecooled 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 areacceptable methods of precooling. Hydrocoolingis 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.

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
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 (50ºF) 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 beheld for 7 to 10 days.

Controlled Atmosphere (CA)Considerations

Temperature
5 ºC
10 ºC
15 ºC
20 ºC
25 ºC

mg CO2 kg-1 h-1
8
14
24
30
33

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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
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 andshould therefore be displayed promptly on arrival.

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 morethan 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
359

(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 instorage (Bruton 1995, Zitter et al. 1996).

and flesh thickness—that is, piece yield. Fruitshould 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 whenstored at 5 ºC (41 °F). Modified atmospheres of
5% O2 combined with 5% CO2 are beneficial inretarding microbial growth and reducing loss infirmness and other quality degradations. Shelf-lifeof honeydew fruit cubes is not reduced by taking
pieces from defective areas such as the groundspot or sunburned regions, but eating quality is
reduced due to lower sugar content, green color,and firmness (Wu and Watada 1999).

Quarantine Issues
Honeydew melons entering the United States must
be disinfested of external feeders (noctuid moths,
thrips, and Copitarisa species) by fumigation withmethyl 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 theserestrictions, but the limited supply and increasing
cost of methyl bromide may make it undesirable
for commercial use in the future.

Special Considerations
Product quality and shelf-life of full-slip, hybrid
honeydew can be extended by applying an aminoacid-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 ofAgriculture, Washington, DC.
APHIS [USDA Animal and Plant HealthInspection 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. Departmentof Agriculture, Hyattsville, MD.

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 areappropriate for fresh-cut processing. Cultivar
selection is essential as there is considerable
variation among cultivars for sugar, firmness,
360

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.

Bruton, B.D. 1995. Etiology, epidemiology, andcontrol of muskmelon fruit rots. In G.E. Lester
and J.R. Dunlap, eds., Cucurbitaceae ’94, pp. 4854. 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 honeydew melon fruits. HortScience 27:1012-1014.
Lester, G.E., and M.A. Grusak. 1999. Postharvest
application of calcium and magnesium tohoneydew 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 andVegetables, 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-grownfruits and vegetables. J. Rio Grande Valley Hort.
Soc. 17:170-175.
Wu, T.Z., and A.E. Watada. 1999. Quality changesof 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.

361

Horseradish

Grades, Sizes, and Packaging

Franciszek Adamicki

Horseradish roots Grade I should be at least 25
cm (10 in) long and 2.5 cm (1 in) in diametermeasured one-third of the distance from the top.
Grade II horseradish roots are 15 cm (6 in) longand 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 (44to 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).

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, andmedicinal 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.

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

Quality Characteristics and Criteria
Several criteria are used for quality evaluationof horseradish, such as uniformity of shape andsize, 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 isharvested at an early stage of development andthe roots used for processing. Horseradish that isharvested when roots are actively growing does
not store as well as roots that are conditioned bycold before harvest.

362

Roots can be stored for 8 to 12 mo at 0 °C
(32 °F) with 98 to 100% RH (Adamicki etal. 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 andharvested 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. Highlevels of CO2 increase respiration but do not cause
greater loss of weight, dry matter, or sugar content

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 polyethylenebags can be placed on refrigerated shelves forseveral days at temperatures below 10 °C (50 °F).

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 rootwhen the root is cut lengthwise. It is the major
reason for loss in market quality of horseradish
roots.

Chilling Sensitivity
Quarantine Issues
Horseradish roots are not chilling sensitive andcan survive temperatures as low as -8 °C (18 °F)(Bohling and Hansen 1980).

None.

Suitability as Fresh-Cut Product
Ethylene Production and Sensitivity
There is no current potential.
Horseradish roots produce a very low amount of
ethylene, <1 mL kg-1 h-1, and are not particularly
sensitive to ethylene exposure.

Adamicki, F., W. Macias, and E. Badełek.
1999. Effect of temperature on the quality andstorage ability of two cultivars of horseradish.
Unpublished.

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.
-1-1

References

Bohling, H., and H. Hansen. 1980. Influence ofcontrolled atmosphere on the respiration activityof achlorophyllous vegetable kinds. Acta Hort.
116:165-170.

-1-1

To get mL CO2 kg h , divide the mg kg h rateby 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

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.

There are no important physiological disorders ofhorseradish root.

363

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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Ryall, A.L., and W.J. Lipton. 1983. Handling,
Transportation and Storage of Fruits andVegetables, vol. 1, 2nd ed. AVI Publishing Co.,
Westport, CT.
Schirmer, H., and B. Tauscher. 1999.
Langzeitlagerung von Meerretich bei
unterschiedlichen Temperaturen. Gemüse 7:449450.
Weichmann, J. 1980. CA storage of horseradish(Armoracia rusticana Ph.Gärtn., B.May. et
Scherb.). Acta Hort. 116:171-178.

364

Jerusalem Artichoke

Quality Characteristics and Criteria

Stanley J. Kays

Tuber size and shape are critical quality attributes
and are strongly modulated by cultivar andproduction conditions. Many clones havean irregular tuber surface topography due tobranching, an undesirable trait.

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, andthe cultivar selected depends on the production
location. Commercial production in the UnitedStates 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 factthat the storage form of carbon in the Jerusalem
artichoke is inulin, a straight chain fructan that ispoorly digested by humans. Inulin can be used as abulking agent in foods when sugar is replaced withan artificial sweetener. The volume previously
occupied by sugar is replaced by the low-calorie
inulin, allowing the total caloric content of theprocessed 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 texturalproperties. Likewise, inulin, whether ingested
as Jerusalem artichoke tubers or as a bulking
agent, is a dietary fiber and confers a number ofhealth advantages. For example, it lowers blood
cholesterol level; promotes Bifido bacteria in thelarge intestine; reduces blood sugar level, lowdensity lipoproteins, and triglycerides; and helps
prevent certain heart diseases (Varlamova et al.
1996).

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 notestablished. Package physical parameters varywith storage temperature, product volume, andother factors.

Precooling Conditions
Generally, precooling is not required, thoughplacing the tubers under favorable lowtemperature 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 insitu field storage. In common storage in root
cellars, champs, or pits, cooling is obtained fromthe natural low temperatures of the outdoor air andsoil (Shoemaker 1927). In the first two options(refrigerated and common storage), tubers are
harvested in fall and placed in storage. With fieldstorage, however, tubers are left in the ground365and harvested as needed. Cold storage is highly
effective, but costly. Regardless, refrigerated
storage is routinely used for seed and freshmarket tubers, especially in situations where fieldstorage 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 freezingor other adverse conditions occurring, andrefrigeration is not available or is prohibitively
expensive.

Retail Outlet Display Considerations

The selection of in situ field storage depends
on several factors. Location is the primary
determinant in the potential success of in situ fieldstorage. Field storage is a viable option in northernhemisphere production areas where cold soil
temperatures prevail throughout the winter, butfreezing 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 ofrefrigeration or some form of common storage.

Tubers can withstand low temperatures without
damage but freeze at -2.2 °C (28 °F) (Whiteman1957). Freezing at -10 °C (14 °F), whether in thefield 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).

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 asthat afforded by mist systems.

Chilling Sensitivity

Ethylene Production and Sensitivity
Optimum Storage Conditions
Tubers are not sensitive to ethylene.
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 atvarious temperatures is shown in the section on
Respiration Rates below.

Respiration Rates

Controlled Atmosphere (CA)Considerations

Temperature
Respiration		mg CO2 kg-1 h-1
0 °C
10.2
5 °C
12.3
10 °C
19.4
20 °C
49.5
Data from Peiris et al. (1997).

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).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

366

Rate of dry
matter loss
g kg-1 day-1
0.162
0.201
0.317
0.801

Physiological Disorders

Special Considerations

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 thatfound 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.

During storage, tubers undergo significant
alterations in carbohydrate chemistry, which,depending on the intended use, can have apronounced effect on quality. Inulin is not one
compound, but a series of molecules of varying
chain length that begin to depolymerize duringstorage (Jefford and Edelman 1963, SchorrGalindo and Guiraud 1997), whether harvested
or left in situ. The degree of polymerizationis critical for uses such as fat replacement or
high-fructose syrups. With the former, as thechain length decreases the ability of inulin
to mimic a lipid diminishes. Likewise, with
progressive depolymerization, the ratio offructose:glucose decreases and, upon hydrolysis,
yields a progressively less pure fructose
syrup. For example, during winter storage thefructose: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.

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 mostserious organisms causing rots at low storage
temperatures. Sclerotium rolfsii Sacc. and Erwinia
carotovora spp. carotovora (Jones) Bergey etal., in contrast, are not significant pathogens attemperatures 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

References
Barloy, J. 1988. Jerusalem artichoke tuber diseases
during storage. In G. Grassi and G. Gosse, eds.,
Topinambour (Jerusalem Artichoke). Proceedingsof a Workshop Held in Madrid, 30 September and1 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 thechanges in the sugar content of certain vegetables
in cold storage. Cont. Boyce Thompson Inst.
13:295-311.

None.

Suitability as Fresh-Cut ProductNo current potential.

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.

367

Kays, S.J. 1997. Postharvest Physiology ofPerishable Plant Products. Exon Press, Athens,
GA.
McCarter, S.M., and S.J. Kays. 1984. Diseases
limiting production of Jerusalem artichokes inGeorgia. 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 andbiochemical effects of gamma radiation on tubersof 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 andhumidity upon length of rest period of tubers ofJerusalem 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 andprophylactics. In A. Fuchs, S.Schhittenhelm, and
L. Frese, eds., Proceedings of the 6th Seminaron 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.

368

Jicama

Grades, Sizes, and Packaging

Marita Cantwell

There are no U.S. grades for jicama. In Hawaii,
however, two grades are recognized based on sizeand freedom from defects (dirt, discoloration,
growth cracks, roughness, insect damage, andmechanical injury).

Cantwell is with the Mann Laboratory,
Department of Plant Sciences, University ofCalifornia, Davis, CA.

Scientific Name and Introduction
Jicama (Pachyrhizus erosus [L.] Urban) is a root
crop of the Legume family (Leguminosae). It isalso 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 isa native crop. Jicama is also produced, to a limited
extent, in Hawaii. Roots are about 85% water, lessthan 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 andfirm, be uniform in shape and size, be free frommechanical damage, and have a crisp, succulent,
white, sweet-starchy flesh.
Horticultural Maturity Indices
Jicama roots can be harvested at various stages ofdevelopment. Young, tender roots harvested fromgreen plants (100 to 150 g; 3.5 to 5.3 oz) are foundin specialty markets. Fully mature roots, however,weigh from 250 to 1,500 g (0.55 to 3.3 lb). Matureroots 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.

After transport in bulk, jicama roots are typically
packed in wooden crates of 9 kg (20 lb) or more orin 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 lossof weight and diminished juiciness of the pulp.
Minimizing mechanical damage to the periderm
during harvest will reduce decay incidence duringstorage.

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 andsuperficial 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) (Cantwell369

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 symptomof chilling injury, and discoloration and loss ofcrisp 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 ismore 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.

Physiological Disorders
See Chilling Sensitivity section above.

Postharvest Pathology
The most common decay organisms foundexternally on jicama roots are species ofPenicillium, Rhizopus, and Cladosporium (Bruton
1983, Cantwell et al. 1992). Most postharvest
decay of jicama is a consequence of mechanical or
chilling injury.

Quarantine Issues
Ethylene Production and Sensitivity
None.
Jicama produces only very low amounts ofethylene, <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 84 to 85 °C
10 to 128 to 1210 °C
9.5 to 19
11 to 1912.5 °C
4 to 820 °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 rateby 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 increaseduring storage; rates decrease during storage attemperatures 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).
370

Suitability as Fresh-Cut ProductFresh-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-lifeof 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 thisleads to an unsightly appearance, high rates ofwater loss, and increased susceptibility to decay.
Wound healing or curing can be achieved byholding 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.

References
Aquino-Bolaños, E.N., M.I. Cantwell, G. Peiser,
and E. Mercado-Silva. 2000. Changes in thequality 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 andcompositional changes in jicama (Pachyrhrizus
erosus) roots. Acta Hort. 318:325-332.
Bruton, B.D. 1983. Market and storage diseases ofjicama. J. Rio Grande Valley Hort. Soc. 36:29-34.
Cantwell, M. 2006. Jicama Recommendationsfor Maintaining Postharvest Quality. Perishables
Handling. At http://postharvest.ucdavis.edu/
produce_information.
Cantwell, M., W. Orozco, V. Rubatzky, and L.
Hernández. 1992. Postharvest handling andstorage of jicama roots. Acta Hort. 318:333-343.
Mercado-Silva, E., and M. Cantwell. 1998.
Quality changes in jicama roots stored at chillingand nonchilling temperatures. J. Food Qual.
21:211-221.
Paull, R.E., and N.J. Chen. 1988. Compositionalchanges in yam bean during storage. HortScience23(1):194-196.

371

Kiwifruit

Horticultural Maturity IndicesJames W. Rushing

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 generalpractice 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 bemarketed locally with a minimum of handling may
be held on the vine until the SSC reaches 10 to
12% (Beevers and Hopkirk 1990).

Rushing is formerly with Coastal Researchand Education Center, Clemson University,
Charleston, SC. He is now retired.

Scientific Name and Introduction
The most common of the edible kiwifruit in theWestern world is Actinidia deliciosa, a perennialof 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. andCalifornia literature. In order of importance inthe 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 shriveledand should be free from sunscald, scars, growth
cracks, insect injury, bruises, internal breakdown,
and decay. At table ripeness, fruit should have atleast 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).

372

Grades, Sizes, and Packaging
Grades include U.S. Fancy, U.S. No. 1, andU.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 isdifficult to define fruit size in terms of length ordiameter. 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 tothroughout the United States. Size designations
are based on number of fruit that can be placedon a single tray. Actual fruit size is based onweight and is defined as the number of uniformly
sized fruit required to constitute an 8-lb sample.
Current designations from the KAC (1999) aresummarized in table 1. Handlers should note thisinformation is subject to change, and the mostrecent information should be reviewed by anyone
packing kiwifruit.

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%, bycount, 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 orfiberboard 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 mastercartons, a common arrangement being a mastercontainer containing twenty 1-lb (0.45 kg) bags.
At the retail level, fruit are sometimes sold in lotsof 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 usedin 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. Hydrocoolinghas been used successfully but is not generally
recommended because the hairs on the fruit
surface tend to retain an excessive amount ofwater, which can promote the growth of decaycausing microorganisms (McDonald 1990). The
decision to precool remains a matter of choice forthe packer, and the process of curing (see Curing)is gaining acceptance. Lallu (1997) reportsthat rapid precooling may exacerbate internal
breakdown associated with chilling injury.

CuringCuring occurs during the delay between harvestand 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 etal. 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.
373

Optimum Storage Conditions

Ethylene Production and Sensitivity

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. (SeeEthylene 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 lessthan 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 0.010µL L-1) ethylene in the storage atmosphere canaccelerate softening without affecting otherripening processes, resulting in unripe fruit thatare excessively soft (McDonald 1990, Crisosto etal. 1999).

Controlled Atmosphere (CA) Conditions
Kiwifruit respond favorably to CA. The potential
for benefit is excellent, with extension ofstorage 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 suchinjuries is moderate as long as management of
the atmosphere is given reasonable attention (seePhysiological Disorders). There is increasing
commercial use of CA during both storage andtransport. Refer to Kader (1997) for selectedreferences on kiwifruit CA research.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 ºC
3
4 to 5 ºC
5 to 710 ºC
1220 to 21 ºC
16 to 22
Data from Hardenburg et al. (1986).

Retail Outlet Display Considerations
Kiwifruit may be displayed on unrefrigerated
counters since it is desirable to have the fruit neareating ripeness at the time of sale.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

Chilling Sensitivity
Physiological Disorders
Lallu (1997) reports that the fruit of A.
deliciosa cv. ‘Hayward’ are chilling sensitive attemperatures 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 ofdiffuse 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.
374

In storage or transit, the flesh of immature fruit
may soften rapidly and have a water-soaked
appearance while the core remains hard andtough (Beevers and Hopkirk 1990). A similar typeof 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

and progresses to the stylar end. The flesh ofdamaged fruit may become somewhat yellow withprolonged storage (Crisosto et al. 1999).
Pericarp granulation and pericarp translucency
may occur independently, but both are associatedwith long-term storage. The presence of ethylene
in storage may exacerbate symptoms. These
disorders may simply be a consequence ofsenescence, as other causes are not well defined(Crisosto et al. 1999).
The presence of ethylene in CA storage cancause white-core inclusions, which are distinct
white patches of core tissue that are obvious inripe 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 goodtemperature 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 tofungal infection (Manning and Beever 1992,
Testoni et al. 1997). Symptoms typically do notoccur until fruit have been stored for several
months, and direct isolation of the fungi usually isrequired to distinguish between fungal pitting andphysiological pitting.

Quarantine Issues
There are no quarantine issues in the UnitedStates. 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 nationalor 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 inretail markets.

Special Considerations
One of the most troublesome concerns forstorage 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 sourcesof ethylene, such as the packing house itself or
nearby roadways; and presence of decaying fruitin the storeroom all influence the efficacy of
ethylene removal. Innovative managers shouldhave a means of measuring ethylene in thestoreroom and in the surrounding area.

375

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 ofKiwifruit. Effective October 15, 1986. U.S.
Department of Agriculture, Agricultural Marketing
Service, Washington, DC.
Beever, D.J., and G. Hopkirk. 1990. Fruitdevelopment and physiology. In I.J. Warrington
and G.C. Weston, eds., Kiwifruit: Science andManagement, pp. 97-126. Ray Richards Publisher,
Auckland, New Zealand.

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. Bestcuring practices for the orchard and packhouse.
New Zealand Kiwifruit Journal (March/April) pp.
35-37.
Manning, M., and D. Beever. 1992. An updateon storage pitting research. NZ Kiwifruit Journal(Feb.) pp. 5-7.

Crisosto, C.H., E.J. Mitcham, and A.A. Kader.
1999. Kiwifruit. Fresh Produce Facts. Universityof California, Davis, CA. At http://postharvest.
ucdavis.edu/produce_information.

McDonald, B. 1990. Precooling, storage, andtransport of kiwifruit. In I.J. Warrington and G.C.
Weston, eds., Kiwifruit: Science and Management,
pp. 429-459. Ray Richards Publisher, Auckland,
New Zealand.

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.

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.

Ferguson, A.R. 1990b. Botanical nomenclature:
Actinidia chinensis, Actinidia deliciosa, andActinidia setosa. In I.J. Warrington and G.C.
Weston, eds., Kiwifruit: Science and Management,
pp. 36-57. Ray Richards Publisher, Auckland,
New Zealand.

Snowdon, A.L. 1990. Soft fruits and berry fruits.
In A Color Atlas of Postharvest Diseases andDisorders of Fruits and Vegetables, vol. 1, General
Introduction and Fruits, pp. 255-266. CRC Press,
Boca Raton, FL.

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. Departmentof 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.
376

Testoni, A., B. Grassi, S. Quaroni, et al. 1997.
Pitting on kiwifruit in storage caused by
Phialophora sp. Acta Hort. 444:751-756.

Kohlrabi
Peter M. A. Toivonen and Charles Forney
Toivonen is with Pacific Agri-Food ResearchCentre, Agriculture and Agri-Food Canada,
Summerland, British Columbia, Canada; Forney
is with Atlantic Food and Horticulture ResearchCentre, 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 amember of the Brassicaceae (Cruciferae) family.
It is a native of northern Europe and grows bestin cool climates. Kohlrabi is grown as an annual,with the enlarged stem being the most commonlyused edible portion. The enlarged stem may
have purple, white, or green skin, but the flesh iswhite. The leaves can also be eaten like collards.
Kohlrabi is available from spring to late fall fromvarious growing regions of North America.

Quality Characteristics and Criteria
Only young kohlrabi should be harvested, sincemature product becomes woody and tough. Leaf
stems are a good indicator of quality; they should
be succulent and tender.

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 andCantwell 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 maintainhigh 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.

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.

Chilling Sensitivity

Grades, Sizes, and Packaging

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.

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-Kohlrabi are not chilling sensitive.

Ethylene Production and Sensitivity

377

Respiration Rates

References

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).

Forney, C.F., and M.A. Jordan. 1999. Anaerobic
production of methanethiol and other compounds
by Brassica vegetables. HortScience 34(4):696699.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 thanrecommended 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 ProductPeeled 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).
378

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. Departmentof 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.

Leek
Jennifer R. DeEll
DeEll is with the Ontario Ministry of Agriculture
and Food, Simcoe, Ontario, Canada.

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 with18 to 24 bunches, with a net weight of up to 13.6
kg (30 lb).

Precooling Conditions
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 ofthe 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 thickpseudostem; 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 basediameter 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 inpolyethylene film bags to prevent moisture loss.

Hydrocooling, crushed ice, and vacuum-coolingare 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, 4weeks 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 polyethylenebags or in nonperforated (sealed) polyethylenebags remain attractive and saleable for up to
10 weeks. They can last up to 10 weeks undercrushed 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. Levelsof 15 to 20% CO2 cause tissue injury.
379

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.

and curvature, though varying degrees ofcurvature have been observed in such treatments.
Senescent yellowing develops more rapidly atwarmer temperatures, and moderate wilting isapparent when leeks lose about 15% of theirweight.

Chilling Sensitivity
Postharvest Pathology
Leeks are not sensitive to chilling and should be
stored as cold as possible without freezing.

Most diseases that attack onions may also affectleeks.

Ethylene Production and Sensitivity
Quarantine Issues
Leeks produce very low levels of ethylene: <0.1
µL kg-1 h-1. Leeks are moderately sensitive toethylene. Detrimental effects include softening
and increased decay.

None are known.

Suitability as Fresh-Cut ProductRespiration 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 11721 °C
11026.7 °C
107 to 119
Data from Hruschka (1978).
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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% perweek 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
380

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 fromthe 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.

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.

381

LemonGrades, Sizes, and Packaging

Kenneth C. Gross and Joseph L. Smilanick

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.

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 isformerly with the Horticultural Crops ResearchLaboratory, 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.

Precooling Conditions
Most packing houses do not precool lemonsbecause the anticipated benefit is too modest, orthey may need to degreen the fruit with ethylene,
which requires 20 °C (68 °F) pulp temperatures.

Scientific Name and Introduction
Lemons (Citrus limon L. Burman f.) are grownyear 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 befirm and have smooth, thin skins. Ripe lemons
should have a pleasant citrus fragrance. Lemonswith 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, dependingon the grade.
382

Optimum Storage Conditions
Yellow lemons harvested when dark green havea 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) dependingon the maturity-ripeness stage at harvest, seasonof harvest, storage time, and production area.
They can be stored for up to 6 mo under the rightconditions. 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 usuallytolerated without harm. Removal of ethylene
from storage rooms can reduce senescence andfungal decay. It is generally recognized that proper
storage of lemons improves quality (juice content,
flavor, and color).
Adequate ventilation must be maintained duringstorage. Cartons should be kept off the floor toprevent them becoming wet from condensation.
Lemons should be stored away from produce
having a strong odor. Also, decay can occur fromskin cuts or scratches caused by rough handling.
Lemons must be handled with care, and shipping
containers should not be dropped on the floor. Anyaffected product should be removed immediately
to prevent mold from spreading.

Controlled Atmosphere (CA)Considerations

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 1215 °C
14 to 24
20 °C
20 to 28
Data from Arpaia and Kader (2001).

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 tothe 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.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

Retail Outlet Display Considerations

Physiological Disorders

Lemons should not receive a water sprinkle or top
ice.

Several disorders of lemon fruit are significant.
Oleocellosis or oil spotting, a rind blemish thatinvolves the breaking of oil cells due to physicalstress on turgid fruits, results in the release of oilthat damages surrounding tissues. Not harvestinglemons when they are turgid and careful handling
reduce the severity of this disorder. Peteca,another rind disorder, begins in white portion ofpeel and develops sunken brown pits. It is favoredby low temperatures before or after harvest,
oil applications in the grove, and an imbalanceof calcium and potassium in the peel. Some
reduction in peteca is obtained by gibberelic acidapplications to trees and by avoiding storage ofsusceptible lemons below 13 °C (55 °F).

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 isusually 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 isdesired, 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 ofMembrane stain, an internal disorder in which themembranes between segments, or carpellary walls,
show irregular brown or black areas. It is reducedby avoiding storage of lemons below 13 °C (55°F) and improving ventilation in storage.

383

Postharvest Pathology

Quarantine Issues

There are three main postharvest pathologicaldiseases of lemon.

Most quarantine concerns for lemons addresseliminating 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 riskof injury to lemons. Harvest and export of fruitfrom certified pest-free zones is another option
to control fruit flies that eliminates risks of fruit
injury, and this approach has also been employedagainst citrus black fly and Fuller rose beetle.
Quarantine authorities are concerned that citrus
black spot, an unsightly rind blemish causedby Guignardia citricarpa that occurs in South
Africa and parts of Asia and South America, could
potentially become established in Mediterraneancountries and in North America.

Green mold and blue mold are caused by
Penicillium digitatum and P. italicum,
respectively. Spores of these pathogens access thefruit 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 isreduced by careful handling to minimize wounds.

Suitability as Fresh-Cut ProductSour 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 byimmersing fruit in soda ash, sodium bicarbonate,or sodium ortho-phenyl phenate after harvest andusing minimal storage temperatures.
Other pathogens are occasionally troublesome inlemon storage, including Alternaria citri and thestem-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 rangesof temperature and RH; excluding ethylene duringtransport and storage; using gibberelic acid before
harvest to delay senescence of the fruit after
harvest; and providing sanitation throughout thehandling system.

384

Lemon sections, prepared by both manual andautomatic processors, are distributed for use in thefood service industry.

Acknowledgments
Some of the information in this chapter is fromthe 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 thischapter.

References
Arpaia, M.L., and A.A. Kader. 2001. Lemon.
Recommendations for Maintaining Postharvest
Quality. At http://postharvest.ucdavis.edu/
produce_information.

Eaks, I.L. 1961. Effect of temperature and holding
periods on physical and chemical characteristicsof 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. Limitationsof modified atmospheres for decay control of
citrus fruits. Phytopathology 59:1031-1032.
Rygg, G.L., and E.M. Harvey. 1959. Storage ofLemons From the Desert Areas of Arizona andCalifornia. 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, AgriculturalMarketing 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 instorage atmospheres on lemon keeping quality.
HortScience 11:114-115.

385

Lettuce

Horticultural Maturity Indices

Mikal E. Saltveit

Head lettuce is harvested when the heads arewell formed and solid (Ryall and Lipton 1979).
Maturity is based on head compactness, and thefirmness of the head is related to its susceptibility
to certain postharvest disorders. Soft heads areeasily damaged, while fairly firm heads havehigher 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.

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 foundoutside 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 iscomposed of upright, large, elongated, and oftencoarser 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 distanceshipment. A greater percentage of all types oflettuce 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 andinternational 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 andturgid, and bright light green.

386

Grades, Sizes, and Packaging
Head lettuce is graded by size and firmness, whileleafy 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 thanon muck (organic) soils. A strong bitter taste
and toughness develops if harvest is delayed or
if lettuce is overmature, and then the productbecomes unmarketable.
Because lettuce is very fragile, it should be
handled as little as possible. Field packing andpalletizing eliminate a major source of mechanicaldamage, but they require specialized handlingequipment and vacuum-cooling facilities to bepractical. The stem is cut at ground level and thehead 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 placedin 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 packagedin 9- to 11-kg (20- to 25-lb) or 24-count cartons.
Butterhead or Boston lettuce is usually packaged

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 orprocessing facility. Lettuce may be cored in thefield or at a local or regional processing facility.
At the processing facility, heads are cut, washedin cold water, and centrifuged to remove excesswater. Cut lettuce is often mixed with other typesof lettuce or greens, shredded carrot, and red
cabbage to produce a salad bag mix. The mix
may be treated with a processing aid composedof 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 respirationand film permeability, it is important to maintainproper temperature and to know the respiratory
characteristics of the enclosed tissue.

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 orindividual polyethylene head wraps are desirable
for attaining high RH; however they shouldbe perforated or be permeable to maintain anoninjurious 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, somemechanical harvesters are available for productdestined for processing into bag mixes. The
attendant greater damage to the tissue and theinduced higher rates of respiration and water
loss requires greater attention to maintaining the
optimal storage conditions of temperature and RH.

Controlled Atmosphere (CA)Considerations
Precooling Conditions
Vacuum-cooling is the preferred method forprecooling 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 headsof 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 duringcooling. Thorough precooling is essential because
mechanically refrigerated trucks do not haveenough 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 iseffective for nonheading lettuce types but should
not be used with head lettuce since the waterretained in the head fosters decay.

Lettuce, especially crisphead and fresh-cut,
respond favorably to CA (Saltveit 1997a). Levelsof 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 whenlettuce 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 oflettuce and inhibits pink rib and butt discolorationcompared to air. Brown stain is intensified when
O2 is reduced to 2 to 3%, but the effect differs bycultivar. 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 toleratea slightly higher CO2 level when packaged thanhead lettuce. Browning is a major problem withfresh-cut lettuce, and is controlled by packaging in387

<1% O2 and 10% CO2 (Lopez-Galvez et al. 1996,
Smyth et al. 1998). The elevated level of CO2 ismore 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 andto 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.

Physiological Disorders
Some of the more common disorders of headlettuce include tipburn, russet spotting, brownstain, and pink rib (Ryall and Lipton 1979, Saltveit
1997b). Hard heads are more susceptible to these
disorders than firm lettuce. Tipburn is of fieldorigin, 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 inductionof the synthesis, accumulation, and oxidation ofphenolic 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 severecases. It is easily controlled by making sure thestorage atmosphere is free of ethylene and that thetemperature 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 iscausedby exposure to >2.5% CO2 and appears
as large, irregularly shaped brown spots or
streaks mostly on the midrib. Pink rib occurs inovermature heads stored at elevated temperatures
and appears as a diffuse pink discoloration of the
midrib; the cause of this disorder is unknown.

Respiration Rates
Temperature
0 °C
5 °C
10 °C
15 °C
20 °C
25 °C

Head lettuce
Leaf lettuce-------mg CO2 kg-1 h-1------6 to 17
19 to 27
13 to 20
24 to 35
21 to 40
32 to 46
32 to 45
51 to 74
51 to 60
82 to 12073 to 91
120 to 173

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

Postharvest Pathology
Bacterial soft rot, the most serious disease of
lettuce, often starts on bruised leaves and results ina 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.

388

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 careto avoid mechanical damage and to minimize
discoloration and pathological problems.
Temperatures must be kept low and RH high toprevent 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 Universityof California, Davis, website “Fresh Produce
Facts” at http://postharvest.ucdavis.edu/produce_
information and from the Produce Marketing
Association’s “Fresh Produce Manual.”

Ryall, A.L., and W.J. Lipton. 1979. Handling,
Transporation and Storage of Fruits andVegetables, 2nd ed., vol. 1, Vegetables andMelons. 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 partialpressure on respiration and quality. J. Agric. Food
Chem. 46:4556-4562.

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. Departmentof Agriculture, Agricultural Research Service,
Washington, DC.
Ke, D., and M.E. Saltveit. 1989. Carbon dioxideinduced brown stain development as related tophenolic 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 withemphasis on romaine and iceberg types. Postharv.
Biol. Technol. 8:179-190.

389

Lime

Grades, Sizes, and Packaging

Jacqueline K. Burns

Persian limes must attain a size of 4.76 cm (1.87in) in diameter and a juice content of 42% byvolume. 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 (18.2kg) cartons for storage and shipping (Roy et al.
1996).

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 typegrown in the United States. Commercial Persian
lime production in the United States is now lessthan 2,000 ha and is limited to south Florida andsouthern California (Saunt 2000). Persian lime
and key lime (Citrus aurantifolia Swing.) trees
are popular in backyard settings, where they arecommonly 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.

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 rateof limes is <10 mg CO2 kg-1 h-1 (Arpaia and Kader
2000).

Optimum Storage Conditions
Quality Characteristics and Criteria
High-quality limes should be oval and firm withsmooth peel and deep green (Persian) or green andyellow (key lime) color. Limes should be turgid
and free from decay, splitting, and blemishes.

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.

Horticultural Maturity Indices

Physiological Disorders

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 othercountries, yellow limes are preferred becauseof their higher juice content (Arpaia and Kader
2000).

390

Stylar-end breakdown can be a significant problem
with limes. Stylar-end breakdown begins as anapparent breakdown of tissues at the stylar endof 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 andCampbell 1994). Exposing limes to temperatures
below the optimum storage temperature canresult in chilling injury characterized by peelpitting. Oleocellosis can develop on the peel
if hand-harvest begins early in the morning or
immediately after rainfall, when the peel is turgid.

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.

Postharvest Pathology and Control

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

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 andhandling and appear in storage. Careful handlingto 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

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.

Appearance of citrus canker (Xanthomonas
axonopodis pv. citri) has restricted movementof limes grown in south Florida. Compliancewith the Citrus Canker Eradication Program(Florida Department of Agriculture and Consumer
Services 2000) is required to market limes fromquarantined areas.

Suitability as Fresh-Cut ProductNo 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.
391

Litchi

Grades, Sizes, and Packaging

Robert E. Paull, Ching Cheng Chen, and Nancy
Jung Chen

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 areused. Fruit are also packed into 0.5-pint (0.12-L)
styrene containers.

Paull, Chen, and Chen are with the Department of
Tropical Plant and Soil Sciences,
University of Hawaii at Manoa, Honolulu, HI.

Precooling Conditions
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 thatvary 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, hasa 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 nobrowning is preferred, along with freedom frombird, insect, and mechanical damage; cracking;and decay.

Horticultural Maturity Indices
Red skin color and flesh have the optimum rangeof 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.

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 fruitor fruit with insect stings (Campbell 1959, Paulland 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.

392

Chilling Sensitivity

Postharvest Pathology

Litchi have low sensitivity to chilling. However,dehydration during storage often leads to lossof skin color and browning and is referred to as
chilling injury.

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 andBilgrami 1973, Scott et al. 1982). Diseaseorganisms 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).

Ethylene Production and Sensitivity
Litchi have a low rate of ethylene production: <1
nL kg-1 h-1. There are no reports on the responseof 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
5 °C
10 °C
20 °C
25 °C

-1

-1

mg CO2 kg h
10 to 16
19 to 29
46 to 74
75 to 128

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
-1

-1

-1

-1

To get mL CO2 kg h , divide the mg kg h rateby 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.

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
Physiological Disorders
The major disorder is the rapid browning of theshell from a bright red color (Paull and Chen
1987, Holcroft and Mitcham 1997). The browningis associated with water loss and injury (insectstings). The browning associated with insect stings
may go through to the pinkish-white inner surfaceof the shell. A breakdown (softening and loss ofturgidity) 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.

Fumigation with SO2 followed by a dip inhydrochloric 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 notapproved on fresh produce in the United States,
except for grapes. Most other countries havesulfite residue limits for edible portions (Tongdee
1994).

393

References
Akamine, E.K. 1960. Preventing the darkeningof fresh lichees prepared for export. Technical
Progress Report 127, Hawaii Agricultural
Experiment Station, Honolulu, HI.
Akamine, E.K., and T. Goo. 1973. Respiration andethylene 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.

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.

Ho, H.H., J.Y. Lu, and L.Y. Gong. 1984.
Observation on asexual reproduction by
Peronophythora litchii. Mycologia 76:745-747.

Prasad, S.S., and R.S. Bilgrami. 1973.
Investigations on diseases of ‘Litchi.’ vol. 3, Fruitrots and their control by postharvest treatments.
Indian Phytopath. 26:523-527.

Holcroft, D.M., and E.J. Mitcham. 1997.
Postharvest physiology and handling of litchi(Litchi chinesis Sonn.). Postharv. Biol. Technol.
9:265-281.

Roth, G. 1963. Postharvest decay of litchi fruit(Litchi chinesis Sonn.). Technical Communication,
Department of Agricultural Technical Services,
Pretoria, South Africa.

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.

Ragnoi, S. 1989. Controlled Atmosphere
Storage of Fruits and Vegetables, pp. 179. CAB
International, Wallingford, U.K.

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 Handlingof Tropical Fruits, Chiang Mai, Thailand, July
1993, pp. 239-249. ACIAR Proceedings no. 50,
ACIAR, Canberra, Australia.

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.

Kader, A.A. 1998. Produce facts—lychee.
Perishables Handling Quarterly, no. 94, Universityof California, Davis, CA.
Nakasone, H.Y., and R.E. Paull. 1998. TropicalFruits. CAB Intl., Wallingford, U.K.
Paull, R.E., and J.N. Chen. 1987. Effect ofstorage temperature and wrapping on quality
characteristics of litchi fruit. Sci. Hort. 33:223236.
394

Tongdee, S.C. 1994. Sulfur dioxide fumigationin postharvest handling of fresh longan andlychee for export. In B.R. Champ, E. Highley,
and G.I. Johnson, eds., Postharvest Handlingof 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 offresh 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.

LonganSaichol Ketsa and Robert E. Paull
Ketsa is with the Department of Horticulture,
Kasetsart University, Bangkok, Thailand; Paullis with the Department of Tropical Plant andSoil 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 comesaway cleanly from the shell and seed.

Quality Characteristics and Criteria
Shell color, size, and shape; seed size; andsweetness are criteria. Fruit should be free of
insect damage and skin blemishes; defective fruit
are culled while being sorted for size. See Jiang etal. (2002) for further information.

Horticultural Maturity Indices
Maturity is judged by shape, skin color, and flavorof each cultivar. Most fruit can be picked from atree with one harvest, unless multiple flowerings
have occurred. No definite harvest index exists forlongan, but growers usually note changes in skinappearance—mature fruit develop a smooth andrelatively darker skin (Wong and Ketsa 1991).

polystyrene containers. Fruit are clipped fromthe stem, as hand removal often leads to someinadvertent 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 treatedwith SO2. SO2 fumigation damages hydrocooled
fruit skin by producing brown spots on boththe inner and outer skin surfaces. It also resultsin 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 andChen 1987). Fruit can be held for 2 to 3 weeks,though the skin loses it yellowish coloration,
becoming brown. At lower temperatures, thereis 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
730 ºC
1 to 23 to 5Controlled Atmosphere (CA)Considerations
Grades, Sizes, and Packaging
One-piece fiberboard crates are used, holding
either 4.5 kg (10 lbs) or 2.25 kg (5 lbs), withplastic liners if fruit are not already packed in

No controlled atmosphere studies have beenreported, though modified atmosphere packaging
in 0.03 mm (1/1000 in) polyethylene bags wastested for 7 days at room temperature, followed by
35 days at 4 °C (39 °F). A modified atmosphere395

of 1 to 3% O2 delays browning and maintains
SSC and vitamin C content (Zhang and Quantick1997). Treatment with 1% O2 results in a slight off
flavor.

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).

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 darkbrown, while SO2-fumigated longan remain
yellowish-brown. The dark brown peel of longanthat develops at very low temperatures is regarded
as chilling injury (La-Ongsri et al. 1993).

Postharvest Pathology
Longan suffers similar postharvest diseases
to litchi. Fungi associated with skin browningand darkening of the skin along with mycelium
include Lasiodiplodia theobromae, Pestalotiopsis
sp., Cladosporium sp., Fusarium sp., andAspergillus niger (Sardsud et al. 1994).

Quarantine Issues
Longan is a fruit fly host. Suitable treatments
include hot air, vapor heat treatment, andirradiation.

Ethylene Production and Sensitivity

Suitability as Fresh-Cut ProductLongan fruit have a low rate of ethylene
production: <1 nL kg-1 h-1. There are no reports on
ethylene sensitivity.

Peeled, deseeded fruit aril can be used as a freshcut product.

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 rateby 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.

396

Special Considerations
Longan are fumigated with SO2 in Thailand andother countries to prevent skin browning andto control postharvest disease (Tongdee 1994).
Though very effective, SO2 fumigation is not
approved for use in the United States for fruit tobe sold as fresh. Asian consumers prefer longan inbunches. They assume that single fruit have fallenfrom the bunch because it has been dropped orthat fruit are not fresh. Individual fruit may also
have a higher rate of weight loss.

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 TropicalFruits. 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. TropicalFruits. CAB Intl., Wallingford, U.K.

Tongdee, S.C. 1994. Sulfur dioxide fumigationin postharvest handling of fresh longan andlychee for export. In B.R. Champ, E. Highley,
and G.I. Johnson, eds., Postharvest Handlingof 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 atmospherepackaging on postharvest storage of longan fruit.
In A.A. Kader, ed., 7th International Controlled
Atmosphere Research Conference, University ofCalifornia, Davis, CA, July 1997, vol. 3, pp. 9096. University of California, Davis, CA.

Paull, R.E., and N.J. Chen. 1987. Changes inlongan 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 ofPostharvest 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 managementof lychee and longan. In Proceedings of theWorkshop on New Technology for Lychee andLongan Production, Chiang Mai, Thailand, pp.
105-120. Thailand Institute of Scientific andTechnological Research, Bangkok, Thailand.

397

Longkong
Robert E. Paull
Paull is with the Department of Tropical Plant andSoil Sciences, University of Hawaii at Manoa,
Honolulu, HI.

Scientific Name and Introduction
There are at least two major types, with anumber 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 andPaull 1998). There is considerable inconsistency
in the naming of the different types (Yaacob andBamroongrugsa 1992). Peninsular Thailand to
Borneo is the major area of cultivation. Besides
the Philippines, L. domesticum is also cultivatedin 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 arerounder and 40 to 50 mm (1.6 to 2 in) in diameter;
longkong is intermediate, nearly seedless, has abrittle 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 withbrown blemishes. The langsat has a thin skinthat contains a milky white sticky sap. Duku hasa thicker—up to 6 mm (0.25 in)—skin and nolatex. Longkong has a slightly thicker skin thanlangsat and less sap that is not sticky. The green
seed is covered by a white translucent flesh thatis slightly sour in langsat. Langsat tends to varyfrom sweet to sour; duku is sweet. Both fruit have
five separate segments with one to five seeds inlangsat and one or two in duku. During ripening,398

astringency in the flesh declines while sugars
increase six-fold (Paull et al. 1987). The skinbruises very easily, leading to brown discoloration.

Horticultural Maturity Indices
Fruit are harvested at the full ripe stage indicatedby 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 isessential to harvest as soon as possible before
over-ripe fruit abscise from the peduncle. Fruit tobe shipped long distances are harvested when 70
to 80% ripe to avoid excessive fruit drop. Fruitshould 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 andnormally sold in single-layer fiberboard cartonsholding 2.25 kg (5 lb) of fruit, with padding, orsometimes in trays with liners.

Precooling Conditions
Room cooling is used because forced-air coolingcauses moisture loss.

Optimum Storage Conditions
The most recent recommendation for storage is
18 °C (46 °F) with 90% RH (Piyasaengthong etal. 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, whichgave 24.3% weight loss (Pantastico 1975). Others
have recommended 11 to 13 °C (52 to 55 °F) with85 to 90% RH for 14 days (Srivastava and Mathur
1955).

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 infruit held in polyethylene film bags. Holding inplastic bags (0.08 mm thickness) reduces weightloss but increases surface browning (Brown andLizada 1984). Preliminary recommendations are
5% O2 and 0% CO2 (Yahia 1998).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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, andchilling injury are the three major disorders.
Mechanical injury (abrasion, impact, andcompression) leads to skin darkening andbrowning. Chilling injury symptoms are pitting
and brown scalding of the skin.

Retail Outlet Display Considerations
Fruit are commonly displayed in overwrappedtrays or closed styrene clam shell containers withno holes at 15 °C (59 °F). They should not be
misted.

Postharvest Pathology
Anthracnose, aspergillus, and rhizopus surface
rots on the skin have been reported. Packing dry
fruit and using fungicides can minimize losses.

Chilling Sensitivity
Quarantine Issues
Chilling leads to skin browning; at 15 °C
symptoms develop after 21 days (Piyasaengthong
et al. 1997).

Longkong is a fruit fly host; irradiation at 300
grays has potential for disinfestation.

Ethylene Production and Sensitivity

Suitability as Fresh-Cut ProductFruit produce low amounts of ethylene, withinternal concentrations of 2 to 6 µL kg-1. There
are no reported responses to ethylene treatment; it
may lead to premature senescence.

No current potential.

Respiration Rates
Respiration rates decline after harvest, and small
fruit have a higher rate than large fruit (Srivastanaand Mathur 1955, Pantastico et al. 1968).
Temperature
9 °C
20 °C

mg CO2 kg-1 h-1
40 to 50
50 to 90

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. TropicalFruits. 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.
399

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 52:505517.
Paull, R.E., T. Goo, and N.J. Chen. 1987. Growthand compositional changes during development oflanzone fruit. HortScience 22:1252-1253.
Piyasaengthong, Y., S. Suanpairoj, P. Pakamat, andC. 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 andR.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. 22:123183.

400

LoquatGrades, Sizes, and Packaging

Changkui Ding

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 (1.2oz). Packages commonly employ soft materials
because of the fruit’s susceptibility to bruising.

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 therose family and is a subtropical evergreen fruit
tree. Fruits grow in loose clusters and are roundor 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 todeep orange. Loquat originated in midwestern
China and is widely cultivated in the subtropicalregions of southern China, Japan, Israel, and theMediterranean 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.

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). Useof polyethylene bags retards weight loss andminimizes decreases in organic acids (Ding et al.
1997).

Controlled Atmosphere (CA) Conditions
No information is available.

Retail Outlet Display Considerations
Horticultural Maturity Indices
The quality of loquats is highly dependent on the
degree of ripening. Loquats harvested at the fullyripe stage have optimum quality. However, incommercial 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 byskin color changes described for each cultivar.

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 ofethylene and are not particularly sensitive toethylene exposure after harvest.
401

Respiration Rates

Special Considerations

Respiration rates of loquat are influenced bytemperature and decrease rapidly over the first
4 days of storage. By the fourth day of storage,
respiration rates of stored fruit were—

Loquats must be handled with care to avoid
mechanical damage, and low-temperature storageis essential for extending postharvest life.

Temperature
1 °C
5 °C
10 °C
20 °C

mg CO2 kg-1 h-1
11.2
12.4
30.6
80.0

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 thedamaged areas usually turn brown or black, so
careful handling and packaging during and after
harvest are important. Also, internal browning andbrown surface spotting occur during long-term or
high-CO2 storage (Ding et al. 1999).

References
Ding, C.-K., K. Chachin, Y. Hamauzu, et al. 1998.
Effects of storage temperatures on physiology andquality 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 ofCalifornia, 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.

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 ProductNo current potential exists.

402

Shinbori, F., and S. Nakai. 1991. Qualitativechanges during maturation and keeping qualities
of loquats fruits. J. Jap. Soc. Hort. Sci. 60(Suppl.
2):590-591.

LuffaStephen Morris and Jenny Jobling

Controlled Atmosphere (CA)Considerations
There is no published information on CA for luffa.

Morris and Jobling are with the Sydney
Postharvest Laboratory, Food Science Australia,
North Ryde, New South Wales, Australia.

Retail Outlet Display Considerations

Specific Name and Introduction

Top-icing is not acceptable due to luffa’s chilling
sensitivity. Water sprays are acceptable.

There are two main species of cultivated luffa(loofah). Angled luffa or Chinese okra (Luffa
acutangula), a green, immature fruit withlongitudinal ridges, is consumed like summer
squash. Smooth luffa or sponge gourd (Luffa
aegyptiaca Mill) is sometimes eaten as avegetable, but mature fruit are mainly used
to make sponges for cosmetics and cleaning(Ellington and Wehner 1996). Both are membersof 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 mostoften 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 basedon size.

Optimum Storage Conditions

Chilling Sensitivity
Fruit are sensitive to chilling at <10 °C (50°F) (Zong et al. 1993). Symptoms include skindiscoloration, watery lesions under the skin, andenhanced 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 issensitive 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 rateby 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.

Angled luffa can be stored for up to 2 weeks at 10
to 12 °C (50 to 54 °F) with 90 to 95% RH (Zonget al. 1992, 1993, Cantwell 1997).
403

Physiological Disorders
Luffas should be handled with care; damage
to longitudinal ribs leads to water loss anddecay. Fruit are susceptible to dehydration andtoughening of the peel.

Postharvest Pathology
No specific information is available.
Quarantine Issues
None are known.

Suitability as Fresh-Cut ProductNo 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 anddecay.

References
Cantwell, M. 1997. Properties and recommended
conditions for storage of fresh fruits andvegetables. 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.

404

Zong, R., M.I. Cantwell, L.L. Morris, and V.
Rubatzky. 1992. Postharvest studies on four fruittype Chinese vegetables. Acta Hort. 318:345-354.

Mandarin (Tangerine)

Grades, Sizes, and Packing

Jacqueline K. Burns

Mandarin are packed in 4/5-bushel cartons forshipping and storage. Marketable mandarin range
from size 56 (56 fruit per carton) to size 210 (210
fruit per carton).

Burns is with the Citrus Research and Education
Center, Institute of Food and Agricultural
Sciences, University of Florida, Lake Alfred, FL.

Optimum Storage Conditions
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 todescribe mandarins with deep orange-red external
color. The mandarin/tangerine citrus group isvery diverse, and attempts have been made toassign members into different categories andspecies. Citrus unshiu (satsuma), C. deliciosa(Mediterranean mandarin), C. nobilis (kingmandarin) and C. reticulata (common mandarin)
are known worldwide, but only C. reticulata andassociated hybrids are of economic importance inthe United States (Saunt 2000). ‘Dancy,’ ‘Fallglo,’‘Robinson,’ ‘Sunburst,’ and ‘Clemantine’ arepopular varieties in the United States. Mandarinlike varieties, either tangors (mandarin × orange
hybrids) such as ‘Temple’ and ‘Murcott’ ortangelos (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

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 tocontrol postharvest decays during storage.

Ethylene Production and Sensitivity
Mandarin are nonclimacteric and do not exhibit
a rise in respiration and ethylene associated withripening. 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 andKader 2000).
Temperature
5 ºC
10 ºC
15 ºC
20 ºC

mg CO2 kg-1 h-1
4 to 86 to 1012 to 20
20 to 30

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

Maturity standards require that mandarin have a
set minimum SSC:TA ratio and have at least 50%
peel surface color break.

405

Degreening

Postharvest Pathology

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 destructionof 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 airchange per hour should enter the degreening
room to avoid buildup of CO2, which caninhibit ethylene action, and to assist in uniform
temperature and ethylene distribution (Wardowski
1996).

Stem-end rot (Diplodia natalensis and Phomopsis
citri) is a significant problem on mandarin,
especially where degreening is required in earlyseason 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 stemand stylar ends, resulting in uneven margins.

Physiological Disorders

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 thatquickly overtake the entire fruit under optimum
conditions.

Mandarin have thin peels that are readily injured
under conditions that promote high peel-watercontent. 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 bydegreening. Oleocellosis can occur on the peelwhen 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 tooleocellosis when peel turgidity is high. Puffinessis characterized by separation of the peel from thepulp on the tree or in storage. Fruit of advancing
maturity appear to be most susceptible topuffiness.
Stem-end rind breakdown, SERB, is characterizedby collapse and sinking of the peel in irregularly
shaped regions near the stem end. SERB isclosely 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 withtemperatures below 5 °C (41 °F) and longer
durations. Mandarin are susceptible to granulation,or section-drying. Susceptibility is influenced byvariety and overmaturation (Grierson 1986).
406

Anthracnose, caused by Colletotrichum
gloesporiodes, is a major decay of mandarin.
Characterized by brown peel lesions, anthracnose
appears on early-season mandarin that haveundergone lengthy degreening periods.

Green and blue mold (Penicillium digitatum and
P. italicum, respectively) develop on mandarin asa result of wounds made during harvesting andhandling (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 mosteffectively controlled by preharvest treatment withcopper-containing fungicides. Careful harvestingand 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.

Quarantine Issues
The appearance of citrus canker (Xanthomonas
axonopodis pv. citri) has restricted movementof 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 fromquarantined areas to domestic markets.
Cold treatment is an approved quarantine
treatment for citrus grown in areas infested withtropical fruit flies. In Florida, the Caribbean
fruit fly (Anastrepha suspensa) may be foundin citrus groves during late spring and summer.
Cold treatment involves storage of fruit below
2 ºC (36 °F) for specified periods to ensure theirfreedom from fly infestation. However, becauseof 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 toincrease resistance to chilling injury.

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 fordegreening Florida fresh citrus fruit. Circular
1170, University of Florida, Institute of Food andAgricultural Science, Gainesville, FL.
Whiteside, J.O., S.M. Garnsey, and L.W. Timmer,
eds. 1988. Compendium of Citrus Diseases. APS
Press, St. Paul, MN.

Suitability as Fresh-Cut ProductSome 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.

407

MangoGrades, Sizes, and Packaging

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.

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.

Scientific Name and Introduction

Precooling Conditions

Mango (Mangifera indica L.) is cultivatedthroughout 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-likesmell and taste.

Fruit are normally forced-air cooled or roomcooled, preferably within 24 h of harvest (Mattern
et al. 1972).

Quality Characteristics and Criteria
Skin coloration, size, appropriate shape forthe variety, appearance, freedom from defects
and decay, absence of fiber in the flesh, anda turpentine-like flavor are the most common
quality parameters. Wilted, grayish discolorationand pitting are undesirable. Some fruit varieties(‘Haden’) have pinhead-sized black spotting thatis not regarded as a defect.

Horticultural Maturity Indices
The general criteria for maturity of most cultivarsof mango are (1) the fruit “shoulders” have risen
above the stem-end and (2) there is a slight skincolor break on the first fruit of a crop. Early fruitfrom 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 indicesinclude SSC and TA, specific gravity, and days
from blooming. These indices depend on cultivar
and season (Hatton et al. 1965, Kanes et al. 1982).

408

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, anddecay 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 andabnormal skin coloration.

Retail Outlet Display Considerations
Mangoes can be displayed at store temperatureand should not be misted. Bruised and diseased
fruit should be removed from display.

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 theliterature regarding effect of ethylene treatment
on quality (Chaplin 1988). This may relate tomaturity 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 2210 °C
23 to 46
15 °C
45 to 9020 °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 rateby 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 highCO2 injury, are induced after harvest, whileothers 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, suchas ‘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); washingwith 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 thatspread 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 thenbecome sunken (Fitzell and Peak 1984).
Alternaria rot (Alternaria alternata), a preharvest
infection, can sometimes be a problem, while thepostharvest wound infections can occasionally be
severe, such as black mold (Aspergillus spp.) andtransit rot (Rhizopus spp.). Disease control begins
in the field followed by postharvest sanitation,
as well as avoidance of latex burn (stain) andmechanical injury. Hot-water treatment (46 °C
for 60 to 120 min) and fungicides can be used,
depending on the cultivar (Spalding and Reeder409

1986). Hot-water brushing at 55 °C (131 ºF) for
20 s shows good control (Prusky et al. 1999).

Jobin-Decor, M.P. 1988. Mango ripening guide.
Queensland Agric. J. 114:369-371.

Quarantine Issues

Johnson, G.I., and L.M. Coates. 1993. Postharvest
diseases of mango. Postharv. News Info.
4:27n-34n.

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 withfruit core temperature of 46 to 48 °C (115 to
118 °F), and irradiation (300 grays) are potential
treatments.

Suitability as Fresh-Cut ProductKanes, O., M. Boulet, and F. Costaigne. 1982.
Effect of chilling-injury on texture and fungal rotof 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.

Fresh-cut pieces and slices are frequently found in
markets. Browning of the flesh can be a problem.

Lakshminarayana, S. 1973. Respiration andripening patterns in the life cycle of the mango
fruit. J. Hort. Sci. 48:227-233.

References

Lelyveld, L.J. van, and J.H.E. Smith. 1979.
Physiological factors in the maturation andripening of mango (Mangifera indica L.) fruit inrelation to the jelly seed physiological disorder. J.
Hort. Sci. 54:283-287.

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 ofmango 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. Departmentof Agriculture, Washington, DC.

410

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 andDisorders 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 ofthe 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.

Medlicott, A.P., J.M.M. Sigrist, and O. Sy. 1990.
Ripening of mangoes following low temperaturestorage. 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-treatedmango fruit. Postharv. Biol. Technol. 3:77-86.
O’Hare, T.J. 1994. The susceptibility of Thaiand Australian mango cultivars to sap injury andpossible 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 andacceptability of mangoes treated with combinationof hot water, imazalil and γ-radiation. Plant Dis.
70:1149-1150.
Yahia, E.M. 1998. Modified and controlled
atmospheres for tropical fruits. Hort. Rev. 22:123183.
Young, T.W., and J.T. Miner. 1961. Relationshipof nitrogen and calcium to ‘soft-nose’ disorder inmango fruits. J. Amer. Soc. Hort. Sci. 78:201-208.

411

Mangosteen

fruit skin damaged by thrips prior to harvest amore attractive appearance.

Robert E. Paull and Saichol Ketsa
Paull is with the Department of Tropical Plant andSoil 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 isalso 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 Paull1998).
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 andturns 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 skinshould be thick and soft, but firm, when ripe.
Fruit have a soft, sweet, slightly acid flesh witha pleasant flavor. Misshapen and damaged fruit
should be removed. Burst latex vessels leavea yellow dried latex on the skin that should be
scraped off, followed by washing the fruit with asoft brush. Fruit are graded to remove damaged
fruit and for size. Some Thai growers andexporters coat cleaned fruit with lacquer, giving
412

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 iswhen the skin has distinct irregular, pink-red
spots over the whole surface. Fruit are at theedible, ripe stage when the skin has darkened to
reddish-purple, no latex remains in the skin, andthe flesh segments separate easily from the skin(Tongdee and Suwanagal 1989). Careful handlingis essential in order to avoid mechanical injury.

Grades, Sizes, and Packaging
There are no U.S. or international standards. Fruitare graded by size and color. Mangosteens arenormally sold in single-layer, fiberboard cartonsholding 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 andAzudin 1986).

Optimum Storage Conditions
Recommendations vary from 4 to 6 °C (39 to 42°F) with 85 to 90% RH for 7 weeks (Pantastico1975) 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 practiceis to store fruit at 12 to 14 °C (54 to 57 °F), giving
storage life of about 20 days without chillinginjury. Application of surface coatings reduces
weight loss and prevents calyx wilting (Choehom1997).

Controlled Atmosphere (CA)Considerations
An atmosphere of 5% O2 and 5% CO2 has beenused 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 weightloss and disease (Daryono and Sabari 1986);
however, it is not clear if the effects are due tothe prevention of water loss or to the modified
atmosphere in the bags.

Retail Outlet Display Considerations
Fruit are commonly displayed in overwrappedtrays 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 returnedto ambient temperature (Uthairatanakij and Ketsa
1996, Choehom 1997).

Physiological Disorders
Fruit damage during harvesting and marketing canaffect >20% of fruit. The “gamboges” disorderoccurs where latex seeps into the flesh (aril),
turning it yellow and giving it a bitter taste.
“Gamboges” also moves onto the outer surfaceof 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. Thisshould not be confused with impact injury that
leads to hardening of the pericarp at the pointof impact and aril collapse, dehydration, pinkcolor development, or browning (Tongdee andSuwanagul 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 todowngrading of the fruit (Tongdee and Suwanagul
1989, Ketsa and Atantee 1998).
Another disorder of mangosteen fruit istranslucent aril (nue-kaew), believed to be
induced by heavy rain during fruit growthand development, even if just before harvest(Laywisakul 1994). The specific gravity of fruitwith translucent aril is >1.0, while that of normal
aril is <1.0. This allows separation of fruit byfloating them in water (Podee 1998). Fruit withtranslucent aril have lower SSC and TA thannormal fruit (Pankasemsuk et al. 1996).

Postharvest Pathology
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).

Botryodiplodia theobromae, Diplodia spp.,
Pestalotia flagisettula, Phomopsis spp., andRhizopus spp. have been reported; they harden theskin and decay the aril.

Quarantine Issues
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).

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.
413

Suitability as Fresh-Cut ProductSome potential exists.

Pantastico, E.B., ed. 1975. Postharvest Physiology,
Handling and Utilization of Tropical and
Subtropical Fruits and Vegetables. AVI, Westport,
CT.

Augustin, M.A., and M.N. Azudin. 1986. Storageof mangosteen (Garcinia mangostana, L.).
ASEAN Food J. 2:78-80.

Podee, R. 1998. Nondestructive Methods for
Separation of Translucent Pulp in Mangosteenby Specific Gravity and X-Ray Computed
Tomography. M.S. thesis, Chiang Mai University,
Chiang Mai, Thailand.

Choehom, R. 1997. Effect of waxing and plant
growth regulators on quality and storage-lifeof mangosteen (Garcinia mangostana L.) fruit
during cold storage. Graduate Special Problem,
Department of Horticulture, Kasetsart University,
Bangkok, Thailand.

Rattanachinnakorn, B., J. Phumhiran, and S.S.
Nanthachai. 1996. Controlled atmosphere storageof mangosteen. In Annual Technical Conference
and Proceedings of the Horticulture ResearchInstitute, Department of Agriculture, Bangkok,
Thailand.

Daryono, M., and S. Sabari. 1986. The practicalmethod of harvest time on mangosteen fruit andits characteristics in storage. Bull. Penelitian Hort.
Indonesia 14(2):38-44.

Tongdee, S.C., and A. Suwanagul. 1989.
Postharvest mechanical damage in mangosteen.
ASEAN Food J. 4:151-155.

References

Ketsa, S., and S. Atantee. 1998. Phenolics, lignin,
peroxidase activity and increased firmness ofdamaged 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. TropicalFruits. 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 disorderof mangosteen fruit (Garcinia mangostana L.).
HortScience 31:112-113.

414

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 theInternational Conference on Tropical Fruits, vol.
1, pp. 411-422. Malaysian Agricultural Researchand Development Institute, Serdang, Salangor,
Maylasia.
Yahia, E.M. 1998. Modified and controlled
atmospheres for tropical fruits. Hort. Rev. 22:123183.

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.

cleanliness, and trim quality. Mushrooms arepacked 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 (32to 39 °F) immediately after harvest. Hydrocoolingand 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 lowtemperature. The same procedure is applied to cut
mushrooms.

Optimum Storage Conditions
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 andabsence of browning or other discoloration are
also quality factors. Visible open caps and absenceof a stipe are negative factors.

Horticultural Maturity IndicesMushrooms are harvested by maturity, not by thesize of the caps. Proper maturity is reached when
the caps are well rounded and the partial veil iscompletely intact. The stipe should have a small
length:thickness ratio and should be sufficient topermit 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,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. Moistureloss is correlated with stipe blackening and veil
opening. Mushrooms should be packed in cartonswith 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 ofmushrooms intended for fresh consumption.

Controlled Atmosphere (CA)Considerations
Mushrooms derive a moderate benefit fromstorage 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
415

yellowing of the cap surface. Levels of O2 <1%
can favor growth of Clostridium botulinum andthe development of off odors and off flavors, aswell as cap opening and stipe elongation. For thisreason, 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 fromgreen onions; they should not be transported ordisplayed together.

Chilling Sensitivity
Mushrooms are not chilling sensitive, but theyfreeze below -0.6 °C (31 °F). Freezing injury
appears as water-soaked and extremely soft caps
(Suslow and Cantwell 1998).

Physiological Disorders
Low storage temperatures are needed to reduce
continued development of mushrooms after
harvest. Common disorders include upwardbending of caps and opening of the veil.
Mushrooms are easily bruised by rough handlingand develop brown discolored tissue.

Postharvest Pathology
Disease is generally not an important source ofpostharvest loss in comparison with physiologicalsenescence and improper handling or bruising.
All diseased caps must be eliminated at harvest.
Bacterial blotch or Pseudomonas spp. can becomea problem during extended storage at elevatedtemperatures (Suslow and Cantwell 1998).

Quarantine Issues
Ethylene Production and Sensitivity
Mushrooms produce very low amounts ofethylene: 0.1 L kg-1 h-1 at 20 °C (68 °F). Since
ethylene causes browning of mushroom caps, theyshould be kept separate from ethylene-producing
fruits and vegetables.

None are known.

Suitability as Fresh-Cut ProductFresh-cut mushrooms are becoming increasing
popular at the wholesale and retail level.

Respiration Rates

References

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).

Carrier Corporation. 1995. Controlled Atmosphere
Handbook. A Guide for Shipment of Perishable
Cargo in Refrigerated Containers. Carrier,
Syracuse, NY.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

416

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.

Salunkhe, D.K., and S.S. Kadam. 1998. Handbookof 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 atmospherestorage of fresh mushrooms. J. Zbej. Agr. Univ.
20:165-168.

417

Nectarine
Carlos H. Crisosto and Adel A. Kader
Crisosto is with the Department of Plant Sciences,
University of California, Davis, CA. Kader waswith the Department of Plant Sciences, Universityof 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 havearisen 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 Reservedand 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 ofnectarines in the United States. Current shipmentsof fresh nectarines have approached 20 million 10kg (22-lb) packages. More than 130 cultivars areraised commercially. In recent years, an importantdevelopment has been the breeding of white-flesh
nectarine cultivars. In the San Joaquin Valley,
harvest of early cultivars starts in mid May, andharvest of late cultivars of nectarines is completed
in mid September. Nectarines are exported mainly
to Canada, Taiwan, Hong Kong, Mexico, andBrazil.

Quality Characteristics and Criteria
Greater consumer acceptance is attained for fruitwith high SSC. TA and SSC:TA are also importantin consumer acceptance. In general, nectarines
have more TA than peaches. No minimum
flavor-quality standard has been established fornectarines. Fruit with 9 to 13.5 N (2 to 3 lb-force)418

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 skinground color, which changes from green to yellow
in most cultivars. A color chip guide is used todetermine maturity of each cultivar except whitefleshed cultivars. A two-tier maturity system isused 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 andAgriculture Division of Inspection Services.
Measurement of fruit firmness is recommended for
cultivars in which skin ground color is masked byfull 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 penetrometerwith 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 theorchard to a packinghouse and cooled as soon as
possible after harvest. At the packinghouse, fruit
are dumped (mostly using dry bin dumps) andcleaned. Sorting is done to eliminate fruit withvisual defects and sometimes to divert fruit ofhigh 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

of the white-flesh and “tree ripe” nectarines arepacked 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 bytrailer to the packing area. Packers work directlyfrom 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 inside-vented bins can be done by the tunnel or theserpentine method. Hydrocooling is normallydone 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 tobe delayed beyond the next day, fruit should bethoroughly 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 substantiallyduring packing and should be thoroughly recooledusing 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 thefreezing point of the fruit and of the temperaturefluctuations in storage and transport systems.
Temperature during truck transportation within
the United States, Canada, and Mexico shouldbe <2 °C (36 °F). Holding stone fruits at these
low temperatures minimizes losses to rottingorganisms, excessive softening, and water losses,
as well as reducing severity of internal browningin susceptible cultivars.

Optimum Temperature
The optimum storage temperature is -1 to 0 °C (30to 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 retentionof fruit firmness, stability of color, and limiting ofinternal 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 becauseof associated development of off flavors andbrowning.

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 inthose stored at 0 °C (32 °F) or below. Recently
released mid- and late-season cultivars have low
susceptibility to internal browning.

419

Ethylene Production and Sensitivity
In the following table, the lower end of the range
is for mature but unripe fruit; higher values are forripe fruit:
Temperature
0 ºC
5 ºC
10 ºC
20 ºC

µL C2H4 kg-1 h-1
0.01 to 5
0.02 to 10
0.05 to 50
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
0 °C
10 °C
20 °C

mg CO2 kg-1 h-1
4 to 616 to 2464 to 110

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 aphysiological 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, andthus are usually detected by consumers. However,there is large variability in susceptibility to IB
among cultivars. In general, nectarines are lesssusceptible to IB than peaches. In susceptible
420

cultivars, IB symptoms develop faster and more
intensely when fruit are stored at temperatures
between about 2 and 8 °C (36 and 46 °F) thanwhen 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 developmentof this disorder have been tested. Among them,preripening fruit before storage is a successfulcommercially 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 ischaracterized 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 usuallyoccurs 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, andfollowing suggested preharvest fungicide sprayguidelines are recommended to reduce inking.

Postharvest Pathology
Brown rot is caused by Monilinia fructicola andis the most important postharvest disease ofstone fruits. Infection begins during floweringand fruit rot may occur before harvest but often
appears postharvest. Orchard sanitation tominimize infection sources, preharvest fungicide
application, and prompt cooling after harvest areamong the control strategies. Also, postharvest
fungicide treatment may be used.
Gray mold is caused by Botrytis cinerea and canbe serious during wet spring weather. It can occur
during storage if the fruit has been contaminatedthrough harvest and handling wounds. Avoiding
mechanical injuries and good temperature
management are effective control measures.

Rhizopus rot is caused by Rhizopus stolonifer andcan 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 spidermite) 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 importrequirements and provide information to assist
exporters in targeting markets and defining what
entry requirements a particular country might havefor nectarines. APHIS, in cooperation with theState plant boards, developed a database called“Excerpt” to track phytosanitary requirements
for each country. APHIS provides phytosanitaryinspections and certifications that declarenectarines free of pests to facilitate compliancewith 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 spidermite), and Ceratitis capitata (Mediterranean fruitfly). If these conditions cannot be met, then fruit
must be treated with an appropriate treatment
prior to shipment. Details of the treatment must berecorded 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 tosatisfy 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, andG.W. Lightner. 1987. Disorders in plum, peachand 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.

421

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 33:110113.
Gorny, J.R., B. Hess-Pierce, and A.A. Kader.
1999. Quality changes in fresh-cut peach andnectarine slices as affected by cultivar, storage
atmosphere and chemical treatments. J. Food Sci.
64:429-432.
Lurie, S. 1992. Controlled atmosphere storage todecrease 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 andnectarines. Hort. Rev. 11:413-452.

422

Netted Melonlarger, about 6 lb (2.7 kg) each, and have a bright,
orange-pink flesh.

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. Departmentof Agriculture, Weslaco, TX. Shellie is now with
the Horticultural Crops Research Laboratory,
Agricultural Research Service, U.S. Departmentof 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 memberof 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 principallyfor domestic and export markets, while Eastern
Choice melons (grown in the eastern UnitedStates) are more perishable and are usedprincipally 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 nettingof Persian melons are similar to those of Western
Shipper type melons, but Persian melons are

Quality Characteristics and Criteria
To meet U.S. grade standards, melons musthave 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), nosunscald (solar injury), flesh and rind free of
decay by fungi or bacteria, and absence of damage(USDA 1981). Damage includes liquid in the seedcavity, 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 areused 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 ofthe 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 willcontinue to soften and become more aromatic after
harvest (Shellie 1995, Ayub et al. 1996). Netted
melons harvested prematurely by cutting thestem prior to abscission-zone development may
produce little aroma, have low SSC, and do notproperly 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, andU.S. No. 2. The difference among grades reflects
levels of tolerance for quality criteria. A minimum423

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 numberof fruit of uniform size and weight that fit into astandard 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 isrecommended to delay ripening and retain sugar
content. Hydrocooling, forced-air cooling, andtop-icing are acceptable, but hydrocooling is mostefficient (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 theserecommended conditions is 10 to 14 days.

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, andfailure 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 4days 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
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 islost 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.

Netted melons have a moderate rate of respiration(Kader 1992).
Temperature
mg CO2 kg-1 h-1
0 °C
5 to 64 to 5 °C
9 to 1010 °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 rateby 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

424

1992). Vein track browning, a darkening of thelongitudinal tracts between netted areas, is causedby 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) andstorage 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 isoften no sign of infection before harvest, but
numerous spongy white lesions may developinternally postharvest. Fungicide application ina hot-water dip, 1 min at 57 °C (135 °F), cansuppress fusarium fruit rot. Other less common
diseases include black rot incited by Didymellabryoniae or Phomopsis cucurbitae, rhizopus softrot (Rhizopus stolonifer), bacterial brown spot
(Erwinia ananas), bacterial soft rot (Erwinia
carotovora), and alternaria rot (Alternaria
alternata).

but limited supply and increased costs may makemethyl bromide undesirable in the near future.

Suitability as Fresh-Cut Product
Harvest maturity, cultivar, growing location,
cultural practices, and postharvest handlinginfluence quality of the processed product. Netted
melons destined for fresh-cut sale should be
harvested at the earliest maturity acceptable forminimum 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 abovechloride 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 atmosphereof 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).

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 ofsubstances with ozone-depleting potentials of 0.2
or greater. Use of methyl bromide for preshipment
and quarantine is exempt from these restrictions,

References
APHIS [USDA Animal and Plant HealthInspection 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 ofAgriculture, Animal and Plant Health Inspection
Service, Plant Protection and Quarantine,
Hyattsville, MD.

425

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).

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 Enhancementof Cucurbit Germplasm, pp. 101-103. Gateway
Printing, Edinburg, TX.
Shellie, K.C., and M.E. Saltveit. 1993. The lack ofa respiratory rise in muskmelon fruit ripening on
the plant challenges the definition of climactericbehaviour. J. Exp. Bot. 44:1403-1406.
Scholz, E.W., H.B. Johnson, and W.R. Buford.
1963. Heat evolution rates of some Texas-grownfruits and vegetables. J. Rio Grande Valley Hort.
Soc. 17:170-175.

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.

Snowdon, A. 1992. Color Atlas of Postharvest
Diseases and Disorders of Fruits and Vegetables.
CRC Press, Boca Raton FL.

Lester, G.E., and B.D. Bruton. 1986. Relationshipof netted muskmelon fruit water loss topostharvest storage-life. J. Amer. Soc. Hot. Sci.
111:727-731.

USDA [U.S. Department of Agriculture].
1981. United States Standards for Grades ofCantaloupes. U.S. Department of Agriculture,
Washington, DC.

Lyons, J.M., W.B. McGlasson, and H.K Pratt.
1962. Ethylene production, respiration, andinternal gas concentrations in cantaloupe fruits at
various stages of maturity. Plant Physiol. 37:3136.

Wang, C.Y. 1990. Chilling Injury of Horticultural
Crops. CRC Press, Boca Raton FL.

Ryall, A.L., and W.J. Lipton. 1979. Handling,
Transportation, and Storage of Fruits andVegetables, 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.

426

Zitter, T.A, D.L. Hopkins, and C.E. Thomas. 1996.
Compendium of Cucurbit Diseases. American
Phytopathological Society, St. Paul MN.

Nopalitos

Grades, Sizes, and Packaging

Marita Cantwell
Cantwell is with the Department of Plant Sciences,
University of California, Davis, CA.

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.

Scientific Name and Introduction

Precooling conditions

Cactus stems (“nopalitos” in Spanish) are therapidly growing succulent stems (cladodes) of
the prickly pear cactus (Opuntia spp.). They area 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, mostcommercial 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).

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 usuallyroom-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.

Quality Characteristics and Criteria
Good-quality nopalitos are fresh, turgid, anda brilliant green color. In the early stages ofgrowth, vestigial true leaves, usually subtended byspines, are present on the stems. The leaves often
abscise by the time nopalitos reach commercial
size; however, green true leaves on the stem arean additional indication of freshness. Nopalitos
should be harvested when young and tender, but
not early in the morning so as to avoid a high acidcontent (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.

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 anddehydration (Cantwell, 1995). Nopalitos stored
under ambient conditions rapidly lose theirbrilliant shiny appearance, become dull green
and may begin to yellow and curve inward due towater 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.
427

Chilling Sensitivity

Postharvest Pathology

Nopalitos are chilling sensitive when stored below
10 °C (50 °F). Chilling damage may be manifested
as a superficial bronzing or discoloration andincreased susceptibility to decay. Symptoms may
appear after 3 weeks at 5 °C (41 °F) (Cantwell etal. 1992) or sooner (Ramayo-Ramirez et al. 1978).

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 notdamaged when cut from the plant. Fungicide dips
reduce postharvest decay of nopalitos but are notused commercially (Ramayo-Ramírez et al. 1978).

Ethylene Production and Sensitivity

Quarantine Issues

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 enhanceyellowing.

None are known.

Respiration Rates
The following are average rates for 10-cm (4-in)
nopalitos over a 7-day period at the indicatedtemperatures. 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
5 °C
10 °C
15 °C
20 °C

mg CO2 kg-1 h-1
16 to 1938 to 4252 to 59
68 to 79

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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

Suitability as Fresh-Cut ProductSome types of nopalitos are spiny, and therefore acleaned 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 to10%) CA may be useful to reduce discolorationand other visual defects of cut nopalitos (Cantwell,2002, unpublished).

Special Considerations
Cactus stems should be harvested and handledwith care to avoid mechanical damage, especiallyfrom spines on one stem penetrating theneighboring stem. Spine damage leads to a rustybrown discoloration and pathological problems

See above section on Chilling Sensitivity.
Because the prickly pear plant is a crassulaceanacid metabolism (CAM) plant and fixes CO2 atnight as malic acid before converting it to sugars
during the day, the acid content of nopalitos
may fluctuate greatly and affect their flavor
428

(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 managementof 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 vidade 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 andquality 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 inpolyethylene bags. In P. Felker, and J.R. Moss,
eds., Proceedings of the 3rd Annual Texas Prickly
Pear Conference, Kingsville, TX, pp. 22-25.

429

Okra

Quality Characteristics and Criteria

Penelope Perkins-Veazie

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.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof 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 ofthe mallow (Malvaceae) family and can be foundas an annual (primarily in the United States) or asa 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 inother countries (Duzyaman 1997). Other names
include quingumbo, bhendi, bhindi, gumbo,
gombo, quaio, and lady’s finger.
In the United States, most fresh market okra isfrom California and the Southern United Statesand 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 completelyround, with no ribs). Pods are prized for theirunique flavor and high mucilaginous content(being used as a thickening agent).

Horticultural Maturity Indices
Okra pods are harvested when immature and highin 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 0.45kg (l-lb) clamshell boxes or as bulk weight orvolume-filled 11.4-kg (25-lb) bins.
Precooling Conditions
Okra should be marketed within 36 h of harvestand shipped under refrigeration. Storage inunventilated containers without refrigeration cancause degradation of color. Some growers usehydrocooling 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,

430

including 5 to 10% CO2 at 5 to 8 °C (41 to 46 °F)
and 3 to 5% O2 and 0% CO2 (Baxter and Waters1986). Levels of CO2 >20% can cause off flavors.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

Retail Outlet Display Conditions
Okra should be kept dry, refrigerated, andhumidified.
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 7days 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 ifheld 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.

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.

Ethylene Production and Sensitivity
Suitability as Fresh-Cut Product
Okra produce small amounts of ethylene duringstorage: 0.5 µL kg-1 h-1 (Baxter and Waters 1986).
Okra pods exposed to >1 µL L-1 ethylene for 3 ormore days show yellowing (Perkins-Veazie, 2002,
unpublished).

Suitability is unknown. Okra is generally
consumed after cooking.

Special Considerations
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; otherdata from Scholz et al. (1963).

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 andethylene evolution in harvested okra. HortScience
25:92-95.

431

Duzyaman, E. 1997. Okra: botany andhorticulture. 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., Proceedingsof 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-grownfruits 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.

432

OliveCarlos H. Crisosto and Adel A. Kader
Crisosto is with the Department of Plant Sciences,
University of California, Davis, CA. Kader waswith the Department of Plant Sciences, Universityof California, Davis, CA. He is deceased.

Scientific Name and Introduction
A member of the Oleaceae family (Olea europaeaL.), 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 partused 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 thewall 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.

[lenticels] through a straw color) indicate whento 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 thegreen stage.

Grades, Sizes, and Packaging
Harvesting of olives represents 50 to 70% of thetotal production labor cost and 30 to 40% of thegross returns from the crop. Harvested fruit begin
to lose moisture immediately. When harvested
during hot, sunny weather, olives should be putin the shade until hauled away. Sun-exposed
fruit gets sunburn and will grade as culls. Roughhandling causes bruises and grade reduction.
A few growers harvest their fruit mechanically,using tree shakers and catching frames. The useof 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 needsof the canneries. Optimum harvesting time isdetermined 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.

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 fromdefects, and oil content of 12 to 25% (depending
on cultivar). These are processed (Greek or Italianstyle) or used for oil extraction.

Horticultural Maturity Indices
For green olives, size and color (even colorationof pale green with a minimum of whitish spots

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 ofchilling injury if olives are stored below 7.5 ºC
433

(46 ºF). This information is for fresh green olives.
Fresh black olives should be processed as soonafter harvest as possible, but if necessary blackolives 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 adjacentto the pit. Over time, the discoloration becomes
more intense and progresses through the flesh
into the skin, at which time the olive has theappearance 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 orderof susceptibility to chilling injury, from mostto 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 atconcentrations >1 µL L-1, which causes a loss ofgreen color and flesh firmness.
Respiration Rates
Temperature
5 °C
7.5 °C
10 °C
20 °C

mg CO2 kg-1 h-1
10 to 20
16 to 24
24 to 32
40 to 80

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.
434

Physiological Disorders
Nailhead is characterized by surface pitting andspotting. It results from death and collapse of
epidermal cells, creating air pockets underneaththe 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 formore 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 toundesirable 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 Mexicoand 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 particularcountry might have for fresh olives. APHIS, incooperation with the State plant boards, developed
a database called “Excerpt” to track phytosanitaryrequirements for each country. APHIS provides
phytosanitary inspections and certifications thatdeclare fresh olives free of pests to facilitate
compliance with foreign regulatory requirements.

Suitability as Fresh-Cut ProductFresh olives are not edible or suitable as a freshcut product.

Special Considerations

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 Storageof Tropical and Subtropical Fruits, pp. 229-243.
CAB Intl., Wallingford, U.K.

Olives for pickling are harvested either unripe, inwhich 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 fromthe 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 andstorage 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 andProcessing. 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 controlledtemperature 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.
435

OnionFranciszek 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 biennialof the Alliaceae family. The edible portions of
the bulb are the enlarged leaf bases and compact
stem. Green onions, also called scallions, areeaten for their immature bulb and green foliage.
The predominant flavor component resultsfrom 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 withgood 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, sunscaldinjury, greening of fleshy scales, sprouting,bruising, doubles, bottlenecks (onions whichhave abnormally thick necks with only fairly welldeveloped bulbs), and any other defects.

Horticultural Maturity Indices
Harvest maturity depends on the purpose forwhich the onions are grown. Onions intended forstorage 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, butthen bulbs tend to have a shorter storage life. To
hasten maturity, tops can be rolled with a lightroller when 10% of them have fallen. About 7
436

days before lifting, bulbs can be undercut by
a blade; such onions should not be used forlong-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 andsize. For U.S. No. 1, the overall length (excludingroots) must be 20 to 61 cm (8 to 24 in), and thediameter 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 1in); 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 mixtureof U.S. No. 1 and U.S. No. 2 onions in which atleast 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 andCreole 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 thesame as above. Containers are usually 9.1 kg (20lb), except for export onions, which are packed in
25-kg (56-lb) containers.

Precooling Conditions
In order to maintain high quality, bunchedgreen onions should be precooled to <4 °C (39°F) within 4 to 6 h of harvest. Hydrocooling,
forced-air cooling, and vacuum-cooling are usedwith crushed ice over the product to maintaintemperature 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 duringstorage. Natural cooling (slow) has a positiveeffect 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 storageis 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 storedin 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 temperatureinduces sprouting. A combination of hightemperature and high RH increases rotting anddecreases quality. Storage below the freezing pointof -1 to -2 °C (28 to 30 °F) is recommended inEurope. Mild type or sweet onions can be kept for
1 to 3 mo; they are stored in common storage withcool, circulating ambient air or in refrigerated coldrooms. Onions grown from seed store better thanthose 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, asprouting 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 inorder to absorb and translocate the sprout inhibitor
to bulbs.
Onions intended for storage should be dried welland cured in the field, under sheds, or in storage.
After 2 weeks of field drying, onions can betransferred to storage rooms for final drying andcuring. Forced-air ventilation at 25 to 27 °C (77to 81 °F) using outside or heated air is commonlyused to dry onions. Onions can be stored anddried 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, outerscales are dry and make a rustling noise whentouched, and the skin color is uniform. Weight lossof 3 to 5% can occur during drying. Losses fromneck rot are reduced by rapid drying immediately
after harvest. After drying and curing, thetemperature should be lowered gradually to thenormal seasonal temperature, or bulbs can beprecooled 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 dryskin.
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 throughsacks is insufficient to maintain proper storage437

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 fromstorage. 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 ofcold-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 andextend 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-storedcontrols (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).

438

Retail Outlet Display Considerations
Onion bulbs can be displayed in small packages
or in bulk at <5 °C (41 °F). This temperatureeffectively retards sprouting for up to 7 mo.
Onions should not be stored with fruits andvegetables 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 thehighest freezing point is -0.8 °C (31.6 °F). Storageat <-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, butconcentrations 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 rateby 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 physiologicaldisorders. Freezing injury causes soft, watersoaked, fleshy scales and rapid decay after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 athigh temperatures produce the highest incidenceof 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 leatheryskin. Scale greening, a green coloration of outerscales, 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).

Blue mold rot also produces watery soft rot ofneck and outer scales, followed by formation ofblue 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. Harvestingat 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
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 theentire bulb. A gray fungal mold then covers theneck 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 duringstorage can decrease this postharvest fungal decay
disease.
Black mold rot presents a black discoloration andshriveling at the neck and on outer scales caused
by Aspergillus niger van Tiegh. Infection usuallyoccurs in the field, but the disease spreads frombulb 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.

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 ofonions in controlled atmosphere. Acta Hort.
38:53-75.
Grzegorzewska, M. 1999. The Influence ofWeather Conditions, Harvest Maturity andCooling Methods on the Quality and Storage
Ability of Onions. Ph.D. thesis, Research Instituteof Vegetable Crops, Instytut Warzywnictwa,
Skierniewice, Poland.
439

Hoftun, H. 1993. Internal atmosphere and wateryscales 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 AgriculturalEngineering 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 decayof “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 anddrying methods on internal atmosphere, outerscale 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 andVegetables, 2nd ed., vol. 1. AVI, Westport CT.
Smittle, D.A. 1988. Evaluation methods for‘Granes’ onions. J. Amer. Soc. Hort. Sci.113:877880.
Smittle, D.A. 1989. Controlled atmospherestorage 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.
440

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.

Orange

Horticultural Maturity IndicesMark A. Ritenour

Maturity indices are based on percentage color
break, SSC, TA, SSC:TA, and juice content.
Specific regulations are established for different
growing regions.

Ritenour is with the Indian River Researchand Education Center, Institute of Food andAgricultural 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 varyfrom spherical to oblong and are seedless (0to 6 seeds) to seeded (>6 seeds). Peel color atmaturity 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 offour groups: (1) round oranges such as ‘Valencia,’‘Hamlin,’ ‘Pineapple,’ and ‘Shamouti’; (2) navel
oranges such as ‘Washington Navel’; (3) blood orpigmented 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 thelargest producer of oranges for the fresh market.
Like other citrus fruits, oranges are nonclimactericwith no postharvest ripening phase.

Quality Characteristics and Criteria
A high-quality orange is mature, with good color
intensity that is uniformly distributed over thesurface. Fruit must be firm with a fairly smoothtexture and shape that is characteristic of thevariety. Fruit should be free from decay, defects,
and blemishes.

Florida: Minimum maturity indices for fresh fruit
shipments change according to harvest date andare 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-bubox).
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 aminimum juice content of 4.5 gal per 1.6-bu box.

Grades, Sizes, and Packaging
U.S. grade standards for sweet oranges are basedon 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 (forexample, cake melanose), growth cracks, chemicalburns, and physiological disorders. See http://
www.ams.usda.gov/AMSv1.0/standards for moredetails 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,
441

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 thanFlorida, 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 andArizona 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 bagsof various sizes are also used to market oranges.
Oranges may be individually seal-packaged(wrapped with various plastic films), but thispractice 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, andincreases shelf-life. Common cooling methods
for oranges include room-cooling and forced-air
cooling. Oranges can also be hydrocooled, but thispractice 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.
442

Optimum Storage Conditions
Under normal weather conditions, fruit store
better on the tree than in cold storage. Coldstorage 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 andtreated 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 ordisorders. Such problems will advance rapidly
once the fruit are removed from cold storage.
Recommended storage conditions are—Temperature Relative
Growing Region
		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 developmentof chilling injury. However, CA is not commonlyused because tolerable O2 and CO2 levels do notsignificantly inhibit decay (Hatton and Cubbedge1977), which limits shelf-life the most. Additionof 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).

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 producedin 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 toroom temperature (about 72 °F). After removing
fruit from chilling temperatures, respiration andethylene production both increase.
The development and severity of chilling injury
in citrus is influenced by both preharvest andpostharvest factors. Preharvest factors include
cultivar, weather conditions, and even locationof fruit on the tree (sun-exposed fruit are more
susceptible to chilling injury). Postharvest
development of chilling injury symptoms canbe reduced by temperature conditioning before
storage, use of high-CO2 atmospheres (forexample, in CA or through the use of wax coatingsor plastic film wraps), intermittent warming,and use of benzimidazole fungicides (such as
thiabendazole and benomyl). The best meansof preventing chilling injury is storing fruit atnonchilling 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 whennatural degreening has been delayed because ofwarm night temperatures. Degreening usuallytakes 1 to 3 days to complete and does notaffect internal quality (SSC, TA, etc.). However,ethylene stimulates decay, such as anthracnose(Brown 1992) and stem-end rot (Barmore andBrown 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—Temperature
Ethylene
RH
Ventilation(<0.1% CO2)

Florida28 to 29 ºC
5 µL L-1
90 to 96%

California
20 to 25 ºC
5 to 10 µL L-1
90%

1 air change
1 to 2 air changes
per hourper hour
Air Circulation 100 ft3 min-1 1 room volume
per 900-lb bin per min

Respiration Rates
Temperature
0 °C
5 °C
10 °C
15 °C
20 °C

mg CO2 kg-1 h-1
2 to 64 to 86 to 1011 to 22
20 to 31

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 theirregular deterioration of albedo cells (whitespongy tissue) and the collapse of the overlaying
flavedo (colored portion of the rind) into irregulargrooves over the fruit surface. Such areas are
weaker and often split, providing entry forpathogenic fungi and subsequent decay. Thisdisorder 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 during443

fruit expansion. Because the disorder is associatedwith advanced fruit maturity, earlier fruit
harvesting may also reduce the problem.
Granulation is caused by gel formation within
juice vesicles that greatly reduces extractablejuice content. It may occur primarily at the stemend (in ‘Valencia’ oranges), or extend through thecenter of the fruit (in navel oranges). In the UnitedStates, this is considered a preharvest disorderthat appears more in fruit exposed to the sun, fruitfrom 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 mechanicaldamage releases oil from the oil glands. When
fruit are very turgid, even slight pressure frombumps and abrasions can result in oil release andspotting. The oil is toxic to surrounding tissue andwill inhibit degreening of that tissue. Symptoms
appear as irregularly shaped green, yellow, orbrown spots that darken over time and make theglands more prominent. The most effective meansof prevention is not harvesting turgid fruit early inthe 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) scatteredover the fruit surface. It can begin to develop
2 days after packing. Collapsed regions turnbronze-brown or brown-black over time. Thisdisorder 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 bymechanical 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 acidto delay peel senescence and reduce incidence of
this disorder.
444

Stem-end rind breakdown (SERB) is characterized
by the irregular collapse and darkening of rindtissue around the stem end of the fruit. A narrow
ring of unaffected tissue immediately aroundthe stem (button) is a distinctive symptom of
SERB. In some growing regions, SERB has beencorrelated with a preharvest imbalance in nitrogenand 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, arecurrently 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 (Geotrichumcandidum), and anthracnose rot (Colletotrichum
gleosporioides).
Factors such as growing region, production
practices, cultivar, rootstock, and postharvest
practices influence susceptibility to each of thesepathogens. For example, stem-end rots are moreprevalent under environmental conditions foundin Florida and Texas. Green mold predominates
in Florida, but blue mold does so in California.
Postharvest decay can be reduced by harvestingat 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.

Quarantine Issues

References

Oranges are a fruit fly host, and when produced
in areas where any fruit fly is found, must betreated for insect control before shipment tosome markets. Approved disinfestation fororanges include methyl bromide fumigation,
cold treatments, and vapor heat treatments. Useof methyl bromide is being phased out and will
no longer be available by the year 2005. Cold
treatments are commonly used but may resultin chilling injury. Irradiation and controlled
atmospheres are potential alternative disinfestation
treatments.

AMS [USDA Agricultural Marketing Service].
1969. United States Standards for Grades ofOranges (Texas and States Other Than Florida,
California and Arizona). U.S. Department ofAgriculture, Washington, DC.

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 todisinfestation treatments, some production areas
have established protocols that are accepted byreceiving markets for certifying “fly-free” areas.
Oranges grown in these areas do not have to betreated before shipment.

Suitability as Fresh-Cut ProductConsumers’ 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 underdevelopment, 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.

AMS [USDA Agricultural Marketing Service].
1997. United States Standards for Grades ofFlorida Oranges and Tangelos. U.S. Department ofAgriculture, Washington, DC.
AMS [USDA Agricultural Marketing Service].
1999. United States Standards for Gradesof Oranges (California and Arizona). U.S.
Department of Agriculture, Washington, DC.
Barmore, C.R., and G.E. Brown. 1985. Influenceof ethylene on increased susceptibility of oranges
to Diplodia natalensis. Plant Dis. 69:228-230.
Brown, G.E. 1992. Factors affecting theoccurrence of anthracnose on Florida citrus. Proc.
Intl. Soc. Citricult. 3:1044-1048.
California Department of Food and Agriculture.
1990. Administrative Code, Title 3. State ofCalifornia, Sacramento, CA.
Eaks, I.L. 1964. The effect of harvesting andpacking house procedures on rind staining ofcentral 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 toChap. 601. Florida Statutes, Lakeland, FL.
Hatton, T.T., and R.H. Cubbedge. 1977. Status ofcontrolled-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.

445

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 fordegreening Florida fresh citrus fruits. Circular
1170, University of Florida, Institute of Food andAgricultural 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 ofFood 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.

446

Papaya(Akamine and Goo 1971). Less mature fruit arelower in sugar and ripen poorly.

Lili Zhou, Robert E. Paull, and Nancy Jung Chen
Zhou, Paull, and Chen are with the Departmentof 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 fruitis 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 (10to 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.

Grades, Sizes, and Packaging
The most common package size is a 4.5-kg(10-lb) carton; larger 10-kg (22-lb) cartons arealso used. Cartons from areas requiring insect
disinfestation are fully sealed to meet regulatory
requirements, while fruit from other areas can bein open-topped cartons. Count size ranges from
6 to 18, depending on fruit and carton size. Fruitare 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 meshsleeves, 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 arecommonly used. Hydrocooling is possible.
However, rapid cooling after insect disinfestation
treatments can lead to skin scalding.

Quality Characteristics and Criteria

Optimum Storage Conditions

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 foundin some Southeast Asian cultivars. Small,dry, brown-black “freckles” on the skin arenonpathogenic and do not detract from ripening or
flavor (Reyes and Paull 1994).

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 islimited by chilling injury, while at 10 to 13 °C(50 to 55 °F) fruit ripens slowly (Chen and Paull1986). Papaya fruit at color-turning (break) stage
can be stored at 7 °C (45 °F) for 14 days andwill ripen normally when transferred to room
temperature (Thompson and Lee 1971, Chen andPaull 1986). Ripe, full-color fruit can be held for>1 week at 1 to 3 °C (34 to 37 °F).

Horticultural Maturity Indices
In Hawaii, minimum grade standard requires
11.5% SSC (Hawaii Department of Agriculture1990), so fruit should have started ripening
before harvest, indicated by some skin yellowing

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%447

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) anddelays ripening (Akamine 1959, Chen and Paull1986). High CO2 (30%) adversely affects internal
color, aroma, and flavor, while there is no residual
effect of 10% CO2 on decay control, though skindegreening 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 shownvariable 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 20mm 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 weightloss 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 theedible 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 unevenbottoms and sides should be avoided; or at least alayer of protection should be placed between racks
and fruit (Paull et al. 1997). Loss of about 8% ofweight 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.

448

Chilling Sensitivity
Chilling injury symptoms include skin scald, hard
lumps in the pulp around vascular bundles, andwater-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 daysin 60% yellow fruit. Skin scald can be induced incolor-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 areheld 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 notstarted 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 fromthe blossom end (Akamine 1966).
Temperature		
5 °C		
15 °C		20 °C - color break
20 °C - ripe		

mg CO2 kg-1 h-1
4 to 615 to 229 to 1870 to 90

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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
A number of nonpathological disorders are seen
in marketed fruit (Paull et al. 1997). Green,slightly sunken areas on ripe yellow fruit arecaused by abrasion injury when fruit were stillgreen (Quintana and Paull 1993). Unsightly skinfreckles (small, brown, slightly raised areas)that are more common on the side of the fruit
exposed to the sun is seasonal, developing whenrainfall and low temperatures occur 2 mo before
harvest (Reyes and Paull 1994). This disorder isnonpathogenic 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 overwith fruit directly exposed to the sun, and where
harvested fruit are left exposed to the sun.
Blossom end defect can be severe at some timesof 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 inotherwise ripe, non-heat-treated fruit (Magalona
1963, Cavaletto 1989). The lumps are thought tobe associated with insect injury, disease, or otherforeign material in the flesh. The condition canalso occur in heat-treated fruit. Premature ripeningof 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 mobefore harvest, at the start of the final phase offruit growth (Qiu et al. 1995).
Intra-ovarian ovaries are common in some strainsof papaya (Nakasone and Arkle 1971). Theseovaries occur as a proliferation of tissue in theseed cavity and can be a threadlike appendage toround or elongated structures of various sizes andshapes. A few fill the entire seed cavity of the fruitand have their own seed cavity.
Sunken, dry, brownish-grey areas are caused bymites feeding on skin during early fruit growth.
The red and black mite (Brevipalpus phoenicis[Geijskes]) generally causes this damage inHawaii.

Postharvest Pathology
The major postharvest diseases are anthracnoseand stem end rot. Postharvest diseases, especiallyanthracnose, 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 enhancedevelopment of postharvest diseases (Somnerand 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 (Akamineand Arisumi 1953, Couey et al. 1984, Glazener
et al. 1984) and fungicide treatment (Couey andFarias 1979).

Quarantine Issues
Fruit fly infestation becomes a problem withpapaya after fruit have 25% skin yellowing (Seo etal. 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 beenshown.
449

Suitability as Fresh-Cut ProductFruit are prepared as deseeded, halved fruit, slices,and chunks. Fresh-cut products made from 60
to 80% yellow-skinned fruit, overwrapped withplastic 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).

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 withspecial reference to storage decay control. Tech.
Bull. 29, Hawaii Agricultural Experiment Station,
Honolulu, HI.

References

Armstrong, J.W. 1994. Tropical and subtropicalfruits. 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.

Akamine, E.K. 1959. Effects of carbon dioxideon quality and shelf life of papaya. Tech. Progr.
Rpt. 120, Hawaii Agricultural Experiment Station,
Honolulu, HI.

Cavaletto, C.G. 1989. Quality of high temperature
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452

Parsley

Grades, Sizes, and Packaging

Julian A. Heyes

Only one grade is available (U.S. No. 1), which
consists of parsley that meet quality criteria andhave similar varietal characteristics; that is, curlyleaf and flat-leaf varieties are not mixed. Parsley isusually packaged in cartons or jumbo crates of 60
bunches, 9 to 11 kg (20 to 25 lb).

Heyes is formerly with the New Zealand Institutefor Crop and Food Research, Palmerston North,
New Zealand. He is now with the Department ofFood Science and Technology, Massey University,
Palmerston North, New Zealand.

Precooling Conditions
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. Bothcurly-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 edibleroot. Parsley has very high vitamin and nutrient
content. It is highest in calcium, iron, and folateof all vegetables studied (Athar et al. 1999) andhas among the highest contents of β-carotene,
thiamin, riboflavin, and vitamins C and E. A highproportion of the carotene is 9-cis β-carotene,
possibly active against cancer and cardiovasculardisease (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 IndicesParsley can be harvested progressively or cut
all at one time. Long petioles are desirable forbunching. Most of the U.S. crop is harvested byhand.

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 toonly 3 days at 18 to 20 °C (64 to 68 °F) with 85 to
90% RH (Lisiewska et al. 1997). The endpoint ofstorage 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 condensationmust be avoided. Aharoni et al. (1989) showedthat nonperforated polyethylene liners delayed
yellowing and decay at low temperature. Parket 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 byusing 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).

453

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 usedduring storage, care must be taken to prevent
condensation during the retail period.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
22 to 385 °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 rateby 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 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 arevery sensitive to it (Joyce et al. 1986, Tsumura etal. 1993). Cantwell and Reid (1993) observed thatparsley 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 notstimulate respiration in parsley (Inaba et al. 1989).

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 ProductParsley’s flavor and aroma were retained betterin perforated film packages than in sealed film
packs (Manzano et al. 1995). Food safety is amajor concern. Chlorinated water is somewhat
beneficial in reducing contamination (Park andSanders 1992), but personal hygiene of the454staff is paramount. Parsley has been implicatedas 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 notdecrease 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) anddiabetes 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.

Benamotz, A., and R. Fishler. 1998. Analysis ofcarotenoids 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 andvegetables. At http://postharvest.ucdavis.edu/
produce_information/storagefreshproduce.
Cantwell, M.I., and M.S. Reid. 1986. Postharvest
handling of fresh culinary herbs. II. Respirationand 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 associatedwith eating fresh parsley—United States andCanada, July-August 1998. J. Amer. Med. Assoc.
281:1785-1787.

Apeland, J. 1971. Factors affecting respiration andcolor during storage of parsley. Acta Hort. 20:4352.

Elkner, K., M. Horbowicz, and R. Kosson. 1998.
Effect of storage on contents of dietary fibre andits composition in some cultivars of red beet, root
parsley and carrot. Veg. Crops Res. Bull. 49:107120.

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.

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.

Bakowski, J., H. Michalik, and L. Umiecka.
1994. Effect of sowing and harvest date on thequality of root parsley and its storability. Biuletyn
Warzywniczy 41:157-167.

Inaba, A., Y. Kubo, and R. Nakamura. 1989. Effectof exogenous ethylene on respiration in fruits andvegetables with special reference to temperature.
J. Jap. Soc. Hort. Sci. 58:713-718.

455

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.

Tschape, H., R. Prager, W. Streckel, et al. 1995.
Verotoxinogenic Citrobacter freundii associatedwith severe gastroenteritis and cases of hemolytic
uraemic syndrome in a nursery school—green
butter as the infection source. Epidem. Inf.
114:441-450.

Lers, A., W.B. Jiang, E. Lomanies, and N.
Aharoni. 1998. Gibberellic acid and CO2 additiveeffect in retarding postharvest senescence ofparsley. J. Food Sci. 63:66-68.

Tsumura, F., Y. Ohsako, Y. Haraguchi. 1993.
Rapid changes in parsley leaves during storage incontrolled or ethylene-containing atmosphere. J.
Food Sci. 58:619-625.

Lisiewska, Z., W. Kmiecik, and A. Budnik.
1997. Effect of conditions and time of storage ontechnological quality changes of parsley leaves.
Folia Hort. 9:21-29.

Tunali, T., A. Yarat, R. Yanardag, et al. 1999.
Effect of parsley (Petroselinum crispum) on theskin of STZ-induced diabetic rats. Phytotherapy
Res. 13:138-141.

Manderfeld, M.M., H.W. Schafer, P.M. Davidson,
and E.A. Zottola. 1997. Isolation and identificationof antimicrobial furocoumarins from parsley. J.
Food Protect. 60:72-77.

AMS [USDA Agricultural Marketing Service].
2002. Quality Standards—Fresh Fruits andVegetables. At http://www.ams.usda.gov/
AMSv1.0/standards.

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.

Yamauchi, N., and A.E. Watada. 1993. Pigmentchanges in parsley leaves during storage incontrolled or ethylene-containing atmosphere. J.
Food Sci. 58:616-618, 637.

Park, C.E., and G.W. Sanders. 1992. Occurrenceof thermotolerant campylobacters in fresh
vegetables sold at farmers outdoor markets andsupermarkets. Can. J. Microbiol. 38:313-316.

Ziyyat, A., A. Legssyer, H. Mekhfi, et al. 1997.
Phytotherapy of hypertension and diabetes inoriental Morocco. J. Ethnopharmacol. 58:45-54.

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 andVegetables, 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.

456

Parsnip

Precooling ConditionsPeter M.A. Toivonen

Parsnips are similar to carrots in requirements andshould 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.

Toivonen is with the Pacific Agri-Food ResearchCentre, Agriculture and Agri-Food Canada,
Summerland, British Columbia, Canada.

Scientific Name and Introduction
The parsnip (Pastinaca sativa L.) is a nativeof 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) andthrives 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 thecrown.

Horticultural Maturity IndicesParsnips are harvested when root diameteris between 2.5 and 7.6 cm (1 and 3 in) at theshoulder.

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 andLentz 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 fornonpackaged product. Packaged products shouldbe held in a cold display case with no ice or water
sprinklers.

Chilling Sensitivity
Parsnips are not chilling sensitive.

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 (25lb) perforated polyethylene bags or 5.5-kg (12-lb)
cartons holding 12 cello bags of 0.5 kg (1 lb) each.

Ethylene Production and Sensitivity
Parsnips produce very little ethylene: <0.1 µL
kg-1 h-1 at 20 °C (68 °F). Exposure to low levelsof ethylene in cold storage causes bitterness,
likely due to accumulation of xanthotoxin(8-methoxypsoralen) (Johnson et al. 1973,
Shattuck et al. 1988).

457

Respiration Rates

Suitability as Fresh-Cut ProductTemperature
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 andLentz (1972).

No potential exists.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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
Physiological Disorders
Surface browning is a significant problem thatis largely associated with bruising and abrasion
injury during harvest (Kaldy et al. 1976, Toivonen1992). Crops grown on coarse sandy soils are
more susceptible, and there are cultivars resistantto browning (Kaldy et al. 1976, Toivonen 1992).
Surface browning also increases with length ofstorage (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 etal. 1982). Some cultivars are resistant to parsnip
canker (Davis et al. 1989).

Some information in this chapter is from theOregon 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 tovarieties, soil conditions and length of storage. In
55th Annual Report of the Canadian Horticultural
Council, pp. 101-102.
Plantenius, H. 1939. Wax emulsions forvegetables. Bull. 723, New York University
Agricultural Experiment Station, Geneva, NY.

Quarantine Issues
There are no known quarantine issues.

458

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.

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 dioxideand 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 ofVegetables, pp. 541-553. Marcel Dekker, New
York, NY.
Toivonen, P.M.A. 1992. The reduction ofbrowning 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. Highhumidity storage of carrots, parsnips, rutabagas
and cabbage. J. Amer. Soc. Hort. Sci. 98:129-132.

459

Passion Fruit

Grades, Sizes, and Packaging

Robert E. Paull and Ching Cheng Chen

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.

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.) andyellow 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 twoparents. 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 to3 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).

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 havea 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.

Quality Characteristics and Criteria

Controlled Atmosphere (CA)ConsiderationSize, shape, skin color, acidity, and SSC are
the major criteria used to evaluate quality. Fruitshould be free of blemishes. SSC is 10 to 18% inyellow fruit and 10 to 20% in the purple type, withthe yellow type having a more acidic flavor.

Modified atmospheres (MA) have been tested on
yellow passion fruit, and a fungicide treatment
before storage is desirable. Film-bagging andvarious 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 associatedwith control of water loss, rather than MA effects.

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 toabscise and fall and are then picked up from theground.

460

Retail Outlet Display Considerations
Fruit should be displayed at ambient temperatureand not misted or iced.

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 theirclimacteric 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).

1978). This disease is most severe following
warm, wet periods. Septoria spot (Septoria
passiflorae) infects fruit in the field and leads touneven 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 toopen the canopy, and application fungicides canminimize these diseases.

Quarantine Issues
Fruit are a fruit fly host and may require treatment.
Irradiation has been successful.

Respiration Rates

Suitability as Fresh-Cut ProductThe climacteric of this fruit normally occurs on
the vine (Biale 1975).

No potential currently exists.

Temperature
5 °C
10 °C
20 °C
25 °C

mg CO2 kg-1 h-1
29 to 58
39 to 78
87 to 194
175 to 349

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. 69:221225.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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.

Physiological Disorders

Arjona, H.E., F.B. Matta, and J.O. Garner. 1992.
Temperature and storage time affect quality ofyellow passion fruit. HortScience 27:809-810.

Shrivel, pulp fermentation, and fungal attack are
the major postharvest problems (Pruthi 1963).
Shrivel is caused by moisture loss without initiallysignificantly 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 (InchBiale, 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 Conference461

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. Ministeriode Agricultura, Pesca y Alimentacion, CanaryIslands, 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 inpolymeric films. Proceedings of the Interamerican
Society for Tropical Horticulture 37:85-88.
Pruthi, J.S. 1963. Physiology, chemistry, andtechnology 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. 7:161170.

462

Pea
Stephen Morris and Jenny Jobling
Morris and Jobling are with the Sydney
Postharvest Laboratory, Food Science Australia,
North Ryde, New South Wales, Australia.

dirt, leaves or other foreign matter, mildew orother diseases, insects, or mechanical or othermeans. There are no USDA grades for snow orsnap 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 3in) long. Green peas are shipped in 13.6-kg (30lb) bushel baskets, or crates. Snow and sugar snap
peas are shipped in 4.5-kg (10-lb) cartons.

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 UnitedStates 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 theresult of a cross between the snow pea and an
unusual tightly podded pea with thick walls. All ofthese 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 mechanicaldamage. Stems and calyxes should be green.

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 seeddevelopment; 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 areprewet to ensure rapid cooling (Ryall and Lipton
1979). Forced-air cooling is the preferred methodof cooling for edible podded peas (NWREC
1998).

Optimum Storage Conditions
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,

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 onpeas, it is essential that they be stored below 2 °C
(36 °F).
463

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 respondmoderately to CA of 2 to 3% O2 and 2 to 3%
CO2, though not all research has found CA to bebeneficial (Suslow and Cantwell 1998).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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

Storage with crushed ice can be beneficial, andwater sprays are acceptable for garden and snowpeas, but these methods should be avoided forsnap peas (Suslow and Cantwell 1998).

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 topremature senescence resulting in yellowing, color
changes in the calyx, and loss of tenderness andflavor (Suslow and Cantwell 1998). Storage at >5°C (41 °F) and exposure to ethylene can accelerate
this problem.

Chilling Sensitivity

Postharvest Pathology

Peas are not sensitive to low temperature andshould be stored as close to 0 °C (32 °F) as
possible without freezing.

Because of high respiration rate, the heatgenerated by unrefrigerated peas will promotedecay. Blemishes that reduce quality can becaused 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 softrot. Botrytis gray mold can be a problem at theblossom-end of fresh-cut pods.

Retail Outlet Display Considerations

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 aremoderately sensitive to ethylene after harvest,
which results in yellowing and increased decay.
The calyx is more sensitive to ethylene than thepod (Suslow and Cantwell 1998).

Quarantine Issues
Respiration Rates
There are no known quarantine issues.
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).
464

Suitability as Fresh-Cut Product
Edible podded peas are suitable for use in freshcut mixtures.

Special Considerations
Keeping peas cold is critical for retaining quality.
Surface moisture should be avoided unless themarketing 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. Effectof 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 andExtension 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 ofPostharvest Diseases and Disorders of Fruit andVegetables, 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 thestorage of green peas. J. Sci. Food Agr. 15:245252.
465

PeachHorticultural Maturity Indices

Carlos H. Crisosto and Adel A. KaderIn California, harvest date of most cultivars isdetermined by change in skin ground color fromgreen to yellow. A color chip guide is used todetermine maturity of each cultivar except whitefleshed cultivars. A two-tier maturity system isused 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 andAgriculture, Division of Inspection Services.

Crisosto is with the Department of Plant Sciences,
University of California, Davis, CA. Kader waswith the Department of Plant Sciences, Universityof California, Davis, CA. He is deceased.

Scientific Name and Introduction
The peach, Prunus persicae, is native to China andPersia (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 ofpeaches in the United States. The development ofwhite-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 peacheswith high SSC. TA and SSC:TA are also importantfactors 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 withfirmness below about 30 N (7 lb-force) measured
on the fruit cheek have high consumer acceptance.

466

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 canbe applied. Maximum maturity is defined as
the minimum flesh firmness (measured with apenetrometer with an 8-mm tip) at which fruit canbe handled without bruising damage. Bruisingsusceptibility 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 isdone to eliminate fruit with visual defects andsometimes to divert fruit of high surface color
to a high-quality pack. Attention to details insorting line efficiency is especially important withpeaches, which have a range of colors, sizes, andshapes. Sizing segregates fruit by either weight ordimensions.
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

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 inside-vented bins can be accomplished by either
the tunnel or the serpentine method. Hydrocoolingis normally done by a conveyor-type hydrocooler
or in situ. Fruit in field bins can be cooled tointermediate 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 thoroughlycooled in the bins will warm substantially during
packing and should be thoroughly recooled after
packing.

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. Smallpeaches stored in air at 0 °C have a longer market
life than large fruit. At both temperatures, largesized ‘Elegant Lady’ and ‘O’Henry’ fruit havea 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 andmore intensely in fruit stored at 2 to 7 °C (36 to 45°F) than in those stored at 0 °C (32 °F) or below.

Optimum Storage Conditions
Ethylene Production and Sensitivity
Optimum temperature for storage is -1 to 0 °C (31to 32 °F). The freezing point varies, depending on
SSC, from -3 to -1.5 °C (27 to 30 °F). RH shouldbe 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 andshipment are retention of fruit firmness andground color. CA of 6% O2 and 17% CO2 at 0 °C
is recommended for reducing internal breakdown
during shipping, but the efficacy is related tocultivar, preharvest factors, temperature, market

The lower end of this range is for mature but unripe
fruit; higher values are for ripe fruit:
TemperatureµL 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 mostcultivars, ethylene application to fruit harvested
at U.S. Mature will ripen the fruit more uniformly
without speeding up the rate of ripening.
467

Respiration Rates
Temperature
0 °C
10 °C
20 °C

mg CO2 kg-1 h-1
4 to 616 to 2464 to 110

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 redcolor development of the flesh (“bleeding”)
usually radiating from the pit may be associatedwith this problem in some peach cultivars. In allcases, flavor is lost before visual symptoms areevident. However, there is large variability in IBsusceptibility among peach cultivars. In general,peach cultivars are more susceptible to IB thannectarine 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 havebeen 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 ischaracterized 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
468

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 forpreharvest fungicide spray intervals will reduce
inking.

Postharvest Pathology
Brown rot, caused by Monilinia fructicola, is themost 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, andprompt cooling after harvest are among the control
strategies. Also, postharvest fungicide treatment
may be used.
Gray mold is caused by Botrytis cinerea. It canbe a serious problem during wet spring weather.
It can occur during storage if fruit have been
contaminated through harvest and handlingwounds. Avoiding mechanical injuries and goodtemperature 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,

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 spidermite), and Ceratitis capitata (Mediterranean fruitfly). If these conditions are not met, fruit mustreceive an appropriate treatment prior to shipment.
Details of the treatment must be recorded on thePC.
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 clearlystate that fruit were produced and inspected inaccordance 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 arefree of Cydia molesta (oriental fruit moth),
Conotracherlus nenuphar (plum curculio),
Rhagoletis pomonella (apple maggot), and fruit
flies (Tephritdae). Peaches imported into theUnited States from other parts of the world aresometimes fumigated with methyl bromide, atshipping 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 peachslices 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, retailhandlers, warehouse managers, and produce
managers have been developed.

Acknowledgments
Some of the information in this chapter is fromthe 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, andG.W. Lightner. 1987. Disorders in plum, peachand 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.

469

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 33:110113.
Gorny, J.R., B. Hess-Pierce, and A.A. Kader.
1999. Quality changes in fresh-cut peach andnectarine 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 handlingfor fresh market. Pub. no. 3331, University ofCalifornia, Davis, CA.
Lill, R.E., E.M. O’Donoghue, and G.A. King.
1989. Postharvest physiology of peaches andnectarines. Hort. Rev. 11:413-452.
Mitchell, F.G. 1987. Influence of cooling andtemperature maintenance on the quality ofCalifornia grown stone fruit. Intl. J. Refrig. 10:7781.

470

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 ofthe family Rosaceae. The fleshy part of pear
fruit consists of the fused base of the calyx(sepals), corolla (petals), and stamens, which areinterpreted 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 insouthern Oregon. In California, production ismainly 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’ duComice,’ and ‘Seckel.’ Other minor varieties
include ‘Winter Nelis,’ ‘El Dorado,’ ‘Kieffer,’ and‘Packham’s Triumph.’

Quality Characteristics and Criteria

cultivar. Pear fruit require a period of cold storageat -1 °C (30 °F) to induce normal ripening anddevelop high dessert quality upon ripening. Whenpear fruit meet the chilling requirement after aperiod 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 IndicesPear fruit are capable of developing good dessert
quality upon ripening only if they are harvested atproper maturity. Pear fruit harvested at improper
maturity are more susceptible to physiologicaldisorders 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 incidenceof core breakdown and CO2 injury (Hansen andMellenthin 1962, Fidler et al. 1973, Mellenthin
and Wang 1974).
One of the most satisfactory and easiest ways ofdetermining proper harvest maturity is to measurefruit firmness. A pressure test using a penetrometeron the pear surface gives an indication of flesh
firmness. Firmness decreases with maturation.
Different varieties have different firmness atmaturity. 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)

A properly ripened pear is buttery with juicy
texture and the aroma and taste distinct to each471

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 andExtension Center to provide an accurate predictionof 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 fullbloom (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’‘Bartlett’

DFFB = 177.5472 - 0.0481 × AHUDFFB = 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 offull bloom or the dates of first commercial harvest
between the lower and higher elevations could be
as much as 3 weeks apart. Predictive models forthe 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.

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 temperaturesof -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 coolingshortens storage life. It has been suggested thatthe 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 exposureof the sides to airflow (Sainsbury and Schomer1957).

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 andMellenthin 1979). Many operators of pear storage
rooms use thermocouples in the air and in fruit
to determine temperatures at selected areas in thestorage. Precise temperature control is needed toprevent freezing when pears are stored at these
low temperatures (Hartman 1931). Intermediate
temperatures of 2.5 to 10 °C (37 to 50 °F) areharmful to some pear cultivars. ‘Bartlett’ pears
stored at this temperature have dry texture andinferior flavor (Porritt 1964). Pears lose moisture
rapidly; hence, it is advisable to hold RH at >90%.
Polyethylene liners are effective in controlling
moisture loss.

Grades, Sizes, and Packaging
Grades include Extra Fancy, U.S. No. 1, Fancy,and Unclassified (or Third Grade) for all winterpear 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 perstandard 20-kg box.
472

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-term high-CO2 treatment improves keeping qualityof ‘d’Anjou’ pears (Wang and Mellenthin 1975).
Treatment with 12% CO2 for 2 weeks immediately
after harvest has a beneficial effect on retentionof ripening capacity. Keeping ‘d’Anjou’ pears ina low-O2 atmosphere (1.0%) with ≤0.1% CO2 canalso maintain higher dessert quality and reduceincidence 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, Drouetand 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 andtexture 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 fruitsis their autocatalytic ethylene production; thatis 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 (Blankenshipand Richardson 1985, Wang et al. 1985, Leliévre
at al. 1997, Agar et al. 2000). The duration ofchilling required for proper ripening is cultivardependent (Wang et al. 1985) and varies withstorage temperature (Sfakiotakis and Dilley 1974,
Gerasopoulos and Richardson 1995). Storage

duration at -1 °C (30 °F), which is required toinduce 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 beenused 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 anduniformly upon reaching the retail markets or forthe 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 storageat -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 theclimacteric-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 toethylene, 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 forinduction of ripening. Nevertheless, it is best to473

avoid storing pear fruit near ripe fruit or otherfresh produce that produces appreciable levels of
ethylene. Preconditioning of pear fruit with 100µL L-1 ethylene at 20 °C (68 °F) for 72, 48, or 24 hwill induce ripening within 3 to 6 days, dependingon the cultivar (Wang and Mellenthin 1972, Chenet al. 1982, Elgar et. al. 1997).
Respiration Rates‘d’Anjou’‘Bartlett’Temperature
Days in StorageDays in Storage°C
1
25 50 100 150 200
1
10
20 90 120
-1 -1-------------------------------------mg CO2 kg h --------------------------------------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 5.92
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 acosmetic 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 otherpear cultivars. The cause of superficial scald isconjugated trienes, the oxidative products of thenaturally 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,

474

warm preharvest weather, delayed cold storage,
high storage temperatures, and high RH duringcold storage.
Conventional control method: The primarymethod 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 aconcentration of 2,700 µL L-1, which can beapplied 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

bins. Fruit at these contact points develop
pinkish (or blackened) ring markings duringstorage (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 ethoxyquinprotection as early as 1 week after harvest or
as late as 3 mo after storage using either ofthese 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 ethoxyquinwithin 2 days after harvest plus an additionalline 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 ofsuperficial scald without inducing black speckand 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 ethoxyquinwithin 2 days after harvest was necessary inorder 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 tominimize development of black speck andpithy 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 canbe either presized or packed with in-line sprayof 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 characterizedby 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 coreand extend into the surrounding flesh. In someinstances, 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 withhigh 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 combinationof low O2 and high CO2 levels in CA storage.
Susceptibility to PBC increases with factors thatinduce 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, CO2should 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 describedabove 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 CA475

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 aphysiological disease and is suspected to beclosely 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 offruit. It was confirmed that BS was induced by≤1.0% O2 in CA storage for longer than 4 mo andwas 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 cellsof 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 withsymptoms appearing when fruit are one-third
to one-half full size. It is a protrusion of thecalyx due to the retarded development of tissues
around the calyx. As the disorder progresses, thecalyx 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 anduniformly discolored from the beginning. The
476

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 toapproximately 1 to 2 cm around the calyx, but it
may cover the entire lower half of fruit in severecases. 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 rootsystem. Excessive subsoil moisture in springdamages feeder roots, inducing developmentof the disorder. Fruit grown on trees with Asianrootstocks (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 theregion of the core. The breakdown may be closely
confined to the core or may extend into thesurrounding flesh. In the early stages, the affected
tissues are soft and watery; they later become darkbrown. The disorder is often associated with an
external skin discoloration resembling senescentscald.
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 instorage 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 tocore 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).

Senescent scald occurs differently in various
pears. Pears can be classified broadly into twogroups 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,’ showa 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 andultimately develop a dark brown discoloration of
the skin called “senescent scald.” This may occur
in cold storage or after fruit are removed fromcold 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 storageand 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 areno 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).

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: thosethat cause primarily postharvest decay and thosethat 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 frompreharvest 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 importantbecause wounded, bruised, or overmature fruit
are more susceptible to many postharvest decay
fungi. Rapid cooling after harvest reduces theincidence of decay in storage, because lowtemperatures reduce both the rate of fungal growthand fruit senescence. Low temperature prevents
development of incipient infections by some fungiin storage, such as those causing white rot andbrown rot.

Postharvest Pathology

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 (bitterrot), Monilinia fructicola (brown rot), M.
fructigena (brown rot), M. laxa (brown rot), andPhytophthora cactorum (phytophthora fruit rot).

A detailed description of pear diseases and control
measures can be found in “Compendium of Appleand Pear Diseases” (Jones and Aldwinckle 1990).
The cause of postharvest decay in pear fruit isoften difficult to identify through symptoms alone.
Many decay pathogens do not sporulate on fruitin 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

Postharvest diseases commonly found in pears
after storage are blue mold (Penicillium spp.),gray mold (Botrytis cuberea Per.), bull’s-eyerot (Pezicula malicorticis [H. Jacks.] Nannf.),alternaria rot (Alternaria alternata [Fr.] Keissler),mucor rot (Mucor piriformis E. Fischer), siderot (Phialophora malorum [Kidd & Beaumont]
McColloch), cladosporium rot (Cladosporium
herbarum [Pers.] Link), coprinus rot (Coprinus
psychromorbidus Redhead & Traquair), fisheye rot
477

(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. 17:6768.
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 andethylene 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 earlymarketing by ethylene treatment. J. Food Qual.
19:375-390.
Chen, P.M., D.G. Richardson, and W.M.
Mellenthin. 1982. Differences in biochemicalcomposition 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. 1997b.
Determination of optimum controlled atmosphereregimes for the control of physiological disordersof ‘d’Anjou’ pears after short-term, mid-termor long-term storage. In E.J. Mitcham, ed., 7thInternational Controlled Atmosphere Research
Conference, July 13-18, 1997, University ofCalifornia, Davis, vol. 2, pp. 85-90. University ofCalifornia, 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 ethoxyquinconcentration, time and method of application,
and a combined effect with controlled atmospherestorage. 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 andits 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.

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., 5thInternational Controlled Atmosphere Research
Conference, vol 1, Wenatchee, WA, pp. 145-156.

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.

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.

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.

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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 tocarbon dioxide and oxygen content of the storage
atmosphere. Proc. Amer. Soc. Hort. Sci. 69:110115.
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. 80:146153.

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 skinspeckling and pithy brown core of ‘d’Anjou’ pears
reported. Good Fruit Grower 39(16):17-18.
Leblond, C., and R. Ularich. 1973. Controle del’evolution de la maturation par divers traitements
theriques et gazeux chez la poire “PasseCrassane.” Bull. Inst. Intl. Froid. 3:69-74.

Hansen, E., and W.M. Mellenthin. 1967. Chemical
control of superficial scald on Anjou pears. Proc.
Amer. Soc. Hort. Sci. 91:860-864.

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 oxygenstorage. J. Amer. Soc. Hort. Sci. 115:784-788.

Hansen, E., and W.M. Mellenthin. 1979.
Commercial handling and storage practices for
winter pears. Spec. Rpt. 550, Oregon Agricultural
Experiment Station, Corvallis, OR.

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.

Harley, C.P. 1929. Relation of picking time toacetaldehyde content and core breakdown of‘Bartlett’ pears. J. Agric. Res. 39:483-493.

Mellenthin, W.M., P.M. Chen, and S.B. Kelly.
1980. Low oxygen effects on dessert quality, scaldprevention, and nitrogen metabolism of ‘d’Anjou’
pear fruit during long-term storage. J. Amer. Soc.
Hort. Sci. 105:522-527.

Hartman, H. 1925. The control of core breakdownin pears. Bull. 216, Oregon State University
Agricultural Experiment Station, Corvallis, OR.
Hartman, H. 1931. A peculiar freezing troubleof pears in cold storage. Bull. 282, Oregon State
University Agricultural Experiment Station,
Corvallis, OR.

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.

Heppner, M.J. 1928. Pear black-end and its
relation to different rootstocks. Proc. Amer. Soc.
Hort. Sci. 24:139-142.

Morin, F., C. Rigault, and C. Hartmann.
1985. Consequences d’un sejour au froid surle metabolisme de l’ethylene au cours de lamaturation de la poire Passe Crassane apres
recolte. Physiol. Veg. 23:353-359.

Hulme, A.C., and M.J.C. Rhodes. 1971. Pomefruits. In A.C. Hulme, ed., The Biochemistry of
Fruits and Their Products, vol. 2, pp. 333-373.
Academic Press, New York, NY.

Pech, J., C. Balagué, A. Latche, and M. Bouzayen.
1994. Postharvest physiology of climacteric fruits:
recent developments in the biosynthesis and actionof ethylene. Sci. Des Aliment. 14:3-15.
479

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 inindividual ‘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 forpremature ripening in ‘Bartlett’ pears. J. Amer.
Soc. Hort. Sci. 97:557-560.
Wang, C.Y., and W.M. Mellenthin. 1975. Effect ofshort-term high CO2 treatment on storage responseof ‘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.
480

Pepper
Gustavo Adolfo González-Aguilar
González-Aguilar is with the Centro deInvestigación en Alimentación y Desarrollo,
Hermosillo, Sonora, Mexico.

Scientific Name and Introduction
Pepper (Capsicum annul L.), also called bell
pepper, chili, chilies, aji, pimiento, paprika, andcapsicum, is a warm-season crop that is a memberof the Solanaceae family. Sweet bell peppers aregreen 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 themost 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, longwax, 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; anddehydrated 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, usuallychili types, are extensively used in combination
with other spices such as turmeric, cumin, andcoriander to produce curry powder, the pungencyof which depends on the pepper cultivars used.
For instance, cayenne powder is a high-pungency
condiment produced from dried mature fruit ofcayenne-type cultivars

Quality Characteristics and Criteria
Good-quality sweet bell peppers are uniform
in shape and are the size and color typical ofthe variety. The flesh (pericarp) should be firm
and relatively thick with a bright skin color andsweet flavor; it should be free from defects suchas 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 anindication 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 andallowed to equilibrate in moisture content incovered 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 andflavor. Seeds may be removed by screening andwater 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 to481

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 offruit.
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. HighRH is necessary to avoid desiccation. Waxing has
been used to reduce desiccation, but it tends toincrease bacterial soft rot. Shelf-life varies among
different pod types. Deterioration is often due tomoisture loss, with some pod types more prone todesiccation 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 beextended 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 andbacterial 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 willappear. Some pepper cultivars can be sensitive tochilling 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
482

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 inboth 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 (41to 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 whenstored below 7 °C (45 °F). Symptoms include
surface pitting, water-soaked areas, decay(especially Alternaria), and discoloration of theseed 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 coloredpeppers 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 useof ethylene to enhance ripening or color change is
not recommended because it stimulates respirationand softening more than coloration. The mosteffective way to color peppers is to hold partiallycolored fruit at 20 to 25 °C (68 to 77 °F) with RH>95%. To maintain quality, store them away fromethylene-producing fruits and ripening rooms.

Respiration Rates
Temperature
5 °C
10 °C
15 °C
20 °C

Quarantine Issues

mg CO2 kg-1 h-1
7 to 810 to 15
24 to 30
32 to 36

There are no known quarantine issues.

Suitability as Fresh-Cut ProductTo get mL CO2 kg h , divide the mg kg h rateby 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.

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.

Physiological Disorders

Special Considerations

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 isunknown; some varieties are more susceptible.
Chilling injury is described above.

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 mechanicaldamage that may cause discoloration andpathological problems. Before packaging, peppers
can be washed with 300 µL L-1 chlorine to reduce
disease. Waxing with fungicides reduces water
loss and disease.

-1

-1

-1

-1

Postharvest Pathology
The most common decay microorganisms are
Botrytis, Alternaria, and soft rots of fungal
and bacterial origin. Botrytis (grey mold) is acommon organism on peppers. Field sanitationand prevention of wounds on the fruit reduce
its incidence. Botrytis grows well at therecommended 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, especiallyon 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 canoccur on washed or hydrocooled peppers whenwater sanitation is inadequate. Peppers are also
affected by many of the disease, virus, insect, andnematode pests that affect tomato.

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 warehousedepends 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 temperatureretards loss of red color and slows insect activity.
Moisture content of chili and other hot peppers
during storage should be low (10 to 15%) toprevent mold growth. A RH of 60 to 70% isdesirable. With a high moisture content, pods
may be too pliable for grinding and may haveto be redried. With lower moisture content(<10%), pods may be so brittle they shatter during
handling, causing loss and release of dust, whichis irritating to the skin and respiratory system.
483

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 oftheir raw material in cold storage at 0 to 10 °C but
prefer to grind peppers immediately and store thedried 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 partiallydried 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 byalleviation of water stress. Plant Physiol. 73:8793.
Brackett, R.E. 1990. Influence of modified
atmosphere packaging on the microflora andquality of fresh bell peppers. J. Food Prot. 53:255257.

484

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 ofAgriculture, Washington, DC.
Miller, W.R., and L.A. Risse. 1986. Film wrapping
to alleviate chilling injury of bell peppers duringcold storage. HortScience. 21:467-468.
Miller, W.R., L.A. Risse, and R.E. McDonald.
1986. Deterioration of individually wrappedand 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 andnon-chilling temperatures. Acta Hort. 412:134142.
Rodov, V., S. Ben-Yehoshua, T. Fierman, andF. 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.

Perennial Culinary Herbs

Precooling Conditions

Kimberly P. Wright

Herbs should be cooled to just above 0 °C (32 °F)
immediately after harvest.

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 usedin foods and cooking. Due to their strong flavors
and aromas, these culinary herbs are generally
used in small quantities.

Quality Characteristics and Criteria

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 isgenerally not used for fresh herbs. MAP has beenshown to retard yellowing in chives (Aharoni et al.
1993).

Herbs should appear fresh and green, with noyellowing, decay, insect damage, or mechanicaldamage. Leaves should be uniform in size. Flavor
and aroma should be strong and characteristic of
the herb.

Retail Outlet Display Considerations

Horticultural Maturity Indices

Chilling Sensitivity

Most herbs for fresh culinary use are best if
harvested before flowering. Exceptions aremarjoram and oregano (sometimes sold withflower buds) and chive blossoms (sometimes usedin salads or as edible garnishes).

These perennial herbs are not chilling sensitiveand should be stored as close to 0 °C (32 °F) as
possible without freezing.

Grades, Sizes, and Packaging

Ethylene production is low, but sensitivity ishigh. Low levels of ethylene can result in leaf
abscission, epinasty, and yellowing. Storage at 0
°C (32 °F) minimizes effects of ethylene on visualquality (Cantwell and Reid 1993, Cantwell 1997).

There are no market grades or sizes for fresh
herbs. They are bunched and tied with twist-ties orrubberbands, packaged in plastic bags or clamshell
containers, and then packed in corrugated cartons.
Perforated polyethylene liners should be used.

Use of water sprinklers is acceptable.

Ethylene Production and Sensitivity

485

Respiration Rates

Suitability as Fresh-Cut Product
0 °C

10 °C
20 °C
-1 -1
mg CO2 kg h
Chives22
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 etal. (1997).
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 toethylene 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 bemaintained during storage and distribution to slow
the rate of decay.

Quarantine Issues
There are no known quarantine issues.

486

Perennial herbs are not currently used in fresh-cut
products.

References
Aharoni, N., O. Dvir, D. Chalupowicz, andZ. 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 andvegetables. 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 andmint, 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.

Persimmon

Horticultural Maturity Indices

Carlos H. Crisosto

Minimum maturity is based on change in skincolor 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 orangeor 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 agreen 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.

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 andJapan, it is also known as Chinese date plum. Fruitare grown throughout warmer parts of the world,
including southern France, other Mediterraneancountries, and the United States. Fruit are a goodsource 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 baseof the fruit. Persimmon has a delicious flavor
and may be eaten fresh as a dessert or may beconsumed dried or candied. In the United States,
a native species—Diospyros virginiana—occurs,
but its fruit are inferior to D. kaki. Another wellknown 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 toorange. Fruit should be firm, (penetration force[8-mm tip] >22.2 N [5 lb-force] for ‘Fuyu’ andsimilar cultivars). Fruit should be free fromgrowth 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 toremove astringency by polymerizing tannins.

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 canbe stored up to 5 mo using ethylene-free CA (3 to5% 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’ andsimilar nonastringent cultivars are sensitive attemperatures between 5 ºC and 15 ºC (41 ºF
487and 59 ºF); they will exhibit flesh browningand softening. Exposure to ethylene aggravateschilling 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 limitof marketability, after 6 and 2 days, respectively.
Thus, removing or excluding ethylene fromtransport and storage facilities is recommended.

Respiration Rates
Temperature
0 °C
20 °C

mg CO2 kg-1 h-1
4 to 820 to 24

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

persimmons are higher than those of nonchilled
fruits. Exposure to ethylene at 0.1 µL L-1 orhigher aggravates chilling symptoms of ‘Fuyu’
persimmons, while CA ameliorates symptoms.
Chilling injury is controlled by avoiding exposureof ‘Fuyu’ fruit to temperatures between 2 °C (36°F) and 15 °C (59 °F). The optimum storage andtransport temperature is 0 °C (32 °F). Exposure
to ethylene >1 µL L-1 during postharvest handlingshould 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 forlonger than 1 mo can result in failure of fruit toripen and development of off flavors. Exposure to
CO2 >10% during storage for longer than 1 mocan cause brown discoloration of the flesh andlead to development of off flavors.
Calyx separation is a problem with somecultivars. It has caused losses in New Zealand.
Growing conditions are all-important, andexcessive nitrogen fertilization should be avoided.
Thinning trees early in the season will enhancecalyx growth and help prevent this disorder.

Postharvest Pathology
Physiological Disorders
Chilling injury is the main physiologicaldisorder. The incidence and severity depend on
temperature, cold temperature duration, and thecultivar. For example, ‘Fuyu’ is chilling sensitive
while ‘Hachiya’ is not. Chilling injury can be amajor cause of deterioration of ‘Fuyu’ persimmons
during marketing. Symptom development isgreatest 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. Respirationand ethylene production rates of chilled ‘Fuyu’
488

Alternaria rot is caused by Alternaria alternata,
which attacks developing fruits. Infections remainquiescent 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 andimports persimmons from Chile without specificrequirements. APHIS issues rules regarding
import requirements and provides information to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 ProductNonastringent persimmon cultivars can beprepared as fresh-cut wedges or slices. Wright andKader (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 (32to 36 °F). Protecting slices from ethylene helps
firmness retention.
Special Considerations
The best method of harvesting fruit is to cut themfrom the tree, leaving the calyx attached to thefruit. It is possible to snap fruit from the tree byhand, but this practice is not recommended as it
can injure the fruit and adjoining shoot. Fruit mustbe handled very carefully to avoid bruising, which
is likely to become unsightly as fruit ripen. Twoor 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 (68ºF), but the excessive softening that results canmake 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 ofslicing and controlled-atmosphere storage on theascorbate content and quality of strawberries andpersimmons. Postharv. Biol. Technol. 10:39-48.

Further Reading
Beede, R.H. 1983. The Storage Performanceof the Fuyu Persimmon and Its Susceptibility
to Chilling Injury. M.S. thesis, Department ofPomology, University of California, Davis, CA.
Collins, R.J., and J.S. Tisdell. 1995. The influenceof 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: aphysiological disorder of persimmons. Orchardistof 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.

489

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.

490

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 aterrestrial member of the diverse Bromeliaceae
family. The pineapple fruit has the distinction of
being selected, developed, and domesticated bypeoples 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 andshape, with flat “eyes” (individual fruitlets) anddeep-green crown leaves that look fresh. Highshell color is not always a good measure ofsweetness. Negative characteristics include dry,brown crown leaves; dull, yellow skin; presenceof mold on the surface or cut stem; and an unfirm
feel.

Horticultural Maturity Indices
Pineapple fruit maturity is evaluated on theextent of fruit “eye” flatness and skin yellowing.
Consumers similarly judge fruit quality byskin 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 tochilling injury (Rohrbach and Paull 1982).

Grades, Sizes, and Packaging
Pineapples are graded by degree of skincoloration, size (weight), absence of defects anddisease, 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 ofAgriculture 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 meetthe standard.
Pineapples are normally packed into cartons of
two different sizes and on the basis of color andsize: (1) a large telescoping fiberboard carton
holding 18 kg (40 lb) and containing 8 to 10 fruitin two layers, flat or upright, for surface and air
shipment and (2) a smaller container of 9 kg (20lb) 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 thebottom of the carton and between layers if fruit
are placed horizontally within the carton. In otherpacks, 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) arerecommended for storage of pineapples for 14 to
20 days, provided fruit are at the color break stage491

(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 (32to 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 effectiveat 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 highinternal concentrations of CO2 (up to 5%) andreduced 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 toperform commercially on individual fruit, resultsin atmosphere of 8 to 10% O2 and 7% CO2, andfruit 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.

492

Chilling Sensitivity
Symptoms of chilling injury include wilting,drying and discoloration of crown leaves, failureof green-shelled fruit to yellow, browning anddulling 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 temperaturesof 15 to 30 °C (59 to 86 °F) (Paull and Rohrbach1985). Susceptible fruit are generally lower inascorbate and sugar and are opaque (Abdullah
and Rohaya 1983, Abdullah et al. 1985, Paull andRohrbach 1985, Swete Kelly and Bragshaw 1993).

Ethylene Production and Sensitivity
The ethylene production rate of thisnonclimacteric 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), andAustralia (Smith 1991). Treated fruit show more
rapid uniform skin degreening and little change inquality. 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
5 °C
10 °C
15 °C
20 °C

mg CO2 kg-1 h-1
2
4 to 710 to 16
19 to 29

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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
Flesh translucency, also called porosity, isassociated with greater fruit sensitivity tomechanical injury, indicated by leakage andoozing 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 haveincreased 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 ofmarketable fruit. Injury can be avoided by carefulhandling 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 resultsin 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 breakleading 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 wateryrot (Rohrbach 1983). Diseased tissue turns darkin the later stages of the disease because of thedark mycelium and spores. Black rot is causedby 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 thepoint of detachment or wounds. The severity ofthe problem depends on the degree of bruising or
wounding during harvesting and packing, the levelof inoculum on the fruit, and storage temperatureduring transportation and marketing (Rohrbachand Schmitt 1994). The rot is commerciallycontrolled by minimizing bruising of fruit during
harvest and handling, refrigerating the fruit, andapplying postharvest fungicides (Rohrbach andPhillips 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 andSchmitt 1994). Low-acid cultivars being growncommercially are most susceptible (Rohrbachand Schmitt 1994). This disease is caused by acomplex of fungi (Rohrbach and Schmitt 1994).
Infection frequently can lead to misshapen fruitthat are culled before packing and shipping.
Yeasty fermentation arises due to the fact thatfruit are not sterile inside, containing many
nongrowing but viable yeasts and bacteria. In
damaged, overripe fruit and fruit with interfruitletcracking, resident yeasts begin to grow or new
yeasts invade. This growth leads to fermentation
and bubbles of gas and juice through cracks in theskin. The skin turns brown and leathery and fruit
become spongy with bright yellow flesh.
Saprophytes (Penicillium sp.) growing on thebroken end of the peduncle and fruit surface arenonpathogenic 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.
493

Thus, insect disinfestation is not required forimport 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 theninfest fleshy parts of the bracts and feed insidethe developing inflorescence, exuding gum fromthe feeding chambers. Control with insecticides isrelatively 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 canfeed on corn, cacao, heliconia, and several otherbromeliads (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, andcrown. Fruit mites feed on developing trichomes
on the white basal leaf tissue and flower bracts andsepals, 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 bybrushing. Preharvest insecticide and ant control
almost eliminate mealybugs (Soler 1992b).
Crickets and locusts may feed on bracts before
harvest.
494

Suitability as Fresh-Cut ProductFresh-cut pineapple is readily prepared at a
central plant or in-store for ready-to-use consumer
pack. Packs contain fresh-cut cylinders with thecore 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 theuse 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 skinyellowing, 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) duringstorage 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 contentsin ‘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 ofendogenous brown spot in fresh Australianpineapples 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.

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.

Hawaii Department of Agriculture. 1968.
Wholesale standards for Hawaiian-grown
pineapple. Hawaii Department of Agriculture,
Marketing Division, Honolulu, HI.

Armstrong, J.W. 1994. Tropical and subtropicalfruits. 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.

Keetch, D.P., and D. B. Balldorf. 1979. The
incidence of certain pineapple fruit blemishes inthe eastern cape and border. Citrus Subtrop. Fruit
J. 551:12-15.

Bowden, R.P. 1969. Further studies on ripeness inpineapple. 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 larecolte sur la qualite gustative de ananas de Coted’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 ofdevelopment. 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., Proceedingsof the International Conference on Postharvest
Handling of Tropical Fruits, pp. 422-426. Chiang
Mai, Thailand, July 1993. Australian Centre forInternational Agricultural Research, Proceedings
no. 50, Canberra, Australia.

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. TropicalFruits. 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. Juicecharacteristics 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 del’ananas II-L’ethrel et son action au cours desphases 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 andProcedures for Introduction of Plant Materials, pp.
145-171. ASEAN Plant Quarantine Centre andTraining Institute, Selangor, Malaysia.
495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, etal., 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 dansl’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. Effectof 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. 22:123183.

496

Plum and Fresh Prune

Horticultural Maturity Indices

Carlos H. Crisosto and Adel A. KaderIn most of the plum cultivars grown in California,
harvest date is determined by skin color changes
specific to each cultivar. A color chip guide isused to determine maturity for some cultivars.
Firmness, measured by squeezing fruit in the palmof the hand (“spring”), is also a useful maturity
index for a few cultivars.

Crisosto is with the Department of Plant Sciences,
University of California, Davis, CA. Kader waswith the Department of Plant Sciences, Universityof California, Davis, CA. He is deceased.

Scientific Name and Introduction
Plums (Prunus salicina) are mainly marketed for
fresh consumption and not for drying. They arealso 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 usedthem to breed many cultivars. The plum industry
has increased throughout California (mainly in thecentral San Joaquin Valley) where most Japaneseplums 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 formany centuries. Through its culture in France, theprune ‘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 withhigh SSC. Fruit TA, SSC:TA, and phenoliccontent (astringency) are also important factors
in consumer acceptance. However, there is noestablished minimum quality standard based onthese factors. Plums with about 10 N (1 kg-force)
flesh firmness (8-mm tip) are considered ready toeat.

A two-tier maturity system is currently used in
California: U.S. Mature (minimum maturity)
and California Well-Mature. Measurementof 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 apenetrometer (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 mostpeach 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 thepackinghouse, plums are dumped (mostly using
dry bin dumps) and washed. Sorting is done toeliminate fruit with visual defects and sometimes
to divert fruit of high surface color to a highquality pack. Sizing segregates fruit either byweight or dimension. In general, plums and fresh
prunes are packed into 12.6-kg (28-lb) volumefilled containers.

497

Precooling Conditions

Chilling Sensitivity

Plums and fresh prunes can be cooled in field binsusing forced-air cooling, hydrocooling, or roomcooling prior to packing. Packed plums and fresh
prunes should be cooled by forced-air cooling tonear 0 °C (32 °F).

Postharvest life varies among cultivars and isstrongly 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 allplum cultivars, a much longer market life wasachieved when stored at 0 °C (32 °F) than at 5 °C
(41 °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.

Ethylene Production and Sensitivity
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 atemperature, high SSC and excellent thermostatic
control are essential to avoid freeze damage.

Controlled Atmosphere (CA)Considerations
The major benefits of CA during storage andshipment are retention of fruit firmness and delayof changes in ground color. Decay incidence isreduced 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 ‘QueenAnn.’

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.

498

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 60µL 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
0 °C
10 °C
20 °C

mg CO2 kg-1 h-1
2 to 38 to 1216 to 24

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 a concern with most plumand fresh prune cultivars. It is expressed as flesh
translucency associated with flesh browning.
Late plum cultivars also develop lack of juicinessin addition to these symptoms. In previous
publications from South Africa, flesh translucency,
specifically in some plum cultivars, has beencalled “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 normallyappear after placing fruit at ripening temperatures
following cold storage at 2 to 8 °C (36 to 46 °F).
Internal browning is a physiological disorderof ‘Italian’ and other cultivars of prunes. It
originates before harvest. It is associated with hightemperatures 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. Fruitrot may occur before harvest but often develops
during postharvest handling. Orchard sanitation tominimize infection sources, preharvest fungicide
application, and prompt precooling after harvest
are control strategies. Fruit cracking makes lateseason cultivars more prone to decay. Postharvest
fungicide treatments may be used to limit decay.
Gray mold is caused by Botrytis cinerea. Thisrot can be serious during wet spring weather.
It can develop during storage if fruit have been
contaminated through harvest and handlingwounds. Avoiding mechanical injuries, effective
temperature management, and postharvest
fungicide treatments are effective control
measures.

and storing them below 5 °C (41 °F) is effective incontrolling 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 spidermite), 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 thephytosanitary 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 accordancewith the “systems approach guidelines” agreed
to by APHIS and the Canadian Food Inspection
Agency. Fruit imports to all of the other Canadianprovinces are unrestricted.
A similar systems approach, between APHIS and
Mexican agencies, facilitates import and assuresplums are free of Cydia molesta (oriental fruitmoth), Conotracherlus nenuphar (plum curculio),
Rhagoletis pomonella (apple maggot), and fruit
flies (Tephritidae).
Suitability as Fresh-Cut ProductFresh-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.

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 fruit499

Acknowledgments
Some of the information in this chapter is fromthe 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 ofincreasing concentrations of CO2 in controlled
atmosphere storage on the development ofphysiological disorders and fungal diseases inplums (Prunus domestica L.). Folia Hort. 4:87100.

Couey, H.M. 1965. Modified atmosphere storageof ‘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 Africangrown 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 andtemperature maintenance on the quality ofCalifornia grown stone fruit. Intl. J. Refrig. 10:7781.
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 andmaturity 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.

Ceponis, M.J, R.A. Cappellini, J.M. Wells, andG.W. Lightner. 1987. Disorders in plum, peachand nectarine shipments to the New York market,
1972-1985. Plant Dis. 71:947-952.

Truter, A.G., J.C. Combrink, and L.J. vonMollendorff. 1994. Controlled-atmosphere storageof plums. Deciduous Fruit Grower 44:373-375.

Combrink, J.C. 1996. Integrated Management ofPostharvest Quality. INFRUITEC, Stellenbosch,South Africa.

Wells, J.M., J.E. Butterfield, and M.J. Ceponis.
1994. Diseases, physiological disorders, andinjuries of plums marketed in metropolitan New
York. Plant Dis. 78:642-644.

Couey, H.M. 1960. Effect of temperature andmodified atmosphere on the storage-life, ripening
behavior, and dessert quality of ‘El Dorado’plums. Proc. Amer. Soc. Hort. Sci. 75:207-215.

500

Pomegranate

Quality Characteristics and Criteria

M. Pekmezci and M. Erkan

Fruit quality depends largely on sugar and acidcontent 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 colorand smoothness are also quality indices. Sourand sour-sweet pomegranates have reddish skin,in contrast to sweet pomegranates which haveyellowish-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.

Pekmezci and Erkan are with the Departmentof 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 theoldest known edible fruits. It is sometimes
called Chinese apple and has been cultivatedextensively in Mediterranean countries (Tunisia,
Turkey, Israel, Egypt, Spain, and Morocco),
Iran, Afghanistan, India, and to some extent in
the United States (California), China, Japan, andRussia. The pomegranate requires a long, hotsummer for fruit to mature, but it can withstandlow temperatures in winter and is drought- andsalt-tolerant.
Pomegranate fruit is nearly round with aprominent attached calyx and a hard, leatheryskin. Surface color varies among commercial
cultivars from yellow with a crimson cheek tosolid 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, orwine. Fruit of the wild-type pomegranate is acidic,
but cultivated cultivars bear fruit with a sweetsour or sweet flavor. There are several types ofedible pomegranate, and there are ornamental
types with double flowers, largely sterile, which
are not grown for edible fruit. Several cultivars aregrown 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 andKaşka 1985, Morton 1987, Patil and Karale 1990,
Llacer et al. 1994, Mars 1994).

Pomegranates are low in vitamin C, an important
nutritional quality component, compared to manyother fruits. Vitamin C content ranges from 0.49
to 30 mg per 100 g juice depending on cultivar(Hussein and Hussein 1972, Küpper 1995). Juicecontent 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 acertain size and skin color. Other maturity indices
are TA and SSC. Each pomegranate type requires
a certain TA:SSC at harvest. TA of pomegranatesvaries 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 pomegranatesvaries from 8.3 to 20.5% at harvest (Küpper
1995). Thus, maturity indices depend on cultivar.
For example, TA <1.85% and SSC ≥17% arerecommended 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).

501

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
MediumLarge
Extra large

150 to 200 g
201 to 300 g
301 to 400 g
401 to 500 g

65 to 74 mm diameter
75 to 84 mm diameter85 to 94 mm diameter
94 to 104 mm diameter

25 to 34 fruit per 5-kg carton
17 to 25 fruit per 5-kg carton
13 to 17 fruit per 5-kg carton
10 to 13 fruit per 5-kg carton

Fruit are generally packed into two-layer tray packs or bulk cartons.
Optimum Storage Conditions

Retail Outlet Display Considerations

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 etal. 1992, 1995, Pekmezci et al. 1998). Storage of‘Wonderful’ at <5 °C (41 °F) resulted in chilling
injury, and severity of symptoms increased withtime and temperature below 5 °C (Elyatem
and Kader 1984). Control of RH is critical instorage because skin desiccates readily at low
RH, resulting in hard, darkened rinds, which areunattractive 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).

Pomegranates should not be water-sprinkled or
top-iced.

Controlled Atmosphere (CA)Considerations
CA storage has the advantage of reducing loss ofTA 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).

502

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 thewhite segments separating the arils (Elyatem andKader 1984).

Ethylene Production and Sensitivity
Pomegranates produce very low amounts ofethylene: <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 notparticularly sensitive to ethylene exposure, though
ethylene at ≥1 µL L-1 stimulates respiration andautocatalytic ethylene. Ben-Arie et al. (1984)
reported that ethylene treatment of ‘Wonderful’
pomegranates caused a rapid but transient rise inCO2 but no change in SSC, TA, or fruit and juice
color. Pomegranates do not ripen after harvest andmust be picked fully ripe.

Respiration Rates
Pomegranate is a nonclimacteric fruit and has avery low respiration rate that declines with time instorage.

seeds (arils) do not develop their typical red color
and are somewhat flattened rather than plump(Ryall and Pentzer 1974).

Postharvest Pathology-1-1Temperature
mg CO2 kg h
5 °C
4 to 810 °C
8 to 1620 °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 rateby 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.

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).

Physiological Disorders
Quarantine Issues
Chilling injury (CI) is the most common
physiological disorder during storage. Incidence
and severity of CI depend on temperature andduration. 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 skintissues. 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 ofstorage 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; thelast irrigation must be done 15 to 20 days before
harvest.
Internal breakdown is another physiologicaldisorder in pomegranate fruit. The pulp-bearing

There are no known quarantine issues.

Suitability as a Fresh-Cut ProductPossibly, but none are fresh-cut at this time.

Special Considerations
Pomegranates do not ripen after harvest and mustbe 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.
503

Elyatem, M.S., and A.A. Kader. 1984. Postharvest
physiology and storage behavior of pomegranate
fruit. Sci. Hort. 24:287-298.

Mercantila. 1989. Guide to Food Transport.
Fruit and Vegetables. Mercantilia, Copenhagen,Denmark.

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 ofAgriculture, Washington, DC.

Morton, J. F. 1987. Fruits of Warm Climates. Julia
F. Morton, Miami, FL.

Hussein, M.A.H., and M.A.S. Hussein. 1972.
Suitability of pomegranate varieties forprocessing. Assuit J. Ag. Sci. 3:303-307.

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.

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 derNachlagerungsphase des Granatapfels (Punica
Granatum L.) der Sorte ‘Hicaznar.’ Ph.D.
thesis, Institut für Obstbau und Gemüsebau derRheinschen, 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. 398:101108.
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, etal. 1994. Present status and future prospects ofunderutilized 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.
504

Onur, C. 1989. Nar muhafazasında bir yenilik[News on pomegranate storage]. Derim 6:88-93.

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 ofTurkey 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 üzerindearaştırmalar [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: Tropicaland 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 andVegetables, vol. 2. AVI, Westport, CT.
Salunkhe, D.K., and B.B. Desai. 1984. Postharvest
Biotechnology of Fruits, vol. 2. CRC Press, Boca
Raton FL.

SeaLand Service. 1991. Shipping guide toperishables. SeaLand Service, Iselim, NJ.
Snowdon, A.L. 1990. A Colour Atlas ofPostharvest Diseases and Disorders of Fruits
and Vegetables, vol. 1, General Introduction andFruits. 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 atmospherepackaging 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):1415.

505

PotatoRonald 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 tolong. Stored potatoes are available year-round;fresh potatoes are harvested year-round, albeit
in small quantities during winter, spring, andsummer. 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 isturgid, well shaped, uniform, and brightly colored(especially reds, whites, and yellows), as well
as free from adhering soil, mechanical damage,greening, sprouts, diseases, and physiologicaldefects.

overmaturity resulting in higher sugar levels. Vinesenescence is used as a preharvest maturity index,
but the correlation between vine senescence andtuber 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 longpotatoes. 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 wholesalemarketed 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 areretailed 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 inbulk. Prepeeled tubers are generally packaged inplastic 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 withindividual quality and size requirements of eachprocessing company. The company requirements
vary with the type of product to be manufactured
and the purchaser. Tubers are delivered toprocessing plants in bulk trucks or bins holding
about 2,000 lb (910 kg).

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 forprocessing potatoes, with both immaturity and506

Optimum Storage Conditions
Long-term storage of potato tubers—up to
12 mo—requires that they be cured. Curingstimulates suberization and wound healing andreduces 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 needduring the night or day. Once cured, a process
requiring 1 to 2 weeks, the tuber temperature islowered 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 intostorage, and heating of tubers before removalfrom storage. Forced movement of air is used toensure uniform temperature throughout the storage
pile. Maintaining 95 to 99% RH is required at all
times to minimize shrink and pressure bruising instorage.
Desired maintenance temperature depends on thedesired end use of the tubers. Respiration rateof 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 seedtubers 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 duringcooking. 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 sugarat 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 instorage after curing is completed.

Controlled Atmosphere (CA) Conditions
The usefulness of CA storage is minimal, andeconomic 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 andflavors, 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 inbulk or in cellophane or paper bags are displayeddry. 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 withreconditioning.

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 notvery sensitive to external ethylene. Low levelsof ethylene elevate respiration, especially inimmature potatoes, and result in weight loss and507

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 ofrespiration. Increased air movement in the absenceof high RH, however, will cause desiccation.
Temperature
5 °C
10 °C
15 °C
20 °C

Immature
Mature (cured)--------mg CO2 kg-1 h-1--------24
6 to 1830 to 40
13 to 1925 to 57
11 to 2232 to 81
14 to 29

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 physiologicaldisorders 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.
508

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 theinterior 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 instorage, 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) andresult in a mahogany discoloration of internal
tissue in some varieties. Much longer periods ofstorage 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 developmentof 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 heatstable 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 inearly potatoes where excessive irrigation is often
applied to maintain cooler soil temperatures inwarm or hot climates. These lenticels are subject
to pathological infection in the soil or during
packing. Infections may remain innocuous; orif transportation conditions are not properly
maintained, they can increase rapidly in severity.
Tubers that appear sound at the packing shed canbecome unmarketable during transit.

Skinning is a common disorder in early crop or“new” potatoes (harvested immature). Soil drying
and vine death enhance skin set, and thus decreaseskinning. Cultivars vary in ability to set-skin, inskin 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, andinternal necrosis are all production problems
related to irregular growth, inadequate water
availability, or widely fluctuating temperatures.
These conditions do not change during harvest andpostharvest handling.

Postharvest Pathology
Diseases are an important source of postharvest
loss, particularly in combination with roughhandling and poor temperature control. Three
major bacterial diseases and a greater number offungal 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 arebacterial soft rot (Erwinia carotovora subsp.
carotovora and subsp. atroseptica), Ralstonia (exPseudomonas, ex Burkholderi) solanacearum,
late blight (Phytophthora infestans), fusarium
dry rot (Fusarium spp.), pink rot (Phytophthoraspp.), 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 ofpotatoes 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 andnematodes are restricted on potato tubers to beimported. 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 andmarketed in plastic trays with sealed plastic wrapwith low O2-transmission characteristics. Storage
requirements for tubers to be processed in thismanner 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.

509

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 PhytopathologicalSociety Press, St. Paul, MN.
510

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 ofCalifornia, Davis, CA.

Prickly Pear

Grades, Sizes, and Packaging

Marita Cantwell

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 bewrapped in tissue paper to reduce scuffing andother physical injury. Fruit may also be packagedin cartons with perforated plastic liners to reducewater loss under dry storage conditions.

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 Opuntiaof the cactus family (Cactaceae). Fruit are also
called cactus pears or cactus fruit, though thesenames can result in confusion with fruits fromother cactus species. The fruit is a berry, typicallyweighs 100 to 200 g (0.2 to 0.4 lb), and consists ofa thick fleshy skin or rind surrounding a juicy pulpthat contains many hard‑coated seeds. Fruit varyconsiderably 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 nearfull ripeness to have color and flavor typical ofeach variety. They should have a high percentageof pulp, low seed content, and peel that is easy toremove. Fruit typically have high sugar content(12 to 17% SSC) and low acidity (0.03 to 0.12%
TA). Cactus pears contain considerable amountsof vitamin C (200 to 400 µg g-1). If harvested atmaturity from good varieties, fruit have a delicate
sweet flavor that differs by variety.
Horticultural Maturity IndicesStage of maturity or ripeness at harvest is very
important for fruit quality since sugar content andsweetness 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 thefloral cavity or receptacle. Peel color is the single
most important index for commercial harvest.

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 (seeSpecial 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, andchilling injury.

Controlled Atmosphere (CA)Considerations
Limited research indicates that holding cactus pearat 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.

511

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 anddark 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 fruitfrom 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 ofethylene, 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 andinclude Fusarium spp., Alternaria spp., andPenicillium spp., but yeasts and bacteria also
cause decay. Hot water dips at 53 to 55 °C (127512

to 131 °F) for 5 min and fungicide-containing
waxes may reduce surface decay, but are noteffective when there is damage to the stem-ends.
For control of decay on stem-ends, see Special
Considerations. Preharvest calcium sprays resultin 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, anda 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 thatway or cured under moderate temperature of 15
to 20 °C (59 to 68 °F) with airflow so that the bitof 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 orglochids.

References
Kader, A. 2000. Cactus (prickly) pear.
Recommendations for maintaining postharvest
quality. At http://postharvest.ucdavis.edu/produce_
information.

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 managementof 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 andpostharvest 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 ofcactus 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.

513

Pumpkin and Winter Squash

Horticultural Maturity IndicesJeffrey K. Brecht

Horticultural maturity coincides withphysiological maturity and is recognizedexternally 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 thumbnailpressure. Development of intense yellow or orange
flesh color (due to synthesis of carotenoids) andaccumulation of sugars and solids are indicatorsof 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), andsensory quality improves more in storage thanon the plant (Edelstein et al. 1989, Harvey et al.
1997).

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 somecan 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 decorationas Halloween jack-o’-lanterns or for their edible
seeds. Winter squash have finer-textured andmilder-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 theAmerican tropics and is prepared in many waysthat overlap the above definitions of pumpkin andsquash (Daniel 1995).

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 fromdamage and decay. There are no standard sizes forpumpkins and winter squashes, though minimum
and maximum weights of individual fruitwithin packages may be specified. Packages arecommonly 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 410kg (800- to 900-lb) bulk bin cartons.

Quality Characteristics and Criteria

Precooling Conditions

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 highsolids, sugars, and starch (Cantwell and Suslow
1998). Overmature flesh can become dry andstringy.

Pumpkins and winter squash should be roomcooled or loaded directly into refrigerated trucks
and containers.

514

Optimum Storage Conditions
All pumpkins and winter squashes should bewell matured, carefully handled, and free frominjury or decay. Pumpkins and winter squashes
are placed on racks, in bulk bins, or in baskets andare often held in ventilated or common storage inproduction areas. Recommended conditions forstorage 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 ofthe 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 wintersquash 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. Weightloss should be kept below 15% to minimize
development of hollow neck (Francis andThomson 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 forbuttercup 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 thanin 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 bothcases 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 inambient 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 lossof flavor. Alternaria rot develops on chilledsquashes after removal from storage (McColloch1962). 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 turnorange-yellow (Yeager et al. 1945). Ethylene
may also cause stem abscission, especially in lessmature 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); datafor butternut from L.L. Morris (unpublished).
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

515

Physiological Disorders

Special Considerations

Damaged areas on fruit turn brown, detractingfrom their appearance. Pumpkins and wintersquash are susceptible to water loss at therecommended 50 to 70% RH, but low RH isnecessary to minimize decay. Yellowing can bea problem for green winter squash varieties andis exacerbated by overmaturity, high storage
temperatures, and ethylene exposure.

A 10- to 20-day curing period at 24 to 27 °C (75to 81 °F) before storage can harden the rind of
pumpkins and winter squashes (Gorini and Testoni1978). However, in New York, curing for 3 weeks
at 27 °C (81 °F) to heal mechanical injuries andto 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.

Postharvest Pathology
Decay is the primary cause of storage lossesof pumpkins and winter squash. Numerous
fungi cause storage rots, including species ofAspergillus, Colletotrichum (anthracnose),
Didymella, Fusarium, Mycosphaerella (blackrot), Rhizopus, and Sclerotinia (Guba 1950,
Abdel-Rahim 1988, Hawthorne 1988, Rathet 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 thesurface. 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 waterat 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 ProductSome large winter squash are cut into sections andseeds removed for retail sale.

516

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 wintersquash to hot-water treatment, temperature andlength of storage. HortTechnology 4:253-255.
Cantwell, M., and T.V. Suslow. 1998. Pumpkins
and winter squashes. Recommendations formaintaining 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 andvining 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.

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.

Lin, W.C., and M.E. Saltveit. 1997. Quality of
winter squash affected by storage air composition
and temperature. In M.E. Saltveit, ed., 7thInternational Controlled Atmosphere Research
Conference, July 13-18, 1997, University ofCalifornia, Davis, vol. 4, pp. 78-83. University ofCalifornia, Davis, CA.

Guba, E.F. 1950. Spoilage of squash in storage.
Massachusetts Agricultural Experiment Station
Bull. no. 457, University of Massachusetts,
Amherst, MA.

McColloch, L.P. 1962. Alternaria rot following
chilling of acorn squashes. Marketing Research
Report 518, U.S. Department of Agriculture,
Washington, DC.

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.

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.

Hawthorne, B.T. 1988. Fungi causing storage
rots on fruit of Cucurbita spp. N.Z. J. Exp. Agr.
16:151-157.

Prange, R.K., and P.A. Harrison. 1993. Effectof 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. 759766. Ithaca, NY.

Hawthorne, B.T. 1989. Effects of cultural
practices on the incidence of storage rots inCucurbita 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 fruitof 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):372373.
Hyodo, H., C. Hashimoto, S. Morozumi, et al.
1993. Induction of wound ethylene production andlignin 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.

Rath, G.C., D. Mishra, and N.C. Nayak. 1990.
A note on fungi causing rotting of cucurbits inOrissa markets. Orissa J. Agr. Res. 3:161-162.
Ryall, A.L., and W.J. Lipton. 1979. Handling,
Transportation, and Storage of Fruits andVegetables, 2nd ed., vol. 1. AVI, Westport, CT.
Schales, F.D., and F.M. Isenberg. 1963. The effectof 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 andstorage conditions in butternut squash (Cucurbita
moschata Duch.) in Argentina. Acta Hort. 368:3336.
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.
517

Quince

Horticultural Maturity IndicesPaul M. Chen

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 instorage, and fruit affected with scab do not store
well.

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 etal. 1973, Jankowiak 1976, Muller and Husistein1979). It is used mostly as a dwarfing rootstock
for pear, but is also used for preserves, jams, andjellies. 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 (Westwood1978).

Quality Characteristics and Criteria
Quince are climacteric fruit (Kader 1992) andrequire a proper ripening process at 20 °C (68ºF) for high quality fruit for processing. Properly
ripened quince of high quality are used chiefly
for jellies, marmalades, and preserves and tosome 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 etal. (1972), Gumbaridze (1972a,b), Kozenko etal. (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).
518

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, mechanicaldamage, and decay (Kader 1992). Since fruit
are rather tender and bruise easily, the shipping
container should be lined with soft pads on bothends. 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.

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 accelerationof 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 andKnapp 1929). Quince is subject to decays similar
to those found on apples and pears (Halsted, 1892,
Tafradzhiiski and Angelov 1977). Treatment withfungicides is necessary to prevent decay duringstorage and marketing (Pierson et at. 1971).

Gumbaridze, N.P. 1972a. Chlorogenic acid fromquince fruit. Soobshch. Akad. Nauk. Gruz. Ssr.
68:729-731.
Gumbaridze, N.P. 1972b. Flavonols of quince
fruit. Soobshch. Akad. Nauk. Gruz. Ssr. 65:701704.
Halsted, B.D. 1892. Some fungous diseases of thequince 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):114115.

References

Kader, A.A., ed. 1992. Postharvest Technology of
Horticultural Crops, 2nd ed. DANR Pub. no. 3311,
University of California, Oakland, CA.

Andrade, P.B., A.R.F. Carvalho, R.M. Seabra, and
M.A. Ferreira. 1998. A previous study of phenolicprofiles of quince, pear, and apple purees by
HPLC diode array detection for the evaluation ofquince puree genuineness. J. Agric. Food Chem.
46:968-972.

Kornatskaia, N.M. 1981. Chemical-technologicalevaluation of some common quince varieties
and hybrids fruit processing. Konservnaia I
ovoshchesushil’naia promyshlennost’ 2:28-29.

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. Structuresof two new ionone glycosides from quince fruit(Cydonia oblonga Mill.). J. Agric. Food Chem.
39:2142-2146.

Kozenko, S.I., G.A. Kleshchunova, and A.N.
Goren’kova. 1976. Amino acid composition ofquince 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 qualitiesof quince fruit under conditions of the lower VolgaRiver 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 tophysiological 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.
519

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 decognassiers a fruits [First observations on several
quince fruit varieties]. Arboric. Fruit 233/234:3638.
Muller, W., and A. Husistein. 1979. Quitte—eine
zu beachtende obstart [Quince—a fruit species ofinterest]. Schweizerische Zeitschrift for Obst- undWeinbau 115(1):4-8.
Pierson, C.F., M.J. Ceponis, and L.P. McColloch.
1971. Market Diseases of Apples, Pears andQuinces. 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. Valueof quince fruit chemical composition, varieties.
Sadocodstvo 12:39.
Shimizu, S., and S. Yoshihara. 1977. The
constituents of the essential oil from Japanesequince fruit, Cydonia oblonga Miller. Agric. Biol.
Chem. 41:1525-1527.
Strandzhev, A., M. Krusteva, and D. Kosturkova.
1978. Determination of pectin substances inquince and their transformations during cold
storage. Khranitelna Promishlenost 27:26-27.
Tafradzhiiski, I., and T. Angelov. 1977. Studyon 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.

520

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.

Radicchio

Horticultural Maturity Indices

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.

Plants are hand-harvested when they reachappropriate size or when the center of the plant
has formed a compact “grumolo” (Pimpini 1990).
The same variety can be harvested very early (45days), early (75 to 90 days), or late (120 to 150days). Varieties that need whitening are harvested
with their roots.

Scientific Name and Introduction

Grades, Sizes, and Packaging

Radicchio (Cichorium intybus L.) is a memberof 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 shapewith 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 iscalled “whitening” (Pimpini 1990). Radicchio isavailable year-round from California, New Jersey,
Mexico, and Italy.

There are no USDA grades. Head size is basedon 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 browningon 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
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 mechanicaldamage, or necrosis on the leaf margins.
Compactness is important but depends on thevariety; for example, ‘Treviso’ and ‘Chioggia’
should have a compact head and very tight leaves,
whereas ‘Verona’ and ‘Castelfranco’ should havean 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).

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 underthese conditions. Storage life is reduced to 11 days
at 6 °C (43 °F) (Botondi et al. 1996), while storageat -2 to -3 °C (27 to 28 °F) can prolong storage to
3 mo by controlling decay (Bertolini and Pratella1993).

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).
521

Retail Outlet Display Considerations
Radicchio can be displayed in the same manner
as lettuce. Water sprays are acceptable, but waterremaining on the leaves at elevated temperatures
promotes bacterial growth.

packing causes cracking of leaves or, in the caseof abrasion, appearance of browning stains on thewhite midribs.

Postharvest Pathology

Radicchio is not chilling sensitive. However, there
have been reports of metabolic disorders after
storage at 0 °C (32 °F) (Botondi et al. 1996).

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)

Ethylene Production and Sensitivity

Quarantine Issues

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).

There are no known quarantine issues.

Respiration Rates

References

Chilling Sensitivity

Temperature
0 °C
6 °C
7.5 °C
25 °C

-1

-1

-1

To get mL CO2 kg h , divide the mg kg h rateby 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 ofdisplay if plants are not misted. Leaf abscission iscommon for some varieties, and reconditioning isoften required. Rough handling during harvest or
522

There is growing interest in fresh-cut lettuceradicchio mixes.

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.

mg CO2 kg-1 h-1
6 to 1010 to 1623
45
-1

Suitability as Fresh-Cut Product

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.

Suslow, T., and M. Cantwell. 1999. Radicchio.
Recommendations for maintaining postharvest
quality. At http://postharvest.ucdavis.edu/produce_
information.

523

RadishRichard 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 areasof the United States and also as a greenhousevegetable. However, mechanization of harvestingand 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 whiteflesh (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 topsthat are dark-green with no yellowing; they may
be slightly wilted. Size varies depending onmarket demand, but larger roots are more likely tobe pithy (Thompson and Kelly 1957, Carione andLucas 1972, USDA 1975).

Horticultural Maturity Indices
Harvest maturity is based on size and market
demand. The diameter of oval types should be
524

between 2 and 3 cm (0.75 to 1.25 in). Bunchedradishes 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 haveclipped 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 byfreezing, growth cracks, insects, or other means.
Bunched radishes have tops that are fresh and freefrom decay and damage caused by freezing, seed
stem, yellowing or other discoloration, diseases,
insects, or other means. In order to allow forvariation 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 plasticbags holding 168 g (6 oz), 224 g (8 oz), 454 g (1lb), 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, personalcommunication).
Radishes are first graded according to diameterto eliminate spikes that are <1.9 cm (0.75 in) andto accumulate Jumbos that are >3.8 cm (1.25
in). The radishes are then conveyed over gradingtables to remove products below acceptable grade
standards. After being graded, they are packagedin cellos using vertical form fill machines. Thesemachines form the breathable poly bag, weighthe specific amount of desired radishes, and seal
the bag or provide a zipper locking system. Thesebags are then hand-packed into wax cartons andtemporarily stored at 2 °C (36 °F) until shipment.

Chilling Sensitivity

Precooling Conditions

Ethylene Production and Sensitivity

Hydrocooling at 0 to 4.5 °C (32 to 40 °F) is thepreferred method. Cello packs are hydrocooled
to restore crispness, bulk stored in bins, and thenplaced in refrigerated coolers before grading.
Bunched radishes are dipped in chlorinated waterat 2 °C (26 °F) to restore crispness and freshness
to the tops and roots, as well as to remove fielddebris. They are then packed into cartons, usually
24 bunches per carton, and hydrocooled; and thecarton is topped with an ice slurry before shipping(Brooker and Pearson 1970, Ryall and Lipton
1972a).

Radishes produce small amounts of ethylene andare not particularly sensitive to ethylene exposure.

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 canbe 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 arefrigerated rack. Bunch radishes should be
refrigerated and can be iced or misted to help
preserve quality.

Radishes are not sensitive to chilling. Store themas cold as possible without freezing.

Respiration Rates
Temperature
Topped Roots
Bunched Roots		with Tops°C-----------mg CO2 kg-1 h-1----------0
14 to 17
3 to 94 to 519 to 21
6 to 1310
31 to 36
15 to 16
15 to 1670 to 78
22 to 42
20 to 21124 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 rateby 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 andshriveling, 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 andassociated with discolored tissue. Overmaturity
or stress during growth can induce dry, cottony
voids, called pithiness, in roots. Yellowing oftops can result from overmaturity, exposure to
ethylene, or elevated storage temperature (Murry
1977, Nonnecke 1989).

525

Postharvest Pathology
The initial lesions of bacterial black spot
(Xanthomonas vesicatoria) are brown and have adiameter 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 andcracked 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 canbecome spongy. This disease favors high RH.
Avoid bruising, hydrocool to 4 °C (40 °F), andstore at 0 to 2 °C (32 to 35 °F) to control these
diseases (Ryall and Lipton 1972a).

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 ofAgriculture, 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 andpointers (radish). United Fresh Fruit and Vegetable
Association, Washington, DC.

Quarantine Issues
There are no known quarantine issues.

Suitability as Fresh-Cut ProductCurrently radishes are cut or diced in packaged
salad mixes and for food service, particularly forincorporation into salad bars.

References
AMS [USDA Agricultural Marketing Service].
1968. United States standards for grades ofradishes. At http://www.ams.usda.gov/AMSv1.0/
standards.
Brooker, J., and J. L. Pearson. 1970. Planning
data for marketing selected fruits and vegetablesin the south, part III, Fresh Vegetable Packing
Handbook. Southern Cooperative Ser. Bull. 152,
Southern Association of Agricultural Experiment
Station Directors, Raleigh, NC.

526

Ryall, A.L., and W.J. Lipton. 1972a. Handling,
Transportation, and Storage of Fruits andVegetables, 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 Departmentof Agriculture. Dover, New York, NY.

Rambutan

Grades, Sizes, and Packaging

Saichol Ketsa and Robert E. Paull

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, clustersof fruit are sold in bunches still attached to thestem.

Ketsa is with the Department of Horticulture,
Kasetsart University, Bangkok, Thailand; Paullis with the Department of Tropical Plant andSoil Sciences, University of Hawaii at Manoa,
Honolulu, HI.

Precooling Conditions
Scientific Name and Introduction
Rambutan fruit (Nephelium lappacium L.) arelarge 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 growon woody stalks in clusters of 10 to 18. The outerskin 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).

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.

Quality Characteristics and Criteria
Quality criteria include fruit size, shape, andweight; bright skin and spine color; uniformity;
absence of defects; and freedom from disease andinsects. High SSC and low TA are desirable (Ketsa
and Klaewkasetkorn 1992). Mechanical injury anddehydration are major causes of appearance loss.

Horticultural Maturity Indices
Skin and spine coloration is the main horticultural
maturity index. Fruit having green skin andgreenish-red spines are sour. Ripe fruit have bothskin and spines red or yellow, depending on thevariety. Between these two stages, sugar content
increases about 20% and acid level decreases byhalf (Mendoza et al. 1982). The acceptable stage is
16 to 28 days after color break, at which time skinand spines are brightly colored (O’Hare 1992).
Over-ripe fruit have a watery texture (Somboon
1984) which may be a senescence-induced tissue
breakdown.

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 fromCO2 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 andKlaewkasetkorn 1995), while wax coatings areless effective (Mendoza et al. 1972, Lam and Ng
1982, Brown and Wilson 1988). A shelf-life of 14
to 21 days can be expected.

527

Retail Outlet Display Considerations
Rambutan should be displayed in trays with aclear 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.

skinned cultivars often following heavy rains
during the last phase of fruit growth. Poor fillinghas been associated with poor nutrition and dry
conditions just after flowering.
Postharvest Pathology

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 whiteand 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.

Postharvest losses to disease are low (Ketsa andKlaewkasetkorn 1992), though stem end rot
and fruit rots are found. Sangchote et al. (1992)
found that the spectrum of fungi associatedwith rambutan decay varied with storage
temperatures. Collectotrichum gloeosporioides
and Botryodiplodia theobromae are considered themost serious pathogens. Other pathogens recorded
include Pestalotiopsis spp. and Phomopsis spp.
(Farungasang et al. 1991).

Ethylene Production and Sensitivity
Quarantine Issues
This nonclimacteric fruit has a very low rate ofethylene production: <0.04 µL kg-1 h-1 (O’Hare etal. 1994). Higher rates of up to 3 µL kg-1 h-1 canoccur if there is a fungal infection. The presenceof 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).

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 notdamage the flesh (Ketsa and Klaewkasetkorn
1992).

Respiration Rates

Suitability as Fresh-Cut ProductRespiration is 40 to 100 mg (about 23 to 57µL) 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 arehigher (Mendoza et al. 1972). To calculate heatproduction, 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.

Suitability is limited, since it is difficult toseparate aril and seed.

References

Physiological Disorders

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.

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 thin-

Farungsang, U., N. Farungsang, and S. Sangchote.
1991. Postharvest diseases of rambutan duringstorage at 13 or 25 °C. In 8th Australasian Plant
Pathology Society Conference, 7-11 October,
1991, Sydney, Australia. Sydney University,
Sydney, Australia.

528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. Effectof modified atmosphere on chilling injury andstorage-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.

O’Hare, T.J. 1992. Rambutan: postharvest
physiology and storage. Trop. Fruit News 26:4-6.
O’Hare, T.J. 1995. Postharvest physiology andstorage of rambutan. Postharv. Biol. Technol.
6:189-199.
O’Hare, T.J., A. Prasad, and A.W. Cooke. 1994.
Low temperature and controlled atmospherestorage 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 HandlingTechnology 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 andMaturity Stages on Biochemical Changes During
Storage of Rambutan (Nephelium lappaceum
Linn.) cv. Seechompoo and cv. Rongrien. M.S.
thesis. Kasetsart University, Bangkok, Thailand.

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 forrambutan cultivars. Tech. Bull. 5. ASEANPHTRC, University of the Philippines, Los Banos,
Philippines.
Mohamed, S., and E. Othman. 1988. Effectof packaging and modified atmosphere on the
shelf life of rambutan (Nephelium lappaceum).
Pertanika 11:217-228.
Nakasone, H.Y., and R.E. Paull. 1998. TropicalFruits. CAB Intl., Wallingford, U.K.

529

Raspberry

Horticultural Maturity IndicesPenelope Perkins-Veazie

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, thoughacid levels are higher and flavor low or lacking at
this color stage.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof Horticultural Science, North Carolina State
University, NC Research Campus, Kannapolis,
NC.

Scientific Name and Introduction
Raspberries (Rubus ideaus L.) are a member ofthe 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 foundin 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.

Grades, Sizes, and Packaging

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, andhave a distinct aroma. Important cultivars include‘Meeker,’ ‘Heritage,’ ‘Tulameen,’ ‘Willamette,’‘Chilliwack,’ and ‘Munger.’

Precooling Conditions

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.

Raspberries should be forced-air cooled to 1 °C
(34 ºF) within 12 h of harvest (Moore and Robbins
1992).

Optimum Storage Conditions

Quality Characteristics and Criteria

Raspberries should be held no more than 2 to 5days, depending on cultivar, at -0.5 to 0 ºC (31 to
32 ºF) with >90% RH.

High-quality raspberries are free of injury, decay,and sunscald; are uniformly colored; and appear
turgid.

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

530

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 thecoldest refrigeration temperature possible without
freezing. As little as 1 day at 20 °C (68 °F) canresult in growth of gray mold (Botrytis cinerea
Pers.).

Physiological Disorders
Shriveling (water loss), leakers (berries withleakage of juice), and UV damage (white
drupelets) are the primary disorders found in
raspberries.

Postharvest Pathology
The most common postharvest diseases are graymold (Botrytis cinerea Pers.) and rhizopus rot(Rhizopus stolonifer Ehrenb.:Fr.) (Ellis et al.
1991).

Chilling Sensitivity
Raspberries are not known to be chilling sensitive.

Quarantine Issues
There are no known quarantine issues.

Ethylene Production and Sensitivity
The presence of ethylene can stimulate growth ofBotrytis 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).

Suitability as Fresh-Cut ProductRaspberries are incorporated into mixed fruit cups.

Special Considerations
Raspberries damage easily; they are one of themost fragile and perishable of all fruits.

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).

Acknowledgments

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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.

Some information in this chapter is from the
University of California, Davis, website on“Produce Facts” at http://postharvest.ucdavis.edu/
produce_information.

References531

Burdon, J.N., and R. Sexton. 1990. Fruitabscission 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 Raspberryand 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 andraspberry fruits. Circular 613, U.S. Department ofAgriculture, 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 qualityof stored, fresh red raspberries after a delay in
Precooling. HortTechnology 2:468-470.
Perkins-Veazie, P., and G. Nonnecke. 1992.
Physiological changes during ripening ofraspberry fruit. HortScience 27:331-333.

532

Rhubarb

Precooling Conditions

Donald N. Maynard

Rhubarb petioles should be precooled to 0 °C
(32 °F) by hydrocooling or forced-air cooling(McGregor 1987).

Maynard is formerly with the Gulf Coast Researchand Education Center, University of Florida,
Wimauma, FL. He is now retired.

Scientific Name and Introduction
Rhubarb, or “pie plant,” (Rheum rhabarbarumL.) is a perennial of the Polygonaceae family.
Fleshy petioles are the edible portion. Petioles
may be green, pink, or white depending on thevariety. Field production in North America ismainly in Washington, Oregon, Michigan, andOntario. Rhubarb is forced in heated structures
in Washington, Michigan, and Ontario. Freshrhubarb is mostly available in late winter throughspring (Foust and Marshall 1991), but limited
supplies are available at other times.

Quality Characteristics and Criteria
Petiole color is associated with quality. The orderof 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.

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
0 °C
5 °C
10 °C
15 °C
20 °C

mg CO2 kg-1 h-1
9 to 13
11 to 1825
31 to 48
40 to 57

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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. Stateand provincial grades have been developed forforced 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).

Physiological Disorders
Petioles lacking small leaf lamina are subject tosplitting 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 lossesof rhubarb (Snowdon 1992). Anthracnose(Colletotrichum erumpens) causes oval, soft,533

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 temperatureis 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 andrecent 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 ofrhubarb (field grown). U.S. Department ofAgriculture, Agricultural Marketing Service,
Washington, DC.

534

Rutabaga

Grades, Sizes, and Packaging

Maria Cecilia do Nascimento Nunes

Grades include U.S. No. 1 and U.S. No. 2, basedon subjective external appearance. Sizes aredefined 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).

Nunes is formerly with the Air Cargo
Transportation Research Group, Department ofSoils 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, Swedishturnips, and turnip-rooted cabbage, is a memberof the Cruciferae. The edible portion is the large,
usually yellow-fleshed storage root. The threemain commercial varieties of rutabagas include‘American Purple Top,’ ‘Laurentian,’ and the‘Thomson strain’ of ‘Laurentian.’ Rutabaga is acool-season vegetable that withstands frost andmild freezing. In North America, rutabaga isprimarily grown in Canada, California, Colorado,
Wisconsin, and Minnesota.

Precooling Conditions
Roots should be cooled as quickly as possible inorder to avoid excessive moisture loss. Brown
surface discoloration called “storage burn” can belargely 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.

Quality Characteristics and Criteria
A high-quality rutabaga is a well-shaped, purpletopped root having a smooth, small neck anda well-defined taproot with a minimum of sideroots. 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).

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 andLentz 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 beas high as 6 and 11%, respectively (Cutcliffeand Anderson 1989). Rutabagas for immediatemarketing 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.

535

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% isinjurious to rutabagas.

Retail Outlet Display Considerations
Rutabagas should be held in a refrigerated
display. Use of top ice is accepted; misting is notrecommended.

Physiological Disorders
Rutabagas freeze at about -1 °C (30 °F), andfreezing 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 afermented odor.
Brown heart or water-core of rutabagas is causedby boron deficiency. Stored roots with brown heart
may suffer tissue breakdown and moisture loss,
becoming spongy. They may also develop brownspots and cracks (Ryall and Lipton 1983).

Postharvest Pathology
Chilling Sensitivity
Rutabagas are not sensitive to chilling and should
be stored as cold as possible. They can stand slightfreezing 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 65 °C
8 to 1210 °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 rateby 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.
536

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 andconidia. Black rot caused by Phoma lingam causes
restricted dry, corky, dark brown or blackishlesions 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 deteriorationof roots during storage (Shattuck and Proudfoot1990).

Quarantine Issues
Rutabagas must be completely free of soil because
many plant pests are soil-borne. A permit toimport rutabagas into Canada is required forareas of New York State (because of the possible
presence of golden nematode, Heterodera
rostochiensis), off-continent United States, and allother countries.

Suitability as Fresh-Cut ProductRutabagas are good candidates for sale inconsumer-size packages. Prepeeled rutabagas
packaged in consumer film bags keep in goodcondition 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). Storageof 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 areawith rutabagas.

Acknowledgments
Some of the information in this chapter is from theAgriculture 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 andstorability of rutabagas. Can. J. Plant Sci.
69:1359-1363.

Franklin, E.W., and E.C. Lougheed. 1975. Storingrutabagas. 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 Instituteof Refrigeration, Paris, France.
Ryall, A.L., and W.J. Lipton. 1983. Handling,
Transportation, and Storage of Fruits andVegetables, 2nd ed., vol. 1. AVI, Westport, CT.
Shattuck, V.I., and K.G. Proudfoot. 1990.
Rutabaga breeding. Plant Breeding Rev. 8:217248.
Suzuki, M., and J.A. Cutcliffe. 1981. Sugars andeating quality of rutabagas. Can. J. Plant Sci.
61:167-169.
Tomkins, R.G. 1959. The biological effects ofsealed plastic containers by prepacked fresh
fruit and vegetables. International Institute ofRefrigeration Bull. 40, annex 3. International
Institute of Refrigeration, Paris, France.
van den Berg, L., and C.P. Lentz. 1973. Highhumidity storage of carrots, parsnips, rutabagas,
and cabbage. J. Amer. Soc. Hort. Sci. 98:129-132.
537

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 roundsorrel (Rumex scutatus); garden sorrel (R. acetosaL.); miner’s lettuce; winter purslane; claytonia(Montia perfoliata [Claytonia perfoliata]);mizuna (Brassica rapa L. subsp. japonica group
Japonica); purslane (Portulaca oleracea L.); androcket salad, roquette, arugula, rucola, or rugula(Eruca vesicaria [L.] Cav. subsp. sativa [Mill.]
Thell). Young leaves are generally used.

or in small sealed plastic bags, trays, or clamshell
containers. These greens may also be packed
as bunches of leaves or plants (Rubatzky andYamaguchi 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-coolingis effective for removing field heat.
Optimum Storage Conditions
Salad greens should be stored at 0 to 2 °C (32to 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 beused.

Controlled Atmosphere (CA)Considerations

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.

CA is generally not beneficial. MAP is mostly
beneficial for controlling RH. However, lamb’s
lettuce retains acceptable quality after 28 days insealed plastic bags with reduced O2 and elevated
CO2 at <4 °C (39 °F) (de Leiris 1987). MAP
reduces yellowing and decay of sorrel (Aharoni etal. 1993).

Horticultural Maturity Indices

Retail Outlet Display Considerations

Greens are harvested as individual leaves, leaf
clusters, or whole plants and should be young,tender, and mild flavored. Plants that haveflowered are usually too strong in flavor and toughin texture for use in raw salads.

Use of water sprinklers is acceptable. Leafy greens
are highly susceptible to water loss and wilting.

Quality Characteristics and Criteria

Grades, Sizes, and Packaging
These crops are not graded or sized in the UnitedStates. Salad greens may be packed in fiberboard
cartons lined with perforated polyethylene bags
538

Chilling Sensitivity
Salad greens are not sensitive to chilling andshould be stored as cold as possible without
freezing.

Ethylene Production and Sensitivity

Quarantine Issues

Salad greens have very low ethylene production
but are highly sensitive to ethylene exposure(Cantwell 1997), which typically results in loss ofchlorophyll leading to yellowing of leaves.

There are no known quarantine issues.

Respiration Rates
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 andYamaguchi (1997), and Piergiovanni et al. (1999).

Suitability as Fresh-Cut ProductIntact leaves are sometimes included in packaged
salad mixes.

Temperature

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 rateby 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 mechanicaldamage, which may result in discoloration anddecay.

Postharvest Pathology
Low temperatures must be maintained throughout
the cold chain to minimize pathological disorders
and prolong shelf-life. Salad greens are typicallysusceptible to the same bacterial soft rot andfungal decay as lettuce.

Special Considerations
Greens must be handled carefully to avoid
mechanical damage and water loss.

References
Aharoni, N., O. Dvir, D. Chalupowicz, andZ. 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 andvegetables. 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.
539

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.

540

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.

Grades, Sizes, and Packaging
No official grades exist; sizing is based on lengthand diameter. Salsify is packaged in plastic liners
or trays wrapped with plastic film to minimize
water loss.

Precooling Conditions
Precooling is not necessary.

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 witha diameter of 2 to 2.5 cm (0.75 to 1 in). Blacksalsify (Scorzonera hispanica L.) belongs to thesame family. Its taproot is larger, more cylindricalin shape, brown-black on the outside, and white
inside. Both are rich in iron, vitamins (B1, B2, andE) and inulin, asparagin, and the glycoside laricin.
Inulin is poorly digested by humans and can beused as a bulking ingredient in foods formulatedwith 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 orbrown-black.

Horticultural Maturity Indices
Harvest is based on root size and time fromseeding—usually after 150 to 210 days.

Optimum Storage Conditions
Under refrigerated conditions, salsify roots canbe stored for 3 to 4 mo at 0 ºC (32 ºF) with 95 to
98% RH (Hardenburg et al. 1986). In the absenceof refrigeration, roots are also commonly stored inclamps (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 withwater 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.

541

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 ofFruits, Vegetables, and Florist and Nursery Stocks,
p. 69. Agricultural Handbook 66, U.S. Departmentof Agriculture, Washington, DC.

Respiration Rates
Temperature
0 ºC
5 ºC
10 ºC
20 ºC

mg CO2 kg-1 h-1
22 to 28
33 to 53
40 to 57
193
-1

-1

-1

-1

To get mL CO2 kg h , divide the mg kg h rateby 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 cichoriacearumDC.), which compromises quality.

Quarantine Issues
There are no known quarantine issues.

Suitability as Fresh-Cut ProductSalsify 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.

542

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.

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, andwhite sapote.
Note regarding respiration data for Sapodilla andrelated fruit:
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 alarge, 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 whentreated at 0.3 kGy (Miller et al. 1997).

LucumaScientific Name and Introduction
The lucuma (lucumo, lucmo, lucma, rucma, ormamon) (Lucuma obovata, HBK) is round orovate 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 (64to 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 changeof 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 isnecessary to disrupt pulp by mechanical meansand 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 wasdeveloped 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
2light-green
creamy-yellow
3yellow-green
yellow
4
green-yellow
dark-yellow
5green-yellow
orange-yellow
Fruit ripened on the tree usually become softand 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).
543

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 isa 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 skincontaining one large single seed surrounded by athin 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 brownspots in pulp, and development of off flavors andaromas.

Ethylene Production
Ethylene production at 27 °C (81 °F) is as muchas 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, or544

oval—and contains one or several shiny black
seeds. It weighs about 70 to 300 g and has adull brown color, thin skin, and yellowish, lightbrown, or red pulp. Sapodilla fruit are prized fora pleasant aroma and sweet taste. Fruit growthfollows a sigmoid pattern (Lakshminarayana andSubramanyam 1966). Fruit are very susceptible tomechanical injury.

Horticultural Maturity Indices
The erratic flowering habit of sapodilla and thepresence 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 softenvery 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 amountsof leucoanthocyanidins. The sucrose content andpulp-to-peel ratio increase during maturation(Pathak and Bhat 1953).
Fruits shed brown scaly external material andbecome smooth when reaching physiologicalmaturity (Lakshminaryana 1980). Fruit ready for
harvest do not show green tissue or latex whenscratched with a fingernail. Fully mature fruit
have brown skin and separate easily from the stemwithout leaking latex. Extent of scurfiness is also agood 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 orwood flats with 25 to 49 fruit (4.5 kg; 10 lb) perflat (McGregor 1987).

Optimum Storage Conditions

Chilling Sensitivity

Postharvest life is 2 to 3 weeks at 12 to 16 °C (54to 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 andWong 1979). Short-term holding of fruit—lessthan 10 h at 4 °C (39 °F)—before storage at 20°C (68 °F) extends storage life up to 24 days withsatisfactory 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).

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 andDesai 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 40days at 10 °C (50 °F).

Modified Atmosphere (MA) and Controlled
Atmosphere (CA) Considerations
Storage life of sapodilla is extended by use of
MA and removal of ethylene (Broughton andWong 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 gaugepolyethylene 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 (Chundawat1991).
‘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).

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 pectincontent, phenolic content, SSC, sugar content, andvitamin 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 Wong1979) but does not reach the climacteric whileon the tree (Lakshminaryana and Subramanyam1966). 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, whilemaleic hydrazide at 0.5 to 1.0 mL L-1 accelerates it(Lakshminarayana and Subramanyam 1966).

Postharvest Pathology
Diseases and pests are rare. Phytophthorapalmivora and species of Pestalotiopsis andPhomopsis can cause fruit rot (Snowdon 1990).
Some species of bacteria are associated with fruit
latex (Pathak and Bhat 1952).

545

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.

Sapotefrom the stem. Poles with knifes at the end arealso used to harvest fruit. Fruit should not beallowed 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).

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 toellipsoid in shape, 7 to 15 cm long, and 10 to 15
cm in diameter. The skin is thick and woody witha russet-brown and somewhat scurfy surface. The
pulp of mature fruit is soft and smooth to finely
granular in texture and salmon pink, orange, andred or reddish-brown in color. The pulp has arich, sweet, almondlike flavor; low fiber content;
and creamy texture. Fruit weigh 0.3 to 3 kg andcontain a large elliptical seed that has a shiny,
hard, dark-brown surface with a light-brown hilumon the ventral side.

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 mostprolific 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
Quality Characteristics and Criteria
Scientific Name and Introduction
Inferior or improperly ripened mamey sapotes willdevelop a pronounced squashlike flavor.
Horticultural Maturity Indices andHarvesting
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 mechanicaldamage. The fruit should be twisted until it breaks
546

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 incolor with a mild, sweet flavor. The pulp is whiteor creamy white with numerous embedded small,shiny, dark-brown seeds.

Harvesting

Postharvest Pathology

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, especiallyduring the rainy season.

The most important pests include the annona seedborer and the ambrosia beetle. The annona seedborer lays eggs in the seeds of very young fruits.
Insects develop in the seeds and emerge as adults
when the fruit matures.

Packaging

White Sapote

Fruit are tray-packed in fiberboard boxes of 4.5 kg(10 lb) capacity (McGregor 1987).

Scientific Name and Introduction

Precooling
Precooling should be done by hydrocooling orforced-air cooling.

Optimum Storage Conditions
Star apple intended for cold storage are picked at
the half-ripe stage, cured in a well-ventilated roomfor 2 days, and held at 3 to 6 °C (37 to 43 °F) with
90% RH for about 3 weeks.

Chilling Sensitivity

White sapote, or zapote blanco, (Casimiroa
edulis llave & Lex) is also known as matasano in
Spanish, meaning “killing healthy person” becauseof the presence of the glucoside casimirosine,
mainly in seeds but also in bark and leaves. This
compound has sedative effects, induces sleep, andcan 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 isthin and smooth and the flesh has a custardlike
texture and sweet flavor.

This fruit is slightly sensitive to chilling injury.

Quality Characteristics and Criteria

Ethylene Production and Sensitivity

Quality fruit are yellow to yellowish-green and 60
to 120 mm in diameter (McGregor 1987).

Ethylene production at 20 °C (68 °F) is 10 to
100 mL kg-1 h-1. The fruit does not respondsignificantly to treatment with ethylene (Pratt andMendoza 1980).

Horticultural Maturity IndicesRespiration Rates
The star apple is a nonclimacteric fruit. The
respiration rate at 20 °C (68 °F) is 25 to 50 mg (13to 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 (37to 43 °F) (Pratt and Mendoza 1980).

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 anunpleasant 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.
547

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 toarmillaria, but some cultivars can be attacked byfruit flies.

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 andUses, pp. 415-441. AVI, Westport, CT.

Acknowledgments
Some of the information in this chapter is from the
University of Florida website at http://ifas.ufl.edu.

Lakshminarayana S., and H. Subramanyam.
1966. Physical, chemical and physiologicalchanges in sapota fruit (Achras sapota L.) during
development and ripening. J. Sci. Food Sci.
Technol. (Mysore) 3:15-154.

References
Akamine, E.K., and T. Goo. 1978. Respiration andethylene production in Mammee apple (Mammea
americana L.). J. Amer. Soc. Hort. Sci. 103:308310.
Bojappa, K.K.M., and T.V. Reddy. 1990.
Postharvest treatments to extend the shelf life ofsapota 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 andmarketing 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 ofgrowth 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.

548

Lizana, L.A. 1980. Lucuma. In S. Nagy, P.E.
Shaw, and W.F. Wardowski, eds., Fruits ofTropical 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 thelucuma (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 blacksapote (Diospyros digyna Jacq.) after storage andripening. 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.

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. Fruitdevelopment and ripening of the star apple(Chrysophyllum cainito L.). HortScience 15:721722.
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-chloroethylephosphonic acid) on ripening of sapota (Achras
zapota L.). Hortic Adv. 8:33-36.
Snowdon, A.L. 1990. Postharvest disease anddisorders 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. 22:123183.

549

Southern Pea

Horticultural Maturity IndicesPenelope Perkins-Veazie and Blair Buckley

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 haveundergone a color change). It is acceptable to havesome pods that have not undergone a complete
color change (green with some purpling in thecase of purplehulls) provided the peas are maturesize. Shelled peas should be light green in color.

Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof 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 apea, and thus differs considerably from the green
or English pea (Pisum sativum) (Peirce 1987).
Prized in the southern United States, southernpeas are rich in folic acid, fiber, and calcium.
Peas are distinguished by pod color, pea color andpattern, 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 darkgreen. Shelled peas should be a mature size, havesmooth skin, and exhibit characteristic color.

550

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 whento harvest for fresh use because the color of theblack hilum does not fully develop until peakmaturity. 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 halfof the expected diameter of mature green pods—
unless it is a cultivar specifically developed foredible 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 [5in] 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 10lb) bags. No grades exist for southern peas usedas 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 meshbags (cabbage sacks) or wooden bushel baskets(becoming less common).

Precooling Conditions

Ethylene Production and Sensitivity

In both shelled and unshelled states, peas arevery 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 ina solution of 100 µL L-1 chlorine to remove heatquickly, preserve green color, and slow microbial
growth. Peas to be trucked for processing areshelled 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.

Ethylene production rate is unknown. Southernpeas are probably sensitive to ethylene witheffects characterized by yellowing of pods.

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 morethan 24 to 48 h at 4 to 5 °C (39 to 41 °F) (Jenkins
1954).

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 rateby 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
Controlled Atmosphere (CA)Considerations

Brown spots, cracking, and seed-coat splitting areproblems with pods and peas.

Effects of CA are unknown.
Postharvest Pathology
Retail Outlet Display Conditions
Peas should be kept under high RH andrefrigerated to slow decay and color loss.

Very little research has been done on postharvest
pathogens of southern pea. Botrytis cinerea (graymold) can quickly develop on pods and shelledpeas (Roland E. Roberts, Texas A&M, 2002,
personal communication).

Chilling Sensitivity
Unknown. Southern peas are probably sensitive
when held at 5 °C (41 °F) or below.

Quarantine Issues
There are no known quarantine issues.

551

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 causedby stinkbugs and due to the presence of puncturesand larvae inside peas as a result of cowpea
cucurlio.

ReferencesFery, 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 ofAgriculture, Washington, DC.
Jenkins, W.F. 1954. Postharvest changes inrefrigerated 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.

552

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 seedgermination. The most common marketedsprout 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.); andwintercress (Barbarea vulgaris R.Br.).

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 thesame 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, andforced-air cooling are common methods.

Optimum Storage Conditions
Quality Characteristics and Criteria
Fresh mung bean sprouts have crisp white
hypocotyls and yellow or green cotyledons.
Symptoms of deterioration include darkeningof the root and cotyledons, development ofdark 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 (suchas mung bean sprouts); while others are moredelicate 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 arenormally harvested after 3 to 8 days when length

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 beincreased by storage under MA in which O2 isreduced and CO2 is increased (Varoquaux et al.
1996). For instance, they can be held for 4 to 5days at 8 °C (46 °F) in packages containing 5%
O2 and 15% CO2. Darkening of sprouts is reduced
and development of sliminess is delayed.
553

Retail Outlet Display Considerations
Sprouts should be held close to 0 °C (32 °F). They
should not be misted.

Darkening of the radicles and browning of thecotyledons are other changes associated with thedeterioration of mung bean sprouts. Cotyledon
color in mung bean sprouts may blacken at low
temperatures, and this may be a symptom ofchilling injury (DeEll et al. 2000).

Chilling Sensitivity
Sprouts are highly perishable and should be stored
as cold as possible without freezing. In somecases, the cotyledons of mung bean sprouts darken
more at lower temperatures. However, due tofaster deterioration at higher temperatures, storageat 0 °C (32 °F) is recommended.

Postharvest Pathology
Development of decay, sliminess, and musty odors
are symptoms of deterioration.

Quarantine Issues
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).

There are no known quarantine issues.

Suitability as Fresh-Cut ProductNo current potential exists.

Respiration Rates

Special Considerations

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).

Sprouts have been associated with humanpathogenic bacteria, such as Aeromonas
hydrophila, Escherichia coli O157:H7, Listeria
monocytogenes, Salmonella spp., and Bacillus
cereus (Brackett 1999). Therefore, the importanceof proper storage and handling, along with goodworker hygiene and sanitation, cannot be stressedenough.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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, somedevelop 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 andare thought to arise from a group of cells that were
injured before or during germination.
554

Acknowledgments
Some information in this chapter is from theInternational 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.

Cantwell, M. 1997. Properties and recommended
conditions for storage of fresh fruits andvegetables. 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 atmospherepackaging of fresh bean sprouts. J. Sci. Food. Agr.
70:224-230.

555

SquashT. Gregory McCollum
McCollum is with the U.S. Horticultural ResearchLaboratory, 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 ofsummer squash: cocozelle, crookneck, scallop,
straightneck, vegetable marrow, and zucchini(Paris 1986). Summer squash are cultivatedthroughout the world and is available yearround. Zucchini is the most widely grown andeconomically important summer squash.

function of the type of squash and market demand.
Squash may be field-packed directly into shipping
containers or transported to the packinghouse infield boxes or bulk bins for washing and sizing
before packing. Squash are packed in a variety ofcontainers including bushel baskets, wire-boundwooden crates, and fiberboard boxes (McGregor
1987). A plastic liner should be used in all wooden
containers to prevent abrasion and retard waterloss.

Precooling Conditions
Room-cooling, forced-air cooling, andhydrocooling are acceptable methods forremoving field heat from summer squash (Lilland Read 1982). Prompt precooling after harvest
reduces the rate of water loss and is essential for
maximum postharvest life.

Quality Characteristics and Criteria

Optimum Storage Conditions

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.

Summer squash are highly perishable andnot 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.

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
556

Controlled Atmosphere (CA)Considerations
Storage in low-O2 atmospheres appears to be oflittle 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 thanfour 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 wellas lead to chilling injury.

Chilling Sensitivity

Physiological Disorders

Summer squash are chilling sensitive and should
not be exposed to temperatures below 5 °C (41°F) (Ryall and Lipton 1979). However, variationin 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).

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 reduceschafing 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
Ethylene Production and Sensitivity
Summer squash produce low to moderate amountsof 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).

Decay caused by fungal and bacterial pathogens
can cause significant postharvest losses in summer
squash. The incidence of decay increases infruit 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
Respiration Rates
There are no known quarantine issues.
-1-1Temperature
mg CO2 kg h
0 °C
24 to 265 °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 rateby 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.

Suitability as Fresh-Cut Product
Summer squash is frequently sliced and marketedin foam trays overwrapped with polyethylene.

Special Considerations
All types of summer squash are extremely tenderand are injured by the slightest scratch, bruise, orscuff. 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.

557

References
AMS [USDA Agricultural Marketing Service].
1984. United States Standards for Grades ofSummer 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 ofAgriculture, Washington, DC.
Leshuk, J.A., and M.E. Saltveit. 1990. Controlled
atmospheres and modified atmospheres for thepreservation 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 inyellow 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. 108:884890.
Paris, H.S. 1996. Summer squash: history,
diversity, and distribution. HortTechnology 6:613.
Ryall, A.L. and W.J. Lipton. 1979. Handling,
Transportation, and Storage of Fruits andVegetables, 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 22:920922.
558

Suslow, T.V., and M. Cantwell. 1998. Squash(soft rind). Recommendations for maintaining
postharvest quality. At http://postharvest.ucdavis.
edu/produce_information.

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 perennialof the Rosaceae family. The edible portion, not atrue berry, is a multiple fruit comprised of manyachenes (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 amaximum 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 ofthe berry’s surface showing red or pink.

Grades, Sizes, and Packaging
U.S. No. 1 grade consists of strawberries withcalyx (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 freefrom 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 and2, with at least 80% meeting U.S. No. 1 grade.
Strawberries are often packaged by pickers in thefield either into open-mesh baskets or into clear
clamshell containers of 1 dry pint or 1 dry quartcapacity. 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 isimportant to begin cooling within 1 h of harvest to
avoid loss of quality and reduction in amount ofmarketable fruit (Maxie et al. 1959). Temperature
management is the single most important factor
in minimizing strawberry deterioration andmaximizing postharvest life. Forced-air coolingis highly recommended, though room-cooling isused 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-lifeand maintains quality. Covered baskets maintainhigher RH around berries, reducing water loss andshrivel.
559

Chilling Sensitivity
Strawberry fruit are not sensitive to chilling andshould be stored as cold as possible without
freezing.

Ethylene Production and Sensitivity
Strawberries produce very low amounts ofethylene: <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).

postharvest. The fungus continues to grow at 0 °C
(32 °F), but growth is slow at this temperature.
Rhizopus rot, caused by Rhizopus stolonifer, isanother 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 thedisease to healthy berries (nesting) (Sommer et al.
1973).

Quarantine Issues
Respiration Rates
Temperature
0 °C
10 °C
20 °C

mg CO2 kg-1 h-1
12 to 20
50 to 100
100 to 200

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

Methyl bromide fumigation is routinely used forstrawberries shipped from the United States toJapan 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 andKader 1997).

Physiological Disorders
Perhaps because of rapid marketing and very shortstorage, few physiological disorders occur after
harvest. CO2 injury, particularly when >15% CO2
is used, is manifested as a bluing of the skin (Keet al. 1991), whitening of inner fruit tissues (Gil etal. 1997), and fermentative off flavors.

Special Considerations

Postharvest Pathology

References

Disease is the greatest cause of postharvest loss.
The most common decay is botrytis rot, also calledgray mold, caused by Botrytis cinerea (Ceponis
et al. 1987). This disease can begin preharvest,
remaining as a latent infection; or it can begin

Ceponis, M.J., R.A. Cappellini, and G.W.
Lightner. 1987. Disorders in sweet cherry andstrawberry shipments to the New York market,
1972-1984. Plant Dis. 71:472-475.

560

Strawberry fruit are very delicate and easily
damaged. Since the harvest crew is responsible
for grading, packing, and gentle handling, theirtraining is critical to packing a quality product.

El-Kazzaz, M.K., N.F. Sommer, and R.J.
Fortlage. 1983. Effect of different atmosphereson postharvest decay and quality of fresh
strawberries. Phytopathology 73:282-285.

Wells, J.M., and M. Uota. 1970. Germination andgrowth of five fungi in low-oxygen and highcarbon dioxide atmospheres. Phytopathology
60:50-53.

Gil, M.I., D.M. Holcroft, and A.A. Kader. 1997.
Changes in strawberry anthocyanins and otherpolyphenols in response to carbon dioxide
treatments. J. Agric. Food Chem. 45:1662-1667.

Wright, K.P., and A.A. Kader. 1997. Effect ofslicing and controlled-atmosphere storage on theascorbate content and quality of strawberries andpersimmons. Postharv. Biol. Technol. 10:39-48.

Kader, A.A. 1999. Fruit maturity, ripening, andquality 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 attributesof strawberries. J. Food Sci. 56:50-54.
Li, C., and A.A. Kader. 1989. Residual effects ofcontrolled 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 formaintaining 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 freshmarket. 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 pearand strawberry fruits. J. Food Sci. 54 (3):656-659.
Sommer, N.F., R.F. Fortlage, F.G. Mitchell, andE.C. Maxie. 1973. Reduction of postharvest lossesof strawberry fruits from gray mold. J. Amer. Soc.
Hort. Sci. 98 (3):285-288.
561

Sweet Cornstarchy while sh2 varieties eventually taste wateryand bland.

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.) isan 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 thesugar 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 arereferred 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 lifeof sweet corn. However, all supersweet varieties
remain extremely perishable.

Horticultural Maturity Indices
Sweet corn harvest maturity is determined by
a combination of ear fill, silk drying, kernel
development, kernel sweetness, and kerneltenderness. The appearance of the juice, orendosperm, 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 awatery 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 lesscommonly 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 somekernels. PVC film is highly permeable to O2 andCO2 while acting as a moisture barrier.
Precooling Conditions

Quality Characteristics and Criteria
High-quality sweet corn has uniform size andcolor (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 themost important factor in consumer satisfaction(Evensen and Boyer 1986). All sweet cornvarieties lose sweetness and aroma during storage,
but the taste of su1 and su1/se varieties becomes
562

Sweet corn is often >30 °C (86 °F) whenharvested, 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 thisextent 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to that of traditional sweet corn varieties and lose
sugar as rapidly (Evensen and Boyer 1986, Olsenet al. 1991), so cooling is still critical with thesenewer varieties. Sweet corn should not be handledin bulk unless copiously iced because it tends toheat 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 fromhusks and kernels (Showalter 1957, Stewart andBarger 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 sweetcorn 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 sweetcorn temperature is needed to ensure propercooling to at least 10 °C (50 °F). Hydrocooling
nomographs for bulk and crated sweet corn areavailable (Stewart and Couey 1963).
After hydrocooling, top-icing is desirable duringtransport 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 andtop ice. Injection of an ice-water slurry (slush ice)
into cartons was as effective as hydrocooling andbetter than vacuum-cooling in maintaining quality(Talbot et al. 1991), probably due to residual ice inthe cartons, since the cooling rate was slower thanfor the other methods.

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 etal. 1990). The former is minimized by prompt
cooling, trimming flag leaves and long shanks, andmaintaining high RH, usually by icing. Dentingof 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 byprompt 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 spurredby an interest in marine transport to export sweetcorn 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 andmaintains 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.

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 andsweetness. 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

Chilling Sensitivity
Sweet corn is not chilling sensitive. It should be
stored as cold as possible without freezing.

563

Ethylene Production and Sensitivity

Quarantine Issues

Sweet corn produces only trace ethylene, andexogenous ethylene is not a problem, though highethylene amounts can lead to husk yellowing
given sufficient exposure time.

There are no known quarantine issues.

Respiration Rates
Temperature
mg CO2 kg-1 h-1
0 °C
30 to 51
5 °C
43 to 83
10 °C
90 to 12015 °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 rateby 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 whenpresent 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.

564

Suitability as Fresh-Cut ProductFresh-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 areto have acceptable shelf-life. Problems during
handling can include off flavors, microbial
survival and growth, and discoloration if thetemperature is not maintained near 0 °C (32 °F).
Especially troublesome is browning when the
kernels are cooked. This browning is greater inkernels from more mature ears and is correlatedwith temperature, storage duration, and extent ofphysical damage.

References
Aharoni, Y., A. Copel, M. Gil, and E. Fallik. 1996.
Polyolefin stretch films maintain the quality ofsweet 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 ofsupersweet (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 offresh 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. Qualityof supersweet corn film-overwrapped in trays.
HortScience 25:322-324.

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-grownfruits and vegetables. J. Rio Grande Valley Hort.
Soc. 17:170-175.

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.

Schouten, S.P. 1993. Effect of temperature and
CA storage on visual quality aspects, sugars, andethanol 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 andhydro-cooled sweet corn. Proc. Fla. State Hort.
Soc. 70:214-219.
Showalter, R.K. 1967. Sweet corn shelf life asaffected 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 ofcooling method and top-icing on the quality ofpeas 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 ofAgriculture, 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 ofvegetables as affected by postharvest treatment. J.
Agr. Food Chem. 2:415-417.
565

Sweetpotato

Grades, Sizes, and Packaging

Stanley J. Kays

Sweetpotatoes are graded into U.S. Extra No. 1,
U.S. No. 1, U.S. Commercial, U.S. No. 2, andUnclassified. 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 and0.53 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 theretail level, roots are typically displayed loose.

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 thatis grown for its fleshy storage roots. Thougha perennial, the crop is grown as an annual.
Sweetpotato is the seventh most important foodcrop in the world. However, in the United States
it is used primarily as an occasional vegetable.
Sweetpotato confers a wide range of healthbenefits (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 incolor, moist (soft) in texture, and very sweet whencooked. The orange/moist types, however, are notpreferred in most other areas of the world, nor bycertain ethnic groups within the United States.

Quality Characteristics and Criteria
Sweetpotato cultivars vary in color (white tocream to orange to purple), flavor (sweet to
nonsweet; mild to intensely flavored), and texturalproperties (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 adevelopmental stage at which they are mature.
Rather the roots continue to grow and underfavorable conditions will enlarge until theinterior of the root becomes anaerobic or rots. As
a consequence, the crop is harvested when the
majority of roots have reached the desired size.

566

CuringRoots 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 isrequired to remove CO2 and replenish O2 becauseroots 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 anddecreasing 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 oftemperature and RH on the rate of wound healing
has been extensively investigated (Morris andMann 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 byformation of a ligninlike wound periderm beneaththe suberized layer. Roots are adequately healed
when the wound periderm is 3 to 7 cells thick, thestatus of which can be assessed using a relatively
simple color test (Walter and Schadel 1982). The
structure and chemical composition of suberin andlignin in both the epidermis and healed wounds
have been characterized (Walter and Schadel1983).

Radiation Treatments

Chilling Sensitivity

Extension of sweetpotato shelf-life via treatment
with gamma irradiation in general offers noadvantage over proper storage temperature
management.

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 andMorris 1956, Picha 1987). Symptoms of chilling
injury include root shriveling, surface pitting,abnormal wound periderm formation, fungal
decay, internal tissue browning, and hardcoreformation (Buescher et al. 1975a, Daines et al.
1976). Synthesis of chlorogenic acid and otherphenolic compounds has been associated withtissue browning symptoms (Walter and Purcell
1980).

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 inroot 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 andincrease 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 todecay 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 tooutweigh the additional expense.

Retail Outlet Display Considerations
Sweetpotatoes are typically displayed loose(unpackaged) in unrefrigerated display cases atapproximately 21°C (70 °F).

Hardcore is a physiological disorder in which
various areas within the root become hard,
apparently due to cold-induced alterations incellular 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 thetemperature 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 synthesisof phenolic compounds and phenolic oxidizing
enzymes, resulting in increased discoloration.
The effect, however, requires exposure of roots567

to ambient ethylene that would normally not
be encountered during storage with proper
ventilation. Therefore, ethylene exposure undernormal storage conditions is a relatively minor
concern.

Physiological Disorders
In addition to chilling-induced hardcore, thesweetpotato is susceptible to other physiologicaldisorders. 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 anotherdisorder found in apparently sound roots; it ischaracterized 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 andexposure to low soil temperatures of 5 to 10 °C(41 to 50 °C) before harvest.

pathogens are typically opportunistic pathogens
that require wounds to gain entry into the root.
Internal cork is a virus-mediated disorder inwhich root tissue develops necrotic lesions duringstorage (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 theinterior, but may also be present on the surface.
Control of postharvest diseases centers on
prevention, since little can be done once theroot 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 theproper temperature. Creating entry wounds via
mechanical damage during movement from thecuring 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 inaccordance to State and Federal laws.

Postharvest Pathology
Storage rots are caused by a number ofmicroorganisms. Among the more commonly
encountered are Lasiodiplodia theobromae (Javablack rot) (synomyous with Botryodiplodia
theobromae and Diplodia gossypina), Ceratocystis
fimbriata (black rot), Erwinia chrysanthemi(bacterial soft rot), Fusarium oxysporum (surfacerot), Fusarium solani (root rot), Macrophomina
phaseolina (charcoal rot), Monilochaetes
infuscans (scurf), and Rhizopus stolonifer (softrot) (for details on etiology, see Clark and Moyer
1988). Timing of infection varies with theorganism 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 rootrot occur during harvest. Harvest and postharvest
568

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. Fruitflies (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 ifroots are used for propagation material because
the disease is transferred in roots and transplants(slips) produced from them. Roots from mostproduction areas can be shipped throughout thecontinental United States, but they may not be
imported because of the risk of viral diseases.
The sweetpotato weevil is the single mostdevastating insect pest of the crop worldwide andis 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 toother areas of the country.

Suitability as Fresh-Cut ProductNo 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, andC.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 andquality 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 andpyruvate 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. Compendiumof Sweet Potato Diseases. American
Phytopathological Society, St. Paul, MN.

Daines, R.H., D.F. Hammond, N.F. Haard, and
M.J. Ceponis. 1976. Hardcore developmentin 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 oftropical 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. Causesof pithiness in sweet potatoes. Tech. Bull. 207,
North Carolina Agricultural Experiment Station,
Raleigh, NC.
Lewis, D.A., and L.L. Morris. 1956. Effects ofchilling storage on respiration and deteriorationof several sweet potato varieties. Proc. Amer. Soc.
Hort. Sci. 68:421-428.
Morris, L.L., and L.K. Mann. 1955. Woundhealing, keeping quality and compositionalchanges during curing and storage of sweet
potatoes. Hilgardia 24:143-183.
Moyer, J.W. 1982. Postharvest disease
management for sweet potatoes. In Proceedingsof 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 oftranspiration and respiration. J. Amer. Soc. Hort.
Sci. 111:889-892.
569

Picha, D.H. 1987. Chilling injury, respiration andsugar 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 insweetpotato. 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 mechanismof chilling injury in sweet potato. XI.
Irreversibility of physiological deterioration. Plant
Cell Physiol. 15:385-388.

570

Swiss Chard

Precooling Conditions

Fabio Mencarelli

Room-cooling is often used, but hydrocooling andvacuum-cooling result in faster cooling.

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 abiennial 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, withthe midrib and petiole completely white or red
depending on the variety. Leaves must not show
any symptoms of yellowing or browning or havesoil residue. Harvested leaves with petioles can be
20 to 50 cm (7.5 to 20 in) long.

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 andrefrigerated 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
Horticultural Maturity Indices
Leaves are periodically hand-harvested beginningabout 60 days after seeding. The harvest season
can last 2 to 3 mo in spring and 4 to 6 mo infall and winter. Sometimes the whole plant isharvested.

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 tocover packaging reduces water loss.

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 andsenescence.

Respiration Rates
Temperature
2 °C
20 °C

mg CO2 kg-1 h-1
18 to 20
29

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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,571

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 ProductNo current potential exists.

References
Gami, D.B., and T.S. Chen. 1985. Kinetics offolacin 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 minimallyprocessed 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.

572

Tamarillo

Grades, Sizes, and Packaging

Marita Cantwell

There are no U.S. grade standards. Fruit are
typically packed into tray packs in single cartonsbased on four or five fruit size categories.

Cantwell is with the Department of Plant Sciences,
University of California, Davis, CA.

Precooling Conditions
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 aresmooth-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, andyellow. The mucilaginous, juicy, seedy pulp has asweet-acid taste reminiscent of the tomato, and thefruit 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 ordiscoloration. Color should be characteristic of thevariety. Good quality tamarillos are juicy whenripe with moderate sugar content (8 to 10%) andTA no higher than 1 to 2%.

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 morediscoloration 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.

Horticultural Maturity Indices
The best maturity index for tamarillo is peel andpulp color. Other indices correlated with skin color
are changes in firmness, juice content, and SSC.
For dark-red-skinned types, which progress fromgreen to dark purple (color due to chlorophyll andanthocyanins) to red, harvesting at the dark purple
stage is considered best. If fruit are harvested
green, flavor score, juice content, SSC, andcolor of ripened fruit are inferior to those of fruit
harvested at the dark-purple stage (Heatherbell etal. 1982, El-Zeftawi et al. 1988).

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 anda 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 Lizana1991).
573

Ethylene Production and Sensitivity

Suitability as Fresh-Cut Product

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).

No current potential exists.

Respiration Rates

El-Zeftawi, B.M., L. Brohier, L. Dooley, et al.
1988. Some maturity indices for tamarillo andpepino fruits. J. Hort. Sci. 63:163-169.

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 Prattand Reid (1976) and Espina and Lizana (1991).

References
Blank, R.H., H.M. Dance, R.E. Hampton, et al.
1987. Tamarillo (Cyphomandra betacea): effect offield-applied fungicides and postharvest fungicide
dips on storage rots of fruit. N.Z. J. Exp. Agric.
15:191-198.

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.

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 notdevelop until fruits start to ripen or are stored forseveral weeks. A good orchard control programwith postharvest applications of fungicides cancontrol 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.
574

Harman, J.E., and K.J. Patterson. 1982. Kiwifruit,tamarillos and feijoas. Maturity and storage.
AgLink HPP 103, Ministry of Agriculture andFisheries, 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. 27:399404.
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, etal. 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.

Tamarind

Quality Characteristics and Criteria

Elhadi M. Yahia

Both green immature pods and brown ripe pods
are normally marketed when 5 to 20 cm (2.0 to 7.9in) long.

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 areabout 30% shell, 30% pulp, and 40% seeds. The
color of the pulp comes from the presence ofseveral anthocyanins, of which vitexene is themost important (Lewis and Neelakantan 1964).
There are also fruit with red pulp; these are notcommonly 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 isa good source of calcium, phosphorous, and ironand an excellent source of riboflavin, thiamin,
and niacin; but it contains only small amounts ofvitamins A and C (Bueso 1980).
Tamarind is of minor importance in the UnitedStates. The two major types are “sweet-fruited”
and “acid-flavored.” Tamarind is considered to beboth 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).

Horticultural Maturity IndicesTamarind 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 andsticky pulp. When fully ripe, the shells are brittle
and easily broken. Mature fruit can be left on thetree 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 separationof 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 thepeduncle or cut using scissors (Hernandez-Tuzonand Lakshminarayana 1982b). Fruit for immediate
processing are harvested by pulling pods awayfrom the stalk. Some can be harvested by shaking
the branches, leaving the remaining fruit to fall
naturally when ripe. In humid climates, fruit arereadily 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 maturetamarind is commonly compressed and packed in575

palm leaf mats or plastic bags and stored at 20 °C(68 °F). It can be stored for a significant length oftime 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.

Special Considerations
Fruit are commonly processed into juices, nectars,
fruit punch, concentrates, and glaceéd andcrystallized fruit. The pulp can withstand thermal
processing without affecting the original flavor
profile (Bueso 1980).
References

Respiration Rates
Tamarind fruit are nonclimacteric. Maximum
CO2 production occurs 4 weeks after fruit set andthen gradually declines (Hernandez-Unzon andLakshminarayana 1982b).

Bueso, C.E. 1980. Soursop, tamarind and chironja.
In S. Nagy and P.E. Shaw, eds., Tropical and
Subtropical Fruits: Composition, Properties andUses, pp. 375-406. AVI, Westport, CT.

Postharvest Pathology

Hernadez-Unzon, H.Y., and S. Lakshminarayana.
1982a. Biochemical changes during development
and ripening of tamarind fruit (Tamarindus indicaL.). HortScience 17:940-942.

Tamarind fruit are very tolerant to pathogens
and insects, except for occasional incidence ofscab. This resistance may be due to the low watercontent and high acid and sugar content, as well as
high polyphenol content in the peel. Ripe fruit aresusceptible to mold, insects, and birds.

Hernadez-Unzon, H.Y., and S. Lakshminarayana.
1982b. Developmental physiology of tamarind
fruit (Tamarindus indica L.). HortScience 17:938940.

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 tamarindseed 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 ProductTamarind is not suitable as a fresh-cut product at
this time.

576

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.

TaroRobert 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 oneof the oldest of food crops, widely distributed
throughout Asia and the Pacific. The plant is also
known as tannier, malanga, dasheen, eddoe, andcocoyam. There is also substantial production in
Egypt and the Caribbean (O’Hare and Asokan1986). There are up to 600 varieties. The root (alsocalled a corm or tuber) is consumed, as are thepetioles and leaves. Corm flesh varies from white
to yellow and red to purple. The corm is high instarch and low in protein and fat. All parts of theplant must be cooked prior to eating because of
the presence of acridity substance(s) associatedwith 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 thelarger cylindrical root upwards of 35 cm (14 in)long and 10 to 15 cm (4 to 6 in) in diameter. Bothare brown. The corm should have no sprouts andbe free from cuts, insects, and disease damage.
The smaller eddoe possesses some degree ofdormancy, while there is no dormancy in thelarger taro corms.

harvested and smaller coromels removed; diseased
areas on main corms are excised. In eddoe, thecoromels are also harvested. Young taro leaves arealso 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, andflesh 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 ofremoval 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 therelated xanthosoma and taro at 27 to 32 °C (81 to
90 °F) reduces weight loss (Passam 1982).

Horticultural Maturity Indices
Roots are harvested when they are the size desiredby the market. Most often this is after they havestopped growing and leaves have begun to dieback 8 to 12 mo after planting. The main corm is

Retail Outlet Display Considerations
Taro should be displayed dry and should not be
misted.

577

Chilling Sensitivity

Suitability as Fresh-Cut Product

Chilling injury leads to pitting and increased
postharvest disease.

Taro must be cooked before eating.

Special Considerations
Ethylene Production and Sensitivity
Taro roots have a very low ethylene production.
There is no known response of taro roots toethylene application.

Corms are roasted, baked, boiled, or deep-fried.
Grated, cooked corm is sometimes mixed withcoconut milk. Corms are boiled, mashed, andsieved for poi.

Respiration Rates

References

Respiration rates of taro have not been
documented.

O’Hare, S.K., and M.P. Asokan. 1986. Edible
aroids: botany and horticulture. Hort. Rev. 8:4399.

Physiological Disorders

Passam, H.C. 1982. Experiments on the storage ofeddoes and tannias (Colocasia and Xanthosomaspp) under ambient conditions. Trop. Sci. 24:3946.

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 inwetland taro. Corm rots can also be associatedwith a complex of microorganisms, including
Fusarium, Sclerotinia, Erwinia, Botryodiplodia,
and Ceratocystis. These decay organisms areassociated with field infection through wounds.
After washing roots to remove soil and thencutting 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 bycooling to control further disease development(Snowdon 1992).

Quarantine Issues
Aphids can be a major problem on taro leaves.

578

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 Disordersof Fruits and Vegetables, vol. 2, Vegetables, pp.
350-357. CRC Press, Boca Raton FL.

Tomatillo

Grades, Sizes, and Packaging

Marita Cantwell
Cantwell is with the Department of Plant Sciences,
University of California, Davis, CA.

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).

Scientific Name and Introduction

Precooling Conditions

The tomatillo, or husk tomato, (Physalis ixocarpa
Brot. ex Hornem) is a warm-season vegetableof the Solanaceae family. The small, spherical,
green or green-purple fruit is surrounded by anenlarged 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 andcooked green salsas and other Latin American
dishes. Tomatillos are available year-round. In the
United States tomatillo are produced mainly onsmall acreages in California, but large volumes areimported from Mexico (Smith et al. 1999).

Forced-air cool or room-cool to retain fresh
appearance of the husk.

Quality Characteristics and Criteria
The freshness and greenness of the calyx (husk)
are quality criteria. Fruit should be firm andbright 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 ofdevelopment. For commercial marketing, theyshould be harvested when fruit are well formed
and have substantially filled the husk but are stillbright green. Overmature fruit that are light green
or yellowing should be avoided, since they are
sweeter and undesirable for most uses.

Optimum Storage Conditions
Tomatillos can be stored under a wide rangeof conditions. At ambient temperatures, thehusks will dry, but the fruit will remain in goodcondition for about 1 week. The freshness of fruitand 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 anddecay) after 3 weeks at 5 °C (41 °F); symptoms
become more pronounced at 2.5 °C (37 °F).

579

Ethylene Production and Sensitivity
Immature tomatillos produce low amounts ofethylene: 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).

been identified. Washing in chlorinated water
reduces superficial mold growth, but this may bedifficult to implement commercially since it isdifficult to remove all moisture inside the husk.
Quarantine Issues
There are no known quarantine issues.

Suitability as Fresh-Cut ProductRespiration Rates
Respiration rates remain relatively constant duringstorage at 5 and 10 °C (41 to 50 °F); rates decreaseduring storage at 20 °C (68 °F). Respiration rates
of developing fruit are about 25% higher thanthose of mature fruit.
Temperature
mg CO2 kg-1 h-1
5 °C
12 to 1410 °C
13 to 19
20 °C
27 to 36
Data for mature-green fruit from Cantwell et al.
(1992).

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 andpostharvest physiology of tomatillo fruits(Physalis ixocarpa Brot.). Sci. Hort. 50:59-70.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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‑1or by 61 to get kcal tonne-1 day-1.

Moriconi, D.N., M.C. Rush, and H. Flores.
1990. Tomatillo: a potential vegetable crop forLouisiana. In J. Janick and J.E. Simon, eds.,
Advances in New Crops: Research, Development,
Economics, pp. 407-413. Timber Press, Portland,OR.

Physiological Disorders

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.

See Chilling Sensitivity.

Postharvest Pathology
Chilling injury can encourage the developmentof black mold caused by Alternaria alternata, thesame organism often found on chill-injured red
tomatoes. Superficial molds occur on the husk
during storage under high RH, but they have not580

Tomato
Steven A. Sargent and Celso L. MorettiSargent 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 isyear round, though winter and spring imports from
Mexico are increasing. Most tomatoes are grownin the field, but the use of protected culture is on
the rise around the world. Dominant suppliers ofgreenhouse-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 ofmechanical injury, shriveling, or decay. Principal
causes for postharvest losses are decay, external
damage incurred during harvest and handling, andharvest at an improper maturity stage.

Horticultural Maturity IndicesDepending 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 isdifficult to accurately determine the completionof physiological maturity. Depending on thegrowing 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
stage

Internal appearance(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 inat 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 andpericarp tissue.
Adapted from Kader and Morris (1976).
Ripeness stages are defined according to thefollowing standards for red-fleshed tomatoes(AMS 1991):
Ripeness
stage

External color(1) Green

Fruit surface is completely green;
the shade of green may vary fromlight 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 thesurface.
(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 notgreen; in the aggregate, shows pinkor red color.
581

(5) Light red				(6) Red				

60 to 90% of the surface is notgreen; in the aggregate, shows
pinkish-red or red.
More than 90% of the surface is notgreen; in the aggregate, shows redcolor.

Tomato Color Standards are based on the USDA
Visual Aid TM-L-1, which consists of a chartcontaining twelve color photographs illustrating
the color classification requirements.

Field-grown tomatoes are typically packed inlidded, 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 anddefects are similar to field-grown tomatoes. These
fruit are sized as follows:

Grades, Sizes, and Packaging

Size
Small
MediumLarge

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, notoverripe or soft, clean, well developed, fairly
well formed, fairly smooth, and uniform incolor. Fruit should be free from decay, freezing
injury, sunscald, and damage caused by bruising,
discoloration, sunken scars, cuts and brokenskins, puffiness, catfaces, other scars, radial orconcentric growth cracks, and hail or insect injury.

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 redcolor. Uniformity of fruit color, stem freshness,and fruit attachment to the stem are importantquality 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.

Tomatoes are rigorously sized with a 0.8 mm(1/32-in) overlap permitted between sizes,
according to the following dimensions (AMS1991):

There are currently no U.S. grade standards forother types of tomatoes. They are all typicallyharvested once ripening has started and are sorted
by defect and color. Roma-type tomatoes arenormally packed in 11.4-kg (25-lb) cartons bycolor, 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 mastercartons to facilitate palletizing.

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
1Will not pass through a round opening of thedesignated diameter when tomato is placedwith the greatest transverse diameter across the
opening.
2
Will pass through a round opening of thedesignated diameter in any position.

582

Weight<99.4 g (<3.5 oz)
99.4 to 256 g (3.5 to 9 oz)>256 g (>9 oz)

Precooling Conditions
Following commercial packing, tomatoes areroutinely palletized and cooled to 20 °C (68 °F)
for ripening or to 12 °C (54 °F) for storage. Whileroom-cooling is common, forced-air cooling ismore uniform and produces better quality fruit.
Packed, palletized tomatoes with pulp temperatureof 28 °C (83 °F) actually increased 2 °C (4 °F)

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.

Ripeness stage Temperature O2(%) CO2(%) Benefit
Mature green 12 to 20 °C 3 to 5 2 to 3 slightRed
10 to 15 °C 3 to 5 3 to 5 moderate
Data from Saltveit (1997).

Retail Outlet Display Considerations
Optimum Storage Conditions
Optimal storage temperatures depend on thematurity 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 storageat <13 °C (55 °F) retards ripening and can leadto development of chilling injury, particularly intomatoes 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) wererated lower in flavor and aroma than those held at
13 °C (55 °F) (Maul et al. 2000).

Tomatoes are normally displayed at the retaillevel in single-layer, corrugated cartons or inplastic 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 packagesof 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, andtypes of tomato. However, since tomato fruit are
sensitive to compression stress, care must be taken
to avoid overloading the display.

Controlled Atmosphere (CA)Considerations
Chilling Sensitivity
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 byseveral factors, such as lycopene synthesis andsugar and chlorophyll degradation (Goodenoughand Thomas 1980, Nakhasi et al. 1991). Storage
in 3% O2 and 97% N2 extended postharvest lifeof 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 internalbruising (disruption of locular gel ripening)
following impacts.

Tomato fruit are chilling sensitive, and therecommended storage temperature varies withthe 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, andstorage decays (see Postharvest Pathology) (Wills
et al. 1998).

Ethylene Production and Sensitivity
Tomato fruit produce moderate amounts ofethylene: 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

583

ripening and other associated metabolic processes(Abeles et al. 1992). For commercial ripening,
green tomatoes should be held at 20 to 21 °C (50to 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 breakerstage 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 atmosphericcomposition.
Air­­*

3% O2 /97% N2†
mg CO2 kg-1 h-1
10 °C
13 to 166
15 °C
16 to 2820 °C
28 to 4112
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).
Temperature

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 theavailability of potassium and inorganic nitrogen584

in the soil. Areas showing blotchy ripening haveless 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 appearanceof 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 decayorganisms 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 suchas 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 andgreenhouse production systems.
Irregular ripening is characterized by theappearance of nonuniform ripening and whiteinternal tissue. It has been associated with feedingof sweetpotato whitefly (Bemisia argentifolii) on
tomato fruit (Hanif-Khan et al. 1997).
Internal bruising is recognized by the appearanceof yellow to green locular gel in ripe tomatoes.
It is caused by an impairment of normal ripeningof 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, internalbruising also affects flavor (Moretti et al. 2002).
Breaker-stage tomatoes are more sensitive tointernal bruising than those handled at the green
stage (Sargent et al. 1992).

Postharvest Pathology
Tomatoes are susceptible to numerous fruit decays
from the field through postharvest handling.
Postharvest decay often develops in wounds andbruised 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 programin the field and during handling, packing, andripening-storage operations.
Causes of bacterial decay include soft rot (Bacillus
spp., Erwinia carotovora ssp., Pseudomonas spp.,
and Xanthomonas campestris) and lactic aciddecay (bacterial sour rot) (Lactobacillus spp. andLeuconostoc mesenteroides) (Bartz et al. 1995,
Conn et al. 1995).
Fungal decay sources include alternaria rot (blackrot) (Alternaria alternata), fusarium rot (Fusariumspp.), 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 (Corynesporacassiicola), 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] andSnowdon [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 offruits 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 ProductDespite 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 thedevelopment 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 sufficientpostharvest 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 becatalytically generated from ethanol using
commercially available units or supplied fromcompressed 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 fromeither a catalytic unit or compressed cylinder isused 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.
585

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 oftomatoes 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 incontrolled atmospheres. Ann. Appl. Biol. 94:445455.

586

Hanif-Khan, S., R.C. Bullock, P.J. Stoffella, et al.
1997. Possible involvement of altered gibberellin
metabolism in the induction of tomato irregularripening 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 temperaturestorage. 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 physiologicalbasis 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 ofmaturation and ripeness of tomatoes. In
Proceedings of the 2nd Tomato Quality Workshop.
Vegetable Crop Series no. 178, University ofCalifornia, Davis, CA.
MacLeod, R.F., A.A. Kader, and L.L. Morris.
1976. Stimulation of ethylene and CO2 productionof 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. Ripeningof mature-green tomato fruit slices. J. Amer. Soc.
Hort. Sci. 113(5):742-745.

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, etal. 1998. Chemical composition and physicalproperties 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, etal. 1999. Delayed ripening does not alleviate
symptoms of internal bruising in tomato fruit.
Proc. Fla. State Hort. Soc. 112:169-171.

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.

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 incontrolled 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.
587

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.

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, andmust be done by immersion, which can be partof the washing procedure. After washing, excesswater should be removed in a well-ventilatedroom at 4 to 5 °C (39 to 41 °F). Lowering thetemperature helps maintain the characteristic
aroma.

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 theworld, 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, anduniform distribution of color are important quality
characteristics.

Horticultural Maturity Indices
Maturity indices do not exist for truffles, but
truffles harvested for immediate sale should becollected 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 andare less prone to superficial mold development.
Grades, Sizes, and Packaging
No standards exist for grading, sizing, or
packaging.
588

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 fluctuationof 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 andcontrols 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 cancontaminate other produce. Only those truffles
that can be sold that day should be displayed
unwrapped; the others should be kept sealed inimpermeable plastic trays in the cold section.

Chilling Sensitivity

Quarantine Issues

Truffles are not chilling sensitive and should be
stored as cold as possible without freezing.

There are no known quarantine issues.

Suitability as Fresh-Cut Product
Ethylene Production and Sensitivity
Truffles produce only very low amounts ofethylene and are not sensitive to ethylene exposure(Mencarelli et al. 1997). Production of ethylene
in storage can therefore be a good indicator ofinternal decay.

Respiration Rates
Temperature
0 °C
5 °C
10 °C

mg CO2 kg-1 h-1
20 to 36
24 to 45
30 to 60

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 canbe a problem. Internal browning of whitefleshed truffles can be caused by overmaturity,
while worms and growing conditions can cause
sponginess.

No current potential exists.

Special Considerations
Truffles need brushing during washing. Excesswater must be removed before storage to avoid
growth of superficial mold. Special care must usedwith 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.

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.

589

Turnip
Penelope Perkins-Veazie
Perkins-Veazie is formerly with the South Central
Agricultural Laboratory, Agricultural ResearchService, U.S. Department of Agriculture,
Lane, OK. She is now with the Departmentof 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 inwarm soils, >25 °C (>77 °F) (Peirce 1987). (Incontrast, rutabagas have large, yellow-fleshedroots and large, smooth leaves, and they grow incool soils.) There are also yellow-fleshed turnips.
Common turnip varieties are ‘Purple Top,’ ‘WhiteGlobe,’ ‘White Egg,’ and ‘Golden Ball.’

Quality Characteristics and Criteria
High-quality turnips are firm and are free ofgrowth cracks, woodiness, rot, injury, andpithiness.

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.

and soft rot. The roots should have a minimum
diameter of 4.4 cm (1.75 in). Turnips are soldbunched 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). Someroots are waxed, but most are packaged as freshroots 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 atemperature differential of 10 °C (50 °F) or moreshould be avoided to prevent cracking.

Optimum Storage Conditions
Turnips can be held 4 to 5 mo at 0 °C (32 °F) with90 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 bemisted.

Chilling Sensitivity
Turnips are not sensitive to chilling and should be
stored as cold as possible without freezing.

Grades, Sizes, and Packaging
Grades of U.S. No. 1 and U.S. No. 2 are based
primarily on external appearance, size, anddefects. U.S. Grade 1 roots are well trimmed, firm,
fairly smooth and clean, and free from injury,
growth cracks, woodiness, water core, dry rot,
590

Ethylene Production and Sensitivity
Turnips produce no detectable ethylene and areinsensitive to ethylene.

Respiration Rates

Special Considerations

Temperature
mg CO2 kg-1 h-1
0 °C
6 to 95 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).

Turnips are susceptible to freezing damage
when held at 0 °C (32 °F). Storage at warmer
temperatures, >5 °C (41 °F), accelerates weightloss 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 andCollins 1991).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

References

Physiological Disorders
Turnips can develop growth cracks fromovermaturity or boron deficiency, brown heartfrom boron deficiency, and pithiness from water
stress (Snowdon 1992). Root shriveling and lossof firmness can occur from storage at >2 °C (36°F) or at low RH.

Peirce, L.C. 1987. Root crops. In L.C. Peirce,
Vegetables: Characteristics, Production, andMarketing, pp. 251-269. J. Wiley & Sons, New
York, NY.
Perkins-Veazie, P., and J.K. Collins. 1991. Colorchanges 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-grownfruits and vegetables. J. Rio Grande Valley Hort.
Soc. 17:170-175.

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), graymold (Botrytis cinerea), and bacterial soft rot(Erwinia crotovora ssp. carotovora) can occur
in harvested roots, generally resulting from field
infection.

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. 339343. CRC Press, Boca Raton, FL.

Quarantine Issues
There are no known quarantine issues.

Suitability as Fresh-Cut ProductTurnips may be peeled and diced as a fresh market
pre-cut product (Snowdon 1992).
591

Waterchestnut

Grades, Sizes, and Packaging

Jeffrey K. Brecht

There are no USDA grade standards. However,mature, dark-skinned corms over 30 mm (1.25in) in diameter with no physical injury fromharvesting are considered marketable (DeRigo andWinters 1964), but corms over 40 mm (1.5 in) in
diameter are more desirable (McGregor 1989).
Corms are usually packed and stored in film bagswith moist sphagnum moss.

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 ahydrophyte (water-loving) and is grown underflooded conditions similar to paddy rice. There
are two types: the sweet hon matai and the starchysui matai, with the former more popular in the
United States. Eleocharis dulcis corms differ fromfruit of the dicot Trapa species (T. bicornis and T.
natans), which are also called water chestnut, inthat they are toxic when eaten raw (Rubatzky andYamaguchi 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 areusually consumed cooked.

Horticultural Maturity IndicesCorms mature after plant tops have died or been
killed by frost. Mature corms are recognized bytheir well-developed, lignified, dark, shell-like
epidermis. Corms keep well underground, andharvest can be delayed for up to 4 mo after tops
senesce (Hodge 1956). Sugar content is more thandouble in corms harvested in December versus
October in the southeastern United States (Twigg
et al. 1957). However, corms became less tenderand more fibrous when harvest is delayed (Brecht
et al. 1992).
592

Precooling Conditions
Though amenable to faster cooling methods
such as hydrocooling and forced-air cooling,waterchestnuts are usually room-cooled forstorage 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 (Ryalland 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 submergedin NaOCl solution soon after harvest. An initialconcentration of about 1,000 µL L-1 falls toessentially zero within 3 to 5 days. Anaerobiosis
was not a problem when 23 kg (50 lb) lots werestored 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 ofCA.

Retail Outlet Display Considerations

Postharvest Pathology

Waterchestnuts should be displayed in refrigerated
units with water spray or mist to keep them fromshriveling.

Decay, caused mainly by Fusarium andGeotrichum spp., is a problem at storage
temperatures of >5 °C (41 °F) and in immaturecorms with chilling injury (Brecht et al.
1992). Black rot (Cerastomella paradoxa) andtrichoderma rot (Trichoderma viride) have beenreported, 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).

Chilling Sensitivity
Chilling injury is only a concern with immaturecorms. 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).

Quarantine Issues
There are no known quarantine issues.

Ethylene Production and Sensitivity
Suitability as Fresh-Cut ProductThere 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 rateby 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 ofcrispness and tenderness, but texture changes areminimal in refrigerated storage if water loss is
minimized (Kays and Sanchez 1984, Brecht et al.
1992).

Fresh, peeled corms could be marketed if
consumer demand is sufficient. A method has beendeveloped 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 adheringsoil, corms should be treated with chlorinatedwater (1,000 µL L-1, pH 7.0) to reduce decay.
Waterchestnuts sweeten during low temperaturestorage, much like potato (Solanum tuberosumL.) tubers and parsnip (Pastinaca sativa L.) roots(DeRigo and Winters 1964). Starch to sugar
conversion can result in doubling or triplingof sugar levels within 1 mo of storage, withno further increase over longer storage times;
maximum sugar levels are reached at 10 °C (50°F) and in early harvested, larger corms (Brecht etal. 1992), but decay can limit storage at 10 °C (50°F) to 1 mo.

593

References
Brecht, J.K., K.A. Bergsma, C.A. Sanchez, andG.H. Snyder. 1992. Harvest maturity and storage
temperature effects on quality of chinese water
chestnuts (Eleocharis dulcis). Acta Hort. 318:313319.
DeRigo, H.T., and H.F. Winters. 1964. Effectsof storage temperatures on physiological andchemical 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. 10:4965.
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 ofchinese water chestnut (Eleocharis dulcis [Burm.
F.] Trin.) corms. Acta Hort. 157:149-159.
Leeper, G.F., and A.K. Williams. 1976. Peeling ofchinese 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 somespecialty 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 andVegetables, 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.
594

Water Convolvulus

Grades, Sizes, and Packaging

Ching Cheng Chen and Robert E. Paull

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).

Chen and Paull are with the Department of
Tropical Plant and Soil Sciences, University of
Hawaii at Manoa, Honolulu, HI.

Precooling Conditions
Scientific Name and Introduction
Water convolvulus (Ipomoea aquatica Forsk.) is
also called ung choi and kang kong. It is a memberof the morning-glory family (Convolvulaceae) andis 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. Youngstems and leaves are consumed after frying
or boiling. It has high protein and carotenoid
contents. It is grown both in ponds and in moistsoil. 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, andpake boong.

Quality Characteristics and Criteria
Plants should have tender tips, and the diameter inthe 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; andstems should be tender (Tisbe and Cadiz 1967).
Plants should be free of dirt and residue, andstems should have a minimum of fibers.
Horticultural Maturity Indices
Young plants are either up-rooted or cut near thewater surface (flooded culture) or ground level(moist soil culture) when about 30 cm (12 in)long. Then they are tied into bundles. Plants withroots attached are less perishable (Cornelis et al.
1985).

Room-cooling is normally used. Vacuum-coolingis 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).

595

Ethylene Production and Sensitivity

References

Water convolvulus produces about 2 µL kg-1
h-1 ethylene at harvest; the rate declines duringstorage. Production can then increase to about
the same level when leaves senesce and turnyellow. Ethylene exposure induces premature leaf
senescence and yellowing.

Austin, D.F. 1991. Associations between the plantfamily 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.

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 9,150kcal 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, thoughbacterial rot does occur. Rapid cooling, goodtemperature management, and sanitation reduce
the problem significantly.
Quarantine Issues
Peach aphid is sometimes found. Thoughsweetpotato weevil may not be able to complete
its life cycle in this vegetable, larvae have beenfound in the hollow stems, and therefore it isregarded as a host (Austin 1991).

Suitability as Fresh-Cut Product
Water convolvulus is sold in Southeast Asianmarkets as part of a meal pack for stir-frying.
596

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. 53:959962.
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. 285289. University of the Philippines, Los Banos,
Philippines.

Watercress

Optimum Storage Conditions

Stephen Morris and Jenny Jobling

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.

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 typicallygrown in running water (Snowdon 1991).

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

Horticultural Maturity IndicesContact with melting ice and water sprays help
in preventing dehydration. Careful handlingis necessary to avoid crushing or bruising thedelicate leaves.

Leaves should be harvested when full size and stillbright-green.

Chilling Sensitivity

Quality Characteristics and Criteria

Watercress is not sensitive to low temperatureand should be stored as cold as possible without
freezing.

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.

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
Precooling Conditions
Watercress should be precooled promptly after
harvest either by hydrocooling or vacuum-cooling(Hruschka and Wang 1979).

Temperature
0 °C
5 °C
10 °C
15 °C
20 °C
25 °C

mg CO2 kg-1 h-1
16 to 2847 to 53
95 to 125
139 to 210
300 to 344
334 to 420
597

Data from Smith (1957) and Hruschka and Wang
(1979).
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 andcrushing of leaves.

Postharvest Pathology
Harvested watercress is highly perishable.
In warm conditions, the stems can becomeslimy as a result of bacterial soft rot caused by
Erwinia carotovora. It is therefore importantthat 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.
598

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 ofPostharvest Diseases and Disorders of Fruits
and Vegetables, vol. 2, Vegetables, p. 219. Wolfe
Scientific, London, U.K.

Watermelon
James W. RushingRushing is formerly with the Coastal Researchand 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 trailingvines 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 inshades 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 mostcommercial varieties is some shade of yellow or
red (Sackett 1974).

reliable method of determining maturity withina given field is to visually examine the fruit forthe changes described above, then cut some fruitin random sectors of the field to check flavor andinternal color development. Some buyers requirethat fruit have some minimum SSC, which iseasily 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 describedabove. Size may be specified in terms of average
weight, minimum weight, or minimum andmaximum weight (AMS 1978). Watermelons may
be shipped in bulk, placed on corrugated bins witha capacity of approximately 1,000 lb (454 kg), or
packed into cartons containing 3 to 6 watermelons
depending on fruit size. Cartons should havespecially designed inserts to help support theweight of the fruit (Close et al. 1971).

Precooling Conditions
Quality Characteristics and Criteria
High-quality watermelons are well formed,
symmetrical, and uniform in shape and have awaxy, bright appearance. The rind should be freeof scars, sunburn, and abrasions with no bruisingor other physical injury; free from anthracnose orother decay; and not overripe (AMS 1978, Suslow
1999).

Horticultural Maturity Indices
As watermelons reach horticultural maturity, theground spot changes from white to pale yellow,
tendrils nearest the fruit may turn brown and dry,
and the fruit surface may become irregular anddull 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 whilemature fruit sounds dull or hollow. The most

Watermelons generally are not precooled andsome 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 thatare 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 ingeneral 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).

599

Controlled Atmosphere (CA) Conditions

Respiration Rates

Watermelons generally do not respond well to CA
or to MAP. Studies with shrink-wrap packaging
of individual fruits, a form of MAP, was notbeneficial, and in some cases decay in MAP was
higher (Biglete 1992).

Temperature
mg CO2 kg-1 h-1
4 to 5 ºC
3 to 410 ºC
6 to 920 to 21 ºC
17 to 25
Data from Hardenburg et al. (1986).

Retail Outlet Display Considerations
Watermelons are usually sold from unrefrigerated
displays. Bulk fiberboard bins with colorfulgraphics have been a popular method of
displaying watermelons for retail sale.

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 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 etal. 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 notcompletely 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 toethylene. Exposure to as little as 5 µL L-1 ethylenecauses 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.

600

Refer to above sections on “Chilling Injury”
and “Ethylene Sensitivity.” A disorder ofpreharvest 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 primarydefense against decay is the exclusion of diseased
fruit from the marketing chain through carefulselection 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 thefield, anthracnose (Colletotrichum orbiculare) andblack 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 becaused 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 researchdemonstrated the disease is not easily transmitted
from fruit to fruit after harvest. Appropriate
grading and temperature management canvirtually eliminate its presence in the marketing
chain (Rushing et al. 1999).

Quarantine Issues

Elkashif, M.E., D.J. Huber, and J.K. Brecht. 1989.
Respiration and ethylene production in harvested
watermelon fruit: evidence for non-climactericrespiratory behavior. J. Amer. Soc. Hort. Sci.
114:81-85.

Watermelons destined for export must be freeof disease, insects, soil, or vegetative debris.
Phytosanitary requirements in the receiving
country should be reviewed prior to shipment.

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.

Suitability as Fresh-Cut ProductPicha, D.H. 1986. Postharvest fruit conditioning
reduces chilling injury in watermelons.
HortScience 21:1407-1409.

The fresh-cut market for watermelon cubes andslices 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).

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.

Special Considerations
Special care should be given to avoid roughhandling injury of watermelon fruit during
harvesting and handling. Fruit that are
inadvertently dropped during harvest or handlingshould 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.

Rushing, J.W., A.P. Keinath, and W.P. Cook. 1999.
Postharvest development and transmission ofwatermelon fruit blotch. HortTechnology 9:33-35.
Sackett, C. 1974. Watermelons. Fruit andVegetable Facts and Pointers. United Fresh Fruitand Vegetable Association, Alexandria, VA.
Sargent, S.A. 1998. Fresh-cut watermelon. Citrus
and Veg. Mag. 62:26-28,44.

References
AMS [Agricultural Marketing Service]. 1978.
United States standards for grades of watermelons.
At http://www.ams.usda.gov/AMSv1.0/standards.

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.

Biglete, N.A. 1992. Packaging And Storageof Watermelon Using Different Shrink-Wrap
Techniques. M.S. thesis, Clemson University,
Clemson, SC.

Suslow, T.V. 1999. Watermelon.
Recommendations for maintaining postharvest
quality. At http://postharvest.ucdavis.edu/produce_
information.

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.
601

Wax Apple

Precooling Conditions

Robert E. Paull and Ching Cheng Chen

Room-cooling is normally used because of the riskof excessive moisture loss with forced-air cooling.

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 thisSoutheast 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 to2 in) wide. It has one to four seeds. The skin canbe green to light red to dark red and has a waxlike
high gloss sheen. The low-acid flesh is white andjuicy (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.

Optimum Storage Conditions
Storage at 2 to 10 °C (36 to 50 °F) is
recommended. However, chilling injury is aproblem 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 ashelf-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 lesseffective, partly due to RH control.

Retail Outlet Display Considerations
Fruit should be displayed in overwrapped trays orclosed polystyrene clamshell containers with no
perforations at 10 °C (50 °F). They should not be
misted.

Chilling Sensitivity
Horticultural Maturity Indices
Wax apples are ready for harvest when theblossom-end is fully expanded and the skin shows
desired market color. Green-skin varieties are
harvested when they reach full size.

Wax apples show pitting and skin scald after 4days 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
Grades, Sizes, and Packaging
There are no U.S. or international standards. Fruitare 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.
602

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 prematuresenescence.

Respiration Rates

References

Respiration declines after harvest (Liao et al.
1983).

Akamine, E.K., and T. Goo. 1979. Respirationand ethylene production of fruits of species andcultivars of Psidium and species of Eugenia. J.
Amer. Soc. Hort. Sci. 104:632-635.

Temperature
10 °C
20 °C

mg CO2 kg-1 h-1
4 to 58 to 11

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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

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. TropicalFruits. CAB Intl., Wallingford, U.K

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 somedarkening of affected flesh. Though fruit have abright 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 besusceptible to anthracnose.

Quarantine Issues
Wax apple is a fruit fly host; irradiation at 300 Gy
may have potential for disinfestation.

Suitability as Fresh-Cut ProductWax apple is often available as a fresh-cut productin Southeast Asian markets in trays with overwrap.
It has some potential as a fresh-cut product.
603

Fresh-Cut Fruits
John C. Beaulieu and James R. Gorny
Beaulieu is with the Southern Regional ResearchCenter, 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 foodservice applications have enjoyed an increasingpresence 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 havetargeted development of fresh-cut fruit products aspart of their long-term business plans. However,processors of fresh-cut fruit products facenumerous challenges not commonly encounteredduring 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 maintainedwith refrigeration. Fresh-cut products are raw,
and even though processed (physically alteredfrom 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 afresh-cut product as fruits or vegetables that havebeen trimmed and/or peeled and/or cut into 100%
usable product that is bagged or prepackaged
to offer consumers high nutrition, convenience,604

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 arecommonly classified as vegetables.
Fresh-Cut Physiology and Physiological
Concerns
Once harvested, fruits are removed from theirsource of water, minerals, and sustenance. Fruittissues continue to respire, using available andstored 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, andmechanical 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 criticalthat temperature-dependent events related torespiration, water loss, pathological decay, andethylene 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-climactericfruit, leafy vegetables, non-fruit vegetables, androots 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 andcauses major tissue disruption as enzymes andsubstrates, normally sequestered within thevacuole, 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

(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 andsubstrates may also contribute to flavor andtexture 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 havenegative 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 beappropriate 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 thephysiology of the fruit and the finished product(and packaging) to accurately determine whenfruit 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 mostcommonly, and sometimes only, assessed visually.
Visual appearance is generally the determinant forcommercial shelf-life. Although some studies havefound 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 somequality 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 withfresh-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 etal. 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 daysin air at 5 °C) by more than 25% (Cantwell andPortela 1997).
Flesh firmness of fresh-cut fruit products canbe maintained by application or treatment withcalcium compounds. Dipping fresh-cut products insolutions of 0.5 to 1.0% calcium chloride is very605

effective in maintaining product firmness (Ponting
et al. 1971, 1972). However, calcium chloride may
leave bitter off flavors on some products. Firmnessof 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 duringstorage in some fresh-cut apple cultivars (Kim etal. 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]) weremore 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 thepresence of O2 converts phenolic compounds infruits 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 theproper amount of O2 is present. Excessive levelsof O2 in a package may allow for cut surface
discoloration to occur, while too little O2 may
606

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 solutionsof acetic, ascorbic, citric, tartaric, fumaric, or
phosphoric acid. However, these acids may leave
off flavors and promote tissue softening andtherefore must be used with care.

Reducing Agents
Ascorbic acid or erythorbate (an isomer ofascorbic acid) are two common compounds usedin the food industry to prevent PPO-mediatedcut-surface discoloration. Ascorbic acid anderythorbate 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, sothey may also reduce surface pH of commodities,
further slowing browning.

Sensory Aspects
Fresh-cut vegetable salads have great consumer
appeal because of their convenience, flexibilityof 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 withaccompaniments. It is generally and unfortunately
assumed that “if it looks good, it tastes good.”
Improving consistency in fresh-cut fruit product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 andPortela 1997). Cantaloupe balls prepared fromfour eastern varieties stored 8 days at 0 °C (32°F) had an average SSC decrease of 9.7% with arange 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 fromfruit 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 offresh-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 (Kimet 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 andKader 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 acidbacteria (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 willprocess 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 lessthan half-slip delivers a fresh-cut product with
optimum visual shelf-life but insufficient sugar orvolatile 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, andcubes 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 beseriously examined when determining the shelflife of fresh-cut fruit products. Nevertheless,the quality of intact vegetables and fruits isoften determined almost exclusively basedon appearance, sometimes to the exclusion offlavor and texture (Sapers et al. 1997). Much
variability exists in the literature regarding
acceptability based on sensory evaluations, andthis variability oftentimes can be attributed to607

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-Shawet al. 1994). However, fruit were not sanitized,
nor were gloves worn during preparation andsubsequent microbial decay and associatedtexture loss most likely limited post-cutting life.
Sterilized, diced cantaloupe stored at 4 °C (39 °F)
in various controlled atmospheres were acceptablefrom 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 flavorscores 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 andwere 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 ofcontainers developed off flavors associated withmicrobial fermentation (Spanier et al. 1998).
Fresh-cut orange segments that had acceptableappearance after 14 days storage were found tohave 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 andmicrobial 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, isdifficult 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 effectstorage temperature has on volatile production andlittle flavor and sensory work has been performedon fresh-cut fruits.
608

Microbiology
Microbial decay can be a major source of spoilageof 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 andmolds. There is no evidence to suggest that lower
aerobic plate counts (APC) or total plate counts(TPC) immediately after processing correlatewith increased shelf-life in fresh-cut vegetables.
However, for fresh-cut fruit, very low APC, TPC,
and especially yeast and mold counts correlatewith increased shelf-life.
The dominant microorganisms associated with
spoilage of fresh-cut vegetables are bacteria(for example, Pseudomonas spp.), whereas thedominant microorganisms associated with the
spoilage of fresh-cut fruit products are yeasts andmolds. In fresh-cut vegetables the proliferationof bacteria may be a symptom associated withtissue 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 fruitwith 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 wascompromised (Cartaxo et al. 1997).
Little research has been performed on foodborne
human pathogens on fresh-cut fruits. Conway etal. (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 growat 5 °C (41 °F). CA had no significant effect on
the survival or growth of L. monocytogenes atelevated temperatures. Botulinal toxin was not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 wasrecovered in some inoculated honeydew samples
stored 9 days at 15 °C (59 °F) in hermeticallysealed packages (Larson and Johnson 1999).

longer than fruit cut with a dull hand-slicer (Gorny
and Kader 1996). Sharpening of machine andhand knives as often as possible prolongs shelflife of fresh-cut fruit because there is less tissue
injury.

Chilling Injury and Holding Temperatures
Factors Affecting Fresh-Cut Fruit Quality
Major factors affecting fresh-cut fruit quality arecultivar (Kim et al. 1993, Romig 1995), preharvest
cultural practices (Romig 1995), harvest maturity(Gorny et al. 1998b), physiological status of theraw product (Brecht 1995), postharvest handlingand cold storage (Watada et al. 1996), processing
technique (Bolin et al. 1977, Saltveit 1997, Wrightand Kader 1997b), sanitation (Hurst 1995), andpackaging (Solomos 1994, Cameron et al. 1995).

General Fresh-Cut Physiology and Physiological
Concerns
Most fruit are very susceptible to bruising andmechanical injury. This is very different frommost 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 andmicrobial invasion, and severe disruption of
the tissue often provokes increased respiration,
ethylene production, and enhanced susceptibility
to water loss and microbial decay. All of thesefactors may contribute to decreased shelf-life via
browning, off color, softening, or decay.
Subsequently, methods for cutting and peelingfruit 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 effecton 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 afreshly sharpened knife retained visual quality

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 whenfruit are subsequently placed at non-chilling
temperatures and may not be visible if maintainedat chilling temperatures (Saltveit and Morris
1990). Nonetheless, precooling whole cantaloupe
to below their optimal long-term storage
temperature shortly before cutting is effective atincreasing product shelf-life (Cantwell and Portela
1997, Lange 1998).
Fruit tissues normally damaged by storage atchilling temperatures are the inedible outer rindor skin portions. During fresh-cut processing,these tissues are normally removed and discarded.
Although the optimal storage temperature formany 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 bychilling.
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 quality609

attributes depending on cultural practices, climate,season, and harvest maturity. For example, thedesirable 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 withbreeding 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 thatcertain cultivars out-perform others with regard to
fresh-cut shelf-life and quality (Kim et al. 1993,
Cantwell and Portela 1997, Lange 1998, Gorny etal. 1999, Anonymous 2000b). However, no single
study can encompass all desirable varieties, andsingling out a “winner” can be compromised byseed source and seasonal/climactic variations.
Furthermore, the industry may also be historicallydriven 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 ofpeach and nectarine slices made from 13 cultivarsof 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). Amongnectarines, ‘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 toyellow-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
610

each, due to severe enzymatic browning on cut
surfaces (Gorny et al. 1998a). However, ‘Bartlett’and ‘Bosc’ pear slices experienced a much greaterloss 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 typicallyuse very large 9-count-per-box fruit. This isbecause large melons are often available at lower
prices in the marketplace, the yield from larger
melon fruits is almost always higher, and thelabor to process one large fruit is often less thanprocessing many smaller fruit. Very little researchhas 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 andfirmness, 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 affecteating 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 havebeen 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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 physicaltreatments (Hoover 1997), and pulsed-microwave
irradiation (Shin and Pyun 1997).

Modified Atmosphere Packaging (MAP)

Storage Time, Temperature, and Atmosphere

Heat Treatment

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 ofvolatile 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 atmosphereto ensure desirable flavor during consumption.

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 York674’), 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 browningin many other cultivars tested (Kim et al. 1994).

Gorny et al. (2002) determined that, comparedto air storage, CA (2% O2 + 98% N2) storageat -1 °C (30 °F) of whole mature-green pears
extended shelf-life of slices 1 to 2 days. There wasa significant reduction in shelf-life of pear slices
stored at -1 °C (30 °F) in air or CA compared toslices 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.

MAP is widely used for fresh-cut vegetables, butwith fruits occasionally undesirable atmospheres
can reduce quality due to off flavor anddiscoloration (Gil et al. 1998).

Irradiation
Irradiation of fresh-cut fruit products may bebeneficial in reducing the number of bacteriapresent 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 arenecessary (Brackett 1987); and these levels aredamaging 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 areyeasts and molds.

611

Chemical Treatments
Retention of fresh-cut product firmness andinhibition of browning are common measuresused to determine efficacy of chemical treatments.
Calcium has been used as an agent for maintaining
firmness of whole produce (Poovaiah 1986), andits use in fresh-cut was inevitable. Other chemicaltreatments 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 justafter 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 actuallyinhibiting 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 notwash freshly cut commodities that develop little
or no browning (cantaloupe and honeydew, forexample), since chemical treatments are seldom
applied and because removal of free surface water(centrifugation or spinning) from the cut fruit canbe damaging. On the other hand, honeydew andcantaloupe 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 andmicrobial counts were lowered throughout storage(Ayhan et al. 1998).
Hydrogen peroxide (H2O2) 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 itemswith minimal to no residue (Bolin and Huxsoll
1989, Sapers and Simmons 1998). However, the612

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 firmnessof 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 affecteddifferently depending on calcium concentration(Lester 1996). Softening was the major factor in
quality loss in kiwifruit slices. However, theseslices had a shelf-life of 9 to 12 days if treatedwith 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 etal. 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 wasan 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 wasmost effective (Gorny et al. 1998a).
Antibrowning Compounds
Many fruits brown rapidly after cutting, andextensive work has been performed to address
this quality loss. Cut surface discoloration or
enzymatic browning, caused by formation ofquinones 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 andexperimental compounds have been investigated.
Nevertheless, enzymatic browning still represents
a major challenge with fresh-cut fruit (Weller et al.
1997, Sapers and Miller 1998).

Ascorbate, citrate, isoascorbate, and sodium
erythorbate are some of the most commonlyused agents to reduce or eliminate cut-surface
discoloration. Ascorbate was more effective
than erythorbate in preventing surface browningin ‘Winesap’ and ‘Red Delicious’ apple plugs
stored 24 h, and 1% citric acid enhanced theireffectiveness (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 etal. 1989). ‘Fuji’ apple slices treated with 2%
ascorbate had no browning or loss of visualquality 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 treatedwith 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, and4-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, acombination 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 thatslices treated with combinations of antibrowningcompounds retained higher levels of malate andhad no decrease in sugar levels at 5 and 10 °C(41 and 50 °F), indicating that higher quality wasmaintained during storage. Fresh-cut mangoes
treated with 1 mM 4-hexylresorcinol, 50 mM
potassium sorbate, and 500 mM ascorbic acidin MAP at 10 °C (50 °F) maintained color andsensory 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 andstored 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 enzymaticbrowning (Joslyn and Ponting 1951, Molnar-Perland Friedman 1990, Gunes and Lee 1997). Threemechanisms 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 (Dudleyand Hotchkiss 1989, Robert et al. 1996); andformation of a colorless cys-quinone adduct(Richard et al. 1991).
When cysteine is used as an inhibitor of
enzymatic browning on sliced apples (Walker andReddish 1964) or pears (Sapers and Miller 1998),
pinkish-red off-colored compounds are formed
due to phenol regeneration with deepcolor formation (Richard-Forget et al. 1992). If
off-color formation can be prevented, cysteine
may prove to be an effective replacement tobisulfites. Cysteine is a naturally occurring
amino acid that has GRAS status for use as adough conditioner (Code of Federal Regulations
21:184.1271 and 21:184.1272). Development of
cut surface discoloration was reduced for only613

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 andlikely was due to the low concentration applied.
Gorny et al. (2002) reported that a post-cuttingdip (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 andpreventing browning. Consumer panelists could
not distinguish between pear slices treated withthe 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 wasnecessary 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 inpreventing 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 thatis readily converted to aroma volatiles in vivo byfresh-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 andpsychrotrophic 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
614

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 theuse 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, thathas hormonelike activity at low concentrations.
Exogenously applied methyl jasmonate is effective
in reducing mold growth on fresh-cut celery andpeppers and may have applications as a naturally
derived fungicide (Buta and Moline 1998).
Edible coatings have been used in an attempt topreserve fresh-cut products because the coatings
act as barriers to water loss and gas exchange,
creating a micromodified atmosphere aroundproducts, and can serve as carriers for other GRAS
compounds (Baldwin et al. 1995a). Ethylene
production and CO2 evolution were reduced inapple slices coated with double layers of bufferedpolysaccharide/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 browningand potassium sorbate to decrease microbial
growth was superior when incorporated into thisedible 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-lifeof 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 Hagenmaier1997). 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 detectedby informal taste panels (Baker and Hagenmaier1997).

Compendium of Recommendations andData 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 offresh-cut fruits. This information may be used asa starting point for design and testing of MAP for
fresh-cut fruit products. Fresh-cut fruit respiration
rates, as well as responding to atmosphericmodification, will vary depending on manyfactors, including variety and maturity of fruit at
cutting.
Table 1. Respiration rates for fresh-cut fruits in air at various storage temperatures________________________________________________________________________________
Fresh-cut productTemperature (ºC)________________________________________________________________

0 to 2.5
4 to 510
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——
Golden11.0-14.0—
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.

615

Table 2. Storage atmosphere recommendations for selected fresh-cut fruits________________________________________________________________________
		
Atmosphere		Fresh-cut productTemperature
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
52-4
10moderate
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.
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623

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 andphysiological changes that hasten loss of productquality (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 whiteblush to the surface that masks varietal color; forexample, white blush on “baby” carrots decreases
the intensity of the underlying orange color.
Differential dehydration of exposed cortex andvascular 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 thesesurface changes with the loss of freshness.
Physiological processes devoted to wound repair
can be beneficial (such as curing potatoes) or
detrimental to quality retention. Physiologicalchanges following wounding include increased
respiration and ethylene production, promotion of
the ripening of climacteric fruit vegetables (suchas melons and tomatoes), and enhanced synthesis
and accumulation of phenolic compounds that624

contribute to tissue browning. These changes aremanaged by the use of low temperatures, creationof reduced O2 or elevated CO2 atmospheres, andapplication of inhibitors of specific chemical
reactions or metabolic pathways.
Wound-enhanced respiration and ethylene
production can deplete carbohydrate storage
reserves and stimulate tissue softening associatedwith fruit ripening (melons, squash, tomatoes)or chlorophyll loss associated with leaf ortissue senescence (spinach, broccoli). In manytissues, wounding produces a signal that induces
the increased synthesis and accumulation ofphenolic compounds. Tissue browning canresult from the oxidation or polymerization of
accumulated phenolic compounds. Lignificationand 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 toensure that an initial low microbial load on freshcut vegetables is maintained during marketing.
The current industry standard washing anddisinfection procedures used on whole produce
are rather ineffective with fresh-cut vegetables
once they have been contaminated with microbial
pathogens. Overall microbial load relative tospoilage organisms usually remain below levelsof concern as long as visual quality remains
acceptable. However, postharvest treatmentsthat 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) andsuffer physiological damage if held at thesechilling temperatures beyond a specific period.
These vegetables include jicama, pepper, sweet
potato, tomato, and zucchini. In contrast to thewhole commodity, which should not be chilled,the increased susceptibility of fresh-cut products
to spoilage often means that the product has alonger 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 soonafter 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 externalchanges requires that fresh-cut vegetables behandled with a greater degree of care than thewhole 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 productcan 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 andstorage 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 isslightly reduced during storage in 5% O2 and 5%
CO2 at 5 °C (41 °F).
Respiration Rates
Temperature

Whole
peeledCubed
Grated1 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 rateby 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 coretemperature 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 duringstorage. Development of off odors can be a major
concern when MAP is used. Temperature abusepromotes soft rot and mold growth.
Whole broccoli heads are hand-cut into florets thatare 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 fromthe florets as well as reduce aerobic plate counts.
Repeated daily washing did not maintain lower
microbial counts for >2 days.

625

The benefit of CA (5% O2 and 4% CO2) may bemarginal 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 (32to 41 °F) reduces respiration by about 50%. Useof appropriate polymeric film in MAP maintained
green color at 0 to 5 °C (32 to 41 °F) for morethan 21 days (Cabezas and Richardson 1997).
Severe off odors and discoloration at cut ends
can develop during MAP storage at 10% CO2 and2.5% 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/moldplate 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 rateby 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 havetypical cabbage flavor with no off notes and626

should be stored at 1 to 3 °C (34 to 38 °F) toensure quality and reduce potential for freezing ofproduct during handling, distribution, and storage.
Fresh-cut cabbage includes diced and shredded
product with cut size varying from 0.63 cm (¼ 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 andpackaged. 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 isrecommended (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 pointof coleslaw mixes in low density polyethylenebags varied with the cabbage to carrot ratio andwith temperature. At 5 °C (41 °F), a 70:30 mix
went anaerobic at 1.8% O2, while 3% O2 was thelimit 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) anddiscoloration 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 etal. 1997). At 11 °C (52 °F), Listeria spp. grewfaster in fresh-cut cabbage packages that had an
atmosphere of <1.8% O2 and >20% CO2 than inair (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 rateby 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, 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 brushor slimy surface. Raw and processed productshould be kept at 1 to 3 °C (34 to 38 °F) to ensure
quality and reduce potential for freezing ofproduct during handling, distribution, and storage.
Most quality loss in cut carrots results fromformation of either white blush or off odor andslimy 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 toremove excess water and packaged in plastic bags.
Dehydration of surface debris on cut and peeled
carrots imparts a whitish translucent appearance tothe 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 andBarth 1998), such as sodium caseinate-stearicacid (Avena-Bustillos et al. 1994), or heating andraising the pH (Bolin and Huxsoll 1991) may be
helpful in reducing white blush. Treatments thatmodify 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 acidbacteria 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 acidbefore 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
peeledmg 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 rateby 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.
627

Celery (Diced, Sliced, Sticks)
Fresh-cut celery petioles have no leaves or brownspots 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 canbe reduced 75% by the application of an edible
coating (Avena-Bustillos et al. 1997). Differential
dehydration of exposed cortex and vascular tissuecaused the stronger vascular strands to projecta few millimeters from the cut end of celery
petioles. Development of pithiness is associatedwith water stress during growth and wounding
during processing (Saltveit and Mangrich1996). 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 qualitychange (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 andcolor.

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.
628

Acid treatments and edible coatings can improve
preservation. Excellent visual quality wasmaintained for 21, 16, 12, or 8 days of storagein 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 garlichas 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		57Data from Burlo-Carbonell et al. (2000).
To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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 productduring handling, distribution, and storage. Tubersize 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 isalso attributable to yeast and bacterial growth. A
10% CO2 atmosphere retards brown discoloration,

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) andstored at 1 to 3 °C (34 to 38 °F) after processing toensure quality and reduce potential for freezing ofproduct during handling, distribution, and storage.
Washing shredded kale with 0.1% NaOCl results
in a 10-fold reduction in aerobic plate countcompared to unwashed products. Fresh-cut kale inperforated (5.96 ± 0.35 mm2 diameter holes with
6.68 cm2 total surface area per sack) polyethylenebags (38 mm thick) become unacceptable due toyellowing 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 processedleeks stored at, 1 to 3 °C (34 to 38 °F) to ensure
quality and reduce potential for freezing ofproduct 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 highCO2, ethanol, and acetaldehyde concentrations(Keteleer et al. 1993).

Respiration Rates
Temperature Whole leaf
Rings				2 mm thickmg 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 rateby 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 aswhole or cored heads. It should be stored at 1 to
3 °C (34 to 38 °F) before and after processing toensure quality and reduce potential for freezing ofproduct 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 andheat-shock can inhibit discoloration, but thesetreatments may result in loss of visual quality.
Unless stressed in the field, lettuce has low levelsof phenolic compounds and tissue browning
occurs after the induction of synthesis andaccumulation of phenolics by wounding. A 90-sec
heat-shock at 45 °C (104 °F) prevented woundinduced browning of iceberg (Loaiza-Velarde etal. 1997, Loaiza-Velarde and Saltveit 2001) andromaine (Saltveit 2000) lettuce.

629

Butterhead Lettuce

Greenleaf Lettuce

Browning of the cut edges of butterhead lettuce isreduced by modified atmospheres rapidly createdby flushing with N2 to get 1 to 3% residual O2 with
CO2 levels of 5 to 10%. Tissue in atmospheresof <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 combinedwith low O2 atmospheres (Steward and Uota
1971).

A 0.5 to 3% O2 and 5 to 10% CO2 CA reduced cutedge browning of greenleaf lettuce (Lopez-Galvez
et al. 1996).

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 tobrown stain varies among cultivars and position ofleaves within the head (Krahn 1977). Shelf-life of
butterhead lettuce was negatively correlated withrespiration rate and susceptibility to CO2. HighO2 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 whenfresh-cut lettuce was stored in <0.5% O2 or >15%
CO2.
Necrosis of butterhead lettuce may be associatedwith microbial growth, such as pectolytic
Pseudomonas (Nguyen-The and Prunier 1989) andother 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 rateby 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.
630

Iceberg Lettuce
The raw product should have <6% pink rib
discoloration, while russet spotting, hooked core,
and tipburn should be <1%. Moisture content oflettuce is extremely important for maintaining
texture and reducing microbial growth. Excess
moisture can be removed in a forced-air tunnel orby 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 ofstorage, only 15% would purchase control lettuce
while 40% would purchase lettuce spin- or airdried for 15 min. Slicing methods can influenceascorbic 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 theheadspace, 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-Anneet 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 6days in air, 8 days in 3% O2, and 12 days in 0.2%O2 (Peiser et al. 1997). Increasing CO2 enhances
the beneficial effect of low O2. A combinationof 0.2% O2 with 7 to 15% CO2 gave a 16-day
shelf-life. A 14-day shelf-life was obtained whenshredded 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 andoff odor (fermentative volatiles, ethanol, andacetaldehyde) in the packages (McDonald et al.
1990, Mateos et al. 1993, Peiser et al. 1997).
Although gram-negative bacteria are numericallydominant, a large yeast population may also
be found. Species of Pseudomonas, Erwinia,
and Serratia were the most frequently isolated
bacteria. Cryptococcus, Pichia, Torulaspora, andTrichosporon spp. were the most common yeasts.
Beuchat and Brackett (1990) studied the effectsof shredding, chlorine treatment, and MAP on
survival and growth of Listeria monocytogenes,
mesophilic aerobes, psychrotrophs, yeasts, andmolds. They found that no significant changes in
populations of L. monocytogenes were detectedduring 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 °C12.0-15.0
5 °C
15.6-27.3
7.5 °C23.1-32.7
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 rateby 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 undereither 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 toensure quality and reduce potential for freezing ofproduct during handling, distribution, and storage.
MAP exerted a beneficial effect on sensory quality
by preventing pink discoloration. Compared toair, 3% O2 and 6, 10, or 14% CO2 MAP delayeddevelopment 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. These631

differences were maintained through 22 days ofstorage. Irradiation at 0.15 kGy caused smaller
reductions in microbial counts. A 10% loss infirmness was observed at 0.35 kGy, while othersensory attributes such as color, generation of off
flavor, and appearance of visual defects were notaffected. 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)

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.

Mushrooms (Sliced)

Whole onions are peeled and trimmed by machineor hand. Washing with chlorinated water can bedone 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.

Fresh-cut mushroom slices are white with nodarkening and wrinkling. Mushroom slices should
be stored at 1 to 3 °C (34 to 38 °F). Wrinkling andbrown 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. Morethan 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 andproduce 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 notrecommended to use low O2 MAP due to theinherent food safety risk.

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 ofproduct during handling, distribution, and storage.
The seed stems and new internal growth shouldbe less than 10%; double centers and translucent
scale should be less than 5%.

Temperature
mg CO2 kg-1 h-1
0 °C
20-60
5 °C
39-88
10 °C
86-124
Data from Gorny (1997).

Browning, yellowing, and development oftranslucence are major factors affecting thevisual quality of diced onion (Blanchard et al.
1996). Cutting causes important biochemicalchanges in tissues, including development ofsulfur aromatic volatiles. These compounds areproduced 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, andpropene 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) andmay be involved in development of bitterness andbrowning of onion puree (Howard et al. 1994).

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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,

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

Respiration Rates (Sliced)632

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 canbe 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 filmthat achieved MAP conditions more rapidly.
Atmospheres containing 1 to 2% O2 prevent theloss 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 packagesof diced onions improves sensory quality. A
storage life of 10 days is possible for fresh-cut
onions packaged in polymeric bags without agas flush and stored at 2 °C (36 °F). Addition ofabsorbents, potassium permanganate and clay, inpackages 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 increasebeyond 100 cfu g-1 (Garg et al. 1990, Blanchard
et al. 1996). Psychrotrophic and mesophilic floraincreased 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 rateby 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 (34to 40 °F) after processing to ensure quality andreduce 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 shouldbe spray-washed before processing and washedafter being cored and cut to reduce microbial
population. Alternatively, cut pepper can be
washed using a combination of open-flume andclose-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 visualquality (El-Bassuoni and Cantwell 1994). Visualquality was maintained and few compositionalchanges 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 andtexture decrease after 6 days in 10% CO2 but weremaintained 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 ripening633

or were already fully red ripe had better shelflife than pieces from mature-green fruit (LopezGalvez et al. 1997). They also found that visualquality was best maintained in air or CA at 0 °C
(32 °F), with important quality loss observed byday 9 at 5 °C (41 °F) and by day 3 at 10 °C (50°F). Decay is caused by both fungi (Alternaria andBotrytis spp.) and soft-rot-causing bacteria. Diced
tissue was more susceptible to decay than slices(Lopez-Galvez et al. 1997).

Respiration Rates
Temperature

SlicedDiced
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 rateby 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 withoutbrown discoloration. Enzymatic browning is amajor 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 preventbrowning 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 someconditions, such pretreatment-induced changes

634

in the cooked product that result in surface
firming (case hardening) and partial separationof the case-hardened superficial layer fromunderlying 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 ofminimally 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 combinedwith 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 atmospheresis necessary to prevent browning and achieve
extended shelf-life. MAP alone will not preventbrowning (Gunes and Lee 1997). Vacuum
packaging of fresh-cut potatoes may create
anaerobic conditions that allow growth of
Clostridium botulinum.

Respiration Rates
Temperature Whole
HalvesSlicesStickspeeled		
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)

Spinach (Whole Leaves, Cut Leaves)

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).

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.

Respiration Rates
Temperature Quarters
peeledShredded Diced
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 rateby 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.

Storage in 0.8 to 3% O2 and 8 to 10% CO2 isbeneficial. 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 thenumber 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 toair (Burgheimer et al. 1967). Increasing CO2
concentrations up to 13% caused a rapid decreasein ascorbic acid and development of off odors that635

were not acceptable after 1 week storage at 7 °C
(45 °F) (McGill et al. 1966). Chlorophyll loss canbe reduced by 50% with ethylene scrubbing. Low
O2 (0.8%) results in a slightly reduced respiration
rate of cleaned spinach leaves.

A 6.5% CO2 and 12% O2 atmosphere is slightly
beneficial.

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 highnumbers of mesophilic, psychrotrophic, andPseudomonadaceae bacteria (Babic and Watada
1996). The pectinolytic species Pseudomonas
fluorescens is probably the major spoilage agent offresh-cut spinach. Microbial populations on freshcut spinach leaves increase during storage in air
and CA at 5 and 10 °C (41 and 50 °F). Populationsof Enterobacteriaceae and Micrococcaceae are notgreatly affected by storage atmosphere.

Fresh-cut tomatoes should have consistent redcolor 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 ripeningstage 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 andremove seeds. For sliced tomato products, wholetomatoes are dipped in 200 µL L-1 chlorinatedwater for more than 1 min before slicing. Various
automated slicing machines have been developed
for tomatoes. Sliced tomatoes can be packed instacking, shingling, or soldier style.

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 rateby 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 andwithout 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 (32to 40 °F) in polymeric bags. Color of shredded
sweet potato darkens and firmness declines duringstorage. 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.
636

Tomato (Sliced, Diced)

Although tomatoes are chilling sensitive, they canbe 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 qualityof diced tomatoes during storage. In addition tothese 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
20 °C

mg CO2 kg-1 h-1
57.6-93.6

To get mL CO2 kg-1 h-1, divide the mg kg-1 h-1 rateby 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.

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%; respirationis 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 withstorage duration. Zucchini slices can be dipped insolutions 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 rateby 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 chemicalchanges of partially processed sweet pepper
fruit. II. Changes of chemical compounds in cut
surface of sweet pepper in relation to differenceof 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 withedible caseinate-acetylated monoglyceride films.
J. Food Sci. 62:351-354.
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637

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Bedding Plants and Seedlings
Hyeon-Hye Kim, Kevin Kern, and William H.
CarlsonKim, Kern, and Carlson are with the Departmentof 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 timeof availability makes it essential. There are twostages of plants in bedding plant production andstorage: plugs and finished plants. Generally,finished bedding plants are hardier and canwithstand greater environmental changes than theplug stage of the same plant. However, storage iseasier when the plant is in the more compact plugstage.

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 temperatureand irradiance. Plant quality improved with theaddition of light compared to that of plants in darkstorage, especially as the duration of storage andstorage temperature increased (Heins and Lange
1992a,c,d, Heins and Wallace 1993a,d). The effectof storage on plugs may vary depending on thespecific 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 aform of short-term storage. As the duration ofshipping increases, cooling plugs prior to shipping
becomes more important and will improve theirpostharvest condition when they reach their
642

final destination (Lange et al. 1991b, Heins et al.
1994b, Kaczperski et al. 1996).
Growers who only have one or two coolers mayneed to store plugs of several species at one time.
Researchers in Michigan (Heins and Lange 1992d,
Heins et al. 1992) showed how to identify acompromise 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, theenvironmental conditions before and after storage
can influence the growth of the plugs following
storage (Heins et al. 1991, 1994b, Heins andLange 1992c, Kaczperski et al. 1996).
A major disease problem associated with plugstorage is botrytis (Lange et al. 1991a,b, Heins etal. 1992, 1994b, 1995). Maintaining a high RH
in a cooler decreases the frequency of watering
but favors the growth of botrytis. The disease isgenerally not a problem on pansies but does affectmany species including impatiens, geraniums, andpetunias. 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 ofirrigations will vary, depending on the temperature
and RH of the cooler. Contact between thefoliage and water should be minimized to avoid
fungal infection. Plugs can be subirrigated withclear water as needed during storage because theplants’ nutritional needs are minimal under low
temperatures (Heins and Lange 1992c, Heinset al. 1994b). Heins et al. (1994b) recommend
applications of certain fungicide tank mixtures forcontrolling botrytis blight and sporulation during
plug storage.

643

Heins et al. 1992
Heins and Lange 1992c
Heins et al. 1994a
Heins et al. 1995
Heins & Wallace 1993d		
5.0-7.5
41.0-45.0									

Begonia, tuberous‘Nonstop Scarlet’
5.0
41.0
3
6
						

		—

Heins and Wallace 1993c—

		41.0-45.0

Heins et al. 1994a
Heins et al. 1995

Dahlia‘Amore / Figaro’
5.0
41.0
2
5
						
5.0-7.5

Heins et al. 1994a
Heins et al. 1995

Celosia‘Cherry Red’
10.0
50.0
2
3
						

41.0-45.0			

Heins et al. 1994a
Heins et al. 1995

Begonia, fibrous‘Vodka’
5.0
41.0
6
6
						

5.0-7.5

Heins et al. 1994a
Heins et al. 1995

Alyssum‘New Carpet of Snow’ 2.5
36.0
56						

References
Heins et al. 1992
Heins et al. 1994a
Heins et al. 1995
Heins and Lange 1992a

Maximum weeks storage
In the dark In the light

Ageratum‘Blue Danube’
7.5
45.0
6
6
						
						
						

Species
Cultivars evaluated Optimal storage temperature
		°C°F

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644
Heins et al. 1994a
Heins et al. 1995
Heins et al. 1991
Heins et al. 1994a
Heins et al. 1995
Lange et al. 1991a
Heins et al. 1994a
Heins et al. 1995
Heins and Wallace 1993e
Heins et al. 1992
Heins et al. 1994a,
Heins and Lange 1992c
Heins et al. 1995
Heins et al. 1994a
Heins et al. 1995

		
2.5
36.0
4
4
						

Impatiens‘Accent Orange’
7.5
45.0
6
6
						
						
						

Lobelia‘Blue Moon’
5.0
41.0
6
6
						
						

Marigold, French‘Hero Yellow’
5.0
41.0
3
6
						
						
						New Guniea impatiens ‘Kientzler Agua’
12.5
55.0
2
3
‘Kientzler Anaea’					‘Kientzler Apollon’‘Kientzler Celerio’‘Kientzler Celsia’‘Kientzler Eurema’‘Kientzler Marpesia’‘Kientzler Melissa’‘Kientzler Octavia’‘Kientzler Saturnia’‘Kientzler Sesia’

References
Heins et al. 1991
Lange et al. 1991b

Maximum weeks storage
In the dark In the light

Geranium‘Pinto Red’
3.0
37.5
—
—
						

Species
Cultivars evaluated Optimal storage temperature
		°C°F

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—continued

645

—

—

Heins & Wallace 1993e

Heins et al. 1994a
Heins et al. 1995

Portulaca‘Fuchsia’
7.5
45.0
5
5
						
41.0-45.0

Heins et al. 1994a
Heins et al. 1995

		
2.5
36.0
6
6
						

5.0-7.5

Heins et al. 1991
Lange et al. 1991b

Petunia‘Ultra Red’
3.0
37.5
—
—
						

		

Heins and Lange 1992dLange et al. 1991a

		
0-2.5
32.0-36.5——						

References

Heins et al. 1991
Heins et al. 1994a
Heins et al. 1995

Maximum weeks storage
In the dark In the light

Pansy‘Majestic Yellow’
2.5
36.0
6
6
						
						

‘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’

Species
Cultivars evaluated Optimal storage temperature
		°C°F

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—continued

646
Heins et al. 1992
Heins and Lange 1992a
Heins et al. 1994a
Heins et al. 1995
Heins and Wallace 1992
Heins et al. 1994a
Heins et al. 1995
Heins et al. 1994a
Heins et al. 1995

		
7.5
45.0
—
—
						Tomato‘Rutgers’
7.5
45.0
3
3
						
						

Verbena‘Romance Mix’
7.5
45.0
1
1
						

Vinca
‘Peppermint Cooler’ 10.0
50.0
56						

References
Heins et al. 1994a
Heins et al. 1995

Maximum weeks storage
In the dark In the light

Salvia‘Red Hot Sally’
5.0
41.0
6
6
						

Species
Cultivars evaluated Optimal storage temperature
		°C°F

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—continued

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 inresistance to drought stress. A hardened plug will
resist drought damage better than a plug grownwith 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 withjust a few plug trays before they commit a large
volume to storage (Heins et al. 1991, Lange etal. 1991a,b, Heins and Lange 1992c, Heins andWallace 1993b). See table 1 for specific species
storage temperatures and light levels.
Finished Plant Storage
Finished bedding plants are those that are ina state ready for sale to the general public.
Generally, finished plants are not stored incoolers 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 applicablefor 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)
BalsamRoss and Aldrich 1976
Begonia (fibrous)
Ross and Aldrich 1976
Celosia
Ross and Aldrich 1976
ColeusRoss and Aldrich 1976
KochiaRoss and Aldrich 1976
Vinca rosea
Ross and Aldrich 1976
Zinnia (dwarf & tall)
Ross and Aldrich 1976		
10-13 °C (50-55 °F)
AgeratumRoss and Aldrich 1976
Aster
Ross and Aldrich 1976
Browallia
Ross and Aldrich 1976
Centaurea cyanus
Ross and Aldrich 1976
DahliaRoss 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
SalviaRoss 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
LarkspurRoss 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 plugstorage table for temperatures and lengths of time
the plants may be stored without damage.
647

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, Cammet 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, andthese are dependent on seed source and lifting dateof 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 toearly winter. Therefore, lifting dates for seedlings
being put into cold storage should be delayed aslong as possible (Camm et al. 1994).
Warehouses or sheds can be used for storageof 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 polyethylenebags 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 withthe tops exposed and placed in a container forstorage. With prolonged storage (>6 mo), root
growth capacity can decline, as well as leadto 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
Sitka spruce
Douglas-fir
Lodgepole pine
Scotch pine
Loblolly pine
Ponderosa pine
Western hemlock
Lawson cypress

Sycamore
Sweetgum
Green ash
Oak
Birch
Yellow poplar
Hybrid poplar*
Eastern cottonwood** hardwood cuttings

References
Aldhous, J.R. 1964. Cold storage of forest nursery
plants: an account of experiments and trials, 19581963. 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 andphosphorus 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.

648

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. Developmentof systems for storage of bedding-plant plugs.
Bedding Plants Foundation, no. F-056, February,
pp. 1-8.

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, PacificSouthwest Research Station, Albany, CA.

Heins, R.D., and N. Lange. 1992b. How to store
begonia and marigold plugs. Greenhouse Grower,
March, pp. 34-38.

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.

Heins, R.D., and N. Lange. 1992c. How to store
salvia and ageratum plugs. Greenhouse Grower,
February, pp. 76-82.

Lange, N., R. Heins, and W. Carlson. 1991a.
Another look at storing plugs. Greenhouse
Grower, February, pp. 18-24.

Heins, R.D., and N. Lange. 1992d. One temp can
fit all. Greenhouse Grower, April, pp. 30-36.

Lange, N., R. Heins, and W. Carlson. 1991b. Storeplugs at low temperatures. Greenhouse Grower,
January, pp. 22-28.

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.

Lantz, C.W., 1989. A guide to the care andplanting of southern pine seedlings. Management
Bull. R8-MB39, U.S. Department of Agriculture,
Forest Service, Atlanta, GA.

Heins, R.D., N. Lange, T.F. Wallace Jr., and
W. Carlson. 1994a. Plug Storage. Greenhouse
Grower.

Nelson, L.J. 1983. Correct conditions extend
bedding plant marketability. The Great Lakes
Vegetable Growers News, October, pp. 8-9.

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 tostore alyssum plugs. Greenhouse Grower, March,
pp. 32-33.
Heins, R.D., and T. Wallace Jr. 1993b. How tostore New Guinea impatiens. Greenhouse Grower,
Fall, pp. 55-58.
Heins, R.D., and T.F. Wallace Jr. 1993d. How tostore vinca plugs. Greenhouse Grower, April, pp.
44-45.

649

Christmas Trees

Moisture Status of Cut Trees

Eric Hinesley and Gary Chastagner

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 aswell as environmental conditions (vapor pressure
deficit, temperature, wind) and cold hardiness.

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 astandard 6- to 7-ft tall (2 m) tree, the retail valueof 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. Thismeans that 75% of the trees experience some formof storage and shipment after harvest. Storage
and shipment times can be several weeks for trees
shipped between countries or less than one day fortrees 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 keepabilityof 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.
650

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 fromthe cut end of a twig encased in a heavy-walled
metal chamber. The drier the twig, the greater thepressure 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 orabout 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 (-28bar) 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 capacityof 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) foreastern 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 thatthreshold.

The values of V1 and V2 vary by species. In
addition, a pressure potential of -3.0 MPa (-30bar) does not correspond to the same value of MC
in various species. The time required to reach aparticular MC also varies by species. For example,
eastern red cedar and Atlantic white cedar dryvery fast when displayed under room conditions,whereas Fraser fir and noble fir dry much slower.
The latter species are regarded as long-lastingtrees, whereas the former have a short shelf-life.
The moisture status of the tree determines its
ability to rehydrate when recut and displayed inwater. Fresh-cut trees typically have an MC in
excess of 100%. When a fresh tree is recut anddisplayed in water, it typically gains weight,
reaching a MC 5 to 10% above the initial value.
Trees without water gradually lose moistureand 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 subsequentabscission 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 andFraser fir, tend to maintain MC and ψ close to theinitial value for at least 4 weeks. Species that havea short shelf-life, such as eastern red cedar andAtlantic white cedar, maintain a high water level
for about 1 wk and then begin to slowly dry evenwhile displayed in water. This process is reflectedby 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 andalso varies among species. Compared to otherspecies, true firs tend to use large quantities ofwater over extended display periods. For example,
a 6-ft (about 2 m) Fraser fir can easily use 4 qt ofwater 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 thetree is maintaining its initial water status. On theother hand, if there is a marked reduction in water
consumption, it probably indicates that the tree isbeginning to dry.

Additives
Many chemicals and home concoctions havebeen tested in hopes of prolonging the life of cut
Christmas trees. Additives are of little benefit andsometimes produce adverse effects. Additives
can undesirably increase water consumption bydisplayed 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 lowtemperatures. Induction of cold hardiness requires
photosynthesis, reduced temperatures, and shorterdays. 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 withproper care. It is not known why cold-hardened
trees keep better than nonhardened trees. Foliar
raffinose increases during fall, although theabsolute amount is small compared to sucrose.
The increase in raffinose is mostly a response651

to lower temperatures. The role of raffinose is
not clear, although in other plants it can reducethe 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 theirability 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 fromexposure to cold temperatures, they can exhibit
severe needle loss due to cold injury. The levelof damage depends on the level of cold hardinessof the trees, the rate of temperature drop, andthe lowest temperatures the trees are exposed
to. People should be aware that tree species, theenvironmental conditions prior to harvest, and theenvironmental conditions that trees are exposed toduring 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 incosmetic 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 whentrees 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 potentiallycause serious problems. States and countries
impose various quarantines in an effort to preventthe introduction or further spread of potentiallyharmful pests. For example, trees grown in areas
infested with the gypsy moth, European pine652

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 thesepests. Many quarantine problems can be avoided
by appropriate scouting, trapping, management
practices, and certification programs. Mechanicalshakers can be used to remove old dead needles
and certain types of insects. The failure to meetquarantine requirements can result in entire
shipments being rejected, causing great loss andinconvenience to producers and importers.
Fumigation. In some instances trees are required
to be treated prior to entry, especially in someforeign 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 ofChristmas trees to methyl bromide is limited.
Chastagner (1990) fumigated several species
typically grown in the Pacific Northwest withmethyl 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 willdiminish in the future, and alternatives are needed.
Increasing development of international markets
will increase the demand for procedures to ensurethat exported trees are pest-free.
Irradiation. Gamma radiation can be used tosterilize or kill insects at all stages of the life
cycle, including larvae and pupae within thewood. 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 periodof years. Dormant branches of Fraser fir, whensubjected to single doses of gamma radiation,
experienced significant needle loss at 0.10 kGy.
Massive needle loss occurred within 2 days forbranches that receive higher doses of radiation. In
addition, there was great intertree variation; forexample, for the 0.1 kGy treatment, needle loss
ranged from 5 to 100% for branches displayed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 virtuallycomplete 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 fourtimes that at 5 °C (41 °F).

Fire Safety
Fresh Christmas trees, if properly watered andmaintained, 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 firerisk, including ignition time, peak heat release rate
(PHRR), total heat released, peak smoke releaserate, 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 minof 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 whenremoved from the flame, it passed the test. If there

was any spread of the flame after the sample wasremoved from the flame, it failed the test. Thereis considerable interspecific variation in the MC
for ignition. In addition, there is often a largetransition zone of MC from the point of initially
failing the flammability test to the point of flash
ignition. For example, Douglas‑fir begins to failthe 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 failthe test. With proper care, winter-hardened noble
fir and Fraser fir can easily be displayed in waterfor 6 to 8 wk without becoming a fire hazard.
The use of flame retardants on trees is notrecommended unless required by law. Flameretardants can damage needles and increasemoisture loss from trees. The best way tominimize 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 thesurface of foliage, supposedly cause better needle
retention, but this has not been confirmed byresearch.
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
653

Table 1. Postharvest quality ratings for Christmas trees, displayed dry or in water(Trees are assumed to be cold-hardened.)		Species
Scientific name		
Arizona corkbark fir
Arizona cypress
Atlantic white cedar
Balsam fir
California red fir
Canaan fir
Colorado blue spruce
Concolor fir
Douglas-fir (coastal)
Douglas-fir (intermountain)
Eastern red cedar
Eastern white pine
European silver fir
Fraser fir
Grand fir
Greek fir
Korean fir
Leyland cypress
Monterey pine
Noble fir
Nordmann fir
Norway spruce
Pacific silver fir
Scotch pine
Shasta fir
Turkish fir
Veitch fir
Virginia pine
Western white pine
White spruce

Abies lasciocarpa (Hook.) Nutt. ssp.
arizonica (Merriam) E. Murray
Cupressus arizonica Green var. glabra(Sudw.) Little ‘Carolina sapphire’
Chamaecyparis thyoides (L.) BSP.
Abies balsamea L.
Abies magnifica A. Murray
Abies balsamea (L.) Mill. var. phanerolepis Fern.
Picea pungens Engelm.
Abies concolor (Gordon & Glend.) Lindl. ex Hildebr.
Pseudotsuga menziesii ssp. glauca (Beissn.) E. Murray
Pseudotsuga menziesii (Mirb.) Franco ssp. menziesii
Juniperus virginiana L.
Pinus strobus L.
Abies alba Mill.
Abies fraseri (Pursh) Poir.
Abies grandis (Douglas ex D. Don) Lindl.
Abies cephalonica Loud.
Abies koreana Wils.
× Cupressocyparis leylandii (Dallim. &A. B. Jackson) Dallim.
Pinus radiata
Abies procera Rehd.
Abies nordmanniana (Steven) Spach.
Picea abies (L.) Karst.
Abies amabilis Douglas ex Forbes
Pinus sylvestris L.
Abies magnifica A. Murray var. shastensis Lemmon
Abies nordmanniana ssp. equitrojani(Asch. & Sint. Ex Boiss.) Coode & Cullen(syn. Abies x bornmuelleriana Mattf.)
Abies veitchii Lindl.
Pinus virginiana Mill.
Pinus monticola Douglas ex D. Don
Picea glauca (Moench) Voss

Rating
Displayed—Dry† Wet

F

E

P/F
P
F
G
F
F
P/G*
P/F
F/G*
P
G
P
G
P
P
G

F/G
P/F
G/E
E
G/E
G/E
P/E*
G
G/E
F
G/E
G/E
E
G/E
G/E
G/E

F
F
G
P/G*
P
F
F/G
P/F

G/E
G
E
E
G
G/E
G
F/G

P/G*
G
F
G
P

E
E
F
G/E
G

Scientific names from Griffiths (1994).
Ratings: Excellent (E) has potential to last 4-6 wk under typical household conditions. Good (G) canlast 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.
654

unless applied at levels sufficiently high to render
trees qualitatively less acceptable to consumers bymaking them sticky. However, minor differences
sometimes occur. For example, drying of eastern
red cedar was slowed by latex colorant, but theoverall drying rate of trees was so fast that thedifference was of little practical significance.
Species ComparisonsSome 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 speciesof Christmas trees is given in table 1. Ratings inthis table should be used as a guide, given thatthe 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 andthe period after placement in water. Some trees
endure well in both phases, such as noble fir andFraser fir. Others do poorly when displayed dry
but endure well in water, such as white spruceand 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 marketingor 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, suchas Nordmann fir.

Tree Handling Recommendations for
Growers and Retailers
Cut Christmas trees can deteriorate under theeffects of heat, wind, sunlight, and extremechanges in temperature. Thus, reducing exposure
to these elements should be the goal of every
grower and retailer. Below is a series ofrecommendations 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 theweather is sunny and warm. Drying can bevery 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 notclear 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 andthus reducing the compaction of trees helps
minimize these problems.
• Avoid baling wet trees under warm
temperatures because doing so can lead topremature 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 temperatureof 33 °F to 50 °F (1 °C to 10 °C), high RH of
85 to 95%, and darkness.
• Use refrigerated trucks, if possible, especiallyon hauls exceeding 400 miles or whenmoving 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 thewind, and standing in water.
• On retail lots, store trees upright or inshallow piles in a shady, cool place outof high traffic areas. If permanent shadeis unavailable, use a tarp or shade cloth655

suspended above the trees and down thesides with at least a 2-ft (61 cm) air-space forventilation.
• Minimize or eliminate walking on baled
trees because it breaks limbs and leadersand crushes foliage. Be especially carefulhandling frozen trees: They are very brittle.
• Trees on display in retail lots in warm market
areas can be misted or sprayed with waterat night to reduce the moisture lost during
daylight hours. Misting trees on the surfaceof storage piles may also be beneficial, but
soaking trees can result in severe mold anddeterioration problems.
• Trees hauled long distances on open trucks
should be smoke-tarped on the front andcovered 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 selltrees such as coastal Douglas-fir in thesetypes of markets unless they can be protectedfrom exposure to potentially damaging
temperatures.

References
Chastagner, G.A. 1990. Insect contaminants—a
problem that is limiting the market for PacificNorthwest 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 thedamage threshold. HortScience 21:1174-1175.

Further Reading
AMS [U.S. Department of Agriculture,
Agricultural Marketing Service]. 1989. UnitedStates standards for grades of Christmas trees.
U.S. Department of Agriculture, Washington, DC.

656

Ahrens, J.F., and G.R. Stephens. 1975. Effectof 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 flammabilityof Christmas trees. Connecticut Agricultural
Experiment Station Bull. no. 760, New Haven,
CT.
Blankenship, S.M., and L.E. Hinesley. 1990.
Tolerance of controlled atmosphere storageof 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 inWashington 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):3135.
Chastagner, G.A. 1986. Effect of postharvest
moisture stress on the keeping qualities of
Douglas-fir Christmas trees. HortScience 21:485486.
Chastagner, G.A. 1987. Trees of the future: treekeepability research needs. Amer. Christmas TreeJ. 31(2):30-34.
Chastagner, G.A. 1989. Maximizing your sales bykeeping 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. PacificNorthwest Christmas Tree Assoc., Northwest
Lookout 17(3):29-34.

Chastagner, G.A., and R.S. Byther. 1984. Impact
of Swiss needle cast on postharvest hydration andneedle retention of Douglas-fir Christmas trees.
Plant Dis. 68:192-195.
Chastagner, G.A., and K. Riley. 1990. Effectof 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 offoliar sprays of antitranspirants on the postharvest
quality of Douglas-fir Christmas trees. California
Christmas Tree Assoc. Bull. 143:36-40.

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):1619.
Hinesley, L.E., and W.T. Huxster Jr. 1991. Retailmerchandising of North Carolina Fraser fir.
Christmas Tree Notes, CTN-017, North Carolina
Cooperative Extension Service, Raleigh, NC.

Davis, T.S., and T.A. Fretz. 1972. The antitranspirant effect on harvested Christmas trees.
Amer. Christmas Tree J. 16(1):3-5.

Hinesley, L.E., and L.K. Snelling. 1991. Vapor
pressure deficit, temperature and light affectpostharvest drying of Fraser fir and eastern whitepine. HortScience 26:402-405.

Dugle, J.R. 1986. Growth and morphology inbalsam fir: effects of gamma radiation. Can. J.
Bot. 64:1484-1492.

Hinesley, L.E., and L.K. Snelling. 1993. “CropLife” does not slow postharvest drying of Fraser
fir and eastern redcedar. HortScience 28:1054.

Griffiths, M. 1994. Index of Garden Plants: The
New Royal Horticultural Society Dictionary.
Timber Press, Portland, OR.

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. 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 23:589591.
Hinesley, L.E. 1990. Grower postharvest handlingof Christmas trees. Christmas Tree Notes, CTN015, North Carolina Cooperative Extension
Service, Raleigh, NC.
Hinesley, L.E. 1990b. Latex colorant slows dryingof redcedar Christmas trees. HortScience 25:673674.
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 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 anddormancy. Amer. Christmas Tree J. 40(2):24-26.
Koelling, M. 1998. Christmas trees do notcause fires: some facts! Amer. Christmas Tree J.
42(4):4,6,8,10,12,14,16,18-21.
657

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 andNorway 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.

658

Cut Flowers and GreensMichael 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 aregrown and harvested as cut flowers or florist
greens; these include ferns and lycopods,
gymnosperms, and angiosperms. Because ofthis diversity, these guidelines include a generalreview of postharvest requirements for cut
ornamentals, followed by brief summaries of therequirements of a selection of the most common
materials used in commercial floriculture. The
references cited are usually the most recent reporton a particular crop and therefore provide anentree to the literature that is the basis for therecommendations.

Quality Characteristics and Criteria
Cut ornamentals are complex plant organs, inwhich 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 scapesand stems. In evaluating factors that affect the lifeof 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 formany ornamentals. Flowers can be divided into
several categories on the basis of their senescence.
Some flowers are extremely long-lived, especiallyin the Asteraceae and Orchidaceae families, whileothers 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 supplyof water. Rapid wilting of shoot tips, leaves, andpetals results from an obstruction of the watersupply 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). Leafyellowing is a complex process that may becaused 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 Stead1997). Very often, this problem is associatedwith the presence of ethylene in the air, but otherenvironmental factors may also be involved.

Factors Affecting Postharvest Quality
Maintaining the freshness of cut flowers and otherornamentals requires an understanding of thefactors that lead to their deterioration. A numberof these factors are different from those that apply659

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 greensare patented cultivars, characterized by specificattributes 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 undercommercial conditions. There is relatively little
published information comparing the postharvest
life of different ornamental cultivars (Van Der
Meulen-Muisers et al. 1999).

The quality and vase life of many cut flowers canbe improved by pulsing them immediately after
harvest with a sugar solution. Pulsing is doneby standing the cut flowers in the solution fora short period, usually less than 24 h, and often
at low temperature. Typical examples include
tuberose, for which storage life and opening aredramatically improved; gladiolus, for which
flowers open further up the spike, are bigger, andhave a longer vase life; and sweet peas, for whichvase 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 thevase solution used at the retail and domestic level.
Potted plants are able to provide their own foodsupply through photosynthesis if they are held in
adequate light conditions.

Light
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 irrigatedand fertilized will produce flowers that look betterand perform better in the vase. However, the large
leaves on roses grown under supplementary lightwith CO2 fertilization make them more susceptible
to postharvest wilting.

The presence or absence of light during storageis generally not a concern except in cases where
yellowing of foliage is a problem. The leaves ofcertain 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 themin 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).

Food Supply
Water Supply
Starch and sugars stored in the stem, leaves,and petals provide much of the food needed forcut‑flower opening and maintenance. The levelsof 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, becausetemperatures are lower, plant water content ishigher, and a whole day is available for processing
the cut flowers.
660

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 coolingof 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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).

water acid (pH ~3.5). Citric acid is commonlyused as a safe acidulant.

Water Quality
Air embolism. Air embolisms occur when small
bubbles of air (emboli) are drawn into the stem atthe 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 beremoved 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-coldsolution (0 °C), placing the stems in deep (>20cm)
water, or treating the flowers with a detergent“pulse.”Growth Tropisms

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 forbacteria, 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—

Certain responses of cut flowers to environmental
stimuli (tropisms) can result in quality loss. Most
important is geotropism (bending away fromgravity) 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 uprightwhenever possible.

• Using clean water to make postharvest
solutions• Cleaning and disinfecting buckets• Using white buckets—dirt is easier to see ina white bucket.
Include a biocide in all bucket and vasesolutions. Ca(OCl)2, NaOCl, Al2(SO4)3, andsalts of 8-hydroxyquinoline are commonly usedbactericides. 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 drasticallyreduced 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 theChemicals commonly found in tap water are toxic
to some ornamentals. Sodium, present in highconcentrations in soft water, is toxic to carnations
and roses and will cause salt burn (burning of theleaf 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 1µL L-1) to damage these flowers.

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,661

transport, or distribution. This technique has many
advantages, including reduced growing time forsingle‑harvest crops, increased product packing
density, simplified temperature management,
reduced susceptibility to mechanical damage, andreduced 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 careand handling. Objective standards such as stem
length, which is still the major quality standard
for many flowers, may bear little relationship toflower quality, vase life, or usefulness. Weightof the bunch for a given length is a method thathas 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 thefactors 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 foranthuriums, orchids, and some other specialty
flowers. The number of flowers in the bunch
varies according to growing area, market, andflower species. Groups of 10, 12, and 25 arecommon for single‑stemmed flowers. Spray‑typeflowers are bunched by the number of open
flowers, by weight, or by bunch size. Bunches areheld together by string, paper‑covered wire, orelastic 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 (smoothside towards the flowers), and polyethylene
662(perforated, unperforated, and blister). Sleeves canbe preformed (although variable bunch size canbe a problem), or they can be formed around eachbunch 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 bepacked in the box, and this may reduce physicaldamage. In addition, flower heads can be placedat both ends of the container for better use of
space. With this kind of flower placement, wholelayers of newspaper are often used to preventthe layers of flowers from injuring each other.
The use of small pieces of newspaper to protect
only the flower heads, however, is probably thebetter practice, since it allows for more efficientcooling of flowers after packing. It is criticallyimportant that containers be packed in such a
way that transport damage is minimized. Some
packers anchor the product by using enoughflowers and foliage in the box so that flowers in
the package, after banding, are immobilized by
the surrounding material. To avoid longitudinalslip, packers in many flower-producing countries
use one or more “cleats.” These are normallyfoam‑ or newspaper‑covered wood pieces that areplaced 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 toprevent geotropic curvature that reduces theiracceptability. Cubic hampers are used for uprightstorage of daisies and other flowers. A new
packaging system uses “proconas”—plastic bases
and a cardboard sleeve—to allow transport offlowers upright in water. This system is more
expensive than traditional boxes, and less canbe packed in it. However, the presence of water
may improve flower quality when they are nottransported under proper temperature conditions.

Specialty flowers such as anthurium, orchid,ginger, and bird of paradise are packed invarious ways to minimize friction damage
during transport. Frequently, flower heads areindividually 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 thequality of harvested flowers is ensuring that they
are cooled as soon as possible after harvest andthat 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, tropicalorchids) should be held at temperatures above 10°C (50 °F).

time for forced‑air cooling ranges from 10 to
40 min, depending on product and packaging.
Flowers should be cooled for three half-coolingtimes, by which time they are 7/8 cool.
If the packages are to remain in a coolenvironment 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 polyethylenecaskets, foam‑sprayed boxes, or boxes with thevents resealed. Ice that is used after precooling isonly 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 canbe achieved using a “tunnel” forced-air coolingsystem.

Once packed, cut flowers are difficult to cool.
Their high rate of respiration and the hightemperatures 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 tocool 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 coolstorage 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 packthem 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.

Chilling Sensitivity

Forced‑air cooling of boxes with end holes orcloseable flaps is the most common and effective
method for precooling cut flowers. Cool air issucked or blown through the boxes. Care must be
taken to pack them so that air can flow through thebox and not be blocked by the packing material or
flowers. In general, packers use less paper whenpacking flowers for precooling. The half‑cooling

Ethylene Production and Sensitivity

Some tropical crops such as anthurium, bird ofparadise, 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 soakingof the petals, and in severe cases collapse anddrying of leaves and petals. Special care needs tobe taken with tropical flowers shipped in a mixed
load. The flowers should be packed in plenty of
insulating material (an insulated box packed withshredded newsprint, for example). These flowers
should not be precooled. If they are to be shippedby refrigerated truck, they should be placed in the
middle of the load, away from direct exposure tocooling air.

A number of flowers, especially carnations,gypsophila, and some rose cultivars, senesce
rapidly if exposed to minute concentrationsof ethylene gas. A number of flowers (such as
carnations and sweet peas) produce ethylene
as they age, and this endogenous ethylene663

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 (nLL-1) in the vicinity of sensitive ornamentals cancause damage and therefore should be avoided.
Storage and handling areas should be designed
not only to minimize contamination of theatmosphere with ethylene, but should also haveadequate ventilation to remove any ethylene
contamination that may occur. Treatment withthe anionic thiosulfate complex of silver (STS) orwith 1-methylcyclopropene (1-MCP) inhibits thedeleterious effects of ethylene whether a productof atmospheric contaminant (exogenous) or
produced by the flower (endogenous) (Macnish etal. 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 evenfor a few days is closely correlated with their
respiration during storage. Rapid coolingand proper refrigeration are thus essential tomaintaining quality and satisfactory vase lifeof 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 inwater 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.

664

Controlled Atmosphere (CA)Considerations
There have been relatively few reported benefitsof CA storage for cut flowers. Any considerationof the use of CA must follow achievement ofproper temperature control and elimination of theeffects of Botrytis during storage. Recommended
atmospheres vary from pure nitrogen (daffodils) tomore conventional atmospheres (carnations).

Retail Outlet Display Considerations
The simple way to ensure rapid rehydration of all
but the most difficult or desiccated flowers is torecut the stems and place them in a clean bucketof 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 withtemperature (Cevallos 1998). Various cultivarsof the same species may have quite different
respiration rates and may respond differently totemperature.

Physiological Disorders

Special Considerations

There are relatively few recognized physiologicaldisorders in the postharvest life of cut flowers andfoliage. “Topple” of tulips, a collapse of the scape,is a disorder associated with low calcium statusof the flowers. Petal blackening in some red roses
has been suggested also to be associated withinadequate calcium and perhaps boron nutrition.

Many special considerations that arise from theunique physiology, handling, and marketing of cut
flowers and foliage are addressed in the following
section for individual crops.

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 handlingareas often results in condensation of wateron the harvested flowers. The most commonly
encountered disease organism, gray mold (Botrytis
cinerea), can germinate wherever free moisture ispresent. In the humid environment of the flower
head, it can even grow, albeit more slowly, at nearfreezing. 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 ProductThere is a small market for edible flowers, andsome high-value fresh-cut salads include petals in
the mix. Obviously chemicals not registered forfood use may not be used in postharvest handlingof flowers intended as food.

Guidelines for Individual Crops
The following section contains guidelines forindividual crops. The content is organizedby 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
DaffodilDelphinium, 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

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Lily, Asiatic lily, Oriental lily
Lisianthus, prairie gentianMarguerite 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 astershould 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, andstraightness, it is suggested that the flowers in abunch should be uniform. The flower head should
be symmetrical, and leaves should be bright green.
The minimum acceptable number of florets perstem varies with cultivar, but is typically 7 to 10.

Ethylene Sensitivity
Alstroemeria

Alstroemeria flowers are ethylene sensitive.

Scientific Name and Introduction
Pretreatments
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 oftypes and colors. All have a long postharvest life,
typically terminated by petal wilting or drop andyellowing of the leaves. The Swedish Consul in
Spain, Klas Alstroemer, had seeds of this species
brought to Europe in 1754. The famous planttaxonomist 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 (asin young plants of ‘Regina’), the stem should becut. If flowers are cut, the remaining stem should
be removed later. At least one flower per stem
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Although untreated alstroemeria flowers have along vase life, petal drop (particularly a problem
if there is ethylene in the environment) can bedelayed 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] orcytokinins).

Storage Conditions
Alstroemeria should be stored at 0 to 1 °C (32to 34 °F). Present information suggests that
alstroemeria can readily be stored for up to 1 weekat 1 °C (34 °F).

Packing
Alstroemeria are normally bunched in groupsof 10, sleeved, and packed in horizontal boxes.
Flower pedicels are affected by gravity and will
bend upwards if temperature control duringstorage is poor.

Special Considerations

Pretreatments

When recutting, remove the whitish or blanchedbottom portion of the stem, if present, formaximum solution uptake and life. Leaf removal
will reduce vase life if enough flowers are notpresent for solution uptake. Since Alstroemeria
is a member of the Amaryllidaceae, a botanicalfamily from which many pharmaceutical products
are derived, it’s not surprising that some humans
get allergic dermatitis from this species.

Pretreatment with STS or MCP prevents thedeleterious effects of ethylene.

Anemone, Windflower

Packing

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 anancient Greek name meaning windflower, fromanemos for wind.

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.

Flowers are usually packed in standard horizontal
fiberboard boxes.

Special Considerations

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.

The anemone’s prominence and beauty inarrangements is a double-edged sword becauseof the flower’s relatively short vase life. It ispreferable not to use anemones as focal points.
Keep stems wrapped during rehydration to help
keep them straight. There is no scientific basis forthe 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 thedaffodils.

Grading and Bunching

Anthurium, Flamingo Flower

Anemones are normally sold in bunches of 10
stems.

Scientific Name and Introduction

Quality Characteristics and Criteria

Ethylene Sensitivity
Ethylene exposure causes petal shatter andreduced vase life.

Anthurium andraeanum. With their brilliant glossy
spathes (the brightly colored ornamental part of
the flower) and slender spadices, anthuriums areclassic tropical flowers. New cultivars provide
a wide range of colors and forms, and their vase
life can be very long. The elegant blooms of thistropical aroid are produced and sold throughout
the world. The true flowers are found on thespadix, the upright organ in the center of the
spathe, which is the decorative petallike organsurrounding the spadix. Although anthuriums are667

sensitive to low temperatures, they have a longvase life when properly handled. The end of theirvase life is usually the result of inability to draw
water from the vase solution and is associatedwith 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 isalso 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 andproceeds upwards. Spadices with open flowers
are noticeably rough. Although producers in somecountries harvest anthuriums when as little as
20% of the spadix is rough, Hawaiian growers
harvest flowers when only 25% of the spadix isstill smooth (75% of the flowers are thereforeopen). Harvesting anthuriums when more mature
increases overall vase life. Avoid flowers thatshow 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 areeasily 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.

668

Ethylene Sensitivity
Anthuriums are not affected by exposure to
ethylene, and anti-ethylene treatments provide nobenefit.

Pretreatments
Some researchers recommend pretreatment toincrease the vase life of anthuriums, but somecultivars (such as ‘Osaki’) achieve maximum
vase life with DI alone. It seems probable thatvase-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 withfresh 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 tochilling 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 precooledwith other flowers nor held in low-temperaturecool-rooms. Anthuriums shipped in mixed loads
at low temperatures should be protected fromchilling exposure by appropriate insulation (forexample, wrapping the flowers in newsprint andpacking 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 incontrolled atmosphere. Vase life after storage wasincreased by 50% when flowers were stored at
12.5 °C (55 °F) in 2% O2 for up to 2 weeks.

Packing

Grading and Bunching

Anthuriums are commonly packed in moist
shredded newsprint or other shredded paper.
Major damage during transportation is the resultof spadices puncturing the spathe of neighboringflowers in the pack. Many producers now sheathe
the flowers in small plastic bags and pack theanthuriums more densely in the box.

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 placedin sleeves.

Ethylene Sensitivity
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 andother 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 lilyfamily, 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 anduniformly green, that there are no yellow leaves,and that leaves do not fall from the fronds when
they are shaken.

Exposure to ethylene will cause leaf-fall insome 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 duringstorage. 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 orplastic 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 aserious problem. To avoid yellowing and leaf fall,
avoid prolonged storage. Certain preservative
solutions aggravate premature leaf yellowing.
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However, preservative should be used in all
arrangements containing this fern, as other itemsin 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 usedin horticulture. A. ericoides ‘Monte Casino’ isparticularly important in the florist trade. Anotherimportant aster for florists is the China aster,
Callistephus chinensis.

Pretreatments
The vase life of asters is often limited by poor
water relations, demonstrated by wilting of theflower or buds. Their vase life has been shown
experimentally to be extended by a 10-sec
pretreatment with a high concentration (1,000µL 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
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 anindication of improper storage and/or growing
conditions.

Grading and Bunching
There are no grade standards as such, apart fromthe standard quality attributes of stem length,
foliage quality, uniformity, and freedom fromdefects. 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).

Asters are packed in traditional flower boxes,
hampers, or proconas.

Special Considerations
It is very difficult to make broad flower carerecommendations for asters because of the large
number of species and cultivars. Keep stems andvase solution clean. It is especially important withasters to remove leaves that might be in the water
since bacteria grow quickly on leaves that areunderwater, contaminating the vase solution andleading to early wilting. Treat with a hydrating
solution, and prepare the preservative solution
properly to minimize contamination by debris andmicroorganisms.

Baby’s Breath, Gypsophila
Scientific Name and Introduction

Ethylene Sensitivity
Members of the Asteraceae are generally
unaffected by exposure to moderate concentrationsof ethylene.

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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 sunlightand will brown and shrivel easily if subjected tothese stress conditions. On the other hand, damp
or rainy conditions increase the risk of gray mold
(Botrytis) and Phytophthora root rot. Gypsophila

is Greek for “gypsum-loving,” in reference to thisspecies’ good growth performance in high-calcium
soils.

benefit because stem blockage prevents uptake. Be
sure stems are rinsed and recut underwater before
placement in STS.

Quality Characteristics and Criteria

Storage Conditions

Gypsophila plants produce flowers on large
panicles whose individual flowers open over aconsiderable time period. Flowering stems areusually cut 20 to 40 cm (8 to 16 in) long. The
degree of maturity at harvest is determined bywhether the flowers are intended for the freshmarket 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 ormarketed within 24 h. Stems are cut when 20 to
30% of the flowers are open if they are to be driedlater or held longer than 24 h. Purchase gypsophilathat has plenty of unopened buds and shows nosigns of water stress, wilting, or disease (brown
florets).

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) totreat with appropriate fungicides. Stems with
about 50% of their flowers open can be kept in apreservative solution (200 µL L-1 Physan) at 1 °C
(34 °F) for up to 3 weeks.

Grading and Bunching

Special Considerations

Stems are gathered into field bunches using rubberbands 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.

Exposure to ethylene causes wilting of open
flowers and sleepiness of opening buds.

Gypsophila harvested in the bud stage (5% offlowers 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 shouldbe held at about 20 °C (68 °F) and 50% RH andwith 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 thendried by hanging bunches upside down in a warm
dry environment.

Pretreatments

Bird of Paradise

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 asolution containing Physan will maintain excellent
display life for several weeks as new buds open on
the panicle. However, STS sometimes is of little

Scientific Name and Introduction

Ethylene Sensitivity

PackingGypsophila may be packed in horizontal boxes or
hampers. Thirty bunches are packed in a standard
box.

Strelitzia reginae. The bird of paradiseinflorescence consists of a boat-shaped bract
containing a series of four or five flowers, so whenan exposed flower withers, another one can bepulled out. Few cut flowers have this capability.
Traditionally, Southern California growers bag
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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 insideor 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 firstemerging orange flowers can barely be seen
through the paper bags. The stems are pulled at
this point. Stems can also be harvested in the tightbud stage before the first flowers emerge. At thisstage the inflorescence is swollen, and there isa slight orange crack on the upper surface. The
inflorescence is mature at the tight bud stage,
and this is the optimum stage for harvest fromthe 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 isoften 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 diseaseproblems is increased.

Ethylene Sensitivity
Strelitzia flowers are insensitive to ethylene andtheir life is not improved by treatment with STS or
1-MCP.

Pretreatments
Flower longevity can be substantially increasedby pulsing buds or flowers for 24 h (48 h is evenbetter) 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 isdifferent from most other flowers. Storage below
this recommended range can result in chilling
disorders, the appearance of brown lesions on theflowers and bracts, and the failure of the flower
to open properly. For short-term storage, holdthe flowers at room temperature or in a tropicalstorage room at 12.5 °C (55 °F). Strelitzia flowers
harvested in the tight bud stage will open and havesatisfactory 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
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 areevenly trimmed. A paper wrapper is placed aroundthe bunched inflorescences to further protect theflowers.

672

Waxed paper bags on each inflorescence andthe 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 normallyprovide good display life.

Bouvardia
Scientific Name and Introduction
Bouvardia spp. Bouvardia flowers are a relatively
recent addition to the florist’s palette. Their brightsalmon, red, and white color range and interestingflower form offer interesting design possibilities.
The genus is named after Charles Bouvard (15721658) who was physician to Louis XIII and
superintendent of the Royal Gardens in Paris.

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).

Quality Characteristics and Criteria
PackingBouvardia 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 forbouvardia, but top quality flowers will be uniform
in maturity and color, free of defects, and havegood quality foliage and long stems. Flowers arenormally bunched; bunches contain 10 stems andare sleeved prior to packing.

Ethylene Sensitivity
Accelerated wilting and abscission result fromexposure 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 theeffects of ethylene. Treatment for 4 to 24 h with

Bouvardia may be packed in horizontal boxes orproconas.

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 bloomsof Zantedeschia aethiopica have long been an
important cut flower, and new green-tinged
and differently shaped variants are increasingly
important. The hybrid “minicallas,” with theirelegant shape and wide range of colors, continue
to increase in importance as cut flowers andpotted 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.
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Quality Characteristics and Criteria

PackingCallas 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 fromthe rhizome and recut to ensure adequate water
uptake. The spadix (the thick fleshy inflorescenceinside the showy spathe) should be visible at thetime of purchase. Watch for bruising of the fleshy
stems due to packaging. If cut too tight, flowers
will usually not open properly.

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 heldat the proper storage temperature.

Special Considerations
The minicallas have fewer postharvest problems
and are generally easier to handle and use becauseof their smaller size.

Grading and Bunching
Quality callas have long stems, are uniform inmaturity and color, and have no defects such as
damage to the spathe or spadix. Both large andmini callas are normally bunched in groups of
10. Minicallas are sometimes sleeved to provide
additional protection.

Carnation, Miniature Carnation
Scientific Name and Introduction

Callas do not require any pretreatments.

Dianthus caryophyllus. Long one of the mostimportant of the commercial cut flowers, thecarnation has benefited enormously from theuse of STS, which can increase its vase life 2to 3-fold. The wide range of colors and forms,
especially for miniatures, allows florists andconsumers to use and enjoy them in many ways.
The genus name, Dianthus, derives from theGreek for “flower of love.” Carnations used to becalled “clove gilly-flowers” in reference to theirintense clovelike aroma. Some modern cultivars
are very fragrant and are used to make perfumes.
Carnations can be stored longer than any otherflower and can be opened to high quality flowers
from very tight buds. Miniature carnations are also
referred to as spray carnations.

Storage Conditions

Quality Characteristics and Criteria

Callas should be stored at 0 to 1 °C (32 to 34 °F).

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 arenormally harvested with the outer petals between

Ethylene Sensitivity
Calla flowers are not ethylene sensitive, althoughsome researchers have shown positive effects of
STS pretreatment. Contrary to popular belief,callas do not produce significant quantities of
ethylene.

Pretreatments

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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 fromoverhead cables to tractor-hauled trailers designed
to hold slings. Standard carnations ship better andlast longer if purchased in the bud stage, while
miniature carnations should be purchased whenat least one flower per stem is open. Fragrantcultivars have more consumer appeal.

Grading and Bunching
Both standard and miniature carnations are gradedby stem strength, stem length, bloom diameter,and freedom from defects. Stem strength isdetermined by holding the stem horizontallyat a point one inch above the minimum length
for the grade. If the deviation of the flower
head is more than 30° from horizontal (withthe natural curvature down), the flower isconsidered defective. Other defects include
slabsides, bullheads, blown heads, singles, sleepy
appearance, splits, discoloration, and damage
from insects and diseases. Standard carnations arebunched and tied at the base and at least one otherplace 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 aminimum 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 bunchand reduce the risk of the neck breaking.

modified by the addition of a mutation of theethylene-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 whencarnations 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 ina solution containing 7% sucrose and 200 µL L-1
Physan. The buds should have been treated firstwith 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 thanmature flowers. Flowers or buds for storage should
be of the highest quality and absolutely free ofpests 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 andnewspaper. 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.

Ethylene Sensitivity
Carnations are ethylene sensitive, and exposure to
ethylene causes premature petal wilting referred
to as “sleepiness.” Some newer cultivars are lesssensitive to ethylene than the standard ‘Sim’
types, and carnations have now been geneticallySpecial Considerations
Spray carnations do not always respond well to
STS because the different flower maturities do nottake up the STS solution equally. It is difficult torecognize water-stressed carnations, but severe675reduction in vase life is the result; so keep themhydrated when held above 0 to 1 °C (32 to 34 °F).

open, as these flowers will last longer than ones
harvested when tighter.

Chrysanthemum, Florist Mum

Grading and Bunching

Scientific Name and Introduction

Standard chrysanthemums are graded by lengthand packed individually. Spray types are gradedby length and bunched. Standards or disbuds ofequal 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 thegreenhouse before the buds open.

Dendranthema × grandiflorum. Less important
than formerly, but still an important cut flower,
chrysanthemums (which come in a wide rangeof colors and forms, including standard andspray, 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.”Ethylene Sensitivity
Quality Characteristics and Criteria
Chrysanthemums are not sensitive to ethylene.
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 failureof 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 greaterand opened into full-sized flowers. Spray varieties
can be harvested when most of the petals on themost 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. Pinchedspray chrysanthemums can be pulled from thesoil and then cut to correct length. Leaves are
removed from the lower third of the stems.
Proper rehydration is vital for good vase life ofchrysanthemums that have been stored or shipped
long distances. Remove chrysanthemum bunchesfrom 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
676

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 acommon, effective germicide, but it discolors thestem 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 thestem 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 nitrateis, however, absorbed into the stem and becomes alasting germicide throughout the life of the flower.

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, and1.6-cm (4-in) buds for up to 3 weeks, at 0 to 1
°C (32 to 34 °F). Bud-cut stems that are held incold storage beyond the recommended time candevelop 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.

short vase life that cannot as yet be increased
substantially with standard postharvest treatments.
Narcissus is a classical Latin name, from theGreek; perhaps, as the origin suggests, an allusion
to narcotic properties. It is not clear whether it wasnamed 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 thewhole plant may be removed and the bulb andleaves then cut from the flower spike. Flowers
should be purchased in the pencil to goose-neckstages. These terms refer to flower position
relative to the stem; pencil being straight up andgooseneck bent downwards to about a 45° angle.

Grading and Bunching
Special Considerations
The main postharvest problems forchrysanthemums are premature foliage yellowing,
wilting, and the failure of the flowers to fully
open. Yellow foliage is cultivar specific and iscaused 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; makesure these stems are cut above this woody tissue inorder to facilitate water uptake, delay wilting, andextend end-user life.

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 theproper storage temperature. Although there are
no formal grade standards for these flowers, themost important quality attributes are maturity,
uniformity of color, and freedom from damage or
disease. Flowers are normally bunched in groupsof 10 or 25, tied with twist-ties, and sleeved in
paper or plastic.

Ethylene Sensitivity
Daffodil
Scientific Name and Introduction
Narcissus cvs. daffodils—symbol of spring andknown for their bright yellow, orange, red, pink,
and white colors—are garden favorites world
wide. Unfortunately, these flowers have relatively

Senescence of these flowers is accelerated
by exposure to ethylene, although theirnatural 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.

677

Pretreatments

Delphinium, Larkspur

Pretreatment with 1-MCP or STS can help extend
vase life of flowers that are likely to be exposed toethylene.

Scientific Name and Introduction

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 canbe 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 thisway 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 incontainers that permit rapid cooling of the flowers,
such as fiberboard boxes.

Delphinium, Consolida spp. The tall spikes ofdelphinium and the smaller spikes of larkspur areimportant accent flowers with colors ranging fromwhite 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 andarranging to remove dirt and debris.

Grading and Bunching
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 thecorrect storage temperature.

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 anaverage of 10 stems per bunch.

Ethylene Sensitivity
Special Considerations
Daffodils exude a gelatinous (slimy) substancethat, 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 withother flowers and used (even recut if required)in arrangements without affecting the life of theother flowers.

678

Delphiniums are very sensitive to ethylene, whichcauses 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 themfrom exposure to ethylene. Because flowers areon spikes and are therefore at different maturity
stages at the time of anti-ethylene treatment, STS
may be more effective than 1-MCP.

Storage Conditions

Grading and Bunching

Delphinium and larkspur should be stored at 0 to
1 °C (32 to 34 °F). For longer term storage, theyshould be wrapped in perforated polyethylene to
reduce water loss.

There are no formal grade standards for
Chamaedorea, but uniformity, size, color, andabsence of defects are important criteria of quality.
Bunches of emerald palm contain 25 stems.

Packing

Ethylene Sensitivity

These flowers are often packed in hampers withor without water, but they may also be packed instandard horizontal boxes. They are somewhat
sensitive to gravity, so horizontally packed flowers
should be precooled and maintained at proper
holding temperatures.

Exposure to ethylene has no deleterious effects on
Chamaedorea fronds.

Pretreatments
No pretreatments are recommended for
Chamaedorea fronds.

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 membersof the palm family (coconut, date-palm, andoil-palm) make up the commercially important
species for food consumption in North America.

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.

Quality Characteristics and Criteria

Special Considerations

Chamaedorea palms are harvested in the wild aswell as being produced in plantations. Fronds are
harvested when fully expanded, mature, and darkgreen. Fronds of Chamaedorea should be darkgreen, clean, and uniform. Avoid fronds whose
leaf tips show marginal necrosis or dead areas andfronds that are beginning to turn yellow.

Early death of the fronds, drying, and inrolling ofindividual 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.

679

Eucalyptus, Silver Dollar Tree

Storage Conditions

Scientific Name and Introduction

Eucalyptus foliage should be stored at 0 to 1 °C
(32 to 34 °F).

Eucalyptus spp. The silvery-green leaves of thejuvenile form of Eucalyptus pulverulenta are avery 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, coloredstamens.

Packing
Eucalyptus is normally packed in horizontal
fiberboard boxes without additional packing
materials.

Special Considerations
Quality Characteristics and Criteria
As with other foliage, eucalyptus performs betterin 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, andwater-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.

680

Handle this species with gloves to prevent handsfrom 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 becauseof its strong fragrance. In fact, most species
and cultivars do not produce excessive amountsof ethylene gas, although some will produce
potentially detrimental quantities of ethylene ifthey 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 areinvestigating the possible use of eucalyptus asflowering 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 landscapespecies. As foliage, mature branches are long
lasting, provide a piney fragrance, and are often
used in arrangements during the Christmas season.

Quality Characteristics and Criteria

Special Considerations

Branches should be harvested when tips andneedles are mature. Soft green growth is more
likely to wilt in the vase. Branches should bemature, with uniform dark green foliage. Avoid
bunches with fungal growth or whose needles are
falling off.

Antitranspirant dips have not been shown to
reduce water stress or to extend user life. Despite
their strong aroma, these foliage materials havenot been demonstrated to produce ethylene. If they
are infected by fungi, it is possible that they may
produce ethylene, but otherwise they are safe tostore with ethylene-sensitive flowers.

Grading and Bunching
Freesia
There are no grade standards for conifer branches
and Christmas greens. Quality foliage is darkgreen and well hydrated and shows no abscission
or fungal infection.

Ethylene Sensitivity
Conifer branches are not usually affected byexposure to ethylene and contrary to what
is commonly suggested, do not produce any
ethylene.

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
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 inplastic to avoid condensation and rots.

Stems are harvested when the first flower
colors and opens. Several flowering stems may
be harvested from one plant. In that case, theuppermost flower stem should be cut just above
the junction of the desired lateral flowering stem.
When the lateral stem reaches maturity, it too isharvested. The upper flowering stem will havemore flowers per stem and better postharvest life
than lateral flowering stems. One or two florets
per stem should be just beginning to open at thetime 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 havegood postharvest characteristics.

Packing
Because of the low value and relative hardinessof these materials they are usually packed loose
in horizontal fiberboard boxes without any
protection.

Grading and Bunching
There are no standard grades for freesias, but they
may be graded according to maturity, number offlowers per stem, and the length of stem. Quality
freesias have at least seven florets per spike and681

have long, straight stems. Flowers are sold inbunches of 10 stems, usually of the same color.

Gerbera, Transvaal Daisy
Scientific Name and Introduction

Ethylene Sensitivity
The open florets on freesia inflorescences are notaffected by exposure to ethylene, but the effectsof this gas are seen in young buds, which fail todevelop.

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 flowersthat 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 uprighthampers.

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 causesignificant ethylene production and reduce life.

682

Gerbera jamesonii and hybrids. Cut gerbera
flowers, known for their remarkable variety incoloration and form, are an increasingly importantpart of the florists’ palette. Their postharvest
life can be substantial if they are given proper
postharvest conditions, but they are sensitive togravity, to light, and to bacterial contamination of
the vase solution. Originally spelled “Gerberia,”
the genus was named after Traug Gerber, aGerman naturalist.

Quality Characteristics and Criteria
Most gerbera varieties should be harvested when
the two outer rows of disk florets have begun toopen; 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 ordergerberas by cultivar name. Unfortunately, the large
number of cultivars makes it difficult to learn thenames 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 theflowers, 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.

Ethylene Sensitivity
Gerberas are unaffected by exposure to ethylene.

are packed horizontally into a fiberboard box insuch a way that the flowers are facing upward andeasily seen while the stems are underneath theflower cards.

Pretreatments
Special Considerations
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 andvase water. After the dip, rinse the flowers ingood-quality water. This treatment causes only
minimum phytotoxicity (brown damage to thestem). The use of 6% sugar plus 200 µL L-1
8-HQC as a preservative has shown to be of somebenefit but can cause stem elongation duringstorage 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 beenscientifically substantiated. Generally, gerberas
should not be stored longer than 1 week; even thisshort 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 thebottom of a cardboard tray so that the flower heads
face up showing their colors while the stems passunder the box. Several rows of flowers can bearranged in each box. The boxes are then hung sothat the stems dangle downward and can be placedin a rehydration solution (hypochlorite is mostcommonly used). Afterward, two trays of flowers

Stem bending is primarily in response to gravity
and is greatly reduced if flowers are held at theproper 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 beenvariously attributed to harvesting of the flower
before the stem has hardened sufficiently and to
microbial plugging of the stem and subsequentwater stress. The tendency to conk varies withvariety 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 meshedsupport or shipping tray when first hydrating tokeep 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. Torchginger flowers are spectacular spikes of red
flowers that give an especially tropical effect inarrangements. The genus is named after the Italianbotanist Prosper Alpinus.

683

Quality Characteristics and Criteria

Special Considerations

No specific maturity standards have beendeveloped for these flowers. They are normally
harvested when all of the flowers on the spikeare open. Make sure flowers do not exhibit chill
damage symptoms such as off-colored (grayish/
bluish) blooms.

Their large size makes gingers difficult to manage.
Since insects sometimes make the trip fromgrower to wholesaler to retailer, make sure flowers
are inspected and any insects removed.

Gladiolus, Glad
Grading and Bunching

Scientific Name and Introduction

There are no specific grade standards for gingers.
Proper maturity and freedom from flower andfoliage defects would be important indicators ofquality. Gingers are large flowers and are therefore
normally packed individually. Some species may
be individually sleeved to protect the delicate
petals.

Gladiolus cvs., hybrids. Still an importantcommercial cut flower despite a substantial
decline in production in recent years, gladiolus
responds well to proper postharvest management.
The smaller flowered and “butterfly” cultivars, aswell 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 ofhybridization programs that commenced in
Belgium around 1841 using South African species.

Ethylene Sensitivity
These flowers do not appear to be particularly
sensitive to ethylene.

Pretreatments
Quality Characteristics and Criteria
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 arechilling sensitive, so they must be held at warmer
temperatures.

Packing
Gingers are packed flat in standard or insulated
fiberboard boxes.

684

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 isopen. Harvesting is carried out so as to leave as
many leaves on the plant as possible. A knife isrun 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 canthen be pulled out of the leaves. It is possible toopen almost all florets on flower spikes if they
are harvested in the green bud stage and handledproperly. However, it is recommended thatcolor be visible in one to three florets at time ofpurchase to help ensure that most florets will open.

Grading and Bunching
Gladioli, like most spike-type flowers, arevery sensitive to gravity and will always tend
to grow away from the ground, particularly atwarm temperatures. This can result in permanent
deformation of the upper part of the spike andconsequent reduction of flower quality. To avoid
deformation, gladioli should be held uprightthroughout 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 arebunched by color and maturity in groups of 10.

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.

PackingGladioli are traditionally packed in tall “gladhampers” 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 willremain 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.

Ethylene Sensitivity
Although exposure to ethylene does not affect thelife of open florets, it can reduce the flower life bycausing abortion of unopened buds (Serek et al.
1995).

Pretreatments
Gladioli respond very well to pulsing with apreservative containing 20% sugar (sucrose or
glucose). Pulse overnight at room temperature
or in the cooler. The flowers can be pulsed in thedark. 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 arenegatively geotropic (they bend away from theforce of gravity), so they are commonly stored
and shipped upright. One beneficial aspect of
low temperature handling and transportation isthat this negative geotropic response is inhibited,

Special Considerations
Some cultivars are sensitive to fluoride, which
can result in deterioration of the petal margin(bleaching, water soaking, then necrosis), failureof florets to open and develop normally, burningof 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 andsignature 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, theMuses supposedly remained young and beautiful
forever like the long-lasting and elegant flowersof heliconia. Lobster claw and crab’s claw are
additional common names for flowers in thisgenus.

685

Quality Characteristics and Criteria

Packing

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.

Heliconias are normally packed in horizontal
fiberboard boxes.

Grading and Bunching
Quality flowers of heliconia are fully mature,
free of defects (damage or discoloration) on theflowers, and have good quality foliage (whenpresent). 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 ofethylene exposure on the vase life of heliconias.

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 areinspected 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 andmale flowers on separate trees, and are therefore
termed “dioecious.” Only female plants are
harvested for specimens possessing fruit.

Quality Characteristics and Criteria
Pretreatments
No pretreatments have proved beneficial forheliconias. Some species may benefit from theflowers being dipped in an antitranspirant, suchas those sold in garden centers for use on woody
plants. However, no antitranspirant product ispresently sold for this use.

Holly is harvested when the fruits are alreadyfully 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
Storage Conditions
Heliconias are native to the tropical Americas, andthey 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).
686

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.

Ethylene Sensitivity

Huckleberry

Exposure to ethylene results in loss of berries andleaves and is a common problem in holly handled
through mass-market outlets.

Scientific Name and Introduction

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.

Vaccinium ovatum. Huckleberry is native to theWest 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.

Packing
Holly may be packed in hampers or horizontal
boxes. In the past, the branches were treated withvarious 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.

Ethylene Sensitivity
Huckelberry is not sensitive to ethylene.

Pretreatments
No pretreatments are required for huckleberry.

Special Considerations
Storage Conditions
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 fruitand leaf fall or to package the product in such a
way as to extend life. However, at wholesale orretail levels there is not presently a product toretard 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 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 byfungal growth (fuzziness) and watersoaked or
discolored leaves. The woody stems sometimes
make huckleberry difficult to recut. Recutting thisspecies is less critical than for other floral crops.
687

Iris, Fleur-de-Lis

Ethylene Sensitivity

Scientific Name and Introduction

Iris are not affected by exposure to ethylene.

Iris cvs., hybrids. Because of their intense yellow,
blue, and purple colors, and the elegant shapeof 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; forexample the “flag” or German iris, which haveeven shorter vase life, have been used in the trade.
Iris is Greek for “rainbow” in reference to therange 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 atthe “pencil stage.” This term describes flowers thatexhibit a line of color vertically, as the sheathing
leaves covering them unfurls, but before theflower petals reflex. The ‘Blue Ribbon’ cultivar
should be harvested more mature, when the edgeof one petal is unfurled. Iris are pulled from thefield 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 andretail florists should purchase iris in the pencil
stage. A major exception is the cultivar ‘Blue
Ribbon,’ which should be more open at the time ofpurchase.

Pretreatments
There are no recommended pretreatments for iris
flowers.

Storage Conditions
Store iris dry, upright, at 0 °C (32 °F) for no morethan 1 week. Some growers store iris with thebulb 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 isrehydrated.

Packing
Iris are normally packed in upright hampers.

Special Considerations
Some increase in vase life has been realized byincluding a high concentration of benzyladenine
in the vase solution, and pretreatments withgibberellins have been shown to overcome thenegative effects of dry storage (Celikel and van
Doorn 1995).

Leatherleaf Fern
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 normallybunched in groups of 10 and tied with rubberbands or twist-ties.

688

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 undersubtropical conditions. The specific epithet
adiantiformis indicates the similarity to the frondsof Adiantum, the maidenhair fern. The Greek

adianton means unwettable—a reference to thefact that fern fronds shed water. It is probably themost commonly used floral green.

The brown bumps (sori or fruit-dots) found on
the back of some fronds have not been reported toreduce life.

Quality Characteristics and Criteria

Lemonleaf, Salal

Avoid wilted or yellow fronds.

Scientific Name and Introduction

None.

Gaultheria shallon. A hardy, long-lived cut
foliage, salal was named for Jean-François
Gaultier, a naturalist and physician from Quebec,
Canada, about 1750.

Ethylene Sensitivity

Quality Characteristics and Criteria

None.

None.

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 timeof purchase, it should provide satisfaction in thevase.

Storage Conditions

Grading and Bunching

1 to 6 °C (34 to 42.8 °F)

Quality foliage has uniform mature green leaves
with no damage, defects, or disease. Salal isusually sold 20 stems per bunch.

Grading and Bunching

Pretreatments

Packing
N/A

Ethylene Sensitivity
Salal is not affected by exposure to ethylene.

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 enhancevase life but does not reduce frond curl. Dipping
leatherleaf in plain tap water can reduce vase life.

Pretreatments
Salal does not require any pretreatments toperform 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 in689

large bins lined with plastic to reduce water loss.

Grading and Bunching

Salal is normally packed in horizontal fiberboard
boxes.

Quality liatris flowers are of proper maturity (nomore than one-third of the flowers on the spikeopen), are free from defects and damage, and havegood quality foliage. They are normally bunchedin groups of 10 and sometimes sleeved.

Special Considerations

Ethylene Sensitivity

Even though the stems are woody, salal is adapted
to standard florists’ procedures for rehydration anduse in arrangements.

Liatris flowers are not affected by exposure to
ethylene.

Packing

Pretreatments
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, andcan open fully if properly treated after harvest.
Members of the Asteraceae (chrysanthemum or
aster family), these species are also unusual in thatflowers open from the top of the stem downwards;
delphinium, gladiolus, snapdragon, and mostother 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.

Pulsing with preservative containing additionalsugar (10 to 20%; about 100 g of sugar per quartor 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 inhampers.

Quality Characteristics and Criteria

Special Considerations

Liatris spikes should be harvested with no morethan 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.

Be careful of fungal problems such as Botrytis(especially for flowers grown outdoors) as wellas 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.

690

Lily of the Nile, Agapanthus
Scientific Name and Introduction
Agapanthus africanus. The globose heads of
agapanthus are a pleasing accent for springand early summer arrangements, providing analternative source of blue. The most common
flower color is blue, but white cultivars arealso available. Miniature, dark blue (‘Storm
Cloud’), and reduced-shatter cultivars have beendeveloped. Agapanthus is Greek for “love flower.”

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 whenpretreated 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 aminimally acceptable number of open florets.

Quality Characteristics and Criteria
Packing
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 witha sharp knife. Ensure that flowers are of proper
maturity. If the neck of flowers is bent upward,
they have been transported at warm temperaturesand 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.

Agapanthus flowers are normally packed inhorizontal fiberboard boxes.

Special Considerations
Premature flower fall is caused mainly by
ethylene, especially for immature flower buds.
The common blue cultivar ‘Mooreanus’ is muchless prone to premature flower fall than the whiteflowering ‘Aldidus.’
Lily, Asiatic Lily, Oriental Lily

Ethylene Sensitivity

Scientific Name and Introduction

Ethylene exposure results in loss of florets from
agapanthus.

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 havebecome increasingly popular as cut flowers andhave excellent vase life, especially if pretreated
to prevent effects of ethylene. Buds open well if
provided with preservative. “Lilium” is from theGreek word lirion, used in the naming of certain
subdivisions of the genus.

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 counteract691

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 purchasedwith color showing on at least one flower. Avoid
bunches with a number of open flowers, since they
probably have been held at warmer temperaturesduring marketing.

dry at 1 °C (34 °F). Flowers should be properly
precooled, and they must be packaged so thatwater loss during storage is minimized (wrapprecooled 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.

Grading and Bunching
Special Considerations
Although there are no grade standards forlilies, the number of buds per stem, the stage ofmaturity, and the color and quality of the foliage
are all important quality parameters. Flowers arenormally 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.

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 affectflower life. Some new cultivars do not shedpollen.

Lisianthus, Prairie Gentian
Pretreatments
After harvest, lilies should be treated with STS
or 1-MCP to extend their vase life. Pulsing with apreservative solution containing 10% sucrose can
improve subsequent bud opening, and it is also
possible to reduce postharvest leaf yellowing insusceptible cultivars by pretreating them overnightwith 2,000 µL L-1 GA3.

Scientific Name and Introduction
Eustoma grandiflora. Introduced into cultivationfrom Texas, production of lisianthus has increased
dramatically, spurred by development, mostly inJapan, of excellent cultivars with a wide range ofcolors and single and double forms.

Quality Characteristics and Criteria
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 latterto 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
692

Stems are harvested when at least one flower isopen. Although requiring extra labor, removal of
immature shoots, whose buds will not develop,
improves display quality. Choose stems with atleast one open flower and several large buds.

Grading and Bunching

Marguerite Daisy, Boston Daisy

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.

Scientific Name and Introduction

Ethylene Sensitivity
Lisianthus is slightly sensitive to ethylene.
Exposure of mature flowers to ethylene will
decrease their ultimate vase life, but the effect isrelatively slight and does not warrant treatment
with 1-MCP or STS.

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-dyedto provide different colors for special holiday
occasions. Their postharvest life is relatively longbut often limited by wilting or yellowing of thefoliage. The specific epithet frutescens means
bushy.

Quality Characteristics and Criteria
Pretreatments
Lisianthus flowers benefit from sugar in the vasesolution 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, andtheir stems will bend upwards if the flowers areheld horizontal at ambient temperatures. For thisreason, lisianthus flowers that will be transported
at warmer temperatures are often packed andtransported in vertical hampers.

Special Considerations
Lisianthus is sensitive to some of the biocidesin preservatives, which may cause browning of
the stems. Aluminum sulfate (200 µL L-1) andhypochlorite (50 µL L-1) are excellent bactericides
to use with lisianthus.

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 outerring 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 eachstem. 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, andthe 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-returncrop. 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.

693

Ethylene Sensitivity
Margeurite daisies, like other members of theAsteraceae, are not affected by exposure tomoderate concentrations of ethylene.

and excessive or ineffective preservative solution.
White flowers often are submerged in dye to getpink, green, red, or blue colors.

Orchids
Pretreatments

Scientific Name and Introduction

Research has shown improved performance withflowers 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 andcause leaf injury.

Cattleya, Cymbidium cvs., and hybrids.
Additional genera in the plant family Orchidaceae
are Dendrobium, Phalaenopsis, Vanda, andPaphiopedilum. 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 willoften last a month in a vase.

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 instandard daisy hampers.

Quality Characteristics and Criteria

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 tocool flowers packed in this way. Poor postharvest
temperature management may explain thedevelopment of yellow foliage and foliar diseasein marguerites.

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 fromplant 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.

Special Considerations

Grading and Bunching

Water in which Margeurites are held often
develops a bad odor. Keep solutions fresh andbuckets clean. Remove dirt and debris from stems
prior to cutting them. Preservative solutions
offer varying degrees of benefit depending onbrand. 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

There are no grade standards for orchids. Freedom
from defects is a primary measure of quality.

Packing694

Ethylene Sensitivity
Some genera such, as Cymbidium andPhalaenopsis, are very sensitive to ethylene;
others, such as Dendrobium, are less sensitive.

Pretreatments

Protea, Pincushion

Pretreatment with 1-MCP is very effective inpreventing the effects of ethylene (Heyes andJohnston 1998) and increasing the life of orchid
flowers and should be standard practice for theseflowers.

Scientific Name and Introduction

Storage Conditions
Temperature can range from 0 to 12.5 °C (32to 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 atroom 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 cushionand protect them from mechanical injury to theblooms. They are then packed 12 to 24 flowers
in each carton. Box inserts hold individual watertubes stationary. Shredded wax paper is tucked
around and between the flowers for additional
protection.

Proteaceae family. The family Proteaceae includes
a diverse range of species of trees and shrubs inthe genus Protea from southern Africa and ofother genera from Australia whose branches andflowers are used for foliage and as cut flowers.
The flowers are normally pollinated by birds andproduce copious amounts of nectar, explaining
the old Afrikaans name of “sugar bush.” Thefamily name refers to the diversity of formsof the flowers. Additional genera are Banksia,
Leucospermum, and Leucodendron.

Quality Characteristics and Criteria
Foliage is cut when mature (no soft tips), and theflowers when at least the outer florets are fully
expanded. Banksias may be harvested when atleast half of the flowers on the cylindrical spikeare open. Make sure leaves are not black.

Grading and Bunching
Quality protea flowers and foliage are freeof 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 bunchesof 5 or 10, depending on quality, size, and market
demand.

Special Considerations
Ethylene Sensitivity
Only some species and cultivars are ethylene
sensitive, which explains why anti-ethylene
treatments like STS and 1-MCP work only someof the time. The two most common ethyleneinduced symptoms are flower discoloration andpremature wilting and flower fall. Demand has
increased for this species prepared as a corsage
and sold through mass market outlets at Easter andMothers’ Day. When sold for corsages the use ofwater picks filled with fresh-flower solution (notplain tap water) is beneficial.

Neither foliage nor flowers of the proteas areaffected 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.
695

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 inproteas. Care must be taken to ensure that there
is no condensation or free water on leaves duringstorage as this greatly increases the incidence of
blackening.

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 inovercoming the poor postharvest reputation of cut
roses. All that is required is proper postharvestcare for those cultivars susceptible to bent neckand appropriate pretreatment of those that are
sensitive to ethylene, especially if they are to be
sold in supermarkets or other ethylene-polluted
areas.

Packing
Quality Characteristics and Criteria
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, thisdisorder can be reduced if the flowers are held
under lighted conditions. Leaf blackening is notdue to low temperature (chilling disorder), nor
is it due to poor water relations. Many species
and cultivars can be easily dried or preserved byjust 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 historicalassociation 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 lastin the vase for 10 days. Unfortunately, many
consumers consider roses to have a very shortvase life. This is partly because poor water uptake
by certain cultivars of purchased roses all too
696

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 failto 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 toseparate from the bud. The marketing life of roses
harvested later will be reduced unless extra care istaken 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 toleave 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 someor all of their sepals (the green protective leaves atthe base of the flower) folded back, but the petals
should not have started unfolding. Brown spots orpatches 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flower and foliage. Defects on the outer “guard”
petals are not normally a cause for down-grading,because these petals are removed by the retailflorist. Leaves and thorns may be removed
manually or mechanically if desired. This
operation has little effect on vase life if flowers areplaced in an effective preservative. The numberof stems per bunch and bunch pattern (single
layer, staggered two-layer) depend on market
preferences.

Packing

Ethylene Sensitivity

Special Considerations

Some cultivars are ethylene sensitive. Treatwith 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.

Removal of those leaves and thorns below thewater line should not reduce vase life if stems areplaced 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 onleaves, 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 retaillevels.

Pretreatments
Roses should be pretreated with 1-MCP or STS
to prevent the effects of ethylene, especially ifthey 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 arehydration 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 shouldbe packed in polyethylene-lined cartons andprecooled. They may be held for up to 2 weeks indry storage if the temperature is maintained close
to the freezing point.

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 condensationcollecting on the outer petals. Botrytis infection is
a common result of the presence of free moistureon the petals of cut roses.

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 havebeen selected for ethylene resistance, and ethylene
normally causes a problem only when present inmoderate 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.

697

Quality Characteristics and Criteria
For local sales, snapdragons are typicallyharvested 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 healthyfoliage. Foliage on the lower third of the stem
should be removed.

Ethylene Sensitivity
Most snapdragon cultivars are sensitive toethylene. 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.

the growth regulator n-dimethylamino succinamic
acid increases flower quality and also counteracts
the excess spike length that sometimes resultsfrom 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 fromhorizontal storage at warmer temperatures.

Storage Conditions
Snapdragons can be stored at 0 to 1 °C (32to 34 °F) for 7 to 10 days if they are wrappedin 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 thebottom 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 uprightin snapdragon hampers at low temperatures.
Pretreatment with naphthyphthalamic acid canovercome this bending, but it is not registered forthis purpose.

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) witha 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 thisoften 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 shouldbe 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
698

Packing
Snapdragons are usually packed upright inhampers or proconas, which reduce the likelihoodof geotropic bending. If flowers are properly
precooled and transported at optimal temperatureof 0 to 1 °C, (32 to 34 °F), they can be packed in anormal horizontal flower box.

Special Considerations
Do not remove more leaves than necessary, as thiscan stimulate flower-fall. Do not use any homebrews, such as antifreeze, as replacements for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 andcultivar.

Ethylene Sensitivity
Statice flowers are sensitive to ethylene, whichcauses accelerated wilting. In standard statice,
this effect is not apparent since the “flowers” arepapery bracts surrounding the true flowers. In
hybrid statice cultivars, effective treatments toinhibit action of ethylene improve flower quality
and vase life.

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 widelyused both fresh and dried. Other species ofLimonium 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. Theirvase life is greatly improved by pretreatments toprevent 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 thebrightly colored bracts) senesce. Hybrid staticecultivars should be harvested when the first flower
on each spike is open. Avoid bunches where
flowers have yellowing stems and leaves andbunches with obvious fungal growth or wilted
flowers. Remove from shipping boxes and recool
flowers immediately. Also remove stem ties andseparate stems to improve air circulation andreduce the likelihood of Botrytis infection.

Grading and Bunching
Quality statice is of the correct maturity and is
free of defects and disease. Standard statice isnormally bunched in groups of 25. Sleeves help
prevent tangling of the delicate branchlets.

Pretreatments
Hybrid statice benefits enormously frompretreatment with STS or 1-MCP and pulse
pretreatment with a solution containing 10%
sugar and 200 µL L-1 Physan-20 for 12 h. Sucrosepresent in the preservative extends the life ofindividual 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 foryears 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 incommercial practice.

699

StockStorage Conditions

Scientific Name and Introduction

Stock should be stored at 0 to 1 °C (32 to 33.8 °F).

Matthiola incana. A very traditional field flower
with spikes of aromatic flowers in a wide rangeof colors, stock continues to be a staple floristry
item. Somewhat sensitive to ethylene and prone tobacterial contamination of the vase solution, stockflowers 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 thansix open florets on each spike. To increase stem
length, growers may pull the plants from theground 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.

Packing
Stock are frequently packed in hampers oraquapacks 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 tokeep the growth of microorganisms in check.
As with baby’s-breath and Marguerite daisy, thevase and bucket solutions can develop a very
unpleasant smell if the correct amount and type ofpreservative solution is not used and if buckets are
not properly sanitized.

Sunflower
Scientific Name and Introduction

Quality stock has long straight spikes of uniform
unblemished flowers and free of defects.

Helianthus annuus. Smaller cultivars of sunflower
have become a very popular florist item, anda range of forms and colors are now widely
available. “Helianthus” is derived from the Greek
helios, the sun, and anthos, a flower.

Ethylene Sensitivity

Quality Characteristics and Criteria

Exposure to ethylene results in water-soaking of
the petals, accelerated senescence of the florets,and epinasty (downward curvature) of the leaves.

Sunflowers are normally harvested when thepetals (the outer flowers or ligules) have unfolded
and are at least vertical. For local market, flowers
are harvested with ligules fully expanded andhorizontal. No yellow, wilted leaves should bepresent. Storage life is often determined moreby leaf yellowing or desiccation than by flower
problems.

Grading and Bunching

Pretreatments
To prevent deleterious effects of ethylene, stock
should be pretreated with 1-MCP or STS.

700

Grading and Bunching

Sweet Pea

Quality sunflowers are of uniform maturity, arefree from defects, and have straight stems andgood quality foliage. Small-flowered cultivars
may be bunched in groups of 10 or 12, and largeflowered types are normally packed individually.

Scientific Name and Introduction

Ethylene Sensitivity
Prolonged exposure of sunflowers to low
concentrations of ethylene results in abscission of
ligules.

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 thesedelicate 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
Pretreatments
The tendency for sunflowers to wilt prematurely inthe 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).

Sweet peas are traditionally harvested when thelast 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 theflower backwards and upwards from the axil ofthe leaf. Sweet peas should have five flowers per
stem, with only one flower open at the time ofpurchase. Avoid bunches with wilting flowers orfrom which buds or flowers have fallen.

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, theflower heads will be permanently bent down; so it
is important to maintain cool temperatures duringtransport and storage.

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 bebunched by color, or in mixed colors, in bunchesof 10.

Ethylene Sensitivity
Exposure to ethylene results in accelerated wiltingof petals, abscission of flowers, and failure ofdeveloping buds to open.

701

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 ina preservative solution containing 4% sucrose at
20 °C (68 °F) overnight.

be harvested with the outer ring of flowers open.
Flowers should have at least the outer whorlof florets open. Avoid flowers with withered or
sleepy florets, as this indicates ethylene-induced
problems.

Grading and Bunching
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 asatisfactory vase life after storage for up to 1 weekat 1 °C (34 °F).

Quality sweet william flowers are of uniform
maturity, are free from damage and evidence ofpests and diseases, and have reasonable stem
length and good quality foliage. Flowers are soldin a grower’s bunch of at least 12 stems.

Ethylene Sensitivity
Packing

Flowers are ethylene-sensitive.

Sweet peas are packed in horizontal boxes or
hampers.

Pretreatments

Special Considerations

Flowers should be pretreated with 1-MCP or STS
to prevent effects of ethylene.

Cultivars vary in the intensity of their aroma, oneof the characteristic and appealing features ofsweet peas.

Storage Conditions
Like carnation, flowers should be stored at 2 to 3
°C (36 to 37 °F).

Sweet William
Scientific Name and Introduction

Packing

Dianthus barbatus. A close relative of thecarnation, normally grown in the field, sweet
william flowers are borne on a short-stemmed
inflorescence. Colors range from white throughintense red and purple and provide strong accentsin an arrangement. The specific epithet barbatusmeans bearded or barbed in reference to thebeardlike growth emerging from the petals.

Sweet william flowers are normally packed inhorizontal fiberboard boxes.

Quality Characteristics and Criteria
Flowers in the sweet william inflorescence
continue developing after harvest, and they should
702

Special Considerations
As with many flowers grown in the field, fungal
infections resulting from the wet foliage andflower conditions sometimes experienced atharvest can be a problem. Make sure flowers are
rapidly unpacked and aerated to reduce possible
disease spread.

Tuberose

Pretreatments

Scientific Name and Introduction

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 andReid 1989). This pretreatment will significantly
improve vase life and opening of buds on theflower spikes. Flowers to be pretreated in thisway should preferably be harvested dry; graded,bunched, and recut; then placed immediately inthe pulsing solution.

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 failureof developing buds to open, so that the life isdetermined by the life of the flowers that wereopen at harvest. Proper pretreatments can greatly
extend the life of tuberose and should routinely be
carried out with flowers intended for storage andtransport.

Quality Characteristics and Criteria
The flowers are normally harvested with two tofour open blooms on the spike. Although earlier
harvest provides a spike that is more resistant totransportation, the buds are unlikely to open after
transport unless properly pretreated. Flowers forthe local market may be harvested with more open
flowers on the spike. It is unfortunately difficult
to determine whether tuberose flowers have beeneffectively pretreated prior to purchase. Look forstraight stems and unblemished blooms and workwith suppliers to ensure that the flowers have been
properly pretreated.

Grading and Bunching
Tuberose are sold in bunches of 10 stems.

Storage Conditions
The optimal temperature for cooling and storageof tuberose is 0 °C (32 °F), but after only shortperiods the buds on the spike fail to open.
Pulse pretreatment with sucrose overcomes thisproblem, and after 6 days storage, flowers open as
well as on freshly cut spikes.

Packing
Tuberose may be packed in hampers orin 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 incorsages and boutonnieres. Proper pretreatmentof the spikes will ensure continued opening of theblooms in the florists’ workroom and consequent
increased utility of each spike.

Ethylene Sensitivity
Tulip
Floret opening is reduced in spikes exposed tohigh concentrations of ethylene; but this effect isprobably not normally of commercial significance,so 1-MCP or STS treatments are not warranted fortuberose.

Scientific Name and Introduction
Tulipa cvs., hybrids. Tulips, one of the classicalcut flowers, were the source of tremendous interest
when they were first brought to Holland from theMediterranean countries where they are native.
703

The most common species, Tulipa gesnerana, wasnamed after C. Gesner, a botanist who lived from1516 to 1565.

Control of RH and proper rehydration following
storage can minimize the problem.

Packing
Quality Characteristics and Criteria
The entire tulip plant, with bulb attached, isharvested when the tepals show 50% color. It ispreferable to harvest in the early morning whentemperatures 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.

Tulips may be packed in hampers or in regularfiberboard flower boxes. Stems and blooms should
be securely wrapped to prevent bruising andbreakage. Tulips packed horizontally must be heldat proper temperature of 0 to 1 °C (32 to 34 °F) to
avoid gravity-induced bending.

Special Considerations
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 arethen removed and the bases of stems are cut toensure adequate water uptake. Tulips are typicallybunched in groups of 10.

Ethylene Sensitivity

End-user life is very species- and cultivardependent, as is the flower maturity stage whensold. Preservative solutions are recommended;
benefits vary from 0 to 150% increase in vase life,
depending on cultivar, flower food brand, andwater quality. Do not place in the same bucketwith 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 bemaintained in an upright position during handlingto prevent stem bending.

Tulips show no response to ethylene nor any
response to inhibitors of ethylene actions orsynthesis (Sexton et al. 2000).

Some people may get dermatitis from continual
handling of tulip flowers.

Pretreatments

Waxflower, Geraldton Waxflower

No pretreatments are required for tulips.

Scientific Name and Introduction

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.
704

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 producedin substantial quantities in Israel and more recently
in Australia and California. Various techniques
have been developed to manipulate the floweringseason, 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at the point,” in reference to the leaves which arehooked at their ends. The crushed leaves give apleasing citrus aroma.

Storage Conditions

The major postharvest problems are the shatteringof 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 witherratic rainfall. Fungicide dips have been usedsuccessfully as a control measure.

Store waxflower at 0 to 1 °C (32 to 34 °F). If
properly precooled and subsequently wrapped inplastic to reduce water loss, flowers can be stored
dry for up to 2 weeks at 1 °C (34 °F). There is nobenefit of wet over dry storage, and dry storage istherefore 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.

Quality Characteristics and Criteria

Packing

Waxflowers are normally harvested with amixture of open flowers and mature buds on eachbranchlet. 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.

Waxflowers are packed in bunches that containvariable numbers of stems (around 10) to provide
a satisfactory bunch.

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.

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

Ethylene Sensitivity
Waxflowers are very sensitive to ethylene, whichcauses loss of flowers, buds, and leaves (Joyce
1993).

× Solidaster luteus. The “×” prior to the genericname 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 atthe Leonard Lille Nursery in Lyon, France.

Pretreatments
Harvested wax flower bunches should betreated with 1-MCP or STS in the same way as
carnations.

Quality Characteristics and Criteria
At least 50% of the flowers should be open. Avoid
old product, as leaf yellowing and desiccation canbe troublesome.

705

Grading and Bunching

References

As with other filler flowers, bunches are made bysize or weight.

Bieleski, R.L., J. Ripperda, J.P. Newman, and
M.S. Reid. 1992. Carbohydrate changes and leaf
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Ethylene Sensitivity
Like other Asteraceae, solidaster flowers are notsensitive to ethylene.

Bovy, A.G., G.C. Angenent, H.J.M. Dons, andA.C. van Altvorst. 1999. Heterologous expressionof the Arabidopsis etr1-1 allele inhibits thesenescence of carnation flowers. Molec. Breed.
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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 stemas they rot underwater and will foul the vasesolution. Make sure that buckets, vases, andsolution are kept clean.

Acknowledgments
Much of the information included is based on
the recommendations of the Society of American
Florists.

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Flower Bulbs
August A. De Hertogh and Marcel Le Nard
De Hertogh is formerly with the Departmentof Horticultural Science, North Carolina State
University, Raleigh, NC. He is now retired. Le
Nard is with Station d’Amélioration de la Pommede Terre et des Plantes à Bulbes, Institut Nationalde 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 (DeHertogh and Le Nard 1993b). All of them are
geophytes (Raunkiaer 1934), a term that not only
includes flower bulbs but also most herbaceousperennials, some fruits such as strawberries, andsome 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 ofbulbs produced. In 2000 (Anonymous 2000), theworld 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” forvery 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 thisnature, 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 andare generally grown by specialized bulb growers.
Thus, they will only be covered briefly in thisreview. 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, andgardens 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 fromfloral 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 andChastagner 1993, Van Aartrijk 1995, 2000) andprevent physiological disorders (De Hertogh andLe 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 developmentfrom initiation to anthesis, which can be a few
weeks to several months;• optimal temperatures required to control theentire 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 fromnone to high;• moisture requirements, which range from none
to high; and• specific diseases and insects that can becontrolled 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).
709

Table 1. Packing and storage temperature requirements of ornamental flower bulbs
					

Requirements

Taxon
Storage
Packing			

Storage 				temperature						Achimenes
Prevent from drying
Peat			
Acidanthera
Dry and ventilatedNone			Allium			giganteum
Dry and ventilated
None
Other alliums Dry and ventilated
None			
Alstroemeria
Prevent from drying
Peat			
Amaryllis			belladonna
Prevent from drying
Peat			
Anemone						
blanda &Dry and ventilatedNonefulgens			
coronaria(summer)Dry and ventilated
None(winter)Dry and ventilated
None°C
10 to 1520
		
25 to 28		20 to 23
1 to 3		
13 to 23

9 to 17

15 to 25		10 to 13

Anigozanthos
Prevent from drying
Not reported
			
Begonia
Prevent from drying
Peat(Tuberous 			hybrids)

2 to 20

Caladium
Dry and ventilatedNone			
Camassia
Prevent from drying
Wood shavings
			
Canna
Prevent from drying
Peat			
Chionodoxa
Prevent from drying
Wood shavings			
CliviaPrevent from drying
Peat			
Colchicum
Prevent from drying
Wood shavings
			

23 to 25710

2 to 517 to 20
5 to 1020
13
17 to 23

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—
continued					

Requirements

Taxon
Storage
Packing			

Storage 				temperature

			

°C

Convallaria
Keep frozen-in
Peat			
Crocosmia
Prevent from drying
Plastic
			CrocusDry and ventilatedNone			
Cyclamen
Prevent from drying
Peat			
DahliaPrevent from drying
Peat			
Endymion
Prevent from drying,
Wood shavings(Scillastore in paper bags		
campanulata)		

-2

EranthisPrevent from drying
Peat			
Eremurus
Prevent from drying
Peat			
Erythronium
Prevent from drying
Peat			
Eucharis
Prevent from drying
Peat			
EucomisDry and ventilatedNone			Freesia
Dry and ventilated
None
Preshipping 			Postshipping						Fritillaria
imperialis
Prevent from drying
Wood shavings
persica &PeatmeleagrisGalanthus
Prevent from drying
Peat			
Galtonia
Prevent from drying
Wood shavings			

2 to 517 to 20
95 to 1020

55 to 75 to 920
13 to 2030
9 to 1323 to 25
2 to 517
17 to 20711

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—
continued					

Requirements

Taxon
Storage
Packing			

Storage 				temperature

			

°C

Gladiolus
Dry and ventilated
None			
Gloriosa
Prevent from drying
Peat			
Gloxinia
Prevent from drying
Peat			
Haemanthus
Dry and ventilated
None			
Hemerocallis
Prevent from drying
Peat			
Hippeastrum
Prevent roots from drying
Peat or wood shavings			
Hyacinthus
Dry and ventilatedNone			
Hymenocallis
Prevent from drying
Peat			
Iris			Dutch hybrids Dry and ventilated
NoneEnglishDry and ventilatedNonehybrids			
Germanica
Prevent from drying
Peathybrids			
reticulata &Dry and ventilated
None
danfordiae			

2 to 10Ixia

Dry and ventilated at
None65-70% RH		

Ixiolirion
Dry and ventilatedNone			
Lachenalia
Dry
Peat
			
LeucojumaestivumDry and ventilatedNonevernumDry and ventilated
None
LiatrisPrevent from drying
None
			
712

10 to 18
5 to 910 to 15
7 to 102 to 1317 to 20
7 to 1020 to 25
17
0 to 520 to 23

20 to 2520
9 to 25

20
2 to 52 to -2

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
Hybrids &Prevent from drying
Peat and polyethylene
other species

2 to 72 to -2

LycorisDry and ventilatedNone			Montbretia
Prevent from drying
Plastic
			MuscariDry and ventilatedNone			
Narcissus
Hardy cultivars Dry and ventilated
None
Paperwhites
Dry and ventilatedNone			
NerinePrevent from drying		
Short-term storage
Peat
Long-term storage
Peat			
Ornithogalum
dubiumDry and ventilatedNonethyrsoides
Prevent from drying
Wood shavings
umbellatum & Prevent from drying
Wood shavings
nutans
Oxalisadenophylla
Prevent from drying
Wood shavings
deppeiDry and ventilated
None			
Polianthes
Dry and ventilatedNone			
Puschkinia
Dry and ventilated
Wood shavings			
Ranunculus			
SummerDry and ventilated
None
WinterDry and ventilated
None
			

13 to 17
2 to 520

17
2 to 30

17 to 21
5 to 99 to 30
23 to 25
20

17 to 20
2 to 520
20 to 23

17 to 20
10 to 13713

Table 1. Packing and storage temperature requirements of ornamental flower bulbs—
continued					

Requirements

Taxon
Storage
Packing			

Storage 				temperature

			

°C

Scadoxus
Dry and ventilatedNone			
Scilla siberica
Dry and ventilated
Wood shavings			
Sparaxis
Dry and ventilatedNone			
Tigridia
In closed boxes
Peat			
Triteleia
Dry and ventilated
None(Brodiaea) laxa

10 to 15

TulipaDry and ventilatedNone			
Zantedeschia
Dry and ventilated
Wood shavings			
Zephyranthes
Dry and ventilated
Polystyrene

17

Adapted from De Hertogh and Le Nard (1993c).

714

20 to 2325
2 to 517 to 20

7 to 1017 to 20

About 75% of the flower bulbs used in the
United States are imported, and the remainder
are domestically produced. In addition, allproduction areas are distant from the sites ofuse, and essentially 99% must be transported
for a few days to several weeks. Thus, alltrucks and shipping containers must be able toprovide the proper temperature, ventilation, andmoisture requirements for the bulbs (table 1). The
normal rate of air exchange for bulbs requiring
ventilation during transport is 150 m3 h-1 (DeHertogh and Le Nard 1993c). In addition, forbulbs like hyacinths and dutch iris, the RH must
be controlled to minimize the development ofdiseases such as Penicillium. Therefore, on arrival,
all bulb shipments must be carefully inspected
for serious diseases and insects, ventilated asneeded, and then properly stored (table 1). Also,stage of development of the apical meristem must
be determined. De Hertogh (1996) summarizedpacking, transportation, and storage requirements
for forcing bulbs.

Major Postharvest Storage Factors
TemperatureBlaauw and his coworkers (Hartsema 1961)
clearly demonstrated that temperature was themost important factor controlling the growth anddevelopment 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 timeof flowering. The optimal temperatures can range
from -2 to 34 °C (28 to 93 °F) depending on thebulb 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 orhigher than the required temperatures, even for

short periods, most bulbs will be physiologicallyinjured (Van Aartrijk 1995 and 2000).
Table 2. Hardiness classifications forornamental flower bulbs
Hardinessclassification

Injured attemperatures below

Tender I
Tender II
Tender III
Semi-hardy
Hardy I
Hardy II
Hardy III

20 °C
10 °C
2 °C
-2 °C
-5 °C
-10 °C-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 periodsof postharvest storage. Thus, the applicationof these requirements must begin immediately
after the grower harvests the bulbs and continue
during transportation and subsequent handlingby the wholesaler, forcer, and retailer. The exact
ventilation requirement is generally very specific.
It can be very low (Eremurus and Liatris, whichmust 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 orwood shavings are used in combination with thevarious packaging materials such as polyethylene.
The second is the control of RH during storage
or transportation, which can minimize root715

development and prevent the development
of diseases such as Penicillium on hyacinths,
Narcissus, tulips, and dutch iris. In addition, thisapproach 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 tochange, users must consult with their appropriate
governmental agency to determine which
pesticides are approved.

EthyleneWith 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 0.1µL L-1 and higher. In general, when the flower has
been formed and is immature, this plant growth
regulator causes either floral abnormalities orcomplete flower abortion. For very sensitive
bulbs, such as tulips, it is advisable to have thestorage rooms analyzed for ethylene. Commercial
ethylene services are available to monitor the levelof ethylene in all floriculture facilities.
Modified Atmospheres
Research on the modification of the O2, N2, andCO2 levels of the storage atmosphere has beenreported for gladioli, lilies, and tulips (De Hertoghand Le Nard 1993d). In Europe, this system isreferred to as “ultra-low oxygen” (ULO) and isused commercially in the Netherlands for lily andtulip bulb storage (Anonymous 1996). However,the specific procedures used and the results havenot been published in refereed journals.

Diseases and Insects
All users of flower bulbs must be familiar withthe 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 eachspecies. Knowledge of the major pests and the716

conditions controlling their development can
assist in either eliminating and/or minimizing theireffects during postharvest storage.

Major Flower Bulb Taxa
Gladiolus (Gladioli)
Cohat (1993) reviewed the physiology, pests, andother aspects of Gladiolus. Many diseases canaffect gladioli in storage, and prestorage fungicidal
dips are generally used. Current registrations must
be consulted for approved fungicides. Corms forcommercial 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 °Cor >30 °C (Cohat 1993, Van Aartrijk 1995).
Planting stock. After being harvested, cleaned,
and then graded, corms and cormlets used asplanting 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 aminimum 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 promotesprouting. 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 areoutside 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 longstorage and thus for very late flowering must be
stored at 2 °C (36 °F) until planted.

Hyacinthus (Hyacinths)
Nowak and Rudnicki (1993) reviewed thephysiology, 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 theheat 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 andstorage of small hyacinth bulbs require precise
conditions to control the bacterium Xanthomonas
hyacinthii (yellow disease). After harvest, thebulbs are stored at 30 °C under highly ventilated
and dry conditions until September 1; they arethen 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 andother 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 ofcommercial bulbs are available for greenhouseforcing as either potted plants or fresh cut flowers.
The first is “prepared bulbs,” which are used forvery 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 areused 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 andsubsequently stored at 17 °C (63 °F).
Iris hollandica (Dutch Iris)
De Munk and Schipper (1993) reviewed thephysiology, pests, and other aspects of dutch iris.
The two major storage diseases of dutch irises are
Fusarium and Penicillium. To assist in controllingthese diseases, it is essential to always handle thebulbs 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 andSchipper 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 ofdiseases. 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 withthe 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 are717

subsequently exposed to 500 µL L-1 ethylene for
24 h. This treatment stimulates flower initiation,
especially with small bulbs of some cultivars andbulbs 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 (41to 48 °F) for 6 to 11 weeks, depending on thecultivar. After being precooled, bulbs should beplanted as quickly as possible and, if transported,
the period should be as short as possible. De
Hertogh (1996) provided forcing programs fordutch 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 beprecooled 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 andspecies 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, andother 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 “commercial-718

sized bulbs” are immediately packed in moist peatin 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 (36to 45 °F) either by case precooling in moist peator 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 thehybrid 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 inmoist peat, wrapped in polyethylene, and packedin 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 lateand year-round forcing the bulbs are “frozen-in”
at -1 to -2 °C (28 to 30 °F) after being precooledfor 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 usedbecause there are fewer negative effects of thelong-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 andOriental 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 thesegroups. With the exception of the hot water
treatment (see below), nonplanted hardy Narcissus
bulbs are never stored at >34 °C (93 °F) (see earlyforcing below), while paperwhites are not stored
at >30 °C (86 °F) (Hanks 1993). Neither groupof bulbs is stored at <0 °C (32 °F) (Van Aartrijk
1995).
Hardy Narcissus. By far, the largest group of
Narcissus comprisesthe hardy cultivars, andhundreds 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 byuse 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 inNorth 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 canbe 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 beplaced at 2 °C (36 °F). Prior to planting, theyrequire 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 thephysiology, pests, and other aspects of tulips.
Without question, tulips are the largest taxa offlower bulbs grown and used throughout theworld. 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 fieldand continue during postharvest storage. There aresubstantial 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 andabnormalities. Thus, the bulbs must be routinely
inspected and the rooms monitored for ethylene;
levels in the storage rooms must not exceed 0.1µL L-1. In storage, Penicillium can be controlledwith 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 aventilation rate of 150 m3 h-1. With the exceptionof 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 thecultivar, 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 encourageenhanced production of large sized bulbs from theplanting stock.
Forcing bulbs. For very early forcing, mostcultivars 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 tobe able to identify the stages of flower initiation(Hartsema 1961), since most cultivars must reachstage G prior to being precooled at 5 to 9 °C (41to 48 °F). For medium and late forcing, bulbs
are placed at 17 to 23 °C (63 to 73 °F) prior to719

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 theneed 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 andstored 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.

720

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 Physiologyof 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.

Hanks, G.R. 1993. Narcissus. In A. De Hertoghand M. Le Nard, eds., The Physiology of Flower
Bulbs, pp. 463-558. Elsevier Science Publishers,
Amsterdam, Netherlands.
Hartsema, A.M. 1961. Influence of temperatureson flower formation and flowering of bulbous andtuberous plants. In W. Ruhland, ed., Handbuch
der Pflanzenphysiologie, pp. 123-167. SpringerVerlag, Berlin.

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 Afwijkingenbij Bolgewassen. Deel 1: Liliaceae. Derde Druk.
Laboratorium voor Bloembollenonderzoek, Lisse,
Netherlands.

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 Physiologyof 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 andStatistical Plant Geography. Clarendon Press,
Oxford, U.K.
Stuart, N.W, S. Parsons, and C.J. Gould. 1970.
The influence of controlled atmospheres duringcold storage on the subsequent flowering of Easterlilies 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.

721

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 andstorage conditions, such as exclusion from lightin closed containers and sleeves, exposure toharmful gases and temperature extremes, poor
air ventilation, high RH, and vibration. These
conditions can lead to deterioration of even thehighest quality plants. Further, the environmental
and physical stresses imposed on plants duringtransit 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 UnitedStates (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 distantfrom 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 arebased 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 diminishedwhen the flower dies rapidly though the leaves
remain green. Problems with shipping may not beapparent immediately following shipping: Buds orflowers may drop several days after unboxing, or
leaves may turn yellow or flowers die prematurely
722

1 to 2 weeks after shipping. Research over the last
25 years has concentrated on factors providing forretention of leaf color while maximizing flower
longevity.
Cultivar selection and production conditions
affect the response of flowering potted plants
to shipping conditions. Chrysanthemum andpoinsettia cultivars vary considerably in theirability to withstand shipping. Hibiscus cultivars
drop buds and flowers as a result of improper
shipping conditions. It is likely that differencesin 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 rolein the ability of potted flowering plants towithstand shipping conditions. High fertilizer
levels during production decreases the qualityof chrysanthemums, campanula, poinsettia, andother plants during and following shipping. In
chrysanthemum, terminating fertilizer at flower
color (3 weeks prior to marketing) resulted ina 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 plantand flower quality following shipping as a resultof 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 beinterrelated 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 andleaves, providing ideal conditions for botrytis,
powdery mildew, or other diseases. Similarly, useof 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

have been shown to minimize the incidence ofpoinsettia bract edge burn in the greenhouse,
during shipping, and in the retail setting. In mostcases, 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, andminimize problems associated with ethylene.
Optimum shipping temperature varies withspecies, 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 andflower quality.
Ethylene can adversely affect quality. Plants
may produce ethylene, or plants may be exposedto ethylene from external sources, such as
combustion engines and dead and decayingorganic 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 andbud drop, premature aging, and leaf yellowing, butother disorders have also been identified (table 2).

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
AzaleaCalceolaria
Chrysanthemum
Cineraria
CrocusCyclamen
DaffodilEaster lily
Freesia
Grape hyacinth
Hyacinth
Hydrangea
Kalanchoe
OxalisRegal geranium
Rose
Tulip

Africian violet
Begonia-elatior
Bougainvillea
Browallia
Christmas cactus
Clereodendron
Crossandra
Cymbidium
Easter cactus
ExacumGloxinia
Hibiscus
Poinsettia
Streptocarpus

Adapted from Sterling and Molemaar (1985) and
Nell (1993).

Regardless of concentration, ethylene becomes
more damaging as temperature increases during
the exposure period. Of course, injury is worsewith higher concentrations and longer exposure
periods. For example, open carnations are 1,000fold more sensitive to ethylene at 21 °C (70 °F)
than at 2 °C (36 °F). One of the most effectivemeans 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.

723

Table 2. Response of flowering potted
plants to ethylene1
Crop

Symptoms

Achimenes
African violet
AzaleaBegonia-elatior
Bougainvillea
Browallia
Carnation
Calceolaria
Clereodendron
Crossandra
Cyclamen
Cymbidium
ExacumGeranium
Gardenia
Gloxinia
Hibiscus
Kalanchoe

Flower/bud drop
Flower wilting
Leaf drop
Flower drop
Flower/bract drop
Flower/bud drop
Failure of flower to open
Flower/bud drop
Flower/bract drop; leaf drop
Flower drop
Flower drop; flower wilting
Wilting of the sepal
Flower wilting
Floret drop
Flower/bud drop
Flower drop
Flower/bud drop
Failure of flowers to open;
petal drying
Petal wilting; bud blasting;leaf yellowing
Petiole droop2
Flower drop

Pachystachus
Poinsettia
Streptocarpus

Adapted from Woltering (1987).
1

The degree of sensitivity to ethylene varies withplant 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.

724

Several chemicals are available commercially thatwill 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 theconditions, 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 PublishingCo., 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

Foliage Plants
Terril A. Nell
Nell is with the Environmental Horticulture
Department, University of Florida, Gainesville,
FL.

Foliage plant production and sales represent asignificant part of ornamental plant productionin 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 oftransport 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. Temperaturesof 10 to 13 °C (50 to 55 °F) are the lowest thatshould be considered for shipping, and even at thisrange some chilling injury may occur with someplants.
Foliage plants should be acclimatized by growers
prior to shipment. Acclimatization is the processof making plants more tolerant to environmental
changes during or after shipment. Growers
acclimatize plants using lower fertilizer levels andtemperatures or reduced light and water during thelast 2 to 4 weeks before shipment. Acclimatizedplants are better adapted to dark storage in transit
and reduced light in stores than nonacclimatizedplants. Requirements and length of shipping
tolerated vary because of the wide diversityof foliage plants. Shipping temperatures havebeen identified for some acclimatized plants intemperature-controlled containers (table 1). These
guidelines are based on simulated shipping tests indarkness.

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 bestat 19 °C, Ficus benjamina at 10 or 13 °C, andDracaena 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 recoveredfrom 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 2days causes severe damage to Scindapsus pictus(satin pothos) and Maranta leuconeura (prayer
plant). Fittonia verschaffeitii (silvernerve plant) isseverely damaged within 8 h at 2 °C (36 °F).
Foliage plants should be turned over rapidly inmarketing 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, andficuses are very sensitive to ethylene.

725

Table 1. Suggested shipping temperatures for acclimatized foliage plants tomaintain quality in refrigerated vans1
Plant name1-15 days shipment

Aglaonema, cv. ‘Fransher’
Aglaonema, cv. ‘Silver Queen’Ardisia crispa
Aspidistra elatior
Brassaia actinophylla
Chamaedorea elegans
Chamaedorea seifrizii
Chrysalidocarpus lutescens
Codiaeum variegatum
Cordyline terminalis
Dieffenbachia picta
Dracaena deremensis
Dracaena fragrans
Dracaena marginata
Ficus benjamina
Ficus nitida
Howeia forsteriana
Nephrolepis exaltata
Peperomia bicolor
Philodendron selloum
Philodendron oxycardium
Phoenix roebelenii
Pleomele reflexa
Rhapis excelsa
Schefflera arboricola
Scindapsus aureus
Spathiphyllum, Mauna Loa
Yucca elephantipes

°C
13-16
16-18
10-13
10-13
10-13
13-16
13-16
13-18
16-18
16-18
16-18
16-18
16-18
13-18
13-16
13-16
10-18
16-18
16-18
13-16
16-18
10-13
16-18
10-13
10-13
16-18
10-13
10-13

1

°F
55-60
60-65
50-55
50-55
50-55
55-60
55-60
60-65
60-65
60-65
60-65
60-65
60-65
55-65
55-60
55-60
50-65
60-65
60-65
55-60
60-65
50-55
60-65
50-55
50-55
60-65
50-55
50-55

16-30 days shipment2
°C
16-18
16-18
—
—
10-13
—
—
16-18
16-18
—
—
—
—
16-18
13-16
—
10-18
—
—
—
—
—
—
—
10-13
—
13-16
10-13

°F
60-65
60-65
—
—
50-55
—
—
60-65
60-65
—
—
—
—
60-65
55-60
—
50-65
—
—
—
—
—
—
—
50-55
—
55-60
50-55

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.

726

Herbaceous Perennials
Arthur C. Cameron
Cameron is with the Department of Horticulture,
Michigan State University, East Lansing, MI.

Introduction
Herbaceous (nonwoody) perennials are adiverse group of plants grown primarily for
their ornamental value in gardens throughout
the world. Storage of herbaceous perennial plantmaterial 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 suchas strawberry, rhubarb, potato, and asparagus
are grown as food crops, but the storage of theirunderground organs is discussed separately inthis handbook. Many herbaceous perennials havesucculent stems and leaves that, in cold or dry
climates, die back in fall to an overwinteringcrown or root structure, while others cease growth
but do not go dormant in response to inclement
weather.
Herbaceous perennials include species in justabout every plant family and vary greatly inadaptability, growth patterns, and tolerance toheat and cold. In fact, it is the great diversitythat presents the most problems, including thatof postharvest storage. Some nurseries carryhundreds if not thousands of species, and methodsof production vary greatly.

Storage of Bare-Root Crowns
Seedlings, rooted cuttings, or divisions can befield-planted, grown, and harvested as bare-root(crowns and roots with soil removed) plants infall. Storage of the bare-root plants is convenient,since they can be trimmed, processed, andpackaged during winter when harvest may not bepractical because of snow, ice, or rain. Throughout
winter and spring, bare-root plants are removed

from storage and shipped to wholesale and retailnurseries.
Grower experience and research results haveestablished 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 togrow plants on sandy soils so that harvesting isinterrupted 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 mosthardy herbaceous perennials, sugars and nutrientsaccumulate 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 tothat in potato, sugar beet, and certain other edible
herbaceous perennials.
If harvested before complete maturation,
bare-root plants will have a much shorterstorage life because of various factors suchas incomplete carbohydrate accumulation,727

insufficient suberization of the roots and crowns,
lack of overwintering buds, and ultimately thedevelopment of molds and rots (Hanchek and
Cameron 1995). In practice, however, growers
often harvest prematurely in fall, especially innorthern regions, since snow can quickly end theharvest 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 reallygo dormant and do not completely die back to theground except in the coldest of winters. In someinstances, the tops can be cut with a rotary mower
to remove excess leaves and stems before harvest
to reduce postharvest cleaning and grading andpotentially increase storage success. However,most species that do not attain full dormancy are
difficult to store for long periods, since many havewounded green tops with a high respiration rate,
fibrous roots, and insufficient carbohydrate storage
reserves. Also, the more green tissue removed, themore 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 ofthe overwintering underground structures.
Considering the diversity of herbaceousperennials, the overwintering root structure canprovide one additional piece of information thatcan 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. Greentissue 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 of728

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 whenharvested 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 andstorability of potato tubers.

Postharvest Grading and Packaging
Ideally, harvested roots and crowns should beprocessed, packed, and immediately cooled
for long-term storage. In practice, herbaceousperennials are often harvested in fall fasterthan they can be processed. Crowns, roots,
and remaining above-ground tissue are rapidly
respiring immediately after harvest because ofwounding, and to prevent fermentation it is criticalto keep plants cool and to provide adequate
ventilation for the tissue. Initial plant temperaturedepends 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 bemonitored closely with hand-held or automatedthermometers. There is a real possibility offermentation when O2 movement is restricted
in large piles or tightly packed crates of plants,
particularly those with green tops or fibrous rootsystems. If temperatures rise in stacks of plantmaterial, then it is critical to add refrigeration,
improve ventilation, or both.

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 healingof harvested herbaceous perennials, but woundhealing 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 ofstorage. Unsealed polyethylene liners (1.5 to 3
mils thick) are used for -2 °C (28 °F) storage.
At below-freezing storage temperatures, theseliners permit O2 movement adequate to supply
the needs of respiration and protect against water
loss (Cameron 1988). These same liners can leadto fermentation and loss of product at higher
temperatures, since they may limit air movement
to such an extent that the supply of O2 can notmeet the increased demands of respiration. Many
herbaceous perennials are packaged in multiplesof 25 with the liners in a cardboard box readyfor shipping later in the season. It is important tomatch box size to crown size since overpacking
can also lead to fermentation and loss of product,
particularly for plants with green tops, fibrousroots, 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 ofapples). Although appropriate for some otherwise
difficult-to-store plants, bulk bins can lead toproblems if extra care is not taken to ensurethat the entire contents are cooled quickly.
Temperatures at the center of the bin need to bemonitored closely, especially for the first 2 to 3
weeks. Heating, fermentation, and eventuallydecay 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 coolingrate. They can be restacked closer together after
they reach storage temperature.

Optimum Storage Conditions
The optimum storage temperature for mosthardy herbaceous perennials is between -2.8 and-2.2 °C (27 to 28 °F) (Mahlstede and Fletcher
1960, Maqbool and Cameron 1994). At thesetemperatures, tissues are generally not frozen,
and respiration and water activity are minimized.
However, not all herbaceous perennials canwithstand subfreezing temperatures, and thefollowing 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 regrowthfollowing storage, regardless of pretreatments andstorage conditions, and are best overwintered as
potted plants. These plants, such as gaillardia andcoreopsis, can be stored as small containerized
plants packed into polyethylene-lined boxes up
to several months. Hibiscus, alcea, sidalcea, andother malvaceous plants are sensitive to lowtemperature storage, even in minimally heatedgreenhouses. Short-term storage of these genera
should be at warmer temperatures. Herbaceousperennials considered very difficult to store forextended 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 tostore as bare-root plants for extended periods.
Even closely related plants can have different
overwintering capacities. Much depends on thespecies, overall plant vigor, and size in the field729

before harvest. Problems encountered duringstorage of bare-root plants include developmentof rots and surface molds, desiccation, and growthof fragile buds after the dormancy requirement
has been met. Each of these problems increases
with storage duration and temperature. Hourlyor daily temperature fluctuations can increasetissue desiccation, condensation on the package,and ultimately surface molds and rots, so it isimportant to maintain constant temperature into
spring.
Molds and bacteria can establish on dead roots orwounded tissue early during storage, especially ifplants are not cooled rapidly. Some surface molds
do not seriously harm the regrowth capacity of thecrowns (Maqbool and Cameron 1994). However,they are unsightly and often cause rejection of a
shipment, which can represent a substantial lossof revenue, considering the time and effort spent
producing and storing the plants up to the timethey are sold. Molds are invariably more severe atelevated 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 havebeen inconclusive (Hanchek et al. 1990).
Bud-break can occur on many perennials such asasters, shasta daisies, geums, lupines, bleedinghearts, 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 canoccur 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 atelevated 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 adequatecooling capacity, so temperatures can rise inspring as the cooling requirement increases.
Premature bud-break can be a serious problem inthese storage facilities.
730

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 plugtrays 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 techniquesborrowed largely from the bedding plant industry.
The shift to plug production has been hastenedby improved uniformity of seed-propagatedherbaceous perennials and increased demand
for large numbers of plants. Typically, plugs
are finished within 6 to 12 weeks of seeding orplacement of the cutting. Producers often sell theirproduct to finishers—greenhouse growers who
pot plugs into larger containers and grow them forretail sale. Traditionally, plugs are purchased andcontainerized in fall, and finished plants are soldthe 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 ismore 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, thoughmost 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 spacerequired. Plugs can be stored for convenience (aswhen 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

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 describedfor bare-root plants. Plug trays were packed inpolyethylene liners and stored in the dark without
any additional water. Many perennial speciesgrown as plugs did not survive direct transferfrom 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 plugstorage under controlled conditions, though moststorage still takes place in minimally heatedgreenhouses. If growers rent storage facilities,
they should ensure that refrigeration capacity isadequate 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.

Mahlstede, J.P., and W.E. Fletcher. 1960. Storageof 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, andW.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, andW.H. Carlson. 1996. Cold treatment, photoperiod,and forcing temperature influence flowering of
Lavandula angustifolia. HortScience 31(7):1150–
1153.

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 herbaceousperennials. J. Environ. Hort. 8(1):29–32.
731

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 shippedin containers and arrive in buyers’ hands byovernight delivery or within a few days. Manyorchid growers do not ship orchids during wintermonths to avoid chilling or freezing injury to theplants. 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 andDendrobium orchids. Potted, blooming orchids
represent a $100 million industry in the UnitedStates alone (NASS 2001). However, for the mostpart, research in proper postharvest handlingof orchids has lagged behind the increase inproduction 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 removalof pollen caps (emasculation) trigger ethylene
production by flowers and result in rapid wilting.
Blooming orchids should be handled carefully sothat accidental pollination and emasculation do
not occur. Accelerated flower wilting as a resultof ethylene evolution following pollination in
Cymbidium, Dortitaenopsis, Dendrobium, andPhalaenopsis orchids is induced by a loss of waterfrom 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). Treatingorchid flowers with the ethylene biosynthesis
inhibitor aminooxyacetic acid (AOA) did not alter

732

their sensitivity to ethylene. Research also showedthat 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 andWang 2000); all treated flowers wilted within 3days after exposure. Thus, AOA has no effect onlongevity 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 theirdisplay-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 effectof 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 highas 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 andtransported at 12 to 18 °C (54 to 64 °F) (Akamine
1976), whereas flowers of temperate orchids suchas Cymbidium may be stored at temperatures as
low as 5 °C (41 °F) (Sheehan 1954).

Optimum Storage Conditions

Shipping Information

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 of15, 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 havesevere leaf loss after storing at 30 °C have delayed
spiking and flowering.

Because of quarantine regulations, internationallyshipped orchids are often removed from their
potting medium. The bare-root plants are allowed
to dehydrate slightly before packing. This isdone for several reasons. Slight dehydration
allows for packing more plants per box, avoids
breaking leaves, and reduces the chances ofmoisture buildup to weaken shipping boxes. Dryer
plants also reduce incidence of rotting before
boxes are opened. Plants are usually packed inlayers alternating with shredded paper or othermaterial. Often, plants are individually wrapped innewspaper, particularly those that have developed
inflorescences.

Preconditioning greenhouse-grown potted
Phalaenopsis plants at 25 °C (77 °F ) for 10days, 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 andhybrids need relatively cool air to initiate theflowering 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 havestarted 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 lastingover 120 days) and flower size (Wang 1997b).
Therefore, most retail stores have adequate lightlevels to maintain blooming Phalaenopsis while
they are being marketed.

Millions of bare-root Phalaenopsis orchids areshipped domestically and internationally eachyear. After the orchids are planted in pots andplaced 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 partsof 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 handlingof 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 andsensitivity in cut orchid flowers. Sci. Hort. 26:5767.
733

Kesta, S., and D. Amutiratana. 1986. Effect ofsucrose, 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. 15:129136.
Sheehan, T.J. 1954. Orchid flower storage. Amer.
Orchid Soc. Bul. 23:579-584.
Wang, Y.T. 1995. Phalaenopsis orchid lightrequirement during the induction of spiking.
HortScience 30:59-61.
Wang, Y.T. 1997a. Effect of postharvest
temperature and storage duration on growthand flowering of the Phalaenopsis orchids.
HortScience 32:517.
Wang, Y.T. 1997b. Phalaenopsis lightrequirements 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.

734

Wang, M.K., and Y.T. Wang. 2000. 1-MCP andSTS counteract ethylene effects on cut orchid
flowers. HortScience 35(3):349.

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 ResearchService, 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 timeafter harvest. Some seeds are used as food (forexample, cereals and legumes) and stored before
consumption, while others are stored to maintainviability and used to produce the next season’s crop.
This section describes basic procedures to maintainseed and pollen viability. More detailed descriptions
or procedures to maintain seed viability forextended periods (for example, for genetic stocks)
are published in Agriculture Handbook 506,
Principles and Practices of Seed Storage (Justiceand Bass 1978) or review articles (Priestley 1986,
Hong and Ellis 1996, Walters 1998a).

Classification of Seed Storage Behavior
Mature seeds generally have higher tolerance forlow moisture levels or temperatures than fresh
fruits, vegetables, or flowers. They acquire thistolerance during maturation on the parent plant,
presumably as a strategy to survive adverse climaticconditions such as drought and winter. The degreeof tolerance varies among species, but three
general categories exist: orthodox, recalcitrant, andintermediate.
Orthodox seeds are produced by most annual orbiennial 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 andcan be easily stored for many years by drying andcooling.

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 somedeciduous forest trees from temperate areas (suchas oak, chestnut, buckeye, and silver and sycamore
maple). As the name implies, recalcitrant seeds are
difficult to store and have shelf-lives usually <1year unless they are cryopreserved.
Intermediate seeds are produced by perennials
of tropical and subtropical origin (such as coffee,
citrus, macadamia, and papaya) and by sometree 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 astratification treatment such as damp media at
5 °C (41 °F).
The best way to identify whether a seed isrecalcitrant or not is to monitor survival while
drying (Hong and Ellis 1996). Seeds that arerecalcitrant lose viability within minutes ofdrying 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 watercontents (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 seedstorage behavior, but there are no hard and fastrules. A compendium listing storage guidelines forover 7,000 species is now available (Hong et al.
1996). Also, useful information on woody speciesgrown in the United States can be gleaned from
Agricultural Handbook 450 (Schopmeyer 1974).
735

Table 1. Guidelines to identify storage behavior of seeds
Trait

Guideline

Some exceptions

Growth habit

Most herbaceous plants produce orthodox seeds

Aquatic species

HabitatMany aquatic species, tropical rainforest species,
and temperate climax forest species produce
recalcitrant seeds

Most native Hawaiian species,
temperate conifers, somemaplesWater content
Most orthodox seeds dry naturally on theat harvest
parent plant		Seed size
Recalcitrant seeds are often large				
Desiccation
Orthodox seeds can survive complete water loss;
sensitivity
recalcitrant seeds cannot		

Seed Storage Behavior and General
Storage Principles
Because they are sensitive to drying, recalcitrant
seeds must be stored at 92 to 98% RH. The beststorage 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 contaminationis 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 canbe preserved for longer periods than recalcitrant
seeds. RH of 40 to 60% appears to provide
736

All immature seeds,
Solanaceae, Cucurbitae
Some aquatic species,
Rutaceae, some Rubiaceae
Orthodox seeds dried very
slowly (for >2 weeks) can be 		
severely damaged

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” whichstate 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, Justiceand Bass 1978). The “100s Rule” states that
adequate longevity for commercial seed storage
purposes (<5 yr) can be achieved by ensuring thatthe sum of the RH and temperature in °F duringstorage does not exceed 100.
These rules were developed as guidelines forcommercial seed storage. They are not valid for
extremely dry conditions, and their applicability
at extremely cold temperatures has not beenadequately tested.
A relatively new rule is that seeds store optimallyat 15 to 25% RH. Storing seeds with RH <15%will not increase shelf-life and may actuallyaccelerate deterioration (Walters 1998b). Seedwater 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 astandard freezer) enhances shelf-life 4- to 5-foldover 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 tomaintain 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.

of development on the parent plant. The hightemperatures, >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 5days in their fruiting structures can simulate slow
drying. Once immature seeds receive a slight andslow desiccation treatment, they can be threshedwith less damage.

Harrington’s rules are approximations and give
relative, rather than absolute, longevities. Absolute
longevity depends on initial seed quality. Seedquality 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, andpriming, affect overall seed quality and hence
seed longevity (Walters 1998a). Infestations ofstorage 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 isretarded 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.

While a brief period of slow drying of <5 days
at 20 °C (68 °F) enhances quality of prematurely
harvested orthodox seeds, prolonged exposureof 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 isinadequate RH control. Generally, exposure ofseeds to high RH first results in a reduction of seedvigor (slower germination) and then a reduction
in germination percentage. The higher the RH or
temperature, the faster seeds deteriorate (refer toHarrington’s rules). Germination percentages ofvegetables 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).

Numerous factors during seed development andmaturation 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 immatureembryos are not fully tolerant of desiccation andare damaged when dried, or because maximum
seed quality is acquired during the final stages

Seed priming is a procedure used to accelerate
germination rates of planted seeds. Seeds areusually 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).

Seed Quality Factors Influencing
Longevity of Orthodox Seeds

737

Anecdotal evidence suggests that seeds harvested
from the wild have a shorter shelf-life thanseeds harvested from cultivated plants. There
are numerous possible explanations. Throughagricultural practices, humans may have selected
for seeds with superior quality. Cultivated plants
may have received optimum growth conditions—
irrigation, fertility, and pest management—andare therefore more robust. Seeds collected fromthe 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 (Justiceand Bass 1978), probably because the seedcoats restrict the movement of air and water.
Seeds of Leguminosae and Malvaceae have atendency toward hard-seededness. The linkage
between embryo dormancy and longevity isdifficult to verify since seed dormancy confounds
measurements of viability for longevity tests.
Clearly, dormant seeds survive longer in thesoil, but this is more likely because they fail togerminate under moist conditions than because
they have more efficient mechanisms to survive inthe dry state.
Given similar storage and harvest conditions,seeds from orthodox species exhibit different
inherent longevities. For example, lettuce andonion 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 isbetter 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 canbe found in Justice and Bass (1978) and Priestley(1986).

738

Table 2. Approximate longevity for various seed storage behaviors and seed species
Storage type Species
		

Optimum
RH

Optimum moisture Time to 50% loss
content of seed1
in viability2		%g H2O per g dw

Recalcitrant

95 to 98

0.6 to 0.8		

2 weeks to 2 months

95 to 98

0.5 to 0.7		

6 to 8 months

90 to 95

0.5 to 0.7		

6 to 14 months

90 to 95

0.35 to 0.45		

9 to 18 months

Intermediate

Tea (Camellia sinensis)
Buckeye (Aesculus
hippocastanum)
Trifoliate orange(Poncirus trifoliata)
Wildrice (Zizania
palustris)

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
200.04 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)200.03 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
739

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 constantstorage at -18 °C (0 °F). Water content on a percentage dry weight or fresh weight basis areoften 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 thesame cultivar may be so great that it precludes
prediction of shelf-life. For example, germinationof 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 wereobtained for potato, pepper, sorghum, onion, andtomato: 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 toensure 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 relationshipis 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, Justiceand Bass 1978, Ellis et al. 1993), but it is notclear whether these treatments control moisturelevel 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 nurserystock should not be dried under the sun and740

should not be stored in a lighted room without aprotective container.

Procedures to Dry Orthodox Seeds
At storage temperatures >0 °C (32 °F), seed watercontent 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 bedamaging, so lower temperatures and high air flow
are recommended. Seeds should be spread out ina thin layer to allow air to circulate through theseed mass and gently mixed daily to ensure evendrying.
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 ofdried seeds in open bins with no RH control iscalled “open storage,” and the water content of
the seed will fluctuate according to the RH andtemperature in the warehouse. Open storage is notrecommended 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 toa 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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 thewater content of the seeds and the temperature atwhich they are stored.
A RH of 20 to 25% produces optimal seed watercontent for storage of most orthodox species(Walters 1998a,b). The equilibrium water content
varies among seeds according to lipid compositionand 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 someproducers to use it exclusively; however, constantdehumidification, especially in conjunction withrefrigeration, may be prohibitively expensive(Walters-Vertucci and Roos 1996). Depending onvolume of seeds handled and risk of mechanicalfailure, it may be safer and more cost-effective tostore seeds in moisture-proof containers.

When seed producers opt to store seeds
in moisture-proof bags, they increase thecomplexity of water content adjustments but
also the flexibility in choosing drying andstorage 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 thedrying and storage temperature need to beconsidered. Generally, seeds are dried at ambient
temperatures or slightly higher to speed up thedrying process and to reduce refrigeration costs(Walters-Vertucci and Roos 1996). The greater
the temperature differences between drying andstorage 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 abrief summary of recommended drying conditions
for given storage temperatures. To date, theseguidelines have proven reliable for all species
tested.

Table 3. Recommended drying conditions for seeds subsequently stored inmoisture-proof containers at various temperatures*
Drying RH for storage at—
Drying temperature
°C
25
15
5

15 °C (59 °F)

5 °C (41 °F)-18 °C (0 °F)

30
22
15†

%
38
30
22

45
38
30

*The given drying temperature and RH combinations give storage RH of 20-25% at theindicated storage temperature.
†
Drying seeds at temperatures less than the storage temperature is not cost effective andtherefore is strongly discouraged; dehumidification is more difficult at lower temperatures,and the refrigeration costs used during drying might be more effectively spent during storage.

741

Cost-Benefit Analyses
Drying and storage conditions used by seedproducers and suppliers largely depend on abalance between the cost of seed preservation andthe necessity to maintain high quality seeds fora certain period. The three main questions thatshould 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 usuallyrequires storage at ≤5 °C (41 °F). Refrigeration isexpensive, but only moderately so if the qualityof the seed would be destroyed by substandard
storage conditions. Generally, dehumidification
requires less energy than refrigeration, making
controlled RH environments a less expensivealternative to refrigeration for the short term
(Walters-Vertucci and Roos 1996). However,
because there is a limit to beneficial effects ofdrying 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 overthe long term than constant dehumidification in a
warm, humid climate. Seeds equilibrate faster atambient temperatures, allowing more seeds to beprocessed 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 withoutcompromising quality.

aging occurs can be monitored with initial andsubsequent germination assays. Different seedspecies have different germination requirementsthat are cataloged in Rule Books published by
the Association of Official Seed Analysts (1999).
Assessments of seed vigor are more difficult thanassessments of germination percentage but usuallyprovide an early warning of deterioration.

PollenPollen can be stored for facilitating seedproduction and breeding. Pollen from somefamilies is desiccation-tolerant—Liliaceae andSolanaceae, for example—and fairly easy tostore, 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 byeither 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 alsoenhances 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
Assessing Changes in Seed Quality
No storage procedure guarantees that seeds willremain viable forever. Seeds eventually lose vigor
and then viability with time. The extent to which
742

Association of Official Seed Analysts. 1999. Rules
for Testing Seeds. Association of Official Seed
Analysts, Lincoln, NE.

Barnabas, B., and G. Kovacs. 1997. Storage ofpollen. 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 andinstructions 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 todetermine 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.

Pammenter, N.W., and P. Berjak. 1999. A review
of recalcitrant seed physiology in relation todesiccation-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 andGermination, pp. 237-271. Marcel Dekker, New
York, NY.
Walters, C. 1998a. Understanding the mechanisms
and kinetics of seed aging. Seed Sci. Res. 8:223244.
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. Seedmoisture, seed drying and energy costs of a seedbank. In Report of the 50th Annual Corn andSorgham 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.

Ohlrogge, J.B., and T.P. Kernan. 1982. Oxygendependent aging of seeds. Plant Physiol. 70: 791794.

743

Almond

Quality Characteristics and Criteria

John M. Labavitch

In-shell almonds should have hulls that are
uniform, with a bright color, and be free ofadhering hull material or debris. The hull should
be intact and free of damage caused by the hulling
operation, insects, or fungi. Kernels should befully formed rather than shriveled. Kernels oflarger 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.

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 originatedfrom bitter-seeded species that evolved in thedeserts and foothills of central and southwest Asia.
Almonds have been cultivated for over 4,000
years, and starting about 450 BC were cultivatedaround the Mediterranean coastline from Turkey
to Tunisia. Almonds were first introduced to
California through the missions, but the largecommercial industry was built with trees broughtby settlers from the Eastern United States thathave thrived in the Mediterranean climate of theCentral 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 almondoil (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 removalfrom the orchard (Thompson et al. 1996). Thisis common if late season rains threaten a delay
in harvest. If limited huller capacity leads tostockpiling of nuts, they will likely be covered andsubjected to periodic fumigation to limit insect
damage. Nuts must be dried to <10% moistureprior to stockpiling.

744

Caveletto et al. (1985) used an assortment ofphysical, chemical, and sensory methods toevaluate the quality attributes of 23 almondvarieties in terms of their use as in-shell, raw,
roasted, and blanched nuts. They determinedcomposition of fats and sugars, described flavor
notes and textural characteristics, and evaluatedthe ability to tolerate processing procedures andsuitability for various products.

Horticultural Maturity Indices
Almond maturation can be monitored externallyby evaluating the extent of hull dehiscence. In
the absence of pressure from insects such as thenaval 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 pickedup 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 southand southwestern faces of the tree higher in the
canopy.

The California industry favors a timely (early)
harvest that limits naval orangeworm egg-layingin split hulls. Thus, harvest should be matchedto the time that the last nut on a tree has begun
to split. Nut removal can be near maximum, andminor 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, emphasizedcharacteristics include the integrity, shape, andhardness of the shell as well as the brightness anduniformity of its color. Freedom from foreignmaterial and signs of insect damage or decay arealso important. Shelled almonds should be free ofshell 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.

even less. Almonds should not be stored with
commodities that have strong odors because theirhigh 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 ina 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 atmospheresof <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 shelledkernels 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.

Optimum Storage Conditions

Respiration Rates

The low water and high fat contents of the kernel
make it relatively stable metabolically and able totolerate low temperatures. The primary objectivesof storage regimes are to maintain the low watercontent. Federal regulations define a safe moisturelevel 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 watercontent 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 longas nuts in the shell (about 6 mo), and pieces for

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 almondkernels 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 by745

late-season rains, they should not be fumigated.
The combination of elevated moisture andtemperature 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 theproblem. Wetting of freshly harvested almonds
followed by heating can cause the problem, andforced-air drying of rain-wetted kernels canprevent it. However, almonds that have been heldin 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 theunopened cotyledons).
While the almond kernel’s content ofpolyunsaturated fatty acids is much lessthan walnuts or pecans, failure to maintainproper storage lead to rancidification. Factors
contributing to rancidification were studied byZacheo et al. (1998).

kernels with insect damage will reduce the numberof whole kernels with excess levels (>1 ng/g) ofaflatoxins. However, lower grades and broken
kernels or kernels sold as animal feed or processedfor oil can still present problems (Schatzki 1996).
Sampling of kernels to test for aflatoxin presents
statistical problems because contamination iscentered 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 tocontrol the insect. In-home control of insects canuse 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 usefulnonchemical insect control approach appears
to be a <1% O2 and 9 to 9.5% CO2 CA regime(Guadagni et al. 1978).

Postharvest Pathology
References
Most infections with pathogens are initiated in theorchard, and because clean-up following harvest is
not absolute, the potential problems are transferredto the postharvest environment. In-shell productis relatively protected unless the shell has beenbroken or penetrated by insects. The most serious
pathogens are fungi such as Aspergillus flavus
and A. parasiticus, which can produce aflatoxinsthat are both toxic and carcinogenic. Damaged
kernels must be discarded prior to storage andlow temperature and RH conditions must be
maintained. Phillips et al. (1979) and King etal. (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 andKing and Schade (1986) have described the effectof various water activities and temperatures on thecompetition between these fungi on stored kernels.
Because of the relationship between insect damage
and pathogen presence, sorting to eliminate whole746

Abdallah, A., M.H. Ahumada, and T.M. Gradziel.
1998. Oil content and fatty acid composition ofalmond kernels from different genotypes andCalifornia 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 ofalmond varieties. Report to the California Almond
Board. Pomology Department, University ofCalifornia, 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.

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.

Zacheo, G., A.R. Cappello, L.M. Perrone, andG.V. Gnoni. 1998. Analysis of factors influencing
lipid oxidation of almond seeds during accelerated
ageing. Lebensm.-Wiss. Technol. 31:6-9.

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 andwater activity and its influence on fungal flora andseed composition. J. Food Sci. 48:615-617.
King, A.D., Jr., and J.E. Schade. 1986. Influenceof almond harvest, processing and storage on
fungal population and flora. J. Food Sci. 51:202205, 215.
Phillips, D.J., B. Mackey, W.R. Ellis, and T.N.
Hansen. 1979. Occurrence and interaction ofAspergillus 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 inalmonds. 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.

747

Hazelnut

tolerance or resistance to allow production east of
the Rocky Mountains with some success.

Niels Maness
Maness is with the Department of Horticultureand Landscape Architecture, Oklahoma State
University, Stillwater, OK.

Scientific Name and Introduction
Corylus avellana L., the filbert or hazelnut, is amember 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 ofCorylus avellana to distinguish them from theshort-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 fromthis 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 thelargest production area in the United States is the
Pacific Northwest, with 99% of production in the
Willamette Valley of Oregon (Mehlenbacher andOlsen 1997). Market uses for the U.S. crop havebeen roughly evenly divided between in-shell andkernel markets, but trends are shifting towards
kernel markets. The major variety in the U.S.
is Barcelona, followed by Davinia, Ennis, andWillamette.
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
748

Quality Characteristics and Criteria
In-shell hazelnuts should be properly sized
to meet the stated market type and should beproperly filled with at least 50% of the shell cavity
occupied by nutmeat. Shells should be free ofcracks and noticeable mechanical injury and clean
and brightly colored; coloring patterns should becharacteristic 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 andoff odor, off flavor, or mold. Water content ofkernels 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 specificationof classes “Extra” and “Class I” in international
trade.
For in-shell markets, larger and particularlyrounded types are preferred. Shelled markets
accommodate both rounded and oblong types, andsize preference depends on the intended end use.
Hazelnut kernel oil content ranges from 57 to over
70%, and total sugars average about 4%; bothvary with variety and growing location (Botta etal. 1994). Hazelnuts are highest among tree nuts in
α-tocopherol content (366 μg/g oil) and are also arich source of vitamin B6 (0.54 to 0.89 mg per 100g) (Richardson 1997).

Horticultural Maturity Indices
In areas where hazelnuts are mechanicallyharvested, 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 iscomplete and when the nut detaches from the baseof the husk (Thompson et al. 1996). In the UnitedStates, most nuts are mature during or by the endof 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 andallow nut drop, nuts are considered maturewhen 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 andfor importation of in-shell or shelled hazelnuts,
and international UN/ECE standards exist for
both in-shell and shelled hazelnuts. Grades areprimarily determined by size, degree of kernel
fill, color, and freedom from defects and foreignmaterial. U.S. No. 1 filberts must contain no morethan 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 morethan 3% are insect injured; and not more than
15% filberts that fail to meet the specified sizeand of which no more than 10% are undersized.
Furthermore, shells are free from surface moistureand the combined shell and kernel moisture
content is not greater than 10%; shells are wellformed, unbroken, not discolored, have adheringhusk covering not more than 5% of the shell area
and are practically free of adhering dirt and otherforeign material.
Size is specified in connection with the grade interms of minimum and maximum diameters thatwill pass through round openings of a screen andare specified separately for round-type varieties
and long-type varieties. See following:______________________________________________________________________
Size
Round-typeLong-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)
Medium45/64 (17.9)
49/64 (19.4)
45/64 (17.9)
34/64 (13.5)
Small—
45/64 (17.9)—
35/64 (13.9)______________________________________________________________________

749

All hazelnuts imported into the United States inlot quantities which exceed 115 lb (52.2 kg) net
weight must meet minimum grade standards as
specified under section 8e of the AgriculturalMarketing Agreement Act. In-shell hazelnuts mustmeet U.S. No. 1 grade and be at least medium sizewith 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 notmore than 0.0002% foreign material; not morethan 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 theexport 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 wellformed, intact, sound, and clean and the kernels
must be sound, clean, sufficiently developed, andfree 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% moistureand kernels not more than 7% moisture, andforeign material may not exceed 0.25% of thetotal in-shell weight. Sizing and statement ofvariety, 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 thespecified size is allowed.
Extra hazelnuts must be 16 mm in diameteror 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 generalappearance, quality, or keeping quality. They must
contain no more than 4% empty nuts on a countbasis; not more than 3% of the weight of in-shellnuts may contain shell defects; and not more than750

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 morein 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 bemoldy, 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 thein-shell nuts retain their essential characteristics asregards 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 sizein 2 mm increments from 22 mm to 14 mm or
less. Sizing for nuts less than 22 mm in diametermust 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 classificationsof Extra, Class I, and Class II also exist; andrequirements 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 notexceed 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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 weightof 5% is allowed for rounded types and 10% foroblong types. To be designated either Extra or
Class I, hazelnut kernels must have a minimum
diameter of 9 mm, with the exception of hazelnutsof the piccolo type or hazelnuts having a similar
designation for which a diameter of 6 to 9 mm isallowed.
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 slightsuperficial defects provided they do not affect thegeneral appearance, quality, or keeping quality.
Total tolerances for defects are 5% by weight or
6% if the lot is specified as “Old Crop.” Of thetotal tolerance, no more than 1% may be rancid,
rotten, moldy, have off odor or off flavor, or bedamaged by insects or rodents; no more than 2%
may be not fully developed, including shrunken
and shriveled, stained, and yellowish kernels; andnot more than 3% may be mechanically damaged
and pieces. Not included in the total tolerance isthat not more than 2% may be twin hazelnuts.
Class I hazelnut kernels must be of good quality,
must be characteristic of the variety and/orcommercial type, and may have slight defects ofform 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 notfully 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 morethan 5% may be twin hazelnuts.
Class II hazelnut kernels may be of any size (ifsize is specified, tolerances apply) and be ofmarketable quality; they may contain defects
provided that kernels retain their essential

characteristics as regards general appearance,
quality, and keeping quality. Total tolerances fordefects 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, andyellowish kernels; and not more than 10% may bemechanically damaged and pieces. Not includedin 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 theclassification “screened,” the size “and less” is notallowed.

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 andunroasted kernels may be stored for 24 mo withminimal loss in quality at temperatures up to 10°C (50 °F). Roasted kernels may only be heldfor 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 suchas 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-shellhazelnuts may be marketed in bulk containers.
Exposure to moisture and high RH should be
avoided.

751

Chilling Sensitivity
Hazelnuts are not sensitive to chilling and arecommonly stored at temperatures at or below
freezing for long term storage.

Ethylene Production and Sensitivity
Ethylene may be used as a harvest aide to enhancematuration of husks for earlier harvest (Lagerstedt1979). 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 withnuts having split or weak sutures. It appears to becaused by an oxidation process that occurs on thepellicle only and may or may not be associatedwith 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 ofaffected 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 prevalentthroughout nut development. It is the major
752

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 ofproducing aflatoxin, has been isolated fromhazelnuts 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 amountsof organic material on the surface of shells,
chlorine concentrations should be monitored andreplenished as necessary to maintain chlorine atconcentrations 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 varietiesof 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 andincluding the States of Montana, Wyoming,
Colorado, and New Mexico; the entire State ofWashington; and all provinces, districts, andterritories of Canada east of and including theprovince of Alberta.

Special Considerations
Hazelnuts marketed in-shell should be sampledperiodically to assess nutmeat quality. Although
the most common nut causing allergy in children
and adults is peanut, hazelnuts may also be anallergenic food additive (Ewan 1996), and thepresence of hazelnut in foods must be declared.

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 tostorage in-shell (Ebraheim et al. 1994). Roasting
temperature and duration interact to decrease
shelf-life with increasing roasting temperatureand 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.

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 ofeating 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. 445:301304.
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.

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 andtiming 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 ofhazelnut (Corylus avellana) protein in complex
food mixtures. J. Agric. Food Chem. 47:42094218.
Lagerstedt, H.B. 1979. Filberts. In R.A. Jaynes,ed., Nut Tree Culture in North America, pp. 128147. Northern Nut Growers Association, Hamden,
CT.
753

Macadamia Nut
Catherine G. Cavaletto
Cavaletto is with the Department of Tropical Plant
and Soil Science, University of Hawaii at Manoa,
Honolulu, HI.

Shortly after this time, the nuts fall to theground and are harvested. Sometimes shakeharvesting is employed to facilitate the harvest
while minimizing the amount of immature nuts
harvested. Recommended harvest interval forground-harvested nuts is 1 mo. Damage by thetropical nut borer (Hypothenemus obscurus [F.])can begin to increase rapidly after 3 weeks on the
ground (Jones 1992).

Scientific Name and Introduction
The family Proteaceae includes about 10 speciesof the genus Macadamia, 2 of which produce
edible nuts: M. integrifolia and M. tetraphylla or
hybrids of these. The major species of commerceis M. integrifolia. Macadamia nuts are native toAustralia and are produced there as well as in
Hawaii, Central and South America, and parts ofAfrica. Nearly all production consists of grafted
trees of cultivars developed in Hawaii or Australia.
The edible kernel is enclosed in a thick, hard shellthat, 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, extraneousmaterial, hollow centers, discoloration, andadhering 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 typicallycontain less oil. Oil content is a major quality
factor that varies with cultivar and maturity and isinversely 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.
754

Grades, Sizes, and Packaging
No U.S. grades are established for macadamia
nuts, but the State of Hawaii has standards andgrades 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-shellnuts and for roasted kernels. Shelled nuts areusually packaged in 11.4 to 22.7 kg (25 to 50 lb)
vacuum-packed or nitrogen-flushed foil bags forthe wholesale market. Larger nitrogen-flushedcontainers are sometimes used.

Optimum Storage Conditions
Macadamia nuts should be husked within 24 h of
harvest, after which the drying process should beinitiated. Freshly fallen nuts contain about 25%
kernel moisture, although nuts that have remainedon the ground for extended periods may have as
little as 10 to 15% moisture. Drying should begin
with ambient air, followed by a gradual increasein temperature that will not exceed 60 °C (140°F) in the final stage of drying. Drying may be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 andfinish drying of kernels alone to 1.5% moisture.
It is important to protect the dry kernels frommoisture and O2, so packaging in a material thatis impervious to moisture is important. Vacuum
packaging or nitrogen flush offers protection
from O2. Exposure to moisture results in lossof crispness and shelf-life. Likewise, prolonged
exposure to O2 results in rancidity. Cold storage isnormally 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.

begin the drying process at ambient temperatureor 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) andto 6% before increasing the temperature to 60 °C(140 °F) (Prichavudhi and Yamamoto 1965).

Postharvest Pathology

Macadamia nuts are not sensitive to chillingprovided they have been dried. Dry kernels
are commonly stored below 15 °C (59 °F) forbulk storage and can successfully be frozen toextend shelf-life. Care must be taken in thawing
frozen nuts to prevent condensation and resulting
moisture gain.

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 andAihara-Sasaki 1999). Delay in husking the nuts
following harvest can also result in mold growthand fermentation. Husking should occur within 24
h of harvest. The thick shell provides considerable
protection for the kernel, but cracked shells andopen micropyles can provide entry of fungi andbacteria as well as ants. When the nuts fall fromthe 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 (Beuchat1978), insufficient to support the growth of moldor bacteria.

Physiological Disorders

Quarantine Issues

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 temperaturesdevelop brown centers when roasted as a resultof high reducing sugar levels. It is necessary to

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).

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 incracking.

Chilling Sensitivity

755

Special Considerations
Kernel stability is related to moisture content
and to oxidative rancidity. Of these, moisture
content is the most critical. Raw kernels withmoisture 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 usuallyaccomplished 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 4-4413.
Jones, V.P. 1992. Effect of harvest interval andcultivar on damage to macadamia nuts caused byHypothenemus 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. Effectof drying temperature on chemical compositionand quality of macadamia nuts. Food Technol.
19(5):129-132.
756

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.

Peanut
Niels Maness
Maness is with the Department of Horticultureand Landscape Architecture, Oklahoma State
University, Stillwater, OK.

Scientific Name and Introduction
Arachis hypogaea L., the peanut or groundnut, isan 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 Statesin the 1980s, 70% of the peanuts grown wererunners, 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 andare now cultivated worldwide, with the majorityof production in India, Asia, and the UnitedStates. In the United States, about 60% of peanuts
are used in a variety of food products, with thereminder 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).

or foreign material and off odor or flavor. Raw
peanuts should be surrounded by a tan, pink, or
red seedcoat (testa) that fully encapsulates theseed, and the interior color of each half-seedshould 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 withgood viability if seed moisture content is <3.3%(Cheng et al. 1997). Peanuts marketed without
seedcoats (blanched) should have an ivory-coloredraw kernel. Peanuts are most commonly consumed
following roasting, which may be accomplishedin-shell or after shelling. Roasted peanut kernels
should be light yellow in color, free of externaloil, contain <6% moisture, and be free of darkcolored kernels.
Peanut seed, and particularly peanut seedcoats, area 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 lesssusceptible to oxidative deterioration and off
flavor development caused by oxidative cleavageof polyunsaturated fatty acids. The ratio of oleic
to linoleic is influenced primarily by genotype,but interactions exist between genotype and theenvironment.

Horticultural Maturity IndicesQuality Characteristics and Criteria
Shelled peanuts should be properly sized tomeet market type, be free of misshapen or
underdeveloped kernels, and be free of any shell

Peanuts are an indeterminant plant, with flowering
followed by underground seed development overa range of time. Assessment of peanut maturity
should be conducted using multiple plants at
757

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
screen size				

Fall-through Other Splits Damage
Damage Foreign Moistureprescribed
types		and minor		material
screens			
defects%						

No. 1 (15/64 x 3/4” slot)
APSA
US

2.00
2.00

1.00
1.00

3.00
3.00

0.75
1.50

1.25
2.00

0.10
0.10

9.00
-----

Splits (16/64” round)
APSA
US

*
**

2.00
2.00

-------

1.50
2.00

2.00
2.00

0.20
0.20

9.00
----

No. 2 (16/64” round)
APSA
US

6.00***
6.00***

2.00
2.00-------

1.00
----

2.00
2.50

0.20
0.20

9.00
----

*

(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% forsound 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%

758

759

5.00

----

-----------

Medium40-50 ct. per oz.***or 18/64 x 3/4” slot
(Report % riding
21/64 x 3/4” slot)

Select16/64 x 3/4” slot
(Report % riding
21/64 x 3/4” slot)

No. 1
16/64 x 3/4” slot
(Report % riding
18/64 x 3/4” slot)
APSA
USMill run
16/64 x 3/4” slot
3.00

3.00
3.00

3.00

3.00

1.00

1.00
1.00

1.00

1.00

3.00

3.00
3.00

3.00

3.00

1.00

1.00
1.50

1.00

1.00

2.00

2.00
2.00

2.00

2.00

0.10

0.10
0.10

0.10

0.10

9.00

9.00
----

9.00

9.00

Grade andFall-throughFall-through
Other Splits Damage
DamageForeign
Moisture
minimumprescribed
16/64 x 3/4”
types			and minor material		
screen size
screensslot 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
9.00

Table 2. Comparison of screen sizes and tolerances (by weight) for American Peanut Shellers Association(APSA) and USDA Grades for shelled runner peanuts

760

*
**

*
**

2.00
2.00

-------

1.50
2.00

2.00
2.00

0.20
0.20

9.00
----

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.

(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 toexceed 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.

*

Splits17/64” round
APSA
US

Grade andFall-throughFall-through
Other Splits Damage
DamageForeign
Moisture
minimumprescribed
16/64 x 3/4”
types			and minor material		
screen size
screensslot screen				defects
		 %										Table 2. Comparison of screen sizes and tolerances (by weight) for American Peanut Shellers Association(APSA) and USDA Grades for shelled runner peanuts—continued

761

3.00

3.00

Medium Virginia
18/64 x 1” slot
APSA & US

No. 1 Virginia
15/64 x 1” slot
APSA & US
1.00

1.00

----

----

As graded

1.25

1.25

1.00

Not lessthan 90.00

3.00

3.00

3.00

2.50

2.00

2.00

2.00

1.75

0.20

0.20

0.10

0.10

0.10

----

----

----

----

----

----

----

**864

**640

**512

Each of the above APSA whole grades may be certified as “with splits” providing all requirements of the grade are met, except that atolerance of 15% is allowed for split kernels of which not more than 3% will pass through 17/64 in round screen.

* (APSA & US)—includes both sound split and broken and sound whole kernels which pass through prescribed screens.
** Unless otherwise specified.

Virginia splits
20/64” round
APSA & US
*3.00
2.00
				
No. 2 Virginia
17/64” round
APSA & US
*6.00
2.00

3.00

Extra large
20/64 x 1” slot
APSA & US
0.75

Fall-through
Other
Sound Split
DamageDamageForeign
MoistureCount perprescribedtypes
or broken		and minor material		
pound		screens		
kernels		
defects			
maximum%										

			Grade andminimum
screen size		Table 3. Comparison of screen sizes and tolerances (by weight) for American Peanut Shellers Association (APSA)
and USDA Grades for shelled Virginia peanuts

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-throughCracked or
DamagedCount per poundand minimumprescribedbroken shells,
kernels
screen size
screenpops, paper, and					
			foreign material
				
			
%			
Jumbo
37/64 x 3”
APSA
US

5.00
5.00

*10.00*10.003.50
3.50**176 (U.O.S.)**176 (U.O.S.)

Fancy
32/64 x 3”
APSA
US

5.00
5.00

*11.00*11.004.50
4.50**225 (U.O.S.)**225 (U.O.S.)* (APSA & US)—not more than 0.5% shall be allowed as dirt or other foreign material.
** Unless otherwise specified.

762

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 theinner hull is brown and the seed coat is pink to
red. Optimum maturity is reached for runnerand Spanish types when 75 to 80% of the innerhull has turned brown and for Virginia types
when 65% of the seed coat has turned deep pink.
Runner peanut maturity can be determined by ahull-scrape method, in which maturity profiles forsamples 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 theAmerican Peanut Shellers Association fficial
Trade Rules for shelled peanuts based primarilyon 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 basedon maturity; freedom from loose shelled peanuts;
discoloration of shell; presence of dirt, shell, andother foreign material; and degree of kernel fillinside 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, lesscommonly, in 50-lb (23 kg) burlap bags for aweek to 10 mo prior to shelling (Smith et al.
1995). After shelling, raw peanuts are often
shipped in bulk containers but may be packaged inburlap 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 theUnited 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 whichcontain 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) duringshelling (McIntosh and Davidson 1971). Peanutmoisture content >10% should be avoided toprevent 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 moistureand 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) withmoisture 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 bruisingand 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.

763

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).

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 arelatively low rate of respiration. During harvestand prior to curing, especially for high-moisturepeanuts, respiration rates may be substantial andsignificant losses in quality can ensue. Freshly
harvested peanuts should be dried soon after
harvest to <10% moisture to assure optimum
quality.

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 inbulk 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 chillingand 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 and764

Physiological Disorders
Shriveled seed trait has been identified as aheritable condition for peanuts. Seed maturenormally but appear shriveled and thus appear
to have been harvested while immature. Seedsof shriveled lines exhibit up to 67% less oil anddouble the amount of sucrose, and defatted meal
contained less protein (Jakkula et al. 1997).
Improper curing of peanuts results in loss ofquality and off-flavor development.
Fermented, fruity off flavor is caused by freezing
temperatures during harvest while peanuts are stillwindrowed (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 storageat 1 to 5 °C (33.8 to 41 °F) and reduction ofmoisture content to <7.5% may be effective in
reducing mold and fungi growth in storage. The

presence of toxic fungal metabolites (mycotoxins)
are a particular concern. The name “aflatoxin”
refers to four metabolites found in contaminatedpeanuts and designated aflatoxin B1, B2, G1,
and G2. Aflatoxins B1 and B2 are metabolites ofAspergillus flavus, and all four aflatoxins may be
produced by Aspergillus parasiticus (Cole et al.
1995). A fifth mycotoxin, cyclopiazonic acid, issomewhat 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 anddrought stress during the last 3 to 6 weeks ofthe growing season (Cole et al. 1989). Lateseason irrigation may be effective in reducing
aflatoxin contamination (Dorner et al. 1989).
When aflatoxin contamination occurs, it iscommon 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, anddetection of ≥15 ppb (nL L-1) aflatoxin leads topositive aflatoxin identification, the irregular
distribution of infection may lead to false negative
designations.
Storage conditions to deter growth of the causalorganisms and subsequent metabolic productionof the mycotoxins primarily involve preventionof rehydration during storage. Decontaminationof contaminated lots is most effectively done withelectronic color sorting, although size and density
separation may also be effective in removal of themost susceptible underdeveloped seed.

Quarantine Issues

virus. During import of peanuts, all lots mustbe labeled with a positive lot identification andmust meet the requirements for segregation 1
peanuts if used for human consumption. Peanuts
with visible Aspergillus flavus mold, or thosecontaining ≥15 ppb aflatoxin, may not be used foredible purposes; they may be used for oil stock.
Such peanuts may be blanched and reseparated
into aflatoxin-negative lots, which may be used foredible 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 foodproduct containing peanuts or peanut oil must belabeled 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, andother handling equipment should be padded
where appropriate and properly maintained toprevent excessive breakage during handling.
Once shelled and roasted, peanuts should be
handled carefully to prevent separation of thehalf kernels and breakage since splits and pieces
are more susceptible to oxidative deterioration
and rancidity development. Peanuts will absorb
lipophilic volatiles from their surroundings orfrom inappropriate packaging that can induce
off flavors. Absorption of ammonia can cause
darkening of nutmeats.

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

765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 andresistance. 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 theSemi-Arid Tropics Center, Patancheru, Peru.
Davidson, J.I., T.B. Whitaker, and J.W. Dickens.
1982. Grading, cleaning, storage, shelling andmarketing of peanuts in the United States. In
H.E. Pattee and C.T. Young, eds., Peanut Scienceand 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 andphytoalexin production in pre-harvest aflatoxin
accumulation of drought-stressed peanuts.
Mycopathalogia 105:117-128.

766

Holaday, C.E., and J.L. Pearson. 1974. Effects ofgenotype and production area on the fatty acidcomposition, total oil and total protein in peanuts.
J. Food Sci. 39:1206-1209.
Jakkula, L.R., S.F. O’Keefe, D.A. Knauft, andK.J. Boote. 1997. Chemical characterization of a
shriveled seed trait in peanut. Crop Sci. 37:15601567.
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 phagedisplay 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. Effectof temperature on shelling runner- and spanishtype peanuts. Rep. 52-65, U.S. Department ofAgriculture, Agricultural Research Service,
Washington, DC.
Moseley, Y.C., H.B. Manbeck, G.L. Barnes, andG.L. Nelson. 1971. Controlled atmosphere forshort 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 28:850859.
Sanders, T.H., P.B. Blankenship, J.R. Vercellotti,
and K.L. Crippen. 1990. Interaction of curing
temperature and inherent maturity distribution indescriptive flavor of commercial grade sizes of
Florunner peanuts. Peanut Sci. 17:85-89.

Sanders, T.H., R.W. McMichael, and K.W.
Hendrix. 2000. Occurrence of resveratrol in edible
peanuts. J. Agric. Food Chem. 48:1243-1246.

Wilson, D.A., and E. Jay. 1976. Effect ofcontrolled atmosphere storage on aflatoxin
production in high moisture peanuts (groundnuts).
J. Stored Prod. Res. 12:97-100.

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 ofchilling injury on windrowed peanuts. Peanut Sci.
16:51-54.
Singleton, J.A., and H.E. Pattee. 1991. Peanutmoisture/size, relation to freeze damage and effectof 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 andstorage from farmer stock to processing. In H.E.
Pattee and H.T. Stalker, eds., Advances in Peanut
Science, pp. 500-527. American Peanut Researchand 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 offood 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.

767

PecanHorticultural Maturity IndicesNiels Maness
Maness is with the Department of Horticultureand Landscape Architecture, Oklahoma State
University, Stillwater, OK.

Kernels are considered mature after oil
accumulation is complete, which coincides withshuck split (Eddy and Storey 1988). Maturation offruit within a tree occurs nonuniformly and can be
influenced by cultivar and weather conditions.

Scientific Name and Introduction

Grades, Sizes, and Packaging

Carya illinoinsis L. is a member of the hickoryfamily (Jugulaceae). The edible seed is surrounded
by a shuck that opens (dehisces) when the seed ismature. Nuts are harvested in late fall and early
winter by mechanically shaking the trees andgathering 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 andare 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.’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 shellcolor, absence of shell defects, kernel defects, andextraneous or foreign material. Sizes of in-shell
pecans are based on number of nuts per 0.45 kg (1lb) and include Oversize (≤55), Extra Large (56to 63), Large (64 to 77), Medium (78 to 95), andSmall (96 to 120). In-shell pecans are packaged inbags containing 36.4 to 54.5 kg (80 to 120 lb) orin palletized containers.

Quality Characteristics and Criteria
Pecan kernels should be yellow-golden to lightbrown in color, be of roughly equal width fromone end to the other, and be free of any shell orother foreign material as well as off odor or flavor.
Water content should be <4% to prevent moldgrowth and retard rancidity development. Water
content <2% increases brittleness that induces
greater kernel breakage during handling andenhances cracking of the testa, which increases O2
permeation of the nutmeat, favoring rancidity. Oilcontent of pecan kernels inversely affects shelflife, and oil content varies from 55 to 75% (byweight) and is influenced by cultivar, geographic
location, and year of production (Wells andMcMeans 1978).

768

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, degreeof kernel fill, moisture content, freedom from shellor extraneous material, and freedom from damage.
When the color of kernels in a lot conforms to
the “light” or “light amber” classification, thesecolor designations may be used to describe the lotin connection with the grade. Size classifications
for halves are based on number of halves per 0.45
kg (1 lb) and include Mammoth (≤250), Juniormammoth (251 to 300), Jumbo (301 to 350), Extralarge (351 to 450), Large (451 to 550), Medium(551 to 650), Small or Topper (651 to 750), andMidget (≥751). Size classification for pieces are
based on the maximum and minimum round
diameter in inches through which the pieces willor 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 1/8in), Midget (0.5 to 0.2 cm, 3/16 to 1/16 in), andGranules (0.3 to 0.2 cm, 1/8 to 1/16 in). Shelledpecans are packaged in 13.6-kg (30-lb) greaseproof boxes, either loose or vacuum-sealed insideplastic bags.

h (Dull and Kays 1988). Vacuum packaging canoffer a further benefit of protection from breakage.
Retail Outlet Display Considerations

Optimum Storage Conditions
Mechanically harvested in-shell pecans should bedried 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 handledwith 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 (18ºF) increase in temperature occurring over 48 h.
This can be accomplished by placing pecans fromfrozen storage sequentially into two rooms forseveral 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 moisturecondensation onto nutmeats during thawing that
could induce a soggy texture and promote moldgrowth.

Modified Atmosphere Considerations
Shelf-life of pecans may be increased by storagein 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 etal. 1990). O2 transmission rates for packaging
materials should be >0.08 mL per 100 cm per 24

Use of packaging to reduce O2 concentration andprevent excessive light exposure is recommended
for shelled pecans. In-shell pecans may bedisplayed in bulk containers. Exposure to moisture
should be prevented.

Chilling Sensitivity
Pecans are not sensitive to chilling and arecommonly 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 widthof halves along the longitudinal axis. It is causedby poor kernel fill during development. Thiscondition 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 indeveloping pecans; larvae hatch soon after kernel769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 ora portion of the nutmeat, has been identified
and attributed to breakdown of oil bodies andsubsequent leakage of oil within the cotyledon.
This leakage increases O2 exposure of oil anddecreases shelf-life by accelerating oxidative
rancidity development.

E. coli is a common shell contaminant, especiallyfor nuts harvested in orchards where animalgrazing is practiced (Marcus and Amling 1973).
Contamination of nutmeats may occur if shells arebroken during harvest or if shells are not properly
sanitized by addition of chlorine to heated soakwater just prior to cracking. Because of highamounts of organic material on the surface of
pecan shells, chlorine should be monitored andreplenished as needed to maintain the desiredconcentration.

Quarantine Issues
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 freezeor potassium insufficiency may also increaseprevalence of sticktights. Kernels from sticktightpecans are often of lower quality due to premature
death of the vascular system feeding thedeveloping kernels.
Vivipary (sprouting of nuts on the tree) renders
affected pecans unmarketable and may be reducedby late season irrigation (Stein et al. 1989) or by
fruit thinning (Sparks et al. 1995).

Postharvest Pathology
The most common decay found in pecans iscaused 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 thathave been isolated from pecans can produce
aflatoxins, a heat-resistant carcinogenic andtoxic 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 activityof 0.65 to 0.70, which will not support growth of
most molds.
770

Pecan shucks, shells, and nuts in the shell, as
well as containers, equipment, and vehicles usedin 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 andsampled periodically to assess nutmeat quality.
Pecan halves and pieces marketed in plasticbags 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 sunlightor excessive UV radiation should be exercised
to prevent darkening of the testa. Increased
temperature during handling can also enhancedarkening and promote development of rancid
flavor. Pecans will absorb lipophilic volatiles inthe environment that can introduce off flavors.
Absorption of ammonia will cause darkening ofnutmeats. 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.

References
Dull, G.G., and S.J. Kays. 1988. Quality andmechanical stability of pecan kernels withdifferent packaging protocols. J. Food Sci. 53:565567.
Eddy, M., and J.B. Storey. 1988. The influenceof harvest date on oil and flavor developmentin 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.

Wells, J.M., and J.L. McMeans. 1978. Rancidity,
iodine values and oil content of 21 pecan cultivars.
Proc. Southeastern Pecan Growers’ Assoc. 71:159162.
Woodroof, J.G., and E.K. Heaton. 1962. Storageof pecans. Research Bull. 149, University ofGeorgia, Georgia Experiment Station, Athens, GA.
Worley, R.E. 1982. Tree yield and nut
characteristics of pecan with irrigation underhumid conditions. J. Amer. Soc. Hort. Sci. 107:3034.

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 andpremature 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 andirrigation scheduling influence pecan growth andproduction. HortScience 24:607-611.
771

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 isa native of western Asia and Asia Minor, and wild
representatives are still found in hot, dry locationsin these areas. The pistachio was introduced toEurope 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 andFerguson 1995).
The pistachio tree is dioecious; thus orchardplantings must include the appropriate ratioof females and males (8:1 in older plantings,
but up to 25:1 in more recently establishedorchards [Kallsen et al. 1995]). At present the
California industry is dominated by one malecultivar (‘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 withpests and diseases, and efforts to evaluate existingalternative germplasm and develop new cultivars
are underway (Parfitt 1995a,b). There are alsoa 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 Ferguson1995). 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 the772

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 sweetand 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 theharvest is timed to the full accumulation of fat andsugar 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 throughivory to rose with full maturation. Activity inthe abscission zones between the nuts and therachis (assessed by a measurable decrease in“fruit removal force”) also indicates maturation.
When fully mature, the nut with its shell will beejected from the hull when pressure is appliedwith the thumb and forefinger at the hull’s distalend (Ferguson et al. 1995). Nuts at full maturity,
as judged by the preceding criteria, will have fullaccumulation of fat and simple sugars (Labavitch
et al. 1982).
Harvest should not be delayed past full maturationof the crop because this will increase losses tonavel 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 shellstaining because of breakdown of the phenolic-compound-rich hull tissues. When harvested thenuts are split and moisture content is high (40 to50%). Trees are shaken (by hand for young trees,mechanically for mature trees) and the nuts arecaught on tarps or a catching frame and transferred
to bins in order to eliminate problems caused bycontact with the soil.
Delays between harvest and further processing
should be minimized because they only
exacerbate problems caused by hull breakdown orcontamination of hull tissues. Problems caused byunavoidable delays in hulling and drying (below)
can be reduced by cold storage of bins at 0 ºC
(32 ºF) and <70% RH without increasing shellstaining (Kader et al. 1980, Thompson 1997). At
the processor, the bins of nuts are dumped, anddebris is removed by passage over an air leg.
Hulls are removed, blanks are removed in a floattank, 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 to48 h) with air heated to no more than 49 ºC (120ºF) (Ferguson et al. 1995).

described testing of a machine vision system thatmight prove useful in sorting of nuts in processing
streams to reduce the incidence of staining in themarketed product. The simultaneous splitting ofshell and hull is generally caused by too tight anadherence of the hull to the shell. The absence of atissue gap between the two pericarp-derived partsof the nut makes it impossible for the shell to split
without triggering hull split. This often leads toshells with adhering hull material (Pearson et al.
1996), considered a defect.

Optimum Storage Conditions
Once they have been dried (see above), nuts canbe 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 muchhigher content of polyunsaturated fatty acids thanpistachio oil.

Controlled Atmosphere Considerations
Grades, Sizes, and Packaging
In-shell and shelled grades exist and aredetermined primarily by kernel size, degree ofdryness, absence of foreign material, and freedom
from defects caused by insects and mold. For thein-shell product, additional grading criteria include
absence of shell pieces and free kernels, shells
without stains and adhering hull material, andabsence of unsplit shells and blanks. A complete
description of U.S. quality standards, grades, andsizes 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 dehiscenceof the hull along its suture at the same time as
the shell within is splitting. This premature hulldehiscence increases “early” problems with
insects and molds (Doster and Michailaides 1999).
Pearson (1996) and Pearson and Slaughter (1996)

While relatively stable when stored in air at 20ºC (68 ºF), storage under high CO2 (Maskan andKaratus 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 ethylenethat might affect nut quality.
773

Respiration Rates

Insect Problems

The low water content of properly stored,
dried pistachios makes them relatively inert
metabolically. Respiratory rates are very low.

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 beenused 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 indicatethat 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).

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, failureof hull split as nuts reach full maturity cancause substantial yield losses. While splitting ismaturation-dependant, it will be reduced by water
stress late in the growing season (mid-Augustthrough September) and failure to maintainadequate boron (120 ppm [mg kg-1] leaf dry
weight). Early in postharvest drying, the split on
partially split nuts tends to widen (Freeman andFerguson 1995).
Blank nuts result when the embryo fails todevelop. This can be caused by promotion ofshell 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 stressare also indicated as causes of blank formation(Freeman and Ferguson 1995).
Pistachios are strongly alternate-bearing andfailure 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 morecommon in “on” years. Of course, crop load ismuch higher in “on” years, and this has a large
effect on assimilate partitioning.

774

Postharvest Pathology
Several fungi are capable of infecting growing
pistachio nuts and causing damage to hulls andkernels. Infection is often facilitated by early
splitting of hulls, which leads to infestations by
a number of hemipteran insects that feed on thenuts and serve as nonspecific vectors for diseases.
Alternaria and Cladosporium species are alsocolonizers of early split nuts. Late season rains
will promote activity of Botryosphaeria dothidea
on pistachio hulls and kernels (Michailides etal. 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 problemsof pistachio, vectoring by insects attracted toearly split nuts (such as navel orangeworm) is
an important contributing factor. In Doster andMichaelides’ (1994) study of Aspergillus molds

in California pistachios, early split nuts hadover 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 canbe 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 sensitivityof detection and inconsistent presentation offluorescence 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 spreadby 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 withmethyl bromide or phosphine has been used fordisinfestation, but the former is being curtailed
and insect resistance to phosphine has beenreported (Zettler et al. 1990). New fumigants arebeing 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 ofpistachio nuts and incidence of fungal decay andinsect 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. Universityof 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 treatmentsfor pistachio nuts to decrease residues andcontrol 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 safetyof pistachio nuts as influenced by postharvest
handling procedures. In Pistachio Association
Annual Report, pp. 44-52.

775

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 andInformation, 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 ofCalifornia, Pomology Department, Davis, CA.
Labavitch, J.M., C.M. Heintz, H.L. Rae, and A.A.
Kader. 1982. Physiological and compositionalchanges associated with maturation of ‘Kerman’
pistachio nuts. J. Amer. Soc. Hort. Sci. 107:688692.
Maskan, M., and S. Karatas. 1998. Fatty acidoxidation 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 andInformation, 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 andInformation, 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.
776

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 andfluorescence in brazil nuts and pistachio nuts. J.
Agric. Food Chem. 40:2453-2457.
Thompson, J.F. 1997. Maintaining quality ofbulk-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.

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 importantcommercial 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 andeastern 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 andrelatively dry at harvest, is generally lost when
the nuts fall to the ground. Harvested nuts (theshell 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 thekernel’s crispness. If water content drops too low,
however, damage to the kernel’s covering canenhance O2 penetration and rancidity.
The skin covering the kernel contains chemicals
that protect fatty acids in the kernel frombecoming rancid. Light-colored kernels earn ahigher price because the light color indicates thatthe 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 ofthe shell, because the shell is an important barrier
to O2 entry. Shell strength and seal integrity arealso 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 Siebert1998); therefore, additional characteristics ofprocessing 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 generallyindicated by browning of the internal packing
tissue. However, harvest should not begin until thehusk 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, asoccurs in some growing regions and can occur atnight, 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 areprimarily determined by size, degree of kernel
fill, color, and freedom from defects and foreignmaterial. Freedom from off flavors (rancidity)
is important. Shelled kernels held for a long
period are particularly susceptible. A complete
777description of Federal quality standards can befound 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 toenhance stability. Edible coatings may be used as
O2 barriers to retard kernel rancidity (Maté et al.
1996).

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 toethylene that might affect quality.

Respiration Rates
The low water content of properly stored walnuts
makes them relatively inert metabolically.
Respiration rates are very low.

Optimum Storage Conditions

Physiological Disorders

Low water content and high fat content of thekernel make it relatively stable metabolically andable to tolerate low temperatures. The primaryobjectives of storage are to maintain the low
water content attained after preliminary drying(to suppress enzyme activity, retain texture, andreduce 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 (Beuchat1978). Lopez et al. (1998) modeled sorptionof 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.

The most serious postharvest physiologicaldisorder 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.

Controlled Atmosphere Considerations
Shelf-life can be extended by storage in <1% O2.
O2 <0.5% (balance N2) or CO2 >80% in air can beeffective in insect control.

778

Insect Problems
Insect damage can contribute to handling andquality problems. The major insect pest is thecodling moth (Cydia pomonella). While nuts
attacked in mid season are likely to be rejected,
minor early codling moth damage can lead tomore serious infestation with navel orangeworm(Amyelosis transitella [Walker]), and this is moredifficult 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 shelland failure of the husk to split. This reduces theharvest 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.

Postharvest Pathology
Most infections with pathogens are initiated in
the orchard and transferred to the postharvest
environment. In-shell product is protected unlessthe 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 andcarcinogenic. It is important that damaged kernels
be discarded prior to storage and that the lowtemperature and RH conditions discussed above
be maintained in order to reduce the chance formold growth. Toxin-producing Penicillium sp.
have also been found on walnuts.

changes in nut quality and stability could haveimportant 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 maintainlow nut moisture in a reduced O2 atmosphere.
References

Quarantine Issues
Insect infestation is a potentially important
problem, as are the fungal infections that often
accompany insect damage. Fumigation withmethyl bromide or phosphine has been used fordisinfestation, but the former is being restricted
and insect resistance to phosphine has beenreported (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 andapplication of the indianmeal moth granulosis
virus for control of navel orangeworm andindianmeal moth (Plodia interpunctella Hübner).
Vail et al. (1991) have reported that these same
walnut storage pests are susceptible to theBacillus thuringiensis insecticidal crystal protein.
Researchers have successfully introduced thegene for the Bt protein into walnut embryos anddemonstrated its efficacy in suppressing larval
development (Dandekar et al. 1998).

Special Considerations
This presentation of quality maintenanceguidelines for walnuts has introduced somediscussion of changes of the fundamental
character of the nut that may be brought about by
the use of genetic engineering. The anticipatedBeuchat, 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, etal. 1998. High levels of expression of full-length
cryIA(c) gene from Bacillus thuringiensis intransegnic somatic embryos. Plant Sci. 131:181193.
Hendricks, L.C., W.C. Coates. R.B. Elkins, etal. 1998. Selection of varieties. In D.E. Ramos,ed., Walnut Production Manual, pp. 84-89. Pub.
no. 3373, University of California, Division ofAgriculture 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. 61:465468,472.
779

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, Universityof 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 andstorage 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.

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