Open Shelf-Life Dating of Food

August 1979

NTIS order #PB80-101629
Library of Congress Catalog Card Number 79-600128

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 Stock No. 052-003 -00694-4
In this study OTA addressed the practicality of open shelf-life dating of food

to disclose food freshness to the consumer. The assessment was undertaken at the

request of the Senate Committee on Commerce, Science, and Transportation.

The Office of Technology Assessment formed a panel of consumer representatives, food retailers, processors, wholesalers, scientific experts, and State and

Federal Government officials. Staffs of the Congressional Research Service, the

U.S. Department of Agriculture, and the Food and Drug Administration provided

background information to the assessment. Individual papers and reports were

commissioned concerning the scientific basis for open dating of food and the critical issues involved. A nationwide mail survey was conducted to gain the consumer’s perspective. In addition, reviews of the draft reports were provided by

Federal agencies and officials, and a wide spectrum of interested individuals.

These wide-ranging contributions were vital to the shaping of the assessment

and to developing congressional options. To all of these people OTA acknowledges

a deep debt of gratitude; however, the report is an OTA staff synthesis and does

not necessarily reflect the position or views of any particular individual.

JOHN H. GIBBONS

Director

ill
OTA Open Shelf-Life Dating of Food Advisory Panel

Jane Anderson

Director of Consumer Affairs

American Meat Institute

Jules Bauermann

Director of Food Technology

H. W. Longacre, Inc.

Lowrie M. Beacham

Special Advisor to the President

National Food Processors

Association

John Bennett

Chief, Weights and Measures

Division

Department of Consumer

Protection

State of Connecticut

Judy Braiman-Lipson

President

Empire State Consumers

Association

Chambers Bryson

Chief, Food and Drug Section

Department of Health

State of California

Mahlon Burnette

Director of Scientific Affairs

Grocery Manufacturers of

America

*Carl D’Alessandro

Assistant to the Administrator

Food Safety and Quality Service

U.S. Department of Agriculture

John DeMoss

Executive Director

Virginia Food Dealers Association

John Farquhar

Vice President, Education and

Technology

Food Marketing Institute

G. William Fouse

Chief, Division of Milk Sanitation

Bureau of Foods and Chemistry

Department of Agriculture

Commonwealth of Pennsylvania

Michael J. Phillips, Chairman

OTA Project Director

Edward Heffron

Chief, Food Inspection Division

Department of Agriculture

State of Michigan

Herman Kammerman

Director, Office of Consumer

Affairs

City of Cleveland, Ohio

James Kirk

Chairman, Department of Food

Science and Human Nutrition

University of Florida

Gary Kushner

Attorney at Law

Leighton, Conklin, and Lemov

Theodore Labuza

Professor, Department of Food

Science and Nutrition

University of Minnesota

*Jeffrey Odum

Staff Assistant

Committee on Laws and

Regulations

National Conference on Weights

and Measures

National Bureau of Standards

Amihud Kramer

Professor, Department of

Horticulture

University of Maryland

Darryl Lund

Professor, Department of Food

Science

University of Wisconsin

Roy Martin

Director of Science and

Technology

National Fisheries Institute

Stan McHugh

Vice President

American Bakeries Company

George Michael

Director, Division of Food and

Drugs

Department of Public Health

Commonwealth of Massachusetts

Sharon Morganstern

Assistant to the President

National American Wholesale

Grocers Association

Daniel Padberg

Chairman, Department of

Agricultural Economics

University of Illinois

*Taylor Quinn

Associate Director of Compliance

Bureau of Foods

Food and Drug Administration

U.S. Department of Health,

Education, and Welfare

Austin Rhoades

Administrative Assistant

Milk Industry Foundation and

International Association of

Ice Cream Manufacturers

Morton Shaevel

Vice President for Research and

Development

Freezer Queen Foods, Inc.

Gary Smith

Professor, Department of Animal

Science

Texas A&M University

Jeri Smith-Fornara

Arizona Consumers Council

Tom Sporleder

Professor of Agricultural

Economics

Texas A&M University

Joe Suiter

Assistant Supervisor

Dairy and Food Division

State of Washington

Dale Watson

Vice President for Produce

Merchandising

Great A&P Tea Company

Ruth Yannatta

California Citizens Action Group

*Ex officio

NOTE: The Advisory Panel provided advice and comment throughout the assessment, but does not necessarily

approve, disapprove, or endorse the report for which OTA assumes full responsibility.

iv
OTA Open Shelf-Life Dating of Food Staff

Joyce C. Lashof, Assistant Director

Health and Life Sciences Division

J. B. Cordaro, Food and Renewable Resources Group Manager*

Walter Parham, Food and Renewable Resources Group Manager

Michael J. Phillips, Project Director

Phyllis Balan Elizabeth Galloway Yvonne Noel

Robert L. Smith, Jr. Ray Hoehle

Contractors and Consultants

Theodore P. Labuza Thomas L. Sporleder

Amihud Kramer James Kirk Dorothy Mayes

Department of Food and Nutrition, University of Minnesota

Leighton, Conklin, and Lemov

Market Facts, Inc.

OTA Publishing Staff

John C. Holmes, Publishing Officer

Kathie S. Boss Joanne Heming

*Through June 16, 1979.
OTA Food Advisory Committee

David Call

Dean, College of Agriculture

and Life Sciences

Cornell University

Cy Carpenter

President

Minnesota Farmers Union

Eliot Coleman

Director

Coolidge Center for the

Study of Agriculture

Almeta Edwards Fleming

Social Program Coordinator

Florence County, S.C.

Martin E. Abel, Chairman

Senior Vice President, Schnittker Associates

Johanna Dwyer, Vice Chairman

Director, Frances Stern Nutrition Center

Lorne Greene

Chairman of the Board

American Freedom From

Hunger Foundation

Richard L. Hall

Vice President, Science and

Technology

McCormick & Company, Inc.

Laura Heuser

Member, Board of Directors

Agricultural Council of America

Arnold Mayer

Legislative Representative

Amalgamated Meat Cutters and

Butcher Workmen of North

America

Max Milner

Executive Director

American Institute of Nutrition

Robert O. Nesheim

Vice President, Science and

Technology

The Quaker Oats Company

Kathleen O* Reilly

Director

Consumer Federation of America

R. Dennis Rouse

Dean, School of Agriculture

Auburn University

Lauren Seth

Agricultural Consultant

Thomas Sporleder

Professor of Agricultural

Economics

Texas A&M University

Sylvan Wittwer

Director and Assistant Dean

College of Agriculture and

Natural Resources

Michigan State University

NOTE: The Food Advisory Committee provided advice and comment throughout the assessment, but does not

necessarily approve, disapprove, or endorse the report for which OTA assumes full responsibility.

vi
Contents

Chapter Page

I.

II.

III.

Iv.

v.

Executive Summary . . . . . . . . . . . . . . . .

Consumer Concerns . . . . . . . . . . . . . . . .

Background. . . . . . . . . . . . . . . . . . . . . . .

State Practices . . . . . . . . . . . . . . . . . .

Practices in Other Countries ., . . . . .

Findings and Conclusions. . . . . . . . . . . .

Overall Findings . . . . . . . . . . . . . . . . .

Specific Findings . . . . . . . . . . . . . . . .

Benefits. ...,. . . . . . . . . . . . . . . . .

costs . . . . . . . . . . . . . . . . . . . . . . . .

Open-Dating Techniques . . . . . . . .

Criteria in Establishing Open Dates

Enforcement and Liability . . . . . . .

Congressional Options . . . . . . . . . . . . . .

Voluntary System . . . . . . . . . . . . . . . .

Mandatory System . . . . . . . . . . . . . . .

Congress Specifies the Detail. . . . .

Leave Implementation of Detail

to Others . . . . . . . . . . . . . . . . . . .

Voluntary/Mandatory System , ., ., .

Consumer Perspective on Open Dating.

Attitudes Toward Open Dating . . . . . . .

Understanding Open Dates . . . . . . . . . .

Preference Among Open Dates . . . . . . .

Differences Among Subgroups of

Shoppers. . . . . . . . . . . . . . . . . . . . . . .

Benefits of Open Dating. . . . . . . . . . . . .

Food Quality.. . . . . . . . . . . . . . . . . . . . .

Nutrition. . . . . . . . ..., . . . . . . . . . . . . .

Food Safety.,.. . . . . . . . . . . . . . . . . . . .

Inventory Control. . . . . . . . . . . . . . . . . .

Education , . . . . . . . . . . . . ..., . . . . . . .

Alternative Open-Dating Techniques . .

Method of Open Dating. , . . . . . . . . . . . .

Pack Date . . . . . . . . . . . . . . . . . . . . . .

Sell-by and Best-if-Used-by Dates. . . .

To Remain in Grade Use-(Sell-)

by Date . . . . . . . . . . . . . . . . . . . . . .

Combination Dates . . . . . . . . . . . . . . .

Implementation, . . . . . . . . . . . . . . . . . . .

Storage Instructions. . . . . . . . . . . . . .

Type of Date Marking. . . . . . . . . . . . .

Exemptions. . . . . . . . . . . . . . . . . . . . . . .

Establishing Open Dates . . . . . . . . . . . .

Alternative Criteria . . . . . . . . . . . . . . . .

Sensory Quality . . . . . . . . . . . . . . . . .

Nutrient Loss . . . . . . . . . . . . . . . . . . .

Perishability Time Categories . . . . . .

Scientific Tests and Data Needed . . . . .

Impact on Technology Development . . .

1

1

3

3

3

5

5

5

5

6

6

7

7

8

8

9

9

10

11

13

13

14

15

18

19

20

20

21

21

21

23

23

23

24

26

26

27

27

27

28

31

34

34

35

36

36

37

Chapter Page

VI. Alternative Open-Dating Systems . . . . . 39

Voluntary System, .., . . . . . . . . . . . . . . 39

Mandatory System.,. . . . . . . . . . . . . . . 39

Voluntary/Mandatory System . . . . . . . . 41

VII. Enforcement and Liability . . . . . . . . . . . 43

Methods o fEnforcement . . . . . . . . . . . . 43

Before-Date Enforcement . . . . . . . . . . 43

Beyond-Date Enforcement . . . . . . . . . 44

Federal/State Enforcement . . . . . . . . . . 45

Liability, . . . . . . . . . . . . . . . . . . . . . . . . . 46

Liability Under the Food, Drug, and

Cosmetic Act . . . . . . . . . . . . . . . . . 46

Civil Liability. .,..... . . . . . . . . . . . . 47

VIII. Economic and Social Costs . . . . . . . . . . . 49

Costs of Open Dating . . . . . . . . . . . . . . . 49

Establishing Shelf Life. . . . . . . . . . . . 49

Dating the Package. . . . . . . . . . . . . . . 49

Enforcement ..,..,.. . . . . . . . . . . . . 49

Comparison With Nutrition Labeling. 50

Impact. . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Processors, . . . . . . . . . . . . . . . . . . . . . 50

Wholesalers and Retailers . . . . . . . . . 50

Consumers . . . . . . . . . . . . . . . . . . . . . 50

Government . . . . . . . . . . . . . . . . . . . . . 51

IX. Array of Congressional Options . . . . . . 53

Congressional Options . . . . . . . . . . . . . . 53

Appendixes

A.

B.

c.

D.

E,

LIST

Application of Open Dating to

Specific Foods . . . . . . . . . . . . . . . . . . . 59

Basic Food Preservation and

Deterioration Modes. , . . . . . . . . . . . . 77

Technological Evaluation of Shelf Life

of Foods. ,. ....., . . . . . . . . . . . . . . . 87

Status of Open Shelf-Life Dating

Regulations for Selected Countries

and International Food Labeling

Organizations, 1978. . . . . . . . . . . . . . 103

Bibliography, . . . . . . . . . . . . . . . . . . . . . 105

OF TABLES

Table No. Page

1. Summary of Open-Date Labeling

Requirements by States, 1978 . . . . . . . . 4

2. Consumer Usefulness of Information on

Food Packages . . . . . . . . . . . . . . . . . . . . 14

3. Consumer Understanding of Freshness

Dates. . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

4. Consumer Preferences for Open Dates. 15

vii
Table

5.

C-1 .

LIST

Figure

No. Page

Major Modes of Deterioration, Critical

Environmental Factors. Shelf Life, and

Type of Open Dating by Food Product . . 32

Weeks of Shelf Life at a Given

Temperature for Given Q10. . . . . . . . . , . 93

OF FIGURES

No. Page

1. Example of Interaction of Congressional

Options . . . . . . . . . . . . . . . . . . . . . . . . . . 54

B-1. Moisture Content v. Water Activity. . . . 83

B-2. Effect of aw on Rate. . . . . . . . . . . . . . . . . 83

C-I. Nomogram of Temperature, Time, and

Quality for the Military Ration Items

Used in the Long-Term Storage Tests ., 88

Figure No. Page

C-2.

C-3.

C-4.

C-5,

C-6.

C-7.

C-8.

C-9.

C-l0.

C-1 1.

C-12

C-13.

C-14.

Constant Shelf Life Lost . . . . . . . . . . . . . 90

First-Order Degradation . . . . . . . . . . . . 90

First-Order Log Plot . . . . . . . . . . . . . . . . 91

Initial Quality Gain Prior to First-Order

Degradation . . . . . . . . . . . . . . . . . . . . . . 91

Shelf-Life Plot .....,... . . . . . . . . . . . . 92

Temperature/Time History . . . . . . . . . . 93

Sequential Regular Fluctuating Profile. 95

Moisture Gain. . . . . . . . . . . . . . . . . . . . . 97

Storage Conditions . . . . . . . . . . . . . . . . . 98

Shelf Life as a Function of aW and

Temperature. .,..... . . . . . . . . . . . . . . 99

Calculated Moisture Content v. Time. . . 100

Senescence Rate as a Function of O, ., . 101

Rates of Permeation and Respiration

Of oz. . . . , , . . , . . . . . . . . , . . . . . , . . . . . 101

. . . Vlll
Executive

Chapter I

Summary

In their concern over the freshness of food, consumers have increasingly

advocated open shelf-life dating—the use of dates on a can or package of food

that gives the consumer some idea of when a product was packed or should be

sold or used. Although such a step appears simple and sensible at first glance, it

entails many scientific and financial uncertainties and involves some complex

choices.

The Senate Committee on Commerce, Science, and Transportation asked

OTA to assess the feasibility of open shelf-life dating of food and to provide Congress with the necessary information to adequately address this area of food

labeling.

This assessment analyzes: consumers’ perspectives on open-date labeling;

benefits and costs; alternative systems and techniques; alternative criteria and

scientific tests to establish open dates; enforcement mechanisms and liability related to open-date labeling; and options available to Congress.

CONSUMER CONCERNS

Ever since the vast majority of Americans

became urbanized, consumers have had no

sure way of knowing how fresh their food

really is. Since they did not grow it themselves or personally know such factors as its

age or storage condition, they have had to

rely on assurances that wholesalers and retailers were abiding by some system that

would eliminate food that was no longer

fresh. Fresh food refers to food in which the

quality has been unchanged from its initial

state. Even under ideal conditions some foods

lose their freshness within 2 or 3 days of being packed, while other foods may remain

fresh for over a year,

survey in 1971 showed that 20 percent had

complaints about food product freshness; a

Nielson survey in 1973 turned up 50 percent

with such complaints. A 1978 survey further

supported this concern by noting that of all

the problems on the minds of consumers

when they shop for food, making sure that

food in supermarkets is fresh heads the list. ’

Facts that lend support to such concerns

are scarce, however. There are no nationwide statistics on the amount of food sold that

is not fresh, although there have been some

individual State studies that indicate there is

a problem.

Recent studies have shown that, indeed, ISkeIly Yankelovich, and White, Inc., “A Study of consumers are concerned over whether or Consumers’ Attitudes and Behaviors Towards Eating at

not the food they purchase is fresh. A U.S. De- Home and Out of Home,” Woman’s Day, Family Food

partment of Agriculture (USDA) consumer Study, 1978.

1
2 . Open Shelf-Life Dating of Food

For example, a study of 25 supermarkets in

Minnesota showed that all of those stores had

some outdated food on their shelves.2 Another

study in that State found that 44 percent of

the baby formula being sold was over age and

that since 64 percent of the store managers

could not read a coded date, they could not

rotate the stock.3 These findings led the State

to adopt mandatory open shelf-life dating for

some foods.

Open shelf-life dating means the use of legible terms such as a day, month, and year as

an indication of when the food was packaged

or by when it should be sold or used. Such

dating is considered by most people to be a

measure of food freshness. It does inform the

buyer about the time lapse between packaging and purchase or use and, to the extent

that such time lapse is synonymous with quality loss, of the quality or freshness as well.

However, such a time lapse is not necessarily

the only factor leading to quality loss—i.e.,

deviation from freshness. Therefore, an open

date is not an absolute assurance of freshness—but it can be an indication.

Dating of food is far from being a new concept—in fact, it started back in the early

1930’s. However, the dates have usually been

in coded form, based on a color-keyed or number/letter system. The codes were originally

designed to aid in controlling food inventories

and to assist in any product recalls, such as

for contaminated foods.

Consumers complain that since they cannot

interpret the codes, they cannot tell whether

or not the food they are buying is fresh. Indeed, sometimes employees at both the retail

and wholesale level cannot read the codes

either and thus are unable to use them as a

means of keeping stocks in-date.

All indications are that consumers do want

dates they can understand. For example, in

‘Minnesota Public Interest Research Group, “Survey

of Minnesota Food Stores, 1972, ” testimony before the

Minnesota State Senate on Open Dating Legislation.

‘Keith Ford, Minnesota Office of Consumer Services,

testimony before the Minnesota State Senate Hearings

on Open Dating Legislation, 1972.

1977 the New York Consumer Protection

Board published a report translating food

manufacturers’ freshness codes. The Board

received over 100,000 requests for copies of

the report.

Currently, no Federal policy exists on open

dating. There is wide variation among the 21

States and the District of Columbia that have

some form of mandatory open dating. For example, different States require different

products to be dated, require different dates

for the same products, and the same dates

can have different interpretations. In addition, none of the States seem to have done

“before and after” studies of open dating.

Even where not required by State law,

some manufacturers have chosen to voluntarily open date their products. However,

since there are no industry guidelines, there

is no uniform system.

The result is often consumer confusion. For

example, a survey conducted for OTA shows

that three out of four consumers can correctly identify the type of date on milk. But only

one in four knows the type of date on breakfast cereal, and only one in three knows the

type of date on ground beef. Of course, milk is

more often open dated than are breakfast

cereal and ground beef.

To further complicate matters, there is no

scientific body of knowledge to accurately

determine dates for various products, no consensus on which type of date or dates—

“pack” (when food was processed or packaged for retail sale), “sell by” (the last date a

food product should be sold), “best-if-usedby” (the date after which food is no longer at

its most acceptable level of quality), or a combination of these—to use for which product,

or even which products to date at all, and no

real guidelines as to how to display the date.

What appears at first to be a simple task of

converting code to open dates readily becomes complex with many unanswered questions.

Even though no action has been taken at

the Federal level, there has been and contin-
Chapter /—Executive Summary ● 3

ues to be much congressional and executive and the Federal Trade Commission on food

agency interest in open dating. Bills have labeling issues. Over 9,000 written responses

been introduced in the U.S. Congress on food were received, 5,000 of which were from conlabeling that would require open dating. sumers. Preliminary results of the consumer

However, only the Senate has approved such responses indicate that consumers do want

legislation, some form of open dating,

In 1978, joint hearings were conducted by

the Food and Drug Administration, USDA,

BACKGROUND

State Practices

Some form of open-date labeling is required in 40 percent of the States, including

the District of Columbia (table 1). But more

revealing than the number of States that have

open dating are the food products covered

and the type of date used.

Perishable foods, such as fluid milk, are

the most common food products open dated.

In 21 States with some form of mandatory

open dating, 12—or 60 percent—have laws

limiting coverage to fluid milk and/or milk

products. *

Open-dating laws or regulations in seven

States and the District of Columbia apply to a

broader class of food products. One State,

Massachusetts, includes both perishables

and nonperishables, or long shelf-life foods.

The type of date used varies by State, but

the majority either require or suggest a sellby date, which is the last date a food product

should be sold. Seventeen States and the District of Columbia fall into this category.

There is some variation among the States,

however, in the requirement for sell-by dates

—particularly for fluid milk and/or milk products. For example, the New Mexico law

states that fluid milk and cream containers

shall be labeled “with a legible sell-by date

*Perishable foods have a short shelf life, usually less

than 30 days. Semiperishable foods have a shelf life of

between 1 and 6 months. Nonperishable or long shelflife foods have a shelf life of more than 6 months,

not to exceed 14 days including the date of

packaging for pasteurized products and 5

days for raw products. ” By contrast, the

Maryland law requires all pasteurized milk

products to have the term “sell by, ” which is

designated as a date “7 days after the day of

pasteurization. ”

In addition to the 21 States requiring some

form of open dating, some food manufacturers voluntarily open date their products,

Some use a pack date, others a sell-by date,

and still others a use-by or best-if-used-by

date. Some explicitly indicate that it is a sellby or use-by date, while others only show a

date.

Therefore, in some areas of the country, a

portion of the food supply has some type of

open date, while in other areas, food does not

carry any date. Even among the States requiring open dating, the same date can have

different interpretations. And in voluntary

open dating by industry, there is no guidance

as to: 1) which products to date, 2) which date

to use, 3) how to display the date, and 4) how

to scientifically determine the date. In sum,

there is no uniform system.

Practices in Other Countries

In contrast, many other countries and international organizations have established

requirements for dating of food products. For

example, open dating, with or without code

dating, is mandatory for prepackaged con-
4 . Open She/f-Life Dating of Food

Table 1.--Summary of Open-Date Labeling Requirements by States, 1978

Form of Effective

State/locale Primary products open date since about

Alabama . . . . . . . . . . . . . . . . . . . Dairy

California . . . . . . . . . . . . . . . . . . Dairy .

Connecticut . . . . . . . . . . . . . . . . Milk

District of Columbia . . . . . . . . .Perishable products

Florida . . . . . . . . . .. . . . . . . . . . Dairy

Georgia . . . . . . . . . . . . . . . . . . . . Milk, eggs

Maryland . . . . . . . . . . . . . . . . . . . Milk

Massachusetts. . . . . . . . . . . . .Perishable & long

shelf life

Michigan. ....,.. .. .. .. .. .. . Perishable products

Minnesota . . . . . . . . . . . . . . . . .Perishable products

with shelf life<90days

Nebraska . . . . . . . . . . . . . . . . . .Eggs

Nevada . . . . . . . . . . . . . . . . . . . . Dairy

New Hampshire. .. .. ... ... ..Cream

New Jersey. . . . . ,. .. ... ... ..Dairy

New Mexico. . . . .. ... ... ... .Milk

Ohio . . . . . . . . . . . . . . . . . . . . . .Perishable products

Oklahoma . . . . . . . . . . . . . . . . . . Meat, eggs

Oregon . . . . . . . . .. .. .. .. .. .. Perishable products

Pennsylvania . . . .. ... ... ... .Milk

Virginia . . . . . . . . . .. .. .. .. .. .Dairy & infant formula

Washington . . . . . .. .. .. .. .. . Dairy & others

Wisconsin . . . . . . . . . . . . . . . . . Smoked fish

Sell-by

Sell-by

Sell-by

Sell-by

Sell-by

Sell-by

Sell-by

Sell-byor

use-by

Sell-by

Sell-by or

use-by

Pack

Sell-by

Use-by

Sell-by

Sell-by

Sell-by

Sell-by

Pack or sell-by

Sell-by

Sell-by

Sell-by

Pack

1975

1973

1973

1974

1976

1973

1971

1979b

1969

1973 —

1973

1973 —

1977

1977

1975

1975

1974

1974

1971

~hisreguiationispresentfybeingchaiiengedincouft. bl~g~r~h~ief~~;l~forff~~foods;andIwl forremaining long shelf-life foods. These dates maychangedependingontheoourt’sdecisionconcerningthelagetityoftheregulation.

SOURCE:OTAsurvey.

sumer food items expected to have a short

shelf life in practically all developed

countries—with the United States a notable

exception. In the developing countries, the

same trend applies, particularly for foods intended for export, except that open dating is

not confined to short shelf-life items.

Some other countries have already moved

from simply code dating to open dating for

long-life products. For example, Japan, Venezuela, and Sweden, while allowing codes, require that the pack date also appear in an

“open’’ form.

The Codex Alimentarius Commission, the

global organization for food-labeling standards, states a general preference for open

dates but requires them only on infant’s and

children’s foods. The European Economic

Community recently adopted open dating for

nearly all food products, with some exceptions. (See appendix D for a breakdown of

open dating throughout the world.)

In view of these international developmerits, the lack of a U.S. policy on open dating

could cause problems and lead to confusion in

future food trade. Therefore, the issue of

open dating has international as well as domestic implications.
Chapter I—Executive Summary ● 5

FINDINGS AND

Overall Findings

. -1 . 1 ..,1 .1 1.

2.

3.

4.

5.

There is little evidence to support or to

negate the contention that there is a direct relationship between open shelf-life

dating and the actual freshness of food

products when they are sold.

The pressure for open shelf-life dating

comes from a consumer perception that

such dating ensures food freshness and

that industry should disclose its coded

dates.

Deterioration in food quality is affected

by environmental factors such as temperature, humidity, and light in relation

to time. Ideally, dating information

should reflect on these factors, but the

technology to measure their influence inexpensively is in various stages of development and is not likely to be applicable

in the near future,

Open dating is applicable for all food

categories because all foods deteriorate.

For most perishable and semiperishable

foods the major modes of deterioration

cause sensory quality loss such as color

loss or off-flavor development, which

can be easily recognized. For long shelflife products, a major mode of deterioration is nutrient loss, such as vitamins A

or C, which cannot be recognized by consumers. In addition, most long shelf-life

foods are packaged such that it is not

possible to examine contents for sensory

quality loss before purchase.

Information gaps exist on: a) the amount

of food sold nationally that is not fresh,

b) the experience of States that have initiated open-dating programs, c) the scientific base to determine and monitor a

freshness date, and d) the costs of open

dating on a product-specific basis.

CONCLUSIONS

Specific Findings

Benefits

1.

2.

3.

4.

Open dating encourages better handling

practices by wholesalers, retailers, and

consumers by expediting the sale or use

of food near the end of shelf life. This

can result in a decrease of consumer

complaints about buying spoiled or stale

foods, Indeed, a USDA study found that

such complaints decreased by 50 percent after the introduction of open

dating.

Open dating can increase consumer confidence in the freshness of food purchased. In the same study, USDA found

that the reduction in consumer complaints about spoiled or stale foods was

reported for both open-dated and nonopen-dated food in the same store. Apparently, because information wa s

available for some foods, shoppers had

more confidence in the freshness of all

foods.

Better handling practices attributed to

open dating could minimize nutrient loss.

A processor could estimate the length of

time the product would be in the distribution system and, given the environmental conditions, determine how these

factors would affect the loss of unstable

nutrients, such as vitamin C.

There is little or no benefit derived from

open dating in terms of improved microbiological safety of foods. For foods in

general, microbiological safety hazards

are a result of processing failures, contamination after processing, and abuses

in storage and handling. These factors

are usually independent of the age of the

product and have little relationship to an

open date,
6 ● Open Shelf-Life Dating of Food

Costs

Very little research has been done to determine costs of open dating. These findings are

based on the best estimates of academic and

industry shelf-life experts and experience by

industry and Government with nutrition labeling.

1. A major initial cost in adopting open

dating is establishing a reliable date.

Estimates are approximately $100,000

for each perishable and semiperishable

food and $200,000 for each long shelflife food (1979 dollars).

2. Major costs to wholesalers and retailers

would be for employee time to inspect

shelves for out-of-date stock and then

dispose of such stock.

3. Enforcement costs for the Federal Government could vary from practically

none to more than $500,000 per year, depending on the enforcement system and

the extent to which the system were

mandatory.

4. Based on nutrition-labeling experience,

total costs of adopting open dating would

be small on a per-dollar sales basis but

nonetheless may add from 0.1 to 1 cent

to the cost of each package of food. In

1975, the average cost of establishing

nutrition information per dollar of sales

was .004 cents, and the average continuing cost of nutrition labeling, which involves complex testing procedures and

more information to be printed on the

label than does open dating, was a minimal amount—especially once it was established. The same should be true for

open-date labeling.

Open-Dating Techniques

There are many possibilities in converting

codes to open dates. The date could be a pack

date, sell-by date, best-if-used-by date, or a

combination of these.

1. A pack date is the day, month, and year

the food product was processed or packaged for retail sale. It is of minimal value

to consumers in that it provides little information as to freshness or how long

products should remain at acceptable

quality. A pack date is, however, the

easiest and least expensive for industry

to implement.

2. A sell-by date is the last date a food

product should be sold in order to allow

a “reasonable” length of time for consumer use. This date is appropriate for

perishable foods such as milk and dairy

products because they have a short shelf

life. It is the most useful date for wholesalers and retailers in their inventory

control, since it states the last day of

sale. However, it does not indicate to the

consumer when foods should be used.

Because it is currently being used on

many perishable foods, it could easily be

implemented by industry for products

with a short shelf life.

3. Best-if-used-by date is the date after

4

which food is no longer at its most acceptable level of quality. It is the preferred single date by consumers and provides the most useful information on

quality. It is more appropriate for foods

that have a long shelf life. It is, however,

the most difficult for wholesalers and retailers to use in inventory management

because they must subjectively determine allowances for home storage in

order to determine the last day of sale.

This date is presently used on some

semiperishable and long shelf-life foods.

However, the full implementation of this

kind of date may require as much as a 2-

year period to scientifically establish it

for a given product at a cost of $200,000

per product.

Combination dates are preferred by consumers to single dates. They provide the

most information, especially a sell-by

and best-if-used-by combination. Combination dates, however, have all of the

disadvantages of single dates.
Chapter /—Executive Summary . 7

Criteria in Establishing Open Dates

There are several criteria that can be used

to establish sell-by and best-if-used-by dates

including: sensory quality, nutrient loss, and

degree of perishability,

1. Sensory quality, such as color, odor, and

flavor, is the most discernible criteria

for establishing sell-by and best-if-usedby dates. For some foods, sensory quality

change may also be an indicator of nutrient quality. However, regulatory agencies would probably not be able to use

sensory criteria to determine whether a

food that is still in date is out of compliance with some quality level, since

tests to determine whether a given product is of some designated sensory quality

require taste panels trained in specific

areas. This is not applicable to regulatory methods. However, if a physical or

chemical method could be correlated

highly with a sensory test, compliance

testing would be simplified.

2. Nutrient loss would be easier to meas3,

ure than would sensory quality, since it

can be done objectively in an analytical

laboratory. However, nutrient content of

the same food commodity can vary; also,

some foods are naturally poor in some

nutrients, are not eaten to provide those

nutrients, and may be of good quality

even if they lost a certain percentage of

the nutrients. Thus, critical nutrient loss

methods are useful only where they are

highly correlated with overall sensory

quality losses,

Perishability time categories, which establish a date by a set number of days

after processing, are more relevant for

highly perishable foods that have a minimum of processing, However, modern

processing conditions and new types of

packaging can increase the shelf life of

some foods to the point where time categories are not meaningful unless continuously modified to reflect new circumstances.

Enforcement and Liability

Open dating raises some unique problems

of enforcement and liability. Enforcement, for

example, raises two serious points: 1) enforcement with respect to quality standards

in establishing the date and 2) sale of a product after the date. Liability in open dating

presents unique difficulties because most

other labeling requirements only involve the

processor, but open dating involves wholesalers and retailers as well. This leads to

questions of who is ultimately liable and

whether existing law is adequate to determine liability.

In general, the findings in these areas are:

1.

2.

3.

4.

5.

An enforcement system where processors establish reasonable dates that

must be approved by the appropriate executive agency has many advantages

over a system where the enforcement

agency performs the necessary laboratory test to determine the validity of

open dates. It is less expensive, would

not lead to a decline in quality specifications for the date, and would avoid questions of a processor’s liability.

Consumer complaint-based enforcement

for products sold at full price after the

stated date (i. e., the consumer complains

to the appropriate authority) is less costly than Government agency inspection

for out-of-date products and can be very

effective,

Some foods that are beyond date could

be sold to consumers, perhaps at a reduced price, because the foods will still

be safe.

Federal/State cooperation on enforcement is feasible. However, in order to

have each State enforce a Federal mandatory program, the Federal Government may have to provide 100 percent of

the costs. If not, the States would prefer

enforcement at the Federal level.

There have been no court decisions on

the questions of liability for deteriorated
8 c Open She/f-Life Dating of Food

food that has been open dated. If there

were a Federal requirement for open

dating, the Federal Food, Drug, and Cosmetic Act (FDCA) seems to provide

several mechanisms by which to ensure

compliance, especially as it relates to

adulteration and misbranding. However,

if literally interpreted, FDCA does not

provide for abuses to food products in

distribution that could cause the date to

be involved. In addition, the meaning of a

sell-by date is somewhat vague. This

date suggests that the product can be

consumed for a reasonable period of

time after the date with no recognizable

difference in the food’s quality. Omission of information disclosing the ensuing consumption period could constitute the omission of a material fact rendering the product misbranded. These

areas should be specifically addressed

in the legislative history of any opendating provisions.

CONGRESSIONAL OPTIONS

There are three basic options for Congress

to consider in the open-dating issue. Congress

can:

Allow the present voluntary system t o

continue by taking no action. Under this

system, the private food sector is developing and adopting open-dating standards.

~. Choose a mandatory system, whic h

would require the use of specific open

dates.

3. Choose a voluntary/mandatory system,

whereby the Federal Government develops guidelines, and processors who elect

to open date are required to follow those

guidelines.

If Congress chooses Options 2 and/or 3, it

can either specify the detail or leave it up to

others, such as an appropriate regulatory

agency or an industry association. In other

words, Congress can legislate which type of

dates for which food and how those dates are

to be determined, or it can delegate the task.

These options are not mutually exclusive.

Congress can select one option, two options,

or a combination of all three. For example,

Congress can decide to leave open dating of

bulk fresh produce as is, under a voluntary

system; make open dating of other perishables and semiperishables mandatory; and

place long shelf-life foods under a voluntary/

mandatory system. In addition, the type of

date selected can vary by individual product.

In short, many potential combinations exist

(see chapter IX for a more detailed discussion).

Voluntary System

If Congress opts for the status quo, it will

be supporting a system in which the private

food sector will presumably continue to develop and adopt open-dating standards.

Pros: The principal advantage to this system is that it allows processors flexibility in

determining whether or not to open date and

minimizes the cost to the Federal Government

and industry, compared with the other systems. Moreover, under this approach 21

States and the District of Columbia have

adopted open-dating laws over the past 8

years and have done so with a minimum

amount of regulatory control and enforcement.

This option would allow time for specific

research to better gauge the cause-and-effect

relationship between open dating and spoilage reduction. Specific areas in which further data is needed include: the amount and

kinds of food sold nationally that are not

fresh, better quantification of costs, and an

improved scientific base to accurately deter-
Chapter l—Executive Summary ● 9

mine freshness dates, The experience of

States that have adopted open shelf-life

dating will be helpful in obtaining the above

data.

Cons: The most serious perceived disadvantage of this approach is the lack of uniformity in deciding: 1) which products to date,

Z) which date to use, 3) how to display the

date, and 4) what scientific guidelines should

be used to determine the date. In addition, inventory-control procedures are relatively

more difficult, which could result in more

food waste than under a mandatory system.

Also, some industries may not adopt the program.

Mandatory System

A mandatory system would require the use

of specific open dates.

Pros: The principal advantages of this

system is that a mandatory system would provide uniform regulations; tighten inventory

control, which could reduce food waste; provide higher quality and nutritive levels for

more food; and set criteria for calculating accurate open dates.

Cons: The principal disadvantage is that,

with the exception of using a “pack date, ” it

would be difficult to implement in the short

run of 2 to 5 years for semiperishable and

long shelf-life foods because of insufficient

data on shelf-life stability of these product

categories. However, since many perishable

products are presently open dated, data are

available to implement a mandatory system

for perishables,

Other disadvantages would be: 1) costs

would increase to Government for developing

and enforcing regulations and to industry for

compliance, compared with a voluntary/mandatory system, 2) out-of-date products maybe

usable but returned and wasted (unless special arrangements are made for their use), 3)

development of regulations would be timeconsuming for both Government and industry,

4) innovation in terms of incentives to develop

new processing techniques to increase shelf

life could be stifled, and 5) small processors

could be forced out of business.

If a mandatory policy is selected, Congress

must decide who should specify the technique, criteria, and type of enforcement system. To specify these areas, there are two

basic ways Congress can legislate. Congress

can either specify the details itself or charge

others with the responsibility for doing so.

Congress Specifies the Detail

Open-dating techniques. Congress could

specify the use of one or a combination of the

following open-dating techniques: pack date,

sell-by date, best-if-used-by date, or some

combination.

Pros: The advantages of a mandated technique by product or product category include

uniformity in all States and less potential consumer confusion.

Cons: The disadvantages include:

It would be more difficult to change a

technique over time than if specifications were left up to the appropriate regulatory agency.

A continuous legal and/or legislative

process may arise in an effort to change

dates over time. This could be an expensive process for industry, Government,

and ultimately for consumers.

Open-dating criteria. In addition, Congress

could decide which criteria must be used for

which date or dates. In other words, which

categories of sensory quality, nutrient loss,

and perishability to use.

Pros: The advantage of mandating specific

criteria used in establishing dates includes

standardization among products and/or product categories.

Cons:

● Neither Congress nor the Secretary of

the appropriate executive branch agency currently may have the technical ability and data necessary to specify criteria

for each food item.

49-394 0 - -9 - 2
10 . Open Shelf-Life Dating of Food

●

●

Technological innovation could be stifled

because criteria could not be easily

changed.

The criteria may not likely be based on

sensory quality parameters because it

would be more difficult to regulate than

would other criteria. This could be an

advantage for some products and a disadvantage for others, depending on

what test index is chosen.

An alternative to mandating specific criteria is to allow a range of criteria. The advantage of mandating some range of criteria

is that both sensory and nutritional criteria

would likely be included within the range.

The disadvantage is that there would not be

standard criteria for similar products.

Enforcement and liability. Congress has

two basic options for determining the enforcement system and for establishing liability as it relates to open-date labeling:

●

●

Use Existing Laws

Pros—Enforcement: Allowing the existing laws to specify enforcement simplifies

the procedure and minimizes the cost and

time for both Government and industry.

Cons—Enforcement: Existing law does

not specify what should be done in the case

of: a) food that is still edible but past date

and b) food that is beyond criteria but not

past date.

Pros—Liability: Existing laws covering

liability already offer several devices

through which manufacturers, wholesalers, and retailers might be held liable for

violations of an open-dating requirement.

Cons—Liability: Since there is no definitive legislative or judicial definition of the

legal significance of an open date, application of existing law remains speculative.

Pass New Laws

Pros—Enforcement: Legislating new enforcement procedures has the advantage

of allowing Congress to address specific

items such as use of State enforcement officials and/or complaint-based enforcement

by consumers for beyond-date compliance

and disposal of edible food that is out-ofdate.

Cons—Enforcement: Writing a new law

to adequately provide for enforcement increases both time and cost to Government

and industry.

Pros—Liability: Writing new legislation

that specifies liability and penalties, if any,

for open-date labeling could provide consumers with more confidence in an opendate labeling system.

Cons—Liability: It is a difficult and burdensome task to ascertain liability to the

firms responsible.

Leave Implementation of Detail

tO Others

Delegating the specifics to either the appropriate executive agency or the private

sector would have the following results: 1) it

relieves Congress of the necessity to make

these determinations and 2) it would be easier to change a technique over time than if

specifications were decided by Congress.

● Appropriate Executive Agency

—Open-Dating Techniques

Pros: The advantages of this option, as

with congressionall y mandated detail, include uniformity of the open-dating technique for all food processors producing a

single product. Also, the regulatory procedure would allow industry and consumers

more involvement than would the detailed

statutory approach.

Cons: The disadvantages of allowing executive discretion include the potentially

large costs in time and money both Government and industry would incur before the

regulations could be developed.

—Criteria

The advantages and disadvantages of

establishing open-dating criteria are the
Chapter l—Executive Summary s 11

same for an executive agency as those discussed for Congress.

● Private Sector

—Open-Dating Techniques

Individual processors could be allowed

to choose the dating techniques and make

them defensible to the appropriate Secretary.

Pros: Allowing individual processors to

have this freedom would allow the marketplace to determine the best system.

Cons:

● Lack of uniformity of date types on similar products could confuse consumers and

retailers.

. The retailer may have problems using

open dating for inventory control when

there is a lack of uniformity on similar

products.

Ž Small processors may use pack dates

since they might not be able to do the necessary research to establish sell-by or useby dates.

As an alternative, an industry association could be allowed the freedom to

choose the dating techniques and make

them defensible to the appropriate Secretary.

Pros:

Ž Date types on similar products would be

uniform.

● Consumers could have input into industry association meetings to establish dates,

especially if the association decision were

subject to Secretarial review.

Cons:

● If the system were voluntary/mandatory,

it would allow nonmembers of the industry

association to do nothing.

Ž If mandatory and nonmembers of the industry association have not had an opportunity to participate in the process of

choosing a technique for dating, this could

lead to legal problems such as antitrust or

restraint of trade.

. There may be more than one industry association to which one processor belongs,

and these associations might establish two

different techniques.

—Criteria

Pros: The advantages of allowing processors to specify criteria for establishing

open dates include:

● Sensory criteria could be part of the input when considered appropriate for the

particular product.

. Through the appropriate Secretary, consumers could have a continuing voice in

what criteria is used.

Cons:

● Secretaries of the regulatory agencies

involved would have an additional burden

of reviewing the criteria submitted to them.

Ž Costs to Government could be quite high

relative to other options.

Voluntary/Mandatory System

A voluntary/mandatory system is one in

which the Federal Government develops

guidelines, and processors who choose to

open-date food products are required to

follow these guidelines.

Pros: This system establishes a mechanism

for uniformity to open-date food products,

and it provides individual food processors the

basic option of determining whether or not to

open-date products.

Cons: Costs to Government would increase

for developing and enforcing regulations and

to industry for compliance. Development of

regulations would be time-consuming for both

Government and industry.

Note that if the Congress chooses this option path, the issues discussed under the mandatory system become relevant.
Chapter II

Consumer Perspective on

Open Dating

this

Since consumers are the ultimate users of open dating, an integral part of

assessment is consumer interest in and perspective on open dates for food.

The background for this section comes from an Office of Technology Assessment

nationwide survey of consumers in 1978 to determine their attitude about opendate information, usefulness and understanding of dates, and preference among

dates. The survey itself consisted of a questionnaire sent to a statistically

selected sample of 3,000 consumers. *

ATTITUDES TOWARD OPEN DATING

According to the survey, almost all shoppers (96 percent) were concerned about getting the freshest food products possible.

About 1 in 10 (11 percent) felt that a lot of

food they buy from grocery stores is spoiled.

Although the consumers were concerned

about food freshness, their awareness of

open dates varied considerably. The dates

themselves—their presence and form—varied by both product and by store.

Nearly all the shoppers (96 percent) were

aware of dates on milk. At least half noticed

dates on other perishable products such as

bread, eggs, ground beef, and round steak.

On a few semiperishable items such as

cheese, luncheon meats, and cereal, a majority of shoppers also noticed dates. However,

*OTA commissioned this survey, recognizing that

other surveys have been completed on this subject. The

OTA survey provides more detailed information on consumer preference and is more recent than the other

surveys. This survey is available on request.

for most other semiperishable items, only a

few noticed the date.

Only about 12 to 14 percent of the shoppers

said they were aware of dates on nonperishable or long shelf-life food items such as

canned soup and canned vegetables, but this

is not too surprising since a smaller proportion of these products are open dated, compared with perishable products.

Eighty percent of the consumers surveyed

considered open dates to be useful. This

figure compares with 67 percent in a 1973

U.S. Department of Agriculture (USDA) study

on open dating and 90 percent in a similar

study by USDA in 1976. Thus, open dates are

considered by many to be useful in food shopping.

The OTA survey found that 62 percent of

the consumers sort through items with an

open date to find the freshest product. This

compares with a 61-percent response to a

similar question in the 1976 USDA study.

Therefore, retailers selling foods with open

13
14 . Open Shelf-Life Dating of Food

dates have an incentive to keep tight control

over their inventory if they want to avoid consumer culling.

Shoppers in the OTA survey were asked to

rank the following four different types of information that may be found on food labels:

1) open date, 2) recipes and cooking instructions, 3) list of ingredients, and 4) nutritional

information (table 2). They were asked to do

this for several perishable and long shelf-life

food items.

The survey found that the open date is the

most important piece of information on the

package label for fresh meat and frozen vegetables and is second in importance to the list

of ingredients on a canned soup label. Thus,

among the various types of information on a

label, open dates are considered useful for

both perishable and long shelf-life foods.

Table 2.—Consumer Usefulness of Information on Food Packages

(percentage of respondents)

—.

Freshness date . . . . . . . . . . . . . . . . . . . . . . . .

Recipes and cooking instructions . . . . . . . . . . . . . .

List of ingredients . . . . . . . . . . . . . . . . . . . . . . . . . . .

Nutritional information . . . . . . . . . . . . . . . . . . . . . . .

a Less th-an”O 5—percent

— —. ————— ——.— ——

Frozen

vegetables

50 -

22

19

10

Canned

soup

‘

-

2 4

19

43

16 i---

Fresh

meat

9 1

-

2

4

3

Frozen

vegetables

7

47

22

22

.

Canned

soup

29 - 

45

10

15

Fresh- -

meat —

(a)

54

30

14

Since different types of open dates with

different meanings appear on various food

products, consumer understanding is a key

factor. Therefore, the survey asked the consumers to identify the correct type of date

on milk, breakfast cereal, and ground beef

(table 3).

The results were mixed. Nearly threefourths of the shoppers knew that the date on

milk is a sell-by date. However, only one in

four identified the date on breakfast cereal

as a use-by date; over one-third thought it

was a sell-by date. For ground beef, only onethird knew the date was a pack date, while

almost another third thought it was a sell-by

date.

Therefore, aside from milk, it seems there

is considerable confusion over the meaning of

specific open dates. The illustrations of various products on pages 16 & 17, with dating

highlighted, give visual evidence to the confusion of consumer understanding.

Table 3.—Consumer Understanding of Freshness Dates

(percentage of respondents)

— -. — - Breakfast Ground ‘

-

Milk cereal beef

When it was packaged. . . . . . . . . . . . . . . . . . .

-—

9 8 34“

Last day it should be sold . . . . . . . . . . . . . . . . . . 74 35 31

Last day it should be used or eaten . . . . . . . . . . 15 26 9

Have never not iced a date on a

package of this product. . . . . . . . . . . . . . . . . . 2 31 26

NOTE Percentages In boldface Indicate correct answers

.-
Chapter II—Consumer Perspective Open Dating ● 15

PREFERENCE AMONG OPEN DATES

With different types of dates now in use, The most preferred form of dating was a

consumer preferences can be useful in deter- combination date rather than a single date. In

mining open-dating policy. The OTA survey, fact, almost two out of three (64 percent) said

therefore, asked consumers to express their they would like to see two dates, either sell-by

preferences for different types of dates or and use-by or pack and use-by. (Consumer

combinations of dates for various food items. representatives on the OTA panel also preSome consistent patterns appeared, as shown ferred combination dates.)

in table 4.

Table 4.—Consumer Preferences for Open Dates

(percentage of respondents)

Preferences among single dates and combinations

Both

Both

Only

Only

Only

Both

sell-by and use-by date . . . . . . . . . . ., . . . . . . . . 37 25

pack and use-by date. . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 37

use-by date. . . . . . . , . . . . 16 42

sell-by date. . . . . . . . . . . . . . . . . . . . 9 60

pack date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 75

sell-by and pack date. . . . . . . . . . . . . . . . . . . . . . 5 59

Preferences among single dates for selected foods

Last Last – ‘ - Would

day day Date not use

used sold packaged date

Perishable products

Milk . . . . . . . . . . . . . . . . . . . 43 37 18 (b)

Ground beef : : : : : : : : . . . . . . . . . . . . . . . . . . . 39 24 33 1

Round steak . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 23 32 1

Semi perishable and nonperishable products

Cheese. . . . . . . . . . . . . . . 44 34 18 2

Canned tuna fish . . . . . . . . . . . . . . . . . . . 43 21 20 8

Frozen vegetables ., . . . . . . . . . . . . . . . . . . 43 24 23 4

Flour . . . . . . . . . . . . . . . . . . . . . . . 35 26 24 11

Cake mix . . . . . . . ..., . . . . . . . . . . . . . . 34 25 22 8

Jelly, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 18 18 17

-. —- —-

Preferences among combination dates for selected foods

Perishable products

Milk

Ground beef ::: :::::::::::::::::::.

Round steak . . . . . . . . . . . . . . . . . . . . .

Semiperishable and nonperishable products

Cheese. . . . . . . . . . . . . . . . . . . . . . . . . .

Sell-by - 

-

and

use-by

. 46

. . . 39

39

s

. 40

—.

Pack

and

use-by

28

33

33

30

‘-Sell-by - ‘Only -

and one

pack date —

8 21

Frozen vegetables . . . . . . . . . . . . . . . . . . . . . . 35 33 8 21

Canned tuna fish . . . . . . . . . . . . . . . . . . . . . 31 32 8 22

Cake mix . . . . . . . . . . . . . 27 29 8 29

Flour . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 30 8 29

Jelly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 23 7 31

aRanked Iower than third most Important

bLessthan05Dercent

Seldom/

never

purchase

1

4

7

1

7

7

3

11

17

No

date

1

2

1

3

6

6

6

16
16 . Open Shelf-Life Dating of Food

Dating Techniques of Various Food Products

What Do They Actually Mean?

7

Remains Fresh l-Week

After Date Shown

Sell By

Buy Before 9 Best When Purchased By
Chapter II—Consumer Perspective Open Dating ● 17

“,

‘

7

Best When Purchased By Sell By
18 . Open Shelf-Life Dating of Food

This leaning towards more than one date

indicates that consumers want as much information as possible on product freshness.

However, a significant minority (19 to 31 percent, depending on the specific food product)

desired only one date.

If just one date were to appear on food

packages, the use-by or best-if-used-by date

was the most preferred. This was true regardless of the perishability or shelf stability

of the product.

Second choice to the use-by/best-if-used-by

date is the date currently placed on specific

products. For example, most respondents

preferred the sell-by date to the pack date for

milk, but just the opposite for ground beef and

round steak.

Among combination dates, a sell-by/use-by

date was preferred for the three perishable

products and for two out of six semiperishable and nonperishable products. The pack/

use-by combination was the second most preferred, and very few respondents preferred

the sell-by/pack combination.

Preliminary results of nationwide hearings

in 1978 by the Food and Drug Administration

(FDA), USDA, and the Federal Trade Commission shed further light on the issue of consumer preference in open dating. For those

consumers requesting a combination of dates,

a pack/use-by date was favored for long shelflife foods and a pack/sell-by or pack/use-by

date for perishables.

In conjunction with the above hearings,

FDA commissioned a food-labeling survey in

late-1978. Summary results of that survey on

open dating are very consistent with the findings of the OTA survey.

DIFFERENCES AMONG SUBGROUPS OF SHOPPERS

A number of demographic variables were ences appeared. For example, in high-income,

examined to determine if certain subgroups high-education, and large households, slightly

within a population might show different at- more respondents felt open dates were usetitudes and behaviors with respect to open ful. Generally, though, demographic differdating of foods. Race/nationality, education, ences were not impressive. At any rate, such

age, income, family size, and religion were ex- differences do not seem crucial for establishplored. ing an open shelf-life dating policy because in

Not surprisingly, in a large number of com- all groups the majority of respondents indiparisons across many items, some differ- cated that open dates were useful.
Chapter Ill

Benefits of Open Dating

As soon as harvested or slaughtered, most foods begin to deteriorate in

quality. Some exceptions are fruits picked prior to ripening, such as bananas,

and red meats and seasoned prepared foods, which first improve in sensory

quality before they deteriorate. Subsequent processing is done to slow down the

rate of deterioration and thus increase shelf life, thereby preventing waste.

The type of process used to preserve food largely determines the shelf life of

a product (e.g., canning gives a longer shelf life than refrigeration). In addition,

environmental conditions can also directly affect food quality and speed up deterioration. Conditions such as high temperature, high humidity, light, and contact

with air (oxygen] all speed up this quality loss.

However, open dating in itself only sets the time of shelf life of foods—by necessity ignoring the changing environmental factors by assuming the food is held

under certain average conditions. If the date is based on these average storage

conditions, the closer to the date (except for a pack date), the lower is the quality.

Ideally, dating information should take into account the environmental factors as a function of time. Although current technology is unable to do this,

technology is being developed that will measure the influence of both time/temperature fluctuations on quality deterioration. Currently, a device can be attached to a food package that can measure the reaction to a specified time/temperature relationship or exposure to some temperature above a set limit. The

device must be designed to respond to temperature change in the same way as

the food product.

Studies on the reliability of these devices indicate two major problems:

1) they become unreliable if exposed to high temperature prior to activation, and

2) in many cases, their responses do not match manufacturers’ specifications.

Although these devices have been modified since the aforementioned studies

were published, the major problem is still to develop an indicator that exactly

matches the sensitivity of a particular food to a change in temperature and/or

other environmental factors. (For more information, see appendix C).

Therefore, with the gap in technology, the focus of this analysis is by necessity one-dimensional (open shelf-life dating) for a multidimensional problem of

food-quality preservation.

Despite the limitations just outlined for open dating, many benefits are attributed to it. This chapter identifies and analyzes these potential areas, including food quality, nutrition, food safety, inventory control, and education.

19
20 ● Open She/f-Life Dating of Food

FOOD QUALITY

Whether open dating benefits product

quality is of primary importance, given the

fact that most food deteriorates with age.

There are no published studies that show that

open dating leads to the availability of higher

quality foods.

An open date may not provide an assurance of high quality, since storage conditions

are critical to the quality of all foods and can

be highly variable. For example, if semiperishable and long shelf-life foods are temperature-abused and are stored long enough, a decline in quality may be detected. A food with

a more recent date that has been mishandled

will be of substantially lower quality than an

older dated food that has been stored under

ideal conditions.

In order to achieve high quality at point of

purchase, then, the food must be of high quality initially and must be handled under proper storage and distribution conditions. If both

of these criteria are not met, the date on the

package (unless it is a pack date) could be

meaningless as well as misleading. Also, storage conditions after purchase could greatly

affect the shelf life of the product.

Nevertheless, today’s consumers believe

an open date assures “acceptable” quality;

such assurance is their primary reason for

wanting an open date. However, in actual

fact, a situation may evolve in which consumers believe that a date will be helpful to

them in terms of “better” quality when the

state of the technological capabilities may be

such that the benefits will be considerably

less than what is expected.

Even foods produced under the same conditions at a single location may undergo many

different time/temperature/humidity changes

when they are distributed around the country. Thus, an open date based on average climatic conditions may be an adequate quality

measure for some northern parts of the country where temperatures are lower, but inadequate if the product were held under high

temperature/humidity changes when distributed around the country. It is possible that requiring an open date could improve the control over foods during distribution to the point

that the date would be an assurance of high

quality.

In an in-store U.S. Department of Agriculture (USDA) experiment where open dating

was introduced, the incidence of consumer

complaints on food items most often cited

previously as spoiled or stale was reduced by

50 percent. Store losses in dollar values and

package rehandling also were reduced.

Attributing these results to open dating

was questioned by those reporting the study

findings. The reason was that the study

showed a reduction in complaints about spoilage for both open-dated and non-open-dated

food in the same store. Thus, some of the improvement may have been because of increased confidence in the freshness of all

food sold in the store (to which open dating

could have contributed), rather than changes

in the food itself—i.e., less spoilage.l

‘Food Dating: Shoppers Reactions and The Impact on

Retail Foodstores, Market Research Report No. 984

(Washington, D, C,: U.S. Department of Agriculture,

1973).

NUTRITION

Open dating could be of some value if used time of the sale of the food. In order to set the

with nutrition labeling. The nutrition label nutritional levels, the manufacturer may

already has a time factor built into it because have made a judgment about the length of

the values on the label are required to be time and environmental conditions involved

within established statistical limits at the in the distribution of the food and how these
Chapter Ill—Benefits of Open Dating . 21

conditions would affect nutrient loss of the Thus, as previously discussed for quality,

most unstable nutrients, such as vitamin C. an open date could be used to ensure imHowever, as with quality, improper storage proved handling conditions that could result

conditions could result in greater nutritional in less nutrient loss. But whether this would

losses than predicted under average condi- improve the nutritional status of Americans

tions. is questionable.

FOOD SAFETY

Open dating has little or no benefit in terms

of improved microbiological safety of foods.

For foods in general, microbiological safety

hazards are a result of processing failures,

contamination after processing, and abuse in

storage and handling. These factors are all

independent of the age of the product and

have little relationship to an open date, In

fact, an open sell-by or use-by date could

have an adverse effect on food safety if conINVENTORY

At the processor level, adequate inventory

control is currently provided by the coded

dates now being used on food packages. Distribution centers of manufacturers and central warehouses of supermarket chains can

also use the code for proper stock rotation,

although they do not always do so.

Consumers, however, feel that inventory

control via coded dates really breaks down at

the end of the distribution chain, The local

store managers and supermarket stock clerks

may or may not use the coded dates. Because

they are in code, consumers cannot use them

sumers took it to be an assurance of food

safety. For example, “Well, it looks, smells,

and feels bad, but the date says it’s good for

another month, so I’ll use it. ” Poor manufacturing processes can still exist with an opendating system, and consumers could be given

a false sense of security. A date with specific

storage information (e.g., “keep cool after

opening”) could, however, reduce hazards.

CONTROL

to decode each product. Open dating could

obviously tighten inventory control by both

the retailer and the consumer.

USDA found that in their in-store experiment, open dates encouraged better food-handling practices by making store personnel

aware of the need for rotation. Confusion

among clerks about when to rotate or remove

products was reduced, and closer attention

was given to expediting sale of products near

the end of their shelf life so they did not have

to be discarded.2

2

Ibid.

EDUCATION

An important benefit of open dating could tion conditions and studying how specific

be the education of the food manufacturer foods deteriorate. Open dating in the long run

and the consumer. Much of the consumer’s would increase the body of knowledge about

education about a particular product usually the quality and chemistry of food products.

comes from the food industry in the form of The food industry as a whole should be ceradvertising and package information. Thus, tain that the information given in an open

the research forced on the manufacturer in date is not misunderstood in terms of quality,

order to establish an open date is a form of safety, and nutritional assurance.

self-education in terms of analyzing distribu-
Chapter IV

Alternative Open-Dating

Techniques

Converting codes to open dates offers many possibilities. The date could be

any of four possible dates, or a combination of dates, and there is a variety of

ways the date could be presented.

Basically, the types of open dates are:

1. date of pack or manufacture,

2. pull date or sell-by date,

3. best-if-used-by date,

4. expiration date or use-by date, or

5. combination of two of the above.

The meaning of these dates is not necessarily obvious. The pack date refers

to the day, month, and year the food product was processed or packed for retail

sale. The pull or sell-by date refers to the last date the food product should be

sold in order to allow the consumer a reasonable length of time in which to use it.

The best-if-used-by date is the date after which the food is no longer at its most

acceptable level of quality. The use-by date is the date after which the food is no

longer at an acceptable level of quality.* The terms “pack,” “sell by,” and

“best-if-used-by” will designate these alternative open dates, respectively.

This section is a general discussion of

open-dating methods. Appendix A offers a detailed discussion by major food category of

the advantages and disadvantages of each

method.

*Food scientists make this distinction between use-by

and best-if-used-by dates. Consumers do not necessariIV see the difference. Many think either of these dates

indicate the date at which food is no longer at an acceptable level of quality.

Pack Date

A pack date is the only date that could be

put into effect in the near future if an open

date were mandated for all food products.

Compared with the other dates, it is also the

least expensive because it requires only historic data—i.e., the time of the event is known

without research or estimation. However, it

may not be the best date for all food products.

23
24 ● Open She/f-Life Dating of Food

The pack date, as defined above, has three

problems:

1.

2.

3.

the condition and length of time the product was held before being packaged is

not considered,

some products such as fresh meat can be

reconditioned and repackaged for sale,

and

ages of separate components in a multicomponent food such as a dried soup mix

could vary.

In regard to the first point, some consumers

feel that manufacturers store food in bulk for

an unreasonably long time before putting it in

the final package. Manufacturers, on the

other hand, feel they should be allowed to

hold commodities for as long as is economically expedient if they use ideal conditions of

storage that minimize possible quality loss.

Examples of kinds of foods that would fall in

this category are foods frozen in bulk before

being packaged, such as concentrated orange

juice, some vegetables, concentrated milk to

be used in ice cream, and flour.

For most perishable foods, a pack date

would be of minimal value to the consumer if

used by itself. For example, with milk and

dairy products, it would only indicate the

date the milk was processed or packaged. It

would not give the consumer any information

as to quality or how long the products should

remain at a level of acceptable quality. For

precut/prepackaged meats, poultry, and fish,

the use of a pack date would give the consumer some information as to general product

quality but may also give a false sense of

quality assurance if the product is repackaged under different conditions to lengthen

shelf life or if held in frozen storage for some

period of time before being offered for retail

sale.

For shelf-stable engineered or multicomponent foods, the shelf life is determined by

the age and quality of the various components—which could vary widely. A pack date

alone would give too little information for the

consumer to make any estimate of quality or

shelf life. Examples of these multicomponent

foods include dried soup mixes, cake mixes,

canned mixed fruits and vegetables, helpertype meals, and meat substitutes.

Foods for which a pack date seems reasonable are prepackaged fresh fruits and vegetables. These food products are not processed

to lengthen shelf life and cannot be frozen for

any part of their storage life without serious

alteration of product quality. Thus, the use of

an open pack date would actually convey to

consumers freshness information (assuming

immediate packing after harvest).

The use of a sell-by or best-if-used-by date

for prepackaged fresh fruits and vegetables

would require the retailer to estimate when

the product would reach its peak of ripeness

or begin to exhibit significant and detectable

loss of quality. Because fruits and vegetables

of different varieties, and even within the

same variety, may mature at different rates

depending on the size, storage conditions, and

other factors, such a date could not be established with a reasonable degree of accuracy.

Sell-by and Best-if-Used-by Dates

Information for scientifically determining

these dates does not always exist, as for the

pack date, so processors and manufacturers

must frequently estimate or create a date. In

order to set a valid sell-by or best-if-used-by

date, the following information must be obtained:

1. a measure of some initial relevant quality factor that can be used to estimate a

decrease in consumer acceptance,

2. a reliable method to measure that quality factor on a statistically sound basis,

3. the distribution system times and conditions,

4. the average time the product is held in

the consumer’s home before use, and

5. the amount of quality loss allowed before the product is considered unacceptable for sale at full price or for use.

A sell-by date could be set if the average

time the product is in the distribution system
Chapter IV—Alternative Open-Dating Techniques ● 25

is known, but it must also assume some

knowledge of how long it will take the average consumer to handle, store, and use the

food in the home under conditions that will retain good quality. Thus, storage and distribution information is necessary to establish any

date other than a pack date. If this knowledge

is not available, the date is not meaningful

and might be misleading.

There are regional problems involved with

use of open dates for products such as dried

snack foods, pasta, and breakfast cereals

that are distributed nationwide and are subject to extremes in temperature and humidity

conditions, For example, for any food where

gain or loss of moisture is related to quality

(e.g., loss of crispness in potato chips), a date

for reaching the critical moisture content

could be established for any given distribution area, but it could be costly to do.

If, on the other hand, the end destination is

unknown, the date could be set for the worst

possible conditions. The problem with this approach would be that a large percentage of

the food going to areas of the country with

moderate conditions would still be good when

marked out of date. For example, if the open

date must be set to allow for moisture gain in

a high humidity area such as Mississippi, national distributors would either have to protect all packages against extreme conditions

and charge consumers for such steps, or suffer product losses. These considerations

could result in some companies withdrawing

from national distribution.

The sell-by date is usually used in conjunction with foods that have a short shelf life

after the date of sale, if properly handled.

Milk and dairy products, such as yogurt, are

labeled in this way, and, in fact, some packages may give further information as to days

of shelf life beyond the selling date.

The sell-by date is the single most useful

date for wholesalers and retailers. Its advantage is that it is unambiguous relative to the

best-if-used-by date. Both wholesalers and retailers know the normal amount of time any

given product requires to move through their

segment of the marketing system. This knowledge in combination with a recommended

sell-by date gives the wholesalers and retailers the means to assure freshness through inventory control.

OTA’s consumer survey found that the sellby date is not the open date that consumers

prefer for food products, however. In both the

perishable, semiperishable, and long shelflife food categories, consumers preferred the

best-if-used-by date to the sell-by date or pack

date. Except for prepackaged fresh meat, the

sell-by date says little or nothing about when

foods should be used or when the quality may

be detectably worse.

A best-if-used-by date, on the other hand,

does not permit wholesalers and retailers the

same ease or potential accuracy in inventory

management that a sell-by date allows. These

dates require wholesalers and retailers to individually and subjectively determine allowance for home storage time on each individual product in order to calculate a sell-by

date—i.e., the date they need for management purposes.

For processors, a best-if-used-by date is

more useful than a sell-by or use-by date.

They feel it is the most informative to the consumer and, with the exception of the pack

date, the least arbitrary and restrictive. To

the processors, the sell-by and use-by dates

imply that at some moment in time a dramatic

change will take place in the quality and suitability of the product. That is, before a given

date, the product is acceptable; afterward, it

is not and must be discarded. This, of course,

is not true, but processors fear that consumers might interpret it this way. Therefore,

they prefer the best-if-used-by date, feeling it

carries the connotation that there is a slow

but continuous loss of quality, and for the

greatest satisfaction to the consumer, the

food should be consumed by that date.

The best-if-used-by date is being examined

by Codex Alimentarius, the international organization for food labeling standards. These

standards say that for all products the first

date that should be looked at is the date of

49-394 0 - 79 - 3
26 . Open Shelf-Life Dating of Food

minimum durability, which translates to a

best-if-used-by date.

A modification of the best-if-used-by date is

the best-if-used-within date. In this instance,

phraseology such as “best if used within 30

days of June 1“ becomes a compromise between what retailers and consumers desire

from an open date. For example, the best-ifused-by date indicates that the product

should be used on or before the date specified. “Best-if-used-within” indicates the product should be used within 30 days of June 1.

The difference between the two dates is that

the former gives only a use-by date. The latter

gives both a sell-by date and use-by date. In

this example, the sell-by date is June 1. The

use-by date is 30 days after, or July 1. These

phrases offer an unambiguous sell-by date

for the retailer, while at the same time giving

consumers a use-by date.

TO Remain in Grade Use- (Sell-)

by Date

An alternative to a use- (sell-) by date or,

more specifically, instead of “best-if-usedby” may be a term that would indicate how

long a food may be held and yet remain at a

quality level practically indistinguishable

from that quality inherent in the original pack

date. This may be accomplished by using a

term such as “to remain in grade, use (sell)

by. ” For example, if a product is found to be

of top quality and is graded and labeled

“grade A,” “prime,” or “fancy,” the open

date would indicate how long it may be expected to remain at top quality. If it is labeled

“grade B“ or “choice,” the open date would

indicate how long the unit is expected to remain at the declared second quality level, etc.

Although such terminology would be limited to products that have precisely defined

and generally recognized and accepted quality grades and standards, for those commodities where it could be used, it would have the

advantage of specifying the quality levels expected to be retained—not just a vague

“best,” or “acceptable.” A corollary benefit

would be that if the date should be exceeded

before use (or sale), there need not be the implication that it is unsafe and should not be

used.

Integrating open dating with grade labeling

has the potential of simultaneously strengthening and appreciably reducing costs of implementing both. It may even be argued that

grade labeling must include open dating,

since “nothing is forever. ” This may be the

solution to the difficult problem of limiting the

life of a grade after it is posted on a label. For

example, a carton of eggs labeled “grade A“

could be assumed to remain “grade A“ forever unless the grade declaration would include an open date. This benefit need not be

limited to perishables. In-grade life of relatively stable foods, such as canned vegetables, can vary substantially not only among

commodities but even within commodities.

A disadvantage of an integrated system is

that it would work only for those products

where the grade is equated with freshnessquality attributes. Products such as beef,

pork, lamb, and poultry would therefore be

excluded, since the grade is based more on

compositional/conformation characteristics.

Another disadvantage is that many consumers have little knowledge of what grades

mean, So, equating an open date with a grade

would result in consumer confusion.

Combination Dates

As reported in chapter II, the OTA consumer survey found that the most preferred dates

were combination dates. Specifically, the

combination of sell-by and use-by dates wa s

most preferred, followed by a pack and useby combination. Obviously, combination

dates supply the most information to consumers.

Such a system is visualized as “retailer sell

by” and “consumer use by” on the same

product— similar to the best-if-used-within

date, which is in itself a combination date. On

some products, a combination date could give
Chapter IV—Alternative Open-Dating Techniques ● 27

the optimum information to both the wholesaler/retailer and the consumer. From a cost

standpoint, combination dates would be more

costly than a single date, In addition, multiple

dates would take more label space, which

from industry’s viewpoint could be used for

other information.

A key issue in using combination dates is

whether they will result in consumer confusion or education. For example, it can be

argued that if only one type of open date were

used on all products, potential consumer understanding could be at a maximum. Conversely, if consumers were confronted with

several different types of open dates, confusion could result.

If one accepts this “inverse” relationship,

one could argue from a consumer viewpoint

that a single type of open date should be used

on all products, regardless of other factors,

such as product deterioration. The alternative viewpoint is that even if this “inverse”

relationship does exist, efforts could be made

to educate consumers on the use of different

types of dates.

Results from the OTA consumer survey

lend support to the latter viewpoint in that

they tend to refute such an inverse relationship. The results suggest that a majority of

consumers think that combination dates

would be beneficial on at least some products. Presumably, if the consumers thought

different kinds of dates for different products

would be confusing, they would not feel that

combination dates would be useful.

The benefit of adopting a standardized

open date for all products is simplicity.

Wholesalers, retailers, and consumers would

know or eventually learn how to use and deal

with that standardized date. However, a

standardized date may not be the optimum

one for certain products.

IMPLEMENTATION

Storage Instructions

Based on the OTA survey and other surveys, it is apparent that consumers feel that

as much information as possible should be included on the food package, including storage

instructions as well as an open date.

As discussed earlier, the shelf life of food is

based on some definite conditions of storage.

If these differ significantly from those anticipated, the shelf life of the food will vary, being shorter if the actual conditions turn out to

be more unfavorable, and being longer if they

should be more ideal. Thus storage instructions, if observed, would enhance the usefulness of open dates, but they raise the increasingly critical problem of space on the label.

Processors in the OTA working group feel

that the presently used instructions found on

some food products such as “keep refrigerated, “ “keep in a cool, dry place, ” and “keep

frozen until used” are adequate. In addition,

available space on the package is not adequate for elaborate storage instructions, and

too many other regulations relating to required information and size of print used

would be affected. There is little doubt that

consumer education about proper storage instructions is an important—and necessary—

part of open dating. Such education might be

accomplished through use of television, pamphlets, or posters, however, rather than the

package label.

Type of Date Marking

With respect to the actual date itself, consumers surveyed and consumer representatives on the OTA working group wanted the

month, day, and year. 1 The most preferred

‘Food Do tin~: Shoppers Reactions and The Impact on

Retail Foods tores, Market Research Report No. 984

(Washington, D. C.: U.S. Department of Agriculture,

1973).
28 . Open Shelf-Life Dating of Food

form was “8 May 78” rather than “May 8,

‘78, ” “ 5/8/78, ” or “8/5/78” because of “possible confusion. ” (Such a form also takes up

less space than “May 8, ‘78.”)

Preliminary results from the 1978 consumer hearings held by the Food and Drug

Administration (FDA), the U.S. Department of

Agriculture (USDA), and the Federal Trade

Commission (FTC) support these findings. In

fact, indications are that the vast majority

prefer an alphanumeric date—"8 May 78” or

“May 8, ’78”—to a date in all numerals—"5/8/78" or “8/5/78.”

Processors, wholesalers, and retailers

have no significant problems with these preferences. However, the possible exclusion of

the year could be made for highly perishable

products such as fresh meat and bakery products, and omission of day of the month for

long shelf-life foods. This is a common feature

found in many countries that open date their

food products.

As far as actual implementation goes, a

three-letter designation could be used for the

month: JAN, FEB, MAR, APR, MAY, JUN, JUL,

AUG, SEP, OCT, NOV, DEC. However, the

fact that these designations require a combination of 20 letters, in addition to numbers,

complicates high-speed printing operations.

Still, too much confusion could result from

using numbers alone. For instance, for the

first 12 days of any month, the day of the

month could also be the number of the month

itself.

For some food packages, there are technological problems in printing dates. Frozen

food packages—especially cardboard—present a challenge because cardboard tends t o

return to its initial shape when a date is embossed on it; the wax loses its effectiveness as

a humidity barrier if the date is cut into it;

and inks do not mark well on wax.

The type of package employed should not

influence the specific information provided

by the date, but it could determine the particular technique by which the date and associated information are applied on the container. For example, it may be impractical and

dangerous to emboss a retortable pouch, and

some type of printing or sticker label might

need to be designed. Also, it is generally

acknowledged that open-date printing would

have to be done at the point of packaging on

preprinted labels with space left for an open

date. It would be difficult to make labels with

the proper information ahead of time because

of the logistics of processing.

Despite the technological problems, the

major impact on food manufacturers of applying open dates would be that more package space would be taken away from them

which must be used for the label. This could

lead to a decrease in the availability of small

single-serving packages that may not have the

added space required.

The impact on other groups would be the

increased need for education. Precision and

brevity of terms and easily recognized dates

are important for the consumer to understand the date itself as well as to help those

involved in the distribution and marketing

system.

EXEMPTIONS

There are specific food products that tainer or wrapping prior to sale; c) salt; and

should be exempted from open dating. These d) crystallized refined sugar.

are: a) bulk fresh fruits and vegetables—

those products sold unpackaged at produc e

counters; b) fresh meats, poultry, and fish The principal

that are cut and prepared in the retail store, fresh fruits and

are not frozen at any time during their poultry, and fish

storage life, and are not packaged in any con- quality of these

reason for exempting bulk

vegetables and fresh meat,

from open dating is that the

products is normally deter-
Chapter IV—Alternative Open-Dating Techniques “ 29

mined by sight, touch, and smell before purchase is made. Because these products are

subject to varying rates and types of deterioration, including physical destruction as a

function of consumer handling, it would not

be possible to arrive at a meaningful shelf-life

date for each product. There would also be

problems in physically placing a date on individual items, and the cost of such a program would be prohibitive.

A date of any kind is not meaningful for

certain foods such as salt and crystallized

refined sugar, which when held under proper

conditions are good for 10 to 20 years. These

products however, do not have an infinite

shelf life because if held at high humidity,

they can cake. From a practical viewpoint,

though, there are very few situations in

which food is actually stored 10 to 20 years.

These foods could be said to have a shelf life

so long that it is not a relevant factor in their

purchase or use.
Chapter V

Establishing Open Dates

In order to establish a fairly accurate open date (except a pack date) for a

particular food, one needs to know how that food deteriorates. All foods begin to

deteriorate at some speed (rate) as soon as they are packaged and continue to

deteriorate until they may no longer be acceptable. Some foods deteriorate relatively quickly and others very slowly.

Food shelf life is not totally dependent on time but also on environmental

conditions such as temperature, humidity, light, and oxygen. The prime factors—temperature and humidity-may increase deterioration as they rise, or

slow the process as they become lower. However, their impact depends on how

widely they vary and on the product itself. Also, as the food deteriorates, the

process may accelerate because of its own momentum.

Examples of possible modes of deterioration, the most critical environmental factors; and the most feasible open date for some perishable, semiperishable,

and long shelf-life foods are listed in table 5. The primary mode, if known for

normal conditions, is in bold italic type. How foods deteriorate may change radically with sterilization procedures, packaging, condition of raw material, etc.

As can be seen in table 5, in no case is safety a concern in any of the normal

deteriorations of food. In cases of certain meats or poultry, foodborne infections

that might be disseminated by the product could make the question of safety

more relevant than for other foods. However, for most food, other factors that

result in an inedible product occur before a point of health hazard is reached if

the product has been properly processed, packaged, and not abused or contaminated.

Most perishable and semiperishable foods

degradate mainly on sensory quality criteria.

For example, fresh meat degrades mainly by

bacterial activity and oxidation that cause an

off-flavor development and loss of color. This

is readily recognizable by consumers.

In contrast, many long shelf-life foods degradate mainly on nutritional criteria. For example, frozen fruits and vegetables are consumed as a major dietary source of vitamins

and minerals. In some cases, vitamin content

may fall below some accepted standard before sensory quality becomes inadequate. In

addition, most long shelf-life foods are packaged so that it is impossible to examine the

contents. Consumers cannot recognize loss of

sensory quality until the product is unpackaged after purchase. Open shelf-life dating is,

therefore, as applicable to long shelf-life

foods as it is to perishable and semiperishable foods, particularly if these foods are

stored in the distribution system or home for

a fairly long period of time. Some type of date

is useful to ensure proper rotation and give

31
32 ● Open She/f-Life Dating of Food

Table 5.—Major Modes of Deterioration, Critical Environmental Factors, Shelf Life, and

Type of Open Dating by Food Product

—— — . —

Shelf life

Date most

suitable for Additional

product information —- Food product

Perishables 

factors (average)

Fluid milk

and products

bacterial growth,

oxidized flavor,

hydrolytic rancidity

7-14 days at

refrigerated

temperature

sell-by length of time

product can be

stored at home

oxygen,

temperature

Fresh bakery

products

staling, microbial

growth, moisture

loss causing

hardening, oxidative

rancidity

2 days (bread)

7 days (cake)

oxygen, sell-by

temperature,

moisture

Fresh red

meat

bacterial activity,

oxidation

3-4 days at

refrigerated

temperature

pack or

sell-by a

oxygen,

temperature,

light

Fresh poultry pathogen growth,

microbial decay

2-7 days at

refrigerated

temperature

sell-by a

length of time

product can be

stored in home

either frozen

or refrigerated

oxygen,

temperature,

light

Fresh fish bacterial growth temperature 14 days when

stored on ice

(marine fish)

pack

(catch date)a

Fresh fruits microbial decay,

and vegetables nutrient loss,

wilting, bruising

temperature,

light, oxygen,

relative humidity,

soil & water,

physical handling

(b) pack a

Semiperishables and perishables

Fried snack rancidity, loss of

foods crispness

sell-by or

best-ifused-by

home storage

information such

as “store in a

cool, dry place”

oxygen, light,

temperature,

moisture

4-6 weeks

Cheese rancidity, browning,

lactose crystallization

temperature processed

cheese

4-24 months;

natural cheese

4-12 months

1-4 months

best-ifused-by

Ice cream sell-by or

best-ifused-by

recommended

home storage

temperature

graininess caused by

lactose crystallize.

tion, loss of solubilization (caking),

Iysine loss

Long shelf-life foods

Dehydrated browning, rancidity,

foods loss of pigment,

loss of texture,

loss of nutrients

fluctuating

temperature

(below freezing)

estimate

of shelf

life beyond

sell-by date;

store in cool,

dry place

moisture,

temperature,

light,

oxygen

dehydrated vege- sell-by or

tables 3-15 best-ifmonths; dehy- used-by

drated meat 1-6

months; dried

fruit 1-24 months

Nonfat flavor deterioration,

dry milk loss of solubilization

(caking), Iysine loss

moisture,

temperature

12 months best-ifused-by
Chapter V—Establishing Open Dates ● 33

Table 5.— Major Modes of Deterioration, Critical Environmental Factors, Shelf Life, and

Type of Open Dating by Food Product—Continued

Food product

Breakfast

cereals

Pasta

Frozen

concentrated

juices

Frozen fruits

and vegetables

Frozen meats,

poultry, and

fish

Frozen

convenience

foods

Canned

fruits and

vegetables

Coffee

Mode of deteriorate ion

(assuming an

intact package)

rancidity, loss of

crispness, vitamin

loss, particle

breakage

texture changes,

staling, vitamin

and protein loss

loss of turbidity

or cloudiness, yeast

growth, loss of

vitamins, loss of color

or flavor

loss of nutrients; loss

of texture, f/aver,

color: and formation

of package ice

rancidity, protein

denaturation, color

change, desiccation

rancidity i n meat

port ions, weeping

and curdling of

sauces, loss of

flavor, loss of

color

loss of flavor,

texture, color,

nutrients

rancidity, loss

of flavor and odor

Critical

environmental

factors

moisture,

temperature,

rough handling

too high or low

moisture,

temperature

temperature

temperature

temperature

oxygen,

temperature

—

Date-mos t

Shelf life suitable for Additional

(average) product information

6-18 months best-if- recommended

used-by storage

or sell-by conditions

pasta with egg best-ifsolids 9-36 used-by

months; macaroni

and spaghetti

24-48 months

18-30 months sell-by or

best-ifused-by

6-24 months best-ifused-by

beef 6-12 months best-ifveal 4-14 months used-by

pork 4-12 months

fish 2-8 months

lamb 6-16 months

6-12 months best-ifused-by

temperature 12-36 months best-ifused-by

oxygen ground, roasted, best-ifvacuum-packed, used-by

9 months;

instant coffee

18-36 months

Tea loss of flavor moisture 18 months best-ifabsorption used-by

of foreign odors

month of high

quality left in

home storage

recommended

storage

conditions

recommended

storage

conditions

recommended

storage

conditions

aThls date applres only If the product IS packaged prior to sale If unpacked or sold In bulk prior to sale this product IS exempt from an open date

-.

bDepend~ on the spec(f(c commodity Sweet corn has a shelf life of 4 to 8 days and apples range from 3 to 8 months at ProPer temperature For this sPeclf(c ‘n fo

rma

!Ion see Theodore Labuza et al Open Shelf Dattng of Foods. Dept of Food Science and Nutrltlon Unlverslty of Minnesota report prepared for the Office of Tech

nology Assessment 1978

NOTE When known the pr)mary mode of deterioration IS In bold (tal!c type
34 ● Open Shelf-Life Dating of Food

the consumer an index of when foods should

be used.

Since the mode of deterioration and critical environmental factors determine the shelf

life of a product, they should be considered in

selecting the type of open date. In general, for

perishable products, the most feasible date is

the pack or sell-by date. For example, almost

all fresh red meat is packaged by the retailer

who deals directly with the public. The meat

may have been slaughtered from 1 day to 2

weeks previously. Since carcasses of properly handled beef are essentially sterile internally, it is the packaging procedure that initiates color change and bacterial spoilage. Because the shelf life of fresh meat is relatively

short beyond the date of packaging, a pack

date or sell-by date may be sufficient for consumer use and understanding.

A best-if-used-by date would also be useful

to the consumer for fresh meat and other perishable products. However, these products

are very sensitive to temperature changes,

which can result in very rapid deterioration.

Thus, the potential for consumer abuse may

be too great for a best-if-used-by date to be a

practical alternative.

In general, the most suitable date for long

shelf-life foods is the best-if-used-by date. For

example, with canned fruits and vegetables,

the date of pack would be the easiest to implement but would not tell the consumer anything about the shelf life of the product. Canners who pack seasonal crops would be in a

difficult position because the date on the cans

would seem old when the product is actually

still well within the shelf life of the product.

This would be especially true in years when

an overabundant crop would force the canner to sell some products the following year.

A sell-by date is not applicable to cans that

are often stored in the home for some long

period of time after being sold. The best-ifused-by date could be useful to consumers

because it would give an appreciation of the

shelf life of the product if conditions of storage were known or uniform. (For a detailed

discussion by product, see appendix A.)

ALTERNATIVE CRITERIA

The general criteria to establish a sell-by

or best-if-used-by date will depend on what

the date is meant to imply. A sell-by date

should mean that there is still high-quality life

left for some time period of home storage

under reasonable conditions. A best-if-usedby date further states this by projecting a

reasonable time period. It is not possible to

set an exact end to shelf life (a definite use-by

date) for any food product.

Such criteria would have to be based on

what degree of change caused by each of the

deteriorative reactions in table 5 would lead

to a “significant” loss in high quality. This

would apply to rancidity, flavor loss, browning, textural change, etc. Such tests for sensory quality (taste panels, preference tests,

etc.), although well-developed and used in

product testing, would be difficult to use in a

regulatory sense to determine whether a specific food was in or out of compliance at a certain date unless the regulators were trained

for each product. What is needed in this

sense is a chemical or physical index that

changes in a similar manner to the sensory

changes.

Sensory Quality

Although more difficult to measure in certain cases, sensory quality is the most important characteristic for consumers and processors alike, and in some cases with foods of

long shelf life, this quality may also be an indicator of nutrient quality. This is not true for

shorter shelf-life foods such as milk.
Chapter V—Establishing Open Dates ● 35

Manufacturers define their own qualit y

standards through elaborate product development studies, many of which include sensory testing, when they put a brand name on

a product with a best-if-used-by date. In this

way, they assume quality loss up to that point

is still acceptable enough that the consumer

will buy the product. If consumers buy the

product and find it below their own quality

standards, they will probably not buy the

product again.

Consumer reaction, then, is the key to quality standards, because Government regulatory agencies would not have available the

needed methods to determine whether a given

food that is still in date is out of compliance

with some quality standard. For example, if

an inspector picked up a can of soup and took

it back to the laboratory, he might not have

the scientific tests available which could determine with any degree of accuracy if that

soup is of a designated quality and therefore

acceptable to the consumer.

Assuring compliance with sensory quality

might be feasible if the sell-by or best-if-usedby date were coupled with official Government or widely accepted industry quality

grades. Thus, instead of merely stating “useby” or “best-if-used-by” when there is no defined “best” quality, the open date could be

preceded by a statement such as “to remain

in grade, use by. ”

The addition of an open date to a grade

declaration would automatically solve the existing serious problem of unlimited guarantee

of a specified quality grade level from the

time the grade is marked on the container until its destruction. The more perishable the

product, the more important would be the

grade/open-date combination, While canned

green beans could well remain in grade for a

year or longer provided the container is undamaged and not exposed for long periods to

high and/or fluctuating temperatures, fresh

green beans could go out of grade in just a

few weeks, or even days,

Open dating, when coupled with quality

grade levels, can be based on accurate,

rapid, and scientifically sound methods of

analysis for some foods. However, open

dating based on retention time within the

grade can be applied only to those few hundred items for which generally recognized

and approved grades already exist. These

items are those for which grade levels can be

measured accurately and precisely.

Nutrient Loss

Another measure of shelf life could be the

loss of a certain percentage of a critical

nutrient, such as vitamin C. This factor would

be much easier to measure than overall quality, since it can be analyzed accurately and

rapidly in the laboratory. The same would be

true for moisture gain or loss of a critical

value that would cause some textural change,

such as loss of crispness of a potato chip.

However, many scientists favor a specific

sensory quality criteria for each type of food

rather than a given percentage loss of an

unstable or critical nutrient for all commodities. Nutrient content of even the same foods

can be quite variable, particularly the vitamin content of many raw agricultural commodities, For example, two tomatoes picked

at the same time can vary significantly in

vitamin C content. More importantly, some

foods are naturally poor in some nutrients,

are not eaten to provide those nutrients, and

may be of good quality even if they have lost a

certain percentage of the nutrients. In other

words, if a food only contains 1 percent of the

U.S. recommended daily allowance of vitamin

C, a 10-percent decrease in this low amount

would most likely have an insignificant effect

on overall nutritional status of the consumer.

If nutrient loss is to be used as one index of

quality loss, foods would have to be examined

on a product-by-product basis. In essence,

this has already been done for nutrition labeling. However, to prove that a loss in nutrients

is of significance to overall quality of each

and every commodity would be difficult.
36 ● Open Shelf-Life Dating of Food

Perishability Time Categories

Some States with open-dating requirements use perishability time categories to establish an open date. The three general categories are: perishable, semiperishable, and

nonperishable. Time categories can be relevant for highly perishable foods that have a

minimum of processing such as fresh meat or

milk. However, processing conditions and

types of packaging can increase the shelf life

of semiperishable and long shelf-life foods to

the point where such perishability time categories are not meaningful unless continuously

modified to reflect new circumstances. For

example, semiperishable foods can be defined as those foods with a shelf life of

greater than 7 days but less than 90. Under

this system, in general temperature and environmental conditions, most potato chips

would be defined as semiperishable. However, if they were packed in a foil pouch

under nitrogen with added antioxidants, the

chips might last for up to 6 months and would

not fit the category.

Some States have met this problem by developing a nonperishable or long shelf-life

food category that can be defined as foods

with a shelf life of greater than 6 months. As

pointed out earlier in this report, this is, in

fact, a scientific misnomer, for all foods

decay at some rate by some means. Even in

the above example with potato chips, if the

new method of packaging gave an average

shelf life of 120 days but the product was

abused in distribution and held at high temperatures (38 0 C) for a few days, it could deteriorate fast enough that it would no longer

meet the criteria of nonperishability. Therefore, perishability terminology cannot be logically backed-up scientifically since one can

control or change shelf life through varying

processing, packaging, and environmental

conditions.

Basing open dating on time categories

could also be a hindrance to implementing

new technology. For example, better packaging can increase shelf life of potato chips

from 90 to 120 days, even in regions with high

humidity. However, this better packaging

would not be used if potato chips could not be

sold at full price after 90 days no matter what

their quality may be.

SCIENTIFIC TESTS AND DATA NEEDED

To develop sell-by or best-if-used-by dates

scientifically, each manufacturer would need

to conduct shelf-stability studies on each

product and determine the point in time at

which sensory quality falls below the point of

consumer acceptance. This is very time-consuming and difficult to determine unless the

food has a short life under constant normal

environmental conditions.

Knowledge of temperature and humidity

conditions encountered during distribution

are necessary to set the sell-by or best-ifused-by dates. A manufacturer can determine this in one of two ways. He can put a

product out in the marketplace, pick up

samples at various times and places in the

marketing channel, and test the quality of the

samples at regular time ntervals to establish

the appropriate date for the product. But for

products with several years shelf life, such as

canned vegetables, these studies could take

as long as 3 to 4 years.

The other alternative for the manufacturer

is accelerated shelf-life tests (ASLT). These

tests would be necessary for new-product development and could be advantageously used

for existing products where shelf life under

normal marketplace conditions is very long.

ASLT involves subjecting the product to two

or three given constant environmental conditions and measuring the rate of quality loss at

each condition. A mathematical formula can

then be established for the rate of deterioration as a function of temperature and/or
Chapter V—Establishing Open Dates ● 37

humidity and used to predict the time needed

to reach an unacceptable amount of change

during distribution and storage.1

In a select sample of 50 food manufacturers, OTA found that the scientific approach described in this section and in the

background report is frequently not utilized

except by major corporations with highly

qualified scientific personnel. The low use of

shelf-life testing results from lack of knowledge and, more importantly, lack of experience in determining the shelf life of established foods as well as the costs involved.2

The major impact of developing scientific

data would fall on the food manufacturer. A

significant amount of time and money must be

used to establish a data base for each product because broad generalizations cannot

suffice, Because of the cost, most manufac-

‘Theodore Labuza et al., “Open Shelf-Life Dating of

Foods, ” Department of Food Science and Nutrition,

University of Minnesota, report prepared for the Office

of Technology Assessment, 1978.

‘Ibid.

turers would probably consider these data to

be of a proprietary nature and would not

release it to the Federal Government or the

scientific literature. Another impact would

be that the wholesalers, distributors, food

brokers, and retailers would need to supply

information on each product’s history, as regards time, temperature, and humidity conditions encountered along the way to final sale.

Since shelf-life testing is product-specific,

it would be very expensive for the Federal

Government to undertake these types of tests

for all food products. The Government could,

however:

1.

2.

Support research into modeling shelf-life

studies for various reactions leading to

loss of quality under variable time/temperature/humidity conditions.

Support or conduct research into development of reasonable cost devices that

could be attached to food packages

which could detect the impact of time,

temperature, and humidity on shelf life

of an individual food.

IMPACT ON TECHNOLOGY DEVELOPMENT

An open-dating system based on perishability time categories with a sell-by date,

such as many States have now adopted, can

inhibit efforts to improve processing technology, packaging methodology, and a distribution system that would extend the shelf life of

many foods. This is because there is no benefit gained in improving a food if it cannot be

sold at full price beyond a certain date after

manufacture. However, if manufacturers are

allowed to use the best-if-used-by date on a

voluntary basis that they feel is reasonable,

the incentive to do research to extend the

date may be greater than it is now.

From the consumer’s viewpoint, however,

extending the date may be a processor’s attempt to make old foods taste and look good,

at the risk of some additives. Many consumers today are extremely distrustful of food

additives used simply to extend shelf life.

Also, consumer distrust may be a reason why

UHT (ultra-high temperature) milk has not

been widely accepted in the United States.

Because of improved sterilization techniques,

this milk can remain shelf-stable for at least 6

months at room temperature.

Another pitfall to consider is that too much

emphasis in product development may be put

simply on extending shelf life and thus decrease efforts to develop a wide variety of

other interesting and convenient foods that

are enjoyable but which may not have an extremely long shelf life. It is impossible, however, to project such an impact at this time.

At present, theoretically accurate and reliable shelf-life indicators for some types of

food products exist that could measure the
38 ● Open Shelf -Life Dating of Food

reaction rate of food to both temperature and

moisture. However, these indicators are not

technologically or economically feasible for

individual consumer-size packages.

If such indicators were in widespread use,

food companies buying commodities or ingredients from other food companies could include a value on the indicator as part of their

specification for the ordered food. Some Government contracts currently mandate use of

shelf-life indicators in shipping frozen food

cases. The use of indicators could well be extended to other cases or pallets of food. However, the indicators may never become inexpensive enough to warrant their use on individual consumer packages, They would probably cost at least as much as the package

itself.

Open dating could have a real impact on labeling technology. There would be increased

incentive to develop quick-drying inks and

ways of printing on difficult surfaces, especially at high speed. At present, it is not possible to do this, and the materials are not available, according to the industry. New unidirectional shrink-film that can be preprinted

without distortion as the label is applied

could be the answer. It is currently used for

bottle labels.

The other major issue is in the area of

quality standards. With the exception of the

commodities for which there are now quality

grades and standards, no specific guidelines

exist for thousands of new, fabricated, and

processed foods. However, the vast sources

of existing knowledge on which Government

and industry quality grades are based could

be tapped.

If a best-if-used-by or sell-by dating system

were imposed, research by Government, universities, and industry laboratories would be

stimulated. They would most likely center on:

1. shelf-life indicators,

2. modes of deteriorations and quality indicators,

3. prediction of packaging requirements,

and

4. more precise and objective methodology

for measuring changes in sensory quality attributes.
Chapter VI

Alternative Open-Dating

Systems

There are three basic systems that could be used for open dating: private

voluntary system, mandatory system, and voluntary/mandatory system. With a

private system, the industry develops and adopts standards voluntarily. With a

mandatory system, the use of open dates would be required by law. If the system

were nationwide, the Federal Government would develop regulatory guidelines.

Under a voluntary/mandatory system, only processors who elect to open date

their products would be required to follow Federal guidelines.

An outline of the three systems is given in this chapter. For an analysis of

congressional options among these systems, refer back to chapter I.

VOLUNTARY SYSTEM

This system is in current use because proc- be followed. Some processors date their prodessors who open date their food products ucts, while others do not. Those that do can

have chosen to do so. It is the preferred sys- select any date, can display it in any fashion,

tern by many processors because it allows and can establish the date by any testing proflexibility in terms of: cedure.

1. whether or not to open date, This nonuniform system also can make it

2. which products to date, more difficult for inventory control in the

3. which date to use, and distribution channel, which can result in food

4. which tests to use to determine the date. waste. In addition, it can increase food waste

in the home because the consumer does not

On the other hand, the system has led to know the food is approaching an unacceptconfusion because there are no standards to able quality level.

MANDATORY SYSTEM

The mandatory system is used in 21 States is no uniformity on a national scale. Since naand the District of Columbia for open dating tionwide distributors must meet different

of some food products—mostly milk and milk State requirements, the result is higher costs,

products. As with the voluntary system, there which mean higher prices for consumers.

39
40 ● Open She/f-Life Dating of Food

A Federal mandatory system is preferred

by many consumer representatives because it

would provide:

l. uniform regulations throughout the

United States,

2. tighter inventory control in the distribution channel, and

3. higher quality and nutritive levels for

some foods.

The major impact of the system would be

on the processor. It would be very difficult for

processors to comply with a mandated sell-by

or best-if-used-by date within the next 2 to 5

years, particularly for semiperishable and

long shelf-life foods. This is because there is a

lack of currently available data on shelf-life

stability for many food products. A mandated

sell-by or best-if-used-by date at this time

would force “manufacturers to guess about

the shelf life of their products and/or to extend the known shelf life of one product to encompass other similar products, which would

not necessarily benefit the consumer. Time to

phase in the program would allow industry to

establish the necessary data on shelf life of

their food products,

An alternative would be that the regulatory agency could mandate that all food in a

certain category had to meet a minimum date.

If a company could not afford testing to demonstrate a longer shelf life, they could use the

established, mandated minimum. If they

could demonstrate a longer shelf life, they

could use that date. If their product could not

meet the minimum shelf life, they would

either have to change the process, go out of

business, or challenge the legality.

Objections to this alternative include the

fact that a minimum shelf life for a product

would be similar to a standard of identity,

which specifies the minimum composition of

many processed foods. The Government

would have to identify criteria for each particular food category and be able to defend

the criteria and the minimum shelf life. For

example, if the Food and Drug Administration

(FDA) developed a best-if-used-by date for

each product category, the agency would, in

effect, be assuring the public that the product

is good.

It is more probable that the regulatory

agency involved would have to go to the opposite extreme and determine the maximum

date that could be put on a product unless the

manufacturer could prove otherwise. Since

the process would have to be repeated for

each specific food, it would be very costly to

the Government.

Manufacturers could presently identify

and indicate the pack date if it were mandated. The pack date would have to be defined as the date the product was put into the

final consumer package for sale and use.

However, there are problems in defining the

pack date, which were discussed in an earlier

chapter, mainly for multicomponent products. If the pack date were mandated, the

printing system for the present codes would

have to be changed, but the system could be

initiated immediately.

The impact of a mandatory system on retailers and wholesalers would vary, generally

by size of operation. That is, smaller businesses tend to have fewer inventory turnovers per unit of time, so they could be adversely affected by out-of-date stock. Mandatory open dating would likely have the least

impact on national chains, the next least impact on smaller independent retailers/wholesalers, and the greatest impact on “mom and

pop” stores. Convenience stores would be affected much like national chains.

Because of the potential adverse impact on

small retail stores, a mandatory system might

exempt smaller stores, based on number of

employees or gross dollar sales. However,

such an exemption could mean that these

stores would receive products that were

pulled after date from shelves of larger

nonexempt stores and shipped to them by distributors (either manufacturers, representatives, or wholesalers). In the end, an exemption could work to the disadvantage of small

retailers, regardless of the intent of the exemption.
Chapter Vi—Alternative Open-Dating Systems ● 41

Some consumers prefer a completely man- last as well as help stock rotation. Under a

datory system, arguing that it would both voluntary system, these benefits are pieceeducate consumers about how long a food can meal.

VOLUNTARY/MANDATORY SYSTEM

This system would combine the characteristics of the voluntary and mandatory systems

by allowing the processors the choice of opendating food products, but requiring that once

they elect to do so, they must do it in a prescribed manner, This is essentially the system

used for nutrition labeling.

A voluntary/mandatory system would have

a number of the advantages of the two other

systems, It would allow the processor to

choose whether or not to open date and to

elect which products to date. However, since

the processor who elects to open date must do

it in a certain way, the result would be

uniform open dating throughout the United

States. Also, because processors would have

a choice about open dating their products,

this system should not have an adverse effect

on smaller processors or retailers,

Of course, another factor to consider is

consumer pressure, Consumers could effectively pressure processors who do not use

open dating by purchasing products from

those firms that adopt open dating.

This had been the case under the voluntary/mandatory system on nutrition labeling,

In 1973, when nutrition labeling regulations

were issued, very few products had a nutrition label, By 1978, 40 percent of the leading

national brands, 25 percent of the remaining

national brands, and 44 percent of private

labels displayed nutrition information on major packaged processed foods. In terms of

dollar sales, this represents 39 percent of the

$24 billion of packaged processed foods sold. ’

The voluntary/mandatory system appeals

to processors because it allows them the option about open dating their products. It also

allows them time to collect scientific data on

a product-specific basis to determine the

dates.

The system also appeals to many consumers because when products are open dated,

every processor must meet specific requirements. This provides for a more uniform system and reduces consumer confusion.

However, compared with the voluntary

system, this system would increase costs to

Government for developing and enforcing the

regulations and would increase costs to industry for complying with the regulations. In

addition, developing the regulations in the

first place would be time-consuming for both

Government and industry.

‘Raymond Schucker, “A Surveillance of Nutrition Labeling in the Retail Packaged Food Supply” (Washington, D. C.: U.S. Department of Health, Education, and

Welfare, Public Health Service, Food and Drug Administration, 1978).
Chapter Vll

Enforcement and Liability

Open dating, as it exists today, has a built-in enforcement mechanism

through the consumer. If a consumer is aware of date marking, understands it,

and uses it, out-of-date products with a sell-by date will not be purchased at full

prices.

In most States, provision is made for sale of these products at a reduced

price. If the product cannot be sold, most manufacturers will take the product

back and refund the retailer. The same is true if consumers feel a product is not

up to the quality desired, they can return it and get their money back from most

retailers.

Some consumers feel, however, that returning a product is too time-consuming and unfair to them. They look to open dating as the institution of a fail-safe

system—i.e., anything purchased with an unexpired sell-by or use-by date would

not be bad; it would presumably be of excellent quality. Unfortunately, as

pointed out in the previous parts of this report, such a guarantee is an impossibility, since unintentional abuse during distribution can severely reduce food

quality even though an item is dated.

The type of enforcement and liability would depend very much on the system used. With a pack date, there is no liability except from the standpoint of

misbranding if it is made mandatory and left off the package. It would be up to

the Federal or State inspection systems to routinely survey the market for such

violations, and the liability would be the same as at present for misbranding.

The sell-by and best-if-used-by dates are another matter, however, as discussed

in this chapter.

If the date were a sell-by or best-if-used-by

date, there could be two types of enforcement. The first would be before-date enforcement. In other words, if a date is based on

some standard such as loss of sensory quality

and the food is found to be below that standard before the date is reached, it would be in

violation. The second type of enforcement

would involve offering a product for sale

after the date (beyond-date enforcement).

ENFORCEMENT

Before-Date Enforcement

Two types of before-date enforcement are

discussed and are presently used for enforcing labeling standards. Note that they lead to

substantially different potential costs and liability.

One method is to construct an enforcement

scheme that would allow processors to establish reasonable dates (be they sell-by or best43
44 . Open Shelf-Life Dating of Food

if-used-by) for each individual product and/or

process within a product. Thus, canned green

beans may have different sell-by dates, for

example, than canned peaches. Also, glazed

frozen shrimp may have longer sell-by dates

than frozen shrimp that are not glazed. Processors in this scheme would be required to

justify the “reasonable” dates chosen, presumably before instituting the system and if

asked by the regulatory agency. Tests and

data would be necessary to support the claim

made for reasonableness by the processor for

his date.

A second method could be for an enforcement agency to spot check products at the

processor and retailer level via laboratory

testing. A regulatory agency could sample

products from the processor’s line or purchase products at retail and perform appropriate laboratory tests for nutritional and/or

sensory characteristics. However, the laboratory testing would vary from quick and

simple for some products to difficult and costly for most products. The regulatory agency

would still need the information of the first

method to determine whether the product

was within the quality limits for the date set.

With spot-check enforcement, food producers might feel the necessity of setting quality

specifications for a date as low as possible in

order to protect themselves in case the product is severely abused during distribution.

The quality standards would probably be

much lower than those at which the processors currently try to sell their products—in

other words, lower than those the consumer

currently expects and finds. It should be

noted that spot-check enforcement of label

claims is presently done by Federal and local

agencies. The Food and Drug Administration

(FDA) is preparing to initiate this enforcement scheme to help enforce nutrition labeling declarations.

The first method would be considerably

less expensive to enforce and would not lead

to a decline in quality specifications for the

date. In addition, the first alternative would

avoid liability questions raised by the second

alternative. The second scheme raises questions about the extent of manufacturers’ liability, especially if the product tested were

purchased at retail. If the product chosen for

testing had been abused in the distribution

channel (e.g., high temperature in frozen

food), processors could conceivably be held

responsible for the actions of distributors

over which they have no control.

Beyond-Date Enforcement

Two alternatives are possible. One is complaint-based enforcement, the other is spotcheck enforcement.

Complaint-based enforcement would involve a consumer’s return of a beyond-date

product, or the out-of-date product would

simply go unsold, thus indicating consumer

displeasure or disinterest. This system would

be possible with sell-by or best-if-used-by

dates, but not a pack date. Enforcement costs

would be minimal.

A second alternative would be to have an

enforcement agency randomly spot-check retail stores for merchandise that was beyond

date. Costs of this alternative would be considerably higher than complaint-based enforcement. In the case of pack dates, spot

checks could be made at the origin of retail

packaging, so this alternative could cover any

type of open date.

Again, the manufacturers who set the highest standard would run the greatest risk of

being in technical violation of their own

standard. For this reason, food should be

allowed to be sold after a sell-by or best-ifused-by date, since the date is only an estimate.

Especially with semiperishable and long

shelf-life foods, there should be no discernible

difference between quality shortly before the

date and shortly after. Even with perishable

foods, open dating is not a safety issue, since

there are laws currently in effect that make it

illegal to sell unsafe food. If consumers refused to pay full price for over-age food, it

could be offered at a reduced price.
Chapter V//—Enforcement and Liability ● 45

FEDERAL/STATE

As discussed earlier in this report, 40 percent of the States have some type of mandatory open-dating law that they are currently

enforcing. Thus, an alternative to exclusive

Federal enforcement would be cooperation

with the States. Basically, this type of cooperation could be achieved either through costsharing programs or model regulations,

Cost-sharing programs can be in the form

of contracts or grants. The most common arrangements are 50-50, although there are

some arrangements with 80 percent Federal

and 20 percent State and some with 90 percent Federal and 10 percent State. Contracts

are formal agreements between Federal and

State governments to perform specific tasks

over a specified time period. Grants are lumpsum payments to States for use at their discretion in a general area.

OTA found that Federal and State officials

prefer contracts over grants for the purpose

of cooperating on enforcement. The advantage for Federal officials is that specific tasks

are identified and both parties know what is

expected for satisfactory performance. For

the States, the advantage is that in most

cases, multiyear contracts can be established

which will provide a continuous source of

funds for the States to perform their tasks.

Grants are viewed as “one-shot” affairs,

and States cannot depend on them for continuous funding, Federal officials also take a

dim view of grants because they are not specific in terms of tasks to perform. This makes

it difficult for Federal officials to judge each

State’s performance.

The basic problem with these cost-sharing

programs is nonparticipation by the States.

The program works only if States feel there is

a need for a specific activity or that they are

going to benefit directly. Thus, States that

presently have open-dating legislation will be

more likely to participate than those that do

not. If States do not participate, there is no

equivalent means of enforcement. This is the

present situation with the Fair Packaging and

ENFORCEMENT

Labeling Act (FPLA). FDA is doing little FPLA

enforcement in States where there are no

contracts.

In the final analysis, the Federal Government must assume enforcement responsibilities if States decide they do not want to cooperate. Experience with cost-sharing or partial-funding programs such as the Wholesome

Meat Act indicate that the States are not likely to cooperate. One-hundred percent Federal

funding may have to be provided to ensure

State cooperation. Otherwise, State officials

are not going to look with much favor or give

priority to a program the Federal Government

will have to take over if States are not willing

to do it.

To qualify for 100-percent” funding, States

must have a law that is at least as encompassing as the Federal law. To illustrate, if a

State has no law or a law that is less than the

Federal law, it would not qualify for funding.

However, if the State had a law that was

more encompassing than the Federal law, it

would qualify.

States adopting the Uniform Model Act

have a history of adding to their laws and

acts, areas that are above and beyond those

of the Federal Government. Thus, if an absolutely uniform open-dating law or regulation is desired, using State enforcement will

not ensure this outcome,

The alternative to a cost-sharing program

is a model State regulation applicable to State

and local jurisdictions. The National Bureau

of Standards has designed such a model for

open dating. The model provides for the use

of a sell-by date on perishable and semiperishable foods but does not address the

basis on which to establish the date and excludes products for which a date would be

useful and feasible. Four States have adopted

the model to date. As a result, the Association

of Food and Drug Officials is considering

preparing its own model regulation for open

dating.
46 . Open Shelf-Life Dating of Food

The Association has designed the Uniform

Food, Drug, and Cosmetic Act, which has

been adopted by some States. The Act could

be amended to include food-labeling areas

like open dating.

The Act as currently written is State-oriented, since each State can change the Act to

meet its individual situation. It is purely a

model and not sufficient in terms of enforcement. A State may adopt the model regulation

but may not enforce it if funds have not been

allocated.

Although there is the possibility of Federal

funds for States that adopt the model Act,

Congress would have to first amend the Food,

Drug, and Cosmetic Act. Presently, FDA does

not have the authority to establish contracts

for which it does not have basic responsibility

by law.

LIABILITY

There is a difference in establishing liability between open-date labeling and most

other food-labeling requirements. For example, in nutrition labeling, basically only the

manufacturer, not distributors, is involved in

compliance, although abuse in distribution

can lead to labels that overstate nutritional

value. In open-date labeling, processors,

wholesalers, and retailers are all involved in

compliance. If a retailer sells a product at full

price that is out of date, the retailer, not the

manufacturer, would be liable. Naturally,

wholesalers and retailers are concerned that

if a Federal open-dating system were implemented, this would in effect increase their

liability.

At present, there is no definitive legislation

or judicial definition of the legal significance

of an open date. A search of the literature

found no court decisions during the last two

decades on the question of liability for spoiled

food that has been open dated. Thus, the discussion of this question must be speculative.

In order to assess possible legal consequences, it is necessary to make certain assumptions about the intent and effect of a

Federal open-dating requirement. First, such

a requirement must avoid as much as possible the technological problems associated

with open-date labeling of some foods. Second, it must provide for specific, uniform, and

scientifically sound criteria by which the

chosen date is established and its validity

measured. Third, it must be designed to

minimize confusion about the attributes of a

food product. That is, the objective of open

dating is to increase consumer awareness

about food freshness; it is not an indicator of

the safety of food. As indicated earlier in this

report, consumer confusion on this point

could have serious consequences.

Liability Under the Food, Drug,

and Cosmetic Act

Food manufacturers and retailers could be

subjected to increased liability exposure

under the Federal Food, Drug, and Cosmetic

Act (FDCA) if a Federal open-dating requirement is intended to relate to the misbranding

and adulteration provisions of that statute.

To the extent that any food is marketed in a

way (for example, without a sell-by or best-ifused-by date, if required) that it becomes misbranded under FDCA, it is an illegal commodity, Additionally, the sale of “spoiled” food is

prohibited by the adulteration provision of

FDCA, whether or not the label of a product

bears an open date.

Liability for such misbranding would flow

to the manufacturer who failed to properly

label the food, as well as to the intermediate

distributors and retailers who sold, or held

for sale, the misbranded product. Liability

would not extend to distributors and retailers

who could demonstrate that they received the
Chapter V/l—Enforcement and Liability ● 4 7

misbranded food and delivered or proffered

delivery of it in “good faith, ”

The FDCA provision that declares as misbranded any food article the label or labeling

of which is false or misleading, if taken literally, raises difficult problems from both a

compliance and enforcement standpoint, The

least of these problems involves food products the label of which might declare that

they were packed on a particular date. If the

“pack date” is not accurate, the product is

misbranded and the manufacturer or packer

of the product would be liable for such misbranding. (A retailer who has purchased the

misbranded product in good faith and sells it

or holds it for sale would probably not be

liable. ) Pack dates are definite in time and

thus can be objectively determined to be

either accurate or false.

On the other hand, the other forms of open

dates that might be selected (“use by, ” “sell

by," “best-if -used-by,” etc. ) only can provide

approximations of the ultimate shelf stability

of the labeled products. Such dates offer

freshness guidelines, but nothing more, and

can never be precise. Different food manufacturers are likely to have different quality

standards for their products, limiting the

“precision” and significance of open dates.

Moreover, storage or handling variables to

which a product is subjected during its distribution cycle, or even during home storage,

can affect the accuracy of all dates other

than a pack date on the package.

The sell-by date raises an additional issue.

The meaning of this date is somewhat vague.

A sell-by date suggests that the product can

be consumed for a reasonable period of time

after the date with no recognizable difference in the quality of the food. The exclusion

of information that indicates the ensuing consumption period could constitute the omission

of a material fact rendering the product misbranded. This should be specifically addressed in the legislative history of any opendating provision.

Literal application of FDCA could result in

misbranding of a product because of distribution abuses—abuses that would render the

open date inaccurate or misleading. For instance, a phrase such as “use by’* on a food

label might lead a consumer to believe the

quality of the food will remain unchanged as

long as it is consumed by the stated date, If

such a product were left an unusually long

time in the sun on a retailer’s loading dock,

for example, that inference would no longer

be true. If and when it is discovered that the

product is “outdated,” it is unlikely that the

fact of its storage irregularity would also be

discovered. One possible solution to this problem might be to provide that as long as a labeled date is objectively accurate in light of

foreseeable marketing conditions at the time

a product is labeled, when measured in terms

of those criteria specified for the establishment of such a date, that product should be

considered to be in compliance with FDCA.

Literal application of FDCA might or might

not also result in an illegal product because

of abuse in distribution. The same issue

arises with respect to the declared net quantity of contents of packaged food. The law

permits FDA to enforce it sensibly by determining the average net quantity of contents.

There is nothing inherent in FDCA that would

suggest that this approach would not be

equally applicable for open dating of food.

Civil Liability

In addition to liability under FDCA, there

are two theories under which a manufacturer, distributor, or retailer could be held

civilly liable to a consumer and/or third party

who purchases and/or consumes a “spoiled”

food product, the label of which bears an

open date, The two potentially applicable

theories are: 1) strict product liability under

tort law and 2) warranty liability under

either the Magnuson-Moss Warranty Act or

the Uniform Commercial Code. The viability

of either of these theories will depend primarily on what an open date—and especially any

qualifying terminology accompanying the

date (“use by," “best-if-used-by,” “freshness

guaranteed if used by,’” etc.)—means to a

consumer purchasing the food product. For
—

48 . Open Shelf-Life Dating of Food

example, if an open date and/or accompanying terminology were construed to constitute

a promise, guarantee, or other affirmation of

fact with respect to a food’s quality, and a

consumer, relying on the dating information,

purchased a food that “spoiled” prior to the

date, that consumer might be able to recover

damages under a breach of warranty theory

of civil liability.

Research in the individual States with

open-date labeling found no court decisions

on the question of liability for spoiled food

that has been open dated. Since product liability is almost entirely a matter of State law,

a discussion of the theories would be speculative.

The criteria by which an open date is established and by which food quality is measured, as well as the legal meaning and significance of the date, will ultimately determine

the viability of the theories noted. These matters should be thoroughly explored and resolved in the legislative history of any opendating provision. In this regard, it is important that the limitations of open-date labeling

be addressed. The legislative history of any

open-dating provision must make clear that

open dates are only guides to freshness, not

safety indications nor guarantees of product

freshness. Otherwise, unintended and potentially onerous legal ramifications could arise

under both criminal and civil law.
Chapter VIII

Economic and Social Costs

Economic and social costs of open dating are an important consideration.

Based on the previous chapters, costs can be discussed in terms of: 1) establishing shelf life, 2) putting the open date on each package, 3) enforcement, 4) comparison with nutrition-labeling costs, and 5) food disposal. At the present time,

there are no exact cost estimates for each of these areas. The costs presented

are the best estimates available.

COSTS OF OPEN DATING

Establishing Shelf Life

Experts interviewed by OTA grouped the

possible costs of establishing the shelf life of

individual food products into two categories.

The first, for perishable and semiperishable

foods, would be about $100,000 per item, requiring at least one investigator and a technician plus facilities for 1 year. Nonperishables

would cost $200,000 per item, taking 2 years

to determine. These would be one-time costs,

but future adjustments in the shelf life would

have to be made with each change in product

formula, package used, and mode of distribution, thus adding to costs in the long run.

Dating the Package

The cost of putting a date on food packages

will vary widely, depending on type of package and method of date placement. For example, for canned products, existing closing machines can be modified to emboss the open

date on the can for a cost of between $1,000

and $3,600 per machine. This is a low cost on

a per-can basis. However, for perishable

products, equipment costs can vary between

$1,500 and $15,000 per food product.

Enforcement

In terms of enforcement, if the program

were self-enforcing—that is, if there were no

penalties for out-of-date food products and

the only enforcement were consumers refusing to pay full price for out-of-date food—

there would be no cost of enforcement per se.

If a legal penalty were involved, the cost of

enforcement could be more than $500,000

per year. ’

Even if the program were self-enforcing,

there would be considerable cost in food

either sold at a lower price or returned to the

manufacturer as unsalable. This cost would

vary widely with the length of shelf life, reliability of the distribution system, and popularity of the items. At present, this cost would

be difficult to estimate.

‘U.S. Congress, Consumer Food Act of 1976, report to

Committee on Commerce and the Committee on Labor

and Public Welfare, U.S. Senate on S. 641, Mar. 4,

1976.

49
50 ● Open Shelf-Life Dating of Food

Comparison With Nutrition Labeling

Because there are no good estimates on

costs of open dating, a comparison with a

similar area of labeling—nutrition labeling—is worthwhile. A survey conducted by

the Grocery Manufacturers of America in

1975 indicated that $8.4 billion worth of food

products would have nutrition labeling that

year, For those products, the initial average

cost of putting the information on labels per

dollar of sales was estimated at .004 cent,

and the average continuing cost at .00016

cent per dollar of sales. Thus, nutrition labeling, which involves complex testing procedures and more information to be printed on

the label than does open dating, costs a

minimal amount once established. The same

should be true for open dating.

IMPACT

Processors

The greatest impact of an open-dating system would be on the food processors, especially if the system were completely mandatory. In this case, much research at high cost

would be entailed for each product/package

system, and at present, there may not be

enough scientists or laboratories trained or

available to do the total job in just a few

years, Industry would need to apply new or

modified films, adhesives, and packaging machines. With a voluntary/mandatory labeling

system, the same costs would exist, but only

those companies who could afford the costs

would undertake the job. This would not tend

to reduce market competition as might happen with a completely mandatory sell-by or

best-if-used-by system.

Wholesalers and Retailers

With a voluntary/mandatory or completely

mandatory system in which enforcement and

liabilities required segregation of product,

retailers would have two related costs. The

first would be more time to inspect shelves to

ensure that no out-of-date products were

present, and the second would be using space

to sell out-of-date products at a reduced cost.

The latter could be eliminated by returning

the product to the food manufacturer, but

that would mean an additional transportation

cost and either a remanufacturing or disposal

cost. At any rate, the result would be a price

increase to the consumer.

Costs of various disposal schemes for outof-date products can vary depending on the

scheme and product category. For example, if

mandatory open dating were imposed on

fresh meat and poultry, without allowance

for reconditioning and redating, the additional costs of open dating could be burdensome for some retailers. The impact would be

greatest on smaller retailers who tend to

have fewer inventory turnovers. Also, economic incentives already exist for retailers to

minimize the amount of meat reconditioned.

Alternative disposal schemes at retail include marking out-of-date stock down in

price, allowing return to processors (where

appropriate), giving the food t o charities, or

simply disposing of it. The first of these is likely the least expensive to the distribution system in the long run, while the latter is likely

the most expensive.

Social costs from mandatory open dating

include potential for less variety of sizes and

more products out-of-stock on retail shelves.

Such reaction would be logical for retailers in

an attempt to minimize past-date merchandise on their shelves.

Consumers

The overall result of open dating, whether

voluntary or mandatory (except for a pack

date) would be to increase the cost of food to

the consumer, since all the above costs would
Chapter Vlll—Economic and Social Costs ● 51

be passed on as increased price, ’ Experts on

the OTA working panel could not make an exact estimate of increased cost, but thought it

could be between 0.1 and 1 cent per package

of food.

The greatest impact on consumers other

than cost would be increased education on

the storage and handling of foods, which

might mean increased quality at point of consumption and an opportunity for purchasing

out-of-date bargains.

Government

With a required open pack date, the overall cost to the Federal Government would not

be much more than under present food package screening and recall procedures on the

basis of misbranding.

If the Government were to mandate a useby or best-if-used-by date with Governmentset standards of quality, a large share of current FDA and USDA budgets would be required for the research to set such standards

for all packaged foods. Since it would have to

be on specific products, consumers would

likely complain that the Government is doing

the industry’s job. In addition, the size of the

enforcement and legal force would have to be

increased to cope with the problem of retail

inspection and control.

If the labeling systems were voluntary, but

with a mandated label format and quality

standards set by the food companies, there

would be little cost impact on the Government

except through FDA and USDA education

offices to help the consumer understand the

label. However, based on problems with nutrition-labeling-education costs, this could be

relatively expensive. Other costs to Government would be in enforcement if the correct

label format were not used. Another problem

would be in setting standards for removal or

segregation of out-of-date food, especially

with respect to the price reduction that

should be used,
Chapter IX

Array of

Congressional Options

This chapter provides a detailed explanation of the interaction among the various

issues surrounding open shelf-life dating. As

stated in this report, there are many possible

combinations, each of which represents a

congressional option. The interaction among

these is detailed below.

The issues discussed in this report that

give

1.

2.

3.

4.

rise to congressional options are:

Whether open shelf-life dating will be

implemented by regulation through an

executive branch agency or required

through a specific law;

Whether open shelf-life dating should be

voluntary, voluntary/mandatory, or mandatory;

Which products or product categories

will be exempt from open shelf-life dating or will have a voluntary/mandatory

or mandatory date established;

The method chosen for open shelf-life

dating.

There are important aspects of these

issues that interact to create an open shelflife dating system for food products. This is illustrated by the decision tree of figure 1.

The first branch, path A, illustrates the

distinction between regulation through the

appropriate executive branch agency or requiring specifics through statutory law. This

is a basic option that underlies each issue

specific to open shelf-life dating.

The second branch, path B, illustrates the

three possibilities for the degree to which

open shelf-life dating would be mandatory.

One possibility is to specifically exempt certain products or product categories or to

allow present voluntary dating to continue.

Another possibility is to opt for a voluntary/mandatory program for certain products

or product categories. A third possibility is to

make open dating mandatory for certain

products or product categories.

The third branch, path C, illustrates that

any of the previous options could be applied

to product categories such as perishables,

semiperishables, or long shelf-life products.

Of course, specific products or more narrowly defined product categories also would be

appropriate at this point in the decision tree.

As an example, a branch could be “strawberries” or “bulk fresh fruits and vegetables, ”

rather than “perishables.”

The extreme right-hand side of the decision

tree illustrates the options for the method

used to convey an open shelf-life date. These

include pack, sell-by, best-if-used-by, and

combination dates. Each of these methods of

dating represents an option by product or

product category.

The decision tree clearly illustrates the interactive nature of the options. That is, if a

particular option is chosen under one of the

four issues, the impact of it will be different

depending on which options under the other

issues are chosen.

53
54 . Open Shelf-Life Dating of Food

——

To clarify the interactions among the options, several examples are given using figure

1 as the basis for the example. These examples will follow specific paths of the decision tree.

Congress might opt to allow the appropriate executive branch agency to set voluntary/mandatory open shelf-life dating on perishables using a sell-by designation for the

date (denoted as decision path “A” in figure

1). This particular path through the decision

tree would mean that the specific decisions

likely would be made by the appropriate executive branch agency, Also, the specifics of

the open-dating system such as the products

Combination

or product categories and the method for designation of the date would be accomplished

by regulation issued by the executive branch

agency rather than written into the law by

Congress. Congress can stop at any point in

the decision tree once the decision is made to

allow an executive branch agency to put open

dating in place via regulation rather than

statutory law.

Note that the alternative paths through the

decision tree are not mutually exclusive. One

path may be chosen for a particular product

category or method for dating while an entirely different path is chosen for another

product category or method.
Chapter /X—Array of Congressional Options ● 55

Another specific path through the decision

tree is for Congress to write a law that would

specifically exempt long shelf-life products

from open dating (denoted as decision path

“B” in figure 1). This would mean that manufacturers of many canned or frozen products

would be exempt from a Government program but could still voluntarily open dat e

their products, as some presently do.

A final example is that Congress coul d

write a law that would place mandatory open

dates on perishable products using a sell-by

designation (denoted as decision path “C”’ in

figure 1). The implementation would be the

responsibility of an executive branch agency,

but the law would be specific with regard to

product category and method used to designate the open date.

Similar open shelf-life dating systems are

depicted by following the various decision

paths through the decision tree. Severa l

paths may be combined to form the basis of

an open-dating system. The consequences of

the various options are found in the main

text.
APPENDIXES

These appendixes provide more detailed information on open shelflife dating of food.

Appendixes A, B, and C provide technical background on the applicability of open dating of food. They summarize a report prepared for

OTA by the Department of Food Science and Nutrition, University of

Minnesota, under the direction of Dr. Theodore P. Labuza. These appendixes were prepared by Dr. Labuza and Linda Kreisman and were reviewed by the OTA panel on open shelf-life dating of food.

Appendix D is a summary of the status of open shelf-life dating

regulations in selected foreign countries and international organizations. It is based on a paper prepared for OTA by Dr. Amihud Kramer.

Appendix E is a detailed bibliography on open shelf-life dating of

food.
Appendix A

Application of Open Dating to

Specific Foods

This appendix contains a

OTA-C-78-001 for various food

condensation of data on shelf life collected in contract

categories. In that contract. the specific modes of deterioration were analyzed, and shelf-life plots presented for each mode. The reader is referred to the specific data and literature references in that report.

In this review, the foods have been broadly classified into perishability categories,

since many States have legislated open dating on a perishability basis. Three categories

were chosen, based on normal processing, distribution, and handling conditions:

Perishable--foods of less than 30 days shelf life in which the major problem is hightemperature abuse.

Semiperishable--foods of greater than 30 days but less than 6 months’ shelf life.

Long shelf-life foods-these are foods of greater than 6 months’ shelf life. In some

cases, they have been described as nonperishable foods. However, as noted in this

report, all foods decay at some rate for certain environmental conditions.

It is noteworthy that this classification is not actually based on the food itself but is

based on the food/process/package/storage conditions. Thus, a long shelf-life food like a

canned food could deteriorate in less than 1 week if held at 40

0 to 500 C or in a few days if

opened and held at room temperature. This point must be remembered when the regulatory aspects of shelf life are considered. It must also be noted that it is difficult to actually

separate the semiperishable and long shelf-life foods.

Modes of deterioration. Fluid milk and fermented milk products such as buttermilk, yogurt,

and cottage cheese deteriorate because of: 1) bacterial growth and 2) lipid reactions, including

both autoxidation and enzymatic hydrolysis. The

shelf life is usually from 7 to 14 days under refrigeration conditions.

Milk products are an ideal medium for growth

of a number of psychrophilic bacteria. The optimum temperature for their growth is 200 to 30° C,

but they also grow well, although more slowly, at

refrigeration temperatures. Following pasteurization, it is generally only the more heat-resistant

(thermoduric) bacteria, some of which can be psychrophiles, that remain. Their numbers should be

quite low, and at low temperatures (0° to 10° C),

the milk should have a fairly long shelf life. Thus,

the best way to prevent spoilage is to prevent recontamination after pasteurization. Growth of

psychrophiles in milk can lead to a variety of offflavors and defects. Among these are bitter,

fruity, rancid, stale, and putrid flavors, and ropiness in milk. One problem associated with establishing standards for acceptable levels of bac59
60 ● Open Shelf-Life Dating of Food

teria in milk is that different species produce different types and intensities of off-flavors and

odors. The off-flavors may be detected at 104 colony forming units per milliliter (cfu/ml) of one

species and not until 107 cfu/ml of another species, The temperature coefficients (Q10's)* for microbial growth in milk range from 3 to 30 and

average around 6.

Enzymatic hydrolysis of triglycerides in milk

can yield free fatty acids that cause rancid

flavors even when present in very low concentrations. Lipase and other such enzymes are generally inactivated by pasteurization, but certain

microbes can produce the enzymes as they grow.

Oxidation of unsaturated fats and phospholipids

can lead to a variety of off-flavors. Sunlight,

fluorescent light, metal ions, excessive agitation

as in homogenization, and a small amount of ascorbic acid and riboflavin favor or catalyze the

oxidative reaction. Addition of antioxidants to

milk is not allowed in the United States. Tocopherols are the only antioxidants known to be present

naturally, although sulfhydryl groups produced

during pasteurization also have antioxidant properties. The use of opaque- or colored-glass milk

containers reduces the catalysis of autoxidation

reactions. The Q10’s for lipid reactions in milk are

from 3 to 4, much lower than for microbial

growth.

In milk conforming to current health standards,

off-flavors and off-odors occur more quickly than

do actual safety hazards or significant nutrient

loss. These sensory quality defects should be used

to set the end of shelf life.

Pack date. In pasteurized milk, the pack date is

the date of pasteurization. Milk quality after pasteurization is highly dependent on sanitary handling, temperature control, and protection from

light. Without a knowledge of these processing

and distribution parameters, the pasteurization

date is not very useful to the consumer. For example, milk unopened in the carton normally is expected to have a shelf life of 7 to 10 days at 6° C. If

held at 0° C, it can last for 20 to 30 days with high

quality, but the consumer usually does not know

this.

Sell-by date. This dating system is currently

used in several States for milk. Usually, the sell-by

date is set as a certain number of days from processing (e.g., 10 days) for all pasteurized milk

within a given State. This system has the advan-

*A measure of sensitivity of food to temperature is called the

temperature coefficient (Q,,,). See app. B, equation 8.

tage of forcing all processing and distribution systems to conform to a minimum standard. It, however, also has the disadvantage of discouraging

higher quality practices and inhibiting introduction of new technology.

For example, ultra-high temperature (UHT)

milk produced in Europe is milk pasteurized at

very high temperatures, giving it a much longer

shelf life (3 to 4 months) at room temperature.

Since it would be classified as pasteurized milk, it

might have to be labeled as a perishable food and

thus there would be no technological advantage in

producing it. A system of setting the shelf life

separately for each batch of milk depending on

initial quality and on quality of processing and

distribution conditions would be more accurate

and just. However, to do this would require further studies to develop time/temperature specifications on microbiological and esthetic milk

qualities, which could be expensive. It would also

require a flexibility within the dating system to

adjust to changes in processing and distribution

systems.

Best-if-used-by date. The high sensitivity of

milk to sanitary treatment and temperature

makes this date unsatisfactory. This is especially

true if control of distribution is not undertaken.

On the other hand, with good distribution control

and knowledge of the initial quality parameter,

one could theoretically place an end-of-shelf-life

date on fluid milk.

Fresh “Bakery Products

Modes of deterioration. The various modes by

which breads and cakes deteriorate include:

1) microbial growth, primarily visible mold

growth on the surface of the product; 2) moisture

loss causing hardening; 3) oxidative rancidity; 4)

nutritional losses; and 5) staling.

The baking process is similar to pasteurization

in that both enzymes and micro-organisms are destroyed by the heat. Thus, bread may be stored at

room temperature in spite of its high water activity. By the time microbial growth begins to be a

problem, the bread has usually been consumed or

other modes of deterioration have already limited

shelf life. Calcium propionate is often added to

bread as a mold inhibitor to slow this process.

Moisture loss can be kept to a minimum by use of

moisture-proof packages, although it can be the

limiting factor in cakes packaged in cardboard.

Staling usually occurs before either oxidative

rancidity or significant nutritional losses. This is
Appendix A—Application of Open Dating to Specific Foods “ 61

especially true of bread and usually true for

cakes, in which rancidity can occasionally be a

problem. Vitamin losses occur very slowly in

bakery products. Loss of available lysine through

nonenzymatic browning occurs more quickly but

is not a significant problem, since bread is not a

significant source of lysine in the diet.

Staling is by far the major mode of deterioration in fresh bakery products. Effects of staling include changes in taste and aroma, increased

opacity of crumb, increased crumbliness, and increased hardness of crumb (with or without moisture loss). Many factors affect the rate and extent

of staling, including the protein content of the

flour used, pentosan content, and monoglyceride

and diglyceride additives. Staling is one of the few

degradative reactions in foods that proceeds

faster at lower temperatures, having an inverse

Q10 of 1.5 to 2.0. The shelf life of breads is usually

considered to be about 2 days and that of cakes

about 1 week.

Aside from the possibly toxic effects of consuming large amounts of moldy bread, there are little

or no safety considerations in determining the

shelf life of fresh bakery products. Most people, in

fact, would reject moldy bread even when one colony forms. Nutrient loss is of minor consideration

since it occurs much more slowly than sensory

quality losses caused by staling.

Pack date. The pack date for bakery products

would let the consumer know when the produce

was made. This would be acceptable for bakery

products, although not the most desirable type of

open date. With a pack date on the product, the

consumer may expect bread to be fresh when it is

in fact very close to staleness. On the other hand,

for cakes, with a shelf life of about 1 week, consumers may feel the product is too old when, in

fact, there is considerable high-quality life left.

The only way a pack date would be acceptable

would be if people had an excellent knowledge of

shelf life.

Sell-by date. A sell-by date sets a limit on the

acceptable amount of staling of bakery products

sold at full price in the marketplace without making a judgment of the amount of staleness the consumer would personally tolerate when actually

eating the product. Sell-by dates are presently required in several States. Bakeries in these States

have found that consumers do tend to pick the

freshest product, but this presents no real problem since deliveries are made every day or every

other day. They also have experienced no trouble

in selling the average products at reduced prices

since they are still edible and have lost no nutritional quality.

Best-if-used-by date. This date tells consumers

that for maximum freshness they should use the

product by that date without fear that if they do

not, they must throw it away. This date would also

be beneficial for the bakeries. They could sell the

products past that date at a reduced price and

therefore would not have to dispose of the product

as could be the case with a use-by date.

For fresh bakery products, either the sell-by or

best-if-used-by date would be suitable.

Fresh Meat

Modes of deterioration. There are essentially

two modes of spoilage for fresh meat products:

bacterial growth and loss of appropriate color.

Consumers relate the characteristic red color

of fresh meat with quality and freshness. This red

color occurs when red oxymyoglobin is formed

because of the oxidation of purplish myoglobin.

Exposure to air and light causes the color change

of oxymyoglobin, generally within 24 hours,

although packaging under a low oxygen atmosphere can delay the reaction. The color change is

also extremely temperature-dependent as reflected in a high Q10, of 20 to 35. It should be realized that although the color may change, the food

still has high flavor quality and nutritional value.

With some meat such as pork the use of a color index is not possible because of its initial color.

Bacterial spoilage is caused mainly by psychotrophs and, with the exception of ground beef, is

primarily a surface problem yielding slime, offcolors, and off-odors. The shelf life of fresh meat

is generally 3 to 4 days at refrigerated temperature, considerably longer than that for browncolor development. The critical factors to guard

against microbial spoilage are: 1) maintenance of

proper temperature, since the Q10’s are relatively

high (3 to 8), and 2) maintenance of proper sanitation to keep the original bacterial load low. At 5°

C, ground beef with an original load of 105 cells/g

has 2 more days of shelf life than that with an

original load of 107 cells/g.

The package atmosphere can also drastically

affect shelf life. A carbon dioxide (CO2

) atmosphere will lower the pH of the meat surface and

retard growth, increasing shelf life by several

weeks without any significant nutritional losses.

It should be noted that the history of the animal

prior to slaughter can also affect shelf life.
62 ● Open Shelf-Life Dating of Food

Proteolytic psychotropic bacteria grow more

quickly in fresh meat at proper storage conditions

than do pathogenic bacteria. Thus, the production

of slime, off-flavors, and off-odors is rapid enough

to occur before the possible development of safety

hazards of pathogenic growth. Using color change

as a sensory-quality criterion also means that sensory changes occur sooner than any safety hazards or significant nutrient loss. However, these

color changes can cause rejection of the meat

while it still has high flavor quality.

Fresh meat that is cut and prepared in the retail store, is not frozen at any time during its storage life, and is not packaged in any container or

wrapping prior to sale could be exempted from

open dating. The quality of fresh meat described

above can be determined by sight, touch, and

smell before purchase is made, In addition, there

would be problems in physically placing a date on

individual items, and the cost of such a program

would be prohibitive.

For fresh meat that is packaged and/or frozen

at some time during its storage life, an open date

is more meaningful because consumers have more

difficulty determining the quality of the product.

An open date would be of more use to consumers

under these conditions and would be more feasible placed on the package as opposed to the individual item.

Pack date. Almost all fresh meat is packaged by

the retailer who deals directly with the public.

This meat may have been slaughtered anywhere

from 1 day to 2 weeks previously. Since carcasses

of properly handled beef are essentially sterile internally, it is the packing procedure that initiates

color and bacterial spoilage, Thus, the pack date

is a good index in determining the shelf life. Since

the shelf life of fresh meat is relatively short

beyond the pack date, this date may be sufficient

for consumer use and understanding, However,

many people freeze meat at home, and the pack

date does not give them any idea of the frozen

product shelf life.

Sell-by date. The sell-by date may not be any

more useful to the consumer than a pack date for

fresh refrigerated meat because it does not tell

the consumer the time at which quality changes

were initiated. However, if the marketer has good

quality control, it represents a better method than

the pack date, as it might reduce wastage,

Best-if-used-by date. In the case of fresh meat,

this date could be “for highest quality, use or

freeze by .“ This date might be most useful to

the consumer. However, as evidenced by the Q10’s

of the deteriorative reactions, high temperature

can result in very rapid deterioration of fresh

meat. Thus, the potential for consumer abuse

prior to the date may be too great for this date to

be a practical alternative,

Poultry

Modes of deterioration. Discussion of the

modes of deterioration of quality will be limited to

those changes occurring after death that affect

wholesomeness and fitness for food. These include: I) microbial decay, 2) pathogen growth, 3)

sensory quality changes, 4) chemical and enzymatic degradation affecting color and rancidity,

and 5) physical decay.

Hundreds of different species of micro-organisms have been reported to grow in poultry meat

and may or may not be pathogenic. In the United

States, fowl foods once were the most frequent

vehicle of dissemination in outbreaks of foodborne infections, and Salmonella were the most

important organisms implicated in these outbreaks. However, according to the Center for Disease Control, poultry has become a minor vehicle

for food poisoning in recent years because of better process controls.

Microbial growth during storage may or may

not cause decay, depending on the type of organism (proteolytic or nonproteolytic). Slime formation occurs at a level of 108 to 109 organisms per

square centimeter (cm2

) of surface, and sensory

spoilage is detectable at 107 to 108 organisms per

c m

2

. Low temperature is the best prevention

against microbial growth. Growth occurs only

very slowly below – 12° C, and it is important

that the temperature doesn’t fluctuate above that,

Since the Q10 for growth is about 3.

Flavor changes are affected by the sex and age

of the animal, amount of fat, and surroundings of

the carcass. They can be monitored by the degradation of inosinic acid into inosine and hyposanthine. Therefore, some chemical index of quality

can be used.

Color change, weight loss, and rancidity development can be retarded by freezing, vacuumpacking, and use of low-oxygen permeable films.

Careful handling of carcasses at low temperature

slows the disappearance of adenosine triphosphate and postmortem glycolysis, Storage at high

temperature leads to irreversible toughening.

Careful handling also reduces bruising and loss of

tissue water (syneresis),

The overall Q1 0 of deterioration of frozen

poultry is about 20, which is very typical of frozen
Appendix A —Application of Open Dating to Specific Foods ● 63

foods and meats in general. The Q10 for fresh

poultry shelf life varies from 2 to 7, depending on

the preprocessing and processing methods used.

The past frequency of foodborne infections that

can be disseminated by poultry makes the question of safety relevant. This, however, cannot be

prevented by an open date. From a consumer

standpoint, nutrient loss and loss of sensory quality are the most important considerations in setting the open date.

Fresh poultry that is cut and prepared in the

retail store, is not frozen at any time during its

storage life, and is not packaged in any container

or wrapping prior to sale could be exempted from

open dating. The rationale for exemption is the

same as discussed for fresh meat, However, for

poultry that is packaged and/or frozen before

sale, an open date is useful to the consumer.

Pack date. The pack date for most poultry is the

date on which the product is slaughtered, cut up,

and put into a package. With a product such as

poultry that has a short shelf life, a pack date—if

done at retail or in a process center—would be a

useful date if it is close to the date of slaughter.

However, temperature abuse would lead to an improper guess by the consumer as to the quality of

the product beyond this date.

Sell-by date. The estimation of a sell-by date

could be made by each producer, based on a

knowledge of the exact processing conditions and

the normal distribution conditions, including the

retail store. The sell-by date would provide some

help to the consumer, but the exact information

regarding how long after the sell-by date the product could be used is missing. Coupled with a sellby date, information on how long the product

could be stored in the home—either frozen or refrigerated—would be most useful.

Best-if-used-by date. From the producers’

standpoint, estimating a sell-by date is almost as

difficult as estimating a use-by date, the only difference being the knowledge of temperature conditions under refrigeration and freezing in the

consumer’s home. Theoretically, a best-if-used-by

date would be the most meaningful date for the

consumer. However, based on presently available

information on poultry shelf life, it would be difficult to estimate a general sell-by or best-if-usedby date. In addition, home storage temperature

can vary by 6° and with a high Q10 this could affect shelf life. Determining these dates would require considerable money to collect the required

information. In addition, different methods and

more control for the grocery store display of products would have to be developed.

Fresh Fish

Modes of deterioration. The major mode of

spoilage for fresh fish is bacterial decomposition

on the surface of the fish. Factors affecting the

keeping quality of fish are: 1) environment where

caught (season, location, bacterial load of water),

2) fish species, and 3) handling conditions (temperature, sanitation). The same factors apply to

shellfish, although since lobsters, clams, and

crabs are sold alive, proper temperature—particularly prevention of any rapid change in temperature—is of paramount importance.

Fresh fish is generally not prepackaged and is

almost always packed and distributed in ice.

Maintenance of surface temperatures below 2° C

is of utmost importance. Shelf-life data show that

a typical marine (saltwater) fish such as cod has a

shelf life of approximately 14 days when stored

on ice. The Q10 values of from 4 to 6 indicate the

importance of keeping fish properly chilled, since

a small change in temperature has a drastic effect on an already short shelf life. For example,

raising the temperature to 10° C would reduce

shelf life to less than 2 days. The Q10’s of growth

for typical spoilage bacteria closely resemble the

actual sensory quality data. As with fresh meat

and poultry, safety from pathogenic organisms

cannot be guaranteed by open dating, it is only

possible by proper sanitation and holding temperatures below 7° C.

The detrimental effects of psychotropic bacterial growth become evident in fresh fish much

sooner than any nutrient loss or safety hazard occurs. Thus, sensory considerations are the limiting factors in determining shelf life.

Fresh fish that is prepared in the retail store, is

not frozen at any time in its storage life, and is not

packaged in any container or wrapping prior to

sale could be exempted from open dating. The rationale for exemption is the same as discussed for

fresh meat. However, for fresh fish that is packaged and/or frozen before sale, an open date is

useful to the consumer.

Pack date. In the case of fresh fish, the pack

date should be termed the “catch date. ” The

catch date marks the beginning of deterioration

and must be known in order to set a sell-by or useby date. However, even with proper temperature

control and sanitary handling, the length of shelf

life varies with each species of fish and also

within species because of season, location, and

bacterial load of the water. Therefore, the catch

date is not technologically useful in setting a shelf

life. From a retailer’s and a consumer’s stand-
64 ● Open Shelf-Life Dating of Food

point, the pack date would be most meaningful,

since one could easily determine if the fish were

old. Even if it were already packaged, a consumer

could then reject it based on experience with old

fish. This is especially true since most consumers

buy fresh fish on or close to the date of consumption.

Sell-by date. This date would have to be set by

the fishing company with knowledge of the catch

environment as well as of the species of fish and

the catch date. Its validity would depend on controlled temperature and sanitary conditions during distribution and retailing, Since most fresh

fish is handled directly by independent fishermen

with no research resources, presently it would be

technologically impossible to set realistic dates

based on real data. The only thing that could be

done would be to set some average values on the

products which might in fact deceive the consumer, especially since abuse may easily occur.

Best-if-used-by date. This date would be no

more useful than a sell-by date for the same reasons. Since most consumers buying fresh fish feel

a need to buy it as close as possible to the actual

time of use, a pack date is more meaningful. The

extreme sensitivity of fresh fish to temperatures

above 2° to 4° C and to unsanitary handling

would make retailers very reluctant to initiate a

use-by date,

Fresh Fruits and Vegetables

Modes of deterioration. The major modes of deterioration of fresh fruits and vegetables can be

classified as: I) enzymatic and chemical reactions

leading to nutrient loss as well as loss of sensory

appeal, and 2) microbial decay resulting in loss of

sensory appeal as well as possible health hazards

if pathogenic organisms are present.

Some of the factors affecting the point of onset

and the rates of these various reactions include

the following:

1.

2.

3.

Growing conditions—such as soil and water

consumption, amount of sunlight, and temperatures—that have a direct effect on the

chemical composition of fruits and vegetables.

The point in the maturation process at which

the fruit or vegetable is harvested, since it

determines the degree of maturity and the

rate of maturity. This effect varies with the

type of fruit or vegetable.

The temperature of harvesting and subsequent storage. The higher the temperature,

4.

5.

6.

the faster the reaction rates (Q10 of 2 to 3),

but damage can also occur if held at too low

a temperature (chill injury), which varies

with each fruit and vegetable,

Any physical bruising or damage occurring

during harvesting and transportation. Punctures and broken skin can allow entry and

growth of micro-organisms; cell rupture

allows mixing of enzymes and substrates

with subsequent decay reactions.

The composition of the storage atmosphere.

Addition or removal of ethylene can speed or

slow ripening; the ratio of CO2 to oxygen has

a direct effect on the rate of respiration, and

lack of humidity can cause wilting,

Sanitation conditions. Washing or disinfecting reduces microbial loads on the surface;

fumigation lowers the extent of insect damage.

The combinations of these various factors influence shelf life so radically that it is extremely difficult to predict. From the standpoint of food safety, most pathogens (except for molds) do not grow

on these products. The presence of mold is easy to

identify visually and can serve as an index for rejection.

Vitamin C is a relatively unstable vitamin. It

degrades more quickly than most nutrients, so its

loss can be used as a standard in judging the end

of shelf life for foods that are major sources of

vitamin C. However, since consumers cannot

measure vitamin loss, consumers judge fruits and

vegetables by their market quality—appearance

and firmness. Market quality has been found to

have a direct relationship to nutritive quality, microbiological contamination, and/or insect contamination. Sensory quality is therefore the primary consideration of the type of open-dating system,

Fresh fruits and vegetables sold in bulk—not

packaged—could be exempted from open dating.

This is because the quality of fruits and vegetables sold in bulk can be determined by sight,

touch, and smell before purchase is made. It

would be very difficult to determine a meaningful

shelf-life date because fruits and vegetables are

subject to varying rates and types of deterioration, including physical deterioration as a function of consumer handling. There would also be

problems in physically placing a date on individual items, and the cost of such a program would

be prohibitive.

For packaged fresh fruits and vegetables, consumers have more difficulty in determining

quality.
Appendix A—Application of Open Dating to Specific Foods ● 65

Pack date. In the case of fresh fruits and vegetables, the pack date would be the date of harvest.

Most consumers in the United States would probably have little knowledge as to when a fruit or

vegetable was harvested unless it was in the

growing season from local markets. In addition,

the great influence of the factors discussed above

on shelf life would make this date inapplicable to

fruits and vegetables that can have extended

shelf lives if stored under ideal conditions. However, a harvest date would be of great help in the

case of vegetables that usually are picked at the

peak of quality and have a relatively rapid deterioration in quality. Sweet corn on the cob is an example, but even here, unless the corn is immediately chilled, it can lose 50 percent of its sweetness in several hours, and the date would be no indication of quality.

Sell-by date. A sell-by date would be extremely

difficult to predict, implement, or enforce, especially for products with a short shelf life. In any

case, consumer judgment by appearance and texture is more valid and is a built-in means of shelflife assessment.

Best-if-used-by date. The conclusions for a sellby date are also true for a best-if-used-by date,

unless advances are made to have absolute control over distribution. If such control were possible, a sell-by or best-if-used-by date could be implemented.

SEMIPERISHABLE FOODS

As noted earlier, this category is given to foods

that do not deteriorate very rapidly but, on the

other hand, do not last for a long time under normal storage conditions. Perishable foods can be

made semiperishable by better handling and by

use of new technology such as controlled atmospheric storage. Long shelf-life foods, if abused,

become semiperishable. Thus, the choice of putting foods into the semiperishable category is

more subjective than objective.

Fried Snack Foods

Modes of deterioration. Common to all fried

snack foods is fat added as a processing agent. All

fats are subject to deterioration by oxidative and

hydrolytic rancidity—the major mode of deterioration of all fried snack foods. The more unsaturated the fat, the more subject it is to rancidity.

A second mode of deterioration of dry-fried

snack foods is moisture gain. Unacceptable loss of

crispness occurs when moisture gain reaches a

water availability (aw

) of 0.4 to 0.5. Hydrolytic

rancidity (an enzyme reaction) can be inhibited by

high-temperature denaturation of the natural

lipase enzymes present in most foods, It also is inhibited by drying to below an aw of 0.2 and at low

temperature.

Oxidative rancidity has a Q10 of about 1.5 to 2.5.

It can be controlled by protecting unsaturated

fats from oxygen, metal ions, light, and high temperature, Addition of phenolic-type antioxidants

is one of the most important means of preserving

fats. Use of fresh oil in processing also is important since the presence of intermediate compounds produced accelerates the reaction.

The shelf life of fried snack foods can also be

extended by packaging under an inert atmosphere. Potato chips in cellophane film coated with

a moisture barrier have a shelf life of 4 to 6 weeks

at 21° C. This can be extended to 6 months by

packaging in a laminated container under nitrogen gas.

No microbiological safety hazards are presented by average fried snack foods since their

water activity is low and they would lose crispness before microbes would grow. The end products of lipid oxidation have been shown to be toxic

in animal studies. However, large amounts of extremely rancid fried foods would have to be consumed for a hazard to appear. Likewise, there is

little nutrient loss because of lipid oxidation,

since only a small portion of the fat oxidizes. Thus

the primary consideration in determining the end

of shelf life is sensory quality.

Pack date. The pack date has the advantage

over the other two types of open dates in that it

could be most easily and cheaply implemented.

However, the disadvantage of the consumer’s

lack of knowledge about shelf life is compounded

in this case by the fact that processing conditions

(temperature, moisture content, use of fresh oil,

and antioxidants) and packaging effectiveness

(type of moisture, light barrier, and headspace

gas) are crucial in determining the length of shelf

life. Since these factors are different for each

product, shelf life must be determined individually for each product. Therefore, a pack date is not

meaningful except to help in stock rotation.
66 . open Shelf-Life Dating of Food

Sell-by date. The sell-by date could be a meaningful date for fried snack foods if the date were

based on meaningful data as to quality changes in

relationship to the environmental and initial oil

characteristics, Companies could, based on typical ingredients, develop tests to measure shelf

life. However, a range would be needed, since distribution conditions could vary, The date would

best be accompanied by some meaningful homestorage information such as “store in a cool, dry

place” or “store away from home appliances and

in a cupboard. ”

Best-if-used-by date. This date for fried snack

foods would be relevant under the same conditions as a sell-by date. It would probably be most

relevant if accompanied by recommendations for

home storage. Abuse conditions, however, could

occur that would lead to loss of quality before the

end of shelf life.

Cheese

Modes of deterioration. Modes of deterioration

for cheese include: 1) undesirable microbial

growth resulting in visible surface-mold colonies,

slime, putrefaction, or gas formation; 2) moisture

loss; 3) chemical reactions such as nonenzymatic

browning, lipid oxidation; and 4) lactose crystallization, In properly packaged, unopened cheese,

surface mold or slime formation and moisture loss

should not occur.

In processed cheese, chemical reactions are

the major deteriorative modes, while in natural

cheese, both undesirable microbial growth and

chemical reactions lead to deterioration.

The shelf life of processed cheese stored at 4°

C is generally about 4 months to 1 to 2 years.

Natural cheese stored at 0° to 2° C has a shelf life

ranging from 4 to 12 months, The Q10 for lipid oxidation is low, about 2, whereas for nonenzymatic

browning, it is about 5. The Q10 for microbial

growth is generally 6 to 8, so that temperature

abuse will generally lead to microbial activity

causing the end of shelf life. It should be noted

that some browning is desirable as it leads to

flavor development, and thus some cheese improves in quality with aging.

Cheese is susceptible to pathogenic growth, notably Staphylococcus aureus. However, contamination with pathogenic organisms only occurs if poor sanitary conditions occur during

processing. The organism cannot grow below 7°

C. Pathogenic growth does not correlate to shelf

life, however. Also, since nutrient loss occurs

very slowly after the initial processing procedures, it does not determine shelf life. Sensory

quality changes from undesirable microbial

growth and chemical reactions, therefore, are the

primary factors in determining the end of shelf

life.

Pack date. Since most consumers do not have

knowledge of the shelf lives of cheese (and they

vary considerably), a pack date is not beneficial

except: 1) to ensure rotation and 2) for those

cheeses that improve in quality as they age.

Sell-by date. Since most consumers store

cheese under refrigeration, a sell-by date could

be a meaningful way of open dating some cheeses

that have a relatively short shelf life (1 to 6

months). For cheese of longer shelf life, it is probably not as meaningful as a use-by date. Of

course, this means that distribution temperatures

must be adequately controlled.

Best-if-used-by date. For cheeses with a long

shelf life that are kept under adequate refrigeration, a use-by date based on good laboratory data

would be a meaningful method of dating. This

would also facilitate stock rotation.

Ice Cream

Modes of deterioration. One primary mode of

deterioration of ice cream is the development of a

grainy texture caused by crystallization of lactose

under fluctuating temperature conditions as a result of the automatic defrost cycles of most freezers, Flavor deterioration caused by fat oxidation

and hydrolysis becomes important during longterm storage,

Sensory quality as measured by adverse texture is the limiting factor in determining shelf life.

Safety hazards or nutrient losses are not of importance since these would occur only if the ice

cream were thawed, and the product would then

be texturally inedible.

Pack date. The pack date would be the easiest

date to implement, but differences in temperature

cycles in different distribution systems far outweigh the relevance of the pack date. It would

help to facilitate turnover, however,

Sell-by date. This date could be determined

with knowledge and control of the temperaturetime conditions encountered in the distribution

system. It would be the most useful date to the

consumer, since most ice cream is consumed

within a relatively short time after purchase.
Appendix A—Application of Open Dating to Specific Foods ● 67

Best-if-used-by date. Determining this date ket. It would therefore not serve a meaningful

would be very difficult, given the uncertainty of purpose.

temperature cycling after purchase from the marLONG SHELF-LIFE FOODS

Some foods have been classified by various

State governments as being nonperishable and

thus not subject to open dating. In fact, some

manufacturers suggest their products have an indefinite shelf life. As pointed out in this report, all

foods deteriorate as a function of the environmental conditions. Open dating of foods with a long

shelf life may be the most meaningful of any food

perishability category because these foods may

remain on the shelf for a fairly long time both

before and after purchase. Some type of date

would help to ensure proper rotation and give the

consumer an index of when the food should be

used,

Dehydrated Foods

Modes of deterioration. In general, the major

modes of deterioration for dried foods include:

1) loss of nutrients, especially vitamins C, B1

, and

lysine; 2) nonenzymatic browning; 3) lipid oxidation; 4) pigment degradation; and 5) moisture gain

to a critical level that causes sogginess, To ensure

against these problems, drying to a specific protective moisture value is critical along with a good

water-impermeable pouch to prevent gain, The

pouch should be vacuum-sealed or gas-flushed,

and should be opaque.

For all dehydrated foods, the moisture content

has a great effect on the rate of the deteriorative

reactions and also on the sensitivity of the rates to

an increase in temperature. For example, the

rates of loss of water-soluble vitamins, nonenzymatic browning, and chlorophyll degradation increase with increased moisture content, Overdrying causes an increase in the rate of lipid oxidation and increases the loss of carotenoid

pigments and fat-soluble vitamins. For some reactions, an increased moisture content increases

the Q10, while in other reactions, the Q10 i s

lowered. Protection from oxygen can slow oxidation reactions, but the cost of oxygen-excluding

packaging must be balanced with the practicality

of adding antioxidants.

A knowledge of the types of deteriorative reactions in each product, their rates, and how these

rates change with temperature, moisture content,

packaging, oxygen availability, and other processing parameters is necessary to determine the

shelf life of any dehydrated food, Hence, shelf life

must be determined separately for each individual product.

In general, the shelf lives of dehydrated vegetables at 210 C vary from as low as 2 or 3 months to

as much as 12 or 15 months. Similarly, meat shelf

life can vary from 1 to 6 months, and dried fruits

from 1 month to 2 years, depending on the above

conditions. The Q10 for these reactions ranges

from 2 to over 10.

Safety hazards from microbes are generally not

a consideration in determining the shelf lives of

dehydrated foods if they are protected from moisture gain. The only microbial growth that can occur is that of xerophilic yeasts and molds that can

grow at water activities from 0.6 to 0.7. This

growth is generally slow and not of a pathogenic

nature and would be easily recognized. Nutrient

losses occur through lipid and vitamin oxidations

and through loss of essential amino acids during

nonenzymatic browning. These have a Q10 of from

2 to 6. Sensory quality losses occur through color

losses (Q10 = 2), nonenzymatic browning leading

to darkening and hardening (Q10 = 4 to 6), and

lipid oxidation (Q10 = 1.5 to 2) resulting in rancidity. Thus both nutrient loss and sensory quality

change must be considered, the shelf life being

limited by whichever becomes unacceptable

sooner, based on some standard set for the

change in the specific reaction allowable.

Pack date. With respect to dehydrated foods, a

myriad of reactions can occur that are a function

of initial quality and processing conditions and

that are influenced by temperature, moisture

change, oxygen level, light, and package permeability. Since consumers are unaware of these factors, a pack date would seem useful only from the

standpoint of stock rotation.

Sell-by date. To implement a sell-by date, a

manufacturer must assess the major mode of deterioration of a particular product and gather information on the distribution system. From this,

an average sell-by date could be instituted. If an
68 ● Open Shelf-Life Dating of Food

estimated shelf life after the sell-by date were

established for various environmental combinations of temperature and humidity in the home,

the product could be offered for sale after the

sell-by date at a reduced price. Although a sell-by

date is a reasonable type of open dating for dehydrated foods, some type of system that would give

estimated shelf life for the food beyond the date

should be included. This information could, of

course, depend on the area of the country.

Best-if-used-by date. The interaction of the effects of environmental conditions illustrated in

the above discussion and the fact that significant

but condition-variable shelf life is left after the

date of sale could make this date inapplicable to

dehydrated foods unless it was based on the product being sold and consumed in specific areas of

the country.

Nonfat Dry Milk

Modes of deterioration. Nonenzymatic browning, resulting in loss of protein nutritional value,

and flavor deterioration are the major deterioration modes of nonfat dry milk, The Q10 of nonenzymatic browning varies from 2.3 to 3, increasing

as relative humidity rises, The Q10’s for flavor

deterioration range from 2 to 16, increasing with

rising moisture content. The shelf life of nonfat

dry milk under normal storage conditions is

around 1 year.

Under normal storage conditions, safety is not

a consideration in setting the shelf life of nonfat

dry milk, unless it was previously contaminated.

Nutrient loss should probably be the major consideration in shelf life. Studies have shown that

flavor change occurs but is not as significant as

nutrient loss.

Pack date. The pack date could be most easily

implemented for dry milk on the date of manufacture. However, the dependence of shelf life on initial moisture content lessens the usefulness of the

pack date without an industrywide standard for

initial moisture, Lack of consumer knowledge of

shelf life is always a disadvantage in using a pack

date, especially for long shelf-life foods.

Sell-by date. The sell-by date could be determined given a basic knowledge of initial moisture

content, package permeability, and temperature/

humidity conditions of distribution, Generally, a

sell-by date is not as useful to consumers as a useby date since it does not define the amount of time

left for home storage, but it conveys more information than a pack date. If average home storage

times were indicated, the sell-by date would be

useful,

Best-if-used-by date. Given the sensitivity to external relative humidity and thus moisture content of nonfat dry milk deteriorative reaction

rates, this date may be difficult to determine.

Moisture gain after the package is opened would

vary greatly with humidity conditions and could

be the determining factor in shortening shelf life.

Obviously, moisture gain would not be a problem

with a small package that is used rapidly, but

would be a problem with slowly used packages.

Therefore, shelf life should be a criterion of the

sealed pouch and not include time after opening,

A best-if-used-by date could be set if all the same

information as in a sell-by date were known.

Breakfast Cereals

Modes of deterioration. The shelf life of most

ready-to-eat dry breakfast cereals is 6 to 1 8

months at ambient temperatures assuming package integrity based on industry estimates. The

modes of deterioration include: 1) moisture gain

resulting in loss of crispness, 2) lipid oxidation

resulting in rancidity, 3) vitamin degradation resulting in loss of nutritional value, and 4) breakage resulting in esthetic undesirability.

Proper packaging can keep the moisture gain

below the critical value of 2 to 3 percent and can

minimize breakage. Turnover of most cereals usually occurs before any significant vitamin loss,

since vitamin degradation proceeds very slowly.

Vitamin A loss, under dry conditions, is the most

rapid, but is still small. Thiamin and riboflavin

loss become important only if abused at high temperatures.

Lipid oxidation is the major mode of deterioration most often resulting in the end of shelf life

because: I) cereals are dried to the monolayer

moisture value or below inhibiting other modes of

deterioration and 2) cereal grains have a high

ratio of unsaturated fats that promotes oxidation.

The Q10 of lipid oxidation in cereals is less than 2,

As a consequence of this low Q10 the potential for

temperature abuse with respect to flavor is also

low. Antioxidants, added to the flakes by spraying

or to the package liner, extend shelf life but do not

affect the Q10.

No safety hazards are presented by over-age

cereals under normal conditions, and there is little nutrient loss at the point of detectable rancidity. Sensory quality is thus the primary consideration in limiting shelf life.
Appendix A—Application of Open Dating to Specific Foods ● 69

Pack date. The use of a pack date would be advantageous in that it would be little different from

the present system. Coded pack dates are presently placed on most cereal package overwraps, if

not on each individual container. The major

change would be to an uncoded date. If a pack

date is used, there is no necessity of setting

criteria concerning the quality of the product or

for analysis of the modes and rates of deterioration. Cost of implementing the use of a pack date

would be minimal and yet the open date would

better facilitate stock rotation than would the

coded date.

A disadvantage, however, would be the possibility of consumers confusing the pack date with a

sell-by or use-by date and thus believing all the

products to be over-age. The obvious disadvantage of a pack date is the lack of any information

about the expected length of the high-quality life

of the cereal—a life that varies more among the

different cereal types than many consumers

would expect. Consumers also may expect a

shorter life in general than is actually the case,

which could result in unnecessary waste. The

pack date does have a consumer advantage in

that it in no way imposes manufacturers’ judgment about the “staying power” of product quality. Consumers are left to make their own judgment.

Sell-by date. A sell-by date has the advantage

of giving consumers some idea of how long to expect high quality. It would always be a future date

in the market so that there would be little room

for confusion, and it is easily policed by retailers

and consumers alike. A sell-by date is not a final

date for use, so it leaves open the possibility of the

retailer selling the product after the date if the

retailer clearly informs the consumer that the

sell-by date is past. The Q10’s of cereal deterioration are so low that temperature variations do not

have an extreme effect on the rate of deterioration unless a cereal is held for long times at high

temperatures. Therefore, the time at which deterioration may become noticeable to the consumer

can be adequately predicted over a fairly broad

temperature range.

The disadvantages of a sell-by date include the

fact that consumers may not know how long they

can expect to store the product at home before

using it, especially if they do not know proper

storage conditions. The other side of this disadvantage is that a sell-by date alone does not give

consumers the date of manufacture, so they must

rely on the manufacturer’s judgment of shelf life.

In addition, temperature is still an important factor, so the end of shelf life would have to be

underestimated to allow for possible temperature

abuse, possibly resulting in the waste of some

product if turnover rates were slow enough.

Best-if-used-by date. This date could be advantageous because it gives the consumer the best

idea of the actual length of high-quality life. Its

use can be considered for cereals because of the

low Q10. However, it should be accompanied with

recommendations for storage conditions, since

long-time abuse of high temperature would invalidate the date,

The major disadvantage of a best-if-used-by

date over a pack or sell-by date would be that it

requires the most accurate knowledge of distribution conditions and deteriorative reaction rates

under these conditions. It should not result in

much product waste because the shelf life of

cereals is long compared with the turnover time,

but it could result in some consumer objection to

the length of the manufacturer’s estimate of shelf

life, especially at the beginning of implementation.

Pasta

Modes of deterioration. The shelf life of pasta

products with egg solids added is generally recognized to be 9 months to 3 years, and that of macaroni and spaghetti to be 2 to 4 years. The modes of

deterioration include: 1) moisture gain or loss, 2)

loss of carotene pigment in the egg solids, 3) absorption of flavors from the package, 4) “staling”

probably caused by lipid oxidation, 5) loss of B

vitamins, and 6) loss of protein quality in enriched

products.

Little or no information is available in the U.S.

literature concerning rates of pigment loss or

flavor deterioration in pasta.

Pasta with a moisture content below 6 percent

is too fragile, and above 13- to 16-percent moisture content, both mold growth and starch retrogradation, which cause toughness when cooked,

occur. Moisture gain or loss has been found to

have a Q10 of 2.6 to 4.9, much higher than that of

lipid oxidation (1.5 to 2.0). The loss of protein

quality has a Q10 of 4 to 6.

Loss of B vitamins occurs very slowly in opaque

packages, but when exposed to light. 50 percent

of the riboflavin and pyridoxine content can be

lost in 19 and 62 days, respectively. This vitamin

loss has not been adequately considered in shelflife studies and is not reflected in the shelf lives

given above. No Q10 data are available.
70 Ž Open Shelf-Life Dating of Food

No microbiological safety hazards can occur

with over-age pasta under normal conditions.

There is some evidence that nutrient losses may

occur primarily because of vitamin B degradation

in nonopaque packages. More information is

needed, however, before nutrient loss can be used

to set shelf life. Loss of sensory quality caused by

toughening or flavor change is at present the primary consideration in determining shelf life,

Because the Q10 of the sensory changes is low,

the advantages and disadvantages of each type of

open dating are very similar to those previously

described in the section on breakfast cereals.

Pack date. A pack date would be most easily

and cheaply implemented, since it would simply

mean uncoding dates already used. It involves no

judgment of quality criteria and is simply a factual date. The disadvantage of using it includes

the possibility that distribution times of pasta

products of 1 to 2 months may lead consumers to

object to a perceived lack of freshness, Consumers would need a knowledge of the actual shelf

life in order to adequately use a pack date.

Sell-by date. The low Q10 of most deteriorative

reactions found for pasta products means that a

date could be set that would be very representative of products distributed within a fairly broad

temperature range, However, if the pasta were to

serve as a protein source in the diet, the high Q10

for nonenzymatic browning could lead to further

deterioration if the product were abused. Much

more data is needed on actual distribution times,

temperatures, and humidities, and on the deteriorative reaction rates under these conditions to

be able to set a sell-by date. The length of time of

acceptable quality remaining after the sell-by

date would have to be standardized, and consumers would have to be informed of this and of proper storage conditions.

Best-if-used-by date. This date gives consumers

the best idea of the manufacturers’ judgment of

the shelf life of the product. However, it requires

the most accurate knowledge of distribution conditions and deteriorative reactions.

Concentrated Juices

Modes of deterioration. Frozen and canned

concentrated juices can deteriorate by: 1) nutrient loss, primarily vitamins C or A; 2) microbial

growth, primarily caused by yeasts and molds;

3) loss of color and flavor; and 4) loss of turbidity

or cloudiness through enzyme reactions.

Vitamin loss tends to be very slow in concentrated juices. Frozen concentrated citrus juices

retain 90 to 97 percent of their vitamin C for 1

year at temperatures as high as 0° C. Canned

pineapple, tomato, and carrot juice may be stored

at 10° to 15° C with minimal loss of vitamins A

and C for 2 years.

The low pH of juices prohibits microbial growth

other than yeasts and molds. Microbial growth occurs in two cases: 1) if the frozen juices are

abused by holding above freezing temperatures or

2) after the cans are opened. Color and flavor

changes occur to the greatest extent in concentrated frozen juices, mainly because of heat treatments needed to inactivate enzymes. New methods of high-temperature, short-time (HTST) pasteurization and canning procedures, coupled with

the addition of aroma concentrate, have made

greater color and flavor retention possible. In

nonpasteurized concentrated juices, loss of

cloudiness and turbidity are the primary limits to

shelf life, With inactivation of the enzyme pectin

methylestenase by HTST pasteurization, however, cloud stability has been significantly increased.

The shelf life of frozen concentrated fruit juices

of – 18° C varies from 18 to 30 months, depending

on the type of fruit. The Q10’s for sensory quality

losses of frozen fruit juices vary from 2 to 8. The

Q10’s for vitamin loss are less than 2. Of concern is

the long storage of bulk product from a bumper

year for sale the next year.

Open-dating considerations for frozen juices

are very similar to those for frozen fruits and

vegetables, with the exception that vitamin deterioration does not occur before sensory quality

defects. Safety hazards from pathogenic organisms should not be of concern because of the low

pH of the product.

Pack date. Since the shelf life of different juices

varies significantly, a pack date may not be meaningful to the consumer. Pack dates, however,

would help in maintaining stock rotation but

would create problems if the juice is packed from

the previous year’s bulk storage.

Sell-by date. The sell-by date for concentrated

juices would be of advantage if distribution conditions were known and abuse—especially for frozen products—were prevented. Some allowance

would have to be made for excess products produced in bumper crop years and held into a second year to ensure against quality loss. A sell-by

date with information as to months of high quality

left in frozen or canned home storage would be

beneficial.
Appendix A—Application of Open Dating to Specific Foods ● 71

Best-if-used-by date. This would be the best

form of dating if adequate knowledge of storage

conditions could be obtained. However, abuse—

especially in the home—could shorten shelf life

significantly.

Frozen Fruits and Vegetables

Modes of deterioration. The mode leading to

loss of quality and nutritional value during storage of frozen fruits and vegetables is very dependent on the type of product, its initial quality, and

the freezing conditions. Microbiological growth

and spoilage should not be a problem if the product is stored below the freezing point, In fact, the

microbial population will gradually decline during subfreezing storage, However, abuse can lead

to growth, but it should not be significant with

respect to pathogens.

The types of changes that can cause loss of sensory quality and nutritive value during storage of

frozen produce include: 1) pigment loss, 2) ascorbic acid oxidation, 3) off-flavor development

caused by either lipid autoxidation or browning,

4) loss of the characteristic flavor notes, 5) weight

loss, 6) package ice formation, and 7) cellular and

structure breakdown (loss of final crispness). The

effects of desiccation because of a highly permeable package can cause a loss of up to as much as

one-fifth of the weight over a storage period of 1

year at – 18° C. This will result in evident

changes in appearance but has little or no effect

on palatability or loss of ascorbic acid or

carotene. Under longer storage, surface dehydration can advance to a stage where objectionable

color and textural changes, as well as a dry appearance, are developed.

The shelf life of frozen fruits and vegetables

can vary from 6 months to 2 years, depending on

the product and on the quality aspect measured.

Also, the temperature coefficients of the quality

losses vary from 2 to 40. Thus, deteriorative reactions with greater temperature sensitivities may

dominate at higher temperatures and be insignificant at lower temperatures. The high sensitivity,

however, indicates that good temperature control

is necessary.

A hazard due to pathogens can occur from frozen fruits and vegetables only if the microbes are

frozen with the initial product (a processing failure), survive the freezing, and then thawing occurs so that the pathogens can grow (a handling

failure). These events are rare enough that they

are not open-dating considerations.

However, nutritive value is another matter.

Frozen fruits and vegetables are consumed for

pleasure and as a major dietary source of vitamins and minerals. In some cases, vitamin content

may fall below some accepted standard before

sensory quality becomes inadequate. Therefore,

if vitamin content is used as the primary opendating consideration, provisions should be made

for the continued sale of over-age frozen fruits

and vegetables up to the point of actual unpalatability y.

Pack date. Because the shelf life of frozen fruits

and vegetables varies from 6 months to 2 years,

the pack date may be the easiest to implement.

However, it would not tell the consumer anything

about the shelf life of the product. The problem of

seasonal packing and of overabundant crops in I

year could be a very difficult problem, since it

could lead to wasting good products.

An extensive education program, perhaps

coupled with a system similar to the British

“three-star” system, could make the sell-by date

beneficial. Under the British three-star system,

home storage life for different temperatures is

defined on the package. Freezer units are rated

on their ability to maintain certain temperatures

( -6°, -12°, and -18° C), and based on the temperature, receive a one- ( k), two- ( A A), or three-

( k + k) star rating. Product packages are labeled

with recommended storage times (either from the

pack date or after a sell-by date) for each of the

star ratings. As with other foods, the pack date

does facilitate stock rotation.

Sell-by date. The sell-by date could be implemented without a home freezer-rating system. The

last date of sale could be determined with a

knowledge of initial product quality distribution

times and temperatures and rates of deteriorative

reactions at these temperatures, However, collecting this data could be expensive.

A sell-by date, coupled with the home-storage

system mentioned above, would be very beneficial

and would eliminate the possible wastage problem from years of high crop production. This system would also facilitate rotation,

Best-if-used-by date. The high Q10 of some of the

deteriorative reactions of frozen fruits and vegetables, together with the uncertainty of home-storage temperature conditions make implementation

of a definite use- by date difficult. Also, a definite

use-by date may be impractical, since surveys

have shown that a major portion of frozen fruit

and vegetable deterioration occurs with the end

user. The optimum date would be a best-if-used-by

date, since it is most appropriate for a food with
72 . Open She/f-Life Dating of Food

long shelf life under controlled conditions and

with some estimate of home storage.

Frozen Meats and Fish

Modes of deterioration. Lipid oxidation and

protein denaturation are the major modes of deterioration in both frozen meats and frozen fish,

However, they occur more rapidly in frozen fish

because of the greater ratio of unsaturated to

saturated fats and the higher percentage of myofribular proteins that become insoluble with storage. Tissue desiccation and myoglobin color

changes also occur with extended frozen storage.

Antioxidants have not been successfully applied for increasing shelf life of frozen meat and

fish. Glazing with various solutions of phosphates,

sugars, monosodium glutamate (MSG), benzoic

acid, and polyhydric and other alcohols, if allowed, can be used in place of the more expensive

wrap-packaging. Effective packaging increases

shelf life and overall product quality by protecting from excessive dehydration, denaturation,

oxidative rancidity, and microbial recontamination.

At – 18° C, the shelf life of fish varies from 2 to

8 months, depending mainly on the species, with

Q10’s varying from 1.5 to 4,5. Frozen shellfish generally have a shelf life at – 8° C of 2 to 4 months,

with the exception of 10 months for crab. Frozen

beef, pork, veal, and lamb at - 18° C have shelf

lives of about 6 to 12 months, 4 to 12 months, 4 to

14 months, and 6 to 16 months, respectively, with

Q10’s of about 2.

The biggest problem is abuse by holding just

below the freezing point. Under those conditions,

excessive deterioration could occur. A freezethaw indicator with the right melting point could

indicate whether this has occurred.

Microbial deterioration with possible pathogenic growth is not a major mode of deterioration

in frozen meats and fish, since freezing temperatures inhibit activity of most microbes. Safety

hazards are therefore not a consideration in open

dating unless the product is abused and stored

above freezing. Even then, spoilage organisms

usually grow faster than the pathogens.

Nutrients in frozen meats are generally well

preserved. Thiamin, riboflavin, and niacin have

shown changes upon freezer storage, but no relationship between these changes and storage temperature have been seem The nutrient losses are

insignificant and are not a good measure of shelf

life in frozen meats and fish, Flavor deterioration

caused by oxidation of fats is usually the primary

limiter of shelf life.

Pack date. The date of packaging is useful in indicating production and facilitating stock rotation. However, since the shelf life is very speciesdependent and consumers have little knowledge

of shelf life, it is not a feasible system.

Sell-by date. A sell-by date for frozen meat and

fish, using the same system as for frozen fruits

and vegetables, would be of benefit to the consumer. The major problem would be abuse—especially holding just below the freezing point—which

would deteriorate the product much sooner than

expected.

Best-if-used-by date. As with frozen fruits and

vegetables, the same information to set a sell-by

date can be used to set a best-if-used-by date if

adequate knowledge of home-storage conditions is

available.

Frozen Convenience Foods

Modes of deterioration. Frozen convenience

foods are precooked meat, vegetable, and pasta

products packaged separately or in combination.

Reheating in a tray is all that is usually necessary

before consumption.

The predominant mode of deterioration of precooked frozen foods is lipid oxidation, causing

rancidity in the meat portion of the product. However, the susceptibility of the product to lipid oxidation is strongly influenced by ingredients, processing, and packaging that go into making the

product.

Changes in gravies and sauces (weeping and

curdling) is the other major deteriorative mechanism. Note, however, that most of the literature on

these convenience foods is more than 10 years

old, and thus this may not necessarily be the major modes of deterioration of today’s products

(that is, few TV dinners or frozen precooked entree products list antioxidants as ingredients).

The shelf life of frozen precooked chicken, beef,

and pork entrees with no sauce or gravy ranges

from 6 to 12 months. With sauces and gravies acting as an oxygen barrier, the shelf life can be increased by over 400 percent. The Q10's range from

2 to 3.5 in the – 23° to – 29° C temperature

range.

The shelf lives of the sauces and gravies are

similar to those for meats, with a Q10 of up to 30.

In considering modes of deterioration, freezer

storage at or below – 18° C has been assumed,

although it is not always the case. At these tem-
Appendix A—Application of Open Dating to Specific Foods ● 73

peratures, microbial growth is not a problem. Precooked frozen foods pose no real health hazard

even if eaten when rancid—unless the product

thaws out and is held at above 7° C, allowing

pathogens to grow in the sauces. Adequate protection such as a freeze-thaw indicator would be

needed to guarantee safety.

Nutrient losses may occur, but the great variety

of ingredients, ingredient history, and packaging

combinations that ultimately appear in the

freezer case make generalizations difficult. Sensory quality changes are the most readily apparent and are the mode of deterioration most

often reported in the literature. However, with

the institution of open dating and further study

into each product, it may be found that nutrient

losses should actually be used as an indicating

chemical factor to predict the end of shelf life of

some frozen convenience foods,

Pack date. The great variation in ingredients,

processing, and packaging of precooked frozen

foods, resulting in a great variation in shelf lives,

makes the pack date relatively useless to the consumer who cannot be cognizant of all variations.

A legible pack date would aid in first-in, first-out

stock rotation but may result in inappropriate

purchasing patterns because of misconceptions

about shelf lives.

Sell-by date. Given assurance of a temperature

range of – 18° C or below in distribution conditions, this date could be determined by producers

for each of their individual products. It would be

especially useful to the consumer if coupled with

label information concerning appropriate length

of storage in different types of home freezers as

discussed for other frozen foods. Even without

this information, however, the sell-by date would

be of more use to the consumer than would a pack

date.

Best-if-used-by date. If the uncertainty of the

frozen distribution system could be removed by

assuring that some maximum time/temperature

exposure would not be exceeded, a best-if-used-by

date would seem to be most appropriate, as with

other frozen foods.

Canned Fruits and Vegetables

Modes of deterioration. Components of canned

fruits and vegetables deteriorate as a function of

temperature in the following order: 1) flavor, 2)

color, 3) texture, and 4) nutritive losses.

Changes in flavor in canned fruits and vegetables during storage can be caused by browning

reactions, staling, and loss of flavor (flat taste).

Browning reactions result in burned and bitter

flavors, especially in fruits canned in syrups, and

to some extent in sweet potatoes. Many vegetables get a “musty” taste, which could be described as “old. ” Products high in starch become

stale tasting as staling of the starch occurs. This

reaction can be accompanied by yellowing.

Changes in color during storage include fading of

both chlorophyll and carotenoid pigments in red

and green vegetables. Fruit and starchy vegetables generally turn dark, or brown, in color.

Changes in texture during storage include softening of some vegetables when stored at high temperatures. Extremely low temperatures can break

down the texture of many vegetables, especially

potatoes, beans, squash, greens, peas, and tomatoes. Other textural changes include a tendency

towards lumping or clumping in beans and peas.

Loss of vitamins tends to occur more slowly

than changes in flavor, color, and texture. Carotene and vitamin A are generally at least as stable

as the overall quality of a given product. However, thiamin and ascorbic acid may or may not

remain at acceptable levels, depending on the

product, when compared with overall sensory

quality.

Containers used for canned fruits and vegetables also deteriorate during storage. Corrosive

products such as fruits tend to have shorter shelf

lives than bland vegetables because of a more

rapid deterioration of the can interior surface.

Also, in rare cases, slight imperfections in the

double seams of cans lead to a loss of vacuum during long-term storage. Storage at extremely low

temperatures can lead to damage of can seams

and subsequent loss of vacuum.

The shelf life of canned fruits and vegetables

ranges from 1 to probably 3 years, depending on

the product and on the quality aspect being measured. The Q10's of the deteriorative reactions are

all quite low, from 1.5 to 2.5, indicating that the

end of shelf life can be predicted over a fairly

broad temperature range. Moisture gain or loss

should not occur through the can wall, and oxidative reactions should be minimal,

A microbial hazard from Clostridium botulinum

in canned fruits and vegetables is the result of

processing failures and is not of importance in

open dating, Most often, sensory quality defects

occur more quickly than vitamin or other nutrient

losses. However, thiamin and vitamin C losses do

occur more quickly in some canned fruits and

vegetables. It has been suggested that acceptable

49-394 0 - 79 - 6
74 . Open Shelf-Life Dating of Food

levels of these vitamins should be used as the

shelf-life basis for canned foods that are significant sources of these vitamins in the list.

Pack date. According to the National Food

Processors Association, the date of pack would be

the easiest to implement but would not tell the

consumer anything about the shelf life of the

product. Canners who have seasonal packs would

be in a difficult position because the date on the

cans would seem old when the product is actually

still well within the shelf life for the product. This

would be especially true in years when an overabundant crop would force the canner to sell

some product the following year. Since the canning industry usually figures that a 3-year shelf

life for most fruits and vegetables is the norm, a 1-

year delay would still result in a more-than-adequate shelf life for a given product. However, the

consumer would have to be convinced of this fact.

This would take much time, effort, and money.

There is also. some chance for confusion among

consumers who could mistake the pack date for a

use-by date.

Sell-by date. This date is not really applicable

to cans that are often stored in the home for some

long period of time after being sold. However, if

some system that indicates shelf life beyond the

selling date were indicated, this would be feasible. It would not account for abuse, however.

Best-if-used-by date. This date could be useful

to consumers because it would give an idea of the

shelf life of the product if conditions of storage

were known. This would also be useful for rotating stock at the grocery level. However, with all

such dating, the actual end of shelf life would

vary with processing, distribution, and home-storage conditions. Probably the most useful way to

present this information would be to give label information of shelf life at several temperatures,

but it is doubtful at the present time that there is

sufficient good data for this format. However,

since there is data for products at ambient conditions, a single date could be embossed on the can

with an explanation of the storage temperature

on which it is based, The canning industry could

collect data on each product for each mode of

deterioration, estimate time/temperature distributions, and then estimate the shelf life left at

several home-storage conditions.

Coffee and Tea

Modes of deterioration. Staling is the major

mode of deterioration of ground roast coffee. Increased humidity increases the rate of staling,

Moisture can cause hydrolysis of the esters,

acetals, and ketals in coffee aroma to compounds

with less-pleasing aromas. Staling is thought to be

caused by loss of flavor volatiles or by chemical

changes in the volatile components caused by

moisture and oxygen absorption. The aroma degeneration is defined as changing from flat to old

to sharply rancid, with a cocoa odor in the advanced stages. Flavor concurrently changes from

flat to bitter, old, and rancid. Unprotected ground

roast coffee borders on unsalability in 1 to 2

weeks, depending on the relative humidity.

The shelf life of ground roast coffee packaged

under vacuum in metal cans depends largely on

the efficiency with which oxygen is removed, In

order to ensure the greatest product stability, it is

necessary to have no residual oxygen in the can.

The difference between 27 “in” of mercury

vacuum and 29 “in” is significant, Nine months’

shelf life is an acceptable industry average,

Instant coffee also loses flavor and stales during storage. Freeze-dried coffee has a longer shelf

life than spray-dried coffee. This extended shelf

life is largely because of the lower moisture content (2 percent) of the lyophilized coffee compared

with 4.5-percent moisture content of the spraydried.

In addition to flavor loss, instant coffee has the

problem of caking because of moisture absorption

when it is exposed to the atmosphere. Isotherms

show that the moisture content of instant coffee

rises rapidly when it is exposed to increasing

relative humidities (RH). At 50-percent RH, instant coffee begins to agglomerate, and above 75-

percent RH, it will turn into a liquid. The shelf life

of unopened instant coffee varies from 18 to 36

months, depending on the type of package. The

Q10’s for coffee staling and moisture absorption

are quite low, 1.5 to 2,0,

Tea is preserved by its low moisture content,

which inhibits growth of micro-organisms. During

storage, tea may undergo staling or lose some of

its aroma. Sometimes foreign or incompatible

odors may be absorbed, Moisture absorption results in caking of instant tea but occurs only if the

jar is opened. Black leaf tea and packaged instant

tea have a shelf life of about 18 months at 21° C,

with a very low sensitivity to changes in temperature, Changes in humidity are more important

considerations in the shelf life of tea, especially

tea bags packaged in boxes.

No microbiological hazards are presented by

over-age coffee or tea, They do not provide a significant source of nutrients in the diet, so nutrient
Appendix A—Application of Open Dating to Specific Foods ● 75

loss is not a consideration. Loss of sensory qualities is the major open-dating consideration.

Pack date. The date of manufacture would not

be advantageous to the consumer because it

would not provide any information about the shelf

life of the product. In fact, an open date of manufacture might result in considerable wastage,

since the consumer might conclude that an older

product is not as good as a newer one and would

buy the product with the latest date on it. This

conclusion would be particularly erroneous in the

case of ground roast coffee, since the greatest

consumption of shelf life occurs after the product

is opened.

The date of manufacture also does not give any

indication of the true age of the coffee or tea,

since the green coffee beans or tea leaves could

vary in age considerably from the time they were

harvested until they were processed and packaged. The date would also not reflect any differences in shelf life caused by different processing

procedures among manufacturers.

For example, two manufacturers of ground

roast coffee may package on the same day and

have the same date of manufacture. One manufacturer, however, evacuates the cans to 29 “in”

of mercury and thereby rids the cans of essentially all of the oxygen. The second manufacturer

evacuates the cans to 27 “in” of mercury and

leaves a residual amount of oxygen. The coffee

produced by the first manufacturer would be expected to have a longer shelf life than that of the

second, yet this fact would not be reflected in the

date of manufacture. The date of manufacture

placed on a product with no explanation of what

kind of date it was would also tend to confuse the

consumer who might interpret it as an expiration

date and assume that it was already beyond its

predicted shelf life.

Many manufacturers use coded dates of manufacture, and this practice could be changed to an

open date for coffee and tea. Open pack dating or

coded dating would assist in stock rotation for the

processor, distributor, transporter, and retailer

to allow a “first-in, first-out” system. A coded

date could also include other information such as

the factory, shift, lot number, etc. to aid in inventory control and tracing of an item should a consumer complaint ever occur or a recall be necessary. The tracing of a consumer complaint would

mean that the code must be placed on each package of food.

Sell-by date. Placing a sell-by date on coffee or

tea products would be beneficial; however, the

shelf life of these products is long, and abuse

might make these dates meaningless. The only

product for which a sell-by date would be applicable would be ground roast coffee packaged

in bags, since the shelf life of this product is much

shorter than that of coffee packaged in vacuum

cans. Some manufacturers already place an open

pull-date on this product for the benefit of the consumer and as an aid in stock rotation, but the

practice of selling ground roast coffee in fold-top

bags is usually localized and has become rather

scarce.

Best-if-used-by or use-by date. The shelf life of

coffee or tea mainly depends on the storage conditions such as temperature and relative humidity—especially after the product has been opened.

Storage of instant coffee or tea mix, for example,

with the lids open or loosely screwed on would

result in moisture pickup and caking of the product. Storage of ground roast coffee in an unsealed

container would result in faster staling.

A use-by date would also result in wastage not

only because the consumer might reject the food

in the grocery store because of the date but also

because an expiration date would give the impression that the product should not be consumed

for health reasons after a certain period of time

when, in fact, no health hazard exists when aged

coffee or tea is consumed. Food deterioration is

also a gradual process, and rarely is a product

good one day and bad the next. Shelf-life predictions for the same product can differ from one

manufacturer to the next, since the end of shelf

life is often a subjective decision, and a consumer

may unjustly reject a product with a conservative

shelf life in favor of the same product produced

by a different manufacturer with a more liberal

shelf-life prediction.

The same storage information collected by the

manufacturer can be used to implement a best-ifused-by date based on minimal changes in flavor

and odor during storage and does not have the

disadvantages discussed above.

Spices, Sugar, and Salt

Modes of deterioration. Flavor, pungency, and

color may be lost from spices by either physical or

chemical routes, The active principles of most

spices are organic compounds in the volatile oil

fraction. Whole spices retain essential oils very

well, as illustrated by the 5-year shelf life of

whole cumin at room temperature. But loss of

these volatiles can be a problem in ground spices.

In ground spices, the temperatures during and im-
76 ● Open She/f-Life Dating of Food

mediately after grinding have been found to be important in retaining essential oils.

Color loss from capsicum spices (paprika and

red peppers) is thought to be an oxidation reaction that may be induced by light, pro-oxidants, or

coupled with other oxidation such as lipid oxidation. Increasing storage temperature and decreasing water activity seem to increase the rate

of color loss as is true of lipid oxidation. In sweet

red paprika, the color seems most stable at aW

0.65. However, at this aW , caking and browning

become problems.

Pure sucrose is not susceptible to microbial or

chemical deterioration, but sugar can become

unacceptable to the consumer if contaminated by

insects or rodent droppings. Excessive moisture

gain leading to caking can also render the package unacceptable. However, these failures are indicative simply of poor storage or packaging failure. Under proper storage conditions, granulated

sugar should be indefinitely shelf-stable.

Brown sugar, which is susceptible to moisture

loss resulting in an extremely hard mass, is sealed

in plastic or waxed bags for retail sale. Confectioners’ sugar is susceptible to moisture gain

resulting in caking, but anticaking agents such as

cornstarch are added to combat this problem. The

shelf life of confectioners’ sugar is about 18

months at 21° C. The Q10 is about 2 for both brown

and confectioners’ sugar, based on moisture gain.

Table salt (NaCl) is not susceptible to microbial

or chemical deterioration. However, pure salt is

very hydroscopic and will absorb moisture from

the surroundings above 75-percent RH. For this

reason, anticaking agents are added to salt to ensure the free-flowing property. Stored in moisture-proof containers, salt will remain indefinitely stable.

Sensory quality (aroma, pungency, taste, and

color) is the determining factor for shelf life of

spices. Although some spices, notably paprika,

are rich in vitamins, they are not consumed for

their nutritive value. Spices imported from areas

with poor sanitary facilities can have high loads

of micro-organisms and be contaminated with

aflatoxin via rodent or insect infestation or inclusion of extraneous plant material, Although contaminated spices can be sources of inoculum for

foods, microbial contamination per se does not

limit shelf life of spices because most spices are

too dry to permit growth. Fumigation with ethylene oxide can be used to reduce the microbial

load of spices.

Neither safety hazards nor nutrient loss occurs

in sugar or salt, No sensory losses occur in salt or

granulated sugar. Functional loss can occur in

brown and confectioners’ sugar because of moisture loss/gain, resulting in loss of free-flowingness.

Pack date. Very little published data are available on deterioration of spices. However, since

wholesalers sell oleoresin, oils, and extracts to industrial users at certain specifications, it would

be surprising if these wholesalers do not have

data on storage stability of spice products.

Considering this lack of published data, however, a legible pack date would be of little or no

value to consumers. Indeed, it is interesting to

speculate whether or not the majority of consumers, with no standards for comparison, have any

idea as to the strength of spices in terms of taste,

pungency, or color. A pack date on sugar or salt

would also be of little or no value,

Sell-by date. A sell-by date with no instructions

for storage or to use within a specified time for

best results is of little value in products such as

spices, sugar, and salt that tend to be stored for

long periods before use in the home.

Best-if-used-by date. A statement to the effect

“for best flavor results, use before “ woul d

be the most useful method of open dating for consumers of ground spices. However, even with adequate data made available. the simple loss of

pungency and color is a subjective judgment. A

use-by date has no relevance for salt and granulated sugar with indefinite shelf life, Instructions

on methods of reversing the hardening and caking

of brown and confectioners’ sugar would be more

beneficial than would a best-if-used-by date.
Appendix B

Bask Food Preservation and

Deterioration Modes

INTRODUCTION

As pointed out in chapter V, in order to establish a fairly accurate open date for a

particular food, one needs to know how that food deteriorates. This appendix contains an

in-depth look at the various modes of deterioration and how they impact on open dating. It

specifically describes the general modes of deterioration leading to the quality and nutritional losses and types of preservation used to slow down the modes.

Biological Decay-Preharvest

Prior to harvest and slaughter, foods—whether

animal or vegetable—are subjected to a myriad

of microbiological diseases, including viruses,

molds, yeasts, and bacteria, In addition, some

foods before harvest can be eaten by insects,

birds, or rodents, or become prone to disease. For

plants, competition by weeds can result in poor

quality. Controls for such ravages can include

pesticides, herbicides, rodenticides, weeding machines, and livestock antibiotics.

Preharvest deterioration as such is not generally considered in open shelf-life dating. However, if

food is subject to damage, its initial quality will be

less. Since processing does not make low-quality

foods better, overall shelf life would be less after

slaughter or harvest, as compared with undamaged foods,

Senescence (Aging)

Once a fruit, vegetable, cereal grain, or animal

product is harvested or slaughtered, it is separated from its source of nutrients and water.

Since it is still a viable living system, the enzymes

continue to operate and utilize the carbohydrate

and nutrient stores. For fruits, this process can be

of benefit because postharvest damage can be

repaired. More importantly, fruits can be picked

prior to optimum maturity and transported long

distances to the marketplace and home, during

which time they develop into a high-quality product, If the fruits were picked at optimum ripeness,

they could rot before consumption during this

transportation. This biochemical process also

operates in the aging of meat to achieve the desired degree of tenderness. However, the state of

the preslaughter animal is very important and affects the final product quality,

Eventually, though, for all foods, postharvest

enzymatic processes lead to degradation of sensory quality, including loss of color, flavor, nutrients, and texture. In addition, the breakdown

products themselves damage the tissues such that

the decaying process becomes more rapid. To prevent this deterioration, three major control methods can be used: 1) lowering temperature, which

slows the rate of the reaction; 2) raising the temperature, which denatures the enzymes and

makes them inactive but changes the sensor y

quality of the foods; and 3) removing or binding

water to reduce water availability (or water activity, aw

), which reduces the ability of the en77

L+ 9-39 L+ 0 -

-

9 - “
—

78 . Open She//-L//e Dating of Food

zymes to operate. Other control methods are addition of acid, thereby lowering pH; reduction of

oxygen level or increase of carbon dioxide (CO2

),

which slows the reactions; and genetic manipulation of the food to altogether prevent the reactions. With respect to open dating, the effects of

aging are important in determining shelf life of

fresh fruits and vegetables; whole grain cereals;

fresh meat, poultry, and fish; and, to some degree,

dairy products.

Microbiological Decay

Micro-organisms are responsible for quality

loss of many foods, especially fresh ones. The

reason is twofold: I) microbes are everywhere in

the environment and can grow very rapidly, and

2) after a food is harvested or slaughtered, it loses

to some degree the ability to fight off microbial attack, If the food is physically damaged—even by

normal trimming and cutting—it becomes more

susceptible to attack,

As noted, microbes can grow rapidly on foods.

Starting with one microbe that divides every 10

minutes, in 5 hours (if the nutrients were available), there would be over 1 billion microbes.

Much of the same controls used for enzymes can

also be used for microbes:

lower temperature to slow growth,

raise temperature to kill microbes,

remove or bind water to slow or prevent

their growth,

lower pH to slow or stop their growth by adding acid or by natural fermentation,

control oxygen (O2

) level to control population or increase CO2 level, and

manipulate food composition to remove nutrients needed by the microbes.

Because in some cases the above methods

change the food into a form not desired by the

consumer or the method is not adequate to extend

shelf life, some chemical means of preservation

must be used to slow the growth or kill the microorganisms. Examples are calcium propionate in

bread; sodium benzoate in some soft drinks; and

natural fermentation that produces alcohol, such

as making wine from grapes. Usually only small

amounts of the chemicals are used, so that they

will have no ill effect on the consumer.

Knowledge of how environmental conditions affect the growth rate of microbes is very important

in predicting shelf life, and thus determining the

open dating of many foods including:

● fresh and ground meats and poultry;

. fresh fish;

●

●

●

●

●

dairy products such as milk, cheese, and

yogurt;

cured meats such as hot dogs, bacon, and

salami;

pasteurized fruit drinks:

fruits and vegetables; and

whole grains.

A second and more serious problem with microorganisms is the fact that some are pathogenic to

humans—that is, they either cause an infection

when ingested or while growing produce chemicals in the food that are toxic to humans. Most

food processes are designed to ensure against

contamination with pathogens or growth of the

pathogen after processing, For example, fermentation of foods with useful microbes produces

alcohol or acid that prevents the growth of pathogens. Some of the major micro-organisms pathogenic to humans in foods are:

Ž Intoxicants

—Staphylococcus aureus,

—Clostridium botulinum,

—Clostridium perfringens, and

—Aspergillus flavus.

● Infectious

—Salmonellae species, and

—Escherichia coli strains.

In most cases, temperatures below 7° C, food

with a water availability of less than 80-percent

relative humidity (aW or water activity of 0.80),

and a pH of less than 4,5 are sufficient conditions

to prevent the growth of pathogens. Open dating

should not be based on the growth of these organisms, since the manufacture and subsequent

handling and distribution should ensure absolute

control of these pathogens. Unfortunately, if the

latter is not done, consumers may have a false

sense of security that a food consumed before its

sell-by or use-by date is safe when in fact it could

cause food poisoning. This fact points to a must in

educating the consumer that open dating is not an

absolute assurance of food quality or food safety,

Chemical Deterioration

During the processing of foods, tissue damage

occurs that causes the release of various food

chemical constituents into the cellular fluid environment. These chemicals can then react with

each other or with external factors to lead to

deterioration of the food and result in a shortening of shelf life, Although many different reactions are important that lead to quality and nutrient loss, the major ones are classified below.
Appendix B—Basic Food Preservation and Deterioration Modes w 79

Enzymatic. As mentioned earlier, normal postharvest enzymatic reactions can lead to a loss in

food quality and shelf life. In addition, destruction

of cell tissues releases enzymes that can lead to

further deterioration. For example, lipoxidase enzymes released from cell organelles called mitochondria can attack lipids and cause rancidity.

Similarly, the polyphenol oxidase enzyme can react with some cell constituents and oxygen, causing a brown color, which is typically seen as a deterioration reaction in bruised or cut fruits such

as apples or bananas, These reactions are usually

very rapid at room temperature once the food is

handled but are controlled in the natural state.

The reactions can also occur in the frozen state

unless the enzymes are denatured by blanching.

Enzymatic reactions are also the major mode of

deterioration of many refrigerated doughs, since

the flour cannot be heat treated because it results

in loss of dough functionality. Control of the enzymatic reactions is the same as was discussed

for senescence.

Knowledge of how environmental conditions affect the rate of these reactions is very important

in predicting shelf life—and thus for open dating.

The major environmental factors are oxygen,

water, pH, and temperature. Other enzymatic

degradations include color losses and vitamin

losses, such as loss of vitamin C in fresh produce.

Lipid oxidation. Many foods contain unsaturated fats that are important in the nutrition of

humans. Unfortunately, these fats are subject to

direct attack by oxygen through an autocatalyticfree radical mechanism that results in rancid offflavors, making the food undesirable to consumers. Very little fat has to oxidize for the consumer

to detect rancidity and reject a food, even though

it may still be edible and nutritious. The free

radicals and peroxides produced in this reaction

can react and bleach pigments, such as in dried

vegetables, if stored for a long time; can destroy

vitamins C, E, and A; can result in protein degradation, thus lowering quality as may happen during storage of whole dry milk; can cause darkening of fat at high temperature, as happens in

deep-fat frying; and can produce toxic substances

during long storage that have been implicated in

some animal studies as potential carcinogens.

Thus, knowledge of the rate of lipid oxidation is

important in foods where it might be the principal

mode of deterioration such as in:

● fried snacks (e. g., chips),

● nuts,

● dried meats/vegetables/f ish/poultry,

● cereals,

●

●

●

●

●

●

●

●

●

●

●

wheat germ,

frozen vegetables/mea ts/fish/poultry,

some dairy products,

semimoist meat products,

precooked refrigerated meats and fish,

cured meat and fish,

coffee,

cooking and salad oils,

margarine,

spices, and

dried vegetables, such as potatoes and carrots.

Rancidity development can be controlled

directly by eliminating oxygen (which is very difficult to do) and by adding antioxidants such as

BHA, BHT, and EDTA. The rate of reaction also

depends on temperature to some degree (rate increases two to three times for every 10° C increase in storage temperature for dry foods) and

on water availability y or water activity (aw

). Foods

if too dry or not dried enough are more subject to

rancidity. For example, as potato chips gain or

lose moisture, they become rancid faster. Moisture gain is more detrimental than loss. Light and

trace metals (such as used in fortification) catalyze the reaction. Rancidity can also occur in the

frozen state where it is more sensitive to temperature changes (rate increase of 6 to 10 times for a

10° C increase in temperature. )

A knowledge of the rate of these reactions can

be used to predict shelf life and thus open date

foods. Knowing how fast oxygen permeates a food

package is also necessary to predict shelf life. In

addition, the consumer must be instructed as to

the extent and control of this reaction so as to better maintain the quality and nutritional value of

the food in the home.

Nonenzymatic browning (NEB). NEB is another

major chemical reaction leading to loss of quality

and nutritional value. This reaction occurs between reducing compounds (such as glucose, fructose, and lactose) and amino acids or proteins. In

addition, browning can result from heating sugars

to very high temperatures (carmelization). In certain cases, the reaction is desirable such as in the

toasting of bread: the crust formed in roasting

meats; malting of barley for beer and spirits manufacture; and the production of syrups, molasses,

and caramel candies.

Undesirable aspects of NEB lead to bitter offflavors; darkening of light-colored dry products,

such as nonfat dry milk; loss of protein volubility;

toughening of protein foods; and, most significantly, a decrease in protein nutritional quality

caused by the binding of an essential amino acid,
80 ● Open Shelf-Life Dating of Food

lysine, in the reaction. NEB is a significant reaction leading to end of shelf life in processed proteins; dry milk and whey powders; dry whole eggs;

dehydrated meat and fish; frozen meat, fish, and

poultry; breakfast cereals; cake mixes; fortified

pasta; intermediate-moisture breakfast bars and

mixes; and some concentrated juices. In concentrated juices, ascorbic acid (vitamin C) acts as the

reducing compound and results in loss of vitamin

value as well.

The environmental factors that control NEB are

temperature, pH, and aw

. NEB is more sensitive to

temperature than is rancidity in dry foods, increasing four to six times in rate for a 10° C increase in temperature. In foods in which both

browning and rancidity can occur, at high temperatures NEB predominates, while at low temperatures rancidity predominates. During processing, exposure time at high temperatures

should be minimized, since it leads to excessive

browning precursors that can shorten shelf life

during subsequent storage. Lowering of pH slows

browning but is not a desirable method of processing because of the flavor problem of added

acid. The major control of browning is through

control of the amount of aw in the food in which

the reaction can occur. The lower the water content, the slower the reaction rate for the foods

mentioned above. However, very moist foods such

as fresh or canned products brown slowly because the reactants are diluted by the high water

content and thus there is aw (0.6 to 0.8) at which

point the food undergoes a maximum rate of

browning.

With respect to open dating, knowledge of the

rate of browning as a function of temperature and

water content is very important in order to predict shelf life accurately. How fast a food package

gains moisture will also significantly affect shelf

life for these types of products.

Other chemical reactions. Other chemical reactions that can lead to food deterioration include

the thermal destruction of vitamins such as vitamins A, B1

, and C; the effect of light on pigments

such as the browning of meat and bleaching of

chlorophyll; the effect of light on riboflavin; the

direct oxidation of vitamin C; and the direct oxidation of carotenoid pigments. In every case, the

effect of temperature, oxygen level, moisture content, and light must be known to be able to predict

the rate of the reaction so that the time to reach

the end of shelf life can be measured. Of importance in all these reactions is a decision as to

what extent of deterioration is considered to be

the end of shelf life. In many cases, this data must

be correlated with actual organoleptic and sensory testing of the food so that the correct index of

deterioration can be chosen.

Physical Deterioration

Physical damage can also lead to loss of shelf

life. The types of physical damage can be classified into various categories, as was chemical deterioration.

Physical bruising/crushing. This mode of deterioration is related to physical abuse of the food

in harvest, processing, and distribution. It is most

important to fruits and vegetables, since physical

abuse leads to microbial attack and decay. Packaging to prevent abuse is a key to long shelf life.

With dry materials such as chips, crushing can

lead to unacceptability based on consumer desires, This cannot be equated to open dating or

loss of shelf life, but proper packaging and care

can eliminate this problem.

Wilting. Fresh leafy and tuber vegetables can

deteriorate if subjected to low relative humidity.

Under these conditions, they lose moisture to the

surroundings, resulting in loss of crispness and an

increased rate of senescence reactions with subsequent quality and nutrient losses. Proper knowledge of the rate of moisture loss for various packaging materials and the maximum allowable moisture loss can be used as one means of setting open

dates of use for fresh produce.

Moisture loss/gain. With some food products

such as candy, semimoist pet foods, cakes, and

bread, moisture loss leads to an increase in hardening. If a limit of hardness is known to be unacceptable, predictions of the time to reach this

level based on equations that describe moisture

change with time can be used as one method of

predicting end of shelf life. From this, the open

date for use can be set. Similarly, one can predict

the moisture loss from flour, pasta, and similar

dry products for which a natural loss of moisture

occurs and a net weight limit is set for sale.

Some products that gain moisture have a textural limit at which they become too soft, such as

potato chips, other dried or fried snacks, and

crackers. In addition, some crystalline foods such

as salt, brown sugar, convenience dry-meal

mixes, dry coffee, dry teas, and dried drink mixes

will gain enough moisture to become sticky and

caked. Predicting shelf life, based on a gain of a

critical amount of moisture, is possible if the

temperature/relative humidity conditions are

known as a function of time and the permeability

of a package to moisture is known.
Appendix B—Basic Food Preservation and Deterioration Modes ● 81

Temperature-induced textural changes. Temperature fluctuations per se can affect physical

modes of deterioration. For example, the continuous rise and fall of temperature around a phasechange point leads to melting of fat and the subsequent deterioration of quality of some candies

and formulated foods. In frozen foods, repeated

thawing and freezing cause loss of tissue moisture

and increased chemical reaction rates. If. the temperature fluctuation does not exceed the thawing

point, package ice, caused by evaporation of the

water from the food into the package space with

subsequent freezing as ice crystals, can occur.

This results in consumer unacceptability. In addition, if the water loss is significant from a particular surface region, freezer burn—an undesirable discoloration caused by enhanced chemical

reaction— can occur. This also is unacceptable to

the consumer. Finally, some temperature fluctuations can result in emulsion destabilization of

products such as mayonnaise, margarine, salad

dressings, and dessert toppings.

Knowledge of the sensitivity of these reactions

to the degree of temperature fluctuation and a

knowledge of the possible fluctuations occurring

in distribution and in the home are needed in

order to predict shelf life, In most cases, manufacturers formulate the product to withstand any

abuse that may occur. Heating itself can also

cause textural changes. In this case, the reaction

is usually desirable as in the canning and/or cooking of vegetables, meat, fish, and poultry, Canning

at high temperatures is usually undesirable for

fruits as they lose their desirable crisp texture

and develop a cooked flavor. However, these textural changes are usually not of concern in the

storage deterioration of foods.

Staling. Staling is a mode of deterioration important in processed wheat flour products such

as bread and cakes. The reaction is basically a

crystallization of amylopectin, one of the major

starches present in wheat flour. The rate is increased as temperature decreases—opposite to

that of the chemical, enzymatic, and microbial reactions discussed earlier, Thus to prevent staling,

the food must not be refrigerated. However, not

refrigerating the food can lead to other reactions,

causing loss of shelf life.

Chemically induced textural changes. As mentioned in the section on chemical deterioration,

both lipid oxidation and nonenzymatic browning

can result in breakdown of proteins, leading to

toughening and an undesirable loss of shelf life.

Control and prediction were discussed previously.

BASIC FOOD- PROCESSING PRINCIPLES

The previous section discussed the modes of

food deterioration that lead to loss of shelf life

and gave examples of prevention. In this section,

the basic principles of the major food process

methods are listed.

Use of Temperature

Heat preservation. The use of heat to preserve

foods is based on the principles of:

● destruction of pathogens,

● destruction of spoilage microbes,

● denaturation of enzymes, and

• softening of tissues to make them more digestible.

Blanching, a food process, is the application of

heat under mild conditions, or at high temperature for a short time, to achieve enzyme degradation, drive out oxygen, and soften food tissues. It

is used as a preprocess step for canning, freezing,

and drying to minimize quality and nutrient losses

before the product is preserved.

Pasteurization is a mild heat treatment used to

reduce the number of live micro-organisms in food

so as to extend shelf life as well as to destroy key

pathogens. A pasteurized product is not sterile,

however, so some spoilage organisms can grow

back and will eventually lead to spoilage. Pasteurization can also be accomplished at high temperature for a short time period, which results in the

same reduction of microbes as under mild heat,

but with less cooked flavor.

Canning is the process of heat treatment to

destroy all organisms of pathogenic nature and

most important spoilage organisms. The safety of

the process is based on the time needed to reduce

the population of Clostridium botulinum by a factor of l-million-million at the most heat-resistant

point in the food, since this micro-organism is the

most heat-resistant and most harmful pathogen.

Not all of these types of organisms are killed, however, since some are more heat-resistant than is

Clostridium botulinum but do not grow under normal canned-food storage conditions. If the food is
82 ● Open Shelf-Life Dating of Food

subjected to high temperature (40° to 50° C), they

will grow, causing the food to spoil. Processing to

destroy these organisms will destroy the food

quality. Because an adequate heat treatment is

used, canned “commercially sterile” foods have

lost some color: have lost 20 to 30 percent of some

vitamins; have a cooked flavor; and have developed a softer texture. Subsequent deterioration is

usually confined to chemical modes of decay that

do not require oxygen, since the can is hermetically sealed.

Cold preservation. The basis of refrigeration

and freezing is that the lower the temperature,

the slower the rate of most deteriorative reactions such as senesence, enzymatic decay, chemical decay, and microbial growth. Microbes, in

fact, usually cannot grow below - 5° to - 10° C

so that freezing stops microbial growth. In some

cases, lower temperature increases deterioration

because the fracture of membranes releases degradative enzymes, which occurs in chill injury

and freezing of some fresh fruits and vegetables.

It has been found also that freezing to just below

the freezing point of some foods increases deterioration by chemical reactions. This is because not

all the water is frozen out and the chemicals are

concentrated in the remaining water. Finally, in

refrigerated foods, some microbes grow better at

lower temperatures, since they can compete better against other spoilage micro-organisms and

have a lower optimum growth temperature.

Control of Water Content

Concentration and drying. As water is removed

from a food, less is available as a solvent and

medium for the deteriorative reactions. Thus,

most chemical reactions decrease in rate as the

water content decreases. Unfortunately, in the

process of removing water, the reactants first

begin to concentrate so that the rate of reaction

can initially increase. To prevent this, the temperature is kept low during the process, or the

water removal is done rapidly enough to get

through the danger zone. The degree of drying or

concentration is best represented by a factor that

describes the aW in the food.

Figure B-1 depicts a typical moisture absorption isotherm that gives the relationship between

moisture content (on a dry basis) and aW . On a

general basis, a significant amount of water must

be removed to lower the aW significantly below 1

(e.g., at 1 g H2O/g solids or 50- percent water, the

aW. is still very close at 1.0). AW can also be defined

as relative vapor pressure or by ERH as defined in

equation 1:

a (1)

where

p = the vapor pressure of water in the food

po = the vapor pressure of pure water at the same

temperature of the food

% ERH = the percent relative humidity in equiIibrium

with the food at which it neither gains nor

loses weight

Of consequence is the fact that for most foods

in their natural state the aW is high, and thus rates

of many reactions including microbial growth are

also high. In order to preserve the food, the aW can

be lowered by concentrating, drying, or by adding

water-binding agents such as sugars and salt. The

point on the isotherm of maximum stability is the

BET monolayer value (mO in figure B-1) which is at

a low aW . In general, the rates of most chemical

reactions follow the pattern shown in figure B-2—

that is, the rate of reaction increases above the

monolayer value, reaches a maximum, then decreases again, Rancidity is unusual in that the

rate increases again below the monolayer value.

Basically, as aW is lowered, microbial decay is

inhibited first, with bacteria being the most sensitive and molds the most resistant to lowered aW.

Browning, enzymatic activity, lipid oxidation, and

nutrient loss also decrease as aW decreases, with

NEB showing a definite maximum rate at an aW o f

0.6 to 0.8.

Concentration is used basically as a preprocess

step for foods such as frozen concentrated juices,

concentrated canned soups, condensed sweetened milk, and in the preparation of a liquid concentrate that is to be spray-dried, such as for dry

milk, dry coffee, dry tea, and some dry food supplements like yeasts. In these latter processes,

preconcentration is used because it is a cheaper

way to remove water than is drying. However, because of viscosity effects, not all water can be

removed, so further drying is required. During

concentration, the temperature is usually low,

since a vacuum is used. Thus, a cooked flavor and

nutrient losses are minimized.

In drying, heat is applied and the relative

humidity surrounding the food is lowered so that

the water will be evaporated from the food. To

achieve both, the air passing over the food is

warmed, supplying the energy to remove the

water and lowering its humidity. Solid piece materials like vegetables for soup mixes are dried in

an air tunnel at 50° to 65° C for 4 to 8 hours.

Slurry material like potatoes are dried in thin
Appendix B—Basic Food Preservation and Deterioration Modes .83

1.0

0.9

0.8

0.7

0.6

0.5

0.4

Typical isotherm

[lower region]

2

Moisture content (g H,O/g dry solids)

4

0.3

0.2

0.1

1

Figure B-1 .—Moisture Content v. Water Activity

Figure B-2.— Effect of aw on Rate

Relative

rate

aW

layers on hot rotating drums (I ZOO to 1400 C) in 2

to 3 minutes. Although the latter process is at a

higher temperature, since it is shorter in time,

less quality and nutrient damage takes place.

Concentrated liquids can be dried by spraying

into a vertical tower through which air at 200

0 t o

250° C is passed. In this case, drying occurs in 3

to 20 seconds, so very little damage takes place.

Freeze-drying creates the least damage, since it is

done at low temperatures in a vacuum. In each

case, the principle is to lower the water content

and thus the aW to a level such that during storage, reactions proceed at a very slow rate. The

optimum for most foods is at the predicted monolayer value.

It is thus imperative that good packaging be

used to prevent the chemical reactions described

above, to prevent moisture gain to the point of

microbial growth, and to prevent any physical

changes caused by moisture gain. If the product

contains unsaturated fat, it must also be vacuum

packed or nitrogen-flushed to slow the reaction.

The rate of oxidation does not drop as much as

desired at low oxygen pressure, but the lowering

of total oxygen availability limits the overall extent of the reaction. Antioxidants actually have a

much better effect on limiting the reaction but

may not be able to be incorporated into all dry

foods, In some cases like cereals, the antioxidants

are lost in the baking process, so they are added

into the packaging material.

Humectant use. Rather than removing water by

drying, the ability of the water present in foods to

act as a medium and solvent can be reduced by

adding water-binding agents (humectants) to the

food. All dry food solid components have this
84 ● Open Shelf-Life Dating of Food

ability, but the lower the molecular weight, the

better the aw

-lowering effect. The common agents

used are called humectants. Sugars and salts are

such agents, having in fact been used as ancient

preservation processes in fermentation, salting,

and sugar curing. Addition of sugar or salt in

these curing processes is required to lower the aW

to a level below which pathogens and/or spoilage

microbes cannot grow, and in the case of fermentation to allow the desirable microbes to grow.

Control of pH by adding acid and growth inhibitors such as antimycotics may be used in conjunction with the humectants where fermentation

is undesirable. The result is a shelf-stable food

that does not require refrigeration. Common examples are the intermediate-moisture pet foods,

confectioneries, some bakery goods, and breakfast tarts. These foods are subject to chemical deterioration because of the high aW and to moisture

loss if left in a dry environment,

Extrusion. Extrusion is a process utilized for

many cereal foods, dry snacks, dry animal food,

and semimoist pet foods. In this process, a dough

is made which is then passed at high pressure by

screw action through a cylinder that is heated.

The heat causes the components to interact, giving the desired flavor, color, and texture, and as

the product releases from the screw, the internal

steam in the paste expands and flashes off, This

results in further textural changes and drying of

the product. In some cases, further air-drying

may also be used. Packaging requirements and

deterioration mechanisms are similar to that

described for dry foods. Of significant importance

is moisture gain that can result in a soft, undesirable texture.

Other methods. Deep-fat frying is a drying

process in that the hot oil provides the heat to

evaporate off the water. In this process, the oil

replaces the water in the pores of the food. In baking, the hot air in the oven serves as the drying

medium—the longer the baking time, the lower

the final moisture of the product. Freezing also

can be considered as a drying process; however,

the liquid water is converted into a solid that

becomes unavailable, It should be noted that for

most foods, about 20 to 30 percent of the water is

still unfrozen at – 200° C. Therefore, reactions

are not stopped by freezing; they are only slowed

down due both to lower aW and low temperature,

Chemical Preservation

Fermentation. Fermentation is one of the oldest

of the known food processes. In this method, a

desirable organism is allowed to partially convert

some of the carbohydrates of the food material

into acid, alcohol, and flavor compounds. This can

be done naturally by changing the environment,

especially the aW , of the food so that the desired

organisms can grow (for example, adding salt to

cabbage which inhibits spoilage but allows desirable bacteria to grow). Industrially, a starter

culture of the desired organism is usually added

to ensure that proper fermentation takes place.

The basic principle of the process is to allow the

formation of desirable chemicals, such as flavor

components and acids or alcohol, the latter of

which prevents the growth of undesirable spoilage or pathogenic organisms. The shelf life of fermented foods is limited by the growth of the desired organism. In some cases, further processing

is done such as in pasteurizing beer, wine, and

vinegar, or the product is kept refrigerated such

as in yogurt and cheeses.

Additives. Chemical additives can be used to

preserve and/or prolong the shelf life of foods.

Each has a specific action by which it operates,

The various classes are listed below.

●

●

●

●

Acids, such as citric and phosphoric acid.

These lower the pH and inhibit undesirable

microbes as well as slow undesirable enzymatic and chemical reactions. Acids also

contribute to flavor,

Humectants, such as salt, sugar, and glycerol. These bind the water present, lowering

the aw

, and thus reduce the rates of

microbial growth, enzymatic activity, and

chemical reactions.

Smoking of foods. This process deposits

chemicals from the smoke of burning wood

chips onto the surface of foods that inhibit

microbial action. The heat also destroys

some of the microbes. Because of potential

toxicity problems, most manufacturers today

use a liquid smoke product from which toxic

components have been extracted.

Metabolic inhibitors, such as calcium propionate and sodium benzoate. These are chemicals that take action against specific types

of microbes. They are used where further

processing of the food results in undesirable
Appendix B—Basic Food Preservation and Deterioration Modes ● 85

quality and nutritional changes. Gases can

also be used as chemical sterilants and to kill

organisms in grain. Ethylene oxide is an example as is chlorine applied in a solution to

the surface of fresh meat.

Anticaking agents, such as the silicates.

These are high water-binding agents used in

dry-powdered or crystalline foods to prevent

caking by selectively binding the water.

Antioxidant, such as BHA and BHT. These

act in the lipid oxidation reaction to slow the

rate and thus extend shelf life.

Chelating agents, such as EDTA and citric

acid. These chemicals tie up trace metals to

prevent them from catalyzing undesirable reactions such as rancidity.

Others. Other chemicals such as calcium

salts are used to prevent softening of fruits

and vegetables during the canning process.

Sodium polyphosphates help to hold water in

cured and canned meats. Sulfite not only inhibits microbes but slows down enzymatic

browning reactions. Some additives are used

for mainly esthetic purposes to enhance or

restore those flavors or colors lost during

normal preservation or for manufacture of

engineered foods. Finally, nutrients can be

added to

tion.

Separation

new foods or

out of milk or

restore those lost during preservaSeparation

processes are used to either create

ingredients, such as making butter

to transform a raw food into a more

DISTRIBUTION

Once a food is preserved and packaged, it is not

stable forever. Each food system slowly decays or

deteriorates to the point where it is unacceptable.

One goal of open dating could be to give consumers information as to the shelf life of the product

so that it is consumed before it is unacceptable.

The loss of acceptability, however, may not mean

the product is inedible—it only means that the established consumer quality unacceptability standard has been exceeded. The problem is therefore

twofold: I) setting a standard for unacceptability

and 2) determining or predicting the loss that occurs from point of distribution to point of consumption.

digestible or more stable form. Making flour from

wheat is an example of the latter. There are many

different processes that incorporate in general

those methods already discussed above. For example, in the manufacture of instant coffee, the

bean is fermented, ground, roasted, leached to

form a liquid (the separation step), concentrated,

then spray-dried and packaged. The shelf life of

the product would depend on the effects of each

step.

Gas Atmosphere Control

The shelf life of many fruits and vegetables depends on the rate of respiration after harvest

which uses up the stored energy. This rate can be

reduced by reducing the oxygen or by increasing

C O2

. The methods are generally classified as CA

Storage (Controlled Atmospheric Storage) and include:

● reduction and control of O2 by use of nitrogen,

● hypobaric storage by pulling a vacuum either

in a large truck or in a pouch, and

● use of both increased nitrogen and increased

C O2 in the headspace.

C O2 can also be injected into the headspace of

dairy and meat packages to reduce microbial

growth and increase shelf life. Vacuum-packaging

with CO2 injection is used to enhance shelf life of

poultry products, Overall, shelf life in these cases

depends on the degree of maturity after harvest,

and temperature and permeability of the package

to oxygen and CO2

.

HAZARDS

Data on actual

various products

shelf-life modes and shelf life of

based on some endpoint standards have been collected and are in the main data

base part of this study. Appendix C discusses the

second problem—that is, based on environmental

factors, how can one predict changes in shelf life.

The important environmental influences include:

●

●

●

●

temperature—increasing, decreasing, fluctuating:

moisture (relative humidity)—gain, loss;

oxygen level; and

light.
Appendix C

Technological Evaluation of

Shelf Life of Foods

INTRODUCTION

Appendix B covered the major modes of deterioration and the principles of processing foods. It can be concluded from that appendix that one of the major environmental

factors resulting in increased loss of quality and nutrition for most foods is exposure to increased temperature. The higher the temperature, the greater the loss of food quality.

Thus, in order to predict the extent of high-quality shelf life so as to be able to put a shelflife date on a product, a knowledge of the rate of deterioration as a function of environmental conditions is necessary. * Coupled with this would be the need for knowledge of

the actual environmental conditions to which the various classes of foodstuffs are exposed.

Basically, for each food item, each mode of deterioration was studied at several temperatures for up to 3 years. In addition, information as to temperatures in warehouses,

boxcars, etc., was gathered. Many reports and tables resulted from the study. However,

much is not applicable today because the various types of foods are processed differently, different packaging systems are used, the distribution system has changed, etc. Nevertheless, one interesting outcome of the report was a nomograph {figure C-1), which gives

the prediction of quality for various food classes based on some rate of deterioration and

a desired shelf life. What this graph says is that given a certain rate of loss, if it is constant, one can predict the amount of change. Unfortunately, this simple method is not correct for many foods and for many modes of deterioration such as nutrient loss, color

change, and flavor change. This appendix covers the basic principles of how temperature

and other environmental factors affect the rate of food deterioration and how this can be

used to predict the sell-by, best-if-used-by, or use-by date. These methods are not needed

for a pack date.

*The U.S. Army supported some major studies during the late-1940’s through 1953 to gain this information for the military food supply. The studies are summarized in S. R. Cecil<s and J. G. Woodroof’s (1962) “Long Term Storage of Military Rations”’ (Ga. Exp’t Station Tech. Bull. 25).

87
88 ● Open Shelf-Life Dating of Food

Figure C-1 .—Nomogram of Temperature, Time, and

Quality for the Military Ration Items Used in the

Long-Term Storage Tests

k - Individual Items M - meats

C- confections D - dairy-type

B bakery or cereal X- miscellaneous (cocoa discs,

V - vegetable or fruit cocoa powder, meat bars,

soup and gravy base)

{a}

(b)

w

71
Appendix C— Technological/ Evaluation of Shelf Life of Foods “ 89

What equation 2 means is that the percent of

shelf life lost per day is constant at some constant

temperature. This is the assumption used in the

nomograph of figure C-1. Mathematically, if equation 2 were integrated, the amount of quality left

with time as a function of temperature becomes

equation 3:

(3)

In terms of shelf life, this becomes equation 4:

(4)

OF LOSS OF SHELF LIFE

other defIned vaIue as measured In a consumer

test)

In many cases, AC is not a very quantifiable,

chemically, or measurable value and must be

based solely on human panel evaluation. In this

case, Ao is assumed to be 100-percent quality and

A e is just unacceptable quality, Thus, the rate of

deterioration becomes the rate constant in equation 5:

This is the assumption used in figure C-1. Technically, the major problem in shelf-life testing is to

verify that indeed n = O so that equation 4 or 5

can be used. This is not easy to do, although some

modes of deterioration are directly applicable to

zero-order kinetics. These include:

● Enzymatic degradation (fresh fruits and vegetables, some frozen foods, some refrigerated doughs);

● Nonenzymatic browning (dry cereals, dry

dairy products, dry pet foods, and loss of protein nutritional value); and

● Lipid oxidation (rancidity development in

snacks, dry foods, pet foods, frozen foods).

Based on this knowledge, one can predict the

shelf life of a food at a given single temperature if

the amount of loss at any time is known, For example, if it is known that a certain food has lost 50

percent of its quality in 100 days if held at some

constant temperature, then:

Based on this, we could construct figure C-2

which gives the shelf life left as a function of time

(k is the slope of the line). As seen at 40 days,

there is 80-percent shelf life left: at 160 days,

there is 20 percent left: etc.

The main problem in establishing this graph is

determining the criteria of what is to be measured. That is, what is A or how much of A must be

lost to give an end of shelf life as perceived by the

consumer. It must be noted that shelf life is not a

function of time; rather, it is a function of the environmental conditions and the amount of quality

change that can be allowed. The second problem

is that since food distribution occurs at variable

temperatures, this data must be collected at sev- .
90 “ Open Shelf-Life Dating of Food

Figure C-2.—Constant Shelf Life Lost

.

\

20 -

10 -

n . 1 I I 1 1 I I I I

20 40 60 80 100 20 40 60 80 200

Days

eral temperatures to be useful, Methods to apply

this graph to variable conditions are described

later,

Quality-Dependent Shelf-Life Loss

Function

As discussed above, the shelf life in many cases

does not follow a simple constant rate of deterioration. In fact the value of n can range for many

reactions from zero to any fractional value or

whole value up to 2. In fact many foods that do not

deteriorate at a constant rate follow a pattern

where n = 1 , which results in an exponential

decrease in rate of loss as the quality decreases.

This does not necessarily mean that the shelf life

of foods that follow this scheme is longer than

those with a constant loss rate, since the value of

the rate constant is very important. Mathematically, the rate of loss is, as shown in equation 6:

(6)

Integrating equation 6 gives a logarithmic function as shown in equation 7:

(7)

A graphical representation of the amount of

quality left as a function of time is not a straight

line as illustrated in figure C-3. If 50 percent is

lost in 100 days as in the previous example, then

at 40 days, there is 76 percent of the quality left.

For a constant rate of loss, there would be 80 percent left, At 100 days, both mechanisms give the

same percent left, but after this time, the quality

loss slows down for the exponential mechanism

and theoretically never reaches a zero value, For

example, at 160 days, there is 33 percent left, and

at 300 days, there is still 12.5 percent left. The

types of deterioration that follow an exponential

equation include:

●

●

●

●

●

●

rancidity (in some cases, as in salad oils or

dry vegetables);

microbial growth (fresh meat, poultry, fish,

and dairy products);

microbial death (heat treatment and storage);

microbial production of off-flavors, slime,

etc. (fresh meat, poultry, fish, and dairy

products);

vitamin losses (canned, semimoist, and dry

foods); and

loss of protein quality (dry foods).

Another way of representing exponential decay in figure C-3 is to plot it in semilog as in figure

C-4. The slope of this line is the rate that is constant at constant temperature. Typically, for exponential decay mechanisms, the rate constant

can be represented by 0,,, which is called the half

life. Mathematically, if one knows the amount of

deterioration at any time at some constant temperature and if it follows a first-order reaction,

figure C-4 can be easily constructed.

Figure C-3.—First-Order Degradation

20 40 60 80 10020 40 60 80 200 20 40 60 80 300

Days
Appendix C— Technological Evaluation of Shelf Life of Foods ● 91

Figure C-4.— First-Order Log Plot

I I I I I I

50 100 150 200 250 300 350

Days

Very little data exists

of She9f-Life Loss

that describes food deterioration by orders other than zero or first. Lee

et al. (J. Food Sci. 42:640, 1977) and Sing et al. (J.

Food Sci. 41:304, 1976) have described the deterioration of vitamin C in liquid foods such as tomato

juice or canned infant formulas by a second-order

reaction. In this case, the reaction is dependent

on both ascorbate and oxygen—as the oxygen is

depleted, the rate of loss of ascorbate becomes

less than that predicted by a first-order reaction,

Labuza (Critical Rev. Food Tech. 3:355, 1971)

has reviewed the area of lipid oxidation kinetics

and has found that oxygen uptake generally

follows a half-order reaction with respect to oxygen for relatively pure lipids. However, addition

of antioxidants changes the order to first order.

In complex foods, however, the data best fit zeroorder kinetics.

When sensory quality change is plotted against

time, not infrequently the axiom “fresh is best”’ is

violated. For example, Kramer et al. (J. Food Qual.

1:23, 1977) found an improvement in sensory

quality of certain prepared frozen foods after

frozen storage for 3 months. After 6 months of

storage, sensory quality began to deteriorate and

continued by approximately a first-order reaction. The entire curve, however, could best be

fitted as a cubic polynomial. Similar results were

obtained with reportable-pouch packed items by

Salunkhe and Giffee (J. Food Qual. 2:76, 1978). A

typical curve for this type of response is shown as

figure C-5.

Such sensory responses can be explained on

the basis of psychophysical characteristics inherent in sensory evaluations. They do not contradict the above general principles of the

kinetics of shelf-life loss. All that is indicated is

that consumers prefer (best) what they are accustomed to, which is not always the freshest

product. Thus, in the case of preference for 3-

month-old frozen foods, the reason was that the

products were initially overspiced and reached

an optimal flavor blend and intensity after 3

months’ storage. In the case of the pouch/canned

products, consumers preferred products that

were slightly degraded over the fresh. These notunusual sensory responses indicate first the great

difficulty in attempting a generalized prediction

equation for shelf life and the need to study each

product individually. They also indicate that

freshest is not always best, although open dating

is predicated on the assumption that consumers

are convinced that freshness and sensory quality

are the same.

Figure C-5.—Initial Quality Gain Prior to

First. Order Degradation

Best

— -- -—- - -

Time
92 . Open Shelf-Life Dating of Food

TEMPERATURE DEPENDENCE OF RATE OF DETERIORATION

The above analyses of loss of quality were

derived for a constant temperature situation. The

temperature-dependent part of the rate of loss

equation is the rate constant k. Theoretically, it

obeys the Arrhenius relationship which states

that the rate constant (or rate) is exponentially

related to the reciprocal of the absolute temperature. A plot of the rate constant on semilog paper

as a function of reciprocal absolute temperature

(l/T) gives a straight line. A steeper slope means

the reaction is more temperature-dependent—

that is, as the temperature increases, the reaction

is faster, It is possible that food can deteriorate

by two different mechanisms with different temperature dependencies. For example, dry potatoes can go rancid and can become brown. The

rates of each would have different temperature

functions. What this means is the dominant mode

of deterioration could change with increasing

temperature to the faster reaction. This could be

a problem in predicting shelf life,

Most data for modes of deterioration in the literature do not give rates or rate constants but

rather are in the form of overall shelf life as a

function of temperature, Mathematically, if only a

small temperature range is used (no more than

20° to 400 C range), the data will give a fairly

straight line if the shelf life for some quality measurement is plotted on semilog paper as a function

of temperature as in figure C-6, This figure illustrates the temperature sensitivity of two foods or

two modes of deterioration, both giving a shelf life

of 200 days at 25° C. Theoretically, to construct

this plot one needs: 1) some measure of loss of

quality, 2) some endpoint value for consumer unacceptability, 3) data to measure the time to reach

this endpoint, and 4) experiments to measure this

loss for at least two temperatures so the line can

be constructed. The more temperatures used, the

better the statistical significance of the data.

It is obvious from the graph that the steeper the

slope, the more sensitive is the food (or the reaction) to temperature. A measure of this sensitivity

is called the Q10 of the reaction that is defined in

equation 8:

Q 10 

=

rate of loss of quality at temperature (T + 10°C) (8)

rate of loss of quality at temperature T ° C

The Q10 can also be calculated from the shelf-life

plot as in equation 9:

Q10 =

shelf Iife at T°C (9)

shelf Iife at (T+ 10°C)

Figure C-6.--Shelf-Life Plot

I 1

20 25 30 35 40 45

Temperature “C

which assumes that the rate is inversely proportional to the shelf life.

As an example from figure C-6, it can be calculated that for food A, the Q10 is:

Thus, food B or reaction B is much more sensitive to an increased temperature than is A.

This graph has practical applications in studying loss of shelf life. To illustrate, if studies at two

different temperatures are made, the shelf life at

some lower temperature can be predicted if the

line is assumed to be straight. One cannot, however, study the deterioration at only one temperature, since it is not possible to predict beforehand
-.

Appendix C— Technological Evaluation of Shelf Life of foods Q 93

the shape of the line or the Q10 exactly. Table C-1

illustrates how important the Q10 would be in predicting shelf life at lower temperatures. It should

be noted that since different reactions may occur

at different temperatures to cause end-of-product

acceptability, the projected line might be incorrect. For example, in figure C-6, reaction B would

cause end of shelf life in 12 days at 300 C, but

below 25° C, reaction A is faster and thus would

be the controlling factor in end of shelf life if the

figure referred to two major deterioration modes

of a single food item.

Table C-1 .—Weeks of Shelf Life at a Given

Temperature for Given Q10

Q 1 0

Shelf life at

2 2.5 3 4 5

50° c . . . . . . . 2 2 2 2 2

40° C . . . . . . . . . . . . . . . . . 4 5 6 8 10

30° C . . . . . . . . . . . . . . . . . . . 8 12.5 18 32 50

20” C . . . . . . . . . . . . . . . . . . 16 31.3 54 2.5 4.8

SHELF-LIFE Prediction FOR VARIABLE TEMPERATURE

Given that data as to the mathematical representation of the reaction causing end of shelf life

can be obtained and a shelf-life plot constructed,

some simple expressions can be derived to predict

the extent of deterioration as a function of variable time/temperature storage conditions. From

this, either a use-by date can be calculated or a

sell-by date evaluated in which some shelf life left

for home storage is figured in.

For zero order, the expression is as follows in

equation 10:

I 1)

1 \

If the time/temperature history is broken up into

suitable time periods as illustrated in figure C-7,

the average temperature in that time period can

be found. The rate constant for that temperature

is then calculated from the shelf-life plot using a

zero-order reaction, and this rate constant is

multiplied by the time during the period. These

then are added up to get the amount lost for a

total of n segments.

If shelf life is based simply on some time to

Figure C-7.—Temperature/Time History

Ti

reach unacceptability. equation 10 can be simpli-

(11)

This equation says that the fraction of shelf life

lost for holding the product at some temperature

is equal to the time [0]) held at that temperature divided by the total time (0s) a fresh product would

last if held at that temperature.

To employ this method, the temperature history

is divided into n suitable time periods; the average

temperature Ti at each time period is evaluated;

the time held at that temperature Oi is then divided by the shelf life (l. for that given tempera-
94 ● Open She/f-Life Dating of Food

ture. The fractional values are then summed up to

give the total fraction of shelf life consumed. The

time left at any storage temperature at which the

consumer may hold the product is the fraction of

shelf life remaining (1 – fc

) times the shelf life at

that storage temperature from the shelf-life plot.

The U.S. Department of Agriculture (USDA) developed this method, referred to as TTT, or

time/temperature/tolerance method (Conference

of Food Quality, Nov. 4, 1960, USDA Agr. Res.

Service, Albany, Calif.). Extensive references to

its use can be found in the literature. For example, Gutschmidt (Lebensmittlen Forschung und

Technol. 7:137, 1974) applied this to storage-life

prediction of frozen chicken with excellent results, It must be remembered, however, that this

only applies for reactions with a zero-order deteriorative mechanism—a constant rate of loss at

constant temperature.

Zero-Order Shelf-Life DevicesPresent Technology

A device that can be attached to a frozen food

package to integrate time/temperature exposure

in the manner discussed above has been developed (Kockums Chemical Company, Biomedical

Science Division, Reston, Va. ), Unfortunately, the

device (i-point TTM) can only be used for reactions with the same temperature sensitivity or Q10

if shelf life is to be predicted. Those available in

1977 were i-point #1 Q10= 140; i-point #2 Q10= 6; ipoint #3 Q10= 36. These devices could be used,

however, to evaluate abuse during storage, and

modifications can be made to get other Q10’s.

The i-point device is based on an enzymatic reaction that is activated by breaking a seal which

mixes the enzyme with a substrate. Color changes

that occur with the subsequent reaction can indicate the days of shelf life left or the extent of degradation. Unfortunately, these devices have temperature responses that change above about

— 10° C, resulting in a different Q10 (of about 2.2).

They also have very rapid response times above

+ 10° C, so they cannot be used for foods with

long shelf life (e.g., dehydrated foods).

The present cost of these devices prohibits

their use on individual packages, but they can be

put on cases or pallets to evaluate abuse conditions, Of course, if they are on the outside of a

food carton, they will respond to temperature

change more rapidly than does the bulk of the

food, so the predicted shelf life would be less than

the period of time the food could actually last.

A different device using the gas diffusion principle, which also integrates time and temperature, is available (Info-Chem, Fairfield, N.J.). After

activation, a gas crosses a permeable barrier in

the device to react with another chemical, causing a color change along a scale. The barrier

property controls the temperature sensitivity. The

Q 10's are: TTW-10 Q 10= 1.68; T T W

-15 Q 1 0= 2.29 ;

T TW

-20 Q10 = 2.88; and TTW-25 Q10= 4.03.

A factor limiting the use of these latter devices

is that they respond much too slowly at temperatures below freezing, so they probably cannot be

used for refrigerated frozen foods. Even at 4° C,

the devices all have a response life of 750 days. If

the reaction rate were faster or the indicator was

made more sensitive, they could be especially

useful for very sensitive refrigerated pharmaceuticals to indicate if the drugs have been abused by

holding at high temperatures. However, the devices are applicable for semiperishable foods

with a shelf life of 30 days to 1 year at 15° to 38°

c.

Other devices are available that integrate time

and temperature but have much shorter response

times. The 3-M Company (Minneapolis, Minn.) and

Tempil Company (South Plainfield, N. J.) have developed abuse temperature/time integrators.

These devices use the melting-point principle in

which a waxy material melts at a given response

temperature and is absorbed by a wick that develops a color along a visible scale (much like a thermometer) as long as the device is held above this

critical response temperature. The device does

not integrate absolute shelf life as the other devices: rather, it integrates exposure to some temperature above a set limit. This, however, is

useful if the product has a very high Q10 (i.e., the

food is very sensitive to high temperature). The

devices are also useful for products with a shelf

life of less than 1 week.

Several studies in the past have been made to

test the reliability of these time/temperature integrators (K. Hu, Food Technology, August 1972; K.

Hayakawa, ASHRAE J., April 1974; C. Byrne, Food

Technology, June 1976; and A. Kramer and J. Farquhar, Food Technology, February 1976). In

essence, they have found that many of these indicators become unreliable if they are exposed to

high temperature prior to activation. In addition,

the response characteristics in many cases do not

match manufacturers’ specifications.

Since these studies were published, the indicators have been modified, so performance may be

better although there is nothing available in the

scientific literature, However, the major problem
Appendix C— Technological Evaluation of Shelf Life of Foods s 95

is still to develop an indicator that exactly

matches the Q10 for the food if it is to be used on an

individual food package to indicate amount of

shelf life left. The Australians have devised such

an indicator that has the capability of electronically setting the exact Q10 desired (J. Olley, Int’1

Inst. of Refrigeration, Australian National Committee, Joint Meeting of Commissions, Melbourne,

Australia, September 1976). The device is useful

as a research tool for monitoring a distribution

system but is not practical for everyday use on

packages. The significance in stimulating further

development of shelf-life devices is that they could

give the shelf life directly and would be a major

benefit to the consumer.

Exponential Decay Shelf-Life

Prediction

As with the mechanism measuring the constant

loss of shelf life, an equation can be developed to

predict the amount of shelf life used up as a function

that

tion

of variable temperature storage for foods

decay by an exponential mechanism. Equa12 is:

(12)

where A is the amount left at the end of the time/

temperature distribution, and k,tll is as was discussed for the constant-loss equation. Unfortunately, there are no reports in the literature for

testing the validity of this equation in the measurement of shelf life as has been done for constant loss rates for frozen foods. However, application of this equation to the calculation of quality

losses, nutrient destruction, and microbial death

during the thermal processing of canned foods

has been successful (M. Lenz and D. Lund, J. Food

Sci. 42: 989, 1977; J. Food Sci. 42: 997, 1977; and J.

Food Sci. 42: 1002, 1977). Therefore, there is no

reason to believe that this equation and approach

is not applicable to predicting storage life of

foods.

Currently there are no devices that have a firstorder response, and the zero-order devices mentioned above should not be used for a food which

decays by first order unless the extent of reaction

which terminates shelf life is only a small fraction

of the total reaction that can occur, Further research is needed in this area.

Sequential Fluctuating Temperatures

In some cases, a product may be exposed to a

sequential regular fluctuating temperature profile, especially if held in boxcars, trucks, and certain warehouses. This is because of the daily

day/night pattern. Many of these patterns can be

assumed to follow either a square-wave or sinewave form as shown in figure C-8. The amount of

deterioration occurring in this storage sequence

can be calculated by the formulas previously

presented if the proper order of reaction is used.

There have been some papers published that

have developed formulas for calculating the

amount deteriorated for either square-wave or

sine-wave functions. The classic papers have

been by Hicks (J. Coun. Sci. Ind. Research, Australia 17:111, 1944), Schwimmer et al. (Eng. Chem.

47:1149, 1955), and Powers (J. Food Sci. 30:520,

1965). Although not stated exactly in these

papers, the derivations they presented were all

for zero-order reactions. Unfortunately, subsequent work by some researchers has unknowingly

used these equations for predicting changes that

occur for first-order reactions such as microbial

growth and vitamin C degradation. Recently,

Labuza (J. Food Sci. 44, 1979) has derived the applicable functions for exponential reactions, but

they have not been tested as of yet.

It also should be noted that using the mean temperature for either the sine or square wave to

predict the loss that occurs does not give the same

results as the actual amount of degradation. This

is because the shelf life (or the reactions causing

it) are exponentially related to temperature; thus

the actual amount of degradation is always more.

Figure C-8.—Sequential Regular Fluctuating Profile

Time
96 ● Open Shelf-Life Dating of Food

Based on this, the reaction can be assumed to be

occurring at some effective temperature that is

greater than T mean. In the same paper Labuza

(1979) has derived the necessary equations.

Other Temperature Effects

Two other phenomena can occur in foods as a

function of temperature that lead to loss of shelf

life—namely, staling and phase change. Staling is

a process which occurs in bakery items and is related to the crystallization of starch components.

In staling, the rate of loss of shelf life increases as

temperature decreases. The kinetics are exponential in nature with a Q10 of around 2 to 3. For a

recent review of staling, see W. Knightly, Bakers’

Digest, No. 5, 51: 52, 1977.

A second area is that of phase change including

thawing, freezing, and fat-melting—solidifying

phenomena. Although no mathematical models

can be developed to predict how these would affect loss of shelf life, it is known that thawed

frozen foods are very subject to microbial deterioration, and the melted fat can oxidize faster as

well as cause loss in desired texture. Commercial

devices that indicate whether a frozen product

has been exposed at temperatures where it can

possibly thaw have been developed by the same

companies that have made the time/temperature

integrators. These are cheap enough to be used on

individual food packages and would be useful to

indicate abuse. However, a major drawback is

that the device could melt before the food does

and thus would not be truthful.

UTILIZATION OF TEMPERATURE-DEPENDENCE EQUATIONS

The previous section outlined the means by

which equations could be used to predict shelf

life, Obviously, these equations could be used to

set a sell-by date in which the fraction of shelf life

used up in the distribution/marketing system

could be calculated. From this, information could

be included on the package that would indicate

the expected shelf life for given storage conditions in the home. Similarly, the same calculations

including specified home storage could be used to

set a use-by date. However, some of the problems

that could occur which would make these calculations meaningless are:

1.

2.

3.

4.

5.

The product used to develop the shelf-life

data or graph may not be the final product

marketed, since the shelf-life studies should

start early in the product development.

As in 1, the product tested may be produced

in the lab or pilot plant and therefore will not

be subjected to the same conditions as would

the product produced in the plant.

The ingredients can vary because of growth

conditions, rain, sunshine, etc., as well as

genetic variety. The ingredients may also be

stored for variable times.

Labels must usually be made early in the

year prior to the growing season so that if effects as in 3 occur, it would be impossible to

account for them.

The calculations to set the date must be developed for the average conditions. Some

6

7.

products thus will be out-of-date before the

time on the label just because of statistical

variation.

Some products may be mishandled by distributors and supermarket personnel and thus

could lose shelf life before the label date.

Product shelf-life tests can only be done on

individual packages. During a large part of

the distribution time, though, these packages

are in cartons, which in turn are in cases,

which are in pallets. Therefore, exposure to

the external conditions is not so drastic—

especially for those cartons in the center—

and the product may have a shelf life greater

than the label states, Good food could then be

wasted.

Since other factors could also be included in

this discussion, it is obvious that setting a true

shelf-life date for each package cannot be done.

Only averages can be calculated, and these only

where good data exist. Collecting this data is a

very time-consuming and expensive process, especially where sensory panel evaluations must be

used. Thus, it is probably best to not require open

dating of all food products but to mandate what

can be put on the label if open dating is used.

Based solely on kinetic implications with respect

to temperature, a sell-by date with home-storage

information or a best-if-used-by date seems most

logical.
Appendix C— Technological Evaluation of Shelf Life of Foods ● 97

MOISTURE EFFECTS ON SHELF-LIFE PREDICTIONS

Moisture Gain or Loss Equation

to Reach Critical Value

Moisture gain by dry or semidry foods can lead

to several modes of deterioration, including microbial growth, loss of crispness, loss of softness,

hardening, and caking. The moisture gain or loss

for a food held at constant temperature and exposed to a given external relative humidity can be

predicted from simple engineering relationships

as reviewed by Labuza et al. (Trans. ASAE 15:

150, 1972). The basic equation 13 is:

P out = vapor pressure outside the package

P in vapor pressur e inside the package— I e , the

vapor pressure of water from the food

A = package surface area

As with temperature, an increase in external

humidity conditions would decrease the time it

would take for a given packaged dry food to reach

the

that

●

●

●

●

●

undesirable moisture content. The factors

would be needed to predict this time include:

The moisture absorption isotherm as in

figure B-1.

The package film permeance k/x. Manufacturers usually list a range of values for a

given packaging film. However, actual values can be obtained by simple tests.

The ratio of the package area (A) to dry

weight (Ws

) contained,

The initial moisture content mo and critical

moisture mo above or below which one

should not go. The critical moisture me—the

point of unacceptability—must be found

from studies of the food at different moisture.

The relative humidity and temperature to

which the product will be subjected, From

this and the isotherm equation me

, the moisture content the food would achieve if it had

no package can be found. In addition, the

value of the vapor pressure of water (Po

) at

the temperature of the test can be obtained

from standard tables.

Given these values, equations 14 and 15 can be

found, which give the time (0) to reach a certain

moisture content (m). The exponential term of

moisture is plotted as a function of time in figure

c-9.

Figure C-9.— Moisture Gain

r

i

v

v

I

I

“,

1234 5 7 9 10 11 —

e (time) OS

As indicated in figure

(14)

(15)

C-9, if condition III were

the actual food-package system, storage under

condition I would decrease the time to reach the

critical moisture by a factor of 11-2, or 5.5 times.

This would occur if the film used had 5.5 times

greater water permeability. The same acceleration in loss of shelf life would occur if the product were stored at a temperature that would raise

the vapor pressure of water (Po

) by 5,5 times. At

100-percent relative humidity, the vapor pressure

of water ranges from about 17 mm Hg (at 20° C) to

72 mm Hg (at 45° C). Therefore, a decrease in the

loss of shelf life of about 4.5 times would occur if

the product were stored at the higher temperature and same relative humidity.

Food package size also can affect shelf life with

respect to moisture gain. Since the ratio of package area to food weight contained (A/W,) decreases by one-third R (where R is the average
98 ● Open Shelf-Life Dating of Food

radius), a package of smaller size has a shorter

shelf life as compared to a larger one.

In practice, in testing for shelf life of foods, researchers use a combination of higher humidity

(percent RH) and temperature (T) than the food

would normally be subjected to. Most food processors suggest, for dry foods, that the average temperature/humidity during distribution is 21° C at

50-percent RH and thus apply some factor by

which the food shelf life under the adverse condition is multiplied by to give the average shelf life,

Using this method and equation 13, the shelf

life of a food for which the mode of deterioration

is moisture gain or loss can be predicted if the external conditions of distribution and marketing

are presumed to remain constant. However, in the

real world, the humidity can vary as well as the

temperature, Fluctuating temperature effects

were discussed previously. In general, higher humidities are associated with higher temperature,

but no exact pattern of correlation exists. For example, if a T/percent RH distribution were known

as in figure C-10, the time 0 to reach a given

change in moisture would have to be calculated

by breaking up total time into n small AOl parts.

For each AO, a Ti and percent RHi could be read

off the graph. Then to get the change in moisture

for that segment of time (starts at mi and ends at

● Determine the vapor pressure P o from a

standard table.

● Derive a new me from the isotherm for the

new external percent RHi

. If me is less than

mi at A@i$ the loss equation would be used; if

it is greater than mi

, the gain equation is

used,

From these steps, the value of m as a function of

time could be calculated, and thus 0, could be

found, These calculations, in fact, could be used

to predict the net-weight losses of cereals and

flour under given variable external conditions—

another currently controversial regulatory issue.

Constant Weight Loss Prediction

Two situations exist in which a more simplified

version of weight loss can be derived: 1) loss of

moisture from frozen foods and 2) loss of moisture

from fresh produce such as meats, fish, vegetables, and fruits, In both cases, a constant external

humidity and constant temperature are assumed,

based on the fact that either frozen or refrigerated storage is used. The solution for both situations is based on equation 13.

Figure C-10.—Storage Conditions

Given that k/x, the area A, the external humidity and Pout are constant, the question is to determine if Pin is constant. By definition, Pin is the

vapor pressure of water in the food. For a frozen

food, Pin is determined solely by the temperature

that pure ice would have at the storage temperature and thus could be read from a standard

table. Since fresh produce have moisture contents

in the range of 60 to 98 percent and the loss of

weight to reach an unacceptable quality is not

large, the vapor pressure pin is equivalent to that

for liquid water at the storage temperature. Thus

equation 13 becomes equation 16:

If mc is the critical moisture content as set by netweight limitations or by quality and mi is the initial moisture for a package containing W, grams

of dry solids of a food, the time to reach end of

shelf life is determined by equation 17:

This equation could be used to predict how long a

food would last for certain conditions. For example, for a vegetable like celery in a package for

which we would want 12 weeks of shelf life before

it lost enough water to lose crispness, at a refrig-
Appendix C— Technological Evaluation of Shelf Life of Foods “ 99

erated storage

could prevail:

P in =

P out =

.“. A p =

If the celery

of 5° C, the following conditions

654 mm H g

80 percent R H X 6.54= 523 mm Hg

normaI condition of storage

1.31 = 654 - 523

had an initial moisture content of

95 percent and there were 10 ounces in the bag,

the dry weight Ws would be 14 grams. Celery

loses its crispness when it loses about 5 percent of

its weight in water (mc = 18; mi = 19). Using polyethylene with a k/x = 1 and a bag of 0.1 m

2

, the

shelf life would be about 3 months based on water

loss, thus achieving the 12 weeks, Of course, in

this time, microbial growth could decay the food.

The realistic problem is defining some critical

moisture content for the particular food. In real

life, both temperature and humidity vary: thus an

iterative procedure as described earlier must be

used based on a constant weight loss by equation

16 for each of these periods.

Moisture Change for Constant

External Temperature and

Humidity Conditions

In a classic research endeavor, Karel and

Labuza developed the mathematical techniques

that combined the equations for prediction of

moisture change with the reaction kinetics of

various modes of deterioration as a function of aw

(Air Force Contract F 41-609-68-C-0015, February

1969, Optimization of Protective Packaging of

Space Foods). These theories were tested in detail

by Mizrahi et al. for predicting loss of shelf life of

dehydrated cabbage undergoing nonenzymatic

browning by a zero-order mechanism (J. Food Sci.

35:799, 1970, J. Food Sci. 35:804, 1970). The results were extremely satisfactory.

The basic steps needed to be able to predict

end of shelf life under these conditions are:

●

●

Store the dehydrated product at several constant temperatures and various relative humidities and measure extent of deterioration

with time. Much data like this is available in

the literature for dehydrated foods, especially concerning vitamin loss. At least three humidities (a w

's) are required. The reaction

order must be determined.

Decide what extent of deterioration is considered to be unacceptable. Plot the log of

the time to reach this extent for constant

temperature versus the aw of the product as

in figure C-11, Generally, a straight line

above the monolayer water activity should

be obtained at constant temperature.

Using either the moisture gain or loss equation and proceeding step by step as previously described, predict the moisture content

change as a function of time for some constant external temperature and humidity

(figure C-12).

Using the m versus 0 graph, divide the time

into small AO segments (figure C-12) a n d

measure the average moisture content in this

time period.

For each moisture content and temperature,

calculate the change in quality using the

previously developed equations.

As noted, these steps have been tested and

found to be very good in predicting shelf life,

Mizrahi and Karel (J. Food Sci. 42:958, 1977) have

recently shown that this procedure can be simplified by storing the food in a very permeable

material at a given high-relative humidity and

Figure C-II .—Shelf Life as a Function

of aW and Temperature

1 1 I I I

0.2 0.4 0.6 0.8 1.0

Water activity
100 . Open Shelf-Life Dating of Food

Figure C-12.–Calculated Moisture Content v. Time

comparing the extent of degradation to any other

condition by a ratio method. As in the above solutions, this assumes constant external temperature and humidity.

Moisture Change Under Variable

External Temperature and

Humidity Conditions

The previous section described predicting the

loss of shelf life for constant external humidity

conditions. The same procedures can be used to

calculate the extent of reaction for variable temperature and humidity conditions applying the

kinetic derivations as a function of temperature

from the section “Shelf-Life Prediction for Variable Temperature. ” The first step would be calculating the moisture content as a function of time

for a variable time/temperature/humidity distribution as previously shown. Then, applying either

zero- or first-order kinetics, the extent of degradation is calculated for small time segments knowing

the moisture content, aw

, temperature, and external relative humidity at that point.

Although this is the real world situation, no

literature exists that has tested this idea, so it is

not known how good the predictions would be for

estimating a shelf-life date that could be used on a

food package. Even more critical is the fact that

the external humidity distribution is even less

well-known for food systems and is not as easily

predicated as is the external temperature distribution, Therefore, only rough estimates can be made

of the actual loss of shelf life.

Of course, another way that this could be controlled would be to use a pouch with a very low

water permeability, thereby eliminating the moisture-change problem. This could extend food shelf

life, but at the expense of using more precious

raw materials (petroleum, aluminum, etc.) and at

greater cost to the consumer, It is this tradeoff

that the consumer must make in terms of food purchase—that is, a longer guaranteed shelf life at a

greater cost, or a possible out-of-date food at

lower cost. In addition, no devices exist that can

integrate time/temperature/humidit y conditions

with respect to shelf life,

OXYGEN EFFECTS ON SHELF LIFE

Introduction

oxygen availability is another factor that can

affect the time to reach end of shelf life and thus

the open date put on a food package. Several reactions in which the rate is a function of oxygen

availability include:

● microbial growth,

● senescence of fruits/vegetables,

● browning of fresh meat,

● rancidity (lipid oxidation), and

● vitamin C deterioration.

Very little information is available on the use of

shelf-life prediction equations with respect to oxygen as well as temperature and moisture content.

Karel (Food Technol. 28:50, 1974) has reviewed

this area. Part of this void is caused by the difficulty in 1) designing simple equipment to control

oxygen levels during experiments that utilize oxygen as one parameter and 2) measuring and controlling oxygen in food packages,
Appendix C— Technological Evaluation of Shelf Life of Foods ● 101

Fruit and Vegetable Senescence

Once fresh produce is harvested, it continues

its biological processes of drawing upon internal

starch and sugar stores for an energy supply.

This will continue until the supplies are depleted

or the buildup of breakdown products affects the

tissue in such a way that spoilage or microbial attack occurs. This rate of biological reactivity is a

function of oxygen availability in terms of oxygen

pressure as described by figure C-13. As seen, the

lower the oxygen pressure (PO 2

), the lower the

rate of oxygen uptake via respiration, or conversely, the lower the rate of loss of stores. Thus,

a low PO2 will give a longer shelf life. Unfortunately, below a certain PO 2 level, an anaerobic process of incomplete breakdown occurs in which

acids and alcohols are produced that also destroy

the food quality. Thus, a lower limit exists.

Some fresh produce is preserved using this

principle of limiting oxygen availability by: 1)

holding under partial vacuum (hypobaric storage), 2) flushing the truck or storehouse with nitrogen to force out the oxygen, or 3) flushing and

sealing in a semipermeable pouch, In addition,

C O2 may also be added. This slows the rate of oxidation by mass action, since CO2 is a product of

the oxidation process. Jurin and Karel (Food

Technol. 17:104, 1963) have done some of the

classic work in this area, They showed that the

shelf life of a food in a pouch can be predicted

graphically.

Figure C-1 3 .—Senescence Rate as a Function of O2

r

* >

Partial oxygen pressure PO,

Basically, figure C-13 illustrates this concept.

The graph is constructed from data of respiration

rates; then the equation for gas permeation into

the pouch is drawn on the graph.

Since the external oxygen pressure essentially

remains constant, except as one travels up or

down a mountain or in a plane, the rate of oxygen

permeation is a constant. Thus, the rate as a function of the internal oxygen level is a straight line,

which can be superimposed over the oxygen uptake graph as in figure C-14. Lines A and B represent two different films of different oxygen permeability.

Figure C-14 can be used to illustrate what

would happen if a product were packaged in a

film with a permeability described by A and at an

initial oxygen partial pressure P,. Initially, oxygen

flow into the pouch is greater than uptake, so oxygen pressure rises, slowing the flow and increasing the uptake. At some point, the two rates are

equal—that is, the flow rate just matches the

reaction rate. In other words, the package will remain at some constant internal oxygen level and

the uptake will become constant. If the total oxygen uptake to reach end of shelf life is known,

the shelf life can be easily calculated by dividing

the total uptake by the constant rate.

To increase shelf life, all one has to do is lower

the film permeability such as seen for B, ensuring

that the new oxygen level is not below the point

where anaerobic glycolysis occurs. This method

has been put into practice with much success, but

few film types are available with sufficiently low

oxygen permeance to be able to control shelf life

to the desired value. Most oxygen-impermeable

films also retain moisture that tends to induce

mold growth on the product surface. In addition,

most data is at a single temperature. Since the Q10

for respiration is about 2 to 3, data must be anaFigure C-14.— Rates of Permeation and

Respiration of O2

R*

*

B
102 ● Open Shelf-Life Dating of Food

lyzed as a function of temperature also, utilizing

the techniques described previously.

Rancidity

Labuza (Critical Reviews of Food Technol. 3,

1977) reviewed the relationship of oxygen to stability of foods with respect to rancidity. A situation similar to that of respiration exists in that

the oxygen uptake follows the same pattern. However, there is no lower oxygen critical limit—the

lower, the better, in fact—and CO2 does not slow

the reaction.

Simon et al. (J. Food Sci. 36:280, 1971) was the

first to apply this to oxidation of a dehydrated

shrimp product using the same type of mathematical and graphical analysis. Karel’s group (J. Food

Sci. 37:679, 1972) did a more in-depth study in

which moisture was also simultaneously diffusing

into the package for potato chips stored at constant temperature and external humidity. Very

elegant computer-based solutions were presented. However, the time to develop the necessary data for equation development for most

foods would be far in excess of that desirable in

shelf-life testing or product development.

Basically, it can be stated that methods can be

developed to predict the end of shelf life when

caused by oxygen-sensitive reactions that also depend on aW and temperature.
Status of

Appendix D

Open Shelf-Life Dating

Regulations for Selected Countries

and International Food Labeling

Organizations, 1978

Country/

organization

BRITISH COMMONWEALTH

United Kingdom Code

Ireland Code or open

India . Code or open

Australia Code or open

New Zealand Code and open

EUROPEAN

Netherlands Open

Switzerland Code or open

Swede n Open

German y Code and open

Yugoslavia Code

USS R Code

ASIATIC

Japan Code in Arabic

or Latin

Thailan d Code

Iraq ., ––

Israe l Code or open

LATIN AMERICAN

Mexic o Code or open

Costa Ric a Code or pack

date

Venezuela. Code or open

Argentina Code or lot no.

Brazi l Code or lot no

AFRICAN AND OTHERS

Philippines

Egyp t

Nigeri a

Date display

Code or open datea

Type of date Day/month/year Month/year only

Open date recommended for short life, 6 months only s 3 months > 3 months

No guidelines

No guidelines —— For code

Open date recommended for short life, < 90 days ~ 3 months

Required for some products Pack ~ 3 months > 3 months

Determined for each product by Commodity Board ––

Recommended for short-life, cold-stored products

Recommended for most milk, meat products; frequently ––

more than one date used voluntarily

Required for short-life, cold-stored products ——

For milk products and others with shelf life < 1 year

Open pack date required

Required only on secondary container Pack or use-by

Open date recommended for some milk, meat, and fish ––

products

Open date voluntary, used for some products ——

WiII conform to Codex Alimentarius--on exports — . Day/month required if code

Use-by

Under consideration

No requirements for open dating

No requirements for open dating

Use-by

——

— .

No specific requirements or guidelines

Inspect all exports for conformance with importing

country regulations

Conform to requirements of importing countries to extent

local facilities allow ——

For code

For code

aaold Ila{lc type )ndlcales mandatory rewlrefneflfs

103
104 • Open Shelf-Life Dating of Food

—

Country/

organization

Libya

INTERNATIONAL

Codex

Alimentarius.

European

Economic

Community.

Central American

Economic

Community,

Code or open datea

Type of date Day/month/year

.—

Code or open Conform to requirements of importing countries to extent

local facilities allow

ORGANIZATIONS

Code or open Open dating required for baby food

Open ——

Code or open Pack

Open dating required for all products

Best-if-used-by

c year

Month/year only

> year

aB~lfj Ila[lc type Iruirates mrrdalov rwulwmm

SOURCE OTA Survey
Appendix

Bibliography

Adams, J. R,, and D. L, Huffman, “Effect of Controlled Gas Atmosphere and Temperatures on

Quality of Packaged Pork, ” J. Food Sci.

37:869-72, 1972.

A1-Delaimy, K. S., and M. E. Stiles. “Microbial

Quality and Shelf Life of Raw Ground Beef,”

Canadian J. PubJic Health 66:317-21, 1975.

American Frozen Food Institute. “The Use of Time

Temperature Indicators in Monitoring the

Distribution of Frozen Foods, ” March 1977,

Anderson, R. H., O. L. Maxwell, A. E. Mulley, and

C. W. Fritsch. “Effects of Processing and Storage on Micronutrients in Breakfast Cereals, ”

Food Technology 30(5):1 10, 1976.

Anderson, R. N., D. H. Moran, T, E. Huntley, and J,

L. Holahan, “Responses of Cereal to Antioxidant,” Food Technology 17:1587, 1963.

Andrae, W. “Effect of Can Materials on the Shelf

Life and Storage Stability of Canned Foods,

III,” Verpacking 15[2):14-16, 1974..

Arafa, A. S,, and T, C. Chen. “Quality Characteristics of Convenience Chicken Products as Related to Packaging and Storage, ” J. Food Sci.

41:18-22, 1976.

Arizona Consumers’ Council. “Freshness Dating

of Perishable Food: The Consumer Issues,””

Arizona Consumer, 1976.

Awad, A., W, D, Powrie, and O. Fennema, Deterioration of Freshwater Whitefish Muscle During Storage at – 10° C,’ J. Food Sci. 34:1,

1969.

Bailey, J. E. “Whole Grain Storage, ” Storage of

Cereal Grains and Their Products, C. M. Christensen, cd., American Association of Cereal

Chemists, St. Paul, Minn., p. 354, 1974.

Barnard, S. E, “Flavor and Shelf Life of Fluid

Milk, ” J. Milk Food Technol. 37(6):346, 1974,

Barnes, E. M., and C. S. Impey. “The Shelf Life of

Uneviscerated and Eviscerated Chicken Carcasses Stored at 10° C and 4° C,” 13r. Poultry

Sci. 16:319-26, 1975,

Beattie, H. G., K. A, Wheeler, and C. S, Pederson.

“Changes Occurring in Fruit Juices During

Storage, “ Food lies. 8:395, 1943.

Berger, K, G. “Practical Applications of an Accelerated Stability Test of Rancidity Problems in

Food Processing, ” 1. Food Technol. 6:253,

1971.

Body felt, F, W., and W. D. Davidson. “Temperature Control, ” J. Milk Food Tech. 38:734, 1975.

Boggs, M. M., W. C. Dietrich, M. D. Nutting, R. L.

Olson, F. E. Lindquist, G. S. Bohart, H, J. Neumann, and H. J, Morris. “Time-Temperature

Tolerance of Frozen Foods, XXI, Frozen

Peas,” Food Technol. 14:181-5, 1960.

Brockman, M. C. “Storage Stability of FreezeDried Foods, ” ASW3AE J,, pp. 54-8, August

1966.

Byrne, C. “Temperature Indicators—The State of

the Art, ” Food Tech., pp. 66-8, June 1976.

Cecil, S. R., and J. G. Woodroof. “The Stability of

Canned Foods in Long Term Storage, ” Food

Technol. 17:131-8, 1963.

Christensen, C. M., ed. Storage of Cereal Grains

and Their Products, American Association of

Cereal Chemists, St. Paul, Minn., 1974.

Chrzanowska, H, “The Determination of the Maximum Storage Period for Enriched Pasta in 3-

Layer Paper Bags, ” Biuletyn Centralrego Laboritorium Technologii. %zetworstw i Przechowa]nietwa Zboz w Warsawie 18:3/4, 1974.

Cort, W. M., B. Borenstein, J. H. Harley, M.

Osadea, and J. Scheiner. “Nutrient Stability of

Fortified Cereal Products, ” Food Technol.

3(4):52, 1976,

Dalhoff, E., and M. Jul. “Factors Affecting the

Keeping Quality of Frozen Foods, ” Progress in

Refrigeration Science and Technology, Vol. 1,

Pergamon Press, New York, pp. 57-66, 1965.

de la Mar, R. R., and F, J. Francis. “Carotenoid

Degradation in Bleached Paprika, ” J. Food Sci.

34:287-90, 1969.

Dhillon, A. S., and A, J, Maurer. “Stability Study

of Comminuted Poultry Meats in Frozen Storage, ” Poultry Sci. 54:1407-14, 1975.

Dornseifer, T. P., and J. P. Powers. “Volatile Constituents of Potato Chips and Changes During

Storage, ” Food Technol. 29:195, 1965,

105
106 ● Open She/f-Life Dating of Food

Downey, W,K, “Lipid Oxidation as a Source of

Off-Flavour Development During the Storage

of Dairy Products, ” J. of Soc. of Dairy Technol,

22(3):154, 1969.

Dyer, W. J., and M, L, Morton. “Storage of Frozen

Rosefish Fillets, ” J. Foods Res. Board of

Canada 16:43, 1959.

Elton, G. A, H. “Some Quantitative Aspects of

Bread Staling,” Bakers’ Digest 43(3):24, 1969.

Ezell, B. D., and M. S, Wilcox. “Loss of Vitamin C

in Fresh Vegetables as Related to Wilting and

Temperature, ” J. Agr. Food Chem. 10:124-6,

1959.

Fabriani, G,, and A, Fratoni. Bibliotheca Nutritia

et Dieta. 17, pp. 196-202, 1972.

Fellers, D. A., and M, M, Bean. “Flour Blend A. 2,

Storage Studies, ” Bakers’ Digest 44[6):42,

1970.

Felt, C. E. “Shelf Life of Packaged Cereals,”

Cereal Chem. 22:261, 1945,

Fennema, O. Nutritional Evaluation of Food Processing, 2nd cd., R. S. Harris and E. Karmas,

eds., AVI Publishing Co., Westport, Corm,, p.

246, 1975,

Finley, P. D., H, B. Warren, and R. E. Hargrove,

“Storage Stability of Commercial Milk,” j.

Milk Food TechnoL 31(12):382, 1968.

Ford, K, Minnesota Office of Consumer Services,

testimony before the Minnesota State Senate

Hearings on Open Dating Legislation, 1972,

Gacula, M,C. “The Design of Experiments for

Shelf-Life Study, ” J. Food Sci. 40:399, 1975,

Gatewood, R,, and W. French. “Industry Reactions to Food Labeling Regulations, ” Business

Horizons, October 1976.

Georgiev, E. V., and T, Khadzhiiski. “Changes in

Essential Oils and Glycerides During Storage

of Raw Materials: Oil Changes During Storage

of Cumin (Cuminum Cyminum) Seed, ” Nauchni

Trudove, Tissh Institut po Khranitelna i Vkusova Promyshlennost 17[2):97-106, Abstrac t

FSTA 5 (1973) 4T194, 1970.

Guadagni, D, G. “Time-Temperature Experience

of Food Quality, ” ASHRAE J, 3(4):66-9,83,

1961.

Guadagni, D, G,, J. L. Bomben, and H. C. Mannheim. “Effect of Temperature on Stability of

Orange Aroma Solution, ” J. Food Sci. 35:3,

1970.

Guadagni, D. G., C. C. Nimmo, and E. F. Jansen,

“Time-Temperature Tolerance of Frozen

Foods, VI, Retail Packages of Frozen Strawberries,” Food Technol. 11:389-97, 1975b.

Gutschmidt, J, “The Storage Life of Frozen

Chicken with Regard to Temperature in the

Cold Chain, ” Lebens. Wiss und Tech. 7:137,

1974.

Hall, C. W., and T. I. Hendricks, Drying Milk and

Milk Products, AVI Publishing Co,, Inc., Westport, Corm., 1966.

Hanson, H. L,, and L. R. Fletcher. “Time-Temperature Tolerance of Frozen Foods, XII, Turkey

Dinners and Turkey Pies, ” Food Technol.

12:40-3, 1958.

Harkin, L., W. F. Dillman, and G. R. Stephens.

“Relation of Code Dates to Quality of Milk

Sold in Retail Markets, ” J. of Food Protection

40(2):1 16-19, 1977.

Harris, N. E., S. J. Bishov, A. R. Rahman, M. M,

Robertson, and A. F. Mabrouk. “Soluble Coffee: Shelf Life Studies, ” J. Food Sci. 39:192,

1974,

Hayakawa, K., and Y. Wong. “Performance of

Frozen Food Indicators Subjected to Time

Variable Temperatures, ” ASHRAE J., April

1974,

Herrmann, J. “Calculation of the Chemical and

Sensory Alterations in Food During Heating

and Storage Processes, ” Ernahrungs

Forschung 15:279-99, 1970.

Herz, K. O. “Staling of Bread—A Review, ” Food

Tech. 19:1828, 1965.

Huss, H. H., D, Dalsgaard, L. Hansen, H. Lodefoged, A, Pedersan, and L. Zittan. “The Influence of Hygiene in Catch Handling or the

Storage Life of Iced Cod and Plaice, ” J. Food

Technol. 9:213-21, 1974.

Hutt, P, “Food Regulations—Coping with More, ”

paper presented at Symposium on Strategies

for Survival, 37th Annual Meeting of Institute

of Food Technologists, 1977.

Jantawal, P. P,, and L. E. Dawson, “Stability of

Broiler Pieces During Frozen Storage, ”

Pou]try Sci. 56:2026-30, 1977.

Kanner, J., S. Harel, D. Paevetch, and 1, Ben-Gera,

“Colour Retention in Sweet Red Paprika (Capsicum Annum L.) Powder as Affected by

Moisture Content and Ripening Stage, ” J. Food

Technol 12:59-64, 1977.

Killoran, J, A Time Temperature Indicating

System for Foods Stored in the Non-Frozen

State, Activities Report, U.S. Army Natick

Labs, 1976.

Kirk, J. “Freshness Dating of Perishable Commodifies, ’ paper prepared for the Office of

Technology Assessment, 1978,

Klose, A, A,, M, F. Poul, A, A, Campbell, and H, L,

Hawson. “Time Temperature Tolerance of

Frozen Foods, XIX,” Food Technol. 13:477,

1959.
Appendix E—Bibliography ● 107

Kopelman, I., and D. Effroni. “Shelf Life and

Microbial Growth of Chilled Reconstituted

Orange Juice, ” Lebens. Wiss. und Tech .

10:131, 1977,

Kramer, A. “International Food Labeling, ” paper

prepared for the Office of Technology Assessment, 1978.

Kroller, W. D. “Temperature-an Important Factor in the Storage of Ground Natural Spices, ”

Zeitschri~t ~ur Lebens. urtd Forschung

160:143-7, Abstract FSTA 8 (1976) 8T372,

1976.

Labuza, T. P. Food and Your Well-Being, West

Publishing Company, Westport, Corm., 1977.

Labuza, T. P. “Interpretation of Sorption Data in

Relation to the State of the Constituent

Water, ” Water Relations in Foods, R. Duckworth, cd., Academic Press (no date).

Labuza, T. P. “Nutrient Losses During Drying and

Storage of “Dehydrated Foods, ” CRC Press

3:217, 1972.

Labuza, T. P., et al. “Open Shelf Life Dating of

Foods, ” Department of Food Science and Nutrition, University of Minnesota, report prepared for the Office of Technology Assessment, 1978.

Labuza, T. P., and Linda Kreisman. “Report on

Open Dating of Semi and Non Perishable

Foods,”’ paper prepared for the Office of

Technology Assessment, 1978.

Lawrie, R. A, “Chemical Changes in Meat due to

Processing—A Review, ” J. Sci. Fd. Agric.

19(5):233, 1968.

Lee, Y, C., J. R. Kirk, C. L. Bedford, and D. R.

Heldman, “Kinetics and Computer Simulation

of Ascorbic Acid Stability of Tomato Juice as

Functions of Temperature, pH and Metal

Catalysts,” J. Food Sci, 43:3, 1977.

Lund, D. B. “Effects of Blanching, Pasteurization,

and Sterilization on Nutrients, ” Nutritional

Evaluation of Food Processing, AVI Publishing

Co., Westport, Corm., 1975.

MacDougal, P. B., and A, A. Taylor. “Color Retention in Fresh Meat Stored in Oxygen—A Commercial Scale Trial, ” J. Food Technol.

10:339-47, 1975.

Maga, J. A. “Bread Staling, ” CRC Crit. Reviews in

Food Tech. 5[4]:433, 1975.

Market Facts, Inc. “Survey of Consumer Attitudes

with Respect to the Open Dating of Food, ”

prepared for the Office of Technology Assessment, 1978,

Massachusetts Consumers’ Council. “Open Code

Dating for Non-Perishable Food Items: A

Report and Proposal, Publication No. 9680-

121-80-4-77-CR, January 1975.

Matz, S. A., ed. Cereal Technology, AVI Publishing

Company, Westport, Corm., 1970.

Matz, S, A. In Snack Food Technology, AVI

Publishing Company, Westport, Corm., ch. 2,

1976.

Meisner, D, F. “Importance of Temperature and

Humidity in the Transportation and Storage of

Bread, ” Bakers’ Digest 27:109, 1953.

Minnesota Public Interest Research Group. “Survey of Minnesota Food Stores, 1972, ” testimony before the Minnesota State Senate on

Open Dating Legislation.

Mountney, G. J., ed. Poultry Products Technology,

2nd edition, AVI Publishing Co., Westport,

Corm., 1976.

The New York State Assembly. “Open Dating, ”

Committee on Consumer Affairs and Protection (no date).

Nielson, A. C. Company. “Study of Consumer Attitudes Toward Product Quality, Northbrook,

111., 1973.

Olley. J. and D. Rakowsky. “Temperature Function Integration and Importance in Storage

and Distribution of Fresh Foods, ” Food Tech.

Austr. 25:66, 1973.

Pintauro, N. Soluble Co~~ee Manufacturing Processes, Noyes Development Corp., Park Ridge,

N. J., 1969.

Pintauro, N. Tea and Soluble Tea Products

Manufacture, Noyes Development Corp., Park

Ridge, N. J., 1977.

Quast, D. G., and M. Karel. J. Food Science 37:584,

1972.

Quast, D, G., and R. O. Teixeira Neto, “Moisture

Problems of Foods in Tropical Climates, ” Food

Tech. 30[5):98, 1976.

Quinn, T. “Labeling of Foods, ” Food Drug

Cosmetic Law Journal, December 1975.

Ragnarrson, J. O., and T. P. Labuza. “Accelerated

Shelf Life Testing of Oxidative Rancidity in

Foods, A Review, ” Int. J. Food Chem., 1977.

Reay, G. A., and J. M. Shewan. “The Spoilage of

Fish and Its Preservation by Chilling,” Advances in Food Research, vol. 2, Academic

Press, Inc., New York, 1949.

Rouse, A. H,, C. D. Atkins, and E. L. Moore. “Factors Contributing to the Storage Life of Frozen

Concentrated Orange Juice, ” Food Technol.

11:218, 1957.

Rutgers University, Department of Food Science.

“Food Stability and Open Dating, ” Conference

Proceedings, New Brunswick, N. J., 1971.
108 • Open Shelf-Life Dating of Food

Rutgers University, Department of Food Science.

Food Stability Survey, Volumes I and 11, New

Brunswick, N. J,, 1971.

Ryan, A, L., and W. T. Pentzer. Handling, Transportation and Storage o.f Fruits and

vegetables, Vol. 2, Fruits and Tree Nuts, AVI

Publishing Co,, Westport, Corm., 1974,

Sapers, G. M. “Flavor and Stability of Dehydrated

Potato Products,” Agric. Food Chem. 23: 1027,

1975.

Sharp, J. G. “Non-Enzymatic Browning Deterioration in Dehydrated Meat, ” Rec. Adv. Food

Sci. 2:65-73, 1962.

Shepherd, A. D. “Relative Stabilities of Various

Frozen Foods, ” Conference on Frozen Food

Quality, USDA Western Regional Res. Lab.,

Albany, Calif., pp. 18-23, 1960.

Sporleder, T. “Abstract of Food Distribution, OTA

Working Group Discussions, ” paper prepared

for the Office of Technology Assessment,

1978.

Sproleder, T. “State Open Dating Laws on Food,”

paper prepared for the Office of Technology

Assessment, 1977.

Stafford, A. E., and D, G. Guadagni. “Storage

Stability of Raisins Dried by Different Procedures, ” J. Food Sci. 42(2):547-8, 1977.

Szklarska-Cyganska, R., and I. Kakowska-Lipinska. Determination of Contents of Available

Lysine in Some Food Products by a Chemical

Method and by a Microbiul Method Involving

Tetrahymena P, W., 1970,

Thomas, M. A,, A. D. Turner, G. Abad, and J, M.

Towner. “The Influence of Types of Skim Milk

Powder Used and Storage Conditions on

Browning Reaction in Processed Cheese

Spread,” Milch wissenscha~t 32(1):12-15, 1977.

Tomiyisu, Y., and B, Zenitani. “Spoilage of Fish

and Its Preservation by Chemical Agents, ”

Advances in Food Research, 7, Academic

Press, Inc., New York, 1957.

Tressler, D. K, “Special Problems Encountered in

Preparing, Freezing, Storing, Transporting

and Marketing Frozen Precooked and Prepared Foods, ” The Freezing Preservation of

Foods, Vol. 4, Tressler, Van Arsdel and Copley,

eds,, p. 39, 1968b.

U.S. Congress. Consumer Food Act of 1976, Report

of Committee on Commerce and Committee on

Labor and Public Welfare, U.S. Senate, on S.

641, Mar. 4, 1976.

U.S. Congress, House Interstate and Foreign Commerce Committee, Subcommittee on Health

and the Environment. Hearings on “Food Safety and Nutrition Amendments of 1978, ” 95th

Cong. 2d sess., July 1978.

U.S. Department of Agriculture. Food Dating:

Shoppers’ Reactions and the Impact on Retail

Foodstores, Market Research Report No. 984,

1973.

U.S. Department of Health, Education, and

Welfare, Public Health Service, Food and

Drug Administration. 1978 Consumer Food

Labeling Survey, Summary Report, May 1979.

U.S. Department of Health, Education, and Welfare, Public Health Service, Food and Drug

Administration. Memorandum from Alexander Grant, Special Assistant to Commissioner for Consumer Affairs, to Consumer Affairs Officers, December 1978.

U.S. Department of Health, Education, and Welfare, Public Health Service, Food and Drug

Administration. A Surveillance of Nutrition

Labeling in the Retail Packaged Food Supply,

1978,

U.S. General Accounting Office. Food Labeling:

Goals, Shortcomings, and Proposed Changes,

1975.

Waletzko, P., and T. P. Labuza. “Accelerated

Shelf-Life Testing of an Intermediate Moisture

Food in Air and an Oxygen-Free Atmosphere, ” J. Food Sci. 41:1338, 1976,

Wang, P. L., E. J. Day, and T, C. Chen. “Microbial

Quality of Frozen Fried Chicken Product Obtained from Retail Store, ” Poultry Sci.

55:1290-3, 1976.

Wickremasinghe, P. L,, and K. P. Perera.

“Chemical Changes During Storage of Black

Tea, ” Tea QuarterJy 43(4):147, 1972.

Wood, E, C., and M. Youngs. “The Keeping Quality of Pasteurized Eggs,” j. Appl. Bact.

32:403-7, 1969.

Yankelovich, Skelly, and White, Inc. “A Study of

Consumers’ Attitudes and Behaviors Towards

Eating at Home and Out of Home, ” Woman’s

Day, Family Food Study, 1978.

0