Food irradiation principles and applications

14 1.2.1 Social and Economic Benefits of Food Irradiation in Relation to Food Security: Preventing Postharvest Food Losses and Extending the Shelf Life of Perishable Foods .... Thus, mic

A JOHN WILEY & SONS, INC., PUBLICATION

NewYork • Chichester • Weinheim • Brisbane • Singapore • Toronto

FOOD IRRADIATION:

PRINCIPLES AND

APPLICATIONS

This book is printed on acid-free paper ©

Copyright © 2001 by John Wiley & Sons, Inc All rights reserved.

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA

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Library of Congress Cataloging-in-Publication Data:

Molins, Ricardo A.,

1948-Food irradiation : Principles and applications / edited by Ricardo Molins.

p cm.

Includes index.

ISBN 0-471-35634-4 (cloth : alk paper)

1 Radiation preservation of food I Title.

TP371.8.M65 2001

664'.0288—dc21 2001017629 Printed in the United States of America.

10 9 8 7 6 5 4 3 2 1

In memory of George G Giddings, Ph.D Colleague, scholar, dear friend, and indefatigable promoter of food irradiation To you I say: Ignorance dies hard, and

progress sometimes comes slowly, but both are inevitable.

This book responds to the need of researchers, industry, and regulators to have asingle source of information comprising all aspects of food irradiation: historical,technical, economic, and regulatory Because food irradiation involves many dis-ciplines within and outside the realm of food science, this book has general chapters

on radiation microbiology and chemistry as they apply to food as well as specificchapters on irradiation of each of the major food groups These are complemented

by additional chapters on process control, economics, and regulatory aspects offood irradiation that are essential in planning the introduction or expansion of thistechnology The title of the book, therefore, is most appropriate in that principlesand applications of food irradiation are indeed extensively discussed Twelve con-tributing authors from America, Asia, and Europe bring together the expertiseaccumulated around the world on this promising food processing technique.Although the contributing authors have striven to present and cite the mostrecent information available on each topic covered in the book, there are notabledifferences in the degree of success achieved by each one These differences, to alarge extent, reflect the prevailing interest on particular applications of food irradia-tion at present and during the past decade as opposed to that in earlier years Thus,research into such applications of irradiation as microbial decontamination of meat,poultry, and minimally processed foods, for example, has attracted more attention

in the 1990s than insect disinfestation of stored dried foods, which was studiedmainly during the 1960s and 1970s Consequently, the information provided in eachchapter dealing with an application of food irradiation represents the state of the artfor that particular application

A major departure this book has from other works in this field is that thecontributing authors, taking into consideration the massive scientific evidence gath-ered over more than half a century, concurred that food irradiation has been ex-haustively proven to be safe and to result in wholesome food Therefore, theyrefused to continue to debate these issues They believe that the unique potentialthis technology has to increase the availability of food and to improve its qualityand safety will eventually lead to its acceptance

I am grateful to my fellow co-authors for accepting my invitation to collaborate

in this book It is a great honor to be here in their company

PREFACE

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Contents

Preface xiii

1 Introduction 1

1.1 Historical Notes on Food Irradiation 1

1.1.1 Notes on the Development of the Food Irradiation Process and Applications 1

1.1.2 Proving the Wholesomeness of Irradiated Foods 12

1.2 Potential Social and Economic Benefits of Food Irradiation 14

1.2.1 Social and Economic Benefits of Food Irradiation in Relation to Food Security: Preventing Postharvest Food Losses and Extending the Shelf Life of Perishable Foods 15

1.2.2 Social and Economic Benefits in Relation to Food Safety: Controlling Pathogenic Bacteria and Parasites in Foods 16

2 Radiation Inactivation of Microorganisms 23

2.1 Introduction 23

2.2 Mechanisms of Inactivation 23

2.3 Mechanisms of Microbial Survival and Repair 24

2.4 Radiation Sensitivity of Specific Microorganisms 25

2.4.1 Bacteria of Public Health Significance 27

2.4.2 Viruses 27

2.4.3 Parasites 31

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2.5 Environmental Factors Affecting Radiation

Sensitivity 31

2.6 Other Issues 32

2.7 Conclusions 32

3 Food Irradiation Chemistry 37

3.1 Introduction 37

3.1.1 Types of Ionizing Radiation and Their Sources 37

3.1.2 Background and Induced Radioactivity 38

3.2 Basic Effects of Ionizing Radiation 39

3.2.1 Primary Effects 39

3.2.2 Secondary Effects 41

3.3 Water Radiolysis 43

3.4 Effects of Ionizing Radiation on Major Food Components 46

3.4.1 Carbohydrates 47

3.4.2 Proteins 50

3.4.3 Lipids 58

3.4.4 Vitamins 64

3.5 Conclusions 68

4 Disinfestation of Stored Grains, Pulses, Dried Fruits and Nuts, and Other Dried Foods 77

4.1 Introduction 77

4.2 Radiation Effects on Insects 80

4.2.1 General Effects of Radiation on Insects 80

4.2.2 Feeding Behaviour of Irradiated Insects 82

4.2.3 Sterilizing Effects of Radiation 83

4.3 Current Disinfestation Methods and Their Drawbacks 85

Contents ix

This page has been reformatted by Knovel to provide easier navigation 4.3.1 Chemical Methods 86

4.3.2 Physical Methods 87

4.4 Irradiation Disinfestation 88

4.4.1 Cereal Grains 88

4.4.2 Pulses 89

4.4.3 Dried Fruits and Nuts 90

4.4.4 Dried-Beverage Crops 92

4.4.5 Dried Foods of Animal Origin 93

4.4.6 Other Dried Food Products 94

4.4.7 Irradiation in Combination with Other Methods 95

4.5 Preventing Reinfestation 97

4.6 Regulatory Approval and Potential Commercial Application of Radiation Disinfestation of Stored Dried Foods 101

5 Irradiation as a Quarantine Treatment 113

5.1 Need for Quarantine Treatment 113

5.2 Types of Quarantine Treatment 113

5.3 Comparison between Irradiation and Other Quarantine Treatment 114

5.4 History of Irradiation Quarantine Treatment 117

5.5 Radiation Quarantine Treatment 118

5.6 Radiation Quarantine Treatment Research 119

5.6.1 Aspects of Importance in Conducting Radiation Quarantine Treatment Research 121

5.6.2 Research Needs 124

5.7 Future Outlook for Irradiation as a Quarantine Treatment 127

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6 Irradiation of Meats and Poultry 131

6.1 Introduction 131 6.1.1 The Origins of Parasitic and Microbial

Contamination of Meats and Poultry 131 6.1.2 Effectiveness of Nonlethal, Preventive

Measures to Control Microbiological Contamination of Meats and Poultry 132 6.1.3 Decontamination Methods of Raw Meats

and Poultry 133 6.2 Irradiation of Meats and Poultry 135 6.2.1 Microbiological Effects of Ionizing

Radiation on Meats and Poultry 135 6.2.2 Combined Effects of Irradiation and

Other Treatments on Meats and Poultry 159 6.2.3 Physical and Chemical Effects of

Ionizing Radiation on Meats and Poultry 163 6.2.4 Effects of Irradiation on Nutrients in

Fresh Meats and Poultry 170 6.2.5 Packaging for Irradiation of Meat and

Poultry 172 6.2.6 Research Needs in Meat and Poultry

Irradiation 173 6.2.7 Outlook on the Future of Meat and

Poultry Irradiation 174

7 Irradiation Processing of Fish and Shellfish

Products 193

7.1 Introduction 193 7.2 Irradiation for Shelf-Life Extension of Seafood

Products 195

Contents xi

This page has been reformatted by Knovel to provide easier navigation 7.2.1 Finfish Products 195

7.2.2 Shellfish and Crustaceans 197

7.3 Potential Human Pathogens of Public Health Concern in Seafood Products 200

7.3.1 Indigenous Potential Pathogens Associated with the Natural Aquatic Environment 200

7.3.2 Potential Pathogenic Microorganisms Associated with Human and/or Animal Fecal Pollution 203

7.3.3 Potential Pathogenic Microorganisms Associated with Processing and Preparation 204

7.4 Low- and Medium-Dose Irradiation for Pathogen Control in Seafood Products 205

7.5 Research Needs in Seafood Irradiation 208

7.6 The Future of Seafood Irradiation 208

8 Irradiation of Fruits and Vegetables 213

8.1 Introduction 213

8.2 Physiology and Biochemistry of Fruit Ripening 214

8.3 Effects of Ionizing Radiation on Ripening, Senescence, and Shelf Life of Fruits 215

8.3.1 Tropical and Subtropical Fruits 215

8.3.2 Temperate Fruits 218

8.3.3 Biochemical Mechanisms Involved in Delay of Ripening in Fruits by Irradiation 218

8.3.4 Effects of Irradiation on the Nutritional Qualities of Fruits 219

8.3.5 Effects of Irradiation on Sensory Quality Attributes 225

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8.4 Control of Postharvest Fungal Rot in Fruits by

Irradiation Alone or in Combination with Other

Treatments 227

8.4.1 Heat Plus Irradiation 228

8.4.2 Combination of Radiation, Heat, and Chemicals 229

8.5 Potential for Radiation Treatment of Vegetables 230

9 Irradiation of Tuber and Bulb Crops 241

9.1 Introduction 241

9.1.1 Factors Contributing to Postharvest Losses of Tuber and Bulb Crops 242

9.1.2 Significance of Sprouting of Tuber and Bulb Crops in Storage 243

9.1.3 Alternate Methods for Control of Sprouting and Shelf Life Extension of Tuber and Bulb Crops 244

9.2 Radiation Treatment for Control of Sprouting and Shelf-Life Extension of Tuber and Bulb Crops 245

9.2.1 Biochemical Mechanisms of Sprout Control by Ionizing Radiation 245

9.2.2 Factors Determining the Efficacy of Radiation Treatment 246

9.3 Effects of Irradiation on Nutritional Components 249

9.3.1 Carbohydrates 249

9.3.2 Proteins and Amino Acids 250

9.3.3 Vitamins 251

9.3.4 Chlorophylls and Glycoalkaloids 252

9.3.5 Flavor and Pungency 253

9.4 Effect of Ionizing Radiation on Technological Properties of Tubers and Bulbs 254

9.4.1 Wound Healing and Storage Rot 254

Contents xiii

This page has been reformatted by Knovel to provide easier navigation 9.4.2 After-Cooking Darkening of Potatoes 256

9.4.3 Other Types of Discoloration in Potatoes 257

9.4.4 Inner-Bud Discoloration of Bulbs 257

9.4.5 Processing Qualities 258

9.5 Effect of Irradiation for Sprout Inhibition on the Potato Tuber Moth 259

9.6 Commercial Irradiation for Sprouting Inhibition: Current Status and Future Outlook 259

10 Irradiation of Minimally Processed Foods 273

10.1 Introduction 273

10.2 Irradiation of Minimally Processed Fresh Produce 275

10.3 Irradiation of Cook – Chill Foods 277

10.3.1 Irradiation of Packaged Conventional Cook-Chill Meals 279

10.3.2 Irradiation of Sous-Vide Foods 282

10.4 Research Needs on the Potential Use of Irradiation on Minimally Processed Foods 284

11 Radiation Decontamination of Spices, Herbs, Condiments, and Other Dried Food Ingredients 291

11.1 Introduction 291

11.1.1 Microbiological Contamination of Dried Food Ingredients and Its Significance for the Food Industry and Public Health 291

11.1.2 Criteria for Microbial Quality of Dried Food Ingredients 293

11.2 Radiation Decontamination of Dried Food Ingredients 294

11.2.1 Spices, Herbs and Dried-Vegetable Condiments 296

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11.2.2 Herbal Teas and Dried Medicinal

Plants 300

11.2.3 Dried Fruits and Vegetables, Dry Soups, and Cereal Products 300

11.2.4 Texturizing Agents 301

11.2.5 Protein and Enzyme Preparations 301

11.2.6 Dried-Egg Products 302

11.2.7 Cocoa Powder and Desiccated Coconut 302

11.2.8 Other Dried Products 302

11.3 Economic Feasibility and Industrial Use of Radiation Decontamination of Dried Food Ingredients 303

11.4 Acceptance and Commercialization of Radiation Decontamination of Dried Ingredients 303

12 Combination Treatments Involving Food Irradiation 313

12.1 Introduction 313

12.1.1 The Hurdle Concept 315

12.2 Combination Treatments Involving Food Irradiation 316

12.2.1 Irradiation and Heat 316

12.2.2 Irradiation and Low Temperatures 319

12.2.3 Irradiation and Modified-Atmosphere Packaging 320

12.2.4 Irradiation and Chemical Preservatives 323

12.2.5 Irradiation and High Pressure 324

13 Development of Irradiated Shelf-Stable Meat and Poultry Products 329

13.1 Introduction 329

Contents xv

This page has been reformatted by Knovel to provide easier navigation 13.2 History 329

13.3 Atoms for Peace 330

13.4 Early Supporting Research 330

13.5 Beef 331

13.6 Pork 332

13.7 Ham 333

13.8 Bacon 333

13.9 Frankfurters 334

13.10 Fish 334

13.11 Chicken 335

13.11.1 Determination of 12D 335

13.11.2 Enzyme-Inactivated, Radiation-Sterilized Chicken 335

13.12 Production of Radiation-Sterilized Food 337

13.13 U.S Enzyme-Inactivated, Radiation-Sterilized Products 337

13.14 The South African Program 338

13.15 Future of Irradiated Shelf-Stable Meat and Poultry Products 339

14 Detection Methods for Irradiated Foods 347

14.1 Introduction 347

14.2 Criteria for a Reliable Detection Method 348

14.3 Physical Methods 350

14.3.1 ESR Spectroscopy 350

14.3.2 Luminescence Measurement 354

14.3.3 Viscosity Measurement 356

14.3.4 Electrical Impedance Measurement 357

14.3.5 Other Physical Methods 358

14.4 Chemical Methods 358

14.4.1 Hydrocarbons 358

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14.4.2 2-Alkylcyclobutanones 360

14.4.3 Ortho-Tyrosine 362

14.4.4 Gas Evolution 363

14.4.5 Other Chemical Methods 364

14.5 DNA Methods 364

14.5.1 DNA “Comet Assay” 364

14.5.2 Agarose Electrophoresis of Mitochondrial DNA 366

14.5.3 lmmunologic Detection of Modified DNA Bases 367

14.5.4 Other DNA Methods 367

14.6 Biological Methods 368

14.6.1 Shift in Microbial Load 368

14.6.2 Direct Epifluorescent Filter Technique Combined with Aerobic Plate Count (DEFT/APC) 369

14.6.3 Limulus Amoebocyte Lysate Test Combined with Gram-Negative Bacterial Count (LAL/GNB) 370

14.6.4 Half-Embryo Test to Measure Inhibition of Seed Germination 371

14.6.5 Other Biological Methods 372

14.7 Conclusions 372

15 Process Control and Dosimetry in Food Irradiation 387

15.1 Introduction 387

15.1.1 Advisory Technological Versus Legal Dose Limits 389

15.1.2 Significance of the Dose-Effect Relationship 390

Contents xvii

This page has been reformatted by Knovel to provide easier navigation 15.2 General Control Considerations 391

15.2.1 Gamma-Ray Facilities 392

15.2.2 Electron-Beam and X-Ray Facilities 393

15.2.3 Product Variations 395

15.3 Commissioning a Facility 395

15.3.1 Description of lrradiators and Their Design 395

15.3.2 Expected Dose Distribution in the Product 397

15.4 Process Qualification 401

15.4.1 Initiating a Treatment 401

15.4.2 Changing a Treatment 402

15.4.3 Extreme Dose Homogeneity Requirements 402

15.4.4 Setting Process Limits 403

15.5 Dosimetry Used in Process Control 404

15.5.1 Dosimetry Guidelines 405

15.5.2 Dosimeter Selection Criteria 405

15.5.3 Dosimetry Systems 407

15.5.4 Absorbed Dose and Its Measurement 407

15.5.5 Traceability and Accuracy 408

15.6 Documentation and Recordkeeping 408

15.6.1 Auditing the Facility 409

15.6.2 Auditing the Process 409

15.6.3 Compliance with Customer and Legal Requirements 409

15.6.4 Inventory Control and Product Release 409

15.6.5 Aspects of International Trade 410

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16 Economic and Technical Considerations in

Food Irradiation 415

16.1 Introduction 415

16.2 Food Irradiation Parameters 415

16.3 Food Irradiation Equipment 416

16.3.1 Gamma lrradiators 416

16.3.2 Machine Source lrradiators 419

16.4 Costs 422

16.4.1 Capital Costs 422

16.4.2 Operating Costs 422

16.4.3 Total Processing Costs 422

16.4.4 Unit Processing Costs 422

16.5 Effect of Throughput on Costs 433

16.6 Effect of Dose on Costs 437

16.7 Effect of Packing Density on Cobalt-60 Utilization Efficiency in Gamma Irradiators 439

16.8 Summary 441

16.9 Bibliographic Notes 442

17 Global Status of Food Irradiation in 2000 443

17.1 Global Developments Affecting the Introduction or Expansion of Food Irradiation 443

17.1.1 Developments in Health-Related Areas Affecting the Introduction or Expansion of Food Irradiation 443

17.1.2 Developments in Environmentally Related Areas Affecting the Introduction or Expansion of Food Irradiation 446

17.1.3 Developments in International Trade Regulations Affecting the Introduction or Expansion of Food Irradiation 446

Contents xix

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17.1.4 Developments in Food Irradiation

Regulations Affecting the Introduction or Expansion of Food Irradiation 447 17.2 Current Commercial Application of Radiation

Processing to Foods and Future Outlook 450 17.3 Notes on Consumer Acceptance of Irradiated

Foods: The Myths and the Facts 451

Index 457

RlCARDO A MOLINS

Institute of Medicine, The National Academics, Washington, DC

1.1 HISTORICAL NOTES ON FOOD IRRADIATION

1.1.1 Notes on the Development of the Food

Irradiation Process and Applications

Although frequently termed "a new technology," food irradiation is anything butnew As described in the excellent reviews on food irradiation history written byJosephson (1983a) and Diehl (1990), the idea of using ionizing radiation to improvethe quality and shelf life of foods had already been expressed in the late 180Os.The generic term, "irradiation," however, appears in the literature only until the1940s, and it is safe to say that it constituted a most unfortunate occurrence because

it brought a direct and conceptually misleading association of a food processingtechnique with the nuclear establishment (Kampelmacher 1983)—opposed bycertain groups because of political and/or environmental considerations beyondthe scope of this book—that persists today Such an association was never madewith X-ray technology, for example, because the dreaded term "radiation" and itspost-war specter were not incorporated in its name This association is speciallystrong in certain languages in which the term "food irradiation" does, in fact,contribute to public confusion In Arabic, for example, "irradiated food" and

"radioactive food" are almost indistinguishable terms Little did the originators

of the food irradiation name imagine that their choice of words would play such anadverse role in the acceptance of this technology, and little was done later toremedy the situation because pro-food irradiation scientists and authorities wereforced, for decades, into a defensive position This resulted in the ironic situation ofhaving to keep an inappropriate name for the technology or being accused of

"trying to hide something."

The term "food irradiation" is inappropriate and generic because it does notdescribe the actual process of applying ionizing radiation in ways that would set it

Food Irradiation: Principles and Applications, Edited by R A Molins

ISBN 0-471-35634-4 © 2001 John Wiley & Sons, Inc.

CHAPTER 1

apart from other processes used in the food industry Thus, microwaves and infraredlight—both of which generate heat—are also forms of radiation, and their use incooking, heating foods in a microwave oven, or simply keeping the food warmunder an infrared light—as is customary in many restaurants—could just as prop-erly be termed "food irradiation." Indeed, shortly after World War II, there waswidespread distribution in the United States of pasteurized fluid milk labeled "ir-radiated" because it had been treated with infrared light to develop vitamin D fromprecursors This practice was later abandoned when milk was directly and routinelyfortified with vitamin D Considering that we have reached an enlightened age,perhaps it is time to do away with this absurd situation and either adopt the morelogical French term "ionization"—already adopted by French-speaking countriesthat have or are developing regulations in this field—or reconsider the proposal ofthe late E Wierbicki to call irradiated foods "picowaved" in reference to the veryshort wavelength of ionizing radiation, and quite in line with the currently commonterm "microwaved." A first step in this direction may be the current increasinglypopular use of the term "electronic pasteurization" in the United States to describeinactivation of pathogenic bacteria in food through irradiation.

In general, the early history of food irradiation (1890s-1940s) is inseparablylinked to that of radiation physics and to the development of the systems andsources to be used in food irradiation This was followed by a period of intensiveresearch and development (1940s-1970s) that overlapped with extensive studies onthe wholesomeness of irradiated foods (1970s) Since the 1970s, however, mosthistorical food irradiation events have been related to regulations The following is

a chronological list of some of the most important dates and landmark events infood irradiation history, or of events that had an impact on the development andadoption of this technology:

1895 W K von Roentgen reported the discovery of X rays

1896 H Becquerel reported the discovery of radioactivity

1896 H Minsch (Germany) published a proposal to use ionizing

radiation to preserve food by destroying spoilagemicroorganisms

1898 J J Thompson reported on the nature of cathode rays (i.e.,

that they are "electrons") Pacronotti and Procelli observedradiation effects on microorganisms

1901 Max Planck published the quantum theory proposal

1902-1903 Rutherford and Soddy published a proposed theory of

radioactive disintegration Marie Curie published her thesis

on the nature of alpha, beta, and gamma radiation

1904 S C Prescott published studies on the bactericidal effect

of ionizing radiation

1905 Albert Einstein published his theory of relativity A British

patent was issued for use of ionizing radiation to kill bacteria

in foods through food irradiation A separate U.S patent

was issued on mixing radioactive material with food forpreservation purposes.

1906 The U.S Pure Food and Drug Act became law

1905-1920 This was a period of basic research on the nature and chemical,

physical, and biological effects of ionizing radiation

1916 Radiation processing of strawberries was evaluated in Sweden

1918 A U.S patent on X-ray multiple-tube processing of food was

issued to Gillet

1921 B Schwartz published on the lethal effects of X rays on

Trichinella spiralis in raw pork Studies were conducted on

elimination of the tobacco beetle by irradiation

1923-1927 Publications on the effects of ionizing radiation on enzymes first

appeared First published results of animal feeding studies totest the wholesomeness of irradiated foods appeared Therodent bioassay (essential in studying the toxicology ofirradiated foods) was developed

1920s-1930s Many important electron accelerator machine developments

took place Atomic/nuclear fission was discovered anddemonstrated

1930 A French patent was issued to Otto Wiist (a German) for the use

of ionizing radiation to preserve foods

1938 The U.S Food-Drug & Cosmetic (FDAC) Act became law.1942-1943 The Massachusetts Institute of Technology (MIT) team (B E

Proctor and colleagues), under a U.S Army contract,demonstrated the feasibility of preserving ground beefthrough irradiation using X rays

Late 1940s Post-World War II era of food irradiation development by U.S

government, industry, universities, and private institutionsbegan Chronic animal feeding studies began by the U.S.Army and by Swift & Company

1950 Beginning of the U.S Atomic Energy Commission food

irradiation program The United Kingdom began its foodirradiation development program (to be followed by manycountries)

1953 President D Eisenhower made his landmark "Atoms for Peace"

address at the United Nations General Assembly Manynations joined the research on peaceful uses of atomic energy,including applications in food preservation The U.S ArmyQuartermaster food irradiation program began

1955 The U.S Army Medical Department 10-year wholesomeness

testing program began

1958 The U.S Food Additives Amendment to the FDAC Act

classified food irradiation as an "additive."

1958-1959 The Soviet Union approved irradiation of potatoes and grains

The first commercial food (spices) irradiation facility wascommissioned in the Federal Republic of Germany.

1960 Canada approved potato irradiation The Federal Republic of

Germany banned food irradiation

1963-1964 The U.S Food and Drug Administration (FDA) approved

irradiation of bacon, wheat, flour, and potatoes (the baconclearance was repealed in 1968)

1964 The Joint FAO/IAEA Division of Nuclear Techniques in Food

and Agriculture was established

1965 The U.S Army Surgeon General declared radiation-sterilized

foods in general "wholesome."

1968 The U.S FDA turned back a U.S Army radiation-sterilized ham

petition and rescinded the 1963 bacon approval, alleginginsufficient data and experimental design/executiondeficiencies

1970 The U.S Army began a new wholesomeness testing program

under revised protocols The international irradiated foodswholesomeness testing project (IFIP) was established atKarlsruhe, Federal Republic of Germany by FAO, IAEA,OECD, and 24 countries

1973 Japan began industrial-scale potato irradiation (the irradiator is

still in operation in Sapporo, making it the longest workingfood irradiator in the world)

1976 The Joint FAO/IAEA/WHO Expert Committee on the

Wholesomeness of Irradiated Food (JECFI) gave a clean bill

of health to several irradiated foods and recommended thatfood irradiation be classified as a physical process

1978 The International Facility for Food Irradiation Technology

(IFFIT) was established at Wageningen, The Netherlands,under the sponsorship of FAO, IAEA, and The Netherlands.Until 1990, IFFIT trained hundreds of scientists fromdeveloping countries in food irradiation and contributed todevelop many applications of radiation processing to foods

1979 The U.S FDA Bureau of Foods formed an internal Irradiated

Foods Committee (final report submitted in July 1980) The

first Codex Alimentarius General Standard on Irradiated Food was adopted (it included conditional and unconditional

clearances for a limited number of foods, based on the 1976findings of the JECFI)

1980 The Joint FAO/IAEA/WHO Expert Committee on the

Wholesomeness of Irradiated Food (JECFI) declared that

"irradiation of any food commodity up to an overall averagedose of 1OkGy presents no toxicological hazards; hencetoxicological testing of foods so treated is no longerrequired." It also found that irradiation up to 1OkGy

"introduces no special nutritional or microbiologicalproblems."

1983 The Codex Alimentarius Commission adopted the Codex

General Standard for irradiated Foods and the Recommended Code of Practice for the Operation of Radiation Facilities Used for the Treatment of Foods (this was the first revision of

the standard of 1979, which made it valid for any food) Also

in 1983, the U.S FDA and Health & Welfare Canadaapproved irradiation of spices; Health & Welfare Canadapublished a proposal to reclassify food irradiation as a

process, and to adopt the new international Codex General Standard and Code of Practice', and the IFIP, founded in

1970, was terminated after achieving its goals; the foundation

of a successor organization was proposed

1984 The International Consultative Group on Food Irradiation

(ICGFI) was established under the aegis ofFAO/IAEA/WHO to evaluate global developments infood irradiation, provide a focal point of advise on theapplication of food irradiation to member states and thethree sponsoring organizations, and to furnish information

as required, through the organizations, to the JointFAO/IAEA/WHO Expert Committee on theWholesomeness of Irradiated Food, and the CodexAlimentarius Commission (See lists of ICGFI codes andrecommended dose limits in Tables 1.1 and 1.2.)

1985 Final Canadian and U.S food irradiation regulations were

published The U.S FDA approved irradiation of pork for

control of Trichinella spiralis.

1986 The U.S FDA approved irradiation to delay maturation, to

inhibit growth, and to disinfect food, including vegetablesand spices

1986-1989 The European Community prepared the first draft to harmonize

the legislation in member states with regard to foodirradiation The United States Department of Agriculture/Food Safety Inspection System (USDA/FSIS) approvedirradiation for control of trichina in pork

1990 The U.S FDA approved irradiation of poultry to

control Salmonella.

1992 The USDA/FSIS approved irradiation of poultry The first

commercial irradiation facility fully dedicated to foodprocessing in the United States was built

1992 At the request of Australia, the World Health Organization

(WHO) convened- an Expert Committee to reexamine thesafety of irradiated foods WHO reaffirms the conclusion thatirradiated foods are safe

Code of Good Irradiation Practice for Insect Disinfestation of Cereal Grains (ICGFI

Document 3), IAEA, Vienna, 1991

Code of Good Irradiation Practice for Prepackaged Meat and Poultry (to control pathogens

and/or extend shelf-life) (ICGFI Document 4), IAEA, Vienna, 1991

Code of Good Irradiation Practice for the Control of Pathogens and Other Microflora in Spices, Herbs and Other Vegetable Seasonings (ICGFI Document 5), IAEA, Vienna,

1991

Code of Good Irradiation Practice for Shelf-life Extension of Bananas, Mangoes and Papayas (ICGFI Document 6), IAEA, Vienna, 1991

Code of Good Irradiation Practice for Insect Disinfe station of Fresh Fruits (as a quarantine

treatment) (ICGFI Document 7), IAEA, Vienna, 1991

Code of Good Irradiation Practice for Sprout Inhibition of Bulb and Tuber Crops (ICGFI

Document 8), IAEA, Vienna, 1991

Code of Good Irradiation Practice for Insect Disinfe station of Dried Fish and Salted and Dried Fish (ICGFI Document 9), IAEA, Vienna, 1991

Code of Good Irradiation Practice for the Control of Microflora in Fish, Frog Legs and Shrimps (ICGFI Document 10), IAEA, Vienna, 1991

Code of Good Irradiation Practice for the Control of Pathogenic Microorganisms in Poultry Feed (ICGFI Document 19), IAEA, Vienna, 1995

Code of Good Irradiation Practice for Insect Disinfe station of Dried Fruits and Tree Nuts

(ICGFI Document 20), IAEA, Vienna, 1995

TABLE 1.1 Codes of Good Irradiation Practice Published by the International Consultative Group on Food Irradiation (ICGFI)

1996 The number of countries having clearances for irradiation of one

or more foods reaches 40, while 28 countries apply foodirradiation commercially A new Study Group on High DoseFood Irradiation is formed jointly by FAO, IAEA, and WHO

to examine the safety and wholesomeness of foods irradiated

at doses above 1OkGy

1997 A Joint FAO/IAEA/WHO Study Group on High Dose Food

Irradiation declared that foods irradiated at any dose are safeand that there is no need for upper dose limits Also in 1997,the U.S FDA approved irradiation of meats for pathogencontrol, and the number of member states belonging toICGFI reached 45

1998 The U.S FDA modified regulations on labeling of irradiated

foods such that the letter size indicating the treatment needed

to be equal in size only to the ingredients listed on the label.The ICGFI initiated procedures to bring about a modification

of the Codex General Standard for Irradiated Foods to

remove all references to a 10-kGy maximum overall absorbeddose, in accordance with the recommendation made in 1997

by the FAO/IAEA/WHO Study Group on High Dose FoodIrradiation

1999 A European Union Directive approved irradiation of spices,

herbs, and condiments; preparation of a final "positive list"

of food items permitted for radiation processing wasscheduled for the end of 2000 Construction of an electron-beam facility devoted to radiation processing of hamburgerpatties was under way in the United States; further facilitieswere in the planning stage at the time of writing A coalition

of American food industry groups headed by the NationalAssociation of Food Processors presented a petition to theU.S FDA to clear irradiation of ready-to-eat foods, as a result

of multiple outbreaks of listeriosis involving such products.Also, the USDA cleared irradiation of meat for pathogencontrol, and

2000 The U.S FDA cleared irradiation for control of Salmonella in

shell eggs, and for decontamination of seeds for sprouting

Although the issuance of the Codex General Standard for Irradiated Foods in 1984

was determinant in moving many countries to enact food irradiation regulations,other countries had approved various food processing applications of ionizingradiation much earlier, as described in Chapter 17 Thus, the Soviet Union clearedirradiation of potatoes and grains in 1958/59, followed by Canada (potatoes, 1960)and the United States (bacon, wheat, flour and potatoes, 1963/64) However, it wasduring the 1980s and 1990s that food irradiation clearances proliferated, possibly as

a result of recurrent outbreaks of foodborne illnesses described elsewhere in thisbook According to the database on food irradiation clearances maintained by theInternational Consultative Group on Food Irradiation (ICGFI 1999), the latestaddition to the list of countries having them is the European Union (EU), whichapproved irradiation of spices, condiments, and herbs in 1998 (Anonymous1999a,b) The list of products approved by the European Union was expected toincrease after December 1999 according to the terms of the corresponding Direc-tives

Although there are historically important events and dates concerning irradiation

of various foods or groups of foods, the prominence that irradiation of meat andpoultry products have had from the toxicologically and regulatory standpoints iswell established Furthermore, irradiation of meats and poultry may soon be the key

to a wider adoption of the technology the world over because of its unique potential

as a control measure of meat- and poultryborne bacterial diseases well known

to, and feared by, the public A recapitulation of the history of food irradiationpublished by Goresline (1982) attributed initial research on this technology, in-cluding the pioneering efforts in the area of meat irradiation, to scientists at theMassachusetts Institute of Technology in the late 1930s and early 1940s Thiswork was undertaken on behalf of the United States Army, which at the timewas seeking new food preservation methods that would allow improvements inthe diet of troops stationed abroad By 1943, scientists had demonstrated thatground beef could be preserved by exposing it to X rays Various foods had been

ICGFr Document8

63,7,1767,13,173,203,20

101010444

5,195,19

Dose Maxima (kGy)

0.2

1.01.02.51.01.05.0

5.03.02.07.03.02.0

10.01.0

Purpose

To inhibit sproutingduring storage

To delay ripeningInsect disinfestationShelf-life extensionQuarantine control"

Insect disinfestationReduction of microbial loadReduction of pathogenicmicroorganisms*7

Shelf-life extensionControl of infection byparasites6

Reduction of pathogenicmicroorganisms6

Shelf-life extensionControl of infection byparasites6

Reduction of pathogenicmicroorganisms6

Insect disinfestation

Food Classes

Class 1: bulbs, roots, and tubers

Class 2: fresh fruits and vegetables

(other than class 1)

Class 3: cereals and their milled products,

nuts, oilseeds, pulses, dried fruits

Class 4: fish, seafood, and their products

(fresh or frozen)

Class 5: raw poultry and meat and their

(fresh or frozen)

Class 6: dry vegetables, spices, condiments,

animal feed, dry herbs, and herbal teas

TABLE 1.2 Advisory Technological Dose Limits for Good Irradiation Practice

9 9

1.0 3.0

>10

>10

>10

Insect disinfestation Control of molds Reduction of microbial load Sterilization

Quarantine control

Class 7: dried food of animal origin

Class 8: miscellaneous foods, including

but not limited to honey, space foods,

hospital foods, military rations, spices,

liquid egg, thickeners

a Minimum dose may be specified for particular pests; for fruit flies > O ISkGy.

^Minimum dose may be specified taking into account that the objective of the treatment is to ensure the hygienic quality of the food.

International Consultative Group on Food Irradiation.

Notes' (1) product grouping into classes (except class 8) is based on similarity in chemical composition (i.e., chemiclearance); (2) maximum dose limits have been set for

good irradiation practice and not from a food safety viewpoint.

Source: IAEA (1998).

sterilized by exposure to ionizing radiation as early as 1951 (Proctor and Goldblith1951).

According to Thayer et al (1986), early research on food irradiation concludedthat only cathode-ray radiation (i.e., electrons) could be applied efficiently andsafely to foods; X rays were considered impractical because of the extremelylow efficiency obtained when converting from electrons to X rays The advent ofnew electron accelerators equipped with solid-state electronics in the late 1990s,however, and the technological advantages that these machines offer in terms ofthroughput and flexibility, as reviewed by Brynjolfsson (1989), and most impor-tantly, in terms of overcoming potential public objections to isotopic sources, hasmade this source of radiation a most attractive prospect for future commercial-scaleirradiation of meats and poultry (Renwick and Hansen 1996)

Extensive research on irradiation of meat, chicken, and other foods was carriedout by the U.S Army after 1953 at its Natick Laboratories in Massachusetts.However, most of the early research focused on sterilization, as opposed to shelf-life extension, and/or "pasteurization" (i.e., radappertization, radurization, andradicidation, respectively, in the lexicon of the time) of meat and poultry products(Sigurbjornsson and Loaharanu 1987) Large-scale testing was also conducted onthe safety and wholesomeness of meat and poultry products irradiated at what arecurrently considered high doses (i.e., > 1OkGy) (Kraybill et al 1956, Ronning et al

1980, Skala et al 1987, Thayer et al 1987) In addition to research conducted in theUnited States, work on food irradiation in the 1950s and 1960s was undertaken bymany countries, including Belgium, Canada, France, Egypt, the Federal Republic

of Germany, The Netherlands, the Soviet Union, and the United Kingdom.Nickerson et al (1986) described the shift in civilian irradiation research em-phasis from sterilization to shelf-life extension in the 1960s; this was a result offindings concerning detrimental effects of high-dose irradiation on the flavor ofvarious food products tested In 1963, the U.S Army petitioned the Food and DrugAdministration (FDA)—and was granted—approval for sterilizing vacuum-packaged, raw bacon using ionizing radiation at 45-56 kGy and 50C (Thayer

et al 1987) This historical first clearance for irradiation of a meat product in theUnited States, however, was rescinded in 1968 because the safety studies thatconstituted the basis for the approval were deemed to have had serious deficiencies(Anonymous 1968) Later, the FDA and the National Research Council of the U.S.National Academy of Sciences conducted additional extensive multigenerationalstudies that involved feeding animals with irradiated chicken, beef, pork andpork products The results, reviewed and discussed by Raica and Baker (1972)and Baker and Chandler (1975), indicated that irradiated products were lexicolo-gically safe

Various international organizations [(the Food and Agriculture Organization ofthe United Nations (FAO), the International Atomic Energy Agency (IAEA), andthe World Health Organization (WHO)] had recognized the potential of food irra-diation to improve the quality and safety of foods since the 1950s An ExpertPanel on Wholesomeness of Irradiated Foods was jointly convened by the FAO,the IAEA, and the WHO in Brussels, Belgium, as early as 1961 This panel

recommended that the wholesomeness of irradiated food products should be studiedbefore such products were consumed.

There is little doubt that one of the most pivotal events in the advancement offood irradiation was the creation, in 1964, of the Joint FAO/IAEA Division ofNuclear Techniques in Food and Agriculture, headquartered at the InternationalAtomic Energy Agency (IAEA) in Vienna, Austria Soon thereafter, a JointFAO/IAEA/WHO Expert Committee on Food Irradiation (JECFI) was also estab-lished

The JECFI convened in 1964, 1969, 1976, and 1980 Its most decisive tion, however, was the 1980 declaration that "irradiation of any food commodity up

interven-to an overall average dose of 1OkGy causes no interven-toxicological hazard; hence, interven-cological testing of food so treated is no longer required" (Anonymous 1981) Inaddition, the JECFI recognized that "irradiation of a food up to an overall averagedose of 1OkGy introduces no special microbiological and nutritional problems."This memorable declaration resulted in the development and eventual adoption of

toxi-the Codex General Standard for Irradiated Foods (CAC 1984a) and its associated Recommended Code of Practice for the Operation of Radiation Facilities Used for the Treatment of Foods (CAC 1984b) The importance of the Codex General Stand-

ard on Irradiated Food cannot be overemphasized (Wehr 1996, WHO 1988a) inview of the recognition of the Codex Alimentarius as the main body of foodstandards for international trade within the Agreement on the Application of Sani-tary and Phytosanitary Measures (SPS), which was one of the most importantinternational agreements emanating from the Uruguay Round of GATT (GeneralAgreement on Tariffs and Trade) negotiations that also created the World TradeOrganization (WTO)

The cooperation between FAO, IAEA, and WHO on food irradiation has beencontinuous and successful over the years In 1983, the three organizations jointlysponsored the creation of the International Consultative Group on Food Irradiation(ICGFI), which has been instrumental in bringing about a solid regulatory andpractical framework for the proper application of food irradiation technology.The ICGFI is an international organization on its own right—and listed as such

in the United Nations roster of specialized UN agencies—although its Secretariathas been at the Food and Environmental Protection Section of the Joint FAO/IAEADivision of Nuclear Techniques in Food and Agriculture, in Vienna, Austria, sinceICGFI was formed In 1999, 45 governments were members of the ICGFI (ICGFI1999)

Because of an increase in the demand for radiation-sterilized foods broughtabout by military, athletic, and hospital needs, FAO, IAEA, and WHO convened

a joint Study Group on High Dose Food Irradiation in 1997 The Study Group(WHO 1997, 1999) examined the available data on high-dose (10-100-kGy) pro-cessing of food and concluded that:

"Doses greater than 1OkGy: a) will not lead to changes in the composition of the food that, from a toxicological point of view, would have an adverse effect on human health; b) will greatly reduce potential microbiological risk to the consumer; c) will

not lead to nutrient losses to an extent that would have an adverse effect on thenutritional status of individuals or populations Therefore, foods treated with dosesgreater than 1OkGy can be considered safe and nutritionally adequate when producedunder established Good Manufacturing Practices."

On the basis of these important conclusions, in 1998 the ICGFI officially

re-quested that the Codex General Standard for Irradiated Foods be modified to delete

all references to a maximum overall absorbed dose of 1OkGy or any other arbitraryvalue, and thus set in motion the corresponding Codex Alimentarius Commissionrevision mechanism of the standard

1.1.2 Proving the Wholesomeness of Irradiated Foods

If cooked foods had not been eaten by humans since the dawn of time, the chemicalchanges induced in food by cooking would have given scientists material forcenturies of research before food control authorities would approve—if ever—thecooking process To a large extent, and despite the fact that any chemical changes

in food brought about by ionizing radiation are no different from, and minimal incomparison to, those caused by heating, as described in Chapter 3, this has been thecase with foods treated with ionizing radiation, for which proof of wholesomenessand safety has been demanded to extremes never before required of food treated byany other processing technique

Research on the wholesomeness of irradiated foods dates back to 1925 (Ludwigand Hopf 1925) Since then, more than 1200 studies have been published on thesubject (CAST 1986) (Many of these reports and publications can be retrievedfrom the Food Irradiation Wholesomeness Collection of the U.S National Agri-cultural Library, 10301 Baltimore Blvd., Beltsville, MD 20705-2351 in CD-ROM,

or from the database entitled Bibliography on Irradiated Foods maintained by

the Federal Research Center for Nutrition, Haid-und-Neu-Strasse 9, D-76131Karlsruhe, Germany.)

The massive research conducted over the years to establish the wholesomenessand safety of irradiated foods, mostly in response to concerns expressed by con-sumer and other groups—including some having agendas of unconditional opposi-tion to this process—is undoubtedly the single, most extensive undertaking of foodscientists ever As such, its mere description would require several volumes Sincethe philosophy of this book is that food irradiation needs no further justification, thewholesomeness of irradiated foods is covered only from a historical perspective.The interested reader is referred to specific excellent treatises on the subject ofwholesomeness and safety of irradiated food (WHO 1994, Diehl 1990) For thoseinterested, a mordant denunciation of the groups actively opposing food irradiation

in the past was provided by Giddings (1986)

Some of the most recent and complete reviews on the assessment of the someness of irradiated foods are those of Thayer (1994) and Diehl and Josephson(1994) The former discusses much of the studies conducted on chicken andalso provides an extensive review on the nutritional adequacy of irradiated foods;

whole-the latter covers whole-the four main aspects of relevance in this regard, individually:radiological safety, microbiological safety, nutritional adequacy, and toxicologicalsafety In addition, these reviews describe the adoption of chemical studies—on thebasis of the "chemiclearance" principle: to complement animal studies used earlier

to test the toxicological safety of irradiated foods Most of these aspects are cussed extensively in the present book within the chapters that cover food irradia-tion microbiology and chemistry (see Chapters 2 and 3, respectively), as well as inthe relevant sections on chemical, physical, and microbiological effects of ionizingradiation of chapters that deal with specific food groups Consequently, this sectiononly highlights some of the classical toxicological and genetic work that demon-strated the safety and wholesomeness of irradiated foods

dis-Toxicological work conducted on radiation sterilization of chicken between

1976 and 1984 by Raltech Scientific Services, under contract with the U.S Army,was reviewed by Thayer et al (1987) No evidence of genetic toxicity or terato-genic effects were found in mice, hamsters, rats, or rabbits fed radiation-sterilizedchicken, nor were any abnormalities detected in multigeneration studies involvingdogs, rats, or mice This and other long-term studies on the toxicology ofirradiated foods were described earlier by Reber et al (1966) and Cohen and Mason(1976)

The positive results of repeated extensive toxicological tests on the effect ofradiation doses higher than 1OkGy on chicken, conducted in the early 1980s, made

it possible to extrapolate the declaration of wholesomeness to other muscle foodsirradiated at doses of up to 1OkGy on the basis of the "chemiclearance principle"(Taub et al 1976, 1980) This international effort was conducted in addition to theextensive toxicological data gathered over the years on radiolytic compounds pro-duced in radiation-sterilized beef and other meat products (Josephson 1983b) Thechemiclearance principle, which consists of evaluating the safety of irradiated foodsprimarily on the basis of chemical data, was proposed by Taub et al (1976) as asolution to the problem posed by having to gather data on wholesomeness andsafety of individual classes of irradiated foods for purposes of regulatory clearance.Because analytic data available for irradiated meats indicated little differences inradiolytic reactions and on the types and amounts of compounds formed in variousmeats, these authors suggested that extrapolation of experimental data from onemeat to another was valid and should be used in future irradiation clearances Areview by Elias (1989) discussed the methodology for assessing the safety andwholesomeness of irradiated foods Just as importantly, this review offered a com-prehensive description of the weaknesses and shortcoming of past toxicologicalstudies

A comprehensive examination conducted by the Joint FAO/WHO/IAEA JointExpert Committee on Food Irradiation (JECFI) of 100 compounds from irradiatedbeef, pork ham, and chicken conclusively demonstrated the occurrence of the samecompounds in nonirradiated foods, and declared irradiated meats and poultrywholesome and safe (Anonymous 1981) Interested readers may refer to that reportfor a comprehensive discussion of the toxicological safety of irradiated meats andpoultry The Council for Agricultural Science and Technology (CAST 1986), in

turn, has published a report that discusses the toxicological work constituting thebasis for declaring irradiated foods wholesome and safe.

The potential genetic toxicity of irradiated meats and poultry has also receivedconsiderable attention from researchers Renner et al (1982) examined this poten-tial hazard in Chinese hamsters, rats, and mice fed irradiated chicken Their con-clusions were the same previously reached by many researchers in that none of thetests evidenced genetic toxicity as a result of consumption of irradiated chickendiets A similar conclusion had been reached by Phillips et al (1980) after exam-ining the potential genetic toxicity of extracts and digests of irradiated and non-irradiated chicken and other foods on Chinese hamster ovary cell cultures.Furthermore, no differences in the reproductive performance of dogs fed thermallyprocessed or gamma- or electron-irradiated chicken over a 3-year period had beendetected by Chappie and Scheidt (1980), either The average dose applied to chick-

en fed to the dogs was 59kGy Mittler (1979) had earlier used 10-month-oldsamples of electron-irradiated ham and gamma-irradiated beef (47-71 kGy in eitherinstance), frozen or thermally preserved beef, and nonirradiated ham to feed

Drosophila melanogaster for evaluation of possible appearance of genetic

aberra-tions attributable to irradiation No incidence of abnormal X or Y chromosomes as

a result of irradiated diets was detected Later work by Thayer et al (1987) firmed that no genetic or teratogenic effects in mice, hamsters, rats, and rabbits fedchicken sterilized by gamma radiation (maximum of 68 kGy, minimum of 46 kGy,

con-578 Gy/min) were present, although these authors reported unexplained reductions

in the hatchability of D melanogaster eggs reared on gamma-irradiated meat.

Potential mutagenicity from irradiated meats and poultry has been examined as

well A modified Ames Salmonella-mammalian enzyme mutagenicity test used by

Fruin et al (1980) to evaluate mutagenicity of frozen beef and chicken sterilizedthermally or by irradiation—using electron or gamma sources—indicated no mu-tagenic activity in any of the meat samples According to Elias (1989), techniquesbased on short-term mutagenicity screening that more closely mimic the actualinteractions between food constituents and digestive secretions have been signifi-cant in demonstrating the safety of irradiated foods

1.2 POTENTIAL SOCIAL AND ECONOMIC BENEFITS

OF FOOD IRRADIATION

Food irradiation applications belong to either one of two basic types: (1) thoseconcerned with preventing food losses and (2) those that result in microbial decon-tamination of food products or in inactivation of foodborne human parasites Theformer group of applications is conducive to safeguarding the food supply againstlosses induced by physiological processes such as sprouting of bulb and tubercrops, or to protecting foods against damage from spoilage bacteria or insect pestsduring storage As a result, these applications are relevant in enhancing foodsecurity The second group, on the other hand, are concerned with the hygienicquality of foods and are conducive to eliminating or minimizing foodborne

biological hazards; therefore, they are related to food safety These include

"cold pasteurization of solid and semisolid foods," and radiation-sterilization offood

1.2.1 Social and Economic Benefits of Food

Irradiation in Relation to Food Security:

Preventing Postharvest Food Losses

and Extending the Shelf Life of Perishable Foods

Recurring famines or food shortages and large population increases in manyareas of the world have placed food security considerations very high in theagenda of many governments and international organizations (WHO 1992).Recognizing this fact and the need to ensure a stable, abundant, and safefood supply to all, the FAO organized the first World Food Summit in Rome in1996

Insect damage to stored dried crops such as grains, pulses, dried fruits, and nutsranks very high among the major causes of postharvest food losses, followed byother causes such as spoilage through sprouting of bulb and tuber crops Foodlosses attributable to insect damage alone are reported to be as high as 15-50%

of the total crop production in some areas (WHO 1988a), often denying a hungryworld the benefits of hard work, improved agricultural practices, and increasedproductivity

Control of insect infestation in stored agricultural commodities, in general, hasrelied on the widespread use of chemical fumigants, a practice quite effective indealing economically with the problem of insect pests of stored foods However, aspointed out by Loaharanu (1994), chemical fumigants are rapidly becoming un-available because of serious health and environmental consequences that areprompting countries to ban them Ethylene dibromide (EDB), for example, wasbanned in most countries because it is a carcinogen, and the same is true of ethyleneoxide (EO), banned by the European Union in 1991 and by the United States—foruse in ground spices—since 1996 One of the last major chemical fumigant pre-sently available, methyl bromide (MB), is scheduled by the Montreal Protocol to bephased out in the near future because of its deleterious effect on the ozone layer,with potentially serious economic consequences to many agricultural commodityexporting countries (Ross and Vail 1993)

Consequently, the search for safe, cost-effective, proven insect control ogies for rapid adoption has brought irradiation to the forefront Irradiation isenvironmentally friendly in comparison to ozone-depleting or contaminating chemi-cal fumigants, leaves no residues in food or in the environment, and has the addedadvantage of being effective against a wide variety of insects

technol-The potential role of irradiation in insect disinfestation of stored staple, driedfoods, and in preventing food losses through inhibition of sprouting of bulb andtuber crops—as described in the corresponding chapters of this book—may have amajor impact on the food security situation in some areas of the world In addition,the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture is

sponsoring a research program focusing on development of shelf-stable foodproducts through processes involving irradiation The main emphasis of theprogram is on rendering perishable or short-lived traditional foods shelf-stable,which could greatly contribute to a more abundant food supply in many coun-tries—especially in those lacking a good cold chain for refrigerated storage—and

to extend the period of availability of some foods having characteristics that makethem hard to store

1.2.2 Social and Economic Benefits

in Relation to Food Safety: Controlling

Pathogenic Bacteria and Parasites in Foods

Regardless of how successful the efforts made by the public and private sectors mayhave been in reducing the number of cases of human illnesses transmitted by freshand processed foods relative to population growth, published figures on the inci-dence of foodborne intoxications and infections indicate that rather than decreasingthese are on the increase worldwide (Todd 1997a,b) In general, however, the globalmagnitude of the foodborne disease problem can only be estimated, since fewcountries have appropriate disease surveillance and reporting systems, and thosethat do are increasingly discovering the vast underestimation of such figures It has

• been calculated that only some 10% of incidents of foodborne disease, at most, arereported in industrialized countries (Motarjemi and Kaferstein 1997), and that thenumber of cases of enteric disease based on actual isolation of pathogenicmicroorganisms from patients is underestimated by a factor of 20-100 (Tauxe1991)

The significance of the foodborne illness problem for society is measured innumber of cases—and hence human suffering—which often cannot be translatedinto material values It does, however, represent a heavy economic burden tosociety as well, and one for which the cost can be quantified The annual cost

of foodborne illness caused by Campylobacter jejuni, Clostridium perfringens, Escherichia coli O157:H7, Listeria monocy to genes, Salmonella spp., Staphylo- coccus aureus, and Toxoplasma gondii in the United States alone has been estimated

at between U.S 6.5-13.3 milliards (one thousand million; equivalent to U.S lions) and U.S $ 19.7-34.9 milliards depending on the parameters used to estimatethe value of human life (Buzby and Roberts 1997) Losses from some specificillnesses were estimated by these authors at U.S $ 0.4 milliard for toxoplasmosis;

bil-U.S $ 0.12-0.25 milliard for listeriosis; bil-U.S $ 0.1-0.3 milliard for Escherichia coli infections; U.S $ 0.7-4.3 milliards for campylobacteriosis, and U.S $ 0.1 milliard for Clostridium perfringens enteritis in 1995 It should be pointed out that

these figures were calculated on the basis of reported cases and that, therefore, theactual numbers and cost figures may be severalfold those presented by the authors

For example, campylobacteriosis and enteritis from C perfringens are seldom

severe enough and/or do not last long enough to merit medical assistance, andthus go largely unreported The situation is similar in other countries The annual

cost of five foodborne, infectious diseases, including medical attention and actualvalue of lives lost, has been calculated at £ 300-700 million in England and Wales[Roberts, J A., 1996 cited in Buzby and Roberts (1997)] According to the latestestimate made by the Center for Disease Control and Prevention (CDC) of theUnited States, the number of annual foodborne pathogen-linked illnesses in thatcountry is 14 million, including 60,000 hospitalizations and 1800 deaths (Anon-ymous 1999c) This report also indicates that bacterial infections account for 72%

of deaths, and that five pathogens are involved in more than 90% of such deaths:

Salmonella (31%); Listeria (28%); Toxoplasma (21%); Norwalk viruses (5%); and Escherichia coli O157:H7 (3%).

Parasitic diseases, on the other hand, continue to afflict millions throughout theworld, at staggering costs to society (Roberts and Murrell 1993) Murrell et al.(1986) indicated that the severity of some of these diseases should increase con-cerns about the need to control them Neurocysticercosis, caused by ingestion of

Taenia solium metacestodes in undercooked pork meat, is a serious public health

problem in some areas of Latin America, Asia, and Africa (Tsang and Wilson

1995) Similarly, toxoplasmosis, caused by Toxoplasma gondii, can be transmitted

to humans through foods, mainly by pork meat and meat from various wild animals

(Dubey 1994) A third human parasite of importance found in pork, Trichinella spiralis, the causative agent of trichinosis, has nearly been eliminated in some

European countries through inspection of each slaughtered swine, followed bypreventive action at the farm level However, this remedy is hardly feasible inthe United States without automation of inspection because abattoir slaughter rates

of 750-1000 hogs per hour are common Although development of enzyme-linkedimmuno adsorbent assays (ELISA) for trichina may facilitate individual, automaticexamination of swine carcasses in the future, these methods are only diagnostic(Eckert 1996)

Irradiation, on the other hand, can provide corrective action on pork carcassespositive for parasites and thus constitute an alternative to condemnation or totechniques presently used for destruction of the larvae (i.e., cooking or freezing).Most importantly, irradiation can be used to "cold pasteurize" solid and semisolidfoods of animal and plant origin, packaged for retail in final form; this not onlyallows inactivation of parasites and/or elimination of potentially pathogenic micro-organisms that may be present, but also prevents food recontamination No otherstrictly physical food processing technique exists that can accomplish these objec-tives without significant increases in food temperature, thus permitting decontami-nation of retail-packaged raw foods

The potential benefits to public health that could be derived through radiationtreatment of certain foods have been reviewed by Todd (1993) and Kaferstein andMoy (1993) These benefits have prompted full endorsement of food irradiationtechnology by many national and international organizations Among these are theWorld Health Organization (WHO 1988b), the American Medical Association

(Food Chemical News, Feb 9, 1987), the American Dietetic Association (ADA

1996), the Council on Agricultural Science and Technology (Thayer et al 1996),and the Institute of Food Technologists (Olson 1998)

ADA (1996), Position of the American Dietetic Association: Food Irradiation, ADA Info,

The American Dietetic Association (http://www.eatright.org/airradi.html).

Anonymous (1968), Radiation and radiation sources; food additives intended for processing

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Anonymous (1981), Wholesomeness of Irradiated Food: A Report of a Joint FAO/ IAEA/WHO Expert Committee on Food Irradiation, WHO Technical Report Series,

659, World Health Organization, Geneva.

Anonymous (1999a), Directive 1999/2/EC of the European Parliament and of the Council of

22 February, 1999 on the approximation of the laws of the Member States concerning

foods and food ingredients treated with ionising radiation, Official J Eur Communities

L 66/16-22.

Anonymous (1999b), Directive 1999/3/EC of the European Parliament and of the Council

of 22 February, 1999 on the establishment of a Community list of foods and food

ingredients treated with ionising radiation, Official J Eur Communities L 66/24-25 Anonymous (1999c), New CDC foodborne illness estimates makes others obsolete, Food Regul Weekly, pp 3-5 (Sept 20, 1999).

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Brynjolfsson, A (1989), Future radiation sources and identification of irradiated foods, Food Technol 43(7): 84-87.

Buzby, J C and Roberts, T (1997), Economic costs and trade impacts of microbial

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CAC (1984b), Recommended International Code of Practice for the Operation of Radiation Facilities Used for the Treatment of Foods, Codex Alimentarius Commission, CAC/Vol.

XV, E-I, CAC/RCP 19-1979 (rev 1), Joint FAO/WHO Food Standards Programme, FAO, Rome.

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Chappie, III, F E and Scheldt, A (1980), Reproductive performance of dogs fed

radapper-tized chicken for 3 years, Proc Eur Meeting Meat Research Workers, 26, Vol I, E-23,

pp 183-184.

Cohen, J S and Mason, V B (1976), Radappertization (radiation sterilization) of foods,

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Natick/TR-77/009 Food Engineering Laboratory, FEL-62, Dec 1976.

Diehl, J F (1990), Safety of Irradiated Foods, Marcel Dekker, New York, pp 1-7.

Diehl, J F and Josephson, E S (1994), Assessment of Wholesomeness of irradiated foods

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Dubey, J P (1994), Toxoplasmosis, J Am Vet Med Assoc 205: 1593-1598.

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as the various forms of heating.

2.2 MECHANISMS OF INACTIVATION

Radiation, whether ionizing or nonionizing (i.e., a photon of energy or an electron),inactivates microorganisms by damaging a critical element in the cell, most oftenthe genetic material This damage prevents multiplication and also randomly ter-minates most cell functions Damage to the genetic material occurs as a result of adirect collision between the radiation energy and the genetic material, or as a result

of the radiation ionizing an adjacent molecule, which in turn reacts with the geneticmaterial In most cells, the adjacent molecule is usually water (Grecz et al 1983)

In the first instance, the effects are straightforward A photon of energy or anelectron randomly strikes the genetic material of the cell and causes a lesion in theDNA The lesion can be a break in a single strand of the DNA or, if the orientation

of the DNA is appropriate, the energy or electron can break both strands on theDNA Single-strand lesions may not be lethal in and of themselves, and may in factresult in mutations However, large numbers of single-strand lesions may exceedthe bacterium's repair capability, which ultimately results in the death of the cell

Food Irradiation: Principles and Applications, Edited by R A Molins

ISBN 0-471-35634-4 © 2001 John Wiley & Sons, Inc.

CHAPTER 2

A double-strand lesion occurs when the photon or electron strikes adjacent areas

on both strands of the DNA This in effect severs the DNA into two pieces Doublestrand lesions are almost invariably lethal, as the mechanism necessary to repair adouble-strand lesion is beyond the ability of virtually all biological systems How-ever, because of the necessary orientation of the DNA in relation to the irradiationsource, double-strand lesions occur much less frequently than do single-strandlesions

The interactions of radiation with molecules adjacent to the genetic material aremore complex The chemistry of the irradiation of water is well known Radiationcauses water molecules to lose an electron, producing H2O+ and e~ These pro-ducts react with other water molecules to produce a number of compounds, includ-ing hydrogen and hydroxyl radicals, molecular hydrogen and oxygen, as well ashydrogen peroxide (Arena 1971) The reactive components of these equations,which are generally believed to be most significant, are the hydroxyl radicals(OH~) and hydrogen peroxide (H2O2) These molecules react with the nucleic acidsand the chemical bonds that bind one nucleic acid to another in a single strand, aswell as with the bonds that link the adjacent base pair in the opposite strand Sincethe location of the ionization of the water molecules is random, the subsequentreactions with the nucleic acids are random As with the direct interaction ofradiation with DNA, the indirect action can result in both single- and double-strandlesions, with the same overall effects

In addition to effects on the genetic material, radiation has a variety of effects onthe other components of the cell Applying radiation to a cell results in the directand indirect interaction with cell components such as membranes, enzymes, andplasmids These interactions may have the potential to be lethal to the cell, in and ofthemselves but in most cases would not be so unless there were also damage to thegenetic material These interactions may have a role in the survival of sublethallyinjured bacteria, in that a cell that has not sustained lethal genetic damage may bedamaged in other ways that complicate or impede survival of the injured cell.The radiation sensitivity of various organic compounds is proportional to theirmolecular weight On the basis of this assumption, it has been estimated that a dose

of 0.1 kGy would damage 0.005% of the amino acids, 0.14% of the enzymes, and2.8% of the DNA within a given cell (Pollard 1966) It is difficult to separate theeffects of genetic damage from the nongenetic damage of irradiation, and thedifferentiation may not be of any practical value However, one important aspect

of this point is that the damage is random and not related to a specific genetic locus

or cell component This is a significant factor in the elucidation of radiation tance of bacteria, especially in relation to the ability of microorganisms to develop

resis-or acquire radiation resistance

2.3 MECHANISMS OF MICROBIAL SURVIVAL AND REPAIR

Since the primary means of inactivation of microorganisms by radiation is damage

to DNA, the mechanisms of survival and repair center on the repair of DNA The