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Food ProcessingPrinciples and Applications

Food ProcessingPrinciples and Applications

Edited byJ. Scott Smith and Y. H. Hui

©2004 Blackwell PublishingAll rights reserved

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Printed on acid-free paper in the United States ofAmerica

First edition, 2004

Library of Congress Cataloging-in-Publication Data

Food processing : principles and applications / edited by J. Scott Smith and Y. H. Hui.—1st ed.

p. cm.Includes index.ISBN 0-8138-1942-3 (acid-free paper)1. Food industry and trade. I. Smith, J. Scott II.

Hui, Y. H. (Yiu H.)

TP370.F626 2004664—dc22

2004007256

The last digit is the print number: 9 8 7 6 5 4 3 2 1

Contents

Contributors, vii

Preface, xi

Part I Principles1. Principles of Food Processing, 3

Y. H. Hui, Miang-Hoog Lim, Wai-Kit Nip, J. Scott Smith, P. H. F. Yu2. Food Dehydration, 31

Robert Driscoll3. Fermented Product Manufacturing, 45

Wai-Kit Nip4. Fundamentals and Industrial Applications of Microwave and Radio Frequency in

Food Processing, 79Yi-Chung Fu

5. Food Packaging, 101Lisa J. Mauer, Banu F. Ozen

6. Food Regulations in the United States, 133Peggy Stanfield

7. Food Plant Sanitation and Quality Assurance, 151Y. H. Hui

Part II Applications8. Bakery: Muffins, 165

Nanna Cross9. Bakery: Yeast-leavened Breads, 183

Ruthann B. Swanson10. Beverages: Nonalcoholic, Carbonated Beverages, 203

Daniel W. Bena11. Beverages: Alcoholic, Beer Making, 225

Sean Francis O’Keefe12. Grain, Cereal: Ready-to-Eat Breakfast Cereals, 239

Jeff D. Culbertson13. Grain, Paste Products: Pasta and Asian Noodles, 249

James E. Dexter14. Dairy: Cheese, 273

Samuel E. Beattie15. Dairy: Ice Cream, 287

Karen A. Schmidt

v

16. Dairy: Yogurt, 297Ramesh C. Chandan

17. Dairy: Milk Powders, 319Marijana Carić

18. Fats: Mayonnaise, 329Susan E. Duncan

19. Fats: Vegetable Shortening, 343Lou Ann Carden, Laura K. Basilo

20. Fats: Edible Fat and Oil Processing, 353Ingolf U. Grün

21. Fruits: Orange Juice Processing, 361Y. H. Hui

22. Meat: Hot Dogs and Bologna, 391Ty Lawrence, Richard Mancini

23. Meat: Fermented Meats, 399Fidel Toldrá

24. Poultry: Canned Turkey Ham, 417Edith Ponce-Alquicira

25. Poultry: Poultry Nuggets, 433Alfonso Totosaus, Maria de Lourdes Pérez-Chabela

26. Poultry: Poultry Pâté, 439Maria de Lourdes Pérez-Chabela, Alfonso Totosaus

27. Seafood: Frozen Aquatic Food Products, 447Barbara A. Rasco, Gleyn E. Bledsoe

28. Seafood: Processing, Basic Sanitation Practices, 459Peggy Stanfield

29. Vegetables: Tomato Processing, 473Sheryl A. Barringer

Index, 491

vi Contents

vii

Sheryl A. Barringer, Ph.D. (Chapter 29)Ohio State UniversityDepartment of Food Science and TechnologyRoom 1102015 Fyffe RoadColumbus OH 43210-1007 USAPhone: 614-688-3642Fax: 614-292-0218Email: [email protected]

Laura K. Basilio, M.S. (Chapter 19)Sensory Evaluation Consultant815 Josepi DriveKnoxville, TN 37918 USAPhone: 865-938-3017E-mail: [email protected]

Samuel E. Beattie, Ph.D. (Chapter 14)Extension SpecialistDepartment of Food Science and Human NutritionIowa State UniversityAmes, IA 50011-1120 USAPhone: 515-294-3357Fax: 515-294-1040E-mail: [email protected]

Daniel W. Bena (Chapter 10)Senior FellowPepsiCo International700 Anderson Hill Road, 7/3-738Purchase, NY 10577 USAPhone: 914-253-3012E-mail: [email protected]

Gleyn E. Bledsoe, Ph.D., C.P.A. (Chapter 27)Biological Systems Engineering DepartmentWashington State UniversityPullman, WA 99164-6373 USAPhone: 509-335-8167Fax: 509-335-2722E-mail: [email protected]

Lou Ann Carden, Ph.D. (Chapter 19)Nutrition and DieteticsWestern Carolina University126 Moore HallCullowhee, NC 28723 USAPhone: 828-227-3515E-mail: [email protected]

Marijana Carić, Ph.D., P.E. (Chapter 17)ProfessorFaculty of TechnologyUniversity of Novi Sad21000 NOVI SAD, Bulevar Cara Lazara 1Serbia and MontenegroPhone: 381 21 450-712Fax: 381 21 450-413E-mail: [email protected]

Ramesh C. Chandan, Ph.D. (Chapter 16)Consultant1364, 126th Avenue NWCoon Rapids, MN 55448-4004 USAPhone: 763-862-4768Fax: 763-862-5049E-mail address: [email protected]

Contributors

Nanna Cross, Ph.D., R.D., L.D. (Chapter 8)Consultant1436 West Rosemont Avenue, Floor OneChicago, IL 60660Phone: 773-764-7749E-mail: [email protected]

Jeff D. Culbertson, Ph.D. (Chapter 12)Professor: Food Science and ToxicologyUniversity of Idaho202A Food Research CenterMoscow, Idaho 83844-1056 USAPhone: 208-885-2572 Fax: 208-885-2567E-mail: [email protected]

James E. Dexter, Ph.D. (Chapter 13)Canadian Grain CommissionGrain Research Laboratory1404-303 Main StreetWinnipeg, Manitoba, Canada R3C 3G8Phone: 204-983-6054Fax: 204-983-0724E-mail: [email protected]

Robert Driscoll, Ph.D., P.E. (Chapter 2)Department of Food Science and TechnologyUniversity of New South WalesSydney, NSW 2052 AustraliaPhone: 0612-9385.4355Fax: 0612-9385.5931E-mail: [email protected]

Susan E. Duncan, Ph.D., R.D. (Chapter 18)ProfessorDepartment of Food Science and TechnologyVirginia Polytechnic Institute and State UniversityBlacksburg, VA 24061 USAPhone: 540-231-8675Fax: 540-231-9293Email: [email protected]

Yi-Chung Fu, Ph.D., P.E. (Chapter 4)Department of Food ScienceNational Chung Hsing UniversityP.O. Box 17-55, Taichung, Taiwan 40227, R.O.C.Phone: 886-4-22853922Fax: 886-4-22876211E-mail: [email protected]

Ingolf U. Grün, Ph.D. (Chapter 20)University of MissouriDepartment of Food Science256 William C. Stringer WingColumbia, MO 65211-5160 USAPhone: 573-882-6746Fax: 573-884-7964Email: [email protected]

Y. H. Hui, Ph.D. (Chapters 1, 7, 21)PresidentScience Technology SystemP.O. Box 1374West Sacramento, CA 95691 USAPhone: 916-372-2655Fax: 916-372-2690Email: [email protected]

Ty Lawrence, Ph.D. (Chapter 22)The Smithfield Packing Co.15855 Hwy 87 WestTar Heel, NC 28392 USAPhone: 910-862-7675Fax: 910-862-5249E-mail: [email protected] or

[email protected]

Miang-Hoog Lim, Ph.D. (Chapter 1)Univ. of OtagoDepartment of Food SciencePO Box 56Dunedin, 9015 New ZealandPhone: 64-3-4797953Fax: 64-3-4797953E-mail:[email protected]

Maria de Lourdes Pérez-Chabela, Ph.D. (Chapters25, 26)

Departamento de BiotecnologiaUniversidad Autonoma Metropolitana–IztapalapaApartado Postal 55-535, C.P. 09340Mexico D.F., MexicoPhone: 52 5 724-4717/4726Fax: 52 5 724-47 12E-mail: [email protected]

viii Contributors

Richard Mancini, M.S. (Chapter 22)Department of Animal SciencesKansas State University216 Weber HallManhattan, KS 66502 USAPhone: 785-532-1269Fax: 785-532-7059E-mail: [email protected]

Lisa J. Mauer, Ph.D. (Chapter 5)Assistant ProfessorDepartment of Food SciencePurdue University745 Agriculture Mall DriveWest Lafayette, IN 47907-2009 USAPhone: 765-494-9111Fax: 765-494-7953E-mail: [email protected].

Wai-Kit Nip, Ph.D. (Chapters 1, 3)Department of Molecular Biosciences and

BioengineeringCollege of Tropical Agriculture and Human

ResourcesUniversity of Hawaii at Manoa1955 East-West RoadHonolulu, HI 96822 USAPhone: 808-956-3852Fax: 808-956-3542E-mail: [email protected]

Sean Francis O’Keefe, Ph.D. (Chapter 11)Associate ProfessorFood Science and Technology DepartmentVirginia Polytechnic Institute and State UniversityBlacksburg VA 24061 USAPhone: 540-231-4437 Fax: 540-231-9293 E-mail: [email protected]

Banu F. Ozen, Ph.D. (Chapter 5)Postdoctoral AssociateDepartment of Food SciencePurdue University745 Agriculture Mall DriveWest Lafayette, IN 47907-2009 USA

Edith Ponce-Alquicira, Ph.D. (Chapter 24)Departamento de Biotecnología, Universidad

Autónoma Metropolitana-IztapalapaAv. San Rafael Atlixco 186, Col. Vicentina,

Apartado postal 55-535, C.P. 09340.México D.F., MéxicoPhone: 5804-4717, 5804-4726Fax: 5804-4712Email: [email protected]

Barbara A. Rasco, Ph.D., J.D. (Chapter 27)Department of Food Science and Human NutritionWashington State UniversityPullman, WA 99164-6376 USAPhone: 509-335-1858Fax: 509-335-4815E-mail: [email protected]

Karen A. Schmidt, Ph.D. (Chapter 15)ProfessorDepartment of Animal Sciences and IndustryKansas State UniversityManhattan, KS 66506-1600 USAPhone: 785-532-5654Fax: 785-532-5681E-mail: [email protected]

J. Scott Smith, Ph.D. (Chapter 1)ProfessorDepartment of Animal Science and IndustryKansas State UniversityCall Hall, Rm. 208Manhattan, KS 66506, USA Phone: 785-532-1219Fax: 785-532-5681E-mail: [email protected]

Peggy Stanfield, M.S., R.D. (Chapters 6, 28)PresidentDietetic Resources167 Robbins Avenue W.Twin Falls, ID 83301 USAVoice/Fax: 208-733-8662Email: [email protected]

Contributors ix

Ruthann B. Swanson, Ph.D. (Chapter 9)Associate ProfessorDepartment of Foods and NutritionUniversity of Georgia174 Dawson HallAthens, GA 30602 USAPhone: 706-542-4834Fax: 706-542-5059Email: [email protected]

Fidel Toldrá, Ph.D. (Chapter 23)Research ProfessorHead of Laboratory of Meat ScienceDepartment of Food ScienceInstituto de Agroquimica y Tecnologia de

Alimentos (CSIC)P.O. Box 7346100 Burjassot (Valencia)SpainPhone: 34 96 3900022Fax: 34 96 3636301E-mail: [email protected]

Alfonso Totosaus, Ph.D. (Chapters 25, 26)Food Science LabTecnológico de Estudios Superiores de EcatepecAv Tecnológico y Av. H. GonzálezEcatepec 55210, Edo. México, MéxicoPhone: +52 55 5710 4560 ext. 307Fax: +52 55 5710 4560 ext. 305E-mail: [email protected]

P. H. F. Yu, Ph.D. (Chapter 1)Department of Applied Biology and Chemical

TechnologyThe Hong Kong Polytechnic UniversityHung Hom, KowloonHong Kong

x Contributors

Preface

In May 2002, the senior editor completed FoodChemistry Workbook, a student workbook to accom-pany his regular textbook, Food Chemistry:Principles and Applications, published in May2000. In this workbook, he edited 30 chapters con-tributed by professionals in the United States andMexico. Each chapter describes the manufacture ofone kind of food product, with an emphasis on theprinciples of food chemistry presented in the text-book. Using some of these chapters as a foundation,but with a different emphasis, this book was born.

There are more than 60 undergraduate programsin food science and food technology in NorthAmerica, with several programs offering food engi-neering or chemical engineering with an emphasison food engineering. Most of them are in the ap-proved list of programs under the leadership of theU.S. Institute of Food Technologists. As such, mostof them also offer a course in the fundamentals offood processing. However, depending on a particu-lar college or program, there are many variables insuch a course for both teachers and students. Thebiggest ones are as follows:

• The placement of emphasis on three interrelatedareas: food science, food technology, and foodengineering.

• The establishment of several courses to coverthe complex topics.

• The division of the course into components,each of which is taught in another course.

The structure and goal of our book combines theabove approaches by grouping the 29 chapters intotwo sections. The first seven chapters cover somebackground information on food processing:

Principles of Food ProcessingFood Dehydration

Food FermentationMicrowave and Food ProcessingFood PackagingFood RegulationsFood Plant Sanitation and Quality Assurance

The remaining chapters discuss the details in theprocessing of individual food commodities such as

Beverages: Soft Drinks (Carbonated) and Beer. Cereals: Muffins, Leavened Bread, Pasta,

Noodles.Dairy Products: Cheese, Dried Milk, Ice Cream,

and Yogurt.Fats and Oils: Mayonnaise, Shortening, and

Processing Technology.Fruits and Vegetables: Orange Juice and

Tomatoes.Meat: Hot Dogs, Fermented Meat.Poultry Products: Poultry Ham, Poultry Nuggets,

and Poultry Pâté.Seafood: Frozen Aquatic Food Products and

Seafood Processing Sanitation

There are many excellent books on the principleson food processing. This book is not designed tocompete with these books. Rather, this book offersanother option, both in the approach and the con-tents. The instructor can use this book by itself oruse it to accompany another textbook in the market.

This book is the result of the combined effort of30 plus authors from six countries who possess ex-pertise in various aspects of food processing andmanufacturing, led by two editors. The editors thankall the contributors for sharing their experiences intheir fields of expertise. They are the people whomade this book possible. We hope you enjoy andbenefit from the fruits of their labor.

xi

We know how hard it is to develop the contents ofa book. However, we believe that the production ofa professional book of this nature is even more dif-ficult. We thank the production team at BlackwellPublishing, and express our appreciation to Ms.

Lynne Bishop, coordinator of the entire project. Youare the best judge of the quality of this book.

J. S. SmithY. H. Hui

xii Preface

Part IPrinciples

Food Processing: Principles and ApplicationsEdited by J. Scott Smith, Y. H. Hui

Copyright © 2004 by Blackwell Publishing

1Principles of Food Processing

Y. H. Hui, M.-H. Lim, W.-K. Nip, J. S. Smith, P. H. F. Yu

Introduction and GoalsFood Spoilage and Foodborne Diseases

Food SpoilageFood Spoilage and Biological FactorsFood Spoilage and Chemical FactorsFood Spoilage and Physical Factors

Prevention and Retardation of Food SpoilageFood Handling and ProcessingFood PreservationFood Packaging and Storage

Sources of InformationProduct Formulations and FlowchartsUnits of Operations

Raw Materials HandlingCleaningSeparatingDisintegratingForming

Meat and Poultry PattiesPastaConfectionery

PumpingMixing

Processing and Preservation TechniquesHeat Application

Heat Exchangers for Liquid Foods Tanks or Kettles for Liquid Foods Pressure Cookers or Retorts for Packaged

FoodsRoasters or Heated Vessels in Constant RotationTunnel Ovens

Heat Removal or Cold PreservationChilling and Refrigeration ProcessFreezing and Frozen Storage

Evaporation and DehydrationEvaporationDrying

Food AdditivesWhy Are Additives Used in Foods?What Is a Food Additive?What Is a Color Additive?How Are Additives Regulated?How Are Additives Approved for Use in Foods?Summary

FermentationNew Technology

Microwave and Radio Frequency ProcessingOhmic and Inductive HeatingHigh-Pressure Processing (HPP)Pulsed Electric Fields (PEFs)High Voltage Arc DischargePulsed Light TechnologyOscillating Magnetic FieldsUltraviolet LightUltrasoundPulsed X rays

PackagingGlossaryGeneral ReferencesSpecific References

INTRODUCTION AND GOALS

This chapter provides an overview of the basic prin-ciples of food processing. The goals of modern foodprocessing can be summarized as follows:

• Formulation. A logical basic sequence of stepsto produce an acceptable and quality food prod-uct from raw materials.

• Easy production procedures. Develop methodsthat can facilitate the various steps of pro-duction.

3

The information in this chapter has been derived from documents copyrighted and published by Science TechnologySystem, West Sacramento, California. ©2003. Used with permission.

Food Processing: Principles and ApplicationsEdited by J. Scott Smith, Y. H. Hui

Copyright © 2004 by Blackwell Publishing

• Time economy. A cohesive plan that combinesthe science of production and manual labor to reduce the time needed to produce theproduct.

• Consistency. Application of modern science andtechnology to assure the consistency of eachbatch of products.

• Product and worker safety. The government andthe manufacturers work closely to make sure that the product is wholesome for public con-sumption, and the workers work in a safe envi-ronment.

• Buyer friendliness. Assuming the buyer likes theproduct, the manufacturer must do everythinghumanly possible to ensure that the product isuser friendly (size, cooking instructions, keepingquality, convenience, etc.).

Obviously, to achieve all these goals is not a sim-ple matter. This chapter is concerned mainly withthe scientific principles of manufacturing safe foodproducts. With this as a premise, the first questionwe can ask ourselves is: Why do we want to processfood? At present, there are many modern reasonswhy foods are processed, for example, adding valueto a food, improving visual appeal, and convenience.However, traditionally the single most importantreason we wish to process food is to make it lastlonger without spoiling. Probably the oldest meth-ods of achieving this goal are the salting of meat andfish, the fermenting of milk, and the pickling of veg-etables. The next section discusses food spoilageand food-borne diseases.

FOOD SPOILAGE AND FOOD-BORNE DISEASES

FOOD SPOILAGE

Foods are made from natural materials and, like anyliving matter, will deteriorate in time. The deteriora-tion of food, or food spoilage, is the natural way ofrecycling, restoring carbon, phosphorus, and ni-trogenous matters to the earth. However, putrefac-tion (spoilage) will usually modify the quality offoods from good to bad, creating, for example, poorappearance (discoloration), offensive smell, and in-ferior taste. Food spoilage could be caused by anumber of factors, chiefly by biological factors, butalso by chemical and physical factors. Consumptionof spoiled foods can cause sickness and even death.Thus, food safety is the major concern in spoiledfoods.

Food Spoilage and Biological Factors

Processed and natural foods are composed mainly ofcarbohydrates, proteins, and fats. The major con-stituents in vegetables and fruits are carbohydrates,including sugars (sucrose, glucose, etc.), polymersof sugars (starch), and other complex carbohydratessuch as fibers. Fats are the major components ofmilk and most cheeses, and proteins are the chiefconstituents of muscle foods. Under natural storageconditions, foods start to deteriorate once the livingcells in the foods (plant and animal origins) aredead. Either when the cells are dead or if the tissuesare damaged, deterioration begins with the secretionof internal proteases (such as chymotrypsin andtrypsin to break up proteins at specific amino acidpositions), lipases, and lyases from lyzosomes todisintegrate the cells, to hydrolyze proteins intoamino acids and starch into simpler sugars (ormonosaccharides), and to de-esterificate fats (trigly-cerides) into fatty acids. The exposure of foods anddamaged cells to the environment attracts micro-organisms (e.g., bacteria, molds, and virus) andinsects, which in turn further accelerate the decom-position of the food. Foods contaminated with mi-croorganisms lead to food-borne illnesses, which, asreported by the Centers for Disease Control andPrevention (CDC), cause approximately 76 millionillnesses and 5000 deaths in the United States yearly(http//www.cdc.gov/foodsafety/). For most foodpoisoning, spoilage has not reached the stage wherethe sensory attributes (appearance, smell, taste, tex-ture, etc.) of the food are abnormal.

Illness from food can be mainly classified as (1) food-borne infection caused by pathogenic bac-teria (disease-causing microorganisms, such as Sal-monella bacteria, multiplying in victim’s digestivetract, causing diarrhea, vomiting and fever, etc.), and(2) food-borne intoxication (food poisoning result-ing from toxin produced by pathogenic microorgan-isms, e.g., Clostridium botulinum and Staphylococ-cus aureus, in the digestive tract). Food-borneillness also has a major economic impact on society,costing billions of dollars each year in the form ofmedical bills, lost work time, and reduced produc-tivity (McSwane et al. 2003). Some genera of bacte-ria found in certain food types are listed in Table 1.1,and some common types of microorganisms foundin foods are listed in Table 1.2. Some major bacter-ial and viral diseases transmitted to humans throughfoods are listed in Table 1.3. The interactive behav-ior of microorganisms may contribute to theirgrowth and/or spoilage activity (Gram et al. 2002).

4 Part I: Principles

Food Spoilage and Chemical Factors

In many cases, when foods are oxidized, they be-come less desirable or even rejected. The odor, taste,and color may change, and some nutrients may bedestroyed. Examples are the darkening of the cut

surface of a potato and the browning of tea colorwith time. Oxidative rancidity results from the liber-ation of odorous products during breakdown of un-saturated fatty acids. These products include aldehy-des, ketones, and shorter-chain fatty acids.

1 Principles of Food Processing 5

Table 1.1. Most Common Bacteria Genera Found inCertain Food Types

Microorganisms Foods

Corynebacterium, Leuconostoc Dairy productsAchromobacter Meat, poultry, seafoodsBacteriodes, Proteus Eggs and meatsPseudomonas Meats, poultry, eggs

Table 1.2. Most Common Pathogenic Bacteria andViruses Found in Foods

BacteriaClostridium botulinum Listeria monocytogenesSalmonella spp. Staphlococcus aureusClostridium perfringens Escherichia coliBotulinum spp. Campylobacter jejuniStreptococci spp. Bacillus cereusLactobacillus spp. Proteus spp.Shigellas spp. Pseudomonas spp.Salnonella spp. Vibrio spp.

VirusesHepatitis A virus EchovirusRotavirus Calcivirus

Table 1.3. Some Major Bacterial and Viral DiseasesTransmitted to Humans through Food

Bacteria/Viruses Disease

BacteriaCampylobacter jejuni CampylobacteriosisListeria monocytogenes ListeriosisSalmonella spp. SalmonellosisSalmonella typhi Typhoid feverShigella dysenteriae DysenteryVibrio cholerae CholeraYersinia enterocolitica Diarrheal diseaseEnterobacteriaceae Enteric disease

VirusesECHO virus GastroenteritisHAV virus Hepatitis type ANorwalk agent Viral diarrheaRotavirus Infant diarrhea

Browning reactions in foods include three non-enzymatic reactions—Maillard, caramelization,and ascorbic acid oxidation—and one enzymaticreaction—phenolase browning (Fennema 1985).Heating conditions in the surface layers of foodcause the Maillard browning reaction between sug-ars and amino acids, for example, the darkening ofdried milk from long storage. The high temperaturesand low moisture content in the surface layers alsocause caramelization of sugars, and oxidation offatty acids to other chemicals such as aldehydes, lac-tones, ketones, alcohols, and esters (Fellows 1992).The formation of ripening fruit flavor often resultsfrom Strecker degradation (the transamination anddecarboxylation) of amino acids, such as the pro-duction of 3-methylbutyrate (apple-like flavor) fromleucine (Drawert 1975). Further heating of the foodscan break down some of the volatiles generated byMaillard reaction and Strecker degradation to pro-duce burnt or smoky aromas. Enzymic browning oc-curs on cut surfaces of light-colored fruits (apples,bananas) and vegetables (potatoes) due to the enzy-matic oxidation of phenols to orthoquinones, whichin turn rapidly polymerize to form brown pigmentsknown as melanins. Moisture and heat can also pro-duce hydrolytic rancidity in fats; in this case, fats aresplit into free fatty acids, which may cause off odorsand rancid flavors in fats and oils (Potter and Hotch-kiss 1995).

Food Spoilage and Physical Factors

Food spoilage can also be caused by physical fac-tors, such as temperature, moisture, and pressureacting upon the foods. Moisture and heat can alsoproduce hydrolytic rancidity in fats; in this case, fatsare split into free fatty acids, which may cause offodors and rancid flavors in fats and oils (Potter andHotchkiss 1995). Excessive heat denatures proteins,breaks emulsions, removes moisture from food, anddestroys nutrients such as vitamins. However, ex-cessive coldness, such as freezing, also discolorsfruits and vegetables, changes their texture and/orcracks their outer coatings to permit contaminationby microorganisms. Foods under pressure will besqueezed and transformed into unnatural conforma-tion. The compression will likely break up the sur-face structure, release degradative enzymes, and ex-pose the damaged food to exterior microbialcontamination.

Of course, many health officials consider physicalfactors to include such things as sand, glass, wood

chips, rat hair, animal urine, bird droppings, insectparts, and so on. These things may not spoil thefood, but they do present hazards. Some of these for-eign substances do lead to spoilage. Furthermore,insects and rodents can consume and damage storedfoods, and insects can lay eggs and leave larvae inthe foods, causing further damage later. Such foodsare no longer reliable since they contain hidden con-taminants. The attack of foods by insects and ro-dents can also contaminate foods further with mi-crobial infections.

PREVENTION AND RETARDATION OF FOODSPOILAGE

Food spoilage can be prevented by proper sanitarypractices in food handling and processing, appropri-ate preservation techniques, and standardized stor-ing conditions.

Food Handling and Processing

The entire process, from raw ingredients to a fin-ished product ready for storage, must comply with astandard sanitation program. In the United States,the practice of HACCP (hazard analysis critical con-trol points), though mandatory for several industries,may eventually become so for all food industries. Atpresent, the application of HACCP is voluntary formost food processors. Similar sanitary programsapply to workers. It is important to realize that afood processing plant must have a basic sanitationsystem program before it can implement a HACCPprogram.

Food Preservation

There are many techniques used to preserve foodsuch as legal food additives, varying levels of foodingredients or components, and new technology.Legal food additives, among other functions, canprevent oxidation and inhibit or destroy harmful mi-croorganisms (molds and bacteria). Vitamin E or vi-tamin C can serve as an antioxidant in many foodproducts, and benzoate in beverages can act as ananti-microbial agent. We can preserve food by ma-nipulating the levels of food ingredients or compo-nents to inhibit the growth of microorganisms or de-stroy them. For example, keep the food low inmoisture content (low water activity), high in sugaror salt content, or at a low pH (less than pH 5). Re-cently, new or alternative technologies are available


to preserve food. Because they are new, their appli-cation is carefully monitored. Perhaps nothing in thelast two decades has generated more publicity thanthe use of X rays in food processing. Although foodirradiation has been permitted in the processing ofseveral categories of food, its general application isstill carefully regulated in the United States.

Food Packaging and Storage

Raw and processed foods should be packaged toprevent oxidation, microbial contamination, andloss of moisture. Storage of foods (when not con-taminated) below �20°C can keep food for severalmonths or a year. Storing foods at 4°C can extendthe shelf life to several days or a week (note thatsome bacteria such as Listeria monocytogenes canstill grow and multiply even in foods at refrigeratedtemperatures).

Newly developed techniques to preserve foods in-clude the incorporation of bacteriocin (so that it re-tains its activity) into plastic to inhibit the surfacegrowth of bacteria on meat (Siragusa et al. 1999),and the application of an intelligent Shelf LifeDecision System (SLDS) for quality optimization ofthe food chill chain (Giannakourou et al. 2001).

SOURCES OF INFORMATION

At present, all major western government authoritieshave established web sites to educate consumers andscientists on the safe processing of food products.Internationally, two major organizations have al-ways been authoritative sources of information.They include The World Health Organization(WHO) and Food and Agriculture Organization(FAO). They also have comprehensive web sites.

In the United States, major federal authorities onfood safety include, but are not limited to (1) the U.S.Department of Agriculture (USDA), (2) the Food andDrug Administration (FDA), (3) the Centers forDisease Control (CDC), (4) the EnvironmentalProtection Agency (EPA), and (5) the NationalInstitutes of Health (NIH).

Many trade associations in western countries haveweb sites that are devoted entirely to food safety.Some examples in the United States include (1) theAmerican Society of Microbiologists, (2) theInstitute of Food Technologists, (3) the InternationalAssociation for Food Protection, (4) the NationalFood Processors Association, and (5) the NationalRestaurant Association.

All government or trade association web sites areeasily accessible by entering the agency name intopopular search engines.

PRODUCT FORMULATIONS ANDFLOWCHARTS

As we have mentioned earlier, for many food prod-ucts, processing is an important way to preserve theproduct. However, for some food products, manyself-preserving factors, such as the ingredients andtheir natural properties, play a role. Three good ex-amples are pickles, barbecue sauces, and hard can-dies. Preserving pickles is not difficult if the endproduct is very sour (acidic) or salty. Traditionally,barbecue sauces have a long shelf life because of thehigh content of sugar. Most unwrapped hard candieskeep a long time, assuming the environment is atroom temperature and not very humid. Mostwrapped hard candies last even longer if the in-tegrity of the wrappers is maintained. For bakedproducts (cookies, bread), measures against spoilagetake second place to consumer acceptance of fresh-ness. So, the objectives of processing foods varywith the products. However, one aspect is essentialto all manufacturers, as discussed below.

For a processed food product, it is assumed thatthe processor has a formula to manufacture the prod-uct. In countries all over the world, small family-owned food businesses usually start with homerecipes for popular products instead of a scientificformula. Most of us are aware of the similar humblebeginnings of major corporations manufacturingcola (carbonated), soft drinks, cheeses, breakfast ce-reals, and many others. When these family busi-nesses started, there was not much science or tech-nology involved. When a company becomes big andhas many employees, it starts hiring food scientists,food technologists, and food engineers to study the“recipe” and refine every aspect of it until the entiremanufacturing process is based on sound scientific,technical, and engineering principles. After that, allefforts are directed towards production. Even now,somewhere, a person will start making “barbecuesauce” in his garage and selling it to his neighbors.Although very few of these starters will succeed,this trend will continue, in view of the free enter-prise spirit of the West.

Although any person can start manufacturingfood using a home recipe, the federal government inthe United States has partial or total control overcertain aspects of the manufacturing processes for


food and beverage products. This control automati-cally affects the recipes, formulas, or specificationsof the products. Although the word “control” hererefers mainly to safety, it is understood that it willaffect the formulations to some extent, especiallycritical factors such as temperatures, pH, water ac-tivity, and so on.

Chapters in the second part of this book will pro-vide formulations for manufacturing various foodcategories (bakery, dairy, fruits, etc). It also providesmany operational flowcharts. Flowcharts differ fromformulas in that they provide an overview of themanufacturing process. For illustration, Figures1.1–1.8 provide examples of flowcharts for the man-ufacture of bakery (bread), dairy (yogurt), grain(flour), fruits (raisins), vegetables (pickles), andmeat (frankfurters, frozen chicken parts), andseafood (canned tuna).

UNITS OF OPERATIONS

The processing of most food products involves rawmaterials; cleaning; separating; disintegrating;forming, raw; pumping; mixing; application meth-ods (formulations, additives, heat, cold, evaporation,drying, fermenting, etc.); combined operations; andforming, finished product. We discuss some of theseas units of operations. Certain items—heating, cool-ing, sanitation, quality control, packaging, and sim-ilar procedures—are discussed as separate topicsrather than as units of operations.

According to the U.S. Department of Labor, thereare hundreds of different categories of food productscurrently being manufactured. Correspondingly,there are hundreds of companies manufacturingeach category of food products. In sum, there are lit-erally thousands of food manufacturers. Two majorreasons for this explosion of new companies are (1) the constant introduction of new products and (2) improvements in manufacturing methods andequipment.

To facilitate the technological processing of foodat the educational and commercial levels, food-processing professionals have developed unifyingprinciples and a systematic approach to the study ofthese operations. The involved processes of the foodindustry can be divided into a number of commonoperations, called unit operations. Depending on theprocessor, such unit operations vary in name andnumber. For ease of discussion, we use the follow-ing units of operations, in alphabetical order, for themost common ones: cleaning, coating, controlling,

decorating, disintegrating, drying, evaporating,forming, heating, mixing, packaging, pumping, rawmaterials handling, and separating.

During food processing, the manufacturer selectsand combines unit operations into unit processes,which are then combined to produce more complexand comprehensive processes. We will now discussthese units in the order they appear in a food proc-essing plant. Although emerging technology playsan important role in food processing as time pro-gresses, this book is designed to provide studentswith the most basic approaches.


Figure 1.1. A general flowchart for the manufacture ofbread.

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Figure 1.2. A general flowchart for the manufacture ofyogurt.

Figure 1.3. A general flowchart for the production offlour from wheat.

Figure 1.4. A general flowchart for the production ofraisins.

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Figure 1.5. A general flowchart for the production ofpickles.

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Figure 1.6. A general flowchart for the production of Frankfurters.

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Figure 1.7. A general flowchart for the production offrozen chicken parts.

Figure 1.8. A general flowchart for the production ofcanned tuna.

RAW MATERIALS HANDLING

Raw materials are handled in various ways, includ-ing (1) hand and mechanical harvesting on the farm,(2) trucking (with or without refrigeration) of fruitsand vegetables, (3) moving live cattle by rail, (4)conveying flour from transporting vehicle to storagebins.

For example:

• Oranges are picked on the farm by hand or me-chanical devices, moved by truck trailers, usuallyrefrigerated, to juice processing plants, wherethey are processed. Of course, the transport musttake into account the size of the trucks, thelength of time during transport, and temperaturecontrol. The major objective is to avoid spoilage.In recent years, the use of modified atmospherepackaging has increased the odds to favor thefarmers and producers.

• Handling sugar and flour poses great challenges.When dry sugar reaches processing plants, viatruck trailers or rail, it is transported to storagebins via a pneumatic lift system. The sugar willcake if the storage time, temperature, and humid-ity are not appropriate. Improper transfer ofsugar may result in dusting and buildup of staticelectricity, which can cause an explosion, sincesugar particles are highly combustible. The sameapplies to finely ground flour.

In handling raw materials, one wishes to achievethe following major objectives: (1) proper sanita-tion, (2) minimal loss of product, (3) acceptableproduct quality, (4) minimal bacterial growth, and(5) minimal holding time.

CLEANING

We all know what cleaning a raw product means.Before we eat a peach, we rinse it under the faucet.Before we make a salad, we wash the vegetables.Before we eat crabs, we clean them. Of course, thedifference in cleaning between home kitchens and afood processing plant is volume. We clean onepeach; they clean a thousand peaches.

Depending upon the product and the nature of thedirt, cleaning can be accomplished using the follow-ing methods or devices, individually or in combina-tion: (1) air, high velocity; (2) brushes; (3) magnets;(4) steam; (5) ultraviolet light; (6) ultrasound; (7)vacuum; and (8) water. There are also other newtechnologies that will not be discussed here.

Water is probably the most common cleaningagent, and its application varies:

• Clams, oysters, crabs, and other shellfish com-monly are hosed to remove mud, soil, and otherforeign debris. If they are contaminated, theymay have to be incubated in recirculating cleanwater.

• City water is not acceptable for manufacturingbeverages. It must be further treated with chemi-cal flocculation, sand filtration, carbon purifica-tion, microfiltration, deaeration, and so on. Thisis not considered a simple cleaning. Rather, it isa process in cleaning.

• Eviscerating poultry can be considered a clean-ing operation if water is used, but the actualprocess of removing the entrails may involvevacuuming in addition to water.

• With a product like pineapples, the irregular sur-faces are usually cleaned by the scrubbing actionof high-pressure water jets.

Just as in a home kitchen where pots and pans re-quire frequent cleaning, the equipment used in afood processing plant is required by state and fed-eral regulations to be cleaned after each use. Afterdirt and mud is removed, some raw products requirespecial sanitizing procedures. The use of sanitizerscan be a complicated matter. It involves types ofsanitizers, federal regulations, expertise, and so on.

SEPARATING

In food processing, separating may involve separat-ing (1) a solid from a solid, as in peeling potatoes;(2) a solid from a liquid, as in filtration; (3) a liquidfrom a solid, as in pressing juice from a fruit; (4) aliquid from a liquid, as in centrifuging oil fromwater; and (5) a gas from a solid or a liquid, as invacuum canning.

One time-honored technique in the separating op-eration is the hand sorting and grading of individualunits (e.g., mushrooms, tomatoes, oranges). At pres-ent, many mechanical and electronic sorting deviceshave replaced human hands for various types of rawfood products. An electronic eye can tell the differ-ence in color as the products are going by on theconveyor belt. Built-in mechanisms can sort theproducts by color, “good” vs. “bad” color. The cur-rent invention of electronic noses shows promise.

Automatic separation according to size is easilyaccomplished by passing fruits or vegetables overdifferent size screens, holes, or slits.


DISINTEGRATING

Disintegrating means subdividing large masses offoods into smaller units or particles. This may in-clude cutting, grinding, pulping, homogenizing, andother methods. Examples include:

• Automatic dicing of vegetables,• Mechanical deboning of meat,• Manual and automatic cutting of meats into

wholesale and retail sizes,• Cutting bakery products with electric knives and

water jets (high velocity and high pressure),• Disintegrating various categories of food prod-

ucts with high-energy beams and laser beams,and

• Homogenization with commercial blenders,high pressure traveling through a valve with very small openings, ultrasonic energy, and so on.

Homogenization is probably one of the most im-portant, if not the most important, stages in dairyprocessing. Homogenization produces disintegra-tion of large globules and clusters of fat in milk orcream to minute globules. This is done by forcingthe milk or cream under high pressure through avalve with very small openings.

FORMING

Forming is an important operation in many cate-gories of the food industry: (1) meat and poultry pat-ties, (2) confections (candies, jelly beans, fruit juicetablets), (3) breakfast cereals, (4) pasta, and (5) va-rieties (some cheese cubes, processed cheese slices,potato chips, etc.).

Meat and Poultry Patties

Patty-making machines are responsible for makingground meat and poultry patties by gently compact-ing the product into a disk shape. Uniform pressureis applied to produce patties with minimal variationin weight. Also, excessive pressure may result intough cooked patties.

Pasta

Spaghetti is formed by forcing dough through extru-sion dies of various forms and shapes before it isdried in an oven.

Confectionery

The shapes and forms in the confectionery industry(e.g., candies, jellies) are made in several ways. Twoof the most popular methods are molds and specialtableting machines. The traditional use of molds isresponsible for confectionery such as fondants,chocolate, and jellies. The product is deposited intomolds to cool and harden.

PUMPING

In food processing, pumping moves food (liquid,semisolid, paste, or solid) from one step to the nextor from one location to another.

There are many types of pumps available, somewith general, others specialized, applicability. Thetype of pump used depends on the food (texture,size, etc.). For example, broth, tomato pastes,ground meat, corn kernels, grapes, and other cate-gories of food all require a “different” pump to dothe job. Two important properties of pumps are (1)ability to break up foods and (2) ease of cleaning.

MIXING

The operation of mixing, for example, includes (1)kneading, (2) agitation, (3) blending, (4) emulsify-ing, (5) homogenizing, (6) diffusing, (7) dispersing,(8) stirring, (9) beating, (10) whipping, and (11)movements by hands and machines.

Examples of mixing include (1) homogenizationto prevent fat separation in milk; (2) mixing and de-veloping bread dough, which requires stretching andfolding, referred to as kneading; (3) beating in air, asin making an egg-white foam; (4) blending dry in-gredients, as in preparing a ton of dry cake mix, and(5) emulsifying, as in the case of mayonnaise.

Commercial mixers for food processing come inmany shapes and forms, since many types of mix-tures or mixings are possible. Two examples are pro-vided as illustration.

1. Mixing solids with solids (e.g., a dry cake mix).The mixer must cut the shortening into theflour, sugar, and other dry ingredients in orderto produce a fluffy, homogeneous dry mix. Aribbon blender is used.

2. Beating air into a product while mixing, aswhen using a mixer-beater in an ice creamfreezer. The mixer turns in the bowl in whichthe ice cream mix is being frozen. This


particular operation permits the mixer toachieve several tasks or objectives: beat air intothe ice cream to give the desired volume andoverrun; keep the freezing mass moving toproduce uniformity and facilitate freezing.

PROCESSING ANDPRESERVATION TECHNIQUES

HEAT APPLICATION

Heat exchanging, or heating, is one of the most com-mon procedures used in manufacture of processedfoods. Examples include the pasteurizing of milk,bakery products, roasting peanuts, and canning.Foods may be heated or cooked using (1) direct in-jection of steam, (2) direct contact with flame, (3)toasters, (4) electronic energy as in microwavecookers, and (5) many forms of new technology.

Whatever the method, precise control of tempera-ture is essential. Heating is used in (1) baking, (2)frying, (3) food concentration, (4) food dehydration,and (5) package closure.

Why are foods heated? All of us know why wecook food at home: to improve texture; to developflavors; to facilitate mixing of water, oil, and starch;to permit caramelization; and so on. Commercially,the basic reasons for heating are simple and mayinclude:

• Destruction of microorganisms and preservationof food. Food canning and milk pasteurizationare common examples.

• Removal of moisture and development of fla-vors. Ready-to-eat breakfast cereals and coffeeroasting are common examples.

• Inactivation of natural toxicants. Processing soy-bean meal is a good example.

• Improvement of the sensory attributes of thefood such as color, texture, mouth-feel.

• Combination of ingredients to develop uniquefood attributes and attract consumer preferences.

Traditional thermal processing of foods uses theprinciples of transferring heat energy by conduction,convection, radiation, or a combination of these. Atpresent, there are newer methods of heating food,such as electronic energy (microwave). Later in thischapter, other new technologies for heating foodswill be discussed.

Foods are heated using various traditional equip-ments that were developed using basic principles offood engineering: heat exchangers, tank or kettle, re-

torts, toasters. Other methods may include direct in-jection of steam, direct contact with flame, and ofcourse, microwave.

Heat Exchangers for Liquid Foods

Since foods are sensitive to heat, special considera-tion is needed. Dark color, burned flavors, and lossof nutrients can result from heating, especially pro-longed heat. Heat exchangers have special advan-tages. They permit (1) maximal contact of liquidfood with the heat source and (2) rapid heating andcooling.

For example, a plate-type heat exchanger is usedto pasteurize milk. This equipment is made up ofmany thin plates. When milk flows through one sideof the plates, it is heated by hot water on the otherside. This provides maximal contact between theheat source and the milk, resulting in rapid heating.The cooling is the reverse: after the milk has beenheated, instead of hot water, cool water or brine isused.

Tanks or Kettles for Liquid Foods

During heating, hot water circulating in the jacketsof the tanks or kettles heats the food; during cooling,circulating cool water or brine cools the food. Thistechnique works for full liquid foods or partial liq-uid foods such as soups.

Pressure Cookers or Retorts for PackagedFoods

The most common method of sterilizing cannedfoods uses pressure cookers or retorts. Beginningwith early seventies, the risk of botulism in cannedfood with low acidity prompted the U.S. Food andDrug Administration (FDA) to implement stringentregulations governing this group of foods. Althoughthe name Hazards Analysis Critical Control Points(HACCP) did not have wide usage at the time, theregulations governing the production of low-acidcanned foods can be considered the earliest form ofthe HACCP program. Large pressure cookers or re-torts are used to ensure that the canned goods areheated above the boiling point of water. The hightemperature is generated by steam under pressure ina large retort designed to withstand such tempera-ture. In this case, convection and conduction of heatenergy are achieved. Steam hits the outside of thecans, and energy is conducted into the can. Some


form of moving or agitating device permits convec-tion to occur inside the cans. Although there areother modern techniques for heating canned foodproducts, many smaller companies still dependheavily on the traditional methods.

Roasters or Heated Vessels in ConstantRotation

Instead of one or two pieces of equipment, this sys-tem contains several units: loading containers, con-veyor belts, hoppers, vats, or vessels. The vessels areusually cylindrical in shape with built-in heating de-vices. Heat is generated via one of the followingmethods:

• Circulation of heated air. This heats the foodproducts inside the vessels.

• Application of direct heat contacting outside ofvessel such as steam, flame (gas), or air (hot).Heat is radiated from the inside walls of thevessels to the food.

This unit system is best for roasting coffee beans ornuts.

Tunnel Ovens

Tunnel ovens can be used for a variety of food prod-ucts. The product is placed on a conveyor belt thatmoves under a heat source. Sometimes, the productis vibrated so that heat distribution is even. Tem-perature control is essential, and products such ascoffee beans or nuts can be roasted using thismethod.

HEAT REMOVAL OR COLD PRESERVATION

Cold preservation is achieved by the removal ofheat. It is among the oldest methods of preservation.Since 1875, with the development of mechanicalammonia refrigeration systems, commercial refrig-eration and freezing processes have become avail-able. A reduction in the temperature of a food re-duces the rate of quality changes during storagecaused by the various factors. At low temperatures,microbial growth is retarded and microbial repro-duction prevented. The rate of chemical reactions(e.g., oxidation, Maillard browning, formation ofoff flavors), biochemical reactions (e.g., glycolysis,proteolysis, enzymatic browning, and lipolysis),and physical changes resulting from interaction offood components with the environment (e.g., mois-

ture loss in drying out of vegetables) can also bereduced.

Most food spoilage organisms grow rapidly attemperatures above 10°C, although some grow attemperatures below 0°C, as long as there is unfrozenwater available. Most pathogens, except some psy-chrophilic bacteria such as Listeria monocytogenesthat commonly grows in dairy products, do not growwell at refrigeration temperatures. Below �9.5°C,there is no significant growth of spoilage or patho-genic microorganisms.

In general, the longer the storage period, the lowerthe temperature required. Pretreatment with inten-sive heat is not used in this process operation, butwith adequate control over enzymatic and microbio-logical changes, the food maintains nutritional andsensory characteristics close to fresh status, result-ing in a high quality product. In comparing chilledand frozen foods, chilled food has a higher qualitybut a shorter shelf life; frozen food has a muchlonger shelf life, but the presence of ice in the frozenproduct may create some undesirable changes infood quality.

Chilling and Refrigeration Process

Chilling process is the gentlest method of preserva-tion with the least changes in taste, texture, nutritivevalue, and other attributes of foods. Generally itrefers to storage temperature above freezing, about16°C to �2°C. Most foods do not freeze until �2°Cor slightly lower because of the presence of solutessuch as sugars and salts. Commercial and householdrefrigerators usually operate at 4.5°C to 7°C.

In low-acid chilled foods, strict hygienic process-ing and packaging are required to ensure food safety.The chilling process is usually used in combinationwith other preservation methods such as fermenta-tion, irradiation, pasteurization, mild heat treatment,chemicals (acids or antioxidants), and controlled at-mosphere. The combination of these methods avoidsextreme conditions that must be used to limit micro-bial growth, thus providing high quality product(e.g., marinated mussels and yogurt.)

Not all foods can be stored under chilled condi-tions. Tropical and subtropical fruits suffer chillinginjury when stored below 13°C, resulting in abnor-mal physiological changes: skin blemishes (e.g., ba-nana), browning in the flesh (e.g., mango), or failureto ripen (e.g., tomato). Some other foods should notbe refrigerated; for example, breads stale faster atrefrigeration temperature than at room temperature.


Starch in puddings also tends to retrograde at refrig-eration temperatures, resulting in syneresis.

Important considerations in producing and main-taining high quality chilled foods include:

• Quick removal of heat at the chilling stage.Ideally, refrigeration of perishable foods starts attime of harvest or slaughter or at the finishingproduction line. Cooling can be accelerated bythe following techniques:– Evaporative cooling. Spray water and then

subject food to vacuum (e.g., leafy vegetables).– Nitrogen gas (from evaporating liquid nitrogen

on produce). Of course, dry ice and liquidcarbon dioxide are used to remove heat for dif-ferent products.

– Heat exchangers. (1) Thin stainless steel plateswith enclosures, circulating on the outside by a chilled or “super-chilled” cooling fluid. (2) Coils with enclosures cooled by differentmeans. Warm bulk liquid foods pass throughthe inside, and heat is transferred to the outside.

• Maintaining low temperature during the chillstorage. This can be affected by:– Refrigeration design (i.e., cooling capacity and

insulation) must be taken into account becausethe temperature can be affected by heat gener-ated by lights and electric motors, peopleworking in the area, the number of doors andhow they are opened, and the kinds andamounts of food products stored.

– Refrigeration load. The quantity of heat whichmust be removed from the product and thestorage area in order to decrease from an initialtemperature to the selected final temperatureand to maintain this temperature for a specifictime.

– Types of food. (1) Specific heat of food: thequantity of heat that must be removed from afood to lower it from one temperature to an-other. The rate of heat removal is largely de-pendent on water content. (2) Respiration rateof food: Some foods (fruits and vegetables)respire and produce their own heat at varyingrates. Products with relatively high respirationrates (snap beans, sweet corn, green peas,spinach, and strawberries) are particularly dif-ficult to store.

• Maintaining appropriate air circulation and hu-midity. Proper air circulation helps to move heataway from the food surface toward refrigeratorcooling coils and plates. Air velocity is especially

important in commercial coolers or freezers forkeeping the appropriate relative humidity becauseif the relative humidity is too high, condensationof moisture on the surface of cold food mayoccur, thus causing spoilage through microbialgrowth or clumping of the product. However, ifrelative humidity is too low, dehydration of foodmay occur instead. Therefore, it is important tocontrol the RH (relative humidity) of the coolerand use proper packaging for the food.

• Modification of gas atmosphere. Chilled storageof fresh commodities is more effective if it iscombined with control of the air composition ofthe storage atmosphere. A reduction in oxygenconcentration and/or an increase in carbon diox-ide concentration of the storage atmosphere re-duces the rate of respiration (and thus matura-tion) of fresh fruits and vegetables and alsoinhibits the rate of oxidation, microbial growth,and insect growth. The atmospheric compositioncan be changed using three methods:– Controlled atmosphere storage (CAS). The

concentrations of oxygen, carbon dioxide, andethylene are monitored and regulated through-out storage. CAS is used to inhibit overripen-ing of apples and other fruits in cold storage.Stored fruit and vegetables consume O2 andgive off CO2 during respiration.

– Modified atmosphere storage (MAS). The ini-tially modified gas composition in sealed stor-age is allowed to change by normal respirationof the food, but little control is exercised. TheO2 is reduced but not eliminated, and CO2 isincreased (optimum differs for different fruits).

– Modified atmosphere packaging (MAP). Thefruit or vegetable is sealed in a package underflushed gas (N2 or CO2), and the air in thepackage is modified over time by the respiringproduct. Fresh meat (especially red meats) ispackaged similarly.

• Efficient distribution systems. To supply highquality chilled foods to consumers, a reliable andefficient distribution system is also required. Itinvolves chilled stores, refrigerated transporta-tion, and chilled retail display cabinets. It re-quires careful control of the storage conditionsas discussed above.

Freezing and Frozen Storage

Freezing is a unit operation in which the tempera-ture of a food is reduced below the freezing point


and a proportion of the water undergoes a phasechange to form ice. Proper freezing preserves foodswithout causing major changes in their shape, tex-ture, color and flavor. Good frozen storage requirestemperatures of �18°C or below, however, it is costprohibitive to store lower than �30°C. Frozen foodshave increased in their share of sales since the freez-ers and microwaves become more available.

The major commodities commonly frozen are (1)fruits (berries, citrus, and tropical fruit) either whole,pureed, or as juice concentrate; (2) vegetables (peas,green beans, sweet corn, spinach, broccoli, Brusselssprouts, and potatoes such as French fries and hashbrowns); (3) fish fillets and seafood, including fishfingers, fish cakes, and prepared dishes with sauces;(4) meats (beef, lamb, and poultry) as carcasses,boxed joints, or cubes, and meat products (sausagesand beef burgers); (5) baked goods (bread, cakes,pastry dough, and pies); and (6) prepared foods (piz-zas, desserts, ice cream, dinner meals).

Principles of Freezing. The freezing process im-plies two linked processes: (1) lowering of tempera-ture by the removal of heat and (2) a change ofphase from liquid to solid. The change of water intoice results in increase in concentration of unfrozenmatrix and therefore leads to dehydration and lower-ing of water activity. Both the lowering of tempera-ture and the lowering of water activity contribute tofreezing as an important preservation method.

In order for a product to freeze, the product mustbe cooled below its freezing point. The freezingpoint of a food depends on its water content and thetype of solutes present. The water component of afood freezes first and leaves the dissolved solids in amore concentrated solution, which requires a lowertemperature to freeze. As a result, the freezing pointdecreases during freezing as concentration in-creases. Different solutes depress the freezing pointto a different degree.

Rate of Freezing. Faster freezing produces smallcrystals, necessary for high quality products such asice cream. There are two main opposing forces af-fecting the freezing rate: (1) The driving forces help-ing to freeze the product quickly include the differ-ence in temperature between the freezing mediumand the product (the bigger the difference, the fasterthe product will cool down), the high thermal con-ductivity of the freezing medium (the efficiency withwhich the refrigerating agent extracts heat), and di-

rect surface contact between the medium and theproduct. (2) On the other hand, the forces that resistfreezing include product packed in large sizes, irreg-ular product geometry that reduces direct contact ofthe product with the freezing agent, product compo-sition that has a high heat capacity, and the thermalconductivity of food packages such as cardboard andplastics that may retard (by acting as an insulator)heat transfer and thus slow down freezing rate.

Quality Changes with Freezing and Frozen Storage.As a consequence of the formation of ice, some neg-ative changes in the quality of food result. The twomajor causes are the freeze concentration effect andlarge ice crystal and recrystallization damage.

Freeze Concentration Effect. The quality ofproducts will change if solutes in the frozen productprecipitate out of solution (e.g., loss of consistency inreconstituted frozen orange juice because of aggre-gated pectic substances, and syneresis of starch pud-ding because of starch aggregation). The increase inionic strength can lead to “salting out” of proteins,causing protein denaturation (reason for tougheningof frozen fish). Increase in solute concentration maylead to the precipitation of some salts; the anion/cation ratio of colloidal suspensions is then dis-turbed, causing changes in pH. Such changes alsocause precipitation of proteins and changes in colorof anthocyanin in berries. The concentration of so-lutes in the extracellular fluid causes dehydration ofadjacent tissues in fruit and vegetables, which are notable to rehydrate after thawing. Lastly, concentrationof reactive compounds accelerates reactions such aslipid oxidation.

Large Ice Crystal and Recrystallization Damage.If the food is not stored under sufficiently cold andsteady temperatures, the ice crystals will grow or re-crystallize to large ice crystals that may cause con-sequential damage to the food texture. Damagessuch as physical rupture of cell walls and mem-branes and separation of plant and animal cellscause limp celery or green beans, drips in thawedberries and meat. Enlarged ice crystals also disruptemulsions (butter and milk), frozen foams (icecream), and gels (frozen pudding and pie fillings),thus making these frozen products less homoge-nous, creamy, and smooth.

Another quality damage relating to ice recrystal-lization is the freezer-burn problem. Freezer burn


occurs when there is a headspace in the packagedfood and the food is subjected to fluctuating storagetemperatures. When the temperature increases, iceat the warmer surface will sublime into the head-space. As the temperature of the freezer or surround-ings cools down, the water vapor recrystallizes onthe inner surface of the package instead of goingback into the product. This leads to dehydration ofthe surface of the product. If the frozen product isnot packaged, the freezer-burn problem is morecommon and more severe.

Types of Common Freezers with Different CoolingMedia.

Cold Air.• Blast/belt freezers are large insulated tunnels in

which air as cold as �40°C is circulated to re-move heat. The process is cheap and simple andis geared toward high-volume production.Rotating spiral tiers and multilayered belts areincorporated to move product through quicklyand avoid “hot spots.”

• Fluidized bed freezers are modified blast freezersin which cold air is passed at a high velocitythrough a bed of food, contained on a perforatedconveyor belt. This produces a high freezing ratebut it is restricted to particulate foods (peas,shrimp, and strawberries).

Cold Surface Freezers.• Plate freezers work by increasing the amount of

surface area that comes in direct contact with theproduct to be frozen. Typically, refrigerant runsin the coils that run through plates or drums onwhich products are laid out. Double-plated sys-tems further increase the rate of heat transfer toobtain higher quality. This system is suitable forflat and uniform products such as fish fillets,beef burgers, and dinner meals.

• Scraped-surface freezers—the liquid or semi-solid food (ice cream) is frozen on the surface ofthe freezer vessel, and the rotor scrapes thefrozen portion from the wall. Typically, icecream is only partially frozen in a scraped-surface freezer to about �6°C, and the finalfreezing is completed in a hardening room(�30°C).

Cold Liquid Freezers.• Brine freezers use super-saturated solutions for

maximum surface contact by immersing the prod-

uct into a liquid freezing agent, especially forirregular shapes such as crabs. Disadvantage—products are subject to absorption of salt as wellas bacteria.

Cryogenic Freezing.• Liquid nitrogen and liquid carbon dioxide

(which vaporize at �178°C and �80°C, respec-tively) freeze product extremely quickly. Suitablefor premium products such as shrimp and crablegs because of the high cost of the nonrecover-able gas.

Tips for Obtaining Top Quality Frozen Product.• Start with high quality product: freezing can

maintain quality but not enhance it.• Get the heat out quickly by removing any noned-

ible parts from the food.• Maintain the integrity of the frozen product:

proper cutting and packaging avoids drips.• Store the product at the coldest temperature eco-

nomically possible in a well-designed and main-tained facility. Use proper inventory techniquesto avoid deterioration.

• Avoid temperature fluctuations during storageand shipping.

EVAPORATION AND DEHYDRATION

Evaporation

During food processing, evaporation is used toachieve the following goals: (1) concentrate foodby the removal of water, (2) remove undesirablefood volatiles, and (3) recover desirable foodvolatiles.

Traditionally, evaporation is achieved via the fol-lowing methods: (1) Use sun energy to evaporatewater from seawater to recover the salts left behind.(2) Use a heated kettle or similar equipment to boilwater from liquid or semisolid foods (e.g., sugarsyrup). (3) An improved method is to evaporateunder a vacuum. The term “vacuum evaporator”refers to a closed heated kettle or similar equipmentconnected to a vacuum pump. One principle to re-member is that a major objective of vacuum evapo-rators is to remove water at temperatures lowenough to avoid heat damage to the food.

There are, at present, many specialized pieces ofequipment used for evaporating food products. But,overall, these three methods are most common.


Drying

Drying differs from evaporating in that the formertakes the food to nearly total dryness or the equiva-lence of 97 or 98% solids. The oldest method of dry-ing food is to put the food under a hot sun. Thispractice probably started thousands of years ago.

Although sun drying is still practiced, especiallyin many third world countries, modern food dryinghas been modified to a nearly exact science. Dryinghas multiple objectives: (1) to preserve the foodfrom spoilage, (2) to reduce the weight and bulk ofthe food, (3) to make the food enjoy an availabilityand consumption pleasure similar to that of cannedgoods, and (4) to develop “new” or “novelty” itemssuch as snacks.

Some well-known products prepared from dryinginclude: (1) dried milk powder, (2) instant coffee,(3) fish and shellfish, (4) jerky, (5) dried fruits, and(6) dried potato flakes.

The central equipment in dehydrating food is dry-ers. There are many types of dryers: spray dryers,drum dryers, roller dryers, and so on. See Chapter 2,Food Dehydration, for additional information.

FOOD ADDITIVES

One popular method of food preservation useschemicals, legally known as food additives in theUnited States. In January 1992, the U.S. Food andDrug Administration (FDA) and the InternationalFood Information Council released a brochure thatpresented an overview of food additives. The infor-mation in this section has been derived from thatdocument, with an update.

Perhaps, the main functional objectives of the useof food additives are (1) to keep bread mold free andsalad dressings from separating, (2) to help cake bat-ters rise reliably during baking and keep cured meatssafe to eat, (3) to improve the nutritional value of bis-cuits and pasta and give gingerbread its distinctiveflavor, (4) to give margarine its pleasing yellow colorand prevent salt from becoming lumpy in its shaker,and (5) to allow many foods to be available year-round, in great quantity and the best quality.

Food additives play a vital role in today’s bounti-ful and nutritious food supply. They allow our grow-ing urban population to enjoy a variety of safe,wholesome, tasty foods year-round. And they makepossible an array of convenience foods without theinconvenience of daily shopping.

Although salt, baking soda, vanilla, and yeast are

commonly used in foods today, many people tend tothink of any food additive as a complex chemicalcompound. All food additives are carefully regu-lated by federal authorities and various internationalorganizations to ensure that foods are safe to eat andare accurately labeled. The purpose of this section isto provide helpful background information aboutfood additives, why they are used in foods and howregulations govern their safe use in the food supply.

Why Are Additives Used in Foods?

Additives perform a variety of useful functions infoods that are often taken for granted. Since mostpeople no longer live on farms, additives help keepfood wholesome and appealing while en route tomarkets sometimes thousands of miles away fromwhere it is grown or manufactured. Additives alsoimprove the nutritional value of certain foods andcan make them more appealing by improving theirtaste, texture, consistency, or color.

Some additives could be eliminated if we werewilling to grow our own food, harvest and grind it,spend many hours cooking and canning, or acceptincreased risks of food spoilage. But most peopletoday have come to rely on the many technological,aesthetic, and convenience benefits that additivesprovide in food.

Additives are used in foods for five main reasons:

1. To maintain product consistency. Emulsifiersgive products a consistent texture and preventthem from separating. Stabilizers andthickeners give smooth uniform texture. Anti-caking agents help substances such as salt toflow freely.

2. To improve or maintain nutritional value.Vitamins and minerals are added to manycommon foods such as milk, flour, cereal, andmargarine to make up for those likely to belacking in a person’s diet or lost in processing.Such fortification and enrichment have helpedreduce malnutrition in the U.S. population. Allproducts containing added nutrients must beappropriately labeled.

3. To maintain palatability and wholesomeness.Preservatives retard product spoilage caused bymold, air, bacteria, fungi, or yeast. Bacterialcontamination can cause food-borne illness,including life-threatening botulism. Antioxi-dants are preservatives that prevent fats andoils in baked goods and other foods from


becoming rancid or developing an off flavor.They also prevent cut fresh fruits such asapples from turning brown when exposed toair.

4. To provide leavening or control acidity/alkalinity. Leavening agents that release acidswhen heated can react with baking soda to helpcakes, biscuits, and other baked goods to riseduring baking. Other additives help modify theacidity and alkalinity of foods for properflavor, taste, and color.

5. To enhance flavor or impart desired color.Many spices and natural and synthetic flavorsenhance the taste of foods. Colors, likewise,enhance the appearance of certain foods tomeet consumer expectations. Examples ofsubstances that perform each of these functionsare provided in Table 1.4.

Many substances added to food may seem foreignwhen listed on the ingredient label, but they are ac-tually quite familiar. For example, ascorbic acid isanother name for vitamin C; alpha-tocopherol is an-other name for vitamin E; and beta-carotene is asource of vitamin A. Although there are no easy syn-onyms for all additives, it is helpful to rememberthat all food is made up of chemicals. Carbon, hy-

drogen, and other chemical elements provide thebasic building blocks for everything in life.

What Is a Food Additive?

In its broadest sense, a food additive is any sub-stance added to food. Legally, the term refers to“any substance the intended use of which results ormay reasonably be expected to result, directly or in-directly, in its becoming a component or otherwiseaffecting the characteristics of any food.” This defi-nition includes any substance used in the produc-tion, processing, treatment, packaging, transporta-tion, or storage of food.

If a substance is added to a food for a specific pur-pose in that food, it is referred to as a direct additive.For example, the low-calorie sweetener aspartame,which is used in beverages, puddings, yogurt, chew-ing gum and other foods, is considered a direct ad-ditive. Many direct additives are identified on the in-gredient label of foods.

Indirect food additives are those that become partof the food in trace amounts due to its packaging,storage, or other handling. For instance, minuteamounts of packaging substances may find theirway into foods during storage. Food packagingmanufacturers must prove to the FDA that all mate-


Table 1.4. Common Uses of Food Additives in Food Categories

Common Uses of AdditivesAdditive Functions/Examplesa Foods Where Likely Used

Impart/maintain desired consistencyAlginates, lecithin, mono- and diglycerides, Baked goods, cake mixes, salad dressings, ice methyl cellulose, carrageenan, glyceride, pectin, cream, processed cheese, coconut, table saltguar gum, sodium aluminosilicate

Improve/maintain nutritive valueVitamins A and D, thiamine, niacin, riboflavin, Flour, bread, biscuits, breakfast cereals, pasta,pyridoxine, folic acid, ascorbic acid, calcium margarine, milk, iodized salt, gelatin dessertscarbonate, zinc oxide, iron

Maintain palatability and wholesomenessPropionic acid and its salts, ascorbic acid, butylated Bread, cheese, crackers, frozen and dried fruit,hydroxy anisole (BHA), butylated hydroxytoluene margarine, lard, potato chips, cake mixes, meat(BHT), benzoates, sodium nitrite, citric acid

Produce light texture; control acidity/alkalinityYeast, sodium bicarbonate, citric acid, fumaric Cakes, cookies, quick breads, crackers, butter,acid, phosphoric acid, lactic acid, tartrates chocolates, soft drinks

Enhance flavor or impart desired colorcloves, ginger, fructose, aspartame, saccharin, Spice cake, gingerbread, soft drinks, yogurt,FD&C Red No.40, monosodium glutamate, soup, confections, baked goods, cheeses, jams,caramel, annatto, limonene, turmeric gum

aIncludes GRAS and prior sanctioned substances as well as food additives.

rials coming in contact with food are safe, beforethey are permitted for use in such a manner.

What Is a Color Additive?

A color additive is any dye, pigment, or substancethat can impart color when added or applied to afood, drug, or cosmetic, or to the human body. Coloradditives may be used in foods, drugs, cosmetics,and certain medical devices such as contact lenses.Color additives are used in foods for many reasons,including to offset color loss due to storage or proc-essing of foods and to correct natural variations infood color.

Colors permitted for use in foods are classified ascertified or exempt from certification. Certified col-ors are man-made, with each batch being tested bythe manufacturer and the FDA to ensure that theymeet strict specifications for purity. There are ninecertified colors approved for use in the UnitedStates. One example is FD&C Yellow No.6, which isused in cereals, bakery goods, snack foods, andother foods.

Color additives that are exempt from certificationinclude pigments derived from natural sources suchas vegetables, minerals, or animals. For example,caramel color is produced commercially by heatingsugar and other carbohydrates under strictly con-trolled conditions for use in sauces, gravies, softdrinks, baked goods, and other foods. Most colorsexempt from certification also must meet certainlegal criteria for specifications and purity.

How Are Additives Regulated?

Additives are not always byproducts of twentiethcentury technology or modern know-how. Our an-cestors used salt to preserve meats and fish, addedherbs and spices to improve the flavor of foods, pre-served fruit with sugar, and pickled cucumbers in avinegar solution.

Over the years, however, improvements have beenmade in increasing the efficiency and ensuring thesafety of all additives. Today food and color addi-tives are more strictly regulated than at any othertime in history. The basis of modern food law is theFederal Food, Drug, and Cosmetic (FD&C) Act of1938, which gives the Food and Drug Administra-tion (FDA) authority over food and food ingredientsand defines requirements for truthful labeling ofingredients.

The Food Additives Amendment to the FD&C

Act, passed in 1958, requires FDA approval for theuse of an additive prior to its inclusion in food. Italso requires the manufacturer to prove an additive’ssafety for the ways it will be used.

The Food Additives Amendment exempted twogroups of substances from the food additive regula-tion process. All substances that FDA or the U.S.Department of Agriculture (USDA) had determinedwere safe for use in specific food prior to the 1958amendment were designated as prior-sanctionedsubstances. Examples of prior-sanctioned sub-stances are sodium nitrite and potassium nitrite usedto preserve luncheon meats. However, at present, ni-trites are called color-fixing agents for cured meatsand not preservatives, according to the FDA.

A second category of substances excluded fromthe food additive regulation process is generally rec-ognized as safe (GRAS) substances. GRAS sub-stances are those whose use is generally recognizedby experts as safe, based on their extensive history ofuse in food before 1958 or based on published scien-tific evidence. Salt, sugar, spices, vitamins, andmonosodium glutamate are classified as GRAS sub-stances, as are several hundred other substances.Manufacturers may also request that the FDA reviewthe use of a substance to determine if it is GRAS.

Since 1958, FDA and USDA have continued tomonitor all prior-sanctioned and GRAS substancesin light of new scientific information. If new evi-dence suggests that a GRAS or prior-sanctionedsubstance may be unsafe, federal authorities canprohibit its use or require further studies to deter-mine its safety.

In 1960, Congress passed similar legislation gov-erning color additives. The Color Additives Amend-ments to the FD&C Act require dyes used in foods,drugs, cosmetics, and certain medical devices to beapproved by the FDA prior to marketing.

In contrast to food additives, colors in use beforethe legislation were allowed continued use only ifthey underwent further testing to confirm theirsafety. Of the original 200 provisionally listed coloradditives, 90 have been listed as safe, and the re-mainder have either been removed from use by FDAor withdrawn by industry.

Both the Food Additives and Color AdditivesAmendments include a provision that prohibits theapproval of an additive if it is found to cause cancerin humans or animals. This clause is often referredto as the Delaney Clause, named for its Congres-sional sponsor, Rep. James Delaney (D-NY).

Regulations known as good manufacturing prac-


tices (GMP) limit the amount of food and color ad-ditives used in foods. Manufacturers use only theamount of an additive necessary to achieve the de-sired effect.

How Are Additives Approved for Use inFoods?

To market a new food or color additive, a manufac-turer must first petition the FDA for its approval.Approximately 100 new food and color additivespetitions are submitted to the FDA annually. Most ofthese petitions are for indirect additives such aspackaging materials.

A food or color additive petition must provideconvincing evidence that the proposed additive per-forms as intended. Animal studies using large dosesof the additive for long periods are often necessaryto show that the substance will not cause harmful ef-fects at expected levels of human consumption.Studies of the additive in humans also may be sub-mitted to the FDA.

In deciding whether an additive should be ap-proved, the agency considers the composition andproperties of the substance, the amount likely to beconsumed, its probable long-term effects, and vari-ous safety factors. Absolute safety of any substancecan never be proven. Therefore, the FDA must deter-mine if the additive is safe under the proposed con-ditions of use, based on the best scientific knowl-edge available.

If an additive is approved, the FDA issues regula-tions that may include the types of foods in which itcan be used, the maximum amounts to be used, andhow it should be identified on food labels. Additivesproposed for use in meat and poultry products alsomust receive specific authorization by the USDA.Federal officials then carefully monitor the extent ofAmericans’ consumption of the new additive and theresults of any new research on its safety to assurethat its use continues to be within safe limits.

In addition, the FDA operates an Adverse Reac-tion Monitoring System (ARMS) to help serve as anongoing safety check of all additives. The systemmonitors and investigates all complaints by individ-uals or their physicians that are believed to be re-lated to specific foods, food and color additives, orvitamin and mineral supplements. The ARMS com-puterized database helps officials decide whether re-ported adverse reactions represent a real publichealth hazard associated with food, so that appropri-ate action can be taken.

Summary

Additives have been used for many years to pre-serve, flavor, blend, thicken, and color foods, andthey have played an important role in reducing seri-ous nutritional deficiencies among Americans.Additives help assure the availability of wholesome,appetizing, and affordable foods that meet consumerdemands from season to season.

Today, food and color additives are more strictlyregulated than at any time in history. Federal regula-tions require evidence that each substance is safe atits intended levels of use before it may be added tofoods. All additives are subject to ongoing safety re-view as scientific understanding and methods oftesting continue to improve.

See Table 1.5 for additional information aboutfood additives.

FERMENTATION

The availability of fermented foods has a long historyamong different cultures. Acceptability of fermentedfoods also differs among cultural habits. A producthighly acceptable in one culture may not be so ac-ceptable to consumers in another culture. The numberof fermented food products is countless. Manufactur-ing processes for fermented products vary consider-ably due to variables such as food groups, form andcharacteristics of final products, kind of ingredientsused, and cultural diversity. Fermented foods can beprepared from various products derived from dairyproducts, grains, legumes, fruits, vegetables, musclefoods, and so on. This book contains an entire chap-ter (Chapter 3, Fermented Product Manufacturing)devoted to the science and technology of food fer-mentation. Please refer to it for further information.

NEW TECHNOLOGY

At present, some alternative or new technologies infood processing are available.

On June 2, 2000, the United States Food and DrugAdministration (FDA) released a report titled“Kinetics of Microbial Inactivation for AlternativeFood Processing Technologies.” This report evalu-ates the scientific information available on a varietyof alternative food processing technologies. Thepurpose of the report is to help the Food and DrugAdministration evaluate each technology’s effec-tiveness in reducing and inactivating pathogens ofpublic health concern.


The information in this section has been com-pletely derived from this report. For ease of reading,all references have been removed. Consult the orig-inal documents for unabridged data. The citationdata for this document are the following: A report ofthe Institute of Food Technologists for the Food andDrug Administration of the U.S. Department ofHealth and Human Services, submitted March 29,2000, revised June 2, 2000, IFT/FDA Contract No.223-98-2333, Task Order 1, How to Quantify the

Destruction Kinetics of Alternative ProcessingTechnologies, http://www.cfsan.fda.gov/~comm/ift-pref.html.

This section will discuss briefly the followingnew technology: (1) microwave and radio frequencyprocessing, (2) ohmic and inductive heating, (3)high-pressure processing, (4) pulse electric fields,(5) high-voltage arc discharge, (6) pulse light tech-nology, (7) oscillating magnetic fields, (8) ultravio-let light, (9) ultrasound, and (10) pulse X rays.


Table 1.5. Answers to Some of the Most Popular Questions about Food Additives

Q What is the difference between “natural” and “artificial” additives?

A Some additives are manufactured from natural sources such as soybeans and corn, which providelecithin to maintain product consistency, or beets, which provide beet powder used as food coloring.Other useful additives are not found in nature and must be man-made. Artificial additives can be pro-duced more economically, with greater purity and more consistent quality than some of their naturalcounterparts. Whether an additive is natural or artificial has no bearing on its safety.

Q Is a natural additive safer because it is chemical-free?

A No. All foods, whether picked from your garden or your supermarket shelf, are made up of chemicals.For example, the vitamin C or ascorbic acid found in an orange is identical to that produced in a labora-tory. Indeed, all things in the world consist of the chemical building blocks of carbon, hydrogen, nitro-gen, oxygen and other elements. These elements are combined in various ways to produce starches,proteins, fats, water, and vitamins found in foods.

Q Are sulfites safe?

A Sulfites added to baked goods, condiments, snack foods, and other products are safe for most people. Asmall segment of the population, however, has been found to develop hives, nausea, diarrhea, shortnessof breath, or even fatal shock after consuming sulfites. For that reason, in 1986 the FDA banned the useof sulfites on fresh fruits and vegetables intended to be sold or served raw to consumers. Sulfites addedas a preservative in all other packaged and processed foods must be listed on the product label.

Q Does FD&C Yellow No.5 cause allergic reactions?

A FD&C Yellow No.5, or tartrazine, is used to color beverages, desert powders, candy, ice cream, cus-tards, and other foods. The color additive may cause hives in fewer than one out of 10,000 people. Bylaw, whenever the color is added to foods or taken internally, it must be listed on the label. This allowsthe small portion of people who may be sensitive to FD&C Yellow No.5 to avoid it. Actually, any certi-fied color added to food is required to be listed on the label.

Q Does the low calorie sweetener aspartame carry adverse reactions?

A There is no scientific evidence that aspartame causes adverse reactions in people. All consumer com-plaints related to the sweetener have been investigated as thoroughly as possible by federal authoritiesfor more than five years, in part under FDA’s Adverse Reaction Monitoring System. In addition, scien-tific studies conducted during aspartame’s preapproval phase failed to show that it causes any adversereactions in adults or children. Individuals who have concerns about possible adverse reactions to aspar-tame or other substances should contact their physicians.

Microwave and Radio Frequency Processing

Microwave and radio frequency heating refer to theuse of electromagnetic waves of certain frequenciesto generate heat in a material through two mecha-nisms—dielectric and ionic. Microwave and radiofrequency heating for pasteurization and steril

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