Food Science Textbook PDF

FOOD SCIENCE  Food Science Texts Series Series Editor Dennis R. Heldman, University of Missouri Editorial Board Richard W. Hartel University of Wisconsin Hildegarde Heyma...

FOOD SCIENCE  Food Science Texts Series Series Editor Dennis R. Heldman, University of Missouri Editorial Board Richard W. Hartel University of Wisconsin Hildegarde Heymann University of Missouri Joseph H. Hotchkiss Cornell University James M. Jay University of Nevada Kenneth Lee Ohio State University Steven J. Mulvaney Cornell University Merle D. Pierson Virginia Polytechnic Institute and State University 1. Antonio Torres Oregon State University Edmund A. Zottola University of Minnesota Norman N. Potter and Joseph H. Hotchkiss, Food Science, Fifth Edition Food Science Texts Series Cameron Hackney, Merle D. Pierson and George J. Banwart, Basic Food Microbiology, 3rd Edition (1997) Dennis R. Heldman and Richard W. Hartel, Principles of Food Processing (1997) Hildegarde Heymann and Harry T. Lawless, Sensory Evaluation of Food (1997) Norman G. Marriot, Essentials of Food Sanitation (1997) James M. Jay, Modem Food Microbiology, 5th Edition (1996) Romeo T. Toledo, Fundamentals of Food Process Engineering, 3rd Edition (1997) Vickie Vaclavik and Elizabeth W. Christian, Essentials of Food Science (1997) Ernest R. Vieira, Elementary Food Science, Fourth Edition (1996) FOOD SCIENCE FIFTH EDITION ~ Springer  The author has made every effort to ensure the accuracy ofthe information herein. However, appropriate information sources should be consulted, especially for new or unfamiliar procedures. It is the responsibility of every practitioner to evaluate the appropriateness of a particular opinion in in the context of actual clinical situations and with due considerations to new developments. The author, editors, and the publisher cannot be held responsible for any typographical or other errors found in this book. Library of Congress Cataloging-in-Publication Data Potter, Norman N. Food science.-5th ed./ Norman N. Potter and Joseph H. Hotchkiss. p. cm. Rev. ed of: Food Science I Norman N. Potter, 4th edl1986. Originally published : New York: Chapman & HalI, 1995. Includes bibliographical references and index. ISBN 978-1-4613-7263-9 ISBN 978-1-4615-4985-7 (eBook) DOI 10.1007/978-1-4615-4985-7 1. Food industry and trade. I. Hotchkiss, Joseph H. II. Title. TP370.P58 1995 664-dc20 95-16000 CIP Cover design: Andrea Meyer, emDASH inc. © 1995, 1998 Springer Science+Business MediaNew York Softcover reprint ofthe hardcover 5th edition 1995, 1998 AII rights reserved. This work may not be translated or copied in whole or in part \\ ithout the written permission ofthe publisher (Springer Science+Business Media,LLC) except for brief excerpts in connection with revicws or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now know or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks and similar terms, even if the are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. 9 8 7 6 springeronline.com To our dear families whose support and encouragement make all things seem possible  Contents Preface xiii Chapter 1 Introduction: Food Science as a Discipline 1 Preparation for a Career in Food Science 2 Activities of Food Scientists 3 References 12 Chapter 2 Characteristics of the Food Industry 13 Components of the Food Industry 15 Allied Industries 18 International Activities 20 Responsiveness to Change 21 Interrelated Operations 22 References 22 Chapter 3 Constituents of Foods: Properties and Significance 24 Carbohydrates 24 Proteins 30 Fats and Oils 33 Additional Food Constituents 35 References 44 Chapter 4 Nutritive Aspects of Food Constituents 46 Food and Energy 46 Additional Roles of Carbohydrates, Proteins, and Fats in Nutrition 49 Protein Quality 52 Bioavailability of Nutrients 54 Vitamins 55 Minerals 60 Fiber 62 Water 62 Stability of Nutrients 63 Diet and Chronic Disease 63 References 67 VII VIII Food Science Chapter 5 Unit Operations in Food Processing 69 Common Unit Operations 69 References 88 Chapter 6 Quality Factors in Foods 90 Appearance Factors 91 Textural Factors 95 Flavor Factors 100 Additional Quality Factors 102 Quality Standards 103 References 112 Chapter 7 Food Deterioration and its Control 113 Shelf Life and Dating of Foods 114 Major Causes of Food Deterioration 115 Some Principles of Food Preservation 128 Control of Microorganisms 128 Control of Enzymes and Other Factors 135 References 136 Chapter 8 Heat Preservation and Processing 138 Degrees of Preservation 138 Selecting Heat 'Ireatments 139 Heat Resistance of Microorganisms 140 Heat 'Iransfer 146 Protective Effects of Food Constituents 149 Inoculated Pack Studies 150 Different Temperature-Time Combinations 151 Heating Before or After Packaging 152 Government Regulations 161 References 161 Chapter 9 Cold Preservation and Processing 163 Distinction Between Refrigeration and Freezing 163 Refrigeration and Cool Storage 165 Freezing and Frozen Storage 175 Some Additional Developments 198 References 199 Chapter 10 Food Dehydration and Concentration 200 Food Dehydration 201 Food Concentration 232 Intermediate-Moisture Foods 240 References 243 Chapter 11 Irradiation, Microwave, and Ohmic Processing of Foods 245 Food Irradiation 245  Contents IX Microwave Heating 256 Ohmic Heating 262 References 263 Chapter 12 Fermentation and Other Uses of Microorganisms 264 Fermentations 264 Microorganisms as Direct Foods 275 Genetic Engineering 275 References 277 Chapter 13 Milk and Milk Products 279 Fluid Milk and Some of its Derivatives 279 Ice Cream and Related Products 292 Cheese 300 Reduced Fat Dairy Products 314 References 314 Chapter 14 Meat, Poultry, and Eggs 316 Meat and Meat Products 316 Poultry 333 Eggs 338 References 343 Chapter 15 Seafoods 345 Fish Procurement 345 Marine Fish 347 Shellfish 351 Fish By-Products 355 Contaminants in Fish 355 Newer Products from Seafood 356 References 357 Chapter 16 Fats, Oils, and Related Products 359 Effects of Composition on Fat Properties 359 Sources of Fats and Oils 361 Functional Properties of Fats 364 Production and Processing Methods 365 Products Made from Fats and Oils 369 Fat Substitutes 376 Tests on Fats and Oils 377 References 379 Chapter 17 Cereal, Grains, Legumes, and Oilseeds 381 Cereal Grains 382 Some Principles of Baking 396 Legumes and Oilseeds 402 Some Special Problems 406 References 407 x Food Science Chapter 18 Vegetables and Fruits 409 General Properties 409 Gross Composition 409 Structural Features 411 Activities of Living Systems 417 Harvesting and Processing of Vegetables 418 Harvesting and Processing of Fruits 424 Fruit Juices 432 Biotechnology 435 References 436 Chapter 19 Beverages 437 Carbonated Nonalcoholic Beverages 437 Beer 442 Wine 445 Coffee 451 Tea 458 References 463 Chapter 20 Confectionery and Chocolate Products 464 Sugar-Based Confections 464 Ingredients 465 Chocolate and Cocoa Products 470 Confectionery Manufacturing Practices 474 References 476 Chapter 21 Principles of Food Packaging 478 Introduction 478 Types of Containers 482 Food-Packaging Materials and Forms 486 Package Testing 502 Packages with Special Features 503 Safety of Food Packaging 509 Environmental Considerations 509 References 512 Chapter 22 Food Processing and the Environment 514 Properties and Requirements of Processing Waters 516 Properties of Wastewaters 519 Wastewater 'freatment 522 Waste Solids Upgrading and 'freatment 526 Lowering Discharge Volumes 528 A Continuing Responsibility 530 References 530 Chapter 23 Food Safety, Risks, and Hazards 532 Safety, Hazards, and Risks 532 Food-Related Hazards 533  Contents XI Microbiological Considerations in Food Safety 539 Effects of Processing and Storage on Microbial Safety 540 Microbiological Methodology 543 HACCP as a Method to Prevent Food-Borne Illness 543 Chemical Hazards Associated with Foods 547 References 558 Chapter 24 Governmental Regulation of Food and Nutrition Labeling 559 Introduction 559 Federal Food, Drug, and Cosmetic Act 560 Additional Food Laws 561 Legal Categories of Food Substances 563 Testing for Safety 566 Food Labeling 567 Nutrition Labeling 569 International Food Standards and Codex Alimentarius 572 References 575 Chapter 25 Hunger, Technology, and World Food Needs 577 Background 577 Nature of Nutritional Problems 582 Some Dimensions of the Problem 583 Approaches to Combat World Hunger 589 Roles of Technology 590 Conclusions 591 References 591 Index 593  Preface It has been nearly 30 years since the first edition of Food Science was published. It and the subsequent three editions have enjoyed worldwide use as introductory texts for curriculums in food science and technology. This favorable response has encouraged us to adhere to the same basic format and objectives of the previous editions. Our goal is to provide readers with an introductory foundation in food science and technology upon which more advanced and specialized knowledge can be built. We are also aware that the book is widely used as a basic reference outside the academic environment. The fifth edition has been substantially updated and expanded where new information exists or was needed. The fifth edition continues to be aimed primarily at those with little or no previous instruction in food science and technology. The text introduces and surveys the broad and complex interrelationships among food ingredients, processing, packaging, distribution, and storage and explores how these factors influence food quality and safety. Foods are complex mixtures of mostly biochemicals and the number of methods available to convert raw agricultural commodities into edible foods is almost endless. It was not our intent to be comprehensive but rather to address the need for insight and appreciation of the basic components of foods and the processes most commonly used in food technology. We also hope to provide insight into the scope of food science for people considering food science as a career. As with previous editions, this one should continue to serve as a reference for professionals in food-related fields that service, regulate, or otherwise interface with food science and technology. Food science and technology, like many other science-based disciplines, has advanced rapidly since the fourth edition was published in 1986. Although many of the basic unit operations have changed little, new knowledge and concerns about biotechnology and foods, food safety, environmental issues, packaging technologies, government regu- lation, globalization offoods, nutrition, and others, as well as new processing technolo- gies such as ohmic heating and supercritical fluid extraction, have emerged. Many of the changes and additions to the fifth edition of Food Science reflect these and other developments which increasingly influence all involved in food processing as well as government agencies around the world. However, true change can only be measured against the broad principles and conventional food production practices of proven value. Therefore, most basic principles and practices continue to be described at an appropriate introductory level in the fifth edition. We would like to acknowledge our colleagues at Cornell University and elsewhere who provided much of the insights and materials for this edition. We are indebted to Mrs. Terry Fowler for her technical assistance with the production of this text. Joseph H. Hotchkiss Norman N. Potter Ithaca, New York XIII FOOD SCIENCE  1 Introduction: Food Science as a Discipline Food Science can be defined as the application of the basic sciences and engineering to study the fundamental physical, chemical, and biochemical nature of foods and the principles of food processing. Food technology is the use of the information generated by food science in the selection, preservation, processing, packaging, and distribution, as it affects the consumption of safe, nutritious and wholesome food. As such, food science is a broad discipline which contains within it many specializations such as in food microbiology, food engineering, and food chemistry. Because food interacts directly with people, some food scientists are also interested in the psychology of food choice. These individuals work with the sensory properties of foods. Food engineers deal with the conversion of raw agricultural products such as wheat into more finished food products such as flour or baked goods. Food processing contains many of the same elements as chemical and mechanical engineering. Virtually all foods are derived from living cells. Thus, foods are for the most part composed of "edible biochemicals," and so biochemists often work with foods to understand how processing or storage might chemically affect foods and their biochemistry. Likewise, nutritionists are involved in food manufacture to ensure that foods maintain their expected nutritional content. Other food scientists work for the government in order to ensure that the foods we buy are safe, wholesome, and honestly represented. At one time, the majority of scientists, technologists, and production personnel in the food field did not receive formal training in food science as it is recognized today. This was because very few universities offered a curriculum leading to a degree in food science. Many of these institutions had departments that were organized along commodity lines such as meats or dairy products. The food industry, government, and academic institutions continue to employ many persons who received their original technical training in dairy science, meat science, cereal chemistry, pomology, vegetable crops, and horticulture. Many others were trained as specialists in the basic sciences and applied fields of chemistry, physics, microbiology, statistics, and engineering. Such training has had the advantages generally associated with specialization. It also has resulted in certain limitations, especially for commodity-oriented individuals in seg- ments of the food industry undergoing rapid technological change. Hence, the more general discipline of food science was established. Now, more than 40 universities in the United States and many more around the world offer degrees in food science. 2 Food Science PREPARATION FOR A CAREER IN FOOD SCIENCE Industry and academic specialists have often differed about the definition of the term food scientist, and what should constitute appropriate formal training. Similarly, the major schools offering a degree in food science have not always agreed on the requirements for such a degree. The Education Committee of the Institute of Food Technologists (1FT) adopted a set of minimum standards for a university undergraduate curriculum in food science. These standards are followed by most universities which offer degrees in food science and reflect the scientific nature of food science. The most recent (1992) recommended minimum standards include both basic science courses and core food science and technology courses for the B.S. degree. The standards are based on a 120-semester-hour or 180-quarter-hour requirement for graduation. Courses should carry three to five semester hours or four to eight quarter hours of credit. The core of food science and technology courses, representing a minimum of 24 semester hours or 36 quarter hours, includes the following, most of which include both lecture and laboratory components: Food Chemistry covers the basic composition, structure, and properties of foods and the chemistry of changes occurring during processing and utilization. Prerequisites should be courses in general chemistry, organic chemistry, and biochemistry. Food Analysis deals with the principles, methods, and techniques necessary for quanti- tative physical and chemical analyses of food products and ingredients. The analyses should be related to the standards and regulations for food processing. Prerequisites include courses in chemistry and one course in food chemistry. Food Microbiology is the study of the microbial ecology related to foods, the effect of environment on food spoilage and food manufacture, the physical, chemical, and biological destruction of microorganisms in foods, the microbiological examination of food stuffs, and public health and sanitation microbiology. One course in general microbiology is the prerequisite. Food Processing covers general characteristics of raw food materials; principles of food preservation, processing factors which influence quality, packaging, water and waste management, and good manufacturing practices and sanitation procedures. Food Engineering involves study of engineering concepts and unit operations used in food processing. Engineering principles should include material and energy balances, thermodynamics, fluid flow, and heat and mass transfer. Prerequisites should be one course in physics and two in calculus. A senior-level "capstone" course that incorporates and unifies the principles of food chemistry, food microbiology, food engineering, food processing, nutrition, sensory analysis, and statistics should be taught after the other food science courses. The specific orientation of this course, that is, whether it's product development or product processing is left to the discretion of the university. These courses are considered minimal. Additional required and optional courses should be integrated into the curriculum. Courses in computer science, food law and regulation, sensory analysis, toxicology, biotechnology, food physical chemistry, ad- vanced food engineering, quality management, waste management, advanced food processing, and so on are important components of a food science program. In addition to the core courses in food science and technology, other typical require- ments for a food science degree include the following:  Introduction: Food Science as a Discipline 3 Two courses in general chemistry followed by one each in organic chemistry and biochemistry. One course in general biology and one course in general microbiology which has both lecture and laboratory. One course dealing with the elements of nutrition. Two courses in calculus. One course in statistics. One course in general physics. A minimum of two courses which emphasize speaking and writing skills. Courses in the humanities and social sciences. This requirement is usually established by the college or university. In the absence of such requirements, about four courses may be selected from history, economics, government, literature, sociology, philoso- phy, psychology, or fine arts. The above minimum requirements provide sound undergraduate training in the field of food science. The terms food scientist and food technologist are both commonly used and have caused some confusion. It has been suggested in the past that the term food technologist be used to describe those with a B.S. degree and the term food scientist be reserved primarily for those with an M.S. or Ph.D. degree as well as research competence. This distinction, however, is not definitive and both terms continue to be used widely and interchangeably. ACTIVITIES OF FOOD SCIENTISTS The educational requirements for a food science degree still fall short of an adequate description of food science. Some suggest that food science covers all aspects of food material production, handling, processing, distribution, marketing, and final consump- tion. Others would limit food science to the properties of food materials and their relation to processing and wholesomeness. The later view imposes serious limitations if it fails to recognize that the properties of food materials can be greatly influenced by such factors of raw material production as amount of rainfall, type of soil, degree of soil fertilization, genetic characteristics, methods of harvest or slaughter, and so on. At the other end, cultural and religious dictates and psychological acceptance factors determine the end use of a product. Psychology and sociology prove important in an affluent society where there is choice, as well as in other areas where customs and taboos sometimes are responsible for malnutrition although there may be no shortage of essential nutrients. Since definitions can be misleading, the activities of today's food scientists can be illustrated by way of examples. It has been estimated that as many as 2 billion people do not have enough to eat and that perhaps as many as 40,000 die every day from diseases related to inadequate diets, including the lack of sufficient food, protein, and/or specific nutrients. Many food scientists are engaged in developing palatable, nutritious, low-cost foods. Inadequate nutrition in extreme cases can produce in children an advanced state of protein defi- ciency known as kwashiorkor, or the more widespread protein-calorie malnutrition leading to marasmus. Dried milk can supply the needed calories and protein but is relatively expensive and is not readily digested by all. Fish "flour" prepared from fish of species not commonly eaten can be a cheaper source of protein. Incaparina, a cereal 4 Food Science formulation containing about 28% protein, is prepared from a mixture of maize, sor- ghum, and cottonseed flour. Incaparina and similar products were developed to utilize low-cost crops grown in Central and South America. Miltone was developed from ingredients-peanut protein, hydrolyzed starch syrup, and cow or buffalo milk-that are readily available in India. As food losses during storage and processing can be enormous, food scientists are involved in adapting and developing preservation meth- ods appropriate and affordable to various regions of the world. Food scientists have developed thousands of food products including those used in the space shuttle program (Fig. 1.1). The first astronauts added a small quantity of water to dehydrated foods in a special pouch, kneaded the container, and consumed the food through a tube. They had to deal with space and weight limitations, little refrigeration and cooking equipment, special dietary requirements dictated by stress and physical inactivity, and weightlessness. There was concern that crumbs or liquid might get loose in the spacecraft and become a hazard. Currently, food scientists are developing systems which "recycle" foods for space voyages into deeper space. If astronauts are to be in space for extended periods without resupply, foods will have to be grown and processed in space. The problems inherent in such systems present unique challenges to the food scientist. Perhaps the largest single activity of food scientists working in industrial organiza- tions is the improvement of existing and development of new food products (Fig. 1.2). In the United States in 1993, there were over 12,000 new products introduced if one considers all products "new" even if they are simply a standard product with only a slight change. Consumers like to have new products available. Industrial food scientists Figure 1.1. An astronaut consuming food aboard the space shuttle. Courtesy of the InStitute ofFood Technolo- gists.  Introduction: Food Science as a Discipline 5 Figure 1.2. A food scientist works "at the bench" to optimize the formulation of a cookie product. Courtesy of the Institute of Food Technologists. must find creative ways to meet this consumer demand for new and different products. Successful product development requires a blend of science and creativity. Food scientists today are often involved in altering the nutrient content of foods, particularly reducing the caloric content or adding vitamins or minerals. Reducing the caloric content is accomplished in several ways, such as replacing caloric food components with low or non-nutritive components. The caloric content of soft drinks is reduced by replacing the nutritive sugar sweeteners (e.g., sucrose) with aspartame or saccharin. Aspartame goes by the trade name Nutrasweet. Aspartame contains the same number of calories as sugar but is 200 times sweeter, so much less is used for the same degree of sweetening, thus reducing the caloric content. In other cases, food scientists reduce the caloric content of fat containing foods by replacing the fat with substances which have similar properties but are not metabolized in the same way as fat. For example, low-fat ice cream can be made by removing the normal milk fat and adding specially treated proteins. These proteins are made into very small particles which give ice cream the smooth texture associated with the fat. Protein has four calories per gram, whereas fat has nine. Thus, the net effect is a decrease in the caloric content of the ice cream. 6 Food Science Food scientists also find ways to add desirable vitamins and minerals to foods. Breakfast cereals are good examples of such foods. Most cereals have some added nutrients and some have a whole day's supply of several nutrients. These vitamins and minerals must be added in such a way as to be evenly dispersed in the product and be stable. They must not adversely affect the flavor or appearance of the food. This requires considerable care. Food processing technology is applied in the design and operation of ships which process fish at sea. These facilities include automatic separators for small and large fish, mechanized fish-cooling tanks, automatic oil extractors, ice-making equipment, complete canning factories, equipment for preparing fish fillets and cakes, and equip- ment for dehydrating fish and preparing dried fish meal. This factory approach prevents spoilage and minimizes protein and fat losses that otherwise would limit how long a fishing vessel could remain at sea. These factories can remain at sea for 2 months or more and range great distances from their home base. The Japanese and Russians have been most active in this kind of development. An important application of food science technology is the controlled-atmosphere (CA) storage of fruits and vegetables. Fruits such as apples, after they are harvested, still have living respiring systems. They continue to mature and ripen. They require oxygen from the air for this continued respiration, which ultimately results in softening and breakdown. If the air is depleted of much of its oxygen and is enriched in carbon dioxide, respiration is slowed. For some fruits, the best storage atmosphere is one that contains about 3% oxygen and about 2-5% carbon dioxide, the rest being nitrogen. Such atmospheres are produced commercially by automatic controls which sample the atmosphere continuously and readjust it. Refrigerated warehouses using CA storage permit year-round sale of apples which previously was not possible due to storage deterioration. Low-oxygen CA storage is also currently used to preserve lettuce quality during refrigerated truck transport and to reduce spoilage of strawberries during air shipment. In the latter case, air in the storage compartment is displaced by carbon dioxide from the sublimation of dry ice. Food science includes quick freezing of delicate foods with liquid nitrogen, liquid or solid carbon dioxide, or other low-temperature (cryogenic) liquids. When fruits and vegetables are frozen, ice crystals form within and between the cells which make up the pulpy tissue. If freezing is slow, large ice crystals form which can rupture the cell walls. When such a product is thawed, the pulp becomes soft and mushy and liquid drains from the tissue. The tomato is particularly susceptible. Under very rapid freezing conditions, as may be obtained with liquid nitrogen at -196°C, minute crystals form and the cellular structure is frozen before it can be ruptured; when thawed, the product retains its original appearance and texture much better than does material subjected to slow freezing. Nevertheless, even with such rapid freezing, only selected types of tomatoes can withstand freezing and thawing satisfactorily. However, less fragile frozen plant and animal foods of increasing variety owe their current commercial excellence to cryogenic freezing. One of the most important goals of the food scientist is to make food as safe as possible. The judicious application of food processing, storage, and preservation methods helps prevent outbreaks of food poisoning. Food poisoning is defined as the occurrence of disease or illness resulting from the consumption of food. Food-borne diseases are caused by either pathogenic (Le., disease causing) bacteria, viruses, parasites, or chemi- cal contaminants. The incidence of such food-borne illnesses in the United States is higher than many think. According to the Center for Infectious Diseases, between  Introduction: Food Science as a Discipline 7 1983 and 1987 there were 91,678 confinned cases. This probably only represents a small portion of the actual cases because of the strict criteria for classifying cases and the underreporting of cases where only one or two individuals were affected. Approximately 92% ofthese cases were due to pathogenic bacteria. However, processed food was implicated in only a tiny fraction of these cases. The largest causes of outbreaks are improper food preparation, handling, and storage, most occurring in homes, institutions, or in restaurants. For example, in 1993, ham- burgers containing undercooked ground beef were served in a fast-food restaurant resulting in several deaths. The causative bacteria was a type of Escherichia coli bacteria known as 0157:H7 which has been associated with raw beef and other prod- ucts. The number of cases of salmonellosis is also on the increase (Fig 1.3). The major cause of this increase is thought to be due to serving undercooked eggs and poultry contaminated with Salmonella enteritidis. Salmonella was found to be the cause of one of the largest food-borne disease outbreaks recorded. Approximately 16,000 people became ill from consuming contaminated milk. This single episode caused a large increase in the number of reported cases (Fig 1.3). Similar increases in botulism can occur due to large outbreaks (Fig 1.4). As pointed out earlier, the majority of food poisoning cases are due to mishandling and not to errors in processing. The processed food industry has a outstanding record of preventing such mishaps when it is considered that billions of cans,jars, and pouches of food materials are consumed annually. Occasionally, however, this excellent record has been broken by a limited outbreak in which persons succumb to toxic food. This may occur when canned foods are not heated sufficiently to destroy the spores of the anaerobic bacterium Clostridium botulinum or susceptible products are not stored properly. For example, in the United States in 1989, three cases of botulism were due to consumption of garlic-in-oil. The product was not sufficiently acidified nor SALMONELLOSIS (excluding typhoid fever) - by year, United States, 1955-1993 30 4 - Outbreak due to Contaminated Pasteurized Milk, IL 25 ~ 1 20 :.o g g - 15 l. § 1 10 1: &. :. o~~~.-~~~~~~~~~~~~-.~~~~~~~~~, 1955 1960 1965 1970 1975 1980 1985 1990 1995 Veor Figure 1.3. Cases of salmonellosis in the United States reported to the Centers for Disease Control. Source: Morbidity and Mortality Weekly Report, 42:50. 1994. 8 Food Science BOTULISM (foodbornel- by year, United State., 1975-1993 100 90 I Oulbreak due 10 Jalapeno Peppe". MI [outbreak due to Potato Salad, NM 80 70 Outbreak due to Sauteed Onions. Il [ J 60 " S Outbreak due to Fermented nsh/Seo Product AL... u. so ~ 0 a. II< 40 30 20 10 0 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 Vear Figure 1.4. Cases of food-borne botulism in the United States reported to the Centers for Disease Control. Source: Morbidity and Mortality Weekly Report, 42:24. 1994. refrigerated to prevent toxin formation. Also in 1989 in Great Britain, 27 people were diagnosed with botulism with one death from consumption of yogurt which contained a hazelnut preserve. Botulinum toxin had apparently developed in the hazelnut preserve before being added to the yogurt. Fish has been implicated in a number of botulism cases, most often because of a lack of knowledge by food handlers of the hazards associated with seafoods. An outbreak of botulism in Kapchunka is an example of how such misunderstanding can be lethal. Kapchunka is a whitefish which is soaked in a salt brine and air-dried without being eviscerated. The fish was then packaged and held at room temperature. C. botulinum in the intesti~al tract of the fish grew and produced toxin, giving botulism to several individuals, one of whom died. Food scientists carefully study each outbreak in the hope of preventing future outbreaks. When foods are heated to destroy pathogens and spoilage organisms, other changes in food components can affect color, texture, flavor, and nutrient values; thus, food scientists must optimize heat processes for specific products to be effective but not excessive. Sometimes pathogens enter food through faulty containers; this was the cause of major recalls of canned salmon contaminated with C. botulinum. Food science researchers have developed methods for tenderizing beef. For example, the application of tenderizing enzyme-salt mixtures to the surface of meat cuts is common household practice. However, commercial tenderization has gone further. Proteolytic enzymes may be injected into the animal shortly before it is slaughtered so that the pumping action of the heart circulates the tenderizer throughout the tissues. When the animal is slaughtered and the meat cuts are prepared, they are more tender than they otherwise would be. Another approach to tenderization is the application of electric current to the carcass after slaughter. Food scientists are studying the modification of beef muscle composition and proper- ties through special feeding practices. The Japanese have produced beef of exceptionally  Introduction: Food Science as a Discipline 9 high quality by the inclusion of beer in the ration, together with controlled exercise. In the United States and other countries, until recently, it was common practice to use the hormone diethylstilbestrol (DES) as a feed adjunct or as an animal implant to stimulate animal growth and reduce feed costs. This compound also slightly increases the moisture, protein, and ash, and decreases the fat levels of beef muscle and lamb. However, under certain conditions DES can cause cancer in mice and in humans, and in 1979, the U.S. Food and Drug Administration prohibited further use of DES in meat production. Food scientists are also studying the production of milk by cows fed minimum synthetic diets, and the organoleptic and functional properties of this milk. It has long been known that many of the nutritional requirements of cows are met by microbial synthesis of complex compounds in the cow's rumen from simpler materials. Finnish scientists have shown that cows can maintain high levels of milk production on mini- mum rations containing purified carbohydrate and no protein, the nitrogen source being supplied by inexpensive urea and ammonium salts. Milk from cows thus fed is quite normal in gross composition, amino acid constitution of its protein, flavor proper- ties, and functional characteristics. These findings are of particular significance since they provide a means for converting low-value cellulosic materials such as forest products and low-cost nitrogen compounds into valuable animal protein of a kind that is highly acceptable to humans. Food scientists are working on the production of flavors by specific enzyme systems acting on basic raw material substrates. Cooked meat flavors have thus been produced from fats, and fruity flavors from carbohydrates. Food scientists are beginning to use new techniques and products emerging from the fields of genetic engineering and biotechnology. Advances in recombinant DNA technology and related methods are providing improved microbial strains and new enzymes to increase yields and cut costs in the fermentation industries. For example, enzymes are required to coagulate the milk proteins for use in the manufacture of cheese. These enzymes have been isolated form natural sources. However, this limits availability and consistency. The genes for these enzymes have been cloned into bacte- ria which then biosynthesize the enzyme in a fermentation vessel. The enzyme is purified and used in cheese manufacture. In addition to countless potential applications in the manufacture of such fermented foods as cheese, bread, wine, beer, sauerkraut, and sausages, the biotechnology is being applied in the production of vitamins, amino acids, flavors, colors, and other food ingredients. Improved cultures and enzymes also are being used by food scientists to convert cellulose and starch to a variety of sweeteners and to convert other substrates, when supplemented with nitrogen, into edible protein. Food scientists always must be concerned with availability and cost of raw materials. Bakers' yeast is commonly grown on molasses; however, the price of molasses, which is a by-product of sugar manufacture, has increased in recent years because much sugar cane has been diverted to the production of alcohol for fuel use. Although other sources of carbohydrates have been used or modified for growing yeast, their costs fluctuate, they lack certain trace minerals and vitamins present in molasses and needed by yeast, and they tend to produce yeast with altered properties. Food scientists are also studying the removal of ions from liquid foods through the combined use of selective membranes and electric current, a process known as electrodialysis. Special membranes can be made that allow passage of cations but restrict movement of anions. Others permit movement of anions but hold back cations. 70 Food Science Such membranes can be assembled into compartmented "stacks" which are connected to the anode and cathode of an electric circuit. Ions in liquids passing through the com- partments tend to migrate to the poles of opposite charge, provided they are not rejected by a specific selective membrane. By proper choice of membranes and stack construction, certain anions, cations, or combinations of both may be removed from food liquids. In this fashion, tart fruit juices can be deacidified. Other membrane separation techniques (e.g., ultrafiltration and reverse osmosis) can separate proteins, sugars, and salts from liquid mixtures and can thus concentrate and change ratios of food constituents. These techniques are being used in new cheese-making processes and to fractionate valuable ingredients from whey, grain steep liquors, and other food liquids. Today, many food production plants depend on computers in their daily operation. The heart of such automatic plants-making baked goods, frankfurters, margarine, ice cream, and dozens of other products-is a computer command center, such as that shown in Fig. 1.5. All formulas are calculated in advance and the metering ofingredi- ents to mixers, ovens, freezers, and other equipment is controlled by microprocessors. Based on daily changes in the cost of formula ingredients, ratios of ingredients as well as operating conditions can be altered quickly by keyboard reprogramming. However, behind this automation is the skill of the formulator, food scientist, and the quality control laboratory. Food scientists have become increasingly concerned with the safety of foods, as they may be affected by pathogenic microorganisms, toxic chemicals such as pesticides, and other environmental contaminants such as bits of glass or metal. In an industrialized society, concentrations of chemicals entering the environment must be monitored and Figure 1.5. Food scientist at computerized controls in a large food processing plant.  Introduction: Food Science as a Discipline 77 limited, but since their complete elimination is impossible, foods may be expected to contain traces of "impurities," as do the air we breathe and the water we drink. Reports of unexpected chemicals in foods increase as the sensitivities of analytical instruments exceed nanogram-detection levels. This makes it imperative to know more about the toxicology of substances that may find their way into food, yet be harmless at low levels. In addition, more must be learned about the concentration of specific chemicals in the higher levels of the food chain. Thus, food scientists are analyzing meat, milk, and eggs from livestock fed crops grown near industrial sites. One interesting study involves potentially harmful levels of heavy metals in meat and eggs from poultry raised on feed containing ground mussels which, in tum, were grown in tanks of seawater on phytoplankton. Food scientists are currently investigating the fate of pesticides during food pro- cessing. Their objective is to know if processes can be developed which eliminate or reduce pesticide residues and how this may affect food safety. They are also investigat- ing, in conjunction with toxicologists, both naturally occurring as well as synthetic toxicants in foods. How these toxicants enter foods and how they might be eliminated are important research topics. Food scientists are involved in establishing international food standards to promote and facilitate world trade and at the same time to assure the wholesomeness and value offoods purchased between nations. Standards generally cover ingredient composition, microbiological purity, and subjective quality factors that often are not agreed upon universally. Wherever possible, standards also must not be discriminatory against one nation or another. This sometimes poses highly perplexing problems. Many countries would agree that Cheddar cheese to be called by this name should be made from cow's milk and contain a moisture content of not more than 39%. In India, however, much ofthe milk comes from the buffalo. Further, a Cheddar-type cheese made from buffalo milk is of poor texture unless somewhat more moisture is retained. Thus, an interna- tional Cheddar cheese standard upholding cow's milk as the raw material source, and a maximum of 39% moisture, could be to the disadvantage ofIndia were such a product produced for export. Similar problems are currently being studied for a wide variety of food items by international committees. Food scientists work in conjunction with nutritionists to develop standards for the optimal nutritional content of the diet and to determine how food processing and storage affects nutrients. One important aspect of this is to investigate how food formulation affects the bioavailability of nutrients. For example, ascorbic acid (vitamin C) can increase the bioavailability of iron in the diet. Other food scientists study how storage affects nutritional content of foods. For example, storing milk in clear contain- ers under display case lights can reduce the vitamin content of this important food. As these examples show, food science is involved in many technical and scientific aspects of food. The activities of food scientists are involved in diverse areas with the common theme of food. Almost limitless other examples might have been chosen: food preservation by irradiation; freeze concentration to remove water without loss of volatiles; the use of chemical additives to enhance the physical, chemical, and nutri- tional properties of foods; mechanical deboning to increase the yields of flesh from red meat, poultry, and fish; quick cooking methods using infrared, dielectric, or microwave energy; optimization of processes to maximize nutrient retention and minimize energy expenditures; and the development of information meaningful to the public and essen- tial to the creation of relevant, coherent food law. 12 Food Science All of these areas, and a great many more referred to in subsequent chapters, provide daily problems for food scientists. Together they help convey a better understanding of the term food science than can any simple definition. References Altschul, A.M. 1993. Low-Calorie Food Handbook. Marcel Dekker, New York. Bauernfeind, J.C. and Lachance, P.A. 1991. Nutrient Additions to Food: Nutritional, Technologi- cal and Regulatory Aspects. Food & Nutrition Press, Trumbull, CT. Catsberg, C.M.K and Kempen-Van Dommelin, G.J.M. 1989. Food Handbook. K Halsted Press, New York. Charalambous, G. 1992. Food Science and Human Nutrition. Elsevier, Amsterdam. Hall, R.L. 1992. Global Challenges for Food Science Students. Food Techno!. 46(9), 92, 94, 96. Harlander, S. 1989. Introduction to Biotechnology. Food Techno!. 43(7), 44, 46, 48. Hood, L.F. 1988. The Role of Food Science and Technology in the Food and Agriculture System. Food Techno!. 42(9), 130-132, 134. Hui, Y.H. 1992. Encyclopedia of Food Science and Technology. Wiley, New York. Institute of Food Technologists. 1992. 1FT Undergraduate Curriculum Minimum Standards for Degrees in Food Science 1992 Revision. Institute of Food Technologists, Chicago. Levine, A.S. 1990. Food Systems: The Relationship Between Health and Food SciencelTechnol- ogy. KH.P. Environ. Health Perspect. 86, 233-238. Morton, I.D. and Lenges, J. 1992. Education and Training in Food Science. A Changing Scene. K Horwood, New York. O'Brien, J. 1991. An Overview of Online Information Resources for Food Research. Trends Food Sci. Techno!. 2(11), 301-304. Ockerman, H.W. 1991. Food Science Sourcebook. 2nd ed. Chapman & Hall, London, New York. Patlak, M. 1991. Looking Ahead to the Promises of Food Science in the Future. News Rep. 61(2), 13-15. Rayner, L. 1990. Dictionary of Foods and Food Processes. Food Science Publishers, Kenley, Surrey, England. Ronsivalli, L.J. and Vieira, KR., 1992. Elementary Food Science. 3rd ed. Chapman & Hall, London, New York. Shewfelt, R.L. and Prussia, S.K 1993. Postharvest Handling: A Systems Approach. Academic Press, San Diego, CA.  2 Characteristics of the Food Industry Regardless of the criteria used to measure it, the food industry is very large, and if food production, manufacturing, marketing, restaurants and institutions are combined, it is the largest industrial enterprise in the United States. An appreciation ofthe size, components, interrelationships, and responsiveness to change of the food industry enlarges food scientists' understanding of the environment in which they operate. The total U.S. food-producing system-including the agricultural sector, food pro- cessing and marketing functions, and supporting industrial activities-generates about 20% of the gross national product and draws on close to one-fourth of the work force. This is greater than the combined efforts employed in the steel, automobile, chemical manufacturing, communications, public utilities, mining, and several other industries. The food-producing industry grows, processes, transports, and distributes our food- stuffs. Approximately, 3 million people work on farms, in orchards, on ranches, in fishing, and other areas and are directly involved in the production of the raw food materials that are subsequently processed into foods. As the chain of activities proceeds, people are engaged in such functions as produce buying, cattle feeding, dairy plant and grain elevator operations, and warehouse management. Food processing (manufac- turing) operations convert raw agricultural commodities into canned, frozen, dehy- drated, fermented, formulated, and otherwise modified forms of food. According to the Survey of Current Business, approximately 1.7 million people were directly employed in food manufacturing alone in 1991 (not counting related businesses). These people earned approximately $44 billion. Transportation of foodstuffs by rail, truck, water, and air, and the associated warehousing, employs an additional 2 million people. Wholesale distribution firms that keep retail outlets stocked are estimated to involve about 700,000 people. Retail distribution, including private stores, chain stores, and supermarkets account for an additional 2 million employees. Restaurants, drive-ins, cafeterias in hospitals, plants, and schools, vending machines, airline feeding, and other foodservice operations utilize about 5 million more people. Technically trained personnel serving the food industry in state, federal, and industrial positions of re- search, development, and quality control number over 25,000. Several million more persons from scores of occupations contribute directly or indirectly to the food produc- tion process. The amount of food produced in the United States is enormous. For example, the production of cheese in 1991 was 6.1 billion pounds; wheat 74 million metric tons; poultry 24 billion pounds, meat 39 billion pounds, and eggs 188 million cases. The food industry is also very large when considered on the basis of sales. In 1980, consumers 73 74 Food Science Table 2.1. Percent of Total Personal Consumption Expenditures Spent for Food in Selected Countries in 1988 Country Percent of Total Phillipines 52 China 48 Korea 36 Greece 35 Portugal 33 Mexico 32 Former USSR 28 Israel 27 Japan 19 France 17 United Kingdom 14 Canada 12 United States 10 SOURCE: World Food Expenditures, Na- tional Food Review 12(4) 26-29 spent $264 billion on food; in 1991, the figure was over $492 billion and rising. Interest- ingly, this is less than 12% of total disposable income. According to figures from the United States Department of Agriculture (USDA), this gives the United States the cheapest food supply in the world (Table 2.1). Nowhere else can people feed themselves as adequately on less than one-eighth oftheir disposable income. The cost offood when compared to disposable income has actually fallen from over 17% in 1960. The low cost offood was not always the case and certainly is not representative ofless developed parts of the world where the majority of one's labor may be required to produce or purchase adequate food. In China, for example, it is estimated that more than 48% of disposable income must go for food. The abundance of food in the United States is not due to more people, animals, and land on today's farms, but is the result of increased efficiency in agricultural operations resulting from application of advances in science and technology. Since 1920, cropland has not significantly increased, but production per hectare has gone up sharply; total numbers of livestock have changed very little, but production per animal has steadily risen. This increased production results from greater uses of fertilizers, agricultural chemicals, animal and pill-nt genetic improvements, and farm mechanization. Each year more food for more people is being produced by fewer farmers. Thus, in 1940 one farmer supplied the food for about 12 people,in 1960 about 28 people, and presently one farmer can produce the food for approximately 80 people. This has had both negative and positive consequences over the years. During the 1950s and 1960s, U.S. farmers produced large food surpluses, which lowered prices. This was alleviated by subsidizing farmers to limit their planting and production of certain commodities, by providing food aid to less developed areas of the world, and by developing processing methods to convert surplus foods into different forms to create new markets. Examples of the latter were conversion of surplus wheat into bulgur (a form of boiled wheat that can be dehydrated and consumed as a cereal) or peeled wheat, which acquires the appearance and some ofthe eating qualities of rice. Further  Characteristics of the Food Industry 75 examples were the conversion of perishable commodities such as sweet potatoes, apples, and milk to more stable dehydrated forms, either for export or for use in other manufac- tured foods. But surpluses have largely disappeared in recent years due to an increasing demand for food worldwide, and U.S. grain is being sought to feed the peoples ofless developed countries as well as to fatten the livestock of the more affluent. The food supply in the United States is marked not only by its quantity but also by its quality, variety, and convenience. Figure 2.1 shows how food was sold in large cities in the early 1900s. Fresh produce underwent heavy spoilage; variety was lacking; what variety there was, was seasonal, and the consequences of unsanitary handling were all too common. In contrast, today's large "superstores" stock as many as 50,000 individual food and nonfood items, and the battle is for shelf space and preferred position. The use of scanners and computers has helped the retail industry manage these large stores. This variety is largely the work of the food processor who may manufacture a basic food in 20 or more forms to entice the food purchaser. The many flavors of yogurt is one example. COMPONENTS OF THE FOOD INDUSTRY The food industry may be divided into segments, or components, in various ways. One ofthe simplest is a functional division into the four major segments of raw material Figure 2.1. Big city marketing of food in the early 18908. Courtesy of u.s. Department of Agriculture. 76 Food Science production, manufacture, distribution, and marketing. Raw material production en- compasses the technologies offarming, orchard management, fishing, and so on, includ- ing the selection of plant and animal varieties, cultivation and growth, harvest and slaughter, and the storage and handling of the raw materials. Manufacturing converts the raw agricultural products into more refined or finished foods. Manufacturing in- cludes the numerous unit operations and processes that many consider to be the core of food technology. Distribution is involved in product form, weight and bulk, storage requirements and storage stability; and product attributes conducive to product sales. Marketing is the selling of foods in commerce and involves wholesale, retail, institu- tions, and restaurants. This overall division is artificial and the segments flow into one another. The food industry is so geared that there is a highly planned organization and rhythm to the functions of the segments. In a well-developed food industry, this involves planning and scheduling of all phases to eliminate or at least minimize both shortages and surpluses among farmer, manufacturer, and distributor. Thus, it is common for large companies to own and manage farms or plantations, processing and distribution facilities, and even the outlets for sale of their manufactured products to ensure smooth operations and high profits. In recent years, for example, many food manufactures have opened national restaurant chains. If the industry is divided according to function, then it is sometimes helpful to know the relative value of the different functions. However, this is not simple to determine because there are great differences between products, as analyses of the percentage of the consumer's dollar spent for production, processing, transportation, and selling of different foods has shown. Currently, in the case of beef, the greatest cost is in farm production and the smallest cost is in processing and packaging. In contrast, for canned tomatoes, the biggest cost is in processing and packaging, and farm production repre- sents one of the smaller costs. A more common way of dividing the food industry is along major product lines. Table 2.2 gives the per capita dollar spent in 1990 on major food categories as well as the per capita consumption of these foods. Thus, of the consumer dollar spent for all foods to be consumed at home in 1990, about $0.27 went for meat, poultry, fish, and egg products, about $0.16 for fresh and processed fruits and vegetables, about $0.12 for dairy products, $0.15 for cereal products, and $0.30 for other products such as edible oils. These values do not necessarily reflect the tonnage or per capita consumption of each of the food categories, as the cost of a unit of each food differs greatly. Of all dollars spent for food, about 42% were spent on food consumed away from home. Food is most often consumed in a different form than that in which it is produced. For example, less than half of the 148 billion pounds of milk produced in the United States in 1991 was consumed as fluid milk. Approximately 17% went into the manufac- ture of butter, over 31 % into cheese, about 9% into ice cream and other frozen desserts, and so on. As the yield is only about 4 kg of butter per 100 kg of milk, and about 10 kg of cheese per 100 kg of milk, this amounted to some 0.5 million tons of butter, and approximately 2.3 million tons of cheese. Other examples of commodity conversions include the transformation of cereal grains into breakfast cereals, soybeans into edible oils, and cereal starches into sugar syrups. One way to define the food industry is to say that it converts or changes raw agricultural commodities into more finished foods. Americans have increased their consumption of fish and shellfish over the last decade but still consume less than in many other countries. Consumption in 1990 was approximately 15 pounds per person. This is 27% higher than it was in 1970-1974. The largest increases have come in fresh and frozen products, whereas canned fish  Characteristics of the Food Industry 17 Table 2.2. Per Capita Food Spending and Selected Consumption Figures Consumption Dollars/Person (Pounds per Capita) 1986 1990 1980--1984 1990 Food expenditures 1326 1652 Food at home 767 956 Cereals and bakery products 106 142 148 185 cereals and cereal products 36 50 bakery products 70 92 Meats, poultry, fish 216 257 182 191 beef 73 84 73 64 pork 45 51 48 46 other meats 30 38 poultry 33 42 45 64 fish and seafood 25 32 eggs 12 12 34 30 Dairy products 97 113 559 568 fresh milk and cream 47 54 other dairy products 49 60 Fruit and vegetables 123 157 fresh fruit 39 49 87 95 fresh vegetables 35 45 76 93 processed fruit 28 36 processed vegetables 21 27 Other food at home 213 287 sugar and other sweets 28 36 148 fats and oils 20 26 64 62 miscellaneous foods 91 129 nonalcoholic beverages 74 82 Foods away from home 560 697 Alcoholic beverages 104 113 SoURCE: ERS-USDA 1991. Food and Nutrient Consumption. FoodReview 14(3) 2-18. rose only 11%. Lesser amounts are consumed in salted and smoked form. In 1991 the total domestic catch of fishery products for human consumption was 9.5 billion pounds of which 6.5 billion was for the fresh or frozen market, with 0.6 billion being canned. During the same period, the United States imported an additional 3 billion pounds. Since everything about the food industry is big, it is to be expected that the number of people employed in food processing and the number of food processing plants are also large. The USDA estimated that there were 380,000 processing, wholesale, and retail firms in the United States in 1990. The estimated number of food processing plants with more than 20 employees in the United States is more than 20,000. The trend is for this number to become smaller and the remaining plants to become larger. This has concerned some who point out monopolistic tendencies in specific branches of the food industry. But a counterinfluence is a growing trend toward diversification within large food companies, including involvement in nonfood ventures. Small food processing establishments, with fewer than 20 employees, and retail outlets may num- ber as many as 500,000. According to the USDA, in 1988 there were over 3 million 78 Food Science people employed in the food processing and marketing and related industries. This number has declined somewhat over the recent years and is not expected to increase in the near future. By comparison, there were only 3 million people directly employed in farming and related activities in 1989. Currently in the United States, nearly one-half of the dollars spent on food goes for food eaten away from home. The trend of increased spending for food eaten away from home has leveled off in recent years, but the general trend has been upward for the last few decades. Actually, the quantity of food consumed outside of the home is less than one-third that eaten at home, the dollar ratio representing higher prices for food away from home. This food away from home is consumed in restaurants, industrial and school cafeterias, hospitals, airplanes, and through vending machines and other outlets. In 1992 the USDA estimated that there were over 730,000 foodservice outlets in the United States. This included restaurants, fast-food outlets, schools, institutions, and cafeterias. These types of foodservice have their own specific requirements for ease of prepara- tion and serving speed, providing new challenges and opportunities for convenience- food manufacturers, suppliers of packaging materials, makers of quick cooking and reconstituting equipment, catering establishments, and an ever-increasing variety of carryout and fast-food franchise chains. Many companies have broadened their activi- ties in response to these changes. Grocery stores have added restaurants and food processing facilities while food manufacturers have acquired restaurant chains and some have become direct marketers of their products. ALLIED INDUSTRIES Many companies which may not directly sell food are nonetheless deeply involved in the food industry. These are the companies that produce the nonfood components that are essential to the marketing offood. A good example is the packaging industry. For example, steel manufacturers make materials for the billions of cans used for food each year. They have worked in depth on the corrosive effects and interactions of different foods with the metals used in the manufacture of cans. They have supported extensive research on improved types of cans where the gauge of the metal may be reduced, thus lightweighting the cans and reducing costs. The same is true of the leading aluminum companies in the development of aluminum cans, aluminum dishes, and foil for food use. Other examples of companies which supply ingredients to the food industry include food ingredients such as color or flavor suppliers (Fig 2.2). The study of can closure, can closure machines, and heat transfer into cans for sterilization has kept food scientists and engineers busy. Companies do extensive research and development in food packaging in glass, paper, and plastic. Tinted glass that screens out ultraviolet rays and thus protects light-sensitive foods and plastic films that provide maximum moisture and oxygen barriers and resistance to heating and freezing are studied by scientists in these companies. Recent advancements in polymers have led to the development of many new types of plastic packages for foods such as those which will withstand the temperatures generated in the microwave oven or the pressures generated during retorting foods in plastic cans. These new technologies have reduced costs and provided many new products and more convenient foods. Chemical manufacturers are important in the food industry because they supply many of the acidulants, preservatives, enzymes, stabilizers, and other chemicals used  Characteristics of the Food Industry 79 Figure 2.2. A flavor chemist compounding flavors for a food. Food Processing Magazine, 55(5)15. 1994. in foods. All of these must be functional and fully satisfy specifications of safety set down by the Food & Drug Administration (FDA) or other regulatory agencies that have responsibility for food safey. Food machinery and equipment manufacturers often are the prime innovators of new food processing methods and systems. They have developed pasteurizers and evaporators, microwave ovens and infrared cookers, freeze-drying systems and liquid- nitrogen freezers, and instrumentation and computer controls. All of these, and many, many more companies in allied industries work directly with food. 20 Food Science In recent years, especially, all industries have become more accountable to govern- ment, consumers, their employees, and each other. This has taken many forms, such as providing the public with more information, assuming greater responsibility for the quality of the environment and the safety of products, conserving resources, and meeting increasingly rigorous government regulations. In the case of the food industry, this trend has led to greater dependence on outside consultants, testing laboratories, and legal expertise. Thus, more of these people are becoming involved in the food production process. INTERNATIONAL ACTIVITIES Food has become a global commodity. Foods are traded and shipped worldwide (Fig. 2.3). It is not unusual to find dozens of types of fine foods from around the world in a modern grocery store. This might include cheeses from Europe, lamb from New Zealand, fresh grapes from Chile, snowpeas from Guatemala, apples from Argentina, beef from Australia, and mangoes from South America. Many U.S. food companies have set up subsidiaries in other countries and many fast-food outlets such as McDonald's have opened stores around the world. The largest McDonald's is reported to be in Moscow. Agricultural imports (food and other products) to the United States amounted to about $22 billion in 1991 which amounted to approximately 10% of all imports. These have included coffee, tea, cocoa, spices, and other products not grown in this country, as well as sugar, fish, and other products to supplement domestic production. Food exports were about $37 billion in 1991 and have grown due largely to increased world demand for cereal grains and soybeans, making the United States the world's largest food exporter. Most major American food companies have vigorous international divi- sions with manufacturing facilities in many parts of the world. Among those with extensive overseas operations are Kraft-General Foods, CPC International, H.J. Heinz, Borden, Campbell Soup, Nabisco Brands, Coca-Cola, Pepsico, Beatrice Companies, Figure 2.3. Large cargo container ship transporting goods internationally. Source: Hand- book of Package Engineering, J. P. Hanlon, Technomic Publishing Co. Lancaster, PA 1992.  Characteristics of the Food Industry 27 Ralston Purina, and General Mills. There is a recent trend to decrease the trade tariffs on many items including food. This can be expected to increase the. international trade in food items. It is common for a U.S. grocery store to stock food items from around the world. When these companies go into food production in foreign countries they do not simply build a plant and resume operations as in the United States. Experience has shown that often they must modify well-known products to suit local tastes. Even the most popular soft drink formulations may vary in certain parts of the world. Another problem facing companies entering operations in a new country is related to available food ingredients. In some countries, the food producer may not import certain essential or important ingredients but must utilize local ingredients such as wheat or cocoa. These may differ substantially from equivalent ingredients used in the United States and thus require extensive reformulation and process changes to achieve acceptable quality. This is further complicated by local food laws, which often prohibit the use of specific food acidifiers, preservatives, or food colors that are permitted in the United States. RESPONSIVENESS TO CHANGE It is often said that the food industry is a stable industry, resistant to the effects of recessions. In the sense that per capita consumption of total food is remarkably con- stant, and for many decades has remained at around 658 kg (1450 pounds) per year, this is true. However, the kind of foods consumed are continually changing and this contributes to great competition within the industry and makes it highly dynamic. People choose the foods they eat in response to many influences. The food industry responds to these choices or more often tries to anticipate these changes so that they can have the desirable products. For example, changes in food use reflect demographic shifts such as the increasing numbers of older Americans, working women, and single- member households. The food products available in the marketplace also reflect the supply of ingredients and nonfood components, which are subject to extremes of weather, political barriers, and changing world demand. Availability and costs of energy influence all phases of food production. Advances in the areas of nutrition, health, and food safety often change eating habits whether the benefits that may result are real or just perceived. According to the U.S. Department of Agriculture, between 1968 and 1988 U.S. residents increased their daily consumption of kilocalories from 3300 to 3600. However, the kinds of foods making up this consumption has changed substantially. For example, fresh and frozen fruits consumption has increased 25% over a the last 20 years. Atti- tudes with respect to fat, cholesterol, and fiber contents of foods have changed. During the same period, red meat consumption has declined by 16%. Government regulation offood additives, food composition standards, and labeling also influence product offer- ings. Technical innovations-from ingredient modifications to new processing and packaging methods to microwave oven and other cooking advances-alter our food supply. The above determine the directions of new product development, marketing, and advertising. New products in great variety are characteristic of the modern food indus- try. In 1991 there were over 12,000 new food products introduced into commerce in the United States (Table 2.3). Currently, there are over 50,000 items representing 22 Food Science Table 2.3. Numbers of New Food Products Introduced Between 1988 and 1993 Category 1988 1989 1990 1991 1992 1993 Baby food 55 53 31 95 53 7 Bakery products 968 1,155 1,239 1,631 1,508 1,420 Baking ingredients 212 233 307 335 346 383 Beverages 936 913 1,143 1,367 1,538 1,845 Breakfast cereal 97 118 123 108 122 99 Candy/gum/snacks 1,310 1,355 1,486 1,885 2,068 2,042 Condiments 1,608 1,701 2,028 2,787 2,555 3,148 Dairy 854 1,348 1,327 1,111 1,320 1,099 Desserts 39 69 43 124 93 158 Entrees 613 694 753 808 698 631 Fruits and vegetables 262 214 325 356 276 407 Pet food 100 126 130 202 179 276 Processed meat 548 509 663 798 785 454 Side dishes 402 489 538 530 560 680 Soup 179 215 159 265 211 248 Total, food 8,183 9,192 10,301 12,398 12,312 12,897 SoURCE: Gt>rman's New Product News, 29(1) 1994. different products, brand names, and sizes in large U.S. food stores, including as many as 3000 pet food items. Many of these products have short life spans. INTERRELATED OPERATIONS As has been stated, the production of specific foods in a highly advanced and organized food industry is a systematic and rhythmic process. The food manufacturer does not simply decide to produce 5000 tons of margarine and then casually do so. If they did, they might find themselves, at one end, unable to procure the necessary vegetable oils at a competitive price and, at the other, without a ready and adequate outlet for the product. These factors alone could make them unsuccessful in the highly competitive food field, where often fractions of a cent per kilogram or per package make the difference between economic success or failure. Throughout all production, manufactur- ing, and distribution operations, these fractions of cents per unit of food product are carefully controlled along with the quality aspects of the product. Since the food indus- try is a low-markup, high-volume industry, and numbers like several hundred thousand units per day-such as cartons of milk or loaves of bread-are common for a single plant, losses of fractions of a cent per unit anywhere along the chain from farmer to consumer can mean losses to the food producer of hundreds of thousands of dollars per year. References Caswell, J.A. and Preston, W.P. 1992. How new products find their place in the marketing system. In The Yearbook of agriculture. U.S. Department of Agriculture, Washington, DC, pp.9-14.  Characteristics of the Food Industry 23 Chou, M. 1992. Trends in food consumption during 1970-1990. Cereal Foods World 37(4),331- 333. Connor, J.M. and Barkema, A.D. 1992. Changing food marketing systems. In The Yearbook of Agriculture. U.S. Department of Agriculture, Washington, DC, pp. 15-21. Donald, J.R 1992. U.S. agricultural outlook. In Agriculture Outlook. U.S. Department of Agricul- ture, Washington, DC, pp. 84-106. Donald, J.R 1993. U.S. agricultural outlook. In Outlook. U.S. Department of Agriculture, Wash- ington, DC, pp. 9-35. Gady, R 1993. Long term outlook and opportunities in food manufacturing. In Outlook. U.S. Department of Agriculture, Washington, DC, pp. 671-678. Rankin, M.D. and Kill, RC. 1993. Food Industries Manual. 23rd ed., Chapman & Hall, London, New York. Ritson, C., Gofton, L. and McKenzie, J. 1986. The Food Consumer. Wiley, Chichester. Russo, D.M. 1992. The year 2000: A food industry forecast. Agribusiness 8(6), 493-506. Senauer, B., Asp, E. and Kinsey, J. 1991. Food Trends and the Changing Consumer. Eagan Press, St. Paul, MN. Stauber, K.N. 1992. Agricultural outlook '94. In Agriculture Outlook. U.S. Department of Agri- culture, Washington, DC, pp. 32-36. Uri, N.D. 1992. Industry structure and economic performance in the food manufacturing indus- tries. J. Int. Food Agribus. Mark 4(1), 95-123. USDA. Economic Research Service. 1991. Food Review. USDA ERS Commodity Economics Division, U.S. GPO, Rockville, MD. 14(1).  3 Constituents of Foods: Properties and Significance A knowledge of the constituents of foods and their properties is central to food science. The advanced student of food science, grounded in the basic disciplines of organic chemistry, physical chemistry, and biochemistry, can visualize the properties and reactions between food constituents on a molecular basis. The beginning student is not yet so equipped. This chapter, therefore, will be more concerned with some of the general properties of important food constituents, and how these underlie practices of food science and technology. Foods are made up mostly of biochemicals (i.e., edible biochemicals) which are mainly derived from living sources such as plants and animals. There are three main groups of constituents in foods: carbohydrates, proteins, and fats, and derivatives of these. In addition, there are inorganic and mineral components, and a diverse group of organic substances present in comparatively small proportions that include such substances as vitamins, enzymes, emulsifiers, acids, oxidants, antioxidants, pigments, and flavors. There is also the ever-present and very important constituent, water. These components are arranged in different foods to give the foods their structure, texture, flavor, color, and nutritive value. In some instances, foods also contain substances that can be toxic if consumed in large amounts. The general composition of a food as well as the way in which the components are organized give a food its individual characteristics. For example, whole milk and fresh apples have about the same water content, but one is a solid and the other a fluid because of the way the components are arranged. The above constituents occur in foods naturally. Sometimes we are not satisfied with the structure, texture, flavor, color, nutritive value, or keeping quality of foods, and so we add other materials to foods to improve one or more properties. These may be natural or synthetic. For example, we may add natural or synthetic fruit flavors to beverages. CARBOHYDRATES Carbohydrates (from "hydrates of carbon") are organic compounds with the basic structure Cx (H2 0)y. Among the most important types of carbohydrates in foods are the sugars, dextrins, starches, celluloses, hemicelluloses, pectins, and certain gums. Chemically, carbohydrates contain only the elements carbon, hydrogen, and oxygen. 24  Constituents of Foods: Properties and Significance 25 Simple carbohydrates are called sugars. One of the simplest carbohydrates is the six- carbon sugar glucose. Glucose and other simple sugars form ring structures of the following form: a H8 CH 2 0H HstJH OH a-D-glucosc HO H HO OH a-D-mannosc OH OH OH a-D-ga lactose These simple sugars each contain 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms [C x (H 2 0)y where x=6; y=6]. They differ in the positions of oxygen and hydrogen around the ring. These differences in the arrangement of the elements result in differ- ences in the solubility, sweetness, rates of fermentation by microorganisms, and other properties of these sugars. Two glucose units may be linked together with the splitting out of a molecule of water. The result is the formation of a molecule of a disaccharide, in this case maltose: Common disaccharides formed in similar fashion are sucrose (e.g., cane or beet sugar) made from glucose and fructose (a five-membered ring), rmaltose or malt sugar from two molecules of glucose, and lactose or milk sugar from glucose and galactose. These disaccharides also differ from one another in solubility, sweetness, susceptibility to fermentation, and other properties. A larger number of glucose units may be linked together in polymer fashion to form polysaccharides (Le., "many sugars"). One such polysaccharide is amylose, an important component of plant starches (Fig. 3.1). A chain of glucose units linked together in a slightly different way forms cellulose. Thus, the simple sugars are the building blocks ofthe more complex polysaccharides, the disaccharides and trisaccharides, the dextrins, which are intermediate in chain length, on up to the starches, celluloses, and hemicelluloses; molecules of these latter substances may contain several hundred or more simple sugar units. Chemical deriva- tives of the simple sugars linked together in long chains likewise yield the pectins and carbohydrate gums. The disaccharides, dextrins, starches, celluloses, hemicelluloses, pectins, and carbo- hydrate gums are composed of simple sugars, or their derivatives. Therefore, they can be broken down or hydrolyzed into smaller units, including their simple sugars. Such breakdown in the case of amylose, a straight chain fraction of starch, or amylopectin, a branched chain fraction (Fig. 3.1), yields dextrins of varying intermediate chain length, the disaccharide maltose, and the monosaccharide glucose. This breakdown or digestion can be accomplished with acid or by specific enzymes, which are biological catalysts. Microorganisms, germinating grain, and animals including humans possess various such enzymes.  A. Fragment of a branched· chain molecule of amylopectin starch. A."f.i~\lAh ~ -----......... B. Chemical structure and linkage 'Fjfj'if':;.. " at pOint of branching. V~\f;t{:1jJ.'~""" "" ~IiI-_otc. CH,OH CH,OH 20H CH,OH ~ ~;to~~~~- 8""" """ """ """) A. Fragment of a straight·chain molecule of amylose starch. B. Chemical structure and linkage. Figure 3.1. Straight chain amylose and branched chain amylopectin fractions of starch. Courtesy of Northern Regional Research Laboratory.  Constituents of Foods: Properties and Significance 27 The chemically reactive groups of sugars are the hydroxyl groups (-OR) around the ring structure, and when the ring is opened, the o 0 / / '" -C (aldehyde group) and the -C (ketone group). H \ Sugars that possess free aldehyde or ketone groups are known as reducing sugars. All monosaccharides are reducing sugars. When two or more monosaccharides are linked together through their aldehyde or ketone groups so that these reducing groups are not free, the sugar is nonreducing. The disaccharide maltose is a reducing sugar; the disaccharide sucrose is a nonreducing sugar. Reducing sugars particularly can react with other food constituents, such as the amino acids of proteins, to form compounds that affect the color, flavor, and other properties offoods. In like fashion, the reactive groups of long-chain sugar polymers can combine in a cross-linking fashion. In this case the long chains can align and form fibers, films, and three-dimensional gellike networks. This is the basis for the production of edible films from starch as a unique coating and packaging material. Carbohydrates playa major role in biological systems and in foods. They are produced by photosynthesis in green plants and are nature's way of storing energy from sunlight. They may serve as structural components as in the case of cellulose, be stored as energy reserves as in the case of starch in plants and liver glycogen in animals, and function as essential components of nucleic acids as in the case of ribose, and as components of vitamins such as the ribose of riboflavin. Carbohydrates can be oxidized to furnish energy. Glucose in the blood is a ready source of energy for animals. Fermen- tation of carbohydrates by yeast and other microorganisms can yield carbon dioxide, alcohol, organic acids, and a host of other compounds. Some Properties of Sugars Such sugars as glucose, fructose, maltose, sucrose, and lactose all share the following characteristics in varying degrees: (1) They are usually used for their sweetness; (2) they are soluble in water and readily form syrups; (3) they form crystals when water is evaporated from their solutions (this is the way sucrose is recovered from sugar cane juice); (4) they supply energy; (5) they are readily fermented by microorganisms; (6) they prevent the growth of microorganisms in high concentration, so they may be used as a preservative; (7) they darken in color or caramelize on heating; (8) some of them combine with proteins to give dark colors, known as the browning reaction; and (9) they give body and mouth feel to solutions in addition to sweetness. A very important advance in sugar technology has been the development of enzymatic processes for the conversion of glucose to its isomer, fructose. Fructose is sweeter than glucose or sucrose. This has made possible the production of sugar syrups with the sweetness and certain other properties of sucrose starting from starch. Commonly, corn starch is hydrolyzed to provide the glucose, which is then isomerized. The United States produces enormous quantities of corn and with this technology has become less dependent on imported sucrose, the availability and price of which can fluctuate greatly. 28 Food Science Some Properties of Starches The starches important in foods are primarily of plant origin and exhibit the following properties: (1) They are not sweet; (2) they are not readily soluble in cold water; (3) they form pastes and gels in hot water; (4) they provide a reserve energy source in plants and supply energy in nutrition; (5) they occur in seeds and tubers as characteris- tic starch granules (Fig. 3.2). When a suspension of starch granules in water is heated, the granules swell due to water upt