Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
4 Enhancing the Food Supply It should be a goat of our country to provide a sufficient variety of foocis throughout the year to meet the energy and nutrient needs of its citizens, promote health, and export value-added food products that im- prove our international competitiveness and trade balance and create jobs. Our food supply should be safe and properly preserved to maintain high quality, yet should be low enough in cost for all to have access to a nutri- tionally adequate diet, irrespective of income. Because of the numerous technological advances in food preservation, some of which are noted in this chapter, and the productive system of agriculture in the United States, we enjoy a relatively abundant, safe, and nutritious food supply. Furthermore, the amount we spend on food at home about 12 percent of disposable personal income is the lowest in the world among countries for which comparable data are available. Micronutrient-deficiency diseases and foodborne illnesses that plagued our nation earlier this century have largely disappeared as a result of the improved supply, preservation, and enrichment and fortification of foods. In addition, technologies developed by foot! scientists since the 1940s are helping to reduce nutrient deficiencies throughout the world, although the challenges are still great. Current dietary needs in the United States go beyond providing suffi- cient food and nutrients. They involve modifying and enhancing the food supply to help combat coronary heart disease, cancer, and other chronic diseases. The safety of the food supply continues to be of concern as we 98
ENHANCING THE FOOD SUPPLY 99 learn more about microbial contamination and the toxic effects of some components of food. Food technologists are producing modified foods to help people meet dietary recommendations (for example, to consume foods with fewer calo- ries or less total fat, saturated fat, and cholesterol). Many of these prod- ucts incorporate newly developed fat and sugar substitutes. More "func- tional foods," as these products are called, will be developed through collaborative efforts among plant geneticists, biotechnologists, and food technologists to enrich or reduce the amounts of biologically active com- ponents in these foods. Functional foods are the wave of the future: for example, a cancer-preventing compound may be increased in a food through addition or by biotechnology. Exciting opportunities and challenges lie ahead as we enhance the food supply for optimal health. Nutritional recommendations per se will not be effective unless people can meet them by eating generally available food products. Technological responses to consumers' concerns and nutri- tional recommendations have already changed the food-product landscape. Low-calorie, low-fat, low-salt, higher-fiber, and fortified foods, as well as decaffeinated coffee, cholesterol-free egg products, and fat and sugar sub- stitutes are all familiar examples. As the driving forces for a healthier, safer, more convenient, competi- tively superior, seasonally invariant, and environmentally friendly food supply have accelerated in recent years, new technical needs have begun to emerge, with actions and contributions in one area affecting the others. The next generation of novel materials, new and hybrid technologies, and unique applications will emerge from the progressively specialized frontiers of scientific research. Their synergistic linkages with the scale and range of existing food-manufacturing practices will offer new opportunities and fresh challenges worthy of special efforts. The impetus for safe foods also re- quires new technologies and associated biological, physical, and engineer- ing concepts. Success will indeed vitalize the science and engineering basis for enhancing the quality, safety, and sustainability of the U.S. food system and for long-term amelioration of increasingly serious global com- petition. In the following examples, applications of biological, physical, and engineering principles form the basis of theoretical and experimental understanding of foods and food systems. ENGINEERING FOODS FOR DIETARY COMPLIANCE Dietary recommendations may be perceived by much of the public as promoting a shift to less food and perhaps to less aesthetically pleasing foods, often resulting in noncompliance. Technology can play a key role in this scenario by creating new formulated foods and modifying whole foods
100 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES THE FOOD-PROCESSING INDUSTRY Based on the value of its shipments, the food-processing industry is the largest manufacturing industry in the United States, employing 1.6 million people. The U.S. food system stretching from farms to grocery stores plays a distinctly vital role in the national economy. As a total system, it employs 14 million people directly and another 4 million in related industries. It contributes nearly 20 percent of the gross national product (GNP). The overall contribution of the food-processing industry to this country is far greater than the mere dollar value of its shipments, the number of its employees, or its position in worldwide competition would indicate. The recent evolution of a scientifically based, integrated, effi- cient system of food engineering, processing, and packaging allows Amer- icans the unique luxury of acting as if food were a constant around which other activities can be planned. This has considerably enhanced the quali- ty of life that we enjoy today. Its total contribution is considerably great- er than its cost to U.S. consumers on average, about 12 percent of disposable income in 1991 (15 percent including beverages). This is much lower than food costs in any other country in the world. The importance of food engineering, processing, and packaging in this area cannot be overestimated. Adding value not only captures the benefit of economic output, but also provides employment and generates government revenues. In today's global economy, value-added processing of consumer-oriented foods has assumed new dimensions. In 1990, inter- national trade in consumer-oriented foods grew at a 4 percent annual rate, while growth in bulk and intermediate commodities was up by only I percent. In the same year, 53.8 percent of U.S. agricultural exports were exported in bulk form, 22.7 percent in intermediate form, and 23.5 percent in consumer-oriented form. However, the United States accounts for only 8 percent of the $140 billion world market for consumer-orient- ed foods. It is reasonable to assume that as disposable income increases across the globe, there will be new demands for consumer-oriented food products. A 15 percent U.S. share of the high-value product market would generate a I to 2 percent increase in GNP ($52 to $104 billion in 1991) and create about 1.5 million new jobs. A critical question is how to tailor a vigorous and dynamic research program to meet the demands and dimensions of the international food trade and take advantage of growing markets. It has been recognized for some time that competition from abroad is favored by lower labor costs and that competing on the basis of cost alone is less successful than competing on the basis of new products and product quality. Improve- ments in cost and quality can be achieved effectively through developing new technologies and by applying recent engineering and manufacturing advances.
ENHANCING THE FOOD S UPPLY The food system comprises the biggest complex of businesses in the United States, involving the production, processing, manufacturing, wholesaling, retailing, and importing or exporting of food. Infrastructures to produce and supply people with their food and drink are enormous and tightly linked. They are dependent on, and use, natural resources as fundamental as air, water, soil, energy sources (e.g., solar, coal, and oil) and elements necessary for materials (e.g., glass, steel, and aluminum). There are an estimated 3 million farmers and an additional 11 million employees in the food industry. Approximately 53 percent of those em- ployed in the food industry work in eating and drinking places, 27 percent in food stores, and 20 percent in food manufacturing and wholesaling. The 380,000 firms that process, wholesale, and retail the nation's food supply have become more international in character, deeper in debt (pri- marily due to mergers and leveraged buyouts), and more concentrated, productive, and profitable. 7 ~ ~ or ingredients to be used in whole foods and enhancing both their health benefits and acceptability. Fortification and Enrichment As knowledge of nutrient needs evolved earlier this century, it be- came apparent that nutrient deficiency diseases were a critical problem in the United States and the rest of the world, and various approaches to solving them were considered. In the end, these public health problems were solved in large part by enriching and fortifying foocls. Enrichment of cereal-grain products with iron, thiamin, riboflavin, and niacin has been a remarkably effective and efficient means of enhancing the nutrient quality of the food supply and is a classic example of an effective, well-designed public health approach to providing needed nutrients. Cereal grains were selected for enrichment because they are eaten frequently by virtually all populations groups. Subsequently, breakfast cereals were fortified. The result has been a significant increase in the amount of these enrichment nutrients available for consumption (Figure 4.1~. Other nutrient-deficiency problems were addressed by fortifying various foods with specific nutri- ents (e.g., iodized salt and vitamin D-fortified milk). Recently, the Food and Drug Administration (FDA) began examining the feasibility of fortify- ing flours and other foods with folio acid to reduce the occurrence of neural tube defects in infants.
102 140 US ~ 100 of to - o en 8 OPPORTUNITIES IN TTIE NUTRITION AND FOOD SCIENCES o - . . . ~:~111111~1 Calories Protein Thiamin Riboflavin Niacin Pyridoxine Nutrients C1 ~ 909-1 913 ~ ~ 925-1 929 ~ ~ 935-1 939 1~1 ~ 947-1 949 957-1 959 ~ ~ 965-1 969 1111111 ~ 975-1 979 1~ ~ 985-1 988 FIGURE 4.1 Nutrients available for consumption, 1909-1988. From U.S. Bu- reau of the Census, Statistical Abstract of the United States: 1992 (112th edition), Washington, D.C. Research Opportunities Provicle nutrients that are bioovailable yet stable in food Iron, zinc, cal- cium, and folio acid fortification of adult and infant foods wouIc! benefit from increased knowledge of the bioavailability of micronutrients. Iron deficiency is the most common nutritional deficiency in the United States, affecting young children, women of childbearing age, pregnant women, and poor people. The typical U.S. diet is estimated to provide only 6 to 7 milligrams (mg) of iron per 1,000 kilocalories (kcal) of food, and women of childbearing age have difficulty achieving their recom- mended dietary allowance (RDA) of 15 mg per day because they generally eat fewer calories. Premenopausal women risk developing a negative iron balance because of menstrual blood loss. Iron deficiency may also be exacerbated by the relatively low amount of iron available from grains, legumes, fruits, and vegetables. Such problems exist in many parts of the developing Florid where there is little meat consumed and in this country among those choosing diets low in red meat. Iron deficiency may increase because all the major dietary guidelines recommend increasing the con- sumption of grains, fruits, and vegetables. Readily bioavailable forms of iron are often the most chemically and biologically reactive, thereby creating color and flavor problems in forti
ENHANCING THE FOOD SUPPLY 103 fled food. Stabilized forms of iron and other fortificants would allow for more effective fortification. identify and understand the mechanisms by which meat and ascorbic acid enhance iron absorption Both ascorbic acid (vitamin C) and meat en- hance the bioavailability of non-heme iron in foods. However, ascorbic acid, an unstable nutrient, is often not a good candidate for processed food or food that might be stored in warm, humid climates. Therefore, we need to discover how meat enhances iron absorption. Several investigators have offered data to support the notion that meat's action is attributable, in part, to amino acids or a peptide. If meat's potent enhancing factor is a peptide (at least in part) and that peptide can be isolated. it would c rove a tremendous boon to the 500 million cases or so of nutritional anemias worldwide. Such a peptide could be added to food; even more important, the major grain crops might be genetically engineered to produce it. Such a development would not only provide relief to the developing world but would allow a greater shift to plant foods in the United States without creating concerns about iron deficiency. Define and resolve potential dietary inadequacies of other nutrients such cars folic acid, vitamin B6, copper, zinc, and calcium These problems could be addressed by adding nutrient mixtures to traditionally fortified foods such as flour. Issues of bioavailability and reactivity of these nutrients with foods have only been partially addressed by food scientists. Consider- ation should be given to fortifying traditionally unfortified foods such as beverages and snacks. Low-Fat and Low-Calorie Foods Compliance with dietary recommendations to reduce fat and calorie intake will not be easily achieved by the general population. Gains in this area require changing behavior as well as modifying and reformulating traditional foods. Because of the energy density of macronutrients (protein, fat, and carbohydrate), one goal is to lower consumption of all of them, but par- ticularly fat. Now the problems begin how do we achieve this laudable modification and still have enough foods with desirable sensory character- istics? This offers some great technological challenges, including, in some cases, the development of low-calorie substitutes for sugars, starches, and fat. However, substitutes cannot directly replace macronutrients unless they have equivalent properties for their intended use. Indeed, eliminat- ing certain macronutrients from food, whether replaced or not, can create serious sensory problems related to flavor and texture. The safety and
04 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES health aspects of these macronutrient manipulations must also be consid- ered while provicling the consumer with acceptable sensory characteris- tics. Some reduction in the fat content of foods of animal origin has been achieved through applier] genetics and altered livestock feeding practices. However, technologies exist to further reduce fat in foods. The most com- mon approach to date is to replace a portion of the fat with an aqueous dispersion of a hydrocoTIoicI such as starch, dextrins, or gums. The objec- tive is to structure carbohydrates or proteins, or both, in such a way that they feel in the mouth like the high-fat food. Interestingly, certain cellulose ethers can be used in a different con- text to reduce fat. These polymers have unique thermal "elation proper- ties that, when put in fried-food batters, act as a barrier to of} absorption. Another fat-reduction technology involves the use of microparticulated proteins processed into spheroidal particles so small that they fee! to the tongue like a fatty, creamy liquid. In this case, 4 kcaT can replace 27 kcal of fat in an ice-cream-like product, since the fat substitute is a hydrated protein at 1.33 kcaT per gram (g), which replaces l g (9 kcal) of fat. The practical applications are almost exclusively in nonheated foods such as frozen desserts, yogurt, and margarine because these proteins are dis- persed en c! denatured if heated and lose their fat-like mouthfeel. Macronutrient replacement has had a significant impact on (lietary patterns. Two-thircds of aclults in the United States consume "light" prod- ucts an average of nearly four times each week. Approximately 10 percent of the new food products introduced in 1990 claimed to be Tow-fat or nonfat products. Among the new (fairy products, 41 percent were low- or nonfat. And 31 percent of new products in the category of processed and fresh meat, poultry, seafood, and eggs were low- or nonfat products. Lower- fat products are not confined to supermarket shelves. Restaurants, fast- food establishments, and school cafeterias are also increasingly offering low-fat fare, although none of these has taken full advantage of this tech- nology, particularly school cafeterias (see box). EATING LESS FAT The Institute for Science in Society has developed a report card on fat-reduction activities, using the goals set by the Healthy People 2000 report of the U.S. Department of Health and Human Services (DHHS): Development of Low-Fat Products- A The food industry has surpassed the year 2000 goal calling for more than 5,000 products to be developed, with the Food and Drug
ENHANCING THE FOOD SUPPLY Administration reporting more than 5,600 new and improved lower-fat products on the market since the publication of The Surgeon General's Report on Nutrition and Health in 1988. As new ingredients are introduced, such as those designed to replace fat, the numbers can be expected to rise. Restaff rants BE Industry-wide surveys of table service and fast-food restaurants show steady progress in adding lower-fat items to menus. According to the National Restaurant Association, 78 percent of restaurants offer at least one lower-fat menu option, such as salads or skinless chicken breasts. Even fast-food restaurants are beginning to provide healthful options. Some restaurants, including a number of hotel chains, are completely revamping their menus. Good progress toward the year 2000 goal is evident among at least 90 percent of restaurants offering low-fat choices. Nutrition Labeling BE Spurred by the Nutrition Labeling and Education Act of 1990, the marketplace will see a complete overhaul of labeling within the next two years. The year 2000 goal is nutrition labeling on all processed foods and at least 40 percent of fresh foods. Under the comprehensive regulations proposed by the DHHS and U.S. Department of Agriculture (USDA), nutrition labeling will be on all processed foods by 1993, as mandated by Congress. Labels will include vital information on fat content. They should be clearer, with less opportunity for misleading health claims and vague descriptors. Important labeling format issues are still to be resolved. The National School Lunch Program C USDA has steadfastly refused to mandate that school lunches meet the recommendations on fat in its joint publication with DHHS, Dietary Guidelines for Americans, 3rd edition, and it has no plans to do so. The year 2000 goal calls for at least 90 percent of schools to meet the guidelines. USDA has promised comprehensive data on the amount of fat in school lunches nationwide when its survey is completed at the end of 1992. But sporadic evidence consistently points out that 35 to 45 percent of calo- ries in school lunches are derived from fat. While supporting the dietary guidelines in school nutrition education programs, USDA's failure to re- quire the fat limits in school meals suggests that schoolchildren must eat much less fat during the rest of the day to keep within the fat recommen- dations of the dietary guidelines. SOURCE: Institute for Science in Society (ISIS), 1992. Eating Less Fat: A Progress Report on Improving America's Diet. ISIS, Washington, D.C. 105 -
106 OPPORTUNITIES IN TTIE NUTRITION AND FOOD SCIENCES Clearly, technology ret ~. _~ has improved the nutritional value and conve- nience of these foods. There is as yet no unequivocal evidence that low-fat or low-calorie foods are lowering fat or energy intake in the total diet, since all the compensation mechanisms have not yet been fully studied. However, foods with lower fat content are available in a convenient, at- tractive, and, for the most part, acceptable form for consumers. Research Opportunities Develop new tow- or no-fat and low-calorie substitutes Critical to the success of low-fat and low-calorie food products is presentation of the sensory attributes (taste, aroma, and mouthfeel) of such foods. Altered lipids and structural fats with modified fatty acid profiles are providing challenging opportunities for research. Consumers are not yet satisfied with the mouthfeel and taste of some low-fat products. Compensation mechanisms in humans should be clearly established If low-fat technology is to succeed in providing clear health benefits to con- sumers, we must understand if and how humans compensate for lowered macronutrient intake. Develop con understanding of how macronutrient replacement might affect the overcall diet Micronutrient intake might be affected in individuals who significantly alter their diet to consume better-tasting, lower-fat, or low-calorie products. As the total fat content of their diets decreases, the ratio of saturated to unsaturated fat might actually increase. Develop barriers to reduce fat uptake in fried foods Since fried foods form a high percentage of appealing fast foods, the development of com- pounds to inhibit fat absorption by the food will provide interesting op- portunities. Sensory Needs of the Elderly One of the most crucial problems facing the elderly is their volun- tary reduction of food and beverage intake, with a consequent reduction in fluids, calories, essential nutrients, and fiber. The anorexia of aging is multifactorial, having both physiological and pathological causes. Obvi- ously, food technology cannot address all the causes of this reduced food intake, but it certainly can make some major contributions. One of the reasons for decreased caloric intake may be impaired den- tition. One study of older subjects with teeth or dentures showed that, compared to subjects with teeth, the denture wearers had a drop of al
ENHANCING THE FOOD SUPPLY 107 most 20 percent in the nutritional quality of their diets (including calories and most of the 19 nutrients studied). Such a drop could accelerate nutri- tional deficiencies or poor health. Decreases in caloric intake have also been seen in people with full dentition. Nonetheless, it must be assumed that, at the least, difficulties in chewing certain foods might affect variety in the diet and certainly would affect enjoyment of foods and quality of life. Taste and smell perceptions are reduced markedly in the elderly, with losses occurring at both threshold and suprathreshold concentrations for taste and especially smell. Flavor, odor, color, and perception also play an important role in food acceptance in the elderly. Designing foods to over- ride these challenges would provide a valuable service to this increasing population. Research Opportunities Enhance our understanding of the sensory physiological processes The operation of individual receptors and the physiology and biomechanics of the sensation process are age-dependent. Therefore it will be necessary to correlate objective measures of sensation such as flavor, taste, texture, and color, with physiological mechanisms in various age groups in order to better understand how to optimize food acceptability at every age. Fur- ther, it has been observed that sensory stimulation is linked to physiologi- cal changes in immune response in humans and gene expression in ani- mals. Therefore, providing good tasting, high-quality food will not only increase the quality of life but may also increase the length of life. Develop products for the elderly and other people with special needs It is possible, for example, to increase fragility and maintain crunchiness of foods or to make chewy foods that require less chewing in order to mini- mize fatigue. Texture, although most directly involved with dentition, is not the only sensory attribute important to the enjoyment of food and food intake. Design foods and beverages with enhanced flavor to increase fluid and food intake Foods for the elderly population should have enhanced fla- vor and aroma to compensate for the reduced perception of these sensory characteristics. Experiments suggest that the thresholds for many odors are often as much as 12 times higher in the elderly than in young persons. As a result, it is not surprising that the elderly have been found to prefer flavor enhancement in a wide variety of foods. Technology can provide almost any flavor, but it can also provide high-intensity flavors. Enzymatic and other biotechnological techniques are available to produce these fla
108 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES vors, and their use in this nontraditional approach might prove beneficial to an elderly population. Such high-intensity flavors could be manufac- tured independently or, through genetic engineering, be produced within the food by the plant or animal itself. Extract objectionable compounds in food Technology could also be used to remove food constituents that are objectionable from a sensory or physi- ological viewpoint. For instance, compounds in the Brassica genus of plants (e.g., cabbage and broccoli) that cause stomach upset might be removed by supercritical fluid extraction (a process now used to decaffeinate cof- fee) with little effect on the food itself. Oligosaccharides like stachyose and raffinose, found in soybeans and other legumes and responsible for the flatulence experienced by people who consume them, could be re- moved by selective extraction or genetic manipulation of the plants. Develop visual cues to replace losses in flavor and taste Studies have shown that color influences the perception of sweetness in flavored and unflavored foods. Color interferes with judgments of flavor intensity and identification and in so doing dramatically influences the pleasantness and acceptability of foods. Functional Foods for Health Traditionally, food scientists and nutritionists have focused their re- search and development efforts upon providing a food supply that is both safe and acceptable from sensory, economic, and nutritional standpoints. The guiding light for nutritional content of foods and diets has been the RDAs. The RDAs were first established in 1943 to provide "standards to serve as a goal for good nutrition." Over the years, good nutrition has typically meant avoiding nutrient-deficiency diseases and maintaining ideal weight. Thus, the traditional view has been that the food supply should provide sufficient energy, macronutrients, and micronutrients to meet the needs of consumers. With the recent surge of research into the role of nutrients in promoting optimal health and the recognition that nonnutrient components of foods may increase or alleviate the incidence of various diseases has come increased interest in designing foods and diets for opti- mal health, not just to prevent classic nutrient-deficiency diseases. Modern genetic engineering techniques make it possible to enhance, suppress, or even transfer genes from one species to another to attain health benefits. Food-processing techniques may achieve the same goal by selectively removing or concentrating components of interest or by devel- oping more acceptable products with a high concentration of health-pro- moting constituents in whole foods.
ENHANCING THE FOOD S UPPLY 109 Nlarious terms are used to describe this new class of foods. "Designer foods" has been used extensively. They have been defined as processed foods supplemented with food ingredients naturally rich in cancer-pre- venting substances. Extracts of garlic, cabbage, licorice, soybeans, and other foods and spices are sources of such ingredients. "Medical foods" encompasses enteral formulas used to feed hospitalized patients and foods for people with rare diseases. Medical foods have been a legal classifica- tion under the jurisdiction of the FDA for decades. The medical foods industry has been a large one in this country for some time, with numer- ous companies and hundreds of products. We will use the term "func- tional foods" to encompass potentially healthful products. A functional food may include any modified food or food ingredient that may provide a health benefit beyond the traditional nutrients it contains. Research Opportunities Use technology to enhance whole foods In order to increase consump- tion of important physiologically beneficial components of fruit, vegetables, and grains, it will be necessary to create foods that have substantially enhanced amounts of these ingredients as whole foods. This will create many technical and functional challenges. Develop disease markers to test the efficacy of foods and food constituents Markers will be needed to monitor the effectiveness of these foods in improving health. Intermediate markers to indicate risk of devel- opment of cancer, heart disease, and other chronic diseases are needed. In addition, methods are needed to assess the impact of the intake of these functional foods on health end points. Resolve the debate on the regulatory and ethical aspects of genetically modified and functionalfoocis The FDA has several regulatory mecha- nisms governing the approval of new food ingredients and additives that are distinct from the approval requirements for new drugs. A new func- tional food may fall between a food and a drug. For example, a new food with greater than usual amounts of a phytochemical that may Tower the risk of a chronic disease may be, for legal purposes, neither a food nor a drug. The manufacturer of this functional food lacks a clear set of guide- lines to follow to ensure the efficacy and safety of the product. Moreover, the Nutrition Labeling ant! Education Act of 1990 places great restrictions on manufacturers' health claims on product labels. Regulatory mechanisms must be developed to govern the approval, naming, labeling, and advertising of functional foods. In the case of a genetically modified food or ingredient, a scientific consensus on the ethi
0 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES cal issues surrounding its consumption should be established prior to in- troducing it into the market. For example, if it becomes possible in the future to use ingredients in functional foods that alter mood or increase physical performance, these foods will require strict safety testing and assessment of any potential psychological impact. IMPROVING FOOD SAFETY Ensuring a safe food supply is a goal of all food producers and food providers. Protection from microbiological spoilage and pathogen con- tamination is the major concern. However, there are naturally occurring toxicants in foods that can cause illness and even death. In addition, cer- tain food components cause allergies in sensitive people. The risk of ad- verse effects from these food components must also be minimized. Microbiological Food Hazards A profusion of food-related illnesses, largely associated with raw milk and dairy products, in the early 1900s led to the introduction of process- ing techniques and safeguards that have made processed foods in the United States today among the safest in the world. Paradoxically, foodborne illnesses are prevalent, ranging from an estimated 6.5 to 81 million cases each year. Most of these illnesses, however, result from improper han- dling of food in the home or in food-service establishments. The leading culprit is improper holding temperature or cooling of foods by food han- dlers. Other major contributing factors include the use of contaminated raw food or ingredients, food preparation by an infected person, and inad- equate cooking of foods. Many recent innovations in food processing increase the quality, sta- bility, and shelf life of foods. Several of them present safety concerns. Examples include modified atmosphere packaging, sons vice processing (in which foods are packaged under vacuum and cooked at low tempera- tures, usually less than 71°C), and aseptic packaging. All three of these technologies delay or prevent microbial spoilage by suppressing or killing the spoilage microorganisms normally present in foods. The principal safety concern is that these practices may provide conditions that allow Clostridium botutinum spores to grow and produce toxin if appropriate safeguards are not implemented. Several newly recognized foodborne pathogens emerged in the 1980s. Among them were Cam~3ylobacter jejuni, enterohemorrhagic Escherichia cold 0157:lI7, Listeria monocytogenes, and Vibrio vulnificus. Considering that the causative agent of more than 50 percent of foodborne outbreaks reported annually is never identified, it is likely that more hitherto uni
ENHANCING THE FOOD SUPPLY 111 dentified pathogens will become recognized agents of disease. The agent responsible for the chronic diarrhea syndrome associated with drinking unpasteurized milk is an example of a yet-to-be-iclentified pathogen. An issue of emerging importance is the increasing number of immunocompromised and elderly people. It is estimated that more than 20 percent of the U.S. population will be over age 65 by 2020. In addition, with major advances in medical treatment, the survival time and number of patients with life-threatening illnesses that result in an impaired im- mune system continue to increase dramatically. People infected with hu- man immunodeficiency virus, for example, are at increased risk of acquir- ing foodborne illness not only through commonly recognized pathogens, but also through pathogens that may be frequently ingested but do not normally cause illness in healthy persons. Reducing foodborne illness will require research in all aspects of the food system, from production to consumption. For example, studies are needed to identify the foods most responsible for transmitting foodborne illness, identify and characterize previously unrecognized foodborne pathogens, reduce the prevalence of pathogens in animals used in food production, develop real-time procedures to detect foodborne pathogens, and develop innovative approaches to educate food handlers. Research Opportunities identify the foods involved most frequently in foodborne fitness At present, the best sources of information for identifying trends in foodborne illness and its prevalence are reports of outbreaks. This information is not de- rived from statistically designed studies that identify foods most frequently involved in foodborne illnesses. Well-designed prospective epi(lemiologi- cal studies are needed for this purpose. The results of such research will enable public health officials to address major problem areas more effec- tively by targeting those foods responsible for the most illnesses. identify and characterize new foodborne pathogens .1 1 r rat 1 . . 1 .11 1 The causes of many outbreaks ot tooct-assoc~atect illnesses are unknown, sometimes because the agent responsible is not a recognized pathogen. Uncovering the iden- tity of new pathogens that may be agents of foodborne disease requires extensive detective work. New technologies are needed to produce ap- pealing pathogen-free processed foods for immunocompromised popula- tions. In addition, studies are needed to verify the microbiological safety of reformulated foods, such as functional foods. Develop innovative ways to produce pathogen-free foods from animals Animals often carry microbial pathogens within their intestinal tract and
119 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES on hide, skin, feathers, and feet. With the frequent occurrence of internal and external contamination of animals by harmful microorganisms, present- day slaughter and primary processing procedures cannot reliably produce pathogen-free raw foods. We need to develop innovative, practical ap- proaches to reduce the conveyance of pathogens that are harmful to hu- mans by animals used in food production. In addition, foolproof safe- guards are needed for new processing techniques such as modified atmosphere packaging and sons vice cooking. Much of the food industry uses hazard analysis and critical control points (EIACCP) procedures to identify and control for potential health hazards or quality loss during the processing of foods. HACCP programs should be designed and out in nlac~? for hnn- dling all raw foods of animal origin. ~~-~ ~ ~ ~ ~~ a ~ ~ ~ .r ~ ~ -^ ^ ~-~ ~ Develop procedures for detecting pathogens in foods that take only min- utes or hours to complete Classical testing procedures for microbial pathogens in foods usually take days to complete. This time period is too long to allow for an effective monitoring system or recall for many foods. Innova- tive approaches to developing real-time assays would allow for the rapid detection of potential microbiological risks in foods. Develop innovative ways to educate food handlers The incidence of salmonellosis, which is principally transmitted by foods, has increased dra- matically during the past two decades. Several approaches have been taken to educate food handlers and consumers about proper food-handling practices, yet the occurrence of foodborne illness continues unabated. Reducing the incidence of foodborne disease is a challenge for the future, with a princi- pal problem being the improper handling of foods by consumers and those involved in commercial food preparation. Innovative approaches of edu- cating consumers and commercial food preparers about proper food-preparation techniques are needed. In addition, consumers should be made aware of the risks of foodborne illness from eating raw or undercooked foods of anlma orlgln. Naturally Occurring Toxicants in Foods Many naturally occurring substances in foods have significant toxic potential. If toxicity can be manifested under any likely circumstances of exposure, then the substance can be classified as a naturally occurring toxicant. The dose of exposure is extraordinarily important. Some of these substances are hazardous at certain doses and beneficial at lower doses. Several categories of naturally occurring toxicants exist
ENHANCING THE FOOD SUPPLY 113 · Natural and normal constituent substances that affect normal con- sumers ingesting normal amounts of the offending "food." Examples in- clude poisonous plants and mushrooms. . Natural, though abnormal, contaminant substances that affect con- surr.ers ingesting normal amounts of the offending food. Examples include mycotoxins from contaminating molds (e.g., aflatoxin in peanuts) and algal toxins in seafood (e.g., paralytic shellfish poisoning and ciguatera poison- ing). · Natural and normal constituent substances that affect consumers ingesting normal amounts of the offending food if it is prepared in an abnormal fashion. An example would be the lectins in kidney beans, which are inactivated by typical heat processing and cooking. · Natural and normal constituent substances that affect normal con- sumers who ingest abnormally high amounts of the offending food. An example would be the cyanogenic glycosides in lima beans. · Natural and normal constituent substances that affect some people with food allergies and sensitivities (e.g., to shellfish and to gluten in wheat). Research Opportunities Identify and evaluate the toxicity of naturally occurring toxicants in foods While all naturally occurring substances are toxic at some level, we are unable to identify all naturally occurring substances that can exert toxic effects at comparatively low doses of exposure. Assessment of the doses of these substances and the circumstances of exposure that pose hazards to consumers is woefully inadequate. Evaluation of the effects of these substances on human health, especially as they relate to cancer, has receiver! very little scrutiny. Systematic study of naturally occurring toxi- cants is needed, especially in light of attempts to develop functional foods with improved health benefits and the increased development of geneti- cally engineered foods (which requires an assessment of the toxicity of the new varieties). Develop methods for easily detecting and quantifying most naturally oc- curring toxicants in foocis Methods are needed to assess the extent of consumer exposure to naturally occurring toxicants. Without this informa- tion, we cannot establish the magnitude of the exposure and the hazard that might be posed by these substances. Such methods would permit us to identify the food sources that contain the highest concentrations of potentially hazardous toxicants. Methods are also needed to screen for toxicants that might be transferred to new plant varieties through genetic . . engineering.
114 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES Improve method:ts for assessing the degree of hazard posed to humans by naturally occurring tox~cants Current toxicological testing methodolo- gies that use experimental animals and isolated cell and organ systems create controversies about the accuracy of extrapolating results from ani- mals to humans and from the high doses administered in the laboratory to the typically low-dose exposure of humans. Toxicological assessments should focus more on the biochemical and physiological mechanisms of action for individual toxicants as a function of dose. Comparative human data should be sought from existing and typical doses and circumstances of exposure. Extrapolations should be made from experimental animals that have metabolic profiles similar to humans'. Other toxicological end points, such as neurobehavioral, developmental, and immunological indexes, need to be included in toxicological assessments. Some substances (e.g., vitamin A and selenium) are essential at low doses but hazardous in excess. Recogni- tion of these "U-shaped" toxicity relationships will be critical to the suc- cessful development of functional foods. Develop genetic engineering technologies to remove undesirable traits fro no foods Genetic engineering offers the opportunity to remove or decrease naturally occurring toxicants in food selectively and specifically. An im- proved understanding of the formation of toxicants in foods will be needed to accomplish such feats. The effect of such genetic alterations on the overall safety of the resultant food must also be studied carefully. Assess the effects of processing on food components and their toxicity There is a need to develop processing technologies that reduce the toxic- ity of potentially hazardous naturally occurring toxicants (e.g., heating to inactivate lectins in kidney beans). However, traditional and novel pro- cessing can also lead to the formation of potentially hazardous chemicals. The identity, concentration, and toxicity of the chemicals induced by pro- cessing need to be determined. Methods are needed to screen for poten- tial toxicants that might be formed during processing and food prepara- tion and for techniques that might diminish the number and potency of such toxicants. Food Allergies and Sensitivities Food allergies and sensitivities are those foodborne diseases that af- fect only certain individuals in the population. A variety of mechanisms may be involved. True food allergies involve abnormal immunological re- sponses to the offending food. The best-known examples are the immedi- ate hypersensitivities, true food allergies involving allergen-specific im- munoglobulin E (IgE) response to naturally occurring food proteins.
ENHANCING THE FOOD SUPPLY 115 IgE-mediated food allergies affect less than 1 percent of the adult popula- tion but as much as 5 percent of children. Symptoms can range from a mild and transitory rash to life-threatening anaphylactic shock or asthma. Celiac disease is probably a true food allergy, involving an abnormal response of the gut-associated lymphoid tissue to proteins from wheat, rye, barley, and oats. However, despite the fact that celiac disease affects 1 in every 3,000 Americans, we do not know the mechanism of the disease or the proteins responsible. Other forms of food sensitivities do not involve the immune system. A good example is lactose intolerance, which affects millions of consumers and results from a deficiency of the enzyme lactase in the intestinal tract and the resulting intolerance to dairy products containing lactose. A host of food idiosyncrasies also exist. In these cases, the role of specific foods or food ingredients in the adverse reaction is often un- proven, and the mechanism of the illness is unclear. Some food icliosyn- crasies, such as sulfite-induced asthma, have been well established, al- though their mechanisms of action remain unknown. Research Opportunities Investigate the prevalence of, and mechanisms behind, food allergies and sensitivities While the mechanism of immediate hypersensitivities is un- derstood, many unknowns remain, such as the prevalence of IgE-medi- ated food allergies, the nature of most food allergens, and the effects of food processing on these allergens. Other forms of true food allergies probably exist, but the mechanisms remain uncertain. The role of delayed hypersensitivities or immune complex reactions in food allergies should be studied and methods of diagnosing them developed. While lactose intolerance has been studied extensively, improved diagnostic procedures and treatment modalities are needed. The role, if any, of food and food ingredients in many other food sensitivities and idiosyncrasies remains to be established. Examples include alleged adverse reactions to monoso- dium glutamate, aspartame, FD&C Yellow #5, other food dyes, butylated hydroxytoluene (BEIT), and butylated hydroxyanisole (BHA). Develop methodologies for assessing the allergenicity of novel proteins created by genetic engineering or other procedures Any novel protein introduced into a food through genetic engineering or other procedures (direct addition or through conventional breeding) has the potential to become an allergen, although the risk is probably remote in most cases. Decision-tree approaches need to be developed to assess the allergenic potential of novel proteins in foods, including an evaluation of the source material and the transferred protein, the level of expression of the novel ~O O O
6 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES protein in the new variety, and the digestibility of, and effect of process- ing on, the novel protein. Improve the diagnosis and management of IgE-mectiatect food allergies and celiac disease Improved diagnostic procedures are needed to evalu- ate adverse reactions to foods. They require better-defined and more readily available materials for oral-challenge studies, wider adoption of appropri- ate challenge protocols, and better-characterized and -standardized food extracts for skin testing and radioallergosorbent tests in IgE-mediated food allergy. Simpler in vitro diagnostic procedures are needed for celiac disease. While there exist pharmacological approaches to treat the symp- toms of true food allergies, the allergies cannot be cured. The key to prevention is avoidance of the offending food. Research is needed to pro- vide the food industry with methods for the detection of allergenic con- taminants of food that can become part of its quality assurance programs. VALUE-ADDED FOOD MANUFACTURING Traditionally, the United States is viewed as the prime example of a technologically superior society that is able to harvest, mine, or purchase raw commodities and, through technology, add value to them for the ben- efit of our citizens and for export. This situation is undergoing a dramatic change, particularly in relation to agricultural products. We are fast be- coming a supplier of inexpensive raw materials to the world and an im- porter of value-added products. Unfortunately, this means fewer jobs, a poorer standard of living for citizens, lower profits, and a poor balance of payments for our country. These changes call for the United States to seize the opportunities offered by developments in the food-processing industry and international food trade. If nutrition is a key to maintaining good health, then food is the vehicle whereby nutrition is delivered in adequate and appropriate amounts and in a safe and acceptable form. This means that consideration of value-added technologies only in terms of economics is too narrow. Value can be added in many forms. A food can be made more nutritious, safer, more convenient, more acceptable, easier to prepare, or more suited to the specific needs of special populations, such as the elderly. All of these examples add noneconomic value and increase the desirability of the raw commodity. Methods of Preservation Drying and fermentation are probably the oldest methods of preserv- ing food. They have been vastly refined over the millennia to increase
ENHANCING THE FOOD SUPPLY 117 quality, safety, nutritional value, and output. Refrigeration and freezing are also traditional methods of preservation that have become common- place. Preservation techniques rely on creating an environment that is hostile to harmful microorganisms, either destroying them or rendering them less active or dormant. Newer preservation techniques include mi- crowave processing, irradiation, extrusion, and various forms of packaging that control the environment or atmosphere in which the food resides. Research Opportunities Learn how to use aseptic packaging with [ow-aci~foods Preservation of iow-acid products through aseptic processing (with conventional or ohmic heaters), especially those containing particulates, is on the horizon. Using aseptic processing for high-acid products, such as tomatoes, has been so successful that a package failure or the introduction of a pathogen after processing carries little risk. Mathematical models must be developed to predict accurately and control the thermal treatments given to complex combinations of low-acid foods. Enhance our understanding of homfoods interact with packaging (or vice versa) during manufacturing anc! storage The effects of radionuclide ir- radiation or microwaves on packaging materials, packaging that protects foods better from freeze-thaw cycles, improved sealants, better reclosures for flexible packages, improved water-based inks, and improved functional barriers all await further research to improve food safety and quality. Compatibility between foods and the materials they come in contact with needs investigation under actual conditions of use to improve their safety and performance. Expand the study of microwaves and use of microwave steriti~.ation in food manufacturing and processing The design of in(lustrial-scale micro- wave sterilization systems and greater scientific understanding of micro- wave-inducec! changes in food products is needed so that microwave tech- nology can be used to help solve these problems. Implementation of integrated statistical process control systems in food manufacturing (such as lIACCP) will enhance the safety and quality of end products and should be inte- grated with on-line sensors and probes. The application of microwave heating to food processing presents many new questions related to the process controls to ensure safety of both low-acid and high-acid foods. Physical and Engineering Properties The quality of a food is a combination of several attributes with a definite range of values. These include nutritional profile, microbiological
11S OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES characteristics, cost, convenience, stability, and sensory properties. The ability of the U.S. food system to provide consumers with high-quality, safe food for proper nutrition depends on improvements in current pro- cesses and equipment and development of new ones. The food manufac- turing industry has traditionally lagged behind other manufacturing sec- tors in the introduction of new and advanced technologies. The reason for this gap is that food materials are heterogenous, their properties change with processing conditions, and on-line sensors for monitoring food qual- ity and safety are not available. The following research priorities have been identified to alleviate some of these problems. Research Op portunities Establish ~ basic understanding of the biological, chemical, and physical properties offood ingredients, products, processes, and packages To de- sign efficient processes, it is essential to understand the macro- and microproperties of food and food ingredients and to minimize undesirable changes caused by processing. The present lack of sufficient data on physical properties (such as theological, thermal, mass, and surface properties) of basic food components under real-use conditions is a problem and a great opportunity for well-trained food scientists. Expand our understanding of water dynamics and of glass and other tem- perature-based transitions in food materials Water dynamics is the study of the physical properties of water as, for example, a solvent, transferrer of heat, and controller of solute diffusion. Studies of water dynamics in food materials and changes in their diffusional and mechanical properties are essential for understanding a number of phenomena in food process- ing and preservation. We also need to evaluate critically the relative im- portance of glass transitions and other temperature-based transitions in amorphous and semicrystalline foods and their effects on the stability of dehydrated and frozen foods. In addition, investigations are needed into the effects that pore structure and composition of foods can have on moisture mobility during various operations such as drying, baking, puff- ing, and extrusion. An understanding of these properties is important in designing continuous processes and their theoretical simulations. , At, Develop new models of process and equipment design Quantitative data on the changes caused by processing are needed to incorporate nutritional and quality attributes in models of processing. We should create appropri- ate data banks and develop predictive models of chemical, physical, and transport properties of foods on the basis of these data. Comprehensive understancling of the properties and structures of food materials can assist , , , -
ENHANCING THE FOOD SUPPLY 119 in predicting nutrient retention during different phases of manufacturing or in tracing toxic materials in the food-processing stream, thereby en- hancing both quality and safety of food. It will also provide food proces- sors with a catalog of properties that can be transformed into both food values and controllable variables, which should lead in turn to increased productivity and the manufacture of better foods. Separation Separation processes are central to most of the unit operations em- ployecI in food processing. Distillation, extraction, leaching, stripping, and various combinations of these processes are widely used to separate edible foods, flavoring and coloring compounds, and other clesirable or undesir- able components from their natural locations in food. The common factor in these techniques is the use of solvents, such as alcohols, hexane, meth ylene chloride, and other organic compounds. The past two decades have witnessed ever-tightening regulations restricting the use of organic chemi- cals in foot! processing, while over the last decade, the energy costs of conventional separation processes have risen sharply. In many cases, bioseparation steps pose the greatest impediment to scaleup ant! commer- cialization of a new process. Given current trends in food manufacturing and recent developments in genetic engineering research, bioseparations are likely to become increasingly critical in terms of cost and safety in coming years. Pressure-ciriven separation techniques such as microfiltration, ultrafiltration, and reverse osmosis, along with chromatographic methods and supercritical fluid extraction, are increasingly being used to obtain desirable end products. Research Opportunities Expand our understanding of both phase equilibrium and mass transfer characteristics of supercritical solvent-biomaterial mixtures Supercritical fluid extraction is an important example of an underresearched, emerging technique that offers very interesting possibilities for bioseparations. It uses nontoxic, environmentally clean solvents, such as carbon dioxicle, that have high dissolving power at moderate temperatures. Because the dis- solving power of supercritical solvents can be varied by manipulating tem- perature and pressure, refluxing processes may be designed to operate as extractive distillation. This process has been successfully applied to biomaterial separations that would be extremely difficult, if not impossible, to per- form on a large scale using conventional separation techniques. Original methods using chlorinated solvents to decaffeinate coffee imparted minute traces of these compounds to the coffee. The first large-scale production
20 OPPORTUNITIES IN TTIE NUTRITION AND FOOD SCIENCES plant using supercritical carbon dioxide to remove caffeine from green coffee beans was constructed in the United States and has been operating since 1979. Scaleup and commercialization of other supercritical fluid extraction processes are currently impaired, for several reasons. Little data on phase equilibrium and mass transfer characteristics of supercritical solvent-biomaterial mixtures have been reported in the literature. Moreover, models of phase equilibrium and mass transfer that are known to apply to simple mol- ecules at moderate temperatures and pressures have been applied only rarely to biomaterial mixtures. Indeed, it is not known which, if any, of the models currently applied to simple systems can be successfully ap- plied to multicomponent mixtures of biomaterials at supercritical tem- peratures and pressures. This is a barrier to developing promising applica- tions such as removal of cholesterol from eggs and daily products, fractionation of animal fats to enhance ratios of unsaturated to saturated fatty acids, and enzymatic reactions in supercritical fluids. Develop new membrane technologies Membrane separation technology is being used on a limited scale for energy-efficient concentration and separation of value-addecl products or pollutants, or both, from a process stream. Other separation techniques may involve adcling natural polysac- charides with unique binding characteristics to bind certain foocI compo- nents. More research is needed to explore the potential of these separa- tion concepts and to use them in food and nonfooc! applications. Biosensors anal Process Control (Jomputer-integrated manufacturing and Biosensors hold great poten- tial for increasing product quality and process efficiency while minimizing waste. Areas of interest range from the design and control of individual unit operations to the synthesis, design, operation, control, and optimiza- tion of integrated food-processing systems. A substantial amount of the cost-effectiveness of manufacturing foods lies in how we handle, sort, and prepare raw materials. Not only are these processes labor-intensive, they also create waste; and poor-quality raw materials produce poor-quality end products. We need to introduce smart conveyor technology, machine vision, and custom design in order to handle substantial production rates in an optimal manner. Research Opportunities Develop Biosensors with simulation capabilities Biosensors are needed that can simulate steady-state and non-steady-state unit operations;
ENHANCING THE FOOD S UPPLY 191 semicontinuous and continuous processes; process control strategies; opti- mization of unit operations, processes, and plants, including Consideration of utilities and waste; scheduling and production planning (e.g., opera- tions research and just-in-time production>; and equipment design. We must develop sanitary sensors that determine the dynamic state of food processes on-line and in real time. In addition to controlling processes, such sensors should provide objective measures of food safety and such attributes of quality as color, flavor, composition, and texture. One new approach is to sense quality changes through theological properties (see page 1221. To do this, we must develop suitable sensing devices and de- termine the Theological properties of various materials, their correlation with the sensory properties, and their changes during the processes. Nondestructive testing for quality management during processing and packaging can be accomplished by developing lower-cost but sensitive and versatile sensors. Use of near-infrared absorption for specific quality measurements and on-line applications is under way in many research laboratories. In the visible and ultraviolet ranges, spectral properties, im- age analysis, and pattern recognition techniques offer possibilities that have already resulted in some practical applications. Improve and use technologies such as nuclear magnetic resonance, mag- netic resonance imaging, ultrasonics, laser, and infrared for biosensor development Such on-line safety sensors can detect pesticides in flesh foods and fruits and vegetables, lethal quantities of microbes in thermally processes! foods, foreign objects in ground meats, and so on. By adapting integrated time-temperature sensors, we can better monitor shelf life of foods. Full utilization of automatic process control, a road already trav- eled by other industries, will enable us to take greater advantage of mod- ern developments such as fuzzy logic and neural networks. Apply computer-bclsed management and control systems to food-process- ing operations The advent of advanced computers has affor~lecT new op- portunities for automation of food engineering, processing, and packaging operations. While decision- and implementation-controlled operations such as scheduling, off-line quality control, logistics, inventory control, and da- tabase management have become feasible and practical with computers, knowleclge-controlled operations such as closed-Ioop process control and automation are constrained by our lack of knowledge of food properties, adequate on-line sensing systems, and appropriate models of the process. Apply fuzzy logic to food-processing control systems "Fuzzy logic" is a heuristically based advanced control technique with potential applications in difficult-to-model systems that have multivariable and nonlinear pro -
122 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES cesses. It is equally effective in dynamic systems where information is incomplete or imprecise. Development and implementation of a self-learning fuzzy control algorithm could offer advantages not available through other means and should be investigated. Rheology Rheology, the study of the deformation and flow of matter, provides insight into the behavior of materials when they are stressed and strained. Understanding and using rheology is essential to improving new product development, processing operations, product quality and shelf life, and correlating food texture to sensory clata. Rheological studies have been conducted extensively to relate food structure to physical and chemical aspects of food. Because of their complexity, measurements of theological properties of food have been largely subjective and generally instrument- clependent. Research Opportunities Expand our understanding ok the Theological behavior offood More know- ledge is needed about the theological behavior of foods as it relates to their structural and physical-chemical aspects. Interaction between heat transfer and rheology (e.g., heat transfer properties of gelatinized sys- tems) needs to be considered. The role of rheological and physical prop- erties in extrusion, baking, and puffing should be studied, and efforts to provide mechanistic bases for the rheological behavior of foods should be expanded. This includes the development of suitable sensing devices, sys- tematic study of the theological properties of various food materials and their correlation with sensory properties, and changes in food materials , . . cLurlug processing. Improve and extend extrusion technology to other high-value-added products Rheology will be more fully applied to food-processing systems when more is known about the effects of extrusion on the macro- and microconstituents of foo(ls, ingredient interaction, and nutrient and flavor retention during processing, and how the extruder mortifies textural prop- erties of ingredients or final products. Packaging Without packaging, goods would rot at the farm, dock, and ware- house, becoming infested with insects and other vermin, while food poi- soning, disease transmission, and product losses would increase substan
ENHANCING THE FOOD SUPPLY 123 tially. Understanding this puts the importance of packaging in perspec- tive. All too often there is so much concern about the disposal of packag- ing materials that we forget that its major role is the preservation of the safety, quality, and nutritional value of food. To food scientists, packaging is a rigorous scientific discipline that includes all the physical, chemical, and biological interactions of the pack- age, the product, the filling and seating system, and the environment. In the past 50 years we have seen an evolution in the food package that has increased dramatically the health and quality of life of consumers and has reduced food waste. We have reduced the volume and weight of material used, extended the shelf life of products to permit national distribution, increased strength to meet the rigors of handling abuse, and improved product access and convenience (e.g., dispensing, childproofing, closing, and storability). Currently, food waste accounts for only 3.3 percent of the municipal solid waste in the United States, while in countries with limited access to food packaging, it can reach 10 times that volume. Metals, glass, paper, paperboard, corrugated plastics, and mixed ma- terials such as the retort pouch and containers for aseptic processing are the major substrates used in packaging in the United States today (Figure // Copolymer / /1 ~ /= ~ ~Copolymer ~ · Machinability · Adhesion · Moisture barrier · Stiffness · Clarity · Puncture resistance · Ink adhesion 1' \ Aluminum metalization \ ·Barr~erto oxygen, \ Inks \ · Graphics quality \ ~ \ Polyethylene \ Copolymer Polypropylene \ / Copolymer · Interlaminar adhesion · Metal adhesion · Stiffness · Moisture barrier J · Seal integrity / · Hot seal strength _/ · Easy opening ~ Tamper evidence FIGURE 4.2 Cross section of a package of dry vegetable soup mix, adapted from the Council on Packaging in the Environment. This cross section illustrates the complexity of modern packaging. The package is approximately 0.002 inches thick and consists of nine different layers, each with a specific function. While such complexity can inhibit recycling efforts, it also can reduce the overall weight of the package and keep food fresher, thus providing waste-prevention benefits.
24 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES 4.2~. Environmental concerns will provide a legion of opportunities in food packaging, including the development of new sensors, edible films, new films made from nonpetrochemical sources, and materials amenable to recycling and biodegradation. Research Opportunities Develop new packaging methods and materials that improve food safety and expand consumer acceptance and convenience As important as envi- ronmental issues are, the food-safety function of packaging is paramount. Controlled- and modified-atmosphere packaging will have the greatest impact in the near future because of the shift from shelf-stable and conve- nience products to freshly prepared and catered products. Some estimates predict that more than half of all food consumed will be in this category by the year 2000. The implications for the food-processing and packaging industry are obvious. Depending on the product involved, reduced oxygen or elevated car- bon dioxide can modify respiration and influence microbiological growth. As a result, shelf life in a well-controlled distribution system can be ex- tended from a small number of days to many days or several weeks. Un- questionably, packages have been and will be developed which can achieve some of these goals. However, because of the distribution distances and safety problems inherent in such products, other technologies will have to combine with packaging to make them an economic success. Sensor technology will be important in packaging. At present, there are sensors that warn of exposure to nonrefrigeration temperatures, as well as color-changing closure systems for moisture-sensitive products. In the future we will see more sophisticated sensors that provide an easy-to- read check on the condition of the contents of a package, such as the awareness indicators now being used on some microwavable food pack- ages. This kind of simplicity is a step in the right direction, but we must go further. We must provide easy-to-read, understandable labeling in an easy-to-open package with a built-in measuring device that delivers easy- to-prepare single servings. When this is accomplished, technology will have indeed contributed to the needs of all consumers, particularly the elderly. Additional specifications for future food packages are outlined in the box. BIOTECHNOLOGY Biotechnology has been defined as a collection of technologies that employ living systems, or compounds derived from these systems, for the production of industrial goods and services. Biotechnology is not new to
ENHANCING THE FOOD SUPPLY THE MODERN FOOD PACKAGE For a modern food package to meet safety requirements, it must: · Meet all regulatory requirements with regard to materials of construction; . Provide acceptable package integrity through final consumer us- age, provide a barrier to microorganisms and other potential contami- nants, and provide protection against infestation by insects, rodents, and other vermin; and . Meet the rigors of processing, distribution, storage, and other performance requirements. provide: odors; ents; . moisture; To meet specific product-protection requirements, the package must · A barrier to the inward or outward transfer of flavors and · An oxygen barrier adequate to preserve color, flavor, and nutri An appropriate barrier to the inward or outward transfer of · A carbon dioxide barrier to retain internal pressure (e.g., car- bonated beverages); · A barrier adequate to preserve gases such as nitrogen or car- bon dioxide used for preservation in applications such as controlled- or m ad if ied-atm osp h e re packagi ng; . both; and . An adequate light barrier for vitamin or color protection, or A thermal barrier- that is, insulation for the purpose of main- taining temperature. Other considerations in developing a modern food package involve: Physical protection of food and package; - Labeling to provide critical information (i.e., product brand iden- tification; net weight; ingredients; content; manufacturer's name, address, and codes; date by which product should be sold or used; preparation instructions; and nutrition labeling); Means of discouraging and indicating tampering; Visibility of contents (in some cases); and · Opening, reclosing, microwavability, dispensing, shatter resistance, safety i n hen d I i ng, an d size of se rvi ng featu res. SOURCE: Institute of Food Technologists, 1990. 125
26 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES the agricultural and food sectors people have been exploiting living sys- tems for the production, processing, and preservation of food for centu- ries. Significant improvements in the food supply have been realized through traditional agronomic and laboratory methods. The "new" biotechnology employs recombinant DNA technology or genetic engineering (see Chapter 3) to selectively improve plants, ani- mals, and microorganisms. Genetic engineering has the potential to be more predictable, controllable, and precise than classical breeding and selection. In addition, genetic improvements can proceed at a much faster pace, and the ability to cross species barriers greatly expands the available gene pool. Genetic Engineering of Crops The efficiency and profitability of producing raw agricultural com- modities could be dramatically improved by increasing crop yields and decreasing agricultural inputs such as fertilizer, herbicides, and pesticides. Although current methodology has been limited for the most part to di- cotyledonous plants such as tobacco, which have little value from a food- procluction standpoint, significant progress has been made in developing the tools of genetic engineering and in verifying its potential for improv- ing agronomic properties of crop plants. Examples of agronomic proper- ties amenable to genetic manipulation include disease and virus resis- tance, insect resistance, herbicide tolerance, and stress tolerance (i.e., saline soil conditions, temperature). In many cases, single genes code for these traits. Introduction of these genes into a variety of plant species and regulation of their expression therein are relatively simple tasks. Success- ful examples of the introduction of genes into plants by genetic engineer- ~ng ~nciucte those cocking tor toxin trom bacillus tnur~ng~ens~s (insect re- sistance>, viral coat proteins (virus resistance), silk moth antibacterial proteins, Tysozymes, cecropins, and attacins (to counteract bacterial diseases). To date, over 35 varieties of plants have been genetically engineered, includ- ing many important crops used in processed foods. Cereal grains serve as the main source of Protein for the vast maioritv A, ~ ~ ~ .1 a. r . . ~ ~ .77 .7 O - _ . , ~ . . ~ ~ . of the world, yet most cereals are deficient in one or more of the essential amino acids, isoleucine, lysine, methionine, threonine, or tryptophan. An understanding of the regulation and rate-limiting steps in the metabolic pathways involved in amino acid biosynthesis opens the door to applica- tion of genetic engineering for improving the nutritional quality of cereal grains. Genetic engineering is being used to increase the concentration of sulfur-containing amino acids (methionine and cysteine) in soybeans, phase- olin (the major storage protein) in legumes, and the amino acids lysine and tryptophan in maize. Increasing the content of essential amino acids
ENHANCING THE FOOD SUPPLY 127 in cereal grains eliminates the need for supplementation in animal diets and ensures a more complete protein source for human consumption. Almost 50 percent of dietary fat is derived from oiTseeds. Gene trans- fer technology has been developed for rapeseed (canola), flax, cotton, sunflower, and safflower seeds, and the tools of biotechnology could be used to improve the fatty acid composition of plant oils. Changes in the amount of unsaturation in the fatty acids of canola oil have been achieved by cloning a clesaturase enzyme that plays a central role in determining the ratio of saturated to unsaturated fatty acids in vegetable oils. Transfer of the gene encoding an enzyme, lauroyl-ACP thioesterase, from the wild California bay tree into commercial canola varieties results in a significant increase in the amount of the medium-chain fatty acids caprate (C10) and laurate (C121. Mectium-chain fatty acids and medium chain triglycerides are used as nutritional supplements to treat dietary disorders and as a high-energy food source for postsurgical hospital patients. Increasing the amount of stearic acic! present in canola would make the product suitable for margarine and confectionery products. lIydrogenation is frequently user] to increase saturated fatty acids in margarine products, thus enhanc- ing texture and consistency. However, hydrogenation also produces bans fatty acids that may raise concentrations of cholesterol in the blood (see Chapter 51. With genetic engineering, it is now possible to increase satu- rated fatty acids by six times without producing any bans fatty acids. Research Opportunities Develop basic tools for genetic manipulation of plants Our basic under- standing of the biochemistry and genetics of plant metabolism must be improved and important agronomic characteristics elucidated. Cloning sys- tems applicable to monocots, including construction of appropriate vec- tors, more efficient gene transfer systems, and a better understanding of gene expression and regulation, must be clevelopecl. Tissue-specific pro- moters to control the timing and level of gene expression in organs and tissues need to be identified. Custom design raw agricultural commodities As we understand how more complex traits are regulated in plants, biotechnology could be used to modify structural, functional, ant! processing characteristics of interest to the food processor and the consumer. Improved nutritional quality (e.g., oil seeds with specific fatty acid profiles and vegetables with enhanced amounts of essential amino acids, vitamins, minerals, or other specific nutrients); naturally sweet or salty varieties; higher solids content; im- prove(1 texture, color, flavor, or aroma; and extended shelf life are prob- ably controlled by multiple genes and present a greater challenge to the
12S OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES plant biotechnologist. Antisense RNA technology will be used to inacti- vate enzymes involved in tissue softening (e.g., polyendogalacturonase in tomatoes), oxidative rancidity, natural toxicant production (e.g., alkyl isothiocyanate in garlic, capsaicin in chilies, d-limonene in oranges, psoralens in parsley, hydrazines in mushrooms, and solanine in potatoes), or other reactions that result in deterioration of quality. Construct functional foods The links between various dietary compo- nents and cancer continue to be elucidated. Over 600 plant-derived chemicals (phytochemicals) with chemopreventive properties have been identified. These include antioxidants such as beta-carotene and vitamins C and E; retinoids such as isotretinoin; flavonoids, mono- and triterpenoids, and isoflavones; hydrolyzable tannins such as ellagic acid; omega-3-fatty acids; sulfur-containing compounds from garlic and onion; and many others. U1- timately, genetic engineering will make it possible to modulate the con- tent of these components in plants. Alternatively, it may be possible to use tissue cultures from plants to produce phytochemicals that can be added to foods as ingredients. The greatest challenge in engineering foods for dietary compliance will be to determine what compositional changes of crop plants are most desirable from a nutritional standpoint. In many cases, the basic information needed to make sound decisions on the role of diet in health and disease is lacking or ohnn~< In Ox Trim .:.rm published. ~ ~ V ~L ~ ELI 14 A_ ~ V ~ ~ AL ~1 ~ ~ C41 I_ Develop analytical methods of assessing the safety of engineered plants Better analytical methods for comparing the composition of engineered and nonengineered plants and for assessing the impact of unanticipated multiple effects are needed. The fate and persistence of engineered pro- teins in plant parts throughout the life cycle of the plant (i.e., growth, fruit ripening, and senescence) and in processed foods must be investi- gated. In vitro and in vivo model systems for validating the safety of whole foods and food ingredients derived from genetically engineered plants must be developed. Genetic engineering will be used to introduce into plants proteins not previously part of the human diet. We need to develop testing methods to assess the potential allergenicity and toxicity of these proteins. Plant Tissue Culture Technology Plants are the source of many useful compounds and mixtures, includ- ing pharmaceuticals, flavors, fragrances, essential oils, enzymes, and pig- ments. Many of these compounds are considered secondary metabolites as they are generally not essential for cell growth. Production of secondary
ENHANCING THE FOOD SUPPLY 129 metabolites in plants is linked to cell differentiation (i.e., formation of roots, shoots, or fruit). Large markets exist for these secondary metabo- lites, which are commonly obtained commercially by extraction from in- tact plants. Many plant-derived ingredients used in foods are extracted from plants grown outside the United States; therefore, supplies are sub- ject to political instability in the supplier countries, as well as natural catastrophes such as drought, floods, microbial and fungal diseases, and insect infestation. Plant tissue culture (PTC) is a technique that allows plant cells to be crown in a solid (callus culture) or liquid (suspension culture) medium, in much the same manner as microorganisms. PTC may provide an alterna- tive source of secondary metabolites. Because PTC involves growth of plant cells in contained and controlled fermentation vats, these systems require minimal land use, are independent of weather conditions, and do not require the use of agricultural chemicals. Examples of PTC-derived food ingredients include pigments (e.g., betalains, annatto, anthocyanins, betacyanin, betaxanthin, lycopene, and other carotenoids), flavor and aroma compounds (e.g., vanillin, ginger, and turmeric), essential oils (e.g., li- monene, menthone, and methyl eugenol), enzymes, antioxiclants, and sweet- eners (e.g., stevioside and glycyrrhizin). Research Opportunities Identify triggers that uncouple cell differentiation from secondary metabolism Creating growth conditions conducive to the production of secondary metabolites in PTC is frequently done empirically by manipu- lating growth media or environmental conditions; yet, metabolic pathways have not been elucidated for many of the secondary metabolites of com- mercial interest and optimum conditions vary for each. Identification of the metabolic triggerts) that uncouples cell differentiation from secondary metabolism would make it possible for undifferentiated cell cultures to produce plant-derived compounds efficiently. Elucidate important traits to target for genetic improvement, including the basic bioc1:~emist;ry and genetics involves] in the metabolic pat1?- ways Undifferentiated cultured plant cells can produce compounds that are never found in the differentiated field-grown plant. Ever ~u new ceil culture-associated, low-molecular-weight compounds have been compiled to date. It has been proposed that the process of Redifferentiation leads to the activation of dormant genes that yield new enzymes which divert the normal biosynthetic chain into new compounds not found in the differen- tiated plant. These new substances could have applications in the food and pharmaceutical industries. A basic understanding of the biochemistry r ~ . .1 a. or . . . 1 r. 1 1 . _ ~ ~ ~
130 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES of these metabolic systems provides a foundation for genetic manipulation of the pathways. Develop methods for selecting stable, high-producing cell lines Simple, rapid, and reliable methods for the selection and maintenance of high- producing cell lines need to be developed. There are no methods (e.g., freezing or freeze-drying) for long-term storage of PTC; therefore, cells must be subcultured on a regular basis to maintain viability. Unfortu- nately, continuous subculture leads to an unexplained loss of viability and productivity. Develop improver! bioreactors and downstream processing and purifica- tion systems for PTC-derived biological materials Plant cells are fragile and require bioreactors that provide gentle agitation yet high oxygen- transfer rates. Significant improvements in plant cell bioreactors must be attained to make PTC an attractive economic alternative to extraction from intact plants. One approach for protecting cells is to immobilize or entrap cells within matrixes. It is critical to develop materials that protect plant cells yet allow rapid diffusion of nutrients and secondary metabolites in and out of cells. Processing and purification systems will need to be adaptecl to maintain the biological activity of PTC-derived materials. Animal Biotechnology Traditional breeding and selection techniques have been used to im- prove meat-producing animals (beef, swine, sheep, and poultry) and fish used as human and animal food sources. The basic principles of biotech- nology can be used for genetic improvement of animals and fish. To date, biotechnology has been used to (1) produce growth promoters, vaccines, and other biologics by recombinant organisms, · 1 .1 1.r. 1 ... ~ /~\ (2) produce transgenic animals with modified composition, and <3: construct transgenic animals to produce pharmaceuticals in their milk, blood, or urine. Research Opportunities Improve basic toolsfor the genetic manipulation of animals Identification and unclerstanding of the physiology of the major genes controlling growth and lactation, reproduction, and disease and stress resistance in animals are needled. The ability to produce transgenic livestock possessing traits of economic value is currently limited by our inability to maintain in culture pluripotent embryonic stem cells from any species except the mouse, by our lack of appropriate promoter-regulatory DNA to control expression of transgenes, and by the lack of knowledge about the physiological conse- quences of the expression of specific foreign genes. To advance the field,
ENHANCING THE FOOD SUPPLY 131 we also must develop a basic understanding of the biochemistry and ge- netics of traits controlled by multiple genes and develop cloning systems with acce "table, selectable markers. In vitro models of gene expression in animal systems and methods for assessing the overall impact of genetic modification on animal metabolism, including potential pleiotropic effects and nutritional implications, must be available. Improve the productivity of meat-producing animals The tools of bio- technology provide us with the opportunity to develop transgenic live- stock that contain genes coding for improved growth characteristics, lacta- tional performance, and resistance to disease anct stress. Antimicrobial agents used as feed additives to alter intestinal microflora, improve ab- sorption of nutrients, decrease protein requirements, and control subclinical diseases can be produced by genetically engineered organisms. In addi- tion, other recombinantly cie rived drugs, monocional antibody vaccines, and immunomoclulators derived from genetically engineered microorgan- isms could have an impact on animal health and meat quality. Safe, effec- tive, reliable, and inexpensive diagnostics for disease detection, pregnancy tests, and detection of pathogenic organisms need to be developed. Improve the nutritional quality offoods derivedirom animals The clon- ing of genes coding for somatotropin or for enzymes that accelerate syn- thesis of beta-agonists into the germline of animals could accelerate growth and significantly improve the composition and nutritional quality of meat. Partitioning the fat and cholesterol in milk and meat and clecreasecI fat content of these products would result in a healthier food supply more consistent with nutritional guidelines. Fermentation Bacteria, yeasts, and molds have been used for centuries as starter cultures for the production of fermented foods. Fermenter! foods provide a major contribution to human diets in all parts of the Florid because fermentation requires little energy and is relatively simple, natural, effi- cient, and inexpensive. Microbial metabolism is responsible for the pro- duction of the acids, carbon dioxide, and alcohol that function as preser- vative agents as well as enzymes that alter the flavor, texture, shelf life, safety, digestibility, and nutritional quality of fermented foocls. Microorganisms produce a variety of secondary metabolites which can be produced via fermentation and purified for use as food ingredients. Microorganisms are metabolically diverse, small, and easy to grow in large quantities on various substrates, making them ideal candidates for the production of secondary metabolites. The types of chemicals produced by microbial fermentation include acidulants, amino acids, vitamins, flavors,
32 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES flavor enhancers, pigments, stabilizers, thickeners, surfactants, sweeten- ers, antioxidants, and preservatives. Genetic engineering techniques offer more precise tools for improv- ing food-grade microorganisms. Although significant research has been conducted on genetic engineering of food-grade microorganisms, no ge- netically engineered organisms have yet been approved by the FDA for use in foods. Several enzymes derived from genetically engineered organ- isms, including rennet (used in cheese making) and alpha-amylase (used for the production of high-fructose corn syrup), have been approved for use in the United States. Research Opportunities Develop basic toolsfor the genetic manipulation of microorganisms The regulatory elements and signal sequences involved in control of gene ex- pression in microbial systems need to be identified and isolated. This will make possible the construction of strains that excrete valuable secondary metabolites into the culture medium, from which they can be readily extracted and purified. Construction of multifunctional integrative cloning vectors will allow the transfer and stable integration into the chromosome of single genes as well as coding for entire metabolic pathways. Efficient and reliable gene transfer systems applicable to bacteria, yeast, and molds need to be cleveloped. Construct microorganisms with unique metabolic properties Identification of microorganisms for metabolic screening will greatly expand the num- bers and types of microorganisms that can be user] in food fermentation ant! in the production of food ingredients. Genetic improvements will be targeted to a specific organism anc! fermentation system and may involve improved processing characteristics (e.g., more consistent and improved leavening of bread and accelerated ripening of cheese), decreased waste (e.g., bacteriophage-resistant organisms that eliminate economic Tosses caused by destruction of cultures by bacteriophage>, enhanced food safety (e.g., microbial production of bacteriocin, which inhibits foodborne pathogens), improved nutritional quality (e.g., microbial production of amino acids or vitamins and engineered yeast for production of low-calorie beer), or en- hanced bioavailability of nutrients (e.g., engineering of the meat factor influencing iron absorption into starter cultures and engineered starter cultures as delivery systems for digestive enzymes). Understand the role of microorganisms as probiotics Microorganisms have been reported to play key roles in maintaining the health of humans anct animals by colonizing the gastrointestinal tract and controlling intestinal
ENHANCING THE FOOD SUPPLY 133 microorganisms capable of producing toxic effects in the host. Lactobacilli assist in the digestion of lactose, provide important digestive enzymes, inactivate toxins, bind cancer-causing chemicals, modulate the gut flora, deconjugate bile acids, and supply B vitamins. Further research is war- ranted, since the exact mechanisms for these effects are not well under- stood. Probiotic effects have been studied extensively in animals, and it is not uncommon to add certain organisms directly to animal feed to en- hance digestibility of the feed and to protect the gastrointestinal tract from microbial invasion. The efficacy of this approach in human diets needs to be tested. Enzymes and Protein Engineering Enzymes are catalysts, generally proteins, that enhance the rate of the synthetic and clegradative reactions of living organisms. The food- processing industry is the largest single user of enzymes, accounting for, on average, more than 50 percent of enzyme sales. Proteases, lipases, pectinases, cellulases, amylases, and isomerases are used extensively to control the texture, appearance, flavor, and nutritive value of processed foods. Although enzymes are produced by animals and plants as well as microorganisms, the enzymes from microbial sources are generally most suitable for commercial applications. Microbial products produced without such limitations as season of the year or geographic location, which might be imposed by plant-derivec3 enzymes. In addition, microorganisms grow quickly, and production costs are relatively Tow. In view of the metabolic diversity of microorganisms, nature has provident a vast reservoir of enzymes that act on all major biological molecules. Unfortunately, enzymes frequently do not function optimally under the conditions of temperature and pH used in food processing. Chemical modification has been used successfully to improve enzymes; however, the general lack of specificity in the reagents and the requirement for difficult and tedious purification and characterization to insure homoge- neity severely limits the power of the method for routine improvement of enzymes. Site-s~ecific mutagenesis, a specializecl form of genetic engi _ . . 1 can be mass J 1 peering, has been used to introduce In tne structure or enzymes minor changes that have dramatic effects on substrate specificity, pH and ther- mal stability, and resistance of the enzyme to proteolytic degradation. For example, substitution of amino acids at specific key locations within the active site of the enzyme subtilisin demonstrated that properties of the enzyme could be altered dramatically, both positively and negatively, when compared to the native enzyme. Site-specific mutagenesis could improve the versatility of enzymes in food systems and decrease the cost of pro- cessing food. This technology could also be used to modify other proteins
34 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES of interest to the food-processing industry, possibly altering functional properties or nutritive value. Enzymes are frequently used in batch food-processing systems; how- ever, they can be immobilized and used in continuous processing systems where applicable. For example, the enzymes used to convert starch in corn to high-fructose corn syrup and the enzyme rennet used in cheese manufacture have been immobilized and used continuously for weeks and sometimes months or years without substantial loss of activity. Cost sav- ings in excess of 40 percent have been achieved by conversion from batch to immobilized enzyme systems. Research Opportunities Develop analytical tools to improve understanding of enzyme structure ancifunction Improved computer modeling systems are needed to pre- dict the structural and functional impact of base pair or amino acid substi- tutions in DNA and protein, respectively. We need to develop models for evaluating the impact that structural changes in enzymes or proteins exert on their behavior in food systems (i.e., interactions with proteins, other macromolecules, and water) and chemical and physical tests for measur- ing properties directly associated with the? desired chnn~ec in native slants and processed foods. Design improved enzymes Enzyme and protein engineering will make it possible to create tailor-made enzymes that function optimally under food- processing conditions. In addition to modifying reaction rate, pH and thermal stability, and resistance of the enzyme to proteolytic degradation, it may be desirable under certain circumstances to modify substrate speci- ficity of enzymes. Theoretically, it will be possible to construct enzymes that modify fat, protein, or carbohydrates in ways not possible with en- zymes that now exist in nature creating the potential for new biological _ 1 , 1 · ~1 . ~ ~1 1 ~1 1 . ~ molecules In food systems. Enzymes could also be engineered to {unction in unusual environments, such as in organic solvents, or under extremes of pressure or temperature for unique food-processing applications. Pro- tein engineering could be used to make noncatalytic proteins catalytic by attaching an active site to an existing protein. It may be possible to engi- neer antibodies that possess catalytic activity; their binding and recogni- tion sites could be used to immobilize the enzyme for food-processing applications. Improve enzymes in intact plants Enzyme- and protein-engineering tech- niques, coupled with plant genetic engineering, could be used to modify
ENHANCING THE FOOD SUPPLY 135 enzymes and proteins in intact plants. For example, methods now exist to construct genes coding for synthetic proteins enriched in essential amino acids. Since cereal grains are deficient in one or more of the essential amino acids isoleucine, lysine, methionine, threonine, or tryptophan, transfer of these genes to plants deficient in these amino acids could improve their nutritive value. Many plant components used in food processing are chemi- cally modified following extraction from the plant (e.g., hydrogenation of oils and cross-linking of starch). Engineering of plants with enzymes ca- pable of chemically modifying starch or oils could eliminate the need for chemical modification after extraction. MOLECULAR BASIS OF FOOD QUALITY Clearly, these are exciting times for researchers involved in the study of the chemistry, physics, and biochemistry of foods. Quality and stability of food products are determined by the molecular properties of their constituents. However, the molecular properties often express themselves in unique, supramolecular structures that have an overriding influence. Techniques for measuring chemical structure, reactivity, and physical properties have become available at an unprecedented rate, and there is every indication that developments will continue. Some, such as nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) imaging, are nondestructive, thus allowing for continuous monitoring of changes. Theoretical interpretation of data has been greatly improved by computer-assisted data processing. All of this promises to aid our under- standing of the complex interactions of molecules that make up tissue or reformulated foods. Improved understanding of the relationship between the molecular structure of food biopolymers and the functional properties of biopoly- mers in food products will be one important application of these new techniques. This will enable us to substitute more readily available, less expensive, or nutritionally or functionally superior ingredients in our food supply. A food biopolymer of particular interest is the class of cyclodextrins, which are six- to eight-membered donut-shaped rings of glucose mol- ecules produced enzymatically from starch (Figure 4.3~. They have the ability to bind noncovalently with many different types of molecules in their "core." In doing so, they alter the physical and chemical properties of the molecularly encapsulated "guest" molecules. Cyclodextrins have many potential applications in food products. For example, they can be used to carry flavors, enhance the solubility of otherwise water-insoluble compounds, and remove such undesirable compounds as cholesterol from food.
136 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES a_ _ FIGURE 4.3 This molecular model illustrates the beta-cyclodextrin molecule and its ability to entrap materials in its hollow "core." Through available molecular modeling systems, it is possible to identify the uses of beta-cyclodextrins in specif- ic applications. Determination of the important properties of biopolymers such as proteins will make it possible to improve structure by biotechnological techniques, both genetic and enzymatic. For example, the use of magnetic resonance techniques in determining the types of interactions and mo- lecular conformations of proteins in gels could allow for both higher qual- ity and more economical production of these products. Research Opportunities Study the role of water in foods One of the most important functional properties of food biopolymers is the ability to bind water. The amount, association with structural elements, distribution, and structure of water are without cloubt critical to the quality of foods. It is perhaps not an exaggeration to suggest that in many ways water is the most important determinant of food quality. Water determines the structure of biopoly- mers and is both the medium of and a participant in most of the reactions that occur in foodstuffs. One of the difficulties in dealing with the prob- lem of water structure in foods is that there is considerable uncertainty about the structure of water itself. Not only does water modify the struc
ENHANCING THE FOOD SUPPLY 137 ture of cellular components, the structure of water is in turn modified by the components of the cell. The large surface area of cellular structures makes the effects at inter- faces of particular importance. The more highly developed structure of water at these interfaces affects its function as a solvent and most likely reduces its ability to disassociate into hydrogen and hydroxyl ions. This latter is of critical importance in determining plI and chemical reactions. Methods for determining water structure are based primarily on relax- ation techniques, measuring either the properties of water directly by proton magnetic resonance or the properties of molecules in water, such as the use of electron spin resonance (ESR) and NMR to study the trans- lational or rotational movements of free radicals and other food constitu- ents. The rate of formation and growth of ice crystals is an important factor in the quality of frozen foods. Much attention has been paid recently to the extremely high viscosity of the glassy state of water in frozen foods. This phenomenon illustrates the importance of water in chemical reac- tions in foods en cl offers a potential for improved quality during frozen food storage. Techniques such as differential scanning calorimetry can distinguish between temperature-inclucecl changes in the glassy state and phase changes brought on by melting of ice crystals. In the 1980s, food scientists realized that they could better under- stand the relationships of food structure, food function, and water in food materials, products, and processes by applying polymer science, with its study of glassy states, glass transitions, and plasticization by water. Food polymer science, emphasizing the basic similarities between synthetic poly- mers and food molecules, provides a practical experimental framework to study real-world food systems that are not at equilibrium. It is being widely applied to explain and predict the functional properties of food materials cluring processing and storage of the final products. Quantify the specific structural changes in the various levels offooc! mac- romolecular organization In spite of the potential promised by polymer science approaches to the study of water in foods, other lines of investiga- tion should not be neglected. In particular, it should also be recognized that, in many cases, the relevant properties of fooc3 molecules result not from their generalized polymer behavior but rather from their specific molecular structure, as should be expected for biological macromolecules, with their well-known ability to assume diverse functions by varying their basic structure (in the case of polymers, their primary sequence). Such aspects are particularly important in foods containing components that retain significant aspects of biologically imposed structure: cells, mem- branes, fat globules, globular proteins, and so on. The specific details of -
13S OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES the interaction of macromolecular functional groups with water are known to be crucial in biological self-or~anization and in maintaining viability, such as the role of hydrophobicity in protein conformation and membrane structure, the role of water structuring in ionic salvation, and specific hydration effects such as hydrogen bonding. Altering the hydration envi- ronment of food molecules, as in processing, often leads to irreversible and undesirable changes in food quality. In many cases, these changes cannot be understood in terms of general polymer theory but must be considered in terms of the specific structural details of the system under consideration. As a result, we need much more study of the molecular details of food polymer hydration particularly under conditions of low water content or low temperatures. Learn more about- the beEc~vior.s of food components in solution A re- lated requirement is the need for greater basic work in simple model systems containing one or only a few components and variables. Until the behaviors of individual food components in solution are understood, and then the interactions of simple combinations of such polymers in solution, there is little hope of significant progress in understanding much more complicated systems. Much more needs to be learned about hydration forces, their role in colloidal stabilization, and whether these forces over- ride more traditional models of colloidal interactions in food systems. Explore mechanical-p1?ysical properties offoods related to bond energies Often the properties of a food are more related to the unique supramolecular architecture of the major food polymers than to their specific molecular properties. Many food polymers like proteins and starches are extensive structures of interacting components joined by noncovalent bonds. Col- lagen and the contractile proteins of muscle are examples of this, as are the cellulose and hemicelluloses of plant cell walls. Many techniques, some rather elegant, have been developed to measure mechanical forces in processed foods. In addition, there has been good progress in under- standing some of the chemical and physical changes occurring in indi- vidual molecules and supramolecular structures during processing. What is lacking is a theory to relate the changes at the molecular or supramolecular level to the overall physical or mechanical properties of the food tissues. For example, how do the noncovalent bonds formed by protein denaturation and aggregation influence a physical measurement such as tensile strength? An understanding of these phenomena would make it possible to modify processing techniques and food formulations to produce foods with any desired physical attribute. In a similar manner, it will be important to establish the contribution to these physical properties of covalent bonds in food biopolymers. Split
ENHANCING THE FOOD SUPPLY 139 tiny of covalent bonds by hydrolysis of polymers is a technique that has been used for centuries to modify physical properties and produce prod- ucts of desirable quality. Examples of this would be tenderization of meat by protein hydrolysis and increased yield and quality of fruit juices by hydrolysis of pectins. However, in most cases results have been achieved by trial and error, without a firm understanding of the number of bonds necessary to be broken to achieve optimal results. Understand free-radical reactions in foods Biopolymers play a critical role in determining the physical-mechanical properties of food tissues. Both covalent and noncovalent bonds between biopolymers govern these properties. An area of great importance in food processing is the effect that mechanical actions such as grinding and cutting have on these pro- cesses. It has been reported that this type of mechanical action can break covalent bonds and form free radicals, which have been associated with food deterioration. Little attention has been given to this phenomenon in food research, although the principle is well established with man-made polymers. Since many of our food products are subjected to these kinds of mechanical stresses, understanding the extent of the changes they cause is critical. Not only would the physical properties of various food polymers such as proteins be affected, but the formation of free radicals could set off chain reactions leading to degradation of lipids and other components in foods. ESR spectroscopy is a powerful tool for measuring the production of radicals in situ and in real time. It measures free radicals directly, rather than just the decomposition products of the radicals. This type of kinetic information makes it possible to understand free-radical reactions occur- ring in food tissues without having to macerate and extract foods, pro- cesses that can themselves create free radicals. These in situ techniques should improve our understanding of other free-radical reactions as well. These other reactions would include those initiated by various forms of reactive oxygen species, thus allowing for improved strategies to counter- act the effects of these free-radical oxidation processes. Enhance understanding of biomembrc~ne changes Understanding of membrane structure and function has increased greatly in recent years, but much remains to be done. Good progress has been made in understanding the interactions of membrane proteins and lipids; however, interaction of membrane components with the proteins of the cell cytoskeleton is just beginning to be understood. These interactions will undoubtedly play a great role in the quality of foods. To give some idea of the significance of membranes in food tissues, it can be calculated that 1 kilogram of lean beef has approximately 8,000
140 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES square meters of membrane surface. Thus, many of the reactions that go on in food result from the chemistry and enzymology of surfaces. Many of the functions of membranes in food tissues are an extension of their meta- bolic roles. These include energy production, the movements of ions and small and large organic molecules, receptor sites for hormones and there- fore for cellular control responses, and involvement in the control of ionic composition and phi of cellular compartments. Membranes are respon- sible for postharvest vectorial metabolism and osmochemistry. In addi- tion, the lipids of membranes are highly unsaturated and their extremely large surface area per unit of weight makes them particularly susceptible to oxidative reactions. These membrane processes are critical in the post- harvest metabolism of fruits and vegetables anc3 the postmortem control of calcium ion concentrations in the sarcoplasm of muscle tissue. Thus, quality control and maintenance are in large part a function of the mem- brane systems. ENVIRONMENTAL ISSUES Sustainability Each step in the food system production, transportation, processing, storage, and marketing has some effect on the environment. Therefore, the concept of sustainability in the food system is critical to a finite world with an expanding population. An important challenge in this age of envi 1 1 ----r--~ =~ no- ronmental and economic concerns is to identify, develop, and implement new systems for producing high-quality, economical, wholesome foods with reduced adverse effects on the environment and with better use of raw materials. Sustainable agriculture attempts to minimize environmental degrada- tion through a range of practices that includes integrated pest manage- ment; low-intensity animal production systems; crop rotations to reduce pest damage, improve crop health, decrease soil erosion, and (for legumes) fix nitrogen in the soil; and tillage and planting practices that reduce soil erosion and help control weeds. In the food-processing industry, proces- sors are beginning to recycle more by-products that were formerly dis- carded. These by-proclucts include the soluble materials in wastewater, such as sugar washed off peaches, tomato juice in flume water, starch removed from potatoes during washing and Fuming operations, and solid materials such as corn husks and crab shells. If suitable uses can be found for these by-products, they can be converted to raw materials or ingredi- ents in feed, food, or other products and removed from the waste stream. An excellent example of sustainability exists in the fishing industry. In 1987, fish processors in Massachusetts designated fish waste disposal as
ENHANCING THE FOOD SUPPLY 141 one of their main future concerns. Regulations at that time prevented offshore disposal of the waste, and fees for landside disposal were steadily increasing, along with its potential for pollution. Scientists developed an economically viable liquid fertilizer from fish waste material for regional crops such as cranberries. Much of the fertilizer was liquefied using en- dogenous enzymes from the fish waste itself. They found that all plant material fertilized with the liquid fish fertilizer had equal or better growth than plants grown using commercial fertilizers. These and further studies have led to the addition of liquid fish fertilizer to the official list of ap- proved cranberry fertilizers. Research Opportunities Develop alternative energy sources and agricultural chemicals U.S. agri- culture depends heavily on fossil fuels to provide power for machinery, for the production and application of fertilizers and pest control chemi- cals, for crop drying, and for many other purposes. Improving our under- standing of plant and pest interactions and the biology and genetics of insects and weeds will enable us to design integrated pest management strategies that reduce the need for pesticides. Advances in biotechnology should lead to the development of plants that are more resistant to pests and less dependent on the application of manufactured fertilizers. There is a need for new, effective pesticides that do not pose long-term health ris as to consumers or to the environment. With additional research, we will learn how to collect and store solar, wind, and other sources of energy more reliably for applications on the farm, including the heating of live- stock buildings and the drying of harvested crops. Identify economically viable uses for by-products of the food industry and develop processes for separating them Information is needed on the iden- tities, composition, and quantities of the solid and liquid by-products gen- erated by the food industry. Research would help to identify the ways in which by-products can be incorporated into new foods, animal feed, or nonfood products. New technologies and devices such as membranes are needed to remove suspended and dissolved by-products from waste water and to separate by-proclucts that become mixed together in a solid or liquid state. Develop databases and water quality standards that will expand the use of water recycling and reuse technologies Food-processing operations are major users of water. Expanded use of water recycling and reuse tech- nologies could reduce the quantity of water used and decrease the dis- posal of by-products of food-processin~, operations. Before these tech
49 OPPORTUNITIES IN THE NUTRITION AND FOOD SCIENCES nologies can be widely expanded, however, the federal government must establish regulatory criteria governing their use. Before the government can do this, however, it must construct a database on the current use of these technologies. Minimum chemical and microbiological standards need to be established for water recycling and reuse. Also needed are residue and quality standards for finished products that come into contact with recycled and reused water. CONCLUDING REMARKS Food science and technology have made remarkable strides in provid- ing people with high-quality, safe, and wholesome foods. Food chemists, food microbiologists, nutritionists, and food engineers have combined their skills and applied many of the basic science advances and new methods to produce today's food supply. It is hard to believe, walking the aisles of the average supermarket with more than 70,000 items, that the formalized field of food science is just over 50 years old. It evolved about the time that technologists were discovering how to fortify foods with iodine, vita- min D, iron, and B-complex vitamins. Food science is a young, dynamic field facing many challenges. Con- sumers have always demanded an array of foods pleasing to the senses. They want food to be convenient and of a composition that enables them to more easily meet dietary guidelines. Many technologies are in place to respond quickly to consumer desires or public health needs. However, scientists must seize the newer techniques developed by molecular biolo- gists to design functional foods for health needs. Food engineers and microbiologists must work together to optimize new processing techniques to ensure the safety of foods while reducing food and packaging waste. In addition, this field must apply its most creative minds to developing the equipment and technologies that will provide us with the value-added foods we need to compete successfully in world markets. Exciting ad- vances certainly await us in the years ahead. -
