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OCR for page 98
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
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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
OCR for page 100
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.
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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.
OCR for page 102
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
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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
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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
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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
-
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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
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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
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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.
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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
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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
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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
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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
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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.
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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
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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
-
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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
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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
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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
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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
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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
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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.
-
Representative terms from entire chapter:
food sciences
