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OCR for page 115
6
Existing Technological Options and
Future Research Needs
THE NEED TO MODIFY THE
NUTRITIONAL ATTRIBUTES OF
ANIMAL PRODUCTS
Research on foocl-proclucing animals has
led to decreased production costs, improved
product quality, and advances in under-
stancling human biological needs. Figure
1 provides a schematic Illustration of some
of the interactions that occur between live-
stock research and production, animal prod-
ucts, life-styles, ant] human health. It is
important to note that all interactions occur
in both directions. In fact, the committee's
major purpose is an example of this namely,
to determine what technological options can
be used to alter animal products to enhance
human nutrition.
The following questions must be taken
into consideration:
· What components of animal products
are important to human nutrition and health?
· What components of animal products
can be altered with current technologies or
through additional research?
· What effect does altering the compo-
nents of animal products have on shelf life,
115
visual appeal, flavor, texture, safety, nu-
trient content, and stability of different retail
products?
· Is there sufficient consumer demand to
justify the research en c] product develop-
ment efforts necessary to generate new
products?
· Are there standards of identity or reg-
ulatory aspects that preclude or seriously
impede the development of new or altered
animal products?
The last question is of particular impor-
tance, for in addition to health-related and
marketplace needs, there must also be in
place the appropriate technology and reg-
ulations needed to develop wholesome, nu-
tritious, and palatable products.
The marketplace is changing in relation
to consumer needs an(l the variety of food
products that can be selected. Each year,
about 6,000 to 8,000 "new" products appear
that are either newly packaged, newly for-
mulatecl, or newly fabricated. Many are in
direct response to consumer concern about
the link between nutrition and diet. The
wide variety of (different dairy products on
the market reflects this.
OCR for page 116
116
Animal Research
1 ~
Livestock Production \
-
Food Processing ~ Food Research and
Product Development
Life-styles
Quality of Life
DESIGNING FOODS
Human
Nutrition
and Health
FIGURE ~1 Schematic of interactions among animal, food, and human
dimensions affecting human health.
It seems likely that animal products or
their components will be increasingly al-
tered, fractionated, ant] formulated to ad-
dress consumer needs and market oppor-
tunities, but this will require additional
inputs in research and technology as well
as reexamination of some current regulatory
policies such as standards of identity.
It is important to recognize who does
research on animal products and how it is
funded. Food product clevelopment can be
clivicled into three distinct phases. First,
the components of the foot] ingredient or
raw material (such as an agricultural com-
mo(lity) must be described. It may be de-
sirable to separate these components for
uses in other applications. In this case, the
processes for separation and reformulation
must be clevelopec3, ant! the characteristics
of and potential applications for the individ-
ual components must be determined. Sec-
ond, it must be determined how the various
components interact to give the food prod-
uct its d~i~erent characteristics. Finally, the
commodity, its individual components, or a
partially modified product must be con-
vertecI into a retail product that is whole-
some, palatable, and in demand. In addi-
tion, the product must have a reasonable
shelf life, conform to all labeling and regu-
latory standards, and, ideally, be nutritious.
The first part of this research is usually
conducted! by the public sector university
or U.S. Department of Agriculture (USDA)
laboratories. Likewise, much of the second
phase is clone in the public sector, but,
depending on the need and the product, a
significant amount may be done in the
private sector (for instance, by a food in-
dustry firm). Some of the technologies d~e-
velope(1 will be patented to protect invest-
ments since the food product per se is
generally not patentable. The third (limen-
sion is primarily the responsibility of the
private sector, mainly because of the market
orientation of these firms.
A variety of sources fund these research
phases. Typical sources inclucle
· State and federal government funcling
of agricultural experiment stations (all three
phases);
· Commodity check-oE funds (all three
phases);
· Competitive government agency grants
(limited amount in the first and second
phases);
· Industry-funded public research (first
and second phases); and
· Private industry, in-house research and
development (primarily the second and third
phases).
OCR for page 117
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
All these research efforts would benefit
somewhat from a more systematic approach,
especially in terms of product development.
There is also a need to better coordinate
work between the public and private sec-
tors. A systems approach baser! on major
topic areas, such as animal products, would
help link some of the public and private
sector programs that are contributing to
similar goals.
CURRENT STATUS OF TECHNOLOGY
MANAGEMENT
Before identifying
~.
potentially useful
changes in technology, the maturity of the
technologies currently in use must be ex-
amined. A too} commonly used for this
purpose in strategic planning and technol-
ogy forecasting is the S-curve, shown in
Figure 6-2 (Becker ant! Speltz, 1986~.
In a young technology (few agricultural
production technologies are young), exten-
sive long-term research is neecled to pro-
duce technical progress. As the technology
grows, significant advances can be made
with smaller and smaller increments of ef-
fort. But as technology matures, each effort
produces smaller and smaller increments of
progress. This is illustrates] by the top curve
in the figure. At the midpoint of the curve,
research productivity declines (see the bot-
tom curve in the figure) and the research
manager must decide whether sufficient
gains can be maple to justify continued effort
(research resources) or whether a new tech-
nology must be ctiscovered, developed, or
perfected to ensure continued technical
progress and product growth or acceptance.
As an example, if one uses a performance
index for the modern broiler chicken that
includes reproductive capacity, hatchabil-
ity, growth rate, feed conversion, body
composition, and the like and plots that
index against time, an S-curve like that
shown in Figure 6-3 might be constructed
(hypothetically, since it is difficult to accu-
rately reconstruct an index). The technolo
o.
o
cat
-
-
._
3
o
a:
/
-
Effort
-
117
-
Effort
FIGURE ~2 The S-curve of technical progress
versus effort. As technology matures, each effort
produces smaller increments of progress (top
curve); at the midpoint of the curve, research
productivity declines (bottom curve). Source: R.
H. Becker, and L. M. Speltz. 1986. Working
the S-curve: Making more explicit forecasts. Res.
Manage. 29:21.
gies involved in shifting this index included
nutrition, genetics, disease resistance and
control, and management; but it is clear
that some new technology was needed clur-
ing the late 1960s or early 1970s. In fact, a
new technology (dotted line in the figure)
was being clevelope(1 recombinant DNA
technology- but it was largely ignored by
poultry scientists and other animal scientists
and is only now, in the late 1980s, appearing
on the food production scene.
The research recommendations discussed
in this section should be useful to research
OCR for page 118
118
100
90
80
70
-
60
o
<~, 40
50
30
20
10
TradlUonal /
Techn°l°gY /
/e
/ Blotechnology
.
! I ~1 1
1950 1960 1970 1980 1990 2000
Year
FIGURE ~ A hypothetical Secure for broiler chicken growth per-
formance. Source: R. H. Becker, and L. M. Speltz. 1986. Working the
S-curve: Making more explicit forecasts. Res. Manage. 29:21.
administrators in selecting the most appro-
priate technological options for improving
the nutritional attributes of animal products.
ASSESSING CURRENT AND FUTURE
TECHNOLOGIES
The committee organized two workshops
to assess (1) the knowledge that is currently
available and that can be implemented im-
mecliately to modify the composition of
animals ant] animal products and (2) the
new technologies that may eventually be
useful for modifying the composition of
animals and animal products. Both work-
shops were held at the National Academy
of Sciences' Woocis Hole Study Center dur-
ing summer 1986.
The objective of the first workshop was
to document current knowledge related` to
the measurement of intact body and carcass
composition; the influence of genetics, nu-
trition, ant! management on the composition
of animal food products; and the influence
of processing technology on the composition
DESIGNING FOODS
of foods made from animal products. The
second workshop was convened to identify
new technologies offering promise for in-
creasing the nutritional quality of animal
products. Special emphasis was given to
identifying those technologies that influence
growth particularly the repartitioning of
fat to muscle.
Papers presenter! at these workshops ap-
pear in the Appendix and are cited through-
out this chapter.
TARGET LEVELS OF NUTRIENTS AND
RELATED RESEARCH PRIORITIES
Determining the Level of Fat in Live
Animals and Carcasses
More than 30 techniques exist to estimate
live animal and carcass composition. Equip-
ment costs range from $1 to over $1 million
(Topel and Kauffman, this volume). For
commercial use, accuracy must be consid-
ered as well as cost ant! practicality. Re-
search is needed to improve certain methods
OCR for page 119
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
ant! to make them less expensive ant] more
practical. Economic imperatives to use these
techniques are also necessary. This calls for
marketing incentives that favor trim, mus-
cular animals, which, at present, are re-
ceiving only minor premiums in the mar-
ketplace.
There is considerable variation in body
composition among animals of the same
species and between different species, de-
pending on growth stage, nutritional his-
tory, en cl genetic base. Pork ant! beef car-
casses average 30 to 35 percent fat and 35
to 50 percent muscle (Topel and Kauffman,
this volume). Increased muscularity should
become important to the livestock industry
as consumer demand for leaner animals
increases and economic pressures mount in
favor of more efficient livestock production.
Many indirect methods of varying degrees
of complexity are available to estimate body
fat. Most ofthe methods have been valiclatecl
for predictability and precision by other
indirect methods but rarely by direct carcass
analysis of an animal. Therefore, the final
choice of an indirect method ultimately
depends on cost, the objective of the meas-
urement, and the physical conditions under
which the method is to be used.
Survey of Method
Older methods of determining fat levels
include linear measurement of live animals
ant! carcasses and the back fat probe for live
animals. Linear measurement is not satis-
factory for live animals but floes provide
good (though not excellent) information about
carcasses. The back fat probe is reasonably
accurate, easy to standardize ant] use, and
inexpensive; but it is slow for large numbers
of animals. While the back fat probe is
considered commercially practical at this
time, it is not widely used (Topel and
Kauffman, this volume).
Other simple techniques include the re-
flectance probe, live weight, ant] visual
assessment. The reflectance probe is widely
119
used in Europe but not in the United States.
It is simple and fast and also indicates some
meat quality characteristics. Growth curves
developed from the live weight of animals
can be used to estimate body composition,
if genetic history is known. However, the
correlation of live weight with fatness can
also be influenced by feeding, environment,
health status, ant] digestive tract contents.
Visual assessment and subjective evaluation
is the most common technique used to
estimate composition, but because of diffi-
culties in distinguishing muscle from fat, it
is of limited value (Topel and Kauffman,
this volume).
Newer methods of fat measurement use
sophisticates] physical and chemical tech-
nologies. Ultrasonic measurement is based
on the principle that high-frequency sound
waves pass through tissue but are reflected
back at the interface between two different
types of tissue. Time variations for return
of reflected signals measure distances be-
tween tissue boundaries. Of the many non-
destructive evaluation techniques, ultra-
sounc] may have the greatest immediate
practical potential (Tope! and Kauffman, this
volume).
Video image analysis could replace or
supplement subjective visual assessment for
grading carcasses. The technique uses a
video camera to create an image that is then
processed by an analog/cligital converter ant]
analyzed by a computer. While application
is not simple, its benefits point toward future
adoption by the U.S. beef industry (Topel
ant] Kauffman, this volume).
Whole-body potassium counting of a live
animal relies on the direct relation of po-
tassium to lean body mass and its indirect
relation to fat. It is a useful research tool,
but the bulky and expensive equipment and
the time required, as well as some uncer-
tainties in measurement, restrict commer-
cial application (Topel en cl Kauffman, this
volume).
Body (lensity methods treat the body as
a two-component system fatty tissue and
OCR for page 120
120
fat-free body each component having a
different and constant density. The propor-
tions of the components are estimated from
the density of the whole body. Problems
arise in measuring the volume of live ani-
mals, and the methoc] is slow; therefore, its
use is limited mostly to research (Topel and
Kauffman, this volume).
The Anyl-ray technique utilizes x-ray at-
tenuation as an index of tissue fatness and
is used commercially for ground meat. The
tissue-saw~ust technique for frozen car-
casses is used only as a research tool. Di-
lution techniques introduce a known amount
of tracer that becomes uniformly distributed
in the boc3`y's water; when equilibrium is
reached, the tracer's concentration is meas-
urecI. Soluble, short-lived radioactive gas
tracers are halogenated gases with an affinity
for fatty tissue. The amount of these gases
taken up is user! in research to estimate
body composition. Urea dilution may be
applicable to both research and industry
(Topel and Kauffman, this volume).
Computerized tomography (CT) presents
body areas by computed synthesis of an
image from x-ray transmission data. The CT
scan is widely used in human medicine and
has great potential as a research too! and
also in genetic selection of breeding stock.
European researchers have adopted com-
puterized tomography faster than Ameri-
cans (Tope! and Kauffman, this volume).
In nuclear magnetic resonance (NMR)
imaging, strong magnetic fields and pulsed
radio waves incluce resonance of protons
within the bo(ly; these protons return to
their original orientation in a measured time
and an image is produced. NMR is being
used in human medicine and has great
potential for application to the livestock
industry, but it is expensive ant! complex
(Topel and Kauffman, this volume).
Near-infiared reflectance is currently used
to predict the composition of plant materials
and may be adapted for analysis of carcass
composition. It is simple and inexpensive,
DESIGNING FOODS
but research is needed to develop it for
commercial use (Topel and Kauffman, this
volume).
Total body electrical conductivity (TO-
BEC) utilizes the principle that muscle
conducts electricity more readily than fat
because of its higher water and electrolyte
contents. In practice, the animal is sur-
rounded by a coil to which a current is
applied, generating an electromagnetic field.
The animal absorbs heat energy, perturbing
the field. The loss of energy detected in the
coil measures the animal's conductive mass.
The theoretical basis of TOBEC has been
confirmed, and the method has been applied
to both human and animal subjects. TOBEC
technology is promising, but more research
is needed to determine its accuracy (Bo-
ileau, this volume).
Influencing the Level of Fat in the
Growing Animal
An animal's belly composition results from
its cumulative growth. Altering the propor-
tion of fat to lean therefore requires regu-
lation and modification of growth. Lipid
composition presents the greatest source of
muscle tissue variation (Allen, this volume).
The primary lipid fraction contributing to
this variation is the triglyceride fraction that
is stored in adipocytes within the muscle.
These deposits are commonly referred to as
marbling, ant] within the range of marbling
found in the longissimus dorsi muscle of
beef, the ether-extractable lipid (primarily
triglyceride) varies from 1.77 to 10.42 per-
cent (mean values for marbling scores) on a
wet tissue weight basis (Savell et al., 1986~.
In the present and near future, the most
promising approach to enhancing the rate
and efficiency of muscle growth (increasing
lean tissue, decreasing fat tissue) is the
administration of recombinant hormones
(Allen, this volume). Recombinant growth
hormone has been shown to have impressive
effects on growth, feet! efficiency, and car
OCR for page 121
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
cass composition in pigs (Etherton, this
volume). Research has also shown that re-
combinant-derived bovine growth hormone
dramatically increases milk production and
mammary growth in dairy cattle (Gorewit,
this volume). Transgenic animals, whose
genes are transmittable to subsequent gen-
erations, may have a place in livestock
production systems, although reproduction
has sufferer] in some early studies (Hammer,
et al., 1985~. It may also be possible to
construct and perpetuate important hor-
mone genes that can be regulatecl at will by
coupling them to promoters that can be
turned on or off at critical periods through
nutritional, pharmacological, or environ-
mental manipulation (Allen, this volume).
Technologies can be used to reduce fat
deposition in the growing animal, which
should facilitate production of animals with
the appropriate amount of fat, thereby pre-
clucling the need for extensive trimming of
fat from carcasses after slaughter. The con-
tributions of genetics, nutrition, and man-
agement to fat reduction in cattle, swine,
poultry, and milk products are reviewed
next.
Cattle
Efficient production of palatable lean beef
must be a primary objective of the beef
industry if it is to maintain its competitive
position over the long term. Traditionally,
production of lean beef has been increased
by breeding cattle of a larger frame size.
These cattle produce beef that contains
more protein ant] less fat than the beef
produced by earlier-maturing (smaller frame
size) strains or by breecis that were favored
in the past (Byers, Cross, and Schelling,
this volume). However, it would! be cost-
effective to modify cattle growth so that
lean beef could be produced regardless of
the animal's frame size. In the future, ge-
netic engineering may be applied to this
problem, but for now, growth management
121
strategies offer immediate application. These
require scientific knowledge of genetics,
nutrition, ant! growth regulation.
An animal's genetics establishes the pat-
terns, limits, and types of growth that can
be obtained. Nutrition affects the rate of
deposition of fat and protein in the growing
animal. As the growth rate increases, the
proportion of protein decreases while the
proportion of fat increases. Thus, animals
manager] in (referred feeding programs will
be leaner at any slaughter weight and will
also be heavier when typical slaughter end
points are reached (Byers, Cross, ant]
Schelling, this volume).
Integrated growth management programs
seek to regulate growth by synchronizing
nutrient supplies and nutrient needs to
support the type of growth desired. The
use of growth hormones, growth hormone
releasing factors, beta-acirenergic agonists,
and immunization strategies to remove neg-
ative feedback on growth may later prove
useful in these programs (Schelling and
Byers, this volume). For the present, ana-
bolic implants are effective as growth pro-
moters, shifting nutrients from fat cleposi-
tion to protein accretion ant! also enhancing
growth rates (Byers, Cross, and Schelling,
this volume).
Current technologies to optimize tissue
growth include synchronization of nutrition
with the animal's needs for protein growth,
continuous clelivery of repartitioning agents
in all phases of growth from birth to slaugh-
ter, and use of intact male animals, which
provide leaner cuts than do cows or castrated
bulls (Byers, Cross, and Schelling, this vol-
ume). Desired results are reduction of fat
deposition; generation of leaner beef through
production rather than trimming; mainte-
nance of desirable beef quality, flavor, an(l
taste; and establishment of beef as a "lean"
product. Research programs should be tar-
geted to yield beef products that meet
consumer preferences, to implement avail-
able technology, ant] to develop new tech
OCR for page 122
122
DESIGNING FOODS
nologies that allow more precise regulation odor in the meat). Other potential applica
lions might result from research showing
that immunization of lambs against soma
tostatin can improve growth and that im
munization of rats against differentiation of
preadipocytes into fat cells can result in a
30 percent reduction in carcass fat (Speer,
this volume). This last technique has been
extended experimentally to sheep, and
theoretically could be applied to any spe
cies, including swine, cattle, and poultry.
Overall, a number of options are currently
available to the producer to change carcass
composition in the market hog, an(l several
other experimental products or procedures
hoicl promise for reducing fatness en cl in
creasing muscularity. However, the pork
industry requires guidance on desirable lev
els of fat in lean tissue to ensure consumer
acceptance of its products.
Ot growth in animals to meet market needs.
S.
wine
Dramatic changes in swine carcass com-
position have occurred during the past 15
years of genetic selection, yielding the mod-
ern lean-type hog. More options are avail-
able to further reduce back fat and increase
muscling such as breeding, nutrition, man-
agement, and endocrinology (Speer, this
volume).
The percentage of fat in market hogs
differs among sex classes with intact males
(boars) being lowest, females (gilts) inter-
mediate, and castrates (barrows) highest.
The percentage offal also varies with weight;
above 90 kg, lean generally plateaus and fat
increases. Nutrition has some influence;
increasing protein intake can reduce fat
deposition, while increasing fat intake has
the opposite effect. Restriction of the ani-
mal's overall feed intake increases the pro-
portion of lean tissue in the carcass. In
addition, the fatty acid composition of die-
tary fats directly correlates with fat clepo-
sition in the animal. Thus, increasing the
percentage of unsaturated fatty acids in the
pig's cliet will cause an increase in unsatu-
rated fatty acids in the carcass tissue (Speer,
this volume).
A number of hormones can be adminis-
tered to improve carcass composition in
favor of lean tissue, including methyTtestos-
terone, epinephrine, ant] the beta-acirener-
gic agonists (Speer, this volume). Porcine
somatotropin, administered by daily injec-
tion, has been shown to improve daily gain,
feed efficiency, and carcass measurements
(Etherton, this volume). It can now be
manufactured in large quantities via genet-
ically engineered bacteria, thus expanding
possibilities for its field application.
A new application of immunology to swine
production may come from recent work on
immunization against androstene steroids
(those compounds that cause boar or sex
Poultry
Fat content varies in ciressed, ready-to-
cook broilers. As the percentage of fat in-
creases, the percentage of protein, minerals,
en cl vitamins (lecreases. Thus, the fat con-
tent of poultry affects its nutritional value
more than does any other factor. Broilers
currently have 2 to 3 percent of their live
body weight as abclominal fat, which is often
cliscarcled before cooking. The total body
fat of broilers ranges from 15 to 20 percent
of live weight ant! is mostly subcutaneous.
Muscle fat varies less than skin or abclominal
fat (Gyles, this volume), but intramuscular
fat is higher in reel muscle (leg and thighs)
than in white muscle (breast).
Several genetic options exist to recluce
fat in broilers. Strain selection against fat is
practiced commercially. Canclidate breeil-
ers can be chosen on the basis of fat content
of spent (lams, but this methoc] is not
currently used. Selection for improved feet]
efficiency is effective both in reducing fat
deposition ant! in improving growth and
carcass yiel :1 and is wiclely used in the
poultry industry. Selection directed against
OCR for page 123
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
very-low-density-lipoproteins in sera re-
duces final carcass fat and is used to some
extent in the poultry industry (Gyles, this
volume).
Nutrition options are considered short
term and palliative compared with genetic
solutions, but many nutritional components
can be manipulated to reduce fat content
in poultry. Changing the energy to protein
ratio in favor of protein; attention to protein
quality in feed; restricting feed intake during
early life or, alternatively, shortly before
marketing; ant! formulating special feeds for
males versus females to precisely meet nu-
tritional requirements can all reduce final
carcass fat percentage. In additions the type
of dietary fat determines the chemical com-
position of carcass fat: a diet rich in unsat-
uratec] fatty acids results in an increased
proportion of unsaturated fatty acids in the
carcass (Gyles, this volume).
Management options include marketing
broilers at younger ages and at a smaller
size and weight to reduce fatness, growing
males and females separately to address
their different feed requirements, and al-
lowing marketing of younger females ant!
older mates (Gyles, this volume).
The most practical of these options to
reduce fatness, subject to the needs of a
particular poultry organization, may be ge-
netic-strain selection against abdominal
fat, selection against very-Iow-density lipo-
proteins in blood sera, and selection for
improved feed efficiency-and nutri-
tional- manipulation of the energy to pro-
tein ratio and restriction of feed energy
shortly before marketing.
Milk
Milk fat, lactose, and proteins are syn-
thesized in the mammary gland cells from
precursors absorbed from the blood. They
are releaser] in the milk by apocrine, mer-
ocrine, or holocrine secretion. Many phys-
iological and environmental factors can in-
fluence milk secretion; among those related
123
to increases in yield are increased body
weight, advancing age, increased level of
nutrition, fall or winter calving, and mocI-
erate or cool environmental temperatures
(Gorewit, this volume).
Fat content in milk can vary, subject to
a variety of factors. Natural variation among
breeds of dairy cows ranges from 3.4 to 5.6
percent milk fat (Bonner, 1974~. Total milk
yield! ant] percentage composition of milk
constituents have a negative genetic corre-
lation, making it difficult to breed to im-
prove both traits simultaneously (Linn, this
volume). Milk fat ant! protein content are
positively correlated (Bonner, 1974~; thus,
genetic selection for lowered] fat content
should also decrease protein content. Cur-
rent dairy industry incentives are geared
toward the maximum production of milk
that contains the maximum content of both
fat and protein.
During a normal lactation of the dairy
cow, the milk yield starts at a high level,
peaks 3 to 6 weeks after calving, and then
gradually declines toward the end of lacta-
tion (Gorewit, this volume). Milk fat an(l
protein percentages are inversely related to
milk yield (Gorewit, this volume); in adcli-
tion milk fat percentage can be affected by
environment/management and health/phys-
iology. Variations occur with stage of lac-
tation, season, and the milking process.
Mastitis can also affect fat content, as can
hormones. However, one of the most im-
portant means for causing variation appears
to be diet (Linn, this volume).
Cows can be made to produce milk with
a lowered fat content by feeding on a high-
concentrate/low-roughage diet (Gorewit, this
volume). This diet also increases the pro-
portion of unsaturated fatty acids in the
milk. However, high-concentrate/low-
roughage diets can cause health problems
in cows, notably rumenitis and liver ab-
scesses, and therefore have not been used
commercially. It has been shown, though,
that milk fat percentage can be lowered
from the normal 3.5 percent to 1.0 percent
OCR for page 124
124
in severe cases of"milk fat depression"
(Linn, this volume).
Other dietary changes can also cause milk
fat depression, inclucling heat-treatec] or
pelleted feeds, the physical form of the
~ ~ ~ ~ ~ ~ ha ~
preferences.
feed, the amount of dietary fat, and the
lushness of pasture. However, high-grain/
low-roughage is the most important type of
fat-depressing diet (Bonner, 19741. It may
speed up nutrient passage, allowing less
time for absorption of milk fat precursors,
and alter rumen fermentation to increase
the proportion of propionate, causing changes
in physiological pathways that lead to de-
creased milk fat synthesis. Furthermore,
insulin levels may rise, inhibiting mobili-
zation of fat from adipose tissue (Bonner,
1974; Linn, this volume). Little research
has been performed on the long-term health
effects of fat-clepressing diets in cows.
Dietary fats themselves can alter milk fat
composition. They can appear in milk fat
without being changed during digestion and
absorption, or they can be hydrogenate by
rumen microorganisms or dehydrogenated
before their incorporation into milk fat.
They can also affect lipid metabolism in the
animal. It is possible to increase the pro-
portion of polyunsaturated fatty acids in
milk fat by increasing their proportion in
dietary fat through the use of oilseect sup-
plements (Linn, this volume). A variety of
dairy products have been test manufactured
from such milk. However, increaser] po-
lyunsaturated fatty acids reduce shelf life
via faster oxidation, which also changes
product flavor, aroma, and color. There are
conflicting reports on the direction of change
in total milk fat content when the proportion
of polyunsaturated fatty acids in the diet is
increased.
Altering the Level of Fat in Animal
Products
Various processing technologies exist that
can alter the fat level or change fat com-
position in animal products. Whether these
DESIGNING FOODS
will be used commercially depends on such
factors as product safety, economics of man-
ufacture, storage life, and effects on sensory
characteristics and product identity, as well
as on ~overnrnent regulations and consumer
Processed Beef, Lamb, and Pork
Commercial production of"95 percent
fat-free" hams has been a notable success.
The technique of"restructuring" a product
probably represents the ultimate in fat re-
duction, since muscle with all visible surface
and seam fat removed still contains about
0.5 to 5.0 percent fat as intramuscular fat
and extractable intra- and intercellular lipids
(Rust, this volume).
The commonly accepted level of 25 to 30
percent fat in cooked sausage is difficult to
reduce without causing the meat to have a
rubbery, tough texture. This can be offset
by added water, but current USDA regu-
lations restrict this practice (Rust, this vol-
ume). It might be better to regulate sausage
composition based on minimum protein
instead of the current fat and water maxi
mums.
It is also possible to substitute a non-
binding protein for some of the fat in sau-
sage. For instance, 10 percent cooker! pork
skins can be substituted for 10 percent pork
fat in (Iry sausage. USDA labeling require-
ments for identifying "mechanically sepa-
rated meat" may discourage processors from
adopting this technology and using this
product because of fear of consumer resist-
ance (Rust, this volume).
Fat can be modified in processed meat
products by substituting vegetable fats and
oils for animal fat. For example, vegetable
oil preemulsified with milk proteins can be
substitutes] for two-thirds of the animal fat
in bologna. Stabilizer! preemuisions can be
used to reduce visible fat in meat products.
However, current USDA labeling require-
ments prevent commercial applications of
either of these proceclures.
OCR for page 125
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
Poultry
Poultry products have a relatively high
nutrient to calorie ratio. Even so, poultry
meat is the current focus of fat-recluction
technologies seeking to increase preference
for poultry in the consumer market. Be-
tween 1965 and 1985, per capita U. S. poul-
try consumption increased 72 percent; how-
ever, this reflected a 54 percent decrease
in whole poultry consumption and a 575
percent increase in further processed poul-
try consumption. Three-quarters of the
poultry consumed in 1985 was cut up or
further processed (Mast and Clouser, this
volume). Thus, the growth potential in this
industry lies in increasing the demand for
poultry convenience foods rather than in-
creasing purchases of whole bircis.
The fat content of skinless, uncooked
poultry is low, ranging from 1.6 to 4.9
percent, depen(ling on the type of bird and
the type of meat (light versus dark). These
amounts of fat increase four- to sevenfold
for meat with the skin intact (Mast ant!
Clouser, this volume). As with most other
meats (beef, veal, pork), less than half of
the fatty acids in poultry are saturated, but
the proportion of polyunsaturated to satu-
rated fatty acids is higher in poultry than in
other meats. When total lipids are decreases]
in poultry, the proportion of phospholipicls
and cholesterol rises en cl the proportion of
triglycericles clecreases. There is slightly
more cholesterol ant! a higher overall fat
content in dark versus light meat because
of the fat depots between muscles. The
depot fat, however, has more triglycericles
than does the intramuscular fat (Mast and
Clouser, this volume).
Consumption of fat from poultry has in-
creased more than threefold since the early
l900s. While this mainly reflects an overall
increase in poultry consumption, chicken
(80 percent of the poultry consumed) has
been higher in fat since the 1960s owing to
changes in breeding and feeding (Mast and
Clouser, this volume). The demand for
125
larger and faster growing birds has led to
production of carcasses with 10 to 15 percent
more fat, most of which lies in the bird's
abclominal fat pad. The fat pad averages 40
grams and is 2.5 percent of total carcass
weight and 10 percent of total body fat.
Consumers remove it before cooking, now
processors are removing it prior to market-
ing. Current poultry production practice
necessitates removal of excess carcass fat at
the processing level, thereby increasing
costs to both processors and consumers.
Poultry frankfurters contain 18 to 22 per-
cent fat versus the 25 to 30 percent fat
found in beef and pork franks. Some pro-
ducers have lowered the fat content of
poultry franks to 13 to 16 percent by using
mechanically deboned poultry from the breast
and neck sections, which contain less fat
than the backs or legs (Mast ant! Clouser,
this volume). However, as with low-fat beef
and pork franks, such products tend to be
rubbery, tough, and less acceptable to con-
sumers.
Fat can also be recluced in fried poultry
products. The four standard] cooking meth-
ods for battered and breaclecl, fries] com-
mercial products all yield a final meat with
similar fat content. Breacled chicken prod-
ucts with reduced fat ant] caloric content
can be manufactured, however, by remov-
ing the skin from the meat prior to breacling
and then hot-air cooking instead of deep fat
frying (which recluces fat by 23 to 31 percent
and calories by 13 to 15 percent), for a total
caloric decrease of 42 to 65 percent and a
final fat content of 27 percent of total calories
(versus 60 percent in conventional cooking)
(Mast and Clouser, this volume). Such cook-
ing systems are likely to become widely
used as consumer demand accelerates for
processed poultry products with lower cal-
ories and fat.
Dairy Products
There is an increasing demand for low-
fat milk products, which are clerived by
OCR for page 126
126
processing whole milk. Processing technol-
ogies can also be used to exploit surplus
milk fat and to separate and concentrate it
for the manufacture of other dairy products.
The cheese-making process concentrates
the protein and fat components of milk,
reduces the water, ant! eliminates the car-
bohydrate. The whey derived from cheese
manufacture can be further processed to
concentrate the highly nutritional proteins
lactalbumin and lactoglobulin. UltrafiItra-
tion is now being used to concentrate whey
proteins, to manufacture cheese base for
further processing, and to concentrate milk
fat and protein for other cheese manufacture
(Hettinga, this volume). Ultrafiltration is a
high-pressure microfiltration process that
selectively segregates components of var-
ious molecular weights. Milk-processing
membranes have been cleveloped with vary-
ing pore sizes to retain fat and protein while
letting lactose, water, ant] salts pass through.
While the United States has a surplus of
butterfat, it is still relatively expensive and
therefore often substituted for, rather than
used in, food formulation.
Methods of Altering Cholesterol Levels
in Animal Products
Milk
The concentration of cholesterol in bovine
milk ranges between 10 and 15 mg/100 ml,
or 0.2 to 0.4 percent of total milk lipid.
Milk cholesterol is 95 percent unesterified;
the balance is esterified to long-chain, usu-
ally saturated, fatty acids. Seventy-five per-
cent of milk cholesterol is dissolved in milk
fat, 10 percent is in the fat globule mem-
brane, and 15 percent is in the skim milk
(Hettinga, this volume). The effects of com-
mercial processing on the concentrations
and distribution of milk cholesterol are poorly
defined, but this information is needec] so
that technologies can be applied to decrease
the cholesterol content of milk.
DESIGNING FOODS
A cholesterol reductase from species of
Eubacterium might have use in converting
milk cholesterol into coprostanol and cho-
lestanol, which are poorly (or not at all)
absorber! by humans. Supercritical carbon
dioxicle extraction also holds promise for
reducing the level of cholesterol in milk.
However, it will be necessary to penetrate
the milk fat globules, which contain most
of the cholesterol, without destroying the
globules themselves (Hettinga, this vol-
ume). In general, supercritical fluid extrac-
tion works by penetrating the structure of
a material to be separated, dissolving soluble
components, and carrying them away. Ad-
vantages of this method compared with
conventional extraction techniques include
reducecl energy costs, higher yields, lower
operating temperatures (yielding better
quality products), and elimination of explo-
sive or toxic solvents. At present, this tech-
nology is too expensive and its technical
feasibility for removing lipids an(l choles-
terol is questionable.
.
Eggs
Annual egg consumption has declined
consistently since the 1940s, from 400 to
260 eggs per capita (Mast and Clouser, this
volume). This is largely attributable to health
concerns about cholesterol, which is present
at the level of 545 mg/100 grams of whole
egg, or about 270 mg per large egg. Much
past research focused on how to reduce egg
cholesterol by altering hens' diets or by
genetic selection; these approaches met with
varying degrees of success (or failure). Over-
all, the nutrient composition of eggs has not
changed greatly in response to modern
industry practices.
Eggs from hens fed the usual commercial
diets differ little in the amount of cholesterol
they contain. While unusual diets can increase
or (lecrease cholesterol, they also tend to have
cleleterious effects on the nutritional value of
the egg or the hen's performance. Drugs
OCR for page 127
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
adcled to hens' diets can reduce cholesterol
in eggs, but they have harmful sicle effects
(Gyles, this volume).
Cholesterol in eggs is not affected by age
of the hen, cage versus floor management,
strain of commercial layer, or geographic
location of feed source. Eggs from meat-
type hens, turkeys, ducks, and quails con-
tain greater concentrations of cholesterol
than chicken eggs; however, the former are
rarely consumed in the United States (Gyles,
this volume).
Reducing cholesterol in eggs through ge-
netic selection would be desirable, but to
date, increases have been obtained only
through breeding. Furthermore, some ex-
periments indicate that when the level of
cholesterol per egg decreases, so does the
number of eggs laid (GyTes, this volume).
The alternative is to modify the egg yolk
after the egg is laid, but only processed eggs
(about 13 percent of all eggs now consumed
are amenable to such tactics. Approaches
have included dilution of whole liquid egg
with egg white ant! removal of portions of
the yolk lipids and cholesterol with "sol-
vents" to reduce the cholesterol content of
the final product, and complete removal of
the yolk and replacement with a substitute
"yolk" made from vegetable oils and other
ingredients to produce a cholesterol-free
product. Numerous U. S. patents have been
obtained toward these ends, nine of which
are discussed in detail by Mast ant! Clouser
(this volume).
Supercritical fluid extraction, which may
be able to selectively extract cholesterol
without removing the polar lipids that are
responsible for functional and sensory prop-
erties in egg products, might be an alter-
native to solvent extraction. Supercritical
fluid extraction utilizes the high-density/
low-viscosity properties of supercritical fluids,
which are gases subjected to high pressures
at temperatures above their critical point.
Supercritical fluids can readily diffuse into
and out of foods, thereby increasing extrac
127
tion efficiency. By varying the fluicl's density
through changes in pressure, its solubility
can be adjusted to preferentially extract
certain components of interest. To date, this
technology has not been used on eggs or
egg products. However, research is under
way to extract cholesterol from the egg yolk
with supercritical carbon dioxide at various
temperatures and pressures (Mast and
Clouser, this volume).
Poultry, Beef, Veal, Pork, and Lamb
The cholesterol content of muscle tissue
varies less than the lipic] content and has
been found to be fairly constant across and
within maturity groups (Stromer et al.,
1966), among yield grades (Rhee et al.,
1982), and across breed type and nutritional
background (Eichhorn et al., 1986~. It is
possible to fincl variation in the cholesterol
content of meat, however, because adipose
tissue tends to have a different concentration
of cholesterol than muscle (Allen, this vol-
ume). Consequently, differences in the
amount of subcutaneous or intermuscular
fat consumed with the lean portion can alter
cholesterol intake. It has been calculated
that 37 to 56 percent of the cholesterol in
a cooker! rib steak of beef originates from
subcutaneous and intermuscular adipose tis-
sue (Rhee et al., 1982~. It is possible that
supercritical fluid extraction could be aciaptec3
to remove cholesterol from meat products.
Methods To Alter Sodium Levels in
Animal Products
Salt is an important ingredient in many
food-processing techniques. However, diets
containing no added salt already provide
1.0 to 1.8 grams of sodium a clay, which
clearly exceeds the daily requirement of 0.5
to 1.0 grams. When salt added by consumers
in cooking and at the table is considered,
per capita ciaily consumption exceeds 3.6
OCR for page 128
128
grams. This does not include salt consump-
tion due to the ingestion of processed foods,
which can be substantial.
Meat Products
Salt (sodium chIoricle) has three major
functions in a meat product: preservation,
promotion of binding properties in proteins,
and flavoring.
Salt is important in preserving dry-curec!
meats (for example, hams and certain sau-
sages); in fact, some research points to an
increased danger of toxins arising if salt in
cured meats is lowered beyond a certain
point. Yet, no minimum effective salt levels
have been set. Clearly, it is necessary to
achieve a brine concentration sufficient to
inhibit growth of molds, yeasts, ant] micro-
bial pathogens. Research on salt/citrate/
phosphate interactions and their effects on
pathogens is needed! (Rust, this volume).
The role of salt in protein-binding prop-
erties is twofoIc3. First, it extracts salt-
soluble myofibrfllar proteins that then en-
capsulate fat particles to create a stable
"emulsion" or meat batter. Second, it pro-
motes swelling of these proteins, which
exposes more bonding sites for water. These
properties are neecled to produce stable
sausages (Rust, this volume).
The flavor preference for sodium chloride
is an acquired taste. Consumers in general
have reclucec! their sodium intake, and the
meat industry has responder! by lowering
the sodium content of many of their prod-
ucts. Other chlorides can be substituted,
but many present flavor problems. For
instance, potassium chloride has a bitter
flavor and can be substituted successfully
for sodium chloride only at or below the 25
percent level. Furthermore, the health ef-
fects of addecl dietary potassium are stfll
unknown (Rust, this volume). On the other
hand, flavoring agents such as spices can be
used to enhance flavor in place of sodium
chloride.
Alkaline phosphates can be combined
DESIGNING FOODS
with sodium chloride to enhance sodium
function in low-soclium products. Generally,
though, these phosphates are mostly the
sodium salts; hence, actual sodium reduc-
tion is minimal. Use of a number of alkaline
potassium phosphates is allowed] under
USDA-Food Safety and Inspection Service
(FSIS) regulations, including dipotassium
phosphate, monopotassium phosphate, po-
tassium tripolyphosphate, and potassium
pyrophosphate. Their use is limited, how-
ever, by solubility problems, lower func-
tionality than their sodium counterparts,
and the potassium flavor problem (Rust, this
volume).
Poultry Products
Processing of poultry can influence the
sodium content of the meat. Immersion
chflling and hot-deboning both leach sodium
from the tissue, the latter to a greater degree
(Mast and Clouser, this volume). Further
processing of poultry into various manufac-
ture(1 products can also increase its sodium
content.
Sodium can be lowered in processed
products by replacing some or all of the
sodium chloride with calcium chloride, mag-
nesium chloride, or potassium chloride. In
poultry franldurters, for example, 35 per-
cent of the sodium chloride can be replaced
by potassium chloride without adverse ef-
fects on flavor. On the other hancl, mag-
nesium chloride at this level causes off-
flavors (Mast and Clouser, this volume).
Enzymatic modification could partially
alleviate the neec! for salt in processed
poultry products, but spices would have to
be addec! to compensate for changes in
flavor. Phosphate combined with salt can
also serve to produce acceptable low-salt
products. Currently, poultry frankfurters
average 2.2 percent sodium chloride, or 860
mg of sodium/100 grams of meat. This leve!
could be reduced to 1.5 percent sodium
(590 mg/100 grams) by adding phosphate or
even 0.5 percent sodium (197 mg/100 grams)
OCR for page 129
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
with appropriate spice formulations (Mast
and Clouser, this volume).
Milk
The salt system in milk appears to be
regulated by the synthesis of carbohydrates,
casein, and citrate and by leakage of blood
constituents into milk. Sodium is present
mainly as free ions in the diffusible fraction.
Its total measured level in milk is 0.6 ma/
liter; mastitis increases this level. A nutri-
tional regimen for the cow that includes
sodium bicarbonate lowers the sodium con-
tent of milk because it lowers plasma so-
dium. Overall, however, genetics, health,
ant] nutrition have minimal effects on mflk's
sodium content (Linn, this volume). Most
of the salt in dairy products is adcled during
processing, as in the manufacturing of cheese.
Methods To Alter Calcium Levels in
Animal Products
Milk
Calcium is secreted by the Golgi appa-
ratus. Average levels of calcium in milk are
30 mmol/liter, but vary slightly with breed
of dairy cattle ant! stage of lactation. Levels
decline with mastitis. Nutrition of dairy
cattle has little effect on calcium content
(Linn, this volume).
Milk is a particularly goof! source of
calcium. Its absorption and utilization by
humans is facflitated by the presence of
vitamin D, obtained from sunlight or forti-
fied into the milk itself (Hettinga, this vol-
ume). Milk can be further fortified by the
addition of extra calcium. Most milk prod-
ucts, especially cheese, are rich sources of
bioavaflable calcium.
Eggs and Poultry
Two large eggs (about 100 grams total)
contain about 57 grams of calcium (Table 4-
2~. This is at least twice the calcium content
129
of poultry flesh, although storage causes
small increases in the calcium content of
poultry meat due to leaching of calcium
from the bones into the muscle. Cooking
does not significantly affect the calcium
content of poultry, but processing options
can increase the calcium content of such
products as poultry bologna and Dankfurters
(Mast and Clouser, this volume). For ex-
ample, turkey and chicken frankfurters can
contain 88 to 104 mg of calcium.
Methocls To Alter Iron Levels in
Animal Products
Milk
Iron is present in milk at low levels,
approximately 0.05 mg/100 grams. It is
bound to lactoferrins, transferring, casein,
fat globules, and xanthine oxidase (Linn,
this volume). Its concentration is not af-
fected by the cow's (lies (Hettinga, this
volume).
Unfortified cow's milk is a poor source of
iron. Only 10 to 12 percent of the iron
present in cows' milk can be absorber] by
human infants, in contrast to the 50 percent
adsorbability of the iron in human milk. But
if cow's milk is fortified with iron sulfate or
iron gluconate, infants can absorb up to four
times the iron they normally get from human
milk. Iron-fortified milk offers the oppor-
tunity to enrich the diets of infants, children,
adolescents, and pregnant women, all of
whom are at risk for iron deficiency.
Fortification must use chelates! iron to
ensure initial transfer to the phosphoserine
groups of casein; this ligand exchange re-
action protects iron from reactive milk lipids
and promotes effective utilization of this
element (Hettinga, this volume).
Eggs and Poultry
Two large eggs (100 grams total) contain
about 2.08 mg of iron, while 100 grams of
poultry flesh (light meat, roasted contain
OCR for page 130
130
1.06 mg of iron (Table 4-101. Slightly higher
values are present in processed poultry
products macle from mechanically cieboned
poultry (Mast and Clouser, this volume).
Poultry giblets heart, gizzard, and liver
are rich sources of iron. Giblets are under-
utilized in the United States because of
their undesirable texture and functional pro-
tein characteristics. These shortcomings may
be improved, though, by chemical, enzy-
matic, and physical agents (Mast and Clouser,
this volume). The technique with the best
potential is acylation the addition of chem-
ical groups to the functional Ran. on amino
acid sicle chains.
Beef, Veal, Pork, and Lamb
O ~
These animal products contain substantial
amounts of heme iron from the hemoglobin
and myogiobin present in the tissues. Heme
iron is unaffected by other components in
the diet, resulting in consistently high ab-
sorption rates. The iron content of beef
ranges from about 2.0 to 3.8 mg/100 grams;
for pork it is 0.8 to 2.0 mg/100 grams; for
lamb it is 1.5 to 3.2 mg/100 grams; and for
veal it is 0.9 to 1.9 mg/100 grams (see the
composition tables in Chapter 4~.
The blood from these animals would pro-
vicle a concentrated, bioavailable source of
heme iron, but it is rarely used in the
formulation of human food products in the
Uniter! States. Blood is, however, user] in
nonfood products such as fertilizers and feed
aciclitives. Mast and Clouser (this volume)
suggest that blood is not used in foods for
humans in the United States because the
consumer has an unfavorable image of blood
as a food ingredient.
RECOMMENDATIONS
Pre- ant! postharvest technologies provide
insights into options that are currently avaiT-
able for reducing the fat content of animal
products. Even though some of these are
now being applied, others have not yet been
DESIGNING FOODS
adopted because of high costs, lack of de-
man(l, procluct-labeling standar(ls, or, in
some cases, the quality stability of such
products in the marketplace. These prob-
lems must be addressed by both basic and
applied research. In acIdition, other pre-
and postharvest areas of research have been
identified that hold promise for reducing
the fat content of animal products.
The more that is known about the basic
biology offactors controlling the partitioning
of nutrients into protein or fat in animals,
the higher the probability of changing these
processes through genetic or metabolic ma-
nipulation. Just as animal biology is ad-
vancing, so is our unclerstanding of food
science and the postharvest research nee(ls.
These research advances are the basis for
improved and new foods composed of or
containing animal products.
The following research recommendations
suggest areas that could lead to useful new
technologies for addressing the reflection of
fat or salt in animal products.
Preharvest Technology
· Recommendation Develop technolo-
gies for determining carcass fat content.
Current methods are time-consuming, costly,
or not sufficiently accurate.
· Recommendation Alter lean to fat ra-
tios of meat ant] fat content in milk through
breeding, nutrition, and management. These
methods have long been used in response
to market incentives and can result in changes
that range from slow to quite rapid.
· Recommendation Alter the fatty acid
composition of meat, milk, and eggs through
dietary or genetic manipulation. Although
this is more difficult to do in ruminants, it
can be accomplished at additional cost. In
nonruminants, carcass fat readfly reflects
the dietary fatty acid pattern. A major lim-
itation is that shelf life of animal products
is decreased if the fatty acid profile is shifted
too far toward the polyunsaturated fatty
acids.
OCR for page 131
TECHNOLOGICAL OPTIONS AND RESEARCH NEEDS
· Recommendation Improve methodol-
ogies for determining the fat and protein
contents of live animals and carcasses. Rapid,
accurate, ant] cost-effective methodologies
would greatly enhance industry's ability to
determine animal or carcass composition
and thus be of great economic value. Such
technology would also be useful for meas-
uring human body composition ant} for mak-
ing humans more aware of the relationship
of obesity to diet and health.
· Recommendation Identify cellular and
molecular mechanisms that control parti-
tioning of feed nutrients into meat, milk,
ant] eggs. It is well known that livestock
species display considerable genetic varia-
bility in their abilities to convert feedstuffs
into muscle, fat, milk, and eggs. To fully
utilize the tools of biotechnology, much
more information is needed about the exact
genes ant] cellular or molecular mechanisms
that contribute to this genetic variation.
With this information, the probability of
being able to optimize favorable responses
through bioregulation or genetic engineer-
ing will be greatly enhanced.
· Recommendation Determine the ex-
tent of genetic variation in the cholesterol
content of meat, milk, and eggs. Without
this information, it is not possible to know
whether genetic selection or engineering
coulc! be used to develop Tower cholesterol
animal products. In abolition, more research
is needed on the metabolism of cholesterol
in the tissues and on the quantity of cho-
lesterol that is essential to the function of
the cell or organelle. This research need
exists for both animals and humans.
· Recommendation Determine whether
oxidative rancidity of animal products can
be reducecl through special feeding or man-
agement of animals. Some research indi-
cates that beetling vitamin E to nonrumi-
nants decreases the rate of oxidative rancidity
in their meat products. More research is
needed to determine whether other natural
or approved synthetic antioxidants are ben-
eficial in extending product shelf life.
131
· Recommendation Develop more cost-
effective methods for producing low-fat an-
imal products by integrated production
management systems. Systems analysis is
an elective method for examining the mul-
titude of biological, physical, and economic
factors that influence the cost-effectiveness
of programs and processes for reducing or
altering fat in animal products.
· Recommendation Expand research in
the area of reproductive physiology that
would permit rapid selection and propaga-
tion of genetically or metabolically superior
animals. Examples include sexing semen
and embryos, splitting embryos, and gene
insertion and gene expression.
Post-Harvest Technology
Postharvest technologies to reduce fat in
animal products can be used quite satisfac-
torfly in many situations. However, these
technologies are not without costs and are
usually associated with some change in prod-
uct characteristics such as texture, flavor,
or shelf life. In abolition (1epencling on the
product and the changes a variety of reg-
ulatory and labeling issues must also be
addressed.
· Recommendation Use physical meth-
ods to reduce fat at the earliest possible
stage in processing. Some such methods are
being used extensively, including trimming
meat, centrifuging milk, ant! separating egg
yolks and whites. Low-fat milk and meat
products are examples of the results that
can be achieved. Furthermore, use of such
procedures would create by-proclucts of lower
economic value that could! be used effec-
tively in food or, preferably, nonfood pro(l-
ucts. The recommendations ma(le in Chap-
ter 5 to allow hot-fat trimming on the
slaughter floor and to change the USDA
grade standards to allow for uncoupling of
yield and quality grades are in concert with
this recommendation.
OCR for page 132
132
· Recommendation
. ~.
Simulate the tex-
tura~ and sensory properties of fat by using
nonfat or low-fat ingredients. Certain poly-
saccharides and proteins might be useful for
this purpose and could produce satisfactory
results in a number of products if labeling
standards were more flexible.
· Recommendation Adopt standards of
identity that reflect toclay's technology and
consumer needs. In some instances stand-
ards are too restrictive, and even though a
technology exists that could be used to
improve a product, it cannot be applied
because of current regulations.
· Recommendation Reduce oxidative
rancidity to extend product shelf life. The
occurrence of oxidative rancidity is one of
the most serious limitations to adequate
shelf life and optimal palatability of many
animal products. Use of certain packaging
tech nolo gie s an d approve c! an tioxician ts an cI
control of certain processing variables help
minimize this problem in some, but not all,
products. For example, skim milk and fresh
pork sausage have shortened shelf lives
because of the incidence of oxidative ran-
cidity.
· Recommendation Use fat substitution
to alter the fatty acid! composition of proc-
essed animal products (that is, to increase
the proportion of unsaturates! fatty acids).
However, the potential for increasing the
susceptibility to oxidative rancidity when
the fatty acic] profile is shifted too far toward
unsaturated fatty acids must be considered
and controlled.
· Recommendation Improve metho(lol-
ogies for the analysis of fat ant] sensory and
other quality characteristics of animal crod-
ucts. Rapid, accurate, and cost-effective
analyses are important to the production
and monitoring of a variety of foot] charac-
teristics.
· Recommendation Utilize molecular
genetics and other biotechnologies to im-
prove fermentation processes that are im-
portant in the manufacture of animal prod-
ucts such as cheese, yogurt, and sausage.
DESIGNING FOODS
For example, the newest technologies could
be used to generate new microorganisms
that could reduce the cholesterol content of
the end product.
· Recommendation Determine how se-
lective extraction of saturated fats and cho-
lestero! can be used to reduce these com-
ponents in animal products. The use of
supercritical carbon dioxide as an extractant
shows promise for this purpose.
· Recommendation Search for ways to
safely and organoleptically reduce or replace
sodium in manufactured animal products.
Sodium chloride plays a critical role in
delaying microbial growth, providing flavor,
and contributing to the functional charac-
teristics of many processed products. There-
fore, it should not be reduced or replaced
without serious consideration of the conse-
quences or until a satisfactory replacement
for sodium chloride is found for use in
products such as cheese and sausage.
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Representative terms from entire chapter:
milk fat
