Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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feeding 8-week-old lean and obese animals either a

control diet (15% corn oil) or an SPE diet (5% corn

oil and 10% SPE). The obese, control-fed animals

gained more weight than the animals fed the SPE

diet, while the lean rats given the fat substitute did

not have significantly different body weights com-

pared to the lean controls. It was concluded that the

obese rats could not defend their higher weights when

the fat content of their diet was diluted using SPE.

0049 The first controlled study using sucrose polyester in

humans was conducted in 1982. The effect of using

SPE in hypocaloric diets for obese persons seeking

weight loss was investigated. The effects of SPE and

a hypocaloric diet were studied in a counterbalanced,

crossover design over two 20-day periods. Partici-

pants also had access to non-SPE-modified snacks in

the evening, which provided an opportunity for sub-

jects to compensate for the calorie/fat dilution. Par-

ticipants showed weak compensation for the missing

calories, resulting in a significant overall reduction

in energy intake (P < 0.05) and fat intake (P < 0.05).

However, a potential confounding factor exists be-

cause subjects were actively trying to lose weight in

this study, which may have reduced their likelihood

of consuming snacks. Thus, this study does not

provide an adequate design to assess energy/fat

compensation.

0050 In another study the fat content of the diet of five

obese men confined to a metabolic ward for 36 days

was diluted by replacing the fat in margarine and

mayonnaise with SPE. Energy intake was measured

during three periods: preintervention baseline (days

1–9), intervention (days 10–28), and postintervention

baseline (days 29–36). During the intervention period,

the manipulation created a 10% reduction of overall

energy of the diet. Participants increased the amount

of food consumed during the SPE period relative

to the pre- and postintervention baselines so that

there was no significant effect of diet on energy

intake (baseline ¼3924 kcal day

1

and SPE¼3812

kcal day

1

). Participants did not selectively ingest

more fat, but rather increased their intake of all

three macronutrients to compensate for the energy

dilution created subsequent to the addition of the

SPE.

0051 Parallel studies in the USA and the UK were the

first to study the effect of olestra in lean individuals.

Twenty-four healthy, lean males participated in each

trial that investigated a SPE manipulation in a break-

fast meal (biscuits/scones and margarine). Subjects

were fed the three breakfasts (control ¼765 kcal,

20 g SPE ¼582 kcal, and 36 g SPE ¼445 kcal) in a

counterbalanced, crossover design followed by self-

selected lunch and dinner meals. Subjects also

recorded any evening snacks to account for 24-hr

energy intake. Despite geographical differences, simi-

lar results were obtained in both studies. The lean

men compensated well when the breakfast was

reduced in energy and fat due to SPE replacement,

but there was very little fat-specific compensation.

The end result was a significant (P < 0.0034 and

P < 0.0066) reduction in fat consumption in the 20 g

and 36 g SPE substitution, respectively, compared to

placebo.

0052Children also appear to compensate well for energy

deficits, but not for fat specifically. In one study

(Birch et al., 1993), the intakes of 29 normally de-

veloping 2–5-year olds were measured during 2 days

per week over 5 weeks. Approximately 14 g of SPE

was substituted for fat (125 kcal) in the children’s

diet over the course of the morning and afternoon. By

the end of the first day, the children had compensated

for some of the energy dilution and by the end of the

second day they had compensated for all but 24 of

125 kcal. Like the adult men, children did not show

macronutrient-specific compensation. Instead, the

manipulation produced a reduction in the percentage

of fat consumed without a reduction in total energy of

the diet because the children increased their intake

from carbohydrate sources.

0053In other studies, neither fat nor energy compen-

sation was detected when SPE was incorporated

into foods. In one study 47 g of SPE was incorporat-

ed into meals and snacks across a day (creating a diet

which derived 20% of energy from fat). This manipu-

lation represents a more severe reduction in the

amount of fat replaced by SPE than in previous stud-

ies. The results were that this level of fat/energy

reduction was not compensated for during the day

that SPE-replaced foods were provided, and only

partial (74%) energy compensation occurred the

following day. Incomplete fat/energy compensation

was also seen in two studies from the Netherlands.

The first incorporated SPE into croissants and found

incomplete short-term energy compensation so that

daily energy intake was reduced. This group also

found that energy was not fully compensated for in

a study which used SPE to replace fat in warm meals

over a longer term (12 days). However, these studies

used control meals that were actually higher in fat

content and energy content than the typical Dutch

meal, as either triglyceride oil or SPE oil was simply

added to dishes. This resulted in a ‘surfeit’ of fat

and energy in the control condition, while the SPE

condition matched more closely the fat and energy

content of the typical Dutch meal. Given this and

other methodological issues, firm conclusions on

energy compensation cannot be based on these data.

0054Overall, therefore, the efficacy of using foods pre-

pared with SPE to reduce fat and/or energy intake is

2258 FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake

equivocal. The existing evidence from the relatively

few studies that have been published suggests that

SPE incorporation into foods may aid in reducing

the amount of fat consumed. The evidence is, how-

ever, less clear regarding SPE’s efficacy in reducing

total energy intake. Again, it is important to note

that all of these studies used covert manipulations:

participants were unaware of the fat manipulation.

This may or may not be representative of how such

products will be consumed in a free-choice, full-

knowledge setting. More studies are, therefore,

needed to clarify the effects of fat replacers on energy

intake.

0055 There has also been considerable focus on possible

negative health effects associated with SPE, especially

olestra, most notably gastrointestinal (GI) complaints

and decreased absorption of fat-soluble vitamins.

Since olestra is nonabsorbable and passes through

the gut unchanged, it has been anecdotally linked

with GI complaints such as diarrhea, bloating, and

cramps. However, one study found no difference in

prevalence of GI complaints following a single epi-

sode of snacking on chips made with triglyceride or

chips made with olestra. Unpublished data from the

Olestra Post-Marketing Surveillance Study (OPMSS)

found only a limited association with one symptom

(bloating) among the highest consumers of olestra. In

addition, OPMSS data indicate that GI complaints

are rarely attributed to fat replacers such as olestra,

while most food-related GI problems are attributed to

beans, and spicy and diary foods. Further, another

study, also using OPMSS data, found that olestra

consumption was not associated with changes in

serum carotenoids or serum concentrations of other

fat-soluble vitamins; however, serum vitamin K was

higher in the highest consumers of olestra. This may

be due to olestra being fortified with vitamins A, D, E,

and K. Thus, according to current measures, olestra

does not present a significant risk of GI upset or

reduced absorption of fat-soluble vitamins.

Conclusions

0056 In this article, we have examined the available data

regarding whether or not reduced-fat foods, espe-

cially those made using fat-replacer technology, are

useful in reducing the current trend to overconsume

dietary fat and energy in western societies. This ques-

tion is difficult to answer because it is only since the

1980s that dietary fat consumption has been a focus

of nutritional research, and many of the advances in

fat-replacer technology are of even more recent vin-

tage. What is clear is that foods that taste good are

consumed more readily than those that do not. Thus,

it is axiomatic that the availability of low- or no-fat

foods that are also highly palatable may aid in com-

pliance with low-fat diets that were previously bland

and unsatisfying. However, while fat-replaced foods

offer consumers new food choices, considering the

conflicting data, it should not be assumed that the

use of fat-replaced foods will, indeed, result in signifi-

cant reductions in fat and energy intake.

0057The research cited in this article supports the notion

that fat-replaced foods may aid in reducing dietary fat

intake, but perhaps not overall energy intake. Most

studies using traditional low-fat foods and currently

available fat-replaced foods have resulted in at least

partial compensation for energy reductions, but have

not resulted in macronutrient-specific (or fat-specific)

compensation. Results from SPE studies are equivocal

in respect to energy compensation, with some finding

energy compensation, while others do not. Better

controlled, laboratory-based human studies are

needed to estimate just how useful SPE replacement

will prove to be in reducing overall fat and energy

intake.

0058Also still unclear is how consumers will use new

and existing fat-replaced foods. Will they be used as a

one-to-one substitution for foods previously high in

dietary fat, or as a license to overeat other rich foods?

It may be that the most important predictors of the

successful use of fat-replaced products will be the

motivation of the consumer to bring about a reduc-

tion in his/her intake of dietary fat. More naturalistic

studies exploring the potential usage patterns of fat-

replaced products are needed to determine their use-

fulness in bringing about these desired dietary

changes, and additional nutrition education regarding

fat-replaced foods is necessary among those with diet-

modifiable diseases, such as type 2 diabetes, cardio-

vascular disease, and hypertension.

0059Because overall energy intake has been shown to be

a critical factor in weight loss and weight mainten-

ance, the use of fat-replaced foods alone should not be

expected to produce spontaneous improvements in

weight management or obesity. Lasting changes in

body weight will still be dependent upon long-term

behavioral change that includes not only modification

of fat intake, but also reductions of overall energy

intake, along with an increase in energy expenditure.

Because fat is the most energy-dense macronutrient,

substituting low-fat foods can substantially reduce

the energy density of the diet, provided these foods

are also low in energy. If the energy density of the diet

is reduced and the volume of intake remains constant,

reductions in total energy intake are likely.

0060These caveats aside, fat-replaced foods, like other

modified foods (e.g., with aspartame or saccharin)

could aid motivated individuals to reduce their intake

of dietary fat and energy. Thus, fat replacers may

FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake 2259

prove a useful tool in reducing fat intake, but, as with

most novel approaches, more detailed investigations

need to be conducted to examine the efficacy of such

products in reducing fat intake. Future studies are

needed to resolve issues of fat and energy balance

using fat-replaced foods, especially those replaced

by SPE, and how such foods can be used to alter the

energy density of the diet. Results of such studies will

have important implications for how fat-replaced

foods should be used in the prevention and treatment

of obesity and related conditions such as cardiovas-

cular disease and diabetes. Longitudinal studies, both

laboratory-based and naturalistic, need to be con-

ducted to determine the best strategies for long-term

compliance with a low-fat, low-energy-density diet.

See also: Energy: Intake and Energy Requirements; Fats:

Fat Replacers; Obesity: Etiology and Diagnosis; Fat

Distribution; Treatment

Further Reading

Bell EA, Catellanos VH, Pelkman CL, Thorwart ML and

Rolls BJ (1998) Energy density of foods affected energy

intake in normal-weight women. Am J Clin Nutr 67:

412–420.

Birch LL, Johnson SJ, Jones MB and Peters JC (1993)

Effects of a nonenergy fat substitute on children’s energy

and macronutrient intake. Am J Clin Nutr 58: 326–333.

Cheskin LJ, Miday R, Zorich N and Filloon T (1998)

Gastrointestinal symptoms following consumption of

olestra or regular potato chips: A controlled compari-

son. JAMA 279: 150–152.

Drewnowski A and Greenwood MRC (1983) Cream and

sugar: human preferences for high-fat foods. Physiology

and Behavior 30: 629.

Duncan KH, Bacon JA and Weinsier RL (1983) The effects

of high and low energy density diets on satiety, energy

intake, and eating time of obese and nonobese subjects.

Am J Clin Nutr 37: 763.

Gatenby SJ, Aaron JI, Morton G and Mela DJ (1993)

Nutritional implications of reduced-fat foods in free-

living consumers. Appetite 21: 178.

Glueck CJ, Hastings MM and Allen C (1982) Sucrose

polyester and covert caloric dilution. Am J Clin Nutr

35: 1352.

Harris RBS (1994) Factors influencing energy intake of rats

fed either a high-fat or a fat mimetic diet. Int J Obes 18:

632.

Harris RBS and Jones WK (1991) Physiological response of

mature rats to replacement of dietary fat with a fat

substitute. J Nutr 121: 1109.

Kendall A, Levitsky DA, Strupp BJ and Lissner L (1991)

Weight loss on a low-fat diet: consequence of the impre-

cision of the control of food intake in humans. Am J Clin

Nutr 53: 1124.

Lissner L, Levitsky DA, Strupp BJ, Kalkwarf HJ and Roe

DA (1987) Dietary fat and the regulation of energy

intake in human subjects. Am J Clin Nut 46: 886.

Mela DJ and Sacchetti DA (1991) Sensory preferences for

fats: relationships with diet and body composition. Am J

Clin Nutr 53: 908.

Miller DL and Cheskin LJ (1999) Acceptance and use of fat-

replaced foods in persons with diabetes: Olestra Post-

Marketing Surveillance Study. Abstract. Society for the

Study of Ingestive Behavior, Annual Meeting.

Miller DL, Castellanos VH, Shide DJ, Peters JC and Rolls

BJ (1998) Effect of fat-free potato chips with and with-

out nutrition labels on fat and energy intakes. Am J Clin

Nutr 68: 282–290.

Rock CL, Thornquist MD, Kristal AR, Patterson RE,

Cooper DA, Neuhauser ML, Neumark-Sztainer D and

Cheskin L (1999) Demographic, dietary and lifestyle

factors differentially explain variability in serum carote-

noids and fat soluble vitamins: baseline results from the

sentinal site olestra post-marketing surveillance study.

J Nutr 129: 855–864.

Rolls BJ and Hammer VA. Fat, carbohydrate and the

regulation of energy intake. Am J Clin Nutr, in press.

Shide DJ and Rolls BJ. Information about the fat content of

preloads influences energy intake in healthy females.

J Am Diet Assoc, (submitted).

2260 FAT SUBSTITUTES/Use of Fat-replaced Foods in Reducing Fat and Energy Intake

FATS

Contents

Production of Animal Fats

Uses in the Food Industry

Digestion, Absorption, and Transport

Requirements

Fat Replacers

Classification

Occurrence

Production of Animal Fats

T J Wertelecki and R K Bodarski, Wroclaw

Agricultural University, Wroclaw, Poland

Introduction

0001 All metabolic processes carried out in animal cells

depend on exogenous energy sources. The level of

anabolic and catabolic processes in plant cells is

lower compared with animal cells, especially with

organisms of stable temperature. The chemical com-

position of food for humans and animals are exogen-

ous sources of energy synthesis, which is in contrast to

the plant world, where one of the energy sources is

solar radiation – the warranty of photosynthesis.

0002 The main energy sources are carbohydrates and

fats and occasionally proteins. The highest values of

energy content derive from lipids (energy donors);

lipids are also an important form of energy store in

animals (acceptor energy). Fat (animal fat) has

another more important function in organisms: stor-

ing metabolic water (endogenous water); as building

timber; creating the structure of muscle; and as pro-

tection for other organs – kidneys, liver, intestine, and

pancreas. The main function of lipids in organisms is

thermostability. Lipids are often connected with lipo-

phil vitamins: A, D, E, and K. Lipids are an important

source of essential and important fatty acids. As

animal fat is vital it is suggested that is impossible to

eliminate fat (animal fat) from the human diet and

especially from that of animal.

Evolution of Human and Animal

Production

0003 The evolution of the species Homo sapiens was con-

nected with the animal world. In the earliest times

human beings were hunters, who trapped animals for

food – meat (protein and fat) and skin were of the

greatest value. From the beginning of hunting,

humans began a new era of human nutrition (with

animal products on the menu). Later on humans bred

animals and so could use animal produce without

hunting: animals were domesticated in Asia nearly

10 000 years ago and in Europe 5000 years ago.

From this time humans started to carry out breeding

programs with animals. Initially breeding animals

was uncharted territory but as civilization evolved,

it was based on developing sciences. The underlying

aim was to increase production value of domestic

animals, but at first civilization developed faster

than animal production. The principles and aims of

breeding focused on one thing only: more animal

products – meat, milk, eggs. At that point the quality

of the product was not an issue, because there was

always a lack of energy and protein.

0004The revolution in the ideas behind animal breeding

started with the development of human food sciences.

A wider knowledge of human nutrition created new

expectations for animal products, especially as far as

quality was concerned. The top priority was animal

protein as a source of amino acids (exogenous) for the

human diet. The production of animal protein in

meat, milk, and eggs increased over time and correl-

ated with this an increase in production of animal fat.

This fat was concentrated in tissue, which is impos-

sible to eliminate in an organism. At the same time,

opinions on the harmful effect of animal fat on

human health were proposed by respected academics,

and the lipid theory of coronary heart disease was

expounded. This opinion changed the culture of

human nutrition towards a decreased use of animal

fat and increased use of plant oils. For example, in the

USA consumption of animal fat was reduced by about

21%, over a 30-year period, and in developing coun-

tries over a similar period (correlated with a marked

lack of protein-energy balance in the diet) the con-

sumption of animal fat increased by about 80%! This

situation created a negative balance between produc-

tion and consumption of animal fat. In developing

FATS/Production of Animal Fats 2261

countries now there is substantial overproduction of

animal fat (with regard to the high breeding value of

domestic animals) (Table 1).

0005 The development of food sciences and chemical

analysis has shown that consumption of animal fat

is beneficial for human health: oily fish, modified

concentrate and ratio of fatty acids in meat, and

eggs. This opinion has suggested the possibility of

the changed value of animal fat preferred by human

food direction.

The Process of Lipid Synthesis in Animal

Organisms

0006 The main function of fat in animal organisms is as an

energy-building store. The animal organism accumu-

lates energy in glycogen stored in muscles and liver,

but it is only 1% of energy used. The main sources

of endogenous energy are accumulated in fatty acids

which create fat tissue. The synthesis of endogenous

animal fat could be conducted metabolically from

carbohydrates, feed fat, and proteins. Part of this

endogenous fat is synthesized in a simple way by

absorbing and building in organs fat form without

transforming it from feed fat. The main precursor of

the fat synthesis process is coenzyme A (Co-A), which

is created by the chemical conversion of carbo-

hydrates and exogenous lipids.

0007 Fat synthesis is an important chemical process

which guarantees the stabilization of the organism.

The main organ of lipid synthesis or degradation is

the liver. The liver is a many-sided organ which is

useful for energy and the process of metabolism.

There are between 800 and 2000 mitochondria in a

cell of the liver. Lipid synthesis in animal cells is an

effect of positive energy balance. Intake delivers a

high energy level compared with requirements. This

energy is supplied by carbohydrates (starch for mono-

gastric animals, as it can be easily digested, and for

ruminants structural carbohydrates such as cellulose

or easily digested starch) and secondly by exogenous

lipids in the form of fat. Occasionally proteins supply

energy for the chemical process in the organism.

0008 Starch is the most important carbohydrate in

animal production: it is used for energy and lipid

synthesis. For example, 1 g of starch provides

4.15 kcal GE g

1

while 1 g of fat provides 9.4 kcal

GE g

1

(GE, gross energy (calorimetric value)).

Excess intake of energy concentrated in carbohy-

drates can be metabolized to fat in the cells of the

liver and stored.

0009 The basic biochemical structure of animal

endogenous lipids is the chylomicron, which can be

transported with blood and deposited in fatty tissue.

Accumulated exogenous fats can be transported from

the digestive tract to the blood and fat tissue without

transformation in a similar way.

0010Fat synthesis is conducted in the organism in two

ways: (1) liponeogenesis – biosynthesis of different

specific fatty acids in liver cells; and (2) lipogenesis –

synthesis of triacylglycerols. Lipogenesis influences

the quality and time ratio of fat synthesis and depos-

ition in tissue. The synthesis of fatty acids depends on

different factors, such as: ACP (acyl carrier protein, a

9 kDa protein), another protein within the SH cyst-

eine group, called the HS enzyme, NADP (nicotin-

amide adenine dinucleotide phosphate), FMN (flavin

mononucleotide) and CoA (coenzyme A) (Figure 1).

This process is calling b-reduction.

0011Synthesis of fatty acids in animal products (fat

tissue) may be conducted in an intermediary path

from exogenous fatty acids. These fatty acids are

transported to reserve tissue or organs either with or

without transformation and as phospholipids of

membrane cells, or to yolk egg lipids. A simple

schema showing transformation and deposition of

fat and fatty acids in chicken is given in Figure 2.

0012In the animal world, for example, in mammalian

species, the synthesis of fatty acid could access acids

with 18 carbon atoms. In energy balance in an

organism easily digested carbohydrates also have an

important function. Some energy is gained from un-

digested carbohydrates by endogenous enzymes fer-

mented by microorganisms from the cecum and colon

intestine. In this way animals may gain short-chain

fatty acids, which are precursors of energy and fatty

acids, especially for monogastric animals.

0013Milk plays an important role in human diets. Syn-

thesis of milk fat is a specific process. The main

components of milk are triacylglycerols. The synthe-

sis of triacylglycerols is conducted in epithelial cells of

the mammary gland in two ways: first, from blood

lipids (rebuilding blood triacylglycerols to milk form)

and second, in de novo synthesis. Sixty percent of

milk (especially long-chain) fatty acids can be gained

from blood fat very-low-density lipoproteins (VLDL)

or from chylomicrons containing ingested fatty

acids directly from the intestine. The main sources

of VLDL and chylomicrons are fat from feed and

endogenous tissue fat. Medium- or short-chain fatty

acids of milk are synthesized in the epithelial cells of

the mammary gland or from blood precursors. The

differences in fat synthesis between mono- and poly-

gastric animals are shown in sources of carbon atoms

for fatty acids. In monogastric animals the source

is glucose while in ruminants it is actetate or beta-

hydroxybutyrate (BHBA). In the next conversion

fatty acids are esterified at the cytoplasmic surface

of the smooth endoplasmic reticulum (SER) of the

mammary epithelial cells to hydroxyl groups of

2262 FATS/Production of Animal Fats

tbl0001 Table 1 Balanceofanimalfatproductionandanimalfatutylization(1000metrictons)andconsumptionofanimalfatinfood

Years

19691984 1999

Typeof

country

TotalproductionTotaldomestic

utylization(infood,

feedandtechnical

industries)

Difference

betweena^b

TotalproductionTotaldomestic

utylization(infood,

feedandtechnical

industries)

Difference

between

d^e

Total

production

Totaldomestic

utylization(infood,

feedandtechnical

industries)

Difference

betweeng^h

abcdefghi

USA52704021þ124958434054þ167469955397þ1598

Developedcountries1844318067þ3762475222555þ21972164719395þ2252

Developingcountries319638706744965721222479749124152666

Typeof

country

Total

consumption

infood(1000

metrictons)

Consumption

percapita

peryear(kg)

Consumption

percapita

perday(g)

Total

consumption

infood(1000

metrictons)

Consumption

percapita

peryear(kg)

Consumption

percapita

perday(g)

Total

consumption

infood(1000

metrictons)

Consumption

percapitaper

year(kg)

Consumption

percapita

perday(g)

USA17988.617.516386.814.518726.714.3

Developedcountries1167710.921.41409311.721.4110888.515.5

Developingcountries26041.02.444781.33.084001.84.2

Sourceofdate:FAOSTAT,FAOStatisticalDatabases,NutritionData,FoodBalanceSheets,AnimalFats,1969,1984,1999,on-linehttp://apps.fao.org-files:01267652.csv(for1969year);01267649.csv(for1984year);

01267623.csv (for 1999 year).

the glycerol molecules. In this way triacylglycerols are

synthesized; they are agglomerated and create micro-

lipid droplets. They are secreted from the SER surface

into the cytoplasm, and transported directly to small

milk fat globules (<0.5 mm) and unite to form larger

droplets. The cytoplasmic lipid droplets may fuse

with each other and be secreted as larger milk lipid

droplets. The size of fat globules in milk ranges from

less than 0.5 to greater than 15 mm. The micro and

cytoplasmic lipid droplets are apparently surrounded

by a nonbilayer coating of protein and gangliosides

(polar lipids); the large lipid droplets are typical

membrane-surrounded milk fat globules.

Types of Animal Product, Nutritive Value,

Quality and Quantity of Animal Fat

Fat and Fatty Acid Content in Animal Product

0014 Muscles and carcass Different species of animals

have different contents of fat in the organism and in

their products Table 2.

0015 The average highest content of fat is in pork and

mutton. In the organism fat accumulates under skin

tissue, around some organs and intestines or between

muscles. Compared with other animal products, the

content of meat fat ranges from 3 to 55% (depending

on animal species).

0016The characteristic value of the poultry carcass is

because of the greatest concentration of fat under skin

Cytosol

Glucose-6-

phosphorus

Pyruvate

Pyruvate and citric acid reaction

Citric acid

Acetyl

coenzyme A

NADPH + H

Fatty acids

Coenzyme A

and m-CoA

Mitochondria

Glucose

fig0001 Figure 1 Simple schema of metabolic fat synthesis.

tbl0002Table 2 Nutrient content in animal species and products,

including fat

Water (%) Protein (%) Fat (%) Minerals (%)

Species of domestic animals

Cattle 54 15 26 4.6

Pig 58 15 24 2.8

Sheep 60 16 20 3.4

Hen 56 21 19 3.2

Mare 60 17 17 4.5

Products Fat content

(g100 g

1

)

Pork 24.5

Beef meat 6.2

Mutton 8.9–31.6

Turkey meat 5.7

Lard 99.5

Feed Liver

Fatty acids, triacylglycerides,

very-low-density lipoproteins,

other fatty acids (from different

tissues) and albumins

Carbohydrates (to glucose)

Fatty acids and

triacylglycerides

Fat tissue and other fat in

organs

Accumulation of fatty acids in

carcass fat structure

fig0002 Figure 2 Route of synthesis and deposition of fatty acids and fat in chicken.

2264 FATS/Production of Animal Fats

tissue and the skin compared with other animals, such

as pigs. Poultry meat, and especially chicken, is a

valuable product, which contains about 20% of fat

(in total with skin). Poultry meat without the skin has

about 5% fat content. This meat has a lower level of

saturated fatty acids (about 33% of all fat content)

and a high level of unsaturated fatty acids – especially

polyunsaturated fatty acids (PUFA) – 14%. Duck

meat has a higher level of fat than chicken or turkey.

In summary, fat content is about 35–45% with skin

and under skin tissue, and 25–27% is saturated fatty

acids (SFA). Meat from game birds like: grouse, par-

tridge, pheasant, and pigeon has a fat content about

5, 7, 9 and 13% respectively, and one fourth of this is

SFA. The composition of fatty acids is in an interest-

ing new product in the human diet – ostrich meat – is

given in Table 3.

0017 An important characteristic of fat quality param-

eters is not only the relation between fat and the

weight of the carcass but also the content of fatty

acids SFA, monounsaturated fatty acids (MUFA),

and PUFA.

0018 Table 4 gives a comparison of the fatty acid content

of different animal species. The highest content of

PUFA is observed in poultry meat and the worse

balance in ratios of fatty acids is in mutton or beef.

Probably the genetic and nutrition sciences works

could modify in future the profile relations of fatty

acids, especially in beef meat.

0019 A higher level of SFA is observed in ruminants than

in monogastric animals (for example, SFA in rumin-

ants may be about 50% of total fat content). This

profile depends on specific rumen degradation.

0020 In cattle there is more MUFA and PUFA in fat

between the muscles compared with under the skin

or around the organs. The quantity and quality of this

intermuscular fat is a decisive factor in the cooking

and taste of this meat (marbling of beef meat). In pig

production the highest level of fat is accumulated in

fat under skin tissue and in particular areas. In the

carcass the deposition of fat is different: there is a low

level in ham and high level in the shoulder.

0021Fish and especially oily fish is an important source

of fat in the human diet in some countries. Fish may

be classified according to the fat content in the car-

cass. In the human diet fish are classified as lean (low

fat content) such as flatfish, cod, where the concen-

tration of body fat is not greater than 5%, and oily

fish, like salmon, trout, and tunny (total fat content is

9–20%). Ocean fish have a genetic tendency to accu-

mulate the highest level of unsaturated fatty acids, in

particular PUFA, which makes up about 20% of total

fat (Table 5).

0022PUFA have an important function in human health.

PUFA are classified in groups omega-3 and omega-6.

A high ratio of omega-6 to omega-3 fatty acids in the

human diet has been linked with an increased risk of

cancer, cardiovascular disease, allergies, depression,

obesity, and autoimmune disorders. Animal fat does

not have a beneficial ratio of fatty acids from omega-

6 to omega-3 groups. Animal products used in dietary

health protection include fish oil, which contains the

highest level of fatty acids in the omega-3 group.

0023One form of fatty acids is conjugated linoleic acid

(CLA), which is found in ruminant meat. This fatty

acid is healthy for humans. Studies have shown that

CLA can change fat to muscle, reduce heart disease,

and fight diabetes.

tbl0004Table 4 Fat level and fatty acid composition of muscles of

different domestic animals

Total fat (%) % intotal fat content

SFAMUFAPUFA

Beef fat 67 43 48 4

Sheep fat 72 50 39 5

Pig fat 71 37 41 15

Chicken fat (meat and skin) 18 33 42 19

Duck fat (meat and skin) 43 27 54 12

SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; PUFA,

polyunsaturated fatty acid.

tbl0005Table 5 Fatty acid content in fish

Product Totalfat

(g 100 g

1

)

20:5n- 3

(g 100 g

1

)

22:6 n- 3

(g 100 g

1

)

Herring 9.0 0.7 0.9

Mackerel 13.9 0.9 1.6

Salmon 5.4 0.3 0.9

Trout 7.7 0.1 0.5

tbl0003 Table 3 Composition of fat in ostrich meat

Component Content

Fat (g 100 g

1

)1.3

Cholesterol (mg 100 g

1

)57

Fatty acids (in % of total fatty acids)

Saturated

16:0 21

18:0 13

Monounsaturated

16:1 4

18:1 31

Polyunsaturated

18:2–6 16

18:3–3 6

20:4–6 5

20:5–3 0.4

22:6–6 0.7

FATS/Production of Animal Fats 2265

0024 Milk The highest concentration of fat is observed

in sheep milk, in contrast with mares’ milk, which

has less fat. Cows’ milk has a fat level of 3.2–4%

(Table 6).

0025 The chemical composition of milk lipids is made up

of glycerophospholipids and sphingolipids (Table 7).

The physical form of milk fat is a sphere (size

2–10 mm). In one molecule of fatty acid of milk

there are 4–20 carbon atoms. In domestic animals

the milk fats that predominate are fatty acids: palm-

itic (C16:0), oleic (C18:1), myristic (C14:0), and to a

lesser extent, capric acid (in small ruminants). In

unsaturated fatty acids linoleic acid (C18:2) and lino-

lenic acids, have an important position in milk fat,

but the ratio between these acids depends on the form

and level of animal nutrition.

0026 In human nutrition when raw milk is not con-

sumed, the main function in diets is fulfilled by butter,

which is a source of energy and vitamin sources.

Butter has a high concentration of short-chain (satur-

ated), fatty acids as well as vitamins A and D.

0027Eggs In laying hens there are two types of produc-

tion: (1) eggs for reproduction: fatty acids are particu-

larly important for the hatchability of eggs during

incubation, and the quality and health of the chick;

and (2) eggs for consumption: fatty acids have an

influence on human health.

0028Eggs for consumption are a good source of lipids

and vitamins. Fat in eggs is centered in the yolk, and is

32 g 100 g

1

of yolk weight. Important components

of Hens’ egg yolk are oleic acid (11 g 100 g

1

), lino-

leic acid (2.61 g 100 g

1

), and arachidonic acid

(0.50 g 100 g

1

)(Table 8). Yolk triacylglycerols

are about 60%, and they are the main source of

fat energy. Monodiacylglycerols are 1.5–6.7%; the

highest level is deposited in high-density lipoprotein

tbl0006 Table 6 Chemical composition of milk and fat content

Species Water(%) Protein (%) Fat (%) Lactose (%) Minerals (%)

Cow 87 3–3.6 3.2–4.4 4.5–4.9 0.7–1.6

Goat 84–87 3.6–4.3 4–7 4.6–5.0 0.85

Sheep (ewe) 80–84 5.2–6.5 4.6–8.3 4.0–4.6 0.95

Mare 91 2 1.1–1.6 5.7–6.4 0.35

Reindeer 68 10.5 17–19 2–2.8 1.5

%oftotalfatmilk

Triacylglycerides 98

Diacylglycerides 0.25–0.48

Monoacylglycerides 0.02–0.04

Phospholipids 0.6–1.0

Cholesterol 0.2–0.4

Glycolipids 0.006

Free fatty acids 0.1–0.4

tbl0007 Table 7 Comparison of important fatty acids in milk from a variety of animals (molar percent)

Fattyacids Rabbit Guinea pig Mouse Rat Sow Cow Sheep Goat

Short-chain

C4:0 <1 <1 <1 <1 The sum of C4:0

to C12:0 ¼2%

11 8 8

C6:0 <1 <1 <1 <1 5 5 5

C8:0 <1 <1 6 1 4 4

Medium-chain

C10:0 27 <1 7 17 3 6 13

C12:0 3 <1 12 13 3 5 7

C14:0 1 2 16 13 2 10 10 12

Long-chain

C16:0 8 34 33 28 28 23 22 24

C18:0 2 3 2 3 6 10 10 12

C18:1 9 31 14 13 35 29 22 17

C18:2 10 23 8 7 14 2 4 3

C18:3 1 4 <1 <1 <1 <1 <1 <1

2266 FATS/Production of Animal Fats

(HDL) fraction and a lower level is in the low-density

lipoprotein (LDL) plasma yolk fraction.

Modification of Quality and Quantity of

Animal Fat

0029 The scientific promoter of lipid metabolism, and in

particular the influence of organic feed compounds

on lipid synthesis in animals, was the German Oskar

Kellner. Kellner ascertained that 1 kg of digested feed

components such as starch, fat, or protein produced

in cattle a particular level of fat, e.g., 1 kg starch

produced 248 g fat, 1 kg protein produced 235 g fat.

The results of trials in practice showed that in reality

the levels of synthesis in organisms depended on

nutrition value, the feed taken, the physiological

conditions of the organism, age, digestibility, and

the development of the digestive tract. One important

point in lipid synthesis is the ratio between quality

and quantity of feed consumption. The interaction

between different feed components such as starch

and cellulose also influences energy metabolism and

energy balance.

0030 Lipid synthesis in an organism is conducted differ-

ently in monogastric and polygastric animals. The

level and system of digestibility and kinds of energy

and lipid precursors (exogenous) are important.

Monogastric Animals (Domestic Animals, e.g.,

Poultry and Pigs)

0031 The highest growth rate, highest protein synthesis

and changing fat relation between protein content

and fat in tissue are characteristic parameters of

slaughtered monogastric animals. When breeding

this group there are only two possibilities for

changing body composition. One is genetic research

and hybridization – there are new genetic lines of

animals which have unusually high muscle content.

The second way is a nutrition combination, using

special balanced diets and special components in

feed, which may modify fatty acid content (Figure 3).

0032 Within the feeding system of young slaughtered

poultry (chickens) there is a specific procedure relat-

ing to quality of feed. The important point is a ratio

between energy content in feed and protein during the

growth phase. The nutrition system must be correl-

ated with body development in the short life span,

which is only 6 weeks. This system allows increased

protein synthesis in muscles compared with fat syn-

thesis in the organism and is dependent on energy

balance.

0033In chicken or turkey endogenous fat is synthesized

from glucose, and the final product of carbohydrate

degradation and digestibility – starch. In poultry diets

95% of starch is given by corn, wheat, and barley.

The level of energy in poultry feed is balanced by

exogenous fat supplementation by oil and tallow.

The maximum level of this supplement is about

10% in feed, but is often 3–6%. The balance of

energy in poultry is important, because when the

balance increases by about 10–25%, fat synthesis is

also increased. At this point feed intake is decreased

and amino acids and minerals intake are also de-

creased (only in negative composition mixture).

0034The influence of systems, contents, and level

of nutrition on development and quality poultry

products has been determined in scientific research.

Change in carcass composition is highest in poultry,

especially in relation to fat and protein content. This

suggests the possibility of modifying carcass compos-

ition by nutritional changes in a short time. One

important factor is increased feed protein level and

decreased growth rate of endogenous body fat.

0035A mean increase in protein concentration in the diet

(1% ¼10 g kg

1

) reduces fat content in the carcass of

chicken 0.7–1.4% (7–14 g kg

1

). A similar effect is

observed using low-energy components in feed.

Research trials have demonstrated that a high level

tbl0008 Table 8 Lipids in egg yolks from laying hens (%)

Specification Percentage share

Triacylglycerides 56.1–65.5

Monodiacylglycerides 1.5–6.7

Free fatty acids 0.7

Cholesterol esters 0.1–0.5

Cholesterol 5.2–6.6

Phospholipids 28.3–31.2

Fat growth

Protein growth

Body mass growth

Accumulated fat

Accumulated

protein

Accumulated

energy (kcal)

Energy intake

(kcal)

800

600

400

200

3000 4000

1000 2000

(a)

(b)

fig0003Figure 3 Influence of (a) feed energy intake and (b) proteinon

body composition in poultry (chickens).

FATS/Production of Animal Fats 2267