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

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of rye plus enzyme in the diets decreased endogenous

level of fat in the body composition of chickens com-

pared with a corn diet. The specific combination of

different energy sources in feed (tallow, soyabean oil,

rapeseed oil, fish oil) may influence the quality and

composition of endogenous fat in poultry. This cor-

relation between composition of feed fat and carcass

fat has been demonstrated in other studies. There was

a strong correlation between dietary fatty acid com-

position and tissue fatty acid composition for all fatty

acids except C14:0, C20:0, C20:2n-6, and C20:4n-6.

0036 Not only energy sources in feed but also protein

levels and sources have an effect on abdominal fat. In

one study, protein concentrates were used in different

combinations, compared with mixtures of a DKA-

grower diet containing 11% fishmeal and 35% of a

1:1 mixture of faba bean and full-fat rapeseed and a

DKA-grower diet containing 18% soyabean meal,

7% fishmeal, and 4% rapeseed oil. These nutrition

combinations influenced differentials in abdominal

fat composition: abdominal fat content was 12, 21,

and 40 g. Of total fatty acids in abdominal fat, 37.55,

33.96 and 30.43% was saturated, and 62.43, 65.74

and 69.39% was unsaturated. When used in the

feeding system in chickens, high-fat yeast (HFY;

Cryptococcus curvatus) reduced the proportion of

oleic acid in breast and thigh muscle in compare to

chicks fed mixtures with tallow or without fat sup-

plementation.

0037The main fat content in poultry is accumulated

under skin tissue. The content of fatty acids in this

tissue can be modified by different feed additives

(Table 9).

0038The influence of nutritional factors on laying hens,

performance and production is important. In repro-

duction eggs of laying hens, the lower content of

linoleic acid or linoleneic acid gives rise to decreased

hatchability, lower weight of embryos and chicks, and

slower rate of development during incubation. Chol-

esterol has an important function in this process, too.

Modification of consumption eggs is very popular,

especially as regards changes of fatty acids and vita-

min content. Changing eggs using the nutrition

system is called nutritionally enriched eggs (NEE)

(Table 10).

0039During feed modification of egg content, it is

important that the cholesterol level is 90% of that

required genetically.

0040In pork production the fatty composition of feed

grains has an important function. In pigs fed mixtures

with high levels of barley, the lard was white and

strong, compared with pigs fed mixtures principally

made up of corn, in which case the lard was yellow

and clammy.

0041There are three important principles in pig produc-

tion:

0042Pigs fed a diet with a lower protein level cannot

produce a high level of protein in muscles (in rela-

tion to genetics);

0043The highest level of protein in a low-energy diet

may increase fat synthesis;

0044All organic components in a low-energy diet may

increase fat synthesis.

tbl0009 Table 9 Fatty acid composition in skin influenced fat

supplements

Specification of fatty supplements to mixture

Corn oil

Tallow

Corn oil 5%

andcod-liver

oil 1%

Ta llo w 5 %

and cod-liver

oil 1%

Fatty acids

Lauric (C12:0) 0.2 0.1 0.0 0.1

Myristic (C14:0) 0.8 2.9 0.8 3.4

Palmitic (C16:0) 16.1 23.4 15.9 23.3

Oleic (C18:1) 28.8 39.2 28.4 32.6

Linoleic (C18:2) 44.0 13.8 39.0 16.4

tbl0010 Table 10 Comparison of the contents of normal and modified eggs and feed additives which could change the fatty profiles in yolk

Feed additives Level of added

components

tomixtures

Nutrient content of NEE compared to ordinary egg: quantity/100 g egg content

Ordinary egg NEE

Fish oil 10–20 kg Total saturated fatty acids (g) 3.3 2.8

Full-fat ground linseed 100–150 kg Total unsaturated fatty acids (g) 6.4 6.9

Rapesced oil 5–10 kg MUFA (g) 4.4 4.4

BHT, BHA, etoxyquin 100–250 g PUFA (g) 1.2 2.2

Vitamin E 100–200 g Linoleic acid (g) (n-3) 1.0 1.3

Omega-6: omega-3 ratio 9.90 1.75

Unsaturated-to-saturated acids ratio 1.94 2.46

Cholesterol (mg) 400 350

NEE, nutritionally enriched eggs; BHT, butylated hydroxytoluene; BHA, butylated hydroxyanisole; MUFA, monounsaturated fatty acids; PUFA,

polyunsaturated fatty acids.

2268 FATS/Production of Animal Fats

Ruminants

0045 The possibility of modifying fat quality and content

in the body and milk of ruminants can be conducted

genetically and nutritionally. In genetic terms cross-

breeding special species of cattle with famous domes-

tic lines is a popular route. For example, the Japanese

meat-cattle Wagyu has a high intramuscular fat

content (shown by marbling of the meat) and a high

ratio of MUFA to SFA. A second example of genetic

modulation in fatty acid composition in beef is cross-

breeding between domestic cattle and bison in the

USA, creating a new species which was called beefalo.

Beefalo meat has less total fat, less saturated fat, less

cholesterol and fewer calories in comparison with

domestic breeds of cattle. In milk fat there are large

differences between species of cattle, for example,

Holstein cattle produce low fat milk (3.2–3.5%),

Ayrshire and Brown Swiss give 3.9–4.0% fat and

the highest content of fat is in milk produced by

Guernsey and Jersey cows (4.6%). Milk fat and

meat content can be modified by nutrition. Fattening

young cattle on grass fields (extensive model) has

decreased fat content in carcass in comparison with

the intensive model of feeding mixtures with grass

and high level of grains. Feeding milk-cattle a mixed

ration with lower effective fiber reduces the fat con-

tent in milk. Similarly, supplementing the diet with

trans fatty acids to inhibit milk fat synthesis decreased

milk fat level.

004 6 In ruminants improving the profile of fatty acids

in the feed does not directly improve the profile

of fatty acids in products, whether milk or meat.

In normal conditions cows only ingest 2.5–3%

of fatty acids in dry matter in their daily feed ration.

Fatty acids are delivered by triacylglycerides, galacto-

lipids, and phospholipids by ruminal microbial lipase

activity, and are modified to stearic acid. This form is

available in the intestine. Unsaturated fatty acids

from feed are biohydrogenated in the rumen to the

saturated acid form and fat in the ruminant’s body

(tallow) are highly saturated. The fat of ruminant

milk content compared to other fats has a high degree

of short-chain fatty acids. The precursors of fatty

acids in the rumen are carbohydrates which produce

volatile fatty acids: acetate, propionate, and butyrate.

Using a fresh grass feed in cows’ nutrition could

modify the content of healthy fatty acids in meat,

giving a decrease in SFA, increased intake of omega-

3 fatty acids and CLA. Studies have shown that the

ratio between omega-6 and omega-3 fatty acids is

decreased from 4:1 to 2.3:1 in the meat of cattle fed

grass. A similar effect is observed in milk cows fed

grass; the content of CLA was three or five times

higher then in ruminants fed grain diets. The final

way of modifying fatty acids in milk is to use pro-

tected fatty acids before rumen degradation.

Seealso: Eggs:DietaryImportance; Fats:Usesinthe

FoodIndustry;Digestion,Absorption,andTransport;

Requirements;FatReplacers;Classification;Occurrence;

Fatty Acids:Properties;Metabolism;Gamma-linolenic

Acid;Analysis;DietaryImportance;Trans-fattyAcids:

HealthEffects; Poultry:Chicken

Further Reading

Ba˛czkowska H and S

sarz A (1987) Z

ywienie Drobiu.

Warsaw: Pan

stwowe Wydawnictwo Rolnicze i Les

ne.

Banaszkiewicz T, Janocha A and Osek M (1995) Wplyw

mieszanek DKA z udzialem surowcow krajowych na

wyniki poubojowe kurczat brojlerow. Biuletyn Nau-

kowy Przemyslu Paszowego 34: 33–41.

Dhiman TR, Anand GR, Satter LD and Pariza MW (1999)

Conjugated linoleic acid content of milk from cows fed

different diets. Journal of Dairy Science 82: 2146–2156.

Dils RR (1983) Milk fat synthesis. In: Mephan TB (ed.)

Biochemistry of Lactation, pp. 141–157. Amsterdam:

Elsevier.

French P, Stanton C, Lawless F et al. (2000) Fatty acid

composition, including conjugated linoleic acid, of intra-

muscular fat from steers offered grazed grass, grass

silage or concentrate-based diets. Journal of Animal

Science 78(11): 2849–2855.

Grudniewska B (1994) Hodowla i uz

ytkowanie s

win

. Olsz-

tyn: Wydawnictwo Akademii Rolniczo-Technicznej.

Horban

czuk O (2001) Nutritive value of ostrich meat.

World Poultry 17: 42–43.

Jackisch B and Jeroch H (1993) Results of further studies of

rye-containing feed mixtures with the enzyme prepar-

ation ‘‘Nutrizym-feed-additive’’ in broiler fattening.

Archives of Animal Nutrition 42: 55–61.

Jamroz D (ed.) (2001) Z

ywienie Zwierza˛t i Paszoz-

nawstwo. Warsow: Wydawnictwo Naukowe PWN.

Kean MG and Allen P (1998) Effects of production system

intensity on performance, carcass composition and meat

quality of beef cattle. Livestock Production Science 56:

203–214.

Larbier M and Leclercq B (1995) Z

ywienie Drobiu.

Warsaw: Pan

stwowe Wydawnictwo Naukowe PWN.

McDonald P, Edwards RA, Greenhalgh JFD and Morgan

CA (1995) Animal Nutrition, 5th edn. Edinburgh: Addi-

son Wesley Longman.

Miller GJ (1986) Lipids in wild ruminant animals and

steers. Journal of Food Quality 9: 331–343.

Minakowski W (1990) Biochemia kre˛gowco

w. Warsaw:

Pan

stwowe Wydawnictwo Naukowe.

Munro HN (1976) Fat content and composition of animal

product. National Academy of Sciences. /www.nap. edu/

openbook.

Narahari D (2001) Nutritionally enriched eggs. 2001.

Poultry International 40: 22–30.

FATS/Production of Animal Fats 2269

PalmquistDL,BeaulieuADand BarbanoDM(1993)Feed

andanimalfactorsinfluencingmilkfatcomposition.

Journal of Dairy Science 76:1753–1771.

ScaifeJR,MoyoJ,GalbraithH,MichieWandCampbellV

(1994)Effectofdifferentdietary supplementalfatsand

oils onthetissuefattyacid compositionandgrowthof

femalebroilers. British Poultry Science 35: 107–118.

SimopoulosAPandRobinsonJ(1999) The Omega Diet.

NewYork,NY:HarperPerrenial.

TrziszkaT(2001)Jajczarstwo.Wrocław:Wydawnictwo

AkademiiRolniczej.

WillhamRL (1976)Geneticsoffatcontentinanimal

products.NationalAcademyofSciences./www.na-

p.edu/openbook.

Uses in the Food Industry

L Boothby, Natland, Kendal, UK

Background

0001 The first oil and fat products to be used by humans,

apart from direct ingestion of vegetable oils from

plants, were from animal sources. As the world’s

meat industry developed, animal fats became useful

byproducts for baked goods. In the early 1900s, the

introduction of hydrogenation, or hardening, revolu-

tionized the usefulness of vegetable oils and enabled

the production of fats and blends, with a wide range

of physical properties overcoming some of the

limitations associated with animal fats. Today’s fat

technologists also modify fats by fractionation and

interesterification or a combination of two or more of

the above methods to give a wide selection of tailor-

made fats and blends. In more recent years, nutri-

tional considerations have increased the usage of

vegetable oils and fats. Similarly, the implication

that trans acids in the diet increase the risk of coron-

ary heart disease by raising low-density lipoprotein

(LDL) cholesterol and reducing high-density lipopro-

tein (HDL) cholesterol levels has led some manufac-

tures, particularly in yellow fats, to use blends with

no hydrogenated oils. Trans acids also occur in

animal and milk fats, albeit at lower levels than

hydrogenated vegetable oils. (See Vegetable Oils:

Dietary Importance.)

Functionality

0002 In addition to being an energy source and fulfilling

nutritional requirements, fats are necessary to carry

out one or more of the following functions in

various applications: (1) incorporate air; (2) provide

lubrication; (3) soften texture; (4) aid moisture reten-

tion; (5) as a heat exchange medium and flavor en-

hancer in fried goods.

Bakery Fats

Properties

0003General-purpose fats or shortenings must have the

following properties to perform satisfactorily in

cake-making:

0004The shortening must be stable in the b-prime

polymorph.

0005There must be a proportion of high melting tri-

glycerols present: 5% is normally sufficient.

0006The ratio of solid to liquid triacylglycerols should

be such as to give a plastic solid over the normal

range of ambient temperatures.

0007The oxidative stability must be sufficient to meet

product shelf-life requirements. (See Oxidation of

Food Components; Triglycerides: Structures and

Properties.)

Properties (1) and (2) are necessary to give a stable,

aerated batter and good texture in the baked product.

Property (3) is achieved by using a suitable blend of

component oils. The shortening must blend readily

with other ingredients during mixing. Plasticity also

depends on the temperature history of the fat. During

processing, rapid chilling is necessary to form a net-

work of inter-locking small crystals which enmesh the

liquid triacylglycerol phase. Slow chilling produces

large, irregular crystals, and in products such as

ghee a continuous liquid phase results. Storage tem-

perature and ambient temperature in the bakery also

affect plasticity. Property (4) is satisfied in most cases

by using unmodified liquid oils for the liquid phase. If

long-shelf-life products are required, oxidative stabil-

ity is increased by using lightly hydrogenated oils for

the liquid phase, e.g., soyabean oil with iodine value

reduced from 130 to 105, or rapeseed oil reduced to

iodine value 95 from 115. (See Ghee.)

0008General-purpose fats are suitable for pastry manu-

facture. b-Phase fats, notably lard, also produce ex-

cellent pastry products. Lard has a long plastic range

but produces cake batters of poor stability and result-

ant poor cake texture. Its use in shortenings is thus

limited to about 20% maximum. However, if costs

permit, changing the polymorph to b-prime by inter-

esterification significantly increases the inclusion

level to 60–70%.

Component Oils

0009The physical characteristics of some typical short-

eningcomponentsaregivenin Table 1.Mostfat

2270 FATS/Uses in the Food Industry

manufacturers have their own stock of standard

hydrogenated or fractionated oils. There is no justifi-

cation, for example, in a refiner carrying a range of

hydrogenated soyabean oils with melting points

ranging from 20



Cto50



C in steps of 5



C since

most user requirements can be met by blending a

limited number of hardstocks. All the figures quoted

for solid glyceride levels were determined by pulsed

nuclear magnetic resonance (pNMR) using Inter-

national Union of Pure and Applied Chemistry

(IUPAC) method 2.150. Tallow, hydrogenated marine

oils, hydrogenated cottonseed oil, hydrogenated palm

oil, and palm stearin are all b-prime fats used exten-

sively as hardstocks for shortening blends. (See Fish

Oils: Composition and Properties.)

Shortening Blends

0010 Typical shortening blends are given in Table 2, to-

gether with their pNMR profiles. Fat suppliers aim to

have a library of formulations which can be used to

give identical end products, so that least-cost options

are always available. Shortening blends without

middle melting triacylglycerols give satisfactory

baked goods but there can be some loss of eating

quality due to the increased level of high-melting

triacylglycerols. Advantages of this type of formula-

tion are an extended plastic range. Most manufac-

turers increase solid triacylglycerol levels by 2–4%

during summer months. Hydrogenated marine oil-

based shortenings possess excellent cake-making

properties but the increasing all-vegetable trend has

seen a decline in this type of shortening.

0011 High-ratio shortenings have similar blends to

the general-purpose fats, except for the addition of

2.8–3.2% a-monoacylglycerol, and in some cases a

similar level of diacylglycerols. High ratio refers to

the higher levels of liquor and sugar to flour that can

be used. Resultant cakes are moister, sweeter, and

resist staling longer than conventional cakes. Short-

enings with 1–2% monoacylglycerol are used to give

intermediate ratios of liquor and sugar.

0012Pourable or fluid shortenings are suspensions of

emulsifiers, sometimes with the addition of a small

level of high-melting b-phase fat, either in liquid

vegetable oil, or in a lightly hydrogenated vegetable

oil to give improved shelf-life.

0013Pumpable shortenings for large bakeries have

similar blends to conventional shortenings. They are

stored and delivered in jacketed tanks with

temperatures maintained between 24 and 28



depending on the blend. At the bakery the shortening

is delivered from controlled temperature storage by

positive displacement pumps and metered into

the mixer. (See Bread: Dough Mixing and Testing

Operations.)

Puff Pastry Fats

0014Puff pastry fats need to be tough and elastic to

achieve the multiple alternate layers of fat and

dough required to produce good lift. Puff pastry mar-

garines seem to be preferred to fats. To achieve the

necessary consistency, relatively high-solid glyceride

contents are used together with correct processing.

An excellent puff pastry fat can be produced from

lard containing 12–15% fully hydrogenated lard.

Tallow-based fats are also produced. Vegetable-

based fats utilize palm stearin and, hydrogenated

palm oil together with other hydrogenated vegetable

oils.

tbl0002Table 2 Typical general-purpose shortening blends and

pulsed nuclear magnetic resonance (pNMR) profiles

Component Not all

vegetable

fat (%)

All

vegetable

fat (%)

1212

Tallow 65

Hydrogenated fish oil (30



C) 80

Hydrogenated fish oil (49



C) 20

Palm oil 25 20

Hydrogenated palm oil (49



C) 5 10

Hydrogenated rapeseed oil (33



C) 40 25

Rapeseed oil 35 30

Hydrogenated rapeseed oil (20



C) 45

Percentage of solid triacylglycerols

(pNMR)



C 35454745



C 22272022



C 12101210



C 3 2 1 1.5

tbl0001 Table 1 Physical characteristics of some shortening

components

Fat Melting

point

(



Percentage of solid

triacylglycerols at

different temperatures (



Stable

polymorph

10 20 30 35 40

Butterfat 30 47 16 5 1 0 b-prime

Lard 36 49 26 8 5 2 b

Tallow 43 55 41 20 15 7 b-prime

Palm 37 50 22 11 5 2 b-prime

Palm (I) 42 52 35 15 9 6 b-prime

Palm (H) 49 95 92 80 63 42 b-prime

Palm stearin (F) 46 67 45 22 18 13 b-prime

Fish (H) 36 60 40 18 6 0.5 b-prime

Fish (H) 49 90 85 70 50 40 b-prime

Rapeseed (H) 33 75 50 15 4 0 b

BSI slip melting point (BS684, Part I, 1.3). I, interesterified;

H, hydrogenated; F, fractionated.

FATS/Uses in the Food Industry 2271

Biscuit Fats

Dough Fats

0015 Biscuit dough fats must be b-prime-stable to avoid

bloom development during the life of the biscuit.

However, certain different criteria are required com-

pared to shortenings:

0016 The melting profile must be sharper for good

eating quality. There must be generally less than

5% solid triacylglycerols at 35



C and 0.5%

maximum at 40



0017 The oxidative stability needs to be high for a long-

shelf-life product, typically 40 h minimum at

100



C (measured by Rancimat instrument). Thus,

liquid oils are normally excluded from blends,

except for some specialized ‘health’ biscuits.

0018 Typical dough fat blends and pNMR profiles are

given in Table 3. Historically, the biscuit industry used

large quantities of hydrogenated marine oils. Palm or

hydrogenated palm oils are normally used to achieve

the b-prime polymorph in vegetable blends.

0019 Biscuit fats can be supplied ready for use in boxes.

The major producers receive blends in road tankers at

temperatures several degrees above the complete

melting point, store in suitable tanks, and subse-

quently chill and texturize as required.

Cream Fats

0020 Biscuit cream fats require medium to high solid tri-

acylglycerol levels at ambient temperatures, together

with a rapid melting profile, and, ideally, zero solid

triacylglycerols at body temperature. On high-speed

production lines the fat must set quickly and give

good coherence to the biscuit. Biscuit creams are

basically mixtures of icing sugar and fat with or with-

out added colors and flavors. Typical cream fats and

their melting profiles are given in Table 4.

0021The lauric oils – coconut and palm kernel – are

ideal starting materials. In addition to rapid melting

they are very bland and can be refined to very low

color levels. Hydrogenated rapeseed and soyabean

oils with high trans acid levels can be used singly or

in combination with lauric fats. In these blends low-

melting saturated acids are partially replaced by trans

acids – mainly elaidic acid, which has a similar

melting point to lauric acid (42



C).

Low

Trans

Acids Blends

0022Suitable low trans acids blends can be formulated

using fractionated or interesterified oils. Examples

are given in Table 5 for different applications. To

achieve zero to trace levels of trans acids it is neces-

sary to use deodorization temperature below 235



particularly if liquid oils are included in the blend;

this precludes the use of physically refined oils.

Frying Oils

0023Frying oils need to be as stable as possible under the

harsh conditions used. This is achieved by using

oils with the lowest possible level of unsaturation

concomitant with good eating quality and very low

trace-metal levels. Thus, hydrogenated oils should be

posttreated to remove traces of catalyst completely.

Stability is also important to achieve a reasonable

shelf-life, particularly in potato crisps and snack

foods, with their large surface area to weight ratios,

and oil contents up to 40%.

0024Oils are delivered in bulk to the snack-food indus-

try. Suitable oils are lightly hydrogenated soya bean

or rapeseed, with linolenic acid levels reduced below

3%, palm olein, and blends of palm oil with vegetable

oils. Sunflower is used successfully to produce health-

branded products. Frozen chip producers require

harder oils to avoid problems during blast-freezing.

Suitable oils are palm or hydrogenated palm oil.

tbl0003 Table 3 Examples of biscuit dough fat blends and pulsed

nuclear magnetic resonance (pNMR) profiles

Animal/vegetable Fat (%) All vegetable Fat (%)

Hydrogenated fish

oil (32



55 Hydrogenated soya

oil (35



Palm oil 35 Palm olein 10

Hydrogenated palm

oil (42



10 Palm oil 40

Percentage of solid

triacylglycerols (pNMR)



C25 28



C8 10



C2.5 4



C 0 0.5

tbl0004Table 4 Examples of biscuit cream fats and melting profiles

Fat

(%)

Fat

(%)

Fat

(%)

Coconut oil 65

Hydrogenated palm kernel oil (34



C) 15 100

Hydrogenated palm oil (42



C) 20

Hydrogenated soyabean oil (34



C) 100

Percentage of solid triacylglycerols (pNMR)



C417460



C4.51420



C223



C000

pNMR, pulsed nuclear magnetic resonance.

2272 FATS/Uses in the Food Industry

These products contain 2–5% oil, which is diluted by

the end users’ frying media.

0025 The catering industry uses palm oil, beef-tallow

liquid vegetable oils, and long-life frying oils based

on lightly hydrogenated vegetable oils. The latter nor-

mally contain a low level of a b-phase fat such as fully

hydrogenated rapeseed oil. Chilling and texturizing

produce a stable pourable frying oil. An antifoaming

agent (methyl polysiloxane) is generally added to

long-life frying oils. Antioxidants are not normally

added; they give protection prior to use but there is

little carry-through to the finished product. Residual

tocopherols in vegetable oils give some benefit. (See

Antioxidants: Synthetic Antioxidants; Tocopherols:

Properties and Determination.)

Processing

Shortenings

0026 Fats and blends are stored above their complete

melting points immediately prior to processing. The

first stage is normally a water precooler to reduce

variations in feed temperature to the main chilling

unit. The main chilling unit is a continuously scraped

surface heat exchanger, comprising a cylinder with

refrigerant on the outside, and inside a rotating shaft

with floating scraper blades. The molten fat is pumped

under high pressure through the annular space whilst

the scraper blades remove chilled fat from the cylin-

der wall. This step initiates the crystallization before

passing to the second unit, sometimes referred to as a

‘B’ unit or ‘puddler’ or ‘worker.’ In the ‘B’ unit the fat

completes most of its crystallization whilst being agi-

tated by a combination of paddles and baffles; most

of the heat of crystallization is dissipated.

0027 Absence of a ‘B’ unit results in nonplastic

shortening. Processing plants normally consist of

several chilling and ‘B’ units linked in series. The

final stage involves further mechanical working by

passing the shortening through an extrusion or tex-

turizing valve immediately prior to filling the con-

tainer – normally polythene-lined boxes. The whole

system generally operates at pressures between 2 and

3 MPa. Depending on the blend, chilling tempera-

tures can vary between 16



C and 22



C and filling

temperatures between 19



C and 25



0028The final stage after filling is ‘tempering’ or

‘annealing’. Containers are stored in a temperature-

controlled environment between 24



Cand28



C for

at least 48 h. This step allows the shortening to stabil-

ize in the b-prime polymorph and extends the plastic

range, so enabling the shortening to be used over a

wider temperature range without loss of performance.

0029Most shortenings have air or, preferably, nitrogen

introduced prior to chilling to give a white appear-

ance; the normal level varies between 8% and 15%

by volume. The level of gas does not influence final

performance and is introduced for cosmetic reasons.

Shortenings without gas perform equally well but

have a pale yellow, petroleum jelly-like appearance.

Colors, such as b-carotene and vitamins, can be

added if required. Colored shortenings do not nor-

mally include nitrogen.

0030Pumpable shortenings are processed similarly but

after texturizing are stored in special temperature-

controlled tanks at tempering temperatures. Further

work softening occurs when the shortening is pumped

into and out of the delivery vehicle, and again just

prior to mixing by the end user. Omission of nitrogen

from pumpable shortenings gives more accurate

metering into the mixer.

Puff Pastry Fats

0031Puff pastry fats can be chilled in a similar manner to

shortenings or on open chilling drums with a scraper

tbl0005 Table 5 Low trans acids blends and pulsed nuclear magnetic resonance (pNMR) profiles

Component oils General shortening Biscuit dough Biscuit cream

12 1212

Palm stearin/coconut 80:20 (I) 15

Palm (I) 40 85

Palm 20

Rapeseed oil 25

Palm/rapeseed oil 83:17 (I) 100

Palm/coconut oil 70:30 (I) 100

Palm kernel oil 15

Palm kernel stearin (F) 100

Fully hydrogenated palm/palm kernel 30:70 (I) 100

Percentage of solid triacylglycerols (pNMR)



C242329277057



C 10 10 8.5 11 8 21



C352504



C11010

FATS/Uses in the Food Industry 2273

blade running the length of drum and refrigerant on

the inside. Moisture condensation can give problems

in the latter process. After chilling, the fat is allowed

to crystallize slowly in long resting tubes or in skips.

The fat is then plasticized before extruding into

blocks. The drum method gives fats of excellent plas-

ticity. No tempering is necessary but low storage

temperatures should be avoided.

Other Fats

0032 Confectionery, toffee, icecream, cream, and frying

fats are chilled, texturized, and packed as shorten-

ings, but without tempering. (See Ice cream: Methods

of Manufacture.)

See also: Antioxidants: Synthetic Antioxidants; Bread:

Dough Fermentation; Fish Oils: Composition and

Properties; Ghee; Ice Cream: Methods of Manufacture;

Oxidation of Food Components; Tocopherols:

Properties and Determination; Triglycerides: Structures

and Properties; Vegetable Oils: Types and Properties; Oil

Production and Processing; Dietary Importance

Further Reading

Bailey AE (1985) In: Applewhite TH (ed.) Industrial Oil and

Fat Products, 4th edn, vol. 3. New York: John Wiley.

Baldwin RR, Baldry RP and Johansen RG (1972) Fat

systems for bakery products. Journal of the American

Oil Chemists Society 49: 473–477.

Hoerr CW (1960) Morphology of fats, oils and shortenings.

Journal of the American Oil Chemists Society 37: 539–

546.

Knightly WH (1981) Shortening systems: fats, oils and

surface-active agents – present and future. Cereal

Chemistry 58: 171–174.

Lefebvre J (1983) Finished product formulation. Journal of

the American Oil Chemists Society 60: 295–300.

Vaisey-Genser M and Ylimaki G (1989) Baking with canola

oil products. Cereal Foods World 34: 246–258.

Digestion, Absorption, and

Transport

T H M Da Costa, Universidade de Brası

lia, Brası

lia,

DF, Brazil

Background

0001 Fats or lipids are the concentrated form of energy in

the diet, providing 9 kcal g

1

(37 kJ g

1

), and have

evolved as the most advantageous form of energy

storage, owing to their hydrophobic characteristics.

Triacylglycerols are the most common of the lipids

either in the diet or as lipid tissue stores. They are

formed by the esterification of glycerol and fatty acids

(1:3 molar ratio). Triacylglycerols vary depending on

the three fatty acid residues they contain; simple tria-

cylglycerols contain a single type of fatty acid residue.

For example, trioleoylglycerol or triolein (a simple

triacylglycerol) has three oleic acid residues, and

mixed triacylglycerols contain two or three different

types of fatty acid residues. The fatty acid moiety

varies greatly in nature, and the ingestion of triacyl-

glycerols containing saturated or unsaturated, long-

and/or short-chain fatty acids depends on the source

of lipids in the diet.

0002Fat is an important food energy source in the West-

ern world, ranging from 30 to 40% of daily energy

intake, equivalent to the daily consumption of

50–120 g in an adult. Other lipids play less important

roles as energy sources under normal physiological

circumstances, but serve as structural components

of cell membranes, metabolic cofactors and as

hormones (phospholipids, sphingolipids, cholesterol,

diacylglycerol, and steroids). The diet constitutes the

major source of lipids for the body and supplies

essential fatty acids and lipid-soluble vitamins that

cannot be synthesized endogenously. Lipogenesis,

de novo synthesis of triacylglycerols from carbo-

hydrate, occurs when there is a high ingestion of the

latter.

0003The first part of this chapter reviews present knowl-

edge on the mechanisms of digestion and absorption

of dietary lipids, mainly triacylglycerols, and the

second part deals with the complex transport system

of lipids in the circulation.

Lipid Digestion and Absorption

0004Owing to their hydrophobic characteristics, lipids are

digested by a dynamic and complex mechanism that

facilitates their solubilization and hence availability

for enzymatic action. The process can be divided into

four main phases: emulsification, hydrolysis of fatty

acid ester bonds by lipases, aqueous dispersion of

lipolytic products in bile acid micelles, and uptake

by the enterocytes (Figure 1).

0005In the process of fat digestion, there is a minor

contribution of lingual lipase, which hydrolyzes

some long-chain fatty acid triacylglycerols, and

gastric lipase, which contributes to the hydrolysis of

short- or medium-chain fatty acid triacylglycerols.

The main process of lipid digestion takes place in

the small intestine. In the duodenum, triacylglycerols

aggregate in droplets and are emulsified by the action

of the bile salts, monoacylglycerols (originating from

intragastric lipolysis), and lysolecithin. The fat

2274 FATS/Digestion, Absorption, and Transport

droplets are attacked by the colipase and pancreatic

lipase complex. Colipase, a pancreatic protein that

protects the lipase from denaturation and anchors it

to the lipid–water interphase of the droplet, permits

access of the lipase to the inner core of triacylglycer-

ols. In fact, when the lipase binds to the interphase of

the lipid droplet, the catalytic rate of the enzyme is

increased (surface activation). Pancreatic lipase

hydrolyzes ester links in the 1–3 positions of the

triacylglycerols releasing fatty acids and 2-monoacyl-

glycerol (Figure 2).

0006 Phospholipids from the diet or secreted in the bile

(lecithin) are attacked by pancreatic phospholipase

, which cleaves the fatty acid at the 2 position,

forming lysophospholipids and lysolecithin, respect-

ively. Lysolecithin aids in the emulsification process.

Cholesteryl esters, the main form of cholesterol in the

diet, are hydrolyzed to free cholesterol by a pancre-

atic enzyme cholesterol esterase and aggregate into

micelles. Cholesterol esterase also hydrolases retinyl

esters. Its action increases the polarity of cholesteryl

and retinyl esters, which are highly hydrophobic mol-

ecules, allowing their micellar solubilization. Free

cholesterol derived from biliary secretion and cell

decay is also incorporated into micelles. When the

proportion of bile acids and phospholipids reaches a

critical micellar concentration, micelles are formed

and take up free fatty acids and monoacylglycerols,

and the expanded micelle is water-soluble.

0007In the aqueous interface between the micelles and

the epithelial cell surface, known as unstirred water

layer, the micelles dissociate, and the concentration of

fatty acids, monoacylglycerols, and lysophosphogly-

cerols increases, and these diffuse freely through the

apical enterocyte membrane. Saturated fatty acids

with a carbon length of 18 are poorly absorbed in

the free state but well absorbed as 2-monoacylglycer-

ols. Very-long-chain fatty acids with high melting

points are less efficiently absorbed. Triacylglycerols

and diacylglycerols, which are not acted upon by the

lipase, do not dissolve well in bile salts and remain in

lipid droplets. Unabsorbed fat in feces is usually

below 5%. Bile salts that are separated from the

micelles remain in the intestinal lumen and are

absorbed in the distal ileum by an active transport

system or are lost in the feces.

0008Short-chain (C:2–C:4) and medium-chain-length

(C:6–C:14) fatty acids are more hydrophilic and are

rapidly absorbed independent of micellar solubiliza-

tion or re-esterification within the intestinal cells.

They are transported via the portal circulation dir-

ectly to the liver. In the newborn, about half of the

Mouth

Stomach

Organs

Process

Emulsification

TG, FA, MG

Hydrolysis

FA, MG

Solubilization

Micelles

BA, PL, MG, FA

Uptake

Esterification

Chylomicrons

Synthesis

re-esterification of TG + apo B

Pancreas

Gall-bladder

Intestine

Linfatic

Vessels

Lingual lipase

Gastric lipase

Pancreatic lipase

Colipase

Bile acids

Enterocyte

Lymph Chylomicros

Blood

Peripheral

Tissues

fig0001 Figure 1 Process of triacylglycerol digestion and absorption showing the organs, enzymes, and processes involved. TG, triacyl-

glycerols; FA, fatty acids; MG, monoacylglycerol; BA, bile acids; PL, phospholipids.

FATS/Digestion, Absorption, and Transport 2275

medium-chain fatty acids from milk can be absorbed

in the stomach. In the enterocyte membrane, a fatty

acid-binding protein (FABP) facilitates the transport

of long-chain fatty acids (carbon chain length > 12)

into the cytosol and reduces the potential cytotoxic

effect of fatty acid soaps. Cholesterol binds to a sterol

carrier protein as it enters the cell. In the enterocyte,

cholesterol is re-esterified with a fatty acid by the

action of the enzyme acyl-CoA:cholesterol acyltrans-

ferase (ACAT). The fatty acids and monoacylglycer-

ols are re-esterified to triacylglycerols within the

endoplasmatic reticulum of the enterocyte, and then

are combined with phospholipids, cholesterol, cho-

lesteryl esters, and apolipoproteins, forming chylomi-

crons. Apo-B

is the structural protein of

chylomicrons. The process of chylomicron assembly

takes place in the Golgi apparatus, and the movement

of triacylglycerides from the endoplasmatic reticulum

to the Golgi appears to be a rate-limiting step in the

process. The union of triacylglycerol to apo-B

re-

quires a microsomal triacylglyceride transfer protein

(MTP). Finally, chylomicrons are released by exocy-

tosis to the lymphatic system and enter the blood

circulation by the left subclavian vein (Figure 2).

Lipid Transport in the Plasma

0009Lipids are transported in the hydrophilic blood

plasma environment as lipoproteins. Lipoprotein

particles consist of a core of triacylglycerol and chol-

esteryl esters, in varying proportions, surrounded by a

more hydrophilic layer of phospholipids, unesterified

cholesterol, and protein. In the circulation or as

a constitutive component, each lipoprotein particle

Mixed micelle

Bile

FA FA + CoA

ACAT

MTP

C + FA

Lymph

ApoB

FAT

DROPLET

INTESTINAL LUMEN

INTESTINAL

CELL

fig0002 Figure 2 Diagrammatic representation of triacylglycerol and cholesterol digestion and absorption in the gastrointestinal tract. A fat

droplet is shown (1) with insoluble triacylglycerols (TG) and cholesteryl ester (CE) in the core. The products of early lipolysis by lingual

and gastric lipases: fatty acids (FA), diacylglycerol (DG) and monoacylglycerol (MG) and also dietary phospholipids with their polar

heads face the outside of the droplet. Pancreatic lipase (2) acts at the water–oil interphase hydrolyzing TG molecules, with the

participation of bile acids (BA) and colipase, which anchors the lipase to its catalytic site. Cholesterol esterase acts on cholesteryl

ester forming free cholesterol (C). Lipolytic products (3) interact with bile acids (BA) and phospholipids (PL), facilitating their

solubilization into micelles (4). In the unstirred water layer, micelles dissociate, and their content diffuses to the enterocyte. Inside

the intestinal cell, fatty acids (FA) are activated and are re-esterified to TG (5). Cholesterol is absorbed and re-esterified with a fatty

acid by the action of the enzyme acylCoA:cholesterol acyltransferase (ACAT) originating cholesteryl ester (CE) (6). Chylomicron (CM)

synthesis requires the enzyme microsomal triacylglycerol transfer protein (MTP) to assemble the structural protein apo-B

triacylglycerols. Mature chylomicrons also incorporate cholesteryl esters to the core, and phospholipids, free cholesterol and

apoplipoproteins to the surface. Chylomicrons exit the enterocytes by exocytosis to the lymph. Adapted with permission from Ros E

(2000) Intestinal absorption of triglyceride and cholestrol. Dietary and pharmacological inhibition to reduce cardiovascular risk. Ath-

erosclerosis 151: 357–379.

2276 FATS/Digestion, Absorption, and Transport

contains specific proteins, termed apolipoproteins

(Figure 3).

0010 There are at least 12 apolipoproteins described and

present in different proportions among the lipopro-

teins (apo-AI, II and IV, Apo-B

and B

100

, apo-CI, II

and III, apo-D and apo-EII, III and IV). The apolipo-

proteins, apart from giving stability to the lipoprotein

particle, also direct the lipoprotein to its site of

metabolism by interactions with specific enzymes

and transport proteins on cell membranes. The ratio

of lipid to protein, which determines the density of

lipoproteins, is important in the classification of the

five major lipoproteins: chylomicrons; VLDL, very-

low-density lipoprotein; IDL, intermediate-density

lipoprotein; LDL, low-density lipoprotein; and HDL,

high-density lipoprotein. As the lipoproteins are

delipidated, the diameter reduces, and the density

increases. The lipoproteins exist in a dynamic state,

and their separation into one of the above classes,

according to their flotation characteristics, refers to

average values. Chylomicrons, the least dense of

all lipoproteins, have the highest proportion of tria-

cylglycerols (85–90%) and transport mainly lipids

from exogenous (dietary) origin. As already men-

tioned, during their assembly in the enterocytes,

they acquire apo-B

. Nascent chylomycrons also

contain apo A-I, apo A-IV, and, to a lesser extent,

apo A-II. Apo A-I and apo A-II enter the circulation in

chylomicrons but are rapidly transferred to nascent

HDL (Figure 3). Apo A-IV secreted by the enterocytes

is likely to mediate the anorectic effect of a lipid meal.

It is proposed that apo A-IV acts as endogenous anti-

oxidant and is involved in fat absorption.

0011VLDL, IDL, and LDL are related particles that

transport endogenous (synthesized in the liver) tri-

acylglycerols and cholesterols to peripheral tissues.

Intestine

Nascent

chylomicrons

(Apo B

Al, AlV)

Liver

VLDL

Remnants

VLDL

(APoE,CII, B

100

)

IDL

(APoE, B

100

)

LDL

(APo B

100

)

Small dense

LDL

Circulating

chylomicrons

(Apo E, CII, ApoB

)

ApoAl

Bile acids

+ cholesterol

LPL

NEFA

ApoE

ApoB

Hepatic

receptors

LPL

CETP

LCAT

CELL

Cholesterol

LCAT

HDL

LPL

CETP

Chylomicrons

remnants

HDL Nascent

Apo Al e All

Adipose tissue

Muscle

fig0003 Figure 3 Scheme for the transport of triacylglycerol and cholesterol in plasma. The classes of lipoproteins are shown: chylomicrons

and chylomicrons remnants; VLDL, very-low-density lipoprotein; IDL, intermediate-density lipoprotein; LDL, low-density lipoprotein;

HDL, high-density lipoprotein, with its subclasses: nascent-HDL, HDL

, and HDL

. The major apolipoproteins associated with each

lipoprotein are presented in parenthesis. Enzymes involved in the process of lipoprotein metabolism: LPL, lipoprotein lipase; HL,

hepatic lipase. Enzymes related to lipoprotein lipid exchange: LCAT, lecithin:cholesterol acyltransferase; CETP, cholesterol:ester

transfer protein. Hepatic receptors are indicated with their ligand for binding to cell-surface Apo-E or Apo-B. For more details, refer to

the text. Adapted with permission from Packard and Shepherd (1996).

FATS/Digestion, Absorption, and Transport 2277