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

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this is the most expensive type of veal on the whole-

sale market.

Marketing

0010 The US Department of Agriculture (USDA) has

official standards for grades of veal. The final

grade is based on evaluation of conformation and

quality, with a consideration for maturity and color

of lean meat. The grades are prime, choice, good,

standard, and utility. In practice, nearly 90% of

the veal carcasses in commerce are not graded by

the USDA.

0011 Veal is a delicate meat which is marketed fresh,

and it is not transported or stored in the frozen

state. In the USA, veal is produced in the dairy pro-

duction areas and is then transported to the popula-

tion centers, mainly along the East Coast. In Europe,

it is produced primarily in Germany, France, and The

Netherlands, and much of the production is then sold

to other countries.

Characteristics of the Meat

0012 The characteristics of veal arise from the fact that it is

from an immature animal. It is tender, moist, and

lean. It is tender because the connective tissue is not

cross-linked to the extent it is in more mature

animals. (See Meat: Structure.)

0013 A distinguishing property of veal is the pale color.

Color is due primarily to the iron-containing pigment

myoglobin. The muscle of newborn or immature

animals has a low content of myoglobin, and as the

animal matures the myoglobin increases. In raising

veal, the iron content of the diet generally does not

exceed the amount required for adequate nutrition.

This minimizes accumulation of myoglobin in the

muscle and consequently keeps the color pale.

0014 As an animal matures, the proportions of bone and

muscle decrease while fat increases. The carcass from

a newborn calf is approximately 25% bone, 68%

muscle, and 7% fat. The carcass from a 12-week-

old animal is about 20% bone, 65% muscle, and

15% fat, while that for pink veal (animal age 16–20

weeks) is about 17% bone, 64% muscle, and 19%

fat.

0015 Differences also exist in the composition of the

muscle retail cuts, as has been documented in the

USDA handbooks. Veal top round in the raw state

contains about 74.8% water, 21% protein, 3.1%

lipid, and 1.1% ash. When the top round is cooked,

the values are 55.5% water, 36.2% protein, 6.3%

lipid, and 1.6% ash. Obviously, the muscle from

immature animals has more water and less fat. (See

Protein: Food Sources.)

Further Processing

0016The vast majority of veal is consumed as fresh prod-

uct. Some specialty sausages, such as bockworst, are

made with veal as the major ingredient. As is the case

with fresh veal, these types of sausages are also noted

for their rather delicate flavor, and for the fact that

they are highly perishable. (See Meat: Sausages and

Comminuted Products.)

Consumption

0017The consumption of veal in the USA, although

never high, has declined markedly during the past

one-third century. In the early 1960s the per capita

disappearance of veal on a retail weight basis was

about 2.5 kg but by the early 1990s the value

had fallen to about 0.5 kg. Veal accounts for only

about 1% of the total consumption of red meat

in the USA.

0018Such average values are difficult to interpret be-

cause of regional and ethnic differences. For grocery

stores overall in the USA, the percentage of sales from

veal is about 1.5%, but in the north-east and Middle

Atlantic regions the percentages are 2.1% and 2.4%,

respectively.

0019Annual per capita consumption values for veal

in some of the European countries, expressed in

kilograms and for the year 1987, are 6.49 for France,

4 for Italy, 2.1 for The Netherlands, and 0.1 for

the UK.

0020The probable explanations for low consumptions

of veal in some countries, e.g., the USA and the UK,

are that it is not readily available at market and

the cost is expensive. The complications of ethnic,

regional, and historical patterns must be considered

in such interpretations and conclusions.

0021Even though veal is a naturally low-fat meat, it is

unlikely that demand will increase in the future.

See also: Meat: Structure; Sausages and Comminuted

Products; Protein: Food Sources

Further Reading

Anonymous (1998) Meat Facts. Washington, DC American

Meat Institute.

Anonymous (1989) Animal Statistical Report. Rijswijk:

PUV.

Anonymous (1988) Larousse Gastronomique. New York:

Crown Publishers.

Fabbricante T and Sultan WJ (1975) Practical Meat Cutting

and Merchandising. Pork, Lamb, Veal, vol. 2. Westport,

CT: AVI.

Kinsman DM (1988) Veal: Meat for Modern Menus.

Chicago, IL NLMB.

5898 VEAL

Metz JHM and Groenestein CM (eds) (1991) New Trends

in Veal Calf Production. Proceedings of the International

Symposium on Veal Calf Production, Wangeningen, The

Netherlands, 14–16 March 1990. EAAP publication

no. 52. Wageningen: Pudoc.

Piwoni R and Kliebenstein J (1983) Marketing Strategies

for Veal Calves. Extension Bulletin. Madison: University

of Wisconsin.

USDA (1972) Official United States Standards for Grades

of Veal and Calf Carcasses. Washington, DC: Govern-

ment Printing Office.

USDA (1989) Agriculture Handbook 8–17 on Veal. Wash-

ington, DC: Government Printing Office.

USDA (1990) Agriculture Handbook 8–13 on Beef.

Washington, DC: Government Printing Office.

Vegetable Fruits See Breadfruit

VEGETABLE OILS

Contents

Types and Properties

Oil Production and Processing

Composition and Analysis

Dietary Importance

Types and Properties

E W Hammond, Greenisle-Consulting, Kettering,

Introduction

0001 Vegetable oils are a group of fats that are derived

from some seeds, nuts, cereal grains, and fruits. It is

important to understand that not all of these vege-

table oils are liquid oils at ambient temperatures. In

addition, not all of the vegetable oils are produced in

commercial quantities, and of those that are, not all

are considered to be edible as in the sense of being a

typical dietary component. This treatise will cover

only edible vegetable oils.

0002 Vegetable oils, as used in foods, are comprised of

complex mixtures of triacylglycerols (TAGs; usually

> 95%) with some minor amounts of diacylglycerols

(usually < 5%). Other minor components are toco-

pherols/tocotrienols (up to 900 mg kg

1

) and phyto-

sterol esters/phytosterols (up to 1%). The vegetable

oil may be characterized confidently with expert

chromatographic analysis by determining its TAG

composition, together with the fatty acid composition

and the minor components. Tables 1–3 list some

vegetable oils that are found in foods and give typical

component analysis. The chemical and physical

properties of such oils will affect how they can

be used in the formulation and manufacture of

foods. The main and important properties are

described below.

Properties

General

0003When foods containing significant amounts of added

edible fats are formulated, the added fat will affect

three main characteristics of the food. The first is

processability during preparation; the second is sens-

ory quality (as related to taste and flavor); and the

third is shelf-life, which may be physical or chemical

in nature. Figure 1 shows the relationship between

some oil types, melting point, rancimat value, and

total amount of both unsaturated and polyunsatur-

ated fatty acids. Rancimat value is a measure of the

oxidation potential of a fat or oil. It is the time in

hours, at a stated temperature (typically 100



C) for

VEGETABLE OILS/Types and Properties 5899

tbl0001 Table 1 Some edible vegetable oils and their typical fatty acid composition (%)

Typeof oil 8:0 10:0 12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 22:0 22:1 24:0

Seeds

Babassu 5.4 6.0 44.3 15.8 8.6 2.9 15.2 1.7 0.1

Coconut 8.1 6.5 48.6 17.7 8.5 2.5 6.5 1.5 0.1

Palm kernel 4.0 4.1 49.7 16.0 8.0 2.4 13.7 2.0 0.1

Sunflower 0.1 0.2 6.8 0.1 4.7 18.6 68.6 0.5 0.4

Sunflower HOL

0.1 0.2 3.0 0.4 5.9 82.4 7.4 0.3 0.3

Rapeseed (leara)

0.1 4.7 0.3 1.7 59.0 21.4 9.9 0.6 1.4 0.4 0.3 0.2

Soybean 10.0 0.2 3.5 21.0 55.3 9.2 0.5 0.3

Cottonseed 1.0 23.9 0.5 2.9 18.5 52.5 0.3 0.4

Peanut 10.1 0.2 3.5 51.4 27.3 0.1 1.6 1.3 3.1 1.4

Cocoa butter 0.1 26.2 0.3 34.4 34.8 2.9 1.1 0.2

Nuts

Almond 0.1 8.5 1.1 1.0 57.0 31.4 0.6 0.1 0.1 0.1

Brazil 0.1 0.2 14.4 0.5 7.9 31.2 45.1 0.1 0.3 0.1 0.1

Cereals

Corn 10.7 0.2 1.5 30.5 55.9 0.8 0.4

Rice bran 13.9 1.9 2.7 41.1 36.4 2.3 1.8 0.2

Wheatgerm 0.2 18.5 0.6 0.5 18.1 55.9 5.3 0.1 0.8

Fruits

Palm 1.0 43.8 0.5 5.0 38.5 10.5 0.3 0.4

Olive 10.8 0.5 3.0 75.5 8.5 0.9 0.4 0.4

High oleic sunflower oil.

Low erucic acid rapeseed oil.

It should be noted that the above values are single sample analyses.

Most origins will offer a distribution of compositions depending upon variety, climate, soil, etc.

tbl0002 Table 2 Some edible vegetable oils and their typical triacyglycerol composition (%)

Typeof oil C30 C32 C34 C36 C38 C40 C42 C44 C46 C48 C50 C52 C54 C56 C58 C60

Seeds

Babassu 2.8 10.1 12.4 16.3 14.0 10.0 8.1 5.3 5.1 6.0 4.0 2.9 3.0

Coconut 3.7 12.7 15.9 18.9 17.2 10.6 7.6 4.1 2.4 2.7 1.6 1.5 1.1

Palm kernel 1.7 6.9 9.2 21.6 16.5 9.9 8.8 6.5 5.3 5.7 2.4 2.5 2.8 0.2

Sunflower 1.4 18.2 76.3 1.7 1.5 0.6

Sunflower HOL

0.2 0.8 12.1 80.3 3.0 2.6 1.0

Rapeseed (leara)

0.3 1.1 15.1 74.2 6.8 1.3 0.6

Soybean 0.2 0.7 5.1 27.1 61.3 4.0 1.2 0.3

Cottonseed 0.6 11.7 44.2 42.3 1.0 0.2

Peanut

4.2 26.4 52.3 7.2 6.4 2.9

Cocoa butter 0.5 19.3 46.8 30.9 1.9 0.4 0.2

Nuts

Almond 0.2 4.5 19.4 75.3 0.5 0.1

Brazil 0.2 0.5 6.7 24.6 68 0.5 0.2

Cereals

Corn 0.2 1.7 3.0 25.1 65.2 3.4 0.9 0.4

Fruits

Palm 0.4 9.2 42.8 38.9 8.4 0.3

Olive 3.4 27.2 68.2 1.0 0.2

The numbers quoted as, for example, C54 are carbon numbers and are equal to the sum of the carbon atoms in the fatty acids of the triacylglycerol, for

example: C54 ¼ 3  18, or C16 þ C18 þ C20.

high oleic sunflower oil.

low erucic acid rapeseed oil C62 ¼ 0.4% and C64 ¼ 0.2%.

Peanut C62 ¼ 0.5% and C64 ¼ 0.1%.

It should be noted that the above values are single sample analyses.

Most origins will offer a distribution of compositions depending upon variety, climate, soil, etc.

5900 VEGETABLE OILS/Types and Properties

the fat or oil to pass through induction to a rapid

oxidation rate. It can be seen that, in general, the

amount of polyunsaturates has the greater effect on

melting point: as polyunsaturates rise, the melting

point reduces. This rise is accompanied by a reduction

in the rancimat time. The rancimat time is a measure

of the ease with which the fat oxidizes (becomes

rancid) and therefore has a relationship to the ultim-

ate shelf-life of a product made with that fat. Gener-

ally, as the level of total unsaturated fatty acids rises

(particularly polyunsaturated fatty acids), so does the

potential of the fat to oxidize and form rancid off-

flavors. As an indicator, linoleic acid (two double

bonds) will have an oxidation rate that is some 50

times greater than oleic acid (one double bond). Thus,

it would be expected that normal sunflower oil

will become rancid more quickly than high-oleic

sunflower oil (Table 1).

0004These comparisons of properties are expressed as

simple links here, although in reality the links can

be quite complex. For example, comparing the data

given for palm oil (PO) and palm kernel oil (PKO),

both incidentally obtained from the palm fruits,

shows that PKO has a lower melting point than PO,

despite the fact that PO has a much higher level of

polyunsaturated fatty acids. However, PKO has a

tbl0003 Table 3 Some edible vegetable oils and their typical tocopherol composition (mg kg

1

)

Type of oil a-tocopherol a-tocopherol b-tocopherol b-tocopherol g-tocopherol g-tocotrienol d-tocopherol d-tocotrienol

Seeds

Coconut 20 5 10 2 1

Sunflower 850 25 20 2

Rapeseed (leara)

220 60 620 16

Soybean 110 10 1250 460

Cottonseed 550 45 330 10

Peanut 250 15 270 10

Cocoa butter 15 5 190

Cereals

Corn 150 10 20 1 720 70 120

Wheatgerm 1900 30 710 180 250 280

Fruits

Palm 240 270 5 40 360 2 55

Olive 110 10

Low erucic acid rapeseed oil.

It should be noted that the above values are single sample analyses.

Most origins will offer a distribution of compositions depending upon variety, climate, soil, etc.

−20

100

120

140

160

Rapeseed

Soybean

Sunflower

HOL sunflower

⬚C h

−1

Corn

Palm oil

Palm kernel

Coconut

Cocoa butter

Melting point (⬚C)

Rancimat (h)

Polyunsaturates (%)

total unsats (%)

fig0001 Figure 1 Relationship for different oils, between melting point, rancimat value and amount of total unsaturated and polyunsaturated

fatty acids.

VEGETABLE OILS/Types and Properties 5901

higher amount of shorter-chain fatty acids that create

lower-carbon-number TAGs with reduced melting

point temperatures (Tables 1 and 2). The rancimat

value for PKO is higher than that for PO and this fully

reflects the lower total amount of unsaturated fatty

acids present in PKO (Table 1).

0005 If corn oil is compared with sunflower oil, there

appear to be anomalies also. The total unsaturates

and polyunsaturates are similar and yet sunflower

oil has the lowest melting point in the group shown.

This is caused by the fact that sunflower oil has a high

content of TAGs, with three linoleic acids in the

structure.

0006 From these points, it will be seen that the final

physical properties of fats are dependent upon the

‘finer’ chemistry of TAG structure and this even in-

cludes the positional distribution of the fatty acids on

the glycerol of TAGs.

Chemical

0007 The main chemical property related to the use of fats

in foods is the potential for oxidation and the devel-

opment of rancidity. This chemical process is nor-

mally termed autooxidation and is an autocatalytic

reaction with oxygen in the air. As stated above,

this potential is closely related to the amount of

polyunsaturated fatty acids present in the fat. Potent

rancid taints can be obtained from soybean and

rapeseed oils that have a descriptor of ‘putty-like.’

The oxidation of linolenic acid (C18:3) results

in volatile compounds found in the process of setting

linseed oil putty. Linseed oil is referred to as a

‘drying’ oil as it oxidizes rapidly in air, forming

polymers that harden the putty. Sunflower oil

oxidizes less rapidly, but it is linoleic acid-rich and

produces potent taints with descriptors such as

‘green bean’ or ‘cut grass.’ As sunflower oil oxidizes

it forms jelly-like polymers. Such taints (aromas)

are found when green beans or grass are cut,

although these are a result of the action of the lipox-

ygenase enzyme as it catalyzes the oxidation of

linoleic acid.

0008 The ultimate chemical shelf-life of a fatty food (or

fat) is dependent on the unsaturation of the fat. How-

ever, the rate of oxidation of the fat will be modified

by the amount and type of tocopherols present

(Table 3). The tocopherols act as natural antioxi-

dants. For example, the tocotrienols in PO are very

important in controlling oxidation of the oil when it

is being used as a frying medium. This activity is most

important when the oil is being heated up to and used

above 150



C. However, the ambient shelf-life of fatty

products is better protected by the presence of g and d

tocopherols. Oils rich in a tocopherol appear to be

less well protected.

0009A second chemical property that sometimes relates

to shelf-life and taints is the possibility of oil hydroly-

sis. The glycerol ester group can be broken either with

water, by straight reaction under slightly alkaline pH

conditions, or through the action of lipase enzyme.

The lipase can arise as a residue in the food materials

or via a microbial action on the food. This latter

process takes place naturally on the fats in, for

example, unheat-treated wheat flours, producing free

fatty acids (FFA). This process does not cause flavor

taint, but may reduce the baking quality of the flour.

0010FFA do not normally cause flavor change at levels

below 2% of the fat. However, they may cause sur-

face activity changes in oils used, for example, in

deep-frying. The result can be foaming of the oil, a

deepening of the fried brown color, and a higher fat

content in the product. The FFA changes the heat and

moisture transfer properties at the product surface,

producing an overfried effect. Where lauric oils (high

content of C12:0, Table 1) are used, the production of

FFA at < 0.01% of the fat can be tasted as a soapy

taint. Thus, where coconut and palm kernel oils are

used, FFA must be guarded against. However, FFA

can be a positive property when it is present in fer-

mented products such as soy sauce or yogurt-type

products based on vegetable oils. (See Fats: Classifi-

cation.)

Physical

0011The melting points given in Figure 1 are actually slip

melting points. The slip melting point is the tempera-

ture at which 5% solid fat remains. To explain this,

it is important to understand that fats are not pure

compounds but are complex mixtures of TAGs. Each

pure TAG type has its own melting point but when

mixed with others the result will be different. Natural

fats therefore do not have sharp melting points but

will have a ratio of solid and liquid fat at any given

temperature. The solid fat content (SFC) is an import-

ant physical property and it is measured using pulsed

nuclear magnetic resonance (pNMR). The SFC may

be described as a graphic curve and is used as a

standard physical property when considering the

function of fats in making certain foods. Figure 2

shows this type of data for a range of important

food vegetable fats.

0012When making foods with fats that have solid prop-

erties at normal ambient temperatures, a further im-

portant physical property is the crystal form of the

fat. Fats are polymorphic, that is, they have more

than one crystal form, and this can be determined

using X-ray diffraction. Typically, fats can crystallize

in three different forms following the sequence:

Alpha ð aÞ)Beta prime ðb

Þ)Beta ðbÞ

5902 VEGETABLE OILS/Types and Properties

The rate of movement from one form to another is

dependent upon the structure of the TAGs together

with the time and temperature. It is a thermodynamic

process. The a form is usually physically unstable

above about 5



C and rapidly transforms to b

. The

form is predominant in most fats used for food

manufacture but may slowly transform over a period

of weeks or months to the b form.

0013 Cocoa butter (chocolate fat) is a special case, has a

more complex crystalline nature, and can exist in six

different forms. Cocoa butter has to be ‘tempered’ for

use in chocolate so as to obtain specifically the crystal

form five (form V). In this form, it retains high surface

gloss and good structure. The six crystal forms and

the shape of the SFC curve for cocoa butter (Figure 2)

are a consequence of its special TAG structure. Cocoa

butter has a predominance of symmetrical TAG,

where positions 1 and 3 of the TAG are occupied by

either 16:0 or 18:0, while position 2 is occupied by

18:1.

0014 In all fats, the melting point increases as they attain

the higher crystal forms. However, with the exception

of cocoa butter and other fats associated with choc-

olate manufacture, the preferred form for use as a

functional ingredient in foods is b

. The b

and b

forms are quite different and have different conse-

quences in food products containing them. The b

form can be likened to a bundle of needles. The

crystals knit together to form a three-dimensional

structure that can hold liquids such as oil or water

droplets within it. The b form is more plate-like with

larger crystals and these do not form a good stable

three-dimensional structure.

0015 The consequences of these physical properties are

very important in food manufacture, the shelf-life of

the food, and its sensory properties. It can be seen

(Figure 2) that the SFC curves for dough fats are

relatively flat. Most dough fats are plasticized before

use, that is, they are crystallized using a scraped sur-

face heat exchanger or rotator. This insures that the

solid fraction of the fat at, say, 25



C, is a fine distri-

bution of b

crystals in which is retained approxi-

mately 75% of liquid fat. This ‘texturized’ fat is

plastic and cream-like and will also retain at least

20% of its volume of water if added at the plasticiza-

tion stage. The resultant plastic fat material is easily

mixed with other dough recipe components to make a

cohesive and homogeneous dough. The relatively low

solid fat content provides a luxurious lubricant effect

in the mouth while eating the product.

0016Cream filling fats (Figure 2) have much higher

solids at ambient temperatures, but the solids fall

rapidly between 20 and 30



C. The b

crystal structure

acts in the same way as for dough fats, retaining

the liquid fat and allowing easy homogeneous

blending. But in addition, the crystal network of

these fats can be gas-filled to create a lower-density

foamed cream filling. The steep decline in solids at the

low-temperature end of the SFC curve provides a

‘clean’ palate, excellent flavor release, and a luxuriant

cooling sensation. This latter point is caused by the

rapid melting of fat and removal of heat from the

tongue and palate of the mouth. At the mid-range

temperature, cream fats are designed to have a par-

ticular slip melting temperature. This suits whether

they are to be deposited or stencilled on to such

materials as biscuit shells. The physical properties

are very important for these processes to be success-

ful.

0017Cocoa butter (Figure 2) shows a convex SFC curve.

There is considerable resistance to melting up to



C and this accounts for the ability of chocolate

to stay hard and glossy over a wide ambient tempera-

ture range. Above 30



C (mouth temperature) the fat

begins to melt very rapidly. This provides a ‘rush’ of

flavor release, a luxuriant creamy sensation, and (for

high-quality chocolate) a distinct cooling of the palate.

By the time body temperature is reached (37.5



there is no solid fat remaining. (See Cocoa: Chemistry

of Processing.)

0018The physical properties described above provide

for a good eating product with a relatively long

shelf-life. However, foods are dynamic materials

and thermodynamic processes strive to obtain the

least energy or lowest enthalpy in, for example,

the fat. The appearance of fat bloom, softening or

shrinkage of fat cream fillings, and softening and

bloom of chocolate coatings can limit shelf-life.

The transformation of a b

fat system to a b fat crystal

in a product will almost certainly be accompanied by

−10

20 25 30 32.5 35

% solid fat measured by pulsed NMR

(⬚C)

37.5 40 45

Cream filling fat

Pastry fat

Puff pastry fat

Biscuit dough fat

Chocolate cocoa butter

fig0002 Figure 2 Comparison for different fats of percentage solid fat

content over a range of temperature.

VEGETABLE OILS/Types and Properties 5903

the development of fat bloom or graining of the fat

phase. In these cases the liquid fat is released and the

product may become ‘oily.’ Fat bloom is shown as

either excessive crystal growth (graining) or a frosted

or moldy appearance on, for example, chocolate

coatings or biscuit surfaces.

0019 While b

fat systems do retain the liquid fat effi-

ciently it is inevitable that, with time, the liquid

phase will migrate out. This is seen particularly

where two fat-containing phases are in contact. Fat

migration changes the composition of the fat and

therefore the SFC. The outcome is usually a

softening of, for example, a chocolate coating.

Often the properties of vegetable fats are not opti-

mum for an application; in this case the physical

properties can be changed. Blending different fats

or chemically modifying them by hydrogenation or

interesterification will do this. In all cases, the chem-

ical make-up is changed and this has a direct effect

on the physical properties.

See also: Chromatography: Gas Chromatography;

Cocoa: Chemistry of Processing; Production, Products,

and Use

Further Reading

Ching Kuang Chow (ed.) (2000) Fatty Acids in Foods

and their Health Implications. New York: Marcel

Dekker.

Gunstone FD, Harwood JL and Padley FB (eds) (1986) The

Lipid Handbook. New York: Chapman & Hall.

Hammond EW (1993) Chromatography for the Analysis of

Lipids. Boca Raton, FL: CRC Press.

Timms RE and Stewart IM (1999) Cocoa butter, a unique

vegetable fat. Lipid Technology Newsletter 5: 101–107.

Oil Production and Processing

W Hamm, Harpenden, UK

Background

0001 Vegetable oils are principally recovered from oilseeds,

with oil-rich fruit such as the fruit of the oil palm and

of the olive tree providing important additional

sources. Solvent extraction is used for oil recovery

from oilseeds, but in the case of palm and olive oil,

the oil is recovered by separating it from the aqueous

phase present in the fruit after crushing. Vegetable

oils are for the most part refined before consumption,

refining comprising a series of steps designed to

produce a bland, stable oil. Refined oils may be modi-

fied in order to change their physical properties.

Virgin, i.e., unrefined, olive oil plays an important

part in the market for vegetable oils.

0002Both refining and oil modification processes are

increasingly being improved in order to conform

to modern standards of a healthy food product.

This entails avoiding the formation of undesirable

artefacts as well as minimizing the removal of valu-

able minor components.

Oilseeds and Oil-rich Fruits Used in the

Production of Edible Oils

0003Vigorous growth in the last half-century of produc-

tion and consumption of vegetable oils has meant that

the world-wide per capita consumption of oils and

fats has risen significantly, with many parts of the

developing world sharing this growth with that in

the industrialized regions. A direct consequence of

this increase in availability has been a substantial

increase in international trade in oils and oilseeds.

At the same time, vegetable oils also find substantial

use in the oleochemicals industry, which therefore

serves as an additional outlet for a limited number

of vegetable oils.

0004The oils used for edible purposes fall into two

categories. The seed oils are produced from annually

planted seeds, and this category includes, besides

soyabeans, rapeseed, sunflower seed, cottonseed,

groundnuts, and many other oil-rich seeds. The oil

content of the major seeds covers a wide range, the

soyabean normally containing less than 20% oil,

whereas many of the others contain in excess of

40% oil after dehulling. The second category of vege-

table oil sources is a smaller group of tree crops,

primarily comprising the fruit of the coconut and oil

palms as well as that of the olive tree. Being tree

crops, these do not have to be replanted annually,

but in consequence, the fruit only becomes available

after some years of cultivation. The fruit of the oil

palm shows a unique characteristic in that the kernel

of the fruit contains an oil (palm kernel oil) that has a

composition that differs radically from the oil in the

fleshy part of the fruit, the mesocarp.

0005From the point of view of applications, it is also

useful to consider vegetable oils on the basis of the

chain length of their major fatty acid components.

Oils containing large proportions of shorter-chain

fatty acids (C12 and C14 chain length), of which

coconut oil and palm kernel oil are the principal

representatives, comprise one group, whereas the

group of oils where the major fatty acids are of C18

chain length includes the majority of the seed oils (see

Table 1).

5904 VEGETABLE OILS/Oil Production and Processing

Oil Recovery

Oilseeds

0006 The extraction of oil from the various oilseeds re-

quires the application of heat and moisture to prepare

the oil-containing cells for rupture and pressure to

press the oil from the seed after size reduction,

size reduction generally being achieved by flaking.

Screw-press expellers have made it possible to operate

virtually continuously but leave 3–5% of oil in the

protein-rich cake. The development of the solvent

extraction process has increased oil recovery and at

the same time has made it economically attractive to

process seeds relatively low in oil content such as

soyabeans. However, the oil obtained using a screw

press contains fewer of the minor components present

in the oil, e.g., phospholipids, and is consequently

easier to refine.

0007 Industrial hexane is the solvent used universally

for the solvent extraction of oil from oilseed, al-

though research into extraction with other solvents,

including supercritical carbon dioxide, has been

reported. Solvent extraction is carried out using

countercurrent percolation of solvent through a bed

of seed flakes. The oil-rich solvent leaving the

extractor is then desolventized in a multiple-effect

evaporator. The solvent recovery sections of the

process generally account for a large share of the

capital investment in a solvent extraction plant, and

despite the use of sophisticated energy-recovery tech-

niques, the energy required for solvent recovery

makes the operating costs for the process consider-

ably higher than the costs of screw-press oil recovery.

This additional cost of production must be offset by

the value of the increased oil recovery.

0008 In the case of seeds having a high oil content, the

oil recovery process in many cases comprises a

screw-press operation followed by solvent extraction

of the partially deoiled cake. Oils containing high

levels of phospholipids, e.g., soyabean and rapeseed

(canola) oil, are water-degummed after extraction

and desolventization as the phospholipids precipitate

during storage and thus interfere with oil handling

and downstream processing. Degumming with water

reduces the phospholipid content of an oil of good

quality to approximately 200 p.p.m., expressed as

phosphorus, equivalent to 0.5–0.6% phospholipids

(see Figure 1). (See Phosphorus: Properties and Deter-

mination.)

0009Cold-pressed oils, i.e., oils recovered from seed

with minimum application of heat during pretreat-

ment and without use of solvent, are becoming popu-

lar in some countries.

Oils Obtained from Tree Crops

0010Palm oil Recovery of the oil from the fruit of the oil

palm (Elaeis guineensis) requires early sterilization of

the harvested fruit bunches if the formation of free

fatty acid in the oil resulting from the action of an

enzyme present in the fruitlets is to be avoided. The

oil palm plantation should therefore be closely linked,

both geographically and organizationally, to a mill

capable of processing the harvested fruit with

minimum delay. The fruit is steam-sterilized, and the

fruitlets are then stripped from the bunch. This oper-

ation is followed by pressing to recover the crude

palm oil, with the palm kernels left in the press

cake. After clarification and drying, the crude palm

oil is ready for downstream processing. One hundred

tonnes of fresh fruit bunches (FFB) can be expected

to produce approximately 23 tonnes of crude palm

oil. Crude palm oil from South-east Asia normally

contains 4–5% free fatty acids (FFA), but palm oil

containing 2–3% FFA can be produced. The crude oil

tbl0001 Table 1 Oil production: oil yield and quality

Seed/fruit Seedcrushed

1999^2000

(million tonnes)

Oilproduction

1999^2000

(million tonnes)

Oil yield (%) Oil yieldcalculatedon FFA of oil

Soya 137.92 25.21 18–19 Dehulled beans 0.3–1.2

Rapeseed 37.46 14.41 38–42 Undehulled seed 1.0–2.0

Sunflower 23.72 9.57 40 Dehulled seed 1.0–2.0

Cottonseed 26.67 3.92 23 Delinted, dehulled seed 1.0–3.0

Groundnut 11.34 4.54 47 Kernels 1.0–3.0

Palm na 20.54 22–28 Oil yield on fresh fruit bunch 3.0–5.0

Coconut 4.85 3.02 60–70 Copra 2.0–4.0

Olive na 2.27 20 Yield excludes kernel oil See section on Olive oil

Calculated as palmitic acid.

Calculated as lauric acid.

na, not applicable.

From Oil World Annual 2000.

VEGETABLE OILS/Oil Production and Processing 5905

is rich in b-carotene, tocopherols, and tocotrienols,

and this feature of the oil is used to enhance its value.

0011 The palm kernels, after separation from fibrous

material, are processed for oil recovery using a

solvent extraction process, as described above for

seed oils. One hundred tonnes of FFB should produce

approximately 2.5 tonnes of palm kernel oil, an oil

rich in short-chain fatty acids.

0012 Olive oil The olive oil production process involves

crushing the fruit followed by a two-stage centrifugal

system that serves to separate the oil and then wash

it. The fruit contains an average of 20% oil, and

the bulk of the oil in the fruit is produced to the

standards required to classify it as virgin or extra

virgin oil. Olive-pomace oil is the oil obtained by

solvent extraction of the residue after the first separ-

ation stage. In the European Union, this oil must

be refined and then blended with a specified amount

of virgin olive oil before it can be sold for human

consumption. Internationally agreed specifications

for the various grades of olive oil require extra virgin

olive oil to have a FFA content not exceeding

1.0% (as oleic acid), whereas virgin olive oil may

contain up to a maximum of 2.0% free fatty acid.

(See Olive Oil.)

0013Rice bran oil Rice bran oil, a byproduct of rice

processing, is mainly produced in East Asia. Like the

palm fruitlet, rice bran contains an enzyme that rap-

idly attacks the oil if it is not heat-deactivated imme-

diately after separation from the crop. In practice,

unrefined rice bran oil often contains high levels of

FFA as a result of delays in processing. The presence

of important antioxidants in rice bran oil, ferulic acid

esters generally referred to as g-oryzanols, has re-

cently led to its use as a component of frying oils in

order to extend the useful life of industrial frying oils.

0014Coconut oil Coconut oil is the oil obtained from the

dried ‘meat,’ generally known as ‘copra,’ of the coco-

nut fruit. The drying of the copra, a necessary step,

prior to oil extraction, is sometimes carried out with

hot gases containing polycyclic aromatic hydrocar-

bons (PAHs). These must be removed during refining

of the oil. Coconut oil has been the most important

of the so-called lauric oils, although palm kernel oil

production is now comparable with that of coconut

oil. (See Coconut Palm.)

Oil Movements

0015The pattern of growth in edible oil production and

consumption has meant that large quantities of crude

edible oil are moved intercontinentally from producer

to user countries. In order to avoid contamination of

vegetable oil cargoes with residues of cargoes previ-

ously carried by the same vessel, various international

bodies such as the London-based Federation of Oils,

Seeds and Fats Associations and the US National

Institute of Oilseed Products introduced regulations

governing the type of cargo that may be carried by a

parcel tanker in the three loadings immediately prior

to loading an oil to be used for edible purposes.

0016The possibility of overheating of the oil during the

voyage or at the time of discharge is also a cause of oil

quality deterioration in the course of long-distance

transportation. Table 2 is a schedule of recommended

cargo temperatures cited in a recent Codex Alimen-

tarius Commission report.

0017Ingress of water into the cargo while at sea can also

be troublesome, as this can lead to hydrolysis of the

triacylglycerols, the major component of the oil,

which manifests itself in an increase of the FFA con-

tent, the process of hydrolysis being considered to be

autocatalytic.

0018A consequence of these oil movements is the need

for substantial storage capacity for vegetable oils at

the receiving port, and large tank farms have been

Seed storage

1000 kg seed (440 kg oil)

Decortication

(Dehulling)

140 kg hulls

860 kg kernels

Breaking/

flaking/

conditioning

Pre-expelling

Solvent extraction

400 kg crude oil

475 kg sunflower meal

0.5% oil

40% protein

280 kg crude oil

Crude

sunflower

oil storage

fig0001 Figure 1 Sunflower oil production: average values for process-

ing of decorticated sunflower seed. Note that oil may be

recovered from either whole or partially decorticated seed.

5906 VEGETABLE OILS/Oil Production and Processing

established over the years in the major receiving

ports, Rotterdam, Hamburg, and New York. As

Malaysia mainly ships refined palm oil fractions

(though this may be re-refined by the receiver), there

is a growing demand for high-quality storage at the

major ports. Nitrogen blanketing of cargoes either

during shipment or in port storage has been recom-

mended. In the case of higher-value fats, e.g., confec-

tionery fat components, shipment in special

containers has been used.

Oil Processing

0019 Although filtered crude oil is sometimes consumed

without any conventional refining, for all practical

purposes, vegetable oils must be refined in order to

make them suitable for consumption in one of the

forms in which oils and fats are used. The refining

processes in use nowadays have a number of object-

ives, the most important of these being

0020 to produce a clear, stable oil free of undesirable

minor components;

0021 to ensure that the refined oil has a good keepability

and retains, as far as possible, those minor

components that are considered to be desirable,

e.g., tocopherols;

0022to avoid structural damage to the oil, e.g., by the

formation of trans-fatty acids and polar com-

pounds (diacylglycerols, polymers);

0023to minimize direct and downgrading losses intrin-

sic to the process;

0024to minimize the cost of processing.

These objectives are achieved by subjecting the oil to

either of the two main processes used by the industry.

Chemical refining relies on the reaction of the FFA

present in the crude oil with an alkaline solution,

normally sodium hydroxide, to reduce the FFA con-

tent of the oil to an acceptable level. Physical refining,

however, makes use of the relative volatility of these

FFA to separate them from the major constituents,

the triacylglycerols, in a steam-stripping operation

carried out at high temperature and low pressure,

each process having advantages and disadvantages

(Table 3). Both processes (see Figure 2) are considered

in more detail in the following sections.

Degumming

0025An important characteristic of vegetable oils is their

phospholipid content, the seed oils being richest in

these (see Table 4). For processing reasons, the phos-

pholipids are often divided into those readily hydrat-

able by water, and the remainder that can only be

hydrated (and become insoluble in oil) by the add-

ition of acids. The water-hydratable phospholipids,

which are frequently removed immediately after ex-

traction, are useful as a source of lecithin and its

derivatives.

0026The removal of nonhydratable phospholipids is

sometimes combined with chemical removal of FFA

but can also be carried out as a separate operation, an

option that becomes particularly important when the

oil is to be refined physically.

0027Citric acid, though more costly to use than phos-

phoric acid for the hydration of phospholipids not

tbl0002 Table 2 Recommended schedule of cargo temperatures (



Oil During voyage On discharge

Min Max Min Max

Sunflower Ambient Ambient Ambient 20

Soyabean Ambient Ambient 20 25

Groundnut Ambient Ambient 20 25

Rapeseed Ambient Ambient Ambient 20

Corn Ambient Ambient Ambient 20

Coconut 27 32 40 45

Palm 32 40 50 55

Palm stearin, RBD 40 45 60 65

Palm olein, RBD 25 30 32 35

Schedule produced by International Seed Crushers’ Association.

tbl0003 Table 3 Advantages and disadvantages of chemical and physical refining of oils

Advantages Disadvantages

Chemical refining

1. Flexibility (ability to process small batches, dark oils) 1. Refining loss (oil downgrading) can be high

2. Moderate deodorization temperature required 2. Relatively high level of effluent formation

3. Better for recovery of valuable minor components in

deodorizer distillate

Physical refining

1. Lower refining loss 1. Higher stripping/deodorization temperatures required

2. Reduced effluent formation 2. More sensitive to residual levels of phospholipids and metals

3. Less labor-intensive 3. Increased bleaching earth consumption

4. Unsuitable for dark oils

VEGETABLE OILS/Oil Production and Processing 5907