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each sample to a solvent ratio of 95%-A to 5%-B,

pumped for 15 min at 1.0 ml min

1

. This column

equilibration step and time are important for consist-

ent retention times and separations. An HPLC system

with an autosampler that will time this period

accurately is a great advantage.

0011 RP column packings are not tolerant of high

sample loadings and are sensitive to small amounts

of other solvents used to dissolve samples. Thus,

sample sizes should not exceed 100 mgin20mlof

solvent. If the sample solvent cannot be that used as

the initial mobile phase for HPLC, then its behavior

in modifying the column condition must be ascer-

tained. Chloroform should be avoided as it often

causes peak splitting, whereas alcohols and hexane

create solubility problems. Toluene is a suitable

general purpose solvent in this application. Typical

chromatography data are shown in Figure 1.

Argentation High-performance Liquid

Chromatography

0012 Vegetable fats used for confectionery production,

such as for chocolate, require fats with specific phys-

ical properties. Such a fat is cocoa butter (CB) and

any of the CB equivalents derived by blending of

native and fractionated fats of vegetable origin. The

specific melting properties and solid/liquid ratios

(measured by pulsed nuclear magnetic resonance

and plotted as solid fat curves) are created by the

presence of a high level (up to 90%) of ‘symmetrical’

monounsaturated TAG. This TAG has oleic acid (O)

at position 2 and a saturated fatty acid, palmitic (P)

or stearic (St), at positions 1 and 3, thus producing

POP-, POSt-, and StOSt-type TAGs. Perhaps the most

rapid method of obtaining quantitative evaluation of

such a fat is via argentation HPLC. In this technique,

the silver atoms form transient ‘complexes’ with the p

electrons of the unsaturated centers (double bonds).

Separation of TAG species depends upon the number

of double bonds, their geometry (whether cis or

trans), and the amount of hindrance caused to any

‘complex’ formation. Thus, monoenes separate from

dienes, from trienes, etc. ‘Complexes’ with trans

double bonds are less efficient than those with

cis double bonds and therefore also separate; trans

being relatively less polar than cis. Where there is

hindrance to ‘complex’ formation (due to fatty acid

position on the TAG), separation may also occur. For

instance, in StOSt, the double bond in oleic is more

hindered than in StStO, resulting in StOSt being

relatively less polar than StStO causing the two to

separate. Figure 2 shows a typical example of the

separation of TAG. (See Cocoa: Production, Prod-

ucts, and Use.)

0013To achieve the separations in Figure 2, a 20 cm 

4 mm column of LiChrosorb Si-60, 5 mm silica

(Merck) coated with 5% silver nitrate, was used.

This packing is not available commercially but can

be prepared freshly for each column. The silver ni-

trate, in a foil-covered round flask, is dissolved in

acetonitrile and diluted with methanol. The silica is

slurried in this and the solvent carefully removed by

Palm oil

350

300

250

200

150

100

Response

01020304050

DGs

LnLnP

LnOM

LnOO

LnOP

PLnP

OOO

StLnO

PLnSt

PPP

POSt

PPSt

StOSt

POO

POP

Retention time (min)

fig0001 Figure 1 NARP-HPLC of refined, bleached, and deodorized Malaysian palm oil. St, stearic; P, palmitic; O, oleic; Ln, linoleic;

M, myristic; DGs, diacylglycerides.

5918 VEGETABLE OILS/Composition and Analysis

rotary evaporation, ensuring constant mixing. When

the packing is apparently dry, the last traces of solvent

are removed by heating the flask to 70



C under

vacuum for 10 min. This material is slurried in

chloroform for column packing and the column

packed to 28 MPa (4000 psi) with toluene for 45 min.

0014 The sample size can be up to 600 mgin30mlof

toluene. The three solvents for HPLC are:

0015 A ¼ toluene/hexane (1:1, v/v);

0016 B ¼ toluene/ethyl acetate (3:1, v/v);

0017 C ¼ toluene with 10 ppm formic acid.

0018 A concave solvent gradient is used from 8%-B to

90%-B in A over 28 min. The regeneration step is

very important and uses solvent C for 12 min

followed by 8%-B in A for 7 min. Solvent flow is

1.5 ml min

1

. Detection of the eluted TAG has to be

done by evaporative system detectors such as the

Tracor 945 (flame ionization type, not now commer-

cially available), or light-scattering instruments such

as the PL-ELS 1000 (Polymer Laboratories). It should

be noted that the quantitative behavior of the two

instrument types is different. The response curves of

the Tracor 945 are essentially linear, while those

of light-scattering instruments are curved and sig-

moid. Calibration is very important if reliable data

are to be obtained, and this should be part of a

written procedure. The analysis time is relatively

long with a turnaround time of about 40 min per

sample, but improvements have been made upon this.

Minor Components

0019Crude vegetable fats are usually at least 95%

TAG. After accounting for any FFA, other minor

components can be present, which can include toco-

pherols, carotenes, gums, waxes, polar lipids

(lecithins), unsaponifiable matter, chlorophyl pig-

ments, hydrocarbons, and mineral constituents

(present possibly as metal soaps of fatty acids).

Refer to individual constituents.

0020There are standard methods published by the

American Oil Chemists’ Society (AOCS) and the As-

sociation of Official Analytical Chemists (AOAC) for

the analysis of the above components. The procedures

are fully documented and tested and may be updated

at suitable periods, so they will not be reproduced

here. However, it is worth mentioning that some of

the older published methods have escaped improve-

ment, and more up-to-date procedures can often be

found.

0021For instance, tocopherols have traditionally been

estimated as a group, after isolation from the

nonsaponifiable fraction of an oil, by reaction

with a,a-dipyridyl and colorimetric analysis. How-

ever, it is known that the tocopherol composition

can aid the identification of a fat and also that

different tocopherol compositions lead to different

stabilities of a fat to oxidation. Accurate analysis

of individual tocopherol compositions can be readily

done by HPLC. Essentially, the extracted and dry

600

800

1000

1200

1400

1600

0 5 10 15 20 25 30

StStSt

StStO

StLSt

StLO

OOO

OOL

DAG

StOSt

StOO

Detector response (mV)

Retention time (min)

fig0002 Figure 2 Argentation HPLC of refined palm oil triacylglycerides. The peak labeling corresponds to fatty acids in the order of

occurrence on the glyceride: St, saturated (i.e., palmitic, stearic, arachidic); O, oleic; L, linoleic.

VEGETABLE OILS/Composition and Analysis 5919

fat is dissolved in the mobile phase solvent. A

15 cm  4mm column packed with 5- mm Chrome-

gasphere silica (E.S. Industries, Marlton, NJ) is used

with a fluorescence detector (e.g., Kontron SFM25

with a flow cell). Excitation is set at 294 nm and

emission at 325 nm. The HPLC system is isocratic

using a solvent of 3% THF in 2,2,4-trimethyl

pentane (iso-octane) as the mobile phase at a flow

of 1.5ml min

1

. The sample is applied via a 25- ml

loop and Rheodyne valve. Complete separation

of tocopherols and tocotrienols is achieved

(Figure 3). The column requires flushing with

10% methanol in chloroform every 200 samples to

remove any build-up of polar lipid material. Figure

3 shows a typical chromatogram from the analysis

of palm oil.

Authentication of Oils

0022The purity of composition of a natural vegetable oil

may be extremely important to the ultimate user. Fats

or oils can be among the most expensive ingredients

used in the manufacture of foods. Thus, there are

situations where, for reasons of unfortunate cross-

contamination or adulteration for profit, it becomes

important to know the authentic composition of a

natural oil. (See Adulteration of Foods: History and

Occurrence.)

0023The chemical composition of natural vegetable oils

is readily obtained by chromatographic analysis. In-

formation on structure can also be obtained by spe-

cific enzyme techniques, and minor components can

be analyzed either by chemical techniques or again by

0 5 10 15 20 25

100

150

200

250

300

350

α T

δ T

δ T3

β T

γ T

γ T3

β T3

α T3

Retention time (min)

Response

fig0003 Figure 3 HPLC analysis of palm oil tocotrienols and tocopherols (conditions are described in the text).

tbl0001 Table 1 Fatty acid composition of a range of rapeseed oils

Sample name Fattyacid (% composition)

12:0 14:0 16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:1 20:2 22:0 22:1 24:0 24:1

German, Winter 0.1 4.2 0.3 1.9 59.7 20.2 8.9 0.5 2.0 0.1 0.3 1.5 0.1 0.2

UK, high yield 0.1 5.1 0.4 1.5 59.7 21.0 9.5 0.6 1.4 0.0 0.3 0.4 0.0 0.0

Denmark, Spring 0.0 4.7 0.3 1.4 57.5 21.7 10.9 0.5 1.6 0.1 0.4 1.0 0.0 0.0

France, Tapidor 0.1 4.7 0.3 1.9 59.4 21.0 9.5 0.5 1.5 0.0 0.4 0.7 0.0 0.0

USA, not known 0.0 4.0 0.2 2.1 61.2 20.0 9.5 0.6 1.5 0.1 0.3 0.5 0.0 0.0

China, high erucic 0.1 2.8 0.1 1.3 17.1 13.2 8.5 0.7 9.0 0.2 1.2 44.0 0.8 1.1

China, high erucic 0.1 1.8 0.3 1.7 16.2 12.0 8.3 0.8 9.0 0.2 1.3 46.0 0.7 0.6

Canada, not known 0.1 4.1 0.5 1.7 58.9 21.2 9.7 0.5 1.7 0.0 0.3 1.0 0.2 0.1

Europe, high erucic 0.1 4.0 0.3 1.0 18.5 14.5 11.0 0.8 6.5 0.8 0.5 41.0 1.0 0.0

UK, high yield 0.1 4.0 0.3 1.6 61.5 20.0 10.0 0.5 1.0 0.0 0.3 0.5 0.2 0.0

UK, not known 0.0 4.9 0.3 1.7 59.4 20.8 9.9 0.6 1.4 0.0 0.4 0.3 0.2 0.1

Laurical(GM)

39.93.92.70.11.830.111.09.10.20.80.40.10.00.00.0

High oleic, UK test crop 0.1 0.2 3.9 0.4 2.4 74.0 9.9 7.0 0.1 1.4 0.1 0.3 0.2 0.1 0.0

Genetically Modified Crop (trade name of Calgene).

5920 VEGETABLE OILS/Composition and Analysis

chromatography. All this information characterizes

the sample being analyzed, but does not necessarily

apply exactly to another oil of the same species from a

different part of the world. Also, it is important that

data be obtained via more than one technique, since

actual differences in oil composition may only

become apparent with certain techniques.

0024 Within a single species of plant, for instance rape-

seed, there can be a number of varieties. It is almost

certain that the oil composition of the varieties will

be different. This statement is even more important

now that genetic modification of oil composition is

being done. Also, if one variety is grown in different

environments, created either by countries or even by

areas of a single country, these situations can lead to

oils of variable composition. The differences may be

small or large, but they will provide statistical range

bands (with statistical means) within which any

particular oil composition might lie. This shows

that to authenticate a particular oil unambiguously,

there must be sufficient world data on the compos-

ition as measured by a number of techniques. Table 1

shows typical analytical data that we have found

for a range of rapeseed crops. Further data about

many vegetable oils are published in The Lipid

Handbook.

See also: Adulteration of Foods: History and

Occurrence; Carotenoids: Occurrence, Properties, and

Determination; Chromatography: High-performance

Liquid Chromatography; Gas Chromatography; Cocoa:

Production, Products, and Use; Contamination of Food;

Fats: Classification; Fatty Acids: Properties; Analysis;

Gums: Properties of Individual Gums; Phospholipids:

Properties and Occurrence; Tocopherols: Properties and

Determination; Physiology; Triglycerides: Structures and

Properties; Characterization and Determination

Further Reading

AOCS (1984) Recommended Practices, 3rd edn. Cham-

paign, IL: American Oil Chemists’ Society.

AOAC (1984) Official Methods of Analysis. Washington,

DC: Association of Official Analytical Chemists.

Christie WW (1982) Lipid Analysis, 2nd edn. Oxford: Per-

gamon Press.

Christie WW (1989) Gas Chromatography and Lipids – A

Practical Guide. Ayr, UK: The Oily Press.

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

Lipid Handbook. New York: Chapman & Hall.

Hammond E (1988) Flame ionisation detection for

the HPLC of lipids. Chromatography and Analysis 1:

7–9.

Hammond EW (1993) Chromatography for the Analysis of

Lipids. Boca Raton, FL: CRC Press.

Hammond EW (1998) Analysis – Tocopherols and Toco-

trienols. Lipid Technology 10: 86–88.

Jeffrey BSJ (1991) Silver-complexation liquid chromatog-

raphy for fast high-resolution separations of triacylgly-

cerols. Journal of the American Oil Chemists’ Society

68: 289–293.

Dietary Importance

J Dupont, United States Department of Agriculture,

Beltsville, MD, USA

This article is reproduced from Encyclopaedia of Food Science,

Background

0001Vegetable oils are derived from oil seeds grown

mainly for their oil. The major food oils consumed

as cooking and salad oils are canola (rapeseed),

corn, cottonseed, olive, palm, palm kernel, coconut,

peanut, safflower, soya bean and sunflower. They are

all triacylglycerols that are liquid at room tempera-

ture, but differ greatly in fatty acid composition

(Table 1). They are classified as short-chain (C

6–8

medium-chain (C

10–12

), and long-chain (C

14–18

). The

plant oils may be saturated (completely hydrogen-

ated) or have one, two, or three double bonds of the

cis configuration. (See Fatty Acids: Properties.)

Energy Value

0002Long-chain acylglycerols provide 38 kJ g

1

, whereas

protein and carbohydrate provide 17 kJ g

1

. Because

of the difference in energy value of oils as compared

with the other energy-yielding nutrients, concentra-

tion in the diet is often expressed as a percentage of

energy (en%). Vegetable oils are highly digestible

(greater than 95%). They are hydrolyzed in the

gastrointestinal tract, yielding free fatty acids (FFAs)

and sn2-monoacylglycerols. By formation of bile mi-

celles, the FFAs and monoacylglycerols come into

contact with the mucosal cell membranes and diffuse

through the membrane. Within the mucosal cells,

they are reesterified to triacylglycerols. They are

made water-soluble by incorporation into chylomi-

crons in the mucosa.

0003Medium-chain fatty acids occur in triacylglycerols

(medium-chain triacylglycerols; MCT) of coconut

and palm kernel oils. The MCTs are much more

water-soluble than are long-chain triacylglycerols.

They are hydrolyzed and enter the mucosal cells

but are partially transported as FFAs in the portal

circulation.

0004Chylomicrons and albumin-bound fatty acids are

transported to the liver, adipose tissue, and other

organs. In the process, chylomicrons are hydrolyzed

VEGETABLE OILS/Dietary Importance 5921

by the action of lipoprotein lipase, and the fatty acids

enter the cells by diffusion and are reesterified to

triacylglycerols. During fasting, the triacylglycerol

fatty acids are released from adipose tissue by hy-

drolysis for use as energy. Fatty acids that enter

the liver are resecreted as very-low-density lipopro-

teins, which are hydrolyzed similarly to chylomi-

crons, yielding low-density lipoproteins (LDLs),

which are taken up by tissues via a receptor-mediated

process. The LDLs are hydrolyzed to yield fatty

acids for energy or reesterification and storage.

(See Lipoproteins.)

0005 Fatty acids are used for energy production in the

mitochondria and peroxisomes of cells. Saturated

fatty acids (SFAs) are oxidized by b oxidation to

yield acetyl coenzyme A (acetyl CoA), which enters

the tricarboxylic acid cycle. Unsaturated fatty acids

require two more enzymatic steps that are needed for

SFAs to change the existing double bonds from cis to

trans and to move them from a g to a b position. Even

so, oxidation of C18:2 n-6 is more rapid than that of

C18:1 n-9. Medium-chain triacylglycerol acids are

preferentially oxidized by peroxisomes rather than

mitochondria. Some of the acetyl CoA produced is

oxidized to hydrogen peroxide, which requires cata-

lase for dismutation to water and oxygen, yielding

heat. This reduces the yield of these fatty acids to

less than the 37.66 kJ g

1

assumed for fats in general.

(See Fatty Acids: Metabolism; Dietary Importance.)

Essential Fatty Acids

0006 Vegetable oils generally have a relatively high con-

centration of polyunsaturated fatty acids (PUFAs)

(Table 1). Exceptions are coconut, palm, and palm

kernel oils, which are primarily saturated, and olive

and canola oils, which have relatively less PUFAs and

more monounsaturated fatty acids. The most abun-

dant PUFA is linoleic acid (C18:2 n-6), with canola

and soya oils having appreciable concentrations of

a-linolenic acid (C18:3 n-3). Because these fatty

tbl0001 Table 1 Percentage fatty acid composition of refined vegetable oils

Oil Fattyacid

6:0 8:0 10:0 12:0 14:0 16:0 16:1 n- 7 18: 0 18:1 n-9 18:2 n-6 18:3 n - 3 20:1 20:4 n - 6 22:1

Canola

4 2 55 26 10 2

Rapeseed, LEAR

4.8 0.5 1.6 53.8 22.1 11.1 1.0 0.1

Soya bean 0.1 10.3 0.2 3.8 22.8 51.0 6.8 0.2

Corn 10.9 1.8 24.2 58.0 0.7

Olive 11.0 0.8 2.2 72.5 7.9 0.6 0.3

Cottonseed 0.8 22.7 0.8 2.3 17.0 51.5 0.2 0.1

Safflower 4.8 1.3 75.3 14.2

Linseed 5.3 4.1 20.2 12.7 53.3

Palm 0.1 1.0 43.5 0.3 4.3 36.6 9.1 0.2 0.1

Palm kernel 0.2 3.3 3.7 47.0 16.4 8.1 2.8 11.4 1.6

Coconut 0.6 7.5 6.0 44.6 16.8 8.2 2.8 5.8 1.8

Peanut 0.1 9.5 0.1 2.2 44.8 32.0 1.3

Number of carbons: number of double bonds, location of distal (from n or o) double bond.

From Canola Council of Canada (1987) Canola Oil^Properties and Performance. Publication No. 60. Winnipeg: Canola Council of Canada.

All other data from USDA (1979) Composition of Foods. Agriculture Handbook 8-4. Washington, DC: US Department of Agriculture.

Low-erucic-acid rapeseed oil.

tbl0002Table 2 Relationship between dietary linoleic acid and

biological effects

Dietaryconcentration

oflinoleic acid (en%)

Reported biological effects

Rat: dermatitis, growth retardation,

infertility, cellular and humoral immune

system defects

Human: dermatitis

1 Deficient Rat: increase in triene: tetraene ratio to

0.4, decrease in eicosanoid production

Mouse: immune system impaired, plaque

formation

Human: increase in triene: tetraene ratio to

0.4, decrease in clotting time

2–3

Rat: maximal amount of C20:4 n-6 in

cellular lipids, increased eicosanoid

production

Mouse: normal plaque formation

Saturation Human: increased plasma cholesterol,

decrease in triene: tetraene ratio to 0.1

4 Rat, guinea-pig, mouse: normal mitogenic

response

5 DMBA rat: mammary cancer

8 Human: decreased plasma cholesterol

Rodents: delayed hypersensitivity

normalized

NMU rat: mammary neoplasia

Excess Guinea-pig: decreased mitogenic

response

15 Rat: prostatic neoplasia, rat colon cancer

5922 VEGETABLE OILS/Dietary Importance

acids (1) cannot be synthesized by animal cells and

(2) have essential metabolic functions, they are

deemed dietary essential fatty acids. Table 2

summarizes current knowledge of the effects of dif-

ferent dietary levels of linoleic acid. (See Essential

Fatty Acids.)

0007 Linoleic acid is a component of ceramides,

which are necessary to maintain the transdermal

water barrier of the epidermis. It is the precursor

by elongation and desaturation (Figure 1) of arachi-

donic acid (C20:4 n-6). Arachidonate is the precursor

of the eicosanoids: prostaglandins, thromboxanes,

prostacyclin, and leukotrienes (Figure 2). The

eicosanoids are autocrine and paracrine factors,

which are physiologically active at concentrations of

pico- and nanograms. They are required for functions

of the cardiovascular, renal, gastrointestinal, immune,

and reproductive systems. (See Prostaglandins and

Leukotrienes.)

0008Many studies indicate that essential fatty acids

are necessary for normal immune function. Essential

fatty acid deficiency impairs B- and T-cell-mediated

responses. These impairments are normalized by

inclusion of essential fatty acids in the diet. Most

studies have used rodents, and the results cannot be

readily extrapolated to humans because the

immune systems of different species respond differ-

ently to dietary fat alterations. (See Immunology

of Food.)

0009a-Linolenic is the precursor for eicosapentaenoic

acid (C20:5 n-3) and docosahexaenoic acid (C22:6

n-3) that are required for brain and retinal develop-

ment and function in animals.

Vitamin E

0010The vegetable oils that contain high concentrations

of PUFA generally contain appreciable quantities of

a- and g-tocopherols (vitamin E) (Table 3). Vitamin E

is a membrane-bound, lipophilic antioxidant closely

associated with arachidonic acid in the membrane.

Vitamin E may protect membranes by trapping

lipid peroxyl free radicals produced from PUFA

under conditions of oxidative stress. (See Toco-

pherols: Physiology.)

n-9

Stearate

Oleate g -Linolenate

∆9D

∆5D

∆4D

Di-homo-g -

linolenate

Eicosapentaenoate

Arachidonate

eicosatetraenoate

Eicosatrienoate

∆6D ∆6D

Linoleate a-Linolenate

n-6 n -3

18:3 (n-3)18:2 (n-6)18:0

18:1 (n-9)

20:2 (n-9)

20:3 (n-9)

22:3 (n-9)

22:4 (n-6)

22:5 (n-6)

Docosahexaenoate

22:6 (n-3)

20:5 (n-3)

20:3 (n-6)

20:4 (n-6)

22:5 (n-3)

20:4 (n-3)

18:3 (n-6) 18:4 (n-3)

fig0001 Figure 1 Families of fatty acids formed from C

precursors by

desaturation (D) and elongation (E). The n-9 pathway is exhibited

in mammals only when there is insufficient n-6 present in the

diet. Reproduced from Vegetable Oils: Dietary Importance, En-

cyclopaedia of Food Science, Food Technology and Nutrition,

Macrae R, Robinson RK and Sadler MJ (eds), 1993, Academic

Press.

tbl0003Table 3 Vitamin E content of fats and oils (mg per 100 g)

Oil or fat a-Tocopherol g-Tocopherol Total

Butter 1.76 + 0.41 0 1.76

Coconut Trace Trace

Corn 11.28 + 6.25 50.76 + 19.00 62.04

Cottonseed 32.46 + 13.10 29.91 + 13.76 62.37

Lard 1.20 0.70 1.90

Olive 7.94 + 6.58 Trace 7.94

Palm 22.79 + 2.86 28.26 + 1.06 51.05

Peanut 15.12 + 4.41 23.20 + 6.90 38.32

Rapeseed 25.82 + 8.06 30.01 + 12.73 55.83

Safflower 39.23 + 3.74 15.76 + 4.40 54.99

Sesame 17.62 + 5.69 32.86 + 5.46 50.48

Soya bean 10.25 + 5.63 50.48 + 20.75 60.73

Sunflower 48.70 5.10 53.80

Data are expressed as the mean plus or minus the standard deviation and

are from Dupont J, White PJ, Carpenter MP et al. (1990) Food uses and

health effects of corn oil. Journal of the American College of Nutrition 9:

438–470.

Sum of a- and g -tocopherol.

VEGETABLE OILS/Dietary Importance 5923

Cardiovascular Effects

0011 Saturated fatty acid in the diet raises plasma choles-

terol, and PUFA lowers it. Many published studies

indicate that lowering plasma cholesterol decreases

the population risk of heart disease. Levels of LDL-

cholesterol are lowered by reducing SFA intake; the

effect of concomitantly increasing PUFA is greater

than that of merely reducing the SFA. Vegetable oils

that increase the percentage of PUFA in the diet con-

tribute to reducing plasma cholesterol. Enrichment of

the diet with PUFA reduces blood pressure and has

favorably influenced the progression of diabetic

angiopathy in adult-onset diabetes mellitus. (See

Cholesterol: Role of Cholesterol in Heart Disease;

Coronary Heart Disease: Antioxidant Status.)

Oncogenic Aspects

0012 Human surveys and animal experimentation support

a role for total fat (excess energy) intake in the devel-

opment of cancer, particularly in mammary tissue.

The impact of linoleic acid intake on mammary

and pancreatic tumorigenesis is not documented in

human studies, nor is its impact on colon carcinogen-

esis as in animal studies. A hypothesis arising from

human studies is that it is displacement of protective

foods such as fruits, vegetables, pulses, and cereals

from the diet by fat-rich foods that is detrimental,

rather than any direct effects of fat in the diet. (See

Cancer: Diet in Cancer Prevention; Colon: Cancer of

the Colon; Margarine: Dietary Importance.)

See also: Cancer: Diet in Cancer Prevention; Cholesterol:

Role of Cholesterol in Heart Disease; Colon: Cancer of

the Colon; Coronary Heart Disease: Antioxidant Status;

Essential Fatty Acids; Fatty Acids: Properties;

Metabolism; Dietary Importance; Immunology of Food;

Lipoproteins; Margarine: Dietary Importance;

Prostaglandins and Leukotrienes; Tocopherols:

Physiology

Further Reading

Dupont J (1990) Lipids. In: Brown M (ed.) Present Know-

ledge of Nutrition, 6th edn, pp. 56–66. Washington,

COOH

PETE

OOH

COOH

OOH

12-HETE

5-HETE

LEUKOTRIENES

GSH

PGF

2α

Thromboxane A

MDA

Prostacyclin

12 OH 17:30[HHT]

PGE

PGD

ENDOPEROXIDE

(PGH

)

COOH

OOH

Leucocyte

lipoxygenase

Blood

platelet

lipoxygenase

Cyclooxygenase

= 5 min

t = 30 s t = 10 min

fig0002 Figure 2 Eicosanoid synthesis from arachidonate. HETE, hydroxyeicosatetraenoic acid; PETE, peroxyeicosatetraenoic acid; PG,

prostaglandin; GSH, glutathione; MDA, malondialdehyde; TX, thromboxane; PGI

, prostacyclin. Reproduced from Vegetable Oils:

Dietary Importance, Encyclopaedia of Food Science, Food Technology and Nutrition, Macrae R, Robinson RK and Sadler MJ (eds), 1993,

Academic Press.

5924 VEGETABLE OILS/Dietary Importance

DC: International Life Sciences Institute Nutrition Foun-

dation.

Dupont J, White PJ, Carpenter MP et al. (1990) Food uses

and health effects of corn oil. Journal of the American

College of Nutrition 9: 438–470.

Dupont J, White PJ and Feldman EB (1991) Saturated

and hydrogenated fats in food in relation to health.

Journal of the American College of Nutrition 10:

577–592.

VEGETABLES OF TEMPERATE CLIMATES

Contents

Commercial and Dietary Importance

Cabbage and Related Vegetables

Leaf Vegetables

Oriental Brassicas

Carrot, Parsnip, and Beetroot

Swede, Turnip, and Radish

Miscellaneous Root Crops

Stem and Other Vegetables

Commercial and Dietary

Importance

S K Roy and A K Chakrabarti, Indian Agricultural

Research Institute, New Delhi, India

Introduction

0001 Vegetables are considered as protective foods supply-

ing carbohydrate, protein, minerals, vitamins, and

crude fiber, which are essential ingredients of a bal-

anced diet. In addition to their role in nutrition, they

increase the attractiveness and palatability of a diet

by providing sensory appeal through their variety of

color and flavor.

General Nutrient Composition

0002 Vegetables in general, except for a few, are not con-

sidered to be the primary source of carbohydrate,

protein, and fat. However, some of them with storage

roots and tubers are rich in carbohydrate, particularly

starch, in amounts comparable to the cereal crops,

and the leguminous vegetables supply as much as

14% protein, while dry seeds supply still more. The

lipid content in most vegetables is less than 0.1%.

Most leafy vegetables and root crops are rich in

minerals. Carrot and leafy vegetables are also high in

carotene (provitamin A) and vitamin C. Deep-green

leafy vegetables are rich in folate (folic acid). Besides,

there are some trace elements required by the body

like copper, manganese, and zinc, which act as enzyme

cofactor. These are found in appreciable quantities

in cole crops, roots crops, and some leafy vegeables.

(See Carotenoids: Physiology.)

0003The nutrient content of a vegetable is dependent

on several factors. The environment in which the

crop is grown, such as temperature, light, moisture,

nutrients, and physical and chemical properties of

the soil, plays an important role. The amount of

nutrient can vary with variety, cultural practices,

stage of maturity, postharvest handling, and storage

conditions. Once the vegetable is harvested, its com-

position goes on changing as a result of physio-

logical and biochemical activities, which are

natural processes.

0004In addition, methods of cooking also influence the

nutrient content of vegetables; in particular, leaching

losses and oxidative changes are considered as deteri-

orative processes. The composition of the same

vegetable grown in different parts of the world is

so different that it becomes difficult to use a general

table of composition as a source of precise informa-

tion of nutritive value of the crop used in the diet.

However, such a table gives an estimate of the prox-

imate composition of the nutrients. The nutrient com-

position of individual vegetables is given in Tables 1

and 2, and trace elements in Table 3. Refer to indi-

vidual nutrients.

VEGETABLES OF TEMPERATE CLIMATES/Commercial and Dietary Importance 5925

Dietary and Commercial Importance

0005 Apart from major nutrients, vitamins, and minerals,

there are some phytochemicals present in vegetables

which have been indicated by rapidly growing scien-

tific evidence to play a major role in promoting health

and in preventing certain diseases. These chemicals

have often been referred to as phytonutrients or

phytoceuticals. Besides, there are some key micro-

nutrients, flavor compounds, and toxic substances

found in vegetables which deserve attention.

Phytoceuticals

0006 Phytoceuticals can be grouped on the basis of their

therapeutical activities or their physical and chemical

constitution. Some of these groups are bioflavonoids,

phenols, phytosterols, thiols, indoles, glucosinolates,

and organosulfur compounds.

0007Bioflavonoids are one of the largest groups of sec-

ondary plant metabolites found in several vegetables.

They have been reported to increase the effectiveness

of vitamin C and are recognized as potent antioxi-

dants. Together with vitamin C they strengthen the

capillaries and protect the body from free radicals.

They are also antiviral and antiinflammatory. Some

of the important bioflavonoids identified from

vegetables are quercetin, kaempferol, myricetin, and

luteolin. There are reports which suggest that querce-

tin (found in onion) can inhibit the growth of several

types of cancer cells, including breast cancer, ovarian

cancer, and leukemia.

0008The higher content of phenols has been linked to

disease resistance in plants. Phenols have also been

found to protect our body from oxidative damage

caused by free radicals. Some tropical root vegetables

like yam, elephant-foot yam, and other vegetables

like green banana and eggplant are rich in phenols.

0009Phytosterols occur in most plants, especially in the

seeds of green and yellow vegetables. Phytosterols

prevent the absorption of cholesterol and facilitate

its excretion from the body. There are some reports

which suggest that phytosterols prevent the develop-

ment of tumors in breast, colon, and prostate glands.

0010Thiols are important sulfur compounds found

in brassicaceous vegetables like broccoli, cabbage,

cauliflower, and kale, and in garlic. There is strong

evidence to suggest that these compounds can pre-

vent cancers of colon, rectum, and breast. Indoles

found in Brassicas bind chemical carcinogens and

activate detoxification enzymes, mostly in the gas-

trointestinal tract.

0011Glucosinolates, which are secondary plant metab-

olites, found mostly in cole crops and other Brassicas,

are powerful activators of enzymes in the liver which

detoxify carcinogens.

0012There are several organosulfur compounds found

in onion and garlic which appear to possess anti-

microbial properties and offer protection against

cardiovascular diseases.

Key Micronutrients

0013Vegetables are the major source of vitamins and min-

erals essential for our body. They are the most im-

portant source of vitamin A; deficiency of vitamin A

in the diet causes blindness. Vitamin A is essential for

growth, bone development, vision, reproduction, and

functioning of the immune system. Vitamin A is syn-

thesized in our body from carotene which is present

in abundance in green leafy vegetables, carrot,

pumpkin, squash, melon, and tomato. Of about 600

carotenoids identified from natural sources, less than

tbl0001 Table 1 Macronutrient composition of temperate vegetables

per 100 g edible portion

Crop Energy

(kcal)

Moisture

(g)

Protein

(g)

Fat

(g)

CHO

(g)

Artichoke 79 77.3 3.6 0.1 16.0

Asparagus 26 91.7 2.5 0.2 5.0

Broad bean 48 85.4 4.5 0.1 7.2

Brussels sprout 45 85.2 4.9 0.4 8.3

Cabbage 24 92.4 1.3 0.2 5.4

Cardoon 10 94.0 0.7 0.1 1.8

Carrot 42 82.2 1.1 0.2 9.7

Cauliflower 27 91.0 2.7 0.2 5.2

Celery 17 94.1 0.9 0.1 3.9

Chicory leaf 13 92.0 1.7 0.3 1.1

Endive 11 95.0 1.3 0.2 1.2

Garden beet 43 87.7 1.7 0.1 8.8

Garlic 30 62.0 6.3 0.1 29.8

Kale 53 82.7 6.0 0.8 9.0

Knol khol 29 90.3 2.0 0.1 6.6

Knol khol green 43 86.7 3.5 0.4 6.4

Leek 77 78.9 1.8 0.1 17.2

Lettuce 14 95.1 1.2 0.2 2.5

Onion 50 86.6 1.2 0.1 11.1

Onion stalk 41 87.6 0.9 0.2 8.9

Parsley 16 90.0 2.2 0.3 1.3

Parsnip 53 81.0 1.2 0.3 11.6

Pea 84 78.0 6.3 0.4 14.4

Potato 97 74.7 1.6 0.1 22.6

Radish 17 94.4 0.7 0.1 3.4

Rutabaga 46 87.0 1.1 0.1 11.0

Spinach 26 90.7 3.2 0.3 4.3

Spinach beet 46 86.4 3.4 0.8 6.5

Sprouting broccoli 32 89.1 3.6 0.3 5.9

Swiss chard 16 92.0 1.8 0.2 1.5

Turnip root 29 91.6 0.5 0.2 6.2

Turnip green 67 81.9 4.0 1.5 9.4

Sources: Gopalan C, Sastri BVR, Balasubramanian SC, Rao BSN,

Deosthale YG and Pant KC (1999) Nutritive Value of Indian Foods.

Hyderabad: National Institute of Nutrition; Watt BK and Merril AL (1963)

Composition of Foods ^ Raw, Processed, Prepared. Agricultural Handbook

No. 8. Washington, DC: USDA.

CHO, carbohydrate.

5926 VEGETABLES OF TEMPERATE CLIMATES/Commercial and Dietary Importance

10% are precursors of vitamin A. In human beings,

b-carotene, a-carotene, and cryptoxanthin are con-

verted to vitamin A, whereas lycopene (present in

tomato) and lutein are not. Most important is

b-carotene. Some of the carotenoids are powerful

antioxidants and have been shown to offer protection

against breast, lung, uterine, prostate, and colon

cancers.

0014Vitamin C (ascorbic acid) is essential for wound

healing, immune response, and allergic reaction. It

is a powerful antioxidant and is found in many

vegetables like broccoli, cauliflower, Brussels sprout,

tomato, pepper, and potato. It protects our body by

scavenging free radicals.

0015Vitamin E is also an antioxidant which prevents

peroxidation of polyunsaturated fatty acids in our

body. Increased intake of vitamin E is believed to

reduce the incidence of heart attack. The combined

action of vitamin E, C, and A has been reported to

tbl0003 Table 3 Important trace elements (mg per 100 g) of some

temperate vegetables

Crop Cu Mn Zn

Beetroot 0.29 0.19 0.91

Brussels sprouts 0.20 0.18 0.30

Cabbage 0.02 0.18 0.30

Carrot 0.10 0.16 0.36

Cauliflower 0.13 0.10 0.40

Knol khol 0.05 0.11 0.24

Onion 0.18 0.28 0.46

Onion stalk 0.45 0.74 2.29

Pea 0.23

Potato 0.16 0.13 0.55

Radish 0.40

Spinach 0.10 0.56 0.30

Source: Gopalan C, Sastri BVR, Balasubramanian SC, Rao BSN,

Deosthale YG and Pant KC (1999) Nutritive Value of Indian Foods.

Hyderabad: National Institute of Nutrition.

tbl0002 Table 2 Micronutrient composition of temperate vegetables per 100 g edible portion

Crop Vitamins Minerals

(IU)

Thiamin

(mg)

Riboflavin

(mg)

Niacin

(mg)

Folic acid

(mg)

Ascorbic acid

(mg)

Artichoke 62 0.23 0.01 – – 0 120 100 2.3

Asparagus 900 0.18 0.20 1.5 109 33 22 62 1.0

Broad bean 15 0.08 – 0.8 – 12 50 64 1.4

Brussels sprout 550 0.10 0.16 0.9 49 102 36 80 1.5

Cabbage 130 0.05 0.05 0.3 32 47 49 29 0.4

Cardoon 120 0.02 0.03 0.3 – 2 70 23 0.7

Carrot 11000 0.06 0.05 0.6 15 8 37 36 0.7

Cauliflower 60 0.11 0.10 0.7 22 78 25 56 1.1

Celery 240 0.03 0.03 0.3 7 9 39 28 0.3

Chicory leaf 4000 0.06 0.10 0.5 – 24 100 47 0.9

Endive 2500 0.07 0.08 0.4 47 8 42 30 2.0

Garden beet 0 0.04 0.09 0.4 – 10 18 55 1.0

Garlic Trace 0.06 0.23 0.4 – 13 30 310 1.3

Kale 10000 0.16 0.26 2.1 70 186 249 93 2.9

Knol khol 20 0.06 0.04 0.3 – 66 41 51 0.5

Knol khol green 6924 0.25 – 0.3 – 157 740 50 13.3

Leek 30 0.23 – – – 11 50 70 2.3

Lettuce 900 0.06 0.06 0.3 25 8 35 26 2.0

Onion Trace 0.08 0.01 0.4 11 11 47 50 0.7

Onion stalk 993 0.05 0.03 0.3 14 17 50 50 7.4

Parsley 5200 0.08 0.11 0.7 38 90 125 40 2.0

Parsnip 0 0.09 0.05 0.7 – 17 40 69 0.7

Pea 640 0.35 0.14 2.9 25 27 26 116 1.9

Potato 40 0.10 0.01 1.2 7 17 10 40 0.7

Radish 5 0.06 0.02 0.5 7 15 35 22 0.4

Rutabaga 580 0.07 0.07 1.1 5 33 66 39 0.4

Spinach 8100 0.10 0.20 0.6 123 51 93 51 3.1

Spinach beet 5862 0.26 0.56 3.3 60 70 380 30 16.2

Sprouting broccoli 2500 0.10 0.23 0.9 54 113 103 78 1.1

Swiss chard 3300 0.04 0.09 0.4 42 30 51 46 1.8

Tumip green 15691 0.31 0.57 5.4 42 180 710 60 28.4

Turnip root 0 0.04 0.04 0.5 4 43 30 40 0.4

Source: Gopalan C, Sastri BVR, Balasubramanian SC, Rao BSN, Deosthale YG and Pant KC (1999) Nutritive Value of Indian Foods. Hyderabad: National

Institute of Nutrition; Watt BK and Merril AL (1963) Composition of Foods ^ Raw, Processed, Prepared. Agricultural Handbook No. 8. Washington, DC: USDA.

VEGETABLES OF TEMPERATE CLIMATES/Commercial and Dietary Importance 5927