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

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artificial sweeteners reduces the energy content and

encourages fluid consumption without decreasing the

nutrient density of the diet. Those drinks sweetened

with aspartame may contain the amino acid phenyl-

alanine in amounts which may be undesirable for

individuals with phenylketonuria, a rare genetic dis-

order or metabolism that requires the patient to

follow a special diet. The more liberal use of artificial

sweeteners, the establishment of acceptable daily

intake levels, and the increased number of sweeteners

available has resulted in a wide range of low-calorie

beverages which are acceptable to many consumers.

Consumers have been advised to insure that they

consume a mixture of sweeteners to avoid large

intakes of any one type. (See Aspartame; Carbohy-

drates: Sensory Properties; Sweeteners: Intensive.)

Consumption Patterns

0004 Information on consumption levels of soft drinks

within the UK is mostly derived from three sources:

the National Food Survey, the Dietary and Nutri-

tional Survey of British Adults, and individual dietary

surveys which are reported in the scientific literature.

The UK National Food Survey omits foods which are

bought for consumption outside the home. Informa-

tion on soft drinks brought into the home is recorded

but this information is not included in the major

analysis of the survey data and is reported separately.

Together with alcoholic drinks, sweets, and choc-

olate, for which no information is collected, soft

drinks are often bought without the knowledge

of the householder and are therefore liable to be

underreported. Individual surveys have focused

little on soft drink consumption in adults, although

there is more information available on children’s

eating habits in this respect. The consumption of

diet and other soft drinks was reported in the Dietary

and Nutritional Survey of British Adults (Table 2).

0005 The consumption of soft drinks in all age groups

continues to increase and in 1989 was reported to be

7524 million liters per year, with a total market value

of £4.7 billion. This figure excludes the consumption

of the increasingly popular fresh fruit juices. Con-

sumption levels as reported in the UK National Food

Survey can be seen in Table 3 and Figure 1.

0006While meal patterns still conform to what could be

considered traditional, there is nevertheless a shift

towards greater emphasis on snacking, particularly

amongst younger age groups. Concern has been

voiced regarding the nutritional quality of the diets

of schoolchildren and snack eating in particular has

been singled out as providing ‘empty calories’ but

little else in the way of nutrients. Soft drinks are

very popular amongst children of all age groups and

tbl0001 Table 1 Nutritional composition of soft drinks per 100 ml

Beverage Moisture

(g)

Energy

(kJ)

Carbohydrate

(g)

Glucose

(g)

Fructose

(g)

Sucrose

(g)

Maltose

(g)

Citrus squash 72.0 398 24.9 10.5 10.5 3.8

Citrus drink 74.1 341 21.3 11.6 9.1 0.5 3.2

Citrus crush (nonconcentrated) 80.1 158 9.9 4.1 4.1 1.6

Low-calorie citrus squash 95.4 37 2.3 1.2 1.1

Low-calorie citrus drink 94.6 86 5.5 1.4 1.4 0.4

Low-calorie citrus crush (nonconcentrated) 98.7 13 0.8 0.2 0.6

Carbonates 90.7 152 9.5 4.0 4.8 1.7

Low-calorie carbonates 99.6 0 0 0.03 0.03 0.06

Ginger ale citrus drink 95.9 62 3.9 1.7 1.6 0.5

Unpublished data with kind permission from the Ministry of Agriculture, Fisheries and Food, UK.

tbl0002Table 2 Consumption (grams per week) of soft drinks by adults

by age

Drink Age (years)

16^24 25^34 35^49 50^65

Low-calorie 778 (18) 1039 (17) 743 (16) 837 (12)

Other 1689 (82) 1073 (68) 889 (56) 667 (47)

Figures in parentheses indicate percentage consuming the drink. Data

from Gregory J, Foster K, Tyler H and Wiseman M (1990) The Dietary and

Nutritional Survey of British Adults, pp. 43, 44, 46. London: HMSO.

0 200 400 600 800 1000

Beverages

Soft drinks

Skim milk

LF milk

Whole milk

g/day

1978

1996

CSFII, USDA

fig0001Figure 1 Trends in liquid food and beverage intakes in the US,

1978 and 1996. Data from the US Department of Agriculture,

continuing Survey of Food Intake by individuals.

SOFT DRINKS/Dietary Importance 5367

are frequently consumed between meals. (See Snack

Foods: Dietary Importance.)

Contribution of Soft Drinks to Nutrient

Intake in Schoolchildren

0007 As many soft drinks are a source of energy, there

is concern that children may obtain a significant

proportion of their total daily energy requirement

from the sugar contained within soft drinks. However,

there is little published evidence to support this. In the

scientific literature soft drinks have been reported to

provide between 0.7% and 4.8% of total daily energy

intake. With the increasing popularity of soft drinks,

the wider variety of those available, and powerful ad-

vertising, it may be possible that children will reduce

the nutrient density of their diet and be nutritionally at

risk by consuming large quantities of soft drinks, re-

placing perhaps more nutrient-dense foods and liquids

such as milk. A dietary study of 143 schoolchildren

aged 11–12 years examined food consumption and

nutrient intake using the 7-day dietary record tech-

nique. Soft drinks, confectionery, and table sugar con-

tributed 10% of dietary energy and 40% of the sugar in

the diet. Soft drinks were consumed at 1800 g per head

each week, providing 4.7% of total energy intake and

contributing 21.4% to total sugar intake. These values

compare well with values obtained in the survey of

British schoolchildren, where the mean consumption

of soft drinks was 1775 g per head per week. There was

no evidence from the anthropometric data that a high

percentage of energy from sugar was associated with

obesity. In fact, the average body mass index was

lowest in the groups with the highest percentage of

sugar intake, hence the putative effect of percentage

of energy from sugar on body weight was not demon-

strated in this study.

0008 In another study investigating 11–14-year-old

Northumbrian children, added sugars contributed

on average 15% of dietary energy and 69% of total

sugar intake. Soft drinks contributed 3% of energy

and 17% of total sugar intake.

0009 It has been estimated that if half the soft drinks

consumed were sweetened with artificial sweeteeners

alone, sugar consumption would fall by about 10%.

Soft drinks are very popular with young children and

are universally consumed, with 85–95% of those chil-

dren surveyed in the UK study consuming these items

during the study period. Soft drinks are without doubt

one of the most commonly selected snacks amongst

schoolchildren and it is reported that children find it

difficult to rank fizzy drinks as either healthy or un-

healthy and that they make their choice according to

taste preference. (See Children: Nutritional Require-

ments; Obesity: Etiology and Diagnosis.)

0010In the British study of 15–18-year-olds there was an

apparent decline in the consumption of soft drinks with

increasing age. Average consumption fell from 200 to

155 g and 220 to 145 g soft drinks per day for female

and male subjects, respectively. By adulthood the con-

sumption of soft drinks has fallen markedly (Table 2).

0011Further studies are required to examine changing

dietary patterns and the influence of increased soft

drink consumption on total energy intake and nutri-

ent density.

Product for Specific Uses

Diabetic Drinks

0012There are a number of soft drinks which are sold

specifically for use by individuals with diabetes melli-

tus. By law these must not contain any sugars other

than fructose, which is metabolized mainly in the liver,

the initial steps in its metabolism being independent of

insulin. Some products are sweetened with sugar alco-

hols (sorbitol, xylitol, mannitol, lactitol) but these

offer no advantage over fructose and do not result in

a reduced-energy drink. It has been suggested that the

daily intake of sugar alcohols should not exceed 25 g as

this may result in osmotic diarrhea. There is also an

increasing number of low-calorie drinks in which the

sugar has been replaced either wholly or in part by an

intense sweetener, reducing the energy content signifi-

cantly. The nature of these drinks enables those on

reduced-energy diets to consume them without adding

significantly to their energy intake.

0013The need for dietetic products of this nature is

recognized by the provisions of the UK Soft Drinks

Regulations (1964, as amended), which exempt low-

calorie soft drinks from limitations imposed on

the saccharin content of soft drinks in general. The

tbl0003 Table 3 Purchase quantity of soft drinks

Drink Quantitypurchased (ml (fl. oz) perperson per week)

1984 1987 1988 1989 1990

Low-calorie 26 (0.91) 58 (2.04) 78 (2.74) 109 (3.85) 129 (4.55)

All soft drinks 844 (29.7) 855 (30.1) 886 (31.2) 1020 (35.9) 1071 (37.7)

Data from Household Food Consumption and Expenditure 1990 (with a study of trends over the period 1940–1990), Ministry of Agriculture, Fisheries and

Food, UK; Annual Report of the National Food Survey Committee. London: HMSO, 1991.

5368 SOFT DRINKS/Dietary Importance

relatively low caloric limits (22 kJ (5 kcal) per 100 ml)

imposed on soft drinks compared with other foods

make it virtually impossible to include carbohydrate

sweeteners in low-calorie soft drinks. (See Saccharin;

Sugar Alcohols.)

Sports Drinks

0014 A range of foods, drinks, and supplements has been

launched to fill the requirements of the ‘get-fit’ craze

for consumption before, during, and after exercise. A

relatively new phenomenon, these drinks are pro-

moted as being designed to replace water and electro-

lytes lost through sweating during exercise. Most of

the drinks are mixtures of sugar, salt, potassium, and

water with a little vitamin C. Some of these drinks

claim to be isotonic and some hypotonic. Dehydration

does impair performance and therefore anything

which decreases dehydration will maintain optimum

performance for longer, although rehydration does not

improve performance per se. In many circumstances

water would be an acceptable alternative.

Infant Drinks

0015 Infant drinks, including baby herbal drinks, have

been developed to provide a thirst-quenching drink

to coincide with the reduced consumption of milk

that occurs in the first year of life. Although manu-

facturers are obliged to recognize that cooled, boiled

water is the best refreshment to offer infants, they

suggest that many will refuse this and offer their

products as an alternative. The infant drinks are

lower in sugar than baby fruit juices and unsweetened

orange juice and usually provide the recommended

daily intake of vitamin C. Potassium citrate is added

as an acidity regulator, reducing the intensity of any

acid, and infant drinks are of lower osmolality than

conventional baby fruit juices. Health educators sug-

gest that after the age of 6 months babies can be

offered regular cows’ milk or diluted natural fruit

juice or water as a refreshment. (See Infants: Nutri-

tional Requirements.)

Soft Drinks and Health

Dental Caries

0016 Extensive evidence suggests that sugars are the most

important dietary factor in the etiology of dental

caries. Caries experience is positively related to the

amount of nonmilk extrinsic sugars in the diet and the

frequency of their consumption. Dental caries is de-

pendent upon bacterial growth on the tooth surface,

metabolism of sugars in the mouth by these bacteria,

and the formation of acid which attacks the teeth. It is

well known that one of the main etiological factors is

the length of time sugar is in the mouth. (See Dental

Disease: Role of Diet.)

0017In younger age groups there has been a shift away

from traditional eating patterns of three or four meals

per day towards an increasing reliance on snack foods,

fast foods, and convenience foods accompanied by a

range of sweetened or naturally sweet soft drinks con-

sumed at frequent intervals throughout the day. There

is therefore particular concern about the effect of soft

drink consumption on dental health. Excessive use of

soft drinks has been attacked on two accounts: first,

almost all of them are fruit-based or carbonated or

both and may therefore be acidic enough to erode the

surfaces of the teeth not covered by dental plaque.

Second, those which contain fermentable carbohy-

drate may serve as a source of substrate diffusing

into the dental plaque, from which microorganisms

inhabiting the plaque can generate acid which, in turn,

brings about the destruction process of dental caries.

0018Carbonated drinks appear to be less cariogenic

than pure orange juice and apple juice drinks and

erosiveness may be more important than cariogeni-

city. Many soft drinks do contain sugars and, if

allowed to reside in the mouth over long periods of

time, as part of a frequent, protracted sugar intake

pattern, then it is likely that they will be able to

contribute to the caries process in which sugars

serve as a substrate for acid formation.

0019Protective factors such as calcium and phosphorus

may help to limit demineralization of teeth. In studies

where iced lollies were fortified with calcium and

phosphorus, this supplement substantially improved

dental properties. Use of intense sweeteners in soft

drinks reduces their viscosity and may assist in

shortening exposure time.

See also: Ascorbic Acid: Physiology; Aspartame;

Carbohydrates: Sensory Properties; Children:

Nutritional Requirements; Dental Disease: Role of Diet;

Infants: Nutritional Requirements; Obesity: Etiology and

Diagnosis; Saccharin; Snack Foods: Dietary

Importance; Sugar Alcohols; Sweeteners: Intensive

Further Reading

Bull NL (1985) Dietary habits of 15–18 year-olds. Human

Nutrition Applied Nutrition 39A (suppl. 1): 1–68.

Department of Health (1989) Dietary Sugars and Human

Disease. Reports on Health and Social Subjects, 37.

London: HMSO.

Department of Health (1989) The Diets of British School-

children. Report on Health and Social Subjects, 36.

London: HMSO.

Department of Health (1991) Dietary Reference Values for

Food Energy and Nutrients for the United Kingdom.

Reports on Health and Social Subjects, 41. London:

HMSO.

SOFT DRINKS/Dietary Importance 5369

Gregory J, Foster K, Tyler H and Wiseman M (1990) The

Dietary and Nutritional Survey of British Adults, pp. 43,

44, 46. London: HMSO.

Hackett AF, Rugg Gunn AJ, Appleton DR, Eastoe JE

and Jenkins GN (1984) A 2-year longitudinal nutritional

survey of 405 Northumberland children initially aged

11.5 years. British Journal of Nutrition 51: 67–75.

Ministry of Agriculture, Fisheries and Food (1964) Soft

Drinks Regulations 1964 (SI No. 760) as amended.

Nelson M (1991) Food vitamins and IQ. Proceedings of the

Nutrition Society 50: 29–35.

Rugg Gunn AJ, Hackett AF, Appleton DR and Moynihan PJ

(1986) The dietary intake of added and natural sugars in

405 English adolescents. Human Nutrition Applied

Nutrition 40A: 115–124.

Sorbic Acid See Preservatives: Classifications and Properties; Food Uses; Analysis

SORGHUM

L W Rooney, Texas A&M University, TX, USA

S O Serna Saldivar, Instituto Tecnologico y de

Estudios Superiores de Monterrey, Monterrey N. L.,

Mexico

Introduction

0001 In terms of total world production, sorghum (Sor-

ghum bicolor L Moench) is ranked fifth among

cereals, with 62.7  10

tonnes in 1999. Production

of sorghum is greatest in the USA, Nigeria, Mexico,

India, China, Sudan, Ethiopia, and Argentina, but

also occurs in other countries. Most African and

Asian countries use sorghum for food, feed, forage,

fuel, and building material. In the western hemisphere

and Australia, sorghum is used mainly for feed and

forage. Speciality types are used for syrup, sugar and

alcohol. (See Cereals: Contribution to the Diet.)

0002 The sorghum plant originated in the northeast quad-

rant of Africa. It belongs to the Gramineae family,

Panicoideae subfamily, and Andropogeneae tribe. It

is a warm-season, annual crop, favored by high day

and night temperatures and intolerant to low tempera-

tures. Improved types germinate, mature, and yield

grain in an average of 120–140 days. Sorghum plants

range in height from 0.6 to 6 m and possess an imper-

fect complete flower that generally self-pollinates. The

grain develops on a branched terminal panicle that can

be compact or very open. Flowering proceeds from the

top of the panicle downward, with each panicle con-

taining 800–3000 caryopses.

0003 An enormous range in morphological diversity

exists in the sorghum crop. The World Sorghum Col-

lection in India has more than 29 000 entries. Sorghum

is classed as grain sorghum, forage sorghum, grass or

Sudan sorghums, and broomcorn. The latter is grown

for its long, fibrous panicle branches that are used to

manufacture brooms. The grain of sorghum is classed

according to pericarp color (white, yellow, or red),

presence or absence of a pigmented testa (with or with-

out tannins), pericarp thickness (thin or thick peri-

carp), endosperm color (white, heteroyellow, or

yellow), and endosperm type (normal, heterowaxy, or

waxy).These kernelcharacteristicsare geneticallycon-

trolled. Brown sorghums have a pigmented testa and

contain tannins; they may have any color pericarp.

Grain Structure and Physical Properties

0004The sorghum kernel is considered a naked caryopsis,

although some African types retain their glumes after

threshing. The kernel weight varies from 3 to 80 mg.

The size and shape of the grain vary widely among

sorghum races. Commercial sorghum grain has a flat-

tened spherical shape, 4 mm long, 2 mm wide and

2.5 mm thick, with a kernel weight of 25–35 mg. The

volumetric weight and grain density range from 708 to

760 kg m

3

and from 1.26 to 1.38 g cm

3

, respectively.

0005The sorghum caryopsis is composed of three ana-

tomical parts: pericarp, endosperm, and germ (Figure

1a). The relative proportion of these structures varies

but in most cases is 6, 84, and 10%, respectively. The

pericarp (Figure 1b) is the fruit coat and is fused to the

sorghum seed. It originates from the ovary wall and is

subdivided into three distinctive parts: epicarp, meso-

carp, and endocarp. The epicarp is the outermost layer

and is generally covered with a waxy film. The meso-

carp varies in thickness and can contain starch gran-

ules. The endocarp is composed of cross and tube cells

and plays a majorrole during germination. (See Wheat:

Grain Structure of Wheat and Wheat-based Products.)

0006The true seed consists of the seed coat or testa,

endosperm, and germ. The endosperm tissue is trip-

loid, resulting from the fusion of a male gamete with

two female polar nuclei. The testa, or seed coat,

is derived from the ovule integuments; in brown

5370 SORGHUM

sorghums, it is thick and contains condensed tannins.

The testa is pigmented when the genetics are B

-B

The endosperm is composed of the aleurone layer,

peripheral, corneous, and floury areas. The aleurone

consists of a single layer of rectangular cells adjacent

to the tube cells or testa. Aleurone cells contain a

thick cell wall, large amounts of proteins (protein

bodies) and enzymes, ash (phytic acid bodies), and

oil bodies (spherosomes). The peripheral endosperm

(Figure 1c) adjacent to the aleurone layer is composed

5µm

6.6µm

222µm

22µm

fig0001 Figure 1 Structure of the mature sorghum kernel viewed with the scanning electron microscope. (a) Cross-section, (b) pericarp,

(c) peripheral endosperm, (d) corneous endosperm, and (e) floury endosperm. P, pericarp; PE, peripheral endosperm; C, corneous

endosperm; F, floury endosperm; G, germ; E, epicarp; M, mesocarp; CC, cross cells; T, tube cells; Te, testa; A, aleurone; S, starch

granule; PB, protein body; PM, protein matrix; CW, cell wall. From Rooney LW and Serna-Saldivar SO (2000).

SORGHUM 5371

of dense cells containing large quantities of protein

and small starch granules. These layers affect the pro-

cessing and nutrient digestibilities of sorghum. Pro-

cessing of sorghum by steam flaking, micronizing,

popping, and reconstitution is designed to disrupt the

endosperm structure to improve the digestibility.

0007 The corneous and floury endosperm cells are com-

posed of starch granules, protein matrix, protein

bodies and a thin cell wall rich in b-glucans and

hemicellulose. In the corneous endosperm, the pro-

tein matrix has a continuous interphase with the

starch granules, with protein bodies embedded in

the matrix (Figure 1d). The starch granules are

shaped polygonally and often contain dents from

protein bodies. The appearance is translucent or

vitreous. The opaque-floury endosperm is located

around the geometric center of the kernel. It has a

discontinuous protein phase, air voids, and loosely

packaged, round-lenticular starch granules, and is

opaque to transmitted light (Figure 1e).

0008 The germ is diploid owing to the sexual union of one

male and one female gamete. It is divided into two

major parts: the embryonic axis and scutellum. The

embryonic axis forms the new plant and is subdivided

into a radicle and plumule. The radicle forms primary

roots, whereas the plumule forms leaves and stems.

The scutellum is the single cotyledon of the sorghum

seed. It contains large amounts of oil (spherosomes),

protein, enzymes, and minerals, and serves as the con-

nection between the endosperm and germ.

Composition

0009 Sorghum grain composition (Table 1) varies signifi-

cantly, owing to genetic and environmental influences,

and is similar to that of maize (Zea mays L). Starch

(75–79%) is the major component, followed by pro-

tein (9.0–14.1%) and oil (2.1–5.0%). The protein

content (N  6.25) of sorghum is more variable and

usually 1–2% higher than maize. Approximately 80,

16, and 3% of the protein is in the endosperm, germ,

and pericarp, respectively. Sorghum generally con-

tains 1% less oil and significantly more waxes than

maize. (See Cereals: Dietary Importance.)

0010 Sorghum starch is composed of 70–80% amylopec-

tin and 20–30% amylose. Waxy sorghums contain

starch with 100% amylopectin; their properties and

uses are similar to those of waxy maize. The gelatin-

ization temperature of sorghum starch is slightly

higher than that of maize starch. (See Starch: Struc-

ture, Properties, and Determination.)

0011 The main protein fraction in the kernel is the pro-

lamines (kafrins), followed by glutelins (Table 1). The

alcohol-soluble prolamine fraction comprises 50% of

the protein. These proteins are hydrophobic, rich in

proline, aspartic, and glutamic acids, and contain

little lysine. They are mainly found in protein bodies

and are affected by nitrogen fertilization. Glutelins

are high-molecular-weight proteins, mainly located

in the protein matrix. The lysine-rich protein fractions

– albumins and globulins – predominate in the germ.

High-lysine sorghums, such as P-721 and certain

Ethiopian types, contain lower levels of kafrins and

higher levels of albumins and globulins. The higher-

lysine sorghum varieties are soft or dented, and are

not produced commercially. (See Protein: Chemistry.)

0012Most of the fiber is present in the pericarp and cell

walls. Aleurone and endosperm cell walls are associ-

ated with ferulic and caffeic acid. Around 85% of the

dietary fiber is insoluble and mainly composed of

hemicellulose and cellulose. The soluble fraction is

rich in pentosans and b-glucans. Sorghum contains

approximately 1.3% pentosans, located mainly in the

pericarp. Approximately 70% of the pentosans are

alkali-soluble, and some 30% are water-soluble. (See

Dietary Fiber: Properties and Sources.)

0013The germ and the aleurone layer are the main con-

tributors to the lipid fraction. The germ provides about

tbl0001Table 1 Composition (%, unless otherwise stated) of sorghum

grain

Component Value

Protein (N  6.25) 11.6

Ether extract 3.4

Crude fiber 2.7

Ash 2.2

Nitrogen-free extract

79.5

Starch 74.1

Fiber

Dietary, insoluble 7.2

Dietary, soluble 1.1

Acid detergent 3.3

Soluble sugars 2.1

Pentosans 1.3

Prolamine

52.7

Glutelins

34.4

Albumins

5.7

Globulins

7.1

Essential amino acids

Lysine 2.1

Leucine 14.2

Phenylalanine 5.1

Valine 5.4

Tryptophan 1.0

Methionine 1.0

Threonine 3.3

Histidine 2.1

Isoleucine 4.1

All values are expressed on a dry-matter basis. Adapted from Rooney LW

and Serna-Saldivar SO (2000).

Calculated by difference.

FAO/WHO suggested pattern (g amino acid per 100 g protein): lysine, 5.44;

leucine, 7.04; phenylalanine plus tyrosine, 6.08; valine, 4.96; tryptophan,

0.96; methionine plus cysteine, 3.52; threonine, 4.0; isoleucine, 4.0.

5372 SORGHUM

80% of the oil. The fatty acid composition consists

mainly of linoleic (49%), oleic (31%) and palmitic

(14.3%) acids. Refined sorghum oil is very similar to

maize oil in quality. (See Fatty Acids: Properties.)

0014 Most of the minerals are concentrated in the peri-

carp, aleurone, and germ. The ash fraction is rich

in phosphorus and potassium and low in calcium and

sodium. Most of the phosphorus is bound to phytic

acid. The germ and aleurone are rich in fat-soluble and

B vitamins. Precursors of vitamin A or carotenes are

found only in yellow and heteroyellow endosperm

cultivars. (Refer to individual vitamins and minerals.)

0015 All sorghums contain phenolic acids, and most con-

tain flavonoids, but only brown sorghums contain

condensed tannins. Tannins protect the kernel against

preharvest germination and attack by insects, birds,

and molds. Brown sorghums always have a pigmented

testa (genes B

-B

-ss) and some have tannins in the

pericarp (B

-B

S-). Sorghums without a pigmented

testa do not contain any condensed tannins. Birds

can and do consume brown sorghums when other

food is unavailable. (See Tannins and Polyphenols.)

Uses of Grain

Milling

0016 Thirty percent of world sorghum production is for

human consumption. For production of most trad-

itional foods, sorghum is first dehulled with a wooden

mortar and pestle. For decortication, the grain is

usually washed, placed in the mortar, and pounded

vigorously with the pestle. The abrasive action frees

the pericarp from the kernel. The pericarp usually

detaches at the mesocarp. Thick pericarp cultivars,

with hard endosperm and round kernels, are pre-

ferred for decortication. The bran or pericarp is sep-

arated from the grain by washing with water or by

winnowing the sun-dried grain. Most sorghums are

decorticated to remove 10–30% of the original grain

weight. Mechanical decortication with rice milling

equipment or abrasive disks is becoming more popu-

lar. The decorticated kernels are reduced into flour by

pounding in the mortar and pestle, with stone mills or

by diesel-powered attrition mills. Flour is sieved to

obtain fractions with an acceptable particle size for

specific products.

0017 Commercial milling of sorghum is practiced in

several countries. The sorghum is decorticated using

abrasive pearlers, followed by degermination and

subsequent sieving, milling, gravity separation, and

sieving to produce low-fat grits, meal, and flour.

Milling of sorghum with wheat roller mills produces

acceptable flour and other products.

Traditional Food Uses

0018The major categories of traditional foods are as

follows: fermented and unfermented flat breads;

fermented and unfermented thin and thick porridges;

steamed and boiled products; snack foods and alco-

holic and nonalcoholic beverages. World-wide, the

most popular unfermented flat breads are roti in

India and tortillas in Central America. For roti, a

portion of the flour is gelatinized, mixed with more

flour, and warm water and kneaded into a dough,

which is shaped or rolled into a circle and baked on

a hot griddle. For tortilla production, whole sorghum

is limecooked, steeped overnight, washed, stone-

ground into a dough, shaped into thin circles, and

baked on a hot griddle. (See Chapatis and Related

Products; Tortillas.)

0019The most popular fermented breads are injera,

kisra, and dosa, consumed in Ethiopia, Sudan, and

India, respectively. About 80% of the Ethiopian sor-

ghum is used for the production of injera. The sor-

ghum flour is mixed with water and a yeast starter

from a previous batch of injera. After fermentation

for 24–48 h, the batter is poured onto a greased pan

for baking. The resulting product is a flexible, brown

pancake containing uniformly distributed fish eyes or

air bubbles. Dosa is consumed in India and is pro-

duced from a mixture of black gram, sorghum, and

rice flour.

0020Porridges can be fermented or cooked with acid or

alkali. To

is an unfermented stiff porridge, very popu-

lar in Mali and Burkina Faso. Decorticated sorghum

flour is cooked in plain water or water acidified with

tamarind juice or made alkaline with wood ashes

(potash). The most popular fermented porridges are

ogi and nasha, widely consumed in West and East

Africa, respectively. Whole sorghum is soaked in

water and allowed to ferment for 2–3 days. The wet

grain is crushed in a slurry of water and sieved to

remove the bran. The fine particles are allowed to

ferment longer. Excess water is decanted and the

resulting slurry cooked in water or milk.

0021For couscous production, sorghum flour is

kneaded with enough water to form agglomerates.

The particles are forced through a coarse screen and

steamed. The cooked product is consumed with a

sauce or milk.

0022Decorticated sorghums are often cooked like rice.

Special types of small-seeded, very hard sorghums are

used as a substitute for rice.

0023Two major kinds of alcoholic beverages are pro-

duced from malted sorghum. The most common type,

called opaque beer, undergoes souring and yeast fer-

mentation and is very popular in southern Africa. The

high-solids beer is sour, alcoholic, pinkish and

SORGHUM 5373

effervescent. (See Fermented Foods: Beverages from

Sorghum and Millet.)

Industrial Uses

002 4 Sorghum grain or sweet sorghum biomass is used for

ethanol production. Yields of alcohol (182



proof)

per tonne of sorghum grain are comparable with

maize (387 vs 372 l). The commercial technology

required to ferment sweet sorghum biomass into alco-

hol has been perfected in Brazil. One tonne of sweet

sorghum biomass has the potential to yield 74 l of

200



proof alcohol.

0025 In Southern and West Africa, sorghum malt is used

for alcoholic and nonalcoholic beverages, weaning

foods, and breakfast foods. Sour-opaque beers are

produced commercially in Southern Africa. Opaque

beer is produced following the basic steps of the

traditional process. Breweries in Mexico, Africa,

and Asia use sorghum grits as an adjunct in brewing

lager beer. In Nigeria, sorghum and maize are used to

produce lager or clear beer without barley malt. Ni-

gerian breweries produce clear beer from a combin-

ation of malted sorghum, sorghum, and/or maize grits

with commercial enzymes to convert the starch to

fermentable sugars because sorghum malt has a low

diastatic power. The quality of clear beer is good, but

the taste differs from barley malt beer.

0026 Sorghum grits, meal, and flour can be used alone or

mixed with wheat flour to produce an array of baked

goods. Sorghum does not contain gluten. Thus, the

amounts of sorghum flour in the blends depend on the

quality of the wheat flour, baking procedure, formu-

lation, and quality of the baked products desired.

New food-type sorghums that produce excellent

yields of flour with a bland flavor and light color

are available. They can be used to extend wheat-

based products without affecting flavor. (See Flour:

Dietary Importance.)

0027 Sorghum can be puffed, popped, shredded, and

flaked to produce ready-to-eat breakfast cereals. Ex-

trusion of sorghum produces acceptable snacks and

precooked products. (See Cereals: Breakfast Cereals.)

0028 In the Sudan, sorghum is wet-milled to produce

starch with properties and uses similar to those of

maize starch. Commercial wet milling of sorghum in

the USA was discontinued in the 1970s because of

poor economics. The enzymatic conversion of starch

to liquid glucose syrup is possible.

Nutritional Value

002 9 Sorghum is an excellent feed for livestock and com-

panion animals. The feeding value of sorghum for

livestock species is generally considered 95% or

more of the feeding value of yellow dent maize.

Brown sorghums are considered to have 80–85%

the feeding value of maize. Sorghum must be properly

processed to enhance its digestibility. Popping, steam

flaking, and reconstitution are used to prepare

sorghum grain in beef cattle feedlots in the USA.

Grinding, rolling, crushing, and pelleting are used

for poultry and swine feeds.

0030Sorghum has a proximate composition, amino acid

contents, and nutritional value similar to those of

maize. However, due to its lower fat content, sor-

ghum usually has a slightly lower gross, digestible,

and metabolizable energy. Lysine and threonine are

the first and second limiting amino acids. The trypto-

phan content is higher than that in maize. High-lysine

cultivars contain approximately 50% more lysine and

promote better weight gains in weaning rats. Fermen-

tation, malting, and other processing methods im-

prove the nutritional value significantly. (See Amino

Acids: Properties and Occurrence.)

0031Most sorghum hybrids do not contain condensed

tannins in contrast to impressions given in some

publications. Kernels that contain condensed tannins

have a clearly pigmented, thick testa. These sorghums

are classed as brown or tannin sorghums. The brown

sorghums are grown in some areas where birds and

molds are major problems. Birds will consume brown

sorghums when other foods are scarce. Animals fed

brown sorghum rations eat more feed and produce

about the same amount of gain so feed efficiency is

reduced significantly.

See also: Cereals: Contribution to the Diet; Breakfast

Cereals; Chapatis and Related Products; Dietary Fiber:

Properties and Sources; Fatty Acids: Properties;

Fermented Foods: Beverages from Sorghum and Millet;

Flour: Dietary Importance; Protein: Chemistry; Starch:

Structure, Properties, and Determination; Tannins and

Polyphenols; Wheat: Grain Structure of Wheat and

Wheat-based Products

Further Reading

FAO (1999) FAOSTAT Database Results, Web Site http://

apps1.fao.org, Yearly Production Database.

Rooney LW and Miller F (1982) Variation in the structure

and kernel characteristics of sorghum. In: Rooney LW

and Murty DS (eds) International Symposium on Sor-

ghum Grain Quality, pp. 143–162. Patancheru, India:

ICRISAT.

Rooney LW, Kirleis AW and Murty DS (1986) Traditional

foods from sorghum: their production, evaluation and

nutritional value. In: Pomeranz Y (ed.) Advances of

Cereal Science and Technology, vol. VIII, pp. 317–

353. St Paul, MN. American Association of Cereal

Chemists.

Rooney LW and Serna-Saldivar SO (2000) Sorghum. In:

Kulp K and Ponte J (eds) Handbook of Cereal Science

5374 SORGHUM

and Technology, 2nd edn, pp. 149–175. New York:

Marcel Dekker.

Rooney LW and Waniska RD (2000) The sorghum kernel:

structure and chemistry. In: Smith C and Frederiksen R

(eds) Sorghum: Origin, History, Technology and Pro-

duction, pp. 689–729. New York: Wiley.

Serna-Saldivar SO and Rooney LW (1995) Structure and

chemistry of sorghum and millets. In: Dendy D (ed.)

Sorghum and Millets: Chemistry and Technology, pp.

69–124. St Paul, MN: American Association of Cereal

Chemists.

Stoskofp NC (1980) Cereal Grain Crops. Reston, VA:

Reston.

Waniska RD and Rooney LW (2000) Structure and

chemistry of the sorghum caryopsis. In: Smith C

and Frederiksen R (eds) Sorghum: Origin, History,

Technology and Production, pp. 649–688. New York:

Wiley.

Sourdough Bread See Bread: Dough Mixing and Testing Operations; Breadmaking Processes;

Chemistry of Baking; Sourdough Bread; Dietary Importance; Dough Fermentation

SOY (SOYA) BEAN OIL

F D Gunstone, Scottish Crop Research Institute,

Invergowrie, Dundee, UK

Background

0001 Soybean is the oilseed produced in the largest

amounts. The extracted oil is also produced in the

largest amounts, though in the next 10–15 years, the

supply of palm oil is expected to exceed that of soy-

bean oil. Soybean meal is the dominant oilseed source

of high-quality protein for both human and animal

use. Other entries in this Encyclopedia deal with the

bean and its protein product: this section is concerned

with soybean oil. Some advantages and disadvantages

have been claimed for this oil. It is widely used on the

basis of its advantages, and much effort is devoted to

overcoming its alleged disadvantages. The advan-

tages are its high unsaturation, its richness in essential

fatty acids, its liquid nature over a wide temperature

range, its extensive use as a pourable semisolid oil

after partial hydrogenation, and its value as a rich

source of phospholipids, antioxidants, and sterols.

Its disadvantages include the need to process it to

remove phospholipids before use and the presence

of linolenic acid, which is considered to promote

oxidative instability and to be the cause of the rapid

development of off-flavors, which limit shelf-life.

Oil Extraction and Refining

0002 Beans are cleaned, dried to about 10% moisture,

dehulled, and flaked before extraction with solvent

(isohexane or hexane) by percolation or immersion.

Oil/solvent is separated from meal/solvent, and the

solvent is removed and recovered for reuse from both

fractions. The crude oil is then refined by degumming

to remove and recover phospholipids, neutralizing to

remove free acids, bleaching to remove undesirable

colours, and deodorizing to remove unwanted odor

and flavor compounds. These processes, and particu-

larly the last, should be carried out at as low a tem-

perature as possible. Formation of trans isomers is

negligible below 220



C, becomes significant between

220 and 240



C, and rises rapidly with respect to

temperature above 240



C. Some 3–24% of the

linolenic present may be isomerized, but linoleic

acid is less reactive, and isomerization does not

usually exceed 2%.

9c12c15c ! 9t12c15c and 9c12c15t and 9t12c15t:

These processes produce a high-quality bland oil,

though for several uses, it may also be necessary to

effect some degree of hydrogenation. Very light hy-

drogenation (brush hydrogenation) is used to reduce

the level of linolenic acid to about 3%. This has the

advantage of extending the shelf-life of food products

containing this material, as linolenic acid is oxidized

about twice as quickly as linoleic acid and gives rise to

oxidation products with a greater off-taste and off-

odor than those resulting from linoleic acid. More

extensive hydrogenation is designed to increase the

melting point of the oil, so that it can be used to make

plastic semisolid fats. This is achieved by raising the

levels of acids with melting points above ambient so

that the triacylglycerols in which they are present are

also solid. These acids are either saturated (stearic)

SOY (SOYA) BEAN OIL 5375

or monounsaturated acids with trans configuration.

These changes also have nutritional consequences.

The ratio of total dietary n-6 (linoleic acid and its

metabolites) to total dietary n-3 acids (linolenic acid

and its metabolites) is considered by many to be too

high, with an excess of the former and a deficiency of

the latter. This is exacerbated when valuable dietary

linolenic acid is reduced through partial hydrogen-

ation. Also, there is now nutritional concern about

trans acids, and serious attempts are being made to

reduce the dietary intake of such acids. (See Vegetable

Oils: Oil Production and Processing.)

Composition of Soybean Oil

0003 The following composition figures for soybean oil

refer to the the crude and refined oils, respectively:

triacylglycerols (95–97 and > 99%), phospholipids

(1.5–2.5 and 0.003–0.045%), free fatty acids (0.3–

0.7 and < 0.05%), plant sterols (0.33 and 0.13%),

tocopherols (0.15–0.21 and 0.11–0.18%), iron (1.3

and 0.1–0.3 p.p.m.), and copper (0.03–0.05 and

0.02–0.06 p.p.m.). It is apparent that refining re-

moves most of the phospholipids and free acids but

only some of the sterols, tocopherols, and metals. The

level of tocopherols remaining in the refined oil is

sufficient to provide a measure of oxidative stability.

Material removed during the refining process con-

tains several products of commercial value to the

food, cosmetics, and pharmaceutical industries.

These include the phospholipids (lecithin), toco-

pherols (vitamin E), and sterols with these industries

relying on the supply of each of these.

0004 The following figures for refined soybean oil have

been cited as target values: FFA (0.05 max), trans

acids (1% max), moisture (0.05% max), impurities

(nil), peroxide value (max 0.5 mEq O

1

), phos-

phorus (max 1 p.p.m.), tocopherols (min 750 p.p.m.),

total metal (max 0.1 p.p.m.), PAH (polycyclic

aromatic hydrocarbons max 25 p.p.b.), colour 5.25

inches max (1.5R–10Y), cold test (min 48 h per



C),

smoke point (min) 220



Fatty Acid Composition

0005 Typical fatty acid composition data for soybean oil

are listed given in Table 1. The oil is rich in linoleic

acid (54%, Codex range 50–57%) and oleic acid

(24%, Codex range 18–25%) but also contains palm-

itic (11%, Codex range 10–13%), stearic (4%), and

linolenic acids (7%, Codex range 5–10%), with only

traces of acids of other chain lengths. Attempts are

being pursued both by traditional mutation seed-

breeding methods and by genetic engineering to pro-

duce soybeans with different fatty acid compositions,

including oil rich in lauric acid as an alternative to

coconut and palmkernel oils, oil with less palmitic

and stearic acid on dietary grounds, oil with more

palmitic and/or stearic acid for use in solid (plastic)

fats without hydrogenation (which adds cost and

produces undesirable trans acids), oil with more oleic

acid on dietary grounds, and oil with less linolenic

acid to enhance the shelf-life without brush hydrogen-

ation. Many such modified oils have been described,

and a typical selection is reported in Table 1. Several

of these are in an advanced stage of development, and

it is likely that these, or materials akin to them, will

become available soon. It is expected that they will

carry a premium price, but details are not yet known.

0006Soybean oil can be converted to a semisolid mater-

ial by partial hydrogenation. For example, soybean

oil of iodine value 133 can be converted to fats of

iodine value *80 and mp 30–37



C depending on the

conditions of hydrogenation. These materials contain

18:0 8–12% compared with 4% in the original oil,

18:1 63–72% (23%), 18:2 9–13% (53%), and 18:3

0–0.3% (7.4%). But these numerical changes in fatty

acid composition do not fully convey the changes that

have taken place for the partially hydrogenated oils

contain 27–40% of trans acids, which will be mainly

18:1 with the trans double bond ranging from D6to

D16 but mainly D8toD13. The trans acids have

higher melting points than their cis isomers and thus

contribute to the hardening process. (See Fats: Clas-

sification; Fatty Acids: Properties.)

Triacylglycerol Composition

0007Although most oils are traded and used according to

their fatty acid composition, it is known that some

properties are related to triacylglycerol composition.

The following data are taken from a paper describing

triacylglycerol composition for soybean oil and for

several modified oils, but only the former is discussed

here. The original paper must be consulted for other

details.

0008Ignoring the minor components, the soybean oil

under study had a fatty composition of palmitic

(10.2%), stearic (4.1%), oleic (23.4%), linoleic

(52.8%), linolenic (8.3%), and other acids (1.2%)

tbl0001Table 1 Fatty acid composition of commodity soybean oil and

some modified soybean oils

16: 0 18:0 18:1 18:2 18:3

Commodity oil 11 4 24 54 7

High-oleic 11 81 4 4

Low-saturated 4 3 31 59 3

High-saturated 25 4 16 44 10

24 19 9 38 10

12 21 63 1 3

Low-linolenic 10 3 44 40 3

5376 SOY (SOYA) BEAN OIL