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concentrate can be further processed by thermal pro-

cessing and homogenization for a better functionality.

Alternatively, soybean protein concentrate can be

made by an acid-leach method to retain isoflavones

and other beneficial phytochemicals, and to prevent

protein denaturation. Soybean protein concentrate is

widely used in the meat industry to bind water and

emulsify fat, and as a key ingredient for many meat

alternatives. It is also used for protein fortification of

various types of food.

0011 Soybean-protein isolate is produced by alkaline

extraction of the defatted flour, followed by precipi-

tation at acid pH. As a result, both soluble and insol-

uble carbohydrates are removed. The resulting

product has a protein content of about 90%

(N 6.25), and is light in color and bland in flavor.

Soybean protein isolate is the most refined soybean

protein product and possesses many functional prop-

erties, including gelation and emulsification. Conse-

quently, it may be used in a wide variety of food

systems, including processed meat, meat analogs,

soup and sauce bases, nutritional beverages, sole-

source foods such as infant formulas and enteral

nutritionals, and dairy analogs.

0012 Textured soybean proteins are produced by ther-

moplastic extrusion of soybean protein flour or con-

centrate under moist heat and high pressure to impart

a fibrous texture. The textured products, which come

in many sizes, shapes, colors, and flavors, are mainly

used in processed meats and snack foods, and as meat

alternatives.

0013 Soybean protein products contain a number of

antinutritional and bioactive components such as

trypsin inhibitors (causing potential adverse effects

on pancreatic function and growth in animal models),

phytates (causing potential adverse effects on mineral

status), phytohemagglutinins (with the unique prop-

erty of being able to agglutinate red blood cells), and

isoflavones (causing potential hormonal and goitro-

genic effects). However, residual levels of these natur-

ally occurring bioactive components, and of those

formed during alkaline/heat processing such as lysi-

noalanine (an unnatural amino acid derivative)

would be expected to be minimal in properly pro-

cessed soybean protein products.

0014 Adverse nutritional effects following consumption

of uncooked and lightly heat-treated soybean protein

have been attributed to the presence of endogenous

inhibitors of digestive enzymes (about 56–64 mg per

gram of protein of trypsin inhibitor activity) and sap-

onins (0–10 mg per gram of protein) and to poor di-

gestibility. To improve the nutritional quality of soy

foods, inhibitors and saponins are generally inacti-

vated by heat treatment or eliminated by fractionation

during food processing. Soybean protein products also

contain about 1–2% of phytic acid, which has long

been recognized to interfere with the absorption of

minerals, especially zinc. Phytic acid is stable to

cooking and probably is not degraded during textur-

ization by extrusion. Although long considered to be

antinutritional factors, because of their estrogenic

properties, soybean isoflavones are now of great inter-

est because of their possible role in preventing many

chronic diseases. Soy-protein flour has an isoflavone

profile approximating that of soybeans (4028–

4808 mg per gram of protein). Protein isolates contain

reduced levels of isoflavones (690–1096 mg per gram

of protein) compared to flours as a result of aqueous

processing during manufacture. A concentrate made

by aqueous alcohol extraction is very low in isofla-

vones (73 mg per gram of protein) because the isofla-

vones are especially soluble in aqueous alcohol and are

thus largely removed during processing.

0015Soybean protein flours, concentrates, and isolates

are good sources of all IAA, but some products could

be marginally deficient in sulfur amino acids (Table 3).

Although the addition of methionine to properly pro-

cessed soybean protein products consumed by adults

has no significant effect on the nutritional value when

nitrogen intake is adequate, the addition of methio-

nine to soy milk preparations increases the nitrogen

retention by malnourished children and improves the

protein quality of soy-based formulas for infants. The

PER value of the methionine-supplemented soybean

protein products is equivalent to that of casein. Be-

cause soybean-protein products have high levels of

lysine, they can be used to fortify cereal proteins,

which are limiting in lysine.

Wheat Gluten

0016According to the CCVP specifications, wheat gluten

is a food product prepared by the wet extraction from

wheat or wheat flours of certain nonprotein constitu-

ents (starch and other carbohydrates), in a manner to

achieve a protein content of 80% or more (N 6.25)

on a dry-weight basis. Although high in protein di-

gestibility, wheat gluten is drastically limiting in

lysine, with a PDCAAS of 36% (Table 4). Therefore,

this protein source should not be used as the sole

source of protein nutrition. However, the low protein

quality of gluten can be improved by the addition of

supplementary protein high in lysine, by supplemen-

tary lysine, or by protein complementation. (See

Protein: Quality.)

Other Vegetable-protein Products

0017Besides soy protein products and wheat gluten, pro-

cessing technology has also been developed for the

PROTEIN/Sources of Food-grade Protein 4875

preparation of a number of other VPP such as pea-

protein concentrate, cottonseed-protein products,

sunflower-protein isolate, peanut flour and canola

(rapeseed)-protein concentrate (Table 4). However,

among these protein products, only the pea-protein

concentrate is distributed and used internationally.

Pea-protein concentrate is a highly functional and

nutritious protein concentrate derived from field

peas. Careful processing to prevent protein denatur-

ation has resulted in a wide range of useful functional

properties. Moreover, due to its high lysine content, it

can be used to greatly improve the nutritional quality

of cereal proteins. Pea-protein concentrate has a pro-

tein digestibility of about 92% and a PDCAAS of

73%, with tryptophan and sulfur amino acids being

the limiting IAA.

0018Like cereal proteins, sunflower-protein isolate and

peanut flour are first limiting in lysine (Table 4).

Sunflower-protein isolate has a high protein digest-

ibility of 94%, and peanut flour has a somewhat

lower protein digestibility of 91%. The PDCAAS

values for sunflower-protein isolate and peanut flour

are about 37 and 50%, respectively, because of the

low lysine concentration.

0019In contrast to peanut and sunflower, canola (rape-

seed) protein concentrate is one of the more balanced

sources of IAA among VPP (Table 4). It is marginally

limiting in lysine, and, along with its moderately low

tbl0003 Table 3 Protein (on a percentage dry weight basis), IAA compositions, protein quality expressed as PDCAAS, and contents of minor

bioactive components in soybean protein products

Nutritionalparameter Flours Concentrates Isolates

Totalprotein%(N6.25)56–5970–7290–92

IAA:expressedasapercentageoftherespectiveIAAintheFAO/WHO(1991)scoringpattern

Histidine 137 131 131

Isoleucine 164 171 175

Leucine 118 120 126

Lysine 110 110 115

Methionine þ cystine 104 108 100

Phenylalanine þ tyrosine 140 141 146

Threonine 115 132 112

Tryptophan 118 127 118

Valine 131 143 148

Protein digestibility (%) 86 94 96

PDCAAS (%) 89 100 96

Trypsin inhibitor activity (mg per gram of protein) 56–64 (raw flour), 16–19 (toasted flour) 8–11 2–29

Phytic acid (mg per gram of protein) 26–37 18–31 11–22

Isoflavones (mg per gram of protein) 4028–4808 104 690–1096

FAO/WHO (1991) Recommended Amino Acid Scoring Pattern (containing, in milligrams per gram of protein included: histidine, 19; isoleucine, 28;

leucine, 66; lysine, 58; methionine þ cystine, 25; phenylalanine þ tyrosine, 63; threonine, 34; tryptophan, 11; and valine, 35.).

tbl0004 Table 4 Protein (on a percentage dry weight basis), IAA compositions and protein quality expressed as PDCAAS of some vegetable-

protein products

Nutritionalparameter Wheat gluten Sunflower-proteinisolate Pea-protein concentrate Peanut flour Canola-protein concentrate

Totalprotein(%)(N6.25)8393556069

IAA:expressedasapercentageoftherespectiveIAAinFAO/WHO(1991)scoringpattern

Histidine 131 140 126 100 126

Isoleucine 114 153 153 114 150

Leucine 95 95 117 91 118

Lysine 38 38 133 55 98

Methionine þcystine 132 100 104 84 177

Phenylalanine þtyrosine 119 135 135 128 112

Threonine 68 94 123 72 123

Tryptophan 87 125 79 71 136

Valine 103 146 142 101 150

Protein digestibility (%) 94 97 92 91 92

PDCAAS (%) 36 37 73 50 90

FAO/WHO (1991) Recommended Amino Acid Scoring Pattern (containing, in milligrams per gram of protein included: histidine, 19; isoleucine, 28;

leucine, 66; lysine, 58; methionine þ cystine, 25; phenylalanine þ tyrosine, 63; threonine, 34; tryptophan, 11; and valine, 35.).

4876 PROTEIN/Sources of Food-grade Protein

protein digestibility of 92%, this gives it a PDCAAS

of about 90%.

0020 The properly processed defatted cottonseed flours

(about 60% protein, N 6.25) (glandless or deg-

landed (liquid cyclone process)) have a PER equiva-

lent to that of casein. Heat and moisture introduced

after removal of lipids significantly decrease the PER.

Fractionation of the various types of cellular proteins

during isolate preparation also produces both favor-

able and unfavorable effects. Storage protein isolates

(99–100% protein) are low in lysine and the sulfur

amino acids, and low in protein quality, but the non-

storage protein isolates (76–85% protein) are high in

all IAA and in protein quality (PER > 2.5). The degree

of fractionation of the seed proteins and, conse-

quently, the nutritive value of the isolates are depend-

ent upon the extraction characteristics of the flour

and on the isolation process. The quality of defatted

cottonseed products also depends upon the level of

physiologically active or ‘free‘ gossypol. Gossypol is a

binaphthyl, dialdehyde, polyhydroxyl pigment which

is highly reactive and deleterious to monogastric

animals, including humans. All of the gossypol in

the seed is in discrete extracellular glands. During

processing, the glands usually are ruptured, and con-

sequently, gossypol is either removed with the oil or

converted to a physiologically inactive form through

interaction with other cellular constituents. Glandless

cultivars of cotton seed have also been developed.

Edible cottonseed protein products, approved by the

US FDA, have a maximum of 0.045% ‘free‘ gossypol.

IAA data and PER values of cottonseed-protein isol-

ates are listed in Table 5. The protein quality of the

minor, nonstorage-protein isolate is higher than that

of the major storage-protein isolate, while the protein

quality of the classical protein isolate is intermediate

between the nonstorage and storage-protein isolates.

0021As can be seen from Table 6, the PER method of

protein-quality determination gives a lower score

than PDCAAS for proteins that are low in sulfur

amino acids such as soy protein products, beans,

and peas. This is because of the higher requirements

for methionine and cysteine by rats compared to

humans. In contrast, those first limiting in lysine,

such as sunflower-protein isolate, have a PER that

corresponds closely to PDCAAS.

0022Addition of beef to vegetable protein sources im-

proves significantly the protein quality of soy, pea,

peanut, sunflower and wheat-gluten-protein sources

but only marginally improves that of rapeseed

(Table 7).

Mycoprotein Products

0023Mycoprotein is the ingredient name for a food-grade

protein source that has been available for food use

only since 1985. As the name suggests, this protein is

made from a type of fungus, Fusarium venenatum

(PTA 2684), that was found in the wild and developed

specifically for the production of food-grade protein.

Mycoprotein production follows a series of steps. The

organism is first grown in an aerobic, axenic, continu-

ous fermentation system using food-grade carbohy-

drate substrates and other components needed for

growth. The mycelium of the fungus is then heat-

treated to reduce the ribonucleic acid content to safe

levels. Single-cell protein sources tend to be high in

nucleic acids, which can lead to excessive blood uric

acid levels, a problem for people prone to gout. Once

tbl0006Table 6 PER and PDCAAS values for some properly processed

vegetable-protein sources

Product PER

(casein ¼2.5)

PER as a

percentage

of casein

PDCAAS

(%)

Rapeseed-protein

concentrate

2.6 104 96

Rapeseed-protein isolate 2.4 96 86

Soy-protein isolate 1.7 68 99

Pea-protein concentrate 1.2 48 68

Kidney beans 1.1 44 68

Pinto beans 0.5 20 63

Lentils 0.3 12 52

Peanut butter 1.7 68 52

Sunflower-protein isolate 1.1 44 37

Rolled oats 1.8 72 63

Wheat cereal 1.4 56 40

Wheat gluten 0.9 36 25

tbl0005 Table 5 Protein (on a percentage dry weight basis), IAA

compositions and protein quality expressed as PER of

cottonseed-protein isolates

Nutritional parameter Nonstorage

protein

Storage protein Classical

Protein (%, N  6.25) 76–86 99–100 92

IAA: expressed as a percentage of the respective IAA in the FAO/

WHO(1991)scoringpattern

Isoleucine 146 121 135

Leucine 120 95 110

Lysine 109 55 82

Methionine þ cystine 145 76 100

Phenylalanine þ tyrosine 140 152 150

Threonine 114 85 99

Tryptophan 134 109 120

Valine 149 143 145

PER 2.7–3.2 1.3–1.7 2.0–2.2

FAO/WHO (1991) Recommended Amino Acid Scoring Pattern (containing,

in milligrams per gram of protein included: histidine, 19; isoleucine, 28;

leucine, 66; lysine, 58; methionine þ cystine, 25; phenylalanine þ tyrosine,

63; threonine, 34; tryptophan, 11; and valine, 35.).

PROTEIN/Sources of Food-grade Protein 4877

the RNA level is reduced, the suspended solids are

centrifuged and recovered in the form of a paste with

75% water content. This is the mycoprotein.

0024 The vegetative growth of fungi, the mycelium, is

in the form of hyphae – thread-like cells that permeate

the growing medium. In the case of F. venenatum

(PTA 2684), these hyphae, after the heat treatment,

become insoluble and are of a length and diameter

that make them suitable for creating products that

mimic meats. To do this, binders, flavorings, and

other ingredients are added and the mixture further

processed to achieve the desired organoleptic and

physical properties.

0025 The introduction of this product onto the market

required considerable toxicity and nutritional testing

because it was a novel food not previously used for

human consumption. As part of these tests, the pro-

tein quality was evaluated. Based on both PDCAAS

and animal and human studies, it was determined

that the protein quality of this mycoprotein is similar

to that of soybeans. It has now been on the market

under the brand name, Quorn

, in the UK and

Europe for some 10–15 years and has secured consid-

erable consumer acceptance. It has recently been

introduced to the USA.

0026 Mycoprotein is typically 12% water, 3% fat, 3%

available carbohydrates, 6% fiber, and 2% ash. B

complex vitamins and mineral nutrients are also pre-

sent in small amounts. The amino acid profile and

protein-quality indices are shown in Table 8.

0027 A number of other features make mycoprotein of

interest beyond being simply a protein source. It can

be modified so as to function as either a fat replacer or

a cereal replacer. Clinical studies have found that it

can help control blood lipids and blood glucose as

well as appetite, effects that may relate to its dietary

fiber content.

Leaf-protein Concentrate

0028Green leaves are protein factories producing good-

quality protein. Because of the low concentration,

high fiber content, and palatability problems, how-

ever, potential sources are rarely exploited for human

food use. When leaves are used as food, they are not

generally considered important protein sources but

rather as vegetables, such as lettuce, spinach, and

cabbage. However, some green forage crops produce

several times more protein per unit area than grain

crops, and there may be circumstances where ex-

tracting the protein for direct human use has eco-

nomic and ecological advantages over feeding it to

domestic animals.

0029Consideration of the possible suitability of this

protein for use as human food goes back at least to

the 1940s and research to develop a potential product

was conducted in the 1960s and 1970s in many parts

of the world. In brief, it has been found that leaf-

protein concentrate (LPC) can be obtained from har-

vested leaves by first pressing out the juice. The

soluble protein in the juice is then heat-coagulated,

the serum drained away, and the solid material dried

and powdered. This produces ‘whole‘ leaf protein

concentrate (WLPC), which is about 45–60% crude

protein, or 34–45% true protein. There are different

types of protein in leaves that can be separated by

coagulating at different temperatures. The green

tbl0007 Table 7 Protein quality expressed as RNPR values of beef,

some potential meat extenders, and their mixtures with beef

Protein sources RNPR (%)

Beef 100

Rapeseed-protein concentrate 95

Rapeseed-protein isolate 90

Soybean-protein concentrate 71

Soybean-protein isolate 67

Pea-protein concentrate 55

Peanut flour 53

Sunflower-protein isolate 40

Wheat gluten 34

Beef þnonmeat products (50:50 protein mixtures)

Rapeseed-protein concentrate 96

Rapeseed-protein isolate 94

Soybean-protein concentrate 83

Soybean-protein isolate 80

Pea-protein concentrate 79

Peanut flour 80

Sunflower-protein isolate 85

Wheat gluten 85

tbl0008Table 8 Protein (on a percentage dry weight basis) and IAA

compositions and protein quality of mycoprotein

Nutritional parameter Mycoprotein

Total protein (%) (N  6.25) 56

IAA: expressed as a percentage of the respective IAA in the FAO/

WHO(1991)scoringpattern

Histidine 184

Isoleucine 186

Leucine 130

Lysine 143

Methionine þ cystine 116

Phenylalanine þ tyrosine 141

Threonine 162

Tryptophan 145

Valine 177

Protein digestibility (%) 78

PDCAAS (%) 91

FAO/WHO (1991) Recommended Amino Acid Scoring Pattern (containing,

in milligrams per gram of protein included: histidine, 19; isoleucine, 28;

leucine, 66; lysine, 58; methionine þ cystine, 25; phenylalanine þ tyrosine,

63; threonine, 34; tryptophan, 11; and valine, 35.).

4878 PROTEIN/Sources of Food-grade Protein

fraction is dominated by proteins from the chloro-

plasts, while the white-protein fraction is largely

from the cell cytoplasm. The nature of these fractions

is such that the white protein appears to be more

suitable for incorporation into foods for humans

since it is bland-tasting, white or off-white in color,

and of a higher protein quality.

003 0 Any plant whose leaves can be eaten safely by

humans is a potential source of LPC, which can also

be used for animal feed. Some of these sources may

currently be largely waste material or may be used as

animal feed such as cassava leaves, or may be weeds

such as dandelions and water hyacinth. Candidates

should not have any toxic or antinutritional factors or

unpalatable flavors, and preferably should provide

high protein yields per unit area, be readily available,

and be easy to harvest and process.

003 1 Investigations have shown that the amino acid pro-

file of whole-leaf protein is very similar from one plant

species to another. Taking alfalfa as an example, the

protein digestibility of the WLPC is about 88%, and

the amino acid score is 107, giving a PDCAAS of 95.

Lysine is the limiting amino acid. The white-protein

fraction has a PDCAAS of 100 (109) (see Table 9). The

WLPC also contains significant amounts of vitamin A

precursors, iron, and other nutrients which may be

reduced in the white-protein fraction.

003 2 While an industrial process for producing WLPC

has been developed, there appears to be little, if any,

commercialization of this material for human use at

present. Efforts have been made to set up facilities in

developing countries as a way of converting this

underutilized protein and nutrient source to useful,

nutritious food and feed.

Microbial-biomass Protein

0033The original term for protein derived from yeast

and bacteria was ‘single cell protein.‘ The term

‘microbial-biomass protein‘ was coined to permit

the inclusion of protein from multicellular fungi,

such as the mycoprotein described above. The interest

in microbial-biomass protein was prompted by the

same concerns of global protein shortages that

brought about the development of LPC. It was also

considered to be a possible way to produce useful

food while reducing waste products and surplus raw

materials resulting from some types of industrial and

agricultural activities such as pulp mill waste liquor.

The former Soviet bloc countries had, in the 1980s at

least, about 100 plants producing microbial biomass

protein, but very few existed elsewhere. The further

development of these potential protein sources would

seem to depend on the economical availability of a

suitable substrate, the assurance that safe food mater-

ials are being produced, the lack of other more famil-

iar or accessible alternatives, and the technology and

facilities to produce attractive food products.

See also: Celiac (Coeliac) Disease; Legislation: Codex;

Mycoprotein; Protein: Food Sources; Quality; Soy

(Soya) Beans: Dietary Importance; Wheat: Grain

Structure of Wheat and Wheat-based Products

Further Reading

Animal Feed Resources Information System, Feed Re-

sources Group, Animal Production and Health Division,

Food and Agriculture Organization of the United

Nations, http://www.fao.org/ag/aga/agap/frg/afris/data/

465.htm

Bickoff EM, Booth AN, de Fremery D et al. (1975) Nutri-

tion evaluation of alfalfa leaf protein concentrate. In:

Friedman M (ed.) Protein Nutritional Quality of Foods

and Feeds, Part 2. New York: Marcel Dekker.

Friedman M (1996) Nutritional value of proteins from

different food sources. A review. Journal of Agricultural

and Food Chemistry 44: 6–29.

Graham R (2001) Mycoprotein – A meat alternative new to

the U.S. Food Technology 55(7): 36–50.

Leaf for Life, http://www.leafforlife.com/pages/leaf_con-

centrate.htm

Pellett PL (1996) World essential amino acid supply with

special attention to South-east Asia. Food Nutrition Bul-

letin 17(3): 204–224.

Pirie NW (ed.) (1975) Food Protein Sources, International

Biological Programme 4. Cambridge: Cambridge Uni-

versity Press.

tbl0009 Table 9 Protein (on a percentage dry weight basis) and IAA

compositions and protein quality expressed as PDCAAS of alfalfa

whole-leaf-protein concentrate

Nutritional parameter Whole-leaf-

protein

concentrate

Green-leaf-

protein

fraction

White -leaf-

protein

concentrate

Total protein (%) (N  6.25) 61.9 45.3 88.7

IAA: expressed as a percentage of the respective IAA in the FAO/

WHO(1991)scoringpattern

Histidine 127 127 154

Isoleucine 194 221 195

Leucine 141 155 142

Lysine 107 101 113

Methionine þ cystine 139 126 148

Phenylalanine þ tyrosine 182 177 185

Threonine 146 139 169

Tryptophan 125 87 218

Valine 177 200 205

Protein digestibility (%) 88 87 96.4

PDCAAS (%) 94 76 100

FAO/WHO (1991) Recommended Amino Acid Scoring Pattern (containing,

in milligrams per gram of protein included: histidine, 19; isoleucine, 28;

leucine, 66; lysine, 58; methionine þ cystine, 25; phenylalanine þ tyrosine,

63; threonine, 34; tryptophan, 11; and valine, 35.).

PROTEIN/Sources of Food-grade Protein 4879

Protein Concentrates See Whey and Whey Powders: Production and Uses; Protein Concentrates and

Fractions; Fermentation of Whey; Principles of Dialysis; Applications of Dialysis

PULSES

D D Dalgetty, B-K Baik and B G Swanson,

Washington State University, Pullman, WA, USA

Introduction

0001 Of all the plants utilized by man, only grasses are

more important than legumes. The term legume

comes from the Latin word ‘legumen,‘ which means

seeds harvested in pods. Leguminosae is the Latin

name of the third largest family of flowering plants.

Of the 18 000 different species within the family

Leguminosae, humans consume only a mere 24

species as food. A common name used to identify

the food legumes is pulses. Pulse is a word most

commonly used in the UK to denote edible legumes

that store their energy in the form of starch. Other

terms for pulses include beans or starchy legumes.

Notable members of the pulses include peas (Pisum

sativum), chickpeas (Cicer arietinum), and the

common bean (Phaseolus vulgaris). Table 1 gives a

list of these and other common pulses with their Latin

designations.

0002Another very important category of food legumes

are the oilseeds. As the name implies, these legumes

store their energy in the form of lipid rather than

starch. The two most common oilseeds are soybeans

(Glycine max) and peanuts (Arachis hypogaea).

0003Food legumes can be further partitioned into sep-

arate classifications based on their growing cli-

mates as cool- and warm-season legumes. The four

main species of cool-season food legumes are peas,

tbl0001 Table 1 Food legumes Latin and common names

Latin name Common name

Arachis hypogaea L. Groundnut, peanut

Cajanus cajan (L.) Millsp. Pigeonpea, red gram, Congo pea, Arhar, Tur, Gongo pea

Cicer arietinum L. Chickpea, Bengal gram, garbanzo gram

Glycine max (L.) Merr. Soybean, soya

Lablab purpureus (L.) Sweet Hyacinth bean, Egyptian bean, Val

Lathyrus sativus L. Khesari, chickling vetch, grasspea

Lens culinaris Medik. Lentil, Masur

Lupinus albus L. White lupine

Lupinus angustifolius L. Blue lupine, New Zealand blue lupine

Lupinus luteus L. European yellow lupine

Macrotyloma uniflorum (Lam.) Verdc. Horse gram, Madras gram, Kulthi

Phaseolus lunatus L. Lima bean, butter bean

Phaseolus vulgaris L. Bean, common bean, Franch bean, field bean, haricot bean, pinto bean, navy bean,

dry bean

Pisum sativum L. Common or garden pea, dry pea

Psophocarpus tetragonolobus (L.) DC. Winged bean, Goa bean, four-angled bean, Manila bean, princess pea

Vicia faba L. Broad bean, faba bean, horse bean

Vigna aconitifolia (Jacq.) Marechal Moth bean, mat bean

Vigna mungo (L.) Hopper Urd, black gram, mung bean

Vigna radiat a (L.) Wilczek Green gram, golden gram, mung bean

Vigna umbellata (Thumb.) Owhi & Ohashi Rice bean, mambi bean

Vigna unguiculta (L.) Walp. ssp. unguiculata Cowpea, black-eyed pea, crowder pea

Voandzeia subterranea (L.) Thouars Bambarra groundnut

4880 PULSES

chickpeas, lentils, and faba beans. Cool-season

legumes are very widespread geographically, with

production concentration in temperate and subtrop-

ical climates. Some production occurs in the tropics at

high altitudes. Cool-season legumes make up nearly

60% of the world pulse production and occupy

around 40% of the world area. However, the distri-

bution of each species over this area is very uneven. In

developing countries, chickpeas and lentils are dom-

inant in production and are a very common staple of

the diet. The other two crops, peas and faba beans,

are typically produced in more developed countries.

Yields of these crops are much higher than for chick-

peas and lentils.

0004 The warm-season food legumes include the

common beans and other tropical pulses such as

cowpeas, lupines, and pigeonpeas. Aside from the

common bean, most warm-season food legumes are

produced in small amounts in specific regions. Warm-

season legumes are well adapted to harsh conditions

such as those in Africa where beans are an essential

crop. These species are also very common in the Asian

and Mediterranean regions.

Distribution and Use of Edible Food

Legumes

0005Among the cultivated legumes, soybeans, peanuts,

dry beans, peas, broad beans, chickpeas, and lentils

are the major crops produced worldwide. The other

legumes are produced in more local settings in some

countries depending on the climate needed to support

the growth and food habits of the population. Table 2

shows the production (in tonnes) of the major food

legumes in developed and developing nations. The

breakdown of total production of food legumes into

regions and countries of the world is illustrated in

Tables 3 and 4. In many developed countries, the

lack of pulse production is caused by low yields,

uncertain harvests, slow maturation, and sensitivity

of legumes to growing conditions at all periods of

development and loss due to pest damage. Another

reason for low production is cost in energy to prepare

legumes with ensured digestibility.

Soybeans

0006Soybeans (Glycine max (L.) Merr.) are grown primar-

ily throughout the world as a food crop. Nearly 46%

of the world soybean production is in the USA. Other

soybean-producing countries include Brazil, Argen-

tina, China, Japan, Korea, India, Indonesia, Thai-

land, and the Philippines. The highest yields per

hectare of soybeans have been achieved in the USA.

(See Soy (Soya) Beans: The Crop.)

Groundnuts or Peanuts

0007The peanut (Arachis hypogaea L.) makes up a large

part of the economy in many developing nations

where most of its production occurs. The major

peanut-producing nations are India, China, and the

USA, of which India contributes 30% of the total

world production. Peanuts are also produced in

tbl0002 Table 2 World production of major food crops (production in

thousand metric tons)

Legume Total

production

Developed

nations

Developing

nations

Soybeans 92,982 64,401 28,581

Groundnuts 18,580 1,801 16,740

Dry beans 14,195 2,116 12,079

Peas 9,807 6,552 3,225

Chickpeas 6,158 346 5,812

Broad beans 4,224 464 5,759

Lentils 1,292 231 1,061

tbl0003 Table 3 Regional food legume production (production in thousand metric tons)

Legume Africa North and

Central America

SouthAmerica Asia Europe Oceania Russia

Soybeans 241 63,088 14,456 15,047 672 103 600

Groundnuts 5,522 1,985 1,121 10,407 27 63 1

Dry beans 1,289 1,945 2,780 7,188 678 5 76

Broad beans 761 61 117 5,588 486 4 –

Peas 342 229 94 5,194 529 107 3,517

Chickpeas 227 260 26 6,839 113 – –

Pigeonpeas 151 30 4 1,938 – – –

Lentils 56 71 53 816 75 – 3

Vetches 53 – – 165 144 1 589

Lupines 11 – 7 1 62 55 114

Unspecified pulses 850 15 4 2,631 336 25 32

PULSES 4881

most African countries. The highest peanut yields are

in Europe, where only small amounts of peanuts are

actually produced.

French Beans

0008 French Beans (Phaseolus vulgaris L.) are widely culti-

vated in semitropical regions of the world. The

leading producer of beans is Brazil, followed by

India, China, the USA, and Mexico. Nearly 50% of

the world production occurs in Asia with over 14 000

cultivars.

Peas

0009 Peas (Pisum sativum L.) are produced mainly in cool

areas. China and Russia contribute about 80% of the

world production. P. sativum has been divided into

the subspecies: hortense, syracium, absyssinicum,

jomardi, elatius, and arvense. Garden peas have

been separated into two types: smooth and wrinkled

seeded. The wrinkled seeded peas tend to be sweeter

than the smooth peas. (See Peas and Lentils.)

Chickpeas

0010 One of the most important legumes in the developing

world is the chickpea (Cicer arietinum L.). Among

developing nations, India produces nearly 80% of the

world production, with other major producers being

Pakistan, Turkey, and Myanmar. World chickpea pro-

duction has seen a decrease in recent years due to

reductions in yield. Chickpeas are subgrouped into

Kabuli and Desi. Kabuli chickpeas are very large

creamy seeds and grow well under irrigated condi-

tions. Desi chickpeas are much smaller and produce

the best yields.

Pigeonpeas

0011 Pigeonpeas (Cajanus cajan (L.) Millsp.) are a very

important crop in Asia, Africa, and South America,

ranking sixth in total world production of the

food legumes, with more than 90% produced in

India.

Lentils

0012The lentil (Lens culinaris Medik) is an important crop

in developing nations, accounting for only 2% of

total world pulse production with 75% of their pro-

duction in Asia. Several lentil cultivars exist, with

differences based on flower color and shape. Lentils

are grouped into small and large seeded subgroups.

The large seeded lentils are grouped into the subspe-

cies macrosperma Baroulina, and the small seeds are

grouped into microsperma Baroulina. Lentils are

grown as a cold-season crop throughout the subtrop-

ics of India, North Africa, Central America, and

South America. (See Peas and Lentils.)

Cowpeas

0013Cowpeas (Vigna unguiculata L.) are cultivated for

their pods and seeds. The seeds are used as a vegetable

and sometimes roasted like peanuts, while the roots

are consumed in South Africa. Cowpeas are grouped

into ‘crowder peas,‘‘brown crowders,‘ and ‘black-

eyed,‘ depending on the color of the seed and its

arrangement in the seedpod. Cowpeas are produced

in Asia, Africa, and the Mediterranean.

Consumption of Food Legumes

0014Food legumes are distributed throughout the whole

world, with different species being popular in differ-

ent regions. Legume preference for different areas of

the world is due to the availability of the food in those

areas. Availability results directly from environmen-

tal conditions favoring their growth. For people in

developing countries of the world, where standards

of living are limited due to a lack of buying power,

legumes are a crucial part of the diet. Since the prices

of other food commodities are unmanageable for the

average family, pulses receive an enhanced level of

consumption. Although legumes constitute a major

portion of the diet in many developing nations, their

most prominent use is in the form of feed for animals.

In developed nations, where yields are significantly

higher, the low market value of legumes provides an

inexpensive source of animal feed. The popularity of

processed cereal crops and knowledge of the antinu-

tritional effects of legumes in these countries also

inhibit the consumption of food legumes.

Africa

0015Cowpeas and groundnuts are the primary legume

crops of West Africa, where consumption of 10–17 g

per day per person is not unusual. In the humid, high-

altitude regions of Central and East Africa, legume

consumption is unusually high. Broad beans, chick-

peas, and lentils are staples, with hyacinth beans,

tbl0004 Table 4 Food legume production by nation (production in

thousand metric tons)

Nation Soybeans Peanuts Otherlegumes

World 92,982 18,580 44,701

China 7,477 3,873 6,858

India 650 5,700 11,107

Russia 460 – 6,508

US 61,970 1,561 –

Brazil 12,810 – 3,011

Mexico 672 – 1,430

Ethiopia – – 1,002

Trinidad and Tobago – – 1,356

4882 PULSES

lupines, lathyrus beans, and peas having local import-

ance.

Asia

0016 The leading consumer of legumes in Asia is India,

whose average pulse consumption is around 34 g per

person per day, with some variation between individ-

ual states. The most popular legume of the Indian

nation is the chickpea, but pigeonpeas, black gram,

mung beans, horse gram, and pea are also very im-

portant. In western Asia, popular legumes include

beans, chickpeas, lentils, and peas. The haricot bean

from America has also been successfully introduced

into western Asia. South-east Asians do not consume

large amounts of legumes, but a variety are grown for

their use as vegetables. In the eastern Asian nations of

China, Japan, Korea, and Indonesia, the dominant

legume crop is the soybean. Soybeans are the basis

of many traditional food products of eastern Asia.

Groundnuts and pulses, along with the soybean, are

very important foods in Indonesia.

0017 In Asian countries, the consumption of pulses tends

to increase with income level. This is primarily due to

the predominance of soybeans in eastern Asia, which

are of a higher value than most pulses. Typically,

legume consumption tends to increase with decreas-

ing income level, but because of the importance of the

soybean in so many Asian dishes, the opposite is true.

Higher income levels also show an increase in the

consumption of animal products, but this does not

change the consumption level of soybeans.

Latin America

0018 By far the most predominant food crop of Central

America and Mexico is maize, followed closely by the

haricot bean. Although many pulses have been intro-

duced into this region, their consumption and pro-

duction are low. An important commercial crop of

this region is the groundnut, which is also consumed

in small amounts as a snack.

0019 Pulse consumption in the islands of the Caribbean

is much higher than in Central America and Mexico.

Pulses such as cowpeas, kidney beans, and pigeonpeas

are popular when mixed with cereals in main dishes.

Most of the pulse consumption in the Mediterranean

is in lower-income families, where as much as 50 g per

person is consumed daily.

0020 In most South American countries, legumes are

a traditional part of the diet, except in the beef-

producing countries of Argentina, Bolivia, and Uru-

guay. The main pulse crop of South America is the

haricot bean, which is indigenous to this region of

the world. Other important crops include lima beans

and lupines. Chickpeas, lentils, peas, broad beans, and

pigeonpeashavebeenintroducedtoSouthAmericaand

arequitesuccessful.Anotherindigenouslegumecropof

SouthAmericaisthegroundnut,whichisgrownprimar-

ily for oil extraction, but some are consumed whole as

food.

Europe

0021Legume consumption in Europe is rather high in Eng-

land and in the poor Mediterranean countries (about

5 kg per year or 13–14 g per day) of southern and

eastern Europe. The summers in southern and eastern

Europe are hot and dry, enabling legume seeds to

grow well and at a relatively low cost. Consumption

of legumes is substantially lower in central and east-

ern European countries (about 2 kg per year or 5–6g

per day). However, in France, the average daily con-

sumption of pulses and nuts is around 10 g.

North America

0022Large quantities of groundnuts are consumed in both

the USA and Canada. Most pulses are consumed in

the warmer, poorer areas of the southern USA. The

highest USA consumption of 24 g per day is in rural

nonfarm families of very low income, with the lowest

consumption rates in high-income families.

Nature and Composition of Food Legumes

Seed Structure

0023The seeds of all legumes are generally very similar in

structure, with major differences being in the method

of energy storage. Pulses store their energy in the

form of carbohydrate, and oilseeds store energy in

the form of lipid. The major components of mature

legume seeds are the seed coat (8%), the cotyledons

(90%), and the embryo (2%). Like cereals, legumes

do have an endosperm at the early stages of develop-

ment, but as the seed matures, the energy is stored in

cotyledons. The seed coat is the only source of pro-

tection for mature legume seeds. Therefore, legume

seeds are unusually vulnerable to breakage, which

can lead to damage to the cotyledons.

0024The seed coat and the cotyledons of legume seeds

are very tightly attached to one another, which can

make hull removal very difficult. The cotyledons of

legume seeds, much like the endosperms of cereals,

are made up of starch and protein. Within the cotyle-

don, the most abundant component is starch, which is

surrounded near the outside of the cotyledons by

protein bodies. The ability to remove the hull from

the cotyledons is very important when trying to

recover these fractions.

0025The outsides of legume seeds are typically charac-

terized by three structures, which include the hilum,

PULSES 4883

the micropyle, and the rhape. The hilum is the point

at which the seed breaks away from the stalk and

looks like a large oval scar. The micropyle, which is

next to the hilum, is a small opening in the seed coat

where the pollen tube enters the valve. The raphe is a

ridge opposite the micropyle and represents the base

of the stalk. The hilum and the micropyle are very

important to permeability and water absorption of

the seed coat of legume seeds. Both vary in appear-

ance, depending on the size and shape of the seed.

0026 Legume seeds are very similar, but they do differ

from each other in color, shape, size, and seed coat

thickness. In general, the thickness of the seed coat is

directly proportional to the lipid content of the seed.

Oilseeds have much thicker seed coats than the

pulses, which are starch-rich.

Chemical Composition

0027 With the exception of peanuts, chickpeas, and soy-

beans, legumes can be described as containing ap-

proximately 10% moisture, 21–25% protein,

0.8–1.5% lipid, 60–65% total carbohydrates, and

2.2–4.0% ash. Table 5 illustrates the proximate com-

position of some commonly consumed food legumes.

The energy provided by legumes falls in the range of

345–350 kcal per 100 g. The exceptions which all

contain higher amounts of lipid are consequently of

a higher caloric value. Along with a high fat content,

soybeans contain the highest amount of crude protein

of all food legumes. Due to the high protein and fat

content of soybeans and peanuts, the total carbo-

hydrate content of these legumes is much lower than

in other legume species.

0028 Carbohydrates Carbohydrates of legumes, much

like the carbohydrates of other grains, can be divided

into water-soluble components, such as sugars and

pectin, and insoluble components, such as starch

and cellulose. Within both the soluble and insoluble

fractions of legume carbohydrates are components

that can be used as sources of energy and those that

cannot be utilized because they are resistant to human

digestive enzymes. (See Carbohydrates: Classification

and Properties.)

0029The most dominant carbohydrate in most legumes

is starch, but some seeds such as winged beans, soy-

beans, and those seeds containing gum tend to lack

starch. Legume starch is located in the cotyledon as

granules embedded in a very thick protein matrix.

The average size of legume starch granules ranges

from 25 to 28 mm, varying between species. The two

primary constituents of starch are amylose and amy-

lopectin, which are glucose homopolymers. Starch is

the primary storage carbohydrate in legumes, but

other carbohydrates such as mono-, di-, and oligosac-

charides as well as cyclitols and sugar alcohols have

received attention because of their association with

flatulence.

0030The mono- and disaccharide content of legumes is

generally less than 4%. Soybeans have been reported

to contain as much as 7% sucrose. Among the oligo-

saccharides found in legumes are raffinose, stachyose,

and verbascose. These compounds are galactosides of

sucrose containing one, two, and three molecules of

galactose, respectively. The human digestive system

does not contain the enzyme a-galactosidase, which is

required for the digestion of such oligosaccharides.

Without the ability to digest these compounds, they

are subject to occasional anaerobic fermentation.

This results in gas production or flatulence, which

can be very discomforting.

0031The other carbohydrate fraction of legumes is diet-

ary fiber, which is composed primarily of cellulose,

hemicelluloses, and lignin. Legumes contain a wide

range of unusual storage dietary fibers with unique

properties. The water-soluble gums making up the

dietary fiber of legumes have the ability to form gels

in water, which provides unique cooking characteris-

tics. Both the soluble and insoluble fractions of diet-

ary fiber are very beneficial nutritionally as they play

key roles in laxation, blood-glucose attenuation, and

blood-cholesterol attenuation.

0032Protein The protein of legume seeds is located pri-

marily within the cotyledon, with only a small por-

tion present in the seed coat. Quantitatively, legumes

are an excellent source of protein, but qualitatively,

they have many problems. Probably the most notable

problem with legume protein is the lack of sulfur-

containing amino acids. Another major problem is

the presence of proteinase inhibitors, which lower

the digestibility of legume proteins considerably.

(See Protein: Food Sources.)

0033The amino acid composition of legumes has been

widely studied and has shown that lysine levels are

very high, while cysteine and other sulfur amino acid

tbl0005 Table 5 Proximate composition of common food legumes

Legume Protein

(%)

Lipid

(%)

Crude fiber

(%)

Ash

(%)

Starch

(%)

Chickpeas 24.7 6.0 1.2–13.5 3.08 37.2–50.0

Lentil 27.7 0.9 3.8–4.6 2.56 34.7–52.8

Lupine 47.4 1.2 3.0 3.3 0.3–0.5

Mung beans 30.5 0.9 1.2–12.8 3.5 37.0–53.6

Navy beans 28.0 – 3.4–6.6 – 27.0–52.7

Pinto beans 28.0 1.9 4.3–7.2 – 51.0–56.5

Smooth peas 27.8 1.1 4.6–7.0 3.1 36.9–48.6

Soybean 49.9 23.3 2.4–5.5 5.3 0.2–0.9

Wrinkled peas 26.1 1.8 7.6 3.5 24.0–36.6

4884 PULSES