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increased susceptibility to fractures, particularly

fractures of the vertebrae, distal forearm (Colles

fracture), and hip. Of these, hip fracture is the most

severe, since patients require a lengthy hospital stay,

there is a high mortality rate (about 20% within 6

months of the fracture), and of those who survive,

many suffer permanent disability and dependency.

Osteoporosis is a major health problem in many

Western countries, but not in Asian countries. A

number of factors are known to increase the risk of

osteoporosis, including insufficient dietary calcium,

low physical activity, and lack of estrogen.

0036 In women, bone mass reduces at a rapid rate in the

first few years after the menopause, owing to the

reduction in estrogen. Hormone-replacement therapy

(HRT) is well known to reduce bone loss in postme-

nopausal women. However, HRT is not appropriate

for all women. Since soya may have estrogenic effects,

it has been hypothesized that it may provide an alter-

native to HRT.

0037 Soya protein containing isoflavones has been

reported to reduce bone loss due to estrogen defi-

ciency in ovariectomized rats. Soya bean isoflavones

have also been shown to have a protective effect on

bone loss in ovariectomized rats, suggesting that the

beneficial effect of soya protein is due to isoflavones.

The effect of isoflavones on bone loss in rats has been

reported to be similar to that for estrogen. The bone-

sparing effect of soya protein isoflavones has been

suggested to be due to a reduction in bone resorption

and/or to an increased osteoblast activity (increasing

bone formation).

0038 In humans, most but not all studies indicate that

soya protein containing isoflavones favorably affects

bone turnover and bone mineral density in the lumbar

spine of perimenopausal and postmenopausal women.

Treatment with ipriflavone, a synthetic isoflavone,

has also been reported to have bone-conserving

effects in postmenopausal women with a low bone

mass, thus confirming that the beneficial effect of

soya protein is likely to be due to isoflavones.

0039 In addition to the effect of soya protein on bone

mineral density, it has also been suggested that

soya protein, when substituted for animal protein,

may indirectly enhance bone strength. Another effect

of soya protein is that it helps to conserve calcium

by reducing urinary calcium excretion. This is due

to the lower sulfur amino acid content of soya

protein.

0040 Soya protein therefore appears to have modest

beneficial effects on bone density. However, studies

to date have been short term and have involved only

small numbers of subjects. In addition, no study has

investigated whether soya protein containing isofla-

vones has an effect on fracture risk.

Soya and Menopausal Symptoms

0041Hot flushes (also known as hot flashes) are a common

symptom among menopausal women in Western so-

cieties but are reported to be much less common in

Japan. Whether this difference is due to the higher

consumption of soya in Japan is not clear. HRT gen-

erally alleviates hot flushes and other menopausal

symptoms such as vaginitis. There is much research

interest in the possibility that soya may provide an

alternative to HRT in this regard.

0042Evidence of benefit of soya in menopausal women

is conflicting. Some researchers have reported an im-

provement in the frequency of hot flushes in women

taking soya protein daily. Others have reported no

effect of soya protein on the number of hot flushes

experienced but found a reduction in the severity of

symptoms. Others have reported a reduction in both

the incidence and severity of hot flushes with soya

protein or an isoflavone extract compared with a

control group. Others have reported no difference in

either the frequency or severity of hot flushes in the

intervention group compared with the control group.

0043Two studies have investigated the effects of

phytoestrogen supplements on vaginal cytology and

found an increase in cell proliferation (an indication

of estrogenic activity) and reversal of menopausal

atrophy. Others have reported no significant effect.

0044There are difficulties in interpreting the results of

these studies. This is because there are differences in

the amounts of soya protein and isoflavones used and

differences in the duration of the studies. Interpret-

ation is also complicated by the fact that the reported

frequency and severity of symptoms tend to decrease

in the control group as well as the intervention group.

Thus, much more research needs to be done before

soya protein can be proposed as a potential alterna-

tive to HRT for the control of menopausal symptoms.

See also: Amino Acids: Properties and Occurrence;

Anemia (Anaemia): Iron-deficiency Anemia;

Atherosclerosis; Cancer: Epidemiology; Diet in Cancer

Prevention; Cholesterol: Factors Determining Blood

Cholesterol Levels; Role of Cholesterol in Heart Disease;

Colon: Cancer of the Colon; Coronary Heart Disease:

Etiology and Risk Factor; Prevention; Dietary Fiber:

Physiological Effects; Bran; Osteoporosis; Plant

Antinutritional Factors: Characteristics; Vegetarian

Diets

Further Reading

Anderson JJB, Anthony M, Messina M and Garner SC

(1999) Effects of phyto-oestrogens on tissues. Nutrition

Research Reviews 12: 75–116.

Anderson JW, Johnstone BM and Cook-Newell ME (1995)

Meta-analysis of the effects of soy protein intake on

SOY (SOYA) BEANS/Dietary Importance 5397

serum lipids. New England Journal of Medicine 333:

276–282.

Bingham SA, Atkinson C, Liggins J, Bluck L and Coward A

(1998) Phyto-oestrogens: where are we now? British

Journal of Nutrition 79: 393–406.

Lissin LW and Cooke JP (2000) Phytoestrogens and cardio-

vascular health. Journal of the American College of

Cardiology 35: 1403–1410.

Messina MJ (1999) Legumes and soybeans: overview of

their nutritional profiles and health effects. American

Journal of Clinical Nutrition 70(Supplement): 439S–

450S.

Messina M and Messina V (2000) Soyfoods, soybean iso-

flavones and bone health: a brief overview. Journal of

Renal Nutrition 10: 63–68.

Messina M, Persky V, Setchell KDR and Barnes S (1994)

Soy intake and cancer risk: a review of the in vitro and

in vivo data. Nutrition and Cancer 21: 113–131.

Potter SM (2000) Soy – new health benefits associated with

an ancient food. Nutrition Today 35: 53–60.

SOY (SOYA) CHEESES

T Ono, Iwate University, Morioka, Iwate, Japan

Introduction

0001 Soy cheeses (soya cheeses) are a curd made from

soymilk (soybean milk) and its processed foods. The

soybean curd is a popular food used in daily meals in

eastern Asia. It is usually called tofu in English. Tofu

is made in a similar process to making cheese from

milk. The soymilk is curdled by adding coagulants

(CaSO

, MgCl

, glucono-delta-lacton (GDL)). Curds

are then pressed into cakes of various types. There are

three types of tofu: soft tofu, medium-soft tofu, and

firm or extra-firm tofu. Soft tofu is not pressed and is

eaten as it is. Medium-soft tofu is the most popular in

everyday use. Firm tofu is used in processed foods

which are fried, grilled, fermented, and dried. Tofu

derivatives are also familiar in eastern Asia.

0002 Tofu has a long history of 2000 years and has

held an important position in the eating habits as

popular foodstuffs in eastern Asia. The composition

and nutrient contents of tofu are similar to those of

cheese made from milk. Soybean products, however,

contain phytoestrogens, such as isofravones, which

may lead to a low incidence of estrogen-related

cancers and low prevalence of climacteric syndrome

and osteoporosis. The rate of these diseases is lower

in Asian peoples who consume a lot of soybean

products.

0003 Soy cheeses (tofu and its derivatives) are now

spreading throughout the world as healthy foods

and a low-cost supply of nutrients.

History of Tofu

0004 It is believed that tofu was invented by Lui An, King

of Hui Nang (178–122 bc) of the western Han

dynasty (202 bc–8) in China. A wall relief showing

tofu making was found in Dahuting tomb no. 1 (Mi,

Henan) in the eastern Han era (25–220). It became

popular among the public in the Song (960–1271).

The technology for making tofu was spread to neigh-

boring countries (Japan, Korea, Vietnam) in the early

stage of the Tang dynasty (618–907). The Chinese

character dou-fu means soybean curd; dou (to)

means soybean and fu means a soft elastic object,

although the object is a solid. Doufu was first written

in the early stages of the Song dynasty (960–1271).

Perhaps the idea for the name derives from nyu-fu

(yogurt); nyu means milk. This nyu-fu was written in

historical documents of the Tang dynasty (618–907).

0005In Japan, the oldest literature about tofu is found in

the record of Kasuga-shrine in 1183. When tofu was

introduced into Japan in the Nara period (761–793),

it was called okabe, and the old cookbook referred

to it as kabe (wall) or shirakabe (white wall). Tofu

became a common food in the eating habits of

Japanese people in the Edo era (seventeenth century)

and cookbooks on its use were published one after

another.

0006The soy curd is called doufu in China, tahu in

Indonesia, tofu in Japan, tobu in Korea, tau fu and

tau kuan in Malaysia, tokwa in the Philippines, and

tau pho and tau hu in Vietnam. The Chinese character

(dou-fu) was spread to eastern Asia through trading

with China at 1000 years ago, and called by the

pronunciation of each country. The name tofu has

now entered into the English language. Tofu is grad-

ually becoming a popular food for health and as a

low-cost supply of proteins in the American contin-

ent, Europe, and Africa.

Manufacturing Process

0007Soybeans are soaked in water overnight, then drained.

The beans are ground as a small quantity of water is

poured over them. The resultant mash is adjusted by

adding 10 times the amount of water as there are

5398 SOY (SOYA) CHEESES

soybeans for medium-soft and firm tofu, or seven

times the quantity of water for soft tofu. The slurry

is allowed to boil gently for about 5 min by steaming

or heating and is then filtered. Alternatively, after the

slurry is filtered, the filtrate (raw soymilk) is then

heated (in the Chinese old style). The heated filtrate

is soymilk and the residue is okara. A small amount of

either calcium sulfate or magnesium chloride is intro-

duced to coagulate the soymilk. The use of the cal-

cium salt (gypsum) is in the original Chinese style

and using magnesium chloride (bittern) from sea salt

is the Japanese style. After the milk has curdled

(above 80



C), a part of the whey is squeezed to make

medium-soft and firm tofu. The curds are ladled into

a rectangular forming container lined with cheese-

cloth. A lid is placed on the container, and the curds

are pressed at 70–80



C to make a block and to

squeeze the whey. The water content of medium-soft

tofu and firm tofu is about 85% and 75–80%, re-

spectively. The tofu block is sometimes soaked into a

tub of cold water to replace the whey with water. On

the other hand, to make soft tofu, the soymilk is

curdled in the container and is packed without press-

ing. Soft tofu (packaged tofu) is also made from a

packaged soymilk containing GDL by heating above



C for 1 h. GDL changes to gluconic acid by

heating and pH decreases to 5.8. Soymilk coagulates

by decreasing pH.

Bean Curd (Tofu)

0008 The types of soft tofu products include silken, dou-

fang (China), oboro (Japan) and packaged. Doufang

(meaning bean flower) and oboro (meaning hazy) are

eaten like yogurt as they are. Silken and packaged are

packaged, have a longer shelf-life, and are used in

salads and various cooked foods. Types of medium-

soft tofu include momen (meaning cotton cloth) tofu

(Figure 1), which is used in various cooked foods. It is

the most popular type of tofu in eastern Asia. Firm

tofu (pressed/firm curd (Figure 1) and curd sheet) is

used as processed foods which are fried, grilled, fer-

mented, dried, and so on. These tofus are available in

grocery stores and supermarkets.

0009Tofu is like a dairy product in that it must be

refrigerated and has a short shelf-life (1–7 days).

Packaged tofu (silken) is often ultrapasteurized and

so has a very long shelf-life (1–2 months). These tofus

are always offered as fresh.

Processed Foods (Derivatives of Tofu)

Tofu Cheese (Cheese Alternative)

0010Firm tofu is scrambled and mixed with casein, soy-

bean oil, modified food starch, salt, citric acid,

sodium citrate, natural flavor, vitamins and minerals,

and the mixture is heated and molded. It is sold as a

cheese alternative containing no cholesterol and no

lactose. There are Cheddar, Mozzarella, garlic and

herb, and other types.

Fried Bean Curd (Aburage)

0011Firm tofu is cut into boards or cubes and deep-fried. A

board-shape one is then swollen with air, and be-

comes something like the skin of fried chicken. It

(a) (b) (c)

(d) (e) (g)(f)

fig0001 Figure 1 (see color plate 127) Photographs of various tofu and its derivatives. a, fried tofu; b, dried frozen tofu; c, furu; d, momen tofu;

e, firm tofu; f, dried tofu; g, choutofu.

SOY (SOYA) CHEESES 5399

is often used for wrapping boiled rice or other foods.

Cube and block types (Figure 1) are eaten like fried

tofu.

Grilled Bean Curd (Yaki-Tofu)

0012 The top and bottom surfaces of a rectangular firm

tofu are roasted till a part is scorched. This process

gives it durability against damage in cooking.

Ganmodoki

0013 Firm tofu is scrambled, mixed with vegetables and

seasonings, molded into a disk shape and deep-fried.

Sometimes beans and seaweeds are mixed. These are

eaten intact or after roasting and cooking.

Dried Bean Curd

0014 Firm tofu is pickled and dried. This is an amber hard

block (Figure 1) and has a very long shelf-life

(6 months). When cooked, it is cut into a chip shape.

Dried Frozen Tofu (Kohri-Tofu)

0015 Firm tofu is cut into rectangular boards, frozen be-

tween 3 and 5



C for 1–7 days, thawed, and dried.

The tofu becomes a porous plate (Figure 1) in this

process and has a very long shelf-life (1 year). This

porous texture is made by tofu proteins denaturing

during freezing. When cooked, its texture is different

from tofu and it is like a sponge with many fine holes.

It is able to contain large quantities of soup in

cooking.

Smoked Bean Curd

0016 Firm tofu is dipped into soy sauce, smoked, and aged

for 1–2 weeks at a low temperature. Its texture is like

smoked cream cheese. It is excellent as a side dish

with alcohol.

Tofu-Kamaboko

0017 Firm tofu is scrambled, packed into a semicylindrical

shape, and steamed. Sometimes beans and vegetables

are mixed in. It is flavored with sugar and salt.

Bean Curd Stick

0018 Curd sheet is cut into stick shapes and deep-fried.

This is used for Chinese cooking.

Fermented Tofu (Furu, Choutofu, Tofuyoh)

0019 There is an original fermented tofu in each district,

particularly in China. It is similar to fermented

cheese, like blue and Brie cheese.

Furu (Figure 1)

0020 Firm tofu is cut into small cubes and these are inocu-

lated over their surfaces with appropriate molds

(Actinomucor elegans, Mucor hiemalis, M. silvaticus,

Rhizopus chinensis, and the like). The molded cubes

are salted in brine containing alcohol (red or white),

moldy rice (Monascus purpureus, M. anka, and the

like) and spices (hot pepper, star anise, bay laurel,

sesame oil, and rose essence), then packed and aged

for 1–6 months. It has a creamy, salty, hot taste and

a strong flavor. There are many synonyms for furu:

sufu, doufuru, fooyue, fuju, and toefuru. Furu is the

standardized name in China. Furu is broadly divided

into three categories by color: red, white, and yellow.

It is eaten with rice gruel or mantou (steamed bread)

at a morning meal, and cooked with meat or vege-

tables as a seasoning in China.

Choutofu (Figure 1)

0021The making process is similar to that of furu. How-

ever, the moldy rice is not added to the brine and

bacterial fermentation occurs in the brine. The

brining period is about 1 month. Choutofu is a kind

of furu, but is differentiated from other furu in China.

It is usually fried before serving and eaten as a relish.

Tofuyoh

0022Tofuyoh is like furu, and is produced in Okinawa,

Japan. Cubes of firm tofu are fermented in brine of

moldy rice and awamori (rice liquor). The mold in-

oculation is neglected when making tofuyoh, and

red moldy rice (Monascucs) and yellow moldy rice

(Aspergillus) are added to the brining solution. It is

eaten as a relish with liquor.

Bean Curd Skin (Yuba)

0023Fresh yuba is the layer of skin that is formed by

simmering soymilk at near boiling point. After

drying, the film becomes yuba. Therefore, it is not a

tofu derivative but rather a product of soymilk. It can

be eaten as a snack, or used in cooking. Yuba is used

in traditional cooking in Japan.

Composition and Nutrients

0024The composition of medium-soft tofu (momen-tofu),

being the most popular, is shown in Table 1, together

with that of cheese (Edam) for comparison. The

equivalent value of momen-tofu is also shown to

compare with cheese composition. The content of

protein, lipid, and carbohydrate is similar in both.

The calories in 100 g are also similar. As concerns

minerals, the sodium content of tofu is 13 times

lower than that of cheese, while the potassium con-

tent is 10 times higher. These mineral proportions

reduce high pressure in blood vessels and may reduce

the risk of a cerebral hemorrhage. The iron content of

5400 SOY (SOYA) CHEESES

tofu is 13 times higher than that of cheese. It is effect-

ive for healing anemia. Tofu is rich in vitamins D, K,

and the B group.

0025 The composition of the main tofu derivatives is

shown in Table 2. The lipid content increases in

deep-fried products. Each content changes propor-

tionally with water content, except for that of fried

products.

0026 The lipid content of tofu is 20% less than that of

cheese, and less in saturated fat and cholesterol. It is

important to eat less saturated fat and cholesterol to

reduce the risk of heart disease. Tofu and its deriva-

tives may play a role in keeping the heart healthy. (See

Cholesterol: Factors Determining Blood Cholesterol

Levels.)

0027 Asian people have a low incidence of estrogen-

related cancers and a low prevalence of climacteric

syndrome and osteoporosis. It is suggested that the

cause is due to consumption of a lot of soybean

products containing phytoestrogens, such as isofra-

vones. Tofu comprises 40–60 mg isofravones 100 g

1

It is reported that people in Japan and Shanghai con-

sume 20–30 mg of isoflavones per day on average.

0028 Tofu comprises 50% protein and 35% fat in a dry-

matter base. The fat in the curd is very stable against

ooze and oxidation by cooking and storing. There-

fore, the tofu curd must support a stable fixation of

lipids. Soymilk for tofu has astringent and soybean

flavors and is not suited for drinking unless it is

already part of your culture. But these flavors are

restrained in tofu and many people can eat tofu.

These characters can be explained by the mechanism

of curd formation.

Mechanism of Curd Formation

0029Tofu curd is made from soymilk. Therefore we need

information about soymilk before we can understand

curd formation. The following is known about soy-

milk. Soymilk is a turbid solution like cows’ milk and

contains particulates (40–100 nm) and soluble pro-

teins and oil globule fractions. The particulate protein

has a higher binding ability with calcium than soluble

protein. The oil globules contain almost all lipids in

soymilk, and exist as a globule (200–400 nm) like oil

body, as shown in a scanning electron micrograph

(Figure 2). The globules disperse in a stable form,

packed with oil body protein and soy proteins. The

oil globules also have a higher binding ability with

calcium than the soluble protein. It is found that in a

mixed solution of oil globules and particulate pro-

teins, both fractions aggregate at the same concen-

tration of coagulants, such as CaCl

. Therefore, these

results show that a mechanism of curd formation can

be illustrated by the behavior of protein particles, oil

globules, and soluble proteins when the coagulants

are added into soymilk, as shown in Figure 3. At first,

protein particles (80 nm) combine with the oil globule

(350 nm) by adding magnesium or calcium ions, and

then the bound globules aggregate with each other

while bringing round water. The curd becomes firm,

tbl0001 Table 1 The compositions of tofu and cheese

Contents Tofu (momen) (Equivalent) Cheese

(Edam)

Water (kcal/100g) 86.8 (41) 41.0

Calories (kcal/100g) 72 (322) 356

Protein (g/100g) 6 (29.5) 28.9

Lipid (g/100g) 4.2 (18.8) 25.0

Carbohydrates (g/100g) 1.6 (7.2) 1.4

Ash (g/100g) 0.8 (3.6) 3.7

Calcium 120 (536) 660

Sodium 13 (58) 780

Potassium 140 (626) 65

Phosphorus 110 (492) 470

Iron 0.9 (4.0) 0.3

Thiamin (B

) 0.07 (0.31) 0.04

Riboflavin (B

) 0.03 (0.13) 0.42

Niacin 0.1 (0.45) 0.1

Tocopherol (E) 0.6 (2.7) 1.3

MAG x11,000 ACCV 7.0kV

WIDTH 12.0 µm

fig0002Figure 2 Scanning electron microgram of oil globules in soy-

milk.

tbl0002 Table 2 The compositions of tofu derivatives

Contents Ganmodoki Fried bean curd Dried frozen tofu

Water (g) 63.5 75.9 8.1

Calories (kcal) 228 150 529

Protein 15.3 10.7 49.4

Lipid 17.8 11.3 33.2

Carbohydrates 1.6 0.9 5.7

Ash 1.8 1.2 3.6

SOY (SOYA) CHEESES 5401

as combining soluble proteins with the pH decrease

caused by calcium binding. This assumes that the oil

is packed with triple layers of proteins, that is, oil

body protein, protein particles, and soluble proteins.

Therefore, the oil in the curd is very stable against

ooze and oxidation during cooking and storing. The

astringent and soybean flavors are also packed in the

oil with triple layers of proteins. When we eat tofu

and its derivatives, there is no oily and astringent

flavor.

0030 The protein particles bind at first on to the oil

globule and become a trigger for curd formation.

Therefore, the protein particulate content in soymilk

is important when making tofu. The particulate con-

tent is influenced by the various species and genetic

variants of soybean. It is known that the soymilk from

glycinin-rich (major soybean protein) soybean con-

tains more particles and the curd shows greater

braking stress. The combination of protein particles

with oil globules decides the quality of tofu. (See

Protein: Functional Properties.)

See also: Soy (Soya) Beans: Processing for the Food

Industry; Soy (Soya) Milk

Further Reading

Guo W (1993) The History of Soybean Cultivation in

China. Hehai, People’s Republic of China: Hehai Uni-

versity Publishing.

Guo ST, Ono T and Mikami M (1999) Incorporation of

soymilk lipid into protein coagulam by addition of

calcium chloride. Journal of Agriculture and Food

Chemistry 47: 901–905.

Honda K (1998) Tofu and Soybean Cooking: The Japanese

Healthy Way. Tokyo, Japan: Japan Publications.

Li L and Li S (2000) Reviews on Chinese fermented soybean

foods. Proceedings of the Third International Soybean

Processing and Utilization Conference, pp. 701–

706. Japan: Korin Publishing.

Messina M, Messina V and Setchell K (1994) The Simple

Soybean and Your Health: How Soy Foods Can Lower

Your Cholesterol and Reduce Your Risk. USA: Avery.

Ono T (2000) The mechanism of curd formation from

soybean milk to make a stable lipid food. Proceedings

of the Third International Soybean Processing and Util-

ization Conference, pp. 51–52. Tokyo, Japan: Korin

Publishing.

Paino J and Messinger L (1990) The Tofu Book. The New

American Cuisine. USA: Avery.

Resources Council, Science and Technology Agency (2000)

Standard Tables of Food Composition in Japan, 5th edn.

Tokyo, Japan.

Shurtleff W and Aoyagi A (1970) The Book of Tofu. USA:

Autumn.

Watanabe T (1997) Science of Tofu – Easy to Understand.

Kyoto, Japan: Food Journal.

Watanabe S, Uesugi S, Zhou XG et al. (2000) Effects of soy

rich diet and isoflavone supplement on healthy women.

Proceedings of the Third International Soybean Process-

ing and Utilization Conference, pp. 203–206. Japan:

Korin Publishing.

Yamori Y (2000) Soybeans for health in the world – lessons

from Okinawan diets and healthy longevity by WHO –

cardiac and immigrant studies. Proceedings of the Third

International Soybean Processing and Utilization Con-

ference, pp. 195–198. Japan: Korin Publishing.

Solute protein

Protein

particle

adding Ca

,Mg

and/or decreasing pH

Soymilk Coagulation

Tofu-curd

Oil

globule

11S

α'

fig0003 Figure 3 (see color plate 128) Formation of tofu-curd from soymilk (speculation). Oil globule is packed with triple layers of the

proteins; oil-body’s (oleosin), particulate and solute proteins.

5402 SOY (SOYA) CHEESES

SOY (SOYA) MILK

T Odo, Iwate University, Morioka, Iwate, Japan

Background

0001 Soymilk (soya milk) is a milky liquid made from the

soybean. Its composition and nutrient and contents

are similar to those of dairy milk. Soymilk has been a

traditional breakfast drink for centuries throughout

South-east Asia. It is made from soaked soybeans

by grinding, heating, and filtering. There are three

types of soymilk: regular (traditional), reconstituted

(modern), and derivatives. Regular soymilk is pre-

pared from whole soybeans by the aforementioned

method. Reconstituted soymilk is made from soy-

beans by a new processing method and adjusted by

adding soybean meal, vegetable oils, and seasonings.

Derivatives of soymilk are made from regular or re-

constituted soymilk and include drinks, yogurt, soy

cheese (tofu), and so on. There are two manufactur-

ing processes for regular (traditional) and reconsti-

tuted (modern) soymilk. The traditional process

involves a heating process after grinding soaked

soybeans. To Chinese people, both in China and over-

seas, traditional (Chinese-style) soymilk is an every-

day regular drink, just like cows’ milk is in the West.

There are many soymilk producers in Hong Kong,

Singapore, Malaysia, Thailand, Taiwan, and China.

However, some people are uncomfortable with the

natural bean (or raw grass)-like flavor of soymilk. In

modern processing, grinding and heating are carried

out, reducing the bean-like flavor, and thus increasing

the popularity for this type of soymilk for many in

Eastern Asia, including Korea and Japan. Soybean

products contain phytoestrogens, such as isoflavones,

which may reduce the incidence of estrogen-related

cancers and prevalence of climacteric syndrome and

osteoporosis. The rate of these diseases is lower in

Asian people consuming a diet high in soybean prod-

ucts. Soy products are now spreading across the

world as healthy foods and as a low-cost source of

nutrients.

History of Soymilk

0002 A stone mill for soaked soybeans, found at Huainam

in China, is thought to have been made in the Western

Han dynasty (202 bc–ad 8). A wall relief showing

milling of soaked soybeans was found in Dahuting

tomb No. 1 (Mi, Henan) from the Eastern Han era

(ad 25–220). These remains indicate that soymilk

was originally produced in China over 2000 years

ago. Tofu made from soymilk became popular in the

Song dynasty (ad 960–1271). The technology for

tofu manufacture eventually spread to neighboring

countries (Japan, Korea, Vietnam, etc.) in the early

years of the Tang dynasty (ad 618–907). Traditional

soymilk is called ‘Doujiang’ in China (‘dou-jian’

means soybean-serous; ‘dou’ means soybean, and

‘jiang’ means a serous liquid). Chinese people went

abroad and lived overseas from the song era (ad 960–

1271), and in the nineteenth century, many emigrated

to South-east Asia in particular (Singapore, Malaysia,

Thailand, and so on). Some people are uncomfortable

with the natural bean flavor of soymilk, and so soy-

milk has not become popular in some countries. A

new processing method (modern style) for soymilk

was developed in the USA in the twentieth century.

In this method, grinding and heating are carried out

simultaneously. The bean flavor is reduced, thus

increasing its popularity. Modern-style soymilk

gradually spread to north-eastern countries (northern

China, Korea, and Japan). There are many soymilk

producers in East Asia, just as there are many dairy

producers in Western countries. Nowadays, modern-

style soymilk has become a very popular beverage

across the world.

Manufacturing Process

0003There are three types of soymilk: traditional, modern

style, and derivatives.

0004Traditional (Chinese-style) soymilk (regular soy-

milk): Soy beans are washed with water and

soaked overnight in cold water. The soaked soy-

beans are then ground, with a small amount of

water being poured over them. The resultant

mash is adjusted by adding 10 times more water

than soybeans. The slurry is filtered and then

boiled gently for 30–60 min. The boil filtrate is

traditional (Chinese-style) soymilk (bean-flavored

soymilk).

0005Modern-style soymilk (reconstituted soymilk):

There are three methods for producing modern-

style soymilk: the Cornell, USDA, and Illinois

methods, after the organizations involved in the

development, i.e., the University of Cornell, United

States Department of Agriculture, and University of

Illinois, respectively. In these methods, enzymes of

the soybean are inactivated by heating before being

dissolved in water, because the bean flavor develops

by enzymatic reactions. There are several modified

SOY (SOYA) MILK 5403

methods for producing modern-style soymilk.

These are as follows:

0006 Cornell method: Soybeans are soaked in 0.05 N

NaOH at 50–65



C for 2 h and washed with

water. The washed beans are ground as hot

water (80–100



C) is poured over them. The

resultant, mash is filtered, and the filtrate is

digested to soymilk by adding water, emulsifier,

sugar, and seasonings, and then homogenized.

0007 USDA method: Dry soybeans are dehulled and

then mashed at a high temperature with an

extruder. The resultant soybean powder is

mixed with water, emulsifier, oils, and season-

ings, and vigorously homogenized. This method

has no filtration process, and whole soybeans

(minus their hull) are used for soymilks.

0008 Illinois method: Cleaned soybeans are selected

by removing dirt, and cracked, damaged, and

discolored soybeans. The soybeans are blanched

for 5 min in boiling water containing 0.25%

baking soda, and blanched again for 5 min in

boiling water containing 0.05% baking soda.

The blanched soybeans are then ground with

hot water (near boiling), and the resulting mash

is adjusted to soymilk with water, emulsifier,

oils, and seasonings, and then vigorously

homogenized. This method has no filtration

process, and whole soybeans are used for soy-

milk. There is also a variation of this method in

which the ground mush is filtered and adjusted

to soymilk.

0009 Other methods: Dried soybeans are dehulled

and ground as hot water is poured over them.

Alternatively, cleaned soybeans can be soaked

and ground with hot water. The resultant

mashes are then filtered. The filtrate is adjusted

to soymilk by adding water, oils, and season-

ings, and then homogenized. Another method

uses lipoxygenase-deficient mutant soybeans

for soymilk processing. The soymilk from this

soybean has no bean flavor, even using the

traditional method.

0010 Soymilk derivatives

0011 Soymilk soft drinks: Soymilk soft drinks are

made from a mixture of reconstituted soymilk

and fruit or vegetable juice, coffee, cocoa, or

cows’ milk. Emulsifier and seasonings are also

added and homogenized. The product is then

ultrapasteurized and packed in aseptic Tetra

brick or retort standing pouches.

0012 Soy yogurt: Soy yogurt is made from recon-

stituted soymilk by using a starter culture (L.

acidophilus, St. thermophilus, etc.) and flavors.

Soymilk is mixed with sugar, glucono-delta-lac-

ton (GDL), starter, flavors, and seasonings. The

mixture is then poured into cups and fermented

for 1–2 days. Soy yogurt is sold in chilled lines.

0013Soy cheese (tofu and its derivatives): Soy cheese

(tofu and its derivatives) is made from trad-

itional soymilk. The soymilk is curdled by

adding coagulants (CaSO

, MgCl

, GDL). The

curds are then pressed into cakes of various

types. There are four types of tofu: soft,

medium, firm, and extra firm. These are dis-

cussed in detail later.

Products

Traditional (Chinese-style) Soymilk (Regular

Soymilk)

0014Regular soymilk has a mellow, bean-like flavor, and is

acceptable to the Chinese people. Tofu curd can be

made from this soymilk. This soymilk is used for

cooking in North-east Asia and is used as a traditional

breakfast drink in South-east Asia.

Modern-style Soymilk (Reconstituted Soymilk)

0015There are two types of reconstituted soymilk. One has

only a slight bean-like flavor and is prepared from

soaked soybeans by grinding together with hot water.

People who often eat soy products prefer the slight

bean-like flavor of soymilk. The bean-like flavor is an

important factor. Some flavors are often added

(masking) to reduce the bean-like flavor in soymilk.

This type of soymilk is drunk in North-east Asia.

Another type of reconstituted soymilk is the Western-

style soymilk (characterized by an off-bean-like flavor)

produced by modern methods (Cornell, USDA, and

Illinois). This white soymilk has a dairy-like taste and

is often ultrapasteurized. It is packed into aseptic

Tetra brik packs or retort standing pouches and is

distributed and sold without the need for refriger-

ation. This type of soymilk is becoming a very popu-

lar beverage in North America and Europe.

Composition and Nutrients

0016Table 1 lists the compositions of traditional soymilk,

bovine milk, and human milk. The protein content of

soymilk is slightly higher than that of bovine and

human milks, the lipid and carbohydrate contents

are 30% lower, and the calories per 100 g are 30%

lower. Therefore, the constituents of soymilk can be

adjusted to be the same as those of bovine milk. In

terms of minerals, the calcium content of soymilk is

50% lower than that of human male, whereas the

potassium content is twice as high. The iron content

of soymilk is 12 times higher than that of bovine and

human milk, and so it is effective in treating anemia.

5404 SOY (SOYA) MILK

Soymilk contains small amounts of the the lipid-

soluble vitamins (A, D, and E) but slightly lower

levels of the vitamin B groups (B

, niacin) than

the other types of milk. (See Protein: Food Sources;

Quality; Vitamins: Overview.)

0017 Soymilk contains less saturated fat and cholesterol

than bovine and human milk. Nutritionists recom-

mend that less saturated fat and cholesterol be con-

sumed so as to reduce the risk of heart disease. It has

been reported that a soy protein intake of about 25 g

per day (roughly the equivalent of four glasses of

soymilk per day) reduces the risk of coronary heart

disease and lowers blood cholesterol levels. Evidence

for these two claims is so compelling that since Octo-

ber 1999, the US Food and Drug Administration

(FDA) has allowed manufacturers of soy products to

cite these claims on the packaging and in advertising.

Soymilk may play a more important role in keeping

the heart healthy than bovine milk.

0018 Soymilk does not contain any lactose, and it is an

ideal milk for lactose-intolerant people. Its popularity

is now increasing in North America and Europe.

Asians have a low incidence of estrogen-related

cancers and a low prevalence of climacteric syndrome

and osteoporosis, and it has been suggested that this is

because they consume a large number of soybean

products, which are high in phytoestrogens such as

isoflavones. Soymilk contains 40–60 mg of isofla-

vones per 100 g. It has been reported that consumers

in Japan and Shanghai consume 20–30 mg per day on

average. (See Lactose.)

Structure of Soymilk

0019 Soy milk is a milky liquid and contains mainly pro-

tein, lipid, and glucide. bovine milk is also an milky

liquid because it contains micellar proteins (100 nm

mean diameter) and Lippitt globules of (5 mm mean

diameter). Soymilk is known to contain a particular

protein (18 nm mean diameter) and oil globules

(350 nm mean diameter). Half of the protein in soy-

milk exists in a particular form, and half is in soluble

form. The glucide in soymilk consists of sugar and

oligosaccharides, which are soluble in solution. The

colloidal solution forms a curd like bovine milk.

Soymilk can be made to curdle by adding coagulants

to make soy cheese (tofu).

See also: Milk: Physical and Chemical Properties; Soy

(Soya) Beans: The Crop; Processing for the Food

Industry; Properties and Analysis; Dietary Importance;

Soy (Soya) Cheeses