Soy milk

Soy milk
Chinese name
Chinese	1. 豆漿(T)/豆浆(S) 2. 豆奶 3. 豆花水 4. 豆腐漿(T)/豆腐浆(S)
Literal meaning	1. bean thick liquid 2. bean milk 3. bean flower water 4. bean thick liquid
Transliterations Mandarin - Hanyu Pinyin 1. dòu jiāng 2. dòu nǎi 3. dòu huā shuǐ 4. dòu fu jiāng Min - Hokkien POJ 3. tau hoe chúi Wu - Romanization 1.dɤɯ tɕiã 4. dɤɯ vʊ tɕiã
Japanese name
Kanji	豆乳
Transliterations - Revised Hepburn tōnyū
Korean name
Hangul	두유
Hanja	豆乳

Soy milk (also called soya milk, soymilk, soybean milk, or soy juice) and sometimes referred to as soy drink/beverage is a beverage made from soybeans. A stable emulsion of oil, water, and protein, it is produced by soaking dry soybeans and grinding them with water. Soy milk contains about the same proportion of protein as cow's milk: around 3.5%; also 2% fat, 2.9% carbohydrate, and 0.5% ash. Soy milk can be made at home with traditional kitchen tools or with a soy milk machine.

The coagulated protein from soy milk can be made into Tofu, just as dairy milk can be made into cheese.

Origins

The oldest evidence of soy milk production is from China where a kitchen scene proving use of soy milk is incised on a stone slab dated around A.D. 25–220.^[1] It also appeared in a chapter called Four Taboos (Szu-Hui) in the A.D. 82 book called Lunheng by Wang Chong, possibly the first written record of soy milk. Evidence of soy milk is rare prior to the 20th century and widespread usage before then is unlikely.^[1]

According to popular tradition in China, soy milk was developed by Liu An for medicinal purposes, although there is no historical evidence for this legend.^[1] This legend first started in the 12th century and was not clearly stated until late 15th century in Bencao Gangmu, where Li was attributed to the development of tofu with no mention of soy milk. Later writers in Asia and the West additionally attributed development of soy milk to Liu An, assuming that he could not have made tofu without making soy milk. However, it is also likely that Liu An has been falsely attributed to the development of tofu by writers after his time. However, some recent writers attributed Liu An to have developed tofu in 164 BC^[2]

Cultural terms

The most common Chinese terms for soy milk are "豆漿" (Pinyin: dòu jiāng; lit. bean + a thick liquid) and "豆奶" (Pinyin: dòu nǎi; lit. bean + milk).

The Japanese term for soy milk is tōnyū (豆乳).

In Korea, "두유(豆乳)" is the word for representing soy milk. "두" and "유" represent soy and milk respectively.

In Singapore, it is known as tau-huey-tzui (豆花水, POJ:tau hoe chúi) in the local Hokkien dialect while in Malaysia it is known as "susu soya" or "air tauhu" in the local Malay language.

Prevalence

Greek Café Frappé prepared with soy milk, topped with additional cinnamon

Plain soy milk is unsweetened, although some soy milk products are sweetened. Salted soy milk is prevalent in China.^[3]

The drink is very popular in the hawker culture of Malaysia, with it being a standard offering accompanying meals at Malaysian Chinese stalls. In Malaysia, soybean milk is usually flavoured with either white or brown sugar syrup. The consumer also has the option to add grass jelly, known as leong fan or "cincau" (in the Malay language) to the beverage. Sellers of soybean milk in Penang usually also offer bean curd, a related custard-like dessert, known to the locals as tau hua which is flavored with the same syrup as the soybean milk. In Indonesian is known as "susu kedele". Yeo's, a drink manufacturer in Singapore and Malaysia, markets a commercialized tinned or boxed version of soybean milk.^[4]

The drink is slowly becoming popular in India as well. Soy has originally been introduced by Mahatma Gandhi in 1935. Nowadays, it is also widely sold in Tetrapaks by various brands like Staeta.

In the West, soymilk has become a popular alternative to cow's milk, with a roughly similar protein and fat content.^[5] Soy milk is commonly available in vanilla and chocolate flavors as well as its original unflavored form. In some Western countries where veganism has made inroads, it is available upon request at cafés and coffee franchises as a cow's milk substitute.

Health

Health benefits

Soy milk has about the same amount of protein (though not the same amino acid profile) as cow's milk. Natural soy milk contains little digestible calcium as it is bound to the bean's pulp, which is insoluble in humans. To counter this, many manufacturers enrich their products with calcium carbonate available to human digestion. Unlike cow's milk, it has little saturated fat and no cholesterol. Soy products contain sucrose as the basic disaccharide, which breaks down into glucose and fructose. Since soy doesn't contain galactose, a product of lactose breakdown, soy-based infant formulas can safely replace breast milk in children with galactosemia.

Soy milk is promoted as a healthy alternative to cow's milk for reasons including:

• Source of lecithin and vitamin E
• Lacks casein
• It is safe for people with lactose intolerance or milk allergy
• Contains far less saturated fat than cow's milk.
• Contains isoflavones, organic chemicals that may possibly be beneficial to health.

In 1995, the New England Journal of Medicine (Vol.333, No. 5) published a report from the University of Kentucky entitled "Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids." It was financed by Solae LLC of St. Louis.^[6] This meta-analysis concluded that soy protein is correlated with significant decreases in serum cholesterol, low density lipoprotein (LDL, bad cholesterol), and triglyceride concentrations. However, high density lipoprotein (HDL, good cholesterol) did not increase. Soy phytoestrogens (isoflavones: genistein and daidzein) absorbed onto the soy protein were suggested as the agent reducing serum cholesterol levels.^[7] In 1998, on the basis of this research, Solae LLC predecessor PTI filed a petition with FDA for a health claim that soy protein may reduce cholesterol and the risk of heart disease. The U.S. Food and Drug Administration granted this health claim for soy: "25 grams of soy protein a day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease." One serving of soy milk (1 cup or 240 mL), for instance, contains 6 or 7 grams of soy protein.

In January 2006, an American Heart Association review (in the journal Circulation) of a decade-long study of soy protein benefits cast doubt on the FDA-allowed "Heart Healthy" claim for soy protein.^[8] The panel also found that soy isoflavones do not reduce post-menopause "hot flashes" in women, nor do isoflavones help prevent cancers of the breast, uterus, or prostate. Among the conclusions, the authors state,

"In contrast, soy products such as tofu, soy butter, soy nuts, or some soy burgers should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins, and minerals and low content of saturated fat. Using these and other soy foods to replace foods high in animal protein that contain saturated fat and cholesterol may confer benefits to cardiovascular health."^[9]

Negative health effects

• A 2008 study found that men who consume an average of half a portion of soy products per day are more likely to have a lower concentration of sperm.^[10] The study found a decreasing trend in sperm concentration correlated with the amount of isoflavones consumed as part of a soy rich diet. The study acknowledges further broader replication is required as it focused predominantly on overweight Caucasian men.^[11] It also concludes by mentioning two other studies, one of which found no correlation between soy intake and sperm levels in men, and one that found a positive correlation between soy intake and sperm levels in men.
• High levels of phytic acid bind to important nutrients like calcium, magnesium, iron,^[12] and zinc during digestion. However, cow's milk is known for significantly slowing the absorption of iron^[13] and calcium from non-dairy sources, e.g., kale and sesame.

Potential medicinal use

It has been reported that soy proteins help to reduce polycystic kidney diseases by attenuating cytosolic phospholipase A2.^[14][15] However, Sankaran et al. and Harold et al. argued that the dietary treatment can only help to ease the symptoms but not cure the disease, and yet it is individual dependent.^[16][17] Ogborn et al. found that polyunsaturated fatty acids play crucial roles to obtain the benefits of the soy protein dietary treatment.^[18]

Preparation

Soy milk can be made from whole soybeans or full-fat soy flour. The dry beans are soaked in water overnight or for a minimum of 3 hours or more depending on the temperature of the water. The rehydrated beans then undergo wet grinding with enough added water to give the desired solids content to the final product. The ratio of water to beans on a weight basis should be about 10:1. The resulting slurry or purée is brought to a boil in order to improve its nutritional value by heat inactivating soybean trypsin inhibitor, improve its flavor and to sterilize the product. Heating at or near the boiling point is continued for a period of time, 15–20 minutes, followed by the removal of an insoluble residue (soy pulp fiber or okara) by filtration.

There is a simple yet profound difference between traditional Chinese and Japanese soy milk processing: the Chinese method boils the filtrate (soy milk) after a cold filtration, while the Japanese method boils the slurry first, followed by hot filtration of the slurry. The latter method results in a higher yield of soy milk but requires the use of an anti-foaming agent or natural defoamer during the boiling step. Bringing filtered soy milk to a boil avoids the problem of foaming. It is generally opaque, white or off-white in color, and approximately the same consistency as cow's milk.

For all raw soybean protein products, heat is necessary to destroy the activity of the protease inhibitors naturally present in the soybean. The pancreas naturally secretes proteases to digest a protein meal. Eating raw soybeans on a regular basis causes the pancreas to hypersecrete, leading to benign tumors of the pancreas.

When soybeans absorb water, the endogenous enzyme, Lipoxygenase (LOX), EC 1.13.11.12 linoleate:oxidoreductase, catalyzes a reaction between polyunsaturated fatty acids and oxygen {hydroperoxidation}. LOX initiates the formation of free radicals, which can then attack other cell components. Soybean seeds are the richest known sources of LOXs. It is thought to be a defensive mechanism by the soybean against fungal invasion.

In 1967, experiments at Cornell University and the New York State Agricultural Experiment Station at Geneva, NY led to the discovery that paint-like, off-flavors of traditional soy milk can be prevented from forming by a rapid hydration grinding process of dehulled beans at temperatures above 80 °C. The quick moist heat treatment inactivates the LOX enzyme before it can have a significant negative effect on flavor. All modern bland soy milks have been heat treated in this manner to destroy LOX.

Normal mature soybeans actually contain three LOX isozymes (SBL-1, SBL-2, and SBL-3) important for undesirable flavor development. One or more of these isozymes have recently (1998) been removed genetically from soybeans yielding soy milk with less cooked beany aroma and flavor and less astringency. An example of a triple LOX-free soybean is the American soybean named "Laura".

The University of Illinois has developed a soy milk that makes use of the entire soybean. What would normally constitute "insolubles" are ground so small by homogenization as to be in permanent suspension.

Commercial products labeled "soy drink" in the West are commonly sold in countries where the word "milk" is available by law only for cow milk. Examples: Australia, Canada, Europe.^[19] Any notions that "soy drink" would be a diluted low quality soy milk are false, one quick look at the ingredients of any common "soy drink" is enough to debunk this urban legend.

Cooking

A bowl of soy milk soup seasoned with salt and vinegar, with vegetables and wonton dumplings.

Bottled soy milk as sold in Thailand

Soy milk is found in many vegan and vegetarian food products and can be used as a replacement for cow's milk in many recipes.

"Sweet" and "salty" soy milk are both traditional Chinese breakfast foods, served either hot or cold, usually accompanied by breads like mantou (steamed rolls), youtiao (deep-fried dough), and shaobing (sesame flatbread). The soy milk is typically sweetened by adding cane sugar or, sometimes, simple syrup. "Salty" soy milk is made with a combination of chopped pickled mustard greens, dried shrimp and, for curdling, vinegar, garnished with youtiao croutons, chopped scallion (spring onions), cilantro (coriander), meat floss (肉鬆; ròu sōng), or shallot as well as sesame oil, soy sauce, chili oil or salt to taste.

Soy milk is used in many kinds of Japanese cuisine, such as in making yuba as well as sometimes a base soup for nabemono.

In Korean cuisine, soy milk is used as a soup for making kongguksu, cold noodle soup eaten mostly in summer.

Tofu is produced from soy milk by further steps of curdling and then draining.

Soy milk is also used in making soy yogurt and soy kefir.

Nutrition and health information

Nutrients in 8 ounces (250ml) of plain soymilk:^[20]

Ecological impact

Using soybeans to make milk instead of raising cows may be ecologically advantageous, because the amount of soy that could be grown using the same amount of land would feed more people than if used to raise cows.^[21] This is debated: grazing land for animals, which requires fewer pesticides, is very different from land used to farm. However, cows require much more energy in order to produce milk, since the farmer must feed the animal, which consumes 40 kilograms (90 pounds) of food and 90 to 180 litres (25 to 50 gallons) of water a day,^[22] while a soy bean needs merely fertilization, water, and land. Because the soybean plant is a legume, it also replenishes the nitrogen content of the soil in which it is grown.

In Brazil, the explosion of soybean cultivation has led to losing large tracts of forest land leading to ecological damage.^[23] However, these cleared forests are planted with soy intended for animal agricultural enterprises, not for human consumption.^[24]

The American soil scientist Dr. Andrew McClung was the first to devise a method to grow soybeans in the Cerrado region of Brazil. He was awarded with the 2006 World Food Prize.^[25]

See also

Notes

References

External links

Advocacy and nutritional information

• American Soybean Association
• Cornell University Food and Brand Lab
• Evaluation of Anti-Soy Data and Anti-Soy Advocates
• Guardian — There's no risk to humans from soya
• Soy Heart healthy claims in dispute
• Soyinfo Center — SoyaScan database and books
• Soy information at Soyatech
• Soy Milk vs Cow’s Milk: A side by side nutrition comparison

Controversy

• Harvard Med School Study — Soy causes low sperm count
• Concerns Regarding Soybeans
• Guardian — Should we worry about soya in our food?
• Health Canada: Soy — One of the nine most common food allergens
• Soya "Link" To Male Infertility
• Soy Allergy Information Page Asthma and Allergy Foundation of America
• Soy Online Service This page provides exclusively and solely anti-soy information

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