Soy milk

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File:Soymilk can and glass.jpg
A can of Yeo's soy milk, poured into a glass
File:Creamy soy milk foam.jpg
Soy milk foam on top of a Greek Café Frappé
File:Alpro soya.jpg
1 l (2.1 pints) package of Alpro chocolate soy milk

Soy milk (also called soya milk or soybean milk) and sometimes referred to as soy drink/beverage and even soy latte) is a beverage made from soybeans originating from China. In Asia, the drink is common among the general population and is often served as a meal. In the West, it has gained popularity as a milk substitute for those who practice veganism or who are lactose intolerant.

Origins

Soy milk may possibly have originated in China,[1] a region where soybean was native and used as food long before the existence of written records[citation needed]. Later on, the soybean and soybean foods were transplanted to Japan. Soybean milk is reputed to have been discovered and developed by Liu An of the Han Dynasty in China about 164 BC. Liu An is also credited with the development of "Doufu" (soybean curd) in China which 900 years later spread to Japan where it is known as "tofu".

Traditional soy milk, a stable emulsion of oil, water and protein, is simply an aqueous extract of whole soybeans. The liquid 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.

Nomenclature

The Chinese term for soy milk is "豆漿" (Pinyin: dòu jiāng; lit. bean + a thick liquid). In Western nations, soy milk products packaged for Chinese-speaking consumers may be labeled "豆奶" (Pinyin: dòu nǎi; lit. "bean milk"). However, there is a product in China that is called dòu nǎi (豆奶) which is a dry miscible powder made of both cow and soy milk. The Japanese term for soy milk is tōnyū (豆乳; "bean milk").

Soy milk is commonly available in vanilla and chocolate flavors as well as its original unflavored form. Plain soy milk is also commonly sweetened, though unsweetened varieties are available.

In many countries, this product may not be sold under the name milk since it is not a dairy product, hence the name soy drink.

Prevalence

Soy milk has developed a cachet in premium coffee blends from Western restaurant chains such as Starbucks.

In Japan soy milk is much less popular than cow's milk, and the consumption of soy milk per capita is far less than that in the U.S. However, the consumption of cow's milk began decreasing around 1995 and that of soy milk began to grow[citation needed]. It is, however, almost always available at Japanese tofu shops and supermarkets[citation needed].

Soy milk has increased in popularity in the West as a substitute for cow's milk. In some Western nations where veganism has made inroads, it is available upon request at some cafés and coffee franchises as a cow's milk substitute, sometimes at an extra cost.



Health

Claims of health benefits


Soy milk is nutritionally close to cow's milk, though most soy milk commercially available today is enriched with added vitamins such as vitamin B12. It naturally has about the same amount of protein (but not the same proteins) as cow milk. Natural soy milk contains little digestible calcium as it is bound to the bean's pulp, which is insoluble in a human. To counter this, many manufacturers enrich their products with calcium carbonate available to human digestion. Unlike milk it has little saturated fat and no cholesterol, which many consider to be a benefit. Lower fat varieties, however, contain less protein than cow's milk.

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

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 the PTI division of DuPont, The Solae Co of St. Louis. 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.[2] On the basis of this research PTI, in 1998, filed a petition with FDA for a health claim that soy protein may reduce cholesterol and the risk of heart disease. The FDA 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.[3] 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."[4]

Claims of negative health effects

However, the soy industry has also received similar criticism [2][3] for reasons including:

  • High levels of phytic acid, which binds to important nutrients like calcium, magnesium, iron[5], and zinc, during digestion.
  • High levels of very weak estrogen-like phytoestrogens, soy isoflavones: genistein and daidzein.
  • Hemagglutinin content: Soybean hemagglutinins are glycoproteins that cause red blood cells to agglutinate or clump together. Hemagglutinins, also found in peas, are concentrated in the whey protein fraction of soy milk. Hemagglutinating activity of raw soybeans is readily destroyed by moist heat treatment. This is similar to a substance found in flu viruses, although it is rather unlikely to be harmful unless the soy milk is taken intravenously.
  • Processing of soybeans, includes genetic modification, to reduce lipoxygenase and thus rancidity and beany flavor, high-alkaline processing may result in lysinoalanine production as seen in caseinate or heated milk processes, nitrosamine formation from very high heat processing may occur, just as nitrates in processed meats such as bologna and hot dogs, react with gastric amino acids to form nitrosamines. Soy contains small amounts of goitrogens, as do cruciferous vegetables such as broccoli.
  • Excessive consumption of soy is also linked to potential thyroid damage.[6]

Although in general soy milk is not suitable for babies or infants, there exist baby formulas based on soy protein, i.e. soy milk, that are used primarily in the case of lactose intolerant children, those allergic to cow's milk or parental preference for a vegetarian or vegan diet. Farley's Soya Infant Formula is approved by the Vegan Society in the UK. These formulas are commonly named "soy milk", but contain extra carbohydrates, fat, vitamins and minerals. However care must be taken that children with "Soy protein intolerance" are not fed soy milk.

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 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 dangerous 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 (just like exercise causes muscles to develop(hypertrophy). This is why the above heating to properly prepare soymilk is essential.

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 rancid, 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 often derivatives of soy milk containing more water or added ingredients.

Cooking

File:Soy milk bottles.jpg
Bottled soy milk sold in Thailand, usual basics and cooking staples

Soy milk is found in many vegan and vegetarian food products and can be used as a replacement for cow's milk in most recipes. Such substitution has a low impact on foods like pancakes, but there is a noticeable difference when making foods such as macaroni and cheese or quiche.

"Sweet" and "salty" soy milk are both traditional Chinese breakfast foods, 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 (榨菜), 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 Cooking, such as in making yuba as well as sometimes a base soup for nabemono.

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

Soy milk is also used in making soy yogurt.

Ecological impact

Using soybeans to make milk instead of raising cows is said to have ecological advantages, as the amount of soy that could be grown using the same amount of land would feed more people than if used to raise cows [7]. This is debated as grazing land for animals is very different from land used to farm, and requires fewer pesticides. However, cows require much more energy in order to produce milk, since the farmer must feed the animal, which consumes 90 pounds of food and 25 to 50 gallons of water a day, while a soy bean needs merely water and land [8]. 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 [4], [5]; however, as noted in the articles, these cleared forests are planted with soy intended for animal agricultural enterprises--not human consumption: "The report, published today, follows a 7,000km chain that starts with the clearing of virgin forest by farmers and leads directly to Chicken McNuggets being sold in British and European fast food restaurants."

It was an American soil scientist, Dr. Andrew McClung, who first devised a method to grow soybeans in the Cerrado region of Brazil. He was rewarded with the 2006 World Food Prize. [6]

See also

References

  1. History of Soy Milk, Soya.be, 2006 [1]
  2. Anderson, JW (August 3, 1995). "Meta-analysis of the effects of soy protein intake on serum lipids". Circulation. Retrieved 2007-07-05. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  3. Sacks, Frank M. (January 17, 2006). "Soy Protein, Isoflavones, and Cardiovascular Health". Circulation. Retrieved 2007-07-05. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  4. "Soy Protein, Isoflavones, and Cardiovascular Health — Conclusions". Circulation. Retrieved 2007-07-05.
  5. Hurrell, RF (September, 1992). "Soy protein, phytate, and iron absorption in humans". Am J Clin Nutr. Retrieved 2007-07-15. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  6. ]http://www.expertclick.com/NewsReleaseWire/default.cfm?Action=ReleaseDetail&ID=18074 Oprah Diagnosed with Thyroid Disease - Are Soy Products to Blame?] September 25 2007
  7. http://www.virtualcentre.org/en/library/key_pub/longshad/A0701E00.htm
  8. http://www.southwestdairyfarmers.com/get_file.sstg?id=4

External links

Advocacy and nutritional informarion
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