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Soy milk
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Soy milk (also called soya milk, 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.
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Encyclopedia
Soy milk (also called soya milk, 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.
Tofu is made by coagulating the protein from soy milk, just as cheese is made from milk.
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. 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.
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. This legend appeared in the 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 development to Liu An, assuming that he could not have made tofu without making soy milk. However, it is likely that Liu An has been falsely attributed to the development of tofu by writers 1000 years later from his time.
Nomenclature
The Chinese term for soy milk is "??" (Pinyin: dòu jiang; lit. bean + a thick liquid). In Western nations, soy milk products packaged for Chinese-speaking consumers may be labeled "??"
. However, there are products in China called dòu nai, which are made from a mix of cow milk powder and ground, dried soybean. The Japanese term for soy milk is tonyu(??) which contains no cow milk. In Singapore, it is known as tau-huey-tzui in the local Hokkien dialect while in Malaysia it is known as "susu soya" or "air tauhu" in the local Malay language.
Soy milk is commonly available in vanilla and chocolate flavors as well as its original unflavored form. Plain soy milk is unsweetened, although some soy milk products are sweetened. Drinking salted soy milk is still very common in China.
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
In the West, soymilk has become a popular alternative to cow's milk, with a roughly similar protein and fat content. 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, usually at an extra cost.
The drink has proved to be very popular in the hawker environment of Penang, Malaysia with it being a standard offering at the numerous coffee shops and hawker centers around the island. The soybean milk, known locally as tau chui or "air tauhu/ susu soya" (in Malay literally tofu water or soy milk) is flavored with either a 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.
VitaSoy is a popular brand of soymilk in China.
Yeo's, a drink manufacturer in Singapore and Malaysia, is marketing a commercialized tinned or boxed version of soybean milk.
Health
Health benefits
Soy milk is nutritionally close to cow's milk. It naturally 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 a human. 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, which is a benefit. 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, it 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
- Polyunsaturated and monounsaturated fats are good for the heart. (It should be noted that whole milk has just as much monounsaturated fat as soy milk; and while it has less polyunsaturated, it contains the omega-3 fatty acids EPA and DHA that soy milk lacks.)
- 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 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. 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. 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."
Negative health effects
However, the soy industry has also received similar criticism for reasons which include (but are not limited to) the following:
- 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. Critics of the study have claimed that the decrease in concentration was due to a corresponding increase in ejaculate volume. While the study found a decreasing trend in sperm concentration with soy intake, it also notes that soy food and isoflavone intake were unrelated to total sperm count, ejaculate volume, sperm motility or sperm morphology and that the clinical significance of the findings remains to be determined.
- High levels of phytic acid bind to important nutrients like calcium, magnesium, iron, and zinc during digestion. However, as a comparison, cow's milk is known for significantly slowing down the absorption of iron and, additionally, calcium from other than dairy sources (like kale, sesame).
Although in general soy milk is not suitable for babies or infants , there exist baby formulas based on soy protein, 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. These formulas commonly 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 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 (just like exercise causes muscles to develop hypertrophy). This is why the above heating to properly prepare soymilk is essential for fatty acid breakdown.
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 . 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 often derivatives of soy milk containing more water or added ingredients.
Cooking
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 (??; ròu song), 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.
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:
| Regular Soymilk | Lite Soymilk (reduced fat) |
|---|
| Calories (gm) | 140 | 100 | | Protein (gm) | 10.0 | 4.0 | | Fat (gm) | 4.0 | 2.0 | | Carbohydrate (gm) | 14.0 | 16.0 | | Sodium (mg) | 120.0 | 100.0 | | Iron (mg) | 1.8 | 0.6 | | Riboflavin (mg) | 0.1 | 11.0 | | Calcium (mg) | 80.0 | 80.0 |
One cup of soy milk is equal to three servings of dairy and two servings of fruit.
Ecological impact
Using soybeans to make milk instead of raising cows is ecologically advantageous, because the amount of soy that could be grown using the same amount of land will feed more people than if used to raise cows . 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 40 kilos (90 pounds) of food and 90 to 180 liters (25 to 50 gallons) of water a day, 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 ; however, these cleared forests are planted with soy intended for animal agricultural enterprises--not human consumption.
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 awarded with the 2006 World Food Prize.
See also
External links
Advocacy and nutritional information
Controversy
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