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Soy milk
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Soy milk (also called soya milk or soybean milk) and sometimes referred to as soy drink/beverage is a beverage made from soy beans. 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 Soy milk may have originated in China, a region where soybean was native and used as food long before the existence of written records. The earliest written record comes from Liu An using it as a medicine, and a later record of the drink as a medicine could be found in Bencao Gangmu. 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".
Nomenclature The Chinese term for soy milk is "??". In Western nations, soy milk products packaged for Chinese-speaking consumers may be labeled "??"
. However, there are products in China that is called dòu nai (??) made from a mix of both 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.
Soy milk is commonly available in vanilla and chocolate flavors as well as its original unflavored form. Plain soy milk is unsweetened, although most products comes as 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 Soy milk has developed a cachet in premium coffee blends from Western restaurant chains.
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.
The drink has proven 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 is flavoured with either a white or brown sugar syrup. The consumer also has the option to add grass jelly, known as leong fan 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 flavoured with the same syrup as the soybean milk.
Yeo's, a local Malaysian company is marketing a commercialised tinned or boxed version of soybean milk. They also market a similar product, but of grass jelly. These products are usually linked, for consumers to mix as they please.
Health Health benefitsSoy 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 cow's milk it has little saturated fat and no cholesterol, which many consider to be 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:
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 effectsHowever, the soy industry has also received similar criticism for reasons including:
- A new study has found that men who consume an average of half a portion of soy products per day are more likely to have a . Soy contains a number of isoflavones that exert an oestrogen-like affect, like daidzein, genistein and glycitein. Some studies have indicated that high consumption of soy isoflavones could affect fertility. The new study, published in the journal Human Reproduction, indicates that there may be a link with reduced sperm count in humans. The research team, led by Dr Jorge Chavarro of the Harvard School of Public Health in the US, analysed the diets of 99 men who attended a fertility clinic with their partners between 2000 and 2006. Those who had an average of half a portion of soy foods per day (~17mg isoflavones) there are ~3.5mg isoflavones/g soy protein - were seen to have sperm concentrations of 41 million less sperm per ml. The normal sperm concentration range is 80-120m per ml. Half a serving is the equivalent of one cup of soy milk or one portion of tofu, tempeh, or soy burgers every other day.
- Soy consumption has been linked to cognitive impairment in male rats. Nevertheless the cited studies are based on rats fed with concentrated phytoestrogens and not common soy beans and it is already well known that concentrated estrogens cause negative effects in males. The common amounts of phytoestrogens in soy beans are not to be compared to concentrated phytoestrogens.
- High levels of phytic acid, which binds to important nutrients like calcium, magnesium, iron, and zinc, during digestion. However, as a comparison, cow 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, 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 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 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.
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 |
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 . 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 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, 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 awarded with the 2006 World Food Prize.
See alsoExternal linksAdvocacy and nutritional informarion
Controversy
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