A can of Yeo's soy milk, poured into a glass
Soy milk (also called soya milk or soybean milk) and sometimes referred to as soy drink/beverage is a beverage made from soy beans.
Origins
Soy milk may have originated in China,[1] 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.[2] 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" . However, there are products in China that is called dòu nǎi (豆奶) made from a mix of both cow milk powder and ground, dried soybean.[3][4] The Japanese term for soy milk is tōnyū which contains no cow 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.
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
Health benefits
- See also: Soybean#Nutrition
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 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.[5] 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.[6] 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."[7]
Claims of negative health effects
- See also: Soy controversy
However, the soy industry has also received similar criticism for reasons including:
- Soy consumption has been linked to cognitive impairment in male rats [8]. Although the cited studies are based on rats fed with concentrated phytoestrogens and not common soy beans, 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 estrogen.
- High levels of phytic acid, which binds to important nutrients like calcium, magnesium, iron[9], and zinc, during digestion. However, as a comparison, cow milk is known for significantly slowing down the absorption of iron[10] 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 (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 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 {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 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 (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 and soy kefir.
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 [11]. 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 [12]. 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 [2], [3]; 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. [4]
See also
Notes
- ^ History of Soy Milk, Soya.be, 2006 [1]
- ^ 「豆漿，利氣下水，制諸風熱，解諸毒」
- ^ Vitasoy ingredients listing
- ^ Hi-C soy milk ingredients listing
- ^ Anderson, JW; BM Johnstone, ME Cook-Newell (August 3, 1995). "Meta-analysis of the effects of soy protein intake on serum lipids". Circulation. Retrieved on 2007-07-05.
- ^ Sacks, Frank M.; Alice Lichtenstein, Linda Van Horn, William Harris, Penny Kris-Etherton, Mary Winston (January 17, 2006). "Soy Protein, Isoflavones, and Cardiovascular Health". Circulation. Retrieved on 2007-07-05.
- ^ "Soy Protein, Isoflavones, and Cardiovascular Health — Conclusions". Circulation. Retrieved on 2007-07-05.
- ^ "Neurobehavioral effects of dietary soy phytoestrogens."
- ^ Hurrell, RF; MA Juillerat, MB Reddy, SR Lynch, SA Dassenko, JD Cook (September, 1992). "Soy protein, phytate, and iron absorption in humans". Am J Clin Nutr. Retrieved on 2007-07-15.
- ^ Iron-Deficiency Anemia
- ^ LEAD digital library: Livestock’s long shadow - Environmental issues and options
- ^ http://www.southwestdairyfarmers.com/get_file.sstg?id=4
References
- Rahab Waweru, M.A., et al. 1967. Effect of processing methods on oxidative off-flavors of soybean milk. Cereal and Food Sciences North Nairobi State University, Ministry of Agriculture. Soy Milk. Soya.be. Soya. Retrieved on August 17, 2005.
- Torres-Penaranda, A.V., et al.1998. Sensory characteristics of soymilk and tofu made from Lipoxygenase-Free and Normal soybeans. Journal of Food Science 63 (6): 1084-1087.
- Smith, A.K. and Circle, S.J. 1972. Soybeans: Chemistry and Technology. AVI publishing.
- Calvert, John (2000). Soymilk Microenterprise: A Treatise on Small-Scale Soymilk Production
- William Shurtleff and Akiko Aoyagi (1979). Tofu & Soymilk Production. Lafayette, California: New-Age Foods Study Center.
- William Shurtleff and Akiko Aoyagi (2000). Tofu & Soymilk Production. 3rd edition. Lafayette, California: Soyfoods Center. ISBN 0-933332-72-6.
- William Shurtleff and Akiko Aoyagi (1994). Soymilk and soymilk products - Bibliography and sourcebook, 1500 to 1993: Detailed information on 3,120 published documents (extensively annotated bibliography), 968 commercial soymilk products, 506 original interviews (many full text) and overviews, 462 unpublished archival documents. Lafayette, California: Soyfoods Center. ISBN 0-933332-84-X.
- Liu, KeShun.1997. Soybeans: Chemistry, Technology, and Utilization. Chapman & Hall.
- Ang, Catharina Y. W., KeShun Liu, and Yao-Wen Huang, eds. (1999). Asian Foods: Science & Technology. Lancaster, Pennsylvania: Technomic Publishing Co.
- Berk, Zeki.1992. FAO (UN) [5].
- Frank M. Sacks MD, et a. (2006) Soy Protein, Isoflavones, and Cardiovascular Health. An American Heart Association Science Advisory for Professionals From the Nutrition Committee in Circulation.
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