Superfood: Soybean

The soybean (U.S.) or soya bean (UK) (Glycine max) is a species of legume native to East Asia. The plant is classed as an oilseed rather than a pulse.

Fat-free (defatted) soybean meal is a primary, low-cost, source of protein for animal feeds and most prepackaged meals; soy vegetable oil is another valuable product of processing the soybean crop. For example, soybean products such as textured vegetable protein (TVP) are important ingredients in many meat and dairy analogues.

Traditional nonfermented food uses of soybeans include soymilk, and from the latter tofu and tofu skin. Fermented foods include soy sauce, fermented bean paste, natto, and tempeh, among others. The oil is used in many industrial applications. The main producers of soy are the United States (32%), Brazil (28%), Argentina (21%), China (7%) and India (4%). The beans contain significant amounts of phytic acid, alpha-Linolenic acid, and the isoflavones genistein and daidzein.

Soybeans can produce at least twice as much protein per acre as any other major vegetable or grain crop, 5 to 10 times more protein per acre than land set aside for grazing animals to make milk, and up to 15 times more protein per acre than land set aside for meat production.

The plant is sometimes referred to as greater bean (Chinese dadou and Japanese daizu). In Vietnam, the plant is called dau tuong or dau nanh. Both immature soybean and its dish are called edamame in Japan, but in English, edamame refers only to a specific dish. The English word "soy" is derived from the Japanese pronunciation of shoyu, the Japanese word for soya sauce; "soya" comes from the Dutch adaptation of the same word.

Chemical composition of the seed

Together, oil and protein content account for about 60% of dry soybeans by weight; protein at 40% and oil at 20%. The remainder consists of 35% carbohydrate and about 5% ash. Soybean cultivars comprise approximately 8% seed coat or hull, 90% cotyledons and 2% hypocotyl axis or germ.

Most soy protein is a relatively heat-stable storage protein. This heat stability enables soy food products requiring high temperature cooking, such as tofu, soy milk and textured vegetable protein (soy flour) to be made.

Since soluble soy carbohydrates are found in the whey and are broken down during fermentation, soy concentrate, soy protein isolates, tofu, soy sauce, and sprouted soy beans are without flatus activity. On the other hand, there may be some beneficial effects to ingesting oligosaccharides such as raffinose and stachyose, namely, encouraging indigenous bifidobacteria in the colon against putrefactive bacteria.

The insoluble carbohydrates in soybeans consist of the complex polysaccharides cellulose, hemicellulose, and pectin. The majority of soybean carbohydrates can be classed as belonging to dietary fiber.

Nutrition

For human consumption, soybeans must be cooked with "wet" heat in order to destroy the trypsin inhibitors (serine protease inhibitors). Raw soybeans, including the immature green form, are toxic to humans, swine, chickens, in fact, all monogastric animals.

Soybeans are considered by many agencies to be a source of complete protein. A complete protein is one that contains significant amounts of all the essential amino acids that must be provided to the human body because of the body's inability to synthesize them. For this reason, soy is a good source of protein, amongst many others, for vegetarians and vegans or for people who want to reduce the amount of meat they eat. According to the US Food and Drug Administration:

Soy protein products can be good substitutes for animal products because, unlike some other beans, soy offers a 'complete' protein profile. Soy protein products can replace animal-based foods—which also have complete proteins but tend to contain more fat, especially saturated fat—without requiring major adjustments elsewhere in the diet. However, as with many dietary health claims, there are opposing viewpoints on the health benefits of soybeans.

The gold standard for measuring protein quality, since 1990, is the Protein Digestibility Corrected Amino Acid Score (PDCAAS) and by this criterion soy protein is the nutritional equivalent of meat, eggs, and casein for human growth and health. Soybean protein isolate has a biological value of 74, whole soybeans 96, soybean milk 91, and eggs 97.

Soy protein is essentially identical to that of other legume seeds. Moreover, soybeans can produce at least twice as much protein per acre than any other major vegetable or grain crop, 5 to 10 times more protein per acre than land set aside for grazing animals to make milk, and up to 15 times more protein per acre than land set aside for meat production.

Consumption of soy may also reduce the risk of colon cancer, possibly due to the presence of sphingolipids.

History

Soybeans were a crucial crop in eastern Asia long before written records. They remain a major crop in China, Japan, and Korea. Prior to fermented products such as Soy sauce, tempeh, natto, and miso, soy was considered sacred for its use in crop rotation as a method of fixing nitrogen. The plants would be plowed under to clear the field for food crops. Soy was first introduced to Europe in the early 18th century and what is now the United States in 1765, where it was first grown for hay. Benjamin Franklin wrote a letter in 1770 mentioning sending soybeans home from England. Soybeans did not become an important crop outside of Asia until about 1910. In America, soy was considered an industrial product only and not used as a food prior to the 1920s. Soy was introduced to Africa from China in the late 19th Century and is now widespread across the continent.

Asia: From about the 1st century AD to the Age of Discovery (15-16th century), soybeans were introduced into several countries such as India, Japan, Indonesia, the Philippines, Vietnam, Thailand, Cambodia, Malaysia, Burma, Taiwan and Nepal. This spread was due to the establishment of sea and land trade routes. The best current evidence on the Japanese Archipelago suggests that soybean cultivation occurred in the early Yayoi period. The earliest Japanese textual reference to the soybean is in the classic Kojiki (Records of Ancient Matters) which was completed in 712 AD.

Many people have claimed that soybeans in Asia were historically only used after a fermentation process, which lowers the high phytoestrogens content found in the raw plant. However, terms similar to "soy milk" have been in use since 82 AD, and there is evidence of tofu consumption that dates to 220.

Uses

Soybeans can be broadly classified as "vegetable" (garden) or field (oil) types. Vegetable types cook more easily, have a mild nutty flavor, better texture, are larger in size, higher in protein, and lower in oil than field types. Tofu and soy milk producers prefer the higher protein cultivars bred from vegetable soybeans originally brought to the United States in the late 1930s. The "garden" cultivars are generally not suitable for mechanical combine harvesting because there is a tendency for the pods to shatter upon reaching maturity.

Among the legumes, the soybean, also classed as an oilseed, is pre-eminent for its high (38–45%) protein content as well as its high (20%) oil content. Soybeans are the second most valuable agricultural export in the United States behind corn. The bulk of the soybean crop is grown for oil production, with the high-protein defatted and "toasted" soy meal used as livestock feed. A smaller percentage of soybeans are used directly for human consumption.

Immature soybeans may be boiled whole in their green pod and served with salt, under the Japanese name edamame,. In English, these soybeans are generally known as "edamame" or "green vegetable soybeans".

In China, Japan, and Korea the bean and products made from the bean are a popular part of the diet. The Chinese invented tofu, and also made use of several varieties of soybean paste as seasonings. Japanese foods made from soya include miso, natto, kinako and edamame. In Korean cuisine, soybean sprouts, called kongnamul, are also used in a variety of dishes, and are also the base ingredient in doenjang, cheonggukjang and ganjang.

The beans can be processed in a variety of ways. Common forms of soy (or soya) include soy meal, soy flour, soy milk, tofu, textured vegetable protein (TVP, which is made into a wide variety of vegetarian foods, some of them intended to imitate meat), tempeh, soy lecithin and soybean oil. Soybeans are also the primary ingredient involved in the production of soy sauce (or shoyu).

Oil: Soybean seed contains about 19% oil. To extract soybean oil from seed, the soybeans are cracked, adjusted for moisture content, rolled into flakes and solvent-extracted with commercial hexane. The oil is then refined, blended for different applications, and sometimes hydrogenated. Soybean oils, both liquid and partially hydrogenated, are exported abroad, sold as "vegetable oil" or end up in a wide variety of processed foods. The remaining soybean meal is used mainly as animal feed.

Meal: Soybean meal is the material remaining after solvent extraction of oil from soybean flakes, with a 50% soy protein content. The meal is 'toasted' (a misnomer because the heat treatment is with moist steam) and ground in a hammer mill. Soybean meal is an essential element of the American production method of growing farm animals such as poultry and swine on an industrial scale that began in the 1930s; and more recently the aquaculture of catfish. Ninety-eight percent of the U.S. soybean crop is used for livestock feed. Soybean meal is also used in lower end dog foods.

Flour: Soy flour refers to defatted soybeans ground finely enough to pass through a 100-mesh or smaller screen where special care was taken during desolventizing (not toasted) in order to minimize denaturation of the protein to retain a high Protein Dispersibility Index (PDI), for uses such as extruder cooking of textured vegetable protein. It is the starting material for production of soy concentrate and soy protein isolate.

Soy Products

Soybeans can be processed to produce a texture and appearance similar to many other foods. For example, soybeans are the primary ingredient in many dairy product substitutes (e.g., soy milk, margarine, soy ice cream, soy yogurt, soy cheese, and soy cream cheese) and meat substitutes (e.g. veggie burgers). These substitutes are readily available in most supermarkets. Soy milk does not naturally contain significant amounts of digestible calcium. Many manufacturers of soy milk sell calcium-enriched products as well. Soy is also used in tempeh: the beans (sometimes mixed with grain) are fermented into a solid cake.

Soy products also are used as a low cost substitute in meat and poultry products. Food service, retail and institutional (primarily school lunch and correctional) facilities regularly use such "extended" products. Extension may result in diminished flavor, but fat and cholesterol are reduced. Vitamin and mineral fortification can be used to make soy products nutritionally equivalent to animal protein; the protein quality is already roughly equivalent. The soy-based meat substitute textured vegetable protein has been used for more than 50 years as a way of inexpensively extending ground beef without reducing its nutritional value.

Soybeans are the bean used in Chinese fermented black beans, douchi, not the sometimes confused black turtle beans. Soybeans are also used in industrial products including oils, soap, cosmetics, resins, plastics, inks, crayons, solvents, and clothing. Soybean oil is the primary source of biodiesel in the United States, accounting for 80% of domestic biodiesel production. Soybeans have also been used since 2001 as fermenting stock in the manufacture of a brand of vodka.

Health Benefits

Omega-3 fatty acids, for example, alpha-linolenic acid C18-3, all cis, 9,12,15 octadecatrienoic acid (where the omega-3 refers to carbon number 3 counting from the hydrocarbon tail whereas C-15 refers to carbon number 15 counting from the carboxyl acid head) are special fat components that benefit many body functions. However, the effects which are beneficial to health are associated mainly with the longer-chain, more unsaturated fatty acids eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) found in fish oil and oily fish. For instance, EPA and DHA, inhibit blood clotting, while there is no evidence that alpha-linolenic acid (18:3n−3, aLNA) can do this. Soybean oil is one of the few common vegetable oils that contain a significant amount of aLNA (others include canola, walnut, hemp, and flax). However, soybean oil does not contain EPA or DHA. Soybean oil does contain significantly greater amount of omega-6 fatty acids in the oil: 100 g of soybean oil contains 7 g of omega-3 fatty acids to 51 g of omega-6: a ratio of 1:7. Flaxseed, in comparison, has an omega-3:omega-6 ratio of 3:1.

Isoflavones: Soybeans also contain the isoflavones genistein and daidzein, types of phytoestrogen, that are considered by some dietitians and physicians to be useful in the prevention of cancer and by others to be carcinogenic and endocrine disruptive. Soy's content of isoflavones are as much as 3 mg/g dry weight. Isoflavones are polyphenol compounds, produced primarily by beans and other legumes, including peanuts and chickpeas. Isoflavones are closely related to the antioxidant flavonoids found in other plants, vegetables and flowers. Isoflavones such as genistein and daidzein are found in only some plant families, because most plants do not have an enzyme, chalcone isomerase which converts a flavone precursor into an isoflavone.

In contradiction to well known benefits of isoflavones, genistein acts as an oxidant (stimulating nitrate synthesis), and blocks formation of new blood vessels (antiangiogenic effect). Some studies show that genistein acts as inhibitor of substances that regulate cell division and cell survival (growth factors).

A review of the available studies by the United States Health and Human Services Agency for Healthcare Research and Quality (AHRQ) found little evidence of substantial health improvements and no adverse effects, but also noted that there was no long-term safety data on estrogenic effects from soy consumption.

Cholesterol reduction

The dramatic increase in soyfood sales is largely credited to the Food and Drug Administration's (FDA) approval of soy as an official cholesterol-lowering food, along with other heart and health benefits. A 2001 literature review argued that these health benefits were poorly supported by the available evidence, and noted that disturbing data on soy's effect on the cognitive function of the elderly existed. In 2008, an epidemiological study of 719 Indonesian elderly found that tofu intake was associated with worse memory, but tempeh (a fermented soy product) intake was associated with better memory. This study replicated other studies.

In 1995, the New England Journal of Medicine (Vol. 333, No. 5) published-Title- "Meta-analysis of the effects of soy protein intake on serum lipids", financed by DuPont Protein Technologies International (PTI), which produces and markets soy through The Solae Company. The meta-analysis concluded that soy protein is correlated with significant decreases in serum cholesterol, LDL (bad cholesterol) and triglycerides. However, HDL(good cholesterol) did not increase by a significant amount. Soy phytoestrogens (isoflavones: genistein and daidzein) adsorbed onto the soy protein were suggested as the agent reducing serum cholesterol levels. On the basis of this research PTI filed a petition with FDA in 1998 for a health claim that soy protein may reduce cholesterol and the risk of heart disease.

The FDA granted the following 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, (1 cup or 240 mL) of soy milk, for instance, contains 6 or 7 grams of soy protein. Solae resubmitted their original petition, asking for a more vague health claim, after their original was challenged and highly criticized. Solae also submitted a petition for a health claim that soy can help prevent cancer. They quickly withdrew the petition for lack of evidence and after more than 1,000 letters of protest were received. On February 18, 2008 Weston A. Price Foundation submitted a petition for removal of this health claim.

An American Heart Association review of a decade long study of soy protein benefits casts doubt on the FDA allowed "Heart Healthy" claim for soy protein and does not recommend isoflavone supplementation. The review panel also found that soy isoflavones have not been shown to reduce post menopause "hot flashes" in women and the efficacy and safety of isoflavones to help prevent cancers of the breast, uterus or prostate is in question.

Phytic acid: Soybeans contain a high level of phytic acid, which has many effects including acting as an antioxidant and a chelating agent. The beneficial claims for phytic acid include reducing cancer, minimizing diabetes, and reducing inflammation. However, phytic acid is also criticized for reducing vital minerals due to its chelating effect, especially for diets already low in minerals.

Phytoestrogen

Soybeans contain isoflavones called genistein and daidzein, which are one source of phytoestrogens in the human diet. Because most naturally occurring estrogenic substances show weak activity, normal consumption of foods that contain these phytoestrogens should not provide sufficient amounts to elicit a physiological response in humans.

Plant lignans associated with high fiber foods such as cereal brans and beans are the principal precursor to mammalian lignans which have an ability to bind to human estrogen sites. Soybeans are a significant source of mammalian lignan precursor secoisolariciresinol containing 13–273 µg/100 g dry weight. Another phytoestrogen in the human diet with estrogen activity is coumestans, which are found in beans, split-peas, with the best sources being alfalfa, clover, and soybean sprouts. Coumestrol, an isoflavone coumarin derivative is the only coumestan in foods.

Soybeans and processed soy foods are among the richest foods in total phytoestrogens (wet basis per 100g), which are present primarily in the form of the isoflavones daidzein and genistein.

Women: A 2001 literature review suggested that women with current or past breast cancer should be aware of the risks of potential tumor growth when taking soy products, based on the effect of phytoestrogens to promote breast cancer cell growth in animals. A 2006 commentary reviewed the relationship with soy and breast cancer. They stated that soy may prevent breast cancer, but cautioned that the impact of isoflavones on breast tissue needs to be evaluated at the cellular level in women at high risk for breast cancer. A high consumption of omega-6 polyunsaturated fatty acids, which are found in most types of vegetable oil including soybean oil, may increase the likelihood that postmenopausal women will develop breast cancer. Another analysis suggests an inverse association between total polyunsaturated fatty acids and breast cancer risk.

Men: Because of the phytoestrogen content, some studies have suggested that soybean ingestion may influence testosterone levels in men. However, a 2010 meta analysis of 15 placebo controlled studies showed that neither soy foods nor isoflavone supplements alter measures of bioavailable testosterone concentrations in men. It has been hypothesized that soy foods and enterolactone may protect against the development of prostate cancer although no significant associations were observed for the soy isoflavones. Furthermore, soy consumption has been shown to have no effect on the levels and quality of sperm.

Brain

There is evidence that estrogen can help protect and repair the brain after injury, and it has been suggested that the phytoestrogens in soy may have a similar effect though this is controversial and there is also evidence that phytoestrogens may be harmful for the recovery of rats that have sustained brain injury. A study of Japanese men between 1965 and 1999 demonstrated a positive correlation between brain atrophy and consumption of tofu. A study on elderly Indonesian men and women found that tempeh consumption was independently related to better memory.

Carcinogenicity

Though raw soy flour is known to cause pancreatic cancer in rats the cooked flour has not been found carcinogenic. Whether soy might promote pancreatic cancer in humans is unknown because studies have not yet attempted to single out soy intake and the incidence of pancreatic cancer in humans, and the amount of soy fed to the rats is proportionately far larger than what humans would normally consume. However, the soy isoflavone genistein has been suggested as a chemopreventive agent against pancreatic cancer, by interfering with the chemical pathways that promote the creation and growth of tumors.

The Cancer Council of New South Wales, Australia has released a statement saying scientific research suggests that overall the moderate consumption of soy products does not appear to present a risk to women with breast cancer, and there is equivocal evidence that consuming large amounts of soy products may have a protective effect against developing breast and prostate cancer. However, the Council does not recommend taking soy dietary supplements as there is no evidence they are either effective or safe at preventing or treating cancers.

Reference : http://en.wikipedia.org/wiki/Soybean

Soy milk - Soy food products

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.

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 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.

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

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. 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 cafes and coffee franchises as a cow's milk substitute.

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.

Though it has been suggested that soy consumption is associated with a reduction in low-density lipoprotein ("bad cholesterol") and triglycerides, a 2006 study of a decade of soy protein consumption found no association between health benefits (such as cardiovascular health or cancer rates) and soy intake, nor was a benefit found for women undergoing menopause. The benefits of soy were found to be related to their ability to replace animal protein, foods high in saturated fats, add dietary fiber, vitamins and minerals.

Though it has been suggested that soy may affect sperm quality and bone mineral density, there is not enough research on the topics to support these associations.

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, 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, soy cream, soy kefir and soy based cheese analogues.

Nutrients in 8 ounces (250ml) of plain soymilk:

                              Regular Soymilk      Lite Soymilk(reduced fat)

Calories (g)                    140                         100

Protein (g)                     10.0                         4.0

Fat (g)                            4.0                           2.0

Carbohydrate (g)          14.0                         16.0

Sodium (mg)                  120                          100

Iron (mg)                        1.8                           0.6

Riboflavin (mg)               0.1                         11.0

Calcium (mg)                   80                            80

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. In the case of organic meat, this is debated, as grazing land for animals, requiring fewer pesticides, is very different from land used to farm. However, with organic food sales at 1 to 2% of total food sales worldwide, this comparison is negligible at present. Moreover, 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, 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 (especially beef and pork production), not for human consumption.

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.

Reference : http://en.wikipedia.org/wiki/Soy_milk

Tofu - Soy food products

Tofu or bean curd is a food made by coagulating soy milk and then pressing the resulting curds into soft white blocks. It is of Chinese origin, and it is also a part of East Asian and Southeast Asian cuisine such as Chinese, Japanese, Korean, Indonesian, Vietnamese, and others. There are many different varieties of tofu, including fresh tofu and tofu that has been processed in some way. Tofu has very little flavor or smell on its own, so it can be used either in savory or sweet dishes, and it is often seasoned or marinated to suit the dish.

Tofu originated in the Han dynasty in ancient China. Li Shizhen in the Ming Dynasty described a method of making tofu in Bencao Gangmu. Tofu and its production technique were subsequently introduced into Korea and then Japan during the Nara period. It also spread into other parts of East Asia as well. This spread likely coincided with the spread of Buddhism because it is an important source of protein in the vegetarian diet of East Asian Buddhism.

Tofu contains a low amount of calories, relatively large amount of iron, and little fat. Depending on the coagulant used in manufacturing, the tofu may also be high in calcium and/or magnesium.

The English word "tofu" comes from the Japanese tofu, which itself derives from the Chinese doufu from "bean" plus "curdled" or "fermented". The English term "bean curd(s)" for tofu has been used since at least 1840.

Tofu is made by coagulating soy milk and pressing the resulting curds. Although pre-made soy milk may be used, most tofu producers begin by making their own soy milk, which is produced by soaking, grinding, boiling and straining dried (or, less commonly, fresh) soybeans.

Coagulation of the protein and oil (emulsion) suspended in the boiled soy milk is the most important step in the production of tofu. This process is accomplished with the aid of coagulants. Two types of coagulants (salts and acids) are used commercially. The third type of coagulant, enzymes, is not yet used commercially but shows potential for producing both firm and "silken" tofu.

History

Tofu originated in ancient China, although little else is known about the exact historic origins of tofu and its method of production. While there are many theories regarding tofu's origins, historical information is scarce enough as to relegate the status of most theories to either speculation or legend. Like the origins of cheese and butter, the exact origin of tofu production may never be known or proven.

What is known is that tofu production is an ancient technique. Tofu was widely consumed in ancient China, and techniques for its production and preparation were eventually spread to many other parts of Asia.

In Asia, Tofu and its production technique were subsequently introduced into Japan in the Nara period (late eighth century) as well as other parts of East Asia. The earliest document of tofu in Japan shows that the dish was served as an offering at the Kasuga Shrine in Nara in 1183. The book Tofu Hyakuchin, published in the Edo period, lists 100 recipes for cooking tofu.

The rise in acceptance of tofu likely coincided with that of Buddhism as it is an important source of proteins in the religion's vegetarian diet. Since then, tofu has become a staple in many countries, including Vietnam, Thailand, and Korea, with subtle regional variations in production methods, texture, flavor, and usage.

Tofu is so highly esteemed in Korean culture that the menus of many Korean restaurants are based almost entirely on tofu, including some which feature only sundubu jjigae (a stew made with soft tofu) and gochujang (red chili paste).

In Malaysia, Singapore, Thailand and Indonesia, tofu or tahu is widely available and used in many Malay dishes such as sayur goreng, masak lodeh, tahu sumbat, rojak, pecal, gado-gado, lontong and some curries. The Malaysian and Singaporean Indians use tofu in their cuisine such as Indian mee goreng and rojak pasembor. The makers of tofu in these countries were originally the Chinese but tofu now is made by non-Chinese as well.

In the West: The first tofu company in the USA was established in 1878. However tofu was not well known to most Westerners before the middle of the 20th century. With increased cultural contact between the West and Asia and growing interest in vegetarianism, knowledge of tofu has become widespread. Numerous types of pre-flavored tofu can be found in many supermarket chains throughout the West.

There is a wide variety of tofu available in both Western and Eastern markets. Despite the daunting variety, tofu products can be split into two main categories: fresh tofu, which is produced directly from soy milk, and processed tofu, which is produced from fresh tofu. Tofu production also creates important side products which are often used in various cuisines.

Preparation

Tofu has very little flavor or smell on its own. Consequently tofu can be prepared either in savory or sweet dishes, acting as a bland background for presenting the flavors of the other ingredients used. As a method of flavoring it is often marinated in soy sauce, chilis, sesame oil, etc.

Eastern methods

In Asian cooking, tofu is eaten in myriad ways, including raw, stewed, stir-fried, in soup, cooked in sauce, or stuffed with fillings. The idea of using tofu as a meat substitute is not common in East Asia. Many Chinese tofu dishes such as jia chang dou fu and ma po dou fu include meat.

Lightly flavored

In Japan, a common lunch in the summer months is hiyayakko, silken or firm Asian tofu served with freshly grated ginger, green onions, and/or katsuobushi shavings with soy sauce. In the winter, tofu is frequently eaten as yudofu, which is simmered in a claypot with some vegetables (ex:chinese cabbage, green onion etc.) using konbudashi.

In Chinese cuisine, Douhua is served with toppings like boiled peanuts, azuki beans, cooked oatmeal, tapioca, mung beans and a syrup flavored with ginger or almond. During the summer, douhua is served with crushed ice; in the winter, it is served warm. And also, many parts of China, fresh tofu is similarly eaten with soy sauce or further flavored with katsuobushi shavings, century eggs, and sesame seed oil.

In Korean cuisine, dubu gui consists of pan fried cubes of firm tofu, seasoned with soy sauce, garlic, and other ingredients. Cubes of cold, uncooked firm tofu seasoned with soy sauce, scallions, and ginger, prepared in a manner similar to the Japanese hiyayakko, are also enjoyed. The popular bar food, or anju, called dubu kimchi, features boiled, firm tofu served in rectangular slices around the edges of a plate with pan fried, sauteed or freshly mixed kimchi in the middle.

In the Philippines, the sweet delicacy taho is made of fresh tofu with brown sugar syrup and sago. The Malaysian version of taho or douhua is called tofufa. Warm soft tofu is served in 'slices' (due to being scooped using a flat spoon from a wooden bucket) in a bowl with either pandan-flavored sugar syrup or palm sugar syrup.

In Vietnam, douhua is pronounced dau hu. This variety of soft tofu is made and carried around in an earthenware jar. It is served by being scooped into a bowl with a very shallow and flat spoon, and eaten with either powdered sugar and lime juice or with a ginger-flavored syrup. It is generally eaten hot, even during summer.

Fried

A common cooking technique in many parts of East and Southeast Asia involves deep frying tofu in vegetable oil, sunflower oil, and canola oil to varied results. Although tofu is often sold preprocessed into fried items, pre-fried tofu is seldom eaten directly and requires additional cooking. Depending on the type of tofu used, the texture of deep fried tofu may range from crispy on the outside and custardy on the inside, to puffed up like a plain doughnut.

The former is usually eaten plain in Chinese cuisine with garlic soy sauce, while the latter is either stuffed with fish paste or cooked in soups. In Japan, cubes of lightly coated and fried tofu topped with a kombu dashi-based sauce are called agedashi-dofu. Soft tofu that has been thinly sliced and deep fried, known as aburage in Japan and yubu in Korea, is commonly blanched, seasoned with soy sauce and mirin and served in dishes such as kitsune udon. Aburage is sometimes also cut open to form a pocket and stuffed with sushi rice; this dish is called inarizushi and is also popular in Korea, where it is called yubu chobap.

Soups, stews, and braised dishes

A rather famous hot Sichuan preparation using firm Asian tofu is mapo doufu. This involves braised tofu in a beef, chili, and a fermented bean paste sauce. In the Shanghai region it is called mala doufu.

Dried tofu is usually not eaten raw but first stewed in a mixture of soy sauce and spices. Some types of dried tofu are preseasoned with special blends of spices, so that the tofu may either be called "five spice tofu" or "soy sauce stewed tofu". Dried tofu is typically served thinly sliced with chopped green onions or with slices of meat for added flavor. Most dried tofu is sold after it has been fried or pre-stewed by tofu vendors.

Soft tofu can also be broken up or mashed and mixed with raw ingredients prior to being cooked. For example, Japanese ganmodoki is a mixture of chopped vegetables and mashed tofu. The mixture is bound together with starch and deep fried. Chinese families sometimes make a steamed meatloaf or meatball dish from equal parts of coarsely mashed tofu and ground pork. In India, tofu is also used as a low fat replacement for paneer providing the same texture with similar taste.

Tofu bamboos are often used in lamb stew or in a dessert soup. Tofu skins are often used as wrappers in dim sum. Freeze-dried tofu and frozen tofu are rehydrated and enjoyed in savory soups. These products are often taken along on camping trips since a small bag of these dried tofu can provide protein for many days.

In Korean cuisine, soft tofu, called sundubu, is used to make a thick stew called sundubu jjigae. Firm, diced tofu often features in the staple stews doenjang jjigae and kimchi jjigae.

As flavoring

Pickled tofu is commonly used in small amounts together with its soaking liquid to flavor stir-fried or braised vegetable dishes (particularly leafy green vegetables like water spinach). It is often eaten directly as a condiment with rice or congee.

Western methods

Generally, the firmer styles of tofu are used for kebabs, mock meats, and dishes requiring a consistency that holds together, while the softer styles can be used for desserts, soups, shakes, and sauces.

Firm western tofus can be barbecued since they will hold together on a barbecue grill. These types of tofu are usually marinated overnight as the marinade does not easily penetrate the entire block of tofu (techniques to increase penetration of marinades are stabbing repeatedly with a fork or freezing and thawing prior to marinating). Grated firm western tofu is sometimes used in conjunction with TVP as a meat substitute. Softer tofus are sometimes used as a dairy-free or low-calorie filler. Silken tofu may be used to replace cheese in certain dishes (such as lasagna).

Tofu has also been fused into other cuisines in the west, for instance used in Indian-style curries.

Tofu and soy protein can be industrially processed to match the textures and flavors to the likes of cheese, pudding, eggs, bacon etc. Tofu's texture can also be altered by freezing, pureeing, and cooking. In the Americas, Europe, Australia and New Zealand, tofu is frequently associated with vegetarianism and veganism as it is a source of non-animal protein.

Nutrition and health information

Protein: Tofu is relatively high in protein, about 10.7% for firm tofu and 5.3% for soft "silken" tofu with about 5% and 2% fat respectively as a percentage of weight.

In 1995, a report from the University of Kentucky, financed by The Solae Company St. Louis, Missouri (the PTI division of DuPont), 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 Food and Drug Administration 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." For instance, 100 grams of firm tofu contains 15.78 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 showed only a minimal decrease in cholesterol levels, but it compared favorably against animal protein sources.

Isoflavones: Soy isoflavones have not been shown to reduce post menopause hot flashes in women or to help prevent cancers of the breast, uterus or prostate. Thus, soy isoflavone supplements in food or pills are not recommended.

A study done by the Pacific Health Research Institute followed over 3,000 Japanese men between 1965 and 1999, which showed a positive correlation between cerebral atrophy and consumption of tofu. According to the Alzheimer's Research Trust, more research is needed.

Health issues

High consumption of tofu has been linked with dementia in older age groups in more than one study, whereas in younger and middle-age age groups it might actually protect the brain. It has been stressed that there is no evidence that eating tofu in moderation can cause any problems, and that further research is needed to confirm both the negative as well as the positive effects.

Reference : http://en.wikipedia.org/wiki/Tofu