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Description and physical characteristics
Soy varies in growth, habit, and height. It may grow prostrate, not higher than 20 cm (7.8 inches), or grow up to 2 meters (6.5 feet) high.
The pods, stems, and leaves are covered with fine brown or gray hairs. The leaves are trifoliolate, having 3 to 4 leaflets per leaf, and the leaflets are 6–15 cm (2–6 inches) long and 2–7 cm (1–3 inches) broad. The leaves fall before the seeds are mature. The big, inconspicuous, self-fertile flowers are borne in the axil of the leaf and are white, pink or purple.
The fruit is a hairy pod that grows in clusters of 3–5, each pod is 3–8 cm long(1–3 inches) and usually contains 2–4 (rarely more) seeds 5–11 mm in diameter.
Soybeans occur in various sizes, and in many hull or seed coat colors, including black, brown, blue, yellow, green and mottled. The hull of the mature bean is hard, water resistant, and protects the cotyledon and hypocotyl (or “germ”) from damage. If the seed coat is cracked, the seed will not germinate. The scar, visible on the seed coat, is called the hilum (colors include black, brown, buff, gray and yellow) and at one end of the hilum is the micropyle, or small opening in the seed coat which can allow the absorption of water for sprouting.
Remarkably, seeds such as soybeans containing very high levels of protein can undergo desiccation yet survive and revive after water absorption. A. Carl Leopold, son of Aldo Leopold, began studying this capability at the Boyce Thompson Institute for Plant Research at Cornell University in the mid 1980s. He found soybeans and corn to have a range of soluble carbohydrates protecting the seed’s cell viability.2 Patents were awarded to him in the early 1990s on techniques for protecting “biological membranes” and proteins in the dry state. Compare to tardigrades.
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.
The majority of soy protein is a relatively heat-stable storage protein. This heat stability enables soy food products requiring high temperature cooking, such as tofu, soymilk and textured vegetable protein (soy flour) to be made.
The principal soluble carbohydrates, saccharides, of mature soybeans are the disaccharide sucrose (range 2.5–8.2%), the trisaccharide raffinose (0.1–1.0%) composed of one sucrose molecule connected to one molecule of galactose, and the tetrasaccharide stachyose (1.4 to 4.1%) composed of one sucrose connected to two molecules of galactose. While the oligosaccharides raffinose and stachyose protect the viability of the soy bean seed from desiccation (see above section on physical characteristics) they are not digestible sugars and therefore contribute to flatulence and abdominal discomfort in humans and other monogastric animals; compare to the disaccharide trehalose. Undigested oligosaccharides are broken down in the intestine by native microbes producing gases such as carbon dioxide, hydrogen, methane, etc.
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
The most important point regarding the use of soybeans for human nutrition is the absolute necessity to cook the soybean with “wet” heat in order to destroy the trypsin inhibitors; serine protease inhibitors. It is not advisable to eat raw soybeans.
Soybeans are considered by many agencies, including the US Food and Drug Administration, to be a source of complete protein.3 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 many vegetarians and vegans or for people who cannot afford meat.
According to the FDA, "Soy protein products can be good substitutes for animal products because, unlike some other beans, soy offers a “complete” protein profile. Soybeans contain all the amino acids essential to human nutrition, which must be supplied in the diet because they cannot be synthesized by the human body. 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."
Because soybeans contain no starch, they are a good source of protein for diabetics.4
However, as with any dietary health claim, there are opposing viewpoints on the health benefits of soybeans.567
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 and eggs for human growth and health. Soybean protein isolate has a Biological Value of 74, whole soybeans 96, soybean milk 91, and eggs 97.8
Consumption of soy may also reduce the risk of colon cancer, possibly due to the presence of sphingolipids.10
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. It is an annual plant that has been used in China for 5,000 years as a food and a component of drugs. Soy contains significant amounts of all the essential amino acids for humans, and so is a good source of protein. Soybeans are the primary ingredient in many processed foods, including dairy product substitutes. The plant is sometimes referred to as greater bean or edamame, though the latter is more commonly used in English when referring to a specific dish.
The English word soy is derived from the Japanese pronunciation of ?? (????, sh?yu), the Japanese word for Soya sauce; soya comes from the Dutch adaptation of the same word.
Soybeans are an important source of vegetable oil and protein world wide. Soy products are the main ingredients in many meat and dairy substitutes. They are also used to make soy sauce, and the oil is used in many industrial applications. The main producers of soy are the United States, Brazil, Argentina, China and India. The beans contain significant amounts of alpha-linolenic acid, omega-6 fatty acid, and the isoflavones genistein and daidzein.
History
Soybeans were a crucial crop in eastern Asia long before written records.[citation needed] 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.[citation needed] Soy was first introduced to Europe in the early 1700s 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
The origins of the soybean plant are obscure, but many botanists believe it to have derived from Glycine ussuriensis, a legume native to central China.4 The soybean has been used in China for 5,000 years as a food and a component of drugs. According to the ancient Chinese, in 2853 BC the legendary Emperor Shennong of China proclaimed that five plants were sacred: soybeans, rice, wheat, barley, and millet.15 Cultivation of soybeans was long confined chiefly to China, but gradually spread to other countries.16
The earliest preserved soybeans were found in archaeological sites in Korea.1718 Radiocarbon dating of soybean samples recovered through flotation during excavations at the Early Mumun period Okbang site in Korea indicates that soybean was cultivated as a food crop in ca. 1000–900 BC.19
From about the first century AD to the Age of Discovery (15-16th century), soybeans were introduced into several countries such as Japan, Indonesia, the Philippines, Vietnam, Thailand, Malaysia, Burma, Taiwan, Nepal and India. 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 3, and there is evidence of tofu consumption that dates to 220. 4
United States
Soy took on a very important role in the United States after World War I. During the Great Depression, the drought stricken (Dust Bowl) regions of the United States were able to use soy to regenerate their soil because of its nitrogen-fixing properties. Farms were increasing production in order to meet with government demands, and Henry Ford was a great leader of the soybean industry.
In 1932-33 the Ford Motor Company spent approximately $1,250,000 on soybean research. By 1935 every Ford car had soy involved in its manufacture. For example, the soybean oil was used to paint the automobiles as well as fluid for shock absorbers. Ford scientists had developed a fiber{see below} from soy protein which was wool-like, very soft, and chosen to be used for the making of suits, felt hats, and overcoats. Ford himself wore a suit made entirely from soybeans, he was even said to have had dinner parties with nothing but soybean based foods on the menu. Ford’s involvement with the soybean opened many doors for agriculture and industry to be linked more strongly than it ever had before.
Henry Ford promoted the soybean, helping to develop uses for it both in food and in industrial products, even demonstrating auto body panels made of soy-based plastics. Ford’s interest led to two bushels of soybeans being used in each Ford car as well as products like the first commercial soy milk, ice cream and all-vegetable non-dairy whipped topping. The Ford development of so-called soy-based plastics was based on the addition of soybean flour and wood flour to phenolformaldehyde plastics.
In 1931, Ford hired chemists Robert Boyer and Frank Calvert to produce artificial silk. They succeeded in making a textile fiber of spun soy protein fibers, hardened or tanned in a formaldehyde bath which was given the name Azlon by the Federal Trade Commission. Pilot production of Azlon reached 5000 pounds per day in 1940, but never reached the commercial market.
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 soymilk 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 they have a tendency for the pods to shatter on 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 leading agricultural export in the United States. 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 (?? edamame?). Because of the proclaimed health benefits of soy, edamame has been featured as an ideal snack alternative in fitness and healthy living magazines such as Real Simple. Edamame is sold in the frozen vegetable section at some larger grocery stores, and as ready-to-eat snackfood in many Asian delis.
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 (), natt? (), kinako () and edamame (). In Korean cuisine, soybean sprouts, called kongnamul (?) are also used in a variety of dishes such as 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).
Archer Daniels Midland (ADM) is among the largest processors of soybeans and soy products. ADM along with Dow Chemical Company, DuPont and Monsanto support the industry trade associations United Soybean Board (USB) and Soyfoods Association of North America (SANA). These trade associations have increased the consumption of soy products dramatically in recent years.
Oil
In processing soybeans for oil extraction and subsequent soy flour production, selection of high quality, sound, clean, dehulled yellow soybeans are very important. Soybeans having a dark colored seed coat, or even beans with a dark hilum will inadvertently leave dark specks in the flour, and are undesirable for use in commercial food products. All commercial soybeans in the United States are yellow or yellow brown.
To produce soybean oil, 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 husks are used mainly as animal feed.
The major unsaturated fatty acids in soybean oil triglycerides are 7% linolenic acid (C-18:3); 51% linoleic acid (C-18:2); and 23% oleic acid(C-18:1). It also contains the saturated fatty acids 4% stearic acid and 10% palmitic acid.
Soybean oil has a relatively high proportion, 7–10%, of oxidation-prone linolenic acid, which is an undesirable property for continuous service, such as in a restaurant. In the early nineties, Iowa State University developed soybean oil with 1% linolenic acid in the oil. Three companies, Monsanto, DuPont/Bunge, and Asoyia in 2004 introduced low linolenic, (C18:3; cis-9, cis-12, cis-15 octadecatrienoic acid) Roundup Ready soybeans. In the past, hydrogenation was used to reduce the unsaturation in linolenic acid, but this produced the unnatural trans-fatty acid configuration, whereas in nature the configuration is cis (see trans fat). This external picture from North Dakota State University compares soybean oil fatty acid content with other oils.
In the 2002–2003 growing season, 30.6 million tons of soybean oil were produced worldwide, constituting about half of worldwide edible vegetable oil production, and thirty percent of all fats and oils produced, including animal fats and oils derived from tropical plants.24
While soybean oil has no direct insect repellent activity, it is used as a fixative to extend the short duration of action of essential oils such as geranium oil in several commercial products.2526
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.4
Flour
Soy flour refers to defatted soybeans where special care was taken during desolventizing (not toasted) in order to minimize denaturation of the protein to retain a high Nitrogen Solubility Index (NSI), for uses such as extruder texturizing (TVP). It is the starting material for production of soy concentrate and soy protein isolate.
Defatted soy flour is obtained from solvent extracted flakes, and contains less than 1% oil.
Full-fat soy flour is made from unextracted, dehulled beans, and contains about 18% to 20% oil. Due to its high oil content a specialized Alpine Fine Impact Mill must be used for grinding rather than the more common hammer mill.
Low-fat soy flour is made by adding back some oil to defatted soy flour. The lipid content varies according to specifications, usually between 4.5% and 9%.
High-fat soy flour can also be produced by adding back soybean oil to defatted flour at the level of 15%.
Lecithinated soy flour is made by adding soybean lecithin to defatted, low-fat or high-fat soy flours to increase their dispersibility and impart emulsifying properties. The lecithin content varies up to 15%.
Meat and dairy substitutes
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. Although soy milk does not naturally contain significant amounts of digestable calcium (the high calcium content of soybeans is bound to the insoluble constituents and remains in the soy pulp), many manufacturers of soy milk sell calcium-enriched products as well.
Soy products also are used as a low cost filler in meat and poultry products. Food service, retail and institutional (primarily school lunch and correctional) facilities regularly use such “extended” products. Extension may result 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.
Cultivation
Soybeans are an important global crop, providing oil and protein. In the United States, the bulk of the crop is solvent-extracted with hexane for vegetable oil and then the “toasted” defatted soymeal (50% protein) makes possible raising of farm animals (eg. chicken,hog,turkey), on an industrial scale never before seen in human history and harking back to the 1930s American promise of a “Chicken in every pot.” A very small proportion of the crop is consumed directly by humans. Soybean products do appear in a large variety of processed foods.
During World War II, soybeans became important in both North America and Europe chiefly as substitutes for other protein foods and as a source of edible oil. It was during World War II that the soybean was discovered as fertilizer by the United States Department of Agriculture. In the 1960-1 Dillion round of the General Agreement on Tariffs and Trade (GATT), the United States secured tariff-free access for its soybeans in the European market. In the 1960s the United States exported over 90% of the worlds soybeans. .11. 12. The soybean is now a leading crop in the United States. Brazil, Argentina, and Paraguay also are significant soybean-exporting nations.
Cultivation is successful in climates with hot summers, with optimum growing conditions in mean temperatures of 20 °C to 30 °C (68°F to 86°F); temperatures of below 20 °C and over 40 °C (68 °F, 104 °F) retard growth significantly. They can grow in a wide range of soils, with optimum growth in moist alluvial soils with a good organic content. Soybeans, like most legumes, perform nitrogen fixation by establishing a symbiotic relationship with the bacterium Bradyrhizobium japonicum (syn. Rhizobium japonicum; Jordan 1982). However, for best results an inoculum of the correct strain of bacteria should be mixed with the Soy bean (or any legume) seed before planting. Modern crop cultivars generally reach a height of around 1 m (3 ft), and take 80–120 days from sowing to harvesting.
Soybeans are native to east Asia but only 45 percent of soybean production is located there. The other 55 percent of production is in the Americas. U.S.A. produced 75 million tons of soybeans in 2000, of which more than one-third was exported. Other leading producers are Brazil, Argentina, Paraguay, China, and India.
Environmental groups, such as Greenpeace and the WWF, have reported that both soybean cultivation and the probability of increased soybean cultivation in Brazil, has destroyed huge areas of Amazon rainforest and is encouraging further deforestation.13 Growing soy also requires the use of pesticides and herbicides.
American soil scientist Dr. Andrew McClung, who first showed that the ecologically biodiverse savannah of the Cerrado region of Brazil could grow profitable soybeans, was awarded the 2006 World Food Prize on October 19, 2006.14