Soybean
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? Soybean |
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| Glycine
max ( L.) Merr. |
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Soybean(s) ( U.S.) or Soya bean ( UK) Glycine max is a species of legume, native to eastern Asia. It is an annual plant, which may vary in growth habit and height. It may grow prostrate, not growing above 20 cm (7.8 inches); up to stiffly erect plants growing to 2 meters (6.5 feet). The pods, stems, and leaves are covered with fine brown or gray pubescence. The leaves are trifoliate (sometimes with 5 leaflets), the leaflets 6-15 cm (2-6 inches) long and 2-7 cm (1-3 inches) broad; they fall before the seeds are mature. The small, inconspicuous, self-fertile flowers are borne in the axil of the leaf and are either white or purple; The fruit is a hairy pod that grow in clusters of 3-5, with each pod 3-8 cm (1-3 inches) long and usually containing 2-4 (rarely more) seeds 5-11 mm in diameter.
Like corn and some other crops of long domestication, the relationship of the modern soybean to wild-growing species can no longer be traced with any degree of certainty. It is a cultural variety (a cultigen) with a very large number of cultivars. However, it is known that the progenitor of the modern soybean was a vine-like plant, that grew prone on the ground.
Beans are classed as pulses whereas soybeans are classed as oilseeds. The word soy is derived from the Japanese word shoyu (soy sauce/soya sauce).
Physical characteristics
Soybeans occur in various sizes, and in several hull or seed coat colors, including black, brown, blue, yellow, and mottled. The hull of the mature bean is hard, water resistant, and protects the cotyledon and hypocotyl (or "germ") from damage. 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.
Cultivation
Soybeans are an important global crop, with political ramifications. It is grown for its oil and protein. The bulk of the crop is solvent extracted for vegetable oil and the defatted soy meal is used for animal feed. A very small proportion of the crop is consumed directly for food by humans.
Soybeans were used as food in eastern Asia long before written records, and it is still a major crop in China, Japan and Korea. They were first introduced to Europe in the early 1700s and 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.
Cultivation is successful in climates with hot summers, with optimum growing conditions in mean temperatures of 20 °C to 30 °C; temperatures of below 20 °C and over 40 °C 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 soybean(or any legume) seed before planting. Modern crop cultivars generally reach a height of 1 m or more, and take between 80-120 days from sowing to harvesting.
Soybeans are native to southeast Asia, but 45 percent of the world's soybean area, and 55 percent of production, is in the United States. The U.S. produced 75 million metric tons of soybeans in 2000, of which more than one-third was exported. Other leading producers are Brazil, Argentina, China, Japan, and India.
Environmental groups, such as Greenpeace and the WWF, have reported that soybean cultivation and the threat to increase soybean cultivation in Brazil is destroying huge areas of Amazon rainforest and encouraging deforestation.
The first research on soybeans in the United States was conducted by George Washington Carver at Tuskeegee, Alabama, but he decided it was too exotic a crop for the poor black farmers of the South so he turned his attention to peanuts. He also encouraged farmers to use crop rotation. Peanuts, soybeans, sweet potatoes or other plants that would replenish the soil with nitrogen and minerals were planted for two years and then cotton on the third year.
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, particularly in Asia.
Soybeans may be boiled whole in their green pod and served with salt, under the Japanese name edamame. Soybeans prepared this way are a popular local snack in Hawai'i, where, as in Japan, China, and Korea, the bean and products made from the bean ( miso, natto, tofu, douchi, doenjang, ganjang and others) are a significant part of the diet.
The beans can be processed in a variety of ways. Common forms of soy (or soya) include soy meal ( used as animal feed), 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 (aka "vegetable oil" in the USA). Soybeans are also the primary ingredient involved in the production of soy sauce (or shoyu).
Oil
In processing soybeans for oil extraction and subsequent soy flour production, selection of high quality, sound, clean, dehulled yellow soybeans is very important. Soybeans having a dark colored seed coat, or even beans with a dark hilum will inadvertently leave dark specks in the flour, an undesirable factor when used in 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. The oils are exported abroad, sold as vegetable oil, or end up in a wide variety of processed foods. New processes increasingly prepare protein isolates for use as food additives or health supplements. The remaining soybean husks are used mainly as animal feed.
The major unsaturated fatty acids in soybean oil triglycerides are linolenic acid,C18:3; linoleic acid, C-18:2; and oleic acid,C-18:1. 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. Two companies, Monsanto and DuPont/Bunge in 2004 introduced low linolenic,(C18:3; cis-9, cis-12, cis-15 octadecatrienoic acid) Roundup Ready soybeans: the former introduced a new soybean seed variety called "Vistive" and the latter Pioneer seed variety 93M20. Dupont/Bunge is marketing its low linolenic soybean oil under the brand name Nutrium. The idea is that reducing or eliminating the triple unsaturated fatty acid, linolenic, also eliminates the tendency to be a paint-like drying oil producing noticeable rancidity..In the past hydrogenation reduced the unsaturation in linolenic acid but produced the unnatural trans fatty acid { trans fat} configuration whereas in nature the configuration is cis.
In the 2002-2003 growing season, 30.6 million metric 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.
Meal
Soybean meal, the material remaining after solvent extraction of soybean flakes, with a 50% soy protein content, toasted (a misnomer because the heat treatment is with moist steam), and ground, in a hammer mill, provided the energy for the American revolution, beginning in the 1930s, of growing farm animals such as poultry and swine on an industrial scale; and more recently the aquaculture of catfish.
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 hammermill.
- 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, is 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%.
Infant formula
Infant formulas based on soy are used by lactose-intolerant babies; and for babies that are allergic to human milk proteins and cow milk proteins. The formulas are sold in powdered, ready to feed, or concentrated liquid forms.
Substitute for existing products
Many traditional dairy products have been imitated using processed soybeans, and imitation products such as soy milk, "soy yogurt" and "soy cream cheese" are readily available in most supermarkets. These imitation products are derived from extensive processing to produce a texture and appearance similar to the real dairy-based ones. Soy milk does not contain significant amounts of calcium, since the high calcium content of soybeans is bound to the insoluble constituents and remains in the pulp. Many manufacturers of soy milk now sell calcium-enriched products as well. Tofu often contains high amounts of this important mineral since calcium salts are used to coagulate the protein in soy milk when creating tofu. Additionally, soy protein has been found to reduce renal excretion of calcium, an effect that is reinforced by the high potassium content of soy products.
Other products
Soybeans are also used in industrial products including oils, soap, cosmetics, resins, plastics, inks, crayons, solvents, and biodiesel. Soybeans are also used as fermenting stock to make a brand of vodka.
Genetic modification
Soybeans are one of the "Biotech Food" crops that are being genetically modified, and GMO soybeans are being used in an increasing number of products. Monsanto is the world's leader in genetically modified soy for the commercial market. In 1995, Monsanto introduced " Roundup Ready" (RR) soybeans that have had a complete copy of a gene (plasmid) from the bacteria, Agrobacterium sp. strain CP4, inserted, by means of a gene gun, into its genome that allows the transgenic plant to survive being sprayed by this non-selective, glyphosate-based herbicide. Roundup kills conventional soybeans. RR soybeans allow a farmer to reduce tillage or even to sow the seed directly into an unplowed field, known as 'No Plow' tillage.
Currently, 80% of all soybeans cultivated for the commercial market are genetically modified. As with other "Roundup Ready" crops, concern is expressed over damage to biodiversity through the loss of wildflowers removed by the roundup treatment, and consequent loss of insects and birds that depend on them. Concern is also for the high amounts of residual toxin since the herbicide is sprayed on the soya crop repeatedly during growth.
Nutrition
Protein
Soybeans are 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 important to many vegetarians and vegans. Soy protein is similar to that of other legume seeds, but has the highest yield per square meter of growing area, and is the least expensive source of dietary protein. The only non-legume to have an almost identical protein profile to soy is the cereal oat (Avena sativa), and perhaps quinoa.
Vitamins and Minerals
Of any studied legume, whole soybeans have the highest levels of phytic acid, an organic acid and mineral chelator present in many plant tissues, especially bran and seeds, which binds to certain ingested minerals: calcium, magnesium, iron, and especially zinc—in the intestinal tract, and reduces the amount the body assimilates. For people with a particularly low intake of essential minerals, especially young children and those in developing countries, this effect can be undesirable. However, dietary mineral chelators help prevent over-mineralization of joints, blood vessels, and other parts of the body, which is most common in older persons. The Journal of Environmental Nutrition (April 2004 volume 27 issue 4) has also stated phytic acid may be considered a phytonutrient, providing an antioxidant effect. Scientific research [1] also indicates that it may reduce the risk of colon cancer. In spite of the chelating effects of phytic acid, soybeans remain a good source of magnesium, potassium, phosphorus, calcium, and manganese. They are also high in fiber and vitamin C.