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 (3845%) 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.
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 Hawaii, and are becoming increasingly popular in the continental United States. 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. Japanese foods made from soya include: miso , natto , tofu 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).
Soybeans grow throughout Asia and North and South America.Archer Daniels Midland (ADM) is among the largest processors of soybeans and soy products. ADM along with DOW, 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.
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. 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 (C18:3); 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, 710%, 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 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 20022003 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.
Soybean oil has also been found effective as an insect repellent in some studies. The commercial product Bite Blocker contains soybean oil as one active ingredient.
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.
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 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.
It has been recommended internationally by pediatric associations that soy formulas not be used as the primary or sole source of nutrition for infants due to the high risk of several deficiencies, including calcium and zinc. Some studies have also indicated that soy may act similarly to the hormone estrogen in developing infants. This has caused some concern that soy formula may cause undesirable side effects, such as reproductive problems. However, no studies to date have shown any negative effects on infants resulting from the estrogen-like compounds in soy formula.
Substitute for existing products
Many traditional "dairy products" have been made without diary using processed soybeans, and products such as "soy milk," "soy yogurt" and "soy cream cheese" are readily available in most supermarkets. These products are derived from extensive processing to produce a texture and appearance similar to 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.
Soybeans are also used in industrial products including oils, soap, cosmetics, resins, plastics, inks, crayons, solvents, clothing, and biodiesel. Soybeans are also used as fermenting stock to make a brand of vodka.
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 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.
Today, very high quality textile fibers are made commercially from "okara" (soy pulp), a by-product of tofu production.
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