The first research on soybeans in the United States was conducted by George Washington Carver at Tuskegee, 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. Peanuts, soybeans, or other legume plants that would replenish the soil with nitrogen and minerals were planted for two years and then cotton on the third year. A two year rotation system alternating maize instead is also a possibility.
Production history
Soybean domestication first occurred in China. Ancient Chinese documents state that soybean agriculture began during the Zhou Dynasty in 664 BC and was introduced to the Zhou heartland from the Manchuria Plain. Archaeologists recovered soybean from a site in Jilin Province and dated charcoal associated with the legume to cal. 900–520 BC.
In 2853 BC, Emperor Sheng-Nung of China named five sacred plants – soybeans, rice, wheat, barley, and millet. Soybean plants were domesticated between 17th and 11th century BC in the eastern half of China where they were cultivated into a food crop. 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, Nepal and India. The spread of the soybean was due to the establishment of sea and land trade routes. The earliest Japanese reference to the soybean is in the classic Kojiki (Records of Ancient Matters) which was completed in 712 AD.
Soybeans were unearthed from archaeological sites in Korea. AMS radiocarbon dating on soybean recovered through flotation during excavations at the Early Mumun Period Okbang site in Korea indicates that soybean was cultivated as a food crop in cal. 1000–900 BC. The best current evidence on the Japanese Archipelago suggests that soybean cultivation occurred in the early Yayoi period.
Many people have claimed that soybeans in Asia, prior to modern times, were only used after a fermentation process, which alters the high increase in phytoestrogens found in the raw plant. However, this appears to be incorrect: The term "soy milk" has been in use since 82 AD, and there is evidence of tofu consumption that dates to 220.
Genetic modification
Soybeans are one of the "biotech food" crops that are being genetically modified, and GM soybeans are being used in an increasing number of products. In 1995 Monsanto introduced "Roundup Ready" (RR) soybeans that have had a copy of a gene from the bacterium, 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 herbicide, glyphosate. Glyphosate, the active ingredient in Roundup, kills conventional soybeans. The bacterial gene is EPSP (5-enolpyruvyl shikimic acid-3-phosphate) synthase. Soybean also has a version of this gene, but the soybean version is sensitive to glyphosate, while the CP4 version is not.
RR soybeans allow a farmer to spray widely the herbicide Roundup and so to reduce tillage or even to sow the seed directly into an unplowed field, known as 'no-till' or conservation tillage. No-till agriculture has many advantages, greatly reducing soil erosion and creating better wildlife habitat; it also saves fossil fuels and sequesters CO2, a greenhouse effect gas. It must be said, however, that the production and use of an artificial herbicide such as Roundup does consume significant quantities of fossil fuels and does not improve wildlife habitat since it is designed specifically to kill most plants (plants tend to remove CO2 and produce oxygen). It should be noted that RR soybeans are not a requirement for no-till agriculture, because Roundup may be sprayed on the field (and weeds) before the soybeans have emerged from the soil.
In 1997, about 8% of all soybeans cultivated for the commercial market in the United States were genetically modified. In 2006, the figure was 89%. As with other "Roundup Ready" crops, concern is expressed over damage to biodiversity. However, the RR gene has been bred into so many different soybean cultivars that the genetic modification itself has not resulted in any decline of genetic diversity, yet as no studies have been objectively done there is no data to support this view.
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 (枝豆, 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 (味噌), natto (納豆), tofu (豆腐) and edamame (枝豆). In Korean cuisine, soybean sprouts, called kongnamul (hangul:콩나물) 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 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, 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 (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, 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 trans fat configuration, whereas in nature the configuration is cis. 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 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
Soybean meal is an ingredient found in some dog food and cattle feeding. According to AAFCO is the product obtained by grinding the flakes which remain after removal of most of the oil from soybeans by a solvent or mechanical extraction process.
Soybean meal is a poor quality protein filler with almost 50% of the protein extracted. It boosts the protein content of low quality pet food and has a biologic value of less than 50% of chicken meal. It's more suited for feed in aquaculture, beef, dairy cattle, horses, poultry, sheep, and swine.
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 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%.
Infant formula
Infant formulas based on soy are used by lactose-intolerant babies and for babies that are allergic to cow milk proteins. The formulas are sold in powdered, ready-to-feed, or concentrated liquid forms.
Nut butter
Soybeans have been made into a spread called soynut butter, similar to peanut butter but with soybeans instead. It is less fattening than peanut butter.
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, but no hormonal effects have been found on long term feeding of such formulas.
In July of 1996, the British Department of Health issued a warning that the phytoestrogens found in soy-based infant formulas could adversely affect infant health. The warning was clear, indicating that soy formula should only be given to babies on the advice of a health professional. They advised that babies who cannot be breastfed or who have allergies to other formulas be given alternatives to soy-based formulas.
Substitute for existing products
Many traditional dairy products have been made without dairy using processed soybeans (e.g. tofu, soy oil, ...), and products such as soy milk, soy yogurt, soy butter 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.
Other products
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 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.
Today, very high quality textile fibers are made commercially from "okara" (soy pulp), a by-product of tofu production.
Nutrition
Soybeans are generally considered to be a source of complete protein, although this is contested by some sources. 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.
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.
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.
Toasted soybeansConsumption of soy may also reduce the risk of colon cancer, possibly due to the presence of sphingolipids.
Omega-3 fatty acids
Omega-3 fatty acids, for example, 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 (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 (aLNA) can do this. Soybean oil is one of the few common vegetable oils that contains a significant amount of aLNA; others include canola, walnut, 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: 100g of soybean oil contains 7g of omega-3 fatty acids to 51g of omega-6: a ratio of 1:7. Flaxseed, in comparison, has an omega-3:omega-6 ratio of 3:1 which may inhbit conversion of aLNA to the biologically active forms EPA and DHA, which is at best limited in humans anyway.
Isoflavones
Soybeans also contain isoflavones, a type of phytoestrogen, that are considered by some nutritionists and physicians to be useful in the prevention of cancer and by others to be carcinogenic and endocrine disruptive. Soy's high levels of isoflavone phytoestrogens, being up to 3mg/g dry weight, are the subject of heated debate and controversy. They are also blamed for some thyroid and reproductive health problems.
Isoflavones are polyphenol compounds, produced primarily by beans and other legumes, including peanuts and chickpeas. Although isoflavones are closely related to the antioxidant flavonoids found in plants, vegetables and flowers, isoflavones such as genistein and daidzein are found in very few plant families. This is because of the restricted distribution of the enzyme, chalcone isomerase which converts a flavone precursor into an isoflavone, to tropical legumes.
Claims of cholesterol reduction
The dramatic increase in soyfood sales is largely credited to the Food and Drug Administration's (FDA) approval of health claims for soy in which studies are conflicting to their cholesterol lowering ability.
From 1992 to 2003, sales have experienced a 15% compound annual growth rate, increasing from $300 million to $3.9 billion over 11 years, as new soyfood categories have been introduced, soyfoods have been repositioned in the market place, thanks to a better emphasis on marketing nutrition.
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."St. Louis, Missouri, a soy producer and marketer. 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 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, in 1998, filed a petition with FDA for a health claim that soy protein may reduce cholesterol and the risk of heart disease. It should be noted that only subjects with serum cholesterol of 250mg/dl and higher showed any improvement in the study.
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, (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.
In January, 2006 an American Heart Association review (in the journal Circulation) of a decade long study of soy protein benefits casts doubt on the FDA allowed "Heart Healthy" claim for soy protein. This review of the literature compared soy protein and its component isoflavones with casein (isolated milk protein), wheat protein, and mixed animal proteins. 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. Thus, soy isoflavone supplements in food or pills is not recommended. 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." The original paper is in the journal Circulation: January 17, 2006. |
