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Facts on Soybeans
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 to 30 Celsius; temperatures of below
20 Celsius and over 40 ?Celsius 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.
Varieties of soybeans
are used for many purposes.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). Soybeans grow throughout Asia and
North and South America.
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.
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
Toasted soybeans 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.
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. For instance they inhibit
blood clotting, thereby reducing heart attack risk, and
control body biochemicals that reduce inflammation and
promote healing.
Oily fish such as salmon, and
sardines are excellent sources of omega-3 fatty acids.
Soybean oil and canola are the only common vegetable
oils that contain omega-3s. However, the very best
vegetable source of omega-3s is homemade flax meal
ground in a coffee/spice grinder or
blender.
Isoflavones
Soybeans also contain
isoflavones, forms of phytoestrogen that are considered
by some nutritionists and physicians to be useful in the
prevention of cancer, though very controversial and also
blamed for some thyroid and reproductive health
problems. Isoflavones are polyphenol compounds, produced
primarily by beans and other legumes, including peanuts
and chickpeas.
Reduce cholesterol
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."[2] St. Louis. 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. 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.
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.
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. The panel also found
that soy isoflavones do not reduce post menopause "hot
flashes" in women nor do isoflavones help prevent
cancers of the breast, uterus or prostate.
The
original paper in the journal Circulation: January
17,2006[4]
Cancer
A 1985 animal study
showed that young rats fed large amounts of soy products
as their primary food source showed an increased risk of
pancreatic cancer. This is probably because rats are
extremely sensitive to dietary protease inhibitors like
those found in soybeans, which can disrupt the action of
digestive enzymes needed to break down protein. This
condition has not been found in many other animals, and
is not known to occur in humans.
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