Since the early twentieth century soybeans have been called the
'golden bean' or 'miracle bean' in America. The English words "soy" and
"soya" are ultimately derived from the Japanese pronunciation of shōyu,
the Sino-Japanese word for soy sauce, through the German adaptation of
the same word, soja.
The plant is known as the "large bean" in
Chinese: or yellow bean. Both the immature soybean and its dish are
called edamame in Japan, but in English, edamame refers only to a
specific dish. The genus name, Glycine, is the same as a simple amino
acid.
Fat-free (defatted) soybean meal is a significant and cheap
source of protein for animal feeds and many packaged meals; soy
vegetable oil is another product of processing the soybean crop. For
example, soybean products such as textured vegetable protein (TVP) are
ingredients in many meat and dairy analogues. Soybeans produce
significantly more protein per acre than most other uses of land.
Traditional
nonfermented food uses of soybeans include soy milk, and from the
latter tofu and tofu skin. Fermented foods include soy sauce, fermented
bean paste, natto, and tempeh, among others. The oil is used in many
industrial applications. The main producers of soy are the United States
(36%), Brazil (36%), Argentina (18%), China (5%) and India (4%). The
beans contain significant amounts of phytic acid, alpha-linolenic acid,
and isoflavones.
The soybean in US or soya bean in UK, AU (Glycine
max) is a species of legume native to East Asia, widely grown for its
edible bean which has numerous uses. The plant is classed as an oilseed
rather than a pulse by the UN Food and Agriculture Organization (FAO).
The
genus Glycine Willd is divided into two subgenera, Glycine and Soja.
The subgenus Soja includes the cultivated soybean, Glycine max, and the
wild soybean, Glycine soja Sieb. & Zucc. Both species are annuals.
Glycine soja is the wild ancestor of Glycine max, and grows wild in
China, Japan, Korea, Taiwan and Russia. The subgenus Glycine consists of
at least 25 wild perennial species: for example, Glycine canescens F.J.
Herm. and G. tomentella Hayata, both found in Australia and Papua New
Guinea. Perennial soybean (Neonotonia wightii) originated in Africa and
is now a widespread pasture crop in the Tropics.
Just like 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 with a very large number of
cultivars.
Soy protein
All spermatophytes
except for the grass/cereal family contain soybean-like 7S (vicilin)
and/or 11S (legumin), {S denotes Svedberg, sedimentation coefficients}
desiccation-tolerant seed storage globulin proteins. Oats and rice are
anomalous in that they also contain a majority of soybean-like protein.
Cocoa, for example, contains the 7S globulin, which contributes to
cocoa/chocolate taste and aroma; whereas coffee beans (coffee grounds)
contain the 11S globulin responsible for coffee's aroma and flavor.
Vicilin
and legumin proteins belong to the cupin superfamily, a large and
functionally diverse 'superfamily' of proteins that have a common origin
and whose evolution can be followed from bacteria to eukaryotes
including animals and higher plants.
2S albumins form a major
group of homologous storage proteins in many dicot species and in some
monocots but not in grasses (cereals). Soybeans contain a small but
significant 2S storage protein. 2S albumin are grouped in the prolamin
superfamily. Other allergenic proteins included in this 'superfamily'
are the non-specific plant lipid transfer proteins, alpha amylase
inhibitor, trypsin inhibitors, and prolamin storage proteins of cereals
and grasses.
Peanuts, for instance, contain 20% 2S albumin but
only 6% 7S globulin and 74% 11S. It is the high 2S albumin and low 7S
globulin that is responsible for the relatively low quality (low lysine)
of peanut protein compared to soy protein. Cereal storage prolamins are
likewise low in lysine, the most important and first limiting amino
acid. Peanut butter and wheat bread, therefore, do not complement each
other as they each suffer from low lysine.
Cultivation
Soybeans are a globally important crop, providing oil and protein. In
the United States, the bulk of the harvest is solvent-extracted with
hexane, and the "toasted" defatted soymeal (50% protein) then makes
possible the raising of farm animals (e.g. chicken, hog, turkey) on an
industrial scale never before seen in human history. A very small
proportion of the crop is consumed directly by humans. Soybean products
do, however, 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. During the war, the soybean was discovered as fertilizer by
the United States Department of Agriculture. In the 1960–1 Dillon round
of the General Agreement on Tariffs and Trade (GATT), the United States
secured tariff-free access for its soybeans to the European market. In
the 1960s, the United States exported over 90% of the world's soybeans.
By 2005, the top soybeans exporters were Argentina (39% of world soybean
exports), United States (37%) and Brazil (16%), while top importers
were China (41% of world soybean imports), European Union (22%), Japan
(6%) and Mexico (6%).
Cultivation is successful in climates with
hot summers, with optimum growing conditions in mean temperatures of 20
to 30 °C (68 to 86 °F); temperatures of below 20 °C and over 40 °C
(68 °F, 104 °F) stunt 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). For
best results, though, 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 around 1 m (3.3 ft),
and take 80–120 days from sowing to harvesting.
The U.S.,
Argentina, Brazil, China and India are the world's largest soybean
producers and represent more than 90% of global soybean production. The
U.S. produced 75 million tons of soybeans in 2000, of which more than
one-third was exported. In the 2010–2011 production year, this figure is
expected to be over 90 million tons.
The average worldwide yield
for soybean crops, in 2010, was 2.5 tonnes per hectare. The three
largest producers had an average nationwide soybean crop yields of about
3 tonnes per hectare. The most productive soybean farms in the world in
2010 were in Turkey, with a nationwide average farm yield of 3.7 tonnes
per hectare. The world record for soybean yield is 10.8 tonnes per
hectare, demonstrated in 2010 by Kip Cullers, a farmer in Purdy,
Missouri. Kip Cullers claims the secret to his record breaking soybean
crop yields year after year is attention to detail, proactive management
style, irrigation, herbicides, keeping plants healthy and stress free
for the entire growing season.
Environmental groups, such as
Greenpeace and the WWF, have reported soybean cultivation and the
probability of increased soybean cultivation in Brazil has destroyed
huge areas of Amazon rainforest, and is encouraging further
deforestation.
American soil scientist 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.
Human sewage sludge can be used as
fertilizer to grow soybeans. Soybeans grown in sewage sludge likely
contain elevated concentrations of metals. Soybean plants are vulnerable
to a wide range of bacterial diseases, fungal diseases, viral
diseases and parasites. One important pest is the corn earworm moth,
which is the most common and destructive pest of soybean growth in
Virginia.
Uses
Approximately 85% of the
world's soybean crop is processed into soybean meal and vegetable oil.
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 soy milk 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 there is a
tendency for the pods to shatter upon reaching maturity.
Among the
legumes, the soybean, also classed as an oilseed, is preeminent for its
high (38–45%) protein content as well as its high (approximately 20%)
oil content. Soybeans are the second-most valuable agricultural export
in the United States behind corn. 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 pods and served with salt, under the Japanese name
edamame. In English, these soybeans are generally known as "edamame" or
"green vegetable soybeans".
In China, Japan, and Korea, the bean
and products made from it 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 , nattō , kinako
and edamame . Also many kinds of food are produced using tofu such as
atsuage, aburaage, and so on. In Korean cuisine, soybean sprouts, called
kongnamul, are also used in a variety of dishes, and are also the base
ingredient in doenjang, cheonggukjang and ganjang. In Vietnam, soybeans
are used to make soybean paste- tương in the North with the most popular
products are tương Bần, tương Nam Đàn, tương Cự Đà as a garnish for phở
and gỏi cuốn dishes, tofu, soya sauce (nước tương, literally: soya
water), soya milk (nước đậu in the North or sữa đậu nành in the South),
and đậu hũ nước đường (tofu sweet soup).
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 (shoyu).
Archer Daniels Midland (ADM) is among the
largest processors of soybeans and soy products. ADM, along with Dow
Chemical Company, DuPont and Monsanto company, support the industry
trade associations United Soybean Board and Soyfoods Association of
North America. These trade associations have increased the consumption
of soy products dramatically in recent years.
Oil.
Soybean seed
contains about 19% oil. To extract soybean oil from seed, 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 meal is used mainly as animal feed.
Soybean 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. Soybean meal is also used in
lower-end dog foods.
Flour
Soy flour refers
to soybeans ground finely enough to pass through a 100-mesh or smaller
screen where special care was taken during desolventizing (not toasted)
to minimize denaturation of the protein to retain a high protein
dispersibility index, for uses such as food extrusion of textured
vegetable protein. It is the starting material for production of soy
concentrate and soy protein isolate.
Soy flour is made by roasting
the soybean, removing the coat, and grinding into a flour. Soy flour is
manufactured with different fat levels. Alternatively, raw soy flour
omits the roasting step.
Defatted soy flour is obtained from solvent extracted flakes, and contains less than 1% oil.
"Natural or full-fat soy flour is made from unextracted, dehulled
beans, and contains about 18% to 20% oil." Its high oil content requires
the use of a specialized Alpine Fine Impact Mill to grind rather than
the usual hammer mill. Full-fat soy flour has a lower protein
concentration then defatted flour. Extruded Full-Fat soy flour, ground
in an Alpine mill, can replace/extend EGGS in baking and cooking.
Low-fat soy flour is made by adding some oil back into defatted soy flour. Fat levels range from 4.5% to 9%.
High-fat soy flour can also be produced by adding back soybean oil to defatted flour at the level of 15%.
Soy
lecithin can be added (up to 15%) to soy flour to make lecithinated soy
flour. It increases dispersibility and gives it emulsifying properties.
Soy
flour has 50% protein and 5% fiber. It has higher levels of protein,
thiamine, riboflavin, phosphorus, calcium, and iron than wheat flour. It
does not contain gluten. As a result, yeast-raised breads made with soy
flour are dense in texture. Among many uses, soy flour thickens sauces,
prevents staling in baked food, and reduces oil absorption during
frying. Baking food with soy flour gives it tenderness, moistness, a
rich color, and a fine texture.
Soy grits are similar to soy flour except the soybeans have been toasted and cracked into coarse pieces.
Kinako is a soy flour used in Japanese cuisine.
Infant formula
Soy-based infant formula (SBIF) is sometimes given to infants who are
not being strictly breastfed; it can be useful for infants who are
either allergic to pasteurized cow milk proteins or who are being fed a
vegan diet. It is sold in powdered, ready-to-feed, and concentrated
liquid forms.
Some reviews have expressed the opinion that more
research is needed to determine what effect the phytoestrogens in
soybeans may have on infants. Diverse studies have concluded there are
no adverse effects in human growth, development, or reproduction as a
result of the consumption of soy-based infant formula.
Meat and dairy alternatives and extenders
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
alternatives (e.g. veggie burgers). These substitutes are readily
available in most supermarkets. Soy milk does not naturally contain
significant amounts of digestible calcium. Many manufacturers of soy
milk sell calcium-enriched products, as well. Soy is also used in
tempeh: the beans (sometimes mixed with grain) are fermented into a
solid cake.
Soy products also are used as a low-cost substitute in
meat and poultry products. Food service, retail and institutional
(primarily school lunch and correctional) facilities regularly use such
"extended" products. Extension may result in 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. The soy-based meat
substitute textured vegetable protein has been used for more than
50 years as a way of inexpensively extending ground beef without
reducing its nutritional value.
Other products
Soybeans with black hulls are used in Chinese fermented black beans, douchi, not to be confused with black turtle beans.
Soybeans
are also used in industrial products, including oils, soap, cosmetics,
resins, plastics, inks, crayons, solvents, and clothing. Soybean oil is
the primary source of biodiesel in the United States, accounting for 80%
of domestic biodiesel production. Soybeans have also been used since
2001 as fermenting stock in the manufacture of a brand of vodka. In
1936, Ford Motor Company developed a method where soybeans and fibers
were rolled together producing a soup which was then pressed into
various parts for their cars, from the distributor cap to knobs on the
dash board. Ford also informed in public relation releases that in 1935
over five million acres (20,000 km2) was dedicated to growing soybeans
in the United States.
Cattle feed
Cattle are often fed soy. Spring grasses are rich in omega-3 fatty acids, whereas soy is predominantly omega-6.
Health benefits
Lunasin is a peptide found in soy and some cereal grains and has been
the subject of research since 1996 focusing on cancer, cholesterol and
cardiovascular disease and inflammation.
Cancer
According to the American Cancer Society, "Studies in humans have not
shown harm from eating soy foods. Moderate consumption of soy foods
appears safe for both breast cancer survivors and the general
population, and may even lower breast cancer risk." They caution however
that soy supplements should be avoided.
Soybean oil is one of the
vegetable oils that contain a significant amount of the omega-3 fatty
acid alpha-linolenic acid (18:3n−3, aLNA). Other plant oils containing
aLNA (or ALA) include canola, walnut, hemp, and flax. Soybean oil has an
omega-3:omega-6 ratio of 1:7. This is a significantly higher omega-3
content than in other vegetable cooking oils. While flaxseed is even
higher with a ratio of 3:1, it is not practical for cooking. For more
information on the health benefits of omega-3 and omega-6 fatty acids,
see Essential fatty acids.
Natural phenols
Soybeans also contain the isoflavones genistein and daidzein, types of
phytoestrogen, that are considered by some dietitians and physicians to
be useful in the prevention of cancer and by others to be carcinogenic
and endocrine disruptive. Soy's content of isoflavones are as much as
3 mg/g dry weight. Isoflavones are polyphenol compounds, produced
primarily by beans and other legumes, including peanuts and chickpeas.
Isoflavones are closely related to the antioxidant flavonoids found in
other plants, vegetables and flowers. Isoflavones such as genistein and
daidzein are found in only some plant families, because most plants do
not have an enzyme, chalcone isomerase which converts a flavone
precursor into an isoflavone.
In contradiction to well known
benefits of isoflavones, genistein acts as an oxidant (stimulating
nitrate synthesis), and blocks formation of new blood vessels
(antiangiogenic effect). Some studies show that genistein acts as
inhibitor of substances that regulate cell division and cell survival
(growth factors).
A review of the available studies by the United
States Health and Human Services Agency for Healthcare Research and
Quality (AHRQ) found evidence of a decrease in LDL ("bad cholesterol"),
but no substantial increase in HDL ("good cholesterol") as a result of
soy isoflavone consumption. The authors found insufficient data among
200 studies to suggest that soy had an effect on bone health, cancer,
kidney disease, endocrine function, reproductive health, neurocognitive
function, or glucose metabolism, but noted that more research was needed
to elucidate its potential impact upon other health conditions.
Glyceollins
Glyceollins are molecules belonging to the pterocarpans family. They
are also found in the soybean and have been found to have an antifungal
activity against Aspergillus sojae, the fungal ferment used to produce
soy sauce. They are phytoalexins with an antiestrogenic activity.
Cholesterol and heart diseases
The dramatic increase in soyfood sales is largely credited to the Food
and Drug Administration's (FDA) approval of soy as an official
cholesterol-lowering food, along with other heart and health benefits.
In
1995, Journal of Medicine (Vol. 333, No. 5) published "Meta-analysis of
the effects of soy protein intake on serum lipids", financed in part by
DuPont Protein Technologies International (PTI), which produces and
markets soy through The Solae Company. The meta-analysis concluded that
soy protein is correlated with significant decreases in serum
cholesterol, LDL (bad cholesterol) and triglycerides. However, 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 filed a petition with FDA in
1998 for a health claim that soy protein may reduce cholesterol and the
risk of heart disease.
The FDA granted the following 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. On February 18, 2008 Weston A. Price Foundation
submitted a petition for removal of this health claim. 25 g/day soy
protein was established as the threshold intake because most trials used
at least this much protein and not because less than this amount is
inefficacious. In fact, there is evidence suggesting that lower amounts
are indeed efficacious.
An American Heart Association review of a
decade long study of soy protein benefits casts doubt on the FDA allowed
"Heart Healthy" claim for soy protein and does not recommend isoflavone
supplementation. 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. However, AHA concludes that
"many soy products 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".
Importantly,
however, the AHA did not conduct a formal statistical analysis of the
22 studies upon which they based their estimate of the potency of soy
protein. When such an analysis was conducted, Jenkins et al. found that
the AHA had considerably underestimated the hypocholesterolemic effects
of soy protein. Further, when the analysis was limited to the 11 studies
that provided evidence that the control and soy diets were matched, soy
protein was found to lower LDL by 5.2 percent. This estimate is in line
with the results of other recently published meta-analyses.
Furthermore, recent research suggests that soy protein decreases
postprandial triglyceride levels, which is increasingly viewed as
important for reducing CHD risk.
Phytic acid
Soybeans contain a high level of phytic acid, which has many effects
including acting as an antioxidant and a chelating agent. The beneficial
claims for phytic acid include reducing cancer, minimising diabetes,
and reducing inflammation. However, phytic acid is also criticized for
reducing vital minerals due to its chelating effect, especially for
diets already low in minerals.
