TECHNICAL PAPER # 73
 
                        UNDERSTANDING SOYBEAN
                       PRODUCTS AND PROCESSING
 
                                 By
                         Harry E. Snyder, Ph.D.
 
                          Technical Reviewers
                               Ellen Craft
                         Gordon L. Brockmueller
                              Joanne Hokes
 
                             Published By
                   VOLUNTEERS IN TECHNICAL ASSISTANCE
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                Understanding Soybean Products and Processing
                          ISBN:  0-86619-316-2
                [C] 1990, Volunteers in Technical Assistance
     
 
                           PREFACE
 
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their situations.
They are not intended to provide construction or implementation
details.  People are urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
 
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis.  Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.  VITA staff included Patrice Matthews
and Suzanne Brooks handling typesetting and layout, and Margaret
Crouch as senior editor and project manager.   VITA Volunteer Dr.
R. R. Ronkin, retired from the National Science Foundation, lent
his invaluable perspective, as a volunteer, to the compilation of
technical reviews, conversations with contributing writers, editing,
and in a variety of other ways.
 
VITA Volunteer Harry E. Snyder, who has a Ph.D. in microbiology
from the University of California at Davis, has taught and done
research in food science and technology for 30 years.   Dr. Snyder
has also published a number of books and articles on soybeans and
other food related topics.  Reviewers Ellen Craft, an agronomist,
and Gordon Brockmueller, a farmer, have extensive experience with
soybean production.  Joanne Hokes' background is in the oilseed
processing industry, including both soybeans and peanuts.  All
three reviewers are long-time VITA Volunteers.
 
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.   VITA offers
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to their
situations.  VITA maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster of
volunteer technical consultants; manages long-term field projects;
and publishes a variety of technical manuals and papers.
 
           UNDERSTANDING SOYBEAN PRODUCTS AND PROCESSING
 
             by VITA Volunteer Harry E. Snyder, Ph.D.
 
1.  INTRODUCTION
 
Soybean Production
 
Since 1950, soybeans have become a valuable part of the world's
food supply and of the systems that produce and deliver food.
Production of soybeans has grown rapidly and in 1990 amounted to
approximately 100 million metric tons (MMT) annually.   This compares
with about 500 MMT each for rice   and wheat and 800 MMT for
coarse grains, predominantly maize.
 
Soybean production is widespread but is centered in temperate
climates.  The United States produces about half of the total; the
other major producers are Brazil (15 MMT), China (10 MMT), and
Argentina (8 MMT).  Soybeans contribute about 20 percent (13 MMT)
of the total vegetable oil and are the world's main, single
source of food oil.  Palm oil accounts for 8 MMT and sunflower oil
6 MMT of the world's total.
 
The flowering of the soybean is sensitive to day length; therefore
cultivars (cultivated varieties) must be selected for the
latitude in which they will be grown.   Poorly chosen cultivars may
flower before the plant has grown to sufficient size to maximize
yield, or the flowering may be so late that the beans freeze
before they are mature.
 
Types of Soybean Products
 
The main soybean products in international trade are beans, defatted
meal, and crude, degummed oil.   The beans are usually purchased
for processing to crude oil and meal.   The crude oil is
further refined to edible oil.   The meal is used mainly as animal
feed, but can be processed into ingredients for human foods:
full-fat flours, concentrates (defatted meals with the soluble
sugars removed), and isolates (purified protein containing at
least 90 percent protein).
 
Soy products made for direct human consumption, for example soy
milk and soy curd, are normally not traded internationally because
of their susceptibility to spoilage, but soy sauce and
certain other fermented products are stable and can be shipped
internationally.
 
Composition of Soybeans
 
The soybean is particularly valuable because both oil and meal
are marketable products.  About 20 percent of the weight of soybeans
is oil and 40 percent is protein.   The rest is carbohydrate,
moisture, and ash.  Properly stored soybeans contain less than 13
percent water.
 
The oil portion is evenly dispersed throughout the bean in structures
called lipid bodies, which are too small to be seen in a
light microscope.  The oil is similar in composition to other
vegetable oils with a high concentration of polyunsaturated fatty
acids that are thought to be useful in the diet to protect
against coronary heart disease.   Extracted oil usually contains 1
to 3 percent of phospholipid or gums, which tend to precipitate
on storage of the crude oil.   For that reason they are usually
removed by washing the oil with water.
 
Other minor impurities in crude soybean oil that are removed in
refining steps are free fatty acids, pigments, and flavor compounds.
Since the oil is a liquid at room temperatures, hydrogen
is added to the polyunsaturated fatty acids to convert the oil
into margarines, shortenings, and other solids.
 
The defatted meal that remains after oil extraction contains
valuable protein that is useful in foods and feeds.   The protein
products available as soy meal or flour contain 44 percent protein
if hulls are added back or 47.5 percent protein without
added hulls.  For animal feed, the soy meal is normally mixed with
other ingredients to give a protein level of about 15 percent in
the final ration.
 
Soy meal is heated not only to remove the extracting solvent, but
also to inactivate proteins that may retard animal growth.  Trypsin
inhibitor is the name of one such protein that has been widely
studied and is known to inhibit growth in young animals.
 
2.  PROCESSING OF SOYBEANS
 
Oil Removal by Solvent Extraction
 
This discussion will emphasize the predominant products and processes
of commercial importance.  The main oil removal process is
solvent extraction.  It yields a complete oil removal (less than 1
percent oil remaining in the meal) and gives a meal that has not
been heat damaged.  Solvent-extraction plants can process 500 to
4,000 tons per day.
 
The conditions under which beans are stored greatly influences
the quality of oil that may later be extracted from them.  To
ensure oil quality the needed storage conditions are as follows:
 
     1) Moisture content:  13 percent or less to prevent mold
growth.  However, very dry beans tend to split when being transferred,
and the splitting lowers the oil quality.
 
     2) Temperature:  as low as feasible to minimize mold growth.
 
     3) Cleanliness:  insects or other contaminants can provide
moisture to start deterioration, which leads to increased temperature,
further increases in moisture, and spoilage.
 
To prepare soybeans for solvent extraction they are cracked into
several pieces and the hulls are removed by blowing air.  Hulls,
which make up about 8 percent of the weight of beans, do not contain
oil and are separated to gain space in the extractors for
the oil-bearing tissue.  The cracked pieces are conditioned by
steam to give a moisture content of about 10 percent at 170 [degrees] F
(77 [degrees] C).  The conditioned pieces are turned into flakes at this
temperature by putting them between smooth rollers.   A flake
thickness of 0.01 inch (0.025 cm) favors rapid solvent extraction.
Thinner flakes extract even more rapidly but also tend to
break into fine particles that clog the beds and cause solvent to
cut channels through the flakes instead of flowing smoothly
through them.
 
The flakes are conveyed to extractors.   These exist in many different
forms, but all use beds of flakes 1 to 3 feet (30 cm to 90
cm) deep.  The solvent, commercial hexane with a boiling point of
about 145 [degrees] F (64 [degrees] C), is pumped over the flake beds so that the
flakes entering the extractor are contacted by solvent that already
contains oil, while the flakes leaving the extractor are
contacted by fresh solvent.
 
A newer procedure for preparing flakes for extraction puts them
through an extruder (or enhancer) to form pellets.   Pellets are
easier to extract and hold less solvent than flakes, making extraction
more efficient.
 
After extraction the hexane is recovered from the oil and from
the meal and reused.  Since the hexane is extremely flammable,
solvent extraction plants must be designed to minimize chances of
sparks or open flames.  Equipment is designed to minimize loss of
hexane for both safety and economic concerns.   The solvent is recovered
in heat exchangers or flushed away by bubbling steam
through the product.
 
Solvent is removed from the defatted flakes by steam injection in
a device called a desolventizer-toaster, which also heats the
flakes to inactivate compounds such as trypsin inhibitor.  The
flakes are then cooled and ground to the correct particle size
for feed mixing.
 
Oil Removal Without Solvent
 
The earliest techniques for recovering oil from oilseeds involved
pressing the seed with devices that used levers or screws.  Later,
hydraulic presses replaced the mechanical presses.   Today's most
efficient way to press oil uses an expeller, a screw-shaped device
rotating within a horizontal, heavy-steel, cylindrical cage.
As the oilseeds enter at one end of the cylinder, they are subjected
to high pressures between the rotating screw and the stationary
cage.  The pressure forces oil through openings in the
cage, while the residual press cake is carried horizontally in
the direction of the shaft and is discharged at the other end of
the cylinder.
 
Expellers work best with oilseeds containing 40 percent oil or
more, but are less effective with soybeans, from which only
three-fourths of the oil is recovered by their use.   Nevertheless,
expellers have great versatility and are the best method if many
different kinds of oilseeds are being crushed.   Expellers are free
of the many safety problems involved in solvent extraction.  Capacities
of individual expellers are much less than for solvent
extraction plants, with the biggest expellers handling about 60
tons/day.  One can choose from a wide range of sizes of expellers
to fit the capacity of the crushing operation.
 
Soybeans need to be prepared for treatment by expellers much the
same as for treatment by solvent extraction.   They should be
cleaned, cracked, and flaked for the greatest oil yield.
 
The meal obtained from expellers contains more residual oil than
from solvent extraction and therefore has a tendency to become
rancid.  Highly rancid meal can be dangerous for animal feeding
because the hydroperoxide content makes the meal toxic.   Another
problem with the meal is that considerable heat is generated
during expelling.  If the meal is scorched by the heat, its nutritive
value may be decreased.
 
Oil Refining
 
Crude soybean oil, whether from solvent extraction or expellers,
is refined to convert it to a high quality, edible oil.   The minor
components in crude soybean oil that are removed during refining
are gums (phospholipids or lecithin), free fatty acids, pigments,
and flavor compounds.
 
The gums are removed because they are insoluble in the oil and
gradually precipitate out of the oil during storage.   The precipitated
material ("foots") is viscous and difficult to remove from
storage tanks or ship bottoms, and so it is often removed at the
crushing plant before the crude oil is shipped to a refinery.  The
recovered gum or lecithin is a valuable by-product and is used by
the food industry as an emulsifier and anti-sticking agent.
 
The gums are removed by washing oil with water.   About 1 to 2
percent water is added to the oil, and after a thorough mixing,
the oil and water are separated by centrifuging.   The gums come
out with the water phase, but some oil is lost as well.   Also, the
oil has to be dried after degumming to remove traces of water.  If
the gums are not recovered for resale as lecithin, they may be
added to soybean meal to increase its caloric value.
 
Free fatty acids are removed because they lower the temperature
at which heated oil begins to smoke.   Smoking oil is undesirable
for cooking.)  To remove free fatty acids, the oil is washed with
a dilute lye (sodium hydroxide or potassium hydroxide) solution.
The lye changes the fatty acids to soaps, and they are removed in
the lye solution by centrifuging.   The fatty acids may be recovered
for soap manufacture, or they may be added to meal.   Sometimes
both gums and free fatty acids are removed in a single
washing with dilute lye.
 
Excessive pigments in the oil do no harm, but the oil darkens
with repeated heating.  Dark oil is considered of low quality, and
manufacturers find that light colored oil sells better than dark
colored oil.  Pigments (and remaining traces of gums, free fatty
acids, and minerals) can be removed by bleaching, which is done
by adding specially mined clays to the oil.   The clays adsorb the
unwanted materials and are separated from the treated oil by
filtration.  Valuable oil is adsorbed along with the unwanted
materials, but normally recovery of the oil is not cost effective.
The bleaching clay is discarded after one treatment.
 
The distinctive flavors of such oils as olive, peanut, or sesame
are desirable.  The distinctive flavor of soybean oil is not desirable,
and so the flavors are removed to produce as bland an
oil as possible.  Flavor compounds are difficult to remove, and
the only effective means is high temperature (500 [degrees] F/260 [degrees] C) steam
distillation under vacuum, a process is called deodorization.
 
Other processes for making soybean oil more useful as food include
hydrogenation to convert the oil to a solid for use as a
shortening or margarine, and winterization to prevent crystals of
fat from forming when the oil is chilled.
 
Soybean Concentrates and Isolates
 
 
Because the protein of soybeans is nutritious and easily available
in high concentrations, people have sought ways to incorporate
it into human diets.  Full-fat or defatted flours as starting
materials contain the soluble carbohydrates that are naturally
present in soybeans.  Some of the sugars (raffinose and stachyose)
are not digested and absorbed but are fermented by microorganisms
in the gut, a process that causes distressing intestinal upsets.
Consequently, processes have been developed to remove the soluble
sugars while concentrating the proteins.   Removal of soluble sugars
from defatted flours gives a concentrate with 70 percent
soybean protein.  Removal of all carbohydrate from defatted flours
gives a product with more than 90 percent soybean protein.
 
Concentrates are produced by making the protein portion of the
flour insoluble in water and then extracting the soluble carbohydrates
with water or water-alcohol mixtures.   The protein can be
made insoluble in water by extracting flours that have been heated
in the desolventizer-toaster and using hot water--150 to 200 [degrees] F
(66 to 93 [degrees] C)--for the extraction.   Alternatively, flours that have
been desolventized under vacuum to maintain protein solubility
can be extracted with water-alcohol (60 to 80 percent ethanol)
mixtures or at a pH of 4.5 to remove soluble sugars.
 
The resulting protein concentrates have varying degrees of protein
solubility.  Protein solubility is measured by a nitrogen
solubility index (NSI) or a protein dispersibility index (PDI).
The higher the NSI or PDI the more soluble the protein.   For example,
concentrates produced by hot-water leaching have low NSIs of
about 5, while concentrates produced by low-pH leaching have high
NSIs of about 70.  High solubility would be useful if the concentrate
were to be used in a high protein drink, whereas use in
weaning food may not require high solubility.
 
Soy-protein isolates are produced by extracting defatted flours,
which have been desolventized under vacuum to maintain protein
solubility, with dilute alkali.   The protein solution is then precipitated
by adding acid and the protein curd is recovered.   If
the protein curd is washed with alkali to remove the acid, the
protein will become soluble, or the curd may be washed with water
and dried as an insoluble protein isolate.
 
Many uses have been found for soybean concentrates and isolates
in the human diet.  They may be mixed with other foods to take
advantage of the protein that they contribute, for its nutritional
value or its improvement of the texture or solubility of the
mixture.  They may be used in infant foods or formulas for their
nutritional value.  Also, concentrates and isolates can be texturized
by putting a suspension of the protein through an extruder.
The extruded proteins have chewy textures that can simulate meats
and cheeses when modified with flavors and colors.
 
One problem with concentrates and isolates that has not been
solved is an off-flavor that resembles the raw soybean.   Apparently,
lipid oxidation (rancidity) occurs during solvent extraction
of the oil.  The oxidized compounds combine with the protein and
their flavors are very difficult to remove.
 
Nonfermented Soybean Products
 
Although most soybeans are utilized as oil and meal as described
above, there is a wide range of other soybean products.   These are
mainly the soybean foods traditional in many parts of eastern
Asia.  Their production may sometimes involve microbial fermentation.
Some products that do not require fermentation are described
below.
 
Soy Sprouts.  Soy sprouts may be eaten as a cooked vegetable
throughout the year.  They are used in soups, salads, and side
dishes.  During sprouting the galactose-containing sugars (raffinose
and stachyose) are metabolized by the soy plant; their disappearance
reduces flatulence problems among consumers and produces
Vitamin C.
 
The dry beans are soaked in water (12 hours is usually sufficient)
and placed in a covered container in the dark.   The container
must have a drain.  The beans are sprinkled with water periodically
to keep them cool and moist, but they should not be submerged.
 
After five to ten days (depending on the temperature), the
sprouts will have reached two inches (5 cm) in length and are
ready to be cooked.  Soybean sprouts are a fresh product and must
be eaten soon after production or they will spoil.   As with any
fresh product, refrigeration may retard spoilage for a week or
two.
 
Fresh, uncooked soy sprouts have an intense beany flavor due to
enzyme activity.  Boiling or steaming the beans for two to four
minutes will inhibit the enzyme activity, minimize the beany
flavor, and still retain a crisp texture in the sprouts.
 
Soy milk.  Presoaked soybeans are ground with water and filtered;
the water extract is known as soy milk.   As with soy sprouts there
is an intense beany flavor that can be minimized by heating either
before or after filtering.  The soy milk may be consumed cold
or hot and may be flavored in many ways.
 
The basic process outlined above may be modified to increase
yield, to minimize off-flavors, and to increase efficiency of the
extraction process.  There are several companies now producing soy
milk on a large scale for sale in Asian countries.   The final
product may be handled by pasteurization and refrigeration in
bottles much the same as cow's milk, or it may be sterilized and
aseptically packaged in cartons.
 
The material remaining after soy milk extraction (soy pulp or
okara) is just as nutritious as the soy milk but is difficult to
market in a palatable form.  When generated in large quantities by
commercial plants, the soy pulp is often sold for animal feed.
 
Soy milk compares favorably with cow's milk in nutrients.  The fat
content is less in soy milk and contains less saturated fat.
There is no lactose in soy milk to cause problems for those people
who are lactose intolerant, but the raffinose and stachyose
sugars can have similar effects.   Soy milk protein lacks enough of
the essential amino acid methionine to satisfy rats in feeding
experiments, but seems to nourish human infants well.
 
Soy Curd.  A protein-fat curd can be precipitated from soy milk
by treating it with calcium salts.   This curd is analogous to the
curd that can be separated from cow's milk and used in cheese
manufacture.  The soy curd (known as tofu) is used in soups,,
cooked with meat and vegetables, or eaten with special seasoning.
 
The process for producing soy curd starts with soy milk.  Calcium
sulfate is dissolved in water and stirred into the hot soymilk
(158 to 176 [degrees] F, 70 to 80 [degrees] C).   A curd forms, and after it settles,
the fluid is poured off and the curd is pressed to remove excess
fluid.  Moisture content of the final curd is about 85 percent.
 
Depending on the process, soy curds of varying textures may be
produced.  A very soft texture may be achieved by using concentrated
soy milk and just enough coagulant to gel the whole mass.
In this case no pressing is used.
 
The final curd may be fried, dried, or frozen to produce a variety
of products with different textures and keeping qualities.
The usual fresh soy curd has a very short shelf-life, which can
be extended by refrigeration.   If the soy curd is pasteurized and
refrigerated, it has a shelf-life of about one week.
 
Fermented Soybean Products
 
Soy Sauce.  The process for making soy sauce is more complicated
and time consuming than for the fresh soybean products.   The raw
materials are usually a mixture of defatted soy flakes and roasted
wheat.  These materials are inoculated with pure mold cultures
Aspergillus oryzae or Aspergillus sojae); with strong aeration
the mold grows rapidly.  In about three days at 86 [degrees] F (30 [degrees] C), the
greenish-yellow material is harvested.   This is the starter culture
(koji) that provides enzymes for carbohydrate and protein
breakdown during the fermentation.
 
The starter mixture is placed in brine containing 17 to 18 percent
sodium chloride and may be inoculated with bacterial and
yeast cultures.  The fermentation tanks are deep to encourage
anaerobic fermentation, which takes six to eight months.
 
To finish the process the fermented mash is filtered to produce
raw soy sauce and a press cake.   The raw soy sauce is heated to
158 to 176 [degrees] F (70 to 80 [degrees] C), which develops flavor and aroma, inactivates
enzymes, and pasteurizes the product.   A final filtration
removes any precipitated substances, and the soy sauce is bottled
and sold.
 
Soy sauce is a dark brown liquid used primarily as a condiment.
It has a salty taste and meaty flavor due to a high content of
aspartic and glutamic acids (as monosodium glutamate).
 
Soy Paste.  Originally soy paste or miso was the press cake remaining
after removal of liquid soy sauce and was recovered as a
condiment.  Now soy paste in produced in a separate fermentation.
Usually a rice- or barley-based starter culture is used.  The
starter is added to cooked whole soybean mash.   After adding salt
and moisture, the mixture is fermented for one to three months.
 
The final product is achieved by pressing and pasteurizing the
soy paste.  This condiment can be used as a base for soups or as a
seasoning for meats and vegetables.   There are many different
types of soy paste depending on differences in starting materials,
fermentation times, and added ingredients; for example, red
peppers.
 
Fermented Whole Soybeans.  Two soybean products fit into this
category:  tempeh from Indonesia and Malaysia, and natto from
Japan.
 
Tempeh production starts with water-soaked, dehulled soybeans
that are boiled for 30 minutes, drained, and surface dried.  The
batch is fermented with the sold Rhizopus oligosporus using a
starter culture from a previous batch.   The inoculated beans are
wrapped to provide a humid enrironment; banana leaves were used
originally as wrappers, but plastic is equally effective.  Aerobic
growth of the mold continues for 1 or 2 days, until the mass of
beans is bound together by the white mycelium of the mold.  The
brief fermentation does not protect tempeh from spoiling, and it
should be handled as a fresh product.
 
Tempeh can be baked, or sliced and fried in coconut or other oil.
It is frequently consumed in soups or as a side dish with a main
meal and is also popular as a snack.
 
Natto is similar to tempeh in that it is a whole-bean product
subjected to a brief fermentation primarily for flavor and texture
development.  Natto production also starts with presoaked
soybeans that are cooked until tender.   After draining and cooling,
the soybeans are inoculated with Bacillus natto, an aerobic
bacterium, and incubated in a quite warm environment (104 to
109 [degrees] F, 40 to 43 [degrees] C) for 12 to 20 hours.  The bacteria produce a
sticky polymer from glutamic acid that binds the soybeans together,
and produce a characteristic musty flavor.
 
Natto is essentially a fresh product and must be consumed soon
after production, but it can be preserved by drying.
 
Food Mixtures.  Soybean protein has an amino-acid composition
that complements the protein of cereal grains.   Thus a mixture of
soybeans with wheat or maize provides protein nutrition for humans
that is superior to soybeans, wheat, or maize eaten alone.
This fact has been recognized in many cultures, where combinations
of beans and cereals are traditional foods.
 
The realization that high quality protein mixtures can be prepared
from relatively low-priced vegetable proteins has led to a
variety of products.  These vegetable protein mixtures were often
developed in government or private laboratories for use by those
who had difficulty in obtaining a nutritious diet.   Names and
countries of origin of some of these products are:   Incaparina
(Guatemala), Faffa (Ethiopia), Maisoy (Bolivia), and Pro Nutro
South Africa).  Although the products are very nutritious (often
they are supplemented with vitamins and minerals) and can be
produced relatively cheaply, they have not become popular foods.
Probably, problems with flavors and textures as well as the perception
of being "poor people's food" are responsible in part for
the low acceptance of these nutritious protein foods.
 
The U.S. government has developed a series of products based on
the concept of a cheap but nutritious vegetable protein mixture.
Corn-soy milk (CSM) and wheat-soy blend (WSB) are two examples.
These food products are used as donated foods for famine relief
or disaster relief.
 
A final example of a mixture of soybeans with wheat to improve
nutrition is composite flour.   As low-income nations have improved
economically, some have dramatically increased their wheat imports.
The wheat is used primarily for various breads and baked
goods, which are popular foods worldwide.   Wheat alone does not
provide nutritious protein, and the wheat flour can be improved
nutritionally by addition of soybean flour.
 
However, the addition of soybean flour must be carefully controlled,
as it decreases the desirable bread-making attributes of
wheat flour.  Breads made with soybean supplemented flours tend to
have lower loaf volumes and to be more dense than those made with
wheat flour alone.  Research has shown that soybean flour added to
wheat flour in amounts up to about 12 percent greatly improve
protein nutrition without adverse effects.   Loaf volume can be
improved by adding such emulsifiers as calcium (or sodium) stearoyl
lactylate.
 
3.  ALTERNATIVE OILSEEDS AND PROCESSES
 
Other Oilseeds Compared with Soybeans
 
Many oilseeds can be used as alternatives to soybeans for production
of edible oil. These include canola, cottonseed, rapeseed,
safflower, and sunflower.  After oil extraction, the remaining
meal is generally useful as an animal feedstuff but may need
special treatment to remove or modify harmful substances.   The
processes for alternative oilseeds are not widely different from
those used for soybeans but do vary somewhat.   For example, dehulling
processes differ depending on the nature of the seed.
 
Most oilseeds contain more oil than the 20 percent present in
soybeans.  Consequently, they are difficult to flake.   In such
cases the meats are put through a press or expeller first to
remove a large part of the oil, and then they are solvent extracted
to remove as much oil as possible.
 
Although other oilseeds are known to produce excellent vegetable
oil, often in higher yields than from soybeans, the protein products
from other oilseeds are generally inferior.   The protein
concentrates and isolates from soybeans are the only such products
commercially available and regularly used in the food supply.
Similarly, the foods from soybeans based on traditional
Asian products are not duplicated by products from any other
oilseed.
 
Alternative Processes
 
The only reasonable alternative to solvent extraction of oil from
soybeans is the expeller, which has already been discussed.
 
For various food products produced from soybeans, such as soy
milk, tofu, tempeh, soy sauce, etc., the size of the equipment
ranges from household size to large commercial units.
 
Most of the products made from soybeans are extensively processed.
It is not often that soybeans themselves are simply cooked
and eaten.  Some possible reasons are the long time needed to
soften soybeans by cooking to make them palatable, the high satiety
value due to the oil content, and problems with intestinal
distress due to the soluble sugars.   Extensive work has been done
at the University of Illinois (USA) International Soybean Program
to develop palatable soybean products for direct use with a minimum
of processing.
 
Because of the wide range of products and processes covered, this
paper gives few details on specific equipment needed, costs of
production, or marketing prospects.   Other sources are listed in
the References.
 
Probably the best sources of information for starting a soybean
processing operation are the people already doing business in
one's own locality.  Starting on a small scale and basing future
decisions on knowledge already gained from experience is recommended.
 
4.  COMMERCIAL TRENDS
 
In the past 50 years there has been a huge increase in the production
of soybeans in the world.  At least 90 percent of that
increased production has been used to produce food oil and animal
feed.  Traditional soybean foods, including soy sauce, soy milk,
and tofu, have continued to be well accepted but with no large
increase in consumption.
 
There is no reason to believe that these trends are about to
change.  As people have become more affluent, they have consumed
more animal products and more vogetable oils.   The soybean is a
source of the kinds of foods people will be demanding in the
future.  Moreover, the relatively low cost of soy protein offers
the possibility of global improvement of nutrition.
 
There will be changes in soybean products and processes.   From
present efforts, one can predict the future development of 1)
processes for efficient and energy-conserving recovery of soybean
products; 2) processes to improve the quality of the extracted
oil; 3) processes to improve the flavor and functionality of
soybean protein products; and 4) new cultivars for specific purposes,
through biotechnology coupled with traditional plant-breeding
techniques.  For example, varieties may be developed with
changes in their fatty acid composition to minimize saturated
fatty acids.  Others may be developed that will yield a superior
tofu.
 
The remarkable versatility and worldwide acceptance of the soybean
as a food source is likely to guarantee increased usage for
years to come.
 
 
                       REFERENCES
 
All addresses are in the USA unless otherwise stated.
 
BIBLIOGRAPHY
 
American Soybean Association.   Soya Bluebook 1989.  St. Louis:
American Soybean Association, 1989.
 
American Oil Chemists' Society Staff and others (eds.), Handbook
of Soy Oil Processing and Utilization.   Champaign, Illinois:
American Oil Chemists' Society, 1980.
 
Applewhite, T.A. (ed.), Bailey's Industrial Oil and Fat Products,
4th ed., vol. 3. New York:  Wiley, 1985.
 
Snyder, H.E. and T.W. Kwon, Soybean Utilization. New York:  AVI
Publ. Co., 1987.
 
Swern, D. (ed.), Bailey's Industrial Oil and Fat Products. 4th
ed., Vols. 1 & 2. New York:   Wiley, 1979 (v. 1), 1982 (v. 2).
 
Wilcox, J.R. (ed.), Soybeans:   Improvement, Production and Uses,.
2nd ed. Madison, Wisconsin:  American Society of Agronomy, 1987.
 
ORGANIZATIONS
 
See Soya Bluebook 1989 for a complete listing of soybean organizations
worldwide.
 
American Soybean Association, P.O. Box 27300, St. Louis, Missouri
63141.  Phone 314-432-1600; FAX 314-567-7642.
 
Soyfoods Association of North America, P.O. Box 234, Lafayette,
California 94549.
 
SUPPLIERS AND MANUFACTURERS
 
See Soya Bluebook 1989 for a complete listing of suppliers and
manufacturers.
 
Bean Machines, Inc., 390 Liberty Street, No. 2, San Francisco,
California 94114 USA.  Phone 415-285-9411.
 
Takai Tofu and Soymilk Equipment Co., 1-1 Inari, Nonoichi-machi,
Ishikawa-ken, 921 Japan.
 
Tiny Tech Plants Pvt. Ltd., Gondal Road, Rajkot 360002, India.
 
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