Agriculture Reference
In-Depth Information
being the preferred type. Discolorations in the seedcoat usually indicate damage during
harvesting or a disease on the grain. As with other grains, the weight per bushel is a
major factor in determining the grade (No. 1, 2, 3, or 4). The best soybean grade
(U.S. No. 1) has a weight of 56 lb/bu (70 kg/hl). It also has minimal heat damage,
foreign material, and split grains.
Soybeans intended for specific markets may have other requirements. For example,
tofu soybeans sold in Japan go through a rigorous selection process to remove blem-
ished seeds, misshapen seeds, and small or large seeds, The processed seeds are pack-
aged and sold for home preparation of tofu, so that appearance is of great importance.
Soybeans intended for industrial processing have fewer restrictions.
3.5.11 Postharvest Processing
Most of the soybeans harvested are intended for industrial processing. Three main
methods
are
used
to
extract
oil
from
soybeans:
distillation,
expression,
and
solvent extraction.
Distillation involves passing steam through cracked soybeans to vaporize oils. As this
steam is cooled, it releases oils of different densities in liquid form. Expression simply
means pressing the grains after they have been cooked. Solvent extraction removes oil
from grain by mixing cracked grains with a nontoxic fat solvent such as hexane at low
temperatures. The solvent is then evaporated and recycled to extract more grain.
Soybean oil intended for human consumption will be further processed to remove
impurities, objectionable odors, and colors. Depending on the end use, the oil may be
hydrogenated to convert it to a semisolid and reduce oxidation. This gives it tempera-
ture stability and reduces breakdown before consumption. Common end products of
soybean oil are margarine and cooking oil.
The soybean meal remaining after oil removal is also used for human consumption.
A common product is textured soy protein (TSP) used in vegetarian dishes and cooking
ingredients such as Hamburger Helper. Processing of the meal also gives tofu and
soymilk. Soybean cake is another product used in animal nutrition. It has a high
protein content and makes up a significant portion of cattle and poultry rations.
Nonfood products using soybean as the main ingredient are too many to mention in the
space available. They range from paint and crayons to furniture and shampoo. Traditional
and genetically modified varieties of soybeans are being released for specific food and
industrial applications such as low saturated fat, high sucrose, or high protein types.
One hectare of soybeans can produce 205,920 crayons.
3.6
OTHER GRAINS
Many other grains are used by humans for food, fiber, and industrial applications. Their
omission is merely due to space limitations not importance in the human diet. Grain
legumes are especially important in some cultures as a source of plant protein.
