Food Lipids: Chemistry, Nutrition, and Biotechnology

Figure 6 Seed cleaner (shaking screens and aspiration).
reduces the yield of oil. Some seeds, such as soybeans, are often dried, dried and
conditioned, or heated prior to dehulling to help free the meat from the hull.
Corrugated roller mills or bar mills, which shear the seed, and impact mills,
which shatter the brittle seed coat, are used. The equipment cuts or breaks the hull,
respectively, to free the meat, a step often referred to as decortication. Sometimes,
the combination of sizing the seed with shaker screens prior to decortication and
using mills with different settings optimized for each seed size increases the efficiency
of decortication. Hull/meat separation systems comprising one or more shaker
screens, aspirators, and gravity tables are effective because the hull is often larger
and almost always lower in density and more buoyant in an airstream than the oilrich
meat. Hulls may be blended back with meal to control protein level, sold as a
separate coproduct for cattle roughage, or burned in boilers to generate steam and
electricity in the process known as cogeneration.
When making edible flours, more complete removal of hulls is required. More
than 90% of the hulls from soybeans must be removed to assure that the minimum
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