Soybean meal is the product obtained after oil has been extracted from whole soybeans. It usually exists in 3 forms: full-fat, defatted or defatted and dehulled, all containing different protein concentrations and metabolizable energy. The meal is usually processed into flakes to facilitate oil extraction from the actual beans.
Soybean meal contains an abundant amount of highly digestible proteins, composed of several essential amino acids for livestock and poultry. Hence, soybean meal is mainly used as a protein supplement in animal feed.
Soybean meal is produced mainly via 2 processes: the expeller process (pressing), and solvent extraction.
In this process, an expeller, consisting of a screw rotating inside a cylindrical cage is used to press the soybeans fed between the screw and barrel. The soybeans are then compressed progressively or step-wise as they move through the barrel.
The soybeans must be cleaned, flaked, cooked and dried before entering the expeller. For dehulled soybean meal, the beans have to be dehulled as well. Flaking enhances oil release as the distance travelled by the oil particles to the surface is shortened, speeding up the process.
In this process, solvents are used to dissolve the oil particles present within the soybeans to separate the meal and oil.
First, the soybeans are prepared for extraction by cleaning, conditioning, drying and flaking the beans fed into the process. The beans can also be dehulled, and classified into split and whole beans via sifting.
Once the beans are flaked and prepared for extraction, non-polar solvents are added for solid-liquid extraction of the oil particles from the soy flakes. Typically, light hydrocarbons consisting mainly of six-carbon alkanes known as “hexane” with a low boiling point are used for oil extraction.
Majority of soybean meal is used in animal feed as a source of protein. Soybean meal is highly palatable, high protein content, but low crude fiber content. Soybean meal can then be fed to different types of animals depending on its type: full fat, defatted, defatted and dehulled. It is suitable for ruminants, pigs, poultry, rabbit, fish, and crustaceans.