Soybean oil processing usually strat from soybean seed oil preparation. The soybeans need to be cleaned, dried and dehulled before sending to the next extraction process. The soybean hulls needs to be removed because they absorb oil and give a lower yield. This de-hulling is done by cracking the soybeans and a mechanical separation of the hulls and cracked soybeans. Magnets are used to separate any iron from the soybeans. The soybeans are also need to be heated to about 75°C to coagulate the soy proteins to make the extraction process much easier.
In the soybean oil processing, you usually should cut the soybeans into flakes and then put them in a percolation extractors and immerged with a solvent. After removing the hexane, the extracted flakes only contain about 1% of soybean oil and is used as livestock meal or to produce food products such as soy protein. The hexane is separated from the soybean oil in evaporators. The evaporated hexane is recovered and returned to the extraction process. The hexane free crude soybean oil is then further refined.
Oil refining is another important process in soybean oil processing. The oil obtained from pressing or solvent extraction process always contains impurities such as phospholipids, FFA, pigment, off-flavor and other impurities. In order to make the oil edible, the impurities must be taken out; such a process is called “Oil Refining”. The oil-insoluble material are removed with filtration and the soluble materials is removed with different processes including degumming (removing of phosphatides), alkali refining (washing with alkaline solution to remove free fatty acids, colorants, insoluble matter and gums) and bleaching (with activated earth or activated carbon to remove colour and other impurities.
