Soya beans meal

There are 3 main processes to extract soybean oil:

• The most common process consists in extracting oil from soybean flakes by solvent. In the USA, virtually all soybeans (99%) are solvent-extracted. This method is the most efficient and about 1.5% oil is left in the resulting soybean meal.
• The second method consists in a mechanical extraction by a screw press (expeller). This method yields less oil and a soybean meal containing more than 5% residual oil.
• The third method combines extruding and expelling of soybean flakes, and uses solvent for oil extraction (Johnson et al., 2018).

Before extraction, the soybean seeds undergoes differents treatments aimed at increasing oil extraction and soybean meal quality (Johnson et al., 2018; Dunford, 2012).

Pre-extraction treatments

Cooking

Cooking the seeds has positive effects on: moisture conditioning of seeds and easing dehulling, oil viscosity reduction, increasing plasticity of seed, breaking of cell walls, protein clotting by denaturation, sterilization and deactivation of thermosensitive enzymes, and destruction of thermolabile antinutritional factors (ANFs) (Dunford, 2012; Laisney 1992).

Crushing and flaking

Crushing and flaking operations promote solvent extraction step by changing the permeability of the soybean flakes (Dunford, 2012).

Dehulling

Dehulling is a facultative process that separates the oil-rich kernel from hulls which represents 8% of the seed and are mainly fibrous containing limited amount of oil. Dehulling also removes antinutritional factors.