There are only a few basic production methods to obtain fats and oils from animal, marine and vegetable sources. These include rendering, pressure expelling and solvent extraction, which are followed by various refining and modifying procedures.
Rendering
Dry rendering and
Wet rendering.
Fat from animal tissues is extracted by heat, chopped and minced tissues are coated with
Water (wet rendering) or
Without water (dry rendering)
Wet method – Steam is used. This process results in good disintegration of cells and efficient separation of fat.
Dry method – Tissue is heated with steam in vacuum containers
Improved method – Division of fatty tissues into fine particle size after which flash heating is applied for 15 seconds. Then the product is pulverized and centrifuged.
This method gives high yield, bland and stable product.
Pressing: Done by pestle and mortar . Oil efficiency is less. Gives natural flavor and De oiled cake good for cattle feed.
Solvent extraction: This is more efficient method than pressure extraction. Commonly used organic solvent in solvent extraction is hexane.
Refining: Oil extracted by above methods is crude and contain many other constituents like free fatty acids (FAA) , unsaporifiable matter, gums, waxes, mucilage, colouring matter, metallic contaminants, undesirable odoriferous constituents etc.
In refining
Suspended particles are removed by filtration and centrifugation
FFA are removed by alkali treatment
De-acidification and de-odorisation are done by blowing steam through hot oil under vacuum.
Remaining FFAs are removed by neutralization
Pigments are removed by bleaching (activated ‘C’ or chemicals)
De-odorisation is done by injecting steam through oil under decreased pressure
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