Abstract: Oils are one the most essential ingredients of our daily food. Chemically oils are esters of fatty acids &glycerol. Esters of glycerol are commonly termed as Glycerides. The fatty acids present in oils may be saturated (or) unsaturated.

Basically, oils are extracted from the oil seeds either by mechanical expelling (or) by solvent extraction. The oils, as extracted from the seeds contain many impurities like Free Fatty Acids, Water, Partial Glycerides, Phosphotides, colouring materials (pigments) like β-carotene & Chlorophyll, Free Sugars, Glycolipids, Sterols, Waxes, toxicants like Gossypol & Afflatoxin, residues of pesticides &insecticides like Parathion & Malathion etc. All these impurities must be removed from the oil as they induce undesired properties in the oil & hamper further processes like hydrogenation.

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