Refining of vegetable oils is essential to ensure removal of gums, waxes, phosphatides and free fatty acid (F.F.A.) from the oil; to impart uniform colour by removal of colouring pigments and to get rid of unpleasant smell from the oil by removal of odiferous matter.
Refining is carried out either on batch operation or as continuous operation. With certain oils even physical refining can be carried out instead of chemical.