The process of EDIBLE OIL REFINING generally comprises Degumming, Neutralization, Bleaching, Deodorization and Winterisation. Chemical refining is the traditional method whereby the free fatty acid of the crude oils is neutralized with Caustic Soda. The resultant Sodium Soaps are removed by Batch Settling or by means of Centrifugal Separators. The neutral oils are subsequently bleached and deodorized. This method can be used for reliably refining virtually all crude oils, including oils of low quality, with the exception of Castor Oil.

In all alternative methods of edible oil refining of Physical refining, the free fatty acids are removed by distillation in one stage of deodorizing. A fundamental criterion for using this method is that the crude oils should be degummed as effectively as possible. However, this is only possible to a limited extent with some crude oil qualities. Other oils, for instance, cottonseed oil or fish oils, are fundamentally not suitable for Physical Refining.