Refining of crude oil is done to remove unwanted minor components that make oils unappealing to consumers, while trying to cause the least possible damage to the neutral oil as well as minimum refining loss. The components to be removed are all those glyceridic and nonglyceride compounds that are detrimental to the flavour, colour, stability, or safety of the refined oils. They are primarily phosphoacylglycerols, free fatty acids, pigments, volatiles, and contaminants.
On the other hand, not all the minor compounds in fats and oils are undesirable. For example, phytosterols are considered of nutritional interest, and tocopherols with vitamin E activity, protecting the oil against oxidation are highly appreciated. Consequently, to reach the maximum oil quality all the steps of the refining process should be carried out with the minimum losses of desirable compounds.