It’s necessary to ensure edible oil is safe enough for eating,so we need to refine crude oil to make that reach the food standards and could be sold in the market.
Crude oil does exists impurities,which not only affects the edible value and safe storage of oils and fats, but also brings difficulties to deep processing. However the purpose of refining is not to remove all impurities in oil, but to remove impurities in oil which has bad effect on eating, storage and industrial production. For example, protein, phospholipid, mucus, water and so on all need to be removed, while beneficial “impurities” such as tocopherol should be preserved.
Therefore, according to the different requirements and uses, remove the unwanted and harmful impurities from the oil to obtain refined oil that meets certain quality standards, which is the purpose of oil refining.