| Abstract: | Originally, oils were not refined but with the introduction of solvent extraction, refining became necessary. Crude cottonseed oil was refined by treating the oil with caustic soda and the same process was used for all other oils that needed refining. The subsequent introduction of centrifugal separators converted the original batch process into a continuous process. Degumming was introduced to obtain lecithin but limited to soya bean oil. Physical refining was introduced for high acidity oils like palm oil after the oil had been degummed to low residual phosphorus levels in the dry degumming process, in which the oil is first of all treated with an acid and then with bleaching earth. In Europe, further degumming processes were developed that allowed seed oil to be physically refined and later phospholipase enzymes were introduced to reduce oil retention by the gums and improve oil yield. Given these various oil purification processes, the refiner must decide which process to use for which oil in which circumstances. The paper provides a survey of what to do and when. It also discusses several topics that require further investigation and development. |
