Clay-heat refining of edible oils

The treatment of crude edible oils with sodium hydroxide solutions is the standard refining procedure in the industry. Refining with NaOH removes free fatty acids, some phosphatides, proteinaceous matter and some colored material. Up to now experience has shown that most oils cannot be deodorized satisfactorily unless they have been caustic-refined. In the past, when most crude oils contained several per cent of free fatty acids, caustic-refining offered itself as a particularly suitable means of preparation for further processing. In recent years the free fatty acid content of crude oils has been, in most cases, only a fraction of 1%, which could very readily be removed in the process of deodorization. A prerequisite for this would be to remove by some other means those substances that interfere with satisfactory deodorizing. It has been found that the process of bleaching can be used for this purpose if the oil is pretreated with 0.1–0.5% phosphoric acid and bleached at 325–350 F. The amount of bleaching clay required depends on the type of oil and its quality, but with many oils up to 2% clay is satisfactory. The amount of phosphoric acid necessary also depends on the type of oil. One of nine papers presented in the symposium “Processing of Edible Oils,” AOCS Meeting, Ottawa, September 1972.