OXIDATIVE STABILITY OF HIGH FATTY-ACID RICE BRAN OIL AT DIFFERENT STAGES OF REFINING

The contents of natural antioxidants and the oxidative stability of rice bran oils at different refining steps were determined. Tocopherols and oryzanols were constant in crude and degummed oils but decreased in alkali-refined, bleached and deodorized oils. The process of degumming, alkali-refining, bleaching and deodorization removed 34% of the tocopherols and 51% of the oryzanols. During storage of deodorized oil for 7 wk, 34% of the tocopherols and 19% of the oryzanols were lost. The maximum weight gain, peroxide value and anisidine value were obtained from alkali-refined oil during storage. The order of oxidation stability was crude greater than or equal to degummed > bleached is approximately equal to deodorized > alkali-refined oil.