چكيده لاتين :
Introduction: In edible oil refining, either by chemical or physical process, the bleaching treatment is a critical step. The adsorbants used for bleaching can remove pigments and other impurities, such as soap, trace metals, phospholipids, and oxidation products. The removal of these impurities improves the sensory quality and the oxidative stability of the deodorized oil.
Materials and methods: The aim of this study was to investigate the adsorption effects of three activated bleaching earths (Persian bentonite, Pakestanish bentonite and German tonsil 131) on color, peroxide value, soap, free fatty acid percent (FFA%), chlorophyll, induction period, trace metals, anisidine value and phosphorus in alkali- refined soybean, sunflower, canolla and palm oils.
Results: The results showed that bleaching decreased colour, peroxide value, soap, chloroplyll, Fe, Cu, P, while the amount of acidity, anisidine value and induction period increased. Although the bleaching earths employed in this study had different chemical and physical properties, their effects on the oil components were insignificant and soyabean oil proved to be more responsive to bleaching by different earth.
Conclusion: It might be concluded that interm of economy, availability and bleaching power, the Persian bentonite might be regarded as the most suitable earth.
