摘要：Four different clays were compared for their capacities to adsorb chlorophyll and carotenoids; two major pigments in vegetable oils at 30 and 100°C. The clays used include Fulmont, Tonsil N, Tonsil ACC and a factory grade bentonitic clay. Extracts of chlorophyll and carotenoids were prepared from rocket plant and carrot, respectively. Each extract was then mixed with a refined, bleached and deodorized edible grade sunflower oil giving two oil blends, one rich in chlorophyll, while the other rich in carotenoids. The concentration of each pigment in the oil was adjusted, so that it will have reasonable absorbance(s) at the wave length(s) specific of each pigment. The removal of chlorophyll as well as carotenoids from each of the two blends was then studied using the four types of clays at different clay loadings at 30 and 100°C. The reduction in the oil absorbance at 670 nm due to bleaching was taken as an indicator of the amount of chlorophyll removed by bleaching. Similarly, the reduction in the total of the oil absorbances at three wave lengths being 432, 455 and 480 nm were taken as an indicator of the amount of carotenoids removed. The results have proved that the adsorption of both pigments obeyed Freundlich adsorption equation in case of one clay only being Fulmont. In view of the results obtained, the effects of temperature, clay type and clay load on the removal of each pigment have been explored. In addition, the four types of clays used were compared for their capacity to remove the phenolic compounds which have a beneficial anti-oxidant property. According to the results of this study it can be stated that carotenoids can be adsorbed on the bleaching clays more efficiently than chlorophyll. In addition, the effect of temperature on pigment removal by bleaching is much more pronounced in case of carotenoids compared to chlorophyll. Also, it has been found that bleaching of vegetable oils using Fulmont clay can yield oils of lighter color compared to other clays, while their bleaching using Tonsil ACC clay can yield oils more stable to oxidation.
