摘要：Soybean oil (SBO) was miscella bleached in hexane using carbonized hulls of Jojoba (Jo), Jatrova (Ja), Peanuts (PN) and Pistachios (P) as alternatives to bleaching clays. Evaluation of bleached crude SBO with carbonized hulls was based on their delta-Free Fatty Acids (ΔFFA), reduction in Peroxide Value (PV), carotenoid content, color index and bleachability. Fullers Earth (FE) and Tonsil N (TN) were used for comparison with the carbonized hulls. Three oil: hexane ratios, 1: 0.5, 1:1 and 1:1.5 by volume and at Room Temperature (RT) and 50°C were used. It was found that oil hydrolysis during miscella bleaching and using seed hulls was very little in all treatments resulted in ΔFFA% between 2.65-3.12 at RT and 2.69-3.09 at 50°C compared to 3.29 ΔFFA% of crude SBO. The results proved that highest reduction in PV was achieved at 50°C and an oil to hexane ratio1:1.5 reaching 73.89 reduction percentage when using PN hulls. Also, Jo hulls resulted in more reduction in PV than FE under all conditions. Whereas Ja, PN and P gave more reduction percentage than TN in all cases. Concerning the effect, of using seed hulls in bleaching SBO, on carotenoid content the results showed that Jo and Ja gave the highest reduction in carotenoid content at oil to hexane ratio of 1:1 and at RT in comparison to the other hulls, TN and FE. Regression analysis indicate a polynomial correlation between the oil characteristics (ΔFFA%, reduction percentage in PV, carotenoid content and bleachability with the three oil: hexane ratios at the two temperatures, RT and 50°C, with r = 1. This study proved that miscella bleaching with carbonized hulls resulted in oils with less FFA, less PV and less carotenoids than the crude SBO. It also proved that it cannot act as a single bleaching agent by itself but it can be bleached with other clays.
