Optimization of bleaching conditions of roasted sesame oil

초록

Roasted sesame oil is famous for its characteristic flavor and high contents of physiologically good components. However, its dark color and low smoke point limit its use in food indust- ry. To make light-colored roasted sesame oil with higher smoke point, bleaching conditions of sesame oil were optimi- zed by determining smoke point, colors, free fatty acid and conjugated dienoic acid formation, carbonyl value, fatty acid composition, refractive index, viscosity, and contents of toco- pherol, sesamol, sesamin, and sesamolin. Roasted sesame oil was mixed with activated acid clay (0.5, 1.0, and 3.0 % ; w/w) at 70, 85, or 100° C for 20 min. The oil was centrifuged at 10,000 rpm and 4° C for 10 min. Bleaching of roasted sesame oil resulted in increase in smoke point and lightness in color. However, it decreased free fatty acid and conjugated dienoic acid contents, carbonyl values, refractive index, and viscosity, suggesting that bleaching could improve physico-chemical quality of roasted sesame oil. The more the bleaching clay was used, the better the oil was. Unlike the amount of acid clay, bleaching temperature did not significantly affect the oil quality. Tocopherol, sesamol, sesamin, and sesamolin were remained relatively constant except in the oil bleached with 3 % acid clay. They were not significantly different with respect to bleaching temperature. Among conditions carried out, 1 % of acid clay and 85° C were thought to be the best bleaching condition to give good quality of roasted sesame oil with better oxidation indicators and higher contents of toco- pherol, sesamin, sesamolin, and sesamols.