Tocopherol distribution and oxidative stability of oils prepared from the hypocotyl of soybeans roasted in a microwave oven

Whole soybeans (Glycin max L.) were roasted by exposure to microwaves at a frequency of 2,450 MHz, and their hypocotyls were separated from other tiss ues (seed coat and cotyledons). The quality characteristics and composition in the hypocotyl oils were studied in relation to their tocopherol distrib utions and were evaluated as compared to an unroasted oil sample. Only mino r increases (P<0.05) in chemical and physical changes of the oils, such as carbonyl value, anisidine value and color development, occurred with increa sed roasting time. Significant decreases (P<0.05) were observed in the amou nts of phospholipids in the oils after microwave roasting. Nevertheless, co mpared to the original level, more than 80% tocopherols still remained afte r 20 min of roasting. These results suggest that the exposure of soybeans t o microwaves for 6 to 8 min caused no significant loss or changes in the co ntent of tocopherols and polyunsaturated fatty acids in the hypocotyls. The refore, a domestic microwave oven would be useful as a simple and quick mea ns for preparing hypocotyl oil of good quality.