Effect of cooking of rice bran on the quality of extracted oil
2006
ANIL KUMAR, H.G. | KHATOON, S. | PRABHAKAR, D.S. | GOPALA KRISHNA, A.G.
While attempting to prepare a nutritionally superior rice bran oil, the effect of cooking of rice bran with various levels of added water on the quality of bran and extracted oil was studied. The rice bran (from IR-64 paddy, Indian variety) used was obtained from a local rice mill having 8% moisture and 19.3% fat. The levels of water incorporated were 0, 6, 12, 25, 50, 100, 200 and 400 g/100 g bran and were heated to boil (or to reach 105-110C) for 20 min and the contents cooled and dried in air. A sample of 100 g bran was heated similarly without the addition of water, which served as a control. The oil extracted from the control bran had color, 80 Lovibond units, free fatty acids (FFAs), 27%, tocopherols and tocotrienols, 103 mg per 100 g (mg%), and oryzanol, 2.39%. The water-treated, cooked and dried bran samples were extracted with hexane to recover the oil which had a lower Lovibond color (65-70), varied FFA (as % oleic acid) (25.4-33.2%) levels, reduced tocopherol and tocotrienol (3.9-62.3 mg%) content and a slightly higher oryzanol content (2.51-2.70%) compared to the oil extracted from the control bran. The changes were observed from the start at 6 and 12 g water/100 g bran addition stage itself and almost all tocopherols and tocotrienols (97-99%) were destroyed, while at the 50- to 400-g water addition stages tocopherol and tocotrienol destruction ranged from 51 to 72%. The study sheds light on the deleterious effect on tocopherols and tocotrienols in rice bran and extracted oil during cooking of rice bran, although there is an improvement in color and texture of cooked bran and color and oryzanol content of the extracted oil.
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