Stabilization of rice bran using microwave: Process optimization and storage studies

The study was aimed to stabilize raw rice bran obtained from freshly milled paddy of PB-1121 variety and conducted in two stages; to understand the effect of microwave power (2, 4, 6 W/g) and exposure time (1, 3, 5 min) in controlling the lipase activity during short term storage so that an optimum treatment combination for stabilizing the rice bran for its subsequent long term storage for at least three month could be devised. Free fatty acid (FFA) content, the primary indicator of lipase activity, was significantly (p < 0.05) affected by microwave treatment. Keeping in view the FFA content, oil yield, visible oil quality, moisture and protein content; treatment combination of 4 W/g + 5 min was found to be optimum in stabilizing the treated rice bran. The bran stabilized by optimized microwave treatment and bran obtained using traditional parboiling stabilization process (Sela) was compared. Microwave treated rice bran could be stored safely for a period of three months without any loss of nutritional quality as well as with high oil quality (FFA - 3%, PV - 7.63 meq/kg, TBA - 0.071 mg MDA/kg). The oil yield from the parboiled rice bran is significantly higher (23%) than microwave treated rice bran (21%).