Abstract: The present study aimed to comparatively investigate the effect of microwave treatment on residual peroxidase and lipase activity in brown rice using rice bran as control and to explore the change in rice quality during microwave treatment. Microwave was found to have a very significant stabilizing effect on brown rice, and the quality of rice was also affected. For the least quality loss and the best enzyme inactivation, the treatment conditions microwave power, treatment time and rice moisture content were optimized to be 700 W, 100 s and 21%, respectively by three-level, three-factor response surface analysis. Under such conditions, the theoretical residual lipase activity and rice broken rate were 15.66μmol/(g ·h) and 18.92%, respectively, with their experimental values being 16.25μmol/(g ·h) and 17.33%. After 4 weeks of the enhanced storage, the free fatty acid value was decreased by 13.7% compared to the untreated rice, demonstrating that the optimized microwave treatment is applicable for the stabilization of brown rice in practice.

Key words: brown rice, microwave stabilization, response surfaces analysis, lipase activity, rice quality