Optimization of microwave parameters to enhance phytochemicals, antioxidants and metabolite profile of de-oiled rice bran

Abstract

The current study delves into the impact of microwave treatment with different wattage and durations on phytoconstituents, antioxidant status, anti-nutritional factors (ANFs), and metabolite profiles of de-oiled rice bran. The total phenolics and flavonoids exhibited both up- and down-regulation based on specific microwave parameters, while an overall up-regulation in flavonol content was observed across all treated groups compared to the control. The DPPH and ABTS free radical scavenging activity, total antioxidant capacity, FRAP, CUPRAC, metal chelating activity, and ascorbic acid content were enhanced in most of the microwaved samples; however, longer microwave exposure at higher wattage led to their diminution. A treatment-specific reduction was observed for ANFs, viz., condensed tannin, oxalate, and phytate. HR-MS-based untargeted metabolomics revealed diverse primary and secondary metabolites that clustered in a group-specific manner, indicating prominent group-wise metabolite variations. Analyses of discriminating metabolites revealed non-significant differences in the overall levels of phenolics, flavonoids, vitamins and cofactors, sugars, amino acids, terpenoids, fatty acids, and their derivatives among the various treated groups compared to the control; however, several individual metabolites within these metabolite classes differed significantly. The current findings suggest that optimized microwaving of de-oiled rice bran can enhance phytochemicals and antioxidants while improving the metabolite profile.