Effects of Ultrafine Grinding on the Composition and Activity of Black Rice Bran Polyphenols
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Abstract:
To investigate the effects of ultrafine grinding on the composition as well as the in vitro antioxidant and α-glucosidase inhibition activities of black rice bran polyphenols, ultrafine grinding was performed to prepare ultrafine black rice bran powder. The compositions, anthocyanin contents, total antioxidant capacities, oxygen radical absorption capacities, peroxide radical scavenging abilities, and α-glucosidase inhibitory abilities of polyphenols of ultrafine and coarse black rice bran powder were determined. The results showed that the particle size of black rice bran was significantly reduced by ultrafine grinding. Compared with those of the coarse powder, the extraction yields of free polyphenols, total polyphenols, and anthocyanins of ultrafine black rice bran powder were increased by 8.27%, 10.72%, and 21.97%, respectively. Furthermore, the extraction yields of phenolic monomers, such as ferulic acid, p-coumaric acid, and vanillic acid, were significantly increased, with no changes in the phenolic monomer composition. Polyphenols of the ultrafine powder exhibited higher antioxidant and α-glucosidase inhibitory abilities than those of the coarse powder. Particularly, free polyphenols were the main contributors to these activities. In conclusion, ultrafine grinding promotes the release of polyphenols and enhances the antioxidant capacity and α-glucosidase inhibitory abilities of black rice bran. This pretreatment method can be applied in the processing and utilization of black rice bran.
