Free phenolic contents and their antioxidant activities of fresh and fermented rice spent water

Abstract

A new rice milling produces large quantities of a wet byproduct, rice spent water (RSW) containing rice polishings. However, RSW is wasted or destined to undervalued uses. Therefore, the objective of this study was to improve the bioaccessibility of phytochemical phenolics in RSW by means of value-added fermentation process. This study was designed accordingly to compare the methanol-extractable free phenolic contents and their antioxidant activity in fresh and fermented RSW. The results showed that methanol extraction yielded 7 fold higher phenolic contents from the fermented RSW than from the fresh. In addition, the DPPH radical scavenging activity and the reducing power of each RSW equivalent were positively correlated with the methanol-extractable phenolic contents of each equivalent before and after the fermentation, respectively. These data suggest that more insoluble bound phenolic compounds may be freely released in RSW during the fermentation and the bioaccessibility of phytochemical phenolics in RSW may be improved.