Improving free, conjugated, and bound phenolic fractions in fermented oats (Avena sativa L.) with Monascus anka and their antioxidant activity

This work aims to investigate the effects of fermentation with Monascus anka on the phenolic components and antioxidant activities of oats. Results revealed that the fermentation process significantly increased total phenolic content, especially free phenolic content. Moreover, the dominate phenolic compositions of free, conjugated and bound phenolic fractions from oats varied with fermentation. Both catechin in free phenolic fraction and ferulic acid in bound phenolic fraction were enhanced more than 100-fold, while the amount of newly generated rutin was up to 355.07 mg/kg in the conjugated fraction. All three phenolic fractions from fermented oats, especially the conjugated fraction, demonstrated greater DPPH and ABTS+ radical scavenging abilities than that of unfermented oats. It was revealed that most of the phenolic compounds had a strong positive correlation with antioxidant activities. Consequently, fermentation may be a potential approach to improve oats' phenolic content and antioxidant capacity for functional foods in health promotion.