Dynamic changes in the phenolic composition and antioxidant activity of oats during simultaneous hydrolysis and fermentation

Solid-state fermentation (SSF) is the preferred method of enhancing the phenolic content of oats, while scientific optimization for improving specific phenolic compounds is limited. In this study, sequential targeting of phenolic conversion in simultaneous hydrolysis and fermentation (SHF) of oats was investigated. The results revealed that SHF with adding cellulase at 0, 6 and 12 days could increase the total phenolic content by 4.4%, 67.8% and 59.1%, respectively, over that of SSF. The a-amylase and CMCase activity were highly correlated with the soluble and insoluble phenolic contents in SHF (-6 and -12) systems (r > 0.8, p < 0.05). Interestingly, the content of phenolic fraction, such as ferulic acid, was up-regulated, whereas sinapic acid was down-regulated. These results indicated that the phenolic conversion occurred in SHF, resulting in variation in DPPH and ABTS(+) radical scavenging abilities. This research provided metabolic understanding of the optimization of phenolic compounds to increase the functional ingredient of oats.