Staged-regulation of phenolic release to enhance its antioxidant activity in oats through enzyme hydrolysis synergistic Monascus fermentation.

Phenolic compounds in oats contribute to their health benefits but predominantly exist in insoluble bound forms with low bioaccessibility. To address this issue, this study developed a phased processing strategy combining enzymatic hydrolysis and Monascus fermentation to enhance the release of bioactive phenolic in oats. Results showed that adding cellulase in the mid-fermentation stage effectively increased the phenolic content by 21.23 times (23.34 mg GAE/g DW), compared with unfermented oats. HPLC analysis revealed substantial increases in free phenolic acids, with vanillic acid and chlorogenic acid contents rising to 215.22 mg/kg (35.92-fold) and 150.90 mg/kg (16.00-fold), respectively. Structural analysis via scanning electron microscopy confirmed the degradation of oat cell walls, supporting microbial growth and facilitating phenolic compound release. The free phenolic fractions exhibited potent antioxidant activities, which were strongly correlated (r > 0.91, p ≤ 0.001) with chlorogenic acid, quercetin, and vanillic acid content. These results demonstrated that the combined microbial-enzymatic approach was a highly effective bioprocessing strategy for producing value-added oat products with enhanced phenolic bioaccessibility and antioxidant capacity.