Dynamic changes in antioxidant activity and biochemical composition of tartary buckwheat leaves during Aspergillus niger fermentation

Aspergillus niger CJ-1 was applied to conduct fermentation process on tartary buckwheat leaves (TBL), and effect of fermentation time on antioxidant ability and chemical compositions was revealed. Antioxidant ability of TBL showed a three-stage change tendency during fermentation, which was relatively consistent with change in chemical compositions. Rutin and quercetin were identified as remarkable contributors among fermentation. Both total polyphenols, rutin and quercetin was positively being correlated with antioxidant activity of TBL. Results indicated that fermentation time influenced antioxidant activity by altering content of TBL phenolic compounds, which showed a three-stage change law: augmenting at the early stage of fermentation, declining at the medium stage of fermentation, and slightly changing during the last stage. This tendency suggested that fermentation was a potent means to promote antioxidant capacity of agro-food unless fermentation time was controlled. This study may provide a theoretical basis for producing fermented foods with high bioactivity.