Solid-state fermentation with fungi to enhance the antioxidative activity, total phenolic and anthocyanin contents of black bean

In the present study, solid-state fermentation of black bean with various GRAS filamentous fungi including Aspergillus awamori, Aspergillus oryzae, Aspergillus sojae, Rhizopus azygosporus and Rhizopus sp. No. 2 was preformed to prepared koji. Mycelial propagation of starter organisms and antioxidative activity, including α-α-diphenyl-2-picyl-hydoxyl (DPPH) radicals, Fe2+-chelating ability, and reducing activity, were examined. Depending upon the starter organism, various amounts of mycelial propagation (23.5–67.3 mg/k koji) were found in the prepared black bean kojis. The methanol extracts of all the black bean kojis, except that prepared with Rhizopus sp. No. 2, exhibited higher levels of DPPH free radical-scavenging activity, Fe2+-chelating activity, and reducing power than did the non-fermented black bean. Taking into account methanol extract content, all the prepared kojis showed greater antioxidative activity than non-fermented black bean. Among the various koji extracts examined, extract of A. awamori-koji exhibited the highest antioxidative activity as did the A. awamori-koji when comparing its antioxidative activity with that of other kojis and non-fermented black bean. In general, the total extractable phenolic compounds and anthocyanins content in black beans increased after fermentation. This might lead to the increased antioxidant activities of black bean kojis observed.