Enrichment of phenolics and free radical scavenging property of wheat koji prepared with two filamentous fungi

In the present study, total phenolic content and antioxidant property of wheat (54% ethanolic extract) was drastically enhanced when fermented with two GRAS filamentous fungi, Aspergillus oryzae and Aspergillus awamori nakazawa. A. oryzae yielded significant (P < 0.05) amounts of phenolic compounds, DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS+ [2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid)] scavenging properties on 4th day of incubation compared to A. awamori on 5th day of incubation. A linear correlation was observed between total phenolic contents and activities of three different carbohydrate hydrolyzing enzymes (α-amylase, β-Glucosidase and xylanase) produced by A. oryzae. However, in case of A. awamori nakazawa, only two enzymes (xylanase and β-glucosidase) were mainly responsible for the release of phenolics. This study demonstrated that fermented wheat grain is a better source of phytochemicals compared to non-fermented wheat. In addition, different carbohydrate cleaving enzymes are responsible for the improvement of phytochemical properties of fermented wheat.