Impact of solid‐state fermentation by Aspergillus niger 4Q and Cyberlindnera fabianii J2 on antioxidant and flavor properties of whole grain barley

Abstract Background and Objectives Aspergillus niger 4Q and Cyberlindnera fabianii J2 were isolated from a traditional Chinese sweet rice wine starter because of their better fermentation characteristics and sensory properties of final products. To understand the impacts of the cofermentation with Aspergillus niger 4Q and Cyberlindnera fabianii J2 in a solid state on the nutritional and physico‐chemical properties of whole grain barley, yellow barley and black barley were used as raw materials. Content of chemical and nutritional compositions, in vitro antioxidant activity, color, and volatile flavor compound analysis of untreated, cooked and fermented barley samples were evaluated. Findings The contents of total phenolic compounds, total flavonoids, and anthocyanin of black barley were 1.25 times, 1.21 times, and 2.05 times higher than those in yellow barley ( p < .05). After fermentation, the proteins, water‐soluble dietary fiber, and β‐glucan contents of both black barley and yellow barley samples were about respectively 1.3 times, 4.6 times, and 1.2 times higher than those in raw materials ( p < .05). Total proportion of phenolic compounds and flavonoids, along with the antioxidant capacity, free radical scavenging rate and Fe 2+ chelating activity were significantly increased ( p < .05). Lighter and brighter color were observed in fermented barleys which might be credit to the reduced anthocyanins. The acidic methyl esters, uniquely existed in untreated barley, were transformed into acetate esters after fermentation. Ethyl 3‐methyl‐acetate, with a fruity aroma, was the major proportion of esters in fermented barley, endued the unique flavor to fermented barley. Conclusions Solid‐state fermentation of yellow barley and black barley by A. niger 4Q and C. fabianii J2 could effectively improve their nutritional and physico‐chemical properties. Significance and Novelty This study may contribute to providing a solution for improving the nutritional and sensory preterits of whole grain barley, as well as a theoretical support for promoting the direct utilization of barley in food processing.