Reduction of off-flavor volatile compounds in okara by fermentation with four edible fungi

Abstract

This study aims to reduce beany flavors and gain new aromatic flavors of okara by using edible fungi. Four edible fungi (Wolfiporia cocos CGMCC 5.55, Wolfiporia cocos CGMCC 5.528, Wolfiporia Cocos CGMCC 5.78 and Tremella fuciformis CGMCC 5.466) were chosen to ferment okara. The volatile compounds in original and fermented okara were investigated by head space-solid phase microextraction-gas chromatography-mass spectrometry and gas chromatography-mass spectrometry/olfactometry. Before fermentation, 13 off-flavor compounds were detected in the okara. Hexanal and cis-6-nonenal were the main off-flavor substances with a relative content of 54.31% and 1.64%, respectively. After fermentation, the content of off-flavor compounds decreased, and new aromatic compounds were generated. The relative content of hexanal decreased to 0.37%, and cis-6-nonenal was not detected. After fermentation with Wolfiporia cocos CGMCC 5.528, phenethyl alcohol and linalool were generated (182.07 μg/L and 83.23 μg/L, respectively). All fermented products had very little characteristics of beany flavor. In conclusion, the use of edible fungi, especially Wolfiporia cocos CGMCC 5.528, can provide an effective and sustainable way to reduce the beany flavor and improve the flavor quality of okara.