Solid-state fermentation of grain sorghum to produce Chinese liquor: Effect of grain properties and fermenting culture

This study evaluated seven U.S. sorghum varieties and nine yeast strains for solid-state fermentation (SSF) to produce Chinese liquor (Xiaoqu baijiu). Among the tested sorghum varieties, Red Waxy had higher single kernel weight, kernel diameter, lower tannin content, and achieved the highest average ethanol concentration (17.7%, v/v). Supplementation of very high gravity fermentation yeast strain HA18 was shown to increase the ethanol concentration consistently regardless of sorghum variety. Strong positive correlations were found between ethanol concentration and crude protein/crude fat contents of distillers dried grains (DDG). Linoleic acid, oleic acid, and palmitic acid were the major fatty acids in sorghum DDG. The major flavor compounds in the fermentation products were ethyl lactate, isobutanol, isoamyl alcohol, phenylethanol, acetic acid, and 2,3-butanediol. The concentrations of these flavor compounds were significantly affected by sorghum grain properties and yeast strain, with more variations of phenylethanol, acetic acid, and 2,3-butanediol.