Ethanol/Moisture Contents in Fermented Grains and their Effects on the Yield and Quality of Chinese Luzhou-Flavor Liquor

The ethanol/moisture contents in fermented grains were measured and systematic experiments were carried out to investigate the optimal operation condition for distillation of Chinese Luzhou-flavor liquor. The results show that from the top surface (0 m depth) of fermentation tank to the bottom (2 m depth), the moisture content in the grains increases linearly from 60.67 wt.% to 70.44 wt.%, while the ethanol content presents a parabolic distribution with maximal content of 6.29 wt.% at 1.5 m depth. It is found that for efficient distillation of fermented grains, there exists an optimal steam flowrate at which the maximum yield of distilled liquor will be achieved. For the grains with given moisture content, the optimal steam flowrate keeps nearly constant with different ethanol contents, while for the grains with given ethanol content, the optimal steam flowrate increases as the moisture content become increased. Combined with the gas chromatography analysis, it is also presented that the distilled liquor obtained from the grains with higher ethanol content and/or lower moisture content will contain higher concentration of alcohol-soluble flavor compounds, so that the distilled liquor has better quality. The findings in this study provide important reference for the optimization of distillation process of Chinese Luzhou-flavor liquor.