Mechanism of n-propanol formation during solid-state fermentation of Chinese liquor

By taking measure samples in brewing workshop and using the synchronize simulate fermentation method in lab, the relationship between n-propanol content and yeasts and bacteria counts in Baiyunbian Daqu fermented grains was analysed and measured. The result showed that n-propanol content had positively correlated relationship with the yeast counts in fermented grains, while it had negative correlated relationship with the bacteria counts. Alcohol content of fermented grains had positively correlated relationship with n-propanol content basically. The n-propanol content in Xiaoqu fermented grains increased sharply after bottling for 24h and it reached the maximum at the 4d. The alcohol content and n-propanol content in pure inoculants which inoculated Saccharomyces cerevisiae and Rhizopus spp. and Daqu fermented liquor were close to each other. It showed that yeast was the main microbes which produced n-propanol in liquor. So the n-propanol was mainly produced as an alcohol by-product during the progress of saccharides anaerobic fermentation in solid state fermentation liquor, instead of decomposing protein progress by bacteria.