Off-odor in baijiu

Chinese liquor has an annual consumption of approximately 4 million kiloliters, creating a sales revenue of 500 billion Chinese Yuan in 2014. Strong aroma type liquors typically have strong fruity, pineapple- and banana-like aroma, accounting for about 70% of total liquor production.Compared with other aroma type liquors, the most characteristic process of making strong aroma liquor is the fermentation carried out in specialized rectangular soil pits, coated by a special mixture of fermentation mud made largely with clay and grain6. During the production of strong aroma type liquor, the pit mud provides a comfortable habitat for fermentation microbes, which are considered to play important roles in contributing to the flavor taste of the liquor The anaerobic microbes in pit mud could produce short chain fatty acids, such as caproic acid and butyric acid which were the main precursor of ethyl caproate. However, the complex microbial community also provides the off-odor through the microflora metabolism.