Changes of physicochemical indexes and microbial communities in the brewing process of Shanxi aged vinegar

Taking Shanxi aged vinegar as research object, the dynamic changes of physicochemical indexes and the diversity of microbial community structure were analyzed during the fermentation. The functional microorganisms in the fermentation process were isolated by pure culture technology, and the isolated strains were identified by morphological observation and molecular biology technology. The results showed that in the alcoholic fermentation stage, the temperature first increased and then decreased, the reducing sugar content and pH decreased, and the alcohol content and total acid content increased slowly. Yeasts and bacteria were dominant, and their biomass reached the maximum after fermentation for 1 d, and then the number of all microorganisms began to decline slowly. The molds mainly existed in the early stage of alcohol fermentation, and then can't detected in the middle stage. In the acetic acid fermentation stage, the temperature first increased and then decreased, the alcohol content gradually decreased to 0, the total acid content increased, and the moisture and pH were basically stable. The yeast biomass decreased gradually, bacteria was the dominant flora, and its biomass first increased and then decreased, reaching the highest on the 3rd day of fermentation, and no mold was detected. A total of 83 strains of fungi and 158 strains of bacteria were isolated from the Jiulao and Cupei of Shanxi aged vinegar, and 33 species were identified, including 2 kinds of molds, 6 kinds of yeasts, 13 kinds of lactic acid bacteria, 11 kinds of Bacillus, and 1 kind of acetic acid bacteria which was identified as Acetobacter pasteurianus.