Microorganisms and flavor formation in vinegar production with solid-state fermentation

The microbial distribution and quantity changes in different layers of vinegar fermented grains at different time were studied, and the factors affecting flavors formation were discussed. Results showed that yeast and lactic acid bacteria rapidly proliferated in the first five days, at the fifth day,the yeast count reached the highest of 3.4×107CFU/g, lactic acid bacteria was the highest of 3.2×107CFU/g, non-volatile acid(mainly lactic acid)generated fast. The acetic acid bacteria rapidly proliferated in the first three days, whereafter, it increased slowly and mainly produced acetic acid. At the eleventh day, the number of acetic acid bacteria reached a peak of 4.0 ×107CFU/g, and then decreased after thirteen days. At the beginning of acetic acid fermentation, the p H value decreased rapidly, but non-volatile acid increased rapidly, and the maximum ratio of non-volatile acid accounted for the ratio of the total acid was acquired at the seventh day, which was 87.22%. The growing rate of total acid during 7-13 d of medium fermentation stage increased maximally. The growth of lactic acid bacteria affected non-volatile acids generation, the growth of acetic acid bacteria affected total acid generation. Suitable fermentation conditions control during acetic fermentation could coordinate their growth and reconcile the taste.