Effects of different fermentation methods on the microflora composition and flavor quality of mixed red sour soup

Red sour soup is a traditional fermented food in Guizhou Province, China. In this study, we investigated the effects of two fermentation methods (intensive fermentation of Lentilactobacillus buchneri lt1-6, Pediococcus ethanolidurans lc2-1, and Kazachstania bulderi ym1-3 and natural fermentation) on the flavor quality of mixed red sour soup. Compared with natural fermentation, intensive fermentation could accelerate the decrease of the pH (3.02 ± 0.01) of mixed red sour soup and increase the contents of total acid (1.83 ± 0.03 g/100 g), total sugar (1.82 ± 0.36 mg/mL), and reducing sugar (0.85 ± 0.03 mg/mL), and color difference values (L∗, a∗, b∗). The abundance and diversity of bacteria exceeded those of fungi in mixed red sour soup and 1-heptanol (2.04%), 2-undecanol (0.72%), heptyl formate (2.67%), geranyl isovalerate (0.67%), and the high content of acetic acid (7.71%) detected only in the intensive fermentation group could enhance and improve the flavor quality of red sour soup. The analysis of the correlation between microbial communities and flavor components indicated that bacteria contributed more to the formation of flavour than fungi in mixed red sour soup. Lentilactobacillus , Lactobacillus , Levilactobacillus , and Pichia were closely correlated with flavours (such as acetic acid, 2, 3-butanediol, phenylethanol, and limonene). This study proved the influences of intensive fermentation of lactic acid bacteria and yeast on the quality and flavor of mixed red sour soup and provided new insights into the industrial production of mixed red sour soup with intensive fermentation. • This study explored the flavor and quality of industrial mixed red sour soup. • Intensified-fermentation had better flavor compared to natural fermentation. • Acetic acid had higher content in intensified-fermentation than natural fermentation. • Significant correlation was observed between volatile compounds and microorganisms.