Bacterial community succession and its correlations with non-volatile flavor compounds during the fermentation of Chinese dry-salted and brined radishes

Chinese salted radish is a traditional fermented vegetable, produced using dry-salted or brined fermentation, yet little is known about the functional bacteria involved in the non-volatile flavor formation. In this study, the dynamics of physicochemical properties and non-volatile flavor compounds, and bacterial community succession during the fermentation of Chinese dry-salted and brined radishes were investigated. Furthermore, correlations between the dominant bacteria and the main non-volatile flavor compounds were discussed. The pH, total titratable acid, and water activity of the dry-salted radish matured on the 30th day were 4.7, 0.43 g 100 g-1 lactic acid, and 0.90, respectively. While these three physicochemical parameters of the brined radish ripened on the 5th day reached 3.4, 0.31 g 100 g-1 lactic acid, and 0.96, respectively. Glucose and fructose, succinic and malic acids, and five free amino acids (proline, cystine, valine, isoleucine, and phenylalanine) were the main non-volatile flavor compounds in dry-salted radish, while lactic acid, arginine, cystine, and alanine were rich in brined radish. Pantoea, Pseudomonas, Rosenbergiella, Acinetobacter, Leuconostoc, and Exiguobacterium were the dominant bacteria in dry-salted radish, and Acinetobacter and Exiguobacterium played important roles in the flavor formation. Lactobacillus almost dominated the whole fermentation and significantly correlated with the formation of lactic acid and free amino acids in brined radish (P<0.05).