Correlation between the quality and microbial community of natural-type and artificial-type Yongchuan Douchi

Yongchuan douchi is a traditional fermented food in China. This study investigated the microbial community of two major types (Natural and artificial) of Yongchuan douchi, and their influences on quality. The results found that natural-type douchi had significantly better quality in its physicochemical properties such as higher amino nitrogen, darker color, and higher umami amino acids after post-fermentation (p < 0.05). A total of 58 volatile components were found in natural-type douchi compared to artificial-type with 42 identified. Microbial analysis found that natural-type douchi had the richness and diversity of the bacterial (fungus) community. However, artificial-type douchi was high in Candida genera may associated with its bitter after taste compared to natural-type. Following post-fermentation, natural-type douchi had higher abundance of Bacillus sp., Enterobacter sp., and Pseudomonas sp., while Bacillus sp., Weissella sp., and Aspergillus sp. compared to artificial-type douchi. Correlation analysis showed that physicochemical properties and sensory quality could be correlated positively or negatively with the microbial composition during the last stage of post-fermentation. In conclusion, the zhiqu process significantly affected the final quality of the two types of Yongchuan douchi as evidenced by the microbial composition in the post-fermentation process.

Automated summary

The natural type Yongchuan douchi had better quality and richness in volatile components after post-fermentation compared to the artificial type, which may be due to the high abundance of Candida genera in the artificial type leading to a bitter aftertaste.