Chemical composition and bacterial community changes during the fermentation of yan yu, a Chinese traditional fermented fish product

Yan yu is a traditional fermented fish product produced by the Dong people of Guizhou Province in southwestern China. However, despite its widespread regional consumption, little is known about the chemical characteristics and bacterial community changes involved during yan yu fermentation. Therefore, the present work assessed the changes in both the chemical and microbiota composition of yan yu during its fermentation. Glucose levels gradually decreased after an initial increase at the beginning of fermentation, whereas increase in lactic acid levels continued after 10 d of fermentation. A rapid increase in free amino acid levels was observed at the beginning, but either remained constant or slowly decreased later in the fermentation. In contrast, biogenic amine (BA), TVB-N, and TBARS levels remained low throughout the fermentation. Bacterial community analyses revealed that Lactiplantibacillus and Tetragenococcus dominated the bacterial community. Moreover, O2PLS-based correlation analysis indicated that these two genera significantly affected the chemical composition of yan yu. Furthermore, lactic acid and free amino acid contents (i.e., two major quality parameters of fermented products) were highly correlated with the occurrence of Lactiplantibacillus and Tetragenococcus. These results are expected to establish a basis for the quality improvement of traditional fermentation of yan yu.