Analysis of bacterial diversity and biogenic amines content during the fermentation processing of stinky tofu

Fermented foods may confer several benefits to human health and play an important role in a healthy and balanced diet. Stinky tofu is an important traditional fermented soy product in Asia. In this study, a comprehensive analysis of bacterial diversity in terms of rarefaction abundance, rank abundance, alpha diversity, and principal coordinates analysis was conducted using next-generation sequencing. The results obtained were further verified by culture-dependent methods. In addition, eight biogenic amines were also quantified to determine their levels in stinky tofu during conventional production. Our study revealed that lactobacillus was the major lactic acid bacteria throughout the fermentation process. Further, some potentially harmful bacterial belonging to the genera Halomonas and Solobacterium, were also found existing in the stinky tofu. In case of biogenic amines, the concentration of putrescine, cadaverine and histamine finally increased to high levels while spermine disappeared after the fermentation was completed. After the soaking step, putrescine, tryptamine and β-phenethylamine increased sharply. This work provided an improved understanding of microbes and biogenic amines content associated with the traditionally consumed fermented food. However, there is a need to understand microbial interactions related to biogenic amines during the fermentation, and the origin and survival strategies of two important pathogens detected in our study.