Improving the quality, safety, and flavor of traditional naturally fermented stinky tofu using a self-screened direct vat starter

In order to enhance the quality and safety of traditional spontaneously fermented stinky tofu, this study compared products prepared via natural fermentation (CK group) and those inoculated with self-screened direct vat starter (DVS group). The dynamic changes in physicochemical properties were monitored throughout the fermentation process. Additionally, the sensory quality, biogenic amines content, and volatile compounds of the mature products were analyzed. Although the DVS group exhibited a higher initial moisture content, which decreased more rapidly during fermentation and ultimately fell below the levels observed in the CK group. Compared to the CK group, the DVS group maintained a consistently lower total acidity but higher pH, amino acid nitrogen content, water-soluble protein content, and protease activity. Furthermore, the DVS group underwent more pronounced color changes. Textural analysis showed that the DVS group initially had lower hardness and chewiness, but these values surpassed the CK group in the later stages. The DVS group also displayed lower elasticity and resilience, whereas cohesiveness was similar between the two groups. At maturity, the DVS group showed superior sensory scores and contained significantly lower levels of biogenic amines than the CK group. A total of 57 volatile flavor compounds were identified in both groups, with aldehydes, alcohols, and ketones being the predominant classes. Although the profiles of key characteristic volatile flavor compounds were highly similar, propanal, eucalyptol, and cyclohexanone were uniquely detected in the DVS group. In conclusion, inoculation with the selected DVS effectively enhanced the nutritional value, safety, and flavor profile of stinky tofu. • Self-screened DVS starter enhances safety by lowering biogenic amines. • DVS inoculation improves nutritional value by increasing amino acid nitrogen. • DVS fermentation improves the final texture attributes like hardness and chewiness. • Propanal, eucalyptol, and cyclohexanone are unique flavor compounds in DVS tofu.