Comprehensive analysis of bacterial succession and flavor components in Xiguajiang with different watermelon juice supplementation during fermentation

This study investigated the physicochemical factors, bacterial communities, and volatile aromatic components in watermelon soybean pastes (WSP) prepared with different ratios of different watermelon juice to koji during the fermentation process. The results indicated that high concentration of watermelon juice could significantly increase the contents of amino acid nitrogen, reducing sugar, and free amino acids, but decreased bacterial diversity. Enterococcus, Bacillus, Enterobacter, Staphylococcus, Pediococcus, Lactobacillus, and Weissella were identified as the dominant genus bacteria in WSP samples, while Enterococcus and Pediococcus were found to account for more than 50% in WSP-4 samples. In WSP samples, this study identified 142 volatile components, the concentration of volatile components was more abundant in WSP-4 samples compared to WSP-2 and WSP-3 samples, especially in the pyrazine family. Furthermore, E-nose results showed that the influence of watermelon juice on the aroma components of WSP samples was mainly focused on the late fermentation periods, but aroma profiles were relatively similar in all WSP samples regardless of watermelon juice concentration throughout the fermentation period. Therefore, this study discovered that controlling the amount of watermelon juice and fermentation time can affect the aroma profiles of WSP samples to a certain extent, and improve the industrial production and food quality.