Mixed fermentation with Lactobacillus plantarum, Bifidobacteriµm animalis subsp. lactis and Candida utilis improves the fermentation quality of Hong Suan Tang

Lactobacillus plantarum NR1-7, Bifidobacteriµm animalis subsp. lactis BZ11 and Candida utilis RY were selected as specific starter cultures to ferment Hong Suan Tang (HST), a traditional hot and sour soup of southwest China made from tomatoes and red peppers. The fermentation conditions were optimized with response surface methodology (RSM). The changes in the physicochemical index, flavor quality, organic acids, and bioactive substances were evaluated. The results showed that the mixed starter fermented HST was quickly acidified, promoting product maturity and significantly reducing the nitrite content, which shortened the fermentation time and improved product safety. Moreover, lactic acid concentration was significantly increased, about 3 times higher than the control group. Sixteen compounds were confirmed to be the critical aroma-active compounds present in the HST. Furthermore, mixed inoculation improved the content of bioactive substances by lowering their degradation. This research sets the basis for the standardized production of HST products.