Na Liu

Red sour soup is a Guizhou specialty condiment made by the natural fermentation of tomatoes and chili. In this study, three components (tomato acid, chili acid, and tomato and chili mixed acid) of split‐fermented red sour soup were explored to compare the quality characteristics and microbial communities in the middle and late fermentation stages. The titratable acidity of mixed acids was lower than that of tomato acid and chili acid in the middle stage, but it was significantly increased in the late stage. The cell viability of lactic acid bacteria was mostly higher than that of yeasts during the whole fermentation. Also significantly increased in the late stage of fermentation were sensory scores and the signal intensity of sour substances. However, the signal intensity of both bitter and salty substances decreased, and the total amount of free amino acids was reduced. In addition, the antioxidant capacity of the samples and the dominant microorganisms were different between the two fermentation stages, Lactobacillus and Kazachstania were the key common genus of the different components of split‐fermented red sour soup. It is anticipated that this study would provide us an insight into the quality characteristics and microbial communities of split‐fermented red sour soup.

In the study, Lactobacillus paracasei H4‐11, Lactobacillus fermentum D1‐1, Lactobacillus casei H1‐8, Lactobacillus reuteri H2‐12, and Kluyveromyces marxianus L1‐1 were screened from traditional fermented rice acid based on several indicators: L‐lactic acid production capacity (13.46 ~ 19.69 g/kg), antioxidant capacity (DPPH clearance ability of 35.36 ~ 56.89%), and savory flavor indicators. Glutinous rice, quinoa, barley rice, and brown rice were selected to carry out rice acid fermentation. Different viable lactic acid bacteria and yeasts were screened, respectively, in the saccharification, acidification, alcoholization, and late acidification stages. Rice acid fermented with L. paracasei H4‐11 and K. marxianus L1‐1 in glutinous rice showed the high L‐lactic acid content (23.09 g/kg). The DPPH free radical scavenging ability in rice acid fermented with L. fermentum D1‐1 and L. paracasei H4‐11, respectively, reached 34.27% and 33.05% in 96 hr. Although quinoa rice acid had the highest L‐lactic acid content (33.74 g/kg) and the DPPH free radical scavenging ability (60.10%), it had the poor taste due to the high astringency intensity and bitter intensity. Rice acid fermented with both L. paracasei H4‐11 and K. marxianus L1‐1 in glutinous rice showed the highest savory flavor and had the lowest astringency and bitter. L. paracasei H4‐11 and K. marxianus L1‐1 were the potential strains for the fermentation of rice acid. These results promote the industrial development of Chinese rice acid.Practical applications: Rice acid as a functional nondairy fermented product is widely accepted by Chinese consumers. However, rice acid fermentation is still a traditional spontaneous process, which causes instability in its flavor and quality. Lactobacillus paracasei H4‐11 and Kluyveromyces marxianus L1‐1 screened in this study contributed to the improvements in the flavor and antioxidant capacity of rice acid. In addition, glutinous rice was confirmed as the suitable fermentation material of rice acid in the study.