Comparison of the Quality of Rice Sour (Baisuan) Soup Prepared with Direct-Vat-Set Strain and Fermented Soup Mother Liquor
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Abstract:
As a special seasoning of Kaili, Guizhou, rice sour soup (RSS) is highly popular, but there are problems such as low yield and unstable quality. Direct-Vat-Set strain powder (Lactobacillus casei, Lactobacillus plantarum) and mother fermentation liquor of RSS were used as the compound starter culture to be inoculated for fermenting RSS. Compared with the traditional fermentated RSS prepared using singly the soup mother liquor, the change trends of the physico-chemical indexes, microbial indexes and sensory quality of RSS over the fermentation process were studied. Liquid chromatography- mass spectrometry (LC-MS) and two-dimensional gas chromatography-time of flight mass spectrometry (GC×GC-TOF/MS) were used to compare and analyze the differences in the flavor substances of the two groups of RSS. The results showed that at the end of fermentation, the total acid content and total number of lactic acid bacteria in the Inoculated Fermentation- 7d group (IF-7) were significantly higher than those in the Natural Fermentation-7d group (NF-7). The pH value and total number of yeast of the IF-7 were lower than those in NF-7 group. The sensory scores of IF-7 group were higher than those of NF-7 group in color, flavor, taste and total score, though there was insignificant difference in flowability. As for the non- volatile flavor substances, the IF-7 group had a total of 21 significant differential metabolites that were higher than those in the NF-7 group, and a total of 6 metabolites that were lower than those in the NF-7 group. As for the volatile flavor substances, 248 and 246 components were detected in the IF-7 group and the NF-7 group, respectively, which were primarily alcohols (mainly propanol, ethanol, etc.), acids (mainly acetic acid, propionic acid, etc.), and esters (mainly propyl acetate, propyl propionate, ethyl acetate, etc.). The content of esters in the IF-7 group was slightly lower than that in the NF-7 group, though little difference was detected in other aspects. The above results showed that the fermentation of RSS by inoculating Direct-Vat-Set strain powder along with fermented soup mother liquor as the starter culture can significantly shorten the production time and improve the product quality and nutritional value.
