Analysis of Bacterial Community Dynamics and Flavor Characteristics in Sichuan Paocai Fermented with Mixed Starter Culture

To investigate the microbial community succession and flavor characteristics during Sichuan paocai fermentation using a composite lactic acid bacteria starter, this study employed acombination of two Lactiplantibacillus plantarum strains and one Enterococcus faecium for 28-day fermentation, with natural fermentation as the control (CK group). The physicochemical parameters, bacterial community structure, and metabolite dynamics were systematically analyzed. Results show that on the 7th day, the brine pH in the composite starter culture group (GA group) decreases to 3.60±0.30, significantly lower than CK group (4.30±0.40). The nitrite peak concentration in GA group (0.30±0.03 mg/kg) is markedly reduced compared to CK group (7.53±0.26 mg/kg) (P<0.05). GA group exhibited accelerates reducing sugar consumption, with residual content (2.11±0.06 g/100g) significantly lower than CK group (2.40±0.10 g/100 g). After 28 days, GA group shows higher total acid (4.56±0.08 g/L) and lactic acid (4.27±0.33g/L) concentrations. Throughout the fermentation process, Firmicutes and Lactiplantibacillus remain the dominant phylum and genus in the GA group, while in the natural fermentation group, Firmicutes and Pediococcus become the dominant phylum and genus after 7 days of fermentation. Among differential volatile compounds (VIP>1), eucalyptol (428.26±21.74 µg/kg) and ethyl acetate (130.03±13.95 µg/kg) in GA group significantly exceed CK group (P<0.05), whereas sulfur-containing compounds are reduced. Sensory evaluation reveals superior scores for GA group. These findings indicate that the composite starter effectively accelerates acidification and enhances flavor quality of Sichuan paocai, providing theoretical basis for starter culture selection and industrial application.