Abstract:[Objective] This study aimed to determine the optimal fermentation conditions for sweet potato kombucha and analyze changes in functional components and in vitro antioxidant activity of the product. [Method] Defined-strains-mixed fermentation was implemented with a consortium composed of Acetobacter xylinus, Zygosaccharomyces bailii, and Lactiplantibacillus plantarum. Single factor experiment and response surface methodology were employed to optimize the fermentation process. Physicochemical indices, functional components, and in vitro antioxidant activity were determined to evaluate the enhancement effects of defined-strains-mixed fermentation. [Result] The optimum fermentation process:fermentation with a strain volume ratio of 2∶1∶1 and an inoculum volume fraction of 6.8% at 31.1 ℃ for 32 h. The total phenol mass concentration of 325.68 μg/mL and total flavonoid mass concentration of 99.61 μg/mL, representing 1.14-fold and 1.42-fold increases over the pre-fermentation levels, respectively. The DPPH, ABTS+, and hydroxyl radical scavenging activities reached 2.21 μmol/mL, 10.08 μmol/mL, and 8.30 μmol/mL, respectively, all of which were significantly enhanced compared with the pre-fermentation levels, with the hydroxyl radical scavenging activity showing the greatest increase. [Conclusion] Defined-strains-mixed fermentation effectively elevates the mass concentrations of functional components and antioxidant capacity in sweet potato kombucha. This study provides data support for the value-added utilization of sweet potato resources and the development of novel kombucha products.
