Investigation of antibacterial activity of heated Kombucha beverages prepared with several herbal teas using response surface methodology

The composition and biological activities of kombucha beverage depends on type of herbal tea, concentration of sucrose and the fermentation time. This study aimed to investigate the effect of different preparation conditions on antibacterial activity of heated kombucha beverages by Response Surface Methodology (RSM). Four types of herbal teas, including black tea, green tea, lemon verbena and peppermint were prepared with three concentrations of sucrose (2, 5 and 8%) and inoculated with active kombucha culture. After 7, 14 and 21 days, beverages were heated by autoclaving and their antibacterial activity against four bacteria including Escherichia coli, Shigella dysenteriae, Staphylococcus aureus and Bacillus cereus was evaluated by well method. The RSM was used to investigate the effect of sucrose concentration, fermentation time and type of herbal tea on antibacterial activity of heated beverages. Increasing sucrose concentration had significant effect (P<0.0001) on antibacterial activity of heated beverages against all tested bacteria. Increasing of fermentation time had significant effect (P< 0.0001) on antibacterial activity of heated beverages against E. coli and S. dysenteriae. Type of herbal tea had significant effect on antibacterial activity against S. aureus and S. dysenteriae. The highest antibacterial activity against E. coli and S. dysenteriae was observed in beverages prepared with lemon verbena. Beverages prepared with green tea showed highest antibacterial activity against S. aureus. The highest antibacterial activity against B. cereus was observed in heated beverages prepared with black tea and peppermint. In general, the results showed significant antibacterial activity of heated kombucha beverages against the tested bacteria.