Comprehensive evaluation of quality and bioactivity of kombucha from six major tea types in China

Kombucha is a kind of fermented tea prepared with a symbiotic culture of bacteria and yeasts (SCOBY) on the basis of sugared black tea infusion. In the current study, six major Chinese tea leaves (dark tea, black tea, oolong tea, white tea, yellow tea, and green tea) were used to prepare kombucha and their physiochemical properties, bioactivity, and sensory quality were compared. The total acidity of kombucha increased as the fermentation proceeded, decreasing the pH value from ∼6.0 to ∼2.5. Moreover, the antioxidant capacity was significantly increased after fermentation compared to fresh tea infusions and this is mostly attributed to the increased total polyphenols concentration (from 1333.25 mg/L to 1683.24 mg/L). Antimicrobial experiments showed fermentation enhanced the antimicrobial effects of kombucha, and oolong tea kombucha showed the strongest bacteriostatic capacity against Staphylococcus aureus (S. aureus) while the yellow tea kombucha showed the strongest bacteriostatic capacity against Escherichia coli (E. coli). Volatile components and sensory evaluation results revealed that the tea types remarkably influenced the flavors of kombucha. Generally, oolong tea kombucha and green tea kombucha had higher overall sensory scores than other samples. In conclusion, the types of tea significantly influenced the quality of kombucha, and fermentation favors the improvement in the anti-oxidant and antimicrobial properties of kombucha.