Flavour chemical dynamics during fermentation of kombucha tea

Main physical and chemical properties, microbial population and flavour compounds of kombucha fermentation were dynamically analyzed. The results showed: the pH values decreased but total acidity increased in kombucha fermentation broth with fermentation time; the concentrations of tea polyphenols and free amino acids firstly increased in the initial stage and then decreased till the end of fermentation; total catechins and canine in kombucha fermentation broth were degraded progressively with fermentation time. Only 21 volatile flavour compounds were identified in the initial kombucha fermentation broth but 56 volatile flavour compounds were identified in the 10 d fermentation. The largest group was acids among which there were 22 different types of acids compounds, accounting for up to 57.21% of all volatile flavour components. Bacteria were more abundant and diverse than yeasts in kombucha fermentation broth during fermentation. We separated and identified 8 main microbial communities in kombucha fermentation broth during kombucha fermentation; 6 bacteria belonged to Gluconacetobacter saccharivorans, Acetobacter sp., Gluconacetobacter sp., Gluconacetobacter europaeus, Acetobacter aced and Lactobacillus fermentum, and 2 yeasts belonged to Saccharomyces cerevisiae and Arxula adeninivorans. According to the production of organic acids i.e., acetic acid, we envisaged that the predominant bacterial species identified were probably Acetobacter sp. and Acetobacter aceti after 5 days fermentation.