Abstract:
The research focuses on studying the effects of microbial fermentation on the phenolic and flavor volatile profiles of two tea leave samples, namely Camellia sinensis and Malus hupehensis. Fermentation of the tea leaves was conducted with Kombucha (SCOBY) and lactic acid bacteria (Lactobacillus acidophilus). Optimization of extraction conditions was performed by analyzing the total phenolic content and antioxidant capacities at varying water to tea ratios, time, and temperature. The optimum conditions that yielded the highest concentrations of polyphenols from Camellia sinensis was reported as 0.5:60 (w/v) at 80 oC for 60 min while the optimum conditions reported for Malus hupehensis were at 0.5:50 at 100 oC for 90min. The polyphenol content and antioxidant capacities of the tea leaves after fermentation with kombucha (SCOBY) was monitored and determined on day 2 and 10. In general, the concentration of polyphenols was modified by kombucha fermentation with an increase in fermentation time. In contrast, lactic acid fermentation did not alter the concentrations of the polyphenols and their antioxidant capacities. The qualitative and quantitative analysis of the polyphenols in the tea extracts before and after fermentation showed that kombucha culture modified the concentrations of polyphenols thus enhancing the quality of the tea extracts while L. acidophilus did not alter the concentrations of polyphenols before and after fermentation.
The research also investigated the effect of kombucha (SCOBY) and L. acidophilus on the flavor volatile profiles in the tea extracts by GC-MS analysis before and after fermentation. A total of 30 flavour volatile components were identified in the leaf extracts of Camellia sinensis among which 14 volatile components were identified on day 10 of kombucha fermentation in comparison to day 0 where only 7 volatile components were identified. In contrast, 28 volatile components were identified in the leaf extracts of Malus hupehensis among which only 10 volatile components were identified when compared to day 0 that reported 14 volatile components. L.acidophilus did not modify the flavour volatile components in the tea extracts before and after fermentation.