Effects of fermentation time on phenolic composition, antioxidant and antimicrobial activities of green, oolong, and black teas

In this study, it was aimed to investigate the effect of fermentation degree on total phenolic content, individual catechins, gallic acid, theaflavins, caffeine content, antioxidant and antimicrobial activity in teas. Green tea, black tea and oolong tea (partially oxidized 7 different degrees) were produced from the same cultivar of tea leaves harvested in first shooting period. The higher degree of fermentation was resulted in higher theaflavins, however in lower individual catechins and total phenolic content. Standard catechins gradually decreased with extended fermentation duration and epigallocatechin gallate decreased 87% from green tea to oolong to black tea. Higher antioxidant activity was observed in green and lower fermented oolong teas. There were significant (p0.9) between DPPH, ABTS assays and total phenolic content, catechin, epigallocatechin gallate, epicatechin, epicatechin gallate and total catechins. Significant (p0.7) were also observed between ORAC and those catechins. Moreover, the tea samples especially green tea showed antibacterial effects against three of the tested pathogenic bacteria Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212, Pseudomonas aeruginosa ATCC 27853 and antifungal effects against Candida albicans ATCC 10231. However, no antimicrobial activity was detected against Escherichia coli. [Display omitted] •Effects of fermentation time on chemical composition and antimicrobial activity of teas were investigated.•Antioxidant activities of short-term oxidized oolong teas were equal to or higher than that of green tea.•Black tea has the lowest catechins, total polyphenolic content and lowest antioxidant activity.•Significant positive correlations were found between the DPPH, ABTS assays and catechins.•The highest antimicrobial activity was detected in the green tea samples.