Influence of Oxidation Degree on Phenolic Composition, Antioxidant and Antimicrobial Activity of Turkish Oolong Teas Processed from the Same Tea Cultivar

In this study, it was aimed to investigate the effect of fermentation degree on total phenolic content (TPC), individual catechins, gallic acid, theaflavins (TFs), 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 TPC. Standard catechins gradually decreased with extended fermentation duration and EGCG 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 (p<0.01) positive correlations (r 2 >0.9) between DPPH, ABTS assays and TPC, catechin (C), epigallocatechingallat (EGCG), epicatechin (EC), epicatechingallat (ECG) and total catechins (TC). Significant (p<0.05), positive correlations (r 2 >0.7) 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