Abstract: This study determined the contents of tea polyphenols, theanine, caffeine and lactic acid in non-fermented and Lactobacillus plantarum fermented black tea beverage by ferrous tartrate colorimetry, nihydrin colorimetry and alkaline titration. Four in vitro antioxidant models were used to study the antioxidant activity. Also, the major aroma components were analyzed by headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). It was shown that after fermentation, the contents of tea polyphenols and caffeine in black tea beverage decreased slightly but theanine and lactic acid increased significantly (P < 0.05). Moreover, the scavenging capacity against some free radicals declined slightly. The GC-MS analysis showed that the contents of some volatile flavor components such as alcohols and ketone significantly increased after fermentation, contributing to enhancing the aroma quality of black tea.

Key words: lactic acid bacteria, fermentation, black tea beverage, antioxidant activity, flavor components