Changes in antioxidant phytochemicals and volatile composition of Camellia sinensis by oxidation during tea fermentation

► Catechins decreased during tea fermentation and it resulted in increase of tannins. ► Caffeine was higher in green tea due to the loss during tea fermentation. ► Total soluble phenolics and antioxidant capacity decreased during fermentation. ► Tea fermentation significantly changed the profile of volatile aroma compounds.