Japanese scientists have studied four traditional Japanese post-fermented teas (awabancha, goishicha, ishizuchi-kurocha and batabatacha) and green tea as a control sample and found the following. The content of caffeine and catechins in the infusions of post-fermented teas was found to be lower than in the infusion of green tea. The most catechin-rich post-fermented tea is ishizuchi-kurocha, while batabatacha is the poorest in catechins. Awabancha, goishicha and ishizuchi-kurocha showed antioxidant activity comparable to the level found in green tea, despite the lower content of catechins. Batabatacha has manifest almost no antioxidant activity.
Since of all the post-fermented teas under the study only batabatacha does not undergo anaerobic fermentation, experts have concluded that the content of catechins and antioxidant properties of tea increase during its anaerobic fermentation involving lactic acid bacteria in the manufacturing process. The researchers have also noted that one of the possible reasons for the lower content of catechins in post-fermented teas compared to green tea is the coarser leaves used for their production and later harvest time.