Background: Inferior Tieguanyin oolong tea leaves were treated with tannase. The content and bioactivity of catechins in extracts from the treated tea leaves were investigated to assess the quality improvement of inferior Tieguanyin oolong tea.

Results: Analysis showed that the esterified catechin content decreased by 23.5%, whereas non-galloylated catechin and gallic acid contents increased by 15.3% and 182%, respectively. the extracts from tannase-treated tea leaves showed reduced ability to bind to BSA and decreased tea cream levels. The extracts also exhibited increased antioxidant ability to scavenge OH-, DPPH radicals, and ferric reducing power as well as decreased inhibitory effects on pancreatic α-amylase and lipase activities.

Conclusions: These results suggested that tannase treatment could improve the quality of inferior Tieguanyin oolong tea leaves.