Abstract: During black tea processing, catechin is converted into a wide variety of oxidized polymers with complicated structures through many pathways, and the unique color and taste of black tea is due to these compounds. Currently, most studies on oxidized dimeric catechin have focused on theaflavins (TFs) and theasinensins (TSs). This review summarizes recent advances in understanding the reaction pathways for the formation of oxidized dimeric catechin, the exogenous polyphenol oxidases responsible for enzymatic oxidation of catechin and their substrate specificity, and the bioactivity of oxidized dimeric catechin and recent advances in applying oxidized dimeric catechin in tea processing. The aim of the present review is to provide a better understanding of the enzymatic oxidation mechanism of catechin and to provide a scientific basis for tea deep processing.

Key words: catechin, exogenous polyphenol oxidase, oxidized dimeric products, theaflavins, theasinensins