Influence of enzyme source and catechins on theaflavins formation during in vitro liquid-state fermentation

Abstract Theaflavins (TFs) are the main components responsible for the bright, orange-yellow color of liquor and fresh, brisk, and astringent taste of black tea. TFs are formed from the enzymatic oxidative condensation of catechins. In this study, we aimed to optimize the production of TFs from catechins in an in vitro liquid-state fermentation system. We examined (1) three different enzyme sources (2) two different times for the addition of catechins and (3) three different ratios (1:2, 1.5:1.5, and 2:1) of key catechins [(-)-epigallocatechin (EGC); (-)-epigallocatechin gallate (EGCG)]. The results indicated that the use of polyphenol oxidase (PPO) promoted a rapid and uniform consumption of catechins, resulting in a sustained high-level production of TFs. The batchwise addition of catechins was the best method for sustained and high-efficiency TFs formation. An EGC/EGCG ratio of 1:2 led to the formation of relatively higher amounts of theaflavin-3ʹ-gallate (TF-3ʹ-G) and TF-3,3ʹ-digallate (TF-D-G), which resulted in a significantly higher total TFs content. These results demonstrate that the batchwise addition of catechin substrates with a high EGCG content using PPO as an enzyme source can improve the formation of TFs. Our results provide a theoretical basis for understanding the mechanisms of TFs synthesis.