Theaflavin Digallate Research Articles

Influence of polyphenol oxidase activity and polyphenol content of tea shoot on quality of black tea

AbstractVariation in polyphenot oxidase activity and levels of total polyphenols and catechins with respect to different clones and shoot components, and its effect on quality of black tea (Camellia sinensis (L) 0 Kuntze, were studied. There was a wide variation in polyphenol oxidase activity of the different clones tested. The optimum fermentation time and polyphenol oxidase activity of different clones exhibited a hyperbolic relationship, viz y = 2.36 + 1129/x, where y = optimum fermentation time in minutes and x = polyphenol oxidase activity in μM catechol oxidised g−1 acetone powder min−1, with an r value of −0.98, which is signi Jicant at P ≤ 0.001. A good non‐linear relationship was found between polyphenol oxidase activity of ji‐esh tea shoots of different clones and the theajavins content of corresponding black teas. Among different shoot components, bud and first leaf had higher levels of polyphenols and catechins than internodes. However, the polyphenol oxidase activity showed a reverse trend: the internodes exhibited a higher enzyme activity compared with other components. Formation of theajavins during fermentation of different shoot components was in good agreement with polyphenol oxidase activity. High performance liquid chromatographic analysis of the theaflavins fraction in tea brew of black teas made from different components of tea shoot showed that buds resulted in black tea with the highest amount of theaflavin gallates, whereas teas produced from internodes had the lowest amount of theaflavin gallates. A new factor, viz theaflavin digallate equivalent, was developed, and the significance of this factor for chemical evaluation of black tea quality is discussed in this paper.

Effects of (-)-epicatechin on oxidation of theaflavins by polyphenol oxidase from tea leaves.

The oxidation of black tea components such as theaflavin, theaflavin monogallates, and theaflavin digallate by partially purified polyphenol oxidase from tea leaves in the presence and absence of equimolar concentrations of (-)-epicatechin was studied in model fermentation experiments under aerobic conditions. The oxidation of theaflavin monogallates was more rapid than that of theaflavin digallate, which was very slow. (-)-Epigallocatechin was not effective in oxidizing theaflavin components, instead it prevented their oxidation.