INFLUENCE OF POLYPHENOL OXIDASE ACTIVITY AND POLYPHENOL CONTENT OF TEA SHOOT ON QUALITY OF BLACK TEA

Variation 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. Copyright © 1990 John Wiley & Sons, Ltd