CHANGES OF FATTY-ACID CONTENTS, LIPOXYGENASE ACTIVITIES, AND VOLATILES DURING BLACK TEA MANUFACTURE

Fatty acid composition in relation to lipolytic and lipoxygenase activities in tea leaf shoots, from different stages of the tea manufacturing process (i.e., withering, rolling, fermentation, and firing) was investigated in a series of black tea manufacturing experiments. More degradation of fatty acids and higher lipoxygenase activity were characteristics of tea leaves allowed to undergo the desiccation/withering process for longer periods of time. The oxidative breakdown of fatty acids was higher in the later part of the rolling process, while lipolytic activity was more prominent in the withering process as well as the earlier stage of rolling. A gradual decline of lipoxygenase activity as well as fatty acid content has been recorded during the fermentation and drying processes. Although the lipids and fatty acid degradation were directly related to the degree of withering, the volatile content of teas manufactured from hard withered leaves (lower moisture content) was unexpectedly lower than that in black teas from normal withered tea leaf shoots.