Occurrence and distribution of lipoxygenase in Camellia sinensis (L) O!Kuntze and their changes during CTC black tea manufacture under southern Indian conditions

The optimal activity of tea lipoxygenase was found to be at pH 7.5 and 9.0, indicating the presence of two types of isoenzymes. Tea lipoxygenase was inhibited by cyanide and a small fraction appeared to be quite heat stable. Clonal and seasonal variations in lipoxygenase activity was significant. An increase in lipoxygenase activity was observed with leaf maturity. The lipoxygenase activity decreases with age from pruning and increases with an increase in plucking interval. The changes of lipoxygenase activity during CTC manufacture revealed that it increased with the degree of withering and upon rolling. However, a gradual decline was recorded during the fermentation and drying processes. The residual lipoxygenase activity in black tea is expected to affect its quality on storage. (C) 1998 Society of Chemical Industry.