Abstract
A relationship between manufacturing processes, namely steaming time, and chlorophyllase activity has been studied. Furthermore, the degree of residual chlorophyllase activity in commercially available green teas was evaluated by measuring the total pheophorbide a (PB a) as an indicator of chlorophyllase activity. The chlorophyllase activity in fresh tea leaves decreased rapidly during steaming and almost disappeared when treated for more than 120 sec. The chlorophyllase activity was scarcely changed during further manufacturing processes. On the other hand, chlorophyllase activity was detected in commercially available green teas. The total PB a content decreased in the order Gyokuro >Matcha>Sencha>Fukamushi sencha and was beyond the standard limit established for chlorella in Gyokuro and some of Matcha and Sencha analyzed. Commercially available green teas contain a relatively low percentage of water and are usually kept in cold, suggesting that chlorophyllase activity would probably be minimal and PB a would not be produced under cold storage conditions. Even though the total PB a content was found in relatively high concentration in commercial samples, this parameter need not be taken into consideration while evaluating the safety of green teas. The PB a content significantly increased by leaving green teas (specially lightly steamed green teas) in water for a long time. Attention to the total PB a content should be paid when using green teas as a food stuff.
