Research in Polyphenol Oxidase Activities of Major Oolong Tea Cultivars in Fujian

Crude polyphenol oxidase (PPO) was separately obtained from Maoxie, Tieguanyin, Huangdan, Rougui, and enzymatic properties were examined. The results were as follows: PPO activities increased curvely with the increase of catechol substrate volume if the volume of catechol substrate ranged in 0.3~0.9 ml, and decreased when catechol substrate content was greater than 0.9 ml, in the reaction system; the enzymatic activities were highest when the ratio of catechol substrate content to PPO content was 1.5:1, the optimum temperature for PPO activities were 45℃、55℃、65℃ respectively, under the condition of 50~90℃ hot water treatment for 1 h, the PPO activities of Maoxie, Tieguanyin, Huangdan, Rougui decreased 34.66%~55.91%, 22.68%~50.89%, 23.14%~53.57%, 31.58%~57.89% respectively, PPO could act under alkaline conditions, the best enzymatic activity was detected under the condition of pH8.6; All the five inhibitors showed some degree of inhibition to PPO activities and the most effective inhibitor was NaHSO3, next to which was L-cysteine, while the most ineffective inhibitor was NaCl.