不同茶樹品種多酚酶活性及其在製茶過程中之變化

Abstract

臺灣重要茶樹品種（系）所含多酚酶活性經調查顯示一般適於製造半發酵茶之品種（系），其所含該酶活性明顯低於紅茶品種（系）。該酶對(+)-Catechin之Km值為2.0×10-3M；平均分子量為1.5×105。在包種茶製造過程中多酚酶在日光萎凋過程活性明顯升高，但在其後的發酵過程該酶因攪拌作用的刺激酶活性隨之呈現波狀起伏的現象。兒茶素類則隨攪拌次數之增加及加重而加速氧化（約氧化6%~10%)，在對照組因缺少攪拌過程，故酶活性變化起伏不大。且兒茶素類的氧化亦不明顯，即茶葉幾乎未發酵，由此推知攪拌的次數及輕重與茶葉發酵時酶的活化與兒茶素類氧化有密切關係。而在紅茶的製造過程中該酣活性從萎凋時即逐漸升高至揉捻時達到最高。約高出茶菁二倍以上，但在隨後的發酵過程中逐次降低，並在乾燥後消失。 The investigation of the main tea varieties (clones) in Taiwan has shown that activities of polyphenol oxidase in the varieties (clones) suitable for semifermented tea manufacture are evidently lower than those for black tea manufacture. This enzyme was found to show a Km of 2.0×10-3M(at 30℃) for(+) catechin. The activities of polyphenol oxidase can be promoted by shaking the fermentation process of Paochung tea manufacture. The activities of this enzyme were found to fluctuate with the shakings. Oxidation of catechins (about 6%-l0% oxidation) increased with times and physical strength of shakings. Little change in the activities of polyphenol oxidase was observed in the check treatment because of lack of shaking suggesting that the oxidation of catechins was not evident. This indicated that obvious fermentation of tea did not take place during the processing. It can be inferred from the results that the times and physical strength of shakings were closely related with the activation of polyphenol oxidase and oxidation of catechins in tea fermentation. The enzyme activity during the process of black tea manufacturing in tea leaves was found to increase continually in the withering period and reached the highest point by rolling, about 2 times more than that in the fresh leaves and decrease along with the fermentation process after rolling, then disappear after drying.