台灣三大半球型烏龍茶主要物化成分之比較及其鑑別

Comparison of Major Physicochemical Constituents in Three Different Semi-sphere Types of Taiwan Oolong Tea and Their Discrimination

劉士綸(Shih-Lun Liu) ； 蔡永生(Yung-Sheng Tsai) ； 區少梅(Shau-Mei Ou)

《臺灣農業化學與食品科學》 48卷2期 (2010/04) Pp. 55-63

https://doi.org/10.6578/TJACFS.2010.007

摘要

The purpose of this study were to compare data of 19 physicochemical constituents, which were obtained in previously reported studies, of 140 semisphere-type Taiwan Oolong tea, belonging to 60 High mountain tea, 46 Dong-ding Oolong tea and 34 Tiehkuanyin collected from famous tea contests, and to investigate the discrimination of them using the stepwise discriminant analysis and principal component analysis (PCA) with linear discriminant analysis (LDA). The results showed that ten out of 19 constituents were significantly different in these three types of tea samples (p＜0.05). They were catechin (C), epigallocatechin gallate (EGCG), total ester-type catechins, total nitrogen, Hunters L, a, and b values, chroma and pH. The characteristics of Tiehkuanyin tea samples were low in pH, total nitrogen and total free-type catechins but high in caffeine and ester-type catechins while that of High-mountain tea samples was rich in free-type catechins contents and high in pH of tea infusions. The Dong-ding Oolong tea samples were in between those two types of tea samples but the content of total free-type catechins were closer to that of High-mountain tea and both were higher than that of Tiehkuanyin. Using results of physicochemical analysis to conduct the stepwise discriminant analysis directly, the results showed that 7 items including pH, total free amino acids, EGC, caffeine, ECG, total catechins and total ester-type catechins, were the most suitable for discrimination. The percentage of successful discrimination was 91.43%. Using PCA with LDA, the first four components could discriminate up to 100% successful rate. In terms of the fermentation level for the Taiwan Oolong tea, our results indicated that it requires clarification from the published data in the literature. This study showed that the catechins contents in High-mountain tea samples were increased instead of decreased, and the fermentation levels for the other two kinds of tea were also quite different from the data in the literature.

關鍵字

高山茶 ； 凍頂烏龍茶 ； 鐵觀音 ； 物化成分 ； 主成分分析 ； 鑑別分析

並列摘要

The purpose of this study were to compare data of 19 physicochemical constituents, which were obtained in previously reported studies, of 140 semisphere-type Taiwan Oolong tea, belonging to 60 High mountain tea, 46 Dong-ding Oolong tea and 34 Tiehkuanyin collected from famous tea contests, and to investigate the discrimination of them using the stepwise discriminant analysis and principal component analysis (PCA) with linear discriminant analysis (LDA). The results showed that ten out of 19 constituents were significantly different in these three types of tea samples (p＜0.05). They were catechin (C), epigallocatechin gallate (EGCG), total ester-type catechins, total nitrogen, Hunters L, a, and b values, chroma and pH. The characteristics of Tiehkuanyin tea samples were low in pH, total nitrogen and total free-type catechins but high in caffeine and ester-type catechins while that of High-mountain tea samples was rich in free-type catechins contents and high in pH of tea infusions. The Dong-ding Oolong tea samples were in between those two types of tea samples but the content of total free-type catechins were closer to that of High-mountain tea and both were higher than that of Tiehkuanyin. Using results of physicochemical analysis to conduct the stepwise discriminant analysis directly, the results showed that 7 items including pH, total free amino acids, EGC, caffeine, ECG, total catechins and total ester-type catechins, were the most suitable for discrimination. The percentage of successful discrimination was 91.43%. Using PCA with LDA, the first four components could discriminate up to 100% successful rate. In terms of the fermentation level for the Taiwan Oolong tea, our results indicated that it requires clarification from the published data in the literature. This study showed that the catechins contents in High-mountain tea samples were increased instead of decreased, and the fermentation levels for the other two kinds of tea were also quite different from the data in the literature.

並列關鍵字

High-mountain tea ； Dong-ding Oolong tea ； Tiehkuanyin ； Physicochemical constituents ； Principal component analysis ； Discriminant analysis