茶湯水色與茶湯內容物含量之關係

Abstract

本研究分兩個部分，以探討茶湯水色與兒茶素類含量間之關聯，並建立利用茶湯水色快速推估茶湯中兒茶素類含量的方法。第一部分為瞭解茶湯水色與兒茶素類含量之影響，分別比較春、秋兩季製程之茶葉後，顯示茶湯水色色差值(∆E)與茶葉中含量較高的兒茶素catechin (C) (R= -0.72, -0.62)、epicatechin-3-gallate (ECG) (R= -0.64, -0.92)、epigallocatechin (EGC) (R= -0.77, -0.92) 及epigallocatechin-3-gallate (EGCG) (R=-0.73, -0.89)相關性較高。隨發酵程度的增加，總兒茶素的含量降低，使茶湯水色改變。在茶湯水色中EGC、EGCG和C為主要影響茶湯L、a、b值的兒茶素成分；進一步正向逐步迴歸分析，可利用方程式EGC = (-0.60) L + (-1.19) a+ 0.79 b + (-0.87) ∆E +55.52；C = (-0.98) L + (-2.80) a +85.46；EGCG = (-5.87) L+ (-11.13) a+487.1推估這三種兒茶素的含量。第二部分是探討不同發酵程度的綠茶、包種茶、番庄茶和紅茶，製程中兒茶素含量的變化，以及製程中兒茶素含量與水色之關係。使用‘臺茶12號’及‘青心大冇’為材料。其中，‘臺茶12號’為例，而茶素類在製程中持續變動，尤其以製作包種茶及番庄茶時，兒茶素類含量會呈現波動變化，而綠茶及紅茶兒茶素變動則相對較小。分析製程中，茶粉水萃液水色與兒茶素類含量之關係，顯示輕發酵包種茶、重發酵番庄茶和全發酵紅茶，兒茶素含量與水萃液水色有高度相關。在輕發酵包種茶的製程中，‘青心大冇’之水萃液b值與兒茶素C、EGC、EGCG、GCG含量顯著相關 (R2依序為0.64, 0.72, 0.69, 0.44, p < 0.01)，而‘臺茶12號’之水萃液b值與 EC、EGC、EGCG含量顯著相關 (R2依序為 0.41, 0.61, 0.52, p < 0.01)。重發酵番庄茶的製程中，‘青心大冇’之水萃液b值與製程中 C、EC、EGC、EGCG含量具有顯著相關(R2依序為0.79, 0.71, 0.66, 0.79, p < 0.01)；‘臺茶12號’的水萃液L、a、b值則與EC、EGC、EGCG、GCG、ECG、CG皆有顯著相關(p < 0.01)，顯著影響茶粉水萃液的顏色。‘青心大冇’紅茶製程中，水萃液的b值與C、EGC、EGCG、ECG含量具有高度相關(R2依序 0.61, 0.76, 0.92, 0.77, p < 0.01)；‘臺茶12號’紅茶製程水萃液L、a、b值則與EC、EGC、EGCG皆有顯著相關(p < 0.01)。‘臺茶12號’及‘青心大冇’之製程樣品水萃液的水色與不同兒茶素異構物的含量相關性不同，顯示有品種差異。由本研究的結果，可初步由茶湯水色或水萃液之L、a、b值，可推估茶葉內較大量兒茶素類物質之含量。

This research is focused on differences caused by oxidation of catechin in color of tea infusion. The relationship of color of tea infusion and catechin content was discussed with two segments of experiment, and we tried to establish a method estimating catechin in tea infusion fast via the color of tea infusion. The first part is to realize the effect of seasons to the relationship between color of tea infusion and catechin level. In a comparison of tea made in spring and autumn, higher correlation was found in ∆E of color of tea infusion with high level of catechin (C) (R=-0.72, -0.62), epicatechin-3-gallate (ECG) (R=-0.64, -0.92), and epigallocatechin (EGC) (R=-0.77, -0.92). As fermentation level increased, a decrement was found in total catechin content, and the color of tea infusion changed. The main catechin isomers that affected the value of L, a,and b were EC, EGC, EGCG and C. Through forward stepwise regression analysis, we can estimate the content of EGC, EGCG, and C by using following formulas: EGC = (-0.60) L + (1.19) a+ 0.79 b + (-0.87) ∆E +55.52, C = (-0.98) L + (-2.80) a +85.46, EGCG = (-5.87) L+ (-11.13) a+487.1. In the second part, we observed the variation of catechin content in the making prosess of tea with different level of fermentation, such as green tea, pouching tea, oolong tea, and black tea. In the experiment, we used ‘TTES No.12’ and ‘Chin-Shin Dah Pan’ as the raw material for tea making. In ‘TTES No.12’, the catechin content varied dramatically in tea making process, especially in pouchung tea andoolong tea , while slightly in green tea and black tea. When analyzing the relationship between color of water extract, from powder of tea which collected in each tea making process, and catechin content, we found catechin content and color of tea powder infusion was highly related in low-fermentation-level pouchung tea, high-fermentation-level oolong tea , and full-fermentation-level black tea. In the process of making low-fermentation-level pouchung tea, the value of b, measured from the color of water extract, significantly correlated with catechin content of C, EGC, and EGCE, GCG (R2= 0.64, 0.72, 0.69, and 0.44. p < 0.01), when using ‘Chin-Shin Dah Pan’. While using ‘TTES No.12’, the value of b was significantly correlated to catechin content of EC, EGC, and EGCE (R2= 0.41, 0.61, and 0.52. p < 0.01). As for making high-fermentation-level oolong tea , the value of b when using ‘Chin-Shin Dah Pan’ was significant correlated to the content of C, EC, EGC, and EGCG (R2 = 0.61, 0.76, 0.92, and 0.77. p < 0.01) in the process of making tea. While, the value of L, a, and b, measured from water extracts of ‘TTES No.12’, all related to EC, EGC, EGCG, GCG, EGC, and CG (p < 0.01). The value of b, measured from black tea water extracts of each making process using ‘Chin-Shin Dah Pan ’, correlated highly with the content of C, EGC, EGCG, and ECG(R= -0.78, -0.87, -0.95,-0.88, p < 0.01). For ‘TTES No.12’ in black tea making process, measured from water extracts, the value of L, a,and b all significantly related with EC, EGC, and EGCG(p < 0.01). In brief, for both ‘TTES No.12’ and ‘Chin-Shin Dah Pan ’,the color of water extracts from each process sampling separately correlated with contents of different catechin isomers, revealing differences within cultivars. According to the results, measurement of L, a, and b from color of tea infusion or water extracts can be used to estimate the contents of major catachin isomers.