電位式茶品發酵度探針之研究

Potentiometric Probe for the Fermentation Degree of Tea

張福祥(Fu-Hsiang Chang) ； 陳柏中(Bo-Chung Chen) ； 陳力騏(Richie L. C. Chen) ； 鄭宗記(Tzong-Jih Cheng) ； 陳右人(Iou-Zen Chen) ； 盧福明(Fu-Mung Lu)

《台灣農學會報》 9卷2期 (2008/04) Pp. 101-113

https://doi.org/10.6730/JAAT.200804_9(2).0001

摘要

部份發酵茶的發酵度為其品質的一個重要參數，但直到目前為止，產、學界仍未提出一個客觀的參數與有效的分析方法。因為茶的發酵本質上為好氧發酵，本研究擬以茶湯的氧化還原電位作為茶品發酵度的新指標。
電極使用白金絲與銀／氯化銀參考電極為電極對來量測此氧化還原電位。量具則使用具高輸入阻抗（大於十億歐姆）的pH電極用電位計以取得茶湯中微弱的氧化還原電位訊號。本系統可於十秒內取得高再現性（相對標準差小於3%）的電位訊號。以標準氧化還原對（黃血鹽／赤血鹽）測試此系統發現其電位值嚴密地遵守能斯特方程式，足見本系統分析值的正確性。
於包種茶室內萎凋期間採樣測試的結果，茶湯氧化還原電位與發酵過程呈規則性的正相關變化。以不同種類的茶作測試，所得到的電位訊號與專家推測的發酵程度呈高度的相關（線性相關係數大於0.9）。

關鍵字

茶 ； 發酵 ； 氧化還原電位

並列摘要

The degree of fermentation used is crucial for the quality of partly-fermented tea, but an objective index and analytical methods are still needed. Since tea fermentation is an aerobic bioprocess, the possibility of using redox potential as a fermentation parameter was investigated in this study.
A platinum wire /Ag/AgC1 reference electrode pair and a pH meter with high input impedance (over Giga ohm) were used to obtain the redox potential. The response was rapid (less than 10 seconds) and reproducible (CV＜3%). The reliability of the home-made system was further proved by its strict Nernst behavior as testing with the standard redox pair, ferrocyanide and ferricyanide showed.
During the indoor withering process in making Bao-Chung tea, a popular semi-fermented tea in Northern Taiwan, the redox potential of tea infusion (with RO water or phosphate buffer) showed a strong correlation with the progress of fermentation. The potentiometric results of several kinds of tea were also strongly correlated with the degrees of fermentation (r^2＞0.9).

並列關鍵字

Tea ； Fermentation ； Redox Potential