Chen P C, Chang F S, Chen I Z, Lu F M, Cheng T J, Chen R L C
Department of Bio-Industrial Mechatronics Engineering, College of Bioresources and Agriculture, National Taiwan University, Taipei, Taiwan.
Anal Chim Acta. 2007 Jun 26;594(1):32-6. doi: 10.1016/j.aca.2007.05.012. Epub 2007 May 13.
Redox potential of tea infusion is suggested as an index for the extent of tea fermentation. The potential was measured between platinum and Ag/AgCl electrode pair with a voltmeter with high input impedance (>1000 Gohms). Phosphate buffer (10 mM, pH 7.0) was used to extract the infusion and served as the supporting electrolytes for the electrochemical measurement. The reliability (the Nernst's behavior) for redox potential measurement was verified with a standard redox couple, ferricyanide/ferrocyanide. Tentative interferences from dissolved oxygen and the major coexisting reducing chemical, ascorbate, were discussed. Redox potential showed strong correlation with the fermentation process during indoor withering process. Eleven kinds of tea with different fermentation extents including Sencha, Pilochun, Pouchong, Formosa oolong tea, Lipton green tea, Lipton black tea, and Taiwanese black tea were tested.
茶汤的氧化还原电位被提议作为茶叶发酵程度的一个指标。该电位是在铂电极与Ag/AgCl电极对之间用一台具有高输入阻抗（>1000 GΩ）的电压表进行测量的。用磷酸盐缓冲液（10 mM，pH 7.0）来提取茶汤，并用作电化学测量的支持电解质。用标准氧化还原电对铁氰化物/亚铁氰化物验证了氧化还原电位测量的可靠性（能斯特行为）。讨论了溶解氧和主要共存还原化学物质抗坏血酸的初步干扰。在室内萎凋过程中，氧化还原电位与发酵过程呈现出很强的相关性。测试了包括煎茶、碧螺春、包种茶、冻顶乌龙茶、立顿绿茶、立顿红茶和台湾红茶在内的11种不同发酵程度的茶叶。
