还原性多酚类与茶叶的抗氧化有关。还原性多酚类被电氧化后,在325 nm处产生新的光吸收峰,茶汤电氧化前后在325 nm处光吸收的差值与还原性多酚类含量成线性关系,利用此关系建立了快速测定茶还原性多酚类含量的新方法。应用本方法测定结果显示,绿茶中还原性多酚类含量较高,而普洱茶中含量极低。
For the purpose of obtaining a preliminary quantitative method to analyze the reductive polyphenols in tea that are extremely unstable under normal condition. Reductive polyphenols are related to the antioxidantive activity of tea, and their determination is important for understanding the extent of chemical reaction that occurs in tea during the manufacturing process. Electrooxidation of the reductive polyphenols led to a new absorption maximum at 325 nm. The optical density difference at 325 nm of tea solution before and after electrooxidation was directly proportional to the content of reductive polyphenols, which was used to measure the content of reductive polyphenols in tea. Reproducibility and accuracy of this analytical method was not satisfactory due to the unstable nature of reductive polyphenols under normal condition. Application of this method to the several teas revealed that concentration of reductive polyphenols was high in green tea and very low in Pu-Erh tea.
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