中文摘要：

[目的]研究普洱茶茶褐素清除DPPH自由基效果的影响因素。[方法]以云南普洱茶为主要研究对象,对不同翻堆样、不同贮藏年限以及新老2种加工工艺普洱茶的茶褐素（theabrownin,TB）进行提取分离,利用DPPH方法研究茶褐素及茶汤的自由基清除效果和抗氧化活性。[结果]普洱茶一翻至四翻茶褐素含量呈先降后升趋势。不同pH值条件下,不同翻堆样含1mg/ml茶褐素溶液随pH值增加DPPH自由基清除率逐步下降,但均低于对照维生素C溶液;不同年限工艺的茶褐素,在pH值3.0~6.0条件下,自由基清除率均缓慢下降,pH值〉6.0时,2001新工艺茶和老工艺茶下降幅度明显,红茶和2005新工艺普洱茶下降趋势不明显。不同浓度条件下,不同翻堆样茶褐素随着浓度增加自由基清除率也增加,一翻至四翻茶褐素中,四翻茶褐素自由基清除率最高达46.56%±0.88%;不同年限、工艺的茶褐素,自由基清除率随浓度增加呈上升趋势,在0.04~0.06mg/ml茶褐素含量条件下红茶自由基清除率呈上升趋势,普洱茶茶褐素呈下降趋势。在pH6.0、含0.1mg/ml茶褐素时,不同翻堆样随翻数的增加自由基清除率上升;不同年限工艺茶汤和茶褐素溶液中,清除自由基率从高到低依次是：2001年新工艺﹥2001年老工艺﹥2005年新工艺,无论是不同翻堆样,还是不同年限工艺生产,在pH6.0、含0.1mg/ml茶褐素条件下,茶汤清除自由基能力均强于茶褐素溶液。上述结果表明影响普洱茶茶褐素清除DPPH自由基效果的因素较大,发酵时间、发酵工艺、贮藏年限、使用浓度及pH值对其均有较大影响,为保证较好的自由基清除效果茶褐素适宜在pH6.0、0.08~0.1mg/ml浓度下添加使用。[结论]该研究结果为未来普洱茶茶褐素功能性产品的开发奠定了基础。

英文摘要：

[Objective] This study aimed to explore factors influencing the effects of theabrownin in Pu-erh tea on scavenging DPPH radicals. [Method] Taking Pu-erh tea as main research object, theabrownin in Pu-erh tea from tea piles with different times of mixture, stored for different years and processed by both the old and new techniques were extracted and isolated. And DPPH method was used to study the effects of theabrownin solution and tea liquor on scavenging radicals and their antioxidant activity. [Result] The result showed that the theabrownin content in Pu-erh tea from tea piles with one to four times of mixture revealed a first declining and subsequently rising trend. Under different pH conditions, the rates of DPPH radical scavenging of 1 mg/ml theabrownin solution made from tea piles with different times of mixture decreased gradually with the increase of pH, and all the rates were lower than that of the control vitamin C solution; the rates of DPPH radical scavenging of theabrownin from tea samples stored for different years and produced by different techniques dropped slowly within pH range 3.0-6.0; when pH was higher than 6.0, the rates of DPPH radical scavenging of theabrownin from tea samples produced by both new and traditional techniques in 2001 declined obviously, while the declining trend was not obvious in either the black tea or the Pu-erh tea produced by new technique in 2005. Under different theabrownin concentrations, the rates of DPPH radical scavenging of theabrownin solution made from tea piles with different times of mixture ascended as the concentration increased and the highest rate occurred in tea pile with four times of mixture, reaching up to 46.56%±0.88%; for tea samples stored for different years and produced by different techniques, the rates of DPPH radical scavenging of theabrownin rose gradually with the increase of the theabrownin concentration; the rate of radical scavenging of theabrownin in the black tea ascended obviously and that in Pu-erh tea was decreasing within the conce