Components and Antioxidant Activity in Teas after Autoclave Treatment

Abstract

In this study, Puerh and Oolong teas were used as materials to investigate the changes in catechins content and to compare their antioxidant activities, with different time periods of autoclave treatment. Tea samples were extracted with methanol and the quantitative variation of each catechin marker component was analyzed by high performance liquid chromatography. Moreover, antioxidant assays were determined according to total phenolic content and scavenging ability of 1, 1-diphenyl-2-picrylhydrazyl (DPPH) free-radicals. Two kinds of tea showed similar results after autoclave treatment. Catechins were transformed from epicatechins into non-epicatechins. Gallate acid content was increased; however, caffeine was not affected. In antioxidant assays, the antioxidant ability of Puerh tea with time in descent order was 10 min ＞ 20 min ＞ control ＞ 30 min ＞ 40 min and of Oolong tea was control ＞ 10 min ＞ 20 min ＞ 30 min ＞ 40 min. In total phenolic content, Oolong tea was rapidly decreased to 36.95% after 10 minutes of autoclave treatment and Puerh tea was gradually decreased from 10 min to 40 min. Finally, this study showed that autoclave treatment directly affected catechins and indirectly affected total phenolic content. Antioxidant ability of teas decreased with the increase of duration of autoclave treatment.