碩士 國立中興大學 生物科技學研究所 101 Tea is widely consumed for over several thousand years in Mandarin China. Up to these days, tea has become the most consumed beverages around the world. In Taiwan, oolong tea is the most popular tea because of its unique flavor and taste. Astringent taste is considered to be one of the characteristics that lower the quality of oolong tea. The main substances causing astringent taste in oolong tea are catechins. Catechins can be further divided into two subgroups, non-gallate-type catechins and gallate-type catecins. It has been shown that gallate-type catecins are far more astringent than non-gallate-type catechins. In tea trees, the main non-gallate-type catechins are (-)-epicatechin (EC) and (-)-epigallocatechin (EGC), and the main gallate-type ones are (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG). Oolong tea produced from leaves of Camellia sinensis L. cultivated at higher altitude are generally tasted less astringent than those grown at lower altitude becaus