摘要或動機

Tea is the most widely accepted and consumed beverage worldwide due to its characteristic aroma and taste. Recent studies have provided the strong scientific basis for understanding the health promoting effects and cancer preventive actions of tea. The components of tea especial the catechins are varied with the conditions of making tea. To understand and determine the chemical composition of tea is very important. Some investigations of the parameters on the storage and making of tea were carried on in this study. The kinds of tea studied were including black tea, oolong tea, green tea, and instant tea bags. A high performance liquid chromatograph combined with UV detector and mass spectrometer used to analyze the components of tea. The results showed that the composition of tea solution is dependant of the exposure of light. One of the components of tea, (-)-epicatechin methylgallate (ECMG) was oxidized to quino form. The concentrations of (-)-catechin gallate (ECG) decreased and one of new compound (M.W. 442) produced with increasing the storage time. From the results show tea made with cold water is better than that made with hot water. The ingredients in green tea were changed faster than those in fermentative black tea and oolong tea. The components of tea can be kept unchanged for a long time at low temperature. In refrigerator, the time can be extended to overnight. 茶由於其具有特殊的芳香氣味及口味，廣泛地被世人用為飲料，近年來的研究證據顯示茶具有促進身體健康和防癌功效，但茶中成分之變化，尤其兒茶素隨茶的種類、茶沖泡保存方式及置放時間而有所不同，因此對於茶中成分及沖泡方式的認知是一門重要的課題。 本實驗主要是探討茶沖泡時間及貯存條件，對於茶液所含兒茶素變化的影響，探討的茶包含紅茶、烏龍茶、綠茶及其茶包。並使用質譜儀及高效能液相層析質譜儀配備紫外光偵測器分析茶液中之成分，實驗結果顯示成分變化速率以未發酵的綠茶較發酵的紅茶和烏龍茶快；低溫儲存時，亦可延緩茶液成分的變化，例如加蓋並存放於冰箱，則茶置放至隔夜其成分均未改變；同時結果顯示成分產生變化者，主要為兒茶素氧化，如將多酚類氫氧基經氧化變成?（quino） ，其次為斷裂再產生聚合其中綠茶以不照光變化較大。本研究並經實驗發現如果以冷開水沖泡綠茶20~30分鐘，咖啡因的溶出量雖略多於沖泡2分鐘的熱茶，但各種兒茶素的溶出量卻遠高之，尤其置放至隔夜茶液成分仍無氧化現象。