|Abstract: ||本研究以市售之烏龍茶為研究對象，探討其茶湯中各成分苦澀味成分如兒茶素類化合物、咖啡因等。甘味成分如胺基酸及茶胺酸及香氣成分等的分析。並嘗試以不同的水溫度（70、80及90℃）和時間（1、2及3 分鐘）萃取烏龍茶，探討其對苦味、澀味、香味及甘味成分之對溶出影響，並分析各種萃取條件所得茶湯中兒茶素類化合物、咖啡因、總胺基酸、茶胺酸及茶色等成分之變化，再依此實驗之結果選擇較佳沖泡條件，以求得茶湯中較多茶多酚含量、較多甘味成分之溶出、較多香氣成分含量及最少咖啡因含量。並以90℃水溫進行烏龍茶之不同沖泡次數對茶湯中成分之探討，其沖泡條件分別為第一泡至第五泡之沖泡時間分別為1、1.5、2、2.5及3分鐘，從第六泡至第十泡沖泡時間都維持3分鐘。同時並自茶湯中抽取香氣成分以GC-MS進行茶湯之香氣成分之定性及定量，並分析各泡茶湯中兒茶素類、咖啡因、總胺基酸及茶胺酸之含量變化可供作泡健康茶及製備飲料茶的依據。 茲將本試驗之結果歸納如下： 1、 不同萃取溫度與時間之茶湯，依所建立之分析結果顯示茶湯中各成分之含量都隨著萃取溫度增加及萃取時間加長而增加。茶湯中之總兒茶素類含量於70℃時1~3分鐘之萃取量為4.35∼7.31 mg/g、80℃為5.03∼7.92 mg/g、90℃為6.04∼10.27 mg/g。總胺基酸含量70℃為0.79∼1.20 mg/g、80℃為0.84∼2.86 mg/g、90℃為1.17∼3.15 mg/g。而咖啡因之含量70℃為0.41∼0.94 mg/g、80℃為0.60∼1.13 mg/g、90℃為0.80∼1.70 mg/g。 2、 烏龍茶在90℃下連續沖泡十次，其各茶湯中總兒茶素之含量分別為5.88、9.84、12.13、10.74、12.31、12.59、12.65、11.73、10.19及9.35 mg/g，累積10次茶湯中之兒茶素化合物量為茶葉中所含兒茶素的88%。 3、 甘味成分的胺基酸在第1泡及第2泡茶湯並不高，僅有1.0~1.2 mg/g，第3~5泡茶湯中分別含有約2.9、3.5、3.0 mg/g左右，第6泡以後到第10泡則仍維持在1.0 mg/g 左右，顯示第3~5泡之茶湯最具甘味。 4、 茶湯中咖啡因含量以第一次沖泡之茶湯量最少，約為0.7 mg/g，隨後2~10次茶湯中之量雖有增減，但均維持在1.5~2.0 mg/g上下。 5、 烏龍茶茶湯之香氣成分GC-MS分析結果共鑑定出36個化合物，如phenylethyl alcohol、methyl jasmonate及linaool及indole等。其主要香氣成分為具類葡萄柚香及溫和花香之indole。在第2泡時有最大之香氣含量約為2898 μg/mL，隨沖泡次數進行至第5泡其含量減為1296 μg/mL，至第10泡其含量僅剩186.5 μg/mL。 6、 茶湯中之DPPH捕捉自由基能力與茶湯中之兒茶素量呈正的相關。 7、 建立茶湯中各成分之分析方法以作為模式評估之參考依據。|
The study focus on commercial oolong tea to investigate the content of its bitter-stringent components such as catechin and caffeine, the sweet components such as amino acids and theanine, and the fragrance components in tea. We attempted to infuse the tea leaves in water at different temperatures (70, 80 and 90℃) and infusion time (1, 2 and 3 min) to extract the oolong tea and investigated the effects of brewing conditions on dissolution of bitter, stringent, fragrant and sweet components in the tea infusions. Furthermore, the effects of various extraction conditions on content variations of tea infusions regarding catechin, caffeine, total amino acids, theanine, and tea color were examined. Based on the experimental results, the better brewing conditions were selected in order to obtain higher catechin content, greater sweet components, greater fragrance, and least caffeine content. We also examined number of oolong tea brewing using 90℃ water on the components of tea infusions. The brewing conditions for the 1st to 5th brewing were 1, 1.5, 2, 2.5 and 3 min, respectively; and from 6th to 10th brewing, 3 min intervals were applied. The fragrant components from the tea infusions were extracted and analyzed qualitatively and quantitatively using GC-MS. The catechin, caffeine, total amino acids, and theanine content variations could serve as criteria for preparing most healthful tea and beverage teas. The results of the study are summarized below: 1. Based on the results of analysis, various components of the tea infusions obtained using different brewing temperatures and times tend to increase with brewing times. The total catechin content for teas brewed at 70℃ for 1~3 min was 4.35 to 7.31 mg/g; those brewed at 80℃ was 5.03 to 7.92 mg/g; and those brewed at 90℃ was 6.04 to 10.27 mg/g. The total amino acids content for teas brewed at 70℃ was 0.79 to 1.20 mg/g; those brewed at 80℃ was 1.17 to 3.15 mg/g; and those brewed at 90℃ was 1.17 to 3.15 mg/g. For caffeine content, teas brewed at 70℃ had 0.41 to 0.94 mg/L; those at 80℃had 0.60 gto 1.13 mg/g; and those at 90℃ had 0.80 to 1.70 mg/g. 2. Ten consecutive brewing at 90℃ gave tea liquid catechin content of 5.88, 9.84, 12.13, 10.74, 12.31, 12.59, 11.73, 10.19 and 9.35 mg/g, respectively. The cumulative catechin content of the 10 brewing accounted for 88% of all catechin in the tea leaves. 3. The sweet component, amino acids were relatively low in the 1st and 2nd infusions, containing 1.0 to 1.2 mg/g, respectively. In the 3rd to 5th infusion, they reached 2.9, 3.5 and 3.0 mg/g, respectively. In the 6th to 10th infusions, there were still ca. 1.0 mg/g content. Thus the 3rd to 5th infusions were particularly sweet. 4. There was the least caffeine content in the 1st infusion of the oolong tea, ca. 0.7 mg/g; in the 2nd to 10th infusions, caffeine content varied, but maintained a level of 1.5 to 2.0 mg/g. 5. Thrity-six compounds were identified by GC-MS for the fragrance of the tea infusions. These included phenylethyl alcohol, metyl jasmonate, linalool and indole etc. The main component was indole with fragrance akin to grapefruit and mild flora scent. The fragrances were at the maximum in the 2nd infusion reaching a content of 2898 μg/mL. These decreased to 1296 μg/mL in the 5th infusion and 186.5 μg/mL in the 10th. 6. In the tea infusions, the free radical scavenging capacity determined by DPPH assay showed a positive correlation with the catechin content. 7. In the study, we established the methods of analysis various components in tea infusions which could be used as a reference for model evaluations.