- 期刊
喝茶澀味的分子機制與科學檢測茶澀度的技術發展
Molecular Mechanism of Tea Astringency and the Development of a Technique to Evaluate Astringency of Tea Infusion Scientifically
摘要
目前已知的五種味覺中，並不包括澀覺。澀覺被認定為是一種觸覺，乃口腔上皮細胞接觸到澀味誘發物質時，所感受到的一種皺縮、拉扯或縮攏的複雜口腔感受。唾液中引發澀味的主要蛋白質為一群富含脯氨酸的蛋白質，簡稱為唾澀蛋白群。唾澀蛋白群會與飲食中的多酚類物質互相纏繞形成複合體而沉澱。這些沉澱物會附著在舌頭和口腔壁上，使得唾液失去原有完整潤滑口腔的功能，隨即刺激口腔內的末梢神經傳遞訊號給大腦而引發澀味的感受。茶湯中會導致澀味的物質有兩大類，即兒茶素類和黃酮醇配醣體，後者所能引起的澀味程度是前者的100-1000倍，然而，兒茶素類的含量遠高於黃酮醇配醣體（約100-1000倍），故飲茶時感受到的澀味應當由兒茶素與黃酮醇配醣體的加成效果所造成。有鑑於目前茶葉比賽上，澀度項目的評分單靠人體的感官品評分析，有其無法避免的缺點，本實驗室利用生物技術將人類的唾澀蛋白群中的一個蛋白質聯結至油體蛋白質，並組合成人造油體來進行茶湯澀度的檢測。當人造油體溶液與待測的茶湯進行混合後，其表面所聯結的唾液蛋白質會與茶湯中的多酚物質結合，導致人造油體聚集而上浮，其上浮速率和待測茶湯的澀度具有正相關性，可用來推算不同茶湯的相對澀度。此系統提供一個簡便、經濟、快速並貼近真實人體感官的澀度檢測。
並列摘要
Astringency, not included in the five basic tastes, is an uncomfortable tactile sense of mouth drying. It is generally caused via the aggregation of polyphenolic compounds and salivary proteins, e.g., proline-rich proteins (PRPs), leading to a rough or dry sensation in the mouth. Two types of polyphenolic compounds, flavanols (also called catechins) and flavonol glycosides, in tea infusion are regarded as the major factors responsible for the astringent sensation in tea drinking. In terms of abundance, catechins are approximately 1000 times higher than flavonol glycosides in tea infusion. However, flavonol glycosides are, in average, 1000 times stronger than catechins concerning astringency. In the tea competition, the evaluation of astringency is a tough mission for the referees when the tea samples are more than several thousands. To overcome this problem, we developed a simple detection kit to evaluate the astringency of tea infusion in a simple, easy and fast manner. One protein of PRPs was linked to oleosin or caleosin via genetic engineering, and the fusion protein was used to constitute artificial oil bodies together with triacylglycerol and phospholipid. The floating rate of artificial oil bodies mixed with tea infusion was proportional to the tea astringency.