萎凋時間及攪拌強度對包種茶前期製程茶菁內容物之影響

Abstract

包種茶製程中，攪拌與靜置是形塑包種茶香氣滋味的關鍵步驟。本研究鎖定第 二次攪拌及靜置過程，由攪拌時機與攪拌力道兩個方面，經由茶菁內容物成分分析，探討攪拌操作的條件對茶菁及後續變化的影響。以台茶12號茶菁，分別於2020年冬季與2021年春季製作包種茶，依慣行方法進行日光萎凋及第一次攪拌靜置，再分別於不同的靜置時間開始進行第二次攪拌，以靜置時間標示不同的第二次攪拌時機處理。攪拌力道的試驗則以2021年冬季茶菁進行包種茶製作，慣行製作至第二次攪拌時，分別以不同趟數的人工攪拌及以攪拌機攪拌不同旋轉圈數，作為兩者攪拌方式的攪拌力道處理。所有試驗處理皆於攪拌前、攪拌後及靜置期間分別取樣，分析茶菁中非揮發性成分含量與揮發性成分組成。沒食子酸、咖啡因及兒茶素異構物的含量，在不同攪拌時機處理間無顯著差異，但攪拌強度較高時，攪拌後的兒茶素含量顯著較高。不同攪拌時機下的茶菁，氣味分子組成以香葉醇、吲哚、羅勒烯及金合歡烯的相對含量有顯著差異，為主要氣味貢獻化合物，其不同的組成比例可區別不同的第二次攪拌時機。在第二次攪拌前，吲哚、苯乙醛、羅勒烯及金合歡烯隨著攪拌啟動時機越晚相對含量增加；在攪拌後靜置期間，吲哚在靜置60至150分鐘後進行攪拌的處理組中相對含量最高，而羅勒烯及金合歡烯在靜置270至330分鐘後進行攪拌的處理組中相對含量有下降的趨勢。以人工攪拌與攪拌機攪拌，在攪拌剛完成時的氣味組成，人工攪拌組中有較高相對含量的反式己烯醛與反式β紫羅蘭酮，而茉莉內酯的相對含量以攪拌機攪拌的處理較高。攪拌後靜置60分鐘，單萜類的芳樟醇、羅勒烯，倍半萜類的橙花叔醇、金合歡烯，以及苯丙烷類衍生物的吲哚、苯乙醛，以攪拌機攪拌的相對含量顯著較高；而在靜置120分鐘時，羅勒烯、吲哚、橙花叔醇及金合歡烯則以人工攪拌相對含量較高。所有處理在靜置過程中都顯示氣味成分的相對含量會持續累積。依據本研究的結果，第二次攪拌時的啟動時機點，約以60至80分鐘為一個循環，第一次靜置時間越長，吲哚、羅勒烯、金合歡烯等成分會有較顯著的累積。攪拌強度越強，會顯著增加攪拌後的兒茶素含量，兒茶素含量越高，在靜置後金合歡烯、苯乙醛及茉莉內酯的表現越顯著。攪拌啟動時機及攪拌強度顯著影響氣味組成及後續的氣味變化，特定的關鍵氣味組成可作為包種茶製作時判別攪拌條件之評估指標。

In the process of manufacturing paochung tea, the shaking and resting process are the crucial steps in the formation of aroma and taste. The study targets the second shaking and resting process in terms of shaking timing and intensity. The volatile organic compounds (VOCs) and the non-volatile constitutes of fresh tea leaves are analyzed to explore the effects of shaking condition. In the experiment of shaking timing, paochung tea was made in the 2020 winter and 2021 spring with cv. TTES No.12 (Jhinhsuan). After sun withering and first shaking process, the treatments of the second shaking process by different resting time interval were acitivated respectively. In the experiment of shaking intensity, paochung tea was made in the 2021 winter. The treatments were performed by manual shaking and mechanical stirring with stirrer respectively. All treatments were sampled before shaking process, and during the resting process after shaking. The VOCs and nonvolatile components of fresh tea leaves were analyzed. The results showed that there was no significant difference in the content of gallic acid, caffeine and catechin isomers between the treatments with various shaking timing while the catechin content was increased in higher shaking intensity. In addition, geraniol, indole, β-ocimene and α-farnesene were the main odor-contributing compounds in the volatile components of fresh tea leaves during the second shaking process, which could distinguish different treatments of shaking timing. Before the second shaking process, the relative content of indole, benzeneacetaldehyde, β-ocimene and α-farnesene was increased with the growth of shaking timing. During the resting period, the relative content of indole was highest in the treatments after resting for 60 to 150 minutes, while the relative content of β-ocimene and α-farnesene was decreased in the treatments after resting for 270 to 330 minutes. Compared to treatments of manual shaking and mechanical stirring with stirrer, the relative content of trans-2-hexenal and trans-β-ionone was significantly higher in manual shaking. In contrast, jasmine lactone had higher relative content in mechanical stirring than manual shaking. Samples that rested for 60 minutes in all mechanical stirring treatments showed higher relative content in linalool and β-ocimene (monoterpenoids), nerolidol and α-farnesene (sesquiterpenoids), and indole and benzeneacetaldehyde (phenylpropanoids). Samples that rested for 120 minutes in all manual shaking treatments have higher relative contents of β-ocimene, indole, nerolidol and α-farnesen. It is worth noting that VOCs had kept accumulating during resting process in all treatments. The results of this study showed that the change of odor components in various shaking timing before the second shaking process had presented a interval of 60 to 80 minutes approximately. As an increasing resting time, there was a significant accumulation in the relative content of indole, β-ocimene and α-farnesene. With a growing level of shaking intensity, the catechin content after shaking process increased significantly. The higher content of catechin, the higher relative content of α-farnesene, benzeneacetaldehyde and jasmine lactone was observed. Thus, the effects of shaking timing and shaking intensity were clearly on VOCs component and subsequent variations of VOCs. The specific odor composition could be used as a key indicator for shaking process during the manufacturing of paochong tea.