永康山茶芽葉性狀，內容物與品質之季節性變化

Abstract

永康山茶是位於中央山脈東側的台灣原生山茶，茶湯具有特殊香氣、滋味，適製成紅茶，具高產量、抗病蟲害等特性，於2019年經由單株選拔選育出‘台茶24號’。永康山茶新育成之品系，目前主要種植於茶業改良場台東分場，而永康山茶之芽葉性狀、內容物與氣象因子之相關性研究較為缺乏。本試驗探討季節對永康山茶芽葉性狀，鮮葉與製成紅茶之內容物含量及揮發性化合物之影響。為瞭解紅茶製作之參數，先測定含水率、細胞膜熱穩定性、多元酚氧化酶(Polyphenol oxidase, PPO)活性之變化，再進行紅茶之製造。試驗中室內萎凋期間細胞膜熱穩定性隨含水率下降而降低。PPO活性於從萎凋0小時至3小時內降至低點，至萎凋15小時後快速上升，於揉捻後下降。於2020年春茶、第一次夏茶、第二次夏茶、秋茶、冬茶，2021年春茶、第一次夏茶、秋茶共8個季節採摘‘永康1號’、‘永康5號’、‘永康13號’、‘永康20號’，對照品種‘台茶8號’、‘台茶18號’、‘台茶21號’之茶菁，每個品種 (系)分別量測標準芽之芽葉性狀，再採鮮葉及製成紅茶；分析茶葉內容物、揮發性化合物；由專家感官品評紅茶，並分析茶葉品質與內容物、芽葉性狀間之關係及上述三者與氣象因子間的關係。經單因子分析及單元線性迴歸分析後，茶葉內容物與芽葉性狀受品種及氣象因子影響。內容物部分，氣溫、日照量、日照時數與鮮葉總多元酚類、兒茶素及咖啡因呈正相關，與胺基酸呈負相關。芽葉性狀部分，氣溫、日照量、日照時數與葉長、葉寬呈負相關，與葉厚呈正相關；雨量與節間徑及節間長呈正相關。所有品種(系)紅茶揮發性化合物在季節間有一定的差異，以種類而言，春茶、夏茶以及秋茶，分別可辨得55、47、64種揮發性化合物。以供試品種中辨得揮發性化合物之相對豐度進行主成分分析，結果春茶與主成分一正相關且成分負荷量較大的化合物為己酸己烯酯、甲基水楊酸、香堇酮，帶有花香及薄荷香味；與主成分二正相關且成分負荷量較大的化合物為長葉烯、二丁基對甲酚，帶有木質香及具溫和的樟木香。夏茶與主成分一正相關且成分負荷量較大的化合物為二丁基對甲酚，帶有木質香；與主成分二正相關且成分負荷量較大的化合物為己酸己烯酯，帶有木質香及青草香。秋茶與主成分一正相關且成分負荷量較大的化合物為二丁基對甲酚，帶有木質香；與主成分二正相關且成分負荷量較大的化合物為異蘭烯、二氫獼猴桃內酯，帶有花香、水果香。供試品種紅茶品質大致上以對照品種高於永康山茶，尤以台茶18號最高，季節性而言以秋季品質最高。本研究分析氣象對茶葉品質、內容物及芽葉性狀的相關性，希冀提供茶葉生產之參考依據。

Yung-Kang tea does belongs to Taiwan indigenous wild tea, located on the east side of Central Mountain Range. Brewed black tea has special flavor and aroma. Yung-Kang tea is suitable for making black tea, and has the characteristics of high yield and resistable to pests and diseases. ‘TTES No. 24’ was named by pure line selection in 2019. The new lines of Yung-Kang tea are mainly cultivated in Tea Research and Extension Station (TRES) Taitung branch. It is deficiency about the research of the correlation between shoot succulent characteristics, contents and climate factors of Yung-Kang tea. This experiment aims to discuss seasonal changes of shoot succulent characteristics, contents of fresh leaf and made black tea. In order to understand the black tea processing parameters, water content, membrane thermostability (MTS) and activitiy of polyphenol oxidase (PPO) are measured. MTS decreased along with water content during indoor withering. The activity of PPO decreased during first 3 hours, increased after 15-hour indoor withering, then decreased after rolling. Plucking fresh tea leaves of 8 cultivars (lines), including ‘Yung-Kang No. 1’, ‘Yung-Kang No. 5’, ‘Yung-Kang No. 13’, ‘Yung-Kang No. 20’, ‘TTES No. 8’, ‘TTES No. 18’, and ‘TTES No. 21’ in spring, 1st summer, 2nd summer, autumn, winter tea season of 2020, and spring, 1st summer, autumn tea season of 2021. The shoot succulent characteristics of every cultivar (line) were measured, and the internal composition contents of fresh leaf and made black tea, volatile compounds of made black tea, and sense evaluation of brewed black tea were analyzed. Finally, the correlations between quality of tea, contents, shoot succulent characteristics and climate factors were analyzed. The contents and shoot succulent characteristics are affected by cultivars (lines) and climate factors via single factor ANOVA analysis and single liner regression. In terms of contents, there is positive correlation between temperature, insolation, insolation duration and content of polyphenol, catechin isomers and caffeine of fresh leaf, there is negative correlation between temperature, insolation, insolation duration and content of amino acid. In terms of shoot succulent characteristics, there is negative correlation between temperature, insolation, insolation duration and length of leaf, width of leaf, there is positive correlation between temperature, insolation, insolation duration and thickness of leaf. There is positive correlation between accumulated precipitation and diameter of internode, length of internode. There are seasonal changes of composition of volatile compounds in all cultivars (lines). In terms of composition of volatile compounds, 55 volatile compounds in spring, 47 volatile compounds in summer, and 64 volatile compounds in autumn are identified. Running principle component analysis (PCA) by relative abundance (REL) of identified volatile compounds. Hexanoic acid-2-hexenyl ester, methyl salicylate, ionone that have flower and mint aroma have positive correlation with principle component 1 (PC1) and more component loading in spring 2021. Longifolene, butylated hydroxytoluene that have woody and mild camphor aroma have positive correlation with principle component 2 (PC2) and more component loading in spring 2021. There is positive correlation between butylated hydroxytoluene that has more component loading and PC1 in summer 2021. There is positive correlation between hexanoic acid-2-hexenyl ester that has more component loading and PC2 in summer 2021. There is positive correlation between butylated hydroxytoluene that has more component loading and PC1 in autumn 2021. There is positive correlation between copaene, 5,6,7,7-tetrahydro-4,4,7-trimethyl-2(4H)-benzofuranone that have flower, fruity aroma, more component loading and PC2. The quality of black tea made of control cultivars is higher than Yung-Kang tea, especially black tea made of ‘TTES No. 18’ has highest quality in autumn 2021. This experiment want to provide reference of tea production via correlation between quality of tea, contents and shoot succulent characteristics.