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Title: | 臺茶十八號茶樹之芽葉性狀、紅茶品質與內容物之季節性變化 Seasonal Variations of Young Succulent Shoot Characteristics, Black Tea Quality and Chemical Composition of TTES No.18 Tea |
Authors: | Tsu-Shin Peng 彭子欣 |
Advisor: | 陳右人(Iou-Zen Chen) |
Keyword: | 氣象因子,逐步迴歸分析,紅茶萎凋,多元酚氧化酶活性,茶葉香氣, Weather factors,Stepwise regression analysis,Black tea withering,Polyphenol oxidase activity,Tea aroma, |
Publication Year : | 2022 |
Degree: | 碩士 |
Abstract: | 茶是繼水之後為人飲用最多之飲品,其中紅茶因其醇厚風味與保健功效而廣受歡迎,佔了世界茶類飲用量的一半以上。‘臺茶十八號’ 為行政院農委會茶業改良場魚池分場育成與命名之茶樹品種,其芽葉酚胺比高,適製紅茶,所製紅茶茶湯具薄荷及肉桂般的獨特香氣,因此亦以商品名「紅玉」廣為人知。 受不同季節下氣象條件與製茶環境差異的影響,於三個主要產季—春、夏、秋所產製之 ‘臺茶十八號’ 紅茶各具特色,然而不同季節之 ‘臺茶十八號’ 紅茶,其茶葉內容物組成差異、製茶過程中之酵素活性變化,以及各季節間不同氣象條件、茶樹生長狀況與上述項目以及感官品質有何關聯性,則尚未辨明。 本文之研究目的為調查與測定不同季節間 ‘臺茶十八號’ 茶樹芽葉性狀、紅茶非揮發性品質成分與揮發性香氣物質組成,以及萎凋過程中茶葉多酚氧化酶活性及含水率變化,並進一步探討上述品質相關因子與氣象因子間的關聯性。為了解茶樹生長狀況,進行芽葉性狀調查,項目包括第一至三葉之葉長、葉寬、葉面積、葉厚,第一、二節間長與徑,以及百芽重。調查結果顯示,春茶具有最大之葉長與葉面積,意即具有最大的茶芽。百芽重以秋茶最大,春茶最小。總多元酚、總游離胺基酸與咖啡因為三大影響茶湯滋味與口感之紅茶重要非揮發性品質成分。‘臺茶十八號’ 紅茶內非揮發性品質成分分析結果,總多元酚含量於2020年以春、夏茶較高,2021年則以春茶最高;咖啡因含量於2020年以春、夏茶含量較高,2021年則以春、秋茶較高,夏茶中最低;游離胺基酸含量於2020年各季節間未有顯著差異,2021年則以春茶最高,夏茶最低。2021年所製紅茶中,各非揮發性內容物普遍以春茶之含量較高,夏、秋茶較低,可能與氣候及製程稍有不同有關,導致兩年間各非揮發性品質成分隨季節變化之趨勢並不一致。對紅茶感官品質具有影響之游離型兒茶素相對於酯型兒茶素之比值,於2021年以夏、秋茶較高,春茶較低。揮發性化合物為提供紅茶香氣者,對於紅茶品質具有關鍵性的影響。以GC-MS分析 ‘臺茶十八號’ 紅茶中揮發性化合物,共辨識出65種化合物。三季茶葉中相對豐度最高者皆為芳樟醇及水楊酸甲酯,且此二者之嗅覺閾值 (odor detection threshold, ODT) 相對較低,推測為 ‘臺茶十八號’ 紅茶中,構成嗅聞感受最重要之香氣化合物。揮發性香氣化合物之主成分分析 (principle component analysis, PCA) 結果顯示,三季茶葉明顯被分成三群,說明三季之 ‘臺茶十八號’ 紅茶確實具有不同香氣組成。2020年感官品評結果以夏茶總分最高,秋茶次之,春茶最低。將感官品評各項分數與非揮發性品質成分含量進行相關性分析結果顯示,酯型相對游離型兒茶素之比值與感官品評總分、香氣以及滋味分數皆呈正相關。以相關性分析及逐步迴歸分析探討不同季節間氣象因子、‘臺茶十八號’ 茶樹芽葉性狀以及紅茶品質之關係,結果顯示,2020年氣象因子與大多數芽葉性狀呈負向迴歸相關;2020年芽葉性狀與非揮發性品成分之間,以葉厚及節間徑兩項性狀與總多元酚和咖啡因呈顯著負相關;2020年氣象因子中,氣溫與感官品評總分具正向迴歸關係,相對濕度則與其具負向迴歸關係,此外,相對濕度與滋味分數亦具負向迴歸關係。總而言之,‘臺茶十八號’ 之芽葉性狀、紅茶中非揮發性及揮發性品質成分,以及茶葉中之多酚氧化酶 (polyphenol oxidase, PPO) 活性,受不同季節下氣象條件差異之影響。氣象因子中以日平均氣溫與紅茶中非揮發性化合物含量呈負迴歸相關,而紅茶品質成分以酯型相對游離型兒茶素之比值與感官品評分數具有正向迴歸關係。本文對於不同季節之 ‘臺茶十八號’ 茶樹芽葉性狀及紅茶品質加以探討,期能作為今後產製臺茶十八號之參考。 Tea is a beverage consumed the most all over the world besides water, and black tea is the most wide-spreading one among all types of tea due to not only its mellow and rich flavor, but also its health benefits. ‘Taiwan Tea Experiment Station No. 18’ tea plant ( ‘TTES No. 18’ ) is a kind of tea tree which was bred and named after by Tea Research and Extension Station , Yuchi Station, Council of Agriculture, Executive Yuan. Its young succulent shoot possess a high ratio of polyphenol to amino acid content, therefore, ‘TTES No.18’ tea leaves was suitable for making into black tea. ‘TTES No. 18’ black tea made under three main producing seasons, which are spring, summer and autumn, has different flavor and characteristics, due to varied weather and tea producing conditions under different seasons. However, difference of tea leaves chemical compositions, changing patterns of oxidation-related enzyme activities during black tea manufacturing process of tea leaves harvested in different seasons, and how weather factors and tea plant growing conditions under different seasons affect parameters mentioned above and also sensory evaluation quality still remain unclear. The purpose of this research is to investigate and analyze the characteristics of ‘TTES No. 18’ young succulent shoots, non-volatile compounds and volatile fragrance compounds (VFCs) of black tea, and polyphenol oxidase activity and also water content changing patterns of tea leaves during black tea withering process. Furthermore, the relationship between weather factors and parameters affecting black tea quality which was mentioned above were also investigated. To understand growing condition of tea plants, characteristics of young succulent shoots were investigated. Results showed that spring tea possess the biggest leaf length and leaf area, which means it has the biggest tea buds. Autumn tea has the heaviest hundred-bud weight and spring tea has the lightest. Polyphenols, free amino acids and caffeine were three of the most important non-volatile compounds that affect taste and mouthfeel of black tea. Results of non-volatile compounds analyzing showed that spring and summer tea produced in 2020 has higher content of polyphenols, whereas content in spring tea produced in 2021 were the highest. Regarding caffeine, spring and summer tea produced in 2020 has higher content, whereas in 2021, content in spring and autumn tea was higher. When it comes to content of amino acid, there was no significant difference between tea produced in three seasons in 2020, whereas in 2021, content was the highest in spring tea and the lowest in summer tea. Every single non-volatile compound content was the highest in spring tea and lower in summer or autumn tea in 2020, and it might due to the slightly varied weather conditions and black tea manufacturing process between the two years, leading to different changing patterns of these compounds within three different seasons. The ratio of gallated to non-gallated catechins was higher in summer and autumn tea which produced in 2021.Black tea aroma is composed of VFCs, and VFCs play a key role to black tea flavor and also quality. A total of 65 kinds of VFCs was identified from ‘TTES No. 18’ black tea produced in three seasons through GC-MS analysis. Methylsalycylate and linalool were the most abundant compounds in tea leaves produced in both three seasons, and they also possess relatively lower odor detection thresholds (ODT), which may infer that the two compounds were the most important VFCs contributing to olfactory feeling of ‘TTES No. 18’ black tea. Results of principle component analysis (PCA) of black tea VFCs showed that samples from three seasons were clearly divided into three clusters, which means that ‘TTES No. 18’ black tea produced in three seasons indeed possess different aromatic features. Results of sensory evaluation of black tea produced in 2020 showed that summer tea has the highest total score and spring tea has the lowest. Results of correlation analysis of each sensory evaluation indicator and non-volatile compounds showed that non-gallated to gallated catechin ratio has positive correlations with three sensory evaluation indicators. Results of correlation analysis and stepwise regression analysis of weather factors, ‘TTES No. 18’ young succulent shoots characteristics and black tea quality affecting factors showed that, weather factors and tea shoots characteristics had mostly negative regression relations in 2020. When it comes to the analysis results of tea shoots characteristics and non-volatile compounds content in 2020, it showed that leaf thickness and internode diameter were negatively correlated with total polyphenols and caffeine content. Lastly, among five weather factors of 2020, average temperature had a positive regression relation with sensory evaluation total score, whereas relative humidity had a negative regression relation with it. In addition, relative humidity also had a negative regression relation with taste score. In conclusion, young succulent shoots characteristics, non-volatile and volatile components, and PPO activities of ‘TTES No. 18’ tea leaves would be affected by varied weather conditions under different producing seasons. Average temperature had a negative regression relation with non-volatile compounds in black tea among five weather factors, whereas non-gallated to gallated catechins ratio had a positive regression relation with sensory evaluation score. This research investigated and discussed young succulent shoots characteristics and black tea quality of ‘TTES No. 18’, and it is hoped that these information would be applicable for producing ‘TTES No. 18’ black tea with high quality hereafter. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/86064 |
DOI: | 10.6342/NTU202204106 |
Fulltext Rights: | 同意授權(全球公開) |
metadata.dc.date.embargo-lift: | 2022-09-30 |
Appears in Collections: | 園藝暨景觀學系 |
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