不同製程冷凍對包種茶萃取之影響

以坪林地區之手採 ‘臺茶12號’ (金萱)茶菁為材料，於條形包種茶的主要製程段點，將半成品茶菁以-20°C冷凍，探討不同製程冷凍之包種茶七次萃取，分別與總萃取量之變化，並分析茶湯之內容物含量。研究結果顯示，茶葉於前期製程階段之日光萎凋與室內萎凋後冷凍，其內容物萃取量較殺菁後冷凍之後續製程低，甚至低於不經冷凍的乾燥毛茶；於殺菁後的製程冷凍，包括殺菁後、揉捻後、初乾後之萃取總量及萃取速率，均明顯優於不經冷凍之毛茶，其中尤其是揉捻後冷凍者，無論在萃取率、多元酚類、游離胺基酸、咖啡因、兒茶素類等，效果更為顯著。七次沖泡過程之萃取模式主要受製程影響。多數處理於第2、3次沖泡時，有較高之萃取量，尤以揉捻後冷凍者更顯著於2泡時萃取量最高，且其沖泡次數與含量間大多呈顯著以上之三次曲線迴歸關係。殺菁前的製程冷凍，其七沖泡間萃取量變化則趨近於線性關係。茶湯的主要內容物成分之萃取模式差異較大。咖啡因之七次沖泡萃取模式，於殺菁之前冷凍的製程，大多呈現二次倒函數的模式，於殺菁之後冷凍的製程則呈現開口向上之二次方程式。前者於第1泡時均已可萃取出大部分的咖啡因，後者則於前兩泡萃取出絕大部分之咖啡因；於第5泡以後，咖啡因萃取量已非常低。總兒茶素之七次沖泡萃取量模式，於殺菁之前冷凍的製程，在沖泡次數間變化不大，主要受EGCG萃取變化量之影響；於殺菁之後冷凍的製程，其七次沖泡萃取模式則呈現二次到三次之迴歸關係，於第2至4泡間之萃取量較高。多元酚類及總游離胺基酸之七次沖泡萃取模式均與總萃取量之萃取模式相近。不同製程冷凍之冷凍茶之萃取率與萃取效率顯然與含水量間之關係不密切，可能與茶菁在製程過程中之內容物變化有關，而殺菁與揉捻是其關鍵步驟。因此，如以萃取量與萃取速率來看，冷凍茶最佳冷凍時機建議在殺菁或揉捻後進行冷凍，尤以揉捻後冷凍之效果最佳。

關鍵字

冷凍茶；不同製程冷凍；高萃取率；萃取效率

並列摘要

Hand-picked fresh leaf of 'TTES No. 12' (Jhinhsuan), which harvested from Pinglin area, was used. At the main processing stage of strip type Paochung tea, the semi-finished fresh leaf is frozen at -20°C, to investigate the changes of total extraction and individual extraction in different freezing timing during Paochung tea processing, and analyzed the content of tea infusion. The results show that the extract content of tea in the early processing stage of freezing after solar withering and indoor withering are lower than that of freezing after panning, and even lower than that of made tea without freezing; The total extract content and extraction rate of Paochung tea processing that freezing after panning, rolling and primary drying, are significantly better than those of made tea, especially those of freezing after rolling, which have more significant effects on extraction rate, polyphenols, free amino acids, caffeine and catechins. The extraction model of seven brewing procedure was mainly affected by the stage of Paochung tea processing. The extract content of most treatments of freezing after panning were higher in the second and third brewing, especially those freezing after rolling, the extract content was the highest in the second brewing, and there was a significant cubic regression between the brewing times and the content. In the process of freezing before panning, the change of extract content between seven brewing approaches to a linear regression. The extraction models of the main contents of tea infusion varried greatly. In the seven times brewing extraction model of caffeine, the freezing process before panning mostly presents the model of quadratic inverse function, and the freezing process after panning showed the quadratic equation of opening up. The former can be extracted most of the caffeine in the first brewing, while the latter can be extracted most of the caffeine in the first and second brewing; After fifth brewing, the content of caffeine extracted was very low. In the seven times brewing extraction model of total catechins, the freezing process before panning had little change between brewing times, which was mainly affected by the change of Epigallocatechin Gallate (EGCG) extraction; In the process of freezing after panning, the seven brewing extraction model showed a quadratic to cubic regression, and the extract content was higher between the second and fourth brewing. The seven times brewing extraction model of polyphenols and free amino acids were similar to that of total extraction. The extraction rate and extraction efficiency of frozen tea which are freezing in different stage during Paochung tea processing are obviously not closely related to the moisture content, which may be related to the changes of the contents of fresh leaves during the Paochung tea processing, panning and rolling which are the key steps. Therefore, in terms of extract content and extraction rate, the best freezing timing of frozen tea is suggested to be freezing after panning or rolling, especially after rolling.