烘焙溫度與時間對球型包種副茶品質改善之影響

Abstract

臺灣所生產的茶葉形式，可由臺灣茶業之發展過程中找尋到其脈絡。1970年代前，臺灣茶業多以生產出口之商業用茶為主；1970年代後，隨著臺灣經濟發展快速工資成本提高，加上臺幣升值，臺茶外銷競爭力大幅下降，而轉為內銷。雖然，國人飲茶風氣盛行，但受工商社會時間應用之影響，便利性的飲茶方式漸成為風行，主要消費方式為沖泡的茶與飲料茶。其中，茶類飲料更在2018年創下新臺幣962億元的產值。由於要求其原料茶葉成本低廉，因此仍以粗製茶或篩分後之次級茶為其原料。粗製茶極易因吸潤與吸收環境氣味，含水量提高，加上暴露在空氣中，容易因脂質氧化而形成油耗味(以下稱為陳味)，完全掩蓋茶原有香味，形成帶有異味(Off-flavor)的茶。通常為了降低茶葉中的水分，以及去除異味或是提高茶葉香氣，會以再烘焙的方式，來修飾茶葉品質。本研究探討帶有異味(含有環境氣味與油耗味)的粗製茶，在不同溫度及不同時間的烘焙下，揮發性與非揮發性內容物之改變，並同時討論其對茶葉品質之影響。 將帶有陳味供飲料使用的四季春副茶(以下稱為陳味副茶)，以熱風循環式焙茶機(俗稱箱型茶葉烘焙機)，烘焙溫度設定在：80℃、90℃、100℃與110℃下，分別處理1小時、4小時、8小時與12小時。烘焙完成後之茶葉進行總多元酚類、總游離胺基酸、個別兒茶素、沒食子酸與咖啡因與揮發性物質分析和茶葉感官品評。 陳味副茶以不同的烘焙溫度與時間處理後，總多元酚類以及咖啡因含量之變化，在不同的烘焙溫度與時間處理下未達到顯著的差異。總游離胺基酸含量則隨著烘焙的時間延長與溫度愈高，含量會顯著減少，由於胺基酸為梅納反應的原料之一，其含量的變化可能與烘焙強度有關。 個別兒茶素中，游離型兒茶素類之表沒食子兒茶素(-)-Epigallocatechin (EGC)和表兒茶素(-)-Epicatechin (EC) 含量之變化，在不同烘焙溫度處理之間有顯著差異，長時間烘焙下，溫度愈高，含量下降的愈多。兒茶素(+)-Catechin (C)含量之變化，在高溫烘焙下，時間愈長則含量增加。酯型兒茶素類的沒食子兒茶素沒食子酸酯 (–)-gallocatechin-3-gallate (GCG)和表兒茶素沒食子酸 Epicatechin-3-gallate (ECG)含量之變化，不管烘焙溫度起溫為低或高，兩者之含量皆在1小時候顯著的下降，之後烘焙時間拉長，含量變化並不大。表沒食子兒茶素沒食子酸(–)-Epigallocatechin-3-gallate (EGCG)在高溫長時間下，含量有較大且顯著的下降趨勢。咖啡因與沒食子酸之含量沒有顯著之差異。 以氣相層析質譜儀分析在不同的烘焙溫度和時間處理後之陳味副茶，可獲得50種可辨認之揮發性化合物，由烘焙前的陳味副茶中偵測到的可辨認之物質有20種，多為醇類、醛類與酮類，少部分芳樟醇氧化物；其中，1-戊烯-3-醇(1-Penten-3-ol)、2-戊烯-1-醇(2-Penten-1-ol)、己醛(Hexanal)、3-己烯-1-醇(3-Hexen-1-ol)、2,5-呋喃二酮，3,4-二甲基-(2,5-Furandione, 3,4-dimethyl-)和碳酸2-（5-甲基-5-乙烯基四氫呋喃-2-基）丙-2-基乙酯(Ethyl 2-(5-methyl-5-vinyltetrahydrofuran-2-yl)propan-2-yl carbonate) 是通常可在較低檔的綠茶中被發現，屬於較負面之揮發物質；苯甲醛(Benzaldehyde)具有特殊杏仁味；己醛(Hexanal)帶有刺激性的青草味，兩者皆是容易在陳年紅茶中被發現的負面揮發性物質。 陳味副茶經過不同的溫度與時間烘焙處理後，可偵測到有明顯氣味描述之化合物約有23種，屬於較負面之揮發性物質如：丙酸(Propanoic acid)、月桂烷(Dodecane)與十四烷(Tetradecane)，是帶有腐敗、不清爽的油脂味；2-已烯醛(2-Hexenal)、4-庚烯醛(4-Heptenal)、水芹醛(Heptanal)具有略帶刺激的青草或油脂氣味等，大致隨烘焙時間延長與溫度提高而減少；右旋檸檬烯(D-Limonene)、苯甲醇(Benzenemethanol)、樟腦(+)-2-Bornanone與反式-β-金合歡烯((E)-.beta.-Farnesene)等，具有正向的揮發性物質會提高；呋喃類之芳香化合物(具有煙燻、肉桂之香氣)更是明顯增加。 感官品評之結果顯示：香氣部分烘焙溫度愈高、烘焙時間愈長，異味感受程度隨之降低，焙火香氣感受度隨之增加且整體香氣品質提升；滋味部分，苦味的感受值與不同之烘焙溫度與時間處理上無顯著的差異；澀味感受隨烘焙溫度愈高有降低之趨勢；甜味的感受值和整體的滋味喜好程度與不同之烘焙溫度與烘焙時間處理上有顯著的差異，烘焙溫度提高與烘焙時間拉長有助於整體滋味的提升。

The form of tea produced in Taiwan can be traced to the development of Taiwan’s tea industry. Before the 1970s, Taiwan's tea industry was mostly based on the production of commercial tea for export; after the 1970s, with the rapid economic development of Taiwan, wage costs increased, coupled with the appreciation of the Taiwan dollar, the competitiveness of Taiwan's tea export declined sharply and turned to domestic sales. Although the Chinese people are prevalent in drinking tea, but due to the influence of time in the industrial and commercial society, convenient tea drinking methods have gradually become popular, and the main consumption methods are brewed tea and beverage tea. Among them, tea beverages set an output value of NT$96.2 billion in 2018. Due to the low cost of the raw material tea, crude tea or sieved secondary tea is still used as the raw material. Crude tea is easy to absorb and absorb environmental odors, and the water content increases. In addition, when exposed to the air, it is easy to form oil consumption odor due to lipid oxidation (here in after referred to as aged-flavor), which completely conceals the original aroma of tea and forms to off-flavor tea. Usually in order to reduce the moisture in the tea, remove the peculiar smell or improve the aroma of the tea, the quality of the tea is modified by roasting. This study explores the changes in volatile and non-volatile content of crude tea with off-flavor (including environmental odor and oil consumption) under different temperatures and different times of roasting, and discusses its impact on the quality of tea. The Paochung vice tea with stale flavor for beverages is used in a hot-air circulation roasting machine, and the roasting temperature is set at: 80°C, 90°C, 100°C and 110°C for 1 hour, 4 hours, 8 hours and 12 hours respectively. After roasting, the tea leaves were analyzed for total polyphenols, total free amino acids, individual catechins, gallic acid, caffeine, and volatile compounds, and the tea sensory evaluation. After the off-flavored Poachung vice tea was treated with different roasting temperatures and durations, the changes in total polyphenols and caffeine content did not reach significant differences under different roasting temperatures and times. The total free amino acid content will decrease significantly as the roasting time increases and the temperature is higher. Since the amino acid is one of the raw materials for the Maillard reaction, the change in its content may be related to the roasting intensity. In individual catechins, (-)-Epigallocatechin (EGC) and (-)-Epicatechin (EC) content changes, treated at different roasting temperatures There is a significant difference between them. After long-time roasting, the higher the temperature, the more the content drops. (+)-Catechin (C) content changes, under high temperature roasting, the longer the time the content increases. Changes in the content of (–)-gallocatechin-3-gallate (GCG) and Epicatechin-3-gallate (ECG). Regardless of whether the roasting temperature is low or high, the content of both will decrease significantly within 1 hour, and the roasting time will be extended afterwards, and the content will not change much. (–)-Epigallocatechin-3-gallate (EGCG) has a large and significant downward trend under high temperature and long time. There is no significant difference between the content of caffeine and gallic acid. Using GC-MS to analyze the off-flavored Paochung vice tea after different roasting temperature and time, 50 identifiable volatile compounds can be obtained. The identifiable ones detected in the off-flavored Paochung vice tea before roasting There are 20 kinds of substances, most of which are alcohols, aldehydes and ketones, a small part of linalool oxides; among them, 1-Penten-3-ol, 2-Penten-1-ol, Hexanal, 3-Hexen-1-ol, 3,4-dimethyl-2,5-Furandione, and Ethyl 2-(5- Methyl-5-vinyltetrahydrofuran-2-yl)propan-2-yl carbonate is usually found in lower-grade green tea and is a relatively negative volatile substance; Benzaldehyde has a special almond flavor; Hexanal has a pungent grassy taste, both of which are negative volatile substances that are easily found in aged black tea. After the aged side tea is roasted at different temperatures and times, about 23 compounds with obvious odor descriptions can be detected, which are relatively negative volatile substances such as: Propanoic acid, Dodecane and Tetradecane, it has a rotten, unrefreshing oily smell; 2-Hexenal, 4-Heptenal, and Heptanal have smell of grass or oil, etc., roughly decreases with the extension of baking time and temperature; D-Limonene, Benzenemethanol, (+)-2-Bornanone and (E)-.beta.-Farnesene, etc., have positive volatile substances will increase; furan-like aromatic compounds (with the aroma of smoke and cinnamon) will increase significantly. The results of the sensory evaluation showed that the higher the baking temperature and the longer the baking time of the aroma part, the lower the degree of peculiar smell perception, the increased perception of roasting aroma and the improvement of the overall aroma quality; the taste part, the perception of bitterness and different baking There is no significant difference in temperature and time treatment; the perception of astringency tends to decrease with the higher the baking temperature; the perception of sweetness and the overall taste preference are significantly different from different baking temperatures and baking time treatments, baking The increase in temperature and the longer baking time contribute to the overall taste improvement.