|摘要: ||本試驗選用購自南投縣名間鄉兩位茶農之綠茶、烏龍茶及佳葉龍茶 (GABA Tea)三種樣品之原葉茶及碎葉茶 (即袋茶)為材料，進行冷泡茶試驗，並以熱泡為對照組，分析不同沖泡溫度、時間、沖泡比例對茶湯中主要物化成分 (茶湯水色、pH值、總兒茶素、總多元酚、總游離胺基酸、GABA含量、個別兒茶素及咖啡因)的變化。並利用消費者型感官品評試驗了解消費者對冷泡茶之喜好性。|
不論是原葉或碎葉，熱泡5min與冷泡茶比較時，在冷泡12 hr時能得到較高量或相當量的總兒茶素及總多元酚含量，若是冷泡與熱泡三泡總和比較時，12 hr時能含有熱泡三泡總和一半的含量。在總游離胺基酸含量方面，冷泡2 hr時即能達到等量或高於熱泡5 min者。GABA茶之GABA含量與游離胺基酸亦有相同的趨勢，顯示冷水沖泡時，對於胺基酸、GABA含量有較好的溶出率。
個別兒茶素則隨著不同發酵程度及不同形式之茶樣，其溶出速率亦有所不同。但冷泡在12 hr之後，游離型兒茶素含量皆比熱泡5 min者高。咖啡因含量顯著以熱泡者較冷泡者高，即使冷泡至12 hr時，其咖啡因含量僅為熱泡茶的1 / 2~2 / 3左右。
以原葉烏龍茶作為試驗茶樣之消費者感官品評試驗，以熱泡5 min與4 hr及12 hr的冷泡茶進行品評。所得結果，其中熱泡者具有較高的香氣得分，但12 hr冷泡茶的滋味得分高於熱泡5 min及冷泡4 hr者，而整體喜好上則是冷泡12 hr與熱泡5 min沒有顯著的差異。
The Green tea, Oolong tea and GABA tea made by two farmers in Ming-Chien with two different packing forms, tea leaves and tea bags, were used as materials. The purpose of this study is to investigate the changes in the color of tea infusion, pH value, total catechins, total polyphenols, total free amino acids, GABA contents, individual catechins and caffeine of 4oC cold-water steeped tea infusions with different time as compared with hot-water steeped one as the control. Using 7-point hedonic scoring, the consumer preference of cold-water steeped tea infusion by 100 consumer-type panelists was evaluated as compared with hot-water steeped one.
The analysis results of color of tea infusion with these three kinds of tea samples showed that the color of cold-water steeped samples was brighter than that of hot water steeped ones and the color of tea infusion using tea leaves were brighter than that of tea bags. The pH value of hot-water steeped tea infusion was found lower than that of cold-water ones, and the pH value of cold-water steeped tea infusion of tea bags at the same steeping time was lower than that of tea leaves.
The contents of total catechins and total polyphenols in cold-water steeped tea infusion for 12 hr were equal to or higher than those steeped in hot water for 5 min, but the contents were only half of those steeped by hot water for 5 min three times in total. The total free amino acid contents of tea steeped with cold water for 2 hr were already equal to or even higher than those steeped in hot water for 5 min. The GABA contents in the GABA tea showed the similar tendency with the total free amino acid contents of GABA tea. It indicates that cold-water steeping has better extraction than that the hot-water steeping.
For the individual catechins, the extraction effectiveness of steeping with cold water was found quite different among different degree of fermentation and types of packing. However, the contents of free-type catechins in tea steeped with cold water for 12 hr were higher than those steeped in hot water for 5 min. The caffeine contents of tea steeped with hot water were significantly higher than those with cold water. The content of caffeine in 12-hr cold-water steeped tea infusion was only 1/2 to 2/3 of those with hot water steeped.
Except GABA tea samples, the contents of all constituents in tea infusion with tea leaves packing type were only reached to 50 - 60 % of those with tea bags packing type. The contents of total catechins, total polyphenols, and total free amino acids in GABA tea samples were found no significant difference between two different packing types, because the tea leaves did not go through the ball rolling step.
Using the tea samples steeped with cold water for 4 hr and 12 hr, and with hot water for 5 min as materials, the results of the consumer preference teat showed that the aroma score of tea steeped with hot water for 5 min was the highest. The taste score of tea steeped with 12-hr cold water were higher than those of other two tea samples. However, there was no significant difference between the 12-hr cold-water steeped tea infusion and the one with 5-min hot-water steeping.