茶葉焙火是為了什麼?

焙火過的茶會增加咖啡因嗎?

烘焙有兩種目的,分別是保持茶葉乾燥與改善茶葉的品質,通常是先去除濕氣與雜氣之後,接下來才是調整茶葉的品質。首先,在不改變茶葉原有的香氣與品質之下,降低茶葉的含水量,一般茶葉含水量要在5%以下,保持乾燥不只能夠延長保存期限,同時也確保茶葉良好的品質[1-2]。

接著溫度升高,隨著水分的蒸發而香氣逐漸顯現,焙火能使茶葉中的成分,像是胺基酸兒茶素醣類果膠質等產生化學變化,進而產生出香氣,還可以適當地增添焙火香氣,依焙火程度不同,香氣程度又可以依序分為清香、熟果香、焦糖香、火味,甚至是火焦味。同時烘焙也會改變茶葉的顏色,茶葉色澤主要是來自於葉綠素,經過烘焙之後,葉色會漸漸由翠綠色轉變為黃褐、紅褐色,甚至是黑褐色[2-3]。

烘焙過程中,茶多酚茶黃質茶紅質等含量略為提高,因此茶湯自然會略帶黃色或紅色,焙火程度越高,茶湯顏色越暗紅,也因為咖啡因單寧酸略微減少而苦澀感相對降低,口感較為滑順。如果是香氣稍弱的茶葉,則可以透過焙火而產生焙火香,提高香氣,但具清香或花香的茶則不能使用焙火,以免破壞原有的香氣[2-3]。

烘焙以茶湯口感轉為甘醇而香味又能適當散發為原則,通常烘焙溫度以不超過110度為宜,烘焙溫度不宜過高,超過130℃可能會有燃燒的風險,而烘焙時間過長,也可能會造成纖維壞死,味道淡化。不過較粗老的葉子需要較高的烘焙溫度將雜味去除,需要烘焙的時間較長,而細嫩的茶葉烘焙溫度則不宜過高,時間也不宜過長。烘焙之後的茶葉帶有火味,經過3-6天之後,火味稍退,大約一週以後茶葉的品質會恢復穩定,而烘焙程度越高,茶葉品質穩定的時間也越久[3-4]。

烘焙能夠去除雜味,還能改善茶葉的香氣與味道,提升茶葉品質,使茶湯呈現另一種不同的風貌,不過也並不表示烘焙越多越好,如果烘焙越多,可能就沒有辦法體會到茶葉最根本的滋味,這樣不是有點可惜嗎?

-Research team @ 茶水部 LittoTea, 澄萃茶藝.

 

The purpose of the tea roast

There are two purposes of the tea roast, keep tea dry and improve the quality of tea. First, keeping tea dry and reducing tea moisture content below 5% help extend the retention period and maintain the good quality of tea[1-2].

The scent appears with the temperature increasing. The roast can activate amino acids, catechins, carbohydrate or pectin in tea to have chemical changes, which would help increase the scent and roasted aroma. The degree of the scent varies with the degree of the roast, fresh scent, ripe fruit scent, caramel aroma, and even a fire burning smell in order. Meanwhile, the roast can change the color of tea as well. Tea color mainly comes from chlorophyll. The emerald color turns to brown, red-brown, or even black-brown with the different degree of the roast[2-3].

Furthermore, the increase of polyphenols, theaflavins and thearubigins in the process of the roast makes tea color look yellow or red. The color becomes darker with the roasting increasing. Meanwhile, caffeine and tannic acid decrease a bit, which makes tea taste softer. The roast helps increase the scent. However, tea that has the floral scent can’t be processed with the roast. Otherwise, the scent would be damaged seriously[2-3].

The initiative purpose of the roast focus on the result that tea tastes softer and the scent appears. The temperature of the roast is not allowed too high, usually below 110 degrees Celsius. There is a risk of burning if the temperature is over 130 degrees Celsius. The fiber of tea and the quality of tea would be damaged as well if the roast time takes too long. Generally, it is believed that old tea takes more time to roast, and also need higher temperature to remove savor. In contrast, fresh tea takes fewer time to roast, and need lower temperature. Tea usually has a burning smell after the roast. The smell would subside a bit around after few days, and the quality of tea becomes stable after a week. It takes more time to make the quality of tea stable with the heavier degree of the roast[3-4]

The roast can remove savor, improve the scent and the taste of tea, and increase the quality. However, the degree of the roast doesn’t equal the better quality of tea. Tea may lose its original flavor with the roast increasing. Original tea is still good, right?

-Research team @茶水部 LittoTea, 澄萃茶藝.

 

Reference

[1]https://kmweb.coa.gov.tw/subject/ct.asp?xItem=162119&ctNode=4029&mp=86&kpi=0&hashid=

[2]http://chalib.com/tealib/teapartnews_sub.asp?TeaPartNewsNo=46&TeaPart=%E7%83%8F%E9%BE%8D%E8%8C%B6(%E9%9D%92%E8%8C%B6)

[3]https://www.facebook.com/ding7116500/posts/1424556257763348

[4]http://library.taiwanschoolnet.org/cyberfair2002/C0234970031/talktea/talktea3.htm

Lynn Chiang

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