茶葉回甘與苦澀的原理

喝茶為什麼會回甘? 又為什麼偶爾會感到苦澀?

茶葉的苦澀與甘甜往往是互相伴隨而來,兩者關係相輔相成。茶葉產生回甘的原因最主要是來自於茶葉中豐富的游離胺基酸醣類胺基酸谷胺酸茶胺酸為主,提供甘味,雖然谷胺酸產生回甘的效果較明顯,不過茶葉中卻以茶胺酸含量較高,谷胺酸次之,而醣類與唾液作用後提供甜味,兩者搭配茶中的茶倍素加強回甘的滋味,這些反應刺激口腔及舌頭,並傳達到大腦而讓我們產生有回甘的感覺[1-3]。

茶葉中的有機酸種類多,隨茶葉種類不同而有差異,其含量大約為乾燥茶葉重量的3%,研究顯示茶中的有機酸會刺激唾液的分泌,減少茶多酚物質造成的苦澀感,進而也會相對提升回甘的感覺,而兒茶素因為分子結構不同,難以刺激到舌頭上的接受細胞,因此並不是回甘味產生的來源[1-3]。

另一方面,茶葉的苦澀主要來自於咖啡因茶多酚,其中茶多酚兒茶素黃酮醇配醣體為主,但兒茶素含量遠高於黃酮醇配醣體,因此苦澀味來源應以兒茶素影響較為明顯。兒茶素會與口腔黏膜細胞結合產生收斂與沉澱,這些反應傳達到大腦後而讓我們產生有苦澀的感覺,澀味又與茶的發酵程度有關,發酵程度越高,茶多酚越少,苦澀味也相對較低,因此未發酵的綠茶兒茶素含量最多,與其他茶類相比,有較多些微的苦澀味是正常的,同時也能得到較多兒茶素對身體健康的好處[4-6]。

其中兒茶素又可以細分為酯型兒茶素非酯型兒茶素,前者澀度較後者高,因此酯型兒茶素非酯型兒茶素的含量比例也會影響茶湯的澀度感覺,不過茶湯苦澀的多寡仍與原料、製茶技術過程與沖泡方法等密切相關,不能只以單一因子來作判別[4-6]。

不論是甘味較重或是苦澀味較重的茶,只是其中營養成分稍有不同,本質上都是茶葉,因此對人體健康均有正面的幫助,下次喝茶時你可以依照自己的口味喜好或是心情好壞來選擇口感不一樣的茶來品嚐哦!

部長茶舖裡的每一種茶葉都是一趟由甘甜與苦澀所激盪的各種旅程: https://www.littotea.com/shop/

-Research team @ 茶水部 LittoTea, 澄萃茶藝.

LittoTea - 茶水部, 烏龍, 紅茶, 四季春
LittoTea – 茶水部

The theory of sweet aftertaste and bitterness

Sweet aftertaste of tea accompanies bitterness. Free amino acids and carbohydrate are the main ingredients to make tea sweet aftertaste. Amino acid, consisting of glutamate and theanine, is the source of sweetness. The interaction of carbohydrate and saliva product the sweetness as well. The theogallin makes the sweet taste stronger and stimulate the tongue, sending this message to our brains and let us feel sweet aftertaste [1-3].

There are many organic acids in tea with the different kinds of tea, which is about 3% of dry tea weight. Research shows that organic acids in tea would stimulate the secretion of saliva, which reduces the bitterness that polyphenols brings to, and relatively increases the sweet aftertaste. However, catechin isn’t the source of sweetness because its molecular structure can’t stimulate the cells on tongue[1-3].

Polyphenols and caffeine are the source of bitterness. Polyphenols are mostly catechin and flavonol glycosideCatechin contributes more to the bitter taste.  Furthermore, the fermentation of the tea also affects the bitterness. The polyphenols reduce while the degree of the fermentation increases. Green tea without any fermentation, therefore, keeps  most catechin. It explains that green tea tastes more bitter comparing to other types of tea. From health perspective, catechin benefits our body a lot [4-6].

Catechin is divided into epicatechin-3-gallate and non-epicatechin-3-gallate. Epicatechin-3-gallate is more bitter than the other one. The ratio of epicatechin-3-gallate and non-epicatechin-3-gallate affects the degree of bitterness. However, the bitterness of the tea might not be concluded to a single factor. The tea processing and brewing are also important to the bitterness [4-6].

Tea, no matter bitter or sweet, carries numerous health benefits. Try different taste of tea to for your health and mood!

Welcome to our healthy tea shop: https://www.littotea.com/shop/

-Research team @ 茶水部 LittoTea, 澄萃茶藝.

 

Reference

[1] http://bpcollection.com/bpc_news/doc.php?id=2254

[2] http://www.jaf.nchu.edu.tw/admin/upload/6323.pdf [3]http://blog.xuite.net/sunnycat30/twblog/313263827-%E5%96%9D%E5%88%B0%E8%8C%B6%E8%91%89%E6%BE%80%E6%BE%80%E7%9A%84%E6%98%AF%E6%AD%A3%E5%B8%B8%E5%97%8E%EF%BC%9F

[3] http://blog.xuite.net/sunnycat30/twblog/313263827-%E5%96%9D%E5%88%B0%E8%8C%B6%E8%91%89%E6%BE%80%E6%BE%80%E7%9A%84%E6%98%AF%E6%AD%A3%E5%B8%B8%E5%97%8E%EF%BC%9F

[4] 茶湯澀味形成的原因 http://kmweb.coa.gov.tw/subject/ct.asp?xItem=161997&ctNode=4029&mp=86&kpi=0&hashid=

[5] 茶之澀味 http://www.tres.gov.tw/mobile_view.php?catid=1680

[6] http://www.jaf.nchu.edu.tw/admin/upload/6324.pdf

Lynn Chiang

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