高级搜索

茶鲜叶萎凋过程中游离氨基酸的动态变化规律

Changes on Free Amino Acids in Fresh Tea Leaves during Withering

  • 摘要: 萎凋是影响白茶、红茶和乌龙茶风味品质的重要工序。本文选用10份茶树品种春茶新梢的一芽二、三叶和中小开面二至四叶为供试材料,在控温控湿(20~22℃、RH 35%~45%)条件下,探讨了不同萎凋程度茶鲜叶的游离氨基酸动态变化规律。结果表明,供试茶样可按嫩度划分为两个类群,且在萎凋过程中均有按鲜叶减重率(0%、15%、30%、45%、60%)区分倾向,而使之区分的游离氨基酸特征组分主要有茶氨酸、天冬氨酸、谷氨酸、精氨酸、苏氨酸和丝氨酸。随着萎凋程度(鲜叶减重率)的加重,尤其是在减重率30%以后,一芽二、三叶和中小开面二至四叶茶样在二维空间的分布渐趋离散,即不同品种茶样中游离氨基酸的组成模式愈加多样。茶鲜叶各游离氨基酸在萎凋过程中的组分变化差异明显,天冬氨酸、谷氨酸、丝氨酸等游离氨基酸含量呈增加趋势,而茶氨酸含量逐渐减少。该研究结果可为基于萎凋工艺的茶叶品质控制提供参考依据。

     

    Abstract: Withering in tea processing significantly affects the flavor of white, black and oolong teas. The spring shoots (i.e., a bud, 2nd and 3rd leaves, or 2nd to 4th leaves on a banjhi bud) harvested from 10 tea cultivars were used in the experimentation. The withering chamber was controlled at 20~22℃ and 35%~45% RH. The changes on free amino acid contents in the tea leaves at various withering stages were monitored. The results showed that the leaf samples could be classified into two groups based on the maturity of the shoots. All teas prepared could be differentiated by their weight losses (i.e., 0%, 15%, 30%, 45% and 60%) at different stages of withering. As the leaf weight decreased, changes were apparent on the typical free amino acids found in teas, including Thea, Asp, Glu, Arg, Thr, and Ser. Especially after the leaves lost 30% of their original fresh weight, the tea samples showed a significant spreading on the 2nd order dimension distribution, indicating diversified amino acid compositions among different varieties of the teas during withering. There appeared a trend in increasing the contents of Asp, Glu and Ser, and declining in that of Thea as the withering progressed.

     

/

返回文章
返回