不同茶类制法对茶多酚和游离氨基酸化学模式的影响

多酚类物质和游离氨基酸是茶叶重要品质成分。本研究将金观音、黄观音、福云6号等7个福建茶树品种春梢鲜叶原料分别加工成4种茶类(绿茶、白茶、红茶和乌龙茶),并分析比较了鲜叶原料及其所制茶类的茶多酚、游离氨基酸总量、儿茶素类和游离氨基酸组分的模式差异。结果表明,基于供试茶样(茶多酚×游离氨基酸)含量的二维"点集"分布视图可将4种茶类及其鲜叶原料划分成3个主要类群:绿茶、白茶和一芽二、三叶鲜叶样;乌龙茶和中、小开面二至四叶鲜叶样;红茶样。鲜叶原料采摘标准是乌龙茶有别于其他茶类的首要影响因素。通过供试茶样儿茶素类和游离氨基酸的靶标检测,采用主成分分析(PCA)可进一步比较白茶与其他茶类化学轮廓的模式差异。茶叶在加工过程中简单儿茶素较酯型儿茶素更易趋于氧化减少,萎凋工序则有助于白茶游离氨基酸(苏氨酸和亮氨酸)的形成或保留。

Chemical Patterns of Polyphenols and Free Amino Acids in Teas Affected by Processing Methods

Polyphenols and free amino acids are important components in terms of tea quality.In this study,specific fresh spring shoots harvested from bushes of 7 different tea cultivars (Camellia sinensis),including Jinguanyin,Huangguanyin and Fuyun 6,were processed into green,white,black and oolong teas.Polyphenols,catechins,and total free amino acids (FAAs) in the fresh leaves as well as the teas made from them were determined for comparison.Based on the scatter plot for the polyphenols and FAAs contents of the 4 teas,3 distinguishable patterns emerged.They were grouped as Type I,which included the green and white teas along with the fresh2nd/3rd-leaf-1 bud leaves,Type II,which consisted of the oolong teas and the fresh 2nd-to-4th-leaf-1 banjhi bud leaves,and Type III,which was the black tea.Maturity of shoots was found to bea key factor that differentiated oolong tea from others.On the other hand,aprincipal component analysis (PCA)using data on catechins or FAAs would be necessary for a satisfactory differentiation on white tea.The non-ester type catechins were more prone to oxidization than the ester type catechins during tea processing,and withering contributed to the increase of FAAs,especially threonine and leucine,in the white tea.