白化和黄化茶树品种绿茶游离氨基酸、儿茶素类及咖啡碱差异分析

为探究以白化和黄化茶树品种鲜叶为原料制成的绿茶滋味品质和代谢物差异，对广德市6个白化品种绿茶(奶白茶)和14个黄化品种绿茶(黄金芽茶)进行感官审评和代谢物分析。结果表明，奶白茶滋味鲜爽而收敛性略弱；黄金芽茶滋味收敛性强而鲜度低于奶白茶。游离氨基酸总量以及呈现鲜味、甜味的游离氨基酸在奶白茶中的含量显著高于黄金芽茶，而贡献收敛性的儿茶素类化合物和没食子酸含量以及呈现苦味的咖啡碱含量在奶白茶中显著低于黄金芽茶。偏最小二乘法判别分析(PLS-DA)表明导致两种绿茶滋味差异的标志性化合物有7种，分别是茶氨酸、精氨酸、谷氨酸、天冬氨酸、表没食子儿茶素没食子酸酯(EGCG)、表儿茶素没食子酸酯和咖啡碱。味觉活性值(Dot)最高的EGCG在黄金芽茶中的呈味贡献显著高于奶白茶。因此，游离氨基酸、儿茶素类化合物、没食子酸和咖啡碱含量差异导致白化和黄化茶树品种绿茶滋味不同。

Differences of Free Amino Acids, Catechins and Caffeine Between Albino and Etiolated Tea Varieties

Green teas processed from shoots of albino tea varieties have an umami taste and premium qualities. In order to explore the taste quality and metabolite differences of green tea made from fresh leaves of albino and etiolated tea varieties, sensory evaluation and metabolite analysis were studied on 6 albino green tea varieties (milk white tea, NB) and 14 etiolated green tea varieties (golden tea, HJY) in Guangde City. Sensory evaluation showed that NB green teas taste fresh and convergence was slightly weak; the taste of HJY green tea had strong convergence and the freshness was lower than that of NB green tea. The total amount of free amino acids and the content of free amino acids with fresh and sweet taste in NB green teas were significantly higher than those in HJY green teas, while the contents of catechins and gallic acids contributing to convergence and the contents of bitter caffeine in NB green tea were significantly lower than those in HJY green teas. The partial least squares discriminant analysis showed that there were 7 signature compounds leading to the taste difference between the two green teas, which were theanine, arginine, glutamic acid, aspartate, epigallocatechin gallate (EGCG), epicatechin gallate and theobromine. The contribution of EGCG with the highest dose-over-threshold (Dot) to the flavor of HJY green tea was significantly higher than that of NB green tea. Therefore, the differences in contents of free amino acids, catechins, gallic acids and theophylline caused the different taste of albino and etiolated tea varieties.