乌龙茶鲜叶游离氨基酸组成轮廓的模式识别研究

Pattern Recognition of Free Amino Acids Profile in Fresh Leaves of Oolong Tea Cultivars

摘要:

为探明乌龙茶品种鲜叶游离氨基酸的组成轮廓特征，以绿茶品种春季幼嫩鲜叶(一芽二或三叶)和成熟鲜叶(中小开面二至四叶)为对照，对采自乌龙茶品种春、秋两季的幼嫩和成熟鲜叶进行高效液相色谱检测分析和统计模式识别。结果表明, 茶树品种、芽叶嫩度和采摘季节对供试鲜叶游离氨基酸组成轮廓均有影响。全部供试茶样可按茶树品种特性划分成乌龙茶与绿茶品种2大类群，且芽叶嫩度对乌龙茶鲜叶游离氨基酸组成轮廓的影响仅次于茶树品种特性引起的茶样组群差异。绿茶与乌龙茶品种春季幼嫩鲜叶、绿茶与乌龙茶品种春季成熟鲜叶、春季乌龙茶品种幼嫩与成熟鲜叶、秋季乌龙茶品种幼嫩与成熟鲜叶、春季和秋季乌龙茶品种幼嫩鲜叶及春季和秋季乌龙茶品种成熟鲜叶间存在客观的类群区分。不同鲜叶来源对供试茶样的游离氨基酸总量及大部分游离氨基酸组分均有显著或极显著影响。较高的甘氨酸、亮氨酸、赖氨酸含量和较低的γ-氨基丁酸含量是乌龙茶品种有别于绿茶品种春季鲜叶的主要差异性成分；相同采摘季节的乌龙茶品种幼嫩鲜叶相较成熟鲜叶拥有更高的精氨酸含量，而不同芽叶嫩度的春季和秋季乌龙茶鲜叶存在不同的差异特征组分。因此，茶树品种遗传特性是影响茶树鲜叶游离氨基酸组成轮廓的主导因子，乌龙茶特定的鲜叶游离氨基酸组成化学模式为其加工品质的形成提供了必要的物质基础。

Abstract:

In order to reveal the characteristics of free amino acids (FAAs) profile in fresh leaves of oolong tea cultivars, young and mature shoots harvested from oolong tea cultivars in spring and autumn were detected by high performance liquid chromatography and classified by statistical pattern recognition, the young shoots (two or three leaves and a bud) and mature shoots (two to four leaves and a banjhi bud) of green tea cultivars in spring were used as controls. The results showed that all tea samples could be divided into two groups, oolong tea cultivars and green tea cultivars. The effect of shoots maturity on the FAAs profile in fresh leaves of oolong tea cultivars was second only to the difference of tea sample groups caused by tea tree variety characteristics. Furthermore, the objective group differences could be verified among young shoots (green tea cultivars vs oolong tea cultivars) in spring, mature shoots of (green tea cultivars vs oolong tea cultivars) in spring, (young shoots vs mature shoots) of oolong tea cultivars in spring, (young shoots vs mature shoots) of oolong tea cultivars in autumn, young shoots of oolong tea cultivars (spring vs autumn), and mature shoots of oolong tea cultivars (spring vs autumn). The different sources of fresh leaves (cultivars, shoots maturity and harvesting season) had significant or extremely significant effect on the total amount of FAAs and most of the components of FAAs. The higher contents of glycine, leucine and lysine and the lower content of γ-aminobutyric acid were the main difference components of fresh leaves in spring between oolong tea and green tea cultivars. The young shoots of oolong tea cultivars had higher content of arginine than mature shoots in the same harvesting season, and there were different characteristic components of fresh oolong tea leaves with different shoot maturity in spring and autumn. Therefore, it was suggested that the genetic characteristics of tea cultivars were dominant factors affecting the FAAs profile in fresh leaves. The specific chemical pattern of FAAs in fresh leaves of oolong tea provided a necessary material basis for the quality formation.