黄金芽茶鲜叶加工过程中色泽变化及内在原因分析

探究黄金芽茶鲜叶加工过程中的色泽变化及其内在原因,以期为黄金芽及此类白化茶树品种鲜叶的加工生产提供一定理论指导。以常规茶树品种鸠坑作为对照,分析黄金芽鲜叶在受热加工过程中外观色泽和内在呈色物质含量的变化,采用UPLC法分析叶黄素、β-胡萝卜素、叶绿素a、叶绿素b、脱镁叶绿素a及脱镁叶绿素b等6种脂溶性色素含量。研究结果表明,黄金芽鲜叶杀青后外观颜色由黄变绿,色差a*值由正值(红色)变为负值(绿色),以叶黄素为代表的黄色素含量显著降低,导致绿色素与黄色素含量比值显著上升,呈现鲜绿色;而后续的闷黄工序可使茶叶外观色泽恢复黄色,原因在于闷黄可使茶叶中的叶绿素a/b含量显著下降,绿色素与黄色素含量比值显著降低,使得闷黄后的成品茶外观色泽和色素含量均与鲜叶更为接近,黄金芽鲜叶的色泽优势由此得以凸显。

Studies on the Color Change and Internal Mechanism of the Huangjinya Fresh Tea Leaves during Tea Processing

This study aimed to explore the dynamic changes of color and pigments content of the Huangjinya fresh tea leaves during processing,with a view to providing theoretical guidance for the processing and production of the fresh tea leaves of Huangjinya as well as this kind of albino tea cultivars.Taking Jiukeng,a conventional tea cultivar,as control,the changes of appearance color and intrinsic pigments contents of Huangjinya during thermal processing were analyzed and the pigments content was determined by UPLC method.Results showed that the appearance color transformed from yellow to green and the value of chromatism a*changed from positive(red)to negative(green)after fixing of Huangjinya fresh tea leaves,since the content of yellow pigments represented by lutein decreased significantly,which resulting in a significant increase in the relative content of green pigments.However,the piling process was able to make the appearance color of tea return to yellow due to the significant improvement in the relative content of yellow pigments caused by the reduction of chlorophyll a/b content.Thus,the appearance color and pigments content of tea products after piling were more similar to those of fresh leaves,so that the color advantage of fresh leaves of Huangjinya cultivars can be fully highlighted.