Under controlled indoor conditions at 20-22℃and 35%-45% RH,withering of the spring tea shoots,i. e.,2 or 3 leaves with a bud (A)and 2 to 4 leaves with a banjhi bud (B),harvested from 10 tea cultivars,including Rougui and Shuixian,was conducted to study the compositional changes in the leaves.Samples were collected at water loss of the leaves at 0,15%,30%,45% and 60% to determine the catechin and alkaloid contents using HPLC.The results showed that the highest contents of catechin monomers and total catechins occurred when water loss of the leaves was in the range of 30% to 45%,indicating transformation of catechinsduring early stage of withering.As the withering progressed,EGCG,EC,ECG and total catechins of the samples began to fall,and EGC and TB reduced gradually,while CAF and alkaloids increased.The scope of the changes were more prominent in Group A than B. The principal component analysis (PCA ) and the cluster analysis rendered a similar classification in dividing the 110 samples into the two types,A and B,which were grouped based on the tenderness of the tea shoots.The PCA results suggested that tea catechins and alkaloids rose and fell due to the oxidization and degradation of catechins by the polyphenol oxidase during the time period.Apparently,withering affected the contents of catechins and alkaloids in the leaves.Therefore,it was conceivable that proper control on moisture loss of the leaves could improve the flavoring and active components of the resultant tea.%以肉桂、水仙等10个茶树品种春季新梢（采摘嫩度为1芽2、3叶和中小开面2～4叶）为供试材料，在控温控湿（22～22℃、RH 35％～45％）条件下萎凋，于鲜叶萎凋失水减重率为0、15％、30％、45％、60％时取样，检测其儿茶素和生物碱含量的变化。结果表明，在萎凋失水率为30％～45％范围内，供试茶样中儿茶素组分含量及总量具有最大值，说明萎凋前期促进儿茶素的转化形成；随着萎凋失水程度加重，儿茶素组分EGCG、EC 和 ECG 含量及其总量呈现先增后减、总体减少趋势，EGC 和 TB 含量以逐步减少为主，而 CAF 含量和生物碱总量则表现为逐渐增加趋势，而且1芽2、3叶各组分变化幅度大于中小开面2～4叶；主成分分析和聚类分析均可获得较为一致的结果，即110份供试茶样均可按芽叶嫩度分成1芽2、3叶型和中小开面2～4叶型2种类型，基于萎凋工序分类的主成分分析显示供试茶样的儿茶素和生物碱在萎凋期间含量呈现递变性增减趋势，表明萎凋过程是儿茶素类物质在多酚氧化酶作用下长时间缓慢氧化和降解的过程。因此萎凋工序对儿茶素和生物碱含量有一定影响，可通过调节鲜叶萎凋失水程度来调控二者的含量及组成比例，从而为茶叶风味品质调整及其活性成分的开发利用提供依据。
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