Study of aroma compound formations and transformations during Jinxuan and Qingxin oolong tea processing

We characterised the formation and dynamic changes in the main aroma compounds produced during the manufacturing process of Jinxuan and Qingxin oolong tea. Thirty-five aroma compounds were investigated. Subsequent principal component and cluster analyses showed that the fresh leaves, spread leaves and rocked leaves of the two varieties of tea were distinguished from each other. Particularly, the aldehyde and ‘other’ compounds showed the highest correlation coefficients (0.71 and −0.70) among the principal. The heat map showed that the proportions of acetic acid, 3-methylbutanal and 2-methylbutanal significantly changed during the manufacturing process of the two tea varieties. The key amino acids (isoleucine, leucine, valine and aspartic acid) and enzymes (branched-chain amino acid aminotransferase, aspartate aminotransferase and acetaldehyde dehydrogenase) involved in the synthesis of 3-methylbutanal and 2-methylbutanal differed between the two varieties during manufacture. Our study reveals the characteristics of different varieties of oolong tea and their aroma formation after manufacture using the same process.     

同时蒸馏萃取法分析4种台式乌龙茶香气成分

以4个台茶品种金萱、翠玉、软枝乌龙、四季春以及乌龙茶对照种黄金桂(黄棪)的鲜叶为原料,按台式乌龙茶工艺制作成乌龙茶,采用同时蒸馏萃取-气质联用法分析香气成分,并比较它们香气成分的差异。结果表明:除金萱样品醇类含量较低之外,其他乌龙茶样品香气组分均以醇类、酯类和碳氢化合物为主,其余组分为少量的醛类、酚类、酮类、羧酸类和含氮化合物等;黄金桂与4个台茶品种乌龙茶主要的香气成分是,橙花叔醇、β-芳樟醇及其氧化物、植醇、α-法呢烯、吲哚、棕榈酸、棕榈酸甲酯、亚油酸甲酯、亚麻酸甲酯、三烯甘油酯、新植二烯、2,6-二甲基-6-(4-甲基-3-戊烯基)-双环(3,1,1)-2-庚烯、2,2,4,6,6-五甲基庚烷、二十二烷、二十五烷等;感官评价结果表明,4个台茶品种所制成的乌龙茶样品质好,得分均比对照样黄金桂高,总体品质超过或明显超过对照。     

不同季节和茶类的金萱品种茶叶香气成分分析

采用GC-MS法对金萱茶树品种不同季节鲜叶加工而成的绿茶、红茶和乌龙茶的香气组分进行分析。结果表明:金萱绿茶春茶和夏茶的香气组成以醇类物质的相对含量较高,秋茶是吡咯类及其衍生物的相对含量较高。金萱绿茶春茶和夏茶的主导香气成分较多,且组成较相似,秋茶的主导香气组分较少,但都有清香、花香或甜香的特征。金萱红茶春茶、夏茶和秋茶都是醇类物质的相对含量较高,且所占比例较其他茶类高,其次是醛类或酯类。金萱红茶秋茶的FI指数最高,香气品质最好,夏茶次之,春茶最次,与感官审评结果一致。金萱乌龙茶春茶是醇类物质的相对含量较高,夏茶和秋茶是吡咯类及其衍生物的相对含量较高。三个季节的乌龙茶中都是橙花叔醇和吲哚的相对含量最高,占其主导香气成分的54%以上。