Oolong tea is a typical semi-fermented tea and is famous for its unique aroma. The aim of this study was to compare the volatile compounds during manufacturing process to reveal the formation of aroma. In this paper, a method was developed based on head-space solid phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) combined with chemometrics to assess volatile profiles during manufacturing process (fresh leaves, sun-withered leaves, rocked leaves and leaves after de-enzyming). A total of 24 aroma compounds showing significant differences during manufacturing process were identified. Subsequently, according to these aroma compounds, principal component analysis and hierarchical cluster analysis showed that the four samples were clearly distinguished from each other, which suggested that the 24 identified volatile compounds can represent the changes of volatile compounds during the four steps. Additionally, sun-withering, rocking and de-enzyming can influence the variations of volatile compounds in different degree, and we found the changes of volatile compounds in withering step were less than other two manufacturing process, indicating that the characteristic volatile compounds of oolong tea might be mainly formed in rocking stage by biological reactions and de-enzyming stage through thermal chemical transformations rather than withering stage. This study suggested that HS-SPME/GC–MS combined with chemometrics methods is accurate, sensitive, fast and ideal for rapid routine analysis of the aroma compounds changes in oolong teas during manufacturing processing.

乌龙茶是典型的半发酵茶，以其独特的香气而闻名。这项研究的目的是比较制造过程中的挥发性化合物，以揭示香气的形成。本文基于顶空固相微萃取/气相色谱-质谱（HS-SPME / GC-MS）结合化学计量学开发了一种方法，以评估制造过程中的挥发性特征（鲜叶，枯萎的叶片，摇晃的叶子和去酶后的叶子）。总共鉴定出24种在制造过程中显示出显着差异的香气化合物。随后，根据这些香气化合物，主成分分析和层次聚类分析表明，这四个样品之间有明显区别，这表明24种已鉴定的挥发性化合物可以代表这四个步骤中挥发性化合物的变化。另外，枯萎，摇摆和脱酶可以不同程度地影响挥发性化合物的变化，我们发现枯萎步骤中挥发性化合物的变化小于其他两种制造工艺，这表明乌龙茶的特征性挥发性化合物可能主要是在摇摆阶段通过生物反应形成，而在酶解阶段则通过热化学转化而不是枯萎阶段形成。这项研究表明，HS-SPME / GC-MS与化学计量学方法相结合是准确，灵敏，快速的方法，是快速常规分析乌龙茶生产过程中香气化合物变化的理想选择。