中文摘要：

为研究真空冷冻干燥对速溶茶粉香味特征及挥发性成分的影响,采用顶空固相微萃取技术（HS-SPME）结合气相色谱-质谱联用仪（GC-MS）,分析乌龙茶浓缩液及其真空冷冻干燥粉的挥发性成分。GC-MS分析结果显示,共鉴定出74种成分,其中浓缩液的主要成分为吲哚、2-乙基呋喃、p-伞花烃,而冻干粉的主要成分为吲哚、正己醛、芳樟醇。聚类分析发现,浓缩液经真空冷冻干燥后2-乙基呋喃等9种成分消失,而新增正己醛等23种挥发性成分。此外,2-庚酮和E-β-罗勒烯经真空冷冻干燥后含量降低,而E-橙花叔醇等7种成分的含量则升高。香气值（OAV）分析表明,浓缩液主要的香气成分是E-2-壬烯醛和（E,E）-2,4-癸二烯醛,冻干粉主要香气成分是1-辛烯-3-醇、芳樟醇和正己醛。该研究结果说明真空冷冻干燥对速溶乌龙茶粉浓缩液的挥发性成分和香味特征有一定影响,为速溶乌龙茶粉的生产提供理论参考。

英文摘要：

In order to investigate the effect of vacuum freeze-drying on the aroma characteristics and volatile matter of instant tea powder,headspace solid-phase microextraction combined with gas chromatography-mass spectrometry（GC-MS） was used to analyze the volatile components in concentrated Oolong tea extract and its tea powder prepared by vacuum freeze-drying.GC-MS analysis showed that 74 volatile components were identified,with the main volatile compounds in concentrated Oolong tea extract being indole,2-ethyl-furan,and para-cymene,and the main volatile compounds in the vacuum freeze-dried Oolong tea powder being indole,hexanal,and linalool.Cluster analysis showed that nine volatile compounds,including 2-ethyl-furan,disappeared,while 23 new volatile compounds,including hexanal,were generated after vacuum freeze-drying.Additionally,the concentrations of 2-heptanone and（E）-β-ocimene decreased during vacuum freeze-drying,while the concentrations of（E）-nerolidol and six other compounds increased simultaneously.The result of odor-activity values showed that（E）-2-nonenal and（E,E）-2,4-decadienal were the main odor-active contributors of the concentrated tea extract.As for the freeze-dried tea powder,the main odor-active compounds were 1-octen-3-ol,linalool,and n-hexanal.These results indicated the significant effects of vacuum freeze-drying on the volatile components and aroma characteristics of concentrated Oolong tea extract and provided a theoretical reference for the production of instant tea powder.