不同干燥方式的桂热2号红茶香气成分分析及判别

目的:对不同干燥方式的桂热2号红茶主要香气成分进行辨识鉴定,实现对红茶干燥方式的判别。方法:制作桂热2号冷冻干燥(D组)、热风干燥(H组)、日晒干燥(S组)、冻干+热风干燥(DH组)红茶样品,采用固相微萃取-气质联用(SPME-GC-MS)技术鉴定香气成分,结合主成分分析(PCA)和感官审评评价香气特征;结合正交偏最小二乘判别分析(OPLS-DA)进行组间差异化分析;结合聚类分析(HCA)进行红茶的干燥方式鉴别。结果:共鉴定出36种香气成分,其中12种成分构成了桂热2号红茶花果甜香的基底;PCA模型得到三个主成分的累积解释率R2X=82.2%,咖啡因、橙花醇、芳樟醇等9种成分对成分组的影响较大;OPLS-DA分析对于DH组与H组间模型拟合度较差,其他组间均具有良好的拟合度,D组与DH组差异成分为咖啡因、芳樟醇等,D组与H组为咖啡因、橙花醇等,D组与S组为咖啡因、橙花醇等,DH组与S组间为芳樟醇、橙花醇等,H组与S组间为苯甲醇等;HCA聚类分析结果为除DH组与H组间判别精度不高,其他组间都能实现判别。结论:GC-MS结合PCA、OPLS-DA、HCA分析能基本实现对多种干燥方式红茶的鉴定、区分和判别,综合评价冻干+热风干燥效果最佳。

Analysis and Discrimination of Aroma Compounds of Guire 2 Black Tea Treated with Different Drying Methods

Objective:The mainly different aroma components of Guire 2 black tea treated with different drying methods were identified to determine the drying methods of black tea. Methods:Solid phase microextraction coupled with gas chromatography-mass spectrometry(SPME-GC-MS)was used to identify the aroma components of Guire 2 black tea samples dried by freeze drying(D),hot air drying(H),sun drying(S),freezing+hot air drying(DH). Principal component analysis(PCA)and sensory evaluation were used to analyze the aroma characteristics. Orthogonal signal corrected least squares discriminant analysis(OPLS-DA)was used to analyze the differences between groups. Cluster analysis(HCA)was used to identify the drying methods of black tea. Results:A total of 36 aroma components were identified,among which the relative contents of 12 aroma components were relatively high,which constituted the base of sweet scent of Guire 2 black tea. Three principal components were extracted by PCA(the fraction of the variation of the X variables explained was 82.2%),and the caffeine,nerol,linalool and so on had a greater impact on the component group. The OPLS-DA analysis had a poor fit to the model between DH and H,and the other groups had a good fit. The difference components were caffeine and linalool(D and DH),caffeine and nerol(D and H,D and S),linalool and nerol(DH and S),benzyl alcohol(H and S). The results of HCA cluster analysis showed that the high discrimination could be achieved except DH and H. Conclusions:The aroma components of Guire 2 black tea could be identified and classified by GC-MS combined with PCA,OPLS-DA and HCA. A comprehensive evaluation indicated that freezing+hot air drying showed the best effect.