基于气相离子迁移谱技术分析杜仲叶茯砖茶加工过程中挥发性成分

为了解杜仲叶茯砖茶加工过程中挥发性成分变化，采用气相离子迁移谱（Gas Chromatography-Ion Mobility Spectrometry，GC-IMS）技术对加工过程中的挥发性成分进行测定，使用Gallery Plot插件绘制了挥发性物质离子迁移指纹谱图，比较不同阶段杜仲叶茯砖茶样本挥发性成分差异，并进行主成分分析。结果表明:杜仲叶茯砖茶原料筛选、渥堆、气蒸与成型（即发花第0 d）、发花第8、25 d及陈化1年等6个阶段样本共检出挥发性成分70种，明确定性的有51 种，包括醛类、酮类、醇类、酯类、吡嗪类、酸类、萜烯类、呋喃类、醚类及含硫化合物等。PCA分析显示，PC1为47%，PC2为27%，累计贡献率为74%，较好的反映了不同茶样之间挥发性成分差异的影响因素。各不同阶段茶样在PCA图上呈分离状态，说明加工过程中各不同阶段茶样挥发性成分存在差异，部分呈青草味和泥土香的吡嗪、醛类和酮类物质相对含量随着加工过程的进行逐步减少，而部分呈药香、果香和醇香的醇类、醛类和酯类物质相对含量逐步增加，最终形成了杜仲叶茯砖茶较好的药香、果香和菌香。2-乙基-3, 5-二甲基吡嗪二聚体在渥堆样本中，2, 4-庚二烯醛和3-甲硫基丙醛在发花阶段样本中以及5-甲基糠醛、丙烯酸正丁酯单体、丙烯酸正丁酯二聚体、糠醛二聚体、2, 3-丁二醇在陈化阶段样本中的相对含量远高于上述各成分在其他阶段样本中的含量，可以作为杜仲叶茯砖茶渥堆、发花和陈化阶段的候选标记物，从而为杜仲叶茯砖茶加工过程中香气成分的调控提供参考。

Analysis of Volatile Compounds in the Manufacturing Process of Eucommia Ulmoides Leaves Fu Brick Tea Based on Gas Chromatography-Ion Mobility Spectrometry Method

In order to examine the variation of volatile components of Eucommia ulmoides leaves Fu Brick Tea during processing, Gas Chromatography-Ion Mobility Spectroscopy (GC-IMS) was employed. The volatile compounds fingerprints of Eucommia ulmoides leaves Fu Brick Tea were plotted using Gallery Plot software. The differences between the samples from the six stages during processing and principal component analysis were assessed, respectively. The results showed that a total of 70 volatile compounds were detected in each sample of the six stages, including raw material screening, piling fermentation, steam and forming stage (the 0th day of flowering), the 8th day, the 25th day of flowering and the 1st year of aging stage. Among these compounds, qualitative analysis of 51 kinds of components were determined, including aldehydes, ketones, alcohols, esters, pyrazines, acids, terpenes, furans, ethers and sulfur compounds. PCA analysis showed that PC1 was 47%, PC2 was 27%, and the cumulative contribution rate was 74%, which was better reflected the influencing factors of the differences of volatile components among different tea samples. The tea samples at different stages were separated on the PCA chart, indicating that there were differences in the volatile components contents of tea samples at different stages in the processing. The relative contents of several kinds of pyrazines, aldehydes and ketones with grass flavor and earthy aroma in tea samples gradually decreased with the processing, while the relative contents of alcohols, aldehydes and esters with medicinal aroma, fruity aroma and mellow aroma gradually increased. Finally, the medicinal, fruity and fungus aroma of Eucommia ulmoides leaves Fu Brick Tea was formed. Moreover, the relative contents of 2-ethyl-3, 5-dimethylpyrazine dimer in the pile fermentation samples, 2, 4-heptadienal and 3-methylthiopropanal in the flowering stage samples, and 5-methylfurfural, butyl acrylate monomer, butyl acrylate dimer, furfural dimer, 2, 3-butanediol in the aging stage samples were higher than compared to other stages. Therefore, these compounds might be the potential indicators of the assessment of the piling fermentation, flowering and aging stage of Eucommia ulmoides leaves Fu brick tea, thus providing a tool for the regular monitoring of aroma components on the manufacturing process of Eucommia ulmoides leaves Fu brick tea.