不同等级径山茶特征香气成分分析

Analysis of the Major Characteristic Aroma Compounds in Different Grades of Jingshan Tea

为深入探究不同等级径山茶的香气差异,采用搅拌棒吸附萃取-气相色谱-质谱-联用技术(SBSE-GC-MS)、顶空固相微萃取-气相色谱质谱联用技术(HS-SPME-GC-MS)以及气相色谱-嗅闻分析技术(GC-O)对特级、一级、二级、三级径山茶的挥发性物质进行分析。从4个等级的径山茶中共鉴定出161种挥发性化合物。通过主成分分析(PCA)和聚类分析(HCA)揭示了不同等级的径山茶之间的差异。运用正交偏最小二乘法判别分析(OPLS-DA)的变量投影重要性(VIP)确定不同等级茶叶样品间的候选差异挥发物并通过相对香气活度值(ROAV)和GC-O的分析进一步对差异化合物进行筛选。18种挥发性化合物,芳樟醇、香叶醇、吲哚、(Z)-茉莉酮、二甲基硫醚等物质被鉴定为不同等级径山茶的关键差异挥发性化合物。其中,二氢芳樟醇、茉莉酸甲酯和吲哚在特级径山茶样品中的含量显著高于其他等级,并与(Z)-茉莉酮、δ-癸内酯和1-辛烯-3-醇等香气活性物质共同构成了特级径山茶样品中清花香的特征香气品质。本研究揭示了不同等级径山茶的特征性挥发物具有显著差异,从化学计量学和多元统计分析的角度为绿茶的等级区分提供参考。

To characterize the difference of odorants among different grades of Jingshan tea,we investigated the super grade,the first grade,the second grade and the third grade of Jingshan tea by stir bar sorptive extraction gas chromatography-mass spectrometry(SBSE-GC-MS),headspace solid-phase microextraction gas chromatography-mass spectrometry(HS-SPME-GC-MS)and gas chromatography-olfactometry(GC-O)analysis.Herein,we detected and identified 161 volatile organic compounds.The differences between the four grades of Jingshan tea were revealed by principal component analysis(PCA)and hierarchical cluster analysis(HCA).The variable importance in projection(VIP)of the orthogonal partial least squares discriminant analysis(OPLS-DA)was used to determine candidate differential volatile compounds among tea samples of different grades and further screening of differential compounds was carried out through analysis of relative odor activity value(ROAV)and GC-O analysis.A total of 18 volatile compounds were identified as key odorants for the discrimination of different grades of Jingshan tea,including linalool,geraniol,indole,(Z)-jasmone,dimethyl sulfide,etc.Among them,the contents of hoterienol,methyl jasmonate,and indole in the super grade Jingshan tea were significantly higher than those in other grades,and together with(Z)-jasmone,δ-decalactone,and 1-octen-3-ol and other aroma-active compounds constitute the characteristic floral aroma of super grade Jingshan tea samples.This study revealed significant differences in the characteristic volatile compounds among different grades of Jingshan tea,providing a reference for distinguishing the grades of green teas by chemometrics combined with multivariate statistical analysis.