不同种类茶叶中挥发性萜类化合物对映异构体研究

发布时间：2019-05-10 14:18

【摘要】：茶叶中的芳香物质即“挥发性香气组分(VFC)”,是评价茶叶品质的重要指标之一。其中香气阈值较低的挥发性萜类化合物是茶叶中最重要的一类香气成分,呈香上表现为令人愉悦的花果香。茶叶中挥发性萜类物质主要分为单萜类和倍半萜类。萜类物质通常存在一对或一对以上的具有不同香气特征和阈值的对映异构体。受以往分析手段的限制,茶叶中挥发性萜类物质对映异构体的分布、含量及其对茶叶香气的具体影响目前尚未明确,限制了人们对茶叶香气成分的科学评价。本研究采用顶空固相微萃取-手性气相色谱质谱联用技术,建立了茶叶中9种挥发性萜类化合物的对映异构体分析方法,查明了不同茶类及不同品种鲜叶中9种挥发性萜类化合物的对映异构体的分布及含量。结果如下:1.建立了茶叶中9种挥发性萜类化合物的对映异构体顶空固相微萃取-气相色谱质谱分析方法。各挥发性萜类化合物对映异构体的LOD及LOQ无显著差异,LOD介于1.27-4.86 ng/g之间,LOQ介于4.24-15.35 ng/g之间;高浓度加标回收率介于83.91%-99.20%之间,RSD值介于8.81%-14.31%之间;低浓度加标回收率介于79.85%-99.78%之间,RSD值介于8.53%-15.28%之间。2.不同茶类中挥发性萜类化合物对映异构体的组成及含量:α-蒎烯仅在正山小种红茶中被检测出,构型以S-(-)-α-蒎烯为主;芳樟醇氧化物A在绿茶及黑茶中主导构型一致,而在部分红茶及乌龙茶中构型相反;芳樟醇氧化物B在乌龙茶中的主导构型与绿茶、红茶、白茶及黑茶中的构型相反;芳樟醇氧化物C和D在所有茶样中的构型均保持一致,且大部分仅检测到单一构型;α-松油醇在不同种类的茶叶中对映异构体分布各异;4-萜品醇在所有可测得的茶样中均以R构型为主导,且仅六堡茶(黑茶)可检测到S-(+)-4-萜品醇;α-紫罗兰酮以单一的R构型存在于红茶、乌龙茶、白茶及黑茶中。定量分析结果表明,芳樟醇在大部分茶样中都具有最高的含量,平均含量白茶红茶乌龙茶绿茶黑茶;芳樟醇氧化物B的含量在茶叶中仅次于芳樟醇,平均含量红茶白茶乌龙茶黑茶绿茶;而其他挥发性萜类化合物在茶样中的含量普遍低于100ng/g,且在不同茶类中含量分布迥异。3.不同茶树品种间挥发性萜类化合物对映异构体的含量差异较大。对23个茶树品种鲜叶中挥发性萜类化合物对映异构体的定量分析结果表明,S-(+)-芳樟醇含量介于1961ng/g-13572 ng/g之间,(2S,5R)-芳樟醇氧化物B含量介于1357ng/g-26234 ng/g之间,(2S,5S)-芳樟醇氧化物A含量介于304ng/g-11540 ng/g之间,芳樟醇氧化物D含量介于253.52ng/g-9858.01 ng/g之间,S-(-)-α-松油醇含量介于4.71ng/g-6.98ng/g之间,R-(+)-α-松油醇含量介于4.68ng/g-6.31ng/g之间,S-(+)-4-萜品醇含量介于1.29ng/g-1.73ng/g之间,R-(-)-4-萜品醇含量介于1.25ng/g-1.52ng/g之间,R-Ionone含量介于0.34ng/g-12.21ng/g之间。
[Abstract]:The aromatic substance in tea, "volatile aroma component (VFC)", is one of the important indexes to evaluate the quality of tea. Among them, volatile terpenoids with low aroma threshold are the most important aroma components in tea, showing pleasant flower and fruit aromas. Volatile terpenoids in tea are mainly classified into monoterpenoids and sesquiterpenoids. Terpenoids usually have one or more pairs of enantiomers with different aroma characteristics and threshold values. Limited by previous analytical methods, the distribution and content of enantiomers of volatile terpenoids in tea and their specific effects on tea aroma have not been clearly defined at present, which limits the scientific evaluation of aroma components of tea. In this study, the enantiomer analysis of nine volatile terpenoids in tea was established by headspace solid phase microextraction and chiral gas chromatography-mass spectrometry. The distribution and content of enantiomers of 9 volatile terpenoids in fresh leaves of different teas and different varieties were investigated. The results are as follows: 1. A method for the determination of nine volatile terpenoids in tea by headspace solid phase microextraction-gas chromatography-mass spectrometry (GC-MS) was established. There was no significant difference in LOD and LOQ among the enantiomers of volatile terpenoids. LOD was between 1.27 and 4.86 ng/g, and LOQ was between 4.24 and 15.35 ng/g. The recovery of high concentration standard addition was between 83.91% and 99.20%, and the RSD value was between 8.81% and 14.31%. The recovery of low concentration was between 79.85% and 99.78%, and the RSD was between 8.53% and 15.28%. 2. The composition and content of volatile terpenes enantiomers in different teas: 伪-pinene was detected only in Zhengshan black tea, and the configuration was mainly S-(-)-伪-pinene. The dominant configuration of linalool oxide A in green tea and black tea was the same, but that in some black tea and oolong tea was opposite, and the configuration of linalool oxide B in oolong tea was opposite to that in green tea, black tea, white tea and black tea, and the configuration of linalool oxide B in Oolong tea was opposite to that in green tea, black tea, white tea and black tea. The configuration of linalool oxide C and D in all tea samples remained the same, and most of them only detected a single configuration, the distribution of enantiomers of 伪-terpinol in different kinds of tea was different, and the distribution of enantiomers of 伪-terpinol in different tea samples was different. 4-terpene alcohol is dominated by R configuration in all tea samples, and only S-()-4-terpene alcohol can be detected in Liupu tea (black tea). 伪-ionone exists in black tea, oolong tea, white tea and black tea with a single R configuration. The results of quantitative analysis showed that linalool had the highest content in most tea samples, and the average content was white tea, black tea, oolong tea, green tea, black tea; The content of camphor alcohol oxide B is second only to linalool in tea, and the average content of black tea, white tea, black tea and green tea is second to that of linalool. The content of other volatile terpenoids in tea samples is generally lower than 100 ng / g, and the distribution of other volatile terpenoids in different tea samples is quite different. The content of volatile terpenoids enantiomers varied greatly among different tea varieties. The quantitative analysis of the enantiomers of volatile terpenoids in fresh leaves of 23 tea cultivars showed that the content of S-()-linalool was in the range of 1961ng/g-13572 ng/g, (2S, 2S. 5R)-linalool oxide B content is between 1357ng/g-26234 ng/g and (2S, 5S)-linalool oxide A content is between 304ng/g-11540 ng/g. The contents of camphor alcohol oxide D and S-(-)-伪-terpineol are between 253.52ng/g-9858.01 ng/g and 4.71ng/g-6.98ng/g, respectively. The content of R-()-伪-terpinol is in the range of 4.68ng/g-6.31ng/g, and the content of S-()-4-terpenoid alcohol is in the range of 1.29ng/g-1.73ng/g. The content of R-(-)-4-terpene alcohol is between 1.25ng/g-1.52ng/g and R-Ionone is between 0.34ng/g-12.21ng/g.
【学位授予单位】：中国农业科学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TS272.7;O657.63

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