顶空固相微萃取-气相色谱-质谱法检测不同等级普洱生茶贮藏样特征挥发性成分

Determination of characteristic volatile components in stored samples of different grades of raw Pu-erh tea by headspace solid-phase microextraction-gas chromatography-mass spectrometry

中文关键词:  普洱生茶  茶叶原料等级  贮藏  挥发性成分  顶空固相微萃取-气相色谱-质谱法

英文关键词:raw Pu-erh tea  grades of tea leaves  storage  volatile components  headspace solid-phase microextraction-gas chromatography-mass spectrometry

中文摘要:

      目的 探究特级(YK-T)、二级(YK-A)、四级(YK-B)普洱生茶贮藏样特征挥发性成分差异。方法 采用顶空固相微萃取-气相色谱-质谱法(headspace solid-phase microextraction-gas chromatography-mass spectrometry, HS-SPME-GC-MS), 结合主成分分析(principal component analysis, PCA)验证、正交偏最小二乘判别分析以及计算相对香气活度值(relative odor activity value, ROAV), 分析筛选3个等级普洱生茶贮藏样关键香气组分。结果 不同等级样品共检测出92种挥发性成分, 主要是以芳香烃类、醇类、酯类以及碳氢类化合物为主。3个等级普洱生茶贮藏样的挥发性成分在种类数量上的差异较小, 但在总含量上YK-T的挥发性物质含量高于其他两个等级。此外, 经长期贮藏后, YK-T普洱生茶贮藏样中挥发性成分酯类物质含量高于其余两个等级茶样。根据变量重要性投影(variable importance projection, VIP)>1、P<0.05共筛选出乙酸松油酯、(+)-柠檬烯、(S)-α-松油醇、芳樟醇、亚油酸甲酯、2,2,6-三甲基-6-乙烯基四氢-2H-呋喃-3-醇、柏木脑、水杨酸甲酯、1,10-癸二醇以及1,2,3-三甲氧基苯等19种挥发性成分为3个等级普洱生茶贮藏样的关键差异性物质。进一步计算筛选出14种挥发性成分的ROAV值, 结果显示乙酸松油酯、(+)-柠檬烯、(S)-α-松油醇、芳樟醇、柏木脑、水杨酸甲酯和1,2,3-三甲氧基苯的ROAV>1, 表明这些关键香气成分对不同等级普洱生茶贮藏样的香气特征具有一定贡献作用。结论 YK-T总体香型以芳樟醇、(+)-柠檬烯和1,2,3-三甲氧基苯所呈现出的花香、柠檬香和陈香为主, 且具有草药味的乙酸松油酯仅在YK-T中检测到, 此香气特征能够将YK-T与其余两个等级的茶样区分开。YK-A和YK-B挥发性成分中以柏木脑呈现出的木香和芳樟醇的花香为主要香气特征, 且YK-A中柏木脑的ROAV值为所有关键差异香气成分中最高, 使YK-A呈现明显木香。本研究为不同等级普洱茶品质差异奠定了一定的理论基础, 也为构建不同等级普洱生茶判别图谱提供了数据支撑。

英文摘要:

      Objective To investigate the characteristic volatile component differences among premium grade (YK-T), second grade (YK-A) and fourth grade (YK-B) raw Pu-erh tea storage samples. Methods Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with principal component analysis (PCA) validation, orthogonal partial least squares discriminant analysis and calculation of relative odor activity value (ROAV) were used to analyze and screen key aroma components of the 3 grades of raw Pu-erh tea storage samples. Results A total of 92 volatile compounds were detected across the different grade samples, primarily consisting of aromatic hydrocarbons, alcohols, esters and hydrocarbon compounds. The differences in the number of volatile components among the 3 grades of aged raw Pu-erh tea samples were relatively small. However, the total volatile content in the YK-T sample was significantly higher than in the other 2 grades. Additionally, after long-term storage, the ester content in the volatile components of the YK-T aged raw Pu-erh tea sample was significantly higher than in the other 2 grades. Based on variable importance projection (VIP)>1 and P<0.05, 19 kinds of volatile compounds were identified as key differentiators: Pinene acetate, (+)-limonene, (S)-α-pinene, linalool, methyl linoleate, 2,2,6-trimethyl-6-vinyl-tetrahydro-2H-furan-3-ol, camphene, methyl salicylate, 1,10-decanediol, and 1,2,3-trimethoxybenzene as key differential volatile compounds among the three grades of stored raw Pu-erh tea samples. Further calculations yielded ROAV values for 14 kinds of volatile compounds, revealing that rosin acetate, (+)-limonene, (S)-α-terpineol, linalool, camphene, methyl salicylate, and 1,2,3-trimethoxybenzene exhibited ROAV>1, indicating these key aroma compounds contribute significantly to the flavor profiles of different grade raw Pu-erh tea storage samples. Conclusion The overall aroma profile of YK-T is dominated by floral, citrus, and aged notes presented by linalool, (+)-limonene and 1,2,3-trimethoxybenzene. Terpineol acetate, which exhibits a herbal aroma, is detected exclusively in YK-T, distinguishing this grade from the other 2. The volatile components of YK-A and YK-B primarily exhibit woody notes from camphene and floral notes from linalool. Notably, YK-A possesses the highest ROAV value for camphene among all key differentiating aroma compounds, resulting in its pronounced woody character. This study establishes a theoretical foundation for understanding quality differences among Pu-erh tea grades and provides data support for constructing discriminant profiles for raw Pu-erh tea of varying grades.