Extraction Of Aroma Components Of PU-ERH Tea And Quantitative Analysis Of Woody Aroma Components

In this study, headspace solid-phase microextraction (HS-SPME) and simultaneous distillation-extraction (SDE) coupled with gas chromatography-mass spectrometry (GC-MS) was applied to analyze aroma components and identify more rich aroma components in pu-erh tea. At the same time, the two extraction methods were compared to determine which was the optimal one. Then, the HS-SPME method was chosen for quantitative analysis of the woody compounds in pu-erh tea samples. The main contents were as follows:1Study on extracting methods of aroma components in pu-erh tea(1) conditional optimization of HS-SPME:The sensitivity and repeatability of four fibers with different polarities were examined and75μm CAR/PDMS was then selected as the optimal one; Taken the total peak area of aroma compounds as refenence standard, the affects of extraction conditions such as brewing proportion of tea and water、extraction temperature and extraction time to extraction efficiency were investigated. The results showed the optimal HS-SPME conditions were:fiber was75μm CAR/PDMS, brewing proportion of tea and water was1:3, extraction temperature was70℃, extraction time was60min.(2) Conditional optimization of SDE:n-pentane was considered as the suitable extraction solvent after checking the extraction efficiency of dichloromethane, n-pentane and diethyl ether. Taken total peak area of aroma compounds as refenence standard, the impact of extraction conditions containing extraction time and tea amount on extraction efficiency were investigated. The results showed the optimal SDE conditions were: organic solvent was n-pentane, extraction time was4h, tea amount was20g.(3) Under the optimized conditions, HS-SPME and SDE coupled with GC-MS was applied to analyze aroma components in pu-erh tea. A total of79kinds of aroma components were identified by two methods, among which67were identified by SPME and61by SDE. Importantly,16components were firstly detected in pu-erh tea. HS-SPME was proved most effective for compounds with high volatile and low molecular weight including alcohols, methoxy-phenolic compounds, aldehydes, ketones and hydrocarbons, and they played major role in the sensory perception of pu-erh tea. By contrast, compounds, with low volatile and high molecular weight containing esters, acid and some other aroma coponents, were apt to be extracted by SDE, and these compounds had small influence on sensorial perception. Therefore, it can be concluded that HS-SPME is more appropriate than SDE for the extraction of aroma compounds from pu-erh tea.2Quantitative analysis of the woody aroma compounds in pu-erh tea samples(1) The extraction efficiencies of five different HS-SPME fibers were evaluated. The results showed that50/30μm DVB/CAR/PDMS fiber exhibited the highest extraction efficiency.(2) On the basis of single factor experiment. Central-Composite experimental design were used to optimize HS-SPME conditions and the total peak area of woody aroma compounds was used as response value. The obtained optimal HS-SPME conditions were: amount of pu-erh tea3.44g, extraction time55.6min, extraction temperature61℃. Under the optimal conditions, the linear regression correlation coefficients (R) for the seven woody aroma compounds were between0.997to0.999, and the limits of detection were below10ng/g. The method accuracy is satisfactory with recoveries between90.76%to112.59%, and their RSD were lower than12%.(3) Under the optimized conditions, the content of the woody aroma compounds in twenty pu-erh tea samples was determined by HS-SPME-GC/MS method. The result showed that the content of Linalool oxide Ⅰ ranged from0.32to2.11μg/g, Linalool oxide Ⅱ ranged from0.40to2.93μg/g, Linalool ranged from0.16to6.18μg/g, α-Cedrol ranged from0.05to4.04μg/g, α-Ionone ranged from0.00to1.34μg/g, β-Ionone ranged from0.40to1.83μg/g, Cedrol ranged from0.00to0.14μg/g.