SDE-GC-MS与P&T-TD-GC-MS提取分析不同香型凤凰单丛茶香气比较

分别采用同时蒸馏萃取(simultaneous distillation extraction,SDE)法和吹扫捕集热脱附解吸(purge and trap thermal desorption,PT-TD)法提取黄栀香和肉桂香两种香型凤凰单丛茶的香气成分并用气相色谱-质谱进行分析比较。结果表明,2种方法提取的香气成分和相对含量比例有很大差异,两者各有优劣,相互补充,结合分析更加完整,更有利于准确地进行香型分类,并发现PT-TD法有更大的运用空间。SDE法提取的萜烯类化合物较多,脂肪族和芳香族的化合物较少,不同香型的区别主要是成分的相对含量比例;PT-TD法提取得到的成分种类多,不同香型的茶区别较大。通过萜酯指数可得PT-TD法提取的香气更为清香,SDE法提取的香气较为浓烈,但两者都体现了凤凰茶清高持久的幽香特性。SDE法的高温加热可能引起成分的改变,PT-TD提取法的成分较能真实地反应茶汤冲泡的特点。结合2种方法分析得出,黄栀香与肉桂香茶的区别明显,黄栀香茶以荜澄茄醇、橙花叔醇等为主,并特有丙酸芳樟酯、δ-杜松烯、萜品油烯等成分;肉桂香茶是吲哚、δ-壬内酯、苯乙腈相对含量多,且含有苯乙醇、苯甲醇、1,5,8-对-薄荷三烯、戊醛等特有成分。

Comparison of Simultaneous Distillation Extraction (SDE) with Purge and Trap Thermal Desorption (P&T-TD) for the Analysis of Aroma Compounds in Tea Made from Two Cultivars of Fenghuang Dancong by Gas Chromatpraphy-Mass Spectrometry (GC-MS)

The volatile compositions of two Fenghuang Dancong tea fragrance types, Huang Zhi Xiang (gardenia Magnolia fragrance) and Rougui Xiang (cinnamon), were extracted using either simultaneous distillation extraction (SDE) or purge and trap thermal desorption (P&T-TD), and then analyzed by gas chromatography-mass spectrometry (GC-MS). The results show that the composition of volatile compounds detected in Fenghuang Dancong tea was different using the two extraction methods, which had their own advantages and complemented with each other. Their combination could provide a more complete and accurate analytical approach to the classification of aroma compounds. More terpenes and less aliphatics and aromatics were obtained with SDE extraction, and differences between the two tea fragrance types existed with respect to the relative contents of aroma compounds extracted by SDE method. But P&T-TD method enabled us to extract a larger number of aroma compounds from Fenghuang Dancong tea, with significant differences being observed between the two fragrance types. Besides T/E index showed that the aroma extracted by P&T-TD method was more fragrant, while that extracted by SDE was more intense; both of them reflected the aroma features of Fenghuang Dancong tea with a long-lasting delicate fragrance. The aroma of the tea may be distorted due to the high temperature in SDE extraction, while P&T-TD method more truly reflected the characteristics of the tea brew. Combining the two extraction methods, the difference between Huang Zhi Xiang and Rougui Xiang tea was more obvious. The predominant compounds of Huang Zhi Xiang were α-cadinol, linalool oxide, dehydrolinalool and nerolidol, and the characteristic components were linalyl propionate, δ-cadinene, terpinolene and so on. The predominant compounds of Rougui Xiang tea were indole, delta-nonalactone, benzeneacetonitrile, and the characteristic components were phenethyl alcohol, benzyl alcohol, 1,5,8-p-menthatriene and valeraldehyde.