不同管理方式的武夷水仙岩茶品质差异及其形成的物质基础

Quality Difference and Its Forming Material Basis of Wuyi Shuixian Rock Tea with Different Management Methods

福建水仙属于小乔木型茶树,是加工武夷岩茶的主要品种之一。目前,武夷山茶园管理过程中存在水仙茶树自然生长的现象(不修剪),其制茶品质与修剪水仙有明显区别。为明确自然生长和修剪条件下,武夷水仙岩茶的香气和呈味物质基础及其差异,本研究采用气相色谱-质谱联用(gas chromatography-mass spectrometry,GC-MS)和高效液相色谱(high performance liquid chromatography,HPLC)技术,结合多元统计分析,探寻自然生长和修剪下武夷水仙岩茶在焙火前(毛茶)和焙火后(成品茶)香气物质、滋味成分与品质的内在联系。结果表明:利用GC-MS技术共鉴定出261种挥发物;通过主成分分析(principal component analysis,PCA)与正交偏最小二乘判别分析(orthogonal partial least squares discriminant analysis,OPLS-DA)可知,自然生长水仙茶树和修剪水仙茶树制成的毛茶和成品茶的香气物质差异明显。与修剪水仙毛茶相比,自然生长水仙毛茶有41种挥发性物质存在显著差异(筛选差异标准:VIP>1,且FC≥1.5或FC≤0.67),己酸己酯、植物醇、异植醇、反式-橙花叔醇等花果香物质的相对含量更高;而β-雪松烯、γ-杜松烯、2-甲氧基呋喃等相对含量更低。与修剪水仙成品茶相比,自然生长水仙成品茶有71种挥发性物质存在显著差异,呈果香型的己酸己酯、己酸甲酯、反式-橙花叔醇、(Z)-β-法呢烯、1-庚醇、2-庚酮等挥发物,呈烘烤香型的3-乙基-1H-吡咯、2-甲酰基-4,5-二甲基吡咯、乙基甲基吡嗪等挥发物的相对含量更高。修剪水仙和自然生长水仙茶焙火前后的香气物质也存在很大差异,分别有91和70种差异物质。通过香气活性值(aroma activity value,OAV)分析表明,(E)-3-己烯醇、吲哚、反式-橙花叔醇、环氧-β-紫罗兰酮、(E)-芳樟醇氧化物、2-苯乙醇、水杨酸甲酯可能是自然生长水仙香气形成的重要物质。主要呈味物质分析表明,自然生长和修剪水仙茶的儿茶素组分和咖啡碱存在明显差异。感官审评结果与理化检测结果一致,表现为自然生长水仙茶花果香浓郁,滋味醇厚,品质更佳。本研究对科学管理茶园和茶叶品质调控有指导作用。

Fujian Shuixian belongs to the semi-tree form of tea plant(Camellia sinensis),which is the main variety for processing Wuyi Rock Tea(WRT).At present,there is a widely phenomenon that Shuixian grows naturally(no-pruning)in the management of tea gardens of Wuyishan,and its quality is obviously different from that of pruned Shuixian.In order to clarify the basis and differences of aroma and flavor substances WRT under natural growth and pruning condi-tions,this study used gas chromatography-mass spectrometry(GC-MS)and high performance liquid chromatography(HPLC)technology,combined with multivariate statistical analysis,to explore the internal relationship among aroma substances,flavor components and quality of WRT before baking(raw tea)and after baking(finished tea)under natural growth and pruning conditions.The results showed that 261 volatile compounds were identified by GC-MS technology.It reveals that there are obvious differences in aroma substances between raw tea and finished tea of the natural growth Shuixian and pruned Shuixian with the help of principal component analysis(PCA)and orthogonal partial least squares discriminant analysis(OPLS-DA).Compared with the raw tea of pruning Shuixian,the raw tea of natural growth Shuixian showed significant differences in 41 volatile substances(Selection standard:VIP>1,and the FC≥1.5 or the FC≤0.67),in which the relative content of hexyl hexanoate,plant alcohol,isophytol,trans-nerolidol are higher,however,the relative content ofβ-cedrene,γ-junitene and 2-methoxyfuran are lower.Compared with the finished tea of pruning Shuixian,the finished tea of natural growth Shuixian showed significant differences in 71 volatile substances,such as hexyl hexanoate,methyl caproate,trans-nerolidol,(Z)-β-farnesene,1-heptanol,2-heptanone with fruity aroma,and 3-ethyl-1H-pyrrole,2-formyl-4with baking aroma,whose relative content are higher.There are also great differences in aroma substances between natural growth Shuixian and pruned Shuixian before and after baking,with 91 and 70 different substances respectively.The analysis of aroma activity value(OAV)showed that(E)-3-hexenol,indole,trans-nerolidol,epoxy-β-ionone,(E)-linalool oxide,2-phenylethanol and methyl salicylate may be important substances for the aroma formation of natural growth Shuixian.Analysis of the main flavor substances showed that there were obvious differences in catechin components and caffeine between natural growth Shuixian and pruned Shuixian.The results of sensory evaluation are consistent with the results of physical and chemical test,showing that natural growth Shuixian with rich fruit fragrance,mellow taste and better quality.This study has a guiding role in scientific management of tea gardens and tea quality control.