内山六安瓜片4个等级茶叶香气的组成及其差异

Differences in Volatile Aroma Compositions among Four Quality Grades of Mountain Lu'an Guapian Tea

为深入探究历史名茶六安瓜片不同等级间香气组分和含量的差异,选用内山六安瓜片特级、一级、二级和三级茶叶样品,以SDE法提取香精油,使用GC-MS配合标样做定性分析,加入癸酸乙酯为内标进行相对定量分析。结果表明,从4个等级的茶叶香精油中共鉴定香气成分96种,包括20种醇、18种酯、17种烯烃、16种醛、12种酮、7种杂环化合物和少量酸类;主要成分为芳樟醇、香叶醇、橙花叔醇、β-紫罗酮、己酸-顺-3-己烯酯、苯甲醛、棕榈酸、芳香醇氧化物Ⅰ型、β-环柠檬醛、α-紫罗酮、顺-3-己烯-1-醇、庚醛和壬醛;从特级、一级、二级至三级,香气成分个数分别为79、60、55个和47个,相对于内标的含量分别为695.94、579.90、541.69和268.50,香气成分个数和香气总含量呈梯度递减;4个等级茶叶的共有高含量香气成分为芳樟醇、橙花叔醇、α-紫罗酮、β-紫罗酮、己酸-顺-3-己烯酯,其含量随着等级降低而减少。六安瓜片的香气化合物包含多种类型且存在一些较稳定的高含量香气化合物,显露清香高爽的香型特征,但4个茶叶等级之间香气组分和含量的差异十分明显。

In order to thoroughly investigate aroma volatile compositions of the historically famous Lu'an Guapian tea,and evaluate their differences among the four quality grades:the super grade,the first grade,the second grade and the third grade,the tea samples processed in the internal mountains of Lu'an,Anhui Province,China were collected and analyzed.Essential oils from each of the four grades of tea samples were extracted by simultaneous distillation extraction(SDE),and then analyzed by gas chromatography coupled with mass spectrometry(GC-MS).The volatile aroma constituents were identified by comparison of mass spectra and retention times with those of authentic standards,and quantified by their relative abundances to the internal standard,ethyl decanoate.A total of 96 aromatic compounds were identified from the four grade teas,including 20 alcohols,18 esters,17 alkenes,16 aldehydes,12 ketones,7 heterocyclic compounds and a few organic acids.The major aromatic constituents were linalool,geraniol,cis-nerolidol,β-ionone,cis-3-hexenyl hexanoate,benzaldehyde,n-hexadecanoic acid,linalool oxide I,β-cyclocitral,α-ionone,Z-3-hexen-1-ol,heptanal and nonanal.The numbers and total abundances relative to the internal standard of these identified aromatic constituents from the super grade,the 1st grade,the 2nd grade and the 3rd grade were 79/695.94,60/579.90,55/541.69,and 47/268.50,respectively.Both the numbers and total abundances were positively related to the tea quality.The tea quality was positively correlated with the number and abundance of aromatic compounds.Conversely,the major aroma components,linalool,cis-nerolidol,α-ionone,β-ionone and cis-3-hexenyl hexanoate,were significantly reduced with the tea quality grades decreased.It was concluded that the high contents of diversified aromatic constituents,especially their major identified constituents in the Lu'an Guapian teas are probably responsible for its overall pleasant and refreshing scent and flavor.However,there were still significant differences in both aromatic constituents and their total abundances,thus also the fragrances,among the four quality grades.