Free Volatile Aroma Compounds Of Cabernet Gernischet Wine In Yantai Region

Among the various factors contributing to the enjoyment of wine,flavor is possibly the most important one.But flavor is mainly composed of many volatile aroma compounds,so the study on the volatile aroma of wine has always been a hot issue recently.In this paper,the volatile aroma compounds of Cabemet Gemischt wine produced in Yantai,China,were analyzed by a series of methods.The main contents are as follows:(1)The GC-O technique was applied to identify the aroma-active compounds in the Cabernet Gemischt wine,the Cabemet Gemischt wine of Chateau Castle and oak-aged Cabemet Gernischt wine.There were 80 aroma-active compounds found in the three wines, 78 of which could be identified.The 5-methylfurfural,Z-whiskey lactone,E-whiskey lactone, 4-methylguaiacol and 4-ethylguaiacol were only found in the oak-aged Cabemet Gemischt wine.The volatile aroma compounds in the other two Cabemet Gernischt wines were generally the same and only differed in the intensity.In all the wine samples,β-damascenone and 3-methylbutanol with the maximum FD factor(FD=625) were considered as the most important odorants.However,isoamyl acetate and linalool were also important aroma contributors only in the oak-aged Cabemet Gemischt wine with a high FD=625.(2)The headspace solid phase microextraction(HS-SPME) followed by gas chromatography-mass spectrum(GC-MS),and the liquid-liquid microextraction(LLME) coupled with GC-MS were selected to quantify the volatile aroma compounds identified by GC-O.For all the volatile aroma compounds,high correlation coefficient(＞0.99) and low standard deviation(＜20%) were obtained.Quantification analysis showed that acids,esters and alcohols were the main volatile aroma compounds in the Cabemet Gernischt wine.Acetic acid,3-methylbutanol,2-methylpropanol,ethyl lactate,diethyl succinate and ethyl acetate were the most abundant aroma compounds.According to the OAV values,ethyl octanoate, ethyl hexanoate,ethyl 2-methylpropanoate,ethyl 3-methylbutanoate,3-methylbutanoic acid andβ-damascenone were the most important volatile aroma compounds.Furthermore,some higher alcohols,fatty acids and aldehydes also could be aroma contributors to the Cabernet Gernischt wine.(3) The volatile aroma compounds in Cabernet Gernischt juice and wine during vinification were also quantified.The alcoholic fermentation was the main process of aroma forming, such as the alcohols,esters and acids.Ethyl octanoate and ethyl hexanoate reached the highest concentration after yeast was inoculated 4—5 days.And when the alcoholic fermentation ended,their concentration dropped quickly with the final concentration of 570μg/L and 300μg/L,respectively.The isoamyl acetate reached the peak in concentration approximately at 7 days after inoculation.Its levels then began to decrease rapidly,reaching final concentration of 214μg/L.The ethyl 3-methylbutanoate,ethyl 2-methylpropanoate and 3-methylbutanoic acid reached the maximum level at the end of alcoholic fermentation.A subsequent measurement taken 12 days and 30 days after inoculation showed no significant change in their concentrations.Moreover,some non-volatile aroma precursors,such as carotenoids, glycoconjugates could be hydrolyzed by acid or enzyme,and released some volatile aroma compounds,taking C_13- norisoprenoids and terpenes for example.(4) The results of principle component analysis(PCA) revealed that the first six principle components extracted could reflect 84.03%of the original messages.The first three principle components were subjected to graphical analysis,and three clusters were obtained from different years:vintage 2002,vintage 2006 and vintage 2007.The oak-aged red wines that stored in the French oak barrels had unique aroma characteristics and discriminated as the fourth cluster.(5) According to the Varimax rotated component matrix of principle component analysis, the important variables responsible for wine classification included:methyl salicylate, 5-methylfurfural,E-whiskey lactone,Z-whiskey lactone,4-methylguaiacol,4-ethylguaiacol, vanillin,ethyl 2-methylpropionate,ethyl hexanoate,furfural,Z-3-hexen-1-ol,decanoic acid, 4-vinylguaiacol,ethyl acetate,acetic acid,benzyl alcohol,α-terpineol and nerol.The discriminant analysis performed by the variables listed above manifested that E-whiskey lactone,vanillin,Z-whiskey lactone,4-ethylguaiacol and 5-methylfurfural were the most important variables for the differentiation of the red wines.(6) The results of discriminant analysis also indicated that the oak-aged red wines could distinctly separate from the non-oak aged wines.The prediction capacity of the cluster model was evaluated by "leave-one-out" cross validation which showed an average of 100%samples could be correctly classified.So the discriminant cluster model had practical significance on differentiating the premium quality oak-aged wine.