The flavour of wine and sparkling wine is significantly influenced by glycosidically bound aromaprecursors in grapes, must and base wines. These odorless precursors are liberated by hydrolysis and enzymatic cleavage due to yeast during alcoholic fermentationwhich triggers the formation of the varietal aroma during the first or second fermentation. Quantitative analysis of glycosylated aromaprecursors allows an evaluation of the aroma potential of a given must or base wine. Furthermore, yeast strains can be assessed regarding their liberation of aromaprecursors.Glycosylated precursors from juice and wine samples were obtained and concentrated by an automated solid phase extraction (SPE) system. An aliquot was analysed by FT-MIR, while the other underwent enzymatic cleavage. The extracted free aroma compounds were analysed by gaschromatography/mass spectrometry (GC/MS). Application of a large-volume injection allowed the detection of trace amounts without any further concentration step. Overall 40 volatiles were quantified using stable isotope dilution assay (SIDA) which were grouped categories: monoterpenes, C6-alcohols, benzene derivatives, C13-norisoprenoids and volatile phenols.Extraction and liberation of aroma compounds from glycosylated precursors were monitored during skin maceration of Riesling and Muscat grapes and varying press regimes. While monoterpenes showed a linear increase, C6-alcohols and benzene derivatives yielded a saturation curve and C13-norisoprenoids did not change at all. During alcoholic fermentation liberation of monoterpenes, C6-alcohols and benzene derivatives followed nearly linear curvature at varying slopes, while bound C13-norisoprenoids even increased.Chemical and sensory analysis of Riesling, Muscat and Chardonnay wines fermented by different yeast strains revealed a significant impact on their composition. Even during secondary fermentation, significant changes were observed in sparkling wines due to the application of various yeast strains.The project (AiF 16627 N) is supported by the German Ministry of Economics and Technology (via AiF) and the Forschungskreis der Ern�hrungsindustrie e.V. (FEI).

From grape to sparkling wine: Analysis of glycosylated aroma compounds during grape processing and fermentation

248th National Meeting (2014)

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