Although wine quality depends on grape composition, blending vodka with grape juice is a poor substitute for wine. During fermentation and storage, many grape flavor compounds are poorly extracted or else transformed, while new wine flavor compounds are generated from grape-derived precursors. Two-dimensional gas chromatography-time-of-flight-mass-spectrometry (GCxGC-TOF-MS) is useful for quantifying trace aroma compounds or their precursors in grapes and wines. Analytical challenges and applications to grape breeding and viticulture will be discussed, especially for compounds responsible �vegetal� aromas. Strategies for comprehensive, '-omics' type measurements using uniformally labeled (e.g. U-13C) isotopic standards will also be presented. The second part of the talk will consider the economic diametric opposite � an inexpensive assay for elemental S pesticide residues on grapes, which can form noxious H2S during fermentation. Our assay has been useful for determining appropriate pre-harvest spray intervals, and is now being extended to characterize 'latent' precursors of sulfurous off-aromas during wine storage.

Relating grape composition to wine aroma chemistry � or, why wine is more than grape juice diluted with vodka

246th National Meeting (2013)

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