Carbonyl compounds primarily result from chemical oxidation of wine components, and are known to affect aroma and color stability. Their analysis in wine is complicated due to their instability and their tendency to react reversibly with bisulfite to form hydroxysulfonate adducts. To distinguish the adducts, published methods break down the sulfonates for the quantitation of total carbonyls by alkaline hydrolysis, but this can increase carbonyls by oxidation, and poorly quantified amounts of weakly bound carbonyls dissociate even without treatment. Both challenges could be overcome if the two components could be quantified in situ. Here, two-dimensional (1H-1H) homonuclear and heteronuclear (13C-1H) single quantum correlations (COSY and HSQC) nuclear magnetic resonance spectra of undiluted wine samples were observed at natural abundance. These techniques achieve simultaneous direct identification and quantification of free and sulfite bound acetaldehyde, pyruvic acid, acetoin, methylglyoxal and a-ketoglutaric acid in wine samples with only a small addition of D2O. A calibration curve was defined with standard samples containing known amounts of each analyte. Limits of detection are approximately 10 mg L-1 and were generally lower when using COSY correlation. The accuracy of the method was tested in wine samples by spiking with a mixture of all analytes at different concentrations. The method was applied to 20 wine samples of various vintages and grape varieties

2D quantitative proton (<sup>1</sup>H) and carbon (<sup>13</sup>C) nuclear magnetic resonance spectroscopy (2D q NMR) for direct analysis of free and sulfite-bound carbonyl compounds in wine

248th National Meeting (2014)

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2D quantitative proton (1H) and carbon (13C) nuclear magnetic resonance spectroscopy (2D q NMR) for direct analysis of free and sulfite-bound carbonyl compounds in wine

2D quantitative proton (¹H) and carbon (¹³C) nuclear magnetic resonance spectroscopy (2D q NMR) for direct analysis of free and sulfite-bound carbonyl compounds in wine