Native concentrations of α-ionone, β-ionone, and β-damascenone were studied in various authentic and commercial wines. In addition, the enantiomeric distribution of α-ionone was determined and its merits as a potential marker for aroma adulteration in wine were discussed. For extraction of volatiles, headspace solid-phase microextraction (HS-SPME) was applied, followed by heart-cut multidimensional gas chromatography coupled to tandem mass spectrometric detection for trace-level analysis. The enantioselective analysis of α-ionone was achieved with octakis(2,3-di-O-pentyl-6-O-methyl)-γ-cyclodextrin as the chiral selector in the separation column for gas chromatography (GC). In all the authentic wines studied, α-ionone showed a high enantiomeric ratio in favor of the (R)-enantiomer. Since an illegal addition of α-ionone in a racemic form changes the enantiomeric ratio, this ratio may serve as an adulteration marker. Concentrations varied between

The C13-norisoprenoid aroma compounds 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) and biosynthetically related vitispirane (VS) are important contributors to the varietal aroma of Riesling wines and are released from glycosidically bound carotenoid breakdown products during bottle aging. TDN is appreciated by numerous winemakers, particularly in aged Riesling wines. Higher levels of TDN, however, are perceived as a “petrol” off-flavor, which is expected to increase due to ongoing climate change. Wines produced from the same Riesling clone, which was grafted on six different rootstocks, varied significantly throughout two vintages in respect to their concentrations of free and bound TDN and VS as well as other volatiles. Over three vintages, the same compounds differed significantly among wines made from eight Riesling clones grafted on the same rootstock. Genetically determined loose grape clusters favored the formation of TDN and yielded wines of stronger sensory petrol intensity. Berry size, however, had no relevant impact on TDN and VS formation.

found in samples described as dusty-musty or nutty-like. In a migration study, transport of off-flavor compounds from affected cork stoppers into the corresponding wine could be observed after a storage period of 13 months. Multivariate statistics on the wines' sensory analysis and chemical data showed a good correlation of the individual off-flavor compound concentration, its sensory description and the off-flavor perceived in the wine.

Native concentrations and enantiomeric distribution of 1,2-propanediol in various wines were studied in order to evaluate its merits as a potential marker for aroma adulteration in wine. Heart-cut multidimensional gas chromatography coupled to mass spectrometry was applied to analyze 1,2-propanediol after salting-out of the polar phase, derivatization with phenyl boronic acid, and extraction with cyclohexane. The enantiomeric separation of the derivative was achieved with heptakis-(6-O-tert. butyl dimethylsilyl-2,3-di-O-acetyl)-β-cyclodextrin as the chiral selector. In all authentic wines studied, 1,2-propanediol showed a high enantiomeric ratio in favor of the (R)-enantiomer, proving its potential as a marker for the adulteration with flavor extracts based on industrial 1,2-propandiol as solvent. Usually, concentrations varied between 15 and 100 mg/L. Higher values (up to 170 mg/L) were found in wines made with high amounts of dry berries. However, despite the higher concentrations of 1,2-propanediol in such wines, no apparent influence on the enantiomeric distribution could be detected. Graphical Abstract Detection of fraudulent aromatization of wines by enantiodifferentiation of 1,2-propanediol as its phenylboronate ester.

Most yeast and bacteria in wine are able to metabolize hydroxycinnamic acids into volatile phenols via enzyme-mediated decarboxylation. Our trials performed in wine and model systems suggest that lysozyme addition prior to fermentation affects both bacterial activity and the release of hydroxycinnamic acids from their tartrate esters. This increases the potential for volatile phenol formation, as microorganisms can only metabolize free hydroxycinnamates. Wines with delayed malolactic fermentation due to lysozyme addition contained significantly higher concentrations of free hydroxycinnamic acids and elevated levels of volatile phenols in some cases. The reason for this is likely related to the side activity of lysozyme in combination with a detoxification mechanism that only occurs under stressful conditions for the yeast. Experiments in model systems indicate that lysozyme can affect the yeast at a pH higher than usually found in wine by attacking chitin in the bud scars of the cell walls and therefore weakening the cell structure. Free hydroxycinnamates can also affect yeast viability, making an increased release during fermentation problematic for a successful fermentation.