Carbohydrate composition of red wines during early aging and incidence on spoilage by Brettanomyces bruxellensis.

Wine is generally considered as hostile medium in which spoilage microbes have to manage with many abiotic factors among which low nutrient content. Wines elaborated in 8 wineries were sampled during the first summer of aging over two consecutive vintages, and analysed for carbohydrate composition. This revealed the systematic presence of many carbohydrates including those useful for the spoilage yeast Brettanomyces bruxellensis.

Brettanomyces bruxellensis phenotypic diversity, tolerance to wine stress and wine spoilage ability.

Brettanomyces bruxellensis is a yeast species found in many fermented matrices. A high level of genetic diversity prevails in this species and was recently connected with tolerance to sulfur dioxide, the main preservative used in wine. We therefore examine other phenotypes that may modulate the ability of the species to spoil wine, in a selection of representative strains.

Quantification of three galloylglucoside flavour precursors by liquid chromatography tandem mass spectrometry in brandies aged in oak wood barrels.

Vanillin-(6'-O-galloyl)-β-glucopyranoside (VGG), 3,4,5-trimethoxyphenyl-(6'-O-galloyl)-β-glucopyranoside (TMPGG), and (6R,9R)-3-oxo-α-ionol-9-O-(6'-O-galloyl)-β-glucopyranoside (macarangioside E) were identified as aroma precursors in oak wood. An LC-MS/MS method was developed and validated to quantify these three galloylglucoside compounds in brandies aged in oak barrels. The detection system consisted of a triple quadrupole mass analyser operating in multiple reaction monitoring (MRM) mode.

Quantification of megastigmatrienone, a potential contributor to tobacco aroma in spirits.

A SPME-GC-MS method was adapted and validated in order to quantify 5 megastigmatrienones and related odorous compounds from oak wood: guaiacol, cis-whisky lactone, trans-whisky lactone, γ-nonalactone, eugenol, vanillin, and acetovanillone in a single run. The five megastigmatrienone isomers (tabanones) were quantified, for the first time, in Cognac, Armagnac and rum, as contributors to tobacco-like aromas. Spirits aged in oak barrels contain higher amounts, but megastigmatrienones are also present in freshly-distilled spirits.

Quantitative solid phase microextraction--gas chromatography mass spectrometry analysis of five megastigmatrienone isomers in aged wine.

Megastigmatrienone is a key flavor compound in tobacco. It has also been detected in wine, where it may contribute to a tobacco/incense aroma, but its importance and concentration in wines had never previously been evaluated. A method was developed and validated for quantifying the five megastigmatrienone isomers in red and white wines.

Characterization of fruity aroma modifications in red wines during malolactic fermentation.

The role of malolactic fermentation (MLF) in the fruity aroma of red wines was investigated by an analytical study on more than 60 volatile compounds in 48 red wines made in varied conditions and supplemented by a sensory study. Lactic acid bacteria (LAB) modify the fruity notes of red wines but without a specific trend. The absence, in the short term, of a lactic mask was emphasized, whereas the existence of a smoked/toasted reduction-like mask note was evoked but not characterized.

A survey of seasonal temperatures and vineyard altitude influences on 2-methoxy-3-isobutylpyrazine, C13-norisoprenoids, and the sensory profile of Brazilian Cabernet Sauvignon wines.

This report has investigated the seasonal temperatures influences (winter and summer) of five vineyards at different altitudes on the concentrations of 2-methoxy-3-isobutylpyrazine (MIBP), alpha- and beta-ionone, and beta-damascenone in 2004 or 2005 vintages of Cabernet Sauvignon wines from Santa Catarina State, Brazil. Sensorial analyses were also carried out on the wine samples and compared to altitude and climate. Significant regression was observed between MIBP concentrations and the vineyard's altitude.