Gilles de Revel

Multi-residue off-flavour profiling in wine using stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A multi-residue method (MRM) for the detection and quantification of eight compounds responsible for off-flavours in wine using stir bar sorptive extraction (SBSE) followed by thermal desorption (TD) and gas chromatography-mass spectrometry (GC-MS) analysis is presented. The extraction and desorption conditions were optimised in order to get the best compromise for the simultaneous analysis of the eight target solutes, belonging to different chemical classes. The analytical conditions enable the quantification of the solutes below their respective organoleptic perception thresholds in wine. The method displayed good linearity over the concentration ranges explored in wine as well as excellent repeatability (RSD below 6%) and good reproducibility (RSD below 24%). The developed methodology was applied to the analysis of several wines and showed good agreement with the results collected with headspace solid-phase microextraction (HS-SPME) or liquid-liquid extraction (LLE) followed by GC-MS or electron capture detection (ECD). Good correlation was also found between the analytical and sensory results.

A HPLC fluorescence-based method for glutathione derivatives quantification in must and wine

A simple and automated high performance liquid chromatography (HPLC) method for the separation and quantitative determination of gamma-glutamylcysteine and reduced glutathione (GSH) in wines is reported. This technique involves the use of a pre-column derivatization with 2,3-naphthalenedialdehyde (NDA), an isocratic separation in presence of beta-cyclodextrine and a fluorimetric detection. The quantification of oxidized glutathione (GSSG) has also been studied, for the first time in wines, using an additive pre-derivatization step for reduction using glutathione reductase. The method has been designed for use in laboratories with limited equipment. The assay has been optimized and presents very good performances in terms of sensitivity and selectivity. Then, it has been validated for linearity, LOD, LOQ, precision and accuracy.

Esters in Wines: New Insight through the establishment of a Database of French wines

This work aimed to establish a database of wine esters from French wines to update the knowledge of wine aroma composition. Thirty odorant esters were quantified by HS–SPME–GC-MS in 183 commercial French wines from 1 to 29 years old and included red, dry white, sweet white, and rosé wines and red wines from carbonic maceration (Beaujolais nouveau; BN). Higher concentrations of ethyl esters of fatty acids (EEFAs) were found in wines made at low temperature (white and rosé). However, the relative composition of EEFAs was similar in all types of wines and mainly depended on the length of the carbon chain. Higher alcohol acetate (HAA) levels were favored in wines made under strict anaerobiosis (BN, white), but the relative composition of HAAs depended on the type of wine. Such variability in the relative compositions of HAAs among wines might originate from differences in lipids, oxygen, and nitrogen status of fermented media. Conversely, concentrations of ethyl esters of branched acids (EEBAs) were higher in wines made with grape skin contact (BN, red). The relative concentrations of EEBAs were similar regardless of the type of wine, with ethyl isobutyrate the most abundant. We hypothesized that this specific EEBAs profile in wines might originate from the redox balance regulation of yeast metabolism. Moreover, concentrations of EEBA increased with wine age at similar rates in white and red wines. On the other hand, chemical hydrolysis during wine aging was observed only in the analytical data for higher alcohol acetates in white wines and for ethyl decanoate and dodecanoate in red and white wines. The results help in understanding the aromatic contribution of esters in aged wine.

Development and validation of method for heterocyclic compounds in wine: optimization of HS-SPME conditions applying a response surface methodology.

Considering the importance of the heterocyclic compounds in terms of wine flavor, this study aims to propose a new rapid and solvent free method to quantify different classes of heterocyclic compounds, such as furans, thiophenes, thiazols and pyrazines, which are products of the Maillard reaction, in wines. The use of a central composite design and the response surface methodology to determine the best conditions allows the optimum combination of analytical variables (pH, NaCl and extraction time) to be identified. The validation was carried out using several types of wine as matrices. The method shows satisfactory repeatability (2.7%<RSD<12%), reproducibility (2.8%<RSD<12%), accuracy and specificity. The optimized method was applied to 29 French wines and significant concentrations of the different heterocyclic compounds were determined, mainly for red wines.

Toward automated chromatographic fingerprinting: A non-alignment approach to gas chromatography mass spectrometry data

In contrast to targeted analysis of volatile compounds, non-targeted approaches take information of known and unknown compounds into account, are inherently more comprehensive and give a more holistic representation of the sample composition. Although several non-targeted approaches have been developed, theres still a demand for automated data processing tools, especially for complex multi-way data such as chromatographic data obtained from multichannel detectors. This work was therefore aimed at developing a data processing procedure for gas chromatography mass spectrometry (GC-MS) data obtained from non-targeted analysis of volatile compounds. The developed approach uses basic matrix manipulation of segmented GC-MS chromatograms and PARAFAC multi-way modelling. The approach takes retention time shifts and peak shape deformations between samples into account and can be done with the freely available N-way toolbox for MATLAB. A demonstration of the new fingerprinting approach is presented using an artificial GC-MS data set and an experimental full-scan GC-MS data set obtained for a set of experimental wines.

Vine Water Deficit Impacts Aging Bouquet in Fine Red Bordeaux Wine

The aim of this study was to investigate the influence of vine water status on bouquet typicality, revealed after aging, and the perception of three aromatic notes (mint, truffle, and undergrowth) in bottled fine red Bordeaux wines. To address the issue of the role of vine water deficit in the overall quality of fine aged wines, a large set of wines from four Bordeaux appellations were subjected to sensory analysis. As vine water status can be characterized by carbon isotope discrimination (δ13C), this ratio was quantified for each wine studied. Statistical analyses combining δ13C and sensory data highlighted that δ13C-values discriminated effectively between the most- and least-typical wines. In addition, Principal Component Analysis (PCA) revealed correlations between δ13C-values and truffle, undergrowth, and mint aromatic notes, three characteristics of the red Bordeaux wine aging bouquet. These correlations were confirmed to be significant using a Spearman statistical test. This study highlighted for the first time that vine water deficit positively relates to the perception of aging bouquet typicality, as well as the expression of its key aromatic nuances.

Perceptive Interactions on Typical Fruity Aroma in Wine

In wine, more than 800 volatiles have been identified and most of them are present at lower or similar levels to their individual perception thresholds. However, recent evidence establishes the significance of low impact odorants in global odor perception. Using the high pressure liquid chromatography (HPLC) method we developed a methodology to prepare aromatic reconstitutions from wine extract fractions instead of pure compounds. The existence of particular perceptive interactions in the expression of fruity aroma was demonstrated. Concerning fresh fruit aroma, an additive effect was observed due to fractions with low fruity note and a masking effect was perceived due to fractions with caramel and lactic aroma.