Capillary electrophoresis in wine science.

Capillary electrophoresis appeared to be a powerful and reliable technique to analyze the diversity of wine compounds. Wine presents a great variety of natural chemicals coming from the grape berry extraction and the fermentation processes. The first and more abundant after water, ethanol has been quantified in wines via capillary electrophoresis. Other families like organic acids, neutral and acid sugars, polyphenols, amines, thiols, vitamins, and soluble proteins are electrophoretically separated from the complex matrix.Here, we will focus on the different methodologies that have been employed to conduct properly capillary electrophoresis in wine analysis.Two examples informing on wine chemistry obtained by capillary electrophoresis will be detailed. They concern polyphenol analysis and protein profiling. The first category is a well-developed quantitative approach important for the quality and the antioxidant properties conferred to wine. The second aspect involves more research aspects dealing with microbiota infections in the vineyard or in the grape as well as enological practices

A grape and wine chemodiversity comparison of different appellations in Burgundy: Vintage vs terroir effects.

This study aimed at assessing the ability of high resolution Fourier Transform Ion Cyclotron Resonance - Mass Spectrometry (FTICR-MS) to differentiate grapes and corresponding wines from distinct vineyards managed by a same producer, according to complex chemical fingerprints. Grape extracts (at harvest) and corresponding wines from four different vineyards, sampled immediately after the alcoholic fermentation over three successive vintages, were analysed by FTICR-MS. Thousands of metabolites that are specific to a given vintage, or a given class (wine, skin or must) could be revealed, thus emphasising a strong vintage effect. The same wines were reanalyzed after a few years in bottle. Within the frame of this study, FTICR-MS along with multivariate statistical analyses could reveal significant terroir-discriminant families of metabolites from geographically close - though distinct - vineyards, but only after a few years of bottle ageing. It is supposed that the chemical composition of a wine holds memories of various environmental factors that have impacted its metabolic baggage at the moment of its elaboration. For the first time, such preliminary results indicate that non-targeted experiments can reveal such memories through terroir-related metabolic signatures of wines on a regional-scale that can potentially be as small as the countless "climats" of Burgundy

High precision mass measurements for wine metabolomics.

An overview of the critical steps for the non-targeted Ultra-High Performance Liquid Chromatography coupled with Quadrupole Time-of-Flight Mass Spectrometry (UPLC-Q-ToF-MS) analysis of wine chemistry is given, ranging from the study design, data preprocessing and statistical analyses, to markers identification. UPLC-Q-ToF-MS data was enhanced by the alignment of exact mass data from FTICR-MS, and marker peaks were identified using UPLC-Q-ToF-MS(2). In combination with multivariate statistical tools and the annotation of peaks with metabolites from relevant databases, this analytical process provides a fine description of the chemical complexity of wines, as exemplified in the case of red (Pinot noir) and white (Chardonnay) wines from various geographic origins in Burgundy

Fluorescence fingerprinting of bottled white wines can reveal memories related to sulfur dioxide treatments of the must.

For the first time, Excitation Emission Matrix (EEM) fluorescence spectroscopy was combined with parallel factor statistical analysis (PARAFAC) and applied to a set of 320 dry white wines of the Chardonnay grape variety. A four component PARAFAC model (C1, C2, C3 and C4) best explained the variability of fluorescence signatures of white wines. Subtle changes were observed in EEMs of white wines from two different vintages (2006 and 2007), where different concentrations of sulfur dioxide (0, 4, and 8 g·hL(-1)) were added to the grape must at pressing. PARAFAC results clearly indicated that sulfur dioxide added to the must subsequently influenced white wine chemistry into three distinct sulfur dioxide dose-dependent aging mechanisms. For both vintages, C1 and C2 were the dominant components affected by sulfur dioxide and likely reacting with phenolic compounds associated with some presumably proteinaceous material. Distinct component combinations revealed either SO2 dependent or vintage-dependent signatures, thus, showing the extent of the complex versatile significance underlying such fluorescence spectra, even after several years of bottle aging

Capillary Electrokinetic Fractionation Mass Spectrometry (CEkF/MS): Technology setup and application to metabolite fractionation from complex samples coupled at-line with ultrahigh resolution mass spectrometry.

Capillary Electrokinetic Fractionation (CEkF) is investigated as a new, simple and robust approach for semi-preparative and analytical sample analysis based on pKa-dependant pH-driven electrophoretic mobility. CEkF was optimized with contactless conductivity detection and conducted with 10 kV reverse voltage for 10 min, then coupled on/at-line to electrospray ionization (ESI) mass spectrometry (MS). We propose a semi-empirical model with 14 representative compounds based on the correlation between sample/medium pH regulating the partial charge, the electrokinetic loading of the capillary and intensity (I) of analytes. According to the model, an empirical function (I = f (pH)) could be derived to calculate the acid dissociation constant (pKa) of various model compounds based on their pH-dependant MS intensity profiles with the RSD less than 4.05. Using the ultrahigh resolution of ion cyclotron resonance Fourier Transform mass spectrometry (ICR-FT/MS), the pKa model was further illustrated in real samples into the structure prediction of important compounds in wine over 2 vintages. The established CEkF was successfully used to selectively fractionate sulfur compounds from the complex wine samples at pH 1.66. The proposed CEkF approach should allow in the future the simultaneous pKa evaluation of multiple constituents without complicated separation out of a complex mixture in metabolomics or environmental chemistry

Exploring the chemical space of white wine antioxidant capacity: A combined DPPH, EPR and FT-ICR-MS study.

The chemical composition and functionality of molecular fractions associated with dry white wines oxidative stability remain poorly understood. In the present study, DPPH assay, electron paramagnetic resonance spectroscopy (EPR) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) were used to explore the chemical diversity associated with the antioxidant capacity (AC) of white wines. AC determined using the DPPH assay and EPR were complementary and enabled differentiation of wine samples into groups with low, medium, and high AC. Mass spectra variations associated with global DPPH- and EPR-derived indices enabled identification of 365 molecular markers correlated with samples with high AC, of which 32% were CHO compounds including phenolic and sugar derivatives, 20% were CHOS and 36% were CHONS compounds including cysteine-containing peptides. This study confirmed the importance of CHONS and CHOS compounds in the antioxidant metabolome of dry white wines. Knowledge about these compounds will enable better understanding of the oxidative stability of white wines and therefore aid in achieving optimum shelf life

Combined nontargeted analytical methodologies for the characterization of the chemical evolution of bottled wines.

Various non-targeted approaches have already shed light on the thousands of compounds that are present at various concentrations in grape and wine. Among them, direct injection Ion Cyclotron Resonance Fourier Transform Mass Spectrometry (FTICR-MS) undoubtedly provides the most comprehensive chemical fingerprints, based on unrivalled resolution on mass measurement, but limited to structural assumptions. Here, we show that the combination of FTICR-MS and Ultra-Performance Liquid Chromatography Mass Spectrometry (UPLC-QTOF-MS), which increases the scope of detectable unknown metabolites and allows the separation between isomers, provides an unprecedented synoptic characterization of the chemical complexity of wines, where results obtained with one platform can directly be validated with data from the other. To that respect, wine ageing appears to be particularly interesting when related to the oeno-diagenesis processes that operate in bottle, and which depend on the actual initial composition of the wine. Applied to Pinot noir red wines from three different appellations in Burgundy, and over three vintages (1979, 1989, 1999), this approach revealed that the ageing chemistry is fundamentally driven by the metabolic baggage at bottling, characterized here by thousands of compounds from various chemical families including carbohydrates, amino acids, or polyphenols, but with a remarkably high distribution of nitrogen and sulfur-containing compounds