Real-Time Detection of Phenylacetaldehyde in Wine: Application of a Microwave Sensor Based on Molecularly Imprinted Silica.

Molecularly imprinted sol-gel silica (MIS) coupled to a microwave sensor was designed and used to detect phenylacetaldehyde (PAA), a chemical tracer of wine oxidation. The developed method is fast, cheap and could replace the classical chromatographic methods, which require a tedious sample preparation and are expensive. To reach our objective, five MIS and their control non-imprinted silica (NIS) were synthesized and their extraction capacity toward PAA was studied in hydro alcoholic medium. The selected polymers, based on this first step, were subjected to a selectivity study in the presence of PAA and three other competing molecules. The best polymer was integrated in a microwave sensor and was used to assess PAA in red wine. The developed sensor was able to detect PAA at the µg·L-1 level, which is below the off-flavour threshold.

Cultivar- and Wood Area-Dependent Metabolomic Fingerprints of Grapevine Infected by Botryosphaeria Dieback.

Botryosphaeria dieback is one of the most significant grapevine trunk diseases that affects the sustainability of the vineyards and provokes economic losses. The causal agents, Botryosphaeriaceae species, live in and colonize the wood of the perennial organs causing wood necrosis. Diseased vines show foliar symptoms, chlorosis, or apoplexy, associated to a characteristic brown stripe under the bark. According to the susceptibility of the cultivars, specific proteins such as PR-proteins and other defense-related proteins are accumulated in the brown stripe compared with the healthy woody tissues. In this study, we enhanced the characterization of the brown stripe and the healthy wood by obtaining a metabolite profiling for the three cultivars Chardonnay, Gewurztraminer, and Mourvèdre to deeper understand the interaction between the Botryosphaeria dieback pathogens and grapevine. The study confirmed a specific pattern according to the cultivar and revealed significant differences between the brown stripe and the healthy wood, especially for phytochemical and lipid compounds. This is the first time that such chemical discrimination was made and that lipids were so remarkably highlighted in the interaction of Botryosphaeriaceae species and grapevine. Their role in the disease development is discussed.

Previously unknown class of metalorganic compounds revealed in meteorites.

The rich diversity and complexity of organic matter found in meteorites is rapidly expanding our knowledge and understanding of extreme environments from which the early solar system emerged and evolved. Here, we report the discovery of a hitherto unknown chemical class, dihydroxymagnesium carboxylates [(OH)2MgO2CR]-, in meteoritic soluble organic matter. High collision energies, which are required for fragmentation, suggest substantial thermal stability of these Mg-metalorganics (CHOMg compounds). This was corroborated by their higher abundance in thermally processed meteorites. CHOMg compounds were found to be present in a set of 61 meteorites of diverse petrological classes. The appearance of this CHOMg chemical class extends the previously investigated, diverse set of CHNOS molecules. A connection between the evolution of organic compounds and minerals is made, as Mg released from minerals gets trapped into organic compounds. These CHOMg metalorganic compounds and their relation to thermal processing in meteorites might shed new light on our understanding of carbon speciation at a molecular level in meteorite parent bodies.

A First Tentative for Simultaneous Detection of Fungicides in Model and Real Wines by Microwave Sensor Coupled to Molecularly Imprinted Sol-Gel Polymers.

A molecularly imprinted silica (MIS) coupled to a microwave sensor was used to detect three fungicides (iprodione, procymidone and pyrimethanil) present in most French wines. Chemometric methods were applied to interpret the microwave spectra and to correlate microwave signals and fungicide concentrations in a model wine medium, and in white and red Burgundy wines. The developed microwave sensor coupled to an MIS and to its control, a nonimprinted silica (NIS), was successfully applied to detect the three fungicides present in trace levels (ng L-1) in a model wine. The MIS sensor discriminated the fungicide concentrations better than the NIS sensor. Partial Least Squares models were suitable for determining iprodione in white and red wines. A preliminary method validation was applied to iprodione in the white and red wines. It showed a limit of detection (LOD) lower than 30 ng L-1 and a recovery percentage between 90 and 110% when the iprodione concentration was higher than the LOD. The determined concentrations were below the authorized level by far.

Systems chemical analytics: introduction to the challenges of chemical complexity analysis.

Understanding complex (bio/geo)systems is a pivotal challenge in modern sciences that fuels a constant development of modern analytical technology, finding innovative solutions to resolve and analyse. In this introductory paper to the Faraday Discussion "Challenges in the analysis of complex natural systems", we aim to present concepts of complexity, and complex chemistry in systems subjected to biotic and abiotic transformations, and introduce the analytical possibilities to disentangle chemical complexity into its elementary parts (i.e. compositional and structural resolution) as a global integrated approach termed systems chemical analytics.

The Antioxidant Potential of White Wines Relies on the Chemistry of Sulfur-Containing Compounds: An Optimized DPPH Assay.

The DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay is an easy and efficient method commonly used to determine the antioxidant capacity of many food matrices and beverages. In contrast with red wines, white wines are poorer in antioxidant polyphenolics, and the more hydrophilic sulfur-containing compounds in them may contribute significantly to their antioxidant capacity. The modification of the classical DPPH method, with a methanol-buffer and the measure of EC20 (quantity of sample needed to decrease the initial DPPH concentration by 20%) has shown that sulfur-containing compounds such as cysteine (0.037 ± 0.003), glutathione (0.054 ± 0.003) or methanethiol (0.104 ± 0.003) appeared to bear antioxidant capacity comparable to well known phenolic compounds, such as catechin (0.035 ± 0.003), caffeic acid (0.057 ± 0.003) and ferulic acid (0.108 ± 0.003), respectively. In the case of white wines, the comparison with REDOX-sensory scores showed that results from this modified DPPH assay are strongly correlated with sensory attributes (r = 0.73, p < 0.1). These results provide an unprecedented illustration of the important contribution of these sulfur-containing compounds to the radical quenching ability of white wines.

Chemical messages in 170-year-old champagne bottles from the Baltic Sea: Revealing tastes from the past.

Archaeochemistry as the application of the most recent analytical techniques to ancient samples now provides an unprecedented understanding of human culture throughout history. In this paper, we report on a multiplatform analytical investigation of 170-y-old champagne bottles found in a shipwreck at the bottom of the Baltic Sea, which provides insight into winemaking practices used at the time. Organic spectroscopy-based nontargeted metabolomics and metallomics give access to the detailed composition of these wines, revealing, for instance, unexpected chemical characteristics in terms of small ion, sugar, and acid contents as well as markers of barrel aging and Maillard reaction products. The distinct aroma composition of these ancient champagne samples, first revealed during tasting sessions, was later confirmed using state-of-the-art aroma analysis techniques. After 170 y of deep sea aging in close-to-perfect conditions, these sleeping champagne bottles awoke to tell us a chapter of the story of winemaking and to reveal their extraordinary archaeometabolome and elemental diversity in the form of chemical signatures related to each individual step of champagne production.

Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter.

Two analytical separation methods-size-exclusion chromatography and asymmetrical flow field-flow fractionation-were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV-visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV-visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical Abstract An innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.

MetICA: independent component analysis for high-resolution mass-spectrometry based non-targeted metabolomics.

BACKGROUND: Interpreting non-targeted metabolomics data remains a challenging task. Signals from non-targeted metabolomics studies stem from a combination of biological causes, complex interactions between them and experimental bias/noise. The resulting data matrix usually contain huge number of variables and only few samples, and classical techniques using nonlinear mapping could result in computational complexity and overfitting. Independent Component Analysis (ICA) as a linear method could potentially bring more meaningful results than Principal Component Analysis (PCA). However, a major problem with most ICA algorithms is the output variations between different runs and the result of a single ICA run should be interpreted with reserve. RESULTS: ICA was applied to simulated and experimental mass spectrometry (MS)-based non-targeted metabolomics data, under the hypothesis that underlying sources are mutually independent. Inspired from the Icasso algorithm, a new ICA method, MetICA was developed to handle the instability of ICA on complex datasets. Like the original Icasso algorithm, MetICA evaluated the algorithmic and statistical reliability of ICA runs. In addition, MetICA suggests two ways to select the optimal number of model components and gives an order of interpretation for the components obtained. CONCLUSIONS: Correlating the components obtained with prior biological knowledge allows understanding how non-targeted metabolomics data reflect biological nature and technical phenomena. We could also extract mass signals related to this information. This novel approach provides meaningful components due to their independent nature. Furthermore, it provides an innovative concept on which to base model selection: that of optimizing the number of reliable components instead of trying to fit the data. The current version of MetICA is available at https://github.com/daniellyz/MetICA.

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 semipreparative 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 ESI/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 < 4.05. Using the ultrahigh-resolution of ion cyclotron resonance Fourier transform MS, the pKa model was further illustrated in real samples into the structure prediction of important compounds in wine over two 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.

The Oxidative Stability of Champagne Base Wines Aged on Lees in Barrels: A 2-Year Study.

In contrast with the elaboration of still wines, the impact of barrel aging before the "prise de mousse" on the aging potential of Champagne base wines has not been studied so far. In the present study, the oxidative stability and related molecular fingerprints of Chardonnay Champagne base wines were reported after 1 year of on lees ageing in new oak barrels for two consecutive vintages. Regardless of the vintage, on lees ageing in new oak barrels improved the wines' oxidative stability estimated by DPPH assay at 1 year, while UHPLC-Q-ToF-MS molecular profiling showed clear chemical modifications according to the ageing period. Oak wood molecular ellagitannins followed a linear extraction during barrel ageing for both vintages. However, the wines' antioxidant metabolome composed by antiradical and nucleophilic compounds clearly appeared vintage- and barrel-aging dependent. These results enrich the understanding of white wines antioxidant metabolome and improve the knowledge of the ageing potential of Chardonnay Champagne base wines by integrating vintage- and barrel-ageing effects.

Chemical Stability of Thiol and Flavanol Sulfonation Products during Wine Aging Conditions.

Bisulfite (HSO3-) is the predominant form of sulfur dioxide, present as free and bound to wine relevant electrophiles under wine acidic pH. While sulfonation reactions of flavanols and thiols have been recently reported as key for wine preservation against oxidation, the transient mechanisms and physicochemical parameters responsible for that remain unknown. In the present study, sulfonation reaction kinetics of thiols and flavanols were monitored under simulated wine aging conditions. The reaction products were then characterized by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis, and their chemical stability during time was determined by 1H NMR spectroscopy. Thiol and flavanol sulfonation reaction yields were both promoted by the presence of iron and oxygen, while their chemical stability was confirmed under the same conditions. The sulfonation derivatives of epicatechin and cysteine were synthesized and quantified in young and aged wines. Higher concentrations were reported for both metabolites in older wines, indicating their participation on the strongly bound sulfur dioxide fraction. These findings offer new prospects for more precise use of sulfur dioxide in winemaking.

1H NMR based sulfonation reaction kinetics of wine relevant thiols in comparison with known carbonyls.

Sulfite addition is a common tool for ensuring wines' oxidative stability via the activity of its free and weakly bound molecular fraction. As a nucleophile, bisulfite forms covalent adducts with wine's most relevant electrophiles, such as carbonyls, polyphenols, and thiols. The equilibrium in these reactions is often represented as dissociation rather than formation. Recent studies from our laboratory demonstrate, first, the acetaldehyde sulfonate dissociation, and second, the chemical stability of cysteine and epicatechin sulfonates under wine aging conditions. Thus, the objective of this study was to monitor by 1H NMR the binding specificity of known carbonyl-derived SO2 binders (acetaldehyde and pyruvic acid) in the presence of S-containing compounds (cysteine and glutathione). We report that during simulated wine aging, the sulfur dioxide that is rapidly bound to carbonyl compounds will be released and will bind to cysteine and glutathione, demonstrating the long-term sulfur dioxide binding potential of S-containing compounds. These results are meant to serve as a complement to existing literature reviews focused on molecular markers related to wines' oxidative stability and emphasize once more the importance of S-containing compounds in wine aging chemical mechanisms.

High molecular diversity of extraterrestrial organic matter in Murchison meteorite revealed 40 years after its fall.

Numerous descriptions of organic molecules present in the Murchison meteorite have improved our understanding of the early interstellar chemistry that operated at or just before the birth of our solar system. However, all molecular analyses were so far targeted toward selected classes of compounds with a particular emphasis on biologically active components in the context of prebiotic chemistry. Here we demonstrate that a nontargeted ultrahigh-resolution molecular analysis of the solvent-accessible organic fraction of Murchison extracted under mild conditions allows one to extend its indigenous chemical diversity to tens of thousands of different molecular compositions and likely millions of diverse structures. This molecular complexity, which provides hints on heteroatoms chronological assembly, suggests that the extraterrestrial chemodiversity is high compared to terrestrial relevant biological- and biogeochemical-driven chemical space.

White Wine Antioxidant Metabolome: Definition and Dynamic Behavior during Aging on Lees in Oak Barrels.

White wines' oxidative stability is related to a flow of chemical reactions involving a number of native wine compounds comprising their antioxidant metabolome. By applying the combination of powerful and modern analytical approaches (EPR, DPPH, and UPLC-qToF-MS-based metabolomics), we could define wine antioxidant metabolome as the sum of molecular antioxidant markers (AM) characterized by their radical scavenging (AM-RS) and nucleophilic (AM-Nu) properties. The impact of on-lees barrel aging of chardonnay wines on the antioxidant metabolome was studied for two consecutive vintages. The identification of wines' antioxidant metabolome allows for a detailed understanding of the transient chemical interplays involved in the antioxidant chemistry associated with well-known antioxidants and opens an avenue towards personalized winemaking. The present study gathers for the first time the dynamics of wines' antioxidant metabolome during on-lees aging. Monitoring the variations of the wine antioxidant metabolome can provide an avenue to better control the winemaking process using the knowledge of how to optimize the wine aging potential.

A key to wine conservation lies in the glass-cork interface.

This study investigates the evolution of the oxygen barrier properties of the bottleneck-stopper system under conditions simulating the conservation of wine in the bottle (presence of model wine, storage position, and temperature) over a long aging period of 24 months. The results highlighted that the oxygen diffusion coefficient of the stopper alone is not modified regardless of the storage conditions. At 20°C, the presence of model wine favors oxygen transfer at the glass-cork interface, accounting for nearly 75% of total oxygen transfer in comparison to cork studied without model wine. Yet, the position of the bottle during storage, vertical (i.e. cork in contact with the vapor phase of the model wine) or horizontal (i.e. cork in contact with the liquid phase), does not influence the oxygen transfer. At higher storage temperatures (35 and 50°C), the barrier properties of the bottleneck-cork system remain stable up to 9 and 3 months, respectively. After this period, an alteration of the barrier properties is observed with an increase of the transfer at the glass-cork interface.

High-Resolution Mass Spectrometry-Based Metabolomics for Increased Grape Juice Metabolite Coverage.

The composition of the juice from grape berries is at the basis of the definition of technological ripeness before harvest, historically evaluated from global sugar and acid contents. If many studies have contributed to the identification of other primary and secondary metabolites in whole berries, deepening knowledge about the chemical composition of the sole flesh of grape berries (i.e., without considering skins and seeds) at harvest is of primary interest when studying the enological potential of widespread grape varieties producing high-added-value wines. Here, we used non-targeted DI-FT-ICR-MS and RP-UHPLC-Q-ToF-MS analyses to explore the extent of metabolite coverage of up to 290 grape juices from four Vitis vinifera grape varieties, namely Chardonnay, Pinot noir, Meunier, and Aligoté, sampled at harvest from 91 vineyards in Europe and Argentina, over three successive vintages. SPE pretreatment of samples led to the identification of more than 4500 detected C,H,O,N,S-containing elemental compositions, likely associated with tens of thousands of distinct metabolites. We further revealed that a major part of this chemical diversity appears to be common to the different juices, as exemplified by Pinot noir and Chardonnay samples. However, it was possible to build significant models for the discrimination of Chardonnay from Pinot noir grape juices, and of Chardonnay from Aligoté grape juices, regardless of the geographical origin or the vintage. Therefore, this metabolomic approach opens access to a remarkable holistic molecular description of the instantaneous composition of such a biological matrix, which is the result of complex interplays among environmental, biochemical, and vine growing practices.

Complex carbonaceous matter in Tissint martian meteorites give insights into the diversity of organic geochemistry on Mars.

We report a huge organic diversity in the Tissint Mars meteorite and the sampling of several mineralogical lithologies, which revealed that the organic molecules were nonuniformly distributed in functionality and abundance. The range of organics in Tissint meteorite were abundant C3-7 aliphatic branched carboxylic acids and aldehydes, olefins, and polyaromatics with and without heteroatoms in a homologous oxidation structural continuum. Organomagnesium compounds were extremely abundant in olivine macrocrystals and in the melt veins, reflecting specific organo-synsthesis processes in close interaction with the magnesium silicates and temperature stresses, as previously observed. The diverse chemistry and abundance in complex molecules reveal heterogeneity in organic speciation within the minerals grown in the martian mantle and crust that may have evolved over geological time.

Attachment of chloride anion to sugars: mechanistic investigation and discovery of a new dopant for efficient sugar ionization/detection in mass spectrometers.

A new method for efficient ionization of sugars in the negative-ion mode of electrospray mass spectrometry is presented. Instead of using strongly hydrophobic dopants such as dichloromethane or chloroform, efficient ionization of sugars has been achieved by using aqueous HCl solution for the first time. This methodology makes it possible to use hydrophilic dopants, which are more appropriate for chromatographic separation techniques with efficient sugar ionization and detection in mass spectrometry. The interaction between chloride anions and monosaccharides (glucose and galactose) was studied by DFT in the gas phase and by implementing the polarizable continuum model (PCM) for calculations in solution at the high B3LYP/6-31+G(d,p)//B3LYP/6-311+G(2d,p) level of theory. In all optimized geometries of identified [M+Cl](-) anions, a non-covalent interaction exists. Differences were revealed between monodentate and bidentate complex anions, with the latter having noticeably higher binding energies. The calculated affinity of glucose and galactose toward the chloride anion in the gas phase and their chloride anion binding energies in solution are in excellent agreement with glucose and galactose [M+Cl](-) experimental intensity profiles that are represented as a function of the chloride ion concentration. Density functional calculations of gas-phase affinities toward chloride anion were also performed for the studied disaccharides sucrose and gentiobiose. All calculations are in excellent agreement with the experimental data. An example is introduced wherein HCl was used to effectively ionize sugars and form chlorinated adduct anions to detect sugars and glycosylated metabolites (anthocyanins) in real biological systems (Vitis vinifera grape extracts and wines), whereas they would not have been easily detectable under standard infusion electrospray mass spectrometry conditions as deprotonated species.