Model Wine Research Articles

Contribution of Lipids to Taste and Mouthfeel Perception in a Model Wine Solution

Contribution of Lipids to Taste and Mouthfeel Perception in a Model Wine Solution

Light-Struck Taste in White Wine: Protective Role of Glutathione, Sulfur Dioxide and Hydrolysable Tannins.

Light exposure of white wine can cause a light-struck taste (LST), a fault induced by riboflavin (RF) and methionine (Met) leading to the formation of volatile sulfur compounds (VSCs), including methanethiol (MeSH) and dimethyl disulfide (DMDS). The study aimed to investigate the impact of different antioxidants, i.e., sulfur dioxide (SO2), glutathione (GSH) and chestnut tannins (CT), on preventing LST in model wine (MW) and white wine (WW), both containing RF and Met. Both MW and WW samples were added with the antioxidants, either individually or in different combinations, prior to 2-h light exposure and they were stored in the dark for 24 months. As expected, the light induced the degradation of RF in all the conditions assayed. Met also decreased depending on the antioxidants added. The presence of antioxidants limited the formation of LST as lower concentrations of VSCs were found in both MW and WW samples. In the latter matrix, neither MeSH nor DMDS were detected in the presence of CT, while only DMDS was found in WW+GSH, WW+SO2+GSH and WW+CT+SO2 samples at a concentration lower than the perception thresholds. Considering the antioxidants individually, the order of their effectiveness was CT ≥ GSH > SO2 in WW under the adopted experimental conditions. The results indicate tannins as an effective enological tool for preventing LST in white wine and their use will be further investigated in different white wines under industrial scale.

Mannoproteins interfering wine astringency by modulating the reaction between phenolic fractions and protein in a model wine system

The positive effect of mannoproteins (MPs) on wine astringency is of great interest during winemaking. Phenolic components with different structural characteristics in wine could elicit different intensities of astringency when combined with salivary proteins. Aiming to use commercial MPs to modulate the unbalanced wine astringency, this work selected three commercial MPs and phenolic fractions (phenolic acids, monomeric/oligomeric procyanidins, polymeric procyanidins) with different mDP extracted from wine. The relationship between the structure and concentration of MPs, phenolic fractions, and astringency was investigated by physicochemical techniques (fluorescence quenching, SDS-PAGE, dynamic light scattering, and isothermal titration calorimetry) and sensory evaluation. Results showed that 0.6 g/L of MPs played a role in reducing wine astringency. MPs were more effective in inhibiting the interaction between monomeric/oligomeric or polymeric procyanidins and proteins than that of phenolic acids, through ternary or competitive mechanisms. Moreover, MPs with high protein portion and high molecular weight exhibited a stronger binding capacity to phenolics or protein, thus showing competing effect with phenolics for binding to protein. This work could provide the wine industry with valuable information for optimizing the application of commercial MPs to modulate wine astringency.

Glycosidically-Bound Volatile Phenols Linked to Smoke Taint: Stability during Fermentation with Different Yeasts and in Finished Wine.

When wine grapes are exposed to smoke, there is a risk that the resulting wines may possess smoky, ashy, or burnt aromas, a wine flaw known as smoke taint. Smoke taint occurs when the volatile phenols (VPs) largely responsible for the aroma of smoke are transformed in grape into a range of glycosides that are imperceptible by smell. The majority of VP-glycosides described to date are disaccharides possessing a reducing β-d-glucopyranosyl moiety. Here, a two-part experiment was performed to (1) assess the stability of 11 synthesized VP-glycosides towards general acid-catalyzed hydrolysis during aging, and (2) to examine whether yeast strains differed in their capacity to produce free VPs both from these model glycosides as well as from grapes that had been deliberately exposed to smoke. When fortified into both model and real wine matrices at 200 ng/g, all VP-disaccharides were stable over 12 weeks, while (42–50 ng/g) increases in free 4-ethylphenol and p-cresol were detected when these were added to wine as their monoglucosides. Guaiacol and phenol were the most abundantly produced VPs during fermentation, whether originating from natural VP-precursors in smoked-exposed Pinot Noir must, or due to fortification with synthetic VP-glycosides. Significant yeast strain-specific differences in glycolytic activities were observed for phenyl-β-d-glycopyranoside, with two strains (RC212 and BM45) being unable to hydrolyze this model VP, albeit both were active on the guaiacyl analogue. Thus, differences in Saccharomyces cerevisiae β-glucosidase activity appear to be influenced by the VP moiety.

Effects of ultrasound on the formation of oxidative pigments in a model red wine solution containing glutathione

Xanthylium cations and its ethyl ester are important pigments derived from (+)-catechin and glyoxylic acid in wine. In this paper, ultrasound treatment was applied in model wine containing glutathione to study its effects on the formation of xanthylium cation pigments triggered by free radicals from the ultrasound cavitation. The changes in color parameters, concentration of pigment compounds and free radicals were investigated during wine storage by the means of ultraviolet visible (UV–vis) spectrophotometer, colorimeter, high performance liquid chromatography with mass spectrometry (HPLC-MS) and electron paramagnetic resonance (EPR), respectively. Results indicate that longer ultrasonic treatment in conjunction with glutathione can significantly enhance the formation of xanthylium cation pigments and accelerate the red wine color evolution, and no extra (+)-catechin was involved, which might be attributed to the stronger 1-hydroxyethyl radicals intensity induced by ultrasound irradiation. In summary, ultrasound treatment can accelerate the oxidative coloration of wine with GSH during ageing, which would contribute to well understand the changing mechanism of wine color properties modified by ultrasound.

Oxygen gas transfer through oak barrels: a macroscopic approach

The oak barrel maturation step is nowadays strongly rooted in the production of quality wines. Two main physico‑chemical phenomena contribute to the modification and improvement of wine: the solubilisation of volatile and non-volatile wood compounds concomitant with the dissolution of oxygen from the air into the wine. Indeed, wood is a porous material and gas transfer (especially oxygen transfer, expressed as oxygen transfer rate or OTR) through oak barrels, is an intrinsic parameter which ensures wine oxygen supply during maturation. Due to its oenological impact, it has been actively studied over recent decades using several approaches based on the same principle: the monitoring of oxygen in a model wine solution in the barrel. This project aimed at assaying barrel OTR by using a new tool based on the theoretical knowledge of gas transfer through porous materials. An oxygen concentration gradient was created on each side of a barrel kept in an airtight stainless-steel tank. The concentration of the oxygen in the atmosphere around the barrel was monitored in order to quantify oxygen transfer, thus the avoiding common drawbacks of interactions between dissolved oxygen ingress kinetics and the consumption of oxygen in the liquid phase by wood components. This study reports for the first time, the diffusion coefficient of entire oak barrels (Q. sessilis) to be between 10-10 and 10-9 m²/s, and it contributes to increasing knowledge on the complex phenomena driving oxygen ingress during the maturation of wine in barrels kept in cellar conditions. The results highlight the important role of wood moisture content in oxygen transfer, and provides a simple and reliable parameter to monitor it: the weight of the barrel. Following methodology developed by the authors, the OTR of a new oak barrel was found to be 11.4 mg/L per year. Taking into account the oxygen released through the wood pores, a new barrel will contribute 14.4 mg/L per year of oxygen to the wine, of which 46 % in the first three months of aging.

Interaction between salivary proteins and cork phenolic compounds able to migrate to wine model solutions

This work reports the study of the interaction of human salivary proteins (SP) with phenolic compounds that migrate from cork stoppers to wine. This study yields valuable data to understand the influence that these compounds may have on the sensory perception of wine from an astringency perspective. For that, three cork fractions containing the phenolic compounds that migrate in greater amounts from cork to model wine solutions were selected. Fraction M1 contains gallic acid, protocatechuic acid, vanillin and protocatechuic aldehyde; fraction M2 comprises essentially gallic acid and ellagic acid, as well as castalagin and dehydrocastalagin; and fraction M3 contains the two isomeric ellagitannins castalagin and vescalagin. The reactivity of each fraction towards SP was M3 > M2 > M1. Within M3 fraction, castalagin showed a higher ability to precipitate SP (mainly aPRPs, statherin and P-B peptide) comparatively to vescalagin. In M1 fraction, caffeic and sinapic acids were the compounds with the highest interaction with SP, mainly cystatins. In addition, there also seems to be a matrix effect (presence of other compounds) that could be affecting these interactions.

A New Classification of Perceptual Interactions between Odorants to Interpret Complex Aroma Systems. Application to Model Wine Aroma.

Although perceptual interactions are usually mentioned and blamed for the difficulties in understanding the relationship between odorant composition and aromatic sensory properties, they are poorly defined and categorised. Furthermore, old classifications refer mainly to effects on the odour intensity of the mixture of dissimilar non-blending odours and do not consider odour blending, which is one of the most relevant and influential perceptual interactions. Beginning with the results from classical studies about odour interaction, a new and simple systematic is proposed in which odour interactions are classified into four categories: competitive, cooperative, destructive and creative. The first categories are most frequent and display a mild level of interaction, being characterised mostly by analytical processing. The last two are less frequent and activate (or deactivate) configurational processes of object recognition with deep effects on the quality and intensity of the perception. These interactions can be systematically applied to interpret the formation of sensory descriptors from the odorant composition, suggesting that qualitatively the system works. However, there is a lack of quantitative data to work with odour intensities reliably, and a pressing need to systematise the effects of creative interactions.

Acetylation of Malvidin-3-O-glucoside Impedes Intermolecular Copigmentation: Experimental and Theoretical Investigations.

Malvidin-3-O-(6-O-acetyl)-glucoside is usually the most abundant acylated anthocyanin in red wines. In this work, intermolecular copigmentation of malvidin-3-O-(6-O-acetyl)-glucoside and malvidin-3-O-glucoside with three phenolic copigments was carried out in model wine solutions, and the influence of the acetylation group was evaluated emphatically using experimental and theoretical approaches. This study found that there was no distinct coloring difference in the two anthocyanins themselves; however, the hyperchromic effects were smaller in malvidin-3-O-(6-O-acetyl)-glucoside solutions with the existence of insufficient copigments. Thermodynamic analysis confirmed that malvidin-3-O-(6-O-acetyl)-glucoside showed weaker affinity (smaller K values) toward the three copigments compared with its non-acylated form. Theoretical analysis also indicated that the existence of the acetylation group changed the spatial conformations and non-covalent interactions (hydrogen bonds and van der Waals forces) of the copigmentation complexes, which might be due to the potential steric hindrance effect. In conclusion, the results revealed that the acetylation group on anthocyanin glycosyl could impede intermolecular copigmentation.

Understanding the Impact of Key Wine Components on the Use of a Non-Swelling Ion-Exchange Resin for Wine Protein Fining Treatment.

The impact of key classes of compounds found in wine on protein removal by the ion-exchange resin, Macro-Prep® High S, was examined by adsorption isotherm experiments. A model wine system, which contained a prototypical protein Bovine Serum Albumin (BSA), was used. We systematically changed concentrations of individual chemical components to generate and compare adsorption isotherm plots and to quantify adsorption affinity or capacity parameters of Macro-Prep® High S ion-exchange resin. The pH (hydronium ion concentration), ethanol concentration, and prototypical phenolics and polysaccharide compounds are known to impact interactions with proteins and thus could alter the adsorption affinity and capacity of Macro-Prep® High S ion-exchange resin. At low equilibrium protein concentrations (< ~0.3 (g BSA)/L) and at high equilibrium protein concentrations in model wines at various pH, the adsorption behavior followed the Langmuir isotherm, most likely due to the resin acting as a monolayer adsorbent. The resulting range of BSA capacity was between 0.15–0.18 (g BSA)/(g Macro-Prep® High S resin). With the addition of ethanol, catechin, caffeic acid, and polysaccharides, the protein adsorption behavior was observed to differ at higher equilibrium protein concentrations (> ~0.3 (g BSA)/L), likely as a result of Macro-Prep® acting as an unrestricted multilayer adsorbent at these conditions. These data can be used to inform the design and scale-up of ion-exchange columns for removing proteins from wines.

Toward Understanding the Mechanism of Wine Oxidation

The electronic configuration of oxygen (O₂) does not allow it to react directly with wine reductants such as polyphenols. It relies on the catalytic intervention of iron (Fe), which redox cycles between its ferrous (Fe(II)) and ferric (Fe(III)) states. O₂ oxidizes Fe(II) to Fe(III), and Fe(III) then oxidizes polyphenols. Low concentrations of copper accelerate oxidation, and nucleophiles, especially sulfite, promote polyphenol oxidation. In wine that is protected from air, Fe exists mainly as Fe(II), but the Fe(III):Fe(II) concentration ratio increases immediately on air exposure, stabilizing at varying speeds and values. The oxidation of Fe(II) in air-saturated model wine and the reduction of Fe(III) by a catechol under nitrogen in model wine were examined separately to better understand the oxidative process. The Fe(III) produced when Fe(II) reacted with O₂ slows the reaction. As in wine, it was important to include sulfite to remove the intermediate hydrogen peroxide, which also oxidizes Fe(II). The reaction was pseudosecond-order in Fe(II), indicating that the transfer of both electrons to O₂ is rate determining. Similarly, when Fe(III) was reduced by the catechol, the Fe(II) produced inhibited the reaction, which overall followed a pseudosecond-order rate law in Fe(III). The rate of Fe(II) oxidation was slower than the rate of Fe(III) reduction, but when the reactions occurred together, as in wine oxidation, Fe(III) and Fe(II) concentrations equilibrated such that their rates equalized. Under the conditions studied, this occurred at 32% Fe(III). This equilibrium was attained quickly, as is the case in red wine. These findings on the oxidative process should help explain the relationships between wine composition, redox state, and Fe(III):Fe(II) concentration ratios.

New insights into ethyl carbamate occurrence in fortified wines

The occurrence of ethyl carbamate (EC) in fortified wines was studied testing different model wines under accelerated ageing (45 °C for 4 months and 70 °C for 1 month), to investigate the possibility of arginine (Arg) being a direct precursor of EC in fortified wines, comparing it with known major precursors, urea and citrulline (Cit). Wine main sugars were appraised as possible catalysts, as previously pointed out. Model wines showed that: Arg can induce the EC formation under accelerated ageing, even without being metabolised by microorganisms; although much less reactive, Arg can play a significant role since high residual levels can occur in young fortified wines; glucose (Glc) and fructose (Fru) suppressed the EC formation from urea and Cit pathways, in about 11–26%.Moreover, Madeira wine samples were investigated in order to appraise the eventual contribution of the alcoholic fortification. The results revealed that this step can promote a decrease of the amount of these EC precursors up to 46%.Despite preliminary, additional information about the EC formation in fortified wines was obrained namely for designing new mitigation strategies, which can pass through the reduction of residual Arg.

Measuring the oxygen consumption rate of some inactivated dry yeasts: comparison with other common wine antioxidants

The aim of the study was to evaluate the oxygen consumption kinetics of some inactivated dry yeasts in comparison with those of sulfur dioxide, ascorbic acid and glutathione.The oxygen consumption rates of three inactivated dry yeasts, sulfur dioxide, ascorbic acid and glutathione at the usual doses in a model wine solution were determined by carrying out noninvasive fluorescence measurements. The results indicate that two of the studied inactivated dry yeasts consume oxygen more effectively than sulfur dioxide. These data suggest that some inactivated dry yeasts may be useful for protecting wine against oxidation.This study shows for the first time that inactivated dry yeasts can actually consume oxygen, therefore opening up an interesting area for future research.

Precipitation of Tannin-Anthocyanin Derivatives in Wine is Influenced by Acetaldehyde Concentration and Tannin Molecular Mass with Implications for the Development of Nonbleachable Pigments.

This study aimed to assess the effect of tannin molecular mass on nonbleachable pigment formation and subsequent stability under wine-like conditions. Tannin fractions of a defined molecular mass range were prepared from grape skins and seeds and reacted with malvidin-3-glucoside for 120 days in three media types: chemically defined wine media with or without acetaldehyde addition or model wine without acetaldehyde. Precipitation was observed after the reaction period and increased in response to both higher tannin molecular mass and acetaldehyde concentration. To confirm whether acetaldehyde-mediated condensation of tannin and anthocyanin modified the solubility of the nonbleachable pigments formed, HPLC-MS was used for the semiquantitative identification of vinyl derivatives and ethyl-linked adducts in soluble and precipitated materials. It was found that the proportion of vinyl derivatives and ethyl-linked anthocyanin was elevated in tannin precipitates relative to soluble pigmented material. Despite substantial losses of tannin due to precipitation, the resulting nonbleachable pigment concentration and color intensity were higher in wine media containing elevated acetaldehyde, when each tannin size category was considered independently. The results of this study indicated that the development of nonbleachable pigments from larger tannins may be limited when acetaldehyde-mediated condensation with anthocyanin predominates in wine, concomitant with precipitation.

Quantification of Volatile Compounds in Wines by HS-SPME-GC/MS: Critical Issues and Use of Multivariate Statistics in Method Optimization

The aim of this review is to explore and discuss the two main aspects related to a HeadSpace Solid Phase Micro-Extraction Gas-Chromatography/Mass-Spectrometry (HS-SPME-GC/MS) quantitative analysis of volatile compounds in wines, both being fundamental to obtain reliable data. In the first section, recent advances in the use of multivariate optimization approaches during the method development step are described with a special focus on factorial designs and response surface methodologies. In the second section, critical aspects related to quantification methods are discussed. Indeed, matrix effects induced by the complexity of the volatile profile and of the non-volatile matrix of wines, potentially differing between diverse wines in a remarkable extent, often require severe assumptions if a reliable quantification is desired. Several approaches offering different levels of data reliability including internal standards, model wine calibration, a stable isotope dilution analysis, matrix-matched calibration and standard addition methods are reported in the literature and are discussed in depth here.

Riboflavin removal by commercial bentonites and charcoals in white and red wine

Riboflavin (RF) represents one of the primary molecules undergoing photo-degradation in wine and its excited form act as intermediate in light-induced oxidation reactions responsible for the light-struck fault. A recent study revealed bentonites (BENs) and charcoals (CHAs) as the most promising fining agents for riboflavin removal in model wine. This work explored their potential on both white and red wine. Eleven BENs and eleven CHAs were compared. BENs exhibited a limited capacity, while decolouring carbons confirmed a great attitude to RF removal in white wine even at low dosages. Nevertheless, CHAs efficiency shows a sensible reduction in red wine.

Characterization of key odor-active compounds in sweet Petit Manseng (Vitis vinifera L.) wine by gas chromatography-olfactometry, aroma reconstitution, and omission tests.

Petit Manseng (Vitis vinifera L.) has become a popular variety in China for the production of semisweet and sweet wines. However, few studies focused on investigating the molecular odor code of its key odorants. In this study, the key odor-active compounds of Chinese sweet Petit Manseng wine were identified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Fifty-five odorous zones were sniffed and identified by application of aroma extraction dilution analysis on a distillate prepared by liquid-liquid extraction and solvent-assisted flavor evaporation. Among them, isoamyl alcohol, ethyl octanoate, isovaleric acid, (E)-β-damascenone, and phenylethanol particularly displayed with highest flavor dilution factors above 1024. The quantification of volatiles by headspace solid-phase microextraction coupled with GC-MS and GC coupled with triple quadrupole MS/MS and a calculation of odor activity values (OAVs) indicated 23 volatiles with OAVs above 1. Ethyl hexanoate showed the highest OAV with 208.8, followed by (E)-β-damascenone (189.0), 3-mercaptohexanol (60.3), isoamyl acetate (45.4), and furaneol (40.1). The aroma of the sweet wine was successfully reconstituted by combining 42 aroma compounds in a model wine solution. 3-Mercaptohexanol, (E)-β-damascenone, furaneol, γ-octalactone + γ-decalactone + γ-hexalactone, and ethyl cinnamate had important influence on the aroma of sweet Petit Manseng wine assessed by omission tests. Moreover, the discrimination of wines from three regions was successfully achieved by partial least squares discriminant analysis based on quantitative results of key odorants. 3-Mercaptohexanol was considered as the most responsible for the region discrimination and had highest concentrations in Petit Manseng wines from Jiaodong Peninsula. PRACTICAL APPLICATION: Understanding of the knowledge in key odorants of Petit Manseng wines could be useful to improve wine quality through viticultural and enological practices.

Discrimination of French wine brandy origin by PTR-MS headspace analysis using ethanol ionization and sensory assessment.

The headspace volatile organic compound (VOC) fingerprints (volatilome) of French wine brandies were investigated by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). Protonated ethanol chemical ionization was used with dedicated experimental conditions that were previously validated for model wines. These included a reference vial containing a hydro-alcoholic solution with the same ethanol content (20% v/v) as the diluted sample spirits, which was used to establish steady-state ionization conditions. A low electric field strength to number density ratio E/N (85 Td) was used in the drift tube in order to limit the fragmentation of the protonated analytes. The obtained headspace fingerprints were used to investigate the origin of French brandies produced within a limited geographic production area. Brandies of two different vintages (one freshly distilled and one aged for 14years in French oak barrels) were successfully classified according to their growth areas using unsupervised (principal component analysis, PCA) and supervised (partial least squares regression discriminant analysis, PLS-DA) multivariate analyses. The models obtained by PLS-DA allowed the identification of discriminant volatile compounds that were mainly characterised as key aroma compounds of wine brandies. The discrimination was supported by sensory evaluation conducted with free sorting tasks. The results showed that this ethanol ionization method was suitable for direct headspace analysis of brandies. They also demonstrated its ability to distinguish French brandies according to their growth areas, and this effect on brandy VOC composition was confirmed at a perceptive level.

Microwave‐induced free radicals production in red wine and model wine by electron paramagnetic resonance spin trapping

Microwave can directly induce the production of 1-hydroxyethyl free radical in red wine and model wine. Free radicals are considered as key intermediates in the wine aging processing by microwave, but their properties have not been determined. Electron paramagnetic resonance (EPR) spin trapping with 5,5-dimethyl-1-pyrrolin N-oxide (DMPO) was used to detect the type of free radicals. After microwave irradiation, spin adducts of hydroxyl free radical were detected in DMPO solution, whereas 1-hydroxyethyl free radical spin adducts were captured in red wine and model wine, because 1-hydroxyethyl free radicals arose from the oxidation of ethanol by hydroxyl free radical in red wine induced by microwave irradiation. Compared with the processing of natural oxidation, the intensity of free radicals induced by microwave in red wine became more strong, and the effects of microwave temperature, time, and power on the intensity of 1-hydroxyethyl free radical spin adducts in model wines were also studied. The intensity of free radical spin adducts increased with the increasing of microwave power and time. The intensity of DMPO/1-hydroxyethyl free radical spin adducts increases at low temperature, but decreased at higher temperatures. Practical applications This study investigated the existence of free radical in the processing of wine aging, and the possible mechanism of microwave irradiation accelerated aging of red wine was studied with model wine. Results revealed that the intensity of 1-hydroxyethyl free radical induced by microwave in red wine and model wine. Therefore, microwave irradiation was considered to be a promising aging technology, so microwave radiation technology can be used in many aging products that sped up the aging processing.

Redox Cycling of Iron: Effects of Chemical Composition on Reaction Rates with Phenols and Oxygen in Model Wine

Wine oxidation is mediated by the redox cycling of iron between two oxidation states: iron(II) is oxidized by oxygen and iron(III) is reduced by phenols. The effects of phenolic structure, pH, and copper on the rates of these reactions were evaluated in model wine. In the absence of a nucleophile, pyrogallol exhibited greater reactivity with iron(III) than 4-methylcatechol, though both compounds ultimately required aid from the nucleophile benzenesulfinic acid for unrestricted reduction of iron(III) to occur, illustrating the differential structure-dependent reactivities of phenols and the importance of nucleophiles to oxidation. It was hypothesized the rate of oxygen consumption would depend on the rate at which iron(II) is recycled from iron(III), though this was not found to be the case: while the rate of iron(III) reduction by 4-methylcatechol in the presence of benzenesulfinic acid decreased with higher pH, the opposite was observed for the rate of oxygen consumption. Furthermore, copper had no effect on the rate of iron(III) reduction, but significantly increased the rate of oxygen consumption, indicating the two reactions do not necessarily occur synchronously despite being coupled through iron. Pseudo-first order rate constants for oxygen consumption were much lower than those for iron(III) reduction, except when nucleophiles are absent, unlikely in wine, suggesting iron(II) oxidation is the rate-determining reaction for the wine oxidation pathway. Therefore, the rate at which wine ages is likely limited not by chemical composition, but by oxygen ingress, though the overall capacity of wine for oxidation may still depend on constituent phenols and nucleophiles, thus a method to assess these factors would be of interest.