Model Wine Research Articles

Characterization and Identification of Yeast Peptides Released during Model Wine Fermentation and Lees Contact.

Aging wine on lees results in the release of different yeast components, including peptides, whose role in wine is unclear. In this study, peptides released in a synthetic must, fermented with an oenological yeast strain, and aged on lees for 180 days were quantified (RP-HPLC) and identified (LC-MS/MS) at different time points. A rapid increase in peptide concentration was observed in the first two months, with over 2600 sequences identified. During the following four months, the peptide concentration remained constant, while their variety decreased slightly, probably due to enzymatic hydrolysis to which longer and less charged sequences were more exposed. The majority of the most abundant peptides were present over the 6-month period. They mostly originated from proteins associated with glycolysis and with different stress-response mechanisms, and they showed different in silico bioactivities. These findings can contribute to understanding the role of yeast peptides in regulating the wine environment during aging.

The aroma of toasted oak wood (<i>Quercus petraea</i>): from sensory analysis to molecular characterisation

The chemical complexity of the aroma compounds developed by oak wood during the toasting process is known to contribute to the quality of wines and spirits after barrel ageing. Molecular characterisation of toasted oak wood has increased steadily in recent years, using the traditional olfactory-guided approach by gas chromatography coupled with olfactometry and mass spectrometry (GC-O-MS); however, few studies have focused on its sensory characterisation. In this study, a sensory characterisation of oak wood (Quercus petraea) was first carried out during toasting in order to identify any descriptors that had not yet been characterised from a molecular point of view. Thus, in the second part of this work, we were able to identify volatile compounds associated with the aroma of toasted oak wood.Based on previous work in oenology, the sensory characterisation of oak wood was carried out in three stages: identification, structuring and description of a sensory space. Data processing of the 215 descriptors generated by the panel of experts revealed six descriptors specific to the aroma of oak wood throughout its toasting (i.e., fresh wood, fresh green, sweet, roasted, spicy and smoky). The results were represented graphically in the form of an aroma wheel, which was used to highlight the descriptors that had not yet been characterised from a molecular point of view. Thus, two volatile compounds were identified: thymoquinone (pencil and cedar odour) and verbenone (fresh, menthol and tealeaf odour). Their evolution in oak wood during toasting and their distribution in different wood species used in oenology (sessile oak, pedunculate oak, American oak, Caucasian oak, acacia and chestnut) were studied. Their sensory impact was studied by assessing their olfactory detection threshold in a model wine solution. The thresholds were evaluated at 49 ng/L for thymoquinone and 193 µg/L for verbenone.

Evaluation of protein-polysaccharide interactions through ζ-potential and particle size measurements to assess their functionality in wine.

Protein-polysaccharide-tannin interactions are important in every aspect of red wine production from physical stability to color, astringency, and body. For this model study, bovine serum albumin (BSA) was selected as the protein, while carboxymethyl cellulose (CMC), mannoproteins, and pectin were the model polysaccharides. Each protein-polysaccharide combination was analyzed for zeta (ζ) potential and particle size at neutral pH and within the wine-like solution. Mixtures were assessed regarding their protective, affinitive, and aggregative behaviors. Based on their individual ζ-potentials, pectin and mannoprotein were most stable at lower concentrations. At higher concentrations, they reduced the suspension's stability and increased the aggregate sizes. CMC consistently increased the stability of any solution under neutral pH conditions. However, with increasing concentrations, these large aggregates are expected to precipitate. Fruit pectin (FP) and BSA interactions seemed to be the main factors in the formation of visible precipitates at neutral pH. FP and the mannoprotein decreased stability enough to cause precipitation without haze formation. The mannoprotein decreased particle sizes, in both the suspension and precipitation, which may indicate greater selectivity toward proteins. FP also decreased the suspended particle sizes under wine conditions. These findings demonstrate the use of ζ-potential and particle size values to characterize macromolecular interactions in model systems and can also be used to indicate effective fining agents. PRACTICAL APPLICATION: This work demonstrates the capabilities of ζ-potential analysis paired with size particle measurements to predict and characterize the interactions between macromolecules in complex systems. The interactions between model wine macromolecules can be evaluated with this technology at a level that cannot be reached with any other analytical technique.

Isolation and characterization of Saccharomyces cerevisiae mutants with increased cell wall chitin using fluorescence-activated cell sorting.

Yeast cell wall chitin has been shown to bind grape pathogenesis-related chitinases that are the primary cause of protein haze in wines, suggesting that yeast cell walls may be applied for haze protection. Here, we present a high-throughput screen to identify yeast strains with high cell wall chitin using a reiterative enrichment strategy and fluorescence-activated cell sorting of cells labelled with either GFP-tagged chitinase or Calcofluor white. To assess the validity of the strategy, we first used a pooled deletion strain library of Saccharomyces cerevisiae. The strategy enriched for deletion mutants with genes that had previously been described as having an impact on chitin levels. Genes that had not previously been linked to chitin biosynthesis or deposition were also identified. These genes are involved in cell wall maintenance and/or membrane trafficking functions. The strategy was then applied to a mutagenized population of a commercial wine yeast strain, S. cerevisiae EC1118. Enriched mutant strains showed significantly higher cell wall chitin than the wild type and significantly reduced the activity of chitinases in synthetic model wine, suggesting that these strains may be able to reduce haze formation in wine.

Aroma Potential of German Riesling Winegrapes during Late-Stage Ripening

The “aromatic maturity” of winegrapes is not fully understood, particularly during the later stages of ripening. The contribution of grapes to wine aroma has historically been challenging to determine, given most aroma compounds originate from nonvolatile precursors. In this study, an analytical approach previously developed for red winegrapes was adapted to assess the “aroma potential” of Riesling from two vineyards in Essenheim and Durbach, Germany, during the 2022 vintage, by extracting and hydrolyzing aroma precursors in an anoxic model wine matrix. Following sensory and chemical analyses of the hydrolysates using flash profiling and gas chromatography, a multiple factor analysis revealed vineyard- and ripening-dependent changes to aroma, even after total soluble solids had plateaued. As samples matured, green apple and fresh/vegetal aromas were prominent among the Durbach hydrolysates, likely due to persistent concentrations of hexanol. Hydrolysates from both vineyards nonetheless developed more pronounced citrus fruit, tropical fruit, and floral aromas, reflecting increased concentrations of various norisoprenoids and terpenoids. Findings suggest delaying harvest past technological maturity could confer greater aromatic intensity and complexity. The analytical approach used here appears promising for future studies on other grape varieties and other factors that could influence aroma, such as viticultural practices and environmental conditions.

A modified pararosaniline hydrochloride method for determination of total and bound sulfur dioxide in wine

An improved pararosaniline hydrochloride (PRA) method for rapid and accurate determination of total and bound sulfur dioxide (SO2) in wine was established. The determination conditions for total SO2 were optimized in model wine systems. The pH of the acidified PRA reagent had a significant effect on the color and the maximum absorption wavelength (λmax) of the reaction system, with its optimum pH 0.48 and a λmax at 549 nm. The addition of ethylene diamine tetraacetic acid (EDTA) could effectively shield the interference of coexisting metal ions present in wine, and a novel approach to double background subtraction was confirmed to remove the matrices interference of red wine color. Under the optimum conditions, the linear range for total SO2 in wine was within 1.00–8.00 mg L−1 (R = 0.9975), with the detection and quantification limits (MDL and MQL) found as 0.02 and 0.06 mg L−1, respectively. The recovery of SO2 ranged from 85.73 % to 105.70 % with the relative standard deviations (RSD) of 0.21 % - 7.78 %, suggesting high sensitivity and accuracy of the method. Combining with the optimized Monier-Williams method, the determination of bound SO2 in wine was also achieved. Sulfite determination can be performed in wine using the rapid, accurate and sensitive method without any pretreatment, and the results were comparable with those of the standard methods.

Intermolecular interactions between malvidin-3-O-glucoside and caffeic acid: Structural and thermodynamic characterization and its effect on real wine color quality

The copigmentation effect between malvidin-3-O-glucoside and caffeic acid was comprehensive inquiry on the model wine solution, theoretical simulation and real wine. Thermodynamic parameters were determined by UV/Visible spectroscopy and Isothermal titration calorimetry (ITC). Theoretical data were obtained employing a dispersion-corrected density functional approach. The effects in real wines were investigated by adding the caffeic acid during different fermentation periods. Results shown that the copigmentation reaction between caffeic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersions forces. Computations show that the polyhydroxyl sugar moiety and phenolic hydroxyl groups are the key active sites. The addition of caffeic acid in post-alcohol fermentation samples evidences an improving color characteristics in the wine.

Decoding Polysaccharides from Two Pichia Yeasts and Their Molecular Interaction with Wine Fruity Esters.

This study extensively characterized yeast polysaccharides (YPs) from Pichia fermentans (PF) and Pichia kluyveri (PK), with a specific focus on their structural attributes and their interaction with wine fruity esters in a model wine system. By finely tuning enzymatic reactions based on temperature, pH, and enzyme dosage, an optimal YP yield of 77.37% was achieved, with a specific mass ratio of cellulase, pectinase, and protease set at 3:5:2. There were four YP fractions (YPPF-W, YPPF-N, YPPK-W, and YPPK-N) isolated from the two yeasts. YPPF-N and YPPK-N were identified as glucans based on monosaccharide analysis and Fourier-transform infrared spectroscopy analysis. "Specific degradation-methylation-nuclear magnetic" elucidated YPPF-W's backbone structure as 1,3-linked α-l-Man and 1,6-linked α-d-Glc residues, while YPPK-W displayed a backbone structure of 1,3-linked α-Man residues, indicative of a mannoprotein nature. Isothermal titration calorimetry revealed spontaneous interactions between YPPK-W/YPPF-W and fruity esters across temperatures (25-45 °C), with the strongest interaction observed at 30 °C. However, distinct esters exhibited varying interactions with YPPK-W and YPPF-W, attributed to differences in molecular weights and hydrophobic characteristics. While shedding light on these intricate interactions, further experimental data is essential for a comprehensive understanding of yeast polysaccharides' or mannoproteins' impact on fruity esters. This research significantly contributes to advancing our knowledge of yeast polysaccharides' role in shaping the nuanced sensory attributes of wine.

Gallic acid improves color quality and stability of red wine via physico-chemical interaction and chemical transformation as revealed by thermodynamics, real wine dynamics and benchmark quantum mechanical calculations

The aim of this study was to explore the copigmentation effect of gallic acid on red wine color and to dissect its mechanism at the molecular level. Three-dimensional studies, e.g., in model wine, in real wine and in silico, and multiple indicators, e.g., color, spectrum, thermodynamics and phenolic dynamics, were employed. The results showed that gallic acid significantly enhanced the color quality and stability of red wine. Physico-chemical interactions and chemical transformations should be the most likely mechanism, and physico-chemical interactions are also a prerequisite for chemical transformations. QM calculations of the physico-chemical interactions proved that the binding between gallic acid and malvidin-3-O-glucoside is a spontaneous exothermic reaction driven by hydrogen bonding and dispersion forces. The sugar moiety of malvidin-3-O-glucoside and the phenolic hydroxyl groups of gallic acid affect the formation of hydrogen bonds, while the dispersion interaction was related to the stacking of the molecular skeleton.

Quantitative analysis of sugars extracted from French oak (<i>Quercus petraea</i>) chips: Effect of toasting temperature

In this study, we conducted extraction experiments using model wine on French oak chips toasted at various temperatures to investigate the extracted sugars. A certain amount of sugars were extracted from the oak chips, and the quantity significantly varied depending on the toasting temperature. Analysis of the composition of the extracted sugars revealed the presence of substantial amounts of xylose and glucose, with the composition showing significant differences based on the toasting temperature. Furthermore, it was elucidated that the extracted sugars included monosaccharides and oligo or polysaccharides. This research represents the first comprehensive analysis correlating the toasting temperature with the extraction of a substantial amount of sugars from toasted chips.

Effects of post-fermentation addition of green tea extract for sulfur dioxide replacement on Sauvignon Blanc wine phenolic composition, antioxidant capacity, colour, and mouthfeel attributes

This study examines the feasibility of replacing SO2 in a New Zealand Sauvignon Blanc wine with a green tea extract. The treatments included the control with no preservatives (C), the addition of green tea extract at 0.1 and 0.2 g/L (T1 and T2), and an SO2 treatment at 50 mg/L (T3). Five monomeric phenolic compounds were detected in the green tea extract used for the experiment, and their concentrations ranged in the order (−)-epigallocatechin gallate > (−)-epigallocatechin > (−)-epicatechin > (−)-epicatechin gallate > gallic acid. At the studied addition rates, these green tea-derived phenolic compounds contributed to ∼70% of the antioxidant capacity (ABTS), ∼71% of the total phenolic index (TPI), and ∼ 84% of tannin concentration (MCPT) of the extract dissolved in a model wine solution. Among wine treatments, T1 and T2 significantly increased the wine's colour absorbance at 420 nm, MCPT, gallic acid and total monomeric phenolic content. TPI and ABTS were significantly higher in wines with preservatives (i.e., T2 > T1 ≅ T3 > C, p < 0.05). These variations were observed both two weeks after the treatments and again after five months of wine aging. Additionally, an accelerated browning test and a quantitative sensory analysis of wine colour and mouthfeel attributes were performed after 5 months of wine aging. When exposed to excessive oxygen and high temperature (50 °C), T1 and T2 exhibited ∼29% and 24% higher browning capacity than the control, whereas T3 reduced the wine's browning capacity by ∼20%. Nonetheless, the results from sensory analysis did not show significant variations between the treatments. Thus, using green tea extract to replace SO2 at wine bottling appears to be a viable option, without inducing a negative impact on the perceptible colour and mouthfeel attributes of Sauvignon Blanc wine.

White Sparkling Wine Proteins and Glycoproteins and Their Behavior in Foam Expansion and Stability

The volume and stability of wine foams are influenced by many components of the matrix, especially proteins. However, the synergistic or inhibiting effects among these protein fractions, as well as their interactions with other wine components, are still under study. The present research aims to understand the individual and cooperative effects of different wine proteins and glycoproteins on the volume and stability of foams. To address this objective, different protein fractions were purified from a Chardonnay white wine and tested in different model wine conditions (with/without ethanol), along with a commercial yeast-based oenological additive. Different fractions were considered, including total protein fraction (FT), Mannoproteins (MP), and non-mannosylated proteins (NMP), as well as a protein fraction soluble in ammonium sulfate (FSA). These protein fractions were characterized, and their foaming properties were evaluated using a modified Rudin apparatus. The results showed that FT exhibited higher foam expansion (FE%) compared to its subfractions (NMP and MP) that, when tested individually, did not guarantee optimal foam formation. This suggests that foaming properties are enhanced when both glycosylated and non-glycosylated proteins are present in the system. Additionally, the foaming behavior was influenced by the presence of ethanol in the model wine. The FSA fraction demonstrated high foam expansion and stability, with ethanol enhancing foam expansion but reducing stability. A commercial yeast-based oenological additive, mainly containing glycoproteins, was also tested and behaved similarly to MP. This study provides valuable insights for sparkling wine producers to optimize practices for enhancing product quality and confirm previous research regarding the role of the synergy between MP and NMP in wine foam formation and stability.

New insight in characterization of red wine astringency using soft tribology method

AbstractThe variation of friction coefficient (μ) of model wine and model saliva mixtures with entrainment speed (VR) on simulated oral surfaces was evaluated by oral tribology. Combined with techniques of dynamic light scattering (DLS), atomic force microscopy (AFM), rheometer, and quartz crystal microbalance with dissipation monitoring (QCM‐D), the correlation between characteristics of the model wine and model saliva mixtures (particle size and morphology, suspension viscosity, adsorption film thickness, and viscoelasticity) and the oral lubrication loss was established. The results showed that the higher the concentration of tannin in the model wine, the larger the size of the complexes with the model saliva, and the higher the thickness, viscoelasticity, and roughness of the adsorption film formed, which resulted in the increase of friction coefficient in the boundary lubrication regime. Different from previous results, it is found that the maximum value of the friction coefficient (μmax) in the boundary regime has the best positive correlation with the astringency perception intensity of the model wine accordingly.

Impact of high hydrostatic pressure and ultrasounds technologies in the autolytic process of Saccharomyces cerevisiae in a model wine system

Autolysis plays a crucial role as a technological tool in the ageing process of specific wines. This includes white, red and sparkling wines. During ageing on the lees, yeasts release different compounds that positively modify the composition of the wine. However, traditional autolytic methods can be time-consuming. This work evaluates the use of different ultrasound (US) and high hydrostatic pressure (HHP) treatments to expedite the autolytic process in Saccharomyces cerevisiae in a model wine system. The results suggest that treating yeast cells with US resulted in a faster release of nucleic acids, proteins, and total polysaccharides compared to HHP treatment. The environmental scanning electron microscopy (ESEM) of the treated lees demonstrated that the impact on the yeast cell surface was more pronounced after exposure to US compared to treatments involving HHP. In conclusion, under these conditions the US treatment effectively triggered autolysis in the wine yeast strain, facilitating the release of macromolecules in a model wine.

Dissolved Oxygen Removal in Wines by Gas Sparging, Its Optimization and Chemical Impact

Sparging is a technique to remove an excess of dissolved oxygen from the wine with inerting gases before bottling to avoid negative consequences for its chemical and sensory properties. However, its effectiveness on these properties has not been studied in depth. This work investigates the effectiveness of different inerting gases (N2, CO2, and argon) in removing dissolved oxygen in different volumes of a model wine. The efficacy of these gases was also studied in white and red wine, as was their effect on the physicochemical characteristics. Sparging with N2 in the model wine gave the best results in terms of cost–benefits, and with CO2 the worst. The scaling in tanks of different sizes allowed us to establish that the N2 expenditure ranged between 0.09 L and 0.23 L of gas per liter of model wine, establishing an index (Lgas/Lwine) that can be very useful for wineries to remove the dissolved oxygen. Sparging treatments in white and red wine showed very similar results to the model wine. The effect on the chemical properties of the wines was, in some cases, different for white and red wine and for each gas used. The incorporation of oxygen and the subsequent sparging produced a significant loss of some volatile compounds of sensory interest and increased the content of others that have a negative sensory effect. In addition, it had a negative effect on the chromatic properties of red wines.

Study on the interaction of tannins and salivary proteins affecting wine aroma volatility: Static HS-SPME and molecular dynamics simulation approaches

The interaction between tannins and salivary proteins might affect intraoral aroma release during wine consumption. In this study, the influence and underlying mechanism of interactions between EGCG and IB5 (salivary proline-rich protein) on wine aroma compounds was analysed by static HS-SPME in vitro and molecular dynamics (MD) simulation. The interaction between IB5 and EGCG could significantly reduce the volatility of most aroma compounds in the model wine by 20 %-70 % (p < 0.05). MD simulations indicated that the energy received by aroma compounds in the mixed system was more pronounced. In addition, the decline rate of rational correlation functions (RCF) of aroma compounds in the mixed system was obviously slower. The analysis of the independent gradient model (IGM) indicated that aroma compounds combined with aggregates of IB5 and EGCG through hydrogen bonds and van der Waals forces. The effect of the interaction between EGCG and IB5 on aroma compounds was confirmed by the volatility and molecular computational simulation. Overall, the results enhance the understanding of the mechanisms affecting retronasal aroma release during wine consumption.

Co-pigmentation of Pinotage anthocyanins with Cyclopia (honeybush) polyphenols in model wine solutions

Co-pigmentation of an anthocyanin-enriched fraction (AEF) of Pinotage wine with honeybush polyphenols (Cyclopia subternata extract and fractions enriched in specific polyphenols) was studied in model wine solutions. The hyperchromic effects and bathochromic shifts depended on the co-pigment sources and co-pigment/anthocyanin ratio. Fraction 2 (F2), enriched in xanthones (mangiferin and isomangiferin), produced the most pronounced co-pigmentation effect at a co-pigment/anthocyanin ratio of 15:1. Greater co-pigmentation effects were observed in model solutions at pH 3.0 (pH 3–4 evaluated) and in the absence of EtOH (0–16 % EtOH evaluated). During storage of solutions (AEF and/or F2) at 15 °C and 25 °C for 12 weeks, myrtillin, petunin, 3′,5′-di-β-D-glucopyranosyl-3-hydroxyphloretin and mangiferin concentrations decreased following first-order kinetics, while peonin and oenin degradation followed fractional-conversion kinetics. Polymeric anthocyanin formation followed zero-order kinetics. Reaction rates increased with an increase in storage temperature. The addition of F2 to the AEF solution produced a darker, more vivid colour and improved the colour stability, however, the yellow-orange colour of F2 and intensification of its colour during storage contributed to increasing red-orange hues. Further research is necessary to elucidate the effect of honeybush polyphenols on the colour and composition of a complete wine as it is more complex than model solutions.

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.

Identification, Quantitation, and Sensory Evaluation of Thiols in Bordeaux Red Wine with Characteristic Aging Bouquet.

Great Bordeaux red wines are known for their distinctive aging bouquet. However, the nature of volatile chemicals underpinning this sensory expression is not fully understood. This work investigated the empyreumatic aging bouquet of a collection of premium Bordeaux red wines using silver-ion (Ag+) solid-phase extraction, cryogenic heart-cutting multidimensional gas chromatography mass spectrometry/olfactometry, and comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry. In doing so, a substantial number of "meaty" odors were revealed. Three detected "meaty" notes were tentatively or unequivocally attributed to furan thiols. Among them, 2-methyltetrahydrofuran-3-thiol (1) with a pleasant "meaty" aroma was reported in wine for the first time. Its trans isomer (trans-1a) was resolved from its racemate by chemical modification, which confirmed its presence in wine. The odor detection threshold of trans-1a in the model wine was determined at 55 ng/L. Moreover, an additive effect between 1 and literature-known 2-methyl-3-furanthiol was observed. By a new ultra high-performance liquid chromatography quadrupole Orbitrap high-resolution mass spectrometry method, the concentration of trans-1a, in addition to those of 2-methyl-3-furanthiol and 2-furfuryl thiol, was measured in the wines at ng/L levels.

Physicochemical properties, antioxidant activities and comprehensive phenolic profiles of tea-macerated Chardonnay wine and model wine

A new type of flavored wine was produced by macerating either green tea or black tea into Chardonnay wine and model wine respectively, where the physicochemical properties (pH, titratable acidity, color) were modulated. Significant (p < 0.05) increases of total phenolic content and antioxidant activity (assessed by DPPH, FRAP and ABTS assays) were also observed in the tea macerated wines. A total of 160 phenolic and non-phenolic compounds were identified by HPLC-DAD-ESI-QTOF-MS/MS, where 55 phenolics were newly found in the tea macerated Chardonnay wine. The interaction between wine and tea phenolics led to additional 29 phenolic compounds and 4 non-phenolic compounds that were not found in either Chardonnay wine or tea. Catechin and epigallocatechin gallate were the most abundant phenolic compounds and contributed to the improved antioxidant activities. This study provided a promising prospect of tea as a novel additive in the production of flavored wine with enhanced functionalities.