Model Wine Research Articles

Relative impact of oenological tannins in model solutions and red wine according to phenolic, antioxidant, and sensory traits

Oenological tannins (OETs) are winemaking processing aids used to facilitate stabilization and fining, to increase the antioxidant capacity, and to promote colour stability of grape juice and wine. A wide variability of pure or mix formulates are available for winemaking purposes, including hydrolysable tannins (gallotannins and ellagitannins), proanthocyanidins from grape skins and seeds (prodelphinidins and procyanidins), and from exotic wood (prorobinetinidins and profisetinidins). In this study, seventeen OETs pure and mix formulates were characterized in terms of polyphenolic content and antioxidant capacity in a model wine and in a red wine after one-month storage, as well as aroma, astringency, and bitterness sensory characteristics in water and red wine. Colour-related features were also analysed in the added red wine after one-month storage. For the first time, correlations among the obtained results in the different matrices were investigated to understand the most suitable OETs for winemaking applications. The results showed a great variability among the formulates studied in terms of phenolic content, which was strictly correlated to their antioxidant capacity. Regarding origin, hydrolysable tannins had the highest antioxidant ability, followed by exotic wood formulates. A strong and positive correlation was found in antioxidant capacity of OETs in model wine and red wine after one-month storage, in particular for ellagitannins, which confirmed also their ability to increase pigments polymerization. By contrast, quebracho tannins resulted the bitterest and most astringent when tasted in water (0.4 g/L), although in-mouth and aromatic descriptors of OETs tasted in water were not correlated with the ones of the added red wine. Therefore, the choice of OETs formulate and its optimal dose requires a characterization in terms of polyphenolic content and antioxidant capacity because these properties were well correlated with those of the added wines in a short storage period, whereas the sensory impact at oenological range doses is mainly dependent on wine features.

Investigating the effect of three phenolic fractions on the volatility of floral, fruity, and aged aromas by HS-SPME-GC-MS and NMR in model wine.

In this study, the volatility of three typical wine aromas in model wine was investigated by HS-SPME-GC-MS, NMR, and sensory evaluation as influenced by different concentrations and structural properties of phenolics. Results showed that three phenolic fractions (phenolic acids, monomeric/oligomeric and polymeric procyanidins) exhibited different matrix effects on floral, fruity, and aged aromas perception. Physico-chemical and sensory analyses together indicated that all fractions reduced the perceived intensity of fruity and aged aroma attributes, and displayed stronger retention effects on fruity aromas at higher mDP and concentrations. Monomeric/oligomeric and polymeric procyanidins promoted highly hydrophobic floral aromas release, whereas inhibiting the volatility of low hydrophobic fruity aromas. NMR confirmed that the reduction in the volatility of rose oxide, ethyl butanoate and whiskey lactone was attributed to interactions with epicatechin. This study aims to provide new thoughts and theoretical support for wine aroma regulation during winemaking by reconstructing the phenolic composition in wine.

Reactivity comparison of three malvidin-type anthocyanins forming derived pigments in model wine solutions

Malvidin-3-O-glucoside (MvG), malvidin-3-O-(6-O-acetyl)-glucoside (MvAG), and malvidin-3,5-O-diglucoside (MvDG) are three representative malvidin-type anthocyanins in red wine. In this study, the influence of structural differences on the formation efficiency of two types of derived pigments ((−)-epicatechin-ethyl-anthocyanins and pyranoanthocyanins) was investigated in model solutions using UHPLC-MS. The results showed that the yields of MvAG were higher than those of MvG to form both types of derived pigments, and the formation rate of pyranoanthocyanin was also relatively higher. In contrast, acetylation slowed the formation of (−)-epicatechin-ethyl-anthocyanins, indicating that the rate of covalent reactions may be linked to the affinity of (−)-epicatechin to copigment with anthocyanins. The condensation rate of MvDG with (−)-epicatechin, mediated by acetaldehyde, was much lower than that of the two monoglucosidic anthocyanins and also exhibited lower yields. In addition, pyranoanthocyanin was not generated from MvDG due to the absence of a free hydroxyl group at the C5 position.

An insight into the thin-layer diffusion phenomena within a porous electrode: Gallic acid at a single-walled carbon nanotubes-modified electrode

• Glassy carbon electrode was modified with single-walled carbon nanotubes. • Electrochemical behaviour of gallic was studied. • Chronoamperometry was applied for clarifying diffusion processes in thin-layer. • Diffusion phenomena were linked to current signal. • A difference in electrochemical behaviour in various buffers was explained. The electrochemical behavior of gallic acid at a single-walled carbon nanotubes-modified glassy carbon electrode, in an acetate buffer, a model wine buffer and the Britton-Robinson buffer was studied. The elucidation of phenomena, related to the electrochemical behaviour, was performed using cyclic voltammetry and chronoamperometry. Analysis of chronoamperometric results revealed that overall processes, responsible for current signal are mostly related to diffusion phenomena. These phenomena can be divided into four processes that take place either in a thin-layer or/and in a solution depending on the buffer used. By comparative analysis of chronoamperometric and voltammetric results “in real time”, the effects of scan rate, concentrations of gallic acid and layer thickness have on voltammetric signal are discussed in the light of diffusion processes that take place in thin-layer. Finally, comparative analyses of cyclic voltammograms and chronoamperograms, recorded at different pH values, have revealed that low sensitivity at high pH values can be attributed to hampered diffusion. These findings can be useful in elucidating electrochemical behaviour of various species (not only of gallic acid) using an electrode containing carbon nanotubes.

The formation mechanism of pinotin A in model wine: Experimental and theoretical investigation

Pinotin A is a crucial pyranoanthocyanin in aged red wine. The formation mechanism of pinotin A was investigated through experimental and theoretical approaches in model wine solution. Using UHPLC-DAD-QTOF, three intermediates were identified in the reaction solution of malvidin-3-O-glucoside and caffeic acid. The pH and oxidative conditions affected the reaction rate by modulating the accumulation of intermediates. Upon preparative HPLC and oxidation experiment, the transformation of intermediate 3 to intermediate 2 was observed through free radical oxidation, p-benzoquinone oxidation and autooxidation. However, the production of pinotin A was only achieved through autooxidation. A three-steps reaction mechanism of reversible addition reaction and decarboxylation, and autooxidation was proposed. The validity of the proposed mechanism was verified through quantum chemistry calculation. The negative variation of Gibbs free energy of the entire reaction was obtained, where the autooxidation step played a crucial role for the spontaneity of the whole reaction.

Acid complexation of iron controls the fate of hydrogen peroxide in model wine

At a key branchpoint in wine oxidation, hydrogen peroxide reacts either with iron(II), leading to the Fenton oxidation of ethanol, or with sulfur dioxide, precluding oxidation. The fate of H2O2 was investigated in anoxic model wines with different pH and acid buffers. In the absence of SO2, anoxic conditions allowed the stoichiometric production of acetaldehyde from H2O2 despite iron(II) being limiting, indicating efficient iron redox cycling. Acetaldehyde production was faster at pH 4.0 than at pH 3.0, attributable largely to increased iron complexation. Citrate allowed the most rapid acetaldehyde formation, while the comparative effects of tartrate and malate were pH-dependent, likely due to differences in their iron-chelating abilities. The inclusion of SO2 greatly diminished acetaldehyde formation, but did not prevent it, and reduced the differential effects of pH and acid composition. Findings overall suggest management of wine acidity can significantly affect the rate and outcome of oxidation.

Understanding the interactive effects of volatile compounds contributing to ‘stone fruit’ aroma nuances in white wines

Background and Aims The sensory experience of wine aroma is challenging to study. Given the presence of numerous and trace level volatiles, the subtle aroma nuances involved, as well as the complexity of human odour processing, the contribution of individual compounds and mixtures can be difficult to determine. In white wines, the volatile compounds eliciting stone fruit aromas are not well understood. Methods and Results Factorial designs were used with odorants added to model wine and assessed using sensory quantitative descriptive analysis. In model Viognier-like wines, several monoterpenes were confirmed to convey stone fruit attributes Apricot and Peach, which were strongly suppressed by aldehydes which imparted Cardboard-like odours. Importantly, lactones increased Apricot aroma when combined with the monoterpenes. For model unoaked Australian Chardonnay wine, sensory-directed screening followed by factorial studies showed that aliphatic ethyl esters, in particular ethyl octanoate, directed Peach aroma. Fatty acids were strong suppressors of the Peach attribute and gave Cheesy odours. Conclusions Apricot and peach aromas in Viognier and Chardonnay, although perceptually similar, were caused by different chemical compound families: grape-derived monoterpenes with lactones and yeast-derived fatty acid ethyl esters, respectively. Significance of the Study Having confirmed the compounds responsible for apricot and peach white wine aromas, there is potential to modify their concentration through established viticultural and winemaking practices.

Impact of tannins on intraoral aroma release and retronasal perception, including detection thresholds and temporal perception by taste, in model wines

Tannins, as an important wine nonvolatile matrix component, can cause astringency, which may affect aroma perception through cross-modal interactions during wine consumption. An aromatic model wine with tannin extracts was evaluated by intraoral aroma release and sensory analysis after wine spitting. Overall, tannin extracts could significantly decrease all initial aroma release, while they could not reduce most aroma release at 150 s after wine spitting. Regarding the sensory evaluation results, the retronasal detection threshold of most aromas increased. The temporal aroma intensity showed a significant decrease at early time points and was almost unaffected at later time points. In addition, temporal dominance of sensation (TDS) curves revealed that the presence of astringency could reduce the dominant time of most aromas. Therefore, although there was good consistency between instrumental analysis and sensory evaluation, the effect of astringency induced by tannins on retronasal perception cannot be ignored.

Role of Grape-Extractable Polyphenols in the Generation of Strecker Aldehydes and in the Instability of Polyfunctional Mercaptans during Model Wine Oxidation.

Polyphenolic fractions from Garnacha, Tempranillo, and Moristel grapes were reconstituted to form model wines of identical pH, ethanol, amino acid, metal, and varietal polyfunctional mercaptan (PFM) contents. Models were subjected to a forced oxidation procedure at 35 °C and to an equivalent treatment under strict anoxia. Polyphenolic profiles significantly determined oxygen consumption rates (5.6–13.6 mg L–1 day–1), Strecker aldehyde (SA) accumulation (ratios max/min around 2.5), and levels of PFMs remaining (ratio max/min between 1.93 and 4.53). By contrast, acetaldehyde accumulated in small amounts and homogeneously (11–15 mg L–1). Tempranillo samples, with highest delphinidin and prodelphinidins and smallest catechin, consume O2 faster but accumulate less SA and retain smallest amounts of PFMs under anoxic conditions. Overall, SA accumulation may be related to polyphenols, producing stable quinones. The ability to protect PFMs as disulfides may be negatively related to the increase in tannin activity, while pigmented tannins could be related to 4-methyl-4-mercaptopentanone decrease.

Monitoring yeast autolysis in sparkling wines from nine consecutive vintages produced by the traditional method

Background and Aims Yeast autolysis is a key step in the production of sparkling wines using the traditional method and a source of polysaccharides, mannoproteins and proteins. The evidence, however, of the enrichment of these macromolecules during ageing is not evident in the literature. In this study, autolysis of yeast lees in sparkling wines (Cava) was monitored over nine consecutive vintages. Methods and Results The concentration of polysaccharides and proteins did not clearly increase over time, probably because these macromolecules are simultaneously released from lees and removed by other processes. In a new approach, the autolytic process was reproduced, and involved recovering the lees and maintaining them in a model wine solution for 1 year. The lees released polysaccharides and proteins, but only a small proportion of that found in the sparkling wines, especially in younger wines. Conclusions This study confirmed that yeast enrich sparkling wines in key macromolecules but in low proportion in comparison with the usual concentration present in sparkling wine. This aspect should be considered by wineries that aim to achieve autolysis attributes, since the majority of sparkling wines are commercialised after short periods of ageing. Significance of the Study This study determined for the first time the true contribution of yeast autolysis to the total polysaccharide and protein concentration of sparkling wines from nine consecutive vintages.

Impact of three phenolic copigments on the stability and color evolution of five basic anthocyanins in model wine systems

Phenolic copigments have important influence on red wine color. In this study, UV–visible spectrophotometer and UHPLC-Q-TOF-MS were combined to investigate the effects of three types of phenolic copigments (gallic acid, (-)-epicatechin, and quercetin-3-O-glucoside) on the stability and color properties of five common 3-O-monoglucosidic anthocyanins in model wine solutions. Results showed low concentrations (0.5 mM) of gallic acid and (-)-epicatechin protected anthocyanins from degradation, whereas high concentrations (8 mM) of them had the opposite effect. Quercetin-3-O-glucoside always improved the stability of anthocyanins despite its additive amount (0.1 mM or 0.4 mM). Even small quantity of (-)-epicatechin led to obvious yellow hue into the solution, and xanthylium derivatives generated from (-)-epicatechin were detected. Antagonistic effect among the three copigments was observed, probably as a result of competition of intermolecular copigmentation. Additionally, the stability of anthocyanins was significantly influenced by their structures: cyanidin-3-O-glucoside, peonidin-3-O-glucoside, and malvidin-3-O-glucoside were more stable than delphinidin-3-O-glucoside and petunidin-3-O-glucoside.

Brine-Releasable Hydrogen Sulfide in Wine: Mechanism of Release from Copper Complexes and Effects of Glutathione.

Copper-sulfhydryl complexes in wine can be disrupted by addition of brine to release free hydrogen sulfide (H2S), and the resulting "brine-releasable H2S" is reported to correlate with formation of H2S during bottle storage. However, both the mechanism of the brine-release assay and factors affecting the stability of copper sulfhydryls under brine-release conditions are not well understood. By varying brine composition and concentration, it is shown that release of copper-complexed H2S requires the presence of a halide (Cl- and Br-) and is not due to a general "salting-out" effect. Release of copper-complexed H2S by the brine dilution assay is highly temperature-dependent. When H2S and Cu(II) are added to a model wine, brine-releasable H2S decreases markedly (∼10-fold) after a 20 min incubation period prior to performing the brine-release assay. In commercial wines, the fraction of added H2S recovered through the brine-release assay was correlated with the initial glutathione (GSH) concentration (r2 = 0.58) but not with initial Cu. Negligible additional release of H2S from organopolysulfanes was observed following addition of a disulfide-reducing agent (tris(2-carboxyethyl)phosphine). As previous studies have reported a correlation between H2S formed under brine-release conditions and normal storage, these results suggest that the susceptibility of a wine to form latent copper-sulfhydryl precursors of H2S following copper addition is dependent on the concentration of sulfhydryls like GSH.

Wine Oligosaccharides: Underutilized or Irrelevant? A Study into the Effects of Oligosaccharides on Wine Taste and Mouthfeel

The taste and mouthfeel of a wine are two of the most important aspects of wine tasting. However, while much is known about phenolic compounds and other macromolecules direct effects on wine taste and mouthfeel, little is known about other wine compounds such as oligosaccharides. This experiment uses Fructo-oligosaccharide (FOS) and Galacto-oligosaccharide (GOS) at two different concentrations, 450 mg/L and 900 mg/L within a simple model wine matrix. A model matrix was used to control for any unknown interactions between oligosaccharides and the multitude of wine components. Oligosaccharides were added individually to the model wine matrix at each concentration to create four treatments. Triangle tests were performed on all treatments against the control base model wine and between the high and low concentrations of each oligosaccharide treatment. Following the triangle tests, each treatment and the control underwent descriptive analysis (DA) using line intensity scales for sweetness, bitterness, astringency, acidity, and viscosity. Triangle test results revealed a significant difference only between the FOS450 and FOS900 samples. The wine matrix was made more complicated by adding polyphenols and still, none of the four oligosaccharide treatment groups were found to be significantly different. DA found no significant differences for the five attributes but did show clear trends in increased sweetness and acidity, decreased bitterness, as well as changes to astringency and viscosity. This suggests there may be more complex interactions happening within the mouth. However, given the lack of significant results in the simple wine model and the more complex wine model wine, any complex interactions between oligosaccharides and other wine compounds are likely to be minimal.

Influence of Vibration on the Consumption of Oxygen and Sulfur Dioxide in Wine Bottles Considering Bottle Position and Headspace Volume

This study investigates the influence of vibration, bottle position, and initial headspace volume on the oxygen (O₂) distribution inside a wine bottle. For this purpose, 0.75-L wine bottles were filled with a model wine and stored either horizontally or vertically under different vibration intensities (no vibration, 500 mm/sec², and 1000 mm/sec²) at a constant frequency of 50 Hz. The bottles were sealed with screwcap or cork closure, with two headspace volumes for each type of closure. Our results indicated that vibration and horizontal bottle position promoted the dissolution of O₂ from the headspace of the bottle into the wine, causing accelerated sulfur dioxide (SO₂) degradation. The effect of vibration was larger in the horizontally stored bottles, indicating that a larger wine surface area promotes O₂ uptake into the wine. In the absence of headspace O₂, vibration and bottle position showed no influence on SO₂-related O₂ degradation. Furthermore, the dissolution of O₂ was faster in bottles with cork closure than in those with screwcap closure due to overpressure caused by the corking process. We concluded that vibration and horizontal bottle position have major effects on the dissolution of O₂ from the headspace of the bottle into the wine, but not on the chemical reaction of the dissolved O₂ with SO₂. The larger surface area of wine contacting the headspace in the horizontally stored bottles and the overpressure created by the corking process accelerate O₂ uptake from the bottles’ headspace into the wine.

Inhibitory Effect on Acrolein by Cyanidin-3-O-glucoside and Its Acrolein Adducts from the Pigment of Mynica Red.

Acrolein (ACR), the simplest α,β-unsaturated aldehyde, possesses high reactivity and toxicity both in vitro and in vivo and results in various chronic diseases. This has attracted increasing interest from researchers to screen various bioactive compounds to control it. In this article, we attempted to discover a new attribute of cyanidin-3-O-glucoside (C3G), including its ACR-scavenging capacity, reaction pathway, and possible application. Our findings revealed that C3G could capture ACR to form mono- and diadducts at room temperature by using liquid chromatography-mass spectrometry, and we further synthesized and elucidated the structures of C3G-ACR and C3G-2ACR using HRMS and 2D NMR. The structural data validated that there were two active sites of C3G for trapping ACR: at C-6 in the A-ring and C-5' in the B-ring. In addition, we found that C3G-ACR exhibited a more remarkable clearing ability than C3G within a short time. More than 65.9% of ACR was eliminated by C3G-ACR within 5 min via further formation of C3G-2ACR, but there was no obvious effect of C3G on ACR. When the incubation time was extended to 120 min, C3G could remove up to 83.2% of ACR. Subsequently, we also observed that mynica red (>5% C3G), as a pigmented food additive, could efficiently eliminate ACR generated in the Chinese liquor model and real red bayberry wine products to form C3G-ACR and C3G-2ACR. Both adducts increased significantly, by 10 times to a 100 times, after adding mynica red to red bayberry wine products for 24 h; they also increased rapidly with prolonged incubation time in the liquor-mynica red model system. Therefore, our findings suggest that C3G or mynica red may be developed as a promising novel ACR inhibitor in fruit wine and assembled alcoholic drinks or as a health food.

Revisiting the mechanism responsible for the light-struck flavor in white wines and Champagnes

The mechanism responsible for the appearance of the light-struck fault upon exposure of white wines and Champagnes to natural or artificial light is examined in light of new experiments involving methionine analogues. The latter show that the formation of volatile sulfur species upon irradiation of riboflavin in the presence of methionine in model wine solutions at pH 3 is not dependent on the existence of neighboring group stabilization of the sulfur-centered cation radical through a 5- or 6-membered cyclic intermediate. Instead, the formation of a dimer radical cation is proposed in agreement with the formation of oxidation products such as dimethyl disulfide at early reaction times and the observed steric effect upon product distribution. The limiting quantum yield for the release of sulfur atoms from a solution of methionine in model wine solutions at pH 3.5 containing riboflavin was found to be 0.26 (435 nm irradiation). No dependence of the quantum yield or product distribution on the irradiation wavelength was found over the range 365–90 nm.

Uptake and Release of Aroma Compounds by an Ethylene Propylene Diene Monomer Rubber Sealing Polymer: Investigating Aroma Carryover in a Model Wine System.

Aromatized wines and regular table wines are often filled on the same bottling line. Sealing polymers in the filling line absorb volatiles from aromatized wines and may migrate due to insufficient cleaning into the subsequently bottled regular wine. Unintentional carryover of volatiles may lead to accusation of illegal aromatization of wine. Absorption, cleaning efficacy, and migration of volatiles into ethylene propylene diene monomer rubber were investigated in a model system. Direct thermal desorption-gas chromatography-mass spectrometry analysis of seven aroma compounds monitored variation in the polymer (μg/g). Absorption of volatiles was mostly driven by their octanol/water partition coefficients. Cleaning of polymers removed 11 to 62% of the absorbed volatiles. Subsequent immersion of cleaned polymers into model wine revealed migration of 20 to 57% of the remaining volatiles. Sensory tests suggested the impact of transferred volatiles into subsequent model wine. For α-ionone, an odor activity value of 1.03 indicated a potential sensory impact.

Roles of free radical on the formation of acetaldehyde in model wine solutions under different ultrasound parameters: A key bridge-link compound for red wine coloration during ageing

In order to explore the effects of ultrasound on the formation of acetaldehyde and its mechanism in model wine solutions, ultrasound conditions and free radicals were investigated by response surface methodology and electron paramagnetic resonance spectroscopy (EPR), respectively. The results indicate that ultrasound does induce the production of acetaldehyde with the maximum amount under the conditions of ultrasound power density 0.2 W/cm2, 48 min and 32 °C. The hydroxyl radicals and the 1-hydroxyethyl free radicals are the main initiator and precursor for acetaldehyde, respectively. Furthermore, the stronger the 1-hydroxyethyl free radicals captured by EPR, the lower the formation of acetaldehyde. In addition, the content of Fe2+and ethanol also exerted a certain influence on the acetaldehyde formation. In conclusion, ultrasound does promote the production of acetaldehyde in the model wine solutions, which is beneficial for well understanding the mechanism of ultrasound in modifying the wine color and accelerating ageing.

Influence of tannins, human saliva, and the interaction between them on volatility of aroma compounds in a model wine.

During wine drinking, aroma release is mainly impacted by wine matrix compositions and oral physiological parameters. Notably, tannins in wine could interact with saliva protein to form aggregates which might also affect the volatility of volatiles. To explore tannins, saliva, and the interaction between them on the volatility of volatiles, the volatility of 16 aroma compounds in the model wine mixed with the commercial tannin extracts, human saliva, or both respectively, was evaluated in vitro static condition by using HS-SPME-GC/MS. The volatility of aroma compounds with high hydrophobicity or benzene ring appeared to decrease more when increasing the tannin levels. Specifically, the volatility of ethyl octanoate, β-ionone, and guaiacol was decreased more than 20% by adding 2 g/L tannin extract. The addition of human saliva could significantly inhibit volatility of most aroma compounds in the model wine. Furthermore, the volatility of most aroma compounds in the mixture of tannins and human saliva was significantly lower than the control or the sample which were added with tannins or human saliva individually. The volatility of some aroma compounds in the mixture of the tannin and saliva was only around 50% or less, relative to the control. Two-way ANOVA analysis showed that there was a synergistic effect between tannin and saliva on decreasing the volatility of most aroma compounds (p < 0.05). Overall, understanding the effect of key factors such as tannins and saliva on volatility of volatiles could help to understand the sophisticated retronasal perceptions during wine tasting. PRACTICAL APPLICATION: The outputs of this research will be helpful in understanding the impact of tannins on retronasal aroma release during wine tasting. It might promote the control of tannins in the viticulture and brewing process to improve the retronasal perception of wine aroma.

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