Unraveling the evolving nature of gaseous and dissolved carbon dioxide in champagne wines: A state-of-the-art review,from the bottle to the tasting glass

In champagne and sparkling wine tasting, the concentration of dissolved CO₂ is indeed an analytical parameter of high importance since it directly impacts the four following sensory properties: (i) the frequency of bubble formation in the glass, (ii) the growth rate of rising bubbles, (iii) the mouth feel, and (iv) the nose of champagne, i.e., its so-called bouquet. In this state-of-the-art review, the evolving nature of the dissolved and gaseous CO₂ found in champagne wines is evidenced, from the bottle to the glass, through various analytical techniques. Results obtained concerning various steps where the CO₂ molecule plays a role (from its ingestion in the liquid phase during the fermentation process to its progressive release in the headspace above the tasting glass) are gathered and synthesized to propose a self-consistent and global overview of how gaseous and dissolved CO₂ impact champagne and sparkling wine science.     

Flow patterns of bubble nucleation sites (called fliers) freely floating in champagne glasses

Laser tomography techniques were used to capture the dynamics of bubbles released from particles (arbitrarily called fliers) freely floating in traditional flutes poured with champagne. By use of long exposure time photography, the trajectories of bubbles released by fliers were found to leave very elegant and characteristic "prints" as they crossed a section of champagne illuminated with a 1 mm thick laser sheet. This characteristic print was made with a succession of lighting filaments. Fine analysis of these prints left by fliers enabled us to deduce the bubbling frequency of each flier (which ranged from about 4 bubbles/s up to about 22 bubbles/s a few seconds after pouring), as well as its velocity through the liquid medium (which ranged from about 0.8 mm/s to about 7.6 mm/s). Finally, this flow visualization technique, very recently applied to the science of champagne and sparkling wines, also proved to be a useful technique to underscore fliers' bubbling instabilities along their rather erratic way through the liquid medium.     

Sekt,Champagner & Co. So prickelnd kann Chemie sein

A glass of sparkling wine or champagne is the preferred drink for the truly extraordinary moments in our lives. The connoisseur already celebrates and enjoys opening the bottle, carefully pouring it into the proper glass, and then admiring its color, aroma, taste, and, last but not least, the fizz. Looking a little bit deeper into the glass we discover that a lot of chemistry is involved, starting from the vineyard up to drinking the sparkling wine or champagne which increases our joy of it even more. What a wonderful start into the New Year! A votre santé!     

Does the Temperature of the prise de mousse Affect the Effervescence and the Foam of Sparkling Wines?

The persistence of effervescence and foam collar during a Champagne or sparkling wine tasting constitute one, among others, specific consumer preference for these products. Many different factors related to the product or to the tasting conditions might influence their behavior in the glass. However, the underlying factor behind the fizziness of these wines involves a second in-bottle alcoholic fermentation, also well known as the prise de mousse. The aim of this study was to assess whether a low temperature (13 °C) or a high temperature (20 °C) during the in-bottle fermentation might have an impact on the effervescence and the foaming properties (i.e., collar height and bubble size) of three French sparkling wines (a Crémant de Loire and two Champagne wines), under standard tasting conditions. Our results showed that sparkling wines elaborated at 13 °C and served in standard tasting conditions (i.e., 100 mL, 18 °C) had better ability to keep the dissolved CO₂ (between 0.09 and 0.30 g/L) in the liquid phase than those elaborated at 20 °C (with P < 0.05). Most interestingly, we also observed, for the Crémant de Loire and for one Champagne wine, that the lower the temperature of the prise de mousse, the smaller (with P < 0.05) the bubbles in the foam collar throughout the wine tasting.     

Is the wall of a cellulose fiber saturated with liquid whether or not permeable with CO2 dissolved molecules? Application to bubble nucleation in champagne wines

In this paper, the transversal diffusion coefficient D perpendicular of CO2 dissolved molecules through the wall of a hydrated cellulose fiber was approached, from the liquid bulk diffusion coefficient of CO2 dissolved molecules modified by an obstruction factor. The porous network between the cellulose microfibrils of the fiber wall was assumed being saturated with liquid. We retrieved information from previous NMR experiments on the self-diffusion of water in cellulose fibers to reach an order of magnitude for the transversal diffusion coefficient of CO2 molecules through the fiber wall. A value of about D perpendicular approximately 0.2D0 was proposed, D0 being the diffusion coefficient of CO2 molecules in the liquid bulk. Because most of bubble nucleation sites in a glass poured with carbonated beverage are cellulose fibers cast off from paper or cloth which floated from the surrounding air, or remaining from the wiping process, this result directly applies to the kinetics of carbon dioxide bubble formation from champagne and sparkling wines. If the cellulose fiber wall was impermeable with regard to CO2 dissolved molecules, it was suggested that the kinetics of bubbling would be about three times less than it is.     

Characterization by optical measurements of the effects of some stages of champagne technology on the adsorption layer formed at the gas/wine interface

This study analyzes the effects of some important factors of champagne technology on the ellipticity and Brewster angle microscopy (BAM) of the air/champagne interface in view of using the optical properties of the adsorption layer of base wine to forecast the stability of the champagne bubble collar. Using standard, ultrafiltered, and ultraconcentrated wines it was observed that champagne can lose amphiphilic macromolecules which adsorb on the inner glass wall of the bottle during storage, particles such as dead yeasts can adhere to the adsorption layer, a weak increase of the ethanol content during bottle fermentation can reduce significantly the ellipticity of the adsorption layer, and CO2 has no significant effect on the properties of that layer. Surprisingly, no visible differences of the adsorption layer were noticed between the experimental champagnes of the 2004 vintage of three vine varieties (Chardonnay, Pinot noir, and Pinot meunier). From analysis of all samples it is proposed that the mean value and standard deviation of the ellipticity measured during 30 min after pouring the wine in a Petri dish are physical quantities which satisfactorily characterize the adsorption layer of champagne. When needed, further characterization of the adsorption layer may be obtained by a detailed analysis of the kinetics of ellipticity during the same period and inspection of the BAM images of the interface.     

Quantification approach for assessment of sparkling wine volatiles from different soils, ripening stages, and varieties by stir bar sorptive extraction with liquid desorption

Stir bar sorptive extraction with liquid desorption followed by large volume injection coupled to gas chromatography-quadrupole mass spectrometry (SBSE-LD/LVI-GC-qMS) was applied for the quantification of varietal and fermentative volatiles in sparkling wines. The analytical data were performed by using suitable standards of monoterpene hydrocarbons (α-pinene), monoterpenols (linalool), sesquiterpenoids (E,E-farnesol, Z-nerolidol, and guaiazulene), C₁₃ norisoprenoids (β-ionone), aliphatic and aromatic alcohols (hexanol and 2-phenylethanol), and esters (hexyl acetate and ethyl decanoate) as model compounds. The wine volatiles were quantified using the structurally related standards. The methodology showed good linearity over the concentration range tested, with correlation coefficients ranging from 0.950 to 0.997, and a reproducibility of 9-18%. The SBSE-LD/LVI-GC-qMS methodology allowed, in a single run, the quantification of 71 wine volatiles that can be quantified accurately at levels lower than their respective olfactory thresholds. This methodology was used for assessment of sparkling wine volatiles from different soils, ripening stages, and varieties. The variety and soil influenced significantly the volatile composition of sparkling wines; lower effect was observed for the ripening stage of grapes picked up one week before or after the maturity state.     

Native ethylene glycol in wine: Application of a dead volume free,very fast “deans heart-cut” system on-line with multi-chromatography

Data about the existence of native HO? CH₂? CH₂? OH (MEG) in natural wines and champagne has led to delicate questions because of legal decisions already made to declare wine or champagne illegal for sale if the MEG concentrations found are above 10 mg/liter. Action has been taken because of the DEG (diethylene glycol) disaster in European wines of 1985…86. An incorrect legal decision was made due to the belief that MEG cannot be produced biochemically by grape vines. A further reason may be lack of correct data on native MEG trace concentrations, as a result of the special behavior of this diol. As first member of a homologous series whose higher members (C₄) are normally found in all wines at quite high concentration levels, MEG shows extremely adsorptive behavior. The solution of the chromatographic problems is summarized in this paper. MEG concentrations in Riesling as example are in the range of 2 to 6 mg/liter and can easily be increased by biotechnological steps to a level of around 10 to 60 mg/liter. This is again due to the specific adsorptive behavior of MEG, which can be enriched on filter surfaces and displaced when the wine acidity changes with changing types. In order to control and guarantee the qualitative and quantitative results of MEG analyses we used a combination of Deans heart cutting on-line with Multi-Chromatography. It was easy to produce false data by many otherwise useful single column or two-dimensional separation processes, etc.     

Specificity and Origin of the Stability of the Sr Isotopic Ratio in Champagne Wines

The ⁸⁷Sr/⁸⁶Sr ratio of 39 Champagnes from six different brands, originating from the whole “Appellation d’Origine Contrôlée” (AOC) Champagne was analyzed to establish a possible relation with the geographical origin. Musts (i.e., grape juice) and base wines were also analyzed to study the evolution of the Sr isotopic ratio during the elaboration process of sparkling wine. The results demonstrate that there is a very homogeneous Sr isotopic ratio (⁸⁷Sr/⁸⁶Sr = 0.70812, n = 37) and a narrow span of variability (2σ = 0.00007, n = 37). Moreover, the Sr concentrations in Champagnes have also low variability, which can be in part explained by the homogeneity of the bedrock in the AOC Champagne. Measurements of the ⁸⁷Sr/⁸⁶Sr ratio from musts and base wines show that blending during Champagne production plays a major role in the limited variability observed. Further, the ⁸⁷Sr/⁸⁶Sr of the musts were closely linked to the ⁸⁷Sr/⁸⁶Sr ratio of the vineyard soil. It appears that the ⁸⁷Sr/⁸⁶Sr of the product does not change during the elaboration process, but its variability decreases throughout the process due to blending. Both the homogeneity of the soil composition in the Champagne AOC and the blending process during the wine making process with several blending steps at different stages account for the unique and stable Sr isotopic signature of the Champagne wines.     

Determination of monomethylmercury in low- and high-polluted sediments by microwave extraction and gas chromatography with atomic fluorescence detection

Laser tomography techniques were used in order to make visible the flow patterns induced by ascending bubbles in flutes poured with champagne. The stability of flow patterns was investigated in flutes showing natural (without any specific surface treatment) as well as artificial effervescence (i.e., engraved at their bottom), all along the first 15 min after pouring. Engravement conditions were found to strongly influence the kinetics and the stability with time of the mixing flow phenomena found in champagne glasses.     

The zeta-potential of the endogenous particles of a wine of Champagne in relation to the foaming behaviour

It was shown that the endogenous particles of the champagnes influence the lifetime, and not the maximum expansion of their evanescent foam (Food Hydrocolloids (1999) 12, 217-226). Actually, champagnes are electrolytic solutions with pH 3 and ionic strength equal to 0.02 mol/l in which bentonites, diatomites, and yeast cells are the more numerous colloids and particles present. In this context, we have investigated the electrophoretic properties of these particles to determine whether they can electrostatically interact with the foam bubbles. Results are that in model alcoholic solutions of proteins at same pH and ionic strength as the champagne, the zeta-potential was not vanishing whereas it dropped down to zero in wines. The zeta-potential of the particles does not vanish either when they are suspended in nanofiltered wines on molecular weight cut-off membrane (porosity=200-300 Da) or when the wines are basified upon addition of sodium hydroxide. This particular behaviour was tentatively assigned to the adsorption of some endogenous organic cationic ions on the particle surfaces, which screened out their electrostatic charge. The possible candidates are discussed.     

Determination of proline in wine using flow injection analysis with tris(2,2'-bipyridyl)ruthenium(II) chemiluminescence detection

Flow injection methodology is described for the determination of proline in red and white wines using tris(2,2′-bipyridyl)ruthenium(II) chemiluminescence detection. Selective conditions were achieved for proline at pH 10, while other amino acids and wine components did not interfere. The precision of the method was less than 1.00% (R.S.D.) for five replicates of a standard (4 × 10⁻⁶ M) and the detection limit was 1 × 10⁻⁸ M. The level of proline in white and sparkling wines using the developed methodology was equivalent to those achieved using HPLC-FMOC amino acid analysis. SPE removal of phenolic material was required for red wines to minimize Ru(bipy)₃³⁺ consumption and its associated effect on accuracy.     

Characterisation by drop tensiometry and by ellipsometry of the adsorption layer formed at the air/champagne wine interface

A foam ring composed of small bubbles on the surface of a champagne glass is one of its hallmarks. The equilibrium state of that ring is linked with the rate of formation and of disappearance of bubbles. The stability of bubbles is usually ascribed to the occurrence and to the properties of an adsorption layer formed at the gas/liquid interface. Our goal is to characterise such an adsorption layer at the gas/wine interface in order to understand its role in bubble stability. Alcohol in wine lowers the surface tension to 49 mN/m. The adsorption of other molecules may cause a further decrease of 2 mN/m. Such a situation makes the study of adsorption by surface tension measurement inaccurate. To overcome this problem, we have diluted the wine four times with water before its surface tension measurement by pendant drop shape analysis. In these conditions, ethanol lowers the surface tension to 64 mN/m and the adsorption of other molecules of the wine can be monitored over 6-8 mN/m. The usual behaviour of such a diluted wine is a lowering of the surface tension during at least 20 min after drop formation. Since the role of macromolecules on the foaming properties of wine had been previously observed, we have chosen to evaluate the effect of this fraction of the wine molecules on its surface properties. Thus, wines were ultrafiltrated on a membrane with a 10000 molecular mass cut-off. The ultrafiltrate (UF) does not show any decrease of its surface tension over a 20-min period while the ultraconcentrate (UC) has a kinetics similar to that of unfiltered wine. Mixtures of UF and UC have behaviours intermediate between those of these products. A technological treatment of the wine with bentonite, believed to lower the content of macromolecules, yields a wine similar to UF. The effect of ultrafiltration was also analysed by spectroscopic ellipsometry. UF has a spectrum similar to that of a water/alcohol mixture with the same ethanol content and its ellipticity is stable during at least 20 min. On the contrary, wine or UC show spectra with the features of an adsorption layer and those characteristics increase during more than 20 min. Two varieties of vine were compared: 'Chardonnay' and 'Pinot noir'. The former is known to have better foaming properties than the latter. Its surface properties measured in this study are also more pronounced than those of Pinot noir. However, the representation of the dilational modulus against the surface pressure (which, in some instances, may be a mathematical transformation of the state equation) puts all the samples (wines, UF and UC of each) on the same master curve, a fact in favour of a common nature for all the adsorption layers. It can be concluded that surface properties of champagne wines are mostly determined by ethanol and by macromolecules with a molecular mass larger than 10000. Moreover, the adsorption layers seem to have the same nature, irrespective of the vine variety and of the concentration ratio of the wine.     

A New Process for Wine Production by Penetration of Yeast in Uncrushed Frozen Grapes

Different types of red and white wines were prepared by fermentation of the juice which was naturally separated from uncrushed frozen grapes during thawing (A) and from the residual juice by fermentation inside the berries (B). Yeast penetrated the skin of uncrushed grapes and fermented the content completely. The new types of wines were compared with wines prepared conventionally from the whole material of frozen grapes. Chemical and chromatographic analysis (gas chromatography (GC) and solid-phase microextraction–GC/mass spectrometry) showed similar profiles of the aroma volatiles but with significant quantitative differences among the new types of wines, which reflected to the differences observed during the sensory evaluations. The majority of identified compounds were esters, with higher amounts found in (A) wines due to the higher concentration of the must which was separated during thawing. The proposed process is new and of industrial interest for the production of different types of wines from the same raw material in one fermentation batch.     

In-line pressurized-fluid extraction-solid-phase extraction for determining phenolic compounds in grapes

A procedure to determine 3-alkyl-2-methoxypyrazines in wines is described. It is based on the headspace solid-phase microextraction (HS-SPME) technique after a clean-up of the sample by distillation (previously acidified to pH 0.5) to remove ethanol and other volatile compounds that can interfere in the SPME. Determination is performed by means of capillary gas chromatography using a nitrogen-phosphorus detector. The method allows quantification of 3-isobutyl-2-methoxypyrazine, 3-sec-butyl-2-methoxypyrazine and 3-isopropyl-2-methoxypyrazine at their natural concentration levels and below their sensory thresholds in Cabernet Sauvignon and Merlot wines. The method was successfully applied to experimental red wines and the evolution of their pyrazine contents during the winemaking process was monitored. Pyrazine content increased during the first maceration day but did not change significantly during alcoholic and malolactic fermentation. Final contents in wines were 12-27 ng/l of 3-isobutyl-2-methoxypyrazine and 5-10 ng/l of 3-sec-butyl-2-methoxypyrazine.     

Multivariate analysis of the polyphenol composition of Tempranillo and Graciano red wines

Vitis vinifera L. cv Graciano is often used as a blending partner of Tempranillo based wines because it is considered to contribute significantly to the quality. The aim of this study is to discriminate between Tempranillo and Graciano monovarietal wines, and those made by the incorporation of 20% of Graciano variety in two different stages (at the end of malolactic fermentation and mixing the two grape varieties in the pre-fermentative maceration stage) of the winemaking process of the Tempranillo variety. To achieve this, supervised and unsupervised pattern recognition tools were applied to the data obtained in the study of the detailed polyphenolic composition, colour and other oenological parameters (143 variables). Patterns related to stages in the winemaking and ageing process, different wines and vintages can be observed using principal component analyses. Furthermore, linear discriminant analysis has been applied in order to characterise the wine samples. From the 143 variables, flavan-3-ols have exerted a profound influence on wine differentiation.     

Application of LC–MS and tristimulus colorimetry to assess the ageing aptitude of Syrah wine in the Condado de Huelva D.O. (Spain), a typical warm climate region

The study of the evolutions of different wine pigment families, copigmentation/polymerisation processes and colour characteristics during the first year of ageing in oak barrel has allowed the assessment of the ageing aptitude of Syrah wines from “Condado de Huelva D.O.”, a warm climate region. A total of 32 anthocyanic pigments were identified, including 14 major compounds from grape and 18 minor derivatives formed during the vinification. The anthocyanin profile changed towards more chemical complexity, being vitisin-like pyranoanthocyanins the predominant minor pigments during the first month of ageing. As wine became older, a progressive increase on the content of 4-vinylcatechin, 4-vinylphenol and 4-vinylcatechol compounds took place. Results showed that copigmentation occurred during the whole process of ageing inducing visual perceptible colour effects. Simultaneously to the copigmentation decrease, the degree of polymerisation increased during ageing, being maximum at 9 months old wines (77%). The colour of wines evolved progressively in a positive way from 3 to 9 months of ageing, becoming darker and with more vivid colour. However, from 9 to 12 months of ageing, the chemical structure of wines was negatively affected resulting in lighter, with more red-orange hues and less vivid colours. The inclusion of the chemical and colorimetric information on the PCA model allows us to reach very good discriminations among the Syrah wines with different wood contact period.     

Evaluation of Anthocyanin Profile and Color in Sweet Cherry Wine: Effect of Sinapic Acid and Grape Tannins during Aging

Cherries are rich in bioactive phenolic compounds and are often fermented into cherry wines. The degradation of anthocyanins during storage will cause color deterioration. The study aimed to utilize sinapic acid and grape tannins in cherry wine to maintain a high fraction in the colored forms of anthocyanins, in order to maximize the color intensity, the latter being associated with good product quality. The effects on the anthocyanin profile and on color parameters of copigments, utilizing spectral measurement combined with UPLC-MS quantitative analysis, have been evaluated in sweet cherry wines. The copigmentation effect of sinapic acid and grape tannin was accompanied by the bathochromic shift and the hyperchromic effect, which lead to an increase in color intensity (lower L*, higher a* and b*). During the aging process, sinapic and grape tannin increased the content of pyranoanthocyanins in cherry wine, especially the addition of sinapic acid makes the cherry wine generate 10-syringyl-pyranocyanidin-3-rutinoside. These results demonstrate that sinapic acid is suitable for adding before alcohol fermentation, while grape tannins can be added before aging.     

Factors That Affect the Accumulation of Strecker Aldehydes in Standardized Wines: The Importance of pH in Oxidation

Strecker aldehydes (SA) can be formed in wine from the degradation of Strecker and, to a lesser degree, via the oxidation of higher alcohols. The objective of this article is to assess the magnitude of the differences introduced by wine compositional factors other than amino acids and Fe, in the accumulation of SA during oxidation. Eight red, two rosé and two white wines were oxidized. The accumulation of SA was analyzed. Whites and rosés presented negative accumulations for isobutyraldehyde, and in general, these wines accumulated smaller concentrations of the other SA than red wines. Only methional and phenylacetaldehyde were accumulated in all of the wines during oxidation. 2-methylbutanal and 3-methylbutanal were accumulated in 9 out of the 12 wines, whereas isobutyraldehyde was accumulated only in 5 out of the 12. 2-methylbutanal was, on average, the least accumulated aldehyde. Methional was the aldehyde formed most homogenously. Most of the observed differences can be attributed to three factors: the pH, oxidation time and native levels of Strecker aldehydes. The influence of pH was particularly intense in the cases of phenylacetaldehyde and methional. An independent test using synthetic wines with Strecker amino acids and 4-methylcatechol with different pHs (4.2, 3.5 and 2.8) was carried out in order to verify the higher pH value, the greater accumulation in SA after oxidation process. The results strongly suggest the important role played by pH in the accumulation of SA in wine oxidation.