Unveiling CO2 heterogeneous freezing plumes during champagne cork popping

Understanding the tasting of champagne and other sparkling wines from a scientific perspective

From uncorking the bottle to the bursting of bubbles in the glass, the science behind the tasting of champagne and other sparkling wine is both traditional and at the forefront of modern developments. The strong interaction between the various parameters at play in a bottle and in a glass of sparkling wine has been the subject of study for around two decades. Indeed, sparkling wine tasting is often seen as the pinnacle of glamor and frivolity for most people, but it should also be considered as a fantastic playground for chemists and physicists to explore the subtle science behind this centuries-old drink, whose prestige today goes well beyond the borders of Champagne and France. This article offers an overview of the physicochemical processes that mark a tasting of champagne or sparkling wine in the broad sense, from the cork popping out of the bottleneck to the formation and bursting of bubbles in your glass, including the choice of the glass and how to serve and drink the wine correctly.

Losses of Yeast-Fermented Carbon Dioxide during Prolonged Champagne Aging: Yes, the Bottle Size Does Matter!

When it comes to champagne tasting, dissolved CO₂ is a key compound responsible for the very much sought-after effervescence in glasses. Nevertheless, the slow decrease of dissolved CO₂ during prolonged aging of the most prestigious cuvees raises the issue of how long champagne can age before it becomes unable to form CO₂ bubbles during tasting. Measurements of dissolved CO₂ concentrations were done on a collection of 13 successive champagne vintages stored in standard 75 cL bottles and 150 cL magnums showing prolonged aging ranging from 25 to 47 years. The vintages elaborated in magnums were found to retain their dissolved CO₂ much more efficiently during prolonged aging than the same vintages elaborated in standard bottles. A multivariable exponential decay-type model was proposed for the theoretical time-dependent concentration of dissolved CO₂ and the subsequent CO₂ pressure in the sealed bottles during champagne aging. The CO₂ mass transfer coefficient through the crown caps used to seal champagne bottles prior to the 2000s was thus approached in situ with a global average value of K ≈ 7 × 10^-13 m³ s^-1. Moreover, the shelf-life of a champagne bottle was examined in view of its ability to still produce CO₂ bubbles in a tasting glass. A formula was proposed to estimate the shelf-life of a bottle having experienced prolonged aging, which combines the various relevant parameters at play, including the geometric parameters of the bottle. Increasing the bottle size is found to tremendously increase its capacity to preserve dissolved CO₂ and therefore the bubbling capacity of champagne during tasting. For the very first time, a long time-series dataset combined with a multivariable model indicates that the bottle size plays a crucial role on the progressive decay of dissolved CO₂ experienced by champagne during aging.

Densities, Viscosities, Thermal Expansivities, and Isothermal Compressibilities of Carbonated Hydroalcoholic Solutions for Applications in Sparkling Beverages

Densities, viscosities, isothermal compressibilities, and thermal expansivities of carbonated hydroalcoholic solutions relevant for sparkling beverages are evaluated by molecular dynamics simulations as a function of temperature and alcoholic degree. They are compared with available experimental data, among which new measurements of densities and viscosities are performed in that respect. The OPC water model seems to yield the most accurate results, and the choice of CO₂ model has little influence on the results. Theoretical densities obtained with the OPC model typically deviate by ∼2 kg m^-3 from experimental data. At low alcoholic degrees (<9% EtOH vol), experimental viscosities lie in between theoretical values derived from the Stokes-Einstein formula and the calculation of transverse current autocorrelation functions, but at higher alcoholic degrees (≥9% EtOH vol), the Stokes-Einstein relation leads to viscosities in quantitative agreement with experiments. Isothermal compressibilities estimated with a fluctuation formula roughly extend from 0.40 to 0.49 GPa^-1 in close agreement with the experimental range of values. However, thermal expansivities are found to significantly overestimate experimental data, a behavior that is partly attributed to the low temperature of maximum density of the OPC model. Despite this discrepancy, our molecular model seems to be suitable for describing several transport and thermodynamic properties of carbonated hydroalcoholic solutions. It could therefore serve as a starting point to build more realistic models for carbonated beverages, from fizzy drinks to sparkling wines.

Recent Progress in the Analytical Chemistry of Champagne and Sparkling Wines

The strong interplay between the various parameters at play in a bottle and in a glass of champagne or sparkling wine has been the subject of study for about two decades. After a brief overview of the history of champagne and sparkling wines, this article presents the key steps involved in the traditional method leading to the production of premium modern-day sparkling wines, with a specific focus on quantification of the dissolved CO₂ found in the sealed bottles and in a glass. Moreover, a review of the literature on the various chemical and instrumental approaches used in the analysis of dissolved and gaseous CO₂, effervescence, foam, and volatile organic compounds is reported.

How Many CO2 Bubbles in a Glass of Beer?

The number of bubbles likely to form in a glass of beer is the result of the fine interplay between dissolved CO₂, tiny particles or glass imperfections acting as bubble nucleation sites, and ascending bubble dynamics. Experimental and theoretical developments about the thermodynamic equilibrium of dissolved and gas-phase carbon dioxide (CO₂) were made relevant to the bottling and service of a commercial lager beer, with 5% alcohol by volume and a concentration of dissolved CO₂ close to 5.5 g L^-1. The critical radius and the subsequent critical concentration of dissolved CO₂ needed to trigger heterogeneous nucleation of CO₂ bubbles from microcrevices once the beer was dispensed in a glass were derived. The subsequent total number of CO₂ bubbles likely to form in a single glass of beer was theoretically approached as a function of the various key parameters under standard tasting conditions. The present results with the lager beer were compared with previous sets of data measured with a standard commercial Champagne wine (with 12.5% alcohol by volume and a concentration of dissolved CO₂ close to 11 g L^-1).

Under-expanded supersonic CO2 freezing jets during champagne cork popping

During champagne cork popping, the CO₂/H₂O gas mixture initially under pressure in the bottleneck freely expands into ambient air and experiences adiabatic cooling. A comparison between the condensation phenomena accompanying cork popping from bottles stored at 20° and 30°C was made. The initial headspace-to-ambient-pressure ratio much exceeded the critical ratio needed for the gas mixture to reach Mach 1, thus forming under-expanded supersonic CO₂ freezing jets expelled from the throat of the bottlenecks. It was emphasized that, after adiabatic cooling and with a saturation ratio for gas-phase CO₂ about twice higher for the bottles stored at 30°C, dry ice CO₂ clusters grow bigger and reach the critical size needed to achieve the Mie scattering of light. Moreover, during the very first millisecond following cork popping, evanescent normal shock waves (or Mach disks) were unveiled in the jets, until the reservoir-to-ambient-pressure ratio goes below a critical ratio.

Carbon Dioxide in Bottled Carbonated Waters and Subsequent Bubble Nucleation under Standard Tasting Condition

Experimental and theoretical developments, including gas-liquid thermodynamics and bubble nucleation, were made relevant to the conditioning and service of three various commercial carbonated bottled waters holding different levels of dissolved carbon dioxide comprised between about 3 g L^-1 and 7 g L^-1. The strong dependence in temperature of the partial pressure of gas-phase CO₂ found within the three batches of bottled carbonated waters was determined. Moreover, in a glass of carbonated water, the process by which the diffusion of dissolved CO₂ in tiny immersed gas pockets enabled heterogeneous bubble nucleation was formalized, including every pertinent parameter at play. From this assessment, the minimum level of dissolved CO₂ below which bubble nucleation becomes thermodynamically impossible was determined and found to strongly decrease by increasing the water temperature and size of the gas pockets acting as bubble nucleation sites. Accordingly, the total number of bubbles likely to form in a single glass of sparkling water was theoretically derived to decipher the role played by various key parameters. Most interestingly, for a given level of dissolved CO₂, the theoretical number of bubbles likely to form in a glass was found to increase by increasing the water temperature.

Monitoring gas-phase CO2 in the headspace of champagne glasses through combined diode laser spectrometry and micro-gas chromatography analysis

During Champagne or sparkling wine tasting, gas-phase CO₂ and volatile organic compounds invade the headspace above glasses, thus progressively modifying the chemical space perceived by the consumer. Gas-phase CO₂ in excess can even cause a very unpleasant tingling sensation perturbing both ortho- and retronasal olfactory perception. Monitoring as accurately as possible the level of gas-phase CO₂ above glasses is therefore a challenge of importance aimed at better understanding the close relationship between the release of CO₂ and a collection of various tasting parameters. Here, the concentration of CO₂ found in the headspace of champagne glasses served under multivariate conditions was accurately monitored, all along the 10 min following pouring, through a new combined approach by a CO₂-Diode Laser Sensor and micro-gas chromatography. Our results show the strong impact of various tasting conditions (volume dispensed, intensity of effervescence, and glass shape) on the release of gas-phase CO₂ above the champagne surface.