MAPPING OF GAS-PHASE CO₂ IN THE HEADSPACE OF CHAMPAGNE GLASSES BY USING AN INFRARED LASER SENSOR UNDER STATIC TASTING CONDITIONS

Abstract

From the chemical angle, Champagne wines are complex hydro-alcoholic mixtures supersaturated with dissolved carbon dioxide (CO₂). During the pouring process and throughout the several minutes of tasting, the headspace of a champagne glass is progressively invaded by many chemical species, including gas-phase CO₂ in large majority. CO₂ bubbles nucleated in the glass and collapsing at the champagne surface act indeed as a continuous paternoster lift for aromas throughout champagne or sparkling wine tasting [1]. Nevertheless, inhaling a gas space with a concentration of gaseous CO₂ close to 30% and higher triggers a very unpleasant tingling sensation, the so-called “carbonic bite”, which might completely perturb the perception of the wine’s bouquet. Therefore, to enhance the champagne tasting experience, monitoring gas-phase CO₂ in the headspace of champagne glasses has become a topic of interest over the last dozen years [2-5].

Based on the Tunable Diode Laser Absorption Spectroscopy (TDLAS), a CO₂-Diode Laser Sensor (CO₂- DLS) with two distributed feedback (DFB) diode lasers emitting at 4986.0 and 3728.6 cm-1 was deve- loped to allow the fine monitoring of gas-phase CO₂ over a large concentration range from 0.5% to 100%. Moreover, to perform the simultaneous spatial mapping of CO₂ along a multipoint array in the headspace of champagne glasses, two couples of galvanometric mirrors were combined with a couple of parabolic mirrors symmetrically positioned on either side of the glass headspace [4,5]. Thereby, the CO₂-DLS shows a very high temporal resolution thus enabling an accurate monitoring and mapping of gas-phase CO₂ in the headspace of glasses.

Real-time monitoring of gas-phase CO₂ was thus performed with the CO₂-DLS, under static tasting conditions, in the headspace of several types of champagne glasses showing distinct shapes and volume capacities (including the 21 cL INAO glass, a worldwide reference for sensory evaluation). Moreover, a brand-new glass recently proposed as a universal glass for the tasting of still and sparkling wines (the 45 cL ŒnoXpert) was also examined. A kind of CO₂ fingerprint, evolving in space and time, was unveiled for each glass type. After a strong increase of the gas-phase CO₂ concentration observed within the several seconds of the pouring step, a vertical stratification of CO₂ was unveiled in the headspace of glasses, with decreasing CO₂ concentrations while moving away from the champagne surface, and as time elapses.