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).