How Many CO 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 CO, 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 (CO) were made relevant to the bottling and service of a commercial lager beer, with 5% alcohol by volume and a concentration of dissolved CO close to 5.5 g L. The critical radius and the subsequent critical concentration of dissolved CO needed to trigger heterogeneous nucleation of CO bubbles from microcrevices once the beer was dispensed in a glass were derived. The subsequent total number of CO 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 CO close to 11 g L).