relative significance of physics and chemistry for beer foam excellence: theory and practice

ABSTRACT Bubble nucleation sites in beer glasses should be uniformly small to ensure that the foam produced comprises homogenously small bubbles with attendant reduced degrees of disproportionation. The latter phenomenon is also hindered by increased film thickness in foam, which in turn will be enhanced by increased localised viscosity, encouraged perhaps by polysaccharide‐polypeptide complexes. Erring on the “high end” of specification for carbon dioxide will promote replenishment of foam through beading. Nitrogen at a relatively low level (15–20 ppm) will hinder disproportionation with limited suppression of hop aroma and introduction of undesirable textural features. Hydrolysed hordein appears selectively to enter beer foams at the expense of the more foam‐stabilising albuminous polypeptides, suggesting that any future procedures that might selectively eliminate hydrolysed hordein components from beer would be expected not only to enhance haze stability but also foam, by eliminating species that preferentially enter into the bubble but have less foam‐stabilizing capability once they are there.