Analyzing Foam Instability in Commercial Beers

Abstract

The foam stability of beer is impacted by positive and negative forces that counteract each other. A series of beers was investigated to assess whether foam performance was primarily impacted by the level of foam-promoting polypeptide or by the presence of inhibitory lipids. The studies involved ultrafiltration of beers and comparison of the foam stability of a standard protein (egg albumin) when foamed in the ultrafiltrates, the retentate, a reference alcohol solution, and the native beer. In all cases, the foam stability of the beers was boosted by adding protein, and there was also evidence of foam-inhibitory material in both the low and high molecular weight fractions. Hydrolysis studies with papain generated some evidence that there may be low molecular weight peptide material that is foam negative. Experiments in which beers and ultrafiltration fractions were treated with an immobilized lipid-binding protein confirmed there are foam-damaging lipids in both the high and low molecular weight fractions from beer. Improved foam performance of commercial beers demands attention both to boosting foam-promoting polypeptide levels and to attending to lipids and lipid oxidation throughout the process.