Foam Formation of Beer and Surface Viscosity

The surface and bulk viscosities not only reduce the draining rate of the lamella but also help in restoration against mechanical, thermal, or chemical shocks. The highest foam stability is associated with appreciable Hs and yield value. 

In many cases, one finds foaming to be undesirable (such as in machine dish-washing and waste-water treatment). The main criteria for antifoaming molecules is that these exhibit following characteristics (Birdi, 2009)  

Do not form mixed monolayers with foaming agents. 

Reduce surface viscosity (thus destabilizing the foam films). 

Low boiling point liquid additives (such as ethanol). 

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