Beer head (also known as the head) is produced by bubbles of carbon dioxide rising to the surface.
The density and longevity of the head will be determined by the type of malt and adjunct from which the beer was fermented. Different mash schedules and cereal sources influence head retention.
In general, wheat tends to produce larger and longer lasting heads than barley.
Formation through carbon dioxide
The carbon dioxide may be produced naturally through the activity of brewers yeast, or artificially by dissolving carbon dioxide under pressure into the liquid. The beer head is created by the carbon dioxide produced as a byproduct of the metabolism of brewer's yeast acting upon starches and sugars found in the wort.
Chemical composition
While the actual foam activity of beer depends on the presence of carbon dioxide, it is the surface-active materials like amphipathic polypeptides from malt that determine size, shape and length of the foam.
Beer foam consists of polypeptides of five different classifications, divided by their relative hydrophobicity. As the hydrophobicity of the polypeptide groups increases, so does the stability of the foam[1].
Carbonation occurs when carbon dioxide is dissolved in water or an aqueous solution. This process is generally represented by the following reaction, where water and gaseous carbon dioxide react to form a dilute solution of carbonic acid.
