Beer head (also head or Kräusen) is the frothy foam on top of beer which is produced by bubbles of gas, typically carbon dioxide, rising to the surface. A head is produced during fermentation, and consists of wort protein, yeast and hop residue. The foam is attributed to yeast eating sugars and building up CO2 in the process. The fermentation may take place in the brewery or it may be a secondary fermentation taking place in the cask or bottle. If the beer is no longer fermenting, due to filtering or pasteurising, then a head cannot naturally occur, so a head is produced by force carbonating the beer by inserting carbon dioxide and sometimes a mixture of carbon dioxide and nitrogen gas.
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.
Read more about Beer Head: Importance, Formation Through Carbon Dioxide, Chemical Composition, Importance of The Glass, Formation of 'Nitrogen Head'
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