The foam on top of beer is called a head. It is caused by bubbles of carbon dioxide rising to the surface. The carbon dioxide may be produced naturally by the activity of the brewers yeast, or artificially by dissolving carbon dioxide under pressure into the liquid. The density and longevity of the head will be determined by the type of starch from which the beer was fermented. Wheat starch tends to produce larger and longer lasting heads than barley starch. Image File history File links Download high resolution version (1201x1800, 130 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Pale lager Beer head ... Image File history File links Download high resolution version (1201x1800, 130 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Pale lager Beer head ... A selection of bottled beers A selection of cask beers Beer is the worlds oldest and most popular alcoholic beverage, selling more than 133 billion litres (35 billion gallons) per year. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... Binomial name Saccharomyces cerevisiae Meyen ex E.C. Hansen Saccharomyces cerevisiae is a species of budding yeast. ... Starch is a complex carbohydrate which is insoluble in water, it is used by plants as a way to store excess glucose. ... Fermentation typically refers to the conversion of sugar to alcohol using yeast. ... Species T. boeoticum T. compactum T. dicoccoides T. dicoccon T. durum T. monococcum T. spelta T. sphaerococcum References:   ITIS 42236 2002-09-22 Wheat (Triticum spp. ... Binomial name Hordeum vulgare L. Barley (Hordeum vulgare) is a major food and animal feed crop, a member of the grass family Poaceae. ...

Description

It consists of foamy bubbles. It is called a head because it is at the top of the beer. The head on beer is sometimes very small, although on some beers it is large, and is large enough, sometimes, to overflow from the beer glass.

Causes

The foam on top of beer is caused by the carbonation created by the carbon dioxide made by the activity of brewer's yeast. 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. Bubbles of carbon dioxide float to the surface of a carbonated soft drink. ... Carbon dioxide is an atmospheric gas comprised of one carbon and two oxygen atoms. ... Brewers yeast (also known as brewers yeast or brewing yeast) can mean any live yeast used in brewing. ...

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.

This process yields the "fizz" and the head to beer.

Rinsing the glass

While glass is completely nonporous, its surface can retain oil from the skin, aerosolized oil from nearby cooking, and traces of fat from food. When these oils come in contact with beer there is a significant reduction in the amount of head (foam) that is found on the beer, and the bubbles will tend to stick to the side of the glass rather than rising to the surface as normal. Also it is important to make sure the glass is well dried after washing. If there is water in the glass it can prevent excitement of the gas by covering designs set in the bottom of the glass, thus making the beer flat.

Forced carbonation

The carbonation in filtered beers is created by injecting carbon dioxide artificially into the beer. Filtered beer is beer which has been cleaned of significant contact with yeast. ...

Nitrogen head

The creamy head on beers such as Guinness is created by a widget. It can also be created by a rocket widget in bottled Guinness. World War II era advert. ... Guinness floating widget The Original Widget The floating widget found in canned Guinness Draught is a hollow sphere, 3 cm (1. ... World War II era advert. ...

External links

• The Tragedy of a Nice Beer Foam Head - Peter Keusch
• Beer Foam - Wolfgang Kunze
• There is plenty of physics involved in opening a bottle of beer - Richard Kingsley
• One beer please - Vivienne Baillie Gerritsen