Beer head

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A glass of beer with a large head of foam Beer wuerzburger hofbraue.jpg
A glass of beer with a large head of foam
A glass of beer with the head having receded, leaving behind noticeable lacing Mai 2012 Weissbier.JPG
A glass of beer with the head having receded, leaving behind noticeable lacing

Beer head (also head or collar) [1] is the frothy foam on top of beer and carbonated beverages which is produced by bubbles of gas, predominantly carbon dioxide, rising to the surface. The elements that produce the head are wort protein, yeast and hop residue. The carbon dioxide that forms the bubbles in the head is produced during fermentation as yeasts break down sugar-rich molecules to produce ethanol and carbon dioxide. The carbonation can occur before or after bottling the beer. If the beer continues fermenting in the bottle, then it naturally carbonates and the head is formed upon opening and pouring the beer. If the beer is pasteurized or filtered then the beer must be force carbonated using pressurized gas.

Contents

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.

Closely related to the beer head is "lacing" or "lace", a white foamy residue left on the inside of the glass as the head recedes or as the beer is drunk. Just as the composition of the beer (proteins, hops, yeast residue, filtration) affects a beer's head, the amount of lacing is also closely controlled by the specific composition of the beer, and beer connoisseurs can tell much by the lacing, though strictly speaking beer quality is not readily apparent by the head or the lacing. [2]

Importance

Consumers tend to place a lot of importance on beer heads: too much of a head is undesirable because it detracts from the mass of the drink (similar to carbonated soda drinks); on the other hand, a poured beer is viewed as incomplete unless it has the specific form of head expected for the type of beer.[ citation needed ] Some connoisseurs view the head on a beer as important because it helps provide the aroma of the beer.[ citation needed ] Another opinion is that it is important for the aesthetic look of the beer. The commercial significance of the head has led to academic studies. [3]

At least one study suggests that the head assists in transport of beer after pouring by damping oscillation (sloshing) and converting vertical movement into horizontal movement. [4]

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. [5]

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.

Importance of the glass

A German wheat beer served in the traditional glassware. The glass has a half litre fill line and is designed with extra space specifically to accommodate the head. Weizenbier.jpg
A German wheat beer served in the traditional glassware. The glass has a half litre fill line and is designed with extra space specifically to accommodate the head.

Beer glassware is often designed to accentuate or accommodate the head. Many other properties of the glass can also influence a beer head, [6] such as a roughened surface at the base of glass known as a widget, providing for nucleation of carbon dioxide deep in the beverage rather than at the surface, resulting in a slower release of gas to the atmosphere.

Glass surfaces 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) [7] [8] 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.

For proper foam formation, it is also important to dry the glass thoroughly after washing. Any water in the glass can prevent excitement of the gas by covering designs set in the bottom of the glass, thus making the beer flat. Conversely, some styles such as Belgian witbier benefit from being poured into a wet glass to control the often abundant head.

Formation of 'nitrogen head'

The creamy head on beers such as Guinness is created by a widget in cans or bottles using nitrogen, or by the process of drawing keg beer from a keg using nitrogen or mixed gas (carbon dioxide and nitrogen). The use of nitrogen, which was pioneered by Guinness, creates a firm head with small bubbles while reducing the excessively acidic taste often produced by using carbon dioxide alone.

Destabilization

One mechanism of destabilization of a beer foam is due to gravitational drainage. The water or liquid between the bubbles will drain and cause the liquid and gas phases to separate. This allows for the bubbles to become close enough to merge. This can be slowed down by increasing the viscosity of the liquid. [9]

Another mechanism of destabilization is ostwald ripening. Gas will diffuse from smaller bubbles to larger bubbles due to the high pressure associated with smaller bubbles. This can be explained by Laplace pressure. This can be slowed by a low solubility of the gas. An example of this is adding Nitrogen to the beer. A large effect can be seen with only a 20ppm addition of nitrogen gas. [9]

Beer froth has been scientifically demonstrated to decay exponentially. [10] This research was awarded the 2002 Ig Nobel Prize in Physics. [11]

See also

Related Research Articles

<span class="mw-page-title-main">Draught beer</span> Beer served from a cask or keg

Draught beer, also spelt draft, is beer served from a cask or keg rather than from a bottle or can. Draught beer served from a pressurised keg is also known as keg beer.

<span class="mw-page-title-main">Real ale</span> Traditionally made and served beer

Real ale is the name coined by the Campaign for Real Ale (CAMRA) for beer that is "brewed from traditional ingredients, matured by secondary fermentation in the container from which it is dispensed, and served without the use of extraneous carbon dioxide".

<span class="mw-page-title-main">Soft drink</span> Sweetened non-alcoholic drink, often carbonated

A soft drink is any water-based flavored drink, usually but not necessarily carbonated, and typically including added sweetener. Flavors used can be natural or artificial. The sweetener may be a sugar, high-fructose corn syrup, fruit juice, a sugar substitute, or some combination of these. Soft drinks may also contain caffeine, colorings, preservatives and other ingredients.

<span class="mw-page-title-main">Homebrewing</span> Small scale brewing of beer, mead, ciders

Homebrewing is the brewing of beer or other alcoholic beverages on a small scale for personal, non-commercial purposes. Supplies, such as kits and fermentation tanks, can be purchased locally at specialty stores or online. Beer was brewed domestically for thousands of years before its commercial production although its legality has varied according to local regulation. Homebrewing is closely related to the hobby of home distillation, the production of alcoholic spirits for personal consumption, but home distillation is generally more tightly regulated.

<span class="mw-page-title-main">Ginger ale</span> Soft drink flavoured with ginger

Ginger ale is a carbonated soft drink flavoured with ginger. It is consumed on its own or used as a mixer, often with spirit-based drinks. There are two main types of ginger ale. The golden style is credited to the Irish doctor Thomas Joseph Cantrell. The dry style, a paler drink with a much milder ginger flavour, was created by Canadian John McLaughlin.

<span class="mw-page-title-main">Carbonated water</span> Water containing dissolved carbon dioxide gas

Carbonated water is water containing dissolved carbon dioxide gas, either artificially injected under pressure or occurring due to natural geological processes. Carbonation causes small bubbles to form, giving the water an effervescent quality. Common forms include sparkling natural mineral water, club soda, and commercially produced sparkling water.

<span class="mw-page-title-main">Foam</span> Form of matter

Foams are two-phase material systems where a gas is dispersed in a second, non-gaseous material, specifically, in which gas cells are enclosed by a distinct liquid or solid material. The foam "may contain more or less liquid [or solid] according to circumstances", although in the case of gas-liquid foams, the gas occupies most of the volume. The word derives from the medieval German and otherwise obsolete veim, in reference to the "frothy head forming in the glass once the beer has been freshly poured".

<span class="mw-page-title-main">Effervescence</span> Fizzing or foaming caused by the escape of gas from a solution

Effervescence is the escape of gas from an aqueous solution and the foaming or fizzing that results from that release. The word effervescence is derived from the Latin verb fervere, preceded by the adverb ex. It has the same linguistic root as the word fermentation.

<span class="mw-page-title-main">Keg</span> Small barrel, commonly used for beer

A keg is a small cask used for storing liquids. Wooden kegs made by a cooper were used to transport nails, gunpowder, and a variety of liquids. Nowadays a keg is normally constructed of stainless steel, although aluminium can be used if it is coated with plastic on the inside. It is commonly used to store, transport, and serve beer. Other alcoholic or non-alcoholic drinks, carbonated or non-carbonated, may be housed in a keg as well. Carbonated drinks are generally kept under pressure in order to maintain carbon dioxide in solution, preventing the beverage from becoming flat.

Degassing, also known as degasification, is the removal of dissolved gases from liquids, especially water or aqueous solutions. There are numerous methods for removing gases from liquids.

<span class="mw-page-title-main">Widget (beer)</span> Device placed in cans and bottles of beer to aid in the generation of froth

A widget is a device placed in a container of beer to manage the characteristics of the beer's head. The original widget was patented in Ireland by Guinness. The "floating widget" is found in cans of beer as a hollow plastic sphere, approximately 3 centimetres (1.2 in) in diameter with two small holes and a seam. The "rocket widget" is found in bottles, 7 centimetres (2.8 in) in length with the small hole at the bottom.

Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid. Aeration processes create additional surface area in the mixture, allowing greater chemical or suspension reactions.

A soda geyser is a physical reaction between a carbonated beverage, usually Diet Coke, and Mentos mints that causes the beverage to be expelled from its container. The candies catalyze the release of gas from the beverage, which creates an eruption that pushes most of the liquid up and out of the bottle. Lee Marek and "Marek's Kid Scientists" were the first to publicly demonstrate the experiment on the Late Show with David Letterman in 1999. Steve Spangler's televised demonstration of the eruption in 2005 became popular on YouTube, launching a chain of several other Diet Coke and Mentos experiment viral videos. Experiments carried out at altitudes ranging from below sea level in Death Valley to the summit of Pikes Peak have demonstrated that the reaction works better at higher elevations.

<span class="mw-page-title-main">Cornelius keg</span>

A Cornelius keg is a stainless steel canister (keg) originally used as containers by the soft drink industry. They can be used to store and dispense carbonated or nitrogenated liquids. Cornelius kegs were originally made by Cornelius, Inc.

<span class="mw-page-title-main">Soda siphon</span> Device used to store and dispense carbonated beverages

The soda siphon, also known as the seltzer bottle, siphon seltzer bottle, or just siphon) is a device for storing and dispensing carbonated beverages while maintaining the internal pressure, thereby preventing it from going flat. The carbonated beverage is dispensed using the internal pressure of the bottle, so the setup is not a true siphon in its operation.

<span class="mw-page-title-main">Sparkling wine production</span> Method in wine production

Sparkling wine production is the method of winemaking used to produce sparkling wine. The oldest known production of sparkling wine took place in 1531 with the ancestral method.

Foam fractionation is a chemical process in which hydrophobic molecules are preferentially separated from a liquid solution using rising columns of foam. It is commonly used, albeit on a small scale, for the removal of organic waste from aquariums; these units are known as "protein skimmers". However it has much broader application in the chemical process industry and can be used for the removal of surface active contaminants from waste water streams in addition to the enrichment of bio-products.

<span class="mw-page-title-main">Grodziskie</span> Style of beer from Poland

Grodziskie is a historical beer style from Poland made from oak-smoked wheat malt with a clear, light golden color, high carbonation, low alcohol content, low to moderate levels of hop bitterness, and a strong smoke flavor and aroma. The taste is light and crisp, with primary flavors coming from the smoked malt, the high mineral content of the water, and the strain of yeast used to ferment it. It was nicknamed "Polish Champagne" because of its high carbonation levels and valued as a high-quality beer for special occasions.

<span class="mw-page-title-main">Beer chemistry</span> Brewery science and beer chemical composition

The chemical compounds in beer give it a distinctive taste, smell and appearance. The majority of compounds in beer come from the metabolic activities of plants and yeast and so are covered by the fields of biochemistry and organic chemistry. The main exception is that beer contains over 90% water and the mineral ions in the water (hardness) can have a significant effect upon the taste.

Carbonated milk or soda milk is a carbonated soft drink. It can be made from powdered milk or fresh milk, and often has added flavor. In addition to modified mouthfeel, carbonated milk also has a longer shelf-life than similarly processed flat milk and a different flavor. It is sold by several companies and is most popular in Asia.

References

  1. ↑ Gregg Smith and Carrie Getty, Beer comes from the gap in the bottom of the glass. The Beer Drinker's Bible (Boulder CO, 1997).
  2. ↑ "What is beer lacing". vinepair.com. 7 December 2016. Archived from the original on 20 February 2018. Retrieved 19 February 2018.
  3. ↑ German, J. B.; McCarthy, M. J. (1989). "Stability of aqueous foams: Analysis using magnetic resonance imaging". Journal of Agricultural and Food Chemistry. 37 (5): 1321. doi:10.1021/jf00089a025.
  4. ↑ "APS Link". Archived from the original on 21 March 2021. Retrieved 7 April 2016.
  5. ↑ Onishi, Akiko; Proudlove, Michael O (1 June 1994). "Isolation of beer foam polypeptides by hydrophobic interaction chromatography and their partial characterisation". Journal of the Science of Food and Agriculture. 65 (2): 233–240. doi:10.1002/jsfa.2740650218. Archived from the original on 20 October 2012. Retrieved 28 October 2018.
  6. ↑ "Glass To Last". Hospitalitymagazine.com.au. 18 February 2010. Archived from the original on 6 March 2010. Retrieved 24 February 2010.
  7. ↑ "Food Physics". www.physics.org. Archived from the original on 8 December 2013. Retrieved 23 October 2013.
  8. ↑ "Physics, lipstick, beer". APS. Archived from the original on 21 March 2021. Retrieved 23 October 2013.
  9. 1 2 Durian, Doug (2010). "Making a frothy shampoo or beer". Physics Today. 63 (5): 62–63. Bibcode:2010PhT....63e..62D. doi: 10.1063/1.3431341 . Archived from the original on 10 June 2020. Retrieved 15 July 2019.
  10. ↑ Leike, A. (2002). "Demonstration of the exponential decay law using beer froth". European Journal of Physics. 23 (1): 21–26. Bibcode:2002EJPh...23...21L. CiteSeerX   10.1.1.693.5948 . doi:10.1088/0143-0807/23/1/304.
  11. ↑ Nadis, Steve (2002). "Bubble won't burst for spoof Nobels". Nature. 419 (6907): 549. Bibcode:2002Natur.419..549N. doi: 10.1038/419549a . PMID   12374943. S2CID   4384351.
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