Beer Measurement

Beer is measured and assessed by bitterness, by strength and by colour. The perceived bitterness is measured by the International Bitterness Units scale (IBU), defined in co-operation between the American Society of Brewing Chemists and the European Brewery Convention.[91] The international scale was a development of the European Bitterness Units scale, often abbreviated as EBU, and the bitterness values should be identical.[92]
Colour

Paulaner dunkel - a dark lager
Beer colour is determined by the malt.[93] The most common colour is a pale amber produced from using pale malts. Pale lager and pale ale are terms used for beers made from malt dried with coke. Coke was first used for roasting malt in 1642, but it was not until around 1703 that the term pale ale was used.[94][95]
In terms of sales volume, most of today's beer is based on the pale lager brewed in 1842 in the town of Pilsen in the present-day Czech Republic.[96] The modern pale lager is light in colour with a noticeable carbonation (fizzy bubbles) and a typical alcohol by volume content of around 5%. The Pilsner Urquell, Bitburger, and Heineken brands of beer are typical examples of pale lager, as are the American brands Budweiser, Coors, and Miller.
Dark beers are usually brewed from a pale malt or lager malt base with a small proportion of darker malt added to achieve the desired shade. Other colourants—such as caramel—are also widely used to darken beers. Very dark beers, such as stout, use dark or patent malts that have been roasted longer. Some have roasted unmalted barley.[97][98]
Strength
See also: Beer measurement#By strength
Beer ranges from less than 3% alcohol by volume (abv) to around 14% abv, though this strength can be increased to around 20% by re-pitching with champagne yeast,[99] and to 55% abv by the freeze-distilling process.[100] The alcohol content of beer varies by local practice or beer style.[101] The pale lagers that most consumers are familiar with fall in the range of 4–6%, with a typical abv of 5%.[102] The customary strength of British ales is quite low, with many session beers being around 4% abv.[103] Some beers, such as table beer are of such low alcohol content (1%–4%) that they are served instead of soft drinks in some schools.[104]
The alcohol in beer comes primarily from the metabolism of sugars that are produced during fermentation. The quantity of fermentable sugars in the wort and the variety of yeast used to ferment the wort are the primary factors that determine the amount of alcohol in the final beer. Additional fermentable sugars are sometimes added to increase alcohol content, and enzymes are often added to the wort for certain styles of beer (primarily "light" beers) to convert more complex carbohydrates (starches) to fermentable sugars. Alcohol is a by-product of yeast metabolism and is toxic to the yeast; typical brewing yeast cannot survive at alcohol concentrations above 12% by volume. Low temperatures and too little fermentation time decreases the effectiveness of yeasts and consequently decreases the alcohol content.
Exceptionally strong beers
The strength of beers has climbed during the later years of the 20th century. Vetter 33, a 10.5% abv (33 degrees Plato, hence Vetter "33") doppelbock, was listed in the 1994 Guinness Book of World Records as the strongest beer at that time,[105][106] though Samichlaus, by the Swiss brewer Hürlimann, had also been listed by the Guinness Book of World Records as the strongest at 14% abv.[107][108][109] Since then, some brewers have used champagne yeasts to increase the alcohol content of their beers. Samuel Adams reached 20% abv with Millennium,[99] and then surpassed that amount to 25.6% abv with Utopias. The strongest beer brewed in Britain was Baz's Super Brew by Parish Brewery, a 23% abv beer.[110][111]
The product that is claimed to be the strongest beer made is The End of History, a 55% Belgian ale,[100] made by the Scottish brewery BrewDog in 2010, who also made Sink The Bismarck!, a 41% abv IPA,[112] and Tactical Nuclear Penguin, a 32% abv Imperial Stout; these are made using the eisbock method of freeze distilling in which the brewery freeze distils a strong ale, gradually removing the ice and freezing again until the beer reaches the strength required,[113][114] a process that may class the finished products as spirits rather than beer.[115] The German brewery Schorschbräu's Schorschbock—a 31% abv eisbock,[116][117][118] and Hair of the Dog's Dave—a 29% abv barley wine made in 1994, both used the same freeze distilling method.[119] A 60% abv blend of beer with whiskey was jokily claimed as the strongest beer by a Dutch brewery in July 2010.[120][121]
Serving
Draught
Main articles: Draught beer, Keg beer, and Cask ale

Draught beer keg fonts at the Délirium Café in Brussels
Draught beer from a pressurised keg is the most common method of dispensing in bars around the world. A metal keg is pressurised with carbon dioxide (CO2) gas which drives the beer to the dispensing tap or faucet. Some beers may be served with a nitrogen/carbon dioxide mixture. Nitrogen produces fine bubbles, resulting in a dense head and a creamy mouthfeel. Some types of beer can also be found in smaller, disposable kegs called beer balls.
In the 1980s, Guinness introduced the beer widget, a nitrogen-pressurised ball inside a can which creates a dense, tight head, similar to beer served from a nitrogen system.[122] The words draft and draught can be used as marketing terms to describe canned or bottled beers containing a beer widget, or which are cold-filtered rather than pasteurised.

A selection of cask beers
Cask-conditioned ales (or cask ales) are unfiltered and unpasteurised beers. These beers are termed "real ale" by the CAMRA organisation. Typically, when a cask arrives in a pub, it is placed horizontally on a frame called a "stillage" which is designed to hold it steady and at the right angle, and then allowed to cool to cellar temperature (typically between 12–14 °C / 54–57 °F),[123] before being tapped and vented—a tap is driven through a (usually rubber) bung at the bottom of one end, and a hard spile or other implement is used to open a hole in the side of the cask, which is now uppermost. The act of stillaging and then venting a beer in this manner typically disturbs all the sediment, so it must be left for a suitable period to "drop" (clear) again, as well as to fully condition—this period can take anywhere from several hours to several days. At this point the beer is ready to sell, either being pulled through a beer line with a hand pump, or simply being "gravity-fed" directly into the glass.
Draught beer's environmental impact can be 68% lower than bottled beer due to packaging differences.[124][125] Home brewing can reduce the environmental impact of beer via less packaging and transportation.[126] A life cycle study of one beer brand, including grain production, brewing, bottling, distribution and waste management, shows that the CO2 emissions from a 6-pack of micro-brew beer is about 3 kilograms (6.6 pounds).[127] The loss of natural habitat potential from the 6-pack of micro-brew beer is estimated to be 2.5 square meters (26 square feet).[128] Downstream emissions from distribution, retail, storage and disposal of waste can be over 45% of a bottled micro-brew beer's CO2 emissions.[127] Where legal, the use of a refillable jug, reusable bottle or other reusable containers to transport draught beer from a store or a bar, rather than buying pre-bottled beer, can reduce the environmental impact of beer consumption.[129]
Packaging
Main articles: Beer bottle and Beverage can

A beer can with the Wikipedia logo
Most beers are cleared of yeast by filtering when packaged in bottles and cans.[130] However, bottle conditioned beers retain some yeast—either by being unfiltered, or by being filtered and then reseeded with fresh yeast.[131] It is usually recommended that the beer be poured slowly, leaving any yeast sediment at the bottom of the bottle. However, some drinkers prefer to pour in the yeast; this practice is customary with wheat beers. Typically, when serving a hefeweizen, 90% of the contents are poured, and the remainder is swirled to suspend the sediment before pouring it into the glass. Alternatively, the bottle may be inverted prior to opening. Glass bottles are always used for bottle conditioned beers.
Many beers are sold in cans, though there is considerable variation in the proportion between different countries. In Sweden in 2001, 63.9% of beer was sold in cans.[132] People either drink from the can or pour the beer into a glass. Cans protect the beer from light (thereby preventing "skunked" beer) and have a seal less prone to leaking over time than bottles. Cans were initially viewed as a technological breakthrough for maintaining the quality of a beer, then became commonly associated with less expensive, mass-produced beers, even though the quality of storage in cans is much like bottles.[133] Plastic (PET) bottles are used by some breweries.[134]
Temperature

Édouard Manet's The Waitress showing a woman serving beer
The temperature of a beer has an influence on a drinker's experience; warmer temperatures reveal the range of flavours in a beer but cooler temperatures are more refreshing. Most drinkers prefer pale lager to be served chilled, a low- or medium-strength pale ale to be served cool, while a strong barley wine or imperial stout to be served at room temperature.[135]
Beer writer Michael Jackson proposed a five-level scale for serving temperatures: well chilled (7 °C/45 °F) for "light" beers (pale lagers); chilled (8 °C/46 °F) for Berliner Weisse and other wheat beers; lightly chilled (9 °C/48 °F) for all dark lagers, altbier and German wheat beers; cellar temperature (13 °C/55 °F) for regular British ale, stout and most Belgian specialities; and room temperature (15.5 °C/59.9 °F) for strong dark ales (especially trappist beer) and barley wine.[136]
Drinking chilled beer began with the development of artificial refrigeration and by the 1870s, was spread in those countries that concentrated on brewing pale lager.[137] Chilling beer makes it more refreshing,[138] though below 15.5 °C (59.9 °F) the chilling starts to reduce taste awareness[139] and reduces it significantly below 10 °C (50 °F).[140] Beer served unchilled—either cool or at room temperature, reveal more of their flavours.[141] Cask Marque, a non-profit UK beer organisation, has set a temperature standard range of 12°-14 °C (53°-57 °F) for cask ales to be served.[142]
Vessels
Main article: Beer glassware
Beer is consumed out of a variety of vessels, such as a glass, a beer stein, a mug, a pewter tankard, a beer bottle or a can. The shape of the glass from which beer is consumed can influence the perception of the beer and can define and accent the character of the style.[143] Breweries offer branded glassware intended only for their own beers as a marketing promotion, as this increases sales.[144]
The pouring process has an influence on a beer's presentation. The rate of flow from the tap or other serving vessel, tilt of the glass, and position of the pour (in the centre or down the side) into the glass all influence the end result, such as the size and longevity of the head, lacing (the pattern left by the head as it moves down the glass as the beer is drunk), and turbulence of the beer and its release of carbonation.[145]