Elements of beer style
Beers may be categorized based on a number of factors.
The visual characteristics that may be observed in a beer are colour, clarity, and nature of the head. Colour is usually imparted by the malts used, notably the adjunct malts added to darker beers, though other ingredients may contribute to the colour of some styles such as fruit beers. Colour intensity can be measured by systems such as EBC, SRM or Lovibond, but this information is rarely given to the public.[why?]
Many beers are transparent, but some beers, such as hefeweizen, may be cloudy due to the presence of yeast making them translucent. A third variety is the opaque or near-opaque colour that exists with stouts, porters, schwarzbiers (black beer) and other deeply coloured styles. Thickness and retention of the head and the lace it can leave on the glass, are also factors in a beer's appearance.
The aroma in a beer may be formed from the malt and other fermentables, the strength and type of hops, the alcohol, esters, and various other aromatic components that can be contributed by the yeast strain, and other elements that may derive from the water and the brewing process.
The taste characteristics of a beer may come from the type and amount of malt used, flavours imparted by the yeast, and strength of bitterness. Bitterness can be measured on an International Bitterness Units scale, and in North America a number of brewers record the bitterness on this scale as IBUs.
The feel of a beer in the mouth, both from thickness of the liquid and from carbonation, may also be considered as part of a beer's style. A more dextrinous beer feels thicker in the mouth. The level of carbonation (or nitrogen, in "smooth" beers) varies from one beer style to another. For some beers it may give the beer a thick and creamy feel, while for others it contributes a prickly sensation.
The strength of beer is a general term for the amount of alcohol present. It can be quantified either indirectly by measurement of specific gravity, or more directly by determining the overall percentage of alcohol in the beer.
Measurement of the specific gravity of the beer has been used to estimate the strength of beer by measuring its density. Several different scales have been used for the measurement of gravity, including the Plato, Baumé, Balling, and Brix scales, with the Plato scale being the most common modern measure.
This approach relies on the fact that dissolved sugars and alcohol each affect the density of beer differently. Since sugars are converted to alcohol during the process of fermentation, gravity can be used to estimate the final alcohol. In beer brewing, a distinction is made between the original gravity, the gravity of the wort before fermentation has begun, and the final gravity of the product when fermentation has completed. Since the concentration of sugars is directly proportional to the gravity, the original gravity gives a brewer an idea of the potential alcoholic strength of the final product. After fermentation, the differences between the final and original gravities indicates the amount of sugar converted into alcohol, allowing the concentration of alcoholic strength to be calculated.
The original gravity of a beer was the basis for determining taxation in both the UK and Ireland from 1880 until the late 20th century, and a legacy of that system remains in the largely arbitrary division of bitter into "bitter", "best bitter", and "special bitter" substyles. In continental Europe, the strength of a beer in degrees Plato is sometimes used by a brewery to distinguish a particular beer produced in a line. For example, Rochefort Brewery produces three beers, all dissimilar in colour, flavour, and aroma; and sells them as Rochefort 6, Rochefort 8, and Rochefort 10, the numbers referring to the original gravities of the beers. Westvleteren Brewery, meanwhile, produces three beers, and calls them Blonde, 8, and 12.
Modern classification of the strength of alcoholic beverages for the purposes of taxation and regulation typically discriminates according to the percentage of alcohol by volume, generally abbreviated as abv. Additionally, although less common, some brewers throughout the world use also alcohol by weight (abw), particularly on low-point versions of popular domestic beer brands. At the relatively low alcohol concentrations of beer, the alcohol percentage by weight is roughly 4/5 of the abv (e.g., 3.2% abw is equivalent to 4.0% abv), but this becomes increasingly inaccurate as the alcohol concentration increases.
Before the development of modern brewing practices and the complete understanding of the biochemistry of yeast, the final abv of a beer could not be precisely controlled, making its value inconsistent and therefore unsuitable as a determinant for taxation or regulation. Contemporarily, though, abv is often used in to determine the duty on beer and cider, and sales of beer and cider above a certain abv is sometimes restricted or prohibited. For example, in Texas, beers below 4% abv cannot be sold as stout regardless of other stylistic considerations.
A variety of yeasts are used in making beer, most of which are strains of either top-fermenting yeast or bottom-fermenting yeast. Different strains impart different flavour and aroma characteristics, and may vary in which complex sugars they can ferment and how high their alcohol tolerance is, both of which are factors in attenuation. Some beers use other microbes in addition to yeasts, such as Lactobacillus or Brettanomyces. For example, the distinctive flavour and aroma of Belgian Abbey ales largely result from the yeast strains used to ferment the beer. There are a few modern styles, notably lambics, where spontaneous fermentation is used — that is, rather than being inoculated in a controlled fashion with a nurtured yeast, the unfermented wort is allowed to be colonized by microorganisms present in the environment.
Most beers use barley malt as their primary source of fermentable sugars, and some beer styles mandate it be used exclusively, such as those German styles developed under Reinheitsgebot. Some beer styles can be considered varietals, in the same sense as wine, based on their malt bill.
Kilned pale malts form the basis of most beer styles now in production, with styles that use other grains as a base distinguished by those grains (for example bock, which uses Munich malt as a base). The Rauchbier and Grätzer styles are distinguished by the use of smoked malt.
The inclusion of some grains such as corn and rice is often viewed as making less of a flavour contribution and more of an added source of fermentable sugars. Rice in particular "is considered by many [craft] brewers what the nasty industrial brewers use to water down their beer".
This is due in large part to the use of rice by large scale American breweries. While it is commonly held that these breweries introduced these grains to their formulas during war shortages, author Maureen Ogle states "The mythology is that these giant beer makers began adding rice and corn to their beer after World War II to water it down, but that's simply not true. The American brewing industry was built in the late 19th century by first-generation German American immigrants such as Adolphus Busch, Adolph Coors and Frederick Miller. Although these men, craft brewers themselves, initially re-created the full-bodied beers of their homeland, many Americans had not developed a taste for the malt-heavy style. They needed a domestic ingredient that would make the beers more effervescent, bubbly and lighter. Rice and corn did that – it was a desired flavor, not inexpensive filler."
Hops contribute bitterness, flavour and aroma to a beer in different ways depending on when they are added during the brewing process. How much hop bitterness and aroma is appropriate varies between beer styles. There are many varieties of hops, some of which are associated with beers from specific regions. For example, Saaz hops are associated with Czech Pilsners; Hallertau and Tettnanger are two of the "noble" hop varieties one expects to find in German beers, and Kent Goldings are an English variety.
Water is the main ingredient in beer, and, though water itself is flavourless, the chemical composition can have an influence on the finished taste; indeed, some brewers regard it as "the most important ingredient in beer". In particular, two styles of beer are especially noted for their water chemistry: pale ale, for which the process of Burtonisation is widespread; and Pilsner.
Fruits and spices are key ingredients in some beer styles. While fruit beers and herb beers are often listed as style categories unto themselves, fruits and spices are sometimes used to contribute to the flavour and aroma profile of other styles. Vegetables have also been used in beers. Honey, molasses, candy sugar, or other fermentable sugars may be added to impart their distinct flavours to a beer. While not an ingredient per se, some brewers have experimented with aging their beer in barrels previously used for bourbon or other distilled spirits, imparting the flavour of both the wood and the spirit to the beer.
Alcoholic beverages made from the fermentation of sugars derived from non-grain sources are generally not called "beer," despite being produced by the same yeast-based biochemical reaction. Fermented honey is called mead, fermented apple juice is called cider, fermented pear juice is called perry (sometimes, pear cider), fermented plum juice is called plum jerkum, and fermented grape juice is called wine. Chinese jiu and Japanese sake are made using much the same process as beer with one additional step in the fermentation as well as using rice instead of primarily barley malt.