Because beer is composed mainly of water, the source of the water and its characteristics have an important effect on the character of the beer. Many beer styles were influenced or even determined by the characteristics of the water in the region. Among malts, barley malt is the most often and widely used owing to its high enzyme content but other malted and unmalted grains are widely used, including wheat, rice, maize, oats, and rye. Hops are a fairly recent addition to beer and are not universally used even today. They contribute a bitterness that balances the sweetness of the malt and have a mild antibiotic effect that favors the activity of brewer's yeast over less desirable organisms. Dozens of strains of natural or cultured yeasts are used by brewers, roughly sorted into three kinds: ale or top-fermenting, lager or bottom fermenting, and wild yeasts. Yeast metabolize the sugars extracted from the grains, producing many compounds including alcohol and carbon dioxide.
Known to the Egyptians, Babylonians, and probably to earlier civilizations, beer became the common beverage in northern climates not conducive to grape cultivation. Although beer and wine are both fermented and undistilled, wine is made from basic materials rich in natural sugar, while beer is made from materials high in starch. Starches must be converted to sugar before fermentation can occur.
Most beers until relatively recent times were ales. Lagers were discovered by accident in the sixteenth century when beer was stored in cool caverns underground for long periods; it has since largely outpaced ale in popularity. (See below for the distinction.) Hops are also a relatively recent addition, although they are now nearly universal in beers. Hops are a citric flower that adds bitterness and flavour to beer, and changes its texture somewhat.
There are many different types of beers including:
Lager beers, probably the most common type of beer consumed, are aged beers of German origin, taking their name from the German lagern ("to store"). Bottom-fermented, they are stored at a low temperature for weeks or months, clearing, acquiring mellowness, and becoming charged with carbon dioxide. Although many styles of lager beer exist, most of the lager beer produced is light in colour, high in carbonation with a mild hop flavour and an alcohol content of 3-5 percent by volume. Styles of lager include: Pilsener, Dortmund, Munich, .
Top-fermented beers, particularly popular in Great Britain and Ireland, include mild, bitter, pale ale, porter, and stout. Top-fermented beers tend to be more flavorful including a variety of grain flavors and fermentation flavors. Stylistic differences among top-fermented beers are decidedly more varied than those found among bottom-fermented beers and many beer styles are difficult to categorize such as the California common beer (produced using a lager yeast at ale temperatures), wheat beers (often produced using an ale yeast and then lagered, sometimes with a lager yeast), or lambics[?] (which employ wild yeasts, naturally-occurring in the Payottenland region of Belgium).
Social aspects of beer Beer is associated with holidays such as Oktoberfest and is often consumed in conjunction with football games. In contrast to wine, beer is generally associated with the lower and middle classes rather than the upper classes.
Beers, and similar beverages made from raw materials other than barley, include hundreds of local African drinks made from millet, sorghum, and other available starch crops; Nordic mead, made from honey; Finnish sahti[?]; Russian/Ukrainian kvass; Chinese samshu, Korean suk, and Japanese sake, all brewed from rice; and pulque[?], an indigenous Mexican beer made from the fermented sap of the agave plant. The Mexicans and the Japanese also brew and export several brands of Western-style beer.
A half pint of beer typically contains about one unit of alcohol (although alcohol content can vary significantly with style and brewer).