The four major ingredients of beer are water, malt, hops and yeast. The particular combination, amount and variety of each of these ingredients determine the final flavor, alcoholic strength and style of the finished beer.
Although almost all modern beer styles use hops, early European brewers originally added spices such as rosemary, coriander, ginger, anise seed, and juniper berries to their beers to impart more complex flavors. Hops are used primarily used today because the bitterness derived from the hops tend to counter-balance the sweetness derived from the malt, and provide a more balanced flavor. Hops may also be added to beer to impart a floral or spicy aroma and flavor. Another benefit early brewers found was that hops also tended to help preserve their beers longer than unhopped beers.
The earliest written records of hop cultivation come from 8th and 9th century A.D. from the Hallertau district in Germany, now famous for their Hallertau Mittelfruh hop variety. The earliest actual brewing records explicitly noting the addition of hops come from 14th century Germany.
Although there are microorganisms that can spoil beer, such as lactobacillus, there are no known human pathogens than can live in beer. This is commonly thought to be due to the alcohol in the beer, however it is actually due to the pH; typically in the range of 4.0 to 4.4.  
Beers fall in to many categories, including lagers, ales, bitters. stouts, wheats, and lambics. There are also "hybrid" beers, such as Cream Ales, Kolsch and California Common Beers (Steam Beers).
Lagers are cold fermented with the Saccharomyces pastorianus variety of yeast, typically between 46 and 56 F. Complete fermentation of lager beers takes from six weeks to nine months. This brewing technique originated in Germany, where the word ‘lagern’ literally means "to store". Common styles of lager beer are Pilsner and Bock. Most beers brewed by the major American breweries are lagers.
Ales are fermented with the ‘S. cerevisiae’ variety of yeast, at temperatures higher than lagers, typically between 55 and 75 F. The higher fermentation temperature of ales tends to produce beers with a more complex, fruity flavor, usually derived from esters produced by the yeast during fermentation. Common varieties of ales include Pale Ale, India Pale Ale, and Brown Ale.
Stouts are made with roasted malts and grains and top fermenting yeast.
Lambic is probably the oldest style of beer produced in the world today. A later style is that of ale. Ales are fermented using top-fermenting yeasts, yeasts which congregate at the top of the wort and tend to work best at higher temperatures than Lager yeasts. The top fermentation and warm fermentation temperatures add complex flavors to the beer. "Real Ale" is a term created by the Campaign for Real Ale, and refers to beers brewed by traditional methods, from traditional ingredients and, vitally, served from the vessel in which they have been conditioned. Real Ale has become a cult drink in the United Kingdom and affcionados happily descrive themselves as "Real Ale Snobs" (non-afficionados tend to use a less family-friendly subrique!).
Barley wine is a strong variety of beer as a result of the large quantity of malt used during fermentation. They are distinguished by their relatively long maturation periods, giving them a richness and variety of flavors. It is thought that the name "barley wine" was given in an attempt to give them equal standing in the drinks market with wine as it is conventionally known.
Bitters are light beers so-called because of the sharp flavor given heavier use of hops. Bitters are traditionally associated with British pub culture, although American varieties such as Goose Island Honkers Ale are available.
Heavy beers are those that contain a higher-than-normal volume of caramalised sugars, thus giving them a "heavy" mouth-feel when drunk.
Lager is a,comparitively, recent introduction. True lagers are brewed at cold temperatures, using bottom fermenting yeast and are then conditioned (or "lagered") for extented periods at very low temperatures. Whilst the ale process adds complexflavors to the beer the lager brewing and conditioning process tends to produce a clean, unified and crisp taste.
Lambic is a sub style of sour ales which was originally produced by brewers around Brussels in the Senne Valley. Lambic comes in two forms, straight (unblended) Lambic and Fruit Lambic. Lambic beers use hops aged for three years to remove any bitterness, and are added primarily for their preservative effect. These beers are allowed to spontaneously ferment by a variety of wild micro-organisms. These micro-organisms include wild yeasts and bacteria such as pediococcus and lactobacillus. The bacteria produce acids during fermentation and are capable of fermenting more sugars that regular yeasts. This results in a beer that can be extremely dry and astonishingly tart.
Due to the specific flavors that the wild yeasts and micro-organisms in this region of the world produce in Lambic beer, production of this style has not spread to other regions like other beers styles of beer have. Versions of Lambics produced with pure cultures tend to lack the depth of flavor that the Belgian brewers are able to produce.
Evolution of Styles
Historically beer styles evolved regionally due to the ingredients that were available to the local brewers. For example, in Scotland hops did not grow well, and were expensive to import. So beers produced by Scottish brewers typically had very low level of bitterness and hop flavor, but well developed malt flavors.
The earliest known evidence of beer and brewing comes from Sumeria around 4,000 B.C. The evidence comes from clay tablets inscribed with the Hymn to Ninkasi, the Sumerian's Goddess of brewing, where the hymn contains a rudimentary recipe for beer.
Most of the world's beer come from German brewers, who established breweries across Europe, North America, Australia and China.
Beer was a staple on the Mayflower and colonists began home brewing early. Even Harvard College had its own brew house. Having greater stability in processing and storage, rum and whiskey soon became more common. With the coming of lager in 1842, however, new interest in brewing - by people with such names as Schaefer, Schmidt, Best, Pabst, Anheuser, Miller, and Busch - revitalized the popularity of beer. Milwaukee's supply of natural ice made it a prime location for the brewing industry, and by the 1870s beer had become America's drink of choice. Anti-German feelings combined with opposition to alcohol led to Prohibition. After an interlude in the 1920s when Prohibition closed the breweries, they reopened in 1933. By World War II beer was no longer seen as "German" and was readily available to troops who continued to drink it when they returned to the United States.
Major league baseball featured beer in its refreshment offerings and the working class found beer, baseball, and the saloon "places" of refuge and camaraderie. Since that time, beer has remained America's alcoholic drink of choice because of its appeal to the working class.
The major national brands have been consolidated and are now controlled by two international conglomerates based in Europe. Since 2002 MillerCoors has been owned by SABMiller, which is based in London. Since 2008 Anheuser-Busch (maker of Budweiser) has been owned by Anheuser-Busch InBev, based in Belgium. Today there are hundreds of locally owned "microbreweries", and imports are important from Europe, Mexico and Japan.
- Alcoholic drinks
- Bud Light Lime
- Home brewing
- Narragansett Beer
- Prohibition in the United States
- Real ale
- Cochran, Thomas C. The Pabst Brewing Company: the history of an American business (1948), excellent business history.
- Downard, William L. Dictionary of the History of the American Brewing and Distilling Industries. (1980). 268 pp.
- Downard, William L. The Cincinnati Brewing Industry: A Social and Economic History. (1973). 173 pp.
- McGovern, Patrick E. Uncorking the Past: The Quest for Wine, Beer, and Other Alcoholic Beverages (2009)
- Rudin, Max. "Beer And America," American Heritage 2002 53(3): 28-38. 0002-8738 online edition