Brewing beer is an art form that has been practiced for centuries. It involves the conversion of grain starches into sugar, the extraction of sugar with water, and the fermentation of the sugar with yeast to produce a lightly carbonated drink. Although the ingredients used in beer vary depending on the style being brewed, all beer is made from four essential components: grains, hops, yeast, and water. Malted barley is the most commonly used grain in beer production, but wheat, corn, rice, and oats can also be used.
As the starches in the wort ferment, ethanol is produced and the beer is carbonated. The distinction between ales, lagers, and darker bock beers began to appear in French and Irish writings as early as the 13th century. Before grains can be used to make beer, they must undergo a malting process. When dispensing beer from a keg, a pressure apparatus called a faucet is used to apply a slight pressure of carbon dioxide (usually 2-6 PSI) to the faucet head for dispensing.
Some brewers add one or more clarifying agents to beer which normally precipitate (accumulate as a solid) from beer along with protein solids and are only found in trace amounts in the finished product. The United States ranks 14th in the world for beer production, with US breweries producing approximately 156.9 billion barrels of beer annually. The natural selection process meant that the most cold-tolerant wild yeasts would be those that would remain actively fermenting in the beer that was stored in caves. As fermentation continues, the pressure increases as CO2 continues to be produced due to the sealed container.
Recently, concern among citizen groups about excessive consumption of alcoholic beverages has initiated additional government regulation of beer. In addition to the beer itself, various acids and cleaning chemicals are required to maintain and sterilize brewing equipment. At each step of the brewing process, decisions made by the brewmaster will determine the qualities of the beer. The weakest beers are dealcoholized beers which usually have less than 0.05% alcohol (also called close beer) and light beers which generally have 4% alcohol.
Brewers who are dedicated to wild beers take advantage of natural yeasts in their immediate environment. The amount, variety, and timing of hops added make a big difference in both taste and fragrance of the beer. While amateur brewers exchange recipes freely, commercial beer recipes remain closely guarded secrets. Usually when a hefeweizen wheat beer is served 90% of it is poured into a glass and then shaken to suspend sediment before pouring it into the glass. In southern Germany (Bavaria), high carbonate content water required beers to be dark and with relatively low hop bitterness.