Beer is produced through steeping a sugar source (commonly Malted cereal grains) in water and then fermenting with yeast. Brewing has taken place since around the 6th millennium BC, and archeological evidence suggests that this technique was used in ancient Egypt. Descriptions of various beer recipes can be found in Sumerian writings, some of the oldest known writing of any sort. Brewing is done in a brewery by a brewer, and the brewing industry is part of most western economies. In 19th century Britain, technological discoveries and improvements such as Burtonisation and the Burton Union system significantly changed beer brewing.
The methods used to produce beer may be unique to a beer style, geographic region, or company.
Barrel aging
Barrel aging is a process used to add maturity and character and additional flavour to a beer. Beers are aged for a period of time in a wooden barrel. Typically, these barrels once housed wine, rum, whiskey, bourbon, tequila, and other wines and spirits. Beers are sometimes aged in barrels to achieve a variety of effects in the final product. Sour beers such as lambics are fully fermented in wood (usually oak) barrels similar to those used to ferment wine, usually including microflora other than Saccharomyces cerevisiae.
Other beers are aged in barrels which were previously used for maturing spirits. Stouts (particularly Russian Imperial Stouts) are sometimes aged in bourbon barrels. Goose Island's Bourbon County Stout was one of the first bourbon barrel-aged beers in the U.S., but the method has now spread to other companies, who have also experimented with aging other styles of beer in bourbon barrels.
By the early twenty-first century, the method of aging beer in used wine barrels had expanded beyond lambic beers to include saison, barleywine, and blonde ale. Commonly, the barrels used for this had previously aged red wine (particularly cabernet sauvignon, merlot, and pinot noir).
Some breweries produce exclusively barrel-aged beers, notably Belgian lambic producer Cantillon, and sour beer company The Rare Barrel in Berkeley, California.
In 2016 "Craft Beer and Brewing" wrote: "Barrel-aged beers are so trendy that nearly every taphouse and beer store has a section of them. "Food & Wine" wrote of barrel-aging in 2018: "A process that was once niche has become not just mainstream, but ubiquitous."
In 2017 Innis & Gunn decided that barrel aging didn't need to take place in a barrel and could be done in as little as 5 days. They attempted to redefine the term to include a forced, wood flavouring process that only they use and that the rest of the industry doesn't recognise as barrel aging. A backlash from other brewers using the term in its traditionally understood sense ensued and the outcome is, to date, unresolved.
Burtonisation
Burtonisation is the act of adding sulphate, often in the form of gypsum, to the water used for the brewing of beer, to bring out the flavour of the hops. The name comes from the town of Burton upon Trent which had several very successful breweries due to the chemical composition of the local water.
In the early 19th century, pale ale was being successfully brewed in London. In 1822, the method had been copied by the Burton upon Trent brewer Samuel Allsopp, who got a more hoppy tasting version of the beer because of the sulphate-rich local water. The clean, crisp, bitter flavour of beer brewed by Allsopp in Burton became very popular and by 1888 there were 31 breweries in the town supplying demand for Burton Ale. The characteristic whiff of sulphur indicating the presence of sulphate ions became known as the "Burton snatch". Later, the chemist C. W. Vincent analysed the waters of Burton and identified the calcium sulphate content as being responsible for accenting the hop bitterness in Burton Ale.
Burtonisation is used when a brewer wishes to accent the hops in a pale beer, such as a pale ale. It is not used for dark beers such as stout. A degree of sulphate ions in the water is also appropriate for emulation of the Czech Pilsener style, and sulphate ions are also distinctive of Dortmunder Export.
Introducing magnesium sulphate into the brewing water, or "liquor", creates a rounder, fuller taste that enhances other flavours in the beer. However, excessive dosage must be avoided to prevent undesirable consequences, which could include a laxative effect.