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Steam beer is a highly effervescent beer made by brewing lager yeasts at warmer fermentation temperatures. It has two distinct but related meanings: *Historic steam beer produced in California from the mid-19th century to the mid-20th century; *Modern California common beer, a competition category name for the beer family which includes steam beers such as Anchor Steam beer. Historic steam beer, associated with San Francisco and the U.S. West Coast, was brewed with lager yeast without the use of true refrigeration〔(【引用サイトリンク】url=http://www.nps.gov/nr/travel/nevada/bre.htm )〕 (by ice or mechanical means). It was an improvised process, originating out of necessity, perhaps as early as the Gold Rush and at least 1860 in Nevada.〔 It was considered a cheap and low-quality beer, as shown by references to it in literature of the 1890s and 1900s. Modern steam beer, also known as ''California common beer'', was originated by Anchor Brewing Company, which trademarked the term ''Steam Beer'' in 1981. Although the modern company has corporate continuity with a small brewery which has made beer since the 1890s, Anchor Steam is a modern craft-brewed lager. The company does not claim any close similarity between its present day product and turn-of-the-20th-century steam beer. There have been various explanations for the use of the name "steam beer." According to Anchor Brewing, the name "steam" came from the fact that the brewery had no way to effectively chill the boiling wort using traditional means. So they pumped the hot wort up to large, shallow, open-top bins on the roof of the brewery so that it would be rapidly chilled by the cool air blowing in off the Pacific Ocean. Thus while brewing, the brewery had a distinct cloud of steam around the roof let off by the wort as it cooled, hence the name. Another explanation is that the carbon dioxide pressure produced by the 19th-century steam-beer-making process was very high, and that it may have been necessary as part of the process to let off "steam" before attempting to dispense the beer. It is also possible that the name or brewing process derive from ''Dampfbier'' (literally ''steam beer''), a traditional German beer that was also fermented at unusually high temperatures and that may have been known to 19th-century American brewers, many of whom were of German descent; Dampfbier is an ale, however, not a lager.〔(Dampfbier )〕〔(Dampfbier: the original Steam Beer? )〕 ==Brewing process== In 19th-century California, not only ice, but even sources of naturally cold water, were probably unavailable to brewers. California brewers, unfamiliar with brewing ale, found a strain of lager yeast which would ferment at higher temperatures. Final flavors of beer are influenced by the strain of yeast and the fermentation temperature. Lager yeast is best used at temperatures from . Classic lagering of beers takes place over a period of time from weeks to many months at a temperature of . Lager yeasts are ''bottom fermenting,'' which is to say that during fermentation they settle on the bottom of the fermenter. Conversely, ale yeast is best used at temperatures from . Fermentation by ale yeasts produces a beer that has a more distinct flavor. Ale yeasts are top-fermenting, that is they settle out on top of the wort after fermenting (fermentation itself takes place in a suspension).〔 Steam Beer uses bottom fermenting lager yeasts at ale temperatures, which results in a very distinctive flavor profile that includes both ale and lager characteristics. While steam beer is considered a specialty microbrew style of beer today, it was originally a cheap beer made for blue collar workers. Wahl and Heinus's ''American Handy Book of Brewing and Malting'' (1902) describes California Steam Beer as “a very clear, refreshing drink, much consumed by the laboring classes.” And while most modern California common beers are all-barley malt, adjuncts were often used in the early days. According to the book, "Malt alone, malt and grits, or raw cereals of any kind, and sugars, especially glucose, employed in the kettle to the extent of 33 percent... Roasted malt or sugar coloring is used to give the favorite amber color of Munich beer." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Steam beer」の詳細全文を読む スポンサード リンク
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