Beer style

Beer styles differentiate and categorise beers by colour, flavour, strength, ingredients, production method, recipe, history, or origin. The modern concept of beer styles is largely based on the work of writer Michael Jackson in his 1977 book The World Guide To Beer. In 1989, Fred Eckhardt furthered Jackson's work publishing The Essentials of Beer Style. Although the systematic study of beer styles is a modern phenomenon, the practice of distinguishing between different varieties of beer is ancient, dating to at least 2000 BC. What constitutes a beer style may involve provenance, local tradition, ingredients, aroma, appearance, flavour and mouthfeel. The flavour may include the degree of bitterness of a beer due to bittering agents such as hops, roasted barley, or herbs; and the sweetness from the sugar present in the beer. Many beer styles are classified as one of two main types, ales and lagers, though certain styles may not be easily sorted into either category. Beers classified as ales are typically made with yeasts that ferment at warmer temperatures, usually between , and form a layer of foam on the surface of the fermenting beer, thus they are called top-fermenting yeasts. Lagers utilize yeasts that ferment at considerably lower temperatures, around , and have the ability to process raffinose, a complex sugar created during fermentation. These yeasts collect at the bottom of the fermenting beer and are therefore referred to as bottom-fermenting yeasts. Lagers constitute the majority of beers in production today. Some beers are spontaneously fermented from wild yeasts, for example the lambic beers of Belgium. Additional markers are applied across styles. The terms "imperial" or "double" are used interchangeably for a higher-alcohol version of a particular style. Originally applied to Imperial stouts, a high-alcohol style of stout brewed in England for export to Imperial Russia, the term imperial can now be applied to any style name to indicate a higher alcohol content.