Style of beer

Beer style is a term used to differentiate and categorize beers by factors such as colour, flavour, strength, ingredients, production method, recipe, history, or origin.

The modern concept of beer style is largely based on the work of writer Michael Jackson in his 1977 book The World Guide To Beer in which he categorised beers from around the world into style groups according to local customs and names. 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.

The study of what constitutes a beer's style may involve provenance, local tradition, ingredients, and/or empirical impression, which is conventionally broken down into several elements; typically - 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.

Yeasts that ferment at warmer temperatures, usually between 15.5 and 24 °C (60 and 75 °F), form a layer of foam on the surface of the fermenting beer, which is why they are referred to as top-fermenting yeasts. Yeasts that ferment at considerably lower temperatures, around 10 °C (50 °F), have the ability to process a chemical compound known as 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 yeast. The majority of beer in production today is fermented in this way and is called lager.

Beers of spontaneous fermentation produced in Belgium using wild strains of yeast are referred to as lambic.

Styles of beer go back at least to Mesopotamia. The Alulu Tablet, a Sumerian receipt for "best" ale written in Cuneiform found in Ur, suggests that even in 2050 BC there was a differentiation between at least two different types or qualities of ale. The work of Bedrich Hrozny on translating Assyrian merchants' tablets found in Hattusa, revealed that approximately 500 years later the Hittites had over 15 different types of beer.

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