Beer is the world's most widely consumed and likely the oldest
alcoholic beverage; it is the third most popular drink overall, after
water and
tea. The production of beer is called
brewing, which involves the
fermentation of
starches, mainly derived from
cereal grains—most commonly
malted barley, although wheat, maize (corn), and rice are widely used. Most beer is flavoured with
hops, which add bitterness and act as a natural
preservative, though other flavourings such as herbs or fruit may occasionally be included. The fermentation process causes a natural
carbonation effect, although this is often removed during processing, and replaced with forced carbonation. Some of humanity's earliest known writings refer to the production and distribution of beer: the
Code of Hammurabi included laws regulating beer and beer parlours, and "The Hymn to
Ninkasi", a prayer to the Mesopotamian goddess of beer, served as both a prayer and as a method of remembering the recipe for beer in a culture with few literate people.