While barley and wheat are the most popular brewing grains, and rice and maize are commonly used as flavorless fermentable adjuncts, there are other grains that can be used to contribute character as well as sugar to beer. Probably the most popular of these minor grains is rye.
While there was once a thriving rye beer brewing tradition in Germany, in the fifteenth century or so, a bad harvest led the rulers of German states to declare that all rye must be reserved for the baking of bread. With the extension of the Reinheitsgebot over all of Germany, rye brewing all but disappeared from Europe.
Today, rye beer survives only in a few places. The medieval German tradition has been revived as modern Roggenbier, and experimental American brewers have created a new style in American Rye Ale. In addition, a few alternative brewing traditions have survived which use rye as an ingredient, including Kvass in Russia and Sahti in Finland.