You’ve probably heard about the German Beer Purity Law of 1516, aka the Reinheitsgebot. It says that the only 4 ingredients allowed in German beer are barley, hops, water and yeast.
Here is the original text, translated into English:
How beer should be served and brewed in summer and winter in the principality
Herewith, we decree, order, express and wish, together with the Privy Council, that from this day forth everywhere in the Principality of Bavaria, in the countryside as in the towns and marketplaces, wherever no other specific ordinance applies, from St. Michael’s Day until St. George’s Day a measure or head of beer shall not be sold for more than one pfennig Munich currency and from St. George’s Day until St. Michael’s Day a measure shall not be sold for more than two pfennigs of the same currency, nor a head for more than three haller. Violators of this decree shall be punished as prescribed below. Whoever should brew a beer other than Maerzen, is forbidden, under any circumstances, to serve or sell a measure for more than one pfennig. We especially wish that, from this point on and everywhere in the countryside as well as in the towns and marketplaces, nothing is to be added to or used in beer other than barley, hops and water. Whosoever knowingly disobeys this decree will be severely punished by the court having jurisdiction over him by having his barrel of beer confiscated whenever this offense occurs. Whenever an innkeeper buys beer at the prescribed price from any brewery in the countryside as well as in the towns and marketplaces, he is allowed to resell it privately to the lowly peasantry for one haller more than the price of the measure or head of beer stipulated above.
Note: “measure” and “head” were units of volume and “pfennig” and “haller” were monetary units in use at that time. “Maerzen” was a somewhat stronger beer brewed in late winter, which is still brewed today.
In the original text, the only ingredients that could be used in the production of beer were water, barley, and hops.Â The Reinheitsgebot is no longer part of German law: it has been replaced by the Provisional German Beer Law (VorlÃ¤ufiges deutsches Biergesetz), which allows constituent components prohibited in the Reinheitsgebot, such as wheat malt and cane sugar, but which no longer allows unmalted barley.
Note that no yeast was mentioned in the original text. It was not until the 1800s that Louis Pasteur discovered the role of microorganisms in the process of fermentation, therefore yeast was not known to be an ingredient of beer. Brewers generally took some sediment from the previous fermentation and added it to the next, the sediment generally containing the necessary organisms to perform fermentation. If none was available, they would just set up a number of vats, and usually yeast would “appear by itself”.
Hops are added to beer as a preservative, and their mention in the Reinheitsgebot meant to prevent inferior methods of preserving beer that had been used before the introduction of hops. Medieval brewers had used many problematic ingredients to preserve beers, including, for example, soot and fly agaric mushrooms. More commonly, other herbs had been used, such as stinging nettles, which are related to hops.
The penalty for making impure beer was also set in the Reinheitsgebot: a brewer using other ingredients for his beer could have questionable barrels confiscated with no compensation.
German breweries are very proud of the Reinheitsgebot, and many (even brewers of wheat beer) claim to still abide by it.