Just a quote form the above site
Because things often went wrong with the beer brewing which nobody could explain with the body of beer brewing knowledge available in early times, the guilty parties were often sought in the mystical realm. Many wondrous herbs and cult objects still surrounded brewing kettles into the late middle ages. Superstition went so far that brewing failures were blamed on "brew witches" or "beer witches". The last known burning of a "brew witch" took place in 1591. This practice can be referred to as the "darkest" chapter of beer brewing history. The end of this superstitious era came when the use of hops caught on. Even though often forbidden at first, this practice prevailed in the long run. For one thing, the beer became less perishable and the brewing process more stabile. Things didn't go wrong as often and fewer witches had to be hunted. With the use of hops the beer revealed its "clear character". Beer began to closely resemble the modern product range, both in taste and appearance. In order to guarantee a high level of reliability, quality and consistency, the Duke of Bavaria, Wilhelm IV, proclaimed the German Beer Purity Law.
Pumpy
