On April 23, 1516 the Ducal brothers Wilhelm IV and Ludwig X issued a decree called the “Reinheitsgebot,” or “Purity Law.” This set an stop towards the adulteration of beer. From then on, only barley (and the malt made from it), hops and water can be employed to produce it. https://franciscoxxwwx.ampedpages.com/heat-resistant-an-overview-62712585