In 1516, the duchy of Bavaria in Germany imposed a law on its beer brewers meant to reserve ingredients like wheat and rye for the baking of bread. The decree restricted brewers to using only barley, hops, water and yeast to make their libations, and set the prices for beer depending on the time of year. The law inadvertently limited brewing to the winter, which favored a cold-tolerant yeast called Saccharomyces pastorianus, which brews lager, over the more common S. cerevisiae, which brews ale.
S. pastorianus is a hybrid, produced from the mating of S. cerevisiae with another yeast called S. eubayanus. Despite lager’s European origins, S. eubayanus hadn’t
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