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One theory about the introduction of the law is that it was intended to preserve wheat and rye – grains desperately needed for bread in a time of food scarcity – and replace them with barley.

• 500 Years of Reinheitsgebot,
  ChemistryViews.org 2016.
  German beer purity law was adopted in 1516 and limited ingredients to barley, hops, and water

• Chemistry Advent Calendar 2016,
  ChemViews Mag. 2016.
  DOI: 10.1002/chemv.201600101