IBU stands for International Bitterness Units and is a standardised measure of the bitterness of beer set by the European Brewing Convention (EBC). The bitterness of beer comes from alpha acids found in hops; the concentration of alpha acids is directly proportional to the theoretical bitterness of the beer.This concentration can be measure in a laboratory and hence a figure assigned to the bitterness of the beer.ell, there is actually no such thing as 80 proof beer. Proof, in short, is a measure of the alcoholic content beverages, used specifically in hard spirits. The proof, specifi … cally, is double the content of alcohol by volume. For example, most vodka is 80 proof, which means it contains 40% alcohol by volume.