alcohol by volume ale altbier american-style lager american pale ale bacteria barley wine beer beer style belgian beer belgium berliner weisse bock british beer brown ale cream ale dortmunder export dubbel dunkel enkel flanders flanders red ale german beer gose gueuze history of beer india pale ale international bitterness units scale lager lambic malt mild ale old ale pale ale pale lager pilsener rye beer saccharomyces cerevisiae saison schwarzbier smoked beer standard reference method steam beer stout tripel vienna lager wheat beer yeast