Schlenkerla Krausen

In the world of German brewing, Kräusen refers to the intense proliferation of bubbles and foam formed during fermentation of a young or 'green" beer. And Aufkräusen (literally to kräusen it up), refers to a historic brewing technique in which some green beer is added to a fully-matured lager. This is a very old and very typically German tradition, and today even English-speaking brewers refer to this technique as krausening. Krausening brings the vibrant freshness of young beer to the more refined, austere flavours of a fully-matured lager.