De Troch Oude Gueuze is created by mixing young (one-year old) Lambic with older Lambic a second spontaneous fermentation in the bottle is obtained. The result is called OUDE GEUZE.
In order to be offcially allowed to call this beer 'Oude Geuze', a real trademark for artisanal beer, the beers used for the mix have to be at least 3 years old.