Gueuze is traditionally produced by mixing one, two, and three-year old lambic. "Young" lambic contains fermentable sugars while old lambic has the characteristic "wild" taste of the Senne River valley. A good gueuze is not the most pungent, but possesses a full and tantalizing bouquet, a sharp aroma, and a soft, velvety flavor. Lambic is served uncarbonated, while gueuze is served effervescent. IBUs are approximate since aged hops are used; Belgians use hops for anti-bacterial properties more than bittering in lambics. Products marked "oude" or "ville" are considered most traditional.