Lambics are fermented and aged in wooden barrels similar to those used to ferment wine. These bacteria ferment sugars into acids, unlike the yeast that ferment sugar into ethanol. Microorganisms ferment the starch-derived sugars into alcohols. These yeasts ferment well at low temperatures. During this rest period, yeast ferment the dough and produce gasses, thereby leavening the dough. They ferment sugars, producing lactic acid as an end product. These bacteria ferment carbohydrates to lactic acid, which preserves the input. Bread supposedly provides the yeast for the pruno to ferment. This is because "S. salivarius" can ferment the glucose yielding lactic acid. As in MacConkey agar, coliform organisms ferment the lactose, and the colonies become red. Some organisms ferment lactose slowly or weakly, and are sometimes put in their own category. This was made by allowing cooked rice or rice gruel to ferment naturally. Malt gives color and the sugar that is needed for the beer to ferment. Most strains of this subspecies cannot ferment sucrose. Through the process of pasteurization, the juice did not ferment.