Alcohol is produced when microorganisms called yeast consume the glucose in the grape juice. This must happen in oxygen-deprived environments, therefore the juice is kept in well-sealed fermenting tanks or barrels. Stainless steel temperature-controlled tanks are more and more the norm to ensure the ideal fermentation circumstances. However some Chardonnays and Sauvignon Blancs are 'barrel-fermented' in air-conditioned rooms for the artisan quality and for the extraction of toasted oak flavors. Alcoholic fermentation generally takes about two weeks, during which time all or most of the sugars will be converted into alcohol, ending with a dry final product (meaning all the fruit sugar has been converted to alcohol). During or soon after the alcoholic fermentation, the secondary or malolactic fermentation may be induced or prevented depending on the grape variety, acidic content or desired style of the wine. Malolactic Fermentation is most common with Chardonnay, particularly from California. This converts the tarter malic acid (as in green apples) into the softer, creamier lactic acid (as in dairy products). The result is a richer colored, buttery flavored wine.