After preparation comes the fermentation process which is a two step process alcoholic fermentation and malolactic fermentation. During alcoholic fermentation the first flavors of the wine are produced. Reds are fermented in large steel or wood containers. Yeast will naturally begin to form in warmer climates although sometimes cultivated yeast is added. In cool climates the juice must be heated to kick off that fermentation process.
Lighter reds spend only two to three days in the first fermentation step.
Classic, full-bodied reds will ferment for a good two weeks or more. The added stems will provide tannin, which makes for drier reds. Fortified wines are half-fermented in a similar manner at which time brandy is added to the juice, stopping the yeast fermenting processes and preserving the sweetness of the wine. White wines are almost always fermented with special cultured yeast for a minimum of a month. Wine makers have the choice of stainless steel or wooden vats and high or low fermentation temperatures.