Inoculum used is Saccharomyces cerevisiae grown in sterile grape juice. Although some winemakers use the naturally present yeast on grape skins for fermentation, it is common to add a yeast type that has been cultures in the lab. This will give the winemaker more preditable result. If cultured yeast are added, the natural yeast must first be neutralized.
Once the yeast is added, alcoholic fermentation begins. In red wine production, the must is typically fermented for shorter time, but at a higher temperature than white wine. Where as white wines may be fermented for a month or more, it is rare foe it to take longer than two weeks for red wines.
White wine fermentation carried out between 12-15 . As fermentation proceeds a lot of heat is produce and this is controlled by the cooling jackets on the fermenter.
Red wine fermentation carried out between 20-29. This helps in removal of skins quite early and easily during fermentation. Fermentation can be carried out in close or open fermenter. During fermentation the skins tend to float, these skins are pushed again back into the medium by mechanical means.