Fermentation in wine & beverage production
Fermentation is an extremely important step in the winemaking process, determining taste and quality. Control of this process is important to warrant the quality of the wine. In the fermentation stage, yeasts convert the sugars to alcohol and carbon dioxide. Alcoholic fermentation takes place in large stainless steel fermentation reactors or vats with or without the addition of pre-cultivated yeast, e.g. usually Saccharomyces cerevisiae, and under rigorous temperature control. The fermentation process takes place at a controlled temperature for quality purposes, to which the wine needs to be cooled at the beginning of fermentation and throughout the process. The fermentation reaction also generates heat that needs to be removed during fermentation. Cooling of the fermentation tanks and barrel room (where some of the white wines are fermented) is one of the major energy uses in a winery.
White wine is fermented after marc separation, while red wine is fermented together with grape marcs. Red wine, and sometimes white wine as well, goes through a second malolactic fermentation. This is a bacterial fermentation that converts the malic acid into lactic acid.
For red wine, the must is fermented for seven to ten days at a temperature between 24 to 27ºC. White wines are fermented at cooler temperatures than reds to achieve the best quality. For white wines, fermentation takes two to forty-five days at a temperature usually between 7 to 18ºC.
- European Commission, 2006. BREF Reference document on Best Available Techniques in the Food, Drink and Milk industries
- University of California. 2005. BEST Winery Guidebook: Benchmarking and Energy and WaterSavings Tool for the Wine Industry.