As the quality of wine is easily influenced by temperature, wine makers use temperature control to slow down or accelerate the winemaking process or to control chemical changes in the wine. This technique is frequently used during fermentation, cold settling, aging, and storage.
During the primary fermentation, the yeast cells feed on the sugars in the must (the grape juice) and multiply and in the process produce carbon dioxide and alcohol. Due to the exothermic nature of fermentation, temperature increases as sugars are metabolized
The temperature during the fermentation affects both the taste of the end product, as well as the speed of the fermentation. The higher the fermentation temperature, the faster the yeast will convert sugars into alcohol and carbon dioxide. While this sounds great on the surface, it is not a good idea to rush the process when it comes to wine making.
Desirable fermentation temperatures vary for red and white wines. Red wines are fermented at higher temperatures, between 68-86°F (20-30°C), to enhance extraction of color, phenolics, and tannins extraction from skins and to limit fruitiness which is undesirable in most red wines. White wines are fermented at lower temperatures, between 45° and 59°F (7 to 15 °C ), to preserve compounds that contribute to aroma and flavor, keep volatile acidity low and preserve clarity. Read more at https://www.wyeastlab.com/com_w_temperatures.cfm
So how do wineries keep their fermenting wine at the correct temperature for the months it takes it to mature? Most wineries cannot rely solely on the natural ambient temperature of the cellar. Heat production is managed by external temperature controlled refrigeration systems to keep the wine at a relatively lower temperature than it would reach naturally in the cellar.
For amateur wine makers, the simplest way to monitor your fermentation temperature is to use a sanitized kitchen thermometer.
After fermentation is complete, wine is stored at a constant temperature. For red wines the temperature should be maintained around 68°F or 20°C and for white wines around 60°F or 15°C.
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