Definition - What does Cool Fermentation mean?
There are many benefits that come along with controlling the temperature of wine during fermentation. Cool fermentation uses techniques that lower the temperature and bring out certain characteristics in the wine. Cold temperatures make fermentation processes last longer, which adds complexity and terroir to the wine; this is best for fruity, young red varietals, rose or white wines.
WineFrog explains Cool Fermentation
During cool fermentation, commercial wine makers use tanks that have a lining with chilled circulating glycol that keeps the jacketed metal tanks cold. Smaller wineries either use cool climates to their advantage or put the carboy filled with wine into a tub of cold water or ice. The ideal temperatures for cold fermentation ranges from 45-70 degrees Fahrenheit depending on if red or white wine is being made.
Since reds fair better with warmer fermentation temperatures, cold fermentation is best for white wines that have subtle tastes and aromas which are brought out with a cooler and longer fermentation process. It is especially important if using cold fermentation that the temperatures remain steady as yeasts will increase with heat or go dormant if too cold.