Kit instructions tell you to ferment your wine within a specific fermentation temperature range. Most manufacturers recommend 65 to 75 degrees F (18 to 24 degrees C). Yeast thrives between these temperatures. This is one of the situations where kit instructions are different from commercial winemaking techniques. In commercial wineries, some white wines are fermented cooler than this, sometimes below 55 degrees F (13 degrees C).
Commercial wineries have the luxury of taking a year (or 2 or more) before they bottle their wines, so they don’t have a problem. For the home winemaker though, if the fermentation area is too cool the wine will ferment very slowly. This will lead to an excess of CO2 gas (fizz) in the wine, and it may not be ready to stabilize and fine. Even worse, the kind of fining agents included with many kits don’t work well at temperatures outside of the 65 – 75 degrees F (18 to 24 degrees) range. Below 64 degrees F (17 degrees C) your wine kit may not clear at all.
Resolving the Fermentation Temperature
If the temperature of the must is below 18 degrees Celsius, warm the must up by wrapping it with a heat belt (available at The Home Vintner stores), or by other means of direct heat. Don’t set it on a heating pad or blanket, as this concentrates the heat and is not good for the wine.
Most of the time the yeast recovers from this treatment and begins fermenting on its own within 24 hours, but if not, double-check the temperature of the must and pitch a new yeast. The window of opportunity for correcting a non-starting yeast is about four days without repercussions because of bacteria, etc., so monitor your fermentation for signs of contamination, and keep close contact with the very knowledgeable staff at The Home Vintner to make sure all is well with your wine.
Sulphite and sorbate, the stabilizers in the kit, work to inhibit yeast activity. There are times you want the yeast to be working, and other times you do not. If by mistake, you add them too soon, your wine may not finish fermenting. If you add the sorbate on day 1, the yeast will never become active, and the kit will not ferment.
