Could you tell me how I might control my fermentation temperature? I have been making wine for 15 or so years from real grapes. Many times the wine's fermentation temperature is too high. What is the best way to control it. Thanks in advance.
Thanks for the great question. This is something that plagues a lot of home winemakers, so I'm glad you brought it up.
For those of you who do not know, a fermentation creates heat. It's usually not a problem during the cooler months or with smaller batches, say 5 gallons or less. But when the weather is hot or you are fermenting in 15 gallon batches or larger, heat can build up and should be on the winemaker's radar.
Depending on the type of wine you are making and the type of wine yeast you are using, you would like your fermentation to around 70° to 75° F. Once you start getting over 80°F. you run the risk of off-flavors and possible spoilage.
There are several ways you can go about keeping a fermentation cool. Unfortunately, most of them are a pain in the behind. For a professional winery it simple. They use fermentation vats with cooling jackets and/or refrigeration coils that keep the temperature stable under computerized control. Sweet! But for us home winemakers we have to use a little more ingenuity to keep our fermentation temperatures stable.
I'll go through a few of the basic methods you can use if the wine fermentation temperature is too high, but it's going to be up to you to figure out which one is going to be most practical for your situation:
Use Smaller Fermenters
This one is pretty basic. A 5 gallon carboy is not going to over-heat as easily as a 15 gallon demijohn. This is because you have more external surface area per gallon as you go down in size. That means the heat can dissipate more readily from a smaller fermenter than it can with a larger fermenter.
Blocks Of Ice
This is the one I hate the most, but is most used by home winemakers. It's simply using blocks of ice in ziplock bags directly into the wine. I hate this for two distinct reasons: 1) you never know when a ziplock bag is going to fail and empty melted ice into the wine, 2) there is very little control. While it's designed to help you out when the wine fermentation temperature is too high, you could easily get the fermentation too cool, stalling the fermentation. For these reasons I do not recommend this method, but it could be used in a pinch.
The basis behind this method is when water evaporates it cools whatever it is touching. By keeping evaporating water against the outside of the fermenter, you can get the fermenter to cool down. A common way of accomplishing this is to sit the fermenter in a bath of water. It does not need to be deep, just a few inches. Next put fabric over the fermenter that drapes into the water. As an example, you could use a cotton t-shirt over a carboy. The water will then wick up the fabric and then evaporates, cooling the fermenter. You an use a fan to blow air across the fermenter to speed up the evaporation. The faster the evaporation, the more the fermentation gets cooled.
This method is done simply by putting a coil of stainless steel tubing in the wine and then running cold water through the tube. This is a great way to cool the wine. The biggest problem with it is that you have to use stainless steel tubing which is expensive. Other metals will corrode which is detrimental to the wine, so stay away from copper, aluminum, etc.
This is the ultimate solution for when a wine fermentation temperature is too high. This method involves using a refrigerator as a temperature controlling device. The obvious issue with this method is you need a refrigerator. The second issue is that the thermostat of a refrigerator does not go high enough. For this reason you will need to buy a electronic temperature controller with the correct temperature range to control the power to the refrigerator.
Unfortunately, all these methods involve some effort on your part. As mentioned before, all them work, it's more a matter of picking out the method that is most practical for your situation.
Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.