4 Ways to Stop Wine Fermentation [Ultimate Guide]
One of the greatest challenges in winemaking is stopping the fermentation.
Fermentation is caused by the yeast which consumes the sugars from the wine and turns them into alcohol.
The fermentation process generally stops on its own when there is no sugar left (so you will have a really dry wine) or when the alcohol concentration reaches about 14-18%, depending on the yeast strain.
However, the question about how to stop fermentation in winemaking rises when your wine reached the desired level of sweetness and you want to keep it just as it is.
So, let’s see how to stop fermentation with three simple methods.
1. Adding Sulfites
If you need to stop an active fermentation then the best way to do this is using sulfites.
However, be aware that this technique is only really effective for fermentations that are nearing completion. You wouldn't want to try and stop an energetic fermentation in this way.
Once the target sugar level has been reached (this is measured using a hydrometer) we add sulfites to the wine must.
Commonly used sulfites in winemaking are Campden tablets, sodium metabisulfite, and potassium metabisulfite.
The temperature then should be reduced to further inhibit fermentation. Below 40°F is ideal for this.
This will stop the active fermentation by stifling the remaining activity, but our work isn't yet finished.
A wine that hasn't fermented to dryness and still contains residual sugar needs stabilized.
This means we need to stop any remaining yeast cells from reproducing and starting to ferment again.
We've stopped one fermentation but another one can begin because the leftover sugar can help yeast reproduce again.
To inhibit further yeast growing, we add a stabilizer called potassium sorbate. The potassium sorbate essentially makes the yeast sterile and unable to strat working again.
You might wonder why we don't use this in the first place to kill off the active fermentation and that's a great question!
It simply doesn't work like that and can only inhibit new fermentations from starting. Potassium sorbate is a bit like a contraceptive for wine yeast!
We must kill off as much yeast as possible with sulfites first.
2. Stopping the Fermentation with Cold Shock
This is the method a winery would use and it's very effective. However, it's labor and time intensive as well as expensive as you need a wine filter.
To stop the fermentation, follow these steps:
The downside of this method is that some of the yeast can be filtered with the wine during the racking process and the fermentation will start again.
You can prevent this by adding potassium sorbate.
3. Stopping the Fermentation Through Pasteurization
Probably the most efficient method for killing the wine yeast is pasteurization.
Yeast normally dies at temperatures above 104 degrees Fahrenheit, so to stop wine fermentation it is sufficient to heat the liquid above that point.
Here is how to stop fermentation with this method :
Alternatively, you can rack the wine directly into the bottles, pasteurize the bottles then seal them.
The downside of this method is that it is difficult to maintain a constant heat for 15 minutes and it is difficult to cool the wine quickly enough.
This process will alter the wine’s flavor and in order to be effective, you should minimize as much as possible the contact of the wine with the outside environment after pasteurization.
4. Stop the Fermentation with Alcohol
This is probably the simplest way to stop fermentation in winemaking. But one that requires expert blending knowledge in order not to ruin our wine.
As we mentioned earlier, yeast stops working when the alcohol concentration is about 16%.
Actually, depending on the yeast strain, the alcohol concentration can be between 14% and 18%.
So you can stop wine fermentation by simply adding more alcohol to your wine, in essence fortifying it. When fortifying wine to stop fermentation you want to bring the ABV up to 20%.
This is how to do it.
The downside of this method is that the added alcohol will not only alter the flavor but if you use vodka, it will also give an unpleasant smell to the wine.
Have you ever stopped wine fermentation before? What method did you use? If you have any questions or tips on how to stop fermentation in winemaking, please leave a comment below.