Makers of sweet wines, which have sugars added to them after the fermentation process occurs, face a problem: the yeasts that ferment the sugars of the grape juice can just as easily eat the sugars added to sweeten the wine. To avoid this, the yeast must be neutralized. This can be done by adding potassium sorbate, a common preservative that comes in powder form. It will prevent the yeast remaining in the wine from reproducing. It will not, however, kill the remaining yeast cells; this makes it essential to remove as many as possible before adding potassium sorbate.
Things You'll Need
Rack the wine thoroughly. This means letting the wine sit until sediments drift to the bottom, then pumping the wine into a clean vessel. It should be done every 30 to 60 days while the wine is fermenting, until there is no sign of any sediments remaining at the bottom of the wine. This racking process will remove most of the yeast from the wine, which is essential to ensure that the existing yeasts don’t eat too much of the sweetening sugar.
Calculate how much potassium sorbate to add. There is no fixed formula for this, but a good guideline is based on the amount of alcohol in the wine (more alcohol means less sorbate is required). A 10 percent alcohol wine needs .20 grams per liter (g/L) of wine, while 11 percent wine needs .17 g/L; 12 percent wine needs .13 g/L, while 13 percent wine needs .10 g/l and 14 percent wine needs .07 g/L. This all assumes a pH of less than 3.5, and adequate sulfur dioxide (necessary to control bacteria; it is a key ingredient earlier in the winemaking process).
Multiply the amount of sorbate you need, in grams per liter, by the amount of wine you are making. For example, if you are making 100 liters of 13 percent alcohol wine, you would need 10 grams of potassium sorbate powder. Since a tablespoon of potassium sorbate weighs about 2.9 grams, this means you need to add roughly 3.3 tablespoons.
Sprinkle the potassium sorbate into the wine, and mix it thoroughly, then store the wine until you are prepared to add sweetener to it.
Wines with lower pH (such as Rieslings) need less potassium sorbate, since it works more effectively with a low pH level.
References and ResourcesNW Winemaking Notes: Potassium Sorbate (Sorbic Acid)
Winemaking: Racking the Wine