Potassium sorbate is known as a wine stabilizer. When active fermentation has ceased and the wine is racked for the final time after clearing, potassium sorbate will stop surviving yeast from multiplying. Yeast living at that moment can continue fermenting any residual sugar. When a wine is sweetened before bottling, potassium sorbate is used to prevent refermentation when it used in conjunction with potassium metabisulfite.
Usage: 1/4 teaspoon per gallon of wine.