Potassium Sorbate is a salt of sorbic acid and is commonly used as a preservative in food and wine. It works by inhibiting yeast cell reproduction, but does not kill them. It cannot stop an active fermentation, but it will prevent renewed fermentation when you sweeten a wine before bottling. Potassium Sorbate acts on enzymes that would cause further assimilation of sugar and refermentation.It must be added to wine before bottling to ensure fermentation does not restart once in the bottle.