Potassium sorbate is a stabilizer used to slow yeast growth and "lock down" the fermentation process. It prevents yeast from acting on any sweeteners that may be added to the wine after the initial fermentation is complete. Whenever potassium sorbate is used, a sulfite must be added at the same time or a compound called geraniol may develop. That's the same stuff that gives geraniums their distinctive smell, and it's also used to keep mosquitoes away. So unless you'd like your fine wine to double as a ladies' fragrance or an insect repellent, you'll probably want to follow the directions in your home winemaking kit closely for this one.