Chaptalization is the process of adding sugar to unfermented grape developed by the French chemist Jean-Antoine-Claude Chaptal, for whom it was named. Contrary to popular belief, this process does not make the wine sweeter but only artificially inflates the alcohol content. Additionally, the sugar in chaptalized wine cannot be tasted.
Potassium Metabisulfite is a common wine or must additive, where it forms sulfur dioxide gas (SO2). This both prevents most wild microorganisms from growing, and it acts as potent antioxidant, protecting both the color, and delicate flavors of wine.
Typical dosage is ¼ tsp potassium metabisulfite, per 6 gallon bucket of must (yielding roughly 75ppm of SO2) prior to fermentation, and ½ tsp per 6 gallon bucket (150 ppm of SO2) at bottling.
Winemaking equipment is sanitized by spraying with a 1% SO2 (2 tsp potassium metabisulfite per L) solution.
Potassium Sorbate is used to inhibit molds, and yeasts in wine. Also known affectionately as “wine stabilizer”, potassium sorbate produces sorbic acid when added to wine. It serves two purposes. When active fermentation has ceased and the wine is racked for the final time after clearing, potassium sorbate will continue fermenting any residual sugar into CO2 and alcohol, but when they die no new yeast will be present to cause future fermentation. When a wine is sweetened before bottling, potassium sorbate is used to prevent refermentation when used in conjunction with potassium metabisulfite. It is primarily used with sweet wines, sparkling wines and some hard cider but may be added to table wines which exhibits difficulty in maintaining clarity after fining.
"When active fermentation has ceased and the wine is racked for the final time after clearing, p̶o̶t̶a̶s̶s̶i̶u̶m̶ ̶s̶o̶r̶b̶a̶t̶e̶the few remaining yeast will continue fermenting any residual sugar into CO2 and alcohol, but when they die no new yeast will be present to cause future fermentation."