Potassium Metabisulfite is a stable source of sulfites in winemaking. The use of sulfur compounds is not a recent innovation. The Dutch shipping companies popularized the use of sulfur in the 16th century by refusing to ship any wines not treated. They insisted on the use of sulfites because the treated wines were the only ones that survived a long sea voyage without spoiling.
Sulfites work by releasing free sulfur dioxide, which inhibits yeast, mold and bacteria. It does this in two ways: one, it kills some of the organisms outright, and two, it blocks the surviving organisms’ ability to reproduce. If your winemaking equipment is physically clean and you’ve rinsed it with a sulfite solution, nothing will grow on it for a short period of time.
To help prevent oxidation, sulfites are also added directly to wine after fermentation. Wine oxidation follows the same pattern that you see in the cut
