Sodium Metabisulfite is a common additive used to preserve and stabilize wines, ciders, and occasionally beers. When added to wine or must, it forms sulfur dioxide gas (SO2). This prevents most wild microorganisms from growing and acts as a potent antioxidant, protecting both the color and delicate flavors of wine. Sodium metabisulfite solutions are also used as sanitizing rinses for winemaking equipment.