Sodium metabisulfite is a versatile winemaking agent that is used primarily as an antioxidant, sterilant, and stabilizer. It is a white, crystalline powder that is soluble in water. Sodium metabisulfite is available in a variety of purities, but the most common purity for winemaking is 99%.
 
When added to wine, sodium metabisulfite releases sulfur dioxide gas (SO2). Sulfur dioxide is a natural preservative that has been used for centuries to prevent wine from spoiling. It works by inhibiting the growth of bacteria and wild yeasts, and by protecting the wine from oxidation.
 
Sodium metabisulfite is a very effective antioxidant and can help to preserve the fresh fruit flavors and aromas of wine. It can also be used to stabilize wine and prevent it from browning.