Knowledge

Is Sodium Metabisulfite the Same as Sulphur Dioxide?

No, sodium metabisulfite and sulphur dioxide are not the same, but they are closely related and often used for similar purposes.

• Sodium Metabisulfite (Na₂S₂O₅):
  It is a white, crystalline powder commonly used as a preservative and antioxidant in food and beverages. When dissolved in water, it releases sulphur dioxide.
• Sulphur Dioxide (SO₂):
  It is a colorless gas with a pungent odor, also used as a preservative, especially in winemaking and dried fruits.

Key Relationship: Sodium metabisulfite acts as a source of sulphur dioxide. When it reacts with acids or even just moisture, sodium metabisulfite releases SO₂ gas. Therefore, their effects are often similar in food processing, but they are chemically distinct compounds.