Sodium metabisulfite

Sodium metabisulfite (Na₂S₂O₅) is an inorganic salt that releases sulfur dioxide in water and acts as a preservative, antioxidant, and reducing agent.

Sulfur dioxide: A colorless, pungent gas formed when sulfur-containing compounds are burned or acidified. Dissolving sodium metabisulfite in water establishes equilibria that can release this preservative gas.
Food preservative: A substance added to food to slow spoilage or preserve quality. Sodium metabisulfite preserves foods by inhibiting microbes and limiting oxidative deterioration.
Sulfite sensitivity: Adverse reactions to sulfites that can include respiratory symptoms, especially in some people with asthma. Sulfite released from the compound can trigger reactions in susceptible individuals.
Sodium bisulfite: An inorganic salt, NaHSO₃, that supplies bisulfite in aqueous solution. It provides related sulfur(IV) chemistry but differs in composition and solution behavior.
Sulfite: An ion containing sulfur in the +4 oxidation state, with formula SO₃²⁻. Sulfite species formed in water account for much of the compound’s antioxidant and reducing behavior.
Winemaking: The production of wine through grape fermentation and subsequent processing. Winemakers use measured sulfite additions to limit oxidation and suppress unwanted microorganisms.
Occupational asthma: Asthma caused or worsened by substances encountered at work. Dust or sulfur dioxide released during handling can aggravate airways in workplaces.
Potassium metabisulfite: An inorganic salt, K₂S₂O₅, used as a sulfite source in food and beverage processing. It supplies similar sulfite chemistry while avoiding added sodium.
Redox reaction: A chemical reaction involving electron transfer and changes in oxidation state. Sodium metabisulfite acts as a reducing agent by donating electrons to oxidizing substances.
Dried fruit: Fruit preserved by removing much of its water through drying. Sulfite treatment helps retain color and slows browning in some dried fruits.

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