Sodium Metabisulfite (E223): Uses & Safety
Sodium metabisulfite (E223) is a chemical preservative used in food, pharmaceuticals, and industry. It acts as an antioxidant and antimicrobial agent.
Things worth knowing about "Sodium metabisulfite"
Sodium metabisulfite (E223) is a chemical preservative used in food, pharmaceuticals, and industry. It acts as an antioxidant and antimicrobial agent.
What is Sodium Metabisulfite?
Sodium metabisulfite (chemical formula: Na₂S₂O₅) is an inorganic sulfur compound also known as sodium pyrosulfite or disodium disulfite. As a food additive, it is designated E223. It appears as a white to slightly yellowish powder with a characteristic pungent odor of sulfur dioxide.
Uses and Applications
Sodium metabisulfite is used across a range of industries and applications:
- Food industry: As a preservative and antioxidant in wine, dried fruits, fruit juices, seafood, potato products, and other foods.
- Pharmaceutical industry: As an antioxidant in injectable solutions and other medications to protect active ingredients from oxidation.
- Photography and chemistry: As a reducing agent in developing solutions.
- Water treatment: To remove chlorine from drinking water.
- Winemaking: To inhibit unwanted yeasts and bacteria and to extend shelf life.
Mechanism of Action
When dissolved in water, sodium metabisulfite releases sulfur dioxide (SO₂) and sulfite ions. These exert their effects through multiple pathways:
- Antioxidant: Sulfite ions bind free oxygen radicals, preventing the oxidation of food components and thus delaying discoloration and quality loss.
- Antimicrobial: Sulfur dioxide inhibits the growth of bacteria, yeasts, and molds by penetrating microorganisms and disrupting enzymatic processes.
Safety and Health Considerations
Sodium metabisulfite is considered largely safe when used as intended within approved limits. However, there are important health aspects to be aware of:
Sulfite Sensitivity
A small portion of the population, particularly people with asthma, may be sensitive to sulfites. Possible symptoms of sulfite sensitivity include:
- Shortness of breath and bronchospasm (airway constriction)
- Skin reactions such as redness and urticaria (hives)
- Headaches and migraines
- Gastrointestinal symptoms such as nausea and diarrhea
- In rare cases, anaphylaxis (severe allergic reaction)
Labeling Requirements
In the European Union, foods containing sulfites at a concentration exceeding 10 mg/kg or 10 mg/l must be labeled accordingly (e.g., “contains sulfites”). This requirement is designed to protect sensitive individuals.
Acceptable Daily Intake (ADI)
The European Food Safety Authority (EFSA) has established an ADI for sulfites of 0.7 mg/kg body weight per day, expressed as sulfur dioxide equivalent.
Occurrence in Foods
Sodium metabisulfite and other sulfites occur naturally in small amounts in fermented products, but are most commonly added intentionally in food processing. Typical sulfite-containing foods include:
- Wine and beer
- Dried fruits (e.g., apricots, raisins, figs)
- Potato products (e.g., french fries, potato chips)
- Seafood and crustaceans
- Fruit juices and soft drinks
- Certain ready-made meals and sauces
References
- European Food Safety Authority (EFSA): Re-evaluation of sulfur dioxide (E 220), sodium sulphite (E 221), sodium bisulphite (E 222), sodium metabisulphite (E 223), potassium metabisulphite (E 224), calcium sulphite (E 226), calcium bisulphite (E 227) and potassium bisulphite (E 228) as food additives. EFSA Journal 2016;14(4):4438.
- Vally, H. & Misso, N.L.A.: Adverse reactions to the sulphite additives. Gastroenterology and Hepatology from Bed to Bench, 2012;5(1):16-23.
- World Health Organization (WHO) / Food and Agriculture Organization (FAO): Sulfur dioxide and sulfites. In: Safety evaluation of certain food additives. WHO Food Additives Series 50, 2003.
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