Introduction: What Is E223?
Have you ever noticed "E223" listed in the ingredients of your favorite wine, dried fruits, or baked goods? This code refers to sodium metabisulfite (Na₂S₂O₅), a widely used food preservative and antioxidant. As a leading manufacturer of food-grade sodium metabisulfite with 20 years of experience and ISO/FDA certifications, we provide high-purity additives that comply with global safety standards.
This article explores:
✔ What sodium metabisulfite is (chemical properties & food-grade specifications)
✔ Its applications (preservation, anti-browning, dough conditioning)
✔ Safety concerns & regulatory limits (FDA, GB 2760, EU standards)
✔ Best practices for industrial use (storage, purity, compliance)
1. What Is Sodium Metabisulfite?
Chemical Definition & Physical Properties
Sodium metabisulfite (Na₂S₂O₅), also known as sodium pyrosulfite, is a white crystalline powder with a sharp sulfur dioxide (SO₂) odor. It dissolves easily in water, releasing SO₂ gas, which acts as a preservative and antioxidant.
Key Properties:
| Property | Value |
|---|---|
| Molecular Formula | Na₂S₂O₅ |
| Appearance | White/yellowish powder |
| Solubility | Highly soluble in water & ethanol |
| Decomposition | Releases SO₂ at >150°C |
| pH (1% solution) | ~4.5 (acidic) |
Food-Grade vs. Industrial-Grade:
Food-grade sodium metabisulfite must meet strict purity standards (e.g., ≥97% purity, low heavy metal content) to ensure safety in consumables.
2. Applications in the Food Industry
A. Preservation (Anti-Microbial Effects)
Sodium metabisulfite inhibits mold, yeast, and bacteria by releasing SO₂, which disrupts microbial enzymes. Common uses:
- Wine & Beer Making – Prevents spoilage; max. 10 ppm in beer (GB 2760).
- Dried Fruits & Vegetables – Extends shelf life by suppressing microbial growth.
- Seafood – Delays blackening in shrimp by inhibiting polyphenol oxidase.
B. Anti-Browning (Color Retention)
Exposure to oxygen causes enzymatic browning in fruits (e.g., apples, potatoes). Sodium metabisulfite:
- Blocks oxidation by chelating metal ions.
- Used in pre-cut produce, potato chips, and dehydrated foods.
C. Dough Conditioning (Bakery Products)
In baking, it:
- Strengthens gluten, improving dough elasticity.
- Acts as a leavening agent in some recipes.
Approved Usage Limits (GB 2760 / FDA):
| Food Category | Max. SO₂ Residue (ppm) |
|---|---|
| Wine | 250 (US), 200 (EU) |
| Dried Fruits | 500–2000 |
| Biscuits/Crackers | 50 (China) |
3. Safety Concerns & Regulatory Compliance
Potential Side Effects
While generally safe, sodium metabisulfite can cause:
- Allergic reactions (asthma, skin irritation in sensitive individuals).
- SO₂ toxicity if inhaled in high concentrations (industrial handling risks).
- Banned in infant foods (risk of gastrointestinal irritation).
Safety Thresholds (Global Standards)
| Region | Max. Allowable SO₂ (ppm) |
|---|---|
| FDA (USA) | Varies by product (e.g., 10 in beer) |
| EU (E223) | 150–200 (wine), 500 (dried fruits) |
| China (GB 2760) | 50 (baked goods), 200 (wine) |
Key Takeaway: Proper dosing is crucial—exceeding limits can lead to regulatory penalties and health risks.
4. Industry Best Practices
A. High-purity Food-grade Sodium Metabisulfite
- Lower impurities = reduced SO₂ off-gassing & safer handling.
- Third-party testing ensures compliance with FDA/GB 2760/EU standards.
B. Proper Storage & Handling
- Store in sealed, moisture-proof containers (prevents premature SO₂ release).
- Avoid contact with acids (triggers rapid SO₂ emission).
C. Alternatives & Blends
Some manufacturers combine sodium metabisulfite with:
- Ascorbic acid (enhances antioxidant effects).
- 4-Hexylresorcinol (prevents shrimp blackening).
5. FAQs (Common Consumer & Industry Questions)
Q1: Is Sodium Metabisulfite Safe?
Yes, when used within regulatory limits. However, asthmatics and sulfite-sensitive individuals should avoid high-SO₂ foods.
Q2: What’s the Difference Between Sodium Metabisulfite & Sodium Sulfite?
| Feature | Sodium Metabisulfite (Na₂S₂O₅) | Sodium Sulfite (Na₂SO₃) |
|---|---|---|
| Structure | Two SO₂ groups | One SO₃ group |
| Reduction Power | Stronger | Weaker |
| Common Uses | Food preservation, bleaching | Water treatment, photography |
Q3: Why Is It Banned in Baby Food?
Infants have underdeveloped detoxification systems, making them more vulnerable to SO₂-induced irritation.
Conclusion: Balancing Preservation & Safety
Sodium metabisulfite is a versatile, cost-effective preservative, but proper usage is key. As a trusted supplier, we ensure our products meet the highest food-grade standards—contact us for certified, high-purity sodium metabisulfite solutions.