Food Additive : E220 Sulfur Dioxide

Sulfur dioxide is the chemical compound with the formula SO₂.

SO₂ is found on Earth and exists in very small concentrations and in the atmosphere at about 1 ppm.

It is a toxic gas responsible for the smell of burnt matches. It is released naturally by volcanic activity. 

SO₂ was first used in winemaking by the Romans, when they discovered that burning sulfur candles inside empty wine vessels keeps them fresh and free from vinegar smell.  It is still an important compound in winemaking as an antibiotic and antioxidant, protecting wine from spoilage by bacteria and oxidation.

SO₂ ( E220 ) is also used as a preservative for dried apricots, dried figs, and other dried fruits, owing to its antimicrobial properties.  As a preservative, it maintains the colorful appearance of the fruit and prevents rotting.

Safety

Sulfur dioxide is mildly toxic and can be hazardous in high concentrations. Long-term exposure to low concentrations is also not recommended.

However, Incidental exposure to sulfur dioxide is routine, e.g. the smoke from matches, coal, and sulfur-containing fuels.

In the United States, the Center for Science in the Public Interest lists the two food preservatives, sulfur dioxide and sodium bisulfite, as being safe for human consumption except for certain asthmatic individuals who may be sensitive to them, especially in large amounts. Symptoms of sensitivity to sulfiting agents, including sulfur dioxide, manifest as potentially life-threatening trouble breathing within minutes of ingestion.