E220: Sulfur Dioxide (Antioxidant & Wine Preservative)

Direct Answer

E220 (Sulfur Dioxide / SO2) is an inorganic gas dissolved in water to generate bisulfite and sulfite ions, providing potent antimicrobial and polyphenol oxidase enzyme-inhibiting properties. INS 220, group ADI is 0.7 mg/kg bw/day.

Source: OIV / EFSA ANS Panel (2016) · Last reviewed Aug 28, 2026

Specs

E-Number Code	E220
INS / Codex Number	INS 220
Functional Class	Preservative, Antioxidant, Enzymatic Browning Inhibitor
Acceptable Daily Intake (ADI)	0.7 mg / kg body weight per day (as SO2 equivalent)
Chemical Formula	SO2
Primary Mechanism	Molecular SO2 penetrates microbial membranes; bisulfite (HSO3-) cleaves disulfide bonds in enzymes and binds acetaldehyde
Common Target Foods	Wines (Contains sulfites declaration >10mg/L), dried apricots, ciders, potato starch
Dietary Compliance	Vegan, Halal, Kosher, Major Allergen Declaration Mandatory
Safety Approval	EFSA Authorized / FDA GRAS (21 CFR 182.3862 - Banned on raw produce)

Free vs Bound SO2 in Oenology

Only 'molecular / free SO2' (active at pH < 3.5) exerts antimicrobial action against wild Brettanomyces and Acetobacter. Bound SO2 complexes with aldehydes and sugars, contributing to total legal sulfite limits.