E221: Sodium sulphite

What is E221?

E221 is sodium sulphite, a sodium salt of sulphurous acid. In food it releases sulphur dioxide, which acts as both a preservative and an antioxidant.

Origin and production

Sodium sulphite is produced by reacting sulphur dioxide with sodium hydroxide or sodium carbonate. It is entirely synthetic and mineral in origin.

Why is it used?

Sulphites prevent the growth of microbes and stop browning in many foods; in baking, sodium sulphite can also be used to weaken gluten in biscuit and cracker doughs. It is found in biscuits, crackers, cakes and, in some countries, in sausages and burgers.

Vegan, vegetarian and halal

E221 is mineral-derived and suitable for vegans and vegetarians. It raises no particular halal or kosher concerns of its own.

Safety and regulation

Sodium sulphite is authorised in the European Union, where sulphites above 10 mg/kg or 10 mg/litre (as sulphur dioxide) must be declared as an allergen because they can trigger reactions in sensitive people, especially some with asthma. EFSA identified a risk of exceeding the acceptable daily intake for some population groups in its re-evaluation of sulphites.

Common in