E220: Sulphur dioxide
Origin:
Sulphur is a common element. Sulphur dioxide is produced by burning sulphur. 
Its use as a preservative is associated with ancient history; it had been 
widely used in ancient Egypt and the Roman Empire.

Function & characteristics:
It is a colourless gas, used as preservative. It prevents enzymatic and 
bacterial spoilage of products. Sulphur dioxide dissolves in the aqueous 
phase of the product; the acid resulting from this reaction is the active 
agent. It is thus most effective in acid and slightly acid foods. It is 
ineffective at neutral pH.

It also acts as an oxidizing agent, with bleaching effects. It is thus used 
as a bleaching agent in flour; however, it oxidises (natural) colours in 
foods, which restricts its usage.

Finally, it stabilises vitamin C in products and prevents discoloration of 
white wine.

Heating removes sulphur dioxide as gas from products.

Products:
Sulphur dioxide may be used in a very broad range of acidic products.

Acceptable Daily Intake:
Up to 0.7 mg/kg body weight.

Side effects:
Due to its oxidising effect, it may reduce the vitamin content in products. 
It is reduced in the liver to harmless sulphate and excreted in the urine. 
It can, however, cause breathing problems in asthmatic patients. In high 
concentrations (above those normally used in foods) it can cause 
gastrointestinal disturbances in some people.

Dietary restrictions:
None – sulphur dioxide and sulphites can be consumed by all religious 
groups, vegans and vegetarians.

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