The use of sulphur in wine dates back to Roman times when sulphur was burnt in storage vessels before filling to prevent spoilage of wine. More recently sulphur dioxide was introduced directly into wine to take advantage of its remarkable properties. The main use of sulphur dioxide is for its anti-oxidant and anti-microbial qualities. This means that it will inhibit the growth of unwanted yeast and bacteria as well as binding to oxygen, which causes wine to spoil. In addition to these properties sulphur is considered low irritant and easy to detect if present in high quantities.
Sulphur is an authorised additive for use as an anti-oxidant in wine (including organic wines), so long as the total addition does not exceed certain limits. Even if sulphur dioxide is not added to wine there will always be a small amount of sulphur dioxide present as it is a by-product of alcoholic fermentation. The addition of sulphur dioxide directly into a wine appears as preservative 220 on a wine label.
For all these benefits of sulphur, there can be a downside: it can exacerbate the dreaded hangover, and it can cause other health side-effects in those sensitive or allergic to it. For that reason, a growing number of producers offer a range of preservative-free or no-added preservative wines.