Why is Sulphur in wine?

All wines contain sulphur dioxide in various forms, referred to as sulphites. Even in completely unsulphured wine it is present at concentrations of up to 10 milligrams per litre.

Commercially made wines typically contain from ten to twenty times that amount.

Why does it matter ?
There are three reasons you might not want sulphur dioxide added to your wine. Firstly, Taste! Sulphur dioxide has an unpleasant smell, like that of a struck match, detectable at very low concentrations. 

Why is it used? Its main functions are to inhibit or kill unwanted yeasts and bacteria, and to protect wine from oxidation. Its also useful in stabilising the wine.

Sulphur dioxide can cause potentially fatal allergic reactions and has been linked with numerous other health problems, including hangover. However, most people dont notice its presence in wine, and the vast majority of vineyards use sulphur to produce their products.

How much is too much?
This depends on the type of wine, the sensitivity of the taster, and the ratio between free and bound sulphur dioxide in the wine.

Free and bound sulphur dioxide
Only a proportion of the SO2 added to a wine will be effective as an anti-oxidant. The rest will combine with other elements in the wine and cease to be useful. The part lost into the wine is said to be bound, the active part to be free.

A good winemaker will try to get the highest proportion of free sulphur to bound that he can. At best this will be about half the amount bound.

Sulphur levels in different types of wine
Red wines do not need any added sulphur dioxide because they naturally contain anti-oxidants, acquired from their skins and stems during fermentation. Conventional winemakers add some anyway.
White wines and rosés do not contain natural anti-oxidants because they are not left in contact with their skins after crushing. For this reason they are more prone to oxidation and tend to be given larger doses of sulphur dioxide.

Sweet wines get the biggest doses because sugar combines with and binds a high proportion of any SO2 added. To get the same level of free sulphur dioxide, the total concentration has to be higher than for dry wines.

Sensitivity to sulphites; Most people can detect sulphur dioxide in water at around 11 mg/l. In wine, the presence of alcohol and acids means that it is less obvious.

For an experienced taster, accustomed to natural wine, sulphur dioxide becomes unpleasant at concentrations of around 20-30 mg/l, depending on the style of wine and the ratio of free to bound sulphur.

For most people the threshold is much higher, but most people have never tasted an unsulphured wine. They may well be able to taste the sulphur, but used to the taste.

How do you tell how much SO2 a wine contains ? Under EU law, any wine containing more than 10mg/l of sulphur dioxide must be labelled as ‘containing sulphites’.

This is not much help as its contained naturally in grapes, that it also includes practically all wines. Secondly, because there is no way of knowing whether the wine in question really contains 11mg/l or 200mg/l.

Organic and biodynamic organisations, such as Nature & Progrés and Demeter, often impose their own restrictions on the wine that carries their labels.

A good natural wine, even one with a tiny addition of sulphur at bottling, will have levels less than half those imposed by the strictest organic organisations. View our range of no Added Sulphur here!