🍷 Sulphites (SO2)

In winemaking, sulphites means sulphur dioxide (SO2) and its salts, such as potassium metabisulphite, added to must and wine. They hold back unwanted yeasts and bacteria and keep the wine from oxidising. Without them wine loses its fresh taste and colour sooner, which is why sulphites are among the most common additives in winemaking.

The OIV names four aims of sulphiting: the microbiological stability of wine, using the reducing and antioxidant properties of SO2, binding substances with unpleasant odours, and inhibiting oxidising enzymes. Sulphur dioxide can be added during winemaking, before bottling, or injected straight into the bottle before filling. A related old practice is fumigating barrels with burning sulphur.

In the EU the total sulphur dioxide in dry red wine may not exceed 150 mg/l, and in white and rosé 200 mg/l. If the wine has 5 g/l of sugar or more, the limits are higher: 200 mg/l for red and 250 mg/l for white and rosé, and 300 mg/l for some sweet wines such as Spätlese. Separate rules apply to sparkling and liqueur wines.

Sulphites are on the list of substances that can cause allergies or intolerances, so in the EU they must be declared on the label when total SO2 exceeds 10 mg/l. In 2022 the European Food Safety Authority (EFSA) revisited sulphites, withdrew the temporary acceptable daily intake for lack of data, and pointed to risks for people who consume a lot of foods containing them.

Why it matters to you. The words ‘contains sulphites’ appear from just 10 mg/l of total SO2 and do not mean the wine is bad. If you are sensitive to sulphites, check the ingredients and remember that they are added not only to wine but also, for example, to fruit juices.