SULPHUR DIOXIDE IN WINE: the great debate
Decanter|February 2021
The use of sulphur dioxide as a preservative in winemaking is a contentious topic, and it elicits strong opinions from producers and wine lovers alike. Rupert Joy gives an overview of the issue, weighing the pros and cons of an SO2-free approach
Rupert Joy

There was a time, not so long ago, when making quality wines without adding sulphur dioxide (SO²) was widely considered close to impossible, largely the preserve of mavericks. Inspired by the philosophies of natural wine guru Jules Chauvet, a small group of independent-minded producers such as Pierre Overnoy in Jura, Marcel Lapierre in Beaujolais, Gramenon in the Rhône and Frank Cornelissen in Sicily sought to relearn ways of making wine without the need to add SO².

Today, as more and more consumers seek out ‘minimal intervention’ wines and the natural wine movement becomes increasingly mainstream, so-called ‘no sulphites added’ (NSA) wine is made all over the world. But the issue remains divisive. At one end of the spectrum are figures such as Champagne’s enfant terrible Anselme Selosse, arguing that SO² ‘lobotomises wine’; at the other, Monika Christmann, former president of the International Vine & Wine Organisation (OIV), warning of deteriorating wine stability caused by a ‘downwards spiral’ in the use of SO² in winemaking.

Sulphur dioxide is naturally produced by yeasts during fermentation, so all wines contain some sulphites. The practice of adding sulphites during the winemaking process to stabilise or preserve wine goes back to at least the 18th century. Conventional producers may add SO² at different stages from harvest to bottling in order to prevent microbial spoilage of wine from unwanted bacteria and yeasts and to minimise oxidation.

Sulphite levels tend to be higher in white and rosé wines and much higher in sweet wines than in red or orange wines, which receive more natural antioxidant protection from tannins in the grape skins. Sulphites are also used as preservatives in a wide range of food and drink products, from dried fruit and shellfish to pizza.

Sulphites in wine have long been blamed for causing ‘wine headaches’. The evidence for this is largely anecdotal, but judging by the number of devices on the market for removing sulphites from wine, such as Clean Wine, Drop It, PureWine, SO²Go, Üllo and Winestiq, there are many wine drinkers who feel that sulphites affect them negatively. Some people unquestionably are sensitive to SO², and sulphite levels in wine are regulated in Europe and other wine-producing regions. In a small proportion of people, high sulphite levels can cause reactions, from shortness of breath to hives, flushing and heart palpitations, or, in very rare cases, anaphylaxis. There is some university-level research suggesting that the liver processes NSA wines better than conventional wines, because SO² destroys vitamin B and glutathione, which help the body to digest alcohol.

Testing the limits

Making wines with no added SO² is fraught with challenges. NSA wines are more liable to wine faults, bottle variation and premature ageing. Jancis Robinson MW once famously described ‘unsuccessful’ NSA wine as ‘more like five-day-old cider with more than a hint of mouse droppings’, highlighting the risks of funky aromas, Brettanomyces (brett), high volatile acidity or ‘mousiness’ in wines without a SO² safety net.

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