Sulphites in Wine: truths and myths explained

Sulphites are commonly used in winemaking, as a protective agent that prevents oxidation and microbiological instability. They are often blamed for headaches and violent hangovers. But are they really to blame? And is there such a thing as a sulphite-free wine? (spoiler alert: there is NOT)

What are sulphites

Sulphites are chemical compounds, which contain the sulphite ion. They occur naturally and can also be artificially synthesised.

Sulphites are used widely in the food industry as a preservative, stabiliser and flavour enhancer, due to their antioxidant and sanitising properties. Sulphites bind with oxygen therefore preventing the oxidation of foodstuff; they also inhibit microbiological activity by blocking the growth and metabolism of bacteria.

In winemaking they are used across all stages of production, from harvest to bottling, and even to sanitise the equipment in the vineyard, winery and cellar, in the form of sulphur dioxide. To avoid oxidation (browning and loss of aromas) and the proliferation of unwanted bacteria, grapes are commonly sprayed with SO2 right after harvest and must is protected during/after fermentation. Levels need to be carefully monitored because too much SO2 will also kill the yeasts responsible for fermentation. On the other hand, this means that fermentation can be stopped if desired (for example to retain a certain amount of sugar in the wine) through the addition of sulphur dioxide.

Before bottling, an additional small amount of SO2 is usually also added to make sure the wine is completely stable when released to market.

Natural vs Added Sulphites

Winemakers that follow lower intervention approaches notably use very little, if any, SO2 throughout the production process. This is based on the belief that if winemaking is too protective the wine becomes too technical and not truly expressive of variety and terroir. Many will still add a small amount of SO2 before bottling to avoid undesired microbiological activity and ensure both the stability and consistency of the finished wine, in each and every bottle.

Yet, all wines, even those to which no SO2 was added, need to be labelled with the warning ‘Contains Sulphites’. Why? Because these compounds occur naturally and will be present in wine, whether or not added by the winemaker. Sulphites are a natural byproduct of yeast activity during fermentation – in other words, if alcoholic fermentation occurs, then sulphites will inevitably be present. All wines with more than 10 mg/L of SO2 need to display the ‘Contains Sulphites’ warning. In practice this means virtually all wines, as the simple process of fermentation will almost always produce SO2 beyond that threshold.

The convenient truth about Sulphites in Wine

A sulphite-free therefore does not exist, no matter what your natural wine buddies might say. A wine might be free of added sulphites but never free of them altogether.

So what are normal and acceptable SO2 levels in wine? In the context of all foodstuff, wine has, even at the highest allowed level, quite low amounts. European regulations allow up to 200 mg/l in white and rosé wines and 150 mg/l in red wines (150 and 100 mg/l, respectively, if the wine is organic). The lower allowed level in red wines is explained by the fact that, due to the presence of tannins and colour compounds – which act as natural preservatives – there’s less need to protect red wines from oxidation and microbiological spoilage.

Sugar and acidity are other factors winemakers need to consider when deciding how much SO2 to add. Sweeter wines are more prone to spoilage as the sugar provides nutrients for bacteria to thrive. Conversely, dry, high acid wines are naturally more stable, with the acidity inhibiting microbiological activity and preventing, to a degree, oxidation.

Even the highest level of allowed sulphites in wine are notably lower than those present in other foodstuffs. Take dried fruits for example, which are among the foods highest in sulphites, with raisins and prunes containing between 500 and 2,000 ppm (parts per million). If you’re sensitive to sulphites, you’ll also want to steer clear of soda, candy, prepared soups, frozen juices, processed meats, potato chips, French fries and dried fruit, all of which contain much higher concentrations than wine.

Are they bad for you?

Allergy to sulphites is not physiologically possible as they are inorganic salts and don’t contain the proteins that cause true allergic reactions. Some people are, however, more sensitive and can have adverse reactions such as headaches, coughing, swelling and diarrhoea. Sulphite sensitivity is extremely rare, although much more probable among people with respiratory conditions, such as asthma. But there are many other components in wine that might, either alternatively or concurrently, cause these symptoms (and actual allergies). Histamines and, of course, alcohol are more likely culprits.

Considering that other foodstuffs have significantly higher levels of sulphites it is not likely that you will get a reaction from your wine if it’s something you haven’t experienced when eating a dried fig.

And you can be confident that skilled, mindulf winemakers only ever use the amount of sulphite they find is strictly needed to bring the best out of their grapes.