Wine is the only food and drink product in Europe that isn’t required to show the list of ingredients on the bottle. Except for one obscure mention: contains sulphites.
Sulphur is a naturally occurring element, representing 0.5% of the Earth composition. It is also an essential nutrient to the vine's growth. Sulphur has been used since antiquity for its cleansing properties and as a wine preservative. Sulphur dust is widely sprayed in the vineyard to protect the vines from mildew, a form of fungus. Barrels can be cleaned and disinfected by using sulphur wicks, or a powdery form. Very few wines in the world are made without the help of sulphur dioxide, which can be introduced throughout the winemaking process in its gas, liquid or solid form.
It acts as a disinfectant and antioxidant, inhibiting the development of bacteria and yeasts, slowly reacting with O2 and numbing enzymes responsible for oxidation. It can also be used to stop fermentation or rid of unwanted types of yeasts, and is applied at bottling to the majority of the wine produced today. While most of it comes from by-products of the petrochemical industry, SO2 is still the most efficient and safest product available to winemakers to prevent oxidation and microbial spoilage and ensure the wine's stability. It is especially relevant for large scale wineries.
Unfortunately, everyone reacts very differently to sulphites and allergy reactions can happen even at concentrations far below toxic levels. It is also used in many other everyday food and drinks, such has dried fruits, fruit juices, pickles and many more, which suggests a cumulative effect could be responsible for allergies.
Sulphites are measured by analysing the total level of SO2 in a litre of wine, aka the sum of the bounded SO2 – SO2 that has already reacted with other wine constituents - and free SO2, expressed in mg/l. Free SO2 protect the wine from oxidation but can also be perceived by the nose and give a tickle in the throat from levels a low as 30mg/l. Part of the total SO2 is naturally produced during fermentation, about 10mg/l in average. For that reason, there will always be sulphites in wine. The rest would be added by the winemaker.
In the EU, a maximum of 150 mg/l total SO2 for red wine (100 if organic) and 200 mg/l for white rose and sweet red wine (150 if organic), is permitted. Limits for sweet wines are however much higher, up to 400 mg/l. The rules vary between countries, but most producers keep levels well under these limits. Organic wines in the USA are free from added SO2. Natural winemakers have yet to be in agreement over the limits of total SO2 in natural wines. Some argue true wines should have no SO2, even if the risks of spoilage and premature oxidation are higher. Most agree that a ‘dash at bottling’ for stability is an acceptable compromise to ensure stability. The French ’Vin Méthode Nature’ label draws the line at 30mg/l, the RAW Natural Wine Fair wouldn't accept any wines showing more than 70mg/l. We at Le Social have a slightly more holistic approach, although we probably wouldn't go above 40mg/l.
Sadly, there isn’t any direct replacement for SO2 available yet to the winemaker, but the majority of wineries are working on lowering their SO2 additions. Whether the solution is coming from high technologies or a more natural is down to the producer’s philosophy.