Sulfites in wine

What is sulphite?

Sulphite, sulphur, SO2, sulphur dioxide, meta bisulphite:... you can call it what you want, but all these terms are used in the agri-food industry to refer to sulphur dioxide, a chemical compound made up of one sulphur molecule and two oxygen molecules (hence its scientific name: SO2).

The sulphite contained in foods, including wine, is not sulphur but a derivative of sulphur.  Sulphur is a mineral naturally present in the soil, while sulphur dioxide is a colourless gas produced by the fermentation of grapes during the winemaking process, and is the result of the combustion of sulphur. Being a water-soluble gas, if it is dissolved and mixed in water, it produces sulphite. No food, including wine, contains sulphur in chemical form (S) obviously!!.

Sulphite in wine

In addition to being naturally present in wine in small quantities, sulphite can be added in varying proportions, which is why in the food industry the term "added sulphite" is generally used. The point, therefore, is not so much the presence or absence of sulphite in a wine, but rather the quantity in which it is present.

Thus, wine without sulphites does not exist. Rather, there can be a wine ''without added sulphites''. 

But what are they really for?  Sulphites have several functions:

Preservative action : by combining with oxygen, sulphites protect wine from oxidation.

Antiseptic and antifungal action : sulphites disinfect barrels and must, eliminating bacteria and moulds.

Stabilising and controlling action : they favour the best yeasts by blocking others.

Solvent and clarifying action : they accelerate the decomposition of the fruit to facilitate the release of tannins and aromas.

Sulphites act as clarifiers by promoting the deposition of polyphenols contained in the skins. Sulphites are essential for products intended for storage and also for transport. Consequently, wines without added sulphites are very delicate and, needing to be consumed within the year, can usually only be sold in the country of production. The export of wines without added sulphites is highly discouraged as their structure is too delicate and fragile to withstand long journeys.

In practice, sulphur dioxide is indispensable to prevent wine from quickly turning into vinegar. The addition of SO2 during fermentation eliminates certain bacteria and yeasts, ensures microbiological balance, prevents the dispersion of aromas, and promotes optimal product evolution. 

The addition of sulphites is an ancestral oenological practice... it was widespread even in ancient times, as evidenced by writings from Homer and Pliny. However, the first official record dates back to the 15th century when authorisation for the addition of sulphur to wine produced within the territory corresponding to present-day Germany was documented for the first time. In the Middle Ages, mixtures of spices and honey were used to mask the taste of vinegar, while in ancient Rome, sulphur candles were burned inside amphorae containing wine to prevent it from turning into vinegar.

How many sulphites?

All wines contain sulphites, but the dose of added sulphites is not the same for all.

Red wines contain smaller quantities. Dry white wines contain a moderate amount, while semi-dry and dessert wines contain the most. In practice, the more residual sugar a wine has, the more sulphites are needed, because the higher the sugar content, the greater the risk of refermentation in the bottle. 

Sulphite dosage also depends on acidity. Wines with low acidity require higher doses of sulphites to ensure good preservation over time. 

In general: 

White wines contain about 100 mg of added sulphites per litre

Red wines contain about 50-75 mg of added sulphites per litre

Wines with fewer sulphites are those with high alcohol content (also called fortified wines): Port, Banyuls or Madeira, for example, contain enough alcohol to prevent a second fermentation in the bottle. Furthermore, in these types of wines, oxidation is a sought-after characteristic, so it is not necessary to prevent it by adding sulphites. 

Sulphites and Health: Let's clarify 

Sulphur dioxide is an allergen, just like nuts, shellfish, and gluten. This means that for some people, it can cause unwanted effects, including itching, hives, sneezing, or abdominal cramps. In the absence of allergies, the quantities of sulphites added to wines do not pose any risk.

A common misconception about sulphites in wine is that they cause headaches, stomach upset and diarrhoea, hangovers, and other unpleasant side effects. However, in most cases, this is not true. The problem is not the sulphite itself (at most its excessive dosage - usually in wines of poor quality and craftsmanship) or the wine itself, even if of considerable quality, consumed in excessive quantities. Adverse reactions to sulphites in wine are usually referred to as "sulphite allergy" having symptoms similar to a classic allergy. In reality, it is HYPERSENSITIVITY, as the immune system is not involved in reactions to sulphites. A true allergic reaction following sulphite consumption (very dangerous) has been documented by EFSA (European Food Safety Authority) but it is an extremely rare event.

The addition of sulphite is not a practice confined solely to oenology; on the contrary, most foods consumed daily contain added sulphites. All products intended for preservation contain a more or less significant percentage of added sulphites. This is the case, for example, with canned legumes and fruit, dried foods (fruit, legumes, nuts), cured meats, and ready meals.

And as we said in the article dedicated to wine calories (if you missed it read here) drinking a good glass of wine goes beyond knowing about sulphites. The rule is always one and the same: Drink little but drink well!