Sulphites and natural wine

Sulphite is the oldest known wine additive. In almost every bottle you can have in Europe, you will notice the “contains sulphite” or equivalent sentence on the label. But what is sulphite, why is added during winemaking? And what about Natural wines?

You may think that sulphite is a product of the industrial revolution, like artificial fertilizer and other chemicals. Wrong! sulphite is added to wine since the Roman Empire. It was one of the oldest additives in winemaking with water, honey, resin, and lead (fortunately the last one is not used anymore).

Roman understood, 2000 years ago, that sulphite has the properties of preserving wine from some flaws. In 2023, sulphite is still present in the wine.

How can we define sulphite? Strangely, sulphite is a “natural product”. It is the result of the reaction between sulfur and oxygen. This reaction can occur naturally in the human body, during wine fermentation, or in other biological systems. In chemistry, it is SO2, the activated form is an ion in a solution (exactly an anion because it has a negative charge, but is not a chemistry blog here).

It is important to understand the role of sulphite in wine processing. If this ion is used for two thousand years, it is not a hazard or the result of a complot of the chemistry industry. This compound has the property to protect wine from various flaws, and not using it makes winemaking a lot much challenging.

Sulphite is an anti-microbial agent and helps to restrain oxidation in the wine. It works by preventing rogue bacteria to multiply and by inhibiting enzymes known as oxidase that speed up oxidation reactions in the must during fermentation. It is also bound with hydrogen peroxide, an oxidizing agent.

Sulphite works better with high acidity. Acidity is measured by the Ph scale, where 7 represents the level of water, neutral. Everything after seven is alkaline, and under seven is acidic. Wine is an acid solution with a Ph between 3 and 4 (for comparison the Ph of Coca-Cola is 2.7). This acidic situation is ideal for sulphite to protect the wine.

In conventional winemaking, sulphite is added at several stages, when the berries are crushed, in the must, after the alcoholic and malolactic fermentation, and at the bottling. The level of free SO2 (part of the SO2 is bounded to something and so non longer active) can be measured at every stage to avoid breaking the maximum sulphites level.

In Europe, there are rules on the maximum level of sulphites in the wine. For conventional wines, it is 150 mg/l for red wine, 200 mg/l for rosé or white wine, and 235 mg/l for sparkling wine. For organic wines, the maximum limit is 100 mg/l for the red and 150 mg/l for the white or rosé wines.

And if you think of it, who will add the maximum amount of sulphites? Mostly industrial companies that sell bottles to supermarkets. They have a large amount of wine, made at scale. They do not want to risk losing it, so they will add the maximum amount of sulphite than can.

At this level, are sulphites dangerous for human health? For most people, no but some people with respiratory issues can have a sensitivity to allergic reactions with sulphite. In rare cases, people can have mild reactions like stomach cramps or even a rash. But in some rare cases, the reaction can be more extreme, like breathing difficulties. Emergency medical assistance is needed in these cases. It is mainly the case for people suffering from severe asthma. That is why you will find “Contain Sulphite” in most wine bottles all over the world.

Sulphite is also an ideal suspect for the morning-after headache. But there is no clear scientific evidence. Alcohol is well known for causing headaches because of dehydration. Another source is the level of histamines, the result of the degradation of an amino acid (fun fact, natural wine may contain fewer histamines than traditional wine).

In natural wine, health is not the primary reason for not adding sulphite (or just a low dose during the bottling). The main reason is purity. If you listen to Jules Chauvet, the father of Natural wine. Jules Chauvet, who died in 1989, was a wine scientist and a winemaker in the Beaujolais region. Chauvet thought was that sulphite was a poison for yeast and other bacteria. Without sulphite in the must, the malolactic fermentation starts more rapidly.

You can also taste this purity. The best way is to find a Natural Beaujolais village and a Beaujolais village the same vintage from an independent winemaker (a “Récoltant”), and you can make the comparison.

Those who followed Chauvet, perfected the method, making sure that no SO2 was added during the fermentation process. They defined several processes that are now standard in the natural wine movement today. They sometimes, but not always, advocate for a small amount of sulphite (less than 30 mg/l) during the bottling.

But not adding sulphite, during fermentation is not an easy task. Sulphites are not an ineffective product; it does help to reduce flaws in the final product. Hygiene is the first answer, starting with the quality of berries, do not collect berries with traces of fungus contamination. That supposes manual harvesting. The second answer is a clean winemaking process with clean material, and finally the third, using lees, yeast cells, and solid content, they are proving that lees have a protective effect against some flows.

This is the natural wine way. But there are other ways to produce wine without added sulphite. Far away from the natural wine movement, by using inert gas and sterile filtration.

Sulphite is not evil, it can cause some health issues, it does protect wine but it also alters it. Using it during the fermentation may conduct in different outcomes. But natural wine doesn’t stop at removing sulphite from the process, it is more than that.