Sulfur dioxide in wine – benefits and harms, home use

Sulfur dioxide (sulfur oxide, sulfur dioxide, additive E220, SO₂) is used in winemaking as a preservative due to its antioxidant and antimicrobial properties. Molecular SO₂ is an extremely effective antibiotic that kills most microorganisms (including wild yeasts) that can lead to wine spoilage. Also, its antimicrobial properties can reduce the amount of volatile acids (for example, acetic bacteria are aerobes and are very sensitive to sulfuric acid, which limits the access of oxygen to the drink).

In addition, sulfur dioxide is credited with antioxidant properties, allegedly preventing wine from oxidizing. Actually SO₂ is not a direct antioxidant, but sulfur is found in wine not only in the form of molecular SO₂, and and in the form of bisulfite (HSO₃-) and sulfite (SO₃^2-). So sulfur bisulfite forms a bond with aldehydes (the culprits of oxidation odors) to form a harmless, odorless molecule. In general, if we summarize all this pseudo-scientific text, it turns out that sulfur dioxide is the most useful and effective tool in the hands of a winemaker, with which he can protect his product and provide him with guaranteed quality.

Of course, sulfur dioxide has a negative effect on the body, because it is toxic. When inhaling a high concentration of SO gas₂(and in the normal state it is just gas) there is a serious poisoning, which affects, first of all, the lungs and can lead to their edema. But, as you understand, the concentration of sulfur in wine is on a completely different level and it can harm only those people who have an individual sensitivity to this gas (for example, in the USA, 2% of the population is allergic to SO0,4). Also, the use of foods treated with sulfur dioxide is highly discouraged for people with asthma. In other cases, this preservative is absolutely harmless, of course, if we are talking about wine.

Surely you have friends who regularly suffer from headaches and redness of the skin in the morning after drinking red wine the day before. Many people blame it on sulfur dioxide. It’s a delusion. White wine contains more SO₂than red, and dessert wines even more. In fact, the negative impact of wine on the body is a complex and not fully understood mechanism. In addition, many people often forget that sulfur dioxide (food additive E220) is used everywhere in the food industry, especially in the production of dried fruits, where, as a result, the level of SO₂ an order of magnitude higher than in any wine.

If this is domestic wine, then no way – we have E220 included in the list of permitted food additives, as completely safe for health (when used in reasonable quantities). In the US, since 1988, all wine producers have been required to write on the bottle “contains sulfites” (contains sulfites), if the level of SO₂ in the drink exceeds 10 parts per million (about 10 mg / l), and this is almost all the wine of the American market. Since 2005, all European wines must also contain such an inscription.

In the USA, as in Australia, up to 250 ml/l of sulfur dioxide is allowed in dry wines and up to 350 ml/l in dessert wines (residual sugar is more than 35 g/l). In the EU, SO content₂ in dry red wines it should not exceed 160 mg/l, in sweet whites it should not exceed 300 mg/l, and for botrytised wines such as Sauternes it should not exceed 400 mg/l.

These do not exist in nature. The fact is that sulfur dioxide is a by-product of fermentation. All wines, without exception, contain between 10 and 100 ppm SO₂, even if sulfur was not used in the winemaking process. But this does not mean that all manufacturers use sulfur dioxide in the preparation of their product. The method of obtaining wine without chemical preservatives or with minimal use of them is called “natural winemaking”.

Fans of the theory of “natural winemaking” believe that sulfur not only kills everything bad, but also kills a lot of good. Such winemakers use only organic, very high-quality raw materials, and also maintain impeccable cleanliness in production. But even they use SO₂. Yes, in minimal quantities and only when bottling a drink (in conventional production, sulfur dioxide is often used and at different stages, for example, after picking berries, during their crushing, during the fermentation process, during bottling), but they are added. Also, sulfur is often used, including by “natural winemakers”, to fumigate wooden barrels that are used to collect juice, ferment or age the drink (it is known that burning 5 g of sulfur in a 225-liter wooden barrel increases the level of sulfur dioxide in wine by 10 -20 mg/l). Be that as it may, there are wines where the sulfur dioxide content is so minimal that it will not even cause allergic reactions in people with preservative sensitivities.

The site www.vinsnaturels.fr (and others like it) has a small list of French wine producers who are engaged in “natural winemaking” without the use of sulfur dioxide.

Any winemaker will tell you that you can’t make good aged wine without using sulfur dioxide. Actually it is not. It is possible to cope with unwanted microflora and fauna with banal sanitation, but it is much more difficult to deal with oxidative processes that greatly affect the taste, color and aroma of the drink without sulfur. Means not to use SO₂ and at the same time to get good wine, you need to be able to control oxidative processes. There are several tricks for this:

1. The lower the pH of the wine (the more acidic it is), the less SO is required.₂ for a normal result. Therefore, it is important to monitor the acidity of wines and increase it if necessary with tartaric acid (the optimal acidity level of must and wine is usually indicated in the recipe).
2. The higher the alcohol content of wine, the more resistant it is to spoilage and oxidation.
3. The use of screw and glass corks instead of corks will prevent oxygen from entering the bottle, which will minimize oxidative processes.

To answer the question briefly, yes, wines with lower acidity and alcohol content are much more prone to spoilage, which means they require more sulfitation. Such wines, of course, include all table dry and semi-dry wines, as well as all others made from fruits and berries with a low acid content without further lowering the pH.

The most practical source of SO₂ for home winemaking is potassium metabisulphite (potassium pyrosulfite, K₂S₂O₅), a salt composed of 57% sulfur dioxide. It can be a powder or Campden tablets, which are more familiar to many experienced winemakers and brewers and can be purchased at almost any wine or brewery store. Typically, one such tablet contains 0,44 g of potassium metabisulphite, half of which is sulfur dioxide. Potassium pyrosulfite is replaced by sodium metabisulphite, but it should only be used to sterilize equipment: a) it is better not to disturb the sodium balance in the body; b) potassium ions in wine are more beneficial. Carefully read the instructions for the purchased tablets or powder, where the dosage and method of administration are usually clearly described.

Describe the full range of applications of SO₂ in home winemaking I will not (see the article mentioned in the paragraph above), but will briefly touch only on the last stage of wine preparation – its storage, assuming that you are engaged in “natural winemaking”. Before bottling wine with normal acidity, add 1 Campden tablet per 4-5 liters to it, after crushing it into a powder or dissolving it in a small amount of pure water (or use about half a gram of potassium pyrosulphite salt).

This amount of sulfur dioxide (approximately 50 mg/l) will slightly increase the sulphation of the wine, while still providing adequate protection against oxidation and bacterial attack. By normal acidity, I mean approximately pH = 3,4…3,5 for red grape wines, 3,2…3,3 for whites. If the pH is higher, SO₂ more will have to be used (for example, if the pH of red grape wine is 3,8, then 100 mg / l of sulfur dioxide should be added to it).