sulfur anhydride

For a long time, much has been said about sulfur dioxide, better known for its most controversial part: sulfites. A chemical compound historically linked to the world of wine and that, without it, would have many problems to preserve its properties.

Sulfur dioxide or sulfur dioxide with the formula SO2, is a product that has always been linked to the production of all kinds of wines. We are talking about an innocuous compound in most cases but which, in certain people and at high concentrations, can cause discomfort. So that you are clear about what this anhydride is and what its effects are, we tell you everything you need to know about it.

What is sulfur dioxide

The group of anhydrides are chemical compounds that are formed from oxygen and any non-metallic chemical element. Regarding sulfur compounds, these are created by combinations of sulfur and other elements. Taking these two parameters into account, we can deduce that this product is a mixture of oxygen and sulfur. This can also be called sulfurous acid and has the formula SO2, as we have mentioned. That is why it is also known as sulfur dioxide or sulfur oxide II.

It is important not to confuse sulfur dioxide and its formula with that of other similar compounds, such as sulfur dioxide, better known as sulfuric acid. Due to the different valencies of sulfur, the reaction between it and oxygen can generate other compounds. This is the case of sulfuric anhydride, as well as sulfuric acid, formed when it reacts with water. In this case, a toxic compound is generated that can cause burns. Therefore, it is never used in wine production. The same happens with sulfur oxide, also called sulfur dioxide II or sulfur oxide VI, with similar effects.

What is it for

Although SO2 in chemistry has many uses, when it comes to wines, its main application is as a preservative. Something that has been applied in wineries for hundreds of years. This compound allows the base for the wine and the final product not to deteriorate over time and maintain its properties in perfect condition.

This anhydrous is added both in the must phase and in the conventional vinification phase. By the way, if you don’t know what the must is, we will tell you that it is the phase in which the wine is not prepared, but we only have the base grape juice and the yeast. Once this must is fermented, the final product is created, which must still mature to achieve the corresponding flavors and aromas. In any of these phases, this compound provides four very interesting effects for the wine.

One of them is its antiseptic nature, by which the final product is properly disinfected without the need for anything else. It also includes an antioxidant function, so that the final product does not deteriorate or turn sour, which is one of the main risks in winemaking. All this without forgetting other effects such as clarifying, which gives the final wine a better color, or its anti-enzymatic character, which prevents unwanted evolutions or changes in the wine.

How is it obtained

When it comes to achieving an adequate concentration of this anhydride in the wine, there are two ways to proceed. The most widely used is to add this compound during the winemaking phase, generally to the must. This process helps to maintain the concentrations within what is recommended, since an excess of this anhydride in the wine can affect its maturation and its flavor, changing it to something not so pleasant.

Another solution is to sulfurize the vineyard. Something that shows how the relationship between sulfur dioxide and food is more than well known, especially as it is the most traditional way of obtaining the presence of this compound. And it is that, among the properties of the must with which the wine is made, we have the presence of sulfur, available naturally in the soil and in the grape. So, if you want to increase its presence, just add more sulfur to the earth.

Sulfur dioxide and sulphites

If we take a look at the label of any current broth, we will see how it refers to the product’s allergens, among which are sulfites. The application of sulfur in wine generates the presence of these compounds, due to the reactions between this compound and the wine or must itself.

Over time, it has been discovered that sulfites in food and drink can cause allergic reactions, especially in people who are sensitive to such compounds or who have asthma problems. The effects of this intoxication are nausea, gastric irritation and even vomiting. However, these appear from high concentrations and do not pose risks beyond a slight discomfort.

According to the World Health Organization, the acceptable number of sulfites ranges from 0.35 to 1.5 milligrams per kilo of weight per day, taking as a reference the average of this range, 0.7 milligrams per kilo. With this reference, we deduce that for a person weighing 80 kilos, the maximum daily amount would be around 56 milligrams of sulfites. 

Given that the current legislation establishes a limit of 150 milligrams of sulphites per liter for red wines and 200 milligrams for white and rosé wines, we see how that person should not drink more than a third of red wine or a quarter of white wine so as not to exceed limits. However, winemakers use quantities much lower than the legal maximum, so you will probably have problems with alcohol sooner than with sulfites, unless you are allergic.

As a last question, it is key to know that all wines that have more than 10 milligrams of sulfites per liter must indicate it on their label. The problem is that, with very rare exceptions, the real concentration is not indicated, which makes it a bit more difficult to adjust consumption. If you have problems with allergies, you can always resort to wines without added sulphites, which contain only the sulfur dioxide of the grape itself.

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