Contains sulphites: these two words on the back label of any wine bottle spark many debates. Why start using it now, and why do winemakers use sulphur in the first place? The first question is easy to answer: even though rumour has it that sulphur was used in Roman times to preserve wine, the earliest evidence of sulphur in wine goes back to the late 15th century in Germany. But why use sulphur at all?
Well, sulphur (as in sulphur dioxide or SO2) is the only chemical/preservative that has antioxidative and antimicrobial properties. Big words, I think I’ve just lost half my audience. For the rest: let’s break it down.
Antioxidative
About 20% of the atmosphere is oxygen. Which is not a bad thing, taking into consideration that we need this oxygen to breathe. Problem is, oxygen can oxidise natural components, changing its properties. For instance, if you take a bite of an apple and put it down for a few minutes, the flesh of the apple exposed to air turns brown. This is because of oxidation. A similar reaction takes place when wine is exposed to air, turning good aromas into something that doesn’t smell that great, and turning the colour from green or red to brown. To prevent oxidation, the winemaker uses sulphur to preserve the fresh flavour and colour of the wine.
Antimicrobial
There are a host of bacteria and wild yeast on a bunch of grapes - on any fresh fruit, for that matter. The problem comes in when the grapes are crushed in the beginning of the winemaking process. The bacteria on the grape skins then come into contact with the juice and the juice (or wine, at a later stage) can become spoilt. Again, sulphur is used as preservative, preventing the wine or juice from being spoilt.
Why not use something else? As mentioned earlier, sulphur is unique in the sense that it is the only chemical with antioxidative and antimicrobial properties. And extremely effective in both cases.
It is important to note at this point that sulphur is a natural product. If you make wine without adding any sulphur during the process, you will still end up with a final product containing traces of sulphur. Certain cheeses, for instance, also contain sulphites, even though sulphur is never added during the cheese making process. Sulphur is also used in a range of other food products, such as dried fruit, processed meat and fruit juice, to name a few. The allowed levels of sulphur in wine are extremely low, though. To give you an indication: the maximum allowed level of sulphur in wine is less than 7% the allowed level of sulphur in dried fruit. To go even further, we actually need small amounts of sulphur as building blocks for some amino acids in our bodies, and they are part of certain enzymes involved in energy transfer.
So, how bad is sulphur for you?
This is a tricky question, which I should really try to avoid. Writing this letter, I’ve done a lot of research to find out exactly how and why sulphur is bad for you. It seems like inhaling sulphur is not a great idea. Lots of information shows the negative effect (especially on your respiratory system) when inhaling sulphur gas. But as far as eating or drinking products containing sulphur is concerned, research information is a lot less clear. With the exception of people with hypersensitive or allergic reactions to sulphur, it is safe to say that the level of sulphur in wine is so low that moderate wine consumption poses no health threat.