Monthly Archives: November 2013

Sulphur Dioxide – the Magic Molecule

Sulphur Dioxide molecule

Sulphur Dioxide molecule

Sulphite additions to food and wine have become a big issue. However, the sulphites, and the sulphur dioxide that they produce have real benefits.

Why is the term sulphite used?
Sulphur dioxide is sometimes injected as a gas, but solid sulphite granules are usually added instead. The acid in wine rapidly splits this up to produce sulphur dioxide which actually does the work.

Sulphur dioxide occurs naturally in wine
This may seem unlikely, but fermentation of grapes produces sulphur dioxide without any help from humans. The amount depends on the the yeasts that are used, but it is a ‘natural’ product.

Why are sulphites added to wine?
There are two main benefits:-

  • Antioxidantif wine is exposed to air, the alcohol is quickly oxidised to acetic acid (vinegar). So, nature’s natural tendency needs to be moderated, if we are to drink the wine before it goes off. Sulphur dioxide attacks the chemicals which would otherwise produce vinegar. This is less of an issue for red wines which have their own antioxidants.
  • Antimicrobial – wine contains yeasts and bacteria. The magic molecule prevents these from multiplying and spoiling the wine.

Which wines have the most sulphur dioxide?
SO2 binds with many compounds in wine, including sugar. Only the unbound sulphur dioxide is able to fend off oxygen and microbes. So, sweet wines need plenty to protect them.

The importance of quality grapes
Rotten grapes make rotten wine, and need more sulphur dioxide to keep the bugs under control. Grapes with plenty of acidity also need fewer additions.

What are the adverse effects?

  • Sensoryan excess of sulphur dioxide produces a smell of burnt matches, but an awful lot needs to be added to have this effect. This fault is rare.
  • Healthis a difficult issue because there is little proof of adverse effects. It may induce asthmatic attacks in some people. It is worth noting that normal food metabolism in the body generates much more sulphites than you would absorb from wine consumption.

Conclusion
In my opinion, the addition of sulphites at the right time and in the right quantity is beneficial, if not essential, for almost all wine.