Next time you pick up a bottle of wine have a look at the back label. It will probably include the warning: ‘Contains Sulphites’ (as well as injunction not to drink wine if you’re pregnant).
Sulphur products are used in winemaking - especially at the time of bottling - as anti-oxidant and anti-bacterial agents, particularly for white wines. They are needed to stabalise colour, keep the wine clean and give the product shelf-life.
But even wines that are made without recourse to sulphur will contain an amount of sulphites in some form. The reason is: the very act of fermentation actually creates sulphur dioxide, some of which will become bound into the wine. Even wines that have never been treated with sulphur will contain concentrations of up to 10 milligrams per litre of SO2. (The same is true,incidentally, for foodstuffs that are fermented, like cheeses and sauerkraut. And you can be sure that sulphur products are used to preserve the flavour and colour in fresh fruits, dried fruits, vinegar, juices, soft drinks, sauces, beer as well as wines.)
Logically then, the back labels on wine bottles should read: ‘Guaranteed to Contain Sulphites.’
EU wine laws have come to terms with this irony by regulating that any wine with more than 10 milligrams per litre of sulphur dioxide must carry the warning that the wine contains sulphites.
Most consumers can’t sense the presence of sulphites on the nose or the palate at twice this level and it’s only at above 30mg/l that experienced tasters can detect the ‘burnt match head’ odour that signals the presence of SO2. White, rosé and particularly sweet wines tend to have higher levels of bound-in sulphur than reds.
The World Health Organisation has set guidelines for the safe ingestion of sulphur dioxide, recommending a daily intake of no more than 0.7 grams per kilogram of body weight. For men of average weight this computes to less than a third of a bottle of a white wine with a concentration of 200 mg/l (the EU limit for dry white wine is 210mg/l – though these days this figure is very high given winemakers’ desire to limit the amount of sulphites they use.).
Sulphur dioxide may cause allergic reactions in some people, especially if one suffers from asthma. Unfortunately, there is no way to tell the amount of SO2 in a given wine but there will always be some. And given modern winemaking techniques and the sensitivities winemakers have around the use of sulphur products - with the move to organic and biodynamic wine growing and cellar practices – there will continue to be less sulphites in wine.