The most frequent question I’m asked about a wine nowadays is “does it contain sulphites?” and my answer is always “yes, virtually every wine contains sulphites, but only a tiny amount”. Sulphites (or sulfites in the USA) is the everyday term for the gas Sulphur Dioxide (SO2). It is added to wine during the bottling process because it is a non-toxic germicide and anti-oxidant, in other words it kills bacteria and prevents any oxygen present in the bottle after corking from spoiling the wine. Wine starts to go off a few hours after opening because exposure to oxygen alters its chemistry and after about 2 days it becomes undrinkable. SO2 stops this happening in the un-opened bottle and keeps the wine fresh, for years if necessary.
Unfortunately, SO2 does have one major drawback which is that, in excess, it has a pungent, prickly smell and can sting the throat. This can be a problem for asthma sufferers but only, to repeat, in excess. SO2 has far wider uses than just the wine trade. Those lovely fresh fruit and vegetable salads in supermarkets and health food shops are all preserved with SO2 (which is why the fresh produce does not very quickly go brown from oxidation), fruit juices are all bottled with it and most processed food is protected with it. And all of them contain far higher levels of SO2 than does wine.
So why do people always ask about SO2 in wine? Because it has recently become the law in several countries for the use of sulphites to be declared on the wine label and most other countries have fallen into line in advance of any possible universal legal requirement. The use of SO2 continues because there is no viable alternative. Even organic wines use SO2 because without it, an unacceptably high proportion of bottles would be spoiled either by infections from wild yeasts and bacteria or by oxidation. Pasteurisation could prevent spoilage but the taste of the wine would be altered and the wine would be “killed” ie it would not age. Pasteurisation is only suitable for cheap wines made to be drunk young.
The amount of SO2 needed to prevent infection and oxidation in a bottle of wine is so small as to be undetectable by our nose or taste buds. Unfortunately, some bottlers do go a bit overboard on the dosing (usually with the cheaper white wines which can be particularly susceptible to oxidation) and the effects can be very noticeable in the newly opened wine. If in doubt, follow this procedure – open the wine but do not immediately sniff the wine or cork and do not pour it. Just leave it for 30 seconds and any excess SO2 will quickly disperse. Then pour the wine, swirl it in the glass and, to be really on the safe side, leave it for another 30 seconds before sniffing, tasting and enjoying.
Some people claim that the SO2 in the wine gives them a headache – to which I always have to make a tactful reply on the lines that if wine is giving you a headache it is more likely to be for a reason other than sulphur, and not having enough space in the recycling bin for all the empties is the most common cause.