Like tannins, sulphites are often mentioned in connection with wine and their role and effects are often misunderstood. All wines contain sulphur dioxide, SO2, in various forms, collectively known as sulphites and even in completely natural wine it is present at concentrations of up to 10 milligrams per liter. The most important thing to understand is that sulphites are an entirely natural bi-product of yeast metabolism during fermentation and would be found in wines even if the winemaker added nothing to the juice.
The Romans used to burn sulphur beneath their upturned amphora or wine containers to sterilize them before use and winemakers have been adding various amounts of sulphites ever since to prevent bacteria and bad yeasts from developing in the wine. In the late 1840s European vineyards were nearly all destroyed by a disease called oïdium and were saved only at the last moment by nation-wide applications of sulpher dust.
Sulphites play a very important role in preventing oxidization and maintaining a wine’s freshness. Even so, compared to processed foods, dried fruit, sodas, packaged meats or even commercial fruit juice the amount of sulphites in wine is miniscule. On visits to Europe over the years, I have often been given bottles of wine made by friends for local consumption, not for export. These fresh wines which were delicious when drunk locally, had been made without the addition of sulphites and were sadly undrinkable by the time I had brought them home to the USA.
U.S. wine labels are required to indicate if the sulphite level exceeds 10 parts per million (ppm). Many red wines contain sulphite levels of 50 ppm but this should be compared with the 2,000 ppm sulphite level of French fries to put it in perspective. Some people blame the sulphites for the headaches they suffer when drinking red wine but in fact red wine has much lower sulphites than white wine and headaches are more likely to be caused by the tannins, the histamines or even the extra alcohol in red wines. Despite some of the hysteria about sulphites, the levels of sulpher dioxide in wines is too small to have any adverse health effects except for those people who are clinically allergic to sulphites, and the FDA estimates this to be less than 1% of the population.
If you have eaten dried fruit or French fries with no ill-effects, then continue to drink your wine and not worry about sulphites.