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What Are Sulfites?

You've just opened a bottle of wine for dinner. On the label, you see these words: Contains Sulfites. What are sulfites? And what are they doing in your wine?

red wine in a glass with a blue background

Photo: USDAgov (Flickr)

Have you ever had a glass of wine that contained sulfites?

You’ve just opened a bottle of wine for dinner. On the label, you see these words: Contains Sulfites. What are sulfites? And what are they doing in your wine?

Chemical Compounds

Sulfites are chemical compounds found naturally in grapes, garlic and other plants. Thousands of years ago, people realized something nifty about sulfites: they kill or slow the growth of bacteria and most yeasts. This comes in handy for winemakers, who add specific yeasts to ferment wine, and don’t want wild yeasts or bacteria to spoil it. Sulfites prevent spoilage in wine, acting as a preservative.

The amount of sulfites naturally in grapes is very small, and there’s a bit more produced during fermentation. But to take full advantage of sulfites’ preservative abilities, winemakers add a little more to the process. The Egyptians sterilized wine containers with sulfites, and sulfites have been added to wine for hundreds of years.

Wine And Sulfites

So the relationship between wine and sulfites goes way back. But in 1985, the Food and Drug Administration required wine with added sulfites to say so on the label. Why?

Researchers had recently discovered that less than one percent of the population is sensitive to sulfites. Most have mild reactions, like an itchy rash. But some folks have life-threatening reactions, including difficulty breathing and low blood pressure.

These rare but serious reactions are most often seen in asthmatics. Not all asthmatics are sensitive to sulfites, but the label’s there for those who need to steer clear. As the old saying goes, in wine–and now on the label–there is truth!

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