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What are Sulfites? A Look at Wine’s Most Misunderstood Compound

Man pouring red wine in glass during dinner party

Wine is fairly complex, which means there’s ample opportunity to throw some part of its greater whole under the bus, depending on what’s currently in fashion. For a while, Merlot took a licking. Then, big buttery Chardonnays played the role of the punching bag. Now, sulfites are the subject of a significant amount of criticism.

Generally speaking, when we’re talking about sulfites, we are talking about the addition of SO2 (sulfur dioxide) to wine. The industry has relied for ages on the compound to preserve, control, and, to some extent, stabilize the end product. It can be argued that it’s a big reason why wine has become a viable commercial product with good shelf life and even age-ability.

The wine industry has relied on sulfur dioxide for ages to preserve, control, and, to some extent, stabilize the end product.

But with the return to minimalistic winemaking (natural wine, low input wine, unfiltered wine), sulfites and other additions are on the hot seat. Now they’re prone to interrogation: Aren’t they responsible for hangovers? Won’t they make the wine stink? Aren’t they more for industrialized food and not wine?

In short, no, no, and no. And this is no dis to the natural wine movement, which is turning out some genuinely interesting wines. Additionally, there’s a very small part of the population that experiences a very real and very serious allergy to the stuff. But it’s fair to say sulfites might be on the receiving end of a bit too much bitching and moaning.

For context, sulfites are prevalent in food. There are horror stories of folks dealing with potentially lethal quantities of them in salad bars especially, where — in the past, especially — big restaurants would treat their greens and produce to sulfur baths in an attempt to keep them fresh. SO2 is added to all kinds of things, in quantities much greater than what shows up in wine. Dried fruit is an obvious example.

sulfites label

Gordon Burns has 40 years of lab experience. He works for ETS Laboratories, one of the country’s premier wine analysis outfits, based in California but with satellite labs elsewhere. While he admits he’s no toxicologist, Burns knows plenty about wine chemistry and the use of sulfites.

“One thing that’s been a constant in wine is the use of sulfites, going back to its very beginnings,” he says. Burns mentions the old methods of way back when producers would burn sulfur candles in wine vessels to keep them from turning. He also brings up the early days of militaries, which relied on S02 to preserve grape juice in transit and over time.

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He says the use of SO2 in winemaking came about for a major reason: “The end process of grapes is actually vinegar if we let it go through that process,” he says. The use of SO2 disrupts that process and also functions as an antioxidant. It helps the wine hold onto its integrity.

Many producers do not add SO2 but even so, the winemaking process itself yields sulfites. “The yeast themselves can produce sulfur dioxide,” Burns says. To add to the confusion, the labeling restrictions are often different from country to wine-producing country. In the end, it’s fair to assume there are some in your favorite bottle, no matter what it says, just not that much in the overall scheme of things.

A woman's hand reaches out to select a bottle of red wine from the shelf of a wine shop

“But we’re talking about tens [of] parts-per-million compared to hundreds and thousands of parts-per-million in other foods,” Burns adds. In his many years at ETS, he can’t recall a wine that had an unhealthy amount of sulfur dioxide in it. He adds that the lab has had more than 10,000 winery clients over that span.

I have certainly tried some impressive wines made without the explicit addition of S02. You could even argue that a few of them were even a bit more vibrant in terms of color and flavor. But treating sulfites like they’re the tool of Big Wine and out to get you with their chemical side effects is, by and large, unfair. It also runs contrary to why they were introduced in wine in the first place.

So, try that sulfite-free wine and if you like it, buy more. Or, stick to your favorite traditionally made bottle. Just don’t go throwing S02 unfairly under the ‘ol bus.

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