Skip to main content

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.

Recommended Videos

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.

Further Reading

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.

Mark Stock
Mark Stock is a writer from Portland, Oregon. He fell into wine during the Recession and has been fixated on the stuff since…
Bubbly? Full bodied and red? Zesty and white? Your favorite wine types, explained
All the primary types of wine (and everything you need to know about them)
Glasses of different kinds of wine

Trying to understand everything about wine all at once is impossible -- and that's the beauty of it. Like music or the person you love, there are always new things to discover. Not only that, but your taste in wine will expand and evolve as you mature. If you don't know that much about it right now, so what? Even the most prestigious wine experts in the world often find themselves at odds with the basics of different types of wine. And anyway, can you think of a ridiculously fun learning opportunity?
So, let's start with the basics. We'll learn that -- just as in life -- there are rules, then exceptions to those rules, then ultimately that there are no rules except be a good person and serve your higher purpose. (OK, maybe this is going a little beyond wine.) Let us open that gate to this particular garden of earthly delight and pop a cork while we're doing it.

Sparkling wine

Read more
You won’t find claret wine in the store, but you’ve probably already had some
A corrupted name with a cool history
Red wine being poured into a glass

Perhaps you’re into period English movies (like, say, anything by Jane Austen). If so, you’ve noticed that when it’s time to break out the good stuff (you know, the bottle from the cellar that needs to be decanted), it’s always a wine called "claret." While I do enjoy the occasional Jane Austen movie, I’ve been a more consistent fan of wine -- but for the life of me, I couldn’t figure out what this claret stuff was, why it was so beloved, and where I could get my hands on it. The short answer is that "claret" is basically British slang for red wines from Bordeaux. The long answer involves ancient Romans, Eleanor of Aquitaine, English corruption of the French language, the Hundred Years’ War, and a dry, brick-red rosé that might not yet be on your radar.

The Romans, great champions of the grape themselves, did bring viticulture to the Bordeaux region -- though, to be honest, they were much more interested in the trading potential of the huge natural harbor located in the Gironde River estuary. Once the empire collapsed, so did those trade routes from the Mediterranean to northern Europe. Ultimately, Bordeaux (along with the rest of southwest France) became part of the large, powerful, and independent duchy of Aquitaine. And this is where our claret wine story begins.
Bordeaux was English for centuries

Read more
Helpful wine terminology so you sound like you know what you’re talking about
Every pursuit has its buzzwords
White wine in a glass

There’s always something to be learned in the vast world of wine. Knowing a bit of the language will keep you from getting lost in translation and potentially buying something you might not like. Plus, you’ll sound informed the next time you’re in a tasting room or perusing a bottle shop, online or in person.
So, while you study up on outstanding regions like Alto Adige and unique styles like white pinot noir, pack this handy term guide with you. The list is a combination of winemaking terminology and the words industry types like to use to describe wines and their very specific styles. It might just expose you to your new favorite bottle or producer.
But first, let's start with wine terminology fundamentals. Someone has poured you a glass of wine, and told you what the varietal is -- maybe it's a malbec or a chardonnay or a blend of different grapes (more on varietals later). What's the first thing you notice? The color -- is the wine butter yellow or brick red? Next comes the nose: What do you smell? Citrus, or perhaps dried cherries?

Now, take your first sip. What's the mouthfeel? Is the wine light or heavy? What other sensations are there besides the taste? If it's a red, there could be tannins, which impart a sandpapery feeling like apple peels or strong black tea. Conversely, white wine's structure usually comes from acidity, which can present like lemon peel or yuzu. Lastly, notice the finish -- does the wine linger on the palate or get out quickly? How do the flavors resolve?
Now that you have a glass in hand, let's get specific

Read more