What are sulfites in wine?
Sulfites are naturally occurring compounds found in all wines, and for the vast majority of drinkers they are completely harmless.
Why Wine has Sulfites
Sulfites, also known as sulphur dioxide or their chemical name, SO2, are produced naturally as a byproduct of the winemaking process. As wine yeasts ferment the grape juice (called ‘must’) into alcohol, they also produce small amounts of sulfites.
But when people talk about sulfites in wine, they are usually referring to any additional sulfites that have been used during the winemaking process. Winemakers have traditionally added sulfites at different stages of production, whether during harvest, fermentation or bottling, because SO2 is an excellent preservative.
In fact, SO2 is used widely as an antimicrobial throughout the food and drink industry – for example, in charcuterie and dried fruit. In the case of wine, the addition of sulfites prevents oxidisation, as well as contamination by unwanted yeasts and bacteria. It’s partly thanks to sulfites that we are able to age wines for so long in bottle, as without them, many would likely spoil.
How do Sulfites Affect Me?
In recent years, sulfites have managed to get a bad reputation. Many people blame their headaches after drinking wine on the presence of SO2. But scientists have found very little basis for these claims. In fact, some believe there may be other culprits.
Research is ongoing into naturally occurring compounds which may contribute to headaches in some people. But for the average person, a headache after drinking wine is most likely a sign you’ve just had a bit too much.
A very small proportion of the population – probably around 1 percent – has a genuine sensitivity to sulfites, ranging from mild to severe. When consuming sulfites in sufficient quantities these people may experience asthma symptoms, hives, flushing and nasal congestion (headaches are not a symptom).
But depending on the individual, the amount of sulfites in a wine may still be too low to provoke reaction. Wine tends to only contain around 20 to 200 parts-per-million (ppm) of sulfites, while in comparison dried fruit can contain up to 2,000 ppm or more. In short: if you can eat a bag of dried apricots without side effects, then your post-wine headache isn’t due to sulfites.
There’s no such thing as an entirely sulfite-free wine. Because it’s produced by yeast, SO2 is a naturally occurring part of the winemaking process and will always be present in your wine at some level.
But increasing numbers of producers – especially those subscribing to the ‘natural wine’ movement, are for various reasons choosing to make wines without the addition of sulfites. That means their wines will contain the minimum amount possible. Some of these wines are truly delicious. But without the addition of sulfites, it can be difficult for winemakers to achieve consistency in flavour, especially as wines age.
Low-sulfite wines can sometimes have unusual or ‘funky’ flavour profiles, which might not be to everyone’s taste. They can also vary quite a bit from vintage to vintage, and even bottle to bottle.
Sulfites are harmless for most of us. But if for any reason you would like to minimise your intake of the compound, try sticking to red wines, as these tend to be lower in SO2 than white and rosé. Avoid sweet wines, as these usually have the highest sulfite levels of all.