The grasp of chemistry and medicine is generally as weak as the arguments are strong - even when those discussing it are notable industry professionals.
Keeping the wine fresh and stable
So is sulfur bad? Not really. Sulfur (used in winemaking in the chemical form sulfite) is the number one preservative of wine. It keeps the fruit notes fresh and will suppress off odors.
In addition, adding sulfite is almost a requirement in order to keep unwanted bacteria, fungi and harmful yeast under control so the wine doesn’t start a second fermentation in the bottle, sees bacterial growth or develops the odd scents of brettanomyces, to give a few examples.
Red wine has more natural antioxidant power thanks to its phenols - pigments and tannins - which can themselves protect fruit notes and keep the wine from going stale. This is why red wine requires less sulfur than white wine. The higher the acidity of the wine, the lower total sulfur is needed, while residual or added sugar in the wine (as tends to be the case in many commercial style red wines, blush wines or sweet wines) requires more.
But adding as much as is allowed is not a good sign. It won’t just mute the pleasant aromas of the wine, it is also a sign of using poor quality grapes or industrial winemaking.
Sulfite, sulfur… Why are wine drinkers worried?
So why add sulfur to wine? Isn’t it better to make wine totally free from additives? To me, less is more when it comes to most additives, but on the subject of adding a small amount of sulfur in order to give the wine stability, I’m a fan. Opening faulty, stinky wines or getting clumps in the glass is simply not my cup of tea.
A proportionally excessive number of consumers believe they have negative reactions to sulfur in wine. All available research speaks against it. In general, sulfites are very safe for humans. That there is a warning label on most wine bottles sold in stores may be the reason people are worried.
If you are one of the 1 in 100 (according to the USFDA) that are overly sensitive to sulfites, you will have an equally strong, or stronger, reaction to dried fruits, raisins, cold cuts, chips, soy sauce or pickled vegetables as to wine.
Reactions range from a mild headache to stomach ache, wheezing (in asthmatics) or in extremely rare cases, life-threatening anaphylactic shock. This is the reason we see those warning labels “contains sulfites” on wine bottles, even those without added sulfite, as the fermentation process itself usually produces more than the 10 parts per million (ppm) that triggers the need for a label.
When do winemakers add sulfite?
There are three key times during the winemaking process when the winemaker can use sulfur. One is when the grapes come in to the winery. At this point, sulfite is generally only used if the grapes are damaged by rot or mold.
A quality winemaker, especially one looking for a spontaneous fermentation, will instead sort out the affected grapes since the sulfur will kill any wild yeast on the grape skins. In large scale commercial winemaking, sulfur might then be added once more during or after the fermentation to avoid spoilage by 'bad' yeast such as brettanomyces.
Again, if you have a clean winery and a clean, quality must, you don’t need to do this. At bottling, however, is when it is a good idea for even a quality producer to adjust the free sulfur to keep the wine in the bottle stable. The “right” amount will give the fruit notes a bright freshness, lock away odd scents and protect against bacterial growth.
An excessively high amount, however, can be noticeable in the wine aroma as matchstick or gunpowder. In addition, it can suppress nuances in scent and flavor and keep the wine from maturing well with age. This, and the signal it sends about the quality of the grapes used, is the reason I like the amount of total sulfite to be as low as possible.
Natural wine discussions
Even the majority of 'natural wine' producers with ambitions for international trade are positive to adding a minimal amount of sulfur in order to secure a stable wine that can make it to the consumer in top shape without constant refrigeration.
These winemakers will often aim for a total of around 20-30 ppm at most, while conventional winemakers tend to land between 50-100 ppm and lower quality bulk wines might rather go over 100 ppm. A few producers have the mindset that all sulfur is evil and won’t compromise on this conviction even if it means the wine might not be poured in prime condition.
Only a few of these die-hards have the exceptional skill and control over their winemaking to still manage to create beautiful, stable wines, though some consumers will have more tolerance for 'funk'.
Here lies the heart of the big 'natural wine debate' that raged most wildly in the wine industry a few years back and still comes to the surface every now and then. Those against sulfur said it was the sole cause of hangovers and muted the wine while those in favor of sulfur said 'natural wine' smelled funky and was often defective.
The less entrenched the discussion gets, the more the consumer stands to gain from limited but controlled use of the most important compound in winemaking.
Upper limits much higher in fruit - test your tolerance
The amounts of sulfites in wine are limited to 160 parts per million (ppm, or mg per liter, equal to 1.3 standard bottles) for red, 210 ppm for white in the EU. The limit is 350 ppm in the USA and 250 ppm in Australia.
Organic wines in EU and Australia and wines from organic grapes in the USA are much lower, while organic wine in the USA is in this sense equal to 'natural wine', allowing for no addition whatsoever. Standard for a dry red wine is around 50-100 ppm. Dried fruit can easily have 1000-2000 ppm with a legal upper limit of 3000 ppm so if you are one of those who believe sulfites in wine are the cause of your hangovers, try eating a handful of dried apricots - don’t do this without doctor’s approval if you have asthma!
If you feel nothing, don’t worry about the sulfites in wine (but perhaps consider a lighter red, or less of it!). Still, there is reason to seek out those winemakers that use minimal sulfite additions. A stable wine with the lowest possible sulfite content is a sign of a knowledgeable winemaker that uses quality grapes in production. That’s nothing to sniff at.
Want to remove sulfites from your wine?
Gadgets like the Üllo wine purifier will filter away free sulfites in your wine when you are ready to drink it, while at the same time aerating your wine. By the time you are ready to drink your wine, the sulfites provide no benefit and removing them can make the wine aromas shine. Read more about the Üllo here.
Chemistry basics for the true wine geeks
Sulfur is one of the chemical elements (S). When we talk about sulfur in wine it is generally in the form of sulfur dioxide (SO2), which has been used in winemaking since Roman times.
SO2 is also a natural byproduct in the natural fermentation of fruits, so wines without added sulfites are not free from SO2. Since SO2 is a gas, sulfur addition is most often made in the form of a sulfite salt, sulfur trioxide (SO3), generally potassium bisulfite. Since SO3 and SO2 start switching between their respective chemical constellations right when hitting the grape juice, it’s not really a big deal that the terminology is used a bit haphazardly.
The available (called 'free') sulfur dioxide binds free radicals that would otherwise oxidize the wine, robbing it of its color, freshness and bright fruit notes.