Contains Sulfites

Few terms on a wine label cause more contention -- and more misunderstanding -- than the little phrase "contains sulfites."  It's on almost every bottle of wine sold in the US, and I'd wager that 95% of consumers don't understand what it really means.

For a wine to be sold in the US, it must have a "contains sulfites" label if there's more than 10 parts per million (ppm) of sulfite -- ususally sulfur dioxide, or SO₂, which has it's Lewis structure pictured here.  That's it -- wines without the "contains sulfites" label will often boast "no detectible sulfites," or "no added sulfites," which are two different things -- the former just has less than 10 ppm, while the latter is a wine made in a minimal-interventionalist process using no sulfite.  However, "no added sulfites" wines will still contain some sulfite, as it's a natural part of the fermentation process (generally 5 to 9 ppm result from fermentation).

Why do you add sulfites to a wine?  Well, mainly to impede secondary fermentation from wild yeast and impede the growth of bacteria that may wind up in the bottle, and also to sterilize the bottles and barrels (and they've been used for this for hundreds of years -- vintners in the 1600's would burn sulphur in their cellars to clean the barrels and bottles, as S+2O->SO₂).  They're also used to prematurely end fermentation for sweet wines.  Finally, they're used to protect both raw juice and finished wine from oxidation.

Now, there is a movement towards making wine with little to no sulfite use (a good article on it is found here), as some people are sensitive to them -- mainly as a slight, unpleasant taste of struck match or rotten egg.  There are a very small percentage of the population who have a true allergy to them (under 1%, and the majority of them are steroid-dependant asthmatics -- around 5% of asthmatics have sulfites as a trigger).  So there is some merit to the "contains sulfites" label, as the people who are allergic to them are deathly allergic to them (a severe asthma attack can be fatal, after all).  Sort of like how many foods are labeled "contains tree nuts."

But, go into a wine store and talk with the customers, and most of them will be completely in the dark about what sulfites are doing in their wine.  For some reason, the American consumer views the "contains sulfites" label as something sinister.  There's a number of myths around this, the most popular of which is "there are more sulfites in American wines than European, because they use traditional winemaking methods and don't need them."  Why they wouldn't need them is unknown -- but the use of sulfites in the US versus Europe depends on the wine (eg, Sauternes and Auslese Rieslings use sulfites like it's going out of style, up to 300+ ppm, while dry table wines tend to be on par, between 15 and 50 ppm).

However, by far the most popular myth of sulfites is "they give me a headache."  My standard response to that is that any wine will give you a headahce... if you drink two bottles of it.  But, seriously, there's no conclusive positive link between sulfites in wine and red wine headaches -- and, in fact, the current thinking is that the problem is another chemical entirely called tyramine, which can act as a trigger for migranes, and also a blood pressure elevator (which can cause pounding headaches), especially for people taking a class of antidepressent called MAOI's.  Of course, the best course of action in that case would be consulting with your physician and/or pharmacist if you think a medication is interacting with your wine, as it could save you from serious problems down the road.

And the odd thing about sulfites?  There's generally more sulfite in the cheese you eat with your wine, than in the wine itself -- a 4 oz serving of hard cheese has more sulfites than a 750 ml bottle of wine!