Wine Time: Wine and Sulfur Dioxide

Categories: Wine Time

metbisulphite.jpg
Image via HomeBrewers.com.
No, that's not cocaine. It's potassium metabisulfite, one of the many forms of sulfites employed by winemakers for a variety of purposes.
A post earlier this week ("Wine of the Week: A Wine with No Detectable Sulfites") inspired a lot of acidic (pun intended) discussion here at Eating Our Words and around the enoblogosphere.

The question of sulfites in wine, their effect on the aroma and flavor of the wine, and their potential impact on health is one of the thorniest issues in the world of wine today -- especially when it comes to the categories of organic, biodynamic, and Natural wine.

Let's start a healthy discussion (pun intended) by debunking some of the common myths associated with sulfites in wine.

1) There is no wine that does not contain sulfites. Even when no sulfur dioxide (SO2) has been added to wine, it will still contain sulfites. Sulfur is one of the natural byproducts (sulfur metabolism) of fermentation (whereby yeast turns sugar into alcohol).

2) Red wine does not contain more sulfites than white wines. Actually, the opposite is true: Because SO2 is used to prevent oxidation of wine and subsequent "browning" of white wine, commercial producers use more SO2 for their white wines.

3) Sulfured (sulfurated) wines are an industry standard and the use of sulfur is widely embraced by every category in the world of wine today. According to the Oxford Companion to Wine, only "a fraction of 1 percent" of winemakers in the world today make wine without the use of S02. Opus One (Napa Valley)? Domaine de la Romanée-Conti (Burgundy)? Yellowtail (Australia)? Yes, they all use SO2.

4) The "sulfite headache" is a myth. Although some people are extremely sensitive to sulfites (according to the FDA about 0.4 percent of Americans are allergic to sulfites), the headache you can experience after drinking wine is more likely due to the high alcohol content of a given wine and to the way the wine is applied (in other words, if you drink a bottle of 17 percent alcohol Pinot Noir from the Central Coast of California without food, you are going to get a headache due to the subsequent dehydration).

5) Despite our knee-jerk reaction to the thought of SO2 being added to wine, its use in winemaking is -- without a doubt -- a good thing. In the nineteenth century (not that long ago, when you consider that wine has been produced by humankind since antiquity), a greater understanding of microbiology revolutionized the fine wine industry. Keep in mind: Before Pasteur (1822-1895), no one understood how microorganisms affect wine and the way it smells and tastes. The application of sulfites today is part of Pasteur's legacy.

sulfites.jpg
So why does the U.S. Alcohol and Tobacco Tax and Trade Bureau require that winemakers write "contains sulfites" on the label? The requirement is owed to the fact that 5 percent of asthmatics can have a violent reaction to sulfites. Until the Common Market Organisation reforms of the 1990s, European Union winemakers were not required to write "contains sulfites" on the label.

So why and how do winemakers use sulfur in winemaking?

1) They use sulfur to clean winemaking vessels and other equipment.

2) They use sulfur to prevent oxidation in wines before, during, and after fermentation. (Because oxygen binds to SO2, it prevents oxygen from binding with other elements in the wine. Premature oxidation can cause a browning of white wine and it can cause unwanted aromas in wine, white and red.)

3) They use sulfur after fermentation to kill unwanted bacteria that could cause undesirable aromas and flavors.

Can the average taster detect SO2 in wine? Yes. If excessive amounts of SO2 have been used in winemaking, you can smell it. It smells like burnt matches.

Do some winemakers use more SO2 than others? Yes. High-volume commercial winemakers tend to use more SO2 because they need their wines to stabilize more quickly in order to ship the wine and create more space in the winery. The biggest offenders? Producers of large-volume, industrial white wine.

How much SO2 is allowed in wine? In the U.S., 350 parts per million. In Europe, 160 ppm for red wine; 210 ppm for white wine (again, the European numbers reflect a greater need for SO2 in the production).

Can fine wine be made without the use of SO2? Yes, definitely. Some of our favorite wines are "unsulfured" and there are many different techniques used to make wines without SO2. But they represent a tiny segment of the wine industry and the resulting wines often have "flaws" and variation that makes them difficult to market.

The bottom line? The wine industry, as we know it, would not exist today without the use of SO2 and we wouldn't have access to the great wines of the world (because they would be too delicate to ship).

Do wines with lower amounts of added sulfites taste better than wines with greater amounts? In my opinion, they do. In my view and experience, minimal use of sulfites (in other words, using the smallest amount possible) reflects the winemaker's will to make better, more honest, more wholesome, and more genuine wine. It takes more time and patience to make wine with lower amounts of added SO2 (and it costs more). But it makes for better wine.

My advice? Look for wines with natural acidity: The higher the natural acidity (and the lower the pH), the lower the amount of SO2 needed to stabilize the wine. If you've been following along here at Wine Time, you know that natural acidity is the key to the wines that Tracie P and I like and drink at home. Buttery Chardonnay from California? More SO2 needed. Dry Chenin Blanc from the Loire Valley, France? Less SO2 needed.

Please share your thoughts/experiences/suggestions on sulfites in wine in the comments section below.



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Tp
Tp

The only thing that I would add is that the Romans began to apply sulfur dioxide to winemaking in the 2nd century AD.

Mike Dutch
Mike Dutch

"How much SO2 is allowed in wine? In the U.S., 350 parts per million. In Europe, 160 ppm for red wine; 210 ppm for white wine (again, the European numbers reflect a greater need for SO2 in the production)."

Huh?  

And are you really saying that the adverse reaction that many people get from over-sulfered German Rieslings is all in their head (eyes)?

Crscicolone
Crscicolone

Ciao Jeremy-  This is the best article I have read on the subject of sulfites in wine.

T.
T.

This is the best article I have seen in print on this very important topic to wine drinkers. Thank you.

Winelush
Winelush

Keep myth busting Jeremy!

awaldstein
awaldstein

Thanks Jeremy...

Informative post. On this issue we agree completely.

See this link that David (co-owner) of Chambers Street Wines in TriBeCa NYC wrote in prep for the tasting tomorrow.

http://chambersstwines.com/

BTW...we met in Brescia a few weeks ago.

Good piece.

Chrissa Chase
Chrissa Chase

Let's not forget the "sulfur dusting" in the vineyard. 

Jeremy Parzen
Jeremy Parzen

Very good point, Chrissa. As per Francesco's comment above.

Thanks for being here! Great to see yall last night! :) 

Francesco Maule
Francesco Maule

Jeremy, someone told to me about the new regulation for organic product in U.S.is it true? 100% organic = no sulphites90% organic with some sulphites70% organic with more sulphitesand probably 50% organic...or something like taht.can you explain me more please?bye

Maurizio
Maurizio

100 percent organic. Products that are completely organic or made of all organic ingredients. sulfites not added and under 10 ppmOrganic. Products that are at least 95 percent organic. sulfites not added and under 10 ppmMade with organic ingredients. These are products that contain at least 70 percent organic ingredients. The organic seal can't be used on these packages.Io farò convegni inutili, ma tu non stai attento e io ti becco

Robin
Robin

What a great, interesting post!  Seriously, thanks for the education.  I'm glad to know the sulfite headache is a myth.  Maybe I just need to be more vigilant about staying hydrated.

For me, it's easier to find the "more natural acidity" in a white with my limited knowledge, but which direction should I be looking in terms of red?  (I'm assuming a big, heavy Cab would not be the way to go if I'm looking for more natural acidity?)

Jeremy Parzen
Jeremy Parzen

Hoping this is helpful, Robin! I wrote this for you! :)

Btw, sulfur is also used in a lot of the fruit we eat. We come into contact with sulfites in all sorts of ways in our foods. 

Big, heavy "Cab" from Napa ain't gonna have a lotta acidity, I'm sorry to say. 

Look for Cabernet Franc from the Loire Valley. 

And thanks for reading and the suggestion! 

Francesco Maule
Francesco Maule

Great post Jeremy! About n. 1: sometimes happens to arrive at no detectable sulphites into a wine. Our laboratory hadn't find in our Sassaia 2010 without sulphites added (less than 2 mg per liter). If you don't use sulphur in vineyard's treatments it can happens. Similar discussion here in Italy: http://www.intravino.com/salut...

Jeremy Parzen
Jeremy Parzen

Folks, for those of you who don't know him, Francesco Maule's family makes one of Italy's most famous unsulfured (and one of my favorite). 

Francesco, so great to see you here! Thanks! 

Doc Ricky
Doc Ricky

Small correction there - the arrow for the bisulfite dissociation into sufite should be bidirectional as well. This is an ionization equilibrium. In fact, in plain water, the second dissociation step requires more energy to drive.

For more info, look for pKa and the Henderson Hasselbalch equation.

Jeremy Parzen
Jeremy Parzen

I'll check it out. Thanks for the heads up! 

Roy Schneider
Roy Schneider

Great post. Lot of great info on the chemistry of winemaking. Thanks!!!

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