Weekly wine defined: Sodium bisulfite
January 30th, 2012 by brynn grimleyBrynn writes:
When embarking on a winemaking endeavor it’s good to have at least a little bit of chemistry know-how, but don’t worry, this is not a chemistry lesson.
The term, sodium bisulfite, as well as a similar term sodium metabisulfite, are words that have oddly enough found their way into recent conversations I’ve had with friends.
Two of my friends from college are getting into amateur winemaking. One already bottled her reds from 2010, while the other is joining in the venture with the 2011 harvest. While sitting with the ladies on New Year’s Eve one of them mentioned sodium metabisulfite — the other had to say the word a few times before she got it down.
This got me to thinking, what is sodium bisulfite? And what in the heck does it have to do with winemaking?
Sodium bisulfite is sold to home winemakers to keep wines from being overexposed to oxygen, which helps keep the flavor of the wine. (Similarly, sodium metabisulfite is used by most commercial wineries for the same purpose).
So how does sodium bisulfite work in winemaking? When it comes into contact with water it releases a sulfur dioxide gas. This gas kills yeasts, fungi and bacteria — all things that might be present in grape juice before the fermentation process happens.
Because winemakers want to control the environment their wines are in, they make it essentially sterile before adding their own, desired amounts of yeast to begin the fermentation process.
Sodium bisulfite is added during the bottling stage of winemaking to again kill any possible bacteria that could be lurking, just waiting to turn the wine into vinegar. This addition also protects the wine’s color, aroma and flavor from the nine-letter word hated by most winemakers: Oxidation.
(*Note, sodium bisulfite should not be confused with sulfites, which are also found in wine. To read about sulfites, see our blog post from March 2011.)
(**Also note, sodium bisulfite should not be confused with sodium bisulfate, which is used as a pH-lowering chemical for swimming pools.)
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January 30th, 2012 at 11:30 am
Hello, Brynn. I notice you use the word “wan” as in “winemakers wan…” I think a better word may be “yearn”. But I have questions as well: 1) do home vintners include the word on their labels, 2)since sulphur has a distinctive odor, is it necessary to decant the wine?
January 30th, 2012 at 12:00 pm
Hi Michael,
Actually, you caught typo. I’ve corrected it, but it was to say “winemakers want” — I left off the “t”.
I don’t believe small-scale, amateur winemakers have to include anything on their label — in fact most don’t even have to have a label — because they aren’t selling their wines commercially. If they get to the size where they start to distribute their wines, then they have to go through the proper channels with the state to become a “bonded” winery. With that comes many hoops and regulations to jump through.
At “commercial” stage, if the amount of sulfites added to a wine is 10 parts per million or more, the label must indicate that sulfites have been added. See my link above from the March 2011 post, it explains this.
But as far as sodium bisulfite goes, that doesn’t show up on a label — however this solution is used often because it acts as a sterilizing agent to clean equipment, etc.
In reference to your second question, in most cases you won’t even know sulfites, or sodium bisulfite has been used in wine. However there are some smaller scale winemakers that might add a little too much, which upon opening a bottle can singe your nose hairs.
Luckily the odor burns off relatively quickly. If you come across a wine that has hints of sulfur, decanting it as you suggest, would be the best way to let the smell burn off. You can also pour the wine in a glass and swirl it around a whole bunch to let the smell dissipate. You likely won’t taste it at all.
Hope that helps!
– Brynn