So, what exactly does "contains sulfites" mean?The term "sulfites" is an inclusive term for free sulfur dioxide (SO2) compounds. Sulfur dioxide is a very important preservative that has been used in winemaking for a very long time (and indeed in most food industries as well), because of its powerful antioxidant and antibacterial properties. SO2 plays a very important role in maintaining a wine's freshness.
How Do Sulfites Get Into Wine?
At various stages of the winemaking process, winemakers can add sulfur dioxide. Sulfur dioxide is also a natural by-product of the fermentation process. Hence there is really no wine that is totally sulfite-free. In any wine you have what is termed as "free SO2" and "bound SO2." Together they make up the "total SO2" level in a wine. Only the "free SO2" is useful and active as a preservative.
The challenge for any winemaker is to maximize the amount of free or usable SO2, while minimizing the level of total SO2. Today, thanks to more careful vineyard and winery handling of both the grapes and the juice, many winemakers can delay the need for SO2 additions until after the fermentation is complete and hence reduce the amount of SO2 that ends up bound to other compounds in the wine.
Globally Limited and Controlled Additions
The reason that winemakers add limited extra amounts of sulfur dioxide to wine is because wine is perishable, prone to oxidation and the development of aldehyde and other off-odors. However, the amount that can be can be added is strictly controlled. In the EU the maximum levels of total sulfur dioxide that a wine can contain are 160 ppm (parts per million) for red wine, 210 ppm for white wine and 400 ppm for sweet wines. As so much wine is exported and imported throughout the world, quite similar levels apply in the US and elsewhere around the globe.
Harmful or Harmless?
Consumption of sulfites is generally harmless, except if you suffer from severe asthma, or do not have the particular enzymes necessary to break down sulfites in your body. As mentioned above, the amount of sulfites that a wine can contain is highly regulated. Any wine containing more than 10 parts per million (ppm) of sulfur dioxide must affix to the label "contains sulfites."
No Added Sulfites
For the most part winemakers are conscientious about SO2 additions and try to keep the additions as low as possible, while at the same time not risking the wine's premature degradation. That said, we are seeing an increasing number of 'natural' wines on the market, where little or no SO2 is added. These wines often carry the words "no sulfites added."
• For more on sulfites on wine see my earlier post for The Kitchn back in 2009.
Mary Gorman-McAdams, MW (Master of Wine), is a New York based wine educator, freelance writer and consultant.
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