I get this question all the time, so here’s my shot at answering the question. There is so much misinformation out there on the topic, feel free to comment and add to the discussion!
Sulfites are found in many foods and drinks. Many conventional dried fruits contain sulfites as a preservative against bacteria as well as to preserve color. Of course, virtually all wine sold in the United States is labeled as containing sulfites. Sulfites have been used in winemaking for over 2000 years. Sulfites in wine stave off bacterial spoilage and prevent premature oxidation.
In the USA, by law, any wine or food containing 10 parts per million (ppm) of sulfites must be labeled as containing sulfites. If the product does not contain more than 10 ppm sulfites, it does not have to be labeled as such. The labeling is required because a small percentage of the population is sensitive or allergic to sulfites. Some people are more sensitive to sulfites than others, which is why some can drink certain styles of wine without problems, while other types of wine can cause allergic reactions. Some people believe wine in Europe is free of sulfites because, in the past, wine producers were not required to label their wines as such. As of November 25, 2005, however, this is no longer true. Wines labeled after this date, containing 10 mg/L (essentially ppm) or more sulfites, must have a sulfite label to be sold in the European Union. In contrast, sulfite labeling in the United States has been required since 1987.
A little known fact is that all yeast creates small amounts of sulfites as a byproduct of fermentation. This means that technically, all beer, wine, and bread contain some sulfites. But most beers do not contain more than 10 ppm of sulfites, they are not required to label as containing sulfites. Some strains of yeast produce more sulfites than others. But sometimes a winemaker needs to add sulfites for quality control. Bacteria thrives better in low-alcohol, sweet environments, thus fewer sulfites are needed when making full-bodied, dry wines. Additionally, wines fermented in stainless steel have lower risk of bacterial spoilage and oxidation when compared to barrel or cask fermentation. Fortunately, with more advanced methods have greatly reduced the amounts needed to produce wines, so today’s wines have vastly fewer sulfites than decades ago. Red wine’s tannins also act as a natural preservative to prevent oxidation, thus red wine does not require as much added sulfites as white wine.
Many organic wine producers avoid adding sulfites as much as possible, but as a result, the winemaking process is more painstaking and time-consuming. Even if a winemaker can claim not to add sulfites to the wine, sulfur can be added to the grapes in the fields. Bordeaux mixture, which contains copper sulfate, is applied to grape vines to prevent powdery mildew and other mold from affecting the grapes. During harvest, residual Bordeaux mixture can remain on the grapes. The Bordeaux mixture can feasibly react with other compounds in the wine to create additional sulfites. Organic and biodynamic practices currently allow limited use of Bordeaux mixture.
Generally, organic and biodynamic wines will have fewer sulfites than their conventional counterparts, but they certainly are not sulfite-free. There are some wine producers that may label their wines as sulfite-free, because they chemically remove the sulfites from the wine. These wines may be difficult to find, as many producers believe this chemical manipulation adversely affects flavour and quality of the resulting wine. Wines shown to have less than 1 ppm of sulfites may label their wine as “No Sulfites”.
Unless you truly have a sulfur allergy or sensitivity, don’t let the sulfite warning faze you. Most people do not experience any side effects from the quantities of sulfites in wine and are more likely to be affected by the alcohol first. Sulfite labeling seems to have caused more confusion than clarity. Check out the articles below for more information.