On October 17, 2012 I came across an interesting post that appeared yesterday on Dr. Vino (Tyler Colman’s excellent wine blog) regarding the legend “contains sulfites” that is required to be affixed to most bottles of wine that are sold in the U.S.

This gives me the opportunity to share some information regarding which sulfite disclosure requirements are in force in the European Union and more in general why wines contain sulfites.

Not unlike in the U.S., EU regulations (see, Article 51 of Commission Regulation (EC) 607/2009 and Article 6 of Directive 2000/13/EC) require that wine labels indicate a “contains sulfites” legend whenever a wine contains “sulphur dioxide and sulfites at concentrations of more than 10 mg/kg or 10 mg/liter expressed as SO2.”

Which now leads us to briefly discuss the reasons why the addition of sulfites is an oenological practice that is generally used in the winemaking process.

Technically, sulfites are chemical compounds (anions) formed by the reaction of a sulfur dioxide molecule (SO2, which is acidic) with basic oxides or an aqueous base.

Sulfur dioxide (or SO2) is a gas that is the product of the burning of sulfur and is broadly used in winemaking as one of the main treatments of must. The purpose it serves is essentially threefold:

• It is an antiseptic agent that fights germs and inhibits undesirable microorganisms (however, its use in the fermentation phase must be controlled because, if certain limits are exceeded, it also inhibits the yeast action);
• It is an antioxidant which helps stabilize the original color of a wine and fights oxidation, thus helping to preserve the organoleptic characteristics of a wine;
• In the maceration phase of the red wine making process, it facilitates the dissolution of anthocyanin pigments from the grape berry skins, which are responsible for the color of red wine.

EU legislation (see, Article 3 of Commission Regulation (EC) 606/2009) sets limits to the maximum SO2 content of wines, which shall not exceed, subject to certain exceptions:

• 150 mg/lt for red wines; and
• 200 mg/lt for white or rosé wines.

As such two different thresholds show, generally speaking white wines contain more SO2 than red wines. This is because in the winemaking process of the former grape skins and seeds are removed right after pressing and before fermentation, while these are retained in the fermentation of red wines. This means that polyphenols (i.e., tannins and natural pigments such as anthocyanins) that are found in grape skins and seeds and that naturally act as antioxidants only get extracted in the red wine fermentation process: hence the need to use more sulphur dioxide in the white wine fermentation process to compensate for such absence.

One thing to be aware of is that, among the exceptions to the maximum SO2 limits indicated above, sweet raisin wines (including Sauternes, Barsac, Tokaji, Trockenbeerenauslese, Albana di Romagna Passito, and ice wines) are permitted to contain up to 400 mg/lt of sulfur dioxide, double the maximum amount permitted for white/rosé wines: this leniency is justified by the high sugar content of such wines, which could trigger natural re-fermentation processes were these not inhibited by SO2. So, be aware that, when you drink that kind of wines, you will likely be assuming more SO2 than with “regular” wines.

One last remark: recently certain producers and organic wine makers have started marketing “no added sulfite” wines. Regardless of how you feel about this emerging trend, one should note that this does not mean that “no added sulfite” wines do not contain sulfites: it only means that none were added to the wine. All wines, in fact, contain some extent of sulfites because these are a natural byproduct of the yeasts that are used to cause the alcoholic fermentation.

Hope you found this informative: feel free to share your opinion by leaving a comment below!