Technique

Volatile Sulfur Compounds and Hydrogen Sulfide in Wine

If you have ever encountered volatile sulfur compounds in wine, of which hydrogen sulfide is the most common, you know how repulsive the smell can be. It can shoot one’s anxiety up a few notches because it always seems to catch you by surprise, and that the source of the problem is often difficult to pinpoint. What’s worse is that the fix will likely require a copper treatment—a chemical addition that you wish you could have avoided — although there are alternate solutions. Volatile sulfur compounds, or VSCs, originate from many sources including elemental sulfur; sulfates or sulfites; sulfur-containing amino acids by microbes; sulfur-containing pesticides; fermentation dynamics and yeast stress; and what is called reductive winemaking where wine is exposed to extremely low levels of oxygen. While VSCs or “reductive aromas” can have faulty characteristics, reductive aromas can also exhibit positive attributes when present in tiny quantities. Hydrogen sulfide (H2S), the focus of this article, is the most recurrent of the problem VSCs in winemaking; it is detected as the unmistakable smell of rotten eggs and at a very low