Chapter 18

Sulfur Dioxide Use in Winemaking

The Debate Over Sulfites in Wine

he use of sulfur dioxide, or sulfites, in wine is a hot topic these days, and a topic with widespread misinformation. The confusion is partly due to misleading warning labels required for wines at far lower levels mandated for foods containing sulfites, giving the impression that sulfites are more dangerous than they really are. Almost all vintners, including most organic practitioners, add a small amount of sulfur dioxide to grapes before fermentation to control oxidation and microorganisms. Wines without sulfur dioxide do not exist. During primary fermentation, yeasts produce approximately 20 mg/L (Schneider, 2019). Any bottle of wine containing over 10 mg/l (10 parts per million) sulfites is required to bear “CONTAINS SULFITES” on the label (Figure 18.3). There are only a very few selected yeast strains producing sulfur dioxide below this limit under optimal nutritional conditions. Sulfite levels tend to be higher in white and rosé wines and much higher in sweet wines than in red wines, which receive more natural antioxidant protection from tannins in the grape skins. Winemaking without sulfur dioxide, while maintaining quality and hygiene standards, requires control of virtually every phase of production from the vineyard to the bottling of wine. Many different substitutes have been tried as an alternative of sulfur dioxide used in wine production. Among these substitutes are chemical preservatives such as sorbic acid, ascorbic acid, dimethyl dicarbonate (DMDC), and lysozyme (Section 18.7).

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