Sulfur dioxide and Wine

When I first read about sulfur dioxide in winemaking, it strikes me as the most important chemical in preserving the quality of wine. It is added as an antioxidant, i.e. to protect the wine against enzymatic oxidation of the polyphenolic compounds, to prevent it from chemical oxidation during processing and in bottle, and as an antimicrobial agent to protect the wine against microbial spoilage. Indeed, sulfur dioxide is added throughout winemaking, almost at each step during the procedure. The concentration of sulfur dioxide in wine is usually very low to cause health hazards. The legal limit in most country is between 300-350 ppm (i.e 300-350 mg per litre). In United States, it is required for the winery to print on its label the presence of sulfites if it exceeds 10 ppm.

Some people are allergic to sulfur dioxide. The common complaints are headache after consuming a small portion of wine. Food allergy occurs when the individual is exposed to the allergen, with its sensitized mast and blood basophil cells releasing histamine and other chemicals. For wine that is produced using grapes susceptible to botrytis cinerea (growth of moulds on the grape skin), a greater concentration of sulfur dioxide is used. Botrytis-infected grapes contain a significant amount of laccase enzyme and aldehydes, both increases the oxidation and binding capability of the grape juice during fermentation. Therefore, a high concentration of sulfur dioxide is required in such wine. In a botrytis wine, the amount of sulfur dioxide used is in the range of 80-120 ppm. For a normal still wine, the amount of free sulfur dioxide is on average 17 ppm.

Reference: Creina Stockley (Oct 2005), "Sulfur dioxide and the wine consumer", The Australian & New Zealand Grapegrower & Winemaker

By Cher Lim
Wine Treasures Pte Ltd
Website: http://www.wine-treasures.com
Email: limce@singnet.com.sg