Chemins Vignerons

Sulfur Dioxide or SO2:
The use of the additive sulfur dioxide is an almost universally accepted winemaking practice. Sulfur dioxide is best known to most as the food additive 220 or 202. Although it is naturally produced in small amounts by wine yeast during alcoholic fermentation, most of the SO2 found in wines has been put there by the winemaker.
Many would be aware that sulfur dioxide can cause severe allergic reactions in some people. SO2 is absolutely necessary, it is very difficult to make wines that have an aging potential beyond a few months if sulfur dioxide is not used during winemaking. Sulfur dioxide is an anti-microbial agent, and is used to help curtail the growth of undesirable fault producing yeasts and bacteria and acts as an antioxidant, safeguarding the wine’s fruit integrity and protecting it against browning.
SO2 is a powerful force in keeping wines fresher longer.
When present in excess, it can cause a healthy ferment to stop before the yeast has converted all the grape sugar to alcohol. Furthermore, as the bacteria responsible for malolactic fermentation are particularly sensitive to SO2, excessive amounts will almost certainly block its onset.
When SO2 is greatly in excess, it can also produce a pungent aroma in white wines, considered by most to be a fault. The aroma is best described as that of a match that has just been struck. The addition of SO2 to the wine at bottling was made to protect it from oxidation in the longer run. The SO2 level of all wines naturally declines over time.