A derivative of sulfur, it is a compound that forms naturally during the same fermentation process that turns grape juice into alcohol. This naturally occurring compound prevents microbial growth. The practice of purposely adding sulfur dioxide at any point in the winemaking process is called sulfiting. Winemakers often supplement during winemaking by adding small amounts of sulfur dioxide to protect fruit quality and prevent oxidation, allowing wine to age well. Some winemakers also spray their vineyard with a sulfur compound to prevent disease and pests. Because sulfites form naturally during fermentation, nearly all wines contain low levels of sulfites even when the winemaker has not supplemented or sprayed the fields. In most instances, the presence of sulfites is not noticeable. On the occasion where excessive amounts are present, undesirable characteristics described as a “biting” sensation on the throat and nose and the smell of a rotten egg may be evident.
U.S. Law dictates that wine with sulfites higher than 10 ppm must state “contains sulfites” on the label. The reason being, these sulfites can cause severe allergic reactions and/or severe headaches in some individuals. The concept of winemaking without sulfites is a new movement that is gaining momentum, the resulting products are referred to as “organic wines”. Wines that are labeled simply “organic” are 100% organic with no sulfites. Wines labeled “made with organically grown grapes” are made with organically grown grapes but contain more sulfites than those that occur naturally.