SULFITES - What Really is IT?
What are sulfites?
Public attention recently has been directed to the use of sulfites as a food preservative. For many years it was a common practice to add sulfites to wine as a protection against oxidation and bacterial spoilage. In addition, small amounts of sulfites can be naturally present in wine and other foods, since the abundant element of sulfur takes many forms as a part of all living things. When used in winemaking, manufactured sulfites are added as sulfur salts or sulfur dioxide solutions to the juice before fermentation until bottling. Unfortunately, winemakers can be excessive in their use of sulfites, which has the effect of masking delicate flavors, assaulting the nose, and causing headaches and allergic reactions to those especially sensitive. However, modern winemaking equipment and sanitation make it possible to produce sound wines without such additives.
What happens when sulfites are added to wine?
Due to its reactive nature, most of the sulfite molecule joins with other substances in the wine. This part of the sulfite is called "bound" sulfite, and since it is bound up it usually can't be tasted or smelled, except at high levels. A smaller part of the sulfite molecule can't find anything to join and wanders freely through the wine, ready to bond with traces of air or other substances or organisms which can cause wine to go stale or spoil. It is this "free" sulfite which has a strong preservative effect in the wine and can be more easily smelled and tasted or cause a sulfite reaction.
How are sulfites measured?
For most measurements, the bound and free sulfite fractions are added together to get what is called the "total" sulfite level in the wine. Since sulfites are a powerful preservative, they are added to wine in small amounts and are measured in " parts per million", abbreviated "ppm". Although the legal limit in wine is 350 ppm, most wines with added sulfites contain less, generally 25-150 ppm. According to federal law, if a wine contains 10 ppm or more of total sulfites, the label must state "contains sulfites".
("Q&A on Sulfites..." excerpted from an article Frey Vineyards.)
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