Sulfite

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A space-filling model of the sulfite anion.

Sulfites (also sulphites) are compounds that contain the sulfite ion SO32− (IUPAC name sulfate(IV) ion).

Contents

Structure

The structure of the sulfite anion

The structure of the sulfite anion can be described with three equivalent resonance structures. In each resonance structure, the sulfur atom is double-bonded to one oxygen atom with a formal charge of zero (neutral), and sulfur is singly bonded to the other two oxygen atoms, which each carry a formal charge of -1, together accounting for the -2 charge on the anion. There is also a non-bonded lone pair on the sulfur, so the structure predicted by VSEPR theory is trigonal pyramidal, as in ammonia (NH3). In the hybrid resonance structure, the S-O bonds are equivalently of bond order one and one-third.

Commercial uses

Wine

Sulfites occur naturally in all wines to some extent.[1] Sulfites are commonly introduced to arrest fermentation at a desired time, and may also be added to wine as preservatives to prevent spoilage and oxidation at several stages of the winemaking.

In the US, wine bottled after mid-1987 must have a label stating that they contain sulfites if they contain more than 10 parts per million.[2]

In the EU an equivalent regulation came into force in November 2005.[3] Organic wines are not necessarily sulfite-free.[2]

Other food

Sulfites are often used as preservatives in dried fruits, and dried potato products.

Most beers no longer contain sulfites. Although shrimp is sometimes treated with sulfites on fishing vessels, the chemical may not appear on the label. In 1986, the Food and Drug Administration in the United States banned the addition of sulfites to all fresh fruit and vegetables which are usually eaten raw.

Health risks

Sulfites are used in increasing amounts as a food preservative or enhancer. They may come in various forms, such as:[4]

Sulfites have recently been recognized as one of the top 9 food allergens[5]. It is an undeclared allergen that may cause breathing difficulty within minutes after eating a food containing sulfites[6], but more commonly causes headaches and skin irritation within a few hours after consumption. Asthmatics and people with allergies to aspirin (also known as salicylate sensitivity) are at an elevated risk for reaction to sulfites.[6] The reaction can, but not often, be fatal and require immediate treatment at an emergency room, and can include sneezing, swelling of the throat, and hives. Sulfites are the main reason why many people suffer headaches after drinking wine (to prevent this, buy only wines thay say "sulfite-free" on the label, though of course this won't prevent hangovers).

Unfortunately, there are no labeling regulations that require products to indicate the presence of sulfites, however, many companies have added "contains sulfites" on product labels where applicable. Regulations do exist to require indication in the ingredients labels if sulfites were added to a product, but this requirement only applies if they were intentionally added in formulation and not if they are contained in an ingredient. If a product includes an ingredient that contains sulfites, such as dried fruit, then the ingredients label will only specify "dried fruit" and is not required to indicate if the dried fruit itself contains sulphites. Also, the products most likely to contain sulfites (fruits and alcoholic beverages) do not require ingredients labels so the presence of sulfites is usually undisclosed.

The lack of labeling requirements make it easy for companies to use sulfites without detection to extend the shelf life of their products, and very difficult for allergy sufferers to avoid products containing sulfites. This also makes it very difficult for people to realize that they have a sulfite allergy because they are not aware of the presence of sulfites in their food, and many of these people suffer chronic headaches and accept headaches and painkillers as a part of their every day life because they unable to pinpoint the cause.

Sulfites are also known to destroy vitamin B1 (thiamin), a vitamin essential for metabolism of carbohydrates and alcohol.

See also: Anaphylaxis

See also

References

  1. ^ Zacharkiw, Bill, Montreal Gazette (July 15, 2008). "Can't hold the sulphites".
  2. ^ a b Breton, Félicien: Many organic wines contain sulfites
  3. ^ "Food Labeling - Community Legislation". European Commission. Retrieved on 2007-09-10.
  4. ^ "Allergies: sulfite sensitivity". WebMD (1 Feb 07). Retrieved on 2007-09-10.
  5. ^ "Sulphites - One of the nine most common food products causing severe adverse reactions". Canadian Food Inspection Agency.
  6. ^ a b "Allergies - Sulfite Allergies". About.com. Retrieved on 2008-02-15.[unreliable source?]
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Article keywords: sodium sulfite, sulfite sensitivity,

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