What Are Sulfite Preservatives?

Sulfite compounds are used as a preservative for food and drink. Sulfites are a family of chemicals that includes sodium sulfite, sodium bisulfite, sodium metabisulfite, potassium bisulfite and potassium metabisulfite. Sulfites are produced naturally during the fermentation of wine. However, the majority of sulfur compounds are produced through chemical synthesis.

How Sulfite Preservatives Work

• Sulfite compounds themselves are not preservatives: They work by chemically breaking down and releasing sulfur dioxide gas. Sulfur dioxide has antioxidant and antimicrobial properties. Indirectly, sulfite additives inhibit the growth of bacteria mold and fungi. Sulfite compounds are applied to some foods by spraying or dipping the foods in sulfite solutions. In other foods and pharmaceuticals, sulfites are mixed directly into the product. Sulfites interfere with natural enzymes that ripen or spoil fruit and vegetables. In the same way, sulfites can help meat maintain its color.

Sulfite Used in Food

• Sulfites are used to preserve the flavor and appearance of foods such as jam, gravy, shrimp, dried soup mixes, dehydrated potatoes and juices. Fresh or dried fruit and vegetables are sometimes dipped or sprayed with sulfites to not only to kill germs but also to preserve appearance and taste. Sulfites keep vegetables from turning brown.

  Sodium metabisulfite and potassium metabisulfite are sometimes added to fermenting beer and wine to inhibit microbes and increase shelf life. The sulfur dioxide does not interfere with the action of the yeast, however.

  Sulfites are also added to meat products. Shrimp and lobster spoilage is greatly reduced when these foods are sprayed or dipped in sulfite solutions. Before the U.S. Department of Agriculture banned the practice, meat packagers once added sulfites to raw meat in order to keep it looking fresh.

Use of Sulfite Preservatives in Medicine

• Drug manufacturers take advantage of the antimicrobial and antioxidant properties of sulfites to preserve and increase the shelf life of medications. Sulfates are added to asthma inhalants, medicines given by injection and eye drops, oral tablets and liquids. The U.S. Food and Drug Administration requires that all food and drugs available in the U.S. containing sulfites list the amounts on their labels.

Side Effects of Sulfites

• In 1999, the World Health Organization published the "Sulfur Dioxide And Sulfites (addendum)" report on the safety concerns of sulfur dioxide and sulfites. In a series of case studies, the researchers documented allergic reactions in adults and children to sulfites in foods and medications. The severity of reactions ranged from itching to anaphylactic shock. In addition, the authors presented the results of studies on rats that linked sulfites to kidney damage, fetal malformation and damage to the lungs and liver.