Calcium propionate is an organic salt formed by the reaction of calcium hydroxide with propionic acid (also known as propanoic acid). Its chemical formula is Ca(OOCCH2CH3)2. The compound occurs in either crystalline or powder form. It is soluble in water and only very slightly soluble in alcohol.
Calcium propionate is used as a food preservative in breads and other baked goods because of its ability to inhibit the growth of molds and other microorganisms. It is not toxic to these organisms, but does prevent them from reproducing and posing a health risk to humans.
Propionic acid occurs naturally in some foods and acts as a preservative in those foods. Some types of cheese, for example, contain as much as 1% natural propionic acid.
Studies indicate that calcium propionate is one of the safest food additives used by the food industry. Rats fed a diet containing nearly 4% calcium propionate for a year showed no ill effects. As a result, the U.S. Food and Drug Administration has placed no limitations on its use in foods. In addition to baked goods, it is commonly used as a preservative in chocolate products, processed cheeses, and fruit preserves. The tobacco industry has also used calcium propionate as a preservative in some of its products.
Beyond its role as a food additive, calcium propionate finds some application in the manufacture of butyl rubber. Adding it to the raw product makes it easier to process the rubber and protects the rubber from scorching during manufacture.