Propionic acid

Propionic acid, or propanoic acid, is a three-carbon carboxylic acid with formula C₃H₆O₂. It occurs naturally in some foods and is used as a preservative and chemical feedstock.

Carboxylic acid: An organic compound containing a carboxyl group, –COOH, which can donate a proton. Propionic acid belongs to this family and derives its acidic behavior from the carboxyl group.
Calcium propionate: A calcium salt of propionic acid used primarily to inhibit mold in food and animal feed. It is a common solid preservative derived from propionic acid.
Johann Gottlieb: A German chemist associated with the early isolation and characterization of propionic acid in the nineteenth century. Historical accounts credit Gottlieb with recognizing the acid as a distinct compound.
Acetic acid: A two-carbon carboxylic acid and the principal acid in vinegar. It is the one-carbon-shorter acid often compared with propionic acid in food preservation.
Propionate: The conjugate base and salts of propionic acid, formed when it loses a proton. Propionic acid becomes propionate in many foods and biological fluids.
Sodium propionate: The sodium salt of propionic acid, used as a food preservative and in other formulations. This water-soluble salt supplies propionate in products where the free acid is less suitable.
Fermentation: The microbial conversion of organic substances into products such as acids, gases, or alcohols. Propionic acid can arise when microbes ferment lactate and other substrates.
Butyric acid: A four-carbon carboxylic acid associated with rancid butter and some fermented foods. Its longer carbon chain distinguishes it from propionic acid among short-chain acids.
pH: A logarithmic measure of hydrogen-ion activity used to describe acidity in aqueous solutions. The undissociated acid fraction depends on pH and influences preservative activity.
Bread: A baked food made from dough, usually based on flour, water, and a leavening agent. Propionate preservatives can delay mold growth in packaged bread.

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