propionihapon

Propionic acid, or propanoic acid, is a carboxylic acid with the formula C3H6O2. It is a colorless, oily liquid at room temperature with a sharp, pungent odor. It is miscible with water and many polar organic solvents. The acid has a pKa of about 4.87, reflecting its moderate acidity, and it partially dissociates in water to yield propionate (propanoate) ions. Its boiling point is around 141°C, and its melting point is about −20.8°C.

Occurrence and production play significant roles in its identity. In nature, propionic acid occurs in dairy products as a metabolite produced by Propionibacterium species during fermentation, contributing to the characteristic flavors of certain cheeses. Industrially, it is produced by oxidation of propionaldehyde or by catalytic oxidation of propanol, and it can also be generated by fermentation of carbohydrates using Propionibacterium strains. Propionic acid forms salts with metals, notably calcium propionate and sodium propionate, which are widely used as food preservatives.

Applications are primarily preservative and intermediate. The principal use is as a preservative in bread, dairy products, and animal feeds to inhibit mold growth, typically in the form of calcium or sodium propionate. It also serves as a chemical intermediate and as a precursor in the synthesis of propionate esters and fragrances. In smaller amounts, it can appear in flavor formulations and cosmetic preparations as a pH adjuster or preservative.

Safety and handling considerations include its corrosive nature and potential to irritate skin, eyes, and the respiratory tract. Proper protective equipment and adequate ventilation are recommended when handling propionic acid. It is readily biodegradable and does not tend to bioaccumulate in the environment.