Propionic acid

Propionic acid is a naturally occurring short-chain fatty acid found in significant amounts in Swiss-type cheeses such as Emmental and Gruyère, where it is produced during the fermentation process by Propionibacterium bacteria. As a food additive, it functions as a mould and rope-inhibitor in bread, baked goods, dairy products, and animal feed. It is particularly effective against Bacillus mesentericus, the bacterium responsible for "rope" spoilage in bread.

JECFA's ADI for propionic acid is "not specified," evaluated in 1973. Propionic acid is a normal human metabolite — the body produces it through gut bacterial fermentation of fibre and through catabolism of certain amino acids. It is rapidly and completely metabolised through the same pathways as other fatty acids, with no accumulation or toxic effects at any realistic dietary intake level.

Propionic acid is universally approved in the EU, US (GRAS), UK, Australia, Japan, and Vietnam. It and its salts (E281 sodium propionate, E282 calcium propionate, E283 potassium propionate) are among the most widely used mould inhibitors in commercial bread baking, extending shelf life without refrigeration. For consumers, propionates are considered safe and are effectively a continuation of the natural fermentation chemistry that already occurs in many traditional foods. There are no known health concerns at normal dietary exposure levels.