Why can calcium propionate help bread resist mold?
Propionate and propionic acid exist in a pH-dependent balance. Uncharged propionic acid can enter microbial cells more readily, then dissociate and disrupt normal pH control and metabolism. This is why propionate preservatives work better under more acidic conditions.
The chemistry has another side: propionic-acid-producing bacteria help make Swiss-type cheese, generating CO2 that contributes to its characteristic holes.
Global Chemical Database