Sodium propanoate or sodium propionate is the sodium salt of propionic acid which has the chemical formula Na(C2H5COO). This white crystalline solid is deliquescent in moist air. Reactions It is produced by the reaction of propionic acid and sodium carbonate or sodium hydroxide. Uses It is used as a food preservative and is represented by the food labeling E number E281 in Europe; it is used primarily as a mold inhibitor in bakery products. It is approved for use as a food additive in the EU, [2] USA[3] and Australia and New Zealand[4] (where it is listed by its INS number 281). Structure Structure of sodium propionate, with methyl groups and H atoms omitted.[5] Color code: red = O, blue = Na. Anhydrous sodium propionate is a polymeric structure, featuring trigonal prismatic Na+ centers bonded to six oxygen ligands provided by the carboxylates. A layered structure is observed, with the hydrophobic ethyl groups projecting into the layered galleries. With hydrated sodium propionate, some of these Na-carboxylate linkages are displaced by water. See also Propionic acid, E 280 Calcium propionate, E 282