Calcium propanoate or calcium propionate has the formula Ca(C₂H₅COO)₂. It is the calcium salt of propanoic acid.Calcium propionate is a naturally occurring organic salt formed by a reaction between calcium hydroxide and propionic acid. It's commonly used as a food additive — known as E282 — to help preserve various food products, including ( 1 , 2): Baked goods: breads, pastries, muffins, etc.