Sodium propionate can be produced by the reaction of propionic acid (E280) with sodium hydroxide in hydrogen peroxide and water. (1)

Comparison of three Propionates in bakery
There are three propionates that are approved as food additives, calcium propionate (E282) is the most used one, then sodium propionate, while potassium propionate (E283) is not common.

Calcium propionate

It is the most used propionate preservative for yeast-leavened baked products, also it enhances calcium nutrition in baked products.

But it is not a good choice for chemical leavened baked products since calcium ions will react with HCO3− from the chemical leavening agents – sodium bicarbonate.

Sodium propionate and Potassium propionate
Sodium propionate and potassium propionate are appropriate for non-yeast leavened baked products (e.g. cakes, tortillas, etc.).

Potassium propionate has the advantage as it doesn’t add sodium to bread and is therefore suitable for low-sodium products.

Chemical leavening agents or baking powder are mixtures that release carbon dioxide in the condition of moisture or with heat. Most of them are made of an acid (such as sodium aluminum phosphate, sodium acid pyrophosphate, monocalcium phosphate) and sodium bicarbonate (NaHCO3).

Specification
Other Names   
Sodium propanoate
Napropion
Sodium  ethanecarboxylate
Propanoic acid sodium salt
CAS Number    137-40-6
Chemical formula    C3H5NaO2, CH3CH2COONa
Molar Mass    96.060 g/mol
Properties

Hygroscopic crystalline powder or granular with a little propionic acid odor, deliquescent in moist air.

Structure
Sodium propanoate chemical structure
Image Source

Solubility
Water solubility is important since this property will influence its uses and function as a mold inhibitor.

In water
Freely soluble in water and with the solubility 100 g/100 mL at 15°C, which is better than that of calcium propionate.

Sodium propionate is a base and dissociates propionate ion after the reaction with H2O. And then propanoic acid generated as propionate ion combines with H2O (or exactly hydrogen ion in H2O).

In Organic solvent

Soluble in ethanol with the solubility 4.4 g/100 mL.

PH Range
PH value is another important role as preservatives need a suitable pH range for their antimicrobial activity.

The optimal pH range of propionates for inhibiting the growth of mold is from 2.5 to 5.5.

As mentioned above, propionates produce propionic acid after dissociation and combination with H2O. Propionic acid can penetrate the cell wall of microbes and lowers its intracellular pH. That results in inhibiting the growth of molds. This is how it works.