What is Sodium Propionate and its Uses?

Introduction to Sodium Propionate

Sodium propionate (C3H5NaO2) is an organic compound. Sodium propionate appears as a white, crystalline powder or granules with a mild, slightly acidic odor. It is soluble in water and is commonly used as a preservative. Sodium propionate is an ester of propionic acid and is classified as an organic salt.

Sodium propionate was first synthesized in the early 20th century. It has found widespread use in the food and pharmaceutical industries. As a preservative, sodium propionate is used to prevent the growth of mold and bacteria in baked goods, dairy products, and other perishable food items. In the pharmaceutical industry, it is used as an excipient in the formulation of certain tablets and capsules. The compound is also used in animal feed to prevent mold growth. Sodium propionate is commonly derived from the reaction between sodium hydroxide and propionic acid, a process that can be carried out under controlled conditions in an industrial setting.

Figure 1 Characteristics of Sodium propionate

Physical and Chemical Properties

Sodium propionate appears as a white crystalline, white crystalline powder, or granular form, odorless or slightly odorous, soluble in water {100 g/100 mL (15°C)}, soluble in ethanol (4.4 g/100 mL), slightly soluble in acetone (0.05%). Sodium propionate is stable to light and heat and is hygroscopic in air. When the 10% Sodium propionate aqueous solution is heated with an equal amount of dilute sulfuric acid, a gas with the odor of propionic acid will be produced. Sodium propionate is obtained by the reaction of propionic acid with sodium carbonate or sodium hydroxide, as shown in the following reaction: C2H5COOH+NaOH=C2H5COONa+H2O

Calcium propionate appears as a white crystalline, white crystalline powder, or granular form, odorless or slightly odorous with the smell of propionic acid. It is soluble in water {39.9 g/100 mL (20°C)}, insoluble in ethanol and ether. Calcium propionate is stable to light and heat and is hygroscopic in air. When the 10% calcium propionate aqueous solution is heated with an equal amount of dilute sulfuric acid, a gas with the odor of propionic acid will also be produced. The calcium propionate used as a food additive is generally a monohydrate. The pH of a 10% calcium propionate aqueous solution is 8-10. Calcium propionate can be obtained by neutralization reaction of propionic acid with calcium carbonate or calcium hydroxide.

Preservation Mechanism

The preservation mechanism of Sodium propionate and Calcium propionate is the same. They are both acid preservatives, mainly releasing propionic acid in acidic media to achieve the purpose of inhibiting bacteria. Propionic acid is a monocarboxylic acid that acts by inhibiting microbial synthesis of β-alanine.

Calcium propionate: The oral LD50 of mice is 3.3g/kg. FAO/WHO (1985) stipulates that ADI is not subject to restrictive regulations. Feeding rats with feed containing 1%, 3%, and 6% calcium propionate for 180 days resulted in increased body weight compared to the control group, with no abnormalities in blood or internal organs. The metabolism of calcium propionate in the human body is similar to Sodium propionate.

Applications and Limits

Sodium propionate has good antifungal properties, with good efficacy against mold fungi and minimal inhibitory effects on bacteria. It can only delay the growth of bacteria such as Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, and has no inhibitory effect on yeast. Sodium propionate should be used in an acidic range, it can be used to inhibit the growth of miscellaneous bacteria during bread fermentation and prevent mold in cheese products. Using Sodium propionate in bread will weaken the function of yeast, resulting in slightly poorer bread foaming.

The preservative performance of calcium propionate is similar to Sodium propionate, with a lower effective dose for inhibiting mold fungi. Using calcium propionate as a preservative in pastries, bread, and cheese can supplement calcium in food. When used during dough fermentation, calcium propionate can inhibit the reproduction of Bacillus subtilis, with the minimum inhibitory concentration at pH 5.0 being 0.01%, and at pH 5.8 being 0.188%, the optimal pH should be below 5.5.

Reference

[1] Filippone A, Lanza M, Campolo M, et al. The anti-inflammatory and antioxidant effects of sodium propionate[J]. International journal of molecular sciences, 2020, 21(8): 3026.

[2] Heseltine W W. A note on sodium propionate[J]. Journal of Pharmacy and Pharmacology, 1952, 4(1): 120-122.

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