EFFECT OF SODIUM ACETATE OR SODIUM PROPIONATE WITH EDTA AND ASCORBIC ACID ON THE INACTIVATION OF LISTERIA MONOCYTOGENES1

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Abstract
Several organic acids or salts approved as food additives enhance the inactivation of foodborne pathogens such as Listeria monocytogenes. Although there has been research on the effects of individual organic acids on the inactivation kinetics of L. monocytogenes, little information exists on their activity when used in combination with other food additives. We undertook to characterize the effects of combinations of 90% sodium acetate or sodium propionate, two salts that inhibit L. monocytogenes, with 8% EDTA (disodium salt) and 2% ascorbic acid on the nonthermal inactivation of a three‐strain mixture of L. monocytogenes. Activity was assessed in Brain Heart Infusion broth (BHI) at various concentrations (0.0–2.0% w/v), pH values (3.0–4.5) and temperatures (4–28C). Samples were removed periodically for up to 175 days and viable counts determined. Survivor curves were generated using a logistics‐based inactivation model and used to calculate “time to a 4‐D (99.99%) inactivation”(t4‐D). The rate of inactivation was directly related to concentration of the acid mixture and temperature of incubation and inversely related to pH. The primary factor effecting inactivation rates was pH, followed by the concentration of the undissociated form of the primary organic acid (acetic or propionic). Evaluation of the mixture components individually and in combination indicated the components acted largely in an additive manner. The results indicate that combinations of primary and secondary organic acids and EDTA may have advantages for enhancing the inactivation of L. monocytogenes in refrigerated, mildly acidic foods, while avoiding organoleptic effects associated with excessive levels of single acids.