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

Several organic acids or salts approved as food additives enhance the inactivation of foodborne pathogens such as Listeria monocytogenes. Al though there has been research on the effects of individual organic ac ids on the inactivation kinetics of L. monocytogenes, little informati on exists on their activity when used in combination with other food a dditives. We undertook to characterize the effects of combinations of 90% sodium acetate or sodium propionate, two salts that inhibit L. mon ocytogenes, with 8% EDTA (disodium salt) and 2% ascorbic acid on the n onthermal inactivation of a three-strain mixture oft. monocytogenes. A ctivity was assessed in Brain Heart Infusion broth (BHI) at various co ncentrations (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-ba sed inactivation model and used to calculate ''time to a 4-D (99.99%) inactivation'' (t(4-D)). The rate of inactivation was directly related to concentration of the acid mixture and temperature of incubation an d inversely related to pH. The primary factor effecting inactivation r ates was pH, followed by the concentration of the undissociated form o f the primary organic acid (acetic or propionic). Evaluation of the mi xture components individually and in combination indicated the compone nts acted largely in an additive manner. The results indicate that com binations of primary and secondary organic acids and EDTA may have adv antages for enhancing the inactivation of L. monocytogenes in refriger ated, mildly acidic foods, while avoiding organoleptic effects associa ted with excessive levels of single acids.