Effect of the competitive growth of Lactobacillus sakei MN on the growth kinetics of Listeria monocytogenes Scott A in model meat gravy

Listeria monocytogenes is a foodborne pathogen capable of growth under refrigeration temperatures. The use of bacteriocin-producing lactic acid bacteria to inhibit Gram-positive pathogen growth may be an important tool to enhance the safety of refrigerated foods. The influence of three different populations of the bacteriocin-producing strain Lactobacillus sakei MN on the growth kinetic parameters of three different populations of L. monocytogenes Scott A co-cultured in model meat gravy at 4, 10, 16, and 22 °C was studied. The Baranyi growth model was used to estimate the kinetic parameters of L. monocytogenes and L. sakei for each strain cultured alone or in co-culture. The highest L. monocytogenes populations were achieved by pure cultures, decreasing in co-culture with the different inocula of L. sakei, at all temperatures. A modified logistic model was applied which includes a factor β that adjusts the effect of L. sakei on L. monocytogenes depending on the environmental conditions. The co-cultures of low (∼1log) L. monocytogenes inocula showed a decrease in β values when temperature increased, indicating that inter-species competition changes with temperature; the 2log- and 4log-inocula of L. monocytogenes co-cultures also showed this behavior but only with the higher initial population of L. sakei.