A mathematical model to predict the antilisteria bioprotective effect of Latilactobacillus sakei CTC494 in vacuum packaged cooked ham

Biopreservation is a strategy that has been extensively covered by the scientific literature from a variety of perspectives. However, the development of quantitative modelling approaches has received little attention, despite the usefulness of these tools for the food industry to assess the performance and to set the optimal application conditions. The objective of this study was to evaluate and model the interaction between the antilisteria strain Latilactobacillus sakei CTC494 (sakacin K producer) and Listeria monocytogenes in vacuum packaged sliced cooked ham. Cooked ham was sliced under aseptic conditions and inoculated with L. monocytogenes CTC1034 and/or L. sakei CTC494 in monoculture and coculture at 10:10, 10:103 and 10:105 cfu/g ratios of pathogen:bioprotective cultures. Samples were vacuum packaged and stored at isothermal temperature (2, 5, 10 and 15 ?C). The growth of the two bacteria was monitored by plate counting. The Logistic growth model was applied to estimate the growth kinetic parameters (N-0, lambda, mu(max), N-max). The effect of storage temperature was modelled using the hyperbola (lambda) and Ratkowsky (mu(max)) models. The simple Jameson-effect model, its modifications including the N-cri and the interaction gamma factor, and the predator-prey Lotka Volterra model were used to characterize the interaction between both microorganisms. Two additional experiments at non-isothermal temperature conditions were also carried out to assess the predictive performance of the developed models through the Acceptable Simulation Zone (ASZ) approach. In monoculture conditions, L. monocytogenes and L. sakei CTC494 grew at all temperatures. In coculture conditions, L. sakei CTC494 had an inhibitory effect on L. monocytogenes by lowering the N-max, especially with increasing levels of L. sakei CTC494 and lowering the storage temperature. At the lowest temperature (2 degrees C) L. sakei CTC494 was able to completely inhibit the growth of L. monocytogenes when added at a concentration 3 and 5 Log higher than that of the pathogen. The inhibitory effect of the L. sakei CTC494 against L. monocytogenes was properly characterized and modelled using the modified Jameson-effect with interaction gamma factor model. The developed interaction model was tested under non-isothermal conditions, resulting in ASZ values >= 83%. This study shows the potential of L. sakei CTC494 in the biopreservation of vacuum-packaged cooked ham against L. monocytogenes. The developed interaction model can be useful for the industry as a risk management tool to assess and set biopreservation strategies for the control of L. monocytogenes in cooked ham.

Automated summary

In this study, the interaction between Listeria monocytogenes and Latilactobacillus sakei in vacuum packaged sliced cooked ham was evaluated and modeled. The results showed that L. sakei had an inhibitory effect on L. monocytogenes, and this effect was stronger at higher levels of L. sakei and lower storage temperatures.