Heat inactivation of Listeria monocytogenes in biofilms
Chmielewski, Revis A.
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Predictive models for the heat inactivation of Listeria monocytogenes in pure and mixed culture biofilms, formed on stainless steel and rubber surfaces and in the presence of food soil were developed using fraction negative data and logistics regression. The validation study indicated that at the 50% probability level of L. monocytogenes inactivation, the predictive model with strain 3990 on stainless steel surfaces was conservative in its estimate of L. monocytogenes biofilm inactivation while the Scott A model was not a reliable predictor of the heat inactivation of L. monocytogenes in a biofilm. The multispecies (L. monocytogenes, Pseudomonas and P. agglomerans) biofilm was an adequate predictor of L. monocytogenes biofilm inactivation and can be used in situations of low occurrence in a food product. A predictive model for the heat inactivation of L. monocytogenes on rubber surfaces was developed. The model provides for three prediction situations in the presence of soil, the fairly conservative assessment of risk using heat resistant Scott A strain and the less conservative predictions based on strain 3990 and Listeria in a mixed culture. For the low soil condition, the Scott A and 3990 strains showed adequate assessment of heat inactivation while the L. monocytogenes in a multi-species biofilm was conservative in its predictions. These predictive models could be used as a guide to apply hot water sanitation when chemical sanitation is ineffective for a process. Heat stress induced the increased production of biofilm for L. monocytogenes Scott A. There were changes in the proteins expression before and after heat stress.