Effect of sublethal thermal injury on the survival and re-growth of Salmonella enteritidis. Model development and application to eggs products

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The European Food Safety Authority and the European Centre for Disease Prevention and Control have published their Community Summary Report on Food-borne Outbreaks in the EU in 2007 and it shows that Salmonella remained the most common cause of foodborne outbreaks. In particular Salmonella enteritidis in eggs has been identified as a major cause of outbreaks. It has been recommended that eggs used in raw or minimally processed foods should be "commercially treated", usually meaning inactivation by heat treatment. The treatment severity has to be low, in order to minimise the damage to the functional properties of the egg. Whilst the enforcement of this recommendation has helped to reduce the number of cases of Salmonella infections, the kinetics of the recovery and possible growth of Salmonella after heat treatments has not yet been quantified satisfactorily. A well-established and verified mathematical model would be especially important in cases where the heat treatment fails or where the food is cross-contaminated. The predictions generated by the model could be integrated into microbiological risk assessments. The project output would also help to improve the general understanding of the recovery process of bacteria injured by heat treatments. The purpose of this project is to model the survival and re-growth of Salmonella enteritidis after mild heat treatments. A mathematical model will be developed based on experiments in broth. It will be adapted to egg products, while bearing in mind that the medium has a significant influence on the recovery of injured cells, for which not all factors are known. The modelling will take into account: the probability of growth in the recovery medium which will depend on the treatment and environmental conditions; both the effect of the severity of the heat treatment and the environmental conditions on the distribution of the single cell lag times; the effect of the environmental conditions on the growth rate.

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