Evaluation of a cross contamination model describing transfer of salmonella spp. and listeria monocytogenes during grinding of pork and beef

Introduction: The cross contamination model (Møller et al. 2012) was evaluated to investigate its capability of describing transfer of Salmonella spp. and Listeria monocytogenes during grinding of pork and beef of varying sizes (50 – 324 g) and numbers of pieces to be ground (10 – 100), in two grinder systems. Methods: Data from 19 trials were collected. Three different evaluation approaches were applied: i) an Acceptable Simulation Zone (ASZ) method compared observed with simulated transfer from the proposed model, ii) each trial was fitted and its respective parameter estimates were integrated in a Quantitative Microbiological Risk Assessment (QMRA) model (Møller et al. 2015), and iii) the Total Transfer Potential (TTP) was calculated for each of the 20 fitted parameter estimates. Results: The ASZ showed that the Møller et al. (2012) model could only describe seven of the 19 trials to an acceptable extent. However, all transfer curves could be fitted to the model structure proposed by Møller et al. (2015). A positive correlation was found between QMRA risk estimates and TTP for the individual trials. Conclusions: Results indicated that transfer estimates were not applicable for unlike processing. QMRA risk estimates and TTP both revealed that risk attribution from grinding was mainly influenced by sharpness of grinder knife > specific grinder > grinding temperature whereas the specific pathogen was of minor importance.