Purpose: The study aimed to apply a modeling approach able to describe and explain the transfer of L. monocytogenes during slicing of cooked ham at retail, based on data generated in a laboratorial setting, in which a manual slicer was experimentally contaminated with the pathogen.
Methods: The slicer was contaminated by slicing a cooked ham piece that has been immersed in a suspension containing L. monocytogenes (8 log CFU/ml). Subsequently, non-inoculated cooked ham was sliced in this slicer, until 190 slices were obtained. This setup was performed nine times, testing different levels of inoculation and blades. Counts of L. monocytogenes were done using a standard method. The results were fitted to existing cross contamination models and a new model was suggested.
Results: The suggested model hypothesized that the input of Listeria is organized in two different environments; one where Listeria transfer ability from the slicer to the ham is high and a second where the transfer is much lower. The model is described by a four-parameter equation Log (Li+k)= log[b1(1-b1)k-1E1,i + b2(1-b2)k-1E2,i], where E1 and E2 represent the levels of L. monocytogenes in the two environments after slicing the contaminated ham. The proposed model presented low RMSE values varying between 0.02 – 0.06.
Significance: The proposed model was able to describe the transfer of L. monocytogenes during slicing of ready-to-eat cooked ham. This model worked with fewer parameters and presented the best fit among the studied models.