Purpose: No data are available on the growth assessment of L. monocytogenes in paneer and the safety of the final product. The goal of this study was to see if paneer acts as a vehicle that supports the growth of L. monocytogenes by conducting the challenge testing experiments in paneer under homemade and industrial scenarios and to compare the results with existing predictive models for validation.
Methods: Growth of L. monocytogenes was assessed by conducting challenge testing with an initial concentration of ca. 500 cfu/g. The paneer was prepared in the laboratory simulating homemade preparation and storage with three different pathogen contamination modes: during coagulum preparation stage, during immersion of the coagulated milk in water, and post-processing surface contamination. For the industrial scenario, using different concentrations of preservatives (2700 ppm and 1350 ppm of potassium sorbate), vacuum packaging without preservatives, and post-vacuum packaging pasteurization treatment. Each trial was conducted using three batches with two replicates each. Results of challenge testing were compared with Combase and FSSP prediction softwares.
Results: The models predicted the growth of L. monocytogenes when contamination occurred during the surface or immersion stage. However, the models were unable to predict the growth if contamination occurred during the coagulum preparation stage. For the homemade scenario, an increase of more than two log CFU L. monocytogenes/g was observed on day 10 when stored at 4°C. For the industrial scenario, a prolonged storage with no or restricted growth of the L. monocytogenes during several weeks was observed.
Significance: This work is the first growth assessment study of L. monocytogenes in paneer under artisanal homemade conditions and industrial conditions where a preservative system was included.