Listeria monocytogenes in Gorgonzola cheese: Study of the behaviour throughout the process and growth prediction during shelf life

When the cheese was stored at thermal abuse condition (8-12 °C), the pathogen concentration on the rind was 4.8 ± 0.3 log CFU/g and after 66 days (about 9 weeks) no significant difference (p > 0.05) was observed; whereas, a growth from 5.4 ± 0.4 to 7.1 ± 0.5 log CFU/g was observed in the core. A second challenge test was performed using three batches of commercial slices of Gorgonzola cheese inoculated by L. monocytogenes and stored at 8 °C. The maximum specific growth rates (μmax, 1/h) of L. monocytogenes estimated ranged from 0.007 to 0.061. The square root model was used to predict the μmax at others temperature and to establish the time necessary to reach the European critical legal limit of 2 log CFU/g, in different storage scenarios. The predictions obtained in this study can be applied to any time-temperature profile, and in particular to the conditions to which the product is most likely to be subject in normal use, up to its final consumption. This study can be considered a valuable contribution also aimed at supporting the monitoring surveys carried out by officers of the Regional Veterinary Authority.