Evaluation of Listeria monocytogenes growth in raw milk at refrigeration temperatures/Valutazione della crescita di Listeria monocytogenes in latte crudo a temperature di refrigerazione

Summary Raw milk consumption has significantly increased in the last few years and it represents a public health risk for the consumers since it can harbour pathogenic microorganisms. The psychrotropic bacterium Listeria monocytogenes was chosen to perform Microbiological Challenge Tests in raw milk at three levels of contamination (1, 10 e 100 cfu/mL) to evaluate its growth at 0°C, 2°C and 4°C. It has been observed that raw milk contaminated with 1 cfu/mL is compliant with the limit of 100 cfu/mL, required by European regulations, for four days at all the tested temperatures. On the contrary, when the contamination is ≈10 cfu/mL, raw milk accomplices the microbiological criterion only at 0°C and 2°C. In order to protect consumers health and observe the European food safety criterion, considering the different levels of contamination of Listeria monocytogenes, we advise to store raw milk between 0°C and 2°C.