[Resistance of Listeria monocytogenes to physical exposure]

The resistance of Listeria monocytogenes to physical processing, particularly heat resistance and radioresistance, is widely dependent on the method involved, the physiological state of the strain used, and, obviously, the substrate in which the organism is. HTST pasteurization of milk would allow at least 11 decimal reductions of the potentially present population of L. monocytogenes, and then greatly minimizes the risks of survival of the organism. On the other hand, high and low pasteurizations of egg products may involve only 4 to 5 decimal reductions and appear then not very reliable towards Listeria. Similarly, meat products cooking can, in some conditions, be inadequate to allow the total inactivation of contaminant L. monocytogenes. A 3 kGy irradiation of meat products should allow, on an average, 6 decimal reductions. These results must incite the manufacturers to take into account factors present in their products which allow L. monocytogenes to better resist and this in order to adapt processing to these conditions of increased resistance.