Abstract
The heat resistance of L. monocytogenes was experimentally examined by heating ground pork samples at 63°C for 30 minutes which is the standard pasteurization procedure for cooked meat products in Japan.
Ground pork samples with and without curing salt addition were inoculated with 102/g or 107/g of serotype 1/2b, 1/2c or 4b strain and heated at 63°C for 30 minutes. Although a slight difference was observed in the heat resistance of L. monocytogenes inoculated at the level of 102/g depending on the strain and the presence or absence of curing salt, it perished within 4 minutes. In samples inoculated with 107/g, the bacterium was detected up to 5 minutes after heating regardless of the strain type. The 4b strain was detected at 10 minutes after heating in the samples containing the curing salts and the 1/2c strain at 20 minutes after heating in the samples without the salt addition.
However, none of the strains survived after 30 minutes heating either with or without salt addition, indicating that the standard heating requirement is sufficient for pasteurization of L. monocytogenes.
