EFFECTS OF IRRADIATION DOSE AND STORAGE-TEMPERATURE ON THE GROWTH OF LISTERIA-MONOCYTOGENES ON POULTRY MEAT

Listeria monocytogenes was inoculated on to raw and cooked minced poultry meat at initial inoculum levels calculated to allow detectable numbers to survive irradiation treatments of 1·0 and 2·5 kGy. The recovery and growth of the surviving organisms was monitored, during storage of the poultry meat at temperatures between 6°C and 15°C. The modified Gompertz function was used to fit sigmoid curves to the L. monocytogenes plate count data. From these curves, values for lag phases and exponential growth rates were obtained. In cooked poultry meat stored at 6°C, the lag duration of L. monocytogenes was 1 day in unirradiated samples and 18 days in samples that had been given a 2·5 kGy irradiation treatment. It was concluded that even if low numbers of L. monocytogenes were to survive the irradiation process, the time required to recover from the irradiation damage would be significant and so growth of this pathogen should not be a problem during the shelf-life of the poultry meat. © 1993 by Academic Press, Inc.