Effects of Irradiation on Survival and Growth of Listeria Monocytogenes and Natural Microflora in Vacuum-packaged Turkey Hams and Breast Rolls

Abstract

The D10-values of L. monocytogenes in breast rolls and hams were 0.52 and 0.47 kGy, respectively. For breast rolls, the log10 reductions of L. monocytogenes following irradiation at 1.0 and 2.5 kGy were 1.5 and 4.7, respectively, while 2.0 and 5.5 for hams. The log10 reductions of APC in breast rolls following 1.0 and 2.0-kGy irradiation were 2.9 and 5.2 while that of hams was < 10 CFU/cm2 after 1.0- and 2.0-kGy irradiation. In 2.0 kGy-irradiated hams, L. Monocytogenes grew to 4.82 log10 CFU/cm2 after 28 d storage at 4 °C, while APC increased to 2.98 log10 CFU/cm2, respectively. In breast rolls after 14 d storage, APC in 1.0 kGy-irradiated samples increased to 7.53 log10 CFU/cm2; and APC increased to 2.63 and 4.68 log10 CFU/cm2 for 2.0 kGy-irradiated breast rolls after 14 and 28 d storage. However, during the storage of breast rolls, L. monocytogenes grew slowly or even stopped to grow in both non-irradiated and irradiated breast rolls due to the competitive inhibition of natural flora in breast rolls. Irradiation greatly reduced L. monocytogenes and APC in turkey hams and breast rolls. However, at least 2.5 kGy irradiation is needed to achieve a 5-log reduction of L. monocytogenes in turkey hams and breast rolls. Some cells survived irradiation and grew during storage after lag phase. To control L. monocytogenes contamination in RTE turkey hams and breast rolls during storage, additional barriers, such as adding preservatives, are necessary in order to ensure the microbial safety of products following low-dose irradiation.