Effect of gamma irradiation on Listeria monocytogenes in frozen, artificially contaminated sandwiches.
Gamma irradiation has been shown to effectively control L monocytogenes in uncooked meats but has not been extensively studied in ready-to-eat foods. The presence of Listeria in ready-to-eat foods is often due to postprocess contamination by organisms in the food-manufacturing environment. Because gamma irradiation is applied after products are packaged, the treated foods are protected from environmental recontamination. Currently, a petition to allow gamma irradiation of ready-to-eat foods is under review by the Food and Drug Administration. This study was conducted to determine if gamma irradiation could be used to control L. monocytogenes in ready-to-eat sandwiches. Ham and cheese sandwiches were contaminated with L. monocytogenes, frozen at -40 degrees C, and exposed to gamma irradiation. Following irradiation, sandwiches were assayed for L. monocytogenes. A triangle test was performed to determine if irradiated and nonirradiated sandwiches differed in sensory quality. We found that the D10-values ranged from 0.71 to 0.81 kGy and that a 5-log reduction would require irradiation with 3.5 to 4.0 kGy. The results of a 39-day storage study of sandwiches inoculated with 10(7) CFU of L monocytogenes per g indicated that counts for nonirradiated sandwiches remained fairly constant. Counts for sandwiches treated with 3.9 kGy decreased by 5 log units initially and then decreased further during storage at 4 degrees C. Sensory panelists could distinguish between irradiated and nonirradiated sandwiches but were divided on whether irradiation adversely affected sandwich quality. Our results suggest that manufacturers of ready-to-eat foods could use gamma irradiation to control L. monocytogenes and improve the safety of their products.
Clardy
S
S
Department of Food Science and Nutrition, Chapman University, Orange, California 92866, USA.
Foley
D M
DM
Caporaso
F
F
Calicchia
M L
ML
Prakash
A
A
D000818:Animals; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004307:Dose-Response Relationship, Radiation; D005511:Food Handling / Q000379:methods*; D005514:Food Irradiation; D005615:Freezing; D005720:Gamma Rays; D006801:Humans; D008089:Listeria monocytogenes / Q000528:radiation effects*; D008461:Meat Products / Q000382:microbiology*; D013649:Taste