Effect of gamma irradiation on Listeria monocytogenes in frozen, artificially contaminated sandwiches

• Published in: Journal of food protection Vol. 65; no. 11; pp. 1740 - 1744
• Main Authors: CLARDY, S, FOLEY, D. M, CAPORASO, F, CALICCHIA, M. L, PRAKASH, A
• Format: Journal Article
• Language: English
• Published: Des Moines, IA International Association of Milk, Food and Environmental Sanitarians 01.11.2002
• Subjects: Animals; Biological and medical sciences; Colony Count, Microbial; Consumer Product Safety; Dose-Response Relationship, Radiation; Food Handling - methods; Food industries; Food Irradiation; Freezing; Fundamental and applied biological sciences. Psychology; Gamma Rays; Humans; Listeria monocytogenes; Listeria monocytogenes - radiation effects; Meat Products - microbiology; Research and development. New food products, dietetic foods and beverages; Taste; Sandwich; Gamma irradiation; Ready to eat meal; Physical dressing; Ionization; Quality control; Packaging; Listeria monocytogenes; Bacteria; Food safety; Conditioning
• ISSN: 0362-028X; 1944-9097
• DOI: 10.4315/0362-028X-65.11.1740

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.