Effect of Gamma Irradiation on Listeria monocytogenes in Frozen, Artificially Contaminated Sandwiches

Abstract

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.

Variations in the radiation sensitivity of foodborne pathogens associated with complex ready-to-eat food products

“…Ionizing radiation can also be used to reduce bacterial load on breads with little effect on product quality (Grecz et al 1985). While the database on radiation inactivation of foodborne pathogens, especially L. monocytogenes, on single-component RTE foods is extensive, the information on the radiation doses need to inactivate on multiple pathogens on complex RTE foods is more limited (McAteer et al, 1995;Foley et al 2001;Clardy et al, 2002;Lamb et al, 2002;IAEA, 2003).…”

“…Sommers and Boyd (2005) found that irradiation (2.5 kGy) of turkey and cheese tortilla wraps, which included a processedpasteurized American cheese product, as opposed to a traditional Swiss or Provolone cheese, did not change the appearance or aroma of the product. Clardy et al (2002) and Lamb et al (2002) found that irradiation (o4 kGy) of frozen sandwiches that included a RTE meat and cheese product produced an organoleptically acceptable product. Chen et al (2004) found that irradiation of frankfurters (3.5 kGy) did not adversely affect their sensory quality.…”

Effects of Electron Beam Irradiation and High Pressure Treatment Combined with Citrus Peel Extract on Seasoned Chicken Breast Meat

“…Therefore, low‐dose irradiation is practiced in the meat industry to minimize these alterations (Clardy et al . ). However, the key issue regarding the low‐dose irradiation is the survival of certain pathogens (Clardy et al .…”

Analysis of sterilization protocols for peptide‐modified hydrogels

“…Radiation within the gamma frequency range (> 3*10 19 Hz) penetrates packaging materials, and can be easily applied on a large scale at ambient temperatures, making it ideal for terminal sterilization. Thus, γ‐irradiation has been studied extensively in both the food1, 5, 6, 13–15 and medical1, 3, 9, 16–27 industries. Irradiation leaves no toxic byproducts,3, 4 making it an attractive alternative to ethylene oxide, a carcinogen which may be retained by implant materials if processing measures to remove it are inadqequate 4, 10…”

“…Despite the promise of γ‐irradiation in sterilization, there are obstacles preventing this procedure from being used to sterilize many food and biomedical products. Aside from misconceptions regarding the safety of irradiated food,7 irradiation causes changes in the flavor, texture, and color of foods, thus affecting their desirability to consumers 13, 14. These changes reflect deterioration of the biological structure of irradiated foods, primarily by oxidation‐induced free radicals.…”