The surfaces of ready-to-eat meats are susceptible to postprocessing contamination by Listeria monocytogenes. This study examined and modeled the growth characteristics of L. monocytogenes on cooked ham treated with lactic acid solutions (LA). Cooked ham was inoculated with L. monocytogenes (ca. 10(3) CFU/g), immersed in 0, 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0% LA for 30 min, vacuum packaged, and stored at 4, 8, 12, and 16°C. LA immersion resulted in <0.7 log CFU/g immediate reduction of L. monocytogenes on ham surfaces, indicating the immersion alone was not sufficient for reducing L. monocytogenes. During storage, no growth of L. monocytogenes occurred on ham treated with 1.5% LA at 4 and 8°C and with 2% LA at all storage temperatures. LA treatments extended the lag-phase duration (LPD) of L. monocytogenes and reduced the growth rate (GR) from 0.21 log CFU/day in untreated ham to 0.13 to 0.06 log CFU/day on ham treated with 0.5 to 1.25% LA at 4°C, whereas the GR was reduced from 0.57 log CFU/day to 0.40 to 0.12 log CFU/day at 8°C. A significant extension of the LPD and reduction of the GR of L. monocytogenes occurred on ham treated with >1.25% LA. The LPD and GR as a function of LA concentration and storage temperature can be satisfactorily described by a polynomial or expanded square-root model. Results from this study indicate that immersion treatments with >1.5% LA for 30 min may be used to control the growth of L. monocytogenes on cooked meat, and the models would be useful for selecting LA immersion treatments for meat products to achieve desired product safety.

Provides gamma radiation D10 data for inactivation data for Y. enterocolitica irradiated under modified atmosphere and information to risk assessors regarding the difference between pathogen presence versus actual virulence.

Unfortunately, contraction of food borne illness due to consumption of contaminated seafood, including shrimp, is an occasional occurrence. Cryogenic freezing and gamma irradiation are safe and effective technologies that can be used to control and inactivate pathogenic bacteria in foods. In this study, the effect of cryogenic freezing and gamma irradiation for inactivation of Salmonella spp. on shrimp was investigated. We found that cryogenic freezing of raw shrimp (-82 o C, 3 min), using a pilot scale industrial liquid nitrogen freezer, resulted in a 1.27 log reduction of Salmonella spp. on whole shrimp, which was maintained during 12 weeks of frozen storage (-20 o C). During our evaluation of selective microbiological media for recovery and enumeration of Salmonella spp. we found that Brilliant Green Sulfur Agar produced results indistinguishable from that of non-selective Tryptic Soy Agar when determining the effect of cryogenic freezing on Salmonella spp. survival. Radiation D 10 values for Salmonella spp. on frozen shrimp were approximately 0.56 kGy. Cryogenic freezing (-82 o C), followed by gamma irradiation (2.25 kGy) produced a >5 log reduction of Salmonella spp., and that reduction was maintained during 12 weeks frozen storage (-20 o C). These results indicate that both cryogenic freezing and gamma irradiation contribute to inactivation of Salmonella spp. on frozen shrimp.

The objective of this study was to evaluate the growth of a multiisolate cocktail of non-O157:H7 STECs (serovars O26, O45, O103, O111, O121, and O145), using catfish fillets (Ictalurus punctatus) under refrigeration and temperature-abuse conditions as a model system for aquaculture-raised finfish.

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