Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2008
Publication Date: November 1, 2008
Citation: Rajkowski, K.T. 2008. Radiation D10-Values on Thawed and Frozen Catfish and Tilapia for Finfish Isolates of Listeria Monocytogenes. Journal of Food Protection. 71(11):2278-2282. Interpretive Summary: Listeria monocytogenes, a food borne pathogen, has caused illness related to the consumption of fish. Finfish isolates have not been studied for their radiation sensitivity. Irradiation, a non-thermal intervention technology, was used to determine the dose level (D-10) to reduce the population of L. monocytogenes by 90%. The L. monocytogenes isolates were inoculated on both a high fat (catfish) and low fat (tilapia) finfish that was either fresh or frozen. The results showed that there was no difference in the D-10 value for L. monocytogenes inoculated on the raw or frozen catfish or tilapia when irradiated at 4 C or -10 C. The average radiation D-10 value obtained was 0.62 (SD=0.09) kGy and is within the reported dose for Listeria. Using these data, producers could utilize irradiation to reduce Listeria from finfish and on other flesh foods to provide a safer product to the consumer.
Technical Abstract: With the popularity of catfish and tilapia in the healthy diet, the consumption and harvesting of farm raised finfish has increased. Since 1987 the bacterial pathogen, Listeria monocytogenes, has been isolated from seafood, particularly farm raised catfish in the United States. Seafood isolates of L. monocytogenes are now available. In order to maintain the raw finfish product, non-thermal interventions to remove bacterial pathogens need to be evaluated using these isolates. A non-thermal intervention process, irradiation, was used to determine the destruct values of the L. monocytogenes seafood isolates along with a non-pathogenic Listeria and a L. monocytogenes previously studied. The irradiation destruct values were obtained for each individual isolate inoculated on raw and frozen catfish or tilapia irradiated at 4 C or -10 C. The D-radiation values obtained for the L. monocytogenes inoculated on the raw or frozen catfish did not differ (P > 0.05) from the values obtained on the raw or frozen tilapia. The D-radiation values ranged from 0.48 to 0.85 kGy. The average D-radiation value obtained was 0.62 (SD=0.09) kGy and is typically reported of those for Listeria. The data obtained has identified a multi-isolate cocktail that can be used for future radiation inactivation studies for L. monocytogenes modeled in finfish.