Survival of Listeria monocytogenes and Salmonella Enteritidis in sea bream (Sparus aurata) fillets packaged under enriched CO2 modified atmospheres

The effect of packaging of fresh sea bream fillets under different modified atmospheres (high levels of CO2 combined with N2) on the behaviour of Listeria monocytogenes and Salmonella Enteritidis was studied. Two different strains of each pathogen were spread over the sea bream fillets stored at either 0 °C or 4 °C for 16 days under standard supermarket lighting conditions (14 h a day). The atmospheres investigated were 60% CO2/40% N2, 70% CO2/30% N2, 80% CO2/20% N2 and air as control. Mesophilic, psychrotrophic and Enterobacteriaceae microbial counts were also performed in control batches. The results indicate that all the CO2 concentrations used favoured the control of pathogen bacteria inoculated, when compared with air conditions especially, when combined with storage at 0 °C. Both storage temperature (0 °C and 4 °C) resulted in a decrease in Salmonella count. The results were more significant for Listeria strains, because during the storage at 4 °C Listeria count increased in all batches, while for samples stored at 0 °C a significant reduction in microbial load except in control batch was observed. Sensitivity differences of inoculated strains against temperature and CO2 concentrations were also discussed.