Studies were carried out to assess the use of high pressure CO2, treatment for controlling pathogenic microorganisms in model food systems. Listeria monocytogenes suspended in distilled water was completely killed after CO2 treatment at 6.18 MPa (61.2 atm) and 35°C for 2 h. Contrary to CO2 treatment, the use of N2 at these experimental conditions failed to exert bactericidal effect. High pressure CO2 treatment at 13.7 MPa (136.1 atm) and 35°C for 2 h was shown to effectively kill Salmonella in spiked chicken meat (>95%) and egg yolk (> 100%), and kill Listeria in spiked shrimp (> 99%), orange juice (> 99%), and egg yolk (> 99.4%). Such treatment was, however, less effective in killing Salmonella in a whole egg-Salmonella mixture. Furthermore, this treatment caused a twofold increase in bacterial numbers in a whole egg-Listeria mixture. N2 gas under similar experimental conditions did not kill the spiked bacteria in these four food systems. High pressure CO2 treatment technique could possibly be applied to reduce microbial load in some food systems.

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