Model for the Effect of Carbon Dioxide on Listeria Monocytogenes in Fresh-cut Iceberg Lettuce Packaged Under Modified Atmosphere

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The fresh-cut iceberg lettuce inoculated with Listeria Monocytogenes (3 log CFU/mL) was packaged in modified atmospheres (10% CO₂/10% O₂, 30% CO₂/10% O₂, 50% CO₂/10% O₂) and then stored at 4°C, 8°C, 16°C, 24°C and 32°C separately. Modified Gompertz model was selected to estimate the growth rate and lag time. Results showed that the growth of L. monocytogens decreased with the increase of concentration of CO₂ and revised Gompertz equation fitted the growth of L. monocytogens at different test conditions. Root Square model was chosen as a secondary model to study the effects. Mathematical evaluation was also conducted with the bias factor (B_f) and accuracy factor (A_f) and residual analysis. Results showed that predictive value of the model is more accurate and reliable in level of α=0.1 and the value of B_f all is in 0.7–1.05, while the value of A_f is acceptable in general.