The impact of modified atmosphere packaging and irradiation on the survival and pathogenicity of Listeria monocytogenes and the design of a mathematical model

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Chung-Lewis, Mei
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The survival of Listeria monocytogenes in packaged, ground containing either CO$\sb2$ (15% or 30%) or air was examined during storage at 5 or 11$\sp\circ$C. Survival was evaluated when electron beam radiation (1.75 kGy) was used as part of a combination treatment. The mathematical model $\rm S\over{S\sb0}$ = exp ($\mu\sb0\sp*$ (1 $-$ exp ($-$Dt)), is derived from the experimental data generated by this study. Fat (protein) content, storage temperature, and atmospheric conditions were the parameters which were applied to derive this equation. The growth ratio can be used to predict the effectiveness of these parameters on the survival of the organism. For example, this equation demonstrates that the number of listeriae increased as the level of CO$\sb2$ decreased in both 5 and 11$\sp\circ$C. By manipulating the proportionality constant, $\mu\sb0\sp*$, and using the exponential data points, a best fit line can be produced to the one that is very similar to the growth curve of an organism The goodness of fit of this line can demonstrate the effect of various treatment protocols to the survival of the organism. (Abstract shortened by UMI.)