Effects and Interactions of Temperature, pH, Atmosphere, Sodium Chloride, and Sodium Nitrite on the Growth of Listeria monocytogenes

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Abstract
The effects and interactions of temperature (5, 19, 28, 37°C), initial pH (6.0 and 7.5), atmosphere (aerobic and anaerobic), sodium chloride content (0.5 and 4.5%), and sodium nitrite concentration (0, 50, 100, 200, 1000 μg/ml) on the growth of Listeria monocytogenes Scott A were determined using Tryptose Phosphate Broth. Growth data were analyzed by regression analysis to generate “best-fit” Gompertz equations, which were used subsequently to calculate lag phase duration, exponential growth rate, generation time, and maximum population density values. The data indicated that the growth kinetics of L. monocytogenes was dependent on the interaction of the five variables, particularly in regard to exponential growth rates and lag phase durations. The data suggest that sodium nitrite can have significant bacteriostatic activity against L. monocytogenes and may provide cured meats with a degree of protection against this microorganism, particularly if employed in conjunction with a combination of acidic pH, vacuum packaging, high salt concentrations, and adequate refrigeration.