Predictive model of Listeria monocytogenes' growth rate under different temperatures and acids

A response surface model of Listeria monocytogenes' growth rate was built in this study under different temperatures (10 degrees C, 15 degrees C, 20 degrees C, 25 degrees C and 30 degrees C) and acid concentrations: citric acid (0-0.4%) and ascorbic acid (0-0.4%); two ingredients which are often used in the food industry as preservatives. Mathematical validation was performed with additional samples at different conditions within the range of the model, obtaining acceptable values of root mean square error (0.0466), standard error of prediction (18.84%), bias factor (1.05) and accuracy factor (1.16). The inhibitory effect on growth was more effective with citric acid than ascorbic acid, possibly due to the major dissociation of citric acid occurring inside microbial cells. The different conditions considered in the model will potentially allow L. monocytogenes' response to be predicted in foods having a similar composition to the chemical and physical factors set out in this paper.