Modelling the antimicrobial effect of food preservatives in bacteria: Application to Escherichia coli and Bacillus cereus inhibition with carvacrol
Adrián Pedreira, Nerea Martínez‐López, José Antonio Vázquez, Míriam R. García
Abstract
Food preservatives exhibit a weak antimicrobial effect that is difficult to describe mathematically. Preservatives are commonly added below the Minimum Inhibitory Concentration (MIC) to avoid organoleptic rejection and may exhibit very different antimicrobial effects. In most cases, they inhibit bacteria growth in the first hours, reduce the stationary phase and increase the final death phase. Mathematical descriptions of these dynamics are complex but critical to understanding and optimising food preservation, such as in the case of active packaging. In this work, we propose a new mathematical model to describe bacteria dynamics with preservatives along the exponential, stationary and death phases. We demonstrate that unknown model parameters can be estimated from measurements of bacterial growth curves at different preservative concentrations (identifiability analysis) and find a closed-form solution of the model that allows us to infer the MIC, as well as the bacteriostatic (inhibition of growth rate) and bactericidal (increase on death rate) effects. To illustrate and validate the model capabilities, we experimentally measure 48 hours growth kinetics of Escherichia coli and Bacillus cereus bacterial strains exposed to carvacrol, a preservative and flavouring agent widely employed in the food industry. We show how the model describes the measured trend during the exponential, stationary and death phases in the log-scaling of bacterial counts and can be used to analyse the antimicrobial properties of carvacrol.