Inhibitory activity of phenolic acids against Listeria monocytogenes: Deciphering the mechanisms of action using three different models.

Phenolic compounds are well known for their antimicrobial activity. They may provide an interesting solution to ensure food safety by preventing the growth of foodborne pathogens while addressing the wishes of consumers for the use of natural preservatives in food and favoring the reuse of agro-industry byproducts. However, their mechanism of action is still not very well understood. Here, we aimed to decipher the complex mechanism of action of eight phenolic acids by decomposing their effects, such as the general effect of the decrease of extracellular pH (γ(pH)) and specific inhibitory effects of the undissociated (γ(Au)) and dissociated (γ(Ad)) forms. We thus developed three different models and applied them to a dataset of Listeria monocytogenes growth rates experimentally obtained in the presence of various concentrations of phenolic acids at several pHs. The model that best fits the dataset was selected for each phenolic acid to explore the potential mechanisms. The results show that the antimicrobial activity is mainly due to the effect of the undissociated forms, except for chlorogenic and gallic acids, for which the antimicrobial activity is mainly due to a decrease in extracellular pH. In addition, the dissociated forms of p-coumaric and ferulic acids show significant inhibitory activity.