Modelling of Listeria monocytogenes Scott A after a mild heat treatment in the presence of thymol and carvacrol: Effects on culturability and viability

The combined effect of thymol, carvacrol and mild heat treatments against Listeria monocytogenes Scott A was assessed in buffered system by plate counting and flow cytometry (FCM). The susceptibility of cells increased when heat treatment was combined with terpenes. The data modelling with Bigelow and Weibull equations showed that the latter was more appropriate to describe the inactivation kinetics. After treatments, cells were no longer able to form colonies on plates; nevertheless, FCM indicated that most of the cells were damaged rather than dead. Treated cells were not able to recover the damage after 6 h. This opens the question if they could recover in a food matrix. FCM can be a helpful technique to better comprehend the physiological state of microorganisms. In the perspective of industrial applications, studies based on predictive microbiology, as well as a deeper comprehension of the action mechanisms of antimicrobials, play a key role for process optimization.