Combined effect of nisin, carvacrol and a previous thermal treatment on the growth of Salmonella enteritidis and Salmonella senftenberg

The aim of this study was to evaluate the combined effect of a previous mild heat treatment (15min at 55?) with the use of antimicrobials, nisin and carvacrol, on the growth of Salmonella enteritidis and Salmonella senftenberg. Natural antimicrobials, alone or combined with a previous mild heat treatment, affected the growth of these two serovars in Tryptone Soy Broth at 37?. Increasing concentrations of carvacrol had a significant effect on both growth rate and lag phase duration of both strains. The time to reach stationary phase was almost doubled in the case of S. enteritidis when a concentration of 0.77mM in carvacrol was added. For S. senftenberg the effect was smaller. The effect of nisin and of heat, applied individually, was lower for both microorganisms. A combination of 1.2 mu M nisin with 0.77mM carvacrol significantly delayed the growth of heat treated cells, compared to the control without antimicrobials, showing additive effects.