Nisin, Carvacrol and Their Combinations Against the Growth of Heat-Treated Listeria monocytogenes Cells

Listeria monocytogenes is a Gram-positive microorganism responsible for one of the most serious food-borne diseases in the world, listeriosis. The aim of this study is to evaluate the combined effect of a heat pretreatment with the use of antimicrobials, nisin and carvacrol, on the growth of L. monocytogenes, and their potential uses as food preservatives. Carvacrol showed a dose-dependent inhibitory effect, while nisin did not, it decreased the growth rate of L. monocytogenes up to 20 %, and it increased lag time for approx. 25 % at any of the concentrations tested (0.13–0.39 mM). When both antimicrobials were combined, a synergistic effect was observed. This effect was further increased when they were combined with a heat pretreatment for 15 min at 55 °C, where no growth was observed for at least 15 days, even at the lowest concentration tested. The effect was proved both in tryptic soy broth and in carrot juice. This study indicates the potential use of carvacrol and nisin applied simultaneously for preservation of minimally processed foods.