| In this study the bactericidal action of several essential oil components (thymol, carvacrol and cymene) on the growth and viability of two Bacillus cereus strains (INRA-AVTZ415 and INRA-AVZ421) and two Listeria monocytogenes strains (STCC4031 and NCTN4032) was evaluated, in culture media and in food substrates (carrot juice, chicken soup and pumpkin cream). When the natural compounds were applied separately, a higher antibacterial effect was observed, showing differences that depended on the essential oil, strain tested, physiological state of the microorganism and composition of the food. When the natural antimicrobials were applied simultaneously, it resulted in a greater bactericidal effect than when the compounds were applied separately, showing a synergistic effect. This study indicates the potential use of thymol, carvacrol and cymene applied simultaneously for preservation of minimally processed foods.; The survivor curves did not follow a first order kinetics, but presented tails. Consequently, the experimental data were modeled using a frequency distribution function (Weibull). This model provided a good description of the experimental results and permitted to establish the conditions for an effective treatment with these compounds.; The potential use of frequency distributions to describe efficiently the growth data of the microorganisms exposed to preservation treatments was also evaluated. The results were analyzed using the normal and gamma distributions, and it was shown that the both distributions could be used to describe correctly the data.; Also the effect of the natural antimicrobials on B. cereus spores was evaluated, showing a potent inhibitory effect on germination. The effect was observed through optical density measurements, plate count, microscopy and flow cytometry with 5(6)-Carboxyfluorescein diacetate (cFDA). The cytometry technique was shown to be very useful for the study of the spore germination. |
