Influence of antimicrobial compounds and modified atmosphere packaging on radiation sensitivity of Listeria monocytogenes present in ready-to-use carrots (Daucus carota)

Radiosensitization of Listeria monocytogenes was determined in the presence of traps-cinnamaldehyde, Spanish oregano, winter savory, and Chinese cinnamon on peeled minicarrots packed under air or under a modified atmosphere (60% O-2, 30% CO2, and 10% N-2). Samples were inoculated with L. monocytogenes HPB 2812 serovar 1/2a (10(6) CFU/g) and were coated separately with each active compound (0.5%, wt/wt) before being packaged under air or the modified atmosphere and irradiated at doses from 0.07 to 2.4 kGy. Results indicated that the bacterium was more resistant to irradiation under air in the absence of active compound. The dose required to reduce L. monocytogenes population by 1 log CFU (D-10) was 0.36 kGy for samples packed under air and 0.17 kGy for those packed under the modified atmosphere. The active compounds evaluated in this study had an effect on the radiation sensitivity of L. monocytogenes on carrots. The most efficient compound was traps-cinnamaldehyde, where a mean 3.8-fold increase in relative radiation sensitivity was observed for both atmospheres compared with the control. The addition of winter savory and Chinese cinnamon produced a similar increase in relative radiation sensitivity but only when samples where packed under modified atmosphere conditions.