Effects of CO 2 on the resuscitation of Listeria monocytogenes injured by various bactericidal treatments

Abstract

To assure the microbiological safety and quality of a food product, a combination of preservation hurdles is often used. Therefore, the effects of carbon dioxide at concentrations of 0, 20, 40 and 60% in modified atmospheres on the resuscitation of Listeria monocytogenes cells injured by mild bactericidal treatments during storage at 7 °C were examined. The bactericidal treatments were intense light pulses (ILP), chlorine dioxide (ClO 2), lactic acid (LA) and heat. The results indicated additional bactericidal effects of CO 2 on cultures treated with LA, ClO 2 and ILP, with additional reductions in viable L. monocytogenes of 0.5–1.0 log cfu/ml. Lag phase duration was significantly different between the different treatments, with non-treated cells having the shortest lag phase, followed by that of heat, intense light pulses, lactic acid and finally ClO 2 treated cells. Maximum growth rate was also estimated and results showed a negative correlation with increasing CO 2 concentrations. A relationship was found between the amount of sub-lethally damaged cells after a mild inactivation treatment and the lag phase duration in the CO 2 environment. Current findings demonstrate the possibility that combining mild decontamination treatments and packaging in a CO 2 enriched environment could reduce the risk of L. monocytogenes infections in food due to an extension of the lag phase.