Listeria innocua dynamic in minimally processed vegetables packaged in ordinary and modified atmospheres

This work was carried out to study the microbiological and safety aspects of Minimally Processed Vegetables (MPV) packed under different conditions. The type strain Listeria innocua DSMZ 20649 was used to study in vitro the growth/survival at different initial parameters. The bacteria was cultured in TSb (Tryptic Soy broth) using a 3x3x3 complete factorial design to assess the impact of temperature (15, 25, 37 °C), initial pH (5.2, 5.7, 6.0) and oxygen (aerobic, microaerophilic and anaerobic conditions) on the microrganism’s growth. In order to verify the behaviour of Listeria innocua DSMZ 20649 in the MPV artificially inoculated, packaged both in ordinary and modified atmospheres, the PCR-DGGE analysis was used. Moreover, the same approach was carried out in order to follow microbial dynamics of MPV products without inoculum. Listeria innocua DSMZ 20649 showed the highest growth in microaerophilic conditions, at 25 °C and at highest pH value. In aerobic condition the strain grew better at low temperature (15 and 25 °C) and in anaerobic condition at 37 °C showed at the lowest pH value the highest growth. The in vivo results showed that Listeria innocua became one of the dominant species at the end of the storage time and that indigenous microbial population highlighted slight shifts during storage.