Comparison of 40 Salmonella enterica serovars injured by thermal, high-pressure and irradiation stress

Aim: To investigate and compare the inherent resistance of 40 Salmonella serovars to heat, irradiation and high-pressure stress. Methods and Results: D-10 values for each of the three stresses were calculated for four serovars, chosen as representatives from a catalogue of 40. Based on these results, conditions for each stress were defined, which produced, on average, a three-log reduction in viability. Heat stress (57degreesC for 13 min), high-pressure stress (350 MPa for 10 min at 20degreesC) and irradiation stress (1.5 kGy at 20degreesC) were applied to all 40 serovars in the collection. Injury and loss of viability for all serovars were determined. Conclusions: Cluster analysis identified five groupings of isolates in terms of resistance to the applied stresses. The independent response of each isolate to all three stresses suggests that there is no relationship between resistances. Significance and Impact of the Study: Each serovar is inherently different. For modelling of real-life food preservation processing the most resistant isolates for that process should be chosen. The results also emphasize the importance of including multiple stress resistant strains when food preservation systems apply multiple stresses.