Advisor(s)
Abstract(s)
Motivation: L. monocytogenes is known to persist in food processing environments, with some strains being routinely isolated (persistent), while others are only occasionally found (sporadic). This raises the question: Are persistent strains more resistant to stress conditions compared to sporadic strains from similar sources? Objective: To investigate the effect of food processing related stresses (pH=6 and 8% NaCl) on the behaviour of L. monocytogenes isolates from alheira sausage, compared to a set of reference conditions (37 °C, 0% NaCl, pH=7). Results: Compared to the reference conditions: High salinity conditions → significantly longer lag times and lower μmax for all isolates Low pH (pH = 6) reduced μmax but also shortened the lag phase for most isolates These sub-optimal conditions were insufficient to promote pathogen decay The persistent strains #2981 and #3048 do not exhibit a particular behavior nor appear to have increased resistance against the conditions tested This result is aligned with recent research. Conclusions: No significant differences were found between persistent and sporadic strains, suggesting that persistence events may not be explained by a better aptitude for growth. However, further research with a larger number of isolates is needed.