Effect of cold adaptation on the survival of Listeria monocytogenes in ice-cream formulations during long-term frozen storage

Abstract

This is the first study to evaluate the survival potential of cold-adapted Listeria monocytogenes in icecream. Cold adaptation enhances survival of this pathogen in ice-cream during the first period of storage compared to non-adapted cells. The viable population of cold-adapted and non-adapted cells was 3 log (36 days) and 4.3 log (27 days), respectively, lower than the initial population (6.3 log) in inoculated ice-cream. This behavior raises concerns for food safety. The viable population of both cold-and non-adapted cells displayed a slight statistical difference in the next period of frozen storage (0.29 and 0.75 log decline at 137 and 182 days, respectively). Significant numbers of L. monocytogenes cells survived for extended periods of time, irrespective of whether they were previously cold-or non-adapted (332 and 182 days respectively). The natural additives utilized (fructose syrup, corn syrup, sesame oil and sesame paste) did not have any significant effect on the response of non-adapted L. monocytogenes in ice-cream during 182 days of storage. On the other hand, the survival of cold-adapted L. monocytogenes is influenced by the ingredients utilized in the ice cream. Sesame paste and corn syrup had an inhibitory action on cold-adapted L. monocytogenes throughout the frozen storage (332 days) possibly as a consequence of lower water activity in samples with these additives. © 2011 Springer-Verlag and the University of Milan.