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.

Short communication: Long-term −20°C survival of Listeria monocytogenes in artificially and process-contaminated ice cream involved in an outbreak of listeriosis

“…It is not known whether increasing the temperature to −10 or 0°C would affect the survival of L. monocytogenes in artificially contaminated or process-contaminated samples. Published studies have examined the population dynamics of L. monocytogenes in ice cream at different frozen temperatures (Palumbo and Williams, 1991;Dean and Zottola, 1996;Gougouli et al, 2008;Mastronicolis et al, 2011). For example, it was determined in one study that L. monocytogenes populations in artificially contaminated ice cream did not significantly differ between storage temperatures of −5, −15, −23, or −33°C (Gougouli et al, 2008).…”

“…For example, it was determined in one study that L. monocytogenes populations in artificially contaminated ice cream did not significantly differ between storage temperatures of −5, −15, −23, or −33°C (Gougouli et al, 2008). However, when assessing cold-adapted versus unadapted L. monocytogenes, another study concluded that cold adaptation increased the pathogen's ability to survive during the first month of storage at −20°C (Mastronicolis et al, 2011). Because in-process contaminants had been exposed to freezing temperatures in the ice cream for many weeks before the current study was conducted, they may be regarded as cold adapted; however, no differences in survival between pathogen contamination states (in-process/cold-adapted vs. artificial) were observed.…”

Growth and membrane fluidity of food-borne pathogen Listeria monocytogenes in the presence of weak acid preservatives and hydrochloric acid

“…Listeria monocytogenes has been associated with a variety of food products, including dairy foods, meat, poultry, and seafood as well as fruits and vegetables (Farber and Peterkin, 2000; Mastronicolis et al, 2011). In 2008, 1,381 confirmed human cases of listeriosis were reported in the European Union and the reported case-fatality rate was 20.5% [European Food Safety Authority (EFSA), 2010].…”