Behaviour of inoculated wild L. monocytogenes in sliced vacuum-packed cold smoked pork
2011
Silins, I., Latvia Univ. of Agriculture, Jelgava (Latvia);Food and Veterinary Service, Jelgava (Latvia). Dienvidzemgale Branch | Liepins, E., Latvia Univ. of Agriculture, Jelgava (Latvia)
The non-spore forming gram-positive bacterium Listeria monocytogenes is a food pathogen bacterium and a causative agent of listeriosis. The aim of the study was to determine the survival limits of L. monocytogenes inoculated in manufactured vacuum-packed cold smoked pork depending on shelf time, supported by water activity (aw) and pH values. Enumeration of L. monocytogenes colony forming units per gram (cfu gE-1) was done according to ISO standard. Water activity (aw) and pH values in pork samples were more or less constant and supported L. monocytogenes growth. The behaviour of L. monocytogenes in cold-smoked sliced pork by shelf time, when environmental factors changed minimally and supported growth, largely depended on the initial contamination level. A lag-phase of bacterial growing process before exponential growth rate of inoculated L. monocytogenes depended on initial cell concentration and had 10 days step level if storage temperature was approximately 5 deg C. A significant Pearson’s correlation (p is less than 0.01) was established between the microbiological test values of L. monocytogenes count changes in sliced and packed cold-smoked pork during storage time of 60 days. The main parameter which maintained negative polynomial growth rate of L. monocytogenes in cold-smoked pork was the decrease of live cell concentration in samples below lg 2.0. The experiments were done at the Faculty of Veterinary Medicine of Latvia University of Agriculture and at a sausage manufacturer’s laboratory.
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