The non-spore forming gram-positive bacterium Listeria monocytogenes is a food pathogen bacterium and the causative agent of listeriosis. The aim of study was to determine the survival limits of L. monocytogenes inoculated in manufactured cold smoked sausages depending on water activity (aw) and pH values. Enumeration of L. monocytogenes colony forming units per gram (cfu gE-1) was done according to ISO standards. The decreasing water activity conditioned by moisture (weight) loss during ripening and pH decrease ensured negative exponential growth rate of inoculated L. monocytogenes lg cfu gE-1 - 0.44 each day. A significant Pearson's correlation (p is less than 0.01) was established between decreased values of L. monocytogenes count, aw (0.99), pH (0.92), moisture % (0.96), and weight loss (0.93) in sausages during ripening. The experiments were done at the Faculty of Veterinary medicine of the Latvia University of Agriculture and in a sausage manufacturer's laboratory.

The survival of inoculated in a cold-smoked sausages Listeria monocytogenes wild strains was studied. The sausages were prepared with and without starter cultures. The survival limits of L. monocytogenes and lactic acid bacteria (LAB) were determined as colony forming units per gram (cfu gE-1) depending on water activity (aw) and pH on 0, 1st, 3rd, 5th, 7th, 14th and 21st days of maturation. The decreasing water activity conditioned by moisture (weight) loss during ripening and pH decrease ensured negative polynomial growth rate of inoculated L. monocytogenes - 0.27 lg (cfu gE-1) each day of ripening time, and - 0.65 lg (cfu gE-1) on the first 7 days of maturation. A significant Pearson’s correlation (p is less than 0.01) was established between decreased values of L. monocytogenes count, aw, salt concentration and LAB growth in sausages during the ripening period of 21 days. The main parameters, maintained negative exponential growth rate of L. monocytogenes in cold smoked sausages, are aw value decrease and LAB (starter culture), which stopped L. monocytogenes growth at the beginning of cold-smoked sausage maturation. If fermentation process went technically and hygienically correctly, the fermented (cold-smoked) sausages could be one of the safest meat products, because in real practice a low level contamination has been seen. The remaining count of L. monocytogenes in cold-smoked sausage depends on the possible initial contamination level and could exceed the European Union regulation value 2.0 lg (cfu gE-1) for ready-to-eat products when contamination at first is more than lg 5.0.