THE EFFECTS OF pH, aW, AND LACTIC ACID BACTERIA ON LISTERIA MONOCYTOGENES IN FERMENTED SAUSAGES

The survival of inoculated in fermented sausages Listeria monocytogenes strain 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 g) depending on water activity (aw) and pH on 0, 1 , 3, 5, 7, 14 and 21 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 g) each day of ripening time, and -0.65 lg (cfu g) on the first 7 days of maturation. A significant Pearson’s correlation (p<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 fermented sausages, are aw value decrease and LAB (starter culture), which stopped L. monocytogenes growth at the beginning of fermented 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 fermented sausage depends on the possible initial contamination level and could exceed the European Union regulation value 2.0 lg (CFU g) for ready-to-eat products when contamination at first is more than lg 5.0.