Effect of different levels of nitrite and nitrate on the survival of Listeria monocytogenes during the manufacture of fermented sausage

The fate of L. monocytogenes during the fermentation of Finnish fermented sausage was examined. L. monocytogenes was able to survive during a 21 d fermentation of sausage with levels of nitrite and salt commonly used in the meat industry today (120 ppm NaNO2 and 3.0% NaCl). Initial numbers of Listeria (103 CFU/g and 105 CFU/g) decreased approximately 1 log 10 CFU/g during the manufacture. Increasing the levels of nitrite/nitrate to those used 30 years ago in meat products had a marked effect on the elimination of Listeria. The numbers of survivors in the sausages was reduced 2.0 log 10 CFU/g during the fermentation of 3 weeks with a combination of 200 ppm NaNO2 and 300 ppm KNO3. With 1000 ppm KNO3, the decrease was 3.3 log 10 CFU/g. L. monocytogenes could not be totally eliminated from highly contaminated sausage by increasing only the levels of nitrite and nitrate. Levels of these additives with best bacteriostatic effect on Listeria are no longer permitted in food.