Behavior of Listeria monocytogenes type1 355/98 (85) in meat emulsions as affected by temperature, pH, water activity, fat and microbial preservatives

The aim of this work was to analyze the effect of temperature (10-30 degrees C), fat content (20-50%), sodium chloride (2.5-5.0%) and preservative concentrations: sodium nitrite (0-150 ppm), lactic acid (50-500 mM) and nisin (0-100 IU/g (international units per gram)) on the growth of Listeria monocytogenes in a meat emulsion system. Individual and simultaneous effects of the parameters were tested and the results were mathematical modeled: inhibition indexes were calculated in each case. The addition of 7.5% NaCl inhibited the growth of L monocytogenes at 20 and 30 degrees C, however, at 10 degrees C, microbial counts reached approximately 10(6) CFU/g. The addition of 50 mM of lactic acid to obtain a pH <= 5 inhibited the growth of L monocytogenes. The combinations of lactic acid with sodium nitrite or with nisin showed an enhancement of the inhibitory effect. However, considering the low toxicity of nisin, the combination of lactic acid (50 mM) and nisin (20 IU/g) would be more acceptable in the prevention of the growth of Listeria monocytogenes. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.