Growth and reducing capacity of Listeria monocytogenes under different initial redox potential.

AIMS: To determine the reducing capacity of Listeria monocytogenes and to highlight the effect of redox potential on its growth parameters.

METHODS AND

RESULTS

The reducing capacity of L. monocytogenes was monitored in Brain Heart Infusion Broth media at different initial redox potential (Eh) and pH at 37 degrees C. The effect of Eh obtained by gas flushing (air, N(2) and N(2)-H(2)) or by adding potassium ferricyanide and dithiotreitol in concentration from 1 to 10 mmol l(-1)on L. monocytogenes growth parameters at pH 6.0, 7.0 and 8.0 was investigated. A total change of 539 mV (+ or - 44 mV) from an initial redox value of +330 + or - 8 mV to a more negative potential in redox curves was observed resulting from L. monocytogenes growth at pH 7.0 at 37 degrees C. A significant influence of pH and redox potential on L. monocytogenes lag phase of growth was shown (P < 0.05).

CONCLUSIONS

Listeria monocytogenes exhibited longer lag phase in reducing conditions and at pH 6.0. The method used to modify the redox potential was shown to have no effect on growth parameters at pH 7.0.

SIGNIFICANCE AND IMPACT OF THE STUDY: The provided information on the extending lag time and the possible delayed growth of this major pathogen in reducing conditions might be useful for its control in foods.