|
Résumé :
|
The effects and interactions of heating temperature (55 to 65 °C), pH (4 to 8), salt (NaCl; 0 to 6%, wt/vol), and sodium pyrophosphate (SPP; 0 to 0.3%, wt/vol) on the heat inactivation of a four-strain mixture of Listeria monocytogenes in beef gravy were examined. A factorial experimental design comparing 48 combinations of heating temperature, salt concentration, pH value, and SPP content was used. Heating was carried out using a submerged-coil heating apparatus. The recovery medium was plate count agar supplemented with 0.6% yeast extract and 1% sodium pyruvate. Decimal reduction times (D-values) were calculated by fitting a survival model to the data with a curve-fitting program. The D-values were analyzed by second-order response surface regression for temperature, pH, NaCl, and SPP levels. Whereas increasing the NaCl concentration protected L. Monocytogenes against the lethal effect of heat, high SPP concentrations increased heat sensitivity. Also, low pH values increased heat sensitivity of L. Monocytogenes. The four variables interacted to affect the inactivation of the pathogen.
|
