MODELLING OF THE AEROBIC GROWTH OF STAPHYLOCOCCUS AUREUS UNDER DIFFERENT CONDITIONS OF WATER ACTIVITY, PH AND POTASSIUM SORBATE CONCENTRATION

ZARITZKY N.; CONTRERAS E.; GIANNUZZI L.

Quimper, Francia

Congreso; Predictive Microbiology Applied to Chiled Food Preservation; 1997

The effects of  water activity (0.90 and 0.92),  pH (5.0, 5.2,5.4,5.6 and 5,8) and concentration of potassium sorbate  (9.9-16.9 mM) on the aerobic growth of Staphylococcus aureus ATCC 6538P, 196-E and FDA-C243 were studied using Brain Heart Infusion Broth. The inoculum was approximately 104CFU/ml and the incubation temperature was 30°C. Samples were periodically enumerated on Tryptic Soy Agar. Gompertz model was used to obtain microbial growth parameters; m (specific growth rate) was obtained as a derived parameter and inhibition indices were also calculated. A linear model was fitted in the cases of bacteriostatic or bactericidal action of the treatment. ATCC strain showed the highest resistance.in the range of tested conditions. Microbial behavior was modeled respect to the main controlling factors  and a response surface was established in terms of  undissociated acid concentration and pH, that could be used to determine  treatment  conditions  producing  microorganism growth inhibition.