Growth kinetics of a native toxigenic isolate of Yersinia enterocolitica CFR 2301 under the influence of incubation temperature, pH, sodium chloride and sodium nitrite

Abstract

Growth attributes such as lag phase duration (LPD) and growth rate (GR) estimates of a native toxigenic isolate of Yersinia enterocolitica CFR 2301 were studied in a broth medium under the influence of incubation temperature, pH, sodium chloride and sodium nitrite. The experimental growth curves derived from the central composite design based on 5 levels of factors namely incubation temperature (12-40°C), pH level (5.5-8.5), sodium chloride (0.5-5.5 %) and sodium nitrite (0-200 ppm) were fitted using Baranyi and Gompertz functions, individually. With both these functions, the observed LPD values were similar ranging from 2.0 to 20.0 h and with GR values ranging from 0.1 to 0.5/h. The predicted values of LPD and GR estimates related well with observed values. The experimental culture broths with GR estimates of 0.4 and 0.5/h revealed positive phospholipase activity that is associated with the toxigenic trait of phospholipase A in the culture of Y. enterocolitica CFR 2301. The generated response surface plots for LPDs and GR estimates show a definite behavioral pattern under the influence of a combination of selected factors and variables. Higher LPDs and lower GR estimates as the indices of microbial safety could be of significance in developing effective food safety protocols in the food chain.