A model of survival curves having an 'activation shoulder

Micha Peleg, University of Massachusetts - Amherst

Abstract

The ‘activation shoulder’ in the isothermal survival curves of B. stearothermophilus spores is probably an indication that the initial number is an undercount and that heat improves their recovery. The inactivation need not follow a first order kinetics. It is described by an empirical model, whose coefficients are determinded by the spores but not by any preconceived kinetic order. When the temperature‘profile ’ and the survival parameters’ temperature dependence are expressed algebraically, the slope of the corresponding non isothermal survival curve, which is initially positive, can be used to generate the survival ratios by numerical methods, as demonstrated with simulated stable and unstable heat treatments using published inactivation data.