Inactivation of microorganisms by sterilization, disinfection, and pasteurization - New mathematical models

Inactivation of Microorganisms by Sterilization, Disinfection, and Pasteurization / New mathematical models Throughout the 20th century the kinetics of microbial inactivation have been described and calculated on the basis of the exponential model. This has offered little in terms of a logically satisfactory explanation, but the computations have served their purpose. In view of increasing demands on sterilisation techniques, the exponential model can no longer satisfy the needs for accuracy in the calculations of "sterilization times", in particular at temperatures below 100 degreesC. This article presents a new approach to microbial inactivation, namely the concept of a "typical resistance time" of microorganisms, as well as refined methods of modelling the inactivation kinetics under a quantitative aspect. On the basis of the assumption that the individual microbial survival times obey a two-parameter distribution, such as the log-normal or the Gamma distribution, new model functions are established which correlate significantly better with all available test data than the classic exponential model. The predictions of "safe sterilizations times" differ considerably (up to a factor 2) between the old and the new approach.