Introduction
This article provides access to a calculator and an introduction to the mathematics derived by Dr Tomas Skoglund that enables the z-value, a term used in microbial thermal death time calculations, to be corrected to comply with Arrhenius calculations. This value can be defined in several ways, including that z is the number of degrees that the temperature must be increased to achieve a tenfold (i.e.,1 log10) reduction in the decimal reduction value (D-value). The D-value is the time required to reduce the number of organisms by 1 log cycle and is an indication of the heat resistance of an organism.
Bigelow and the Arrhenius models
There are two main approaches to calculating the bactericidal effectiveness of a heat process namely the Bigelow and Arrhenius methods. Both methods require the use of constants to allow for the temperature dependence of the kinetics of thermal destruction. The Bigelow method uses z-value (SI unit K or °C) and the Arrhenius model uses activation energy (Ea, SI unit J/ mol).