Derivation of a rigorous equation for the calculation of the F‐value in isothermal sterilization processes

The use of simplified equations utilizing the Z‐and F‐values to calculate the level of sterilization achieved in isothermal processes is very common in industry. This method assumes that the Z‐value is independent of temperature. This is a simplifying assumption that is not based on a physically realistic microbial inactivation model. In the present work the appropriate equations for the Z‐ and F‐values were derived with kinetic theory and utilized to predict the level of sterility obtained during isothermal sterilization. The F‐value obtained with the proposed equation was always higher than the F‐value obtained when the simplifying assumption was made. Therefore, the use of the equation proposed here for the F‐value results in more realistic and generous estimates of the lethal effect on microorganisms produced by isothermal sterilization processes. Tables of the F‐values so obtained are provided.