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.
Biotechnology Chemistry, Pharmaceutical