Food technologists and microbiologists generally have limited information on the effect of temperature on the D-values of pathogenic and spoilage organisms. It is often necessary to model the D-value at a higher or lower temperature than the reference value.

This can be done in two ways, using the Bigelow (1921) method or the Arrhenius equation. The most commonly used method is the Bigelow method.

An article "Predicting the effects of temperature on the D-value calculated using the Bigelow and Arrhenius methods" has been added to the website. This provides an introduction to a free calculator for determining the Decimal Reduction Time (D) for a microorganism at a higher or lower temperature knowing the D-value at the reference temperature and the Z-value. The calculator compares the D-values obtained by the Bigelow and Arrhenius models and also gives the activation energy (Ea) and inactivation rate(ko).