ERROR-ESTIMATES FOR APPROXIMATE KINETIC-PARAMETERS USED IN FOOD LITERATURE

For convenience, the z-value has been traditionally used to describe temperature dependence of reaction rates in food materials. This approximate parameter z linearizes a more common non-linear relationship described by the Arrhenius equation for temperature dependence. Whereas researchers have been concerned about the range over which such approximate linear relationships may be valid, this study provides quantitative data to that effect for the first time. The nature and extent of error in using the z-value, as compared to the use of Arrhenius parameters, has been mathematically analyzed. It is shown that for every time-temperature history, there exists an unique reference temperature that minimizes this error. If 121-degrees-C is always used as the reference temperature instead, severe calculation errors are possible for higher temperature processes such as UHT processing and lower temperature processes such as inactivation of enzymes. A formula is proposed to preserve the full Arrhenius accuracy while still using the available z-values for reactions.