Kinetic parameters for thermal inactivation of cut green beans lipoxygenase calculated using unsteady-state methods

Kinetic parameters describing lipoxygenase inactivation during heating of cut green beans were determined using two unsteady-state procedures. The model used an analytical solution for heat conduction in a finite cylinder to predict time–temperature profiles, and a trial and error and a non-linear regression of experimental lipoxygenase retentions to estimate kinetic parameters. Thermal diffusivity and convective heat transfer coefficient were determined experimentally, but thermal conductivity was estimated. Mean values obtained, with standard deviations between parenthesis, were k76°C=27.2 (9.4) s–1; k82°C=92.9 (7.5) s–1; k88°C=212.1 (52.7) s–1; k94°C=407.8 (56.7) s–1; Ea=160.7 (8.1) KJ mol−1 using the trial and error procedure; k85°C=150 (26.3) s–1 and Ea=164 (4.7) KJ mol−1 using the non-linear regression method. Predicted and observed lipoxygenase retentions showed good agreement.