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

Kinetic parameters describing lipoxygenase inactivation during heating of c ut green beans were determined using two unsteady-state procedures. The mod el 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 r egression of experimental lipoxygenase retentions to estimate kinetic param eters. Thermal diffusivity and convective heat transfer coefficient were de termined experimentally, but thermal conductivity was estimated. Mean value s obtained, with standard deviations between parenthesis, were k(76 degrees C)=27.2 (9.4) s(-1) k(82 degreesC) = 92.9 (7.5) s(-1); k(88 degreesC) = 212 .1 (52.7) s(-1): k(94 degreesC) = 407.8 (56.7) s(-1); E-a = 160.7 (8.1) KJ mol(-1) using the trial and error procedure: k(85 degreesC) = 150 (26.3) s( -1) and E-a = 164 (4.7) KJ mol(-1) using the non-linear regression method. Predicted and observed lipoxygenase retentions showed good agreement.