Simultaneous Modelling of the Thermal Degradation Kinetics of Pectin Methylesterase in Lettuce (Lactuca sativa L.) and Carrot (Daucus carota L.) Extracts: Analysis of Seasonal Variation and Tissue Type

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The thermal degradation kinetics of pectin methylesterase (PME) from carrot and lettuce were studied. Fresh extracts were exposed to temperatures from 55 to 70 °C until the enzyme was inactivated. A model based on the presence of two forms of the enzyme, one active and one non-active, is proposed. The natural variability of the PME activity was taken into the model in the form of normally distributed random effects. The common model parameters obtained (cleavage constant (0.0395±0.0062 s⁻¹), degradation constant (0.556±0.112 s⁻¹), cleavage energy of activation (469±23 kJ mol⁻¹) and degradation energy of activation (488±18 kJ mol⁻¹)) show that the PME degradation kinetics of the two vegetables can be explained with a single set of parameters.