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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.
Rico, D., Martin-Diana, A., Barry-Ryan, Catherine, Henehan, G., Frias, J. :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. Bioscience, Biotechnology, and Biochemistry Vol. 71 (2007) , No. 10, pp. 2383-2392