title: 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.
abstract: The thermal degradation kinetics of pectin methylesterase (PME) from carrot and lettuce were studied. Fresh extracts were exposed to temperatures from 55 to 70 degrees 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.
authors.affiliation: Postharvest Technology Unit, Dublin Institute of Technology (DIT), School of Food Science and Environmental Health, Faculty of Tourism and Food, Ireland. daniel.rico@dit.ie
authors.forename: Daniel
authors.initials: D
authors.lastname: Rico
authors.forename: Ana B
authors.initials: AB
authors.lastname: Martín-Diana
authors.forename: Catherine
authors.initials: C
authors.lastname: Barry-Ryan
authors.forename: Gary T M
authors.initials: GT
authors.lastname: Henehan
authors.forename: Jesús M
authors.initials: JM
authors.lastname: Frías
mesh_terms: D000595:Amino Acid Sequence; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000378:metabolism*; D018552:Daucus carota / Q000201:enzymology*; D006358:Hot Temperature; D007700:Kinetics; D018545:Lactuca / Q000201:enzymology*; D008969:Molecular Sequence Data; D010936:Plant Extracts / Q000737:chemistry; D012621:Seasons; D017386:Sequence Homology, Amino Acid
chemical_list: D010936:Plant Extracts; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase