title: Modeling the kinetics of the pectin methylesterase catalyzed de-esterfication of pectin in frozen systems.
abstract: The applicability of the William, Landel, and Ferry (WLF) equation with a modification to take into account the effect of melt-dilution and an empirical log-logistic equation were evaluated to model the kinetics of diffusion-controlled reactions in frozen systems. Kinetic data for the pectin methylesterase catalyzed hydrolysis of pectin in four model systems with different glass transition temperatures: sucrose, maltodextrin (DE = 16.5-19.5), carboxymethylcellulose (CMC) and fructose in a temperature range of -24 to 0 degrees C were used. The modified WLF equation was evaluated with a concentration-dependent glass transition temperature (T(g)) as well as the glass transition temperature of the maximally freeze-concentrated matrix (T(g)') as reference temperatures. The equation with temperature-dependent T(g) described the reaction kinetics reasonably well in all the model systems studied. However the kinetics was better described by a linear relationship between log(V(0)/V(0ref)) and (T - T(ref)) in all cases except CMC. The log-logistic equation also described the kinetics reasonably well. The effect of melt-dilution on reactant concentration was found to be minimal in all cases.
authors.affiliation: Department of Food and Microbial Technology, Laboratory of Food Technology, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium.
authors.forename: Netsanet Shiferaw
authors.initials: NS
authors.lastname: Terefe
authors.forename: Minh Tri
authors.initials: MT
authors.lastname: Nhan
authors.forename: David
authors.initials: D
authors.lastname: Vallejo
authors.forename: Ann
authors.initials: A
authors.lastname: Van Loey
authors.forename: Marc
authors.initials: M
authors.lastname: Hendrickx
mesh_terms: D002265:Carboxylic Ester Hydrolases / Q000737:chemistry*; D002384:Catalysis; D003198:Computer Simulation; D004789:Enzyme Activation; D004951:Esterification; D005615:Freezing; D007700:Kinetics; D000432:Methanol / Q000138:chemical synthesis*; D008956:Models, Chemical; D010368:Pectins / Q000737:chemistry*; D044367:Phase Transition; D044366:Transition Temperature
chemical_list: D010368:Pectins; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D000432:Methanol