| Abstract
| - The kinetics of the pectin methylesterase (PME)-catalyzed de-esterification of pectin was studied at25 °C in the presence of sucrose, fructose, maltodextrin (DE = 16.5−19.5), and carboxymethylcelluloseat different concentrations and in the presence of maltodextrin and sucrose at different concentrationsin a temperature range between +25 and −4 °C in subcooled and frozen states. The objective wasto determine whether the reaction is diffusion-controlled, to gain insight about the factors determiningthe diffusion of the reactants, and to determine the effect of the carbohydrates, low temperature, andfreezing on the structural conformation of the enzyme. The results indicate that the PME-catalyzedde-esterification of pectin is diffusion-controlled. Nevertheless, the diffusion is not controlled by themacroviscosity of the reaction medium, but rather by the microviscosity experienced by the diffusants.Low temperature in the temperature range studied does not affect the structural conformation of theenzyme, while freezing seems to have some effect. Keywords: Pectin methylesterase; macroviscosity; microviscosity; diffusion-controlled; glass transition
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