Degradation Kinetics of D-Galacturonic Acid and Sodium D-Galacturonate in Subcritical Water

Abstract

The degradation process of D-galacturonic acid in subcritical water was measured from 160 to 220°C. The process at any temperature obeyed first-order kinetics. The temperature dependence of the degradation rate constant could be expressed by the Arrhenius equation, and the activation energy and the frequency factor were estimated to be 131 kJ/mol and 4.81 × 1012 s-1, respectively. The degradation process of sodium D-galacturonate in subcritical water was also measured from 160 to 190°C. Sodium galacturonate was more easily degraded than galacturonic acid. The degradation process of sodium galacturonate did not obey the first-order kinetics, but could be expressed by the Weibull equation. According to the Arrhenius equation, the activation energy and the frequency factor were estimated to be 147 kJ/mol and 1.26 × 1015 s-1, respectively, for the degradation of sodium galacturonate. The pH of the reaction mixture at room temperature was also measured for the degradation of both the galacturonic acid and sodium galacturonate.