Discoloration Kinetics of L-Ascorbyl 6-Palmitate Powders with Various Water Contents

Abstract

The discoloration of L-ascorbyl 6-palmitate, with water contents ranging from 2 to 10% (w/w) during storage at temperatures of 60 to 90°C, was investigated by monitoring the absorbance at 500nm of its solutions dissolved in methanol. The discoloration process of the substrate was expressed by the modified Weibull equation under all conditions, and the kinetic parameters were evaluated. The activation energy and frequency factor were estimated based on the Arrhenius equation for the substrates of various water contents, and the enthalpy-entropy compensation held for the discoloration process. Comparison of the discoloration kinetic parameters for L-ascorbyl 6-palmitate with those for L-ascorbic acid revealed that the discoloration of L-ascorbyl 6-palmitate was weaker than that of L-ascorbic acid.