Kinetics of Disappearance and Discoloration of L-Ascorbic Acid 2-Glucoside Powders with Different Water Contents

The disappearance and discoloration of L-ascorbic acid 2-glucoside powders with water contents of 2 to 12% (w/w) during storage at a temperature from 70 to 90°C were investigated. The disappearance of L-ascorbic acid 2-glucoside with the higher water content proceeded faster at the higher temperature. The disappearance process was expressed by the Weibull equation. The change in the L-ascorbic acid was analyzed by assuming that both the hydrolysis and decomposition of L-ascorbic acid were expressed by first-order kinetics. A kinetic comparison of the overall disappearance by the hydrolysis indicated that the hydrolysis was not the sole route for the disappearance. The discoloration kinetics was also analyzed on the basis of the modified Weibull equation. It was shown that the enthalpy-entropy compensation held for all the processes involved in the overall disappearance of L-ascorbic acid 2-glucoside, its hydrolysis, the decomposition of L-ascorbic acid and the discoloration of L-ascorbic acid 2-glucoside. It was also demonstrated that the discoloration was suppressed by the glucosylation of L-ascorbic acid, but that L-ascorbic acid 2-glucoside was more easily discolored than L-ascorbyl 6-palmitate.