A KINETIC MODEL FOR OXIDATION OF ASCORBIC ACID AND BETA-CAROTENE

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Abstract
A kinetic model of ascorbic acid oxidation in an aqueous solution, in which dissolved oxygen concentration is held constant, was developed. The model consists of consecutive reactions, , where A is ascorbic acid, B is an intermediate, C is an oxidized product, kA is a zero-order rate constant with respect to ascorbic acid concentration, kB is a first-order rate constant with respect to intermediate concentration. When it was assumed that A and B gave the same response to chemical determination of A, the model fitted the observation well. The model shows that it is possible for the time course of the reaction to have either first- or zero-order feature in accordance with initial concentrations of A and the ratios of kA to kB. In addition, it was also used for the description of beta-carotene degradation.