Abstract
The amphilic antioxidant, such as acyl ascorbate, would be expected to be a useful food additive. In this study, the antioxidative action of acyl ascorbate was examined, because knowledge of its behavior in aqueous solution is required for its effective use for food. First, the degradation kinetics of (+)-catechin in aqueous solution at various pHs and temperatures were empirically expressed by the Weibull equation. The rate constant, k, was the lower at the lower pH and temperature. The temperature-dependency of the k value was analyzed on the basis of the Arrhenius equation, and it was indicated that the enthalpy-entropy compensation held during the degradation. Second, octanoyl l-ascorbate was synthesized by the condensation of l-ascorbic and octanoic acids in acetone using immobilized lipase from Candida antarctica, and the degradation kinetics of catechin in aqueous solution in the presence of octanoyl ascorbate was examined. The dependency of the k value in the catechin solution with octanoyl ascorbate on the concentration of the ascorbate was obviously different from that with ascorbic acid. That is, the degradation was suppressed at low octanoyl ascorbate concentrations, while proceeded fast at a high concentration, suggesting the formation of the micelle for octanoyl ascorbate at high concentrations.
