Oxidation experiments with β-carotene were performed in oleic acid solvent with addition of an antioxidant, α-tocopherol. A kinetic model was proposed based on a reaction mechanism consisting of the oxidation of β-carotene, oleic acid, and α-tocopherol; the antioxidation reactions of β-carotene and oleic acid by α-tocopherol; the cross-reaction of β-carotene and oleic acid; and the radical-exchange reaction of β-carotene and α-tocopherol. The model quantitatively described the oxidation behavior of β-carotene over a wide range of temperatures, oxygen compositions, and initial antioxidant concentrations. The model simulated well the time over which β-carotene was almost totally consumed under practical storage conditions at room temperature in air.Paper no. J10672 in JAOCS 81, 389-394 (April 2004).KEY WORDS: Antioxidant, β-carotene, kinetic model, oleic acid, oxidation, α-tocopherol.β-Carotene, having biological activity as an active oxygen quencher, is commonly dissolved in a lipid when used as a food additive because of its high solubility therein. β-Carotene is easily oxidized in air, resulting in a loss of activity. A lipid is also easily oxidized; hence, β-carotene oxidation in a lipid solvent proceeds via a co-oxidation mechanism accompanying the lipid oxidation. To prevent oxidation during processing and long-term storage in a food system, an antioxidant such as α-tocopherol is usually added to the system. In a practical food system, β-carotene, lipid, and antioxidant co-exist, so that not only the co-oxidation of β-carotene in lipid solvent but also protection of β-carotene and lipid by the antioxidant occur. To determine the amounts of antioxidant required to protect β-carotene in a practical system, one must understand the mechanism of oxidizing β-carotene in the lipid solvent to which antioxidant is added so as to construct a kinetic model based on the oxidation mechanism. Only a few studies have been made on oxidation kinetics in the presence of β-carotene, lipid, and antioxidant (1,2). In those studies, the antioxidative effect of α-tocopherol and β-carotene on lipid oxidation was discussed, and lipid oxidation was reported to be suppressed by adding α-tocopherol together with β-carotene. However, the mechanism for oxidation of β-carotene in a lipid solvent in the presence of antioxidant is still not elucidated, and a kinetic model has never been constructed.In our previous study (3), we proposed a kinetic model for the co-oxidation of β-carotene in oleic acid as a lipid solvent based on a reaction mechanism that consisted of β-carotene oxidation, oleic acid oxidation, and the cross-reaction of β-carotene and oleic acid. A model for β-carotene oxidation in the presence of the antioxidant α-tocopherol also was constructed, in which not only the antioxidation of β-carotene by α-tocopherol but also the co-oxidation and radical-exchange reaction of β-carotene and α-tocopherol were incorporated (4).In this study, a kinetic model describing β-carotene oxidation in oleic acid solvent with addition of α-tocop...

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