Oxidation kinetics of soybean oil in the presence of monoolein, stearic acid and iron

The oxidation kinetics of soybean oil containing 1% (w/w) monoolein, 1% (w/w) stearic acid and 0.005% (w/w) iron was evaluated at 55 °C under light. The oxidation rates were determined by oxygen consumption and peroxide formation. Addition of monoolein, stearic acid or iron to the soybean oil accelerated the rate of lipid oxidation during the storage. Monoolein increased the rate of oxygen consumption whereas iron increased the rate of peroxide decomposition. The reaction order of soybean oil was found to fit first-order kinetics and was not affected by the addition of monoolein, stearic acid or iron. The rate constants were 2.55 × 10−2, 2.94 × 10−2, 2.91 × 10−2, 3.02 × 10−2 h−1, and the half-lives were 27.18, 23.58, 23.82, 22.95 h for the soybean oil, monoolein, stearic acid and iron samples, respectively.