Kinetics of Soy Lecithin Oxidation at High Concentrations: The Effect of Antioxidants

The azobisisobutyronitrile (AIBN)-initiated oxidation of soy lecithin (RH) is studied in a wide range of RH (0.027−0.4 mol/L) and AIBN (0.01–0.043 mol/L) concentrations. It is found that at high concentrations of lecithin the oxidizability parameter a = kp/(2kt)0.5, where kp and kt are the constants of the rate of chain propagation and termination, is significantly reduced, while regardless of the concentration of lecithin, a linear dependence of the initiation rate on (Wi)0.5 is maintained. The antiradical activity of antioxidants (AOs) of different classes at [RH] = 0.4 mol/L is assessed, showing that the antiradical activity of phenols in lecithin is significantly lower than in hydrocarbons. The antiradical activity and inhibitory effects in the oxidation of lecithin decrease in the following order: α-tocopherol > 3,6-di-tert.butyl-1,2-benzoquinone > quercetin > 2,4,6-tri-tert.butylphenol.