Temperature Dependency of Rate Constants of Edible Oil's Autoxidation

Temperature dependency of rate constants of edible oil's autoxidation was estimated. One of us showed"' that the rate process of autoxidation of edible oils was expressed by an equation as below, and that the effects of brightness on the rate constants, ko, k,, k2, and k3, in the equation could be measured individually. dP/dt=k0M+k1MP-2k2P2-k3P Here, P is the concentration [mmol/kg-oil] of peroxides in the oil, and M is that of active methylene residues that are not oxidized yet at time t. The rate constants ko, k,, k2, and k3 represent the reaction rates of initiation period, chain reaction period, dimmer formation, and decomposition of Pin the termination period of autoxidation, respectively. In this paper, we show the effects of temperature on the rate constants, i.e., temperature has little effect on ko (the activation energy E0=11 kJ/mol), and it has such ordinary effects on k,, k2, and k3, as on a rate constant of a usual chemical reaction (El, E2, E3=60-90 kJ/mol). The results show that the equation is useful to estimate the effects of conditions (processing and preservation) on each stage of autoxidation, and that a simulation can be done with the equation assuming arbitrary temperature conditions. (Received March 7, 2000)