Analysis of the autoxidation rate of edible oils

The rate process of autoxidation of edible oils is expressed by an equation shown below, dP/dt= k(0)Mt=k(1)MP-2 k(2)P(2)-k(3)P where P is the concentration [mmol/kg-oil] of peroxides (peroxiradical + hydroperoxide), M is that of active methylene residues, which are not oxidized yet at time t, k(2)P(2) is the formation rate of the dimer of P, and k(3)P is the degradation rate of P [(mmol/kg)/day] from which secondary products come. M is given by subtracting oxidized active methylene from the total amount of it, M(max), in unoxidized oil, i. e., M=M(max)-(P+2 k(2) integral P(2)dt+k(3) integral Pdt) As M(max) is the characteristic value for each kind of oil, the right hand side of the rate equation becomes the function of P only. Consequently, the rate constants k(1), k(1), k(2), and k(3) can be measured by the peroxide value, because P equals the peroxide valueX1/2. The 1 st., 2 nd., 3 rd., and 4 th terms of the rate equation correspond to the periods of initiation, chain reaction, termination and degradation of P, respectively. By measuring the rate constants k(0), k(1), k(2), and k(3), in preservation tests of oils under various conditions (ex, temperature, light), we can estimate the effects of the conditions on autoxidation rate. For example, this paper describes how the brightness showed effects on k(0), k(1), and k(3), but that it had no effects on k(2), the formation rate constant of the dimer of P.