Kinetics of change in the concentration of lipid hydroperoxides (LOOH) and carbonyls (LCO) were simultaneously investigated during peroxidation of canola and olive oils at 90C. Depending essentially on the fatty acid compositions, the canola and olive oils exhibited one-step and two-step, respectively, multiphase peroxidations before attaining the typical termination phase. Higher and lower rates of the LOOH formation and decomposition, respectively, in the second than in the first step of the canola oil peroxidation were attributed to the dominant peroxidation of linolenic acid in the first step, and the added peroxidation of oleic and linoleic acids in the second step. The kinetics of change in [LCO], which was affected by the potency of constituting antioxidative compounds, indicated that the canola il would be safe to use till the end of the first peroxidation step whereas the olive oil should be discarded at its induction period.

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