Cut-off conjugated diene values for rejection of vegetable oils

To determine the cut-off conjugated diene values for rejection of oleic, oleic-linoleic, and linolenic groups of vegetable oils, kinetics of change in the conjugated diene (CDV) and carbonyl (CV) values of olive, sunflower, and canola oils were investigated over oxidations at 60 °C and 90 °C. With respect to the cut-off CVs for sensory (24 μmol g−1) and toxicological (41 μmol g−1) rejections of edible fats and oils, the CDVs at the induction periods (IP) of the oils studied at 60 °C were adopted as the cut-off values for rejection purposes. The cut-off CDVs for discarding the oils were calculated to be 9.0, 13.5, and 13.0 μmol g−1 for the olive, sunflower, and canola oils, respectively. Moreover, the ratio between IP and CV at IP (OPIC, h g μmol−1) provided a more comprehensive measure than each one alone to show the higher oxidative stability of the olive oil (36.2 and 2.95 at 60 °C and 90 °C, respectively) than the canola (16.6 and 2.21 at 60 °C and 90 °C, respectively) and sunflower (8.72 and 1.67 at 60 °C and 90 °C, respectively) oils. •Simultaneous kinetics of change in conjugated diene and carbonyl values.•Cut-off conjugated diene values to discard different groups of vegetable oils.•A new measure to evaluate oxidizability on primary and secondary oxidations.