Kinetics of simultaneous change in the values of peroxide and weight gain during peroxidation of various groups of vegetable oils

Abstract

The values of peroxide (PV) and weight gain (W) were simultaneously monitored in a kinetic regime of oxidation at 90 °C for the oleic (olive), oleic-linoleic (sesame, corn, peanut, rice bran, and sunflower), and linolenic (canola and soybean) groups of vegetable oils. Given the values of calculated oxidizability (Cox) and polyene index (PI), the lowest oxidizable fatty acid composition belonged to the olive oil (2.43 and 0.87), followed by to the peanut (2.82 and 1.41), rice bran (3.92 and 1.43), canola (4.47 and 3.60)/sesame (5.04 and 2.86), corn (5.94 and 3.74), and sunflower (6.77 and 5.72)/soybean (7.23 and 3.66) oils. The oils were of various initial quality indicators and total contents of tocopherols (141–753 mg kg⁻¹) and phenolic compounds (57–261 mg kg⁻¹). The ratio between the induction period (IP) and the rate of change in PV (O_i = 14–818 L mmol⁻¹ h²) and W (O_iw = 4–103 % h²) during IP was of very good correlation (R² > 0.98), indicating interchangeable application of the kinetic parameters O_i and O_iw to evaluate initiation oxidizabilities. No correlation was obtained between the kinetic parameters representing the steeply rising part of the PV (r_n = 0.0303–0.1403 h⁻¹) and W (r_nw = 0.0610–0.2335 h⁻¹) curves. This was attributed to the fact that the former stands for the formation and decomposition of lipid hydroperoxides overall, but the latter represents the decomposition of lipid hydroperoxides and polymerization reactions at the same time.