Kinetic analysis of non‐isothermal oxidation of bioactive milk lipids

Abstract

AbstractThe oxidation of pure docosahexaenoic acid (DHA, C22:6 ω3), eicosapentaenoic acid (EPA, C20:5 ω3), conjugated linoleic acid (CLA, C18:2), and trans‐vaccenic acid (TVA, C18:1 t11) was assessed using differential scanning calorimetry (DSC) at six heating rates (3–18 K min−1) within a range of 300–600 K. The DSC spectra were analyzed using iso‐conversional kinetics to calculate the pre‐exponential factor (Ao), activation energy (Eo), and reaction model (f(α)). The Eo for DHA, EPA, CLA, and TVA varied from 33–40, 36–49, 48–64, and 64–92 kJ/mol, respectively. The Ao were 2.87 ± 0.03, 4.42 ± 0.21, 24.94 ± 1.31, and 580.91 ± 4.61 min−1 for DHA, EPA, CLA, and TVA, respectively. The comparison of the numerically reconstructed model with theoretical values showed that the oxidation of DHA and EPA was best described by an Avrami‐Erofeev model, while a three‐dimensional diffusion model best described the oxidation of CLA and TVA.Practical applicationsThe application of iso‐conversional kinetics to study the oxidation of bioactive milk lipids provides a mathematical tool for describing the oxidation regardless of the complexity of the process. The oxidation of bioactive milk lipids can be modeled using the obtained values of the kinetic triplet. Such modeling can be performed without knowing the mechanisms, which typically involves the use of sophisticated analytical techniques. The obtained results may enable further process development, design, and optimization.