Shelf-life prediction of flaxseed oil blended with different antioxidants: Kinetic and thermodynamic study using Rancimat methodology

Abstract

Omega-3 fatty acids are essential to health and have been associated with benefits like reduced inflammation, improved heart health, and protection of the brain against aging. Flaxseed oil is rich in healthy fatty acids. However, it can be oxidized in short periods due to its high content of polyunsaturated fatty acids. Blending this oil with suitable antioxidants is therefore highly recommended to extend its shelf life. Trolox, gallic acid, and caffeic acid were used as fortifying antioxidants in this study. The selected antioxidants were added to flaxseed oil in different concentrations (30, 60, and 90 ppm) and the blended samples were then evaluated for their thermo-oxidative stability (induction period, IP), oxidation kinetics (rate constant, k), oxidative stability enhancement, using Rancimat as accelerated shelf life test (ASLT) at 363, 373, and 383 °K. Prediction of shelf-life of all samples at room temperature (298 °K, IP25) were then measured. The Arrhenius equation and activated complex theory were used to estimate activation energies (Ea), activation enthalpies (ΔH), and entropies (ΔS), which varied from 89.34 to 104.31 kJ/mol, from 78.30 to 97.88 kJ/mol, and from −31.01 to −54.62 kJ/mol, respectively. Results showed that the kinetic parameters of lipid oxidation varied greatly among the type and concentrations of antioxidants used. Trolox-fortified oil had the highest IP at all tested temperatures and the longest predicted shelf life at ambient temperature (298 °K). Finally, results assessed the suitability of the Rancimat apparatus as a quick methodology for predicting the shelf life of edible oils.