A DSC study of the thermoxidation of chia seed oil Effect of different antioxidants

Abstract

Chia seed oil presents a high amount of PUFAs ( 80%) being very susceptible to the lipid oxidation. Thermoxidation of chia seed oil was investigated under non-isothermal conditions (10-350°C) in an oxygen atmosphere. Also, the effect of the addition of different antioxidants (2500 ppm rosemary extract, 2500 ppm green tea extract, 1500 ppm tocopherols and 2500 ppm ascorbyl palmitate) to the chia seed oil was evaluated. Temperatures of the extrapolated onset and the first and second peak of the exothermic process recorded at different heating rates ranged between 139.5-168.2ºC (onset), 173.4-212.6ºC (peak 1) and 199.8-265.1º (peak 2). These temperatures were used to calculate the activation energies and the Arrhenius kinetic parameters of thermal-oxidative decomposition of the oil, using the Ozawa-Flynn-Wall (OFW) method. The DSC thermograms showed two peaks which are associated with the primary and secondary products of lipid oxidation, respectively. Activation energy (Ea) of the thermoxidation of chia seed oil (onset) was 67.9 kJ/mol and increased up to 89.9 kJ/mol in case of the addition of rosemary extract, 74.1 kJ/mol for green tea extract, 71.1 kJ/mol for ascorbyl palmitate and decreased to 62.9 kJ/mol for tocopherols.