Oxidative stability of microalgae oil and its acylglycerol mixture obtained by enzymatic glycerolysis and the antioxidant effect of supercritical rosemary extract

Abstract

The oxidative stability of microalgae oil (MO) and its enzymatic glycerolysis product (GP) have been determined by using the accelerated oxidation methods differential scanning calorimetry (DSC) and Rancimat at temperatures in the range 50–90 °C. Kinetic analyses of MO and GP provide Arrhenius activation energy and activation enthalpy and entropy, temperature coefficients, Q10 and oxidative stability index at 20 °C (OSI20), based on secondary and tertiary oxidation products. Susceptibility of microalgae oil to oxidation has been compared to that of fish and vegetable oils, with OSI20 values of 647 h for MO and 381 h for GP. The tcoeff and Q10 values are very similar to those observed for fish and vegetable oils. Protective effect from oxidation of a supercritical rosemary extract (RE) for both MO and GP have been evaluated. In the presence of this antioxidant, up to twofold increase of OSI20 has been obtained for MO. Lower protection for GP was observed. Activity antioxidant Index (AAI), related to the mechanism of action of the antioxidant, should be carefully examined for a reliable determination of OSI20 values.