Characterization and incorporation of extracts from olive leaves obtained through maceration and supercritical extraction in Canola oil: Oxidative stability evaluation

Abstract

Olive leaves (OL) are considered a potential source of bioactive compounds mainly due to its high content of phenolic compounds, widely known as natural antioxidants. The main objective of this study was to compare the performance of three OL extracts obtained by different extraction techniques in protecting canola oil against oxidative damage. The technologies evaluated were maceration with ethanol/water 75:25 (v/v), supercritical fluid extraction with CO2 (SC–CO2) and SC-CO2 with 10% ethanol as modifier (SC–CO2/EtOH). Each extract was analyzed as for total phenolic compounds (TPC), antioxidant activity (ABTS assay) and phenolic composition by reversed phase liquid chromatography-quadrupole-time of flight mass spectrometry. The oxidative stability of canola oil with or without the incorporation of 250 mg/kg of each extract was assessed during five weeks of storage at 60 °C. Peroxide, K232, K270, and Rancimat values, besides tocopherols content were determined. Macerated extract showed the highest TPC and antioxidant activity, but both SC-CO2 extracts were more effective in preserving tocopherols. In addition, SC-CO2 extracts delayed the oxidation progress as they lead to higher induction periods than control and macerated extracts, and a slower increase in peroxide values. Results obtained reinforce the use of supercritical fluid technology to obtain antioxidants compounds from natural sources.