Valorization of Lyophilized Olive Mill Wastewater: Chemical and Biochemical Approaches

Abstract

Lipid composition and antioxidant activity have been carried out in order to valorize the composition of olive mill wastewater extracts with different solvents (supercritical carbon dioxide, n-hexane, dichloromethane and ethanol). The antioxidant activity was evaluated using ABTS (2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)) and DPPH (2,2-diphenyl-1-picrylhydrazyl) tests. The total phenolics and flavonoid contents were, also, determined. The chemical composition of the extracted oil was established, respectively, by gas chromatography–flame ionization detector and high-performance liquid chromatography methods. The results showed that the oleic acid and equivalent carbon number of forty-eight were the major compounds of the analyzed oils. Residual olive mill wastewater from the Sousse region displayed the highest DPPH radical-scavenging activity (31.10 ± 0.10 μg/mL). The chemical analysis of extracts of OMWs showed that the n-hexane fraction contained an abundance of oleic acid (61.62%) and an equivalent carbon number of forty-eight (53.14%). The best antioxidant activity was determined for the ethanol fraction (14.5 μg/mL). The final results showed a significant difference and variations in polar and apolar components. Moreover, n-hexane extracts showed high percentages of Monounsaturated fatty acids (MUFA) with 64% of OMWs oil composition and the dichloromethane extracts contained the largest amount of flavonoids (160.30 ± 1.70 mg EQ/g DM).