Extraction of Antioxidant Phenolic Extracts from the Two Main Liquid Effluents of the Olive Industry

The olive industry is experiencing significant growth, which is only held back by the environmental and management issues that its by-products can cause. The two most polluting effluents produced are a new aqueous phase, or ‘alpechín ’, obtained from alperujo, which is the most important waste generated in the olive oil industry, and brine in the table olive industry. The high organic and phytotoxic loads of both, together with the conductivity of the brines, make their reuse difficult and pose a real technological challenge owing to the environmental problems they cause. This study demonstrates that the application of thermo-malaxation (45–65 °C, 60–90 min) followed by three-phase centrifugation (>3500× g) allows the removal of the most active phenolics, including hydroxytyrosol, 3,4-dihydroxyphenylglycol, and tyrosol from the alperujo in a 30% solution, yielding a partially detoxified solid phase and a liquid phase rich in the most active phenolics. Furthermore, the application of an industrial chromatographic process (0.6 mm diameter rigid strong-cationic resins) enables the removal of between 50% and 75% of the phenolic load from the liquid fraction of the aforementioned system and from the brines of the table olive industry. The high antioxidant activity of the extracted phenolics was verified using in vitro assays.