Extraction and Quantification of Polyphenols of Olive Oil Mill Wastewater from the Cold Extraction of Olive Oil in the Region of Khenchela-Algeria

Abstract

In the olive industry, the extraction operation requires large quantities of water; therefore, this industry generates large quantities of olive oil mill wastewater (OMW), which is heavily loaded with polyphenols. The objective of this work is to extract and quantify main phenolic compounds from OMW after the evaluation of its physicochemical properties. The extraction of phenolic compounds was done by the liquid-liquid method with ethyl acetate, acetone and methanol to find the most suitable solvent. The amount of total polyphenols was evaluated by the Folin-Ciocalteu method using gallic acid as standard phenolic acid. The amount of flavonoids was determined by the aluminum trichloride method. The results of physicochemical analysis have shown that the OMW is an acidic liquid (pH = 5.05 ± 0.03) and it has a high electrical conductivity (EC= 14.40 ± 0.25 mS/cm), high humidity (H = 86 ± 3.1%). It was too loaded with organic matter (OM = 8.3 ± 0.05%), dry matter (DM = 16.2 ± 0.81%), mineral matter (MM% = 1.25 ± 0.07), total suspended solids (TSS = 0.9 ± 0.05%) and fatty matter (FM = 2.02 ± 0.04%). The results of the extraction show that the content of total phenolic and flavonoids in the methanolic extract of OMW are respectively 950 ± 14.2 µg GAE/ mg of extract and 80.6 ± 17.27 µg QE/mg of extract. The LC-MS results revealed the presence of 10 phenolic compounds. The major identified was quinic acid with a concentration of 23.940 ppm. According to the results obtained, methanol is the suitable solvent for the extraction of polyphenols and flavonoids from OMW that have great importance in the pharmaceutical and food industries.