Ultra-Turrax Homogenization–Assisted Extraction of Bioactive Compounds from Olive Pomace Using Response Surface Methodology

Abstract

Olive pomace (OP), by-product of olive oil extraction, consists of residual pulp, skin, and seeds, rich in bioactive compounds. OP represents a valuable yet underutilized resource. This study aims to optimize the extraction of polyphenols (total phenolic compounds, ortho-diphenols, and flavonoids), and the evaluation of antioxidant activity (radical scavenging activity) from OP. The optimization study was carried out using response surface methodology (RSM) with Box-Behnken design (BBD), using for the first time the Ultra-Turrax-assisted homogenization, to enhance the extraction efficiency from OP. The three independent variables selected were solvent concentration (X₁: 40; 60; and 80%), extraction time (X₂: 2; 10; and 20 min), and extraction speed (X₃: 1; 3; and 5 (rpm)). The results revealed that all developed models regarding phenolic contents and antioxidant activity, through experimental design, expressed high levels of significance (p-value > 0.05) with good concordance between predicted and experimental data (R² = 0.9980–0.9884). The optimal conditions for phenolic extraction and antioxidant activity were achieved using 61.20% ethanol, 15.82 min, and a stirring speed of level 3. Under these conditions, the obtained contents for total phenolic compounds, ortho-diphenols, flavonoids, and antioxidant activity were 60.28 g GAE/kg, 39.82 g GAE/kg, 20.95 g CE/kg, and 78.02%, respectively. Moreover, the predicted optimal conditions were experimentally validated. These results indicate the great potential of OP as a source of bioactive compounds, with potential uses in several industrial applications.