Production of polyphenol extracts with antioxidant activity from olive pomace: process modeling and optimization

Abstract Olive pomace, the solid by-product derived from the olive oil extraction process, is a rich but still underutilized source of bioactive polyphenols. Among the proposed recovery technologies, solvent extraction seems to be the simplest and economically viable method to achieve this purpose. In this study we investigate the recovery of polyphenols from olive pomace by a one-step extraction procedure using aqueous ethanol as solvent, with the aim to model and optimize the proposed process. A central composite rotatable design (CCRD) comprising 2 4 factorial points, eight axial points and six replicates was used to evaluate the effects of temperature (T), extraction time ( E ), liquid-to-solid ratio ( R ) and ethanol concentration in the solvent ( C ) on the extraction yield. The experimental results were correlated by a reduced second-order polynomial model. The statistical analysis of the results showed that all the main factors ( T , E , R , C ) and two binary interactions ( T – E , R – C ) had significant effects on the extraction yield. Under the best conditions ( T = 70 °C, E = 240 min, R = 48 mL/g, C = 50 %) more than 95 % of the extractable polyphenols were recovered. A mechanically stirred batch extractor operating under these conditions was used to produce dry extracts with a polyphenol content of 69.46 mg GAE (gallic acid equivalents) per gram and an antioxidant activity of 32.72 mg TE (Trolox equivalents) per gram. Overall, the results obtained indicate that polyphenol-rich extracts suitable for a variety of food and non-food applications can be easily obtained from olive pomace by subjecting it to the optimized extraction treatment.