Stabilization of Refined Olive Oil with Phenolic Monomers Fraction and Purified Hydroxytyrosol from Olive Mill Wastewater

Abstract

The aim of this study was to enhance the refined olive oil (ROO) quality stabilization during storage with phenolic compound fractions obtained from C18 silica gel fractionation of olive mill waste (OMW) ethyl acetate extract. HPLC–DAD–ESI/MS analysis was used to identify the main phenolic compounds present in the obtained fractions. 16 compounds were identified belonged to four classes: simple phenols, secoiridoids, flavonoids, and lignans. In this study, Diosmetin was identified for the first time in OMW and the major compound was hydroxytyrsol. On the other hand OMW extract and its related fractions conserved their antioxidant activity until 110 min heating at 185 °C. In addition, physicochemical characteristics such as peroxide value as well as conjugated dienes (CD) and conjugated trienes (CT) were determined to evaluate the oxidation of OMW polyphenols-enriched ROO during storage. Results demonstrated that OMW monomeric fraction and hydroxytyrosol improved the quality of ROO by decreasing peroxide value and absorptions at specified wave lengths at 232 and 270 nm related to conjugated dienes and trienes formation, respectively. This study suggests that the enrichment of ROO with phenolic compounds from OMW mainly hydroxytyrosol makes the oil more functional with a higher stability. Phenolic compounds from OMW with antioxidant activity improve the stability of ROO during storage and hence would be used as a natural alternative for chemical additives.