Exploiting Virgin Olive Oil By-products Using Hydrodistillation

Virgin olive oil processing results in a large amount of biomass (leaves, pomace, stones and wastewater) during harvesting, pruning and production. In recent years, these by-products have been studied as possible sources of bioactive compounds, and several techniques have been developed, including microwave, ultrasound, subcritical extraction, high hydrostatic pressure, a pulsed electric field, and high-voltage electrical discharge. However, these techniques can be expensive, and may require specialized staff to implement them. Therefore, this study proposes a novel method. Hydrodistillation is a simple and fast technique that can recover valuable compounds from olive oil biomasses. As it uses water as a solvent, it is sustainable, does not harm the environment, and is compatible with industrial practice. This paper presents the results of a hydrodistillation experiment on olive leaves, olive pomace and olive stones. Two fractions were obtained: a “phytocomplex” fraction from inside the boiler, and a “hydrolate” fraction from inside the condenser column. HPLC–DAD–MS and GC–MS analyses characterized and differentiated these two fractions. In general, more bioactive compounds, notably phenolic, were recovered from the phytocomplex fraction than the hydrolate fraction. Total phenolic compounds (mg tyr/ kg oil ) in the phytocomplex fraction were 11903.51, 4007.33, and 2469.42 mg tyr/ kg oil for olive leaves, olive pomace and olive stone, while in the hydrolate fraction they were 67.67, 1.98, and 29.05 mg tyr/ kg oil , respectively. Furthermore, interesting phenolic compounds typical of Olea europaea L. were found for both matrices. The main families were phenolic alcohols, secoiridoids and flavonoids. In particular, oleuropein, hydroxytyrosol, and tyrosol were recovered from the phytocomplex fraction of leaves and pomace. Finally, the analysis revealed higher amounts of volatile compounds in the hydrolate fraction than the phytocomplex fraction for leaves, stone and pomace. The main class of compounds were esters, ketones, aldehydes, alcohols, terpenes, phenols and their derivatives. Graphical Abstract