Solvent-resistant ultrafiltration to recover bioactive compounds from wet olive pomace extracts

Abstract

To contribute to the circular economy in olive mills, wet olive pomace can be employed as a source of valuable phenolic compounds. These compounds are efficiently extracted with ethanol/water 50:50 (v/v), at 40 °C. Here, the ultrafiltration membranes UF010104, UF010801v3 (from SolSep BV), and UP005 (Microdyn Nadir) have been tested to purify the phenolic compounds present in the hydroalcoholic extracts of the pomace. Several membrane conditioning protocols were explored, being the most adequate a short pre-treatment consisting of soaking the membrane in the working solvent for 2 h. All the considered membranes permitted the recovery of the biophenols of interest in the permeate stream, being most of the organic matter retained. A powerful analytical methodology based on liquid chromatography coupled to mass spectrometry (LC-ESI-QToF-MS) allowed the evaluation of the individual rejection of 43 compounds. The UF010104 membrane displayed the highest permeate flux (15 L h−1·m−2, at 2.5 bar) and high rejection of the total solids (67 ± 3%, at 2.5 bar), thus achieving the purification of the phenolic compounds in the permeate stream. The cleaning of the membranes used in organic solvent media was also investigated.