Emulsion Formation and Stabilizing Properties of Olive Oil Cake Crude Extracts

• Main Authors: Firdaous Fainassi, Noamane Taarji, Fatiha Benkhalti, Abdellatif Hafidi, Marcos A. Neves, Hiroko Isoda, Mitsutoshi Nakajima
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Processes
• Subjects: olive oil extraction by-product; interfacial tension; oil-in-water emulsion; protein; saponin; polyphenol
• Online Access: https://www.mdpi.com/2227-9717/9/4/633

The surface-active and emulsifying properties of crude aqueous ethanolic extracts from untreated olive oil cake (OOC) were investigated. OOC extracts contained important concentrations of surface-active components including proteins, saponins and polyphenols (1.2–2.8%, 7.8–9.5% and 0.7–4.5% (<i>w/w</i>), respectively) and reduced the interfacial tension by up to 46% (14.0 ± 0.2 mN m⁻¹) at the oil–water interface. The emulsifying ability of OOC extracts was not correlated, however, with their interfacial activity or surface-active composition. Eighty percent aqueous ethanol extract produced the most stable oil-in-water (O/W) emulsions by high-pressure homogenization. The emulsions had average volume mean droplet diameters of approximately 0.4 µm and negative ζ-potentials of about -45 mV, and were stable for up to 1 month of storage at 5, 25 and 50 °C. They were sensitive, however, to acidic pH conditions (<5) and NaCl addition (≥25 mM), indicating that the main stabilization mechanism is electrostatic due to the presence of surface-active compounds with ionizable groups, such as saponins.