Interfacial characteristics and microchannel emulsification of oleuropein-containing triglyceride oil-water systems

- Interfacial activities of olive leaf extract and oleuropein were investigated.
- Packing density of oleuropein at triglyceride oil-water interface was characterized.
- Oleuropein-stabilized O/W emulsions were produced by microchannel emulsification.
- Monodisperse oleuropein-stabilized O/W emulsions were obtained.
- Successful emulsification was performed for 15 h using suitable triglyceride oils.

This study investigated the adsorption characteristics of olive leaf water extract and its major phenolic compound, oleuropein, at the triglyceride oil-water interface. We also investigated the preparation characteristics of food-grade triglyceride oil-in-water (O/W) emulsions stabilized by oleuropein using microchannel (MC) emulsification. Refined soybean oil, extra virgin olive oil, refined olive oil, and medium-chain triacylglyceride (MCT) oil were used as triglyceride oils. Both olive leaf extract (OLE) and highly purified oleuropein had a pronounced ability to decrease the interfacial tension at the refined soybean oil-water interface. The packing of oleuropein molecules at the triglyceride oil-water interface was estimated on the basis of their surface excess concentration and area occupied per molecule, determined from the Gibbs adsorption equation. MC emulsification was performed using a silicon grooved MC array plate (model CMS6-2). The continuous aqueous phase contained 0.6 wt.% of oleuropein. Monodisperse, oleuropein-stabilized O/W emulsions with an average droplet diameter of 25 μm and coefficient of variation (CV) of < 5% were produced in all systems, except the MCT oil-containing system, even in the absence of a cross-flowing continuous phase. This successful MC emulsification was observed without droplet coalescence for 15 h of continuous operation. Our findings demonstrate that the use of oleuropein, which has an interfacial activity, is capable of producing monodisperse O/W emulsions using MC emulsification and stabilizing the generated oil droplets when appropriate types of triglyceride oils are used.