On the preparation of lecithin-stabilized oil-in-water emulsions by multi-stage premix membrane emulsification

We report on the preparation and characterization of lecithin-stabilized oil-in-water emulsions (10 or 20 wt% corn oil, 2 wt% lecithin, pH 3, 100 or 150 kPa) by multi-stage premix membrane emulsification using a Shirasu porous glass membrane (mean pore size 8 μm). Structural characteristics of the emulsions such as droplet size distribution, mean droplet diameter, and morphology were measured by using a laser light scattering and optical microscopy, respectively. As the number of passes through the membrane increased from 1 to 5, the transmembrane flux decreased from 30 to 1 m3 m−2 h−1. It demonstrates that lecithin emulsifier, even if its net charge is negative (pKa ∼ pH 1.5), tends to foul SPG membrane by blocking the membrane pores, which was attributed to the possible interaction between positive groups on the lecithin molecules with anionic silanol groups on the membrane surface.