Preparation of monodisperse water-in-oil-in-water emulsions using microfluidization and straight-through microchannel emulsification

摘要

Water-in-soybean oil-in-water (W/O/W) emulsions with an internal water phase content of 10–30% (vol/vol) were prepared by a two-step emulsification method using microfluidization and straight-through microchannel (MC) emulsification. A straight-through MC is a silicon array of micrometer-sized through-holes running through the plate. Microfluidization produced water-in-oil (W/O) emulsions with submicron water droplets of 0.15–0.26 μm in average diameter (d av,w/o) and 42–53% in CV (CVw/o) using tetraglycerin monolaurate condensed ricinoleic acid esters (TGCR) and polyglycerin polycondensed ricinoleic acid esters (PGPR) as surfactants dissolved in the oil phase. The d av,w/o and viscosity of the W/O emulsions increased with an increase in internal water phase content. Straight-through MC emulsification was performed using the W/O emulsions as the to-be-dispersed phase and polyoxyethylene (20) sorbitan monooleate (Tween® 80) as a surfactant dissolved in the external water phase. Monodisperse W/O/W emulsions with d av,w/o/w of 39.0–41.0 μm and CVw/o/w below 5% were successfully formed from a straight-through MC with an oblong section (42.8×13.3 μm), using the TGCR-containing systems. The d av,w/o/w of the monodisperse W/O/W emulsions decreased as the internal water phase content increased because of the increase in viscosity of the to-be-dispersed phase. Little leakage of the internal water droplets and no droplet coalescence or droplet break-down were observed during straight-through MC emulsification.