Electrospraying of submicron alginate beads in Canola oil

Abstract

In this study, we investigated the electrospraying phenomena of alginate solutions in an oil medium to produce submicron alginate beads. The alginate spray dope solution, dispersed with CaCO3 particles, were electrosprayed into acidified canola oil under continuous flow. The formation of the Ca2+ crosslinked alginate beads suspension in the oil was confirmed by confocal laser microscopy, with bead diameters ranging from 200 to 900 nm. Dynamic light scattering analysis showed that bead sizes were significantly reduced (p < 0.05) from 872 ± 37 to 472 ± 23.2 nm when the applied voltage increased from 5 to 15 kV at 1.5 cm electric field distance. Additionally, alginate bead size decreased from 472 ± 23.2 to 228.2 ± 21.5 nm as the solution conductivity increased from 7 to 21 mS/cm, while increasing Span®80 concentration from 0.1 to 0.5% (w/w) reduced the bead size from 581.2 ± 43.6 to 472 ± 23.2 nm. Conversely, increasing alginate (from 2 to 6% w/w) or acetic concentrations (from 0.1 to 0.5%, w/w) resulted in an increased bead size (from 327.4 ± 22.8 to 524.3 ± 53.9 nm and 380.4 ± 1.4 to 472 ± 23.2 nm, respectively). During the 8 d storage period at 4 °C, the alginate beads suspension in canola oil remained visually uniform; however, sedimentation of beads was observed at 22 °C. Overall, this study demonstrated that submicron alginate beads of various sizes can be obtained by electrospraying aqueous alginate solution in an oil medium, through adjusting solution properties and processing parameters.