High throughput production of double emulsions using packed bed premix emulsification

- W/O/W emulsions were successfully prepared using packed bed premix emulsification.
- Effective droplet break-up was achieved with a droplet to pore size ratio of 0.3.
- Droplet break-up mechanism was found to be similar to that of O/W emulsions.
- High throughputs and high initial encapsulation efficiencies were obtained.
- Only food grade ingredients were used.

We explored the potential of packed bed premix emulsification for homogenizing coarse food grade W/O/W emulsions, prepared with sunflower oil. Using packed beds with different glass bead sizes (30-90 μm) at different applied pressures (200-600 kPa), emulsions with reasonably uniform droplet size (span ~ 0.75) were produced successfully at high fluxes (100-800 m3 m− 2 h− 1). Sodium chloride was used as a release marker: after five homogenization cycles, the produced emulsions were found to retain almost all of their initial content (99%). As was previously found for single emulsions, the packed bed system proved to be effective in breaking up the W/O/W emulsion droplets, with droplet to pore size ratios as low as 0.3. Results were analysed through the pore Reynolds number, Rep, which characterizes the flow inside the packed bed, and were related back to the droplet break-up mechanisms occurring. At high Rep, droplet break-up was expected to be governed by shear forces while at low Rep, there is a shift from shear based to spontaneous droplet break-up.