Preparation of stable food-grade double emulsions with a hybrid premix membrane emulsification system

• Beetroot juice encapsulated in W/O/W emulsions using premix emulsification system.
• Stability of the W/O/W emulsions is related to their high viscosity.
• Processing at low viscosity followed by controlled swelling resulted in stable W/O/W emulsions.

In this study we demonstrate that food-grade double emulsions can be successfully prepared using a hybrid premix emulsification system. A coarse emulsion containing beetroot juice as inner water phase, sunflower oil as oil phase and 0.5% or 1.0% whey protein isolate solution as outer water phase was prepared using a rotor stator system. This emulsion was further refined, using a bed of glass beads (diameter 71 μm), through which the emulsion was pushed at different applied pressure (200–500 kPa) and number of passes (1–5). All applied pressures lead to much smaller droplets while the juice remained encapsulated (>98%). The viscosity of the emulsions increased due to swelling of the internal water phase, and this implies that it is possible to encapsulate the components efficiently at relatively low internal water phase fraction at which the emulsions can be handled easily, while allowing them to obtain their final viscosity later.