We compare different emulsification devices for the production of W/O/W double emulsions. Rotor-stator devices (colloid mill and tooth rim dispersing machine), high pressure homogenization (standard and modified process) as well as a rotating membrane system were used. For better comparability, we produce double emulsions of different oil drop sizes with each device by changing process parameters. A standard double emulsion recipe was chosen for all emulsions.

Encapsulation efficiency of water in the double emulsions, measured by DSC technique, is found to be directly dependent on oil drop size of the double emulsions for each emulsification device. The bigger the oil drops, the higher is the encapsulation efficiency. Double emulsions with comparable oil drop sizes produced with different devices show more or less the same encapsulation efficiency.

This finding indicates that coalescence is mainly influenced by geometrical parameters like oil drop size. The differing drop breakup mechanisms in the different emulsification devices do not show any influence on encapsulation efficiency. It can thus be concluded that loss of inner water droplets by coalescence mainly takes place after the production process. The choice of the emulsification device does not directly influence encapsulation efficiency. Conventional high shear devices are as suitable for the production of double emulsions as membrane processes.