Influence of hydrostatic pressure and gas content on continuous ultrasound emulsification

Ultrasound is one means among others of producing emulsions mechanically. Droplet disruption in sonicated liquid–liquid systems is considered to be controlled by cavitation. Both hydrostatic pressure and gas content of the liquids influence the probability and intensity of cavitation. Continuous ultrasound emulsification experiments were carried out to elucidate the effect of these parameters on the result of droplet disruption. Maximum energy density in the apparatus decreases with increasing hydrostatic pressure, probably due to partial suppression of cavitation which is the main mechanism of power dissipation. At constant energy density there is no significant influence of hydrostatic pressure on the emulsification result, however. Corresponding results were obtained for the influence of the gas content. Gas saturation or partial degassing prior to emulsification lead to a shift in maximum energy density. But, again, at constant energy density no clear effect on the droplet size of the emulsion is observed.