Production of water-in-oil nanoemulsions using high pressure homogenisation: A study on droplet break-up

In this paper we compare the efficiency of a Microfluidizer to a high pressure valve homogeniser (HPH) for the production of oil continuous emulsions by investigating the effect of pressure, number of passes, phase viscosities and salt addition on droplet size. The results obtained show that the Microfluidizer and HPH have similar emulsification efficiency, giving droplets of ∼60 nm diameter at a pressure of 50 MPa. By increasing the pressure to 100 MPa the droplet diameter was reduced by 10 nm in both devices. Increasing the number of passes in the HPH caused an increase in droplet size probably as a consequence of the temperature increase from multiple passes causing an increase in coalescence. Changing the viscosity ratio from 0.001 to 1 resulted in a minimal change in droplet size indicating that the flow is elongational when break-up occurs rather than turbulent as expected.