Fig. 1 shows that by increasing the concentration of PGPR the droplet size of the emulsion decreases. This demonstrates the dynamic equilibrium in emulsification between droplet break-up and coalescence (Niknafs et al., 2011); at low concentrations of PGPR there is not enough emulsifier to rapidly coat and stabilise newly formed droplets and therefore coalescence occurs. After one pass the difference in droplet size as a function of emulsifier concentration is more pronounced than after five passes. This indicates that at lower emulsifier concentrations the emulsifier requires several passes to completely adsorb to the interface of droplets. The minimum droplet size is seen at 9 wt.% PGPR after 5 passes. It is likely that at 1% PGPR there is enough emulsifier to cover and stabilise the droplets, however, as the concentration of PGPR is increased further, the slight decrease in droplet size is due to reduced interfacial tension during droplet deformation (Feigl et al., 2007).