Development of microfluidization methods for efficient production of concentrated nanoemulsions: Comparison of single- and dual-channel microfluidizers.

Nanoemulsions are being increasingly utilized within the pharmaceutical, food, personal care, and chemical industries because of their unique physicochemical properties and functional performances: high optical clarity; prolonged stability; enhanced bioavailability; and novel rheology. For commercial applications, it is important to be able to produce nanoemulsions containing small droplets using efficient homogenization processes. In this study, we compared two microfluidization methods for fabricating nanoemulsions: (i) single-channel microfluidization and (ii) dual-channel microfluidization. The influence of emulsifier concentration, homogenization pressure, disperse phase volume fraction, and initial emulsifier location (oil versus water phase) on particle size was examined. For both devices, the mean particle diameter decreased with increasing emulsifier concentration and homogenization pressure, and there was a linear log-log relationship between mean particle diameter and homogenization pressure. At a similar emulsifier level and homogenization pressure, dual-channel microfluidization produced smaller droplets and narrower distributions than single-channel microfluidization. This effect was attributed to a higher droplet disruption efficiency and/or lower droplet recoalescence rate for the dual-channel system. The dual-channel method could successfully produce nanoemulsions even at high oil concentrations (50%), whereas the single-channel method was only effective at producing nanoemulsions at relatively low oil concentrations (10%). This study demonstrates that dual-channel microfluidization is an efficient means of producing fine nanoemulsions with high oil loading levels, which may be advantageous for many commercial applications.