variables. For emulsification by low-energymethods composition
variables will have a much higher influence than preparation
variables, however for shear emulsification, the influence of
preparation variables will be determinant.
Examples of recent literature about optimization of nanoemulsions
obtained by shear include the study of the influence of
different variables and the correlation of droplet size with them
[51]. In this paper two different industrial scale emulsifier
equipments were studied, and the Sauter diameter was correlated
with viscosities, stabilizers, volume fractions and pressure for a
jet mill, number of disc mixers for a static mixer, and passage
number for the two equipments. For both, an equilibrium size is
reach for high number of passages resulting in constant droplet
size.
For other systems, optimum pressure or passage number can
exist if coalescence is facilitated by high pressures or passage
number. In Ref. [52] a food system is studied with a high pressure
microfluidizer to emulsify and using a surfactant and different
polymers for stabilizing the emulsions. The competing phenomena
of breaking and coalescence are discussed taking into account
the effect of stabilizers.
In Ref. [53], optimization of nano-emulsion preparation by
submitting a coarse emulsion to subcritical water conditions is
presented. The optimization was studied by selective variation
of composition parameters (surfactant and oil concentration),
and preparation parameter (temperature). For this system small
sizes, 40 nm, are obtained.
For other condensation methods, variables whose effect is
commonly studied are the surfactant oil ratio and the ratio between
surfactants when a surfactant mixture is used.