Changes in oil-in-water emulsion size distribution during the atomization step in spray-drying encapsulation

© 2015 Elsevier Ltd. All rights reserved. During atomization of emulsions, dispersed oil droplets are susceptible to breakup changing the emulsion size distribution, a critical parameter in encapsulation applications. We investigated the influence of the different atomization parameters on the size and size distribution of the sprayed emulsion and defined rules for the choice of conditions which will make it possible to maintain a specific emulsion size. Oil-in-water emulsions were prepared with different aqueous phase viscosity, oil fraction, and emulsion droplet size and sprayed with two different atomization systems: a two-fluid nozzle with external mixing and a rotary atomizer. For both systems, two different breakup regimes were identified: (1) monomodal and (2) bimodal distribution breakup; and a critical Capillary number was determined for each breakup regime. These findings can be used to predict oil droplet breakup and define the right atomization conditions and/or emulsion formulation for controlling sprayed emulsion structure in microencapsulation applications.