The formation of oil droplets in plasticized starch matrices is studied by using well-defined conditions similar to extrusion. A method based on double staining and confocal scanning microscopy was developed to investigate the role of coalescence during droplet formation. The results indicate that coalescence takes place at all process conditions studied. The apparent critical capillary number was used to quantify the coalescence intensity and to separate the influence of interdependent process parameters on the coalescence. The intensity of coalescence increased with shear rate and oil content whereas an increase in blend viscosity reduced the extent of coalescence. Besides, the results showed that the critical dispersed phase concentration (Phi(c)), below which no coalescence takes place, depends on applied shear rate and decreases with increasing shear rate. (C) 2012 Elsevier Ltd. All rights reserved.