Droplet impact and spreading: Droplet formulation effects

This work investigates a food application, where 2.8 mm droplets containing maltodextrin DE5 at 20 and 40 wt% in water, impact a smooth anhydrous milkfat surface at 1.7 to 4.1 ra s(-1) velocities. Results show that greater maximum spread diameters are achieved with the higher impact velocities and lower viscosity droplets. Incorporating surfactants to lower the liquid-vapour interfacial tension (from 72 to 32 mN m(-1)) did not affect the maximum spread diameter but significantly limited droplet recoil, giving final spreading extents that cover close to three times the surface area compared to droplets without the surfactant. From these results, simple formulation and operating guidelines are proposed to achieve a maximum final droplet spread diameter for air-suspension particle coating operations. (C) 2007 Elsevier Ltd. All rights reserved.