Analysis on particle morphology development during pilot-scale spray drying of maltodextrins

The effects of dextrose equivalent (DE) and drying air temperature (Tin) on the morphology and bulk density of spray-dried maltodextrin powders were investigated on a large pilot-scale spray dryer. Maltodextrin DE6, DE21, and DE38 solutions of 25 w/w% were dried at least six times at 160 °C and 180 °C. Particle morphologies were analyzed using scanning electron microscopy and advanced morphology analysis. DE6 powders mainly consisted of spherical particles, supplemented by particles with smooth undulations, whereas DE21 and DE38 powders predominantly contained wrinkled and dented particles. DE21 particles displayed wrinkles with sharper edges, whereas DE38 particles were more creased. Besides particle morphology, bulk density was evaluated. Increasing the Tin resulted in smaller, less wrinkled particles with higher circularity. The lowest loose bulk density, 351 kg·m−3, was obtained at low DE and high Tin. Increasing DE and decreasing Tin increased the loose bulk density to 449 kg·m−3. A similar trend was observed for tapped and apparent particle densities. Results could be linked to the viscoelastic behavior of the maltodextrins, drying rates imposed by drying conditions, and morphologies of maltodextrins previously observed during earlier single droplet drying (SSD) studies.