Effect of process conditions on the microencapsulation of coffee oil by spray drying

Microencapsulation is a good alternative to transform liquid food flavourings, such as coffee oil, into stable and free-flowing powders. Thus the aim of this study was to evaluate the influence of process conditions on the microencapsulation of coffee oil by spray drying, using gum Arabic as encapsulating agent. The effect of total solid content (10-30%), oil concentration with respect to total solids (10-30%) and inlet air temperature (150-190 degrees C) on the encapsulation efficiency, oil retention, moisture content and powder hygroscopicity were evaluated by a complete 2(3) central composite rotatable design. Both encapsulation efficiency and oil retention were negatively influenced by oil concentration and inlet air temperature, and positively affected by total solid content, which could be related to the emulsion viscosity and droplet size. Particles produced at the optimized process conditions (30% of total solids, 15% of oil with respect to total solids and inlet air temperature of 170 degrees C) were evaluated for oxidative stability and showed to be stable during storage at 25 degrees C, but not at 60 degrees C. At this temperature, pure oil presented higher lipid oxidation than encapsulated, confirming the protective effect of microencapsulation on the oxidative stability of this product. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.