Single droplet drying of milk in air and superheated steam: particle formation and wettability

Superheated steam drying has been receiving research attention in recent years due to its increasing industry prevalence in the food and agricultural sector. There is however a gap of knowledge in superheated steam spray drying involving the drying of droplets with dissolved solids as most application to date are solely on solid materials. With this constraint, it is vital to understand and study the effect of superheated steam on the particle formation process as well as on the final particle. The aim of this work is to explore the potential of superheated steam in the spray drying of milk. Specifically, this report examines how superheated steam influences the migration of fats, protein, and lactose in milk during the particle formation process. Studies were conducted by drying fresh milk, using a single droplet drying technique in a superheated steam environment and a hot air environment at a fixed temperature of 110°C. The wettability of the dried single particle was examined using contact angle measurements. The surface of superheated steam-dried milk particles revealed a relatively higher wettability when compared to air-dried milk particles. This suggests that superheated steam promoted the presence of hydrophilic components such as lactose on the exterior surface of the particle. These results have therefore shown the possibility of using superheated steam to control component relocation in multicomponent solutions based on the component hydrophilicity. By recognizing the potential of application of superheated steam in spray drying, engineered multicomponent particles with specific features can be produced.