Electrostatic-enhanced atomization for spray drying of milk

An embedded-electrode, two-fluid, electrostatic-induction spray-charging nozzle was used to atomize and charge spray droplets in a pilot-scale spray-drying unit. A dielectric barrier made out of Teflon® (PTFE) was installed within the spray-dryer to impede deposition of charged droplets onto the walls of the spray-dryer. Concentrated whole milk (500 g/kg solids) was atomized with induction electrode potentials of 0, 300, 600, 750, and 900 V and atomizing air pressures of 140, 280 and 410 kPa. Charging increased the volume median particle diameter of the dried milk. No significant differences in moisture contents or vacuole volumes of the dried powder were found. Atomizing air pressures had a significant (α = 0.05) effect on apparent particle density, true particle density, volume median diameter and solubility index. There was a significant effect of charging voltage on the solubility index. Particle size analysis and scanning electron microscopy revealed that 140 kPa was insufficient for complete atomization.