Exploring the drying behaviour and particle formation of high solids milk protein concentrate

• Drying and dissolution behaviours of MPC were observed at a droplet level.
• Dissolution rate of MPC particle decreased with increase of initial solids content.
• Slower drying rate led to higher surface presence of lactose and protein.
• Surface enrichment of fat occurred during atomisation (droplet generation).
• Bulk and surface compositions influenced droplet drying behaviour.

Milk protein concentrate (MPC) powders are valuable dairy products, but the understanding of their drying behaviour and particle formation during convective dehydration especially at high concentrations is currently limited. This study aims to improve the understanding of the drying behaviour of MPC, particularly the influence of concentration on compositional redistribution, and particle formation from droplets. We utilised the glass-filament single droplet drying technique to monitor the thermal-moisture drying histories of MPC droplets and used the Reaction Engineering Approach (REA) to model their drying kinetics. Across the range of solids content tested, the rate of moisture removal and final moisture content of dried MPC particles achieved were relatively similar. However, increase in solids content of MPC droplets led to reduced shrinkage and increased rate of temperature rise during drying. The in situ rehydration study indicated slower rehydration with the increase of concentration. Surface composition of dried MPC particles was analysed using X-ray photoelectron spectroscopy (XPS) and the findings indicated the importance of bulk and surface compositions in determining droplet drying behaviour and particle formation during drying.