The compositional effects of high solids model emulsions on drying behaviour and particle formation processes

• Drying of emulsions following compositions observed across human lactation periods.
• Extent of droplet shrinkage decreased with increase of initial solids content.
• Surface fat enrichment occurred during droplet generation and drying processes.
• High fat emulsion exhibited earlier skin development but delayed crust formation.
• Process conditions and droplet characteristics influenced droplet drying behaviour.

This paper investigates the drying behaviour and particle formation of emulsions modelled after a range of compositions observed in human milk at different lactation periods. The knowledge on drying kinetics would be relevant to understand important drying conditions in processing dairy products with similar compositional makeup while shrinkage kinetics and surface characterization provide a greater comprehension of the influence surface-active milk components have on product functionality. Droplet drying histories of model emulsions are presented through the glass-filament single droplet drying (SDD) method combined with the Reaction Engineering Approach (REA) modelling. For droplets with both initial solids of 20 wt.% and 40 wt.%, model emulsion (ME) with the highest lactose content exhibited the most shrinkage (normalized particle size being 0.68 and 0.81 respectively), followed by those with highest protein content (0.70 and 0.81), whereas those with the highest fat content showed the least shrinkage (0.73 and 0.84). In situ rehydration study found that ME with the highest fat content exhibited the earliest skin formation but delayed crust formation. The X-ray photoelectron spectroscopy (XPS) analysis which observed an overrepresentation of surface fat across all three MEs regardless of the drying technique indicated the occurrence of surface fat enrichment during ME droplet generation and drying processes.