Physical characteristics of spray-dried dairy powders containing different vegetable oils

• Free fat in spray-dried formulations increased as expected with increasing outlet temperature.
• Emulsion viscosity was Newtonian before homogenisation and shear thinning after.
• Oil type affected emulsion viscosity but not powder physical characteristics.
• Oil type did not affect fat globule size of emulsion or in reconstituted formula.

The objective of this study was to investigate the physical characteristics of spray-dried dairy powders formulated with different oil types, spray-dried at different outlet temperatures. A model fat-filled dairy formulation (target 40% w/w total solids, comprising protein, oil and lactose) containing lactose (23.9%), sodium caseinate (5.11%) and sunflower (SO) or palm (PO) oil or a 50:50 mixture of SO/PO (in all cases 11.5% total oil) were heat-treated, homogenised and spray-dried at an outlet temperature of 80 or 90 °C. Increasing outlet temperature reduced water content, water activity and tapped bulk density, irrespective of oil type, and increased solvent-extractable free fat for all oil types. Onset of glass transition (Tg) and crystallisation (Tcr) decreased at the lower outlet temperature. Oil type had no effect on powder moisture, water activity (aw), powder bulk density, particle size, fat globule size of emulsion or fat globule size of reconstituted fat-filled dairy powders.