Physicochemical properties of spray dried nanoemulsions with varying final water and sugar contents

• Free fat in powders was decreased by reducing the FGS of emulsions pre spray drying.
• Reducing emulsion FGS resulted in lower Tcr in ensuing powders.
• Partial replacement of lactose with sucrose resulted in reduced Tg but increased Tcr.
• Higher RH's were required to crystallize powders containing sucrose.
• Sucrose presence in powders caused a reduction in crystallization.

The objective of this study was to investigate the physicochemical properties of spray dried nanoemulsions having different final water and sugar contents. Formulations consisting of lactose or a 70:30 mixture of lactose: sucrose (23.9%), sodium caseinate (5.1%) and sunflower oil (11.5%) in water were heat treated (100 °C, 30 s), homogenized (17 MPa) or microfluidized (100 MPa) and spray dried at two different outlet temperatures (80 or 90 °C). Nanoemulsions produced by microfluidization were more stable and less viscous than control emulsions and had lower solvent extractable free fat. Increasing dryer outlet temperature reduced water content, water activity, particle size, tapped bulk density, with a consequent increase of onset temperature of glass transition (Tg) and crystallization (Tcr) of lactose in powders. Reduction of fat globule size by microfluidization lowered Tcr of lactose, an effect attributed to the lower level of protein in the continuous phase. Partial replacement of lactose with sucrose decreased Tg and delayed crystallisation. The study demonstrated that the physical properties of powders can be altered by reducing the fat globule size of emulsions pre spray drying.