Spray drying at higher solids concentrations improves drying efficiency, and reduces the overall energy cost of milk powder production. As the performance of the evaporator prior to spray drying is limited by viscosity, several methods can be employed to reduce feed viscosity such as thermal pre-treatment or ultrasound. The method employed in this study was hydrodynamic cavitation (HC) on milk protein concentrate (MPC80). Rheological properties of the protein milk were observed to improve, with a reduction in viscosity by 20% and 56% upon the application of a cavitation rotor speed of 25 Hz and 50 Hz, respectively, due to the breakdown in protein gel structure and hence a decrease in the elastic modulus of the proteins. While HC did not adversely affect solubility, with the powders having on average a solubility of 97.5% at a reconstitution temperature of 50 °C, both bulk and tapped density increased when the emulsion was subjected to HC, owing to a reduction in particle size. This study therefore suggests the potential of using HC for a more efficient drying of high solids milk, while maintaining and/or improving the physicochemical properties of powders.
Bibliographical noteFunding Information:
The first author (K. Li) is thankful for the support of Monash University via the Monash Graduate Scholarship. This project is funded by the Australian Research Council ( ARC ) and the Dairy Management Inc . through the ARC Linkage program ( LP140100922 ). K. Li would also like to thank the South Dakota State University (SDSU) and the staff at the Institute for Dairy Ingredient Processing, Dairy Science Department, for hosting her from May to August 2016 and for providing the facilities to undertake this study.
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- High solids
- Hydrodynamic cavitation
- Milk protein concentrate
- Spray drying