Innovative processing strategies for the development of highly-dispersible, protein-enriched dairy powders

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McSweeney, David J.
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University College Cork
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The application of milk protein concentrate (MPC) powder ingredients, in the formulation of nutritional products (e.g., follow-on infant formula, protein bars, clinical and sports performance beverages) continues to drive research interest among scientists to better understand, predict and control the physical and functional properties of such powders. They represent a rich source of versatile milk proteins and are prepared from the ultrafiltration and diafiltration of skim milk, followed by evaporation and spray drying. However, the primary technological hurdle limiting their application is suboptimal rehydration performance in water, specifically slow and/or incomplete dispersion and solubility. This presents a significant challenge for the food and beverage industry, particularly in relation to creating more sustainable manufacturing conditions and optimising the quality of final products. The objective of this thesis was to investigate the impact of composition (e.g., protein content), processing parameters (e.g., heat treatment) and novel technologies (e.g., gas injection) on the physical and functional properties of MPC powders. Initial studies on MPC ingredients demonstrated that high-protein content (>65%, w/w) negatively influenced bulk powder (e.g., density and flowability) and rehydration properties, with results generally improving as protein content decreased to 40-55% (w/w). Heat treatment of liquid MPC prior to spray drying demonstrated that thermal processing (≥100 °C for 30 s) significantly increases concentrate viscosity and impairs powder rehydration performance, likely due to protein aggregation, but can provide a pH-dependent improvement in heat stability. Research involving the injection of nitrogen gas (N2) into liquid MPC prior to spray drying generated regular and agglomerated (i.e., fines returned to the top of the spray dryer) powders with distinct physical and bulk handling properties and significantly improved dispersion and dissolution. Regular MPC powders produced using N2 injection (NI) had lower density, poorer flowability, increased specific surface area, and altered surface composition. However, these powder particles underwent significant breakdown during reconstitution in both ambient and warm water, demonstrating that NI directly prior to spray drying can enhance the dispersion and solubilisation of micellar casein-dominant dairy powders. These powders were further processed downstream of drying using milling to alter powder properties and yielded samples with higher density, lower air content and altered surface composition, and while they did not disperse and solubilise to the same extent, their rehydration properties remained better than those produced without NI. This thesis provides new insights into the relationship between processing modifications and the physicochemical properties of milk protein concentrate, and will support the development of techno-functional, protein-enriched dairy ingredients for incorporation into nutritional food and beverage products.
Dairy , Powders , Milk protein concentrate , Rehydration , Spray drying
McSweeney, D. J. 2022. Innovative processing strategies for the development of highly-dispersible, protein-enriched dairy powders. PhD Thesis, University College Cork.