The post-dehydration processing and the effects on the structural modifications and functionalities of milk protein powders
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Date
2017
Authors
Ji, Junfu
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Publisher
University College Cork
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Abstract
The variability of the raw materials, the diversity of the chemical compositions and the heterogeneity of structures are believed to contribute to the complexity in the physicochemical behaviours of dairy powders. Post-dehydration technology is widely used as an effective method to modify the structural properties and potentially improve the functionalities of dairy powder. In the present study, the dairy powders were firstly agglomerated by fluidised bed (FB) to investigate the effects on their rehydration processes. Then milk protein isolate powder (MPI) was used as the model system, which was agglomerated by fluidised bed and high shear mix (HS) granulators, using different liquid binders and comparing different granule sizes. The impact of both agglomeration methods on powder structures, as well as the consequent effects on the rehydration abilities, flowability and water adsorption are investigated. MPI agglomerated by FB had the more irregular shapes and porous structures. However, densely packed structures of HS granules caused the higher bulk density and lower porosity. Their shapes were more like spheres with smoother surfaces. FB agglomeration significantly improved the dynamic wetting of MPI and micellar casein powders, by requiring shorter wetting time, being more quickly penetrated by water droplets and absorbing more water by capillary force. But the influences on whey protein were limited, only if using lecithin as a liquid binder. Agglomeration exhibited no advantageous effects on the solubilisation of milk protein powders. The HS granules even delayed the release of materials. The denselypacked structures made MPI adsorbed least moisture and showed the slowest adsorption kinetics. Meanwhile, these MPI granules have significantly better powder flow behaviours. The study provided information about the post-dehydration process as a useful technique to modify the structures of dairy powders, which could be helpful to enhance the wetting process, control the water adsorption and improve the powder flowability.
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Keywords
Dairy powder , Agglomeration , Powder rehydration , Coating , Powder structures
Citation
Ji, J. 2017. The post-dehydration processing and the effects on the structural modifications and functionalities of milk protein powders. PhD Thesis, University College Cork.