Browsing by Author "Udabage, P"

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    Reconstitution properties of micellar casein powder: effects of composition and storage
    (Elsevier, 2011-11-01) Schokker, EP; Church, JS; Mata, JP; Gilbert, EP; Puvanenthiran, A; Udabage, P
    A problem associated with micellar casein (MC) powders is their poor reconstitution properties. In this study, we prepared MCs with different salt and protein compositions and having different reconstitutabilities directly after production. Reconstitutability further decreased during storage at 30 degrees C. Differential scanning calorimetry, infrared spectroscopy, and small angle X-ray scattering showed that the powders were very similar on a molecular or sub-micellar level, indicating that the loss of reconstitutability is probably controlled by higher order structural changes, such as cross-linking between casein micelles, possibly involving intermolecular beta-sheet formation. The reconstitutability of MC could be improved by adding sodium caseinate to the concentrated milk before spray drying. This novel approach to improve reconstitutability can easily be incorporated into the existing processing protocol. We propose two possible mechanisms for the protecting effect of the non-micellar caseins.(C) 2011 Elsevier Ltd. All rights reserved.
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    Structure of casein micelles in milk protein concentrate powders via small angle x-ray scattering
    (Royal Society of Chemistry, 2011-01-01) Mata, JP; Udabage, P; Gilbert, EP
    The stability of milk protein concentrate (MPC) powders and their solubility in water is presumed to depend on the interfacial and internal structure of the casein micelle. This study reports the internal micellar structure for MPC powder for the first time. We have investigated the nanostructure of MPC powders and of dilute solutions thereof using small-angle X-ray scattering (SAXS). In addition, we have measured the scattering from the primary components of MPC in their powder and solution state to enable an assessment of their contribution to the overall scattering from the whole system. The interfacial and internal structural detail of the casein micelle is still an area of debate and we have considered the two popular models for casein micelles, namely the submicelle and nanocluster models; we find that the latter adequately describes the observed experimental results. The scattering curve for the powders may be described by three characteristic regions. The first region up to 0.03 A-1 is interpreted to correspond to the scattering from a sharp and smooth interface. The second inflexion point, observed at [similar]0.045 A-1, may be attributed to a mean intercluster correlation length of colloidal calcium phosphate (CCP) nanoclusters distributed within casein micelles. This is the first time such a feature has been observed in the powder state but its presence is reminiscent of a similar feature observed previously with solvent contrast variation small-angle neutron scattering. We interpret that its presence here is due to an enhancement of the scattering contrast by virtue of the removal of water from the system (and replaced by air) combined with an increase in particle density due to drying. The third inflexion at 0.1 A-1 may be interpreted, in common with other authors, as a signature of colloidal calcium phosphate nanoparticles.© 2011, Royal Society of Chemistry