Characterisation of fractionated skim milk with small-angle X-ray scattering

Small-angle X-ray scattering, low field nuclear magnetic resonance, dynamic light scattering and rheological methods were used to investigate the structure and properties of fractionated microfiltrated milk with adjusted pH (6.6 or 5.8) and subjected to high-pressure homogenisation (300 MPa) to select suitable process variables for making cast cheese in a novel way. A new model was used to describe the data from small-angle X-ray scattering. High-pressure homogenisation was shown to disrupt casein micelles at pH 5.8, but not at pH 6.6, indicating that some dissociation of colloidal calcium phosphate was necessary to cause micellar disruption. This in turn was shown to significantly increase viscosity and reduce diffusion of water in the matrix.