• Mouro, C. Rondeau
• Duyhoven, J. Van
• Salami, S.
• Mariette, François

Abstract

Since several years, Pulsed-Field Gradient (PFG)-NMR diffusometry and NMR relaxometry have been used as non-invasive, selective techniques to investigate structures of porous materials through the measurement of displacements of molecules in porous systems. In this work, we used these techniques to study the diffusion and relaxation of different probe structures (dendrimers “spherical and non-flexible” and polyethyleneglycols (PEGs) “linear chain and flexible”) in suspensions of two different casein systems. The first one is the native phosphocaseinate (NPC) system where casein exists as large colloidal particles, 50-600 nm in diameter (mean ≈150 nm), called “caseins micelles”. The second one is the sodium caseinate (SC) system where casein forms self-assembled aggregates of about 11 caseins and ~ 20 nm in diameter that are expected to overlap and interpenetrate even at low concentrations (HadjSadok, Pitkowski et al. 2008) Pitkowski, Durand et al. 2008) and which behave as an ordinary entangled polymer system (Bouchoux, Debbou et al. 2009). Survey results were analyzed by taking into account obstruction effects from the particles, the structure of the probe and that of the casein dispersions as well as the variation of dispersion viscosity. The results were also analyzed using the Rouse model and were compared with previous investigations (Le Feunteun and Mariette 2007; Le Feunteun and Mariette 2008). These investigations allowed not only a better understanding of probe diffusion in casein systems but also a description of their microstructure as a function of protein concentration.

Topics

• porous
• impedance spectroscopy
• dispersion
• polymer
• mobility
• Sodium
• viscosity
• Nuclear Magnetic Resonance spectroscopy
• dendrimer
• normal-phase chromatography