Fluid Immobilization – A Structure-Related Key Mechanism for the Viscous Flow Behavior of Concentrated Suspension Systems

Abstract

Abstract The role of fluid immobilization (FIM) is not only of great importance for solid food systems with respect to their stability, but is also a crucial factor for the rheological behaviour of suspension systems [1]. Besides the fluid binding mechanisms known for porous solids an additional hydro-dynamically induced fluid immobilization (HIFI) is of importance for suspensions in flow. The contribution of the HIFI-mechanism is taken into account by a particle or aggregate shape factor, which for non-spherical or non-cube-like shapes depends additionally on the orientation in the flow field. In many food suspension systems sphere- or cube-like particles with hydrophilic or hydrophobic surface properties build aggregates in the watery and/or fat continuous phases. Such particle aggregates are characterised by different surface and volume FIM-properties. The fluid fraction which is immobilized at the surface f sif depends on surface characteristics like fluid adhesion, interfacial tension and roughness. The volume related immobilized fluid fraction f vif depends on porosity, pore size distribution or packing density.