Surface Texture of Particle Gels

Surface properties of protein gels have been assessed in terms of surfaces roughness, surface glossiness, and surface wetness. A simple mechanical device has been developed based on the Texture Analyser (Stable Micro Systems, Surrey, UK) for accurate measurements of surface friction forces. Surface friction forces of whey protein gels were investigated as a function of surface sliding speed and normal load. It was found that the surface friction of whey protein gels containing a small amount of NaCl became much less sliding-speed dependent but much more normal-load dependent. Thicker layers of surface water and much rougher surfaces of salt-containing gels are possible explanations. Confocal microscopy observations revealed that the protein gel without salt addition has a smooth and flat surface, while the gel with added salt has a much rougher surface.