Rheology and Tribological Properties of Ca-alginate Fluid Gels Produced by Diffusion-controlled Method

A new method has been developed for the production of alginate fluid gels. By using the turbulent flow field generated within a pin stirrer, fluid gel particles can be produced in a reproducible and controlled manner. Using this approach yielded an average particle diameter smaller than 10 μm for all alginate fluid gels produced. A weak gel-like behaviour is reported for the produced materials, which displayed a gradual increase of G′ upon increasing polymer concentration. Steady shear results revealed the existence of an apparent yield stress, indicating that a significant interparticle potential persisted after the production process had finished. Soft-tribology was used to assess the lubrication properties of Ca-alginate fluid gels. The entrainment of particles in the ball-on-disc contact resulted in a localised increase of friction in the mixed regime, which was found to be dependent on both particle intrinsic properties and the surface roughness of the disc. An increase of polymer concentration resulted in an overall decreased friction for systems with similar particle dimensions. These distinct but complementary functional responses of fluid gels, arising from increasing alginate concentration, offer real possibilities towards building microstructures with enhanced sensory attributes.