From Rheology to Tribology: Multi-scale Dynamics of Microgels, Food and other Soft Matter Systems

  • A/Prof Jason Stokes, Division of Chemical Engineering, School of Engineering, University of Queensland, Australia
  • The design of next generation foods requires an advanced knowledge of structure and dynamics at multiple length scales. Food and other soft materials are designed and assembled using multiple structuring technologies to carry particles, oil and air without destabilisation and phase separation. However, there is a strong push for innovative and nutritious foods that are low in fat, sugar and salt without compromise in sensory properties. This is pushing products into a formulation space where existing design rules no longer apply, and it is apparent that improved understanding on structure-property-function relationships are required. This paper explores the universal rheological properties of yielding and gelling soft matter systems, focusing on foods and microgel suspensions, and the relationship to their underlying microstructure. Nanoscale structures at air and liquid interfaces are also shown to play a major role in the properties of emulsions and foams. In addition, recently developed techniques in thin film rheology and tribology (lubrication) are highlighted that are enabling an understanding on how materials behave during oral processing. These techniques show that the physical properties of the individual phases, microstructure and nanostructure become increasingly important as the material is confined to a thin film. An oral biomimetic has also been developed that considers the interaction between product constituents and a saliva film. This is leading to a superior understanding on in-mouth properties with potential use in design of healthier foods with superior sensorial properties, while such techniques and insights may also be applicable in pharmaceutical and biomedical applications.