Nano Science and Technology Institute

R&D Profile: New Routes to Gels and Glasses, or How to Apply Analogies between Soft Matter Physics and Food Systems: A. Stradner, University of Fribourg, CH

We believe that nanotechnology can make important contributions to food sciences and technology in several areas.

Anna Stradner

R&D Profile Courtesy of Anna Stradner, Adolphe Merkle Institute, University of Fribourg, Switzerland

Dr. Stradner is a featured speaker at next month’s NSTI Nanotech conference.

Gels and glasses represent classes of non-equilibrium solids that play an important role in various food and materials science applications (1). In addition, they have attracted the attention of experimentalists and theoreticians in modern soft condensed matter physics. This has already resulted in a much better understanding of phenomena centered around liquid-solid transitions encountered in colloidal model suspensions (2, 3). However, experimental investigations in systems with industrial relevance are often hampered by problems such as high turbidity, complex time dependence, and the non-ergodicity of the resulting solid-like samples. Here we show that the application of novel developments in instrumentation for the investigation of dense and strongly attracting colloidal suspensions yields improved insight into the behavior and properties of food related mixtures (4, 5). Moreover, we develop new concepts for the understanding of non-equilibrium solid states in food colloid – biopolymer mixtures in the region of the state diagram, where liquid-liquid phase separation competes with dynamical arrest. This interplay and the possibility to modify it by playing with interparticle interaction strength and range lead to interesting phenomena and – once fully understood – will provide a tool kit to produce food gels with tailored structural and mechanical properties.

spinodal

Solid-like materials can be obtained via a variety of different arrest mechanisms. In the case of medium strength attractive particles, gels can form via an arrested spinodal decomposition process.

This study has to be seen in a larger context. We believe that nanotechnology can make important contributions to food sciences and technology mainly in three areas, which represent the focus of our nanotechnology-based food research: (1) Utilizing concepts from colloid physics to create self-assembled food systems with novel properties: The issue of non-equilibrium solid-like properties is of outstanding importance for food processing as well as the final food products. Only improved understanding of the mechanisms involved will allow controlling and tuning the structural, optical and mechanical properties. (2) The application of novel methods and instrumentation originally developed in nanomaterials science and soft matter physics: Experimental studies of food systems often require us to cover an extremely large range of length and time scales. We thus put a major effort into the development of new experimental tools that allow us to investigate equilibrium and non-equilibrium properties of these systems. (3) The development of nanocomposite-based packaging materials: Here we synthesize and study functionalized synthetic colloidal particles in order to create advanced composite materials for food packaging with optimized safety and shelf life properties.

  1. R. Mezzenga, P. Schurtenberger, A. Burbidge, and M. Michel, Nature Materials, 2005, 4, 729.
  2. V. Trappe and P. Sandkühler, Curr. Opin. Colloid Int. Sci., 2004, 8, 494-500.
  3. F. Cardinaux, T. Gibaud, A. Stradner, P. Schurtenberger, PRL, 2007, 99, 118301.
  4. S.K. Bhat, R. Tuinier, P. Schurtenberger, J. Phys.: Condens. Matter, 2006, 18, L339-L346
  5. S.K. Bhat, M. Michel, A. Stradner, P. Schurtenberger, to be submitted to Soft Matter
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