Interparticle interactions and gelation impact structure, rheology.

You already know that most foods are composed of a network of small particles and large molecules that are held together by various intermolecular and colloidal forces. A food's structure, texture and stability are significantly influenced by the strength of these interactions, especially protein-protein and protein-lipid interactions.

Foods are generally in a metastable state. Their texture depends on the structural changes that occur as they're processed. Researchers at the U.K.'s University of Leeds wanted to better understand the relationship between a product's texture and its processing history. They used a combination of computer simulations and lab experiments on model systems to relate the structure and rheology of aggregated networks of milk protein particles to the interparticle interactions and conditions that control the gelation process.

The effort included undertaking a computer simulation of particle gelation; examining structure using various image analysis techniques; investigating the rheology of various gels and emulsion droplets; and studying protein-lipid interactions.

Investigators made substantial progress in relating the structure and rheology of simulated particle gels to the nature of interparticle interactions. Simulations of monodisperse systems demonstrated the effect of an energy barrier on the kinetics of aggregation and the fractal character of the aggregated network structure. The simulations also showed the effect of bonding strength and non-bonded interactions on the pore-size distributions and rheological behavior at small and large deformations.

By comparing simulation and microscopy studies, researchers established the dependence of the structure of aggregated particle systems on the nature of interparticle interactions and polydispersity. Small-deformation and large-deformation rheological properties of simulated aggregated particle networks successfully reproduced the mechanical properties of some real milk protein gels, emulsion gels and adsorbed protein layers. Scientists closely correlated the rheological properties of emulsions, emulsion gels and protein-lipid interactions inferred from interfacial studies.

The scientists continue to work in this area. Their other research efforts include investigating the structure and dynamics of milk proteins at fluid interfaces, the creaming, flocculation and rheology of emulsions, and the interactions of surfactants and biopolymers in food colloids.

Further information. Eric Dickinson, University of Leeds, Department of Food Science, Leeds LS2 9JT, England, U.K.; phone: [phone]; fax: [phone]; email: [e-mail].