Protein-protein interactions explain the temperature-dependent viscoelastic changes occurring in colloidal protein gels.

Denaturation of protein solutions can be induced by higher temperatures and the presence of non-polar organic solutions. The denatured proteins form aggregates and gels through protein interactions occurring between their amino acid side chains. Depending on the involved side chains, the denaturation conditions lead to different gel properties. As model systems, a variety of food proteins were gelled through different mechanisms to cover a whole range of protein-protein interactions. Especially the temperature dependence of the viscoelastic properties in a simple rheometer method was found to be very different. These differences could be explained by the different thermodynamic properties of the involved protein-protein interactions. Electrostatic interactions were shown to weaken the resulting gel upon temperature increase whereas entropically driven interactions such as hydrophobic or covalent links were strengthened with increased temperatures. A proposed model explaining these results can be used to assess protein interactions in hydrogels in a non-invasive way and could also have applications to describe the temperature behavior of other hydrogels.