Activation energy of the disruption of gel networks in relation to elastically stored energy in fine-stranded ovalbumin gels

The aim of this study was to relate the activation energy of the disruption of ovalbumin networks to elastically stored energy (i.e. recoverable energy, RE) obtained from mechanical deformation tests. To this end, heat-set ovalbumin gels were prepared at a fixed volume fraction and pH, but varying incubation temperatures. The activation energy required to disrupt the gels was derived from the Arrhenius equation. Increasing incubation temperature from 65 to 95 °C during gel formation resulted in a gradual increase in the activation energy up to a factor of ~8. Gels obtained at or just below the protein denaturation temperature of around 75 °C had significantly lower recoverable energy (RE). These latter gels also had lower fracture stress and strain. At incubation temperatures above 70 °C RE was constant around 75%, although a steady increase in activation energy was observed. This demonstrates that storing energy in a protein network is not directly related to the interactions that make up the network. A combination of electron microscopy, water holding, and stress relaxation experiments were performed to study the different energy dissipation modes. It was shown that different dissipation modes for various gels were comparable, and this explains why the RE was similar, with the exception of gels prepared at lower incubation temperatures where (micro) fracture events could have occurred that lowered the RE. These results suggest that RE is not a network characteristic related to microstructural or smaller length scale interactions, but the result of various material-related energy dissipation mechanisms.