Résumé
Wheat gluten proteins are insoluble in water and are among the most complex protein networks in nature. In spite of their extensively use in particular for bread making, their viscoelastic properties and their structuration are still largely unknown. Here we report the visco-elastic behavior of model systems composed of gluten proteins near the liquid-solid transition. We build model systems by dispersing in ethanol-water mixtures two major protein groups, gliadin and glutenin, that we have purified from gluten. We find a slow evolution over time scales of the order of days of the linear frequency dependence complex modulus of the samples. Interestingly, we find that all data acquired at different protein concentrations and different times after sample preparation can be scaled onto a master curve, showing a cross-over from a soft solid at low frequency to a visco-elastic fluid at high frequency. We are currently using scattering techniques to unveil the peculiar structure of the protein network that would lead to the self-similar visco-elasticity.