The main physicochemical properties of nanostructured silica/wheat gluten hybrid composites are presented. The extraction experiments suggest that the protein phase is intimately encased within the silica matrix, with silica–protein interactions driven by hydrogen bonding, as indicated by IR spectra. Spectroscopic results also show that silica induces a higher degree of constraint of the wheat gluten matrix, despite less aggregation. Moisture diffusion properties of the hybrid materials are investigated by a combined “desorption/sorption” approach. While the reduction of the moisture diffusivity in the presence of silica can be described by the geometrical impedance of a “sintered” porous solid, a time-dependent relaxation/restructuring of the composite apparently occurs during the sorption-desorption cycle.