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.