  The structure of model gluten protein gels prepared in ethanol/water is
investigated by small angle X-ray (SAXS) and neutrons (SANS) scattering. We
show that gluten gels display radically different SAXS and SANS profiles when
the solvent is (at least partially) deuterated. The detailed analysis of the
SANS signal as a function of the solvent deuteration demonstrates
heterogeneities of sample deuteration at different length scales. The
progressive exchange between the protons (H) of the proteins and the deuteriums
(D) of the solvent is inhomogeneous and 60 nm large zones that are enriched in
H are evidenced. In addition, at low protein concentration, in the sol state,
solvent deuteration induces a liquid/liquid phase separation. Complementary
biochemical and structure analyses show that the denser protein phase is more
protonated and specifically enriched in glutenin, the polymeric fraction of
gluten proteins. These findings suggest that the presence of H-rich zones in
gluten gels would arise from the preferential interaction of glutenin polymers
through a tight network of non-exchangeable intermolecular hydrogen bonds.
