The behaviour of the high molecular-weight glutenin subunit 1Dx5, the 58 kDa central repetitive domain and α-gliadins at the air-aqueous interface

The surface pressure-molecular area (Π-A) relationship for spread layers of the high molecular-weight glutenin subunit 1Dx5, a 58 kDa peptide derived from the central repetitive domain of the subunit, and an α-gliadin fraction was measured by means of a surface film balance (Langmuir trough). The aqueous phase was a 10 mM acetate buffer, pH 4.0, either with or without 100 mM NaCl. Subunit 1Dx5 generated much higher surface pressures than the 58 kDa peptide, whereas the α-gliadin fraction generally gave higher surface pressures than subunit 1Dx5. Furthermore, subunit 1Dx5, but not the 58 kDa peptide or the α-gliadin fraction, formed a highly cohesive film. The differences in the interfacial hehaviour of subunit 1Dx5 and the 58 kDa peptide were ascribed to significant hydrophohic interactions for the subunit. The reversibility of a compression-expansion cycle was generally greater for the second cycle than for the first. For subunit 1Dx5 and the α-gliadins, hut not the 58 kDa peptide, the reversibility was increased when NaCl was present in the aqueous phase.