What is gliadin?

Seed storage proteins (about 85% of endosperm proteins) are traditionally classified into monomeric (gliadins) and polymeric (glutenins) proteins, based on their solubility.

On the basis of electrophoretic mobility at low pH the wheat gliadins may be separated into the slowest group named the ω-gliadins and three faster groups, named the α, β and γ-gliadins.

The amino acids sequences of some gliadins are known. A very common N-terminal sequence found in α, β and γ-gliadins is Val-Arg-Val-Pro-Glu-Leu-Glu-Pro.

Due to the differences in cysteine content the gliadin components may be divided into S-rich (α, β and γ-gliadins) and S-poor (ω-gliadins) components.

All gliadin components have extremely high glutamic acid content. In some ω-gliadins the glutamic acid content is higher than 50%.

Although not major participants in the gluten polymer, the monomeric gliadins contribute to dough physical/chemical properties by extensive hydrogen bonding with the gluten polymer.

Gliadins are rather hydrophobic, hence their solubility in water or salt solution. More hydrophobic gliadins (the γ-gliadins) increase bread loaf volume, while gliadins from more hydrophilic end of the spectrum decrease loaf volume.
What is gliadin?