Wheat Gluten – Properties and Composition
Commercial wheat gluten extracted form wheat or wheat flour and dried is a cream/tan- colored free flowing powder of bland flavor.
When hydrated it regains virtually all of its original functionality. Compositionally, it is a lipid protein complex with some included starch.
Wheat flour, with addition of water and input of mixing energy, can form doughs that posses the unique ability to trap and retain gases during fermentation permitting the dough to expand and subsequently to bake into an aerated, palatable loaf of bread.
This ability is directly attributable to the formation of a cohesive and viscoelastic mass, namely gluten, which occurs when flour is hydrated in an aqueous medium.
The two major protein components of gluten that contribute to viscoelasticity are glutenin and gliadin, which differ markedly in their chemical and physical properties.
Glutenin proteins are multichained, with very high molecular weight. When isolated from wheat gluten, glutenin exhibits pronounced resiliency but little extensibility and therefore appears to provide the elastic properties of gluten.
Gliadin from wheat consists of some 50 single chained proteins of relatively low molecular weight.
Upon isolation from wheat gluten gliadin are portably extensible and quite sticky and therefore seem to provide the extensibility and cohesively properties of gluten.
The viscoelasticity of hydrated wheat gluten is attributed several factors including its water compatibility and ability to swell and undergo physicochemical interactions.
As the gluten takes up water, it goes through glass transition where the proteins change form a hard glassy stage to one that is rubbery and elastic.
An unusual property of gluten that sets it apart form other plant proteins is the low level of polarity of its amino acid structure.
Gluten proteins are very high in Glutamic acid about 35% of the total protein and are notably low in the basic amino acids.
The gluten proteins therefore have no potentials therefore have no potential negative charges and little potential charges. Resulting in a low charge density.
Repulsion forces within the gluten proteins are thereby weak, allowing for enhanced interaction, which is important in dough formation.
Yet another property of gluten is that about 35% of its total amino acids posses hydrophobic side chains, leading to greater surface hydrophobicity and hydrophobic interactions.
Hydrophobic interactions among gluten protein may have an important role stabilizing gluten structure as well as in theological and baking properties of dough.
Wheat Gluten – Properties and Composition
