Gluten in wheat flour: Composition and properties

The grain proteins determine the viscoelastic properties of dough, in particular, the storage proteins that form a network in the dough called gluten. Gluten are capable of having extensibility and elasticity required for bakery products and pasta. Gluten was associated with the water absorption, mixing time, and strength index of dough.

Gluten is a complex mixture of hundreds of related but distinct proteins, mainly gliadin and glutenin (more than 80%). Similar storage proteins exist as secalin in rye, hordein in barley, and avenins in oats and are collectively referred to as “gluten.” The gliadins (ω-, αand γ type) are relatively small molecules that are soluble in alcohols, which may act as a plasticizer in dough systems.

Gluten has four important properties: it absorbs twice its weight in water, it is sticky, it is extensible; this means it will stretch when pulled and it is elastic; when stretched it will return to near its original size.

Gluten is shown to be polymers with molecular weights (MW) in the millions, formed from smaller proteins.

Wheat flour quality is directly related to the wheat gluten formed by mixing the flour with water and with the use of appropriate application of mechanical work to form a viscoelastic network, whose structure is the basis for bakery products and pasta.

The wheat gluten proteins correspond to the major storage proteins that are deposited in the starchy endosperm cells of the developing grain. These form a continuous proteinaceous matrix in the cells of the mature dry grain and are brought together to form a continuous viscoelastic network when flour is mixed with water to form dough.

Gluten may be defined as the ‘cohesive, visco-elastic proteinaceous material prepared as a by-product obtained by isolation of starch from wheat flour. A biological definition might include the origins of the gluten–protein complex as being derived from the ‘storage proteins of the wheat grain’.
Gluten in wheat flour: Composition and properties

What is gluten?

Gluten is a protein composite found primarily in the grains of wheat, barley and rye. Less commonly known relatives of wheat such as spelt, triticale, kamut, farro and einkorn also contain gluten.

Gluten is formed when two wheat proteins - glutenin and gliadin – form cross links when they are hydrated. Most breads, pastas, baked goods, and seasonings contain gluten. It gives elasticity to dough and will help it rise and maintain its shape.

It can be used as a thickener in soups and desserts. It has so many uses and can be described as different names or aliases.

As it is metabolized or broken down, it can give some people tremendous problems. In short, the body’s immune system can see it as a toxin and therefore launch an attack against it.

Varied and multiple symptoms are created depending on what tissues of the body are attacked. Even small amounts of exposure may produce symptoms ranging from eczema, itching, headache, upset stomach, fatigue, sneezing and congestion to name a few.
What is gluten?

Glutenin in flour

Flour itself does not contain gluten. One of gluten’s main protein fractions in the flour is gliadin which a complex mixture.

At least forty different components may be identified in a single wheat variety. Gluten’s other main protein fraction is glutenin.

Glutenin are protein polymers consisting of high and low molecular weight glutenin subunits HMW-GS and LMW-GS linked though disulphide bonds.

The polymeric glutenin protein have molecular sizes ranging up into the tens of millions of Daltons. The great length of these chains is presumed to confer in wheat its unique dough forming properties.

Glutenin is thought to provide most of the strength also called tenacity, to gluten, while gliadin provides its stretchiness or extensibility. Glutenin also provides elasticity to gluten; that is its ability to bounce back one it is stretched or pressed.

The network of glutenin and gliadin is formed when the long glutenin molecules cross link with hooks on the globular gliadin molecules.

This network is very stretchy and liable, and it appears that the combination of gliadin and glutenin responsible for gas retention in wheat four dough.

The stretchiness lets the dough structure hold on the gas of carbon dioxide, which is produced by yeast or baking powder and form the crumb or texture of the bread.

In cases of gluten intolerance, the gliadin fraction is the cause of the symptoms; the glutenin fraction is not.
Glutenin in flour