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 does it mean by gluten sensitivity?

Among gluten-related disorders, gluten sensitivity is an emerging entity that is characterized by a wide array of manifestations. In particular, patients complain of IBS (Irritable bowel syndrome)-like symptoms and extraintestinal manifestations that occur shortly after the ingestion of gluten. Symptoms improve or disappear when gluten is withdrawn from the diet, and recur if gluten is reintroduced.

Gluten is found in grains such as wheat, barley, rye, and a cross between wheat and rye called triticale. It is a complex protein formed of two protein structures: gliadin and glutenin, connected by disulfide bridge. Gluten is the magical protein responsible for the capability for bread dough to rise and contain carbon dioxide. Gluten components create a 3D network when flours are mixed with water, giving dough elasticity and viscosity.

The clinical presentation of gluten sensitivity is a combination of IBS-like symptoms, including abdominal pain, bloating, bowel habit abnormalities (either diarrhea or constipation), and systemic manifestations such as ‘foggy mind’, headache, fatigue, joint and muscle pain, leg or arm numbness, dermatitis (eczema or skin rash), depression and anemia.

People with gluten sensitivity have problems with gluten. It is different from celiac disease, an immune disease in which people can't eat gluten because it will damage their small intestine.

Some of the symptoms of gluten sensitivity are similar to celiac disease. They include tiredness and stomachaches. It can cause other symptoms too, including muscle cramps and leg numbness.
What does it mean by gluten sensitivity?

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?

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?

The importance of gluten in flour for baking

The principle functional protein of wheat flour is gluten. Gluten has the important property that when it is moistened and worked by mechanical action, it forms an elastic dough.

This dough may be stretched in two directions and form sheets or films, or it may be stretched in all directions under the pressure of expanding gas and form bubbles as does bubble gum. Gluten from strong flour is more perfect colloidal gel, as shown by its greater hydration capacity than gluten from soft flour.

Baking quality of flour depends on both the quantity and quality of gluten that can be formed from it.

Yeats breads are prepared from soft dough using hard wheat flours to form gluten structure that is strong and elastic.  The structure may contain starch and sugar or other ingredients such as eggs and fat. The yeast is responsible for the production of CO2 within the gluten structure.

The wet gluten is a cohesive, elastic mass that expands greatly on baking to form a light porous ball. Baked gluten contains about 85% protein, 8% lipids and variable amounts of starch depending on the thoroughness of washing.

Wheat starch does not form elastic films as does gluten; rather, the moistened starch, when heated forms a paste and stiffens or more correctly gelatinizes.

Baking the gluten shows that it expands greatly as the steam within it expands and that it coagulates when heated to form the structure of the baked product.

Generally, cookies are produced using soft wheat flour that ahs relatively weak gluten strength (e.g. pastry flour, a blend of soft red and soft wheat).

The cookies usually consist of high fat and sugar contents, and low moisture content.
The importance of gluten in flour for baking

What is gluten intolerance?

Gluten is a protein found in many cereal grains and is the main protein in wheat. Gluten is also a type of prolamin, a protein fraction found in a variety of grains.

It is an adverse food-induced with a known external trigger factor. Gluten intolerance is often used as a broad term that includes celiac disease and non-celiac gluten sensitivity. Technically, though, gluten intolerance is simply a non-autoimmune and non-allergenic condition that creates uncomfortable symptoms within the persons consumes gluten.

Gluten intolerance can cause a surprisingly wide variety of symptoms and health problems. While most people associate gluten intolerance with digestive problems, it can also cause or it’s associated with complications far beyond the digestive tract.

The irritation causes abdominal pain, produces inflammation, destroys the small intestine’s lining and reduces absorption of important nutrients.

With the advance of biochemical markers for gluten intolerance, several studies have proven the present of a specific antibody-verified, gluten free diet validated, gluten intolerance in a large sector of society (12-18%).
What is gluten intolerance?

Celiac Disease

Celiac disease is a gluten sensitive enteropathy of autoimmune origin, characterized by inflammation and villous atrophy of the small bowel mucosa, that impairs nutrient absorption.

Celiac disease is also known as celiac sprue, nontropical sprue and gluten-sensitive enteropathy. Individual with celiac disease do not tolerate gluten, a protein present in wheat, rye, barley and possible oats.

The normal small bowel mucosa a is thrown up in a series of concertina-like folds called the valvulae conniventes. The absorptive surface of the mucosa is configured as millions of villi covered by columnar epithelial cells.

In advanced celiac disease, the valvulae are thinner and more widely spaced than normal. The damage may be restricted to the duodenum or may involve the full length of the small intestine.

Individuals with severe disease may malabsorp all nutrients to some degree, especially the macronutrients, fat-soluble vitamins, electrolytes, calcium, magnesium, zinc, iron, folate and vitamin B12.

As a result of nutrient deficiencies, patients often develop anemia and have low bone mineral density.

Other symptoms, such as severe abdominal pain, nausea and vomiting are much less common.

The diarrhea of celiac disease is classically describe as high volume, pale, loose to semi formed and foul smelling.

Celiac disease is one of the the most common chronic disorders in Europe and the US affecting about 1% of the population.
Celiac Disease