What is Gluten?

Gluten is a composite of the proteins gliadin and glutenin. These exist, conjoined with starch, in the endosperms of some grass-related grains, notably wheat, rye, barley (also present in smaller quantities in oats) and also spelt & kamut which are ancient forms of the grain. Gliadin and glutenin comprise about 80% of the protein contained in wheat seed. Being insoluble in water, they can be purified by washing away the associated starch. Worldwide, gluten is an important source of nutritional protein, both in foods prepared directly from sources containing it, and as an additive to foods otherwise low in protein. The seeds of most flowering plants have endosperms with stored protein to nourish embryonic plants during germination, but true gluten, with gliadin and glutenin, is limited to certain members of the grass family. The stored proteins in maize and rice are sometimes called glutens, but their proteins differ from wheat gluten by lacking glutenin. The glutenin in wheat flour gives dough its elasticity, allows leavening and contributes chewiness to baked products like bagels.

When dough made with wheat flour it is kneaded, gluten forms when glutenin molecules form a cross-link network with gliadin molecules making dough elastic. If the dough is mixed with yeast, sugar fermentation produces bubbles of carbon dioxide which, trapped by the gluten network, cause the dough to swell or rise. Baking coagulates the gluten, which, along with starch, stabilizes the shape of the final product. Gluten, dried and milled to powder and added to ordinary flour dough, improves rising and increases the bread's structural stability and chewiness. This has lead to an increase in extreemely glutenous products such as pizza base and bagels. Breads flours tend to have more gluten in them than flour for cakes and pastries, as it is needed to give rise and shape to the product.

Gliadins & Other Allergens in Wheat

There are 3 types of gliadins:

• á-/â-gliadins - soluble in low percentage alcohols.

• ã-gliadins - ancestral form of cysteine-rich gliadin with only intrachain disulfide bridges

• ù-gliadins - soluble in higher percentages, 30–50% acidic acetonitrile.

People with gluten-sensitivity or ceoliacs disease are sensitive to á, â, and ã gliadins. Those with wheat-dependent exercise-induced anaphylaxis, urticaria and Baker's asthma are sensitive to ù-gliadins.Gliadin can also fuse with and enzyme called superoxide dismutase, which turns it into glisodin. This prevents the breakdown of gluten protein in the stomach. Another proteinase inhibitor found in wheat is prolamin, again making gluten difficult for the digestive system to process. Prolamins and the closely related glutelins, a recent study in Japan found that glutinins are a more frequent allergen, however gliadins are associated with the most severe disease. Glutenin (wheat glutelin) is a predominant allergen in wheat. Nine subunits of LMW-glutinen have been found to bind to wheat allergy associated IgE. At present many of the allergens of wheat have not been characterized; however, the early studies found many to be in the albumin class. A recent study in Europe confirmed the increased presence of allergies to amylase/trypsin inhibitors (serpins) and lipid transfer protein (LPT).but less reactivity to the globulin fraction. The allergies tend to differ between populations (Italian, Japanese, Danish or Swiss) indicating a potential genetic component to these reactivities. These enzymic inhibitors present in wheat make it difficult for the body to process, leading to the allergies that have been mentioned.