a substance found in wheat, which gives bread its texture. It consists of two proteins, glutenin and gliadin. Wheat also contains two other proteins, albumin and globulin, which are soluble in water and dissolve when the flour is wetted.
The molecules of glutenin are in the form of long chains, those of gliadin shorter. When dough is kneaded, the long glutenin molecules are pulled out straight. The shorter gliadin molecules make links across the strands, so that the gluten forms an elastic network. The change in texture as this happens can be felt. When the bread is baked the gluten coagulates and becomes firm, giving the distinctive fibrous structure of bread.
Several minutes’ kneading are required to ‘develop’ or draw out the strands of gluten; but excessive kneading must be avoided because it would overstretch and break the strands, so that the dough would lose its springiness. Adding fat to dough lubricates the strands of gluten so that they slip and do not become fully stretched. This gives a softer, ‘cakey’ texture. In making pastry it is important to knead as little as possible, to avoid developing the gluten. Leaving raw pastry to ‘relax’ allows any stretched strands to return to their original shape.
Different types of wheat contain differing amounts of gluten. The largest amounts are found in the durum wheat used to make pasta; it requires long kneading to achieve the required springy texture. The ‘hard’ wheat used for bread flour contains smaller but still substantial amounts. ‘Soft’ wheat contains the least, and is therefore used for cake flour.
Other cereals do not contain gluten, though they do have other proteins. That is why rye, barley or maize bread never has the texture characteristic of wheaten bread.
Ralph Hancock is an encyclopedist with a special interest in food history and food science.
