Flour is produced from the endosperm of the wheat. The endosperm contains about 80 percent of the total amount of protein in the whole kernel. Gliadin and glutenin make up most of this and are usually present in most equal proportions. Variations in their relative proportions may significantly affect gluten formation. Gliadin seems to be a key player in the volume attained in breadmaking, imparting viscosity and extensibility. Glutenin provides elasticity and strength to the dough. Both of these proteins are directly affected by both environment and genetics. Environmental conditions influence protein quantity while genetics seem to determine protein quality. In other words, even low-quality wheat can produce some high-protein flours.
The quality of wheat is determined, rather tautologically, by how well it performs in the task it has been given. Good cake flour will rely upon the same factors to produce lovely tender cakes that would produce horrible, flat, gummy bread. American hard wheat flours, with their high protein content and ability to absorb large amounts of water, may make it difficult to produce European hearth bread with crisp, brittle crust and open crumb. Just remember that each type of flour was created with a specific purpose in mind-how well it lives up to that promise determines how ‘good’ it is. Quality flours perform well over a boad range of protein contents.