Gliadins and glutenins are storage proteins and are collectively referred to as gluten. These are the proteins we commonly associate with wheat flours. Gluten proteins are readily soluble only in alcohol or acidic or basic solutions. When mixed with plain water, as in bread making, they do not dissolve and form a tough, spongy dough. This dough can trap air bubbles produced by yeast or other leavening agents.
Gluten proteins can vary in quality.
Wheat breeders have discovered that certain types have superior bread-making capability. These superior proteins can be identified through a laboratory procedure called electrophoresis. Through this procedure it is possible to screen breeding materials and to select for or against these higher-quality glutens. These are proteins that appear to convey superior quality. While gluten proteins can vary in quality, greater variation is often seen in quantity.