Seed Proteins: Soluble and Insoluble

Seed proteins are classified by a particular aspect of their chemical behavior, which also determines their behavior during cooking: the kind of liquid in which they dissolve. This may be pure water, water and some salt, water and dilute acid, or alcohol (these types are called “albumins,” “globulins,” “glutelins,” and “prolamins”). Most of the proteins in legumes and nuts are soluble in a salt solution or water alone, so during ordinary cooking in salted water, bean and pea proteins become dispersed in the moisture within the seeds and the cooking liquid surrounding them. By contrast, the main storage proteins in wheat, rice, and other grains are acid-soluble and alcohol-soluble types. In ordinary water, these proteins don’t dissolve; instead they bond to each other and clump up into a compact mass. Wheat, rice, corn, and barley kernels develop a chewy consistency in part because their insoluble proteins clump together in the grain during cooking and form a sticky complex with the starch granules.