The Protein Dispersibility Index (PDI) is a means of comparing the solubility of a protein in water, and is widely used in the soybean product industry.

Soy flour refers to soybeans ground finely enough to pass through a 100-mesh or smaller screen where special care was taken during desolventizing (not toasted) to minimize denaturation of the protein to retain a high protein dispersibility index, for uses such as food extrusion of textured vegetable protein.