Soy protein products are mainly used as ingredients in formulated foods and seldom are seen by the public. They consist of four broad categories. (1) Most soy proteins are derived from "white flakes," made by dehulling, flaking and defatting soybeans by hexane extraction. These may then be milled into defatted flours or grits containing approximately 50-54% protein; extracted with ethanol or acidic waters to remove flavor compounds and flatulence sugars, producing soy protein concentrates containing 65-70% protein; or processed into soy protein isolates containing 90+% protein by alkali extraction of the protein, removal of fiber by centrifugation and reprecipitation and drying of the protein. (2) Full-fat products are made in enzyme-active and in toasted forms. (3) Various dried soyfoods, including soy milk and tofu, are produced. (4) Mixtures of soy proteins with cereals, dried milk or egg fractions, gelatin, stabilizers and emulsifiers are offered for specific baking, whipping, breading and batter applications. Texturized products, resembling meat chunks or bacon chips, are made by extrusion of flours and concentrates or spinning of isolates. Soy protein ingredients are used in compounded foods for their functional properties, including water and fat absorption, emulsification, aeration (whipping) and heat setting and for increasing total protein content and improving the essential amino acids profile.
