Define the Soybean Protein Isolates?
Soy protein isolates are the most pure and refined soy protein available. Isolated soybean proteins (ISP), or soybean protein isolates, are the most concentrated form of commercially available soybean protein products. They contain over 90% protein, on a moisture free basis. Soy protein isolates have been known and produced for industrial purposes, mainly as adhesives for the paper coating industry, well before World War II. ISP's for food use, however, have been developed only in the early fifties. The specification of the Association of American Feed Control Officials, Inc. (AAFCO) defines ISP as "Major proteinaceous fraction of soybeans prepared from dehulled soybeans by removing the majority of non-protein components and must contain not less than 90% protein on a moisture-free basis."
The basic principles of ISP production are simple. Soybean protein isolates are obtained by selective solubilization of the protein (e.g. alkaline extraction), followed by purification of the extract and precipitation of the protein (e.g. by acidification to the isoelectric point). Isoelectric isolates are insoluble in water and have practically no functional features. They can be converted to sodium, potassium or calcium proteinates by dissolving isoelectric proteins in the appropriate base and spray-drying the solution. Sodium and potassium proteinates are water-soluble. They are used mainly for their functional properties, such as emulsification or foaming. One of the by-products of the protein isolation process, the insoluble residue, is also commercialized for its remarkable water absorption capacity and as a source of dietary fibre. Since spray-drying is the common drying method in the production of ISP, the primary physical form of ISP in commerce, is that of fine powders. Structured forms, such as granules, spun fibres and other fibrous forms are made by further processing. Being almost a pure protein, ISP can be made to be practically free of objectionable odour, flavour, colour, anti-nutritional factors and flatulence. Furthermore, the high protein concentration provides maximum formulation flexibility when ISPs are incorporated into food products. These and other advantages have been the source of highly optimistic forecasts regarding the widespread use of ISP. The various uses of ISP in food applications are discussed herewith.