Soy Protein - Production Methods

Production Methods

Edible soy protein "isolate" is derived from defatted soy flour with a high solubility in water (high NSI). The aqueous extraction is carried out at a pH below 9. The extract is clarified to remove the insoluble material and the "supernatant" is acidified to a pH range of 4-5. The precipitated protein-curd is collected and separated from the whey by centrifuge. The curd is usually neutralized with alkali to form the sodium proteinate salt before drying

Soy protein concentrate is produced by immobilizing the soy globulin proteins while allowing the soluble carbohydrates, soy whey proteins, and salts to be leached from the defatted flakes or flour. The protein is retained by one or more of several treatments: leaching with 20-80% aqueous alcohol/solvent, leaching with aqueous acids in the isoelectric zone of minimum protein solubility, pH 4-5; leaching with chilled water (which may involve calcium or magnesium cations), and leaching with hot water of heat-treated defatted soy meal/flour.

All of these processes result in a product that is 70% protein, 20% carbohydrates (2.7 to 5% crude fiber), 6% ash and about 1% oil, but the solubility may differ. One tonne of defatted soybean flakes will yield about 750 kg of soybean protein concentrate.