Preparation and characterization of rice protein isolates

Various enzymes were used to treat a protein-enriched rice flour for the production of rice protein isolates. The rice flour containing 49% protein was a by-product from the processing of brown rice for syrup production. The treatment sequence of alpha-amylase followed by glucoamylase was most effective, resulting in a product with 85% protein content. The product was then treated with a mixture of cellulase and xylanase, which raised the protein content in the insoluble fraction to 91%. Inorganic impurities, such as the metal manganese in the starting rice flour, were effectively removed. The recovered rice proteins, practically intact according to electrophoretic analysis, had relatively poor solubility and emulsification properties; however, these functional properties were improved substantially by adding xanthan gum as a functionality-enhancing agent.