Effects of alkaline deamidation on the chemical properties of rice bran protein

The water solubility of rice bran protein (RBP) was improved by deamidation under alkaline conditions. The degree of deamidation was found to be a major factor in improving the solubility of RBP. The decrease in molecular mass or the degradation of peptide bonds was not detected in deamidated RBP under the conditions used. The thermal property and secondary structure of deamidated RBP measured by differential scanning calorimetry and Fourier transform infrared spectroscopy indicated that the secondary structure of RBP was well preserved during alkaline deamidation. By raising pH and temperature for deamidation, the generation rates of constituent amino acid racemization and lysinoalanine increased. The highest solubility (∼90%) of RBP was achieved by treatment at pH 12 and 120°C for 15 - 30 min by enduring side reactions. Moderate solubility (∼40%) could be achieved by deamidation at pH 8 and 100°C for 30 min to minimize side reactions.