Glycosylation of rice protein with dextran via the Maillard reaction in a macromolecular crowding condition to improve solubility

The study aims at improving the solubility of rice protein (RP) by covalent coupling of proteins to polysaccharide via Maillard reaction in macromolecular crowding conditions. The formation of RP-dextran conjugates (RPC) was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, size exclusion chromatography and infrared spectra. The optimum conditions for the Maillard reaction between rice protein and dextran were 90 °C, pH 11, 60 min, and the mass ratio of RP to dextran was 1:3. The solubility of the RP-dextran conjugates in the buffer solution of pH 7–9 was greater than 80%. The high solubility of the RP-dextran conjugate was due to the introduction of dextran. Dextran covalently bound to RP has many hydrophilic hydroxyl groups, which reduced the ratio of hydrophobic groups on the surface of RP. At the same time, the emulsification and foaming properties of the RP-dextran conjugates were greatly improved compared to that of original RP. The application of crowded conditions can be used as a new way to enhance the reaction, improve the solubility of rice protein, while retaining the protein structure, thus contributing to the industrialized application of rice proteins.