The role of heating time on the characteristics, functional properties and antioxidant activity of enzyme-hydrolyzed rice proteins-glucose Maillard reaction products

This study analyzed the influence of Maillard reaction on the physicochemical, functional properties and antioxidant activity of hydrolyzed rice dreg protein. Maillard reaction between glucose and rice dreg protein hydrolysates produced from various proteases, including trypsin, Neutrase 0.8L and flavourzyme were undertaken. The results of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis and FTIR spectrometer verified the occurrence of Maillard reaction and the formation of MRPs. Analysis on the structure and characteristics of Maillard reaction products (MRPs) at different heating time revealed that the pH of MRPs decreased sharply in the early stage, while the browning intensity of MRPs largely improved. The grafting degree of the MRPs increased to maximum at 90 min and then declined. All amino acids content was decreased with the extended reaction time, and the degradation of lysine and arginine was rapid. The Maillard reaction and the thermal degradation were dominant before and after 90 min, respectively. The solubility of MRPs remained stable independent of the heating time while the emulsifying activity improved at extended reaction time. The MRPs obtained greater antioxidant activity after the Maillard reaction. • Maillard reaction between glucose and rice protein hydrolysates were investigated. • Maillard reaction could be an effective method to improve the emulsifying activity. • The MRPs obtained greater antioxidant activity after Maillard reaction. • The Maillard reaction and the thermal degradation process are separated at 90 min.