Structural and functional properties of Maillard reaction products of protein isolate (mung bean,Vigna radiate(L.)) with dextran

The objective of this study was to determine the functional and structural properties of Maillard reaction products of mung bean [Vigna radiate (L.)] protein isolate with dextran obtained under the temperature of 80°C or 90°C with different times (0, 1, 2, 3, 4, 5, and 6 h). The mung bean protein isolate–dextran conjugate had better solubility, emulsifying activity, and emulsifying stability than mung bean protein isolate; however, the protein aggregation decreased the solubility, surface hydrophobicity, emulsifying activity, and emulsifying stability of mung bean protein isolate–dextran conjugate. In general, these functional properties of mung bean protein isolate–dextran conjugate obtained at 80°C with lower degree of glycosylation and browning degree were better than mung bean protein isolate–dextran conjugate obtained at 90°C. Both vicilin (8S) and legumin type (11S) globulins both participated in the graft reaction, the subunit with a molecular weight of 21 kDa that contributed to 11S globulin might be the most vulnerable to dextran followed by the 60, 32, and 26 kDa subunits. Maillard reaction between mung bean protein isolate and dextran led to a decreased fluorescence intensity and a bathochromic shift. The fluorescence intensity of mung bean protein isolate–dextran conjugate generally decreased, and λmax of mung bean protein isolate–dextran conjugate first increased and then decreased. The grafted mung bean protein isolates had lower α-helix content but higher β-sheet content. As the Maillard reaction between mung bean protein isolate and dextran proceeded, the α-helix contents of the mung bean protein isolate–dextran conjugates were significantly increased and then decreased, and the β-sheet content generally decreased and then increased. Excessive grafted dextran and more protein aggregation was observed in mung bean protein isolate–dextran conjugate obtained at 90°C, which induced structural changes that might have impaired the functions. Our findings suggest that conjugation of mung bean protein isolate with dextran through the Maillard reaction is an effective way of improving the functional properties of mung bean protein isolate for its application in the food industry.