Abstract: Ultrasonic was applied to assist the Maillard reaction between zein and dextran. The reaction conditions were optimized using one-factor-at-a-time and orthogonal array design methods and the reaction products were characterized for structural and functional properties. The results indicated that the maximum degree of grating (DG) of 18.28% was obtained under the following conditions: 50.15 min ultrasonic irradiation, ultrasonic power 300 W and sugar concentration 0.025 g/mL, which increased by 44.58% compared with that obtained by water bath heating. Fourier transform infrared (FTIR) analysis showed that zein covalently bound to dextran confirming the occurrence of glycosylation. Functional characterization showed that the solubility, emulsifying capacity, emulsion stability, foaming ability and foam stability of zein-dextran conjugate produced under ultrasonic irradiation were improved significantly compared with zein and hot water bath, which indicated that ultrasonic irradiation could promote the efficiency of glycosylation and improve the structure and properties of the products, broadening the scope of application of zein.

Key words: ultrasonic irradiation, zein, Maillard reaction, grafting degree, structural and functional properties