Abstract: The present work aimed to improve the bioavailability of zein. We employed microbial transglutaminase as a biocatalyst, and chitosan with a molecular mass of 1 500 Da as an acyl acceptor to modify zein by glycosylation reaction. The functional properties of glycosylated zein were studied in comparison with its intact and cross-linked counterparts. The results of Fourier transform infrared (FT-IR) spectroscopy and free amino group content indicated that chitosan was covalently conjugated to zein under the catalysis of transglutaminase. The surface hydrophobicity of glycosylated zein was decreased significantly compared with that of the original and cross-linked ones, suggesting a significant improvement in the water solubility of zein. Meanwhile, antioxidant activities, including 1,1-diphenyl-2-picrylhydrazyl (DPPH), superoxide anion and hydroxyl radical scavenging activities, reducing power and Fe2+-chelating capacity of glycosylated zein were increased significantly, and its EC50 value for DPPH radical scavenging activity was 0.945 mg/mL. Water-binding capacity, oil-binding capacity, emulsifying properties and the absolute value of Zeta potential of glycosylated zein were decreased significantly. These results can provide a basis for the application of glycosylated zein in the food industry.

Key words: zein, chitosan, transglutaminase, antioxidant activity, physicochemical properties