Preparation, structural characterization and functional properties of a novel selenium chelating peptide derived from the hydrolyzate of wheat protein

Organic selenium has been widely studied for its ability to better fulfill the physiological functions of selenium. In this study, a novel organic selenium (wheat protein hydrolyzate chelated selenium, WPH-Se) was prepared by chelating the hydrolyzate of wheat protein hydrolyzed by alkaline protease (WPH) with selenium, its preparation process was optimized; and structural and functional properties were investigated. The results showed that the highest selenium content of 10.97 mg/g was obtained in the chelate under the optimal conditions (peptide/selenium mass ratio 2:1, temperature 80°C, pH 8, time 60 min). UV-Vis, FTIR, DSC and SEM provided more information for the characterization of WPH-Se. During the chelating process, selenium ions might be effectively bound to WPH through carboxyl, carbonyl and amino ligands, and the C=O bond and -NH, -OH groups might be the sites. At different pHs, the solubility of WPH-Se was generally lower than that of WPH, which reached a maximum of 32.69% at pH 6. The EAI of WPH-Se was higher than that of WPH, which reached a maximum of 0.84 m2/g, and the ESI reached a maximum of 47.3 min at pH 10. The free sulfhydryl content of WPH-Se was greater than that of WPH, which reached a maximum of 12.78 μmol/g at pH 8. WPH-Se was superior to WPH in terms of foaming ability and emulsification properties. WPH-Se contained a certain amount of aromatic amino acids (7.962%) and a relatively high amount of hydrophobic amino acids (38.490%), and had high nutritional value. Wheat protein peptide chelated selenium would be a useful functional additive, this study would provide data to support further research and application of selenium dietary supplements.