Abstract: In order to develop a kind of calcium supplement with high bioavailability, and improve added value of egg white protein, egg white was enzymatically modified and then chelated with calcium. Enzyme screening for the modification of egg white showed that the optimum hydrolysis mode for egg white was sequential hydrolysis with alcalase and neutrase. After this, process optimization for the enzymatic modification of egg white and chelating reaction between modified egg white and calcium was conducted using orthogonal array design. The optimal conditions for the stepwise double enzymatic hydrolysis of egg white were substrate concentration of 6%, alcalase/substrate ratio of 1:100, hydrolysis pH of 8.0 and hydrolysis time of 3 h; neutrase/substrate ratio of 1:25, hydrolysis pH of 7.0 and hydrolysis time of 3 h. In addition, the optimal preparation conditions for calcium-chelating egg white peptide were the ratio between peptide and CaCl2 (m/m) of 2.5:1, reaction pH of 9.5, substrate concentration of 4%, and reaction temperature of 55 ℃. Under the optimal conditions, the yield of soluble calcium and degree of hydrolysis were 21.15 mg/L and 8.66%, respectively. Therefore, sequential dual-enzyme hydrolysis method is better than single-enzyme hydrolysis method for the preparation of egg white peptide. The obtained egg white peptides can form a kind of bridging bidentate complex with calcium. The calcium content in the calcium-chelating egg white peptide was up to 8.75%.

Key words: egg white peptide, calcium-chelating egg white protein, enzymolysis, preparation