Abstract:Casein was used as the raw material，trypsin was selected as hydrolytic enzyme，and calcium chelating activity was taken as the index. Single-factor test and orthogonal test were carried out for five factors including substrate concentration，enzyme amount，pH，temperature and enzymatic hydrolysis time. The structure characteristics of calcium chelated peptides and calcium peptide chelates under optimal enzymatic hydrolysis were characterized by high performance gel filtration chromatography，amino acid automatic analysis，uv-visible spectrum and infrared spectroscopy.The results showed that：7%substrate concentration，0.8%enzyme dosage，pH 8.7，53 ℃ hydrolysis temperature，and 3 h hydrolysis time were the optimal condi－tions with the activity of chelate calcium of 46.78 μg/mL. The relative molecular weight of peptides below 3 kDa in the optimal enzymatic hydrolysis accounted for 92.11%.Amino acids analysis indicated that the content of glutamate，serine and aspartic acid with strong chelating activity had increased significantly after chelating reaction.According to the results of ultraviolet and infrared spectroscopy，the structure of calcium chelated peptide changed significantly before and after the chelation.And its main binding sites were-NH2，-COOH.