Characterization of Bovine Casein Tryptic Hydrolysates

Bovine casein was hydrolyzed with trypsin, the amino nitrogen and free amino acid content, as well as the degree of hydrolysis ( DH ) of hydrolysates were determined. The distribution of relative molecular mass was analyzed by SDS-PAGE electrophoresis and Sephadex-G50 gel chromatography. The results indicated that, under the condition of 50 g/L substrate concentration, pH 4.5, amount of the enzyme ( m )∶amount of the substrate ( m ) = 1∶1 000, the DH increased with the increase of hydrolysis time. The increase of DH was fast at the beginning, but after 3 hours, it slowed down, and the DH was 20.48% after 6 hours of hydrolysis. The essential amino acid content in hydrolysates was 73%～80% of the total free amino acids, this percentage decreasing with hydrolysis time. The relative molecular mass of hydrolysates decreased with the increase of DH . The distribution of relative molecular mass ranged from 2 500 to 3 400 after 2 and 3 hours of hydrolyzation.