Study On The Casein Enzymatic Characterization

Caseins contain4major caseins: αs1-casein, αs2-casein, β-casein, κ-casein.αs1-casein andαs2-casein collectively referred to as α-casein. All3major caseins were separated, and thepurity of each peak was assessed using SDS-PAGE, the purity of the three components were89.50%,96.51%,90.99%. Casein, α-casein, β-casein and κ-casein, were subjected tohydrolysis with trypsin for a period of time, this topic analysis the degree of hydrolysis,molecular weight distribution, the secondary structure and particle size distribution abouthydrolyzates. Analysis of casein and its components on the difference in sensitivity of trypsin,combination of the hydrolysates molecular structure and microstructure variation, clarify theintrinsic relationship between protein composition and structure and enzymatic sensitivity.The casein and the three components were hydrolyzed by trypsin for72h. The degree ofhydrolysis showed a very significant increase trend (P<0.01). The degree of hydrolysis ofα-casein hydrolyzate increased with different rates of linear form. There is no apparentfunction form between the changes in the degree of hydrolysis and enzymatic time of β-caseinand κ-casein protease.Hydrolysates of four proteins with Fourier transform infrared spectroscopy scan, thesecondary structure of the casein changes significantly were the increased of β-sheet and thereduction of β-turn, α-casein hydrolysates produced more β-turn structure.β-sheet structureshowed a downward trend in β-casein hydrolyzate. It was obserered that α-helical content wasalmost no change and β-sheet content has a change but no law was found during thehydrolyzate of κ-casein protein from different periods.The molecular weight distribution of the casein and hydrolysates of the threecomponents were detected by SDS-PAGE and gel exclusion chromatography. The molecularweight of the casein and the three components after hydrolysis10min, the change is verysignificant (P<0.01), It can be seen that enzymatic fastest is κ-casein from the results in thetable of the gel exclusion chromatography, but in the SDS-PAGE electrophoresis, themolecular weight of β-casein enzymolysis after electrophoresis bands9.4kDa. No obviouselectrophoretic bands were observed of κ-casein and α-casein after enzymatic for1h.Thechange in molecular weight of four protein hydrolysates are gradually enzymatic polypeptidefrom the molecular weight of low molecular weight polypeptides.The particle size distribution of casein hydrolyzate and the three components ofhydrolysates were detected by a laser particle size analyzer. In the enzymatic process, since the colloidal stabilization structure is destroyed, the hydrolysates of protein aggregate in ashort time. The size range of the α-casein hydrolyzate increasingly concentrated and theparticle size is getting smaller and smaller. Within the beginning30min enzymatic, theβ-Casein hydrolyzate particle size distribution did not change significantly, and in the first10min, the particle size of κ-casein changes ignificantly, followed a similar trend asα-caseinother proteins.