Study On Functional Properties Of Bovine Collagen And Antioxidant Activity Of Polypeptide

Collagen HWSC,PSC and ASC were obtained by hot water extraction,enzyme extraction and acid extraction,respectively from bovine nose meat.The surface morphology of ASC was the same as that of PSC,showing uniform multi-layer aggregated structure.While the structure of HWSC was mostly irregular sheet.The absorption intensities of the main characteristic peaks of the FTIR spectra of the three collagen proteins were different,but the spectral positions were almost the same.The content of glycine was the highest in total amino acids in ASC,PSC and HWSC,accounting for 32.4%,31.8%and 31.6%,respectively.And the content of amino acids were 20.2%,20.3%and 19.5%respectively.None of the three extraction methods changed the triple helix structure of collagen.And all the three collagen samples were type I collagen.Collagens were mainly composed ofα₁chains（130 k Da）andα₂chains（120 k Da）.High molecular weightβ-components about 140 k Da were observed in three collagens,which confirmed the presence of intermolecular crosslinking.But PSC produced more additional bands below 100 k Da.The Td of ASC,PSC and HWSC were 92.89℃,98.86℃,and 86.73℃,respectively.The Tm values of ASC,PSC and HWSC were 207.41℃,201.9℃and 206.5℃,respectively,indicating the destruction of the internal crystal structure of collagen.The thermal degradation temperatures of ASC,PSC and HWSC were similar and were 301.24℃,307.14℃and 302.31℃,respectively.The thermal denaturation temperatures of PSC were the highest,followed by that of ASC.The solubilities and foaming properties of the three collagens in acidic environment were much higher than those in alkaline environment.Both the EAI and ESI of ASC and PSC were superior to that of HWSC and had good emulsifying properties.Three collagens were pseudoplastic fluids,while ASC was more prone to shear thinning behavior.PSC could form semi-solid gel,and HWSC was harder and less prone to deformation than ASC and PSC.The lactation effect of collagen was investigated by establishing animal model.The lactation effect of collagen was tested by using bromocriptine to establish the animal model of postpartum hypogalactia in mice.Compared with the blank group,the daily lactation of the mother rats and the net weight gain of litter were significantly increased in the collagen experimental group.The subcutaneous mammary glands of female mice in the experimental group were widely distributed in the chest and abdomen.The mammary tissues were hypertrophic and the glands were pink.The appearance of the mammary glands of female mice were basically the same as that of the blank group,and the mammary glands index were also significantly increased.In the HE staining experiment,the number of acinar cavities and ducts in the mammary gland of female mice increased and the proliferation expanded in the experimental group.The interlobular adipose connective tissues in the mammary glands decreased.And the mammary gland lobules basically returned to normal,which reached a similar degree to the structure of female mice in the blank group.The concentrations of prolactin in serum and mammary tissues of the experimental group were significantly higher than that of the model group and showed no significant difference with that of the blank group.Collagen polypeptides were obtained by enzymatic hydrolysis of collagen with alkaline proteases.And enzymatic hydrolysis of collagen were optimized on the basis of single factors and response surfaces.The optimal conditions of enzymatic were concentration of 2%,p H 8.09,enzymatic temperature of 55.4℃and enzymatic time of 5 h,the reducing power value of collagen peptide was 0.405.Using glutathione（GSH）as control,collagen polypeptides and antioxidant activities were comprehensively evaluated from five aspects of·OH radical scavenging,DPPH·radical scavenging,ABTS+·radical scavenging,reducing power and metal ion chelating abilities.Antioxidant capacity varied showed linear variation with the concentration of GSH and collagen polypeptide.At the same concentration,the DPPH radical scavenging ability,the ABTS+·radical scavenging ability and reducing power of GSH were stronger than those of collagen polypeptide.While the·OH radical scavenging rate and chelating ability of metal ferric ions of collagen polypeptide were higher than those of GSH indicating that collagen polypeptide had a good antioxidant function.