Extracted Collagen Protein And Collagen Peptide Preparation From The Yak Skin

China has a wealth of yak resources.The various components in yak skin has significant functional properties because of its unique environmental advantages,such as anti-hypoxia,anti-rheumatism and other effects.This article focuses on the related research on collagen in yak skin.Three kinds of collagen were extracted and their physicochemical properties were determined.Next,free radical scavenging rate was used as an index to hydrolyze collagen to prepare collagen antioxidant peptide and optimize the enzymolysis process.Thus,the functional properties and stability of antioxidant peptides in different environments were explored.Finally,a variety of separation methods were used to fractionate the antioxidant peptides and determine the antioxidant capacity of different peptides to obtain the target peptide with high antioxidant activity.It will lay a certain theoretical foundation for further enriching the field of collagen research and obtaining high-quality collagen.The main research results are as follows:Yak skin was utilized to prepare the acid-soluble collagen?ASC?,pepsin-soluble collagen?PSC?and hot woter soluble collagen?HWSC?,whose structures and properties had been analyzed.The results of FTIR and SDS-PAGE showed that ASC and PSC were type I collagen with three-helix structure,the structure is??1?₂?2.But HWSC becames gelatin because of degeneration;Imidates analysis showed that the amino acid contents of ASC,PSC and HWSC were 264.1 residues/1000 residues,276.6 residues/1000 residues and 274.9residues/1000 residues,respectively,which showed high thermal stability.Scanning electron microscopy?SEM?observation shows that the structure of PSC is relatively loose with more voids than ASC and HWSC.Self-assembly turbidity experiments showed that the degree of assembly of PSC is higher than that of ASC,which had better fibroblast capacity.Transmission electron microscopy?TEM?showed that ASC and PSC had a typical D-periodic striation with D-cycles of?68.2±5?nm and?69.3±3?nm,respectively.?2?In order to obtain collagen anti-oxidant peptides,using·OH,DPPH·,and O₂^-·radical scavenging rate as an indicator,alkaline protease,neutral protease and papain were used to hydrolyze yak skin collagen.The results showed that the alkaline protease hydrolyzate had the highest free radical scavenging activity.On the basis of single factor,response surface analysis was performed with·OH scavenging rate as the response value,and the enzymolysis conditions were optimized by using enzymolysis time,enzyme dosage and substrate concentration as independent variables.Finally,the optimal hydrolysis conditions were as follows:hydrolysis time 6.99 h,enzyme dosage 6355.04 U/g,substrate concentration 3.55%.The·OH radical scavenging rate obtained under the optimal conditions was 83.12%.?3?The functional properties of yak skin collagen antioxidant peptide such as solubility,water absorption,emulsification,foaming and oil absorption were studied.Antioxidant peptide solubility was higher than 85%.Emulsifying property and foaming property all showed the tendency of decreasing and then increasing with the increase of p H.Antioxidant peptides have good water absorption and poor water retention.At temperatures up to 40°C,antioxidant peptides have the greatest ability to absorb oil.However,its water holding capacity and foam stability are relatively low.Antioxidant peptide stability assay showed that the yak skin collagen antioxidant peptide has good heat resistance.The retention of antioxidant activity under acidic conditions?p H?6?is higher than that of alkaline conditions.After in vitro simulated gastrointestinal reactions,the antioxidant capacity decreased to about 60%,but still has a certain ability to withstand gastrointestinal enzyme digestion.?4?According to different molecular weight and polarity,and using ultrafiltration,gel filtration chromatography and reverse phase high performance liquid chromatography techniques,yak skin collagen antioxidant peptides were isolated and purified,then the strongest free radical scavenging activity were obtained.Finally,the amino acid sequence of the antioxidant peptide of yak skin collagen was identified as Phe-Leu-Pro-Gln-Pro-Pro-Gln-Glu with a molecular weight of 954.5 by mass spectrometry.