Evaluation Of Antioxidant Function And Application Of Sheep Plasma Peptide

China is a big country of production and consumption of mutton and sheep blood is one of the main by-products,mainly used for processing blood sausage,blood tofu and other traditional food processing or used as forage blood meal,but most of the blood is discarded,causing great waste of resources and environmental pollution.In order to improve sheep blood utilization ratio and added value,the polypeptide sequence and function prediction software was constructed by Unity,and the sheep plasma peptide sequence and function after hydrolyzed by enzyme were predicted in this paper.On this basis,7 kinds of enzyme were used to prepare sheep plasma protein peptide,and the best protease was screened out and the technological conditions were optimized based on total antioxidant capacity.Ultrafiltration,Semi preparation high performance liquid chromatography(RP-HPLC),AKTA(Applied Komatsu Technology America)protein rapid purification system and high performance liquid chromatography quadrupole / electrostatic field high resolution mass spectrometry(HPLC-QE HRMS)were used to purify and identify the antioxidant peptides from sheep plasma.Finally,we evaluated the application effect of sheep plasma protein antioxidant peptide in the preservation of lamb patties,and the results provide ideas for the development and utilization of sheep plasma peptide.The main conclusions of this study are as follows:(1)The sequence and function prediction software of enzyme hydrolysate polypeptide was constructed.A protease database and a database of active peptides with known functions and sequences were established,and 456 data were collected.The active peptide database contained information about the function,amino acid sequence,isoelectric point(PI)and references of the active peptide.The protease database contains the source of the protease,the site of the enzyme,the reference and so on.Sequence and functional peptide prediction software was established based on the database,and the database can be invoked by a polypeptide sequence and function prediction software program.The function of the target enzyme cut to the protein of the known primary structure is realized by the protease of the known enzyme cut site.The active peptide was matched with the active peptide database to predict the function of the active peptide,so as to realize the function of protein hydrolysis by single enzyme or several single enzyme.It is predicted by software that trypsin and chymotrypsin can be used to hydrolyse sheep plasma proteins to get antioxidative peptides.(2)The best protease to obtain antioxidant peptide from sheep plasma protein was screened and the preparation process was optimized.Based on the prediction results and practical applications,7 proteases,including alkaline protease,neutral protease,pepsin,trypsin,flavor protease,papain and chymotrypsin,were used to enzymolysis the plasma protein of sheep.The results showed that the alkaline protease was able to obtain the antioxidant peptide of sheep plasma with the highest total antioxidant capacity and high degree of hydrolysis.Using single factor test and orthogonal test,the total antioxidant capacity and degree of hydrolysis were used as indicators to optimize the technology of alkaline protease enzymolysis of sheep plasma protein.The optimal conditions were 55?,pH 11,6 h,and the total antioxidant capacity reached 36.27 ? 0.36 U/mL.(3)Polypeptide higher antioxidant activity in blood protein peptide prepared under optimal conditions were purified and identified,analyzed its antioxidant properties and amino acid sequence characteristics.Sheep plasma protein hydrolysate was under ultrafiltration by 10,5,3 kDa ultrafiltration group,the antioxidant activity of fraction which molecular weight less than 5 kDa was significantly higher than that of other ultrafiltration components.9 fractions could be obtained by semi preparation high performance liquid chromatography(RP-HPLC).The antioxidant activity of F1 and F2 was higher.After purification of AKTA protein fast separation and purification system,4 fractions were obtained by F1,and 5 fractions were obtained by F2.The antioxidant activity of F1-2 and F2-1 fraction was significantly higher than that of other fractions;F1-2 and F2-1 fraction were subjected to HPLC-QE HRMS.The spectrum identification is composed of 3 and 2 peptide segments,respectively.They were all 1000-2000 Da small peptides.The peptides contained abundant amino acids,such as glycine,histidine,lysine and other antioxidant peptides.(4)The effect of sheep plasma protein antioxidant peptide on the quality of mutton patties was studied.Sheep plasma antioxidant peptides can maintain the color stability of the mutton patties during storage by inhibiting the oxidation of lipid and protein.The 2% addition of plasma protein peptide can significantly inhibit the formation of high myoglobin,lipid oxidation and protein oxidation,improving the a* value of meat patties,and the effect is better than vitamin C treatment.The 1% addition has bacteriostasis,providing a new direction for the utilization of sheep plasma protein peptide.