Polypeptide Preparation Of Sheep Liver Protein And Its Antioxidant Activity

Sheep liver is one of the by-products of mutton processing,which is rich in protein,fat,carbohydrate,calcium,phosphorus,iron,thiamin,niacin,ascorbic acid,vitamin A and other nutrients.In addition,the sheep liver also has the effect of nourishing the liver,improving eyesight,and blood.Due to the lower processing level of mutton processing enterprises in China,most sheep liver in addition to selling to businesses processed into feed,also as the raw foods such as cold fresh retail for catering enterprises,low added value,and resources have not been fully utilized.According to reports,the protein content of the sheep liver is higher,about 17.90 g/100 g and contains a variety of bioactive substances.So the protein resource of sheep liver byproduct needs further development.In this paper,sheep liver as raw material,the basic nutritional components of sheep liver were analyzed.The optimal protease was obtained from alkaline protease,neutral protease,trypsin and papain by alkaline protease as an index.Based on the single factor test of the effects of enzyme dosage,pH,enzymolysis time,ratio of material to liquid and hydrolysis temperature on the degree of hydrolysis,the optimum enzymatic hydrolysis conditions were as follows: the enzymolysis temperature 51 ?,pH 8.5,enzymolysis time 4.1 h,enzyme content 0.40%.The results showed that the hydrolyzate of the sheep liver was(40.31 ±0.24)% under the optimum conditions of enzymatic hydrolysis.The ultrafiltration separation of sheep liver protein peptides were carried out by using hollow fiber ultrafiltration membrane module with molecular weight of 3KDa and 10 KDa.The components of SLP-?(<3KDa)? SLP-?(3~10KDa)? and SLP-?(>10KDa)were obtained.The components of SLP(sheep liver hydrolysate)and ultrafiltration components of the physical and chemical properties were studied.The results showed that the physical and chemical properties of the components with different molecular weights were different,and they had certain solubility,emulsifying and emulsifying stability,foaming and foaming stability,water holding capacity,oil holding property and good viscosity characteristics.Analysis of the amino acid components of the four components,which were full of amino acids,rich in nutrients,and contain 17 amino acids.The content of essential amino acids,hydrophobic amino acids,branched chain amino acids and aromatic amino acids in components of SLP-II(3~10KDa)were the highest among the amino acids in different molecular weight components.The antioxidant amino acids and umami amino acids of SLP were the highest.The sheep liver polypeptide of different components had certain antioxidant capacity and the ability of DNA damage protection.In the determination of scavenging DPPH free radical,hydroxyl radical and superoxide anion free radical,ABTS free radicals,reducing power,chelating metal ion capacity,the molecular weight of 3~10KDa(part SLP-?)was the strongest antioxidant activity.In the protective effect of DNA damage,the component SLP-?(molecular weight less than 3KDa)had the strongest protective effect on DNA damage.