| The natural source of antioxidant peptides has potential application in the field of food and medicine which has attracted researcher's attention worldwide.As new kind of high quality protein resources,pecan meal protein is of high nutritional value for the functional food development and consumption.The main focus of this research is to extract the walnut protein,followed by preparation,isolation and purification of antioxidant peptides and antioxidant activities in vitro and in vivo.1.According to the degree of hydrolysis and total antioxidant activity as index;through single factor experiment,the pecan meal antioxidant peptide hydrolysis process response surface method and the optimum process were as follows: Alcalase alkaline protease as enzyme source,temperature 58,time 3 h,enzyme concentration 5700 U/g,p H 8.5.Under this optimal combination,the absorbency is 0.276,and the total antioxidant value is the highest.2.By ultrafiltration membrane filtration of pecan antioxidant peptide crude preparation,pecan antioxidant peptide crude <3KDa,3-5KDa,5-10 KDa and >10KDa four kinds of pecan antioxidant peptide according to molecular weight,and physicochemical properties of these four peptides were determined: pecan enzymolysis kinetics model DH=3.3036ln[1+(5.8372E0/S0+0.1503)t],the experimental results showed that the model is reliable.The solubility of pecan protease in different components was related to p H,and the solubility was the lowest at the isoelectric point,and the solubility increased gradually under the alkaline condition.With the increased molecular weight of pecan peptide,the solubility of the hydrolysates of the pecan meal was reduced.After pecan protein hydrolysis,water holding and oil holding property decreased,the water holding capacity of the highest component was 2.59 m L/g,and the oil holding capacity was 1.77 m L/g.Pecan protein hydrolysates of emulsifying and emulsion stability,foaming capacity and foaming stability in the test range of p H had similar changes,the lowest at isoelectric point.With the increase of p H its emulsifying properties and foaming properties were increased under alkaline conditions conducive to processing product of the enzyme,and the four group showed no obvious difference.The results of differential thermal scanning of pecan peptide showed that the peptide after enzymatic hydrolysis had a better resistance to heat.3.The <3KDa group obtained by ultrafiltration separation after the product of Pecan polypeptide points had the strong antioxidant activity.Therefore,<3KDa polypeptide by intragastric administration in mice showed that the antioxidant activity of the components of pacan peptide was high and can improve SOD,CAT and GSH-Px activity and decrease the content of oxidation products of MDA in the serum,liver and spleen in certain concentration dependent manner.Two different components,B1 and B2,are isolated and purified by the DEAE-52 anion exchange column.The antioxidant activity of B1 was higher than that of B2.The obtained B1 components were further purified by dextran gel G-50,and two fractions of C1 and C2 with different molecular weight were obtained.Among them,C1 with high molecular weight showed strong antioxidant activity.C1 components were identified by reverse high performance liquid phase mass spectrometry(LAYLQYTDFETR).The scavenging capacity of hydroxyl radical,DPPH radical scavenging and ABTS radical scavenging capacity of the new antioxidant peptide were 47.42%,56.25% and 67.67%,respectively,after 0.1mg/m L synthesis. |
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