Preparation And Physicochemical Properties Of High Antioxidant Peptides Derived From Peanut Protein

The yield of peanut(Arachis hypogaea L)is abundant in China,meanwhile with large consumption.Peanut meal,as a main by-product of peanut oil,had been used in low-value products such as feed for a longtime.But peanut meal is high in protein content and amino acids,which is a high-quality plant protein material with high conversion value.The preparation and modification of high antioxidant peptides derived from peanut protein provide a great way to the development and utilization of peanut meal resources.In this study,peanut meal protein is used as raw material,the protein is modified by extrusion and ultrasonic treatment firstly.After,Alcalase was used to optimize the best enzymatic hydrolysis process through single factor and response surface experiments,and then ultrafiltration is used to separate the enzymatic hydrolysis products.The physical and chemical properties of the separated components were researched,the results are as follows:With peanut meal protein as the raw material,the extrusion technology and ultrasonic treatment technology were optimized through single factor experiments.The protein content and oil content were used as the response indicators to obtain the best process.The extrusion conditions were screw speed 150 r/min,moisture content 12%,and rod temperature 120?;ultrasonic treatment conditions are treatment time 25 min,material-to-liquid ratio 1:7.Under this condition,the protein content reached 54.11% and the oil content reached 6.00%.Using the degree of hydrolysis(DH)as an indicator,the peanut protein enzymatic hydrolysis process was optimized through single factor and response experiments.Through single factor experiment analysis,the optimal enzymatic hydrolysis process conditions were obtained as follows: temperature 55?,p H value 10.0,substrate concentration 5%,amount of enzyme added 6000 U/g,enzymatic hydrolysis time 160 min.Then the temperature(A),enzyme amount(B)and substrate concentration(C),which have the greatest influence on the degree of hydrolysis were analysised by the Box-Behnken combination of response surface experiments.17 groups of experimental programs were designed to found the optimal enzymatic hydrolysis process conditions.The optimal enzymatic hydrolysis process conditions combined with hydroxyl radical scavenging ability and ABTS free radical scavenging ability experiments,as follows: enzyme amount 7150 U/g,substrate concentration 6.0%,temperature 55.0?,p H value10.0,enzymatic hydrolysis time is 160 min.Under this technological condition,the hydrolysis degree of high antioxidant peptides derived from peanut protein reached 36.04%,the regression equation is well fitted,and the optimal process of the regression model is reliable and has practical value.High antioxidant peptides derived from peanut protein were separated and purified by ultrafiltration,3 components with molecular weights of >10 k Da,3-10 k Da and <3 k Da were obtained.The oxygen radical adsorption capacity(ORAC)experimental results showed that the group <3 k Da The antioxidant activity is the highest,with the ORAC value of 1684.98 ?mol/g TE,which is significantly higher than that of glutathione.The physical and chemical properties of each component were analyzed.The total free sulfhydryl group content and the exposed sulfhydryl group content in each component were <3 k Da,3-10 k Da and >10 k Da from high to low.The solubility test results show that the solubility of <3 k Da and 3-10 k Da components is significantly higher than that of >10 k Da components.The solubility of <3 k Da components is the lowest under neutral conditions,while 3-10 k Da and >10 Both k Da components appear under strong acid conditions.In the foamability experiment,the highest foamability value of the <3k Da component and the 3-10 k Da component was at p H=5,and the highest foamability value of the >10k Da component was at p H=1.<3k Da and 3-10 k Da have good foaming stability at p H=1.And in acidic medium,the foaming stability of 3-10 k Da component at p H=3 is much higher than <3k Da component and >10k Da Components.In the emulsification experiment,the emulsification of >10k Da component is better than that of 3-10 k Da component,while the <3k Da component is the worst.The emulsification stability with p H has the same trend as emulsification.In the water-holding and oil-holding experiments,the water-holding capacity of components >10 k Da is better,indicating that high antioxidant peptides derived from peanut protein has a well water-holding capacity and is less soluble in water.High antioxidant peptides derived from peanut protein with different molecular weights all have good oil retention,and the oil retention of each component is about 2 m L/g.The oil retention of >10 k Da is higher than the other two components,and the molecular weight and its oil retention are present proportional relationship.