Preparation,Isolation,Purification And Structural Identification Of Antioxidant Peptides From Salted Egg White And Their Product Development

Salted egg white is rich in high-quality protein and has high nutritional value.However,salted egg white is usually discarded due to its high salt content.This causes a lot of high-quality protein resources to be wasted.On the other hand,the products,which ferment and decompose from salty egg white when exposed to the air for a long time will cause pollution to the air and water sources.In this study,salted egg white was used as a raw material to explore the enzymatic preparation,separation,purification and structure identification of antioxidant peptides from the salted egg white.The single factor and response surface method were used to optimize the craft recipe of salted egg white enzymatic hydrolysis product(SEW)peptide soft candy.The main research contents and results are as follows:(1)Pepsin,trypsin,dispase protease,alkaline protease and papain were used to enzymatically hydrolyze salted egg whites.The optimal protease for enzymatic hydrolysis of salted egg white was determined as a dispase protease by determining the content of peptide in SEW and the DPPH radical scavenging activity by SEW.the effects of substrate concentration,enzymolysis temperature,enzymolysis time,p H,and the amount of protease added on the content of peptides in the enzymolysis product of salted egg white and the DPPH free radical scavenging activity by SEW.The optimal process conditions which were obtained by single factor and response surface optimization: substrate concentration 4.8%,p H 6.6,enzymolysis temperature 52℃,and enzyme hydrolysis content 7000U/g for 4h.The content of peptide in SEW was 164.59mg/g,and DPPH free radical scavenging rate is 78.24%.(2)The SEW was separated by ultrafiltration into 3 components: <5KD(SEWI),5-10KD(SEWI)and> 10K(SEWII).The DPPH,ABTS free radical scavenging activity and reducing power were used to determine the antioxidant activity of each component.The results show that the components SEWI and SEWII have the strongest activity of DPPH and ABTS free radical scavenging activity.The free radicals scavenging activity of EWI and SEWII were 68.37% and 68.20% respectively when the concentration of DPPH was 10 mg/m L;the free radicals scavenging activity of SEW II and SEWI for ABTS was 80.43% and 75.72% respectively at 1 mg/m L.In addition,SEWII(0.294)and SEWI(0.252)also had a strong reducing activity.The results show that both SEWII and SEWI have strong antioxidant activity.In order to more accurately identify the active peptide structure,SEWI was selected for further purification.Eight fractions were purified from fraction SEWI by semi-preparative reversephase high-performance liquid chromatography(RP-HPLC).Fractions 1 and 6 showed strong antioxidant activities.VVHF(500.27Da)and DTQAMPFR(964.44Da)were identified in fraction 1,and WSL(404.20Da)and WMSP(519.21Da)were identified in fraction 6 using LC-MS/MS.(3)The optimal process conditions for the single factor and response surface optimization experiment of salted egg white peptide soft candy were: gelatin dosage28.3%,salted egg white peptide 3%,edible vanilla flavor 3%,sugar ratio 2.6 and citric acid 0.15%.,Under this optimized condition,the color,texture,taste,and flavor of the peptide soft candy were the best and the sensory score was 83 points.Antioxidation analysis results show that when the solid content of the salted egg white peptide soft candy solution was 125mg/m L,the DPPH free radical scavenging activity was 85.5%;the absorbance of reducing power was 0.356;The ABTS free radical scavenging activity was 73.7%.