Research On Preparation Of Antioxidant Peptides Derived From Egg White Protein With High Activity And Its Synergist

Research on preparation of antioxidant peptides derived from egg white protein withhigh activity and its synergist was granted by the National863Key Technical Project（No.2007AA10Z329）. In the current work, five aspects had been researched, and themain conclusions are listed below:（1） The article first emphasized on the establishment of the regression model ofantioxidant peptide preparation derived from egg white protein. Alcalase, pepsin, trypsinwere used to hydrolyze the egg white protein and optimized through preliminaryone-factor-at-a-time test and response surface methodology （RSM）.（2） The mathematical models obtained through RSM can be expressed by thefollowing quadratic equations.（3） In this study, the egg white hydrolysates, which were prepared by the alcalase,trypsin, and pepsin under their respective optimal and/or recommended conditions, weresequentially separated by the ultrafiltration membranes in the cut-off MW at30,10and1kDa. The collected fractions within different molecular weights were investigated andcompared for their antioxidant activities. The results showed that the AH showed higherantioxiadant activity than those of the TH and PH. Therefore, alcalase could beconsidered as the optimal proteinase for preparation of antioxidant peptide derived fromegg white protein.（4） DPPH, ABTS radicals scavenging, ORAC-FL test, and FRAP tests wereinvestigated to evaluate the antioxidant activity of the egg white protein （EWP） and itshydrolysates fractions with different molecular weight. All the results indicated the theEWP-III enjoyed the best antioxidant activity.（5） The EWP-III was further applied to Sephadex G-25column to obtain theseparated fractions by size exclusion chromatography. The DPPH radical and ABTSradical scavenging activities of the separated fractions were also tested. The resultsshowed that EWP-III-3exerted the best antioxidant activity, and could be considered as the antioxidant peptide.（6） The effects of temperature, pH and metal ions (inclusing NaCl, K+, Ca²⁺, Mg²⁺,Fe²⁺, and Zn²⁺) on stability of antioxidant activity of peptide derived from egg whitewere investigated. The results showed that the peptide from egg white could mamtain itsantioxidant activity below60℃and the most suitable temperature of peptide storagewas below25℃. When the temperature reached above80℃, the activity significantlydecreased （P<0.05）. The peptide kept its activity when the pH value was between4¹0.Especially, it had the best antioxidant stability at pH6.0.（7） In the study of synergist study, the effects of single or complex addition of NaCl,carbohydrate, citric acid on the antioxidant activity of peptide derived from egg whiteprotein was evaluated based on the index of DPPH radical scavenging activity. Theresults indicated that NaCl, maltose and citric acid could enhance the antioxidant activityof peptide derived from egg white protein significanlly（P<0.05）. They could be used asan antioxidant synergist single but reached up to the best effect when triadic combination.The best synergist combination obtained through RSM optimization was1.4%NaCl，3.0%maltose and0.24%citric acid. Under this condition, the IC50value of antioxidantpeptide derived from egg white protein on DPPH radical was0.27mg/ml and thesynergism value reached up to3.96.