Generation And Characteristics Of Antioxidant Peptides From Duck Meat During Post-Mortem Aging

A large number of small peptides and free amino acids are released,due to degradation of muscle protein by endogenous enzymes during post-mortem aging.Therefore,post-mortem aging not only contributes to meat tenderness but it may also generate peptide fractions with physiological significance,such as antioxidant effects.At present,the major studies on the antioxidant peptides derived from animal concentrate on enzymatic hydrolysis and fermentation,however little is reported on the generation and characteristics of antioxidant peptides during post-mortem aging.In this study,the changes of antioxidant activity of peptides in duck meat during 7 days of post-mortem aging were evaluated by chemical models in vitro.Then the antioxidant peptides were purified by using consecutive chromatographic methods and the amino acid sequences of the peptides were identified by LC-MS/MS.In addition,the effects of the processing conditions and a simulated gastrointestinal digestion on the antioxidant activity of small peptides were studied.At last,the effect of different cooking conditions and a simulated gastrointestinal digestion on the antioxidant activity of duck meat was also investigated.The details contents and results are shown as follows:1.In vitro antioxidant activity of small peptides from duck meat during post-mortem aging.The present research was performed to investigate endogenous release of antioxidant peptides in duck meat during post-mortem aging times(0 h,6 h,12 h,1 d,3 d and 7 d).As aging time increased from 6 h,the shear force values of duck meat were significant decrease,and the content of animo acids and small peptides(<5 kDa)was significant increased.The antioxidant activity of small peptides w.ere evaluated by the DPPH radical scavenging activity,FRAP,ORAC.The results showed that the small peptides possessed varying degrees of in vitro antioxidant activity.In addition,as aging time increased,the antioxidant activity of small peptides in duck meat increased significant.And the peptides formed in the samples after 3 days post-mortem exhibited highest DPPH radical scavenging,FRAP and ORAC.2.Purification and identification of antioxidant peptides from duck meat after post-mortem aging.Antioxidant peptides from aged duck meat were isolated and purified by ultrafiltration and gel filtration chromatographic,the initial extract was purified into three fractions(A-C)in which fraction C exhibited the highest antioxidant activity.In total 18 peptides were sequenced and identified in the fractions by LC-MS/MS.Among these peptides,the peptides of fraction C possessed the lowest molecular weight and consisted of the highest amount of hydrophobic amino acid,which might be responsible for the antioxidant property of aged duck meat.These six peptides were synthesized,and the DPPH radical scavenging activity,FRAP and Fe2+-chelating were evaluated.Among these peptides,the LINHA showed the highest DPPH radical savenging activity(93.54%).3.Stabilty of antioxidant peptides from duck meat after post-mortem aging.The antioxidant stability of small peptides from duck meat after 3 days post-mortem aging were evaluated in different conditions such as temperature and time,pH,NaCl concentration and a simulated gastrointestinal digestion.The antioxidant peptides preserved a high stability in the presence of diverse NaCl or upon various time heating.The antioxidant activitiy were strengthened by heating at 100?,whereas they were lost under alkaline conditions.During in vitro digestion,the antioxidant activity increased with pepsin treatment but then decreased following trypsin digestion.Pepsin hydrolysed peptides into short fragments and results in the increased exposure of internal hydrophobic amino acids.With further treatment by trypsin,peptides can be hydrolysed completely and more free amino acids were released,leading to the decline in surface hydrophobicity.4.Effect of cooking and in vitro digestion on the antioxidant activity of duck meat during post-mortem aging.The main purpose of this study was to investigate the effect of cooking temperatures(65?,100? and 121 0C)for different times(0 min,10 min,20 min and 30 min)on the antioxidant activity of small peptides from duck meat after 0 and 7 days post-mortem,the peptides were evaluted by the DPPH radical scavenging activity and reducing power.The results showed that the sample at 7 days post-mortem after cooking at different temperature was significant higher than that sample of day 0.In addition,the cooked samples possessed higher antioxidant activity than raw samples.The sample after cooked with higher antioxidant activity(65?-30 min,100?-20 min and 121?-10 min)were select for in vitro digestion,we found that the DPPH radical scavenging activity significant decrease but the reducing power significant increase after gastrointestinal digestion.