Study Of Identification And Antioxidant Activity Of Peptides From Jinhua Ham

Jinhua ham is a prime example of traditional meat products from China.Although it is always used as a gift in people's life for its functional effects,the functional ingredients and mechanism have not been elucidated.Researches in the past several decades mainly focused on the material selection,processing optimization and the control of protein and fat degradation.The main objective of these studies was to improve the quality and flavor of the product.Consumers are concerned more about nutrition in modern times.Typically,Jinhua ham generally takes at least 8-10 months for the processing.During the long ripening period,muscle proteins are hydrolyzed to varying extents to produce many small peptides and free amino acids.With the gradual development of natural antioxidant peptides,the large amount of peptides generated during the processing of ham may have antioxidant activity on body functions that may ultimately influence health.In this study,the in vitro and in vivo antioxidant activities of peptides extracted from Jinhua ham were investigated.The effects of the extraction,processing and storage conditions and digestive stability on the antioxidant peptides were also studied.Several antioxidant peptides were isolated and identified.In addition,the possibility of practical application was also studied.The detailed contents and results are shown as follows:1 In vitro and in vivo antioxidant activity of peptide fractions extracted from Jinhua hamIn this study,the peptides were extracted from Jinhua ham.Free radical scavenging activity,Fe2+-chelating ability and lipid peroxidation inhibition activity in a linoleic acid emulsion system were measured.In vivo antioxidant activity of peptides extracted from Jinhua ham was investigated using animal models.Changes of antioxidant enzymes's activity and malondialdehyde(MDA)content of serum,liver,pancreas and duodenum in mice were developed.The degradation of lactic acid in the muscles was also detected for the comprehensive evaluation of physiological activity of peptides extracted from Jinhua ham.The results showed that when peptide fraction concentration was 1.5 mg/mL,·OH scavenging activity was up to 90%;when peptide fraction concentration reached 5 mg/mL,DPPH·scavenging activity was about 95%.Besides,Fe2+-chelating ability was significantly higher than that of BHT and GSH.In addition,it showed ability in lipid and protein peroxidation inhibition activity(P<0.05).Jinhua ham peptides fraction could significantly decrease the serum creatine content in mice,and the antioxidant enzymes catalase(CAT),glutathione peroxidase(GSH-PX)and total antioxidant capacity(T-AOC)returned to normal levels.The MDA content of pancreas and liver added with low level of Jinhua ham peptide fraction was reduced by 67%and 15%respectively than that of oxidation group(P<0.05).The activities of superoxide dismutase(SOD)and GSH-PX added with high level of Jinhua ham peptide fraction in the pancreas could be recovered to the normal level.Adding with Jinhua ham peptide fraction could improve the T-AOC of the duodenum;even low level of peptide group could increase the activity by 65%than the oxidation group(P<0.05).In addition,Jinhua ham peptides fraction could reduce the accumulation of lactic acid in the muscles of mice,indicating the antifatigue activity to a certain extent.In conclusion,the peptide fraction showed strong in vitro and vivo antioxidant activity.2 Stability of antioxidant peptides extracted from Jinhua hamThe effects of NaCl concentration,temperature,pH,light intensity and a simulated gastro-intestinal(GI)digestion were assessed to determine the stability of antioxidant peptides extracted from Chinese Jinhua ham.Antioxidant peptide fraction showed good stabilities when NaCl content was less than 6%,temperature was lower than 60?and withhold from light directly(P<0.05).However,the antioxidant peptide fraction lost antioxidant activities rapidly under alkaline condition.The results of a simulated GI digestion system showed that antioxidant activity increased with pepsin treatment but declined with further hydrolysis with trypsin.Pepsin was effective to hydrolyze peptides into smaller fractions leading to the increased exposure of internal hydrophobic amino acids,but trypsin could hydrolyze peptides into more free amino acids resulting in the decline in surface hydrophobicity which affected antioxidant activity of peptides.These suggest that antioxidant peptides extracted from Jinhua ham could maintain their antioxidant activities under the GI digestion.3 Purification and identification of antioxidant peptides extracted from Jinhua hamJinhua ham extracts were separated into five fractions(A-E)by size-exclusion chromatography.Each fraction was subjected to a simulated GI digestion system and fractions showing strong antioxidant activities were collected and subjected to LC/MS/MS spectrometry for further purification and identification.The results showed that fraction C,D and E possessed high·OH and DPPH·radical scavenging activity.After the GI digestion,the free radical scavenging activity of fraction C,D and E drastically decreased while the Fe2+-chelating ability increased to around 90%compared to initial activities of fractions C,D and E(P<0.05).Using MS/MS analysis,33 peptides were identified in these fractions.Several key peptides were selected for synthesis and determined their antioxidant activity.The strongest DPPH·radical scavenging activity was peptide GKFNV which showed 92.7%antioxidant activity at a concentration of 1 mg/mL and the peptide LPGGGHGDL showed the highest·OH scavenging activity.On the other hand,KEER may contribute to Fe2+-chelating ability in fraction C after GI digestion.In conclusion,Jinhua dry-cured ham seems to be a potential source of antioxidant peptides generated during the dry-curing process and GI digestion.4 Comparison of antioxidant activity of Jinhua ham and commercial dry-cured hams in United StatesThe objective of this study was to evaluate the antioxidant activity of peptides extracted from a wide variety of dry-cured hams produced in the southeastern United States.Commercial dry-cured hams were obtained from 6 different ham processors,representing curing and drying times ranging from 3 months to 2 years,and process variations used to produce the finished products including cooked,uncooked,smoked or unsmoked dry-cured hams.Low molecular weight peptides were extracted from each of the hams included in the study,followed by measurement of hydroxyl radical scavenging activity,2,2-diphenyl-1-picrylhydrazyl(DPPH)scavenging activity,Fe2+ chelating ability and antioxidant impact on linoleic acid by the ham extracts.Compared antioxidant activities between them and Jinhua ham to determine if differences in commercial ham processes and processing time could be related to production of antioxidant peptides.The results showed a wide range of salt concentration,peptide concentration and antioxidant activity,and Jinhua ham showed the highest salt content,low peptide content and antioxidant activity was higher than other 6 samples.The results of this study demonstrate that current commercial practices for production of dry-cured hams produce a wide range of antioxidant properties.Salt content can affect the activity of enzymes,which will induce the difference of peptide composition.Thus peptide composition is more important than peptide content in the antioxidant activity of peptide fraction.5 Peptides extracted from Jinhua ham as a natural antioxidant in Cantonese sausageThe present work was to apply the peptides extracted from Jinhua ham in Cantonese sausage as natural antioxidants for retarding lipid,protein oxidation and maintaining the antioxidant ability of enzymes.The peptides were individually added to Cantonese sausage with various concentrations of 0.01,0.03,0.05,0.07 g/100g.The Cantonese sausages were stored at 37? for 20 days and sampled at 0,5,10,15 and 20 day.The results showed that the antioxidant activity of peptides from Jinhua ham increased with the increase of peptide concentration.When peptide concentration reached 0.05 g/100g,its ability to inhibit lipid oxidation,protein oxidation and retain antioxidant enzymes activity was higher than the control group(P<0.05).The antioxidant activity of peptides against lipid oxidation was lower than the group added with BHT,but the ability of inhibit protein oxidation and retain antioxidant enzymes activity was higher than that from BHT group.In conclusion,the peptides extracted from Jinhua ham showed antioxidant activity in Cantonese sausage.