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Preparation Of Bioactive Peptides From Fish Scale Gelatin By Emzymatic Hydrolysis

Posted on:2011-05-09Degree:MasterType:Thesis
Country:ChinaCandidate:J HuFull Text:PDF
GTID:2121360308964002Subject:Aquatic Products Processing and Storage Engineering
Abstract/Summary:PDF Full Text Request
Gelatin is derived from various animals and plants. The hydrolyzation of fish scales gelatin is a good way to enhance industrial utilization of ?sh gelatin, and alleviate the waste pollution problem. Alcalase, a specific protease, was selected to hydrolyze Tilapia Scale gelatin based on the current research findings on structure-activity relationship of bioactive peptides and primary structure of gelatin.The Angiotensin-I-converting Enzyme (ACE) inhibitory activity and the superoxide radical scavenging activity of hydrolysates were measured. Hydrolysates of fish scale gelatin were concentrated by ultrafiltration and their bioactivity were evaluated. The amino acid composition and molecular weight distribution of the bioactive peptides were studied. The impact of digestive proteases on ACE inhibitory activity and the superoxide radical scavenging activity of hydrolysates were evaluted. These bioactive peptides derived from fish scale gelatin show great promise in functional food.The protein content of fish scale gelatin were measured(90.15 %).The result from amino acid composition analysis showed that the content of hydrophobic and antioxidant amino acid were high, 39.43% and 48.83% respectively. The gelatin was rich in proline and hydroxyproline, which highly contributed to both ACE inhibitory activity and superoxide radical scavenging activity. Alcalase, a specific protease, was selected to hydrolyze Tilapia Scale gelatin. The optimal hydrolytic conditions for degree of hydrlysis (DH) were determined by response surface methodology based on single factor experiments. The results showed that the optimal hydrolytic conditions are temperature 54.5℃, pH 7.7, substrate concentration 1.8% and the ratio of alcalase / substrate 1.0%.The relationship between DH and bioactivity was studied under the above optimal conditions of Alcalase. These results showed that hydrolysates with different DH displayed different ACE inhibitory activity and superoxide radical scavenging activity. The unhydrolyzed gelatin showed no bioactivity. There existed a optimal DH (or hydrolyzing time) in the preparation of bioactive peptides by emzymatic hydrolysis. The hydrolysate showed the highest superoxide radical scavenging activity after 4h hydrolysis with DH 14.11%, and its 50% inhibitory concentration (IC50) was 0.36 mg/ mL. Whereas, the hydrolysate showed the highest ACE inhibitory activity after 6h hydrolysis , and its IC50 was 0.56 mg/mL with DH 15.54%.A RP-HPLC assay was developed for determination of ACE inhibitory activity of samples by modification of traditional spectrophotometric assay. Methanol-water(60∶40, with 0.1%TFA)) was secleted as mobile phase in quantification of hippuric (HA). This method was showed to be less time consuming without no need to extraction HA from the ACE reaction mixture, and can be used for the screening of ACE inhibitory peptides. The ACE inhibitory activity and the superoxide radical scavenging activity increased by ultrafitration with molecular weight cut-off 5000Da and 10000Da. The 5000Da permeates had the highest content of peptides and showed the highest bioactivity. These results suggested that ultrafitration was an effective technique to enrich for bioactive peptides derived from emzymatic hydrolysates of proteins.The amino acid composition and molecular weight distribution of the superoxide radical scavenging peptides were studied. These results showed that more than 80% peptides had molecular weight of less than 5000Da, and the component with the highest superoxide radical scavenging activity was rich in antioxidant amino acid. The amino acid composition and molecular weight distribution of the ACE inhibitory peptides were also were studied. More than 90% peptides had molecular weight of less than 5000Da. The retention rate of proline, hydroxyproline and tryptophane which significantly contributed to the ACE inhibitory activity were very high. The ACE inhibitory activity mainly derived from the peptides with proline, hydroxyproline and tryptophane as C-terminal.The impact of digestive prpteases on ACE inhibitory activity and the superoxide radical scavenging activity of hydrolysates were investgated by simulated gastrointestinal digestion. There were no significant diffreence in the both two kinds of bioactivity after simulated gastrointestinal digetion, suggesting that these hydrolysates were highly resistant to digestive proteases.
Keywords/Search Tags:Fish scale gelatin, Emzymatic hydrolysis, Angiotensin-I-converting Enzyme Inhibitory Activity, Superoxide Radical Scavenging Activity
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