Preparation Of Oilgopeptides From Tilapia

China is the largest country for Tilapia production and the output increases annually,and its value-added processing becomes more and more necessary.In this paper,preparation of oligopeptides from Tilapia enzymatic hydrolysate using resins was investigated,the main results were as follows:(1)Preparation of enzymatic hydrolysate from Tilapia.The optimal technology is mixed of 5%cooked Tilapia homogenate with 2300u/g fish protein and reacted at pH 8.0 and 55℃for 4h, the undissolved solids in the slurries were removed by centrifugation.Under this enzymatic condition,the average degree of hydrolysis(DH) is 17.86%.(2)Removal of free amino acids from the enzymatic hydrolysate.Amino acids were separated from the enzymatic hydrolysate using cation exchange resin 732.The adsorption condition of free amino acids by cation exchange chromatography was pH3.0 and the flow rate kept at 1mL/min;amino acids were desorbed with 1mol/L NaOH at elution rate 1mL/min.The changes of remaining protein(or polypeptides),amino acids content and average hydrolysis degree in the eluant showed that cation exchange resin 732 had high capacity for adsorbing free amino acids but not for peptide.The adsorption for free amino acids accounts for 82.16%but only 36.30%for peptides.However,there was no significance between the average hydrolysis degree changes.Apart from free amino acids,some small molecular peptides which have high percentage of alkaline amino acids were also eluted by 1mol/L NaOH.The elution rate was 78.07%.(3)Seperation of oligopeptides.Static exchange experiment indicated that macroporous resin AB-8 effectively adsorbed oligopeptides from free amino acids-removed enzymatic hydrolysate. The condition for macroporous resin chromatography was optimized by analyzing the changes of oligopeptides ultraviolet adsorption,amino nitrogen content,average hydrolysis degree,average peptide chain length,fischer ratio and ion chromatogram.The purified enzymatic hydrolysate was passed through the column directly and the flow rate kept at 1mL/min;oligopeptides were eluted with 5%ethanol at 1mL/min.Oligopeptides with average peptide chain length from 1.18 to 6.43 were obtained.However,the ultraviolet spectrum and amino acid analysis of oligopeptides showed that the oligopeptide contains more than 6 kinds of amino acids,indicating that the products were not highly purified.