Preparation Of Yak Bone Collagen Peptide Chelating Calcium

This paper selected yak bone as materials to prepare calcium chelating peptides. The yak collagen peptides was prepared by hydrolyzing with protease using peptide yield as the main index of single factor and response surface experiment and the experiments were used to optimize the hydrolysis conditions. Extracted soluble calcium from yak bone powder after hydrolysis, extraction conditions were optimized by single factor and response surface experiment too. On this basis, lab made peptides and calcium were chelated also under the optimization of single factor and response surface experiment. Ultraviolet Spectrophotometry, Infrared Absorption Spectrosco--py, X-ray Diffraction and Scanning Electron Microscope were used to analysis the structure of calcium chelated yak bone collagen peptides.And it's digestion characteristics and stability were also studied in this experiment,the results are as follows.Alkaline was selected as the optimal protease. The best enzyme hydrolysis conditions were:substrate concentration of 3.5%, Ratio of enzyme to substrate 4000 U/g, pH7.0, reaction time 4h,temperature 50?,in this case polypeptide yield was 22.06%. Choose hydrochloric as the best acid, the optimum extraction conditions were temperature 67?, time 75min, hydrochloric acid volume 18mL, hydrochloric acid concentration 1mol/L,on this condition extracted calcium content is 112.18mg/g. Lab made calcium as chelate source, the molecular weight of each peptide segments after ultrafiltration were chelated with calcium and between 2kD and 5kD were found with the highest chelating rate. Optimal conditions were peptide calcium ratio 2:1, pH8.0, polypeptide concentration 25mg/mL,time 90min and temperature 45?,at this time chelating rate was 76.04%.UV absorption scanning analysis showed the sample after chelation had blue shift. Infrared analysis indicated that the absorption peaks of calcium chelating peptides appeared red shift, blue shift, disappear and increase, collagen peptides and calcium chelation reaction occurred and its site maybe is the amino, carboxyl of collagen peptide side chains and internal peptide bond. X-ray diffraction analysis showed that after the chelating peptide produced a new absorption peak and generated a new material. After scanning electron microscopy find samples before and after chelation shape and texture changed.The stability of the calcium chelating peptides is high in alkaline, neutral environment, slightly in acidic. Temperature 80? treatment 10min to 60min had no significant effect on the stability. Gastrointestinal digestion simulation showed that the calciums in samples were slowly released during the 2 hours digested in simulated gastric environment. Then after simulated digestive the calcium dissolution rate was gradually reduced and finally remained at 50% around.