Study On Increasing Calcium Absorption Effect With Collagen Polypeptides From Skin Of Walleye Pollock

The coastline in our country is so strip and the fishery resources are very rich.Marine fisheries is one of the fastest growing industries of our country in recent years,and the aquatic products processing as well as the high value of the resourceutilization has become an important issue of marine fisheries. Aquatic productsprocessing produces large amounts of scraps and wastes. But little is used to producefish meal or fish feed and the utilization is low. These not only result in an enormouswaste of resources, but also pollute the environment. The skin of Walleye Pollock isused as raw material of the paper. Gelatin is extracted with hot water and brokendown by enzymes into collagen polypeptide which is separated into series ofpolypeptide. The increasing calcium absorption effect of collagen polypeptides isstudied with promoting calcium absorption test on rats. The mechanism of promotingcalcium absorption with collagen peptides is investigated preliminary by testing thecombination of peptide and calcium in solution and simulated digestion study. Themain research results are as follows：1、The main component of Pollock skin is moisture. The protein content accountsfor95.40%of the total dry matter content and collagen accounts for73.26%of thetotal protein content. With the hot-water extraction method, gelatin is extracted6hunder the conditions of70°C and the extraction rate is15.12%. Composite enzyme ofalkaline protease and pancreatin are selected to hydrolyze collagen for about15min,120min,180min under conditions of50°C, pH8.0-8.2and enzyme-to-substrate ratioof l:200. After ultrafiltration, the hydrolysis product is concentrated by rotaryevaporation and lyophilized to obtain series of polypeptide powder of Mr.<2500Da,2500<Mr.<6000Da and Mr.>6000Da. The basic indicator measurement resultsshow that the purity of the collagen polypeptide can reach85%or more, and theaverage molecular weight of each rung polypeptide powder is within the range of the molecular weight of the peptide to which it belongs.2、Using rats as experiments, calcium deficiency model is built with self-madelow calcium diet. Series of polypeptide powder which is not bound specifically withinorganic calcium source is gavaged in vitro to explore the increasing calciumabsorption effect of series of polypeptide. The measured results show: The peptidescan promote the growth of rats. The high molecular weight collagen peptide cansignificantly increase the calcium absorption rate. While the medium and lowmolecular weight collagen peptide can very significantly increase the calciumabsorption rate in rats. The high molecular weight collagen peptide can improve thecalcium retention, the medium molecular weight collagen peptide can significantlyimprove the calcium retention rate, and the low molecular weight collagen peptidecan very significantly improve the calcium retention rate. The collagen peptide canimprove femur index of rats and promote bone growth. It can increase bone calciumcontent and the smaller the molecular weight is, the more obvious the effect is.Thetested peptides can increase the calcium and phosphorus content in serum andimprove the alkaline phosphatase activity. In summary, the collagen peptides canpromote calcium absorption well in rats.3、The solution is prepared with the proportion of peptide and inorganic calciumin animal experiments. By purification and preliminary identification of compound insolution, the peptide is predicated to bind calcium into soluble complex compound ofpeptide and calcium. By assaying the changes of chelation rate, we find that thecomplex compound has good low temperature stability. Under high temperatureconditions, the peptide may be denatured and is not conducive to bind calcium and thechelation rate will be low. Under slightly acidic or alkaline conditions with pH of2.0or9.0, the H+or OH-can interfere with the combination of peptide with calcium. Butunder neutral conditions with pH of7.4, the calcium ions can bind the amino groupand carboxyl strongest. The coexisting components lactose is conducive to thecombination of peptide with calcium and cellulose not. With the changes of chelationrate in analog digestion test, we find: Bound with peptide to form soluble complexes, calcium can avoid forming insoluble precipitates by the other ingredients in thedigestive tract. While the small peptides can also combine calcium to ensure thecalcium reach the site of calcium absorption smoothly and promote the intestinalabsorption of calcium. This also helps to explain the promoting calcium absorptioneffect of collagen polypeptide in animal experiments and the mechanism of promotingcalcium absorption of collagen peptides in the intestine is investigated preliminary.