| Collagen is widely used in food,cosmetics and medical treatment,and has become an irreplaceable part of people's lives.With people's doubts about the safety of collagen from terrestrial mammals,and some religious restrictions,collagen and its derived products from aquatic products have attracted more and more attention and needs from the public.The by-products of fish products processing contain a lot of collagen,but the utilization rate is extremely low,resulting in waste of resources.Therefore,the extraction of collagen from these processing by-products is studied.The application of protein has very important significance.The traditional extraction method is inefficient,so it is of practical significance to study the method of ultrasonic pretreatment assisted acid enzyme combined extraction.Collagen macromolecules cannot be directly absorbed and utilized by the human body.The more widely used method is collagen peptides.For example,collagen peptides chelate with calcium ions to form Peptide-calcium chelate as calcium supplements.Because the types of collagen enzymatic hydrolysis products are closely related to enzymes and enzymatic hydrolysis environment,the collagen peptides obtained by common enzymatic hydrolysis methods are quite different from the real digestion products of the human body.Therefore,it is of great significance to simulate the preparation of collagen peptides and Peptide-calcium chelates that are closer to human digestion products.In this paper,first of all,using the skin from the processing by-product of white carp as the raw material,the three methods of acid extraction,acid enzyme combined extraction and ultrasonic-assisted acid enzyme combined extraction were studied to optimize the extraction process and determine the collagen configuration;Then use in vitro simulated digestion to judge the optimal digestion site of collagen,determine the target collagen polypeptide with high oxidation resistance,based on the enzyme membrane coupling in vitro simulation of the optimal digestion site digestion environment,and use ultrafiltration device to efficiently prepare the target collagen polypeptide;Finally,use the target collagen polypeptide and calcium supplementation is used to prepare peptide-calcium chelate.The chelation conditions,changes in properties and morphology after chelation and the stability of chelation products were studied,and calcium chelate peptides were identified..The main research contents and results are as follows:(1)Using white carp processing scraps(skin,scales,fins)as raw materials,it was found that the collagen contained in the fish skin is as high as 0.36 ± 0.05 g/g,and it is easier to extract,the extraction rate is 13.89 ± 0.81%.Make sure that fish skin is the best raw material for collagen extraction.Collagen is extracted by acid extraction,acid enzyme extraction and ultrasonic pretreatment assisted acid enzyme extraction to obtain collagen products ASC,APSC and UAPSC respectively.It is found that among the five acids of lactic acid,citric acid,acetic acid,hydrochloric acid and nitric acid,lactic acid is the best acid for acid extraction,and the extraction can reach 13.89 ±0.81%.The extraction rate of collagen extracted with lactic acid and pepsin increased to 37.92 ± 0.98%(2.73 times that of acid extraction).After ultrasonic acid pretreatment on the basis of acid enzyme extraction,the optimal ultrasonic conditions are optimized to be 60 k Hz,180 W,15min,and the collagen extraction rate can be significantly improved to 75.81 ± 0.40%(5.47 times that of acid extraction).And infrared spectroscopy,circular dichroism spectroscopy and ultraviolet spectroscopy can show that the three methods of extraction are all type ? collagen.Ultrasound-assisted acid enzyme combination method can be used as an efficient collagen extraction method.(2)Next,the collagen digestion characteristics were studied,and the degree of hydrolysis,molecular weight changes,and oxidation resistance during the simulated oral-gastric-intestinal digestion process were dynamically monitored to determine that the main digestive site of collagen is the intestine.The product collagen peptides were analyzed by molecular weight,and four fractions of 0-1 k Da,1-3 k Da,3-5 k Da,and>5 k Da were obtained.The collagen peptide with a high antioxidant activity and a molecular weight of less than 3 k Da was determined as the target product..Collagen peptides with molecular weights less than 3 k Da were prepared based on enzyme membrane coupling in vitro simulated intestinal digestion using ultrafiltration devices.The optimal preparation conditions were optimized: the substrate concentration was1.5%,the speed of the peristaltic pump was 300 m L / min,and the amount of enzyme added was 2000 U / g.And it was determined that the collagen polypeptide has better hygroscopicity and water holding capacity than collagen,the collagen polypeptide has better foaming property and better emulsion stability under alkaline conditions.The research provides a theoretical basis for the application of collagen peptides.(3)Finally,the collagen peptide-calcium chelate was studied,and the prepared low molecular weight peptide was chelated with calcium ions to obtain the best chelating process for peptide calcium chelation: peptide calcium mass ratio 2:1,p H 8,temperature 50?,time 10 min.Under the best conditions,the calcium chelating ability can reach 22.16 ± 0.55 mg/g.IR analysis showed that calcium ion formed Peptide-calcium chelate with collagen polypeptide mainly through carboxyl oxygen,hydroxyl oxygen and amino nitrogen.Particle size and circular dichroism analysis showed that calcium ions folded peptides to form irregular granular nanoparticles with smaller particle sizes.SEM showed that calcium ions significantly changed the morphological structure of collagen peptides.Stability analysis shows that the prepared Peptide-calcium chelate can be properly thermally processed,the calcium retention rate is maintained at about 90% in the range of 50-90?,and is more suitable for addition to neutral foods,which can maintain a higher calcium retention rate.Peptide-calcium chelates have higher resistance to pepsin and trypsin and maintain a higher calcium retention rate in the presence of the two enzymes.And 10 kinds of calcium chelating peptides were identified. |
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