Research On Process Of Preparation,Purification And Physicochemical Properties For Collagen Peptides Of Sturgeon Skin

China is the world’s largest freshwater fish breeding country where a lot of fish skin and scraps were produced in the couse of processing.The wastes most were abandoned or directly buried which not only caused environmental pollution, but also was a waste of resources. If the resources could be used to deep processing, it would bring huge economic benefits. This topic, as sturgeon raw materials, mainly studied the preparation, isolation, purification and its physical and chemical properties for collagen protein peptide of sturgeon skins, which provided a strong theoretical basis for collagen in further scientific research and application.Sturgeon is a kind of bony fishes, thick skin with bones which were not easy to be directly hydrolyzed. Therefore, this paper first studied acid treatment for the influence on collagen protein peptide of sturgeon skins by enzymatic hydrolysis. It showed that skins after swelling sturgeon with lactic acid became fleecy and were beneficial to be hydrolyzed lately. As hydrolysis degree and short peptide yield indexes, the result indicated that the best process condition of lactic acid treatment is lactic acid concentration2%, solid to liquid1:5, time2h, temperature30℃, the hydrolysis degree was as high as43.58%, short peptide yield was55.84%. However, without lactic acid swelling processing, the hydrolysis degree was only20.5%and reduced13.08%Contrasting to the treatment of the lactic acid. Visibly, acid treatment process had significant effect on the result of enzymatic hydrolysis later.By single-factor experiments, alcalase and papain hydrolysis conditions were studied, and the optimal conditions for the alcalase hydrolysis of sturgeon skin protein were determined:the enzyme hydrolysis temperature50℃, pH10.0, substrate concentration80g/L, and enzyme dosage4%(the substrate protein), enzyme hydrolysis time6h; the optimal conditions for the Papain were:enzyme hydrolysis temperature55℃, pH8.5, substrate concentration100g/L, and enzyme dosage4%(the substrate protein), enzyme hydrolysis time6h. Basis on single-factor experiments, as final hydrolysis degree (DH) of hydrolysis product and peptide yield indexes, the method of two-step enzymatic hydrolysis was used to determine the best hydrolysis conditions:on the conditong of substrate concentration100g/L, firstly hydrolyzed for4h with papain dosage2%at55℃, pH8.5, then hydrolyzed for2h with alcalase dosage2%at55℃, pH8.5, the hydrolysis degree (DH) of collagen protein for sturgeon skin was50.35%and peptide yield was53.50%. This paper studied deodorization and decoloration technology conditions on fish skin hydrolysate with active carbon and yeast fermentation. By contrast to the two kinds of ways, the optimal process parameters of decoloration and deodorization were sured for sturgeon skin collagen hydrolysate:first at pH4.0, activated carbon content0.5%, temperature40℃, the hydrolysate was decolored for40min, removed activated carbon by ultrafiltration, and then through yeast fermentation at pH4.5, temperature35℃, yeast amount1%, time0.5h, after high temperature sterilization and removing yeast by ultrafiltration, clariying, light yellow no odor and a light wine fragrance hydrolysate was obtained. The purpose of decoloring and deodorization was to be achieved.This paper contrasted to researches on the effect of ion exchange resin and nanofiltration desalination for fish skin collagen hydrolysate. showed that the nanofiltration desalination was better than ion exchange resin, and the optimal nanofiltration desalination technology parameters were gained at material liquid concentration2.5%, temperature20℃, pressure0.5MPa, nanofiltration100min.After ultrafiltration, the content of peptides whose molecular weight was under2000Da reached as highy as98.46%, and the peptides ranged from180to1000Da reached85.35%which attened the purpose of separation and purification.Finally, the study on physical and chemical properties of sturgeon skin collagen peptide showed that the protein content reachd as high as91.85%, and collagen peptides had good apparent low viscosity. The short peptide isoelectric point was8.4, well water-retaining property. Hydroxyproline content reached as highy as5.21%, essential amino acids was10.62%.