Study On Enzymatic Extraction Technology Of Pigskin Collagen

Collagen, a most abundant protein, is widely distributed in skins, tendons, cartilages and constitutes about 25%-30% by weight of all proteins in human or other animal bodies. Collagen structure is characterized by containing domains with repetition of the Gly-Xaa-Yaa prolinrich tripetide and the trimeric collagen triplehelices. As the result of its special structure, collagen has its corresponding special biological characteristics, such as low immunogenicity, biocompatibility, degradation and hemostasis. The use of collagen is more and more common and has expended to many other fields, such as biomedical materials, foods, cosmetics and feedstuffs.In this paper, we extracted typeâ… collagen from pigskin using pepsin. In the extraction, the technologies of degreasing, effects of temperature and pH on enzymolysis were sudied in details together with some useful suggestions to prepare collagen for different uses. The conclusions were given below:(1) In the degreasing process using Na₂CO₃, we found that the effect of degreasing is proportional to the reaction time and the amount of Na₂CO₃. By the analysis of remaining oil, the degrasing can be satisfied in 3 hours with 3% Na₂CO₃.(2) The pretreated skin was enzymolyzed under same conditions but at different temperatures of 4℃,16℃and 35℃respectively. The analytical results of the reaction process and the products using Kjeldahl's method, LC and infrared spectrum and DSC indicate: The reaction temperature increased, the reaction rate can be speeded, there are more extracts, and the molecular weight range can be widened. The complete triplehelices structure can be retained at 4℃during the enzymolysis process. It meets the require of biomedical metrials. The basic triplehelices structure can be retained at 16℃but have low thermal stability. As a result of this reason, we can obtain collagen that has low thermal stability requirment through enzymolysis in cool water bath to reduce cost. Collagen with low molecular weight, low thermal stability, and uncompleted triplehelices structure can be obtained from enzymolysis at 35℃. Hence collagen polypeptide which have better absorbability by human can be prepared at 35℃to decrease the reaction time and increase the productivity.(3) Other conditions were the same, but pH was adjusted by formic acid or acetic acid to 1.5, 2.0, 2.5, respectively. The analytical results of the reaction process and the products using Hyp content analysis, LC and infrared spectrum and DSC indicate: The smaller the pH value is, the quiker reaction rate was. Under same pH, the effect of formic acid on reaction rate is stronger than acetic acid. The enzymolysis reaction can obtain narrow molecular weight distributing and complete triplehelices structure when the acetic acid was used only as the solvent. The molecular weight distributing is narrower without formic acid, and also the triplehelices structure destroyed completely. A pepsin of 1,500 molecular weight was got both in the processes under pH of 1.5 and 2.0, we can get this product if needed.