Preparation And Physicochemical Characteristics Of Collagen From Deep-Sea Redfish (Sebastes Mentella)

China is a large fishery country, but a huge amount of fishery processing wastes lead to severe resource waste and environment pollution due to the lower process level. The outbreak of bovine spongiform encephalopathy, foot-and-mouth disease, Streptococcus suis and H1N1 influenza crisis have resulted in anxiety among users of collagen from land-based animals in recent years. Additionally, collagen obtained from pig can't be used as a component of some foods for religious and custom reasons. The collagen was prepared and characterized from the processing wastes of deep-sea redfish to improve the fishery processing level and seek the alternative collagen sources. The results were as follows:1. The abundant ash and fat in the materials could be removed effectively by EDTA and hexane treatment with high recoveries of protein. The yields of collagen from skin, scale and bone (SKC, SCC and BOC) were 47.5%,6.8%and 10.3%, respectively. The denaturation temperatures of SKC, SCC and BOC were 16.1℃, 17.7℃and 17.5℃, respectively, which were lower than that of most other fish species and land-based mammalian. The amino acid profiles of these collagens were similar with lower imino acid content, which might be the reason for the lower denaturation temperature. All the collagens were type I mainly and maintained their triple helical structures well with slight differences of molecular structure. SKC possessed higher degree of intermolecular cross-link and molecular order, but the extent of peptide chain unwinding was also higher due to the existence of less hydrogen bond compared to SCC and BOC.2. The yield of acid-solubilized collagen (ASC,47.5%) was lower compared to pepsin-solubilized collagen (PSC,92.2%), but the purity of ASC (76.3 mg Hyp/g collagen) was significantly higher than PSC (74.8 mg Hyp/g collagen). The intrinsic viscosity of ASC (15.9 dL/g) was greater than PSC (14.6 dL/g), indicating a higher average molecular weight of ASC on account of the high proportion of polymers of collagen. The denaturation temperatures of ASC and PSC were 16.1℃and 15.7℃, respectively, suggesting the triple helical structure of PSC was still predominant. The amino acid profiles of ASC and PSC were similar with lower imino acid content than most other species, which might be the reason for the lower denaturation temperature. SDS-PAGE and FTIR showed both ASC and PSC were type I mainly with slight structure differences. ASC held its triple helical structure well, and possessed a higher extent of intermolecular cross-link. While the structure of PSC was changed slightly due to the loss of N- and C-terminus domains, but the triple helical structure was still predominant as a result of the formation of more hydrogen bond.3. The ultrasonic-assisted extraction of pepsin-solubilized collagen from deep-sea redfish skin was optimized using response surface methodology. About 93.6% of collagen could be obtained under the optimum conditions of extraction for 18 h after ultrasonic treatment for 15 min at 505 W. The yield and characterization of collagen was not significantly different from that prepared with conventional method. However, the extraction time was decreased to 18 h from 40 h and consequently the extraction efficiency was significantly improved by ultrasonic treatment.4. The pepsin hydrolysate of deep-sea redfish skin was separated into three fractions by DEAE-cellulose column chromatography. SDS-PAGE pattern and amino acid composition suggested that the fractions were type I collagen (PSC-Ⅰ,79.4%), type V collagen (PSC-Ⅴ,8.4%) and non-collagenous substances (NC,2.1%), respectively. No typeⅢcollagen was found in the skin unlike mammalian. The intrinsic viscosity and viscosity transition temperature span of PSC-Ⅰ(14.4 dL/g and 8℃) were significantly higher than those of PSC-Ⅴ(13.5 dL/g and 5℃) as a result of higher inter- and intramolecular crosslink. The denaturation temperature of PSC-V (17.8℃) was obviously higher than PSC-Ⅰ(15.9℃), which was contributed to the higher total imino acid content (17.1%) and hydroxylation degree of proline and lysine (44.7%) than PSC-Ⅰ(14.7% and 35.8%). FTIR indicated some differences in the secondary structure of the two collagens, but both of them held their special triple helical structure. Compared to PSC-Ⅴ, PSC-Ⅰpossessed higher intermolecular crosslink and lower peptide unwinding due to the existence of more hydrogen bond.