| Collagen, gelatin and collagen hydrolysate were prepared from bovine skins in different preparative processes. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed that the molecular weight distribution of collagen was very narrow (about 200 and 100 kDa forβandαchains respectively), compared with those of gelatin (less than 300 kDa and with wide distribution) and collagen hydrolysate (less than 50 kDa and with wide distribution). The isoelectric points of collagen, gelatin and collagen hydrolysate were 8.26, 4.88 and 4.54 respectively, determined by Zeta potential titration. Circular dichroism (CD) spectra revealed that there were a positive peak around 221 nm and a negative peak around 192 nm for collagen, which were the characteristics of collagen triple helix. However, gelatin and collagen hydrolysate did not have positive peaks around 220 nm, suggesting random coils. The denaturation temperature of collagen was about 37.5℃, determined by viscosity method, whereas there were no helix-coil transitions for gelatin and collagen hydrolysate in the heating processes. Collagen reaggregated to fibrils under physiological conditions. In contrast, gelatin and collagen hydrolysate lost the ability of fibril formation. Collagen was more resistant to trypsin hydrolysis compared with gelatin and collagen hydrolysate. In addition, collagen membran(e58N/mm2)had higher extension strength than gelatin membrane(36N/mm2)and presented remarkable fibril shape as observed by scanning electron microscope (SEM). Therefore, collagen isolated from bovine skins can be a high...
|
PDF Full Text Request