Study on the self-assembly property of type I collagen prepared from tilapia (Oreochromis niloticus) skin by different extraction methods

Type I collagen was prepared from tilapia (Oreochromis niloticus) skin by acetic acid and pepsin process at 4 degrees C, respectively (ASC and PSC), and hot-water method separately at 25, 35 and 45 degrees C (C-25, C-35 and C-45). Their structure and self-assembly property were discussed. SDS-PAGE patterns suggested that pepsin hydrolysis and the 35 and 45 degrees C extraction produced collagen with much reduced proportions of - and -chains. Fourier transform infrared spectroscopy spectra revealed that pepsin hydrolysis did not change the conformation of collagen, but higher extraction temperature did. Self-assembly curves and atomic force microscopy (AFM) observations showed that only ASC, PSC and C-25 could self-assemble into fibrils with D-periodicity, but the reconstruction rate of C-25 was lower. Besides, PSC had relatively higher resolution ratio compared with others. Overall, pepsin-extracted collagen displayed higher solubility and better fibril-forming capacity, having the potential of applying in biomaterials and food-packaging materials.