The preparation, physicochemical properties and rheological processing characteristics of collagen from scale of tilapia (Oreochromis niloticus)

Objective With the advantages of low antigenicity, good biocompatibility and biodegradability, collagen has great development potential and broad application prospects. Fish collagen has become a hot research topic for scientists in recent years due to its lack of problems such as disease transmission and religious beliefs. Tilapia (Oreochromis niloticus) is one of the economically important fish species in China, and its processing waste, fish scales, is a good source of collagen. However, the lack of rheological property studies has limited the application and promotion of tilapia collagen, and this study aims to develop fish scale collagen and investigate its rheological properties.

Methods In this study, fish scales, a processing by-product of O. niloticus, were used as the raw material to optimise the extraction process of collagen using one-way test and orthogonal. The structure of O. niloticus scale collagen was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), ultraviolet (UV) absorption, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Meanwhile, the effects of the concentration and the temperature of the collagen solution on the steady state rheological properties and dynamic rheological properties were investigated.

Results The optimal extraction conditions for tilapia (O. niloticus) scale collagen included using 0.5 mol/L acetic acid as a solvent, a material-liquid ratio of 1∶10 (W∶V), a swelling time of 2 days, and performing two extraction cycles. Under these conditions, the extraction yield of tilapia scale collagen was 21.45% ± 0.44%. Structural analysis confirmed the collagen as O. niloticus type Ⅰ collagen with a α1₂α2 structure, with an electrophoretic purity of 90.03% ± 0.91%. Liquid chromatography-tandem mass spectrometry experiments revealed that both α1 and α2 subunits consisted of 339 uninterrupted Gly-X-Y triplets, comprising 70.28% and 75.33% of the total amino acids, respectively. FTIR and XRD analyses indicated the retention of an intact triple helix structure in tilapia scale collagen. Steady-state rheological tests demonstrated that collagen solutions exhibited typical non-Newtonian fluid behavior and showed shear-thinning characteristics across tested shear rates and temperatures. Dynamic rheological properties revealed that at a frequency of 0.01 Hz, elastic behavior predominated in collagen solutions as concentration increased. Solutions with higher viscosity (15~20 mg/mL) transitioned from solid-like elastic to liquid-like viscous behavior with increasing scanning frequencies. Moreover, with rising temperature, collagen solutions exhibited increasingly liquid-like viscous behavior across the frequency range tested.

Conclusion In this study, collagen with an intact triple helix structure of tilapia scales was developed, which has the potential to be applied as a hydrogel wound dressing and injectable biomaterial.

Significance This study can provide theoretical guidance and technical support for the large-scale production and popular application of high value-added collagen.