Physicochemical properties of gelatin produced from Nile tilapia skin using chemical and fermentation pretreatments

In this study, we aimed to verify the effectiveness of fermentation as a pretreatment in Nile tilapia (Oreochromis niloticus) skin gelatin production and to assess its effects on the extracted gelatin. Chemical-gelatin (CG) and fermentation-gelatin (FG) were extracted using hot water from tilapia skin after immersion in chemical reagents (sodium hydroxide and butanol) and after fermentation with Bacillus velezensis FEL-BM21, respectively. FG presented a higher recovery (27.40%), yield (49.99%), and imino acid (proline and hydroxyproline) content (177.17 ± 0.35 residues/1000 residues) than CG, but had a lower molecular weight. Fourier transform infrared and circular dichroism spectroscopy confirmed that the collagen was denatured, and scanning electron microscopy revealed that FG had a more continuous filamentous structure than CG. Furthermore, except for transmittance (66.19% at 450 nm and 86.36% at 620 nm), FG exhibited higher gel strength (492.81 g), gelling point (28.93 °C), and melting point (18.33 °C) than CG. These findings suggest that fermentation can be used to treat gelatin raw materials without negatively affecting the structure of gelatin. Moreover, fermentation has potential industrial applications as an alternative to chemical treatment.