Frabrication of carboxymethylchitin nanofibers and fish gelatin hybrid gels with robust gel performance

Compared to animal gelatin, the application of fish gelatin (FG) in the food industry is limited due to its lower gel hardness, gelation temperature, and melting temperature. To address these issues, we developed hybrid gels using carboxymethyl chitin nanofibers (CMC-NFs) with FG to enhance its gel properties. The chitin was carboxymethylated by monochloroacetic acid, increasing the negative potential from −6 mV to −35 mV. This modified chitin was then defibrillated into CMC-NFs through high-pressure homogenization to improve its water dispersibility. The addition of 0.1% CMC-NFs significantly increased the hardness of FG gels from 533 g to 989 g, which was notably higher than the ∼600 g hardness of porcine gelatin. Additionally, the gelation and melting temperatures of FG reached 17 °C and 32 °C, respectively, which are very close to the 20 °C and 35 °C of porcine gelatin. Mechanistic studies revealed that FG and CMC-NFs (0.1%) molecules formed a synergistic gel network, facilitated by hydrogen bonding and hydrophobic interactions. This interaction significantly increased the α-helix content in the secondary structure of the FG protein from 15.26% to 21.18%, thereby enhancing the FG-dominated three-dimensional network structure with CMC-NF molecules. Increasing the concentration of CMC-NFs further elevated the gel's melting temperature while reducing its hardness due to phase separation. This study not only presents a viable method for enhancing the gelling properties of modified FG but also offers a feasible solution for expanding FG's applications in the food industry.