Encapsulation of Fish Oil in Pullulan/Sodium Caseinate Nanofibers: Fabrication, Characterization, and Oxidative Stability

This study aims to enhance the oxidative stability of fish oil through encapsulation in pullulan/sodium caseinate (PUL/NaCAS) nanofibers. Electrospinning was employed to produce three formulations: control (0% fish oil) and samples with 5% and 10% fish oil. Characterization of the emulsions showed that increasing oil content led to larger droplet size and reduced viscosity. Scanning electron microscopy (SEM) analysis revealed surface imperfections and a gradual increase in fiber diameter with higher oil loading. Fourier transform infrared (FTIR) spectroscopy confirmed molecular interactions, and fibers with 10% fish oil showed a shift toward a more amorphous structure. Fish oil incorporation also enhanced hydrophobicity and thermal stability, as indicated by thermal and wettability measurements. Antioxidant assays include 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and total phenolic content (TPC), which showed the highest bioactivity at 5% fish oil, with a slight decrease at 10%, likely due to structural saturation. Encapsulation at 5% fish oil significantly reduced lipid oxidation during storage (hydroperoxide values decreased from 8.6 to 4.8 mM at 60 °C/15 days), demonstrating the protective effect of the nanofiber matrix. Docking and density functional theory (DFT) analyses confirmed stable DHA/EPA-caseinate interactions and increased electronic stability, supporting the experimental results. Compared with conventional carriers such as spray-dried or maltodextrin-based systems, PUL/NaCAS nanofibers offered superior oxidative stability, bioactivity, and a biodegradable matrix. Overall, the 80PUL:20NaCAS:5% fish oil formulation represents a versatile platform for stabilizing omega-3 oils, with potential applications in food preservation, nutraceutical delivery, and functional packaging.