Carrageenan-Based Antimicrobial Films Integrated with Sulfur-Coated Iron Oxide Nanoparticles (Fe₃O₄@SNP)

Recently, antibacterial nanocomposite films containing sulfur nanoparticles (SNPs) have been attracting attention in the food packaging field; however, due to the hydrophobic properties of SNPs, dispersion in hydrophilic biopolymers is nonuniform. Therefore, the functionality of SNPs is not fully utilized. For addressing this, sulfur-coated Fe3O4 hybrid nanoparticles (Fe3O4@SNP) with a core–shell structure were synthesized. Functional nanocomposite films of carrageenan were fabricated by integrating with Fe3O4, SNP, and Fe3O4@SNP nanoparticles, and their properties, including mechanical strength, UV–vis barrier, water vapor permeability (WVP), surface morphology, thermal stability, water contact angle (WCA), surface color, and antibacterial activity, were studied. The Fe3O4@SNP hybrid nanoparticles were dispersed uniformly in the carrageenan matrix. Fe3O4@SNP blocked UV light more effectively (T280 = 1.3 ± 0.2%) than SNP (T280 = 46.5 ± 0.0%). In addition, Fe3O4@SNP showed stronger antibacterial activity against Escherichia coli and Listeria monocytogenes than SNP. SNP showed 0.63 and 2.87 log CFU/g reduction of E. coli and L. monocytogenes, respectively, whereas Fe3O4@SNP exhibited 3.20 and 4.59 log CFU/g.