Chitosan is a multifunctional biopolymer that is widely used in the food and medical fields because of its good antibacterial, antioxidant, and enzyme inhibiting activity and its degradability. The biological activity of chitosan as a new food preservation material has gradually become a hot research topic. This paper reviews recent research on the bioactive mechanism of chitosan and introduces strategies for modifying and applying chitosan for food preservation and different preservation techniques to explore the potential application value of active chitosan-based food packaging. Finally, issues and perspectives on the role of chitosan in enhancing the freshness of food products are presented to provide a theoretical basis and scientific reference for subsequent research.

Nitrite is one of the main pollutants in the water worldwide. In this study, we have applied the reverse suspension crosslinking methodology based on chitosan (CS) and Fe₃O₄ (FeO) to synthesize the novel magnetic nanomaterial of chitosan (CS-FeO). The physical and chemical properties of CS-FeO were further characterized by scanning electron microscopy, particle size distribution, thermogravimetry, fluxgate magnetometer, Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and energy dispersive spectroscopy. Results revealed that CS-FeO showed high thermal stability in the temperature ranging from 50 to 200°C. CS-FeO showed high crystallinity and magnetism and was easily and quickly separated from aqueous solution in the presence of an external magnetic field. The molecular structure of CS-FeO showed that the core-shell structure of CS-FeO was established with FeO as the core and CS as the shell. Furthermore, the adsorption rate of nitrite by CS-FeO reached under optimal conditions. Moreover, CS-FeO showed high regeneration capability with Na₂SO₄ used as the eluent. Our study demonstrated evidently that CS-FeO can be potentially used to remove nitrite from drinking water sources and industrial wastewater, suggesting the promising future of the application of CS-derived magnetic nanomaterials in the areas of environmental protections.