A facile preparation strategy for multifunctional hydrogel films with adjustable performance in food preservation

Abstract

Plant polyphenols represent valuable additives for food packaging; however, their poor hydrophilicity necessitates complex pre-treatments. In this study, we propose a simple and eco-friendly strategy for the direct incorporation of hydrophobic polyphenols into packaging films. Using carboxymethyl chitosan and oxidized carrageenan as substrates, we successfully introduced hydrophobic polyphenols into multifunctional hydrogel films through borate ester bonds. The mechanical strength of these films was further enhanced by schiff base bonds. The prepared hydrogel films exhibited antibacterial rates exceeding 98 % against Escherichia coli and Staphylococcus aureus, and demonstrated excellent antioxidant and UV shielding properties. As the oxidation degree of carrageenan increased, the water vapor permeability rate of the hydrogel films decreased from 1.34 × 10⁻¹ ⁰ g·m⁻¹ ·s⁻¹ ·Pa⁻¹ to 3.13 × 10⁻¹ ¹ g·m⁻¹ ·s⁻¹ ·Pa⁻¹ , while the oxygen permeability rate decreased from 40.61 meq/kg to 20.04 meq/kg. This design effectively mitigates the deterioration of fruits and vegetables caused by dehydration and oxidation. Furthermore, the hydrogel films containing carrageenan with a medium oxidation degree exhibited superior mechanical properties, with tensile strength increasing by 4.8-fold and the ability to bear a load of 200 g. The banana preservation experiments demonstrated that hydrogel films can effectively delay the deterioration of bananas. Notably, the film exhibited excellent biodegradability, degrading by 90 % in soil within 60 days, underscoring its significant potential for developing functional and environmentally friendly food packaging systems.