Rapidsynthesis of an antifreeze and photocatalytic antibacterial multifunctional hydrogel for low-temperature preservation of marine fish

Globally, billions of tons of food are lost or wasted annually due to microbial contamination. Hydrogels are a new type of fresh-keeping material because of their porous three-dimensional network structure, offering enhanced loading capacity. However, traditional hydrogel packaging materials often suffer from limitations such as poor frost resistance, lack of catalytic antibacterial activity, and low factory application rate. In this study, firstly, carbon dots (CPCDs) catalyzing oxygen under visible light irradiation with broad-spectrum antibacterial activity (The minimum photocatalytic antibacterial concentration of H. alvei and P. fluorescens was 62.5 μg/mL) were synthesized. A hydrogel was rapidly formed using polyvinyl alcohol (PVA) and gelatin within 14 min of one-time freezing at −20 °C through hydrogen bonds, and excellent photocatalytic antibacterial activity and timely preservation were achieved by loading CPCDs. The low swelling (3.0) of the hydrogel and a release rate of <20% reduced the loss of CPCDs, thereby achieving a sustained antibacterial effect. Additionally, In the DSC experiment, no significant peak was observed between −80 °C and − 20 °C. The hydrogel was not crystallized and maintained its flexibility, which proved that the hydrogel had good frost resistance. The hydrogel could be completely peeled off from the surface of the Oncorhynchus mykiss fillet with a force of <0.5 N without any residue. The hydrogel showed no significant cytotoxicity and could extend the shelf life of O. mykiss fillet by >3 days. These findings underscored the potential of the developed hydrogels as efficient materials for the rapid preservation of frozen seafood.