Self-healing carboxymethyl chitosan hydrogel with anthocyanin for monitoring the spoilage of flesh foods

Self-healing hydrogels prepared with biopolymers have been widely applied in various engineering fields. In this study, the carboxymethyl chitosan (CMC) hydrogels were fabricated through crosslinking with oxidized alginate (ADA), which can be applied in smart food packaging fields. The concentration of oxidized alginate has greatest impact on the physicochemical properties of the hydrogels. Due to the dynamic properties of Schiff base linkages and hydrogen bonds, the hydrogel demonstrated self-healing. Higher concentrations of oxidized alginate result in weaker self-healing ability of the hydrogels. The self-healing properties endowed the hydrogel with 3D printable capacity. The anthocyanin (An) in the hydrogel exhibited a color change when exposed to acidic and basic gases, making the hydrogel potentially useful for smart indicators. These intelligent indicators can be used to detect the freshness of chicken, pork and fish. In addition, the hydrogel showed excellent biodegradable properties and can be degraded in lake, soil and simulated seawater. The self-healing, biodegradable and pH sensitive hydrogels has the potential to be applied in smart food packaging.