Preparation and characterization of carboxymethyl chitosan/nano-MgO/red cabbage anthocyanins multifunctional films via colloid formation and its application on shrimp preservation

The objective of this study was to evaluate the properties of carboxymethyl chitosan (CMCS)-based nanocomposite films incorporated with nano-MgO and red cabbage anthocyanin (RCA). The MgO content of 0.2% (w/v) resulted in a colloidal film-forming solution with a 60 nm-level diameter. The tensile strength of the consequent film was improved from 7.83 to 25.04 MPa with the film thickness increasing from 63.50 to 85.73 µm, whereas elongation at break decreased from 35.8% to 12.50%. Without affecting the optical transmittance, the incorporation of MgO and RCA significantly enhanced the UV-shielding ability and thermal stability of the CMCS/MgO/RCA films, and significantly decreased their water vapor permeability and water solubility. The SEM result showed that nano-MgO were homogeneously distributed in the CMCS matrix, and the nanocomposite films exhibited improved hydrophobicity with the water contact angle increasing from 45.1° to 76.7°. ATR-FTIR and XRD analyses revealed the molecular interactions in films, including hydrogen bonds , electrostatic attraction, and hydrophobic interaction. Compared to the control, the CMCS/MgO/RCA films exhibited enhanced antioxidant activity and potent antibacterial ability against Escherichia coli and Staphylococcus aureus with the inhibition zone diameter increasing by 67.8% and 50.9%, respectively. Moreover, the addition of RCA made the film color change from red to green within pH 3–12. The obtained films showed great potential in shrimp preservation by suppressing the rise of pH and generation of the total volatile basic nitrogen.