Effect of CuZnAl-MMO Composite Antimicrobial Nanofilms on Cherry Preservation

In post-harvest processing, cherries face challenges such as decay and microbial infections. Traditional preservation methods pose potential toxicity and chemical residue issues. To address these issues, an organic-inorganic hybrid strategy was employed to construct a nanofilm composed of chitosan (CS) and polyvinyl alcohol (PVA) reinforced with CuZnAl-MMO nanoparticles. Through analyzing the morphology, mechanical properties, hydrophobicity, and barrier performance of nanofilms, the self-assembly of CuZnAl-MMO with CS/PVA was demonstrated, resulting in enhanced mechanical strength and hydrophobicity of nanofilm. Especially, compared to CS/PVA-0% MMO nanofilm, the tensile strength of CS/PVA-6% MMO nanofilm was mildly enhanced by 35%, and the contact angle was increased from 43.4° to 67.9°. Additionally, the water vapor transmission rate and oxygen transmission rate of CS/PVA-6% MMO nanofilm decreased by 43.2% and 80.3%, respectively, compared to CS/PVA-0% MMO nanofilm. This was attributed to the self-assembly process, leading to the reorganization of carbon chain channels within the film, thereby enhancing barrier performance. This restructuring facilitated the creation of a microenvironment conducive to cherry storage, enhancing both moisture resistance of the nanofilms and the development of a gas-modified atmosphere. The study revealed that as the content of CuZnAl-MMO in the nanofilm gradually increased, the antimicrobial properties of nanofilms against Gram-negative bacteria (E. coli), Gram-positive bacteria (S. aureus), and gray mold fungus sequentially strengthened. Furthermore, results from the cherry preservation experiment indicated that the nanofilm significantly reduced the rate of decay, weight loss, and the total bacterial count on the surface of cherries, while also slowed down the decrease in hardness. The nanofilm improved the respiration rate of cherries, leading to a rise in CO₂ concentration to 16.1% within the packaging bag. The successful promotion of gas-modified atmosphere within the nanofilm proved advantageous for cherry preservation. In conclusion, the inhibitory effects of CuZnAl-MMO nanofilm on microorganisms and the enhancement of cherry preservation performance suggested that this novel preservation method had certain application prospects. The research aimed to provide theoretical basis for the application of CuZnAl-MMO composite antimicrobial nanofilms in the field of fruit and vegetable preservation.