Novel eco-friendly antimicrobial UV-blocking PBAT/PBS/TiO2 nanocomposite films for improved shelf-life of bananas

Novel nanocomposite poly (butylene adipate-co-terephthalate) (PBAT)/polybutylene succinate (PBS) blend films functionalized with titanium dioxide (TiO2) nanoparticles (0, 0.9, 1.8, 2.7, 3.6 and 4.5% w/w) were produced using cast-sheet extrusion. Atomic force microscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and dynamic mechanical thermal analysis were used to investigate film morphology and structure. The crystallinity of the films was modified due to interactions between the nanoparticles and the PBAT/PBS blends, as confirmed by FTIR and XRD. Tensile strength and elongation of films slightly reduced with TiO2 addition up to 4.5% in both machine direction (MD) and cross direction (CD). The tensile strength of the T5 films was nearly 25% less than the control films. Adding TiO2 gave excellent UV-blocking properties with slightly reduced water vapor by 16.5% and oxygen permeability by 4% for films with maximum loading. The film surface became more hydrophilic, as evidenced by the reduced contact angle. The results, as acquired from turbidity measurements, show that films with 3.6% TiO2 loading and above have high antimicrobial activity against both Bacillus cereus (Gram-positive) and Escherichia coli (Gram-negative). The relative area of microbial growth on agar media exhibited better antibacterial capacity against Escherichia coli than Bacillus cereus, with a sharp reduction of microbial growth at TiO2 contents above 2.7%. Films containing TiO2 (≥0.9%) effectively delayed ripening and increased peel yellowness of packaged bananas during storage for 6 days at room temperature. The developed PBAT/PBS/TiO2 nanocomposites films hence showed enhanced UV-resistance and antimicrobial properties, while maintaining adequate mechanical strength necessary for food packaging. The film is an eco-friendly alternative antimicrobial food packaging to extend the shelf-life of fresh produce.