Novel pomelo peel pectin-chitosan bilayer films with gallic acid and CaCl2: Fabrication, characterization, and enhanced antimicrobial-mechanical properties

This study aimed to extract and characterize pectin from pomelo peel and evaluate the chemical, physical, mechanical, and antibacterial attributes as well as the functional activity of the resulting pectin-chitosan-based bilayer film. The extraction of pectin from pomelo peel showed good potential to be used as a base material for biodegradable films with a yield of 24.91%, methoxyl content of 9.38% and a degree of esterification of 58.89%. FTIR analysis showed that pectin interacts with CaCl 2 through ionic bonds, while chitosan and gallic acid form hydrogen bonds. These interactions enhance network stability and influence the film’s microstructure. Pectin-chitosan bilayer films produced with the addition of CaCl 2 (0.5% w/v) significantly enhanced film elongation (34.94%) and reduced water pavor permeability (3.63 × 1010g·m -1 ·s -1 ·Pa -1 ), indicating improved mechanical flexibility and barrier properties. Incorporation of gallic acid (5% w/w) effectively increased antibacterial activity against Escherichia coli (15.90 mm) and Staphylococcus aureus (16.85 mm). After being buried in soil for 25 days, the films showed a high degree of degradation, and the film with the highest concentration of CaCl 2 and gallic acid in particular was completely degraded. Overall, pectin-chitosan bilayer films showed great potential as sustainable biodegradable materials for food packaging applications. • Bilayer packing of pectin/chitosan with CaCl 2 and gallic acid was constructed. • FTIR confirmed ionic and hydrogen bonding in the pectin/chitosan bilayer film • Films with CaCl2 and gallic acid added showed good mechanical properties and low water vapor permeability and solubility. • The bilayer film was effective in inhibiting the growth of Escherichia coli and Staphyloccus aureus.