Multifunctional active packaging based on layer-by-layer engineered chitosan/whey protein-citral coatings on polylactic acid/bacterial cellulose films for enhanced bread preservation.

The development of biodegradable active packaging that combines mechanical robustness with sustained antimicrobial functionality remains challenging. This study reports a multifunctional active film integrating a polylactic acid/bacterial cellulose (PLA/BC) composite substrate with surface-confined bioactivity via layer-by-layer (LbL) assembly. Citral-loaded whey protein concentrate and chitosan were sequentially deposited to spatially decouple structural reinforcement from antimicrobial function. The optimized multilayer film exhibited a compact stratified architecture with strong interlayer adhesion, high tensile strength (42.14 MPa), enhanced oxygen barrier performance (peroxide value, 9.11 meq/kg), and pronounced antifungal activity against Penicillium expansum and Aspergillus niger. Moreover, the LbL coating enabled sustained and simulant-responsive citral release, alleviating rapid volatilization associated with bulk incorporation. Bread storage tests demonstrated delayed mold development and improved textural and microstructural stability, resulting in an extended mold-free shelf life relative to uncoated PLA/BC films and commercial polyethylene packaging. Overall, this hierarchical design provides a viable strategy for sustainable active food packaging.