Preparation and Properties Study of PCM@ECD Bilayer

This study reports the fabrication of a core-shell active bilayer membrane (PCM@ECD) via a combined tape-casting and layer-transfer methodology. The inner core layer comprised Pectin-Chitosan (PC) microcapsules, synthesized by complex coacervation, encapsulating Orange Peel Essential Oil (OPEOM) with an embedding efficiency of 83.08%. The outer shell layer consisted of Ethyl Cellulose (EC) doped with zinc-doped carbon dots (Zn-CDs, average size: 1.72 nm). The microencapsulation of OPEOM facilitated the sustained release of its active components, primarily limonene, and significantly enhanced its stability. The incorporated Zn-CDs conferred potent UV-shielding properties, attributed to π→π* and n→π* electronic transitions across the 200–400 nm wavelength range. Optimized at loadings of 15% (w/w) OPEOM and 0.01% (w/w) Zn-CDs, the composite bilayer film demonstrated superior functional performance: enhanced tensile strength (28.7 ± 1.2 MPa), a 38.2% reduction in water vapor permeability (WVP), exceptional UV-blocking efficacy (>95% at 350 nm), significant antibacterial activity (inhibition rates of 87.0% and 66.7% against Shewanella putrefaciens and Pseudomonas sp., respectively), and high antioxidant capacity (79.97% DPPH radical scavenging). This work pioneers a synergistic preservation strategy utilizing Zn-CDs and OPEO microcapsules, demonstrating significant potential for application in high-moisture food systems.