pH-Sensitive Polycaprolactone/Gelatin Active Packaging Containing Rosemary-Loaded Chitosan Nanoparticles

pH-sensitive indicators are used to check the health of the packaged food products. This study aimed to develop a bilayered, biodegradable polycaprolactone (PCL)/gelatin film, containing pH-sensitive chitosan nanoparticles (ChiNPs). Rosemary extract was encapsulated in ChiNPs, resulting in the formation of encapsulated ChiNPs [rosemary-loaded chitosan nanoparticles (RChiNPs)]. Different concentrations of nanoparticles were used in the PCL and gelatin layers. Dynamic light scattering, zeta potential, scanning electron microscopy, Fourier-transform infrared spectroscopy, water vapor transmission rate, tensile strength (TS), elongation at break, degradation test were performed to evaluate the nanoparticles and layers. The results showed RChiNPs sensitivity to varying pH levels and their uniform size distribution (600–700 nm). The layers had a smooth surface. Increasing the concentration of RChiNPs increased the TS (modulus of elasticity is up to 111 MPa in bilayer films) and degradation rate of the film. In conclusion, the engineered film exhibited superior properties compared to each individual layer.