Development of Zein–PEG400/PVA–Chitosan Bilayer Films for Intelligent Packaging

Zein exhibits excellent biodegradability, thermal stability, UV resistance, and water barrier properties, making it a promising candidate for food packaging applications. However, pure zein films suffer from brittleness and poor mechanical strength, which limit their practical use. In this study, a unique bilayer packaging film (ZP/P-C) was developed using a layer-by-layer solution casting technique, where hydrophobic zein was coated onto a polyvinyl alcohol and chitosan composite layer (P-C). Incorporating PEG400 into the zein layer improved the interfacial compatibility of the bilayer film, increasing its uniformity and toughness. The resulting bilayer films demonstrated enhanced mechanical properties, flexibility, and water vapor barrier performance. Specifically, the ZP7.5/P-C bilayer film showed an elongation at break of 68.74% and a modulus of elasticity of 187.19 MPa. It had a water vapor permeability of 6.60 × 10-11 g·m·m-2·s-1·Pa-1 and provided near-complete UV protection within the 200-350 nm range. Furthermore, an intelligent detection bilayer film was created by integrating anthocyanin extract into the zein layer. Adding anthocyanin improved the film's antioxidant properties and allowed it to respond colorimetrically to total volatile basic nitrogen. The bilayer film ZPBA1.0/P-C displayed an excellent antioxidant activity (45.8%) and remarkable color change (ΔE = 20.2) in response to ammonia, effectively indicating shrimp spoilage in 48 h (ΔE > 10). This investigation spotlights the potential of zein-based bilayer films in active and intelligent food packaging, offering innovative strategies to improve food safety and extend the shelf life of perishable goods.