High-barrier multilayer nanocomposite films constructed with flexible whey protein worm-like aggregates for sustainable food packaging

The design of biodegradable films with high barrier performance has become increasingly important for sustainable food packaging. In this study, multilayer nanocomposite films were prepared by incorporating whey protein isolate (WPI) fibrillated worm-like aggregate (WLA) into a carboxymethyl chitosan (CMC) and sodium alginate (SA) matrix through layer-by-layer (LbL) assembly. Controlled fiber aggregation of WPI was achieved via combined thermal and EDC/NHS covalent coupling treatments, producing WLA with distinct conformational flexibilities. Structural characterization by FT-IR and SAXS confirmed that the incorporation of WLA strengthened interactions and reduced microdomain correlation length, thereby promoting a more compact and homogeneous interlayer structure. These structural improvements resulted in notable enhancements in mechanical strength, moisture resistance, water vapor and oxygen barrier properties. Moreover, the optimized 11-layer CMC/SA film with the most flexible WLA exhibited excellent preservation performance when applied to oxidation-sensitive food models. Compared with conventional petroleum-based materials, the bio-based multilayer nanocomposite films maintained product freshness and visual quality throughout storage. The findings highlight the crucial role of protein aggregate flexibility in modulating film microstructure and functionality, providing a promising route for constructing high-barrier, eco-friendly packaging materials suitable for practical applications in the food industry.