Interfacial Interactions and Structural Evolution of Gelatin/Zein Nanofiber Composites Modulated by Poly(Vinyl Alcohol)

Synthetic polymers are commonly incorporated into natural polymer nanofibers to enhance their overall performance. In this study, we investigated the effects of different poly(vinyl alcohol) (PVA) concentrations (0%, 2.5%, 5%, 7.5%, and 10% w/v) on the properties of gelatin/zein nanofibers. With increasing PVA concentration, fiber diameter significantly decreased from 976 ± 165 nm to 262 ± 60 nm, followed by a gradual increase to 396 ± 81 nm, indicating that PVA plays a crucial role in fiber diameter regulation. At higher concentrations (7.5% and 10% w/v), PVA became dominant, inducing protein aggregation and porous channel formation, which in turn increased the water vapor permeability of the composites. Rheological and mechanical analyses revealed that at these concentrations, the composites exhibited enhanced flexibility while maintaining network stability, demonstrating strong application potential. Furthermore, PVA incorporation induced a slight increase in the primary decomposition temperature (from 320.77 °C to 328.67 °C), indicating enhanced intermolecular compatibility and restricted segmental mobility within the protein–PVA network. Overall, these results establish a theoretical basis for tailoring fiber architecture and interfacial compatibility in natural–synthetic polymer composites. Further, the structural attributes of the resulting fibrous mats indicate their potential for food processing applications beyond conventional food packaging, including use as filtration media.