Electrospun-derived cashew gum/poly(vinyl alcohol) films as high‑oxygen-barrier flexible food packaging

In the search for sustainable alternatives to fossil-based packaging, valorizing underutilized polysaccharides is often limited by trade-offs between mechanical performance and barrier properties. This work presents a previously underexplored route to convert cashew gum (CG), an abundant agro-industrial by-product, into high-performance continuous films by blending it with poly(vinyl alcohol) (PVOH), electrospinning, and thermal annealing of fibers. Three formulations were developed targeting high CG content (over 30% w/w) and electrospinning stability. The influence of solution properties (polymer ratio and additives, polyethylene oxide (PEO), and glycerol), morphology, and structure on film performance was investigated. Two formulations produced continuous, non-porous films, whereas the formulation with the highest CG content and lowest PEO content retained some internal porosity. The films exhibited UV-blocking ability (up to 90%), high elongation at break (>200%), and excellent oxygen barrier properties at low humidity (0% RH and 25% RH) and moderate barrier properties at 60% RH. At 0% RH, permeability was below the detection limit, whereas at 25% RH, it reached 3 × 10^-21 m³·m·m^-2·s^-1·Pa^-1, comparable to fossil-based high-barrier materials. Water vapor permeability depended on blend composition, with the lowest value being 4 × 10^-14 kg·m·m^-2·s^-1·Pa^-1. The biodegradation of the films reached 65-80% after 65 d under composting and 36-41% after 115 d in soil, increasing with CG content. These results demonstrate the feasibility of using underutilized agro-industrial by-products to produce flexible CG/PVOH films with high oxygen barrier performance under dry and semi-dry conditions, supporting their further development as candidate barrier materials for food-packaging systems.