Tailoring highly stretchable, ultra-barrier, and transparent gelatin/PVA emulgel-templated oleofilms: Effect of oil saturation degree

• Gelatin/PVA emulgels achieve 100% oil binding capacity and high stability. • Lipid physical state dictates the structural and functional performance of oleofilms. • Solid PKS crystallinity acts as an active filler, reinforcing the polymer matrix. • Solid lipid domains create a tortuous path, reducing WVP by up to 50%. • Vitamin E loaded PKS film offers superior controlled antioxidant retention. Emulgel-templated oleofilms enable the effective entrapment of vegetable oils within water-soluble polymeric matrices. However, these structures often suffer from critical functional trade-offs where improved barrier properties compromise film flexibility or transparency. This study investigated how modulating the degree of oil saturation, rather than merely increasing total oil content, can mitigate these limitations. Hence, oleofilms were fabricated by casting new structured emulgels that were formulated from a gelatin-polyvinyl alcohol base and a fixed mass fraction ( w oil = 0.1) of sunflower, palm fruit, and palm kernel stearin (PKS) oils. Among the formulations, PKS, characterized by the highest degree of saturation, yielded emulgels with superior gel strength (16.17 ± 2.6 g) and centrifuge stability (64.99 ± 1.35 %). Consequently, the PKS-based oleofilm exhibited a significantly enhanced mechanical performance (tensile strength: 32.11 ± 2.29 MPa, elongation at break: 594.91 ± 0.1 %), barrier properties (oxygen permeability: 1.06 ± 0.01 × 10 - ³ g/m²·s, and water vapor permeability: 0.038 ± 0.01 g mm/m² d kPa), contact angle (92.2 ± 0.4 °), thermal stability (glass transition: 66.15 ± 0.28°C, and melting temperature: 256.7 ± 0.4°C), as compared to other samples. Moreover, oleofilms were loaded with vitamin E (at 1% wt of total dry matter), and they showed superior antioxidant capacity (up to 14.35% radical scavenging activity) than the non-loaded control (oil-free) sample. Ultimately, the superior attributes of the PKS-based oleofilm suggest significant potential for packaging high-fat and high-moisture foods (e.g., salmon or cheese), as well as for developing biomedical materials such as controlled-release wound dressings.