Decoupling chemical and structural-driven function on barrier properties of PVA-lignin blends

In this work, polyvinyl alcohol (PVA) solutions were doped with kraft lignin to prepare composites with enhanced barrier properties. Bulk kraft lignin was converted into nanoparticles (KLNPs) through a self-assembly approach, aiming to increase the availability of phenolic hydroxyl groups responsible for antioxidant activity. The PVA-lignin solutions were processed via casting and electrospinning, rendering materials based on the same chemical system but with different additive loadings and structural features. Due to processing limitations, the maximum KLNPs weight contribution in casted films was restricted to 1.5 wt%, whereas through electrospinning we have incorporated up to 3.0 wt% without compromising mechanical integrity of the resulting material. Casted films were homogeneous and transparent materials with improved UV-shielding and water barrier performance compared to neat PVA. In contrast, the electrospun membranes formed by PVA nanofibers with 519 nm average diameter rendered opaque and high porous materials within PVA fiber network, exhibiting increased surface wettability. The antioxidant performance of the blends, evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, increased with lignin nanosizing and concentration, with electrospun membranes showing a 10% higher scavenging efficiency than casted films. Finally, the performance of the materials in food preservation was tested in pork meat samples under accelerated degradation conditions. Decoupled analysis of barrier and active properties demonstrated a behavior highly dependent on the manufacture process and the lignin concentration. While casted films reduced lipid oxidation by a 71% mainly through barrier properties, the overall malondialdehyde (MDA) inhibition capacity of electrospun membranes was 56% with the main activity attributed to the lignin content.