Chemical Interaction Between Starch-Polyvinyl Alcohol Matrix With Barley Microfibers: Structural, Barrier, and Viscoelastic Performance in Extruded Films

In this study, the effect of microwave (MW) treatment on obtaining barley microfibers and their effect on the chemical, structural, and viscoelastic properties of films based on starch (S) and polyvinyl alcohol (P) was inspected. SEM, FTIR, and TGA analysis revealed that MW treatment effectively achieves the defibrillation and the destabilization of hydrogen bonds of the hemicellulose and lignin molecules, resulting in the obtention of barley microfibers (BM). XPS analysis allowed identification of the oxidation and crosslinking mechanism of S, P, and S/P films containing BM during the extrusion process. PBM and SPBM films showed an increase in CC proportions linked to the crosslinking phenomena and promoted stronger OCO interactions, which increased the storage modulus from 195.5 to 380.8 MPa and from 78.0 to 134 MPa, respectively. Conversely, SBM showed lower interactions CC and high COH bonds that reduced the component adhesion. Thus, the matrix type and extrusion process determined the chemical interaction with BM, resulting in films with different rigidity that can be useful in different sustainable packaging solutions.