Combination of crosslinked zein film enhances the water barrier and mechanical properties of deacetylated konjac glucomannan/agar-based bilayer films

A bilayer strategy was employed to enhance the water-barrier properties of deacetylated konjac glucomannan/agar films by incorporating a crosslinked zein film using a layer-by-layer casting approach. SEM and Raman spectroscopy confirmed strong adhesion between the two layers, with the bilayer films fracturing as a single unit upon rupture, demonstrating successful fabrication of the deacetylated konjac glucomannan/agar-zein bilayer films. ATR-FTIR and ¹³C CPMAS NMR spectra revealed the esterification between the [sbnd]COOH groups of citric acid and the [sbnd]OH groups of zein, with the esterification degree increasing with up to 10 % critic acid. This reaction increased the crosslinking degree of zein, resulting in denser zein films and significantly improving water-barrier capacity from 29.86 to 8.09 × 10⁻¹³ g·m·m⁻²·s⁻¹·Pa⁻¹, as well as tensile strength from 12.39 MPa to 20.29 MPa. These findings provide insights into the development of macromolecule-based bilayer/multiplayer films with desired practical features for food packaging applications.