Films from xylan/chitosan complexes: preparation and characterization

Abstract

Films from colloidal suspensions of cationic polyelectrolyte complexes of xylan (Xyl) and chitosan (Ch) were formed and characterized by measuring: oxygen and water vapor barrier properties, solubility, and mechanical properties. High xylan content (Xyl/Ch mass ratio: from 70/30 to 85/15) was used, and a low amount of plasticizer (10 wt% glycerol) was always added. At 50% relative humidity (RH), all films had promising oxygen barrier properties (<0.3 μm cm3/day m2 kPa) and good mechanical properties for applications such as food packaging (stress at break of 10 MPa and strain at break of 12.2% for 70/30 Xyl/Ch film). All films showed a moderate water vapor transmission rate: 19.6–21.3 g/(h m2). Although solubility was relatively high (26.5–35.4%), the integrity of the films was maintained after immersion in pH 5.0 buffer solution for 24 h. The 70/30 film was the most transparent, uniform, and deformable of the formulations evaluated, showing low crystallinity according to X-ray diffraction results. Dynamic mechanical analysis revealed a high correlation between its viscoelastic behavior and changes in RH (from 0 to 80% RH). Studies conducted using an agar disc diffusion protocol showed antimicrobial activity against Escherichia coli and Staphylococcus aureus bacteria only in the contact area under the film discs.