Melt Extrusion Of Environmentally Friendly Poly(L-Lactic Acid)/Sodium Metabisulfite Films For Antimicrobial Packaging Applications

Food packaging materials compounded with antimicrobial additives can substantially diminish the incidence of foodborne diseases. Here, poly(L-lactic acid) (PLA) films containing sodium metabisulfite (NaM) were produced by melt extrusion as an attempt to develop a new biodegradable material with antimicrobial properties for packaging. Life cycle assessment (LCA) simulations revealed that the environmental footprints of the PLA film did not change upon NaM addition, and that NaM is more eco-friendly than silver nanoparticles. The PLA/NaM films with NaM content varying from 0.5 to 5.0 wt.% were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and optical and mechanical properties determinations. The optical properties were sustained after the addition of NaM, but high NaM contents degraded the light transparence of the PLA matrix at some extent. The thermal stability and tensile properties of the PLA film decreased proportionally to the NaM content, while no changes were observed on T-g, T-m, and X-c, as determined by DSC. Agar diffusion tests revealed that the PLA/NaM films had no antimicrobial activity on Saccharomyces cerevisiae at 35 degrees C, which was related to the limited migration of NaM from the glassy PLA matrix. The biodegradable PLA films compounded with NaM through melt extrusion display adequate optical, thermal, and mechanical properties to cover most food packaging applications, representing an essential step toward the development of eco-friendly packaging materials that can potentially exhibit an antimicrobially active surface.