High-pressure treatment of water-filled co-extruded polylactide films: Effect on microstructure, barrier, thermal,...

The impact of high-pressure treatments (450 and 600 MPa) on the morphological, thermal, structural, and barrier properties of commercial coextruded polylactide (PLA) packaging films has been explored to evaluate their applicability in food processing. Pouches filled with water as a food simulant were subjected to high-pressure treatment for 15 min at ambient temperature. Results indicated no significant changes in the visual appearance, color, integrity, or water barrier properties of the post-process pouches. However, high-pressure treatment affected mechanical property results. Thermal analysis of the film showed endothermic double melting peaks (165.12 and 170.55°C), which did not change with the pressurization; however, the exothermic crystallization peak (118.08°C) varied significantly. Both SEM and AFM micrographs demonstrated that the surface morphology and roughness parameters (arithmetic mean [S_a ] and root mean square height [S_q ]) of the films were significantly affected by the HP treatment, which is further complemented by the FTIR spectra and XRD diffractogram. Melt rheology (175-205°C) of the pressure-treated films showed a significant drop (20-30%) in mechanical rigidity (G') when compared to the untreated sample. Changes in the microstructure/crystallinity in the PLA films were indicated by van Gurp and Palmen plot. PRACTICAL APPLICATION: The results reported here can help to improve the design of the coextruded packaging materials so that it can be successfully implemented to high-pressure processing and high pressure-assisted thermal processing of food.