Reactive extrusion‐processed shape‐memory food packaging films made from native and carboxymethylated plantain flour/polystyrene blends

Abstract

Several alternatives have been proposed to improve the properties of starch-based films. However, single step processing and modification procedures such as reactive extrusion (REx) have been little studied in conjunction with carbohydrate polymers. Films were prepared from native and carboxymethylated plantain (Musa ssp., group AAB, sub-group clone Harton) flour/polystyrene (PS) blends, with glycerol as a plasticizer, by REx using a twin-screw extruder with chromium octanoate (Cr(Oct)3) as a catalyst (Cat), followed by thermo-molding. The structural, physicochemical, thermal, surface, mechanical (shape memory) and antimicrobial properties relevant to the potential use of the films in food packaging applications, were then exhaustively characterized. The developed films could be used as shape materials due to their mechanical properties, which featured elastic, creep, and plastic zones, as long as the following mechanical thresholds are not reached: 1.00% strain and 1.14 MPa stress (for the film with the best characteristics). The results of the TGA, mechanical properties tests and antimicrobial activity assay suggest that Maillard reactions can occur simultaneously with the cross-linking reactions generated by the Cat between the natural and synthetic polymers. The films made with the carboxymethylated flour were less hydrophilic than those prepared using the native flour due to the establishment of a higher dipole moment.