Effect of branched polyethyleneimine and citric acid on the structural, physical and antibacterial properties of corn starch/chitosan films

To improve the antibacterial and physical properties of corn starch/chitosan films effectively, starch/chitosan/polyethyleneimine (PEI) blend films crosslinked by citric acid (labeled SCPC) with different contents (2.5 %, 5.0 %, 7.5 % and 10.0 %) were prepared by the solution casting method. The films were characterized in detail. The results showed that the addition of 3.75 % PEI improved the tensile strength and elongation at break of the starch/chitosan film simultaneously, but the thermal stability decreased. After CA was incorporated, the tensile strength and thermal stability of the films were enhanced significantly. FTIR, XRD, and 1H NMR analyses revealed strong interactions among CA, PEI and starch-chitosan. All films showed smooth and homogenous fragile cross-sections. The water vapor permeability of the film decreased overall after PEI and CA addition. Moisture uptake (MU) accelerated after PEI addition, but the balanced MU was reduced by CA cross-linking. All films showed an inhibitory effect on E. coli and S. aureus, and CA incorporation significantly improved the inhibition ability of the film. The SCPC film with 3.75 % PEI and 5.0 % CA addition has the best comprehensive properties, which endowed its application in the bioactive packaging field.