Physicochemical properties and antibacterial activity of polylactic acid/starch acetate films incorporated with chitosan and tea polyphenols

Polylactic acid (PLA)/starch acetate (SA) base film was prepared by scraping film method with PLA as the base film material, modified SA as the filling phase and polyethylene glycol (PEG) as plasticizer. Chitosan (CS)/tea polyphenol (TP) antibacterial agent was coated on the surface of PLA/SA base film by coating method. The morphology and structure of the composite film were characterized by FTIR, XRD, SEM and thermogravimetric analysis, and the mechanical, optical and antibacterial properties were tested and analyzed. The results showed that CS/TP compound antibacterial agent was well combined with PLA/SA base film. Compared with the PLA/SA base film, when the content of TP (based on the mass of PLA/SA base film, the same below) was 0.4%, the tensile strength of the composite film increased by 29.33%, had good mechanical strength (24.96 ± 0.65 MPa), and the elongation at break increased by 29.34%; There was no obvious change in transparency, the light transmittance decreased by 0.86%; At the same time, the antibacterial composite film had good antibacterial effect on Escherichia coli, Staphylococcus aureus and Bacillus subtilis. PLA/SA/CS/TP antibacterial composite film could be used in food packaging, especially those designed to protect food from light and microbial decay.