Antimicrobial biodegradable packaging films from phosphorylated starch: A sustainable solution for plastic waste

This study focused on developing biodegradable packaging films based on starch as an alternative to non-biodegradable such as petroleum-derived synthetic polymers. To improve its physicochemical properties, potato starch was chemically modified through phosphorylation. Starch phosphorylation was carried out using cyclic 1,3-propanediol phosphoryl chloride (CPPC), produced phosphorylated starch (PS), and analyzed using Fourier transform infrared (FT-IR), X-ray diffraction (XRD), Nuclear magnetic resonance (NMR), and Thermogravimetric analysis (TGA). The thermal stability of PS increased to 292 °C due to the formation of starch phosphate ester in comparison to pure starch (281 °C). Moreover, using glycerol as a plasticizer, the solvent casting method was employed to synthesize the PS/PVA biofilms. The synthesized biofilms (PPS) were further characterized using FT-IR, TGA, Mechanical testing, and Scanning electron microscopy (SEM). The result indicated that blend films have higher tensile strength (41.61 MPa) and elongation at break (240 %) than pure PVA film (29.84 MPa, 102 %). The soil burial study showed that the biodegradation of PPS blend films increased to 63.79 %. Nevertheless, the blend film showed decreased solubility, water absorption, water vapor transmission rate, and moisture content with PS, while its surface hydrophobicity increased from 61.2° to 95.6°. PPS blends have stronger antibacterial activity against S. aureus than E. coli. Accordingly, the prepared PPS III biofilm was further used for brown bread packaging. Compared to LDPE packaging, the bread wrapped in PPS III blend film exhibited enhanced visual appearance and extended shelf-life. The novelty of our work lies in the modification of starch using CPPC, which was further used to fabricate biodegradable films. Therefore, the developed biofilm may be a reference for additional research and can potentially replace synthetic, non-degradable polymer-based films in the packaging industry.