DESIGNING STARCH-CONTAINING, ANTIMICROBIAL, PLASTIC FILMS FOR BIODEGRADABLE FOOD PACKAGING

Abstract

Conventional single-use plastic packaging has contributed significantly to the health and well-being of our society but also negatively impacted our environment due to its persistence after use. Since recycling is not a complete solution, rapidly biodegradable materials like thermoplastic starch (TPS) blends offer a more sustainable alternative. Additionally, to stave off the premature breakdown of starch-containing materials as well as extend the shelf life of enclosed foods, microbial control strategies need to be developed. To overcome the inherent brittleness of TPS, this work explores the potential of xylitol and erythritol as melt plasticizers for waxy corn starch (̴100% amylose). Characterizations revealed that both xylitol and erythritol can gelatinize and plasticize starch under 25% wt. Particularly, xylitol demonstrated superior plasticizing and compatibilizing effects, leading to a ductile TPS packaging film with uncharacteristically high elongation at break (EB, 422% ± 48%). The ductile TPS was blended with up to 70% Ecovio bioplastic without requiring compatibilizers and retaining much of its EB value (298 ± 24%). Using xylitol as a melt plasticizer also enhanced the mechanical and hydrophobic qualities of the TPS/Ecovio film as well as its oxygen permeability and puncture extension. Furthermore, polymerized curcumin copolymer (PCEG) was investigated as a grafted coating onto the developed TPS/Ecovio® blend. The antimicrobial activity of PCEG and PCEG coating film was evaluated against foodborne bacteria. The polymerized curcumin by itself demonstrated antimicrobial activity against the gram-negative bacteria Escherichia coli BL21 and Pseudomonas aeruginosa PA01, as well as the gram-positive bacterium Staphylococcus aureus. Additionally, the PCEG-coated films showed surface inhibition of Glutamicibacter soli (IAI-3), a gram-positive bacterium making polymerized curcumin copolymer coatings a suitable approach to add antimicrobial features in thermoplastic starch composites for biodegradable food packaging.