Biodegradability of selected poly(lactic acid) composites for sustainable food packaging applications

To support a sustainable economy, the development of advanced and environmentally friendly food packaging systems is essential. This study presents innovative biodegradable composites based on polylactic acid (PLA), incorporating grape pomace and copper (Cu) nanoparticles as functional fillers to improve packaging performance. The composites exhibited rapid swelling when exposed to liquids. Grape pomace promoted a stable swelling behavior, maintaining a rate of ~1.2% over 100 days, leading to degradation through filler dissolution and increased porosity. In contrast, Cu nanoparticles initially enhanced structural integrity but later underwent surface delamination, accelerating swelling and degradation. Composites with lower Cu content showed a consistent swelling rate of around 4% for 20–60 days, followed by gradual disintegration. Higher Cu concentrations induced swelling via delamination, while erosion debris limited fluid penetration, resulting in slow and sustained biodegradation over 100 days. Antibacterial tests indicated that grape pomace composites lacked antimicrobial activity, whereas Cu-containing composites demonstrated significant antibacterial effects against Enterococcus faecalis and Klebsiella species, as well as strong antifungal activity against Candida albicans. These findings highlight the potential of PLA composites with grape pomace and Cu nanoparticles for biodegradable food packaging, offering tunable degradation behavior and enhanced antimicrobial properties.