Development of nanopillar-structured poly(lactic acid) films incorporating grape pomace-derived activated carbon for smart food packaging applications

To address environmental concerns in the food packaging industry, there is a growing demand for biodegradable materials with enhanced functional properties. Poly(lactic acid) (PLA) is a promising biodegradable polymer for food packaging, yet it exhibits limitations in barrier performance, mechanical strength, and antibacterial activity. This study focuses on enhancing PLA films by incorporating activated carbon (AC) derived from grape pomace (GP), an abundant byproduct of wine production, thereby promoting a sustainable and circular bioeconomy approach. Biochar (BC) was produced via pyrolysis of GP at 350, 450, 550, and 650 °C for 1 and 2 hours. The optimal BC (obtained at 550 °C for 1 hour) exhibited a porous morphology suitable for further activation. ACs were then synthesized from both raw GP and BC at 450 °C and 550 °C for 1 hour. The most effective variants, AC_550_1h and ACBC_550_1h, were selected based on their superior porosity and used to fabricate PLA films at different loadings (1, 2, 3, 4, and 5 wt.%). The films were characterized using FTIR, XRD, SEM, EDS, and optical profilometry, and evaluated for their adsorption capacity (water and ethanol) and mechanical properties. The optimal formulation, PLA_3ACBC, exhibited enhanced elasticity and adsorption capacity, along with the successful formation of surface nanopillars—confirmed via profilometry. These nanopillars significantly improved antibacterial performance against E. coli and S. aureus compared to smooth, unmodified films. The results show that AC addition enhances the sorption and mechanical behavior of PLA films up to a threshold (3 wt.%). Beyond this concentration, particle aggregation and microcrack formation reduce film performance. Films incorporating AC from BC retained their mechanical integrity better at higher loadings than those using AC from raw GP. This study demonstrates a sustainable strategy for valorizing grape pomace into high-performance activated carbon additives for biodegradable food packaging.