Assessment of Reprocessed Polylactic Acid from Controlled Virgin Feedstock for Food Packaging Applications

The growing impact of fossil‑based plastics on the environment has driven interest in bioplastics such as polylactic acid (PLA), a biobased and compostable polyester widely used in food packaging but with limited properties. Although designed for composting, preventing the contamination of traditional recycling streams is essential¹. In industrial production, defective parts and burrs discarded can be reprocessed into pellets from a controlled source, avoiding complex washing². Studies have evaluated performance after reprocessing cycles³; however, for food contact applications, the potential migration of substances, including non‑intentionally added substances, remains a challenge.

This study evaluates the reuse of industrial discarded PLA parts for food contact. Films were produced from virgin and reprocessed PLA through melt extrusion and hot pressing, with reprocessing simulated by one additional extrusion cycle to the virgin material. Melt flow index (MFI), tensile properties, overall migration (ethanol 50 % v/v, 10  days, 40 °C), and water vapor transmission rate (WVTR) were assessed. Volatile (VOCs), semi‑volatile (SVOCs) and non‑volatile (NVOCs) compounds were identified through chromatographic/mass‑spectrometric techniques. The migration of metals (Ba, Co, Mn, Zn, Cu, Fe, Li, Al, Ni, Eu, Gd, La, Tb, As, Cd, Cr, Pb, Hg, Sb) was tested in 3 % acetic acid (60 °C, 10  days).

Results showed a slight rise in MFI, indicating minimal degradation. Tensile strength and modulus decreased slightly but not significantly. WVTR remained comparable. Overall and metal migration increased marginally but stayed well below the legal limits. The reprocessed PLA exhibited more VOCs and NVOCs absent in the virgin sample. Aldehydes and oligomers predominated, though most showed low migration, underscoring the importance of clean equipment. Metal migration stayed below specific limits. Overall, the reprocessed PLA retained functional properties and kept the migration of key substances within established limits.

1. Regulation (EU) 2025/40.
2. Silva, T. et al. J. Polym. Sci. 63, 2043–2054 (2025).
3. Agüero, Á. et al. Polymers. 15, 285 (2023).