UV/blue-light-blocking polylactide films derived from bio-sources for food packaging application

Transparent biodegradable packaging materials capable of blocking the broad-spectrum of UV and blue light (200-500 nm) are crucial for packaging of light-sensitive food. This study offers a fully bio-based solution based on polylactide and natural light absorbers, aloe-emodin (AE) and riboflavin (RF), whose combined UV-vis absorption spectrum covers all the light between 200 and 500 nm. AE and RF were bonded to polylactide chains by serving as initiators for the ring-opening polymerization of lactide, resulting in the synthesis of light-blocking polylactides, PLA-E and PLA-R. To fabricate UV and blue light-blocking polylactide film (PLA/E_mR_n), PLA-E and PLA-R were blended with commercial polylactide. For the PLA/E_mR_n film containing only 0.87 mass% AE and RF group introduced by PLA-E and PLA-R, the transmittance against the UV-B, UV-A and blue light was only 38.8 %, 27.7 % and 25.5 %, respectively. Meanwhile, the film maintains high transparency (91.4 %) and good tensile strength above 59 MPa. Furthermore, the PLA/EmRn film exhibits an extended capacity for light-blocking, which may help reduce the photodegradation of the photosensitive nutrient riboflavin. Its protective performance surpasses both the polylactide film and commercially available PET packaging films. This study offers an eco-friendly strategy for developing UV/blue light-blocking food packaging based on all renewable resources.