Evaluation of wood tannins as multifunctional additives in PLA films for active food packaging applications

Food packaging is essential for preserving food quality, yet it still relies on petroleum-based, non-renewable materials that raise environmental concerns due to their limited biodegradability. This challenge highlights the urgent need to transition toward fully bio-based and renewable alternatives. Moreover, beyond acting as a physical barrier, modern food packaging must provide active functions like antioxidant and UV protection to extend shelf life. A promising approach to address this demand involves the incorporation of naturally derived functional additives into biopolymer systems. Tannins, naturally occurring polyphenolic compounds often obtained as by-products in agro-industrial processes, represent a promising waste-derived and bio-based alternative, due to their intrinsic antioxidant, antimicrobial, and UV-blocking properties. The present study aimed to develop an active, bio-based food packaging film using polylactic acid (PLA) as a biobased and compostable matrix and tannins as multifunctional active agents, adopting a melt-compounding extrusion approach to ensure industrial scalability. The first phase of the research focused on identifying the most suitable plasticizer/compatibilizer (polyethylene glycol (PEG) or sorbitol) and its optimal concentration to improve PLA/tannin compatibility under melt-processing conditions, ensuring structural integrity, mechanical performance, and processability. Subsequently, PLA-based films were extruded with increasing concentrations of tannins to evaluate their functional performance. The incorporation of tannins provided the films with significant antioxidant activity and high UV-blocking properties, both of which are essential for preventing the oxidative degradation of light-sensitive food products. The results demonstrate that upcycled tannins from agro-industrial waste can convert standard biopolymers into multifunctional systems for sustainable active food packaging.