Challenges in lignin integration within biopolymer matrices: Toward stable and effective lignin nanoparticles as additives for sustainable food packaging
Chiara Marcoaldi, Veronica Acampora, Virginia Venezia, Cristina Prieto, Rossella Grappa, Brigida Silvestri, Giuseppina Luciani, José M. Lagarón
Abstract
Lignin nanoparticles (LNPs), synthesized from Kraft lignin (KL) using a green, cost-effective and scalable hybrid process, were incorporated into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) to develop sustainable food packaging materials . Electrospun fibers with varying LNPs content were annealed into continuous films (PHBV/LNPs). The morphological, thermal, optical, antioxidant, antimicrobial, barrier, and mechanical properties of the films were evaluated and compared with those of PHBV/KL films. Results showed that PHBV/LNPs films exhibited superior properties compared to PHBV/KL ones. Indeed, LNPs ensured better dispersion within the polymer matrix than neat KL, resulting in enhanced thermal stability, UV-Vis blocking properties and reliable antioxidant performance (% DPPH inhibition of about 90 % even after 20 days of film production). PHBV/LNPs films reduced bacterial counts against S. aureus by approximately 10 times (R∼1) compared to PHBV/KL ones. Moreover, the addition of LNPs did not alter the mechanical properties of pure PHBV, maintaining its suitability for food packaging, while not significantly affecting water barrier properties, particularly for oxygen permeability a reduction up to 10 times lower than neat PHBV was observed, thus outperforming conventional petroleum-based plastics. Therefore, the uniform size distribution of the LNPs facilitated their dispersion within the polymer matrix without the need for additional chemical functionalisation, ultimately resulting in a stable and effective material suitable for active food packaging applications.