Hemicellulose/PVA-based bioactive films for food packaging: Effect of the molecular weight of avocado pruning waste-derived hemicellulose on biocomposite properties

The rising demand for sustainable packaging and urgent need for circular strategies in the agri-food sector motivate exploring biopolymer packaging from agri-food by-products. This study presents an efficient method for utilizing avocado pruning waste (APW) by extracting hemicelluloses for polyvinyl-alcohol (PVA)-based food packaging films. Autohydrolysis and tangential-flow diafiltration produced hemicellulose fractions with varying molecular weights: >50, 50-8, 8-1, and 1 kDa. High Mw-hemicelluloses exhibited high antioxidant power (>70 %) owing to their rich ferulic and trans-cinnamic acids, while low Mw-fractions demonstrated superior antimicrobial capacity, with a Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) against L. monocytogenes of 9 mg/mL and 14 mg/mL, respectively. Hemicellulose-enriched PVA-based films displayed heightened antioxidant capacity (>40 %) and excellent UV-light blocking efficiency (>80 %) with minimal transparency loss (80 %). Low Mw-range fractions decreased water solubility (8.4 % and 7.6 % for 5 % <1 kDa and 8-1 kDa films, respectively) enhancing water absorption properties (swelling degree of 766 % for 5 % <1 kDa and 992 % for 10 % 8-1 kDa films, respectively), whereas high Mw-range fractions strengthened mechanical properties and biodegradability (67 % and 59 % improvement, respectively). The differential effects of APW-derived hemicelluloses on PVA films underscore their potential as bio-based polymer source for the packaging industry, showing improved mechanical and bioactive properties.