Active chitosan films incorporated with Hedychium coronarium essential oil distillation wastewater: Structure, properties and preservation mechanism

The high cost of specialized plant-derived extracts limits the large-scale application of chitosan-based active packaging films. Here, we developed a low-cost, biodegradable active packaging film by incorporating Hedychium coronarium essential oil distillation wastewater (HODW) into chitosan (CS). HODW was rich in hydroxyl-containing compounds, predominantly 2,3-dihydro-3,5-dihydroxy-6-methyl-4 H -pyran-4-one (DDMP, 24.4%) and maltol (2.8%), which formed hydrogen-bonding networks with the CS matrix. The composite film with 2.5% (v/v) HODW showed a water vapor transmission rate (WVTR) of 8.73 g/(m 2 ·h) (40% lower than pure CS), tensile strength of 11.42 MPa (4.2-fold increase) but reduced elongation at break (21.8% vs. 32.6% for pure CS). Its DPPH and ABTS radical scavenging activities reached 78.2% and 82.5%, respectively. Inhibition zone against Staphylococcus aureus and Escherichia coli were 8.90 ± 0.58 mm and 10.10 ± 0.32 mm, corresponding to 5.9- and 2.7-fold increase over pure CS. In a 12-day blueberry preservation test, the film limited weight loss to 4.2–4.9%, retained 68–75% of vitamin C, and prevented visible mold growth. The films disintegrated completely within 45 days in natural soil, and the residual film-forming solution exhibited no phytotoxicity to mung bean sprouts. This work provides a viable waste-valorization strategy for producing green active packaging materials.