Biochar-Stabilized Tea Tree Oil in Chitosan Membranes for Sustainable Antimicrobial Packaging

This study developed an active packaging material by incorporating tea tree oil (TTO)-loaded lotus stalk biochar (BC@TTO) into a chitosan (CS) matrix. Biochar was prepared from lotus stalks via pyrolysis at 600 °C and characterized, revealing a mesoporous structure with a specific surface area of 35.9 m²/g. Adsorption studies demonstrated that BC exhibited high affinity for TTO, following pseudo-first-order kinetics and the Langmuir isotherm model, with a maximum adsorption capacity of 295.6 mg/g. Chitosan-based composite membranes with varying BC@TTO contents (1-7 wt%) were fabricated by solution casting. The incorporation of BC@TTO significantly enhanced the tensile strength, elongation at break, barrier properties (water vapor and oxygen), and antioxidant/antibacterial activities of the membranes, with optimal performance observed at 3 wt% loading. However, higher loadings led to filler aggregation, reduced transparency, and compromised mechanical properties. In vitro release studies indicated that TTO release followed the Avrami model, suggesting a diffusion-controlled mechanism. Preservation tests on blueberries showed that the CS-3BC@TTO membrane effectively reduced weight loss and maintained fruit quality during storage. This work presents a promising strategy for designing bioactive packaging materials with sustained release functionality for food preservation applications.