Microcrystalline Cellulose-Stabilized Pickering Emulsions for Integrating Hydrophobic NADES into Agar Films: Structure–Function Relationships and Controlled Release Behavior

In this study, a microcrystalline cellulose (MCC)-stabilized Pickering emulsion approach was developed to integrate hydrophobic natural deep eutectic solvents (NADES; menthol:decanoic acid, 1:1 molar ratio) into agar-based biopolymer films. MCC was evaluated not only as a filler but also as a functional interfacial component governing hydrophobic phase distribution and structural organization. SEM analysis showed that MCC concentration significantly influenced morphology; films with 0.2% MCC exhibited a more homogeneous structure, whereas 0.5% MCC led to heterogeneous and irregular formations. Mechanically, films with 0.2% MCC showed higher elongation at break (16.37%) compared to 0.5% MCC (9.86%), while tensile strength remained similar (2.75-2.78 MPa). Increased MCC content enhanced surface hydrophobicity, as indicated by higher contact angle values. The 0.5% MCC films exhibited high moisture content (85%) and water solubility (93%), attributed to increased free volume and structural irregularity. Swelling index exceeded 40% in 0.2% MCC films but decreased at higher MCC levels. HS-GC-MS analysis revealed temperature-dependent controlled release of menthol, with significant release at 50 °C compared to 25 °C. Antimicrobial tests demonstrated broad-spectrum activity (8.9-24.2 mm). These results highlight MCC as an effective stabilizer for hydrophobic NADES integration and support the potential of these films for active packaging applications.