Fully bio-based grease resistant composite coating: chitosan-Genipin-microfibrillated cellulose for sustainable paper food packaging.

As awareness of health concerns continues to rise, the development of new generations of sustainable food packaging materials has emerged as a focal point of significant attention. This study presents the development of a fully bio-based grease resistant composite coating composed of chitosan (CS), genipin (GP), and microfibrillated cellulose (MFC) for sustainable paper food packaging. The synergistic effects of crosslinking between CS and GP, combined with electrostatic interactions between CS and MFC, enabled the formation of a dense, interconnected coating layer on paper substrates. Systematic optimization of coating formulations revealed that a 2 wt% CS, 0.1 wt% GP, and 15 wt% MFC composition achieved maximum grease resistance (kit rating: 12/12) at a remarkably low coating weight of 4 g/m, outperforming existing chitosan-based coatings requiring higher application weights for medium performance. The composite coating significantly enhanced mechanical properties, with two kinds of food wrapping paper after coating exhibiting tensile strength improvements of 25 % and 13 %, and burst strength increases of 25 % and 41 %, respectively. Additionally, water vapor transmission rates decreased by 22 % and 28 %, demonstrating enhanced moisture barrier functionality. Practical evaluations have confirmed the coating's robust resistance to various organic solvents, as well as its stability in hot oil. Simulated food contact tests using fried chicken and sausages revealed no detectable grease penetration or structural compromise in coated papers. This study establishes the CS/GP/MFC coating as a high-performance, environmentally sustainable alternative to fluorinated and non-biodegradable materials, with broad applicability in grease resistant food packaging systems.