Microwave heating uniformity enhancement based on multi-walled carbon nanotube/chitosan packaging

Non-uniform heating is a major challenge in microwave food processing. To address this, we developed a biodegradable, microwave-active composite film by incorporating carboxyl-modified multi-walled carbon nanotubes (MWCNT-COOH) into a chitosan (CS) matrix. MWCNT-COOH markedly improved dielectric properties and formed a homogeneous, well-dispersed network within CS, enhancing interfacial compatibility and thermal conductivity. The optimized CS/MWCNT-COOH-0.9 film acted as an efficient microwave-absorbing and heat-conducting layer. When used as a film on model foods (rice balls) under 700 W microwave irradiation, it substantially improved heating uniformity, as evidenced by infrared thermography. The film reduced core-to-surface temperature gradients and eliminated hotspots and cold spots by converting microwave energy into heat via dielectric loss and Joule heating, followed by redistribution through thermal conduction. This work provides a practical packaging solution to enhance microwave heating for ready-to-eat foods and advanced processing technologies, with the final packaging exhibiting environmentally friendly characteristics.