Cellulose based microcapsules with binary phase change core for dual-functional thermal buffering and responsive antimicrobial food packaging.

Frozen foods are vulnerable to quality deterioration and biological contamination during unexpected cold-chain interruptions. Herein, we report a multifunctional smart packaging film (CCMP) that integrates active thermal management with temperature-responsive antimicrobial defense. Through interfacial polymerization, cellulose-based microcapsules (CA@CM) were engineered to achieve the secure co-encapsulation of a binary phase-change material (PCM) core and a natural antimicrobial agent, cinnamaldehyde (CA). The CCMP films demonstrated thermal stability, mechanical robustness, and broad-spectrum antimicrobial activity against food-spoilage fungi (Mucor racemosus and Penicillium roqueforti) and bacteria (Staphylococcus aureus and Escherichia coli). By serving as thermal buffers against external thermal fluctuations, the resulting composite films exhibited a latent heat absorption capacity (85.37 J/g) and low thermal conductivity (1.07 W/mK). Upon temperature elevation, the liquefaction of the PCM facilitated the release of CA, thereby enabling on-demand antimicrobial release when the risk of microbial proliferation increased. Simulated cold-chain interruption assays using an ice cream model showed that the CCMP films delayed temperature rise and melting by 30 min relative to the control while maintaining structural integrity.