Green Food Packaging with Integrated Functions of High-Efficiency Radiation Cooling and Freshness Monitoring

An optimal temperature environment is crucial for ensuring that the freshness of agricultural products is maintained during transportation. However, packaging materials often have a limited ability to dissipate heat and cannot accurately indicate the condition of the products, leading to significant losses in the logistics. Here, in order to achieve the fresh delivery of agricultural products, we constructed a ZnO-nanorods/cellulose membrane-starch membrane@blueberry anthocyanins (ZnO-NRs/CM-SM@BA) packaging material that has efficient heat dissipation to delay spoilage and the ability to accurately indicate the freshness of agricultural products via color changes. The ZnO-NRs/CM layer exhibited high visible reflectivity (94.4%) and infrared emissivity (98.8%) with the help of the rod-like structure of the ZnO-NRs, which contributed to a substantial reduction of heat input and a strong dissipation of heat accumulation. Compared with a PE film when in outdoor mode, the obtained membrane was able to realize passive cooling of 6.5 °C. Furthermore, the addition of anthocyanins caused Zn-NRs/CM-SM@BA to be sensitive to pH changes, showing different colors in the face of different pH environments. When applied to monitor the freshness of agricultural products, ZnO-NRs/CM-SM@BA showed a significant color change from celadon to pink with the decay of the agricultural products. The prepared ZnO-NRs/CM-SM@BA combines intelligent packaging materials with passive radiation cooling materials, thus making a superior contribution to reducing unnecessary losses in agricultural product logistics and expanding the single indicating role of intelligent packaging to the field of thermal management.