Smartphone-assisted fluorescent film based on the Flu grafted on Eu-MOF for real-time monitoring of fresh-cut fruit freshness

Indicator migration within intelligent packaging systems can compromise the safety of the food matrix and the accuracy of coloration, particularly in high humidity packaging. Herein, Eu-BDC-NH₂-Fluorescein (MOF-Flu) nanofillers were synthesized by the amide coupling, followed by an analysis of their structural, morphological characteristics, and optical response. The MOF-Flu and microcrystalline cellulose (MCC) nanomaterials were embedded into a sodium carboxymethyl cellulose (CMC-Na) substrate to fabricate enhanced packaging films. Several beneficial properties, including superior hydrophobicity and water resistance, improved mechanical properties, and enhanced thermal stability, were observed for CMC-Na/MOF-Flu compared to CMC-Na/MCC. Additionally, the MOF-Flu composite film exhibited improved UV–visible barrier properties, exceptional resistance to pigment migration, and good time-temperature stability. Finally, a significant linear correlation (R² = 0.9938, LOD: 1.79–2.90 N/cm², RSD: 2.16%, recovery: 103.93%) was established using a smartphone application to display the relationship between the S_RGB-values of MOFs-based films and hardness of fresh-cut Narcissus mangoes at 4 °C. The digital sensing platform utilizing smartphones has pioneered a powerful approach for the on-site rapid quantitative assessment of fresh-cut fruit freshness, significantly enhancing the precision and convenience of intelligent packaging. Furthermore, the developed indicator material MOF-Flu can accurately and non-destructively monitor changes of fruit freshness, alleviating concerns regarding dye contamination during migration.