Amino-functionalized MIL-53(Al)@ PLA indicator for real-time colorimetric detection in intelligent fish packaging

Ensuring the freshness and safety of perishable foods requires intelligent indicators capable of real-time spoilage monitoring. In this study, a high-performance colorimetric indicator was developed by incorporating an amino-functionalized aluminum-based metal-organic framework, NH 2 -MIL-53(Al), into a poly(lactic acid) (PLA) matrix. The composite film (NH 2 -MIL-53(Al)@PLA) exhibited uniform particle dispersion and improved thermal stability up to approximately 450°C, alongside a 2.5% reduction in moisture absorption compared to neat PLA. While the tensile strength and elongation at break decreased from 40.58 to 13.36 MPa and 27.25% to 1.12%, respectively, the film demonstrated significant antibacterial activity via a modified well assay against Escherichia coli and Staphylococcus aureus , yielding clear inhibition zones of 21.20±0.10 and 30.34±0.22 mm, respectively. Notably, the indicator showed a rapid and irreversible colorimetric response to volatile amines, achieving a low limit of detection (LOD) of 5.24 µM (gas-phase equivalent of 128.12 ppm) and a limit of quantification (LOQ) of 15.90 µM. ICP-OES migration studies confirmed high food safety, with negligible aluminum release in water (