Advanced fluorescent materials for intelligent food freshness monitoring: design, mechanisms, and multi-target applications

Fluorescent biopolymer-based intelligent monitoring systems enable rapid, intuitive, and quantifiable optical transduction of chemical signals associated with food spoilage, including volatile bioamines, pH shifts, and redox reactions, representing a highly promising strategy for food freshness assessment and intelligent packaging. This review systematically outlines recent progress in the design and construction of such intelligent platforms by integrating five representative fluorescent materials—metal–organic frameworks (MOFs), metal nanoclusters (MNCs), carbon dots (CDs), aggregation-induced emission (AIE) materials, and fluorescent dyes—into biopolymer matrices including polysaccharides and proteins. Core stimulus–response mechanisms are comprehensively discussed, covering fluorescence resonance energy transfer (FRET), intramolecular charge transfer (ICT), photoinduced electron transfer (PET), excited-state intramolecular proton transfer (ESIPT), and AIE, which collectively give rise to fluorescence enhancement/quenching, ratiometric responses, colorimetric transitions, and multichannel signal output. For lanthanide MOFs, particular emphasis is placed on the regulation of coordination chemistry, including metal nodes, ligand structures, pore microenvironments, and the antenna effect, which govern energy transfer efficiency, adsorption affinity toward biogenic amines, and sensing sensitivity. Representative applications of single-channel, multichannel, and monitoring–preservation integrated systems with antibacterial and antioxidant capabilities are comparatively evaluated in real food matrices such as meat, aquatic products, and dairy products, with key performance indicators including sensitivity, response time, stability, visualization efficiency, and practical applicability highlighted. Finally, critical challenges are identified concerning precise coordination structure modulation, signal stability in complex food environments, fluorescent component migration and biosafety, green scalable fabrication, and regulatory compliance. Future directions are also prospected, highlighting synergistic opportunities from coordination chemistry, high-throughput screening, machine learning, and sustainable biopolymer processing. This review provides theoretical support and design principles for developing robust, safe, reliable, and practically viable fluorescent biopolymer-based intelligent food monitoring systems.