Fluorescent sensors and microdevices: a comprehensive review on real-time visual monitoring of freshness in meat and aquatic products.

The rapid deterioration of meat and aquatic products demands advanced monitoring technologies. This review focuses on recent advances in fluorescent sensors for their freshness monitoring. It first analyzes and compares the signal providers, transduction mechanisms, and response patterns of these sensors. Next, it discusses how these sensors apply to key biochemical freshness indicators across the spoilage process. These indicators range from early autolytic metabolites (adenosine triphosphate and hypoxanthine) to later microbial spoilage markers (volatile amines, biogenic amines, pH, and sulfides), with a comparative analysis presented. Furthermore, a dedicated section evaluates the integration of these technologies into microdevices, including filter papers, polymeric membranes, gels, and bio-based membranes. Portability and real-time capability are identified as the primary bottlenecks for practical adoption. Finally, the review outlines the challenges and future directions for commercializing fluorescent sensors. Overall, this review aims to offer a holistic theoretical reference for developing practical freshness monitoring sensors.