Fluorescent probes for cysteine recognition in complex food systems: response pathways, design strategies, and analytical challenges

Cysteine (Cys), a semi-essential amino acid with critical functions in food system, requires precise detection due to its dual role in food quality control and health risk assessment. Fluorescent probes have emerged as effective tools for Cys sensing, providing distinct advantages in sensitivity, selectivity and biocompatibility over conventional analytical techniques. This review comprehensively summarizes the development of fluorescent probes that have been successfully utilized for detecting exogenous or endogenous Cys in food matrices. To date, nearly forty small-molecule probes have been developed for application in the food sector, and these probes are classified into seven categories based on their structures and mechanisms of action. Furthermore, a growing number of nanoprobes, employing carbon dots, quantum dots, and metal nanoclusters, have increasingly been explored for Cys detection in the food sector, capitalizing on the unique photophysical properties of nanomaterials. These documented probes vary considerably in response times, excitation/emission profiles, linear detection ranges, detection limits, and optimal experimental conditions, thus providing adaptable tools for Cys determination across diverse food samples. This review exclusively focuses on probes applied to Cys analysis in complex food matrices, identifies existing analytical bottlenecks and provides novel insights into designing advanced Cys probes for specific screening in food industry.