Fuente: "milk OR dairy products" J AOAC Int. 2026 Jul 10:qsag064. doi: 10.1093/jaoacint/qsag064. Online ahead of print.ABSTRACTBACKGROUND: Cysteine (Cys) is an essential amino acid for the human body. It naturally exists in various foods and serves as a crucial additive in the food industry, so accurate quantification of Cys is vital for food. Several probes for detecting Cys have been developed. However, the majority of fluorescent probes exhibit limitations in food applications.OBJECTIVE: This study aimed to develop a dual-channel near-infrared fluorescent probe (NC-NIR) for selective and sensitive quantification of Cys in various food samples.METHODS: The detection performance of the NC-NIR probe was systematically evaluated, including its dual-channel response spectra, reaction mechanism, limit of detection (LOD), selectivity, response time, and feasibility for analyzing actual samples.RESULTS: The probe (NC-NIR) exhibits high selectivity and low LOD = 34 nM) for the detection of Cys. The NC-NIR probe exhibits dual-channel fluorescence response toward Cys, exhibiting emission wavelengths at 550 nm and 825 nm. Furthermore, NC-NIR exhibits near-infrared characteristics that can overcome background fluorescence in food, and has been successful in detecting Cys content in apples, jujubes, broccoli, pears, onions, and milk slices.CONCLUSIONS: This dual‑channel NIR probe offers a promising near-infrared strategy for in-situ quantification of Cys in food samples.HIGHLIGHTS: A dual-channel, low background, high selectivity and low LOD probe for the detection of Cys in food samples.PMID:42432851 | DOI:10.1093/jaoacint/qsag064