Fast and Sensitive Measurement of Off‐Flavors in Recirculating Aquaculture Systems

RATIONALE: Geosmin and 2-methylisoborneol (2-MIB) are odor-active compounds responsible for earthy off-flavors in fish, creating significant quality concerns in recirculating aquaculture systems (RAS). Their extremely low odor thresholds make rapid and highly sensitive detection essential for maintaining product quality and consumer acceptance in aquaculture production. METHODS: A novel analytical method was developed using static headspace sampling combined with proton transfer reaction-mass spectrometry (PTR-MS) for the detection of geosmin and 2-MIB in aquaculture water. Sample preparation was optimized by sodium chloride addition to enhance salting out, incubation at 90 °C, and maximization of headspace injection speed into the PTR-MS system to improve analyte sensitivity. RESULTS: The optimized method achieved detection limits of 19 ng·L⁻¹ for geosmin and 4 ng·L⁻¹ for 2-MIB with a total sample screening time of less than 10 minutes. Detection limits were within the same low ng·L⁻¹ range as the odor thresholds of these compounds, enabling quantification at sensorily relevant concentrations associated with off-flavor perception. CONCLUSIONS: This PTR-MS-based approach provides a rapid and sensitive method for objective detection of geosmin and 2-MIB in aquaculture water at concentrations relevant to sensory off-odor impairment. The method shows strong potential for routine monitoring in RAS and may be extended to other volatile compounds and aqueous analytical applications.