Volatile compounds in flavor-tainted fish from the Upper Wisconsin River.

Fillets from Walleye pike (Stizostedion vitreum) and Northern pike (Esox lucius) captured from the Upper Wisconsin River were analyzed for volatile components using simultaneous steam distillation-extraction and GC-MS techniques. Based on comparative odor assessments of eluting GC fractions and GC-MS analysis between control and tainted fish, trace amounts (ppb) of alkylphenols (2-isopropyl-, 4-isopropyl-, 2,4-diisopropyl-, 2,5-diisopropyl-, 2,6-diisopropyl-, 3,5-diisopropyl-, 5-methyl-2-isopropyl-, and 2-methyl-5-isopropyl-) and thiophenol were identified as the principal contributors to flavor-tainting found in fish during the spring of the year. Geosmin and 2-methylisoborneol were major contributors to mustiness flavor-tainting occurring in fish captured in the late summer and were more abundant in downstream fish than in upstream control fish.