Flavor tainting of fish in the Upper Wisconsin River caused by alkyl- and thiophenols

Compounds responsible for pronounced off-flavors in Walleye pike (Stizostedion vitreum) and other sportfish in the Upper Wisconsin River were identified by gas chromatography-mass spectrometry and sensory techniques. Alkylphenols (2-isopropyl-, 3-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 found to be the principal contributors to flavor tainting in fish which was most pronounced in the spring. Data indicated that thiophenol entered the river sporadically through discharges from paper mills. Analysis of fish, river sediments, insects, and woods supported a hypothesis that alkylphenols were indirectly derived from paper pulping activities, and that the food chain of fish was involved in the transport of alkylphenols from the environment to fish.