Off-Flavors in Pond-Cultured Channel Catfish

Abstract

A serious problem in pond culture of fish is the absorption of compounds from the aquatic environment which impart disagreeable flavor in the fish. “Musty” or “muddy” off-flavor is caused by geosmin (trans, 1, 10,-dimethyl-trans-9- decalol) and 2-methylisoborneol. These compounds can be produced by various species of algae and actinomycetes. Aquarium studies with mono-species cultures of geosmin-producing algae indicate that channel catfish can absorb off-flavor compounds exclusive of the digestive tract. Geosmin was absorbed at sensorily detectable levels within 24 hours. Off-flavor can be purged from catfish relatively quickly by holding in clean water for 4-10 days. Temperature influences rate of flavor removal and also rate of weight loss by the fish. Although the “musty-muddy” flavor has been regarded as the predominant pond-related off-flavor in fish, a recent study in which catfish from 220 commercial ponds was sensorily evaluated showed that it accounted for only 17% of the off-flavor. “Sewage” was the dominant flavor in 25% of the off-flavor samples. “Stale”, “rancid”, “metallic”, “moldy”, “petroleum”, and “weedy” were other off-flavors described. Geosmin was chemically identified in the fish with the “musty-muddy” flavor; the other compounds have not been identified.