The Recovery of Flavor Quality by Channel Catfish

• Published in: North American journal of aquaculture 2000-05, Vol.62 (3), p.189-194
• Main Authors: Dionigi, Christopher P., Johnsen, Peter B., Vinyard, Bryan T.
• Format: Article
• Language: English
• Subjects: 2-Methylisoborneol; Freshwater; geosmin; Ictalurus punctatus
• ISSN: 1522-2055; 1548-8454
• DOI: 10.1577/1548-8454(2000)062<0189:TROFQB>2.3.CO;2

Intensive production of channel catfish Ictalurus punctatus requires copious feeding. Nutrients from uneaten feeds and fish excreta contribute to the growth of microorganisms. Certain microbes that occur frequently in aquaculture systems produce the “muddy and earthy” off‐flavor metabolites 2‐methylisoborneol (MIB) and geosmin. Fish containing MIB or geosmin can exhibit an off‐flavor that makes them unacceptable for harvest as food fish. Following the cessation of exposure to MIB or geosmin, fish depurate off‐flavors. The minimum period required for fish to regain flavor quality is a critical concern for aquaculturists; scant information concerning this period prompted our investigation. Channel catfish were harvested from three commercial ponds, and fish from each pond were sorted into four size‐classes (0.4–0.8 kg, 0.8–1.3 kg, 1.3–1.6 kg, and 1.6–2.3 kg) on 30 August (summer) and on 18 October (autumn) 1993. Each group of fish was transferred into individual 2,000‐L fiberglass tanks, and each tank was supplied with groundwater (14 L/min). Geosmin was observed at the fall harvest only. Periods required for the mean MIB concentration of each group of fish to reach an estimated acceptance threshold of 0.7 μg/L were similar at both harvests and ranged from about 96 to 150 h. Periods required for a population of fish to recover flavor quality (defined as the point when more than 80% of the fish had MIB concentrations below the level that would cause rejection as food fish) were greater than periods required for the mean MIB concentration to reach 0.7 μg/L and ranged from 150 to 500 h.