Off flavor characterization and origin in French trout farming

The results of a study on off-flavor problems in four French trout (Onchorynchus mykiss) farms are presented. Methodological aspects on sensory analyses and volatile compounds quantification in fish are discussed. Detection of odorous compounds by gas chromatography–mass spectrometry shows that significant concentrations of geosmin (up to 18 μg/kg in fat) are found in trout. The sensory evaluation, the presence/absence of geosmin in the flesh and the identification of off-flavor compounds producers demonstrate the implication of Microcoleus in the appearance of earthy/musty off-flavors. The presence of this particular cyanobacterium is linked to the deterioration of water quality during the water recirculation period. Correlations between chemical and sensory detection in the flesh indicate that the taste evaluation enables the differentiation of the four categories “non-tainted”, “slightly-tainted”, “tainted” and “strongly-tainted”. However, the average concentrations of geosmin found for these different intensities are relatively limited, from 0.2 to 4.9 μg/kg. Finally, recommendations are made to allow a more effective control of off-flavor occurrences.