Case study on depuration of RAS-produced pikeperch (Sander lucioperca) for removal of geosmin and other volatile organic compounds (VOCs) and its impact on sensory quality

Effect of depuration on content of geosmin in pikeperch (Sander lucioperca) produced in a commercial RAS farm
was examined during a 15-day period. Concentrations of geosmin in the fish were related to geosmin content in
the water. For depuration, half of the water volume in a 230 m3 production tank was replaced daily with
geosmin-free water. After 8 days of depuration and absence of feeding, content of geosmin in the fish was
reduced from 710 ± 245 ng/kg to 165 ± 50 ng/kg (mean ± SD, p < .01). Additional depuration for 7 days
only reduced the geosmin content to 135 ± 24 ng/kg. Geosmin concentration in the water was initially 34 ng/L
but declined to 10 ng/L after 15 days. Changes in geosmin concentrations in water of the depuration tank
indicated that geosmin was released by the fish during the depuration. In addition to removal of geosmin, the
depuration also decreased concentrations of 28 different volatile compounds from the fish. Sensory analysis
showed decrease in intensity of geosmin flavor upon depuration and improved the overall sensory quality of the
fish after 2 weeks of depuration. Our study shows that geosmin and other off-flavors in pikeperch from RAS
production can efficiently be removed to be a level that is below the threshold to most consumers.