Characterisation of aroma-active and off-odour compounds in German rainbow trout (Oncorhynchus mykiss). Part II: Case of fish meat and skin from earthen-ponds farming

•First report of odorants by GC-O and AEDA in German aquacultural rainbow trout fish.•Orthonasal sensory evaluation and instrumental investigation of odour substances.•Identification of 75 odour-active constituents in aquacultural rainbow trout fish samples.•Newly reported are rotundone, 4-ethyloctanoic acid and (E,Z,Z)-2,4,7-tridecatrienal.•12 earthy/musty compounds including geosmin, 2-methylisoborneol, and 8-heptadecene.

Odorous molecules in earthen-ponds rainbow trout aquaculture farming in Germany were investigated with a special focus on musty-earthy off-odorants. To this aim, fish meat and skin were extracted using solvent-assisted flavour evaporation (SAFE) and were mildly concentrated; extracts were subsequently analysed by means of one- and two-dimensional high-resolution gas chromatography coupled with mass spectrometry and olfactometry (GC-MS/O and 2D-HRGC-MS/O). Aroma extract dilution analysis (AEDA) of the solvent extracts revealed the presence of 76 odorants of which 75 were successfully identified. Thereby, rotundone (black pepper) is described for the first time as an odour-active substance in fish. Moreover, a series of compounds is described for the first time in German aquaculture rainbow trout fish, including, amongst others, (E,Z,Z)-2,4,7-tridecatrienal, (E)-4,5-epoxy-(E)-2-decenal, 4-ethyloctanoic acid, 3-methylindole (skatole), d-limonene, and indole. The analytical findings were further compared to sensory evaluation of the samples, and previously obtained data on the respective aquacultural water.