Composition of rainbow trout filets (Oncorhynchus mykiss): Reference data for the analysis of added water

Rainbow trouts (Oncorhynchus mykiss) obtained from Bavarian aquaculture farms (BY) (18 samples) and from retail markets (H) (24 samples) were filleted by hand in the laboratory and the fillets (without skin) were analysed for their composition. For both sample groups, mean contents of water (BY: 74.0 %; H: 73.4 %), protein (BY: 19.7 %; H: 19.0 %), fat (BY: 5.3 %; H: 7.0 %) and ash (BY: 1.4 %; H: 1.2 %) were in accordance with literature data for rainbow trout fillets. Furthermore, the fillets were analysed for their total phosphorus (as P2O5; BY: 0.57 %; H: 0.54 %) and non-protein nitrogen (NPN) content (BY: 2.4 %; H: 2.3 %) as well as for their pH (BY: 6.41; H: 6.42). Based on the data presented, a maximum water/protein ratio of 4.5 and a nitrogen factor of 3.04 are proposed as reference values for the analysis of added water in rainbow trout fillets.