Two-stage processing of salmon backbones to obtain high-quality oil and proteins

Traditional processing technologies for fish by‐products containing significant amounts of oils usually either give high amounts of oil or maximised solubilisation of proteins. Due to lower yields and insufficient quality, the proteins or the oil is considered as secondary products. The proposed concept combines a gentle thermal separation of oil followed by enzymatic hydrolysis of the remaining protein‐rich fraction. The first stage, thermal treatment (40 °C) of fresh salmon backbones, separated up to 85% of the oil from the raw material and gave high‐quality oil (PV = 0.2 ± 0.0 meq kg−1, 0.16 ± 0.05% free fatty acids). Separation of a significant part of the oil gave reduced mass flow into the enzymatic stage, which then requires less enzymes and reduced energy consumption. Among the tested enzymes: Trypsin, Corolase PP and Mixture of Papain and Bromelain gave the highest yield of fish protein hydrolysates (FPH), while use of Protamex and Corolase PP resulted in FPH with the best sensory properties leading to the lowest bitterness.