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

Abstract

Summary 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.

Energetic and Economic Evaluation of Zero-Waste Fish Co-Stream Processing

“…Production of premium oil and protein-rich hydrolysate was conducted in a novel two-stage process, see Figure 5 . The principles of this process are given in the work of Slizyte et al [ 45 ]. The process differs from the thermal process (concept III) as it uses a gentler, mild thermal extraction during the first stage to obtain premium quality oil.…”

“…The aqueous phase was evaporated to 50 wt.% concentration or dried. The aim of the gentle processing of the fish co-stream is to increase the quality and amount of value-added products and even utilise them as food instead of feed [ 45 , 54 ].…”

“…Traditionally enzymatic hydrolysis and/or thermal treatments are used for processing of fish co-streams [ 5 , 12 ]. The new technological concept presented by Slizyte et al [ 45 ] produces high-quality fish oil and protein-rich fractions more sustainably and profitably. A techno-economically feasible and sustainable zero-waste process is needed to reach full utilisation of this co-stream’s potential [ 46 ].…”

Comparison of amino acid release between enzymatic hydrolysis and acid autolysis of rainbow trout viscera

“…Oil constitutes a valuable co-product and both the enzymatic hydrolysis, and the silage process can affect its quality through oxidation. Other authors have previously demonstrated that oil obtained by centrifugation after a mild thermal treatment before the hydrolysis significantly reduces the oxidation values and is more stable [ 35 ]. Moreover, the presence of oil reduces the efficiency of the enzymatic hydrolysis by preventing the access of the enzymes to the protein and reducing the energy transfer in the heating of the mass in the hydrolysis process.…”

Enzyme-Assisted Extraction of Fish Oil from Whole Fish and by-Products of Baltic Herring (Clupea harengus membras)

“…However, some methods, such as enzymatic hydrolysis using specific enzymes, allow the simultaneous extraction of both fractions from, e.g., whole fish or fish by-products, such as skin, heads, fins and viscera [18]. For example, a two-stage processing using mild thermal treatment together with enzymatic treatment allows the separation of high-quality oil and protein fractions [19]. Additionally, pH-shift processing can be used to extract proteins while removing up to 50% of the lipids [20].…”