Protein hydrolysate from salmon frames: Production, characteristics and antioxidative activity

Abstract

Protein hydrolysates from two forms of salmon frames named “chunk” and “mince” were produced and characterized. Both samples were subjected to hydrolysis using alcalase and papain at 1%–3% (w/w protein) for 0–240 min. Hydrolysate prepared with either protease at 3% for 180 min had the solid yield of 24.05%–26.39%. Hydrolysates contained 79.20%–82.01% proteins, 6.03%–6.34% fat, 9.81%–11.09% ash, and 4.02%–5.80% moisture. Amino acid profile showed that all hydrolysates had glutamic acid/glutamine (113.45–117.56 mg/g sample), glycine (77.86–86.18 mg/g sample), aspartic acid/asparagine (76.04–78.67 mg/g sample), lysine (61.97–65.99 mg/g sample), and leucine (54.30–57.31 mg/g sample) as the predominant amino acids. The size distributions determined by gel filtration chromatography varied, depending on proteases and the form of frame used for the hydrolysis. Different hydrolysates showed varying antioxidant capacities. Thus, protein hydrolysates from salmon frame could be used as a nutritive supplement in the protein deficient foods. Practical applications Frames of salmon are by‐products from salmon fish processing industries. The frames contained the remaining meat, hence they can be used for the preparation of protein hydrolysates. Generally, hydrolysates from fish by‐products have been regarded as a promising food supplement, because they are rich in amino acids. Additionally, hydrolysates possess antioxidant activity, which is of health benefit. To produce the hydrolysate with less time consumption, the use of frame chunk instead of minced frame can be of better choice. Thus, frame of salmon, especially in chunk form, could be used as a raw material for production of protein hydrolysate using alcalase. The hydrolysate produced from salmon frame could serve as an alternative nutritive supplement to tackle the nutrition inadequacies in foods.

Bitterness of fish protein hydrolysate and its debittering prospects

“…The more the hydrolysis, the higher the extent of degradation of native protein structure and the more the exposure of hidden hydrophobic peptides causing bitterness are attained (Fu, Liu, Hansen, Bredie, & Lametsch, 2018). This claim was reconfirmed by Idowu et al (2018), who reported the influence of DH on bitterness of FPH from salmon frame. FPH from salmon frame produced with Alcalase with higher DH possessed higher hydrophobic amino acid and bitterness than its counterpart prepared using papain with less DH.…”

“…However, peptides containing bulky hydrophobic groups toward their C-terminal, have been regarded as the major causes of bitterness (Yarnpakdee et al, 2015). Hydrophobic groups of amino acids responsible for bitterness are Trp, Phe, Iso, Try, Val, and Leu (Idowu et al, 2018). It was documented that bitterness was attributed to hydrophobic amino acids in peptides, irrespective of amino acid sequence (Matoba & F I G U R E 1 Biological activities of bioactive peptides Hata, 1972).…”

“…The molecular weight (MW) of peptides is regarded as another factor that affects bitterness of FPH (Humiski & Aluko, 2007). FPH with different MW differed in the intensity of bitterness (Idowu et al, 2018). Aubes-Dafau, Capdevielle, Seris, and Combes (1995) isolated bitter peptides derived from hemoglobin hydrolysate using ultrafiltration.…”

“…Industrially, fish are usually processed as dressed eviscerated fish or fillets, in which a lot of by‐products in fish processing plant are generated (Klomklao & Benjakul, ). These by‐products include head, viscera (kidney, roe, and liver), trimmings (which consist of skin, muscle, and bone), and frames (Idowu, Benjakul, Sinthusamran, Sookchoo, & Kishimura, ). They are often discarded into sea, water channels, and oceans, leading to intense environmental pollution, high cost of waste disposal and less profit for fish processing industries (Klomklao & Benjakul, ).…”

“…Those leftovers have been processed into fish meal, fertilizer, and animal feed with low market value (Hsu, ). To increase their value, fish protein hydrolysates (FPH) have been manufactured via hydrolysis process, mainly by enzymatic hydrolysis to recover bioactive compounds and essential nutrients from those by‐products (Idowu et al, ; Nalinanon, Benjakul, Kishimura, & Shahidi, ; Thiansilakul, Benjakul, & Shahidi, ). Certain proteases are commonly employed during enzymatic hydrolysis to cleave fish proteins.…”