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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.

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Extraction Clown featherback skinFreeze-drying -82.08% total collagen recovery -27.64% yield of ASC -44.63% yield of PSC -330-333 residues/1000 residues of glycine -201-202 residues/1000 residues of imino acid -type I, comprising (α1) 2 α2-heterotrimer -T max = 35.23-36.28 °C -pI = 5.54-5.68 Salt precipitation Dialysis Characteristics of collagen Collagen ExtractionGraphical Abstract and PSC were 27.64 and 44.63% (dry weight basis) with total collagen recovery of 29 82.08%. Both collagens contained glycine as the major amino acid with relatively 30 high content of proline, hydroxyproline and glutamic acid/glutamine. Nevertheless, 31 they had the low content of cysteine, histidine and tryrosine. The collagen was 32 characterised as type I, comprising (α1) 2 α2-heterotrimer. Pepsin-aided process did not 33 affect triple-helical structure of PSC as determined by FTIR spectra. Thermal 34 transition temperature of ASC (36.28 °C) was slightly higher than that of PSC (35.23 35 °C). However, no differences in isoelectirc point (5.54-5.68) between ASC and PSC 36 was observed. Therefore, collagen from the skin of clown featherback could be 37 successfully extracted for further applications. 38 39