Skin waste from tuna processing needs to be utilized, such as extraction of its collagen and gelatin. Their functional properties can be improved by enzymatic hydrolysis for conversion to peptides. Thus, the research objectives were to examine the characteristics and antioxidant activity of collagen, gelatin, and the derived peptide from yellowfin tuna skin. Collagen was extracted using 0.75 M acetic acid at 4 °C, while gelatin was prepared using 0.25% citric acid and extracted at 65 °C. Hydrolysis was carried out with 2% Alcalase, followed by fractionation with a molecular weight cut off sieve for both collagen and gelatin. Collagen yield was 22.6% with pH value of 6.63 and whiteness of 96.7%. Gelatin yield was 20.0% with pH value of 4.94 and whiteness of 51.0%. Hydrolysis for three hours resulted in 52.7% and 45.2% degree of hydrolysis for collagen and gelatin, respectively. The molecular weights of collagen peptides ranged from 2.94 to 11.93 kDa, while those of gelatin peptides ranged from 3.54 to 16,620 kDa. Antioxidant activities of these peptides were higher than those before hydrolysis. The high antioxidant activity (IC₅₀) of collagen peptides were found in <3, 3–10, and 10–30 kDa fractions as well as in the gelatin peptides.

Around 40% of the total catch weight of fish is regarded as byproducts, consisting of skin, fins, bones, scales, viscera, etc. The utilization of these byproducts is important to increase their commercial values as well as to prevent environmental pollution. Meanwhile, nowadays, it is getting a global trend to provide foods and other industrial materials which have been accredited as halal products for Moslem communities. As a way of processing fish byproducts to meet the halal criteria, preparation of collagen and gelatin would be useful to fulfill the market demand. As a result of screening studies on fishery byproducts, fish skin has been found to be the good source for halal collagen and gelatin, which show satisfactory quality compared with those from bovine sources which could cause bovine spongiform encephalopathy (BSE).

The utilization of bigeye tuna skin as a source of collagen has been increasing the value of these skins. In this study, the quality of the skin was studied first. The skin after 14 h freeze-drying showed a high protein level (65.42% ± 0.06%, db), no histamine and a lack of heavy metals. The collagens were extracted through acid and acid-enzymatic methods. The enzymes used were bromelain, papain, pepsin, and trypsin. The two highest-yield collagens were pepsin-soluble collagen (PSC) and bromelain-soluble collagen (BSC). Both were type I collagen, based on SDS-PAGE and FTIR analysis. They dissolved very well in dimethyl sulfoxide and distilled water. The pH ranges were 4.60–4.70 and 4.30–4.40 for PSC and BSC, respectively. PSC and BSC were free from As, Cd, Co, Cr, Cu, and Pb. They showed antioxidant activities, as determined by the DPPH method and the reducing power method. In conclusion, bigeye tuna skin shows good potential as an alternative source of mammalian collagen. Although further work is still required, PSC and BSC showed the potential to be further used as antioxidant compounds in food applications. Other biological tests of these collagens might also lead to other health applications.

AbstrakLimbah filet ikan patin terutama kepala dan tulang memiliki potensi sebagai bahan baku pembuatanhidrolisat protein karena mengandung bioaktif peptida. Hidrolisat protein merupakan protein yangdihidrolisis menjadi peptida melalui proses enzimatis atau kimiawi. Penelitian ini bertujuan menentukanaktivitas pengikatan kalsium pada hidrolisat protein dari limbah filet ikan patin. Penelitian ini terdiri dari duatahap. Tahap pertama terdiri dari pembuatan hidrolisat protein secara enzimatis menggunakan konsentrasienzim papain yang berbeda. Hidrolisat protein tersebut dianalisis derajat hidrolisisnya menggunakanmetode SN-TCA sedangkan aktivitas pengikatan kalsium dengan menggunakan AAS. Tahap kedua yaituanalisis uv scanning untuk melihat penyerapan maksimum hidrolisat protein dan analisis komposisi asamamino untuk melihat komposisi asam amino yang terkandung dalam hidrolisat protein. Derajat hidrolisisyang dihasilkan dari penelitian ini berbanding lurus dengan konsentrasi enzim yang digunakan. Aktivitaspengikatan kalsium tertinggi oleh hidrolisat protein yaitu sebesar 122,73 mg L-1. Hidrolisat protein tersebutmemiliki derajat hidrolisis 43,13% dengan konsentrasi enzim 6% (v/v). Intensitas serapan pada hidrolisatprotein dengan penambahan kalsium lebih rendah apabila dibandingkan dengan intensitas absorpsihidrolisat protein, hal ini mengindikasikan adanya aktivitas pengikatan kalsium oleh hidrolisat protein.Komposisi asam amino tertinggi pada hidrolisat protein limbah filet ikan patin yaitu asam glutamat.

In this paper, we report the extraction and characterization of gelatin from the abundant industrial fishery waste of Pangasius skin and swim bladder and its application as the base material for hard capsule shells. The yield of gelatin ranged between 19 and 23, content of moisture is 7.69.2, ash is 1.11.7, pH is 4.15.2, gel strength is 238278 bloom, and viscosity is 6574.7 mP. SDS-PAGE showed all gelatins have chains of α1, α2, and β-peptides. The skin, swim bladder, and mixed gelatins were successfully used in the production of hard capsule shells. The dimensions, weight, disintegration time, and water content properties of the hard capsules from these Pangasius wastes were akin to the standards of commercial capsules.