Antioxidant Activity and Potential Bioactive Peptides from Skin Protein Hydrolysate of Yellowfn Tuna (Thunnus albacares) Sitti Hardiyanti Rachman, Joko Santoso* , and Sugeng Heri Suseno ARTICLE INFO Received: December 16, 2022 Accepted: March 27, 2023 Published: April 12, 2023 Available online: August 15, 2023 *) Corresponding author: E-mail: jsantoso@apps.ipb.ac.id Keywords: Antioxidant Bioactive Peptides Defatting Enzymatic Hydrolysis Tuna Skin Hydrolysate This is an open access article under the CC BY-NC-SA license (https:// creativecommons.org/licenses/by- nc-sa/4.0/) Abstract The tuna fllet industry produces abundant skin by-products with high protein, which has the potential as a raw material for fsh protein hydrolysate (FPH) for a source of bioactive peptides. Exploration of bioactive peptides from fsh skin is generally from hydrolyzed gelatin and collagen. The study aimed to produce FPH directly from tuna skin as an antioxidant and identify potential bioactive peptides. The research began by defatting using multiple concentrations of NaH- CO 3 and immersion times. The defatted fsh skin was produced as FPH by en- zymatic hydrolysis method using diferent papain enzyme concentrations and hydrolysis times. The selected treatments were assessed for antioxidant activity and bioactive peptides. The results showed that the defatting process using a 0.50% NaHCO 3 for 30 minutes generated the highest reducing fat content in value was 80.53%. Using papain enzyme gave a signifcant efect on the DH of FPH, with value was 29.72-67.64%. Therefore, FPH obtained from diferent concentrations for 4 hours was chosen to characterize the antioxidant activity and bioactive peptide. Hydrolysis using 5% enzyme papain showed the highest antioxidant activity of DPPH, ABTS, and reducing power with values of 0.965 mg/mL, 0.495 mg/mL, and 0.415 absorbances, respectively. FPH possesses a molecular weight of 10.15-48.50 kDa. Functional groups detected were amides A, B, I, II, and III. Glycine, proline, and arginine became amino acids dominant of FPH. Based on the diversity of biopeptide compounds, several biological function candidates were detected, namely antioxidants, ACE inhibitors, and antifbrinolytics which have the potential to be used as nutraceutical products. Cite this as: Rachman, S. H., Santoso, J., & Suseno. S. H. (2023). Antioxidant Activity and Potential Bioactive Peptides from Skin Protein Hydrolysate of Yellowfn Tuna (Thunnus albacares). Jurnal Ilmiah Perikanan dan Kelautan, 15(2): 248-263. http://doi. org/10.20473/jipk.v15i2.41625 Copyright ©2023 Faculty of Fisheries and Marine Universitas Airlangga 248 JIPK TAN) (JURNAL ILMIAH PERIKANAN DAN KELAU Research Article Scientifc Journal of Fisheries and Marine JIPK. Volume 15 No 2. November 2023 e-ISSN:2528-0759; p-ISSN:2085-5842 Sinta 1 (Decree No: 158/E/KPT/2021) Available online at https://e-journal.unair.ac.id/JIPK Department of Aquatic Product Technology, Faculty of Fisheries and Marine Science, Bogor Agricultural University, Bogor. Indonesia