<![CDATA[Skipjack tuna (Katsuwonus pelamis) bones are a byproduct of the fishing industry that are rich in protein and have potential as a source of bioactive peptides. This study aimed to determine the antioxidant activity of protein hydrolysates from raw and cooked skipjack tuna bones using the ABTS method. Hydrolysis was performed using bromelain at concentrations of 4%, 6%, and 8% at 55 °C for 4 hours pH 7.0), followed by enzyme inactivation at 85 °C for 20 minutes. Antioxidant activity was measured by IC50 determination using a UV-Vis spectrometer at 734 nm. The results showed that the antioxidant activity of skipjack tuna bone samples with the highest total protein content was observed at an enzyme concentration of 8%, namely 35.55% (raw fish bones) and 36.24% (cooked fish bones). The highest degree of hydrolysis in the raw fish bone sample reached 82.15 % and in the cooked fish bone sample reached 86.81 % with 8 % enzyme. Qualitative amino acid tests (ninhydrin, Biuret, xanthoprotein, and Millon) yielded positive results, indicating the presence of aromatic amino acids (tyrosine, tryptophan, phenylalanine) that contribute to antioxidant activity. The lowest IC50 value was obtained in the raw fish bone sample at an 8 % concentration, namely 10.03 mg/ml, and in the cooked fish bone sample at 6.19 mg/ml at an 8 % enzyme concentration. The higher the enzyme concentration, the higher the antioxidant activity.]]>
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