Potential Antioxidant Activities from Milkfish Bone with Different Retorting Time

Bioactive peptides derived from fish-processing by-products have attracted considerable attention as natural antioxidants. This study investigated the production and antioxidant properties of hydrolysates obtained from milkfish (Chanos chanos) bone through high-temperature extraction at 121^°C for 30, 60, 90, and 120 min. The hydrolysates were centrifuged, neutralized with phosphoric acid, freeze-dried, and evaluated for molecular weight distribution, degree of hydrolysis (DH), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity, and ferrous ion-chelating ability. The dried hydrolysates contained 85.10-89.27% protein with DH values ranging from 67.88%-72.10%. The hydrolysate extracted for 30 min was mainly distributed within the 30-70 kDa molecular weight range, whereas longer extraction times predominantly produced peptides with molecular weights below 14.4 kDa. The hydrolysate obtained after 90 min exhibited the highest DPPH radical-scavenging activity (98.50 ± 0.89% at 12 mg/mL), whereas the hydrolysate produced after 30 min showed the greatest ferrous ion-chelating ability (80.86 ± 0.57% at the same concentration). Further prolongation of retorting time did not improve antioxidant performance. These findings indicate that controlled high-temperature extraction effectively generates milkfish bone hydrolysates with strong antioxidant potential, supporting their potential application as functional ingredients in food and nutraceutical products.