Characterization and antioxidant activity of protein hydrolysate from milkfish (Chanos chanos)

Milkfish (Chanos chanos) is a promising source for producing fish protein hydrolysate (FPH), which exhibits valuable bioactive and functional properties. This study aimed to evaluate the effects of hydrolysis time and bromelain concentration on the characteristics and antioxidant activity of milkfish-derived FPH. A completely randomized factorial design was used with variations in hydrolysis time (5, 6, and 7 h) and enzyme concentration (5, 6 and 7%), each treatment replicated three times. Parameters measured included moisture, fat, ash, soluble protein, degree of hydrolysis, molecular weight, yield, amino acid composition, and antioxidant activity. Results showed that enzyme concentration had no significant effect, while hydrolysis time significantly influenced soluble protein content, degree of hydrolysis, and antioxidant activity. The optimal condition was 5 h of hydrolysis with 5% enzyme addition, resulting in 15.31% moisture, 5.47% ash, 0.21% fat, and 42.94% soluble protein. Under these conditions, the yield was 16.84%, with a degree of hydrolysis of 32.04%, molecular weights ranging from 10.03 to 98.80 kDa, and an IC50 value for antioxidant activity of 1.58 mg/mL The hydrolysate contained essential amino acids (His, Thr, Val, Met, Phe, Ile, Leu, Arg, Trp, Lys) and non-essential amino acids (Cys, Glu, Asp, Ser, Gly, Pro), indicating its strong potential as a functional food ingredient with antioxidant benefits.