Optimization of hydrolysis conditions for production of angiotensin-converting enzyme inhibitory peptides from Basa fish skin using response surface methodology

Basa fish skin free from fat and noncollagenous proteins was hydrolyzed by different proteinases to produce angiotensin-converting enzyme (ACE) inhibitory peptides. Protamex hydrolysates were found to have the highest ACE inhibitory activity. Response surface methodology (RSM) was applied to optimize the hydrolysis conditions of Protamexincluding enzyme-to-substrate ratio, hydrolysis time, and solid (fish skin)-to-liquid (water for hydrolysis)at a temperature of 50 degrees C and a pH of 7.0. The mathematical model demonstrated a good fit with the experimental data. An enzyme-to-substrate ratio of 6,108 U/g, a hydrolysis time of 1.24 h, and a solid-to-liquid ratio of 1:8.05 g/mL were found to be the optimal conditions to achieve the highest value of ACE inhibitory activity. The IC50 of the hydrolysates for ACE inhibitory activity was 1.417 mg/mL under these conditions.