Effect of enzymatic hydrolysis on the production of free amino acids from boarfish (Capros aper) using second order polynomial regression models

• Boarfish is underutilized fish species.
• The effect of extraction conditions on taurine content and free amino acids from boarfish.
• Taurine from Boarfish can be obtained using enzymatic hydrolysis.
• Higher yield of free amino acid can be obtained using enzymatic pre-treatment followed by acid hydrolysis.

The objective of this study was to investigate the effect of acid concentration and hydrolysis time on the release of free amino acids from Boarfish protein hydrolysates. Second order polynomial models were developed to investigate the effect of acid concentration (0–6 M HCl) and hydrolysis time (0–18 h) on the level of free amino acids and taurine for Alcalase and Protease pre-treated samples. The polynomial models developed were found to be significant (P < 0.0001) and showed a good fit with the experimental data (R2 > 0.85). HCl concentration a negative effect on the yield of free amino acids irrespective of enzymatic pre-treatment. The highest concentration of taurine (7.23 mg/g) in the case of the control was found to degrade with an increase in acid concentration and hydrolysis time. HP-SEC analysis showed a significant reduction in the average molecular weight of protein hydrolysates obtained after acid hydrolysis indicating the release of amino acids and/or the degradation of proteins into smaller peptides. This study demonstrates that the use of enzymatic pre-treatment followed by acid hydrolysis results in a high yield of free amino acids and low molecular weight peptides.