Effects of pressure-assisted enzymatic hydrolysis on functional and bioactive properties of tilapia (Oreochromis niloticus) by-product protein hydrolysates

Fish by-product protein can be converted into valuable food and nutraceutical ingredients via proteolysis. The existing process suffers from many limitations such as extended reaction time and nonselective hydrolysis. In this study, protein from tilapia fish by-products was transformed into functional peptides using pressure-assisted enzymatic hydrolysis. Proteins were extracted from the tilapia by-products by isoelectric solubilization and precipitation method. The effects of pressure (38–462 MPa) and hydrolysis time (6–35 min) on the properties of the hydrolysates were investigated using a central composite design. Pressure enhanced protein hydrolysis with a maximum trichloroacetic acid-solubility index (TCA-SI) of 23% obtained at 250 MPa for 35 min. Pressure and time were also vital in improving soluble protein content (5.7 mg/mL), reducing power (44 μg AAE/g), and solubility (71%) of the hydrolyzed products. Improved antioxidant activity, indicated by a significant decrease in IC₅₀ values from 653 μg/mL to 304 μg/mL, was recorded. The combined process facilitated the release of low-molecular-weight peptides and essential amino acids. However, water and oil holding capacities were found to be decreased. Pressure-assisted enzymatic hydrolysis could provide an effective approach for recovering bioactive peptides from fish by-products for industrial applications.