Effect of High Hydrostatic Pressure (HHP) on the Enzymatic Hydrolysis of Fish Gelatin

Fish gelatin offers an alternative source for gelatin production; however, it possesses weaker functional properties, such as a low melting temperature and gel strength. Protein hydrolysates, produced through the hydrolysis of food proteins, demonstrate a wide range of biological activities, including antihypertensive, hypocholesterolemic, antimicrobial, and antioxidant properties. High hydrostatic pressure (HHP) is a non-thermal technology that can modify protein structures by inducing unfolding, thereby enhancing enzymatic accessibility and hydrolysis efficiency. Therefore, this study aimed to investigate the effects of different HHP parameters (400 and 500 MPa for 5, 15, and 30 min) and different Alcalase concentrations (2 and 4% wt/vol) on the production of fish protein hydrolysate. The results showed that HHP-assisted enzymatic hydrolysis increased the degree of hydrolysis and antioxidant capacity. However, when the pressure increased from 400 to 500 MPa, the degree of hydrolysis and antioxidant capacity decreased. FTIR spectroscopy was used to characterize the secondary structural changes of gelatin during HHP-assisted hydrolysis. The spectra revealed that more visible peaks of fish gelatin hydrolysate samples between 1000 and 1100 cm^-1 attributed to the asymmetric stretching of phosphate group (PO₄ ^3-) were observed. Protein unfolding is an important factor in increasing HHP-assisted hydrolysis. In conclusion, HHP combined with enzymatic hydrolysis is a promising alternative to produce protein hydrolysates with improved properties.