Effects of Fish Drying Methods on Functional, Antioxidant, and Antimicrobial Properties of African Catfish Protein Hydrolysates

The study enzymatically hydrolyzed protein isolates from fresh and processed (freeze-dried and oven-dried) fillets of African catfish (ACF). The functional, antioxidant, and antimicrobial potentials of the ACF fillet protein hydrolysate (ACFPH) were investigated to expand the possibilities for their potential application in human health. ACF fillet was obtained and divided into three parts: the first part was freeze-dried, the second was oven-dried, and the last part was left fresh. Protein isolates were prepared from them and hydrolysed with pepsin. The degree of hydrolysis (DH) and peptide chain length (PCL) were calculated. The study analyzed the ACF fillet protein hydrolysates’ water and oil absorption capacity (functional properties). Antioxidant activity was estimated through ferric reducing power, metal chelating, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays. The antimicrobial activity was tested using agar disc methods. The DH was time-dependent and indirectly proportional to PCL. Freeze-dried catfish fillet protein hydrolysate (FD-CFPH) was better hydrolyzed with 87 ± 3.54 % hydrolysis degree, and gave the least PCL value of 1.15. Fresh catfish fillet protein hydrolysate (FR-CFPH) was better water absorbent than FD-CFPH and oven-dried catfish fillet protein hydrolysate (OD-CFPH). FD-CFPH displayed the best oil absorption capacity (23.7 ± 1.75 mL/g). All antioxidant assays displayed concentration-dependent activity. FR-CFPH displayed the highest metal chelating activity and DPPH radical scavenging potential, while OD-CFPH showed the highest ferric reducing power. All the pepsin-produced ACFPH resulted in a high antifungal activity against Penicillium camemberti, but only FD-CFPH at the highest concentration was effective against Aspergillus flavus. For each examined bacterium, no discernible inhibitory zone was observed, suggesting that the hydrolysates were ineffective against the bacteria. The potential functional and antioxidant activities elicited by the ACFPH suggest that it could be employed to develop nutraceutical and therapeutic products for alleviating oxidative stress-related ailments.