Potential of Subcritical Water Hydrolysis to Valorize Low-Valued Ray-Finned Fish (Labeobarbus nedgia): Effects of Hydrolysis Temperature and Pressurization Agent.

Subcritical water (SCW) hydrolysis was applied to valorize the low-valued ray-finned fish (Labeobarbus nedgia) into valuable protein hydrolysates, employing N(2) and CO(2) as pressurization agents at varying temperatures (140, 160, 180, and 200 °C). The degree of hydrolysis (DH) and total free amino acid content increased with temperature for both pressurizing agents. The highest DH (54.5 ± 0.4%) and total free amino acid content (210 ± 1 mg/g(prot)) were observed at 200 °C when CO(2) gas was used as the pressurizing agent. Predominantly, glycine and alanine were released for both pressurizing agents. The antioxidant activity, evaluated through three different assays, increased with temperature and was found to be the highest at 200 °C. This study illustrated the advantages of the intensified SCW technology by using CO(2) as a pressurization agent in valorizing low-valued ray-finned fish (Labeobarbus nedgia), as animal residue rich in proteins, for the production of valuable protein hydrolysates with a high fraction of valuable free amino acids, which could offer potential applications as a functional ingredient in the food industry.