Bioactivity and Functionality of Gelatin Hydrolysates from the Skin of Oneknife Unicornfish (Naso thynnoides)

Abstract

ABSTRACT Skin gelatin of oneknife unicornfish (Naso thynnoides) was hydrolyzed using a crude protease from Bacillus sp. under optimum hydrolysis conditions. The resulting hydrolysate was subjected to centrifugal ultrafiltration to produce fractions of ≤10 KDa molecular weight. Antioxidant, antihypertensive, and functional properties of the hydrolysate fraction were determined. Results showed that 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity (63%) and ferric reducing antioxidant power (25.90 trolox equivalent (mM mg−1) increased with increasing protein concentration in the fraction. Angiotensin-converting enzyme (ACE) inhibitory activity was directly proportional to the protein concentration, with the highest value obtained at 33.97% and IC50 determined to be 10.17 µg mL−1. Gel electrophoresis revealed that the gelatin hydrolysates contained mostly peptides, with a molecular weight ranging between 5 KDa and 30 KDa. Amino acid profile of the hydrolysates showed that it is rich in residues of glycine (Gly) (40.70%) and glutamic acid+glutamine (Glx) (25.40%). The hydrolysate was soluble over a wide pH range (79.38–97.12%). Foaming properties increased, while emulsion properties decreased with increasing concentration of the gelatin hydrolysates. The results of the present study revealed the potential of the oneknife unicornfish gelatin hydrolysates as a food ingredient with antioxidant and antihypertensive properties.