Use of pyloric caeca extract from bigeye snapper (Priacanthus macracanthus) for the production of gelatin hydrolysate with antioxidative activity

Proteolytic activity of pyloric caeca extract (PCE) from bigeye snapper (Priacanthus macracanthus) was studied. The highest activity was observed at 55 °C and pH 8.0 when casein, Nα-Benzoyl-dl-arginine-p-nitroanilide (BAPNA) and Nα-p-Tosyl-l-arginine methyl ester hydrochloride (TAME) were used as the substrates. The activity was inhibited markedly by 1 mg/ml soybean trypsin inhibitor, whereas E-64, pepstatin A and EDTA exhibited a negligible effect on activity. The results suggested that a trypsin-like enzyme was most likely the major proteinase in PCE. As determined by activity staining, two proteolytic activity bands with apparent molecular weights of 55 and 24 kDa were found. Gelatin hydrolysate from bigeye snapper skin prepared using PCE exhibited the increases in 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and ferric reducing antioxidative power (FRAP) as degrees of hydrolysis (DHs) increased (P < 0.05). Hydrolysates derived from gelatin using Alcalase combined with PCE showed the highest ABTS radical scavenging activity (P < 0.05). Gelatin hydrolysate prepared using Alcalase in combination with Neutrase or PCE at 500 and 1000 ppm, respectively, retarded the oxidation in both linoleic acid oxidation and lecithin liposome oxidation systems. The antioxidative peptide of gelatin hydrolysate had a molecular weight of 1.7 kDa.