Effect of enzyme type, enzyme to substrate ratio, temperature and hydrolysis time on the yield and antioxidant effect of Saurida tumbil protein hydrolysate

It has become a hot topic to make optimal use of fisheries products and make them value added as well as find natural food substances which can effectively inhibit oxidative stress and improve human health. Given this, Saurida tumbil muscle was hydrolyzed by Alcalase and Papain at two concentrations of 2 and 4%, and at two hydrolysis times of 90 and 180 min and their antioxidant properties were compared. Antioxidant activity of the protein hydrolysates were investigated by ferrous chelating and ferric reducing, 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2 -azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl free radical scavenging activity tests. Samples hydrolyzed by Papain showed higher protein recovery than those hydrolyzed by Alcalase (59.9% versus 20.06%). The protein hydrolysate prepared by Papain enzyme showed significantly higher activity in removal of DPPH (IC50=2.44 mg/mL) and hydroxyl (IC50=3.93 mg/mL) free radicals than those prepared by Alcalase enzyme (DPPH IC50=2.80 mg/mL, hydroxyl IC50=8.59 mg/mL). ABTS radical scavenging activity did not show any significant difference between hydrolyzed samples with Papain or Alcalase enzymes. Hydrolyzed samples with Alcalase enzyme showed higher ferrous chelating activity (IC50=5.33 mg/mL) and ferric reducing activity (optical absorption=0.13±00 at 700 nm) than those hydrolysate prepared by Papain enzyme. Generally, the type of enzyme, its concentration and the time of hydrolysis affected the yield and antioxidant properties of Saurida tumbil muscle protein hydrolysates and hydrolysis with papain at concentration of 4% for 180 min provided the best properties.