Preparation of Reactive Oxygen Scavenging Peptides from Tilapia (Oreochromis niloticus) Skin Gelatin: Optimization Using Response Surface Methodology

Gelatin extracted from tilapia skin was hydrolyzed with Properase E. Response surface methodology (RSM) was applied to optimize the hydrolysis condition (temperature [T], enzyme-to-substrate ratio [E/S], pH and reaction time [t]), to obtain the hydrolysate with the highest hydroxyl radical (center dot OH) scavenging activity. The optimum conditions obtained were T of 44.2 degrees C, E/S of 2.2%, pH of 9.2, and t of 3.4 h. The predicted center dot OH scavenging activity of the hydrolysate under the optimum conditions was 60.7%, and the actually experimental scavenging activity was 60.8%. The hydrolysate was fractionated by ultrafiltration, and 4 fractions were collected. The fraction TSGH4 (MW < 2000 Da) showed the strongest center dot OH scavenging activity with the highest yield. Furthermore, reactive oxygen species (ROS) scavenging activities of TSGH4 with different concentrations were investigated in 5 model systems, including superoxide anion radical (center dot O-2), center dot OH, hydrogen peroxide (H2O2), peroxynitrite (ONOO-), and nitric oxide (NO center dot), compared with reduced glutathione (GSH). The results showed that TSGH4 significantly scavenged these ROS, and could be used as a functional ingredient in medicine and food industries.