Antioxidant activity of optimized GAS protein hydrolysate
Antioxidants play an important role in food industries for purposes of nutritional preservation and prevention of color and flavor deterioration. Analysis of antioxidant activity on GAS protein hydrolysate showed higher ferrous chelating (46.80%) and hydroxyl radical scavenging activities (80.58%) compared to BHT (36.09% and 51.93%), respectively (data not shown). However, BHT showed higher reducing power (2.52%) compared to GAS protein hydrolysate (0.62%). The ferrous ion (Fe2+) is a pro-oxidant that interacts with hydrogen peroxide (Fenton reaction) to produce reactive oxygen species (ROS) and the hydroxyl (OH) free radical, which may initiate and/or accelerate lipid oxidation (Stohs, 1995). The complex formation of the ferrous ion is disrupted when chelating agents are present, resulting in decreased of color (Thiansilakul et al., 2007). As for reducing power, the presence of antioxidants in GAS protein hydrolysate causes the reduction of the ferricyanide complex to its ferrous form. These results suggested that GAS protein hydrolysate possibly contained amino acid or peptides which act as electron donors that could react with free radicals to form a more stable compound.