Comparative study on antioxidative activity of yellow stripe trevally protein hydrolysate produced from Alcalase and Flavourzyme

Antioxidative activities of protein hydrolysates from yellow stripe trevally (Selaroides leptolepis) prepared using Alcalase 2.4 L (HA) and Flavourzyme 500 L (HF) with the degree of hydrolysis of 15% by pH-stat method were determined. Both protein hydrolysates exhibited the antioxidative activity in a concentration dependent manner. HF generally showed the greater antioxidative activity than HA (P < 0.05) as indicated by the higher 2,2-diphenyl-1-picryhydrazyl (DPPH) radical scavenging activity, reducing power and metal chelating activity. Antioxidative activity of both hydrolysates was stable when heated at 90 degrees C for 10 and 30 min and subjected to a wide pH range (2-12). Nevertheless, metal chelating activity decreased in very alkaline and acidic pH ranges. HA and HF at 200 ppm retarded the formation of conjugated diene and thiobarbituric acid reactive substances (TBARS) in lecithin liposome system. HF possessed the stronger antioxidative activity than HA (P < 0.05). However, alpha-tocopherol at 200 ppm showed the higher antioxidative activity in the system.