Abstract: Wheat gluten is a main by-product of wheat starch processing. Enzymatic hydrolysis is an effective way of improving the solubility and functionality of wheat gluten; however, protease type may influence the functionalities of wheat gluten hydrolysates such as antioxidant activities. Six frequently used proteases including Alcalase, Neutrase, Pepsin, Flavourzyme, Pancreatin and Papain were used for the hydrolysis of wheat gluten, and the degree of hydrolysis and antioxidant capacity of four-hour hydrolysates were evaluated in terms of polypeptide yield, molecular weight distribution, 1,1-diphenyl-2- picrylhydrazyl (DPPH) radical scavenging activity, superoxide radical anion (O2- ·) scavenging activity, and hydroxyl radical (·OH) scavenging activity. The results showed that Flavourzyme hydrolysate exhibited the highest polypeptide yield (91.44%), containing up to 76.9% polypeptide with a molecular weight of less than 3 000 D. Papain hydrolysate at a concentration of 3 mg/mL exhibited the best DPPH radical scavenging activity (65.12% scavenging percentage, P < 0.01), followed by Flavourzyme hydrolysate (58.43%) and Alcalase hydrolysate (55.29%). Alcalase hydrolysate exhibited the best superoxide anion radical scavenging activity (58.68% scavenging percentage, P < 0.01), followed by Flavourzyme hydrolysis (49.25%). Alcalase and Papain hydrolysates exhibited the best hydroxyl radical scavenging activity (scavenging percentages of 59.23% and 58.16%, respectively). Therefore, protease type had a notable effect on antioxidant activities of wheat gluten hydrolysates. In addition, Flavourzyme hydrolysis gave a significant improvement in the degree of hydrolysis and the formation of small polypeptides; moreover, Alcalase, Papain and Flavourzyme resulted in improved antioxidant activities of hydrolysates.

Key words: protease, wheat gluten, antioxidant activity, free radical scavenging activity