In vitro antioxidant activity of protein hydrolysates prepared from corn gluten meal

BACKGROUND: Corn gluten meal (CGM), a major by-product of corn wet milling, is mainly used as forage in China. Because of its particular amino acid composition, in which there are large amounts of hydrophobic amino acids such as leucine, alanine and phenylalanine, CGM protein was thought to be a good resource to obtain antioxidant peptides. CGM protein was hydrolysed with a biochemical grade alcalase and the derived hydrolysates were assessed for their antioxidant properties in different in vitro assay systems, including inhibiting activity on lipid peroxidation, by reducing power, hydroxyl radical scavenging activity, and DPPH radical scavenging activity. The effects of concentration and molecular weight (MW) of hydrolysates on antioxidant activity were investigated. RESULTS: The results showed that CGM hydrolysates were effective antioxidants, and there was a dose-dependent relationship between hydrolysate concentration and antioxidant activity; the highest antioxidant activity was found in peptides 500-1500 Da, and the antioxidant activity of peptides below 500 Da or peptides above 1500 Da were all lower than that of total hydrolysates. CONCLUSIONS: The finding showed that the antioxidant activity of CGM hydrolysates was related to molecular weight and hydrolysate concentration, and the active antioxidant fraction should be in the peptides fraction of 500-1500 Da. CGM protein hydrolysates can be a source of natural antioxidant and used as a food additive. (c) 2008 Society of Chemical Industry.