Peptide profiles and antioxidant capacity of extensive hydrolysates of milk protein concentrate.

Milk protein concentrate was hydrolyzed using one-step enzymatic hydrolysis. Both the peptide profiles and antioxidant activities of the resulting extensive hydrolysates of milk protein concentrate (EMPH) were analyzed using a peptidomics approach based on liquid chromatography-tandem mass spectrometry. The results demonstrated that the degrees of hydrolysis of the 4 EMPH by Alcalase-Protamex, Alcalase-Protease A 2SD, Alcalase-Flavorzyme, and Alcalase-ProteAXH were 12.02%, 16.85%, 15.87%, and 15.77%, respectively. Using size exclusion chromatography, 99.85% of the peptides in the Alcalase-Protease A 2SD hydrolysate were shown to have a molecular weight of <3 kDa. A total of 33 common peptides were identified in the EMPH by liquid chromatography-tandem mass spectrometry, 16 of which were identified as bioactive peptides using bioinformatics. The peptide profiles and the coverage of master proteins of the 4 EMPH were different. The EMPH also exhibited strong free radical scavenging capacity, as indicated by the results of the 1,1-diphenyl-2-picrylhydrazyl radical, 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), hydroxyl radical, and reducing power assays. The results of this study provided useful information on the peptide profiles and antioxidant activity of EMPH.