Preparation of antioxidant peptide from egg white protein and improvement of its activities assisted by high-intensity pulsed electric field

BACKGROUND: Egg white protein powder was hydrolyzed by three proteasesalcalase, trypsin, and pepsinto produce antioxidant peptides. Three kinds of hydrolysates were prepared under optimal enzymatic parameters that were obtained from the preliminary one-factor-at-a-time test and response surface methodology. Thereafter, three enzymatic hydrolysates were sequentially fractionated by ultrafiltration membranes in cut-off MW of 30, 10, and 1 kDa, and tested in terms of their reducing power (RP). Effects of high-intensity pulsed electric field (PEF) were further investigated on the antioxidant peptides to improve their activities. RESULTS: Alcalase hydrolysates possessed stronger RP ability than the other two hydrolysates, particularly for the fraction within < 1 kDa. After PEF treatment, this fraction showed an improvement of RP ability within 4 h; however, the effects were reversible. High-performance liquid chromatographic analysis showed some MW changes of PEF-treated sample compared with control. CONCLUSIONS: Amongthe three kinds of proteases, alcalase could be regarded as the most appropriate enzyme for preparation of bioactive peptide from egg white protein, with the best antioxidant activity. Also, PEF showed some effects on the peptide and could be further applied to improve its antioxidant activity. (C) 2011 Society of Chemical Industry